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Ultrasonic Control of Polymer-Capped Plasmonic Molecules
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  • Yingying Cai*
    Yingying Cai
    Institut für Physikalische Chemie, Georg-August-Universität Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
    *Email: [email protected]
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    Orcidhttps://orcid.org/0000-0002-6556-9324
  • Swagato Sarkar
    Swagato Sarkar
    Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany
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  • Yuwen Peng
    Yuwen Peng
    Institut für Physikalische Chemie, Georg-August-Universität Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
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  • Tobias A. F. König
    Tobias A. F. König
    Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany
    Center for Advancing Electronics Dresden (cfaed), Technische Universität Dresden, Helmholtzstraße 18, 01069 Dresden, Germany
    Faculty of Chemistry and Food Chemistry, Technische Universität Dresden, Bergstraße 66, 01069 Dresden, Germany
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    Orcidhttps://orcid.org/0000-0002-8852-8752
  • Philipp Vana
    Philipp Vana
    Institut für Physikalische Chemie, Georg-August-Universität Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
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    Orcidhttps://orcid.org/0000-0001-6032-3854
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ACS Nano

Cite this: ACS Nano 2024, 18, 45, 31360–31371
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https://doi.org/10.1021/acsnano.4c10912
Published October 31, 2024

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Abstract

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Plasmonic molecules (PMs) composed of polymer-capped nanoparticles represent an emerging material class with precise optical functionalities. However, achieving controlled structural changes in metallic nanoparticle aggregation at the nanoscale, similar to the modification of atomic structures, remains challenging. This study demonstrates the 2D/3D isomerization of such plasmonic molecules induced by a controlled ultrasound process. We used two types of gold nanoparticles, each functionalized with hydrogen bonding (HB) donor or acceptor polymers, to self-assemble into different ABN-type complexes via interparticle polymer bundles acting as molecular bonds. Post-ultrasonication treatment significantly shortens these bonds from approximately 14 to 2 nm by enhancing HB cross-linking within the bundles. This drastic change in the bond length increases the stiffness of the resulting clusters, facilitating the transition from 2D to 3D configurations in 100% yield during drop-casting onto substrates. Our results advance the precise control of PMs’ nanoarchitectures and provide insights for their broad applications in sensing, optoelectronics, and metamaterials.

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Introduction

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Plasmonic nanoparticles (NPs), e.g., Au and Ag, exhibit localized surface plasmon resonance when their conduction electrons oscillate in resonance with incident light. (1) Assembling these NPs into clusters introduces new collective optical properties that are hybridized from the plasmonic coupling between its primary building blocks. (2) Controlling plasmonic assemblies in terms of particle geometry, materials, and spatial arrangement provides a potent means to manipulate light–matter interactions; (1,3−5) these assemblies thus hold significant potential in various fields, such as sensing, (6,7) optoelectronics, (8,9) and metamaterials. (10,11)
Plasmonic molecules (PMs) are a class of plasmonic assemblies that mimic molecular structures. (1,10,12) Their plasmon modes follow symmetry rules similar to those of real molecules, where atomic orbitals hybridize to form molecular orbitals, thus offering predictable optical behaviors. (1,5,13) For molecules, it is well known that different isomers (e.g., tetrahedral vs square planar for AB4-molecules) exhibit distinctly different hybridizations. Understanding and controlling the structural isomerization of PMs can lead to advancements in designing optical devices with tunable properties. (13−15) Despite these advancements, achieving such 2D/3D isomerization of PMs remains a significant challenge. Although various assembly methods have been developed, realizing different isomers still necessitates a complex redesign of assembly pathways. The lithographic method provides convenient access to programming structures larger than 10 nm but is generally restricted to 2D patterns. (16,17) DNA-scaffolding, while capable of customizing diverse architectures, requires dedicated design and fabrication efforts for each structure. (18,19) Solvent-assisted templating can produce 3D structures in the form of larger superlattices (7,20) but tends to yield 2D formations for much smaller clusters due to capillary forces. (11,21) Once these nanostructures are completed, their spatial arrangement is fixed and is rarely able to be rearranged.
In recent years, colloidal self-assembly has made significant strides in fabricating nanostructures with high structural fidelity and efficiency. (3,15,22) Structures such as chain-like, (23,24) molecular-like, (25−27) and core-satellite (28−30) configurations have been achieved through sophisticated balancing of close-range attractive forces to bond NPs and long-range repulsive forces to confine the assembly degree. (31,32) In this context, synthetic polymer-capped NPs have shown great potential. The polymer shells not only facilitate precise control over interparticle interactions through monomer formulation, e.g., via electrostatic interactions, (23) acid–base neutralization, (25,27) and hydrogen bonding (HB), (26,30) but also provide necessary steric hindrance that aids in controlling the assembly’s structure. (27,33) For instance, our recent work has demonstrated the efficacy of using a pair of polymer-capped AuNPs, each with HB-donor and HB-acceptor moieties, to construct ABN-type PMs with accurate control over the coordination number N. (26)
Moreover, polymer engineering is versatile in tuning mechanical properties through architectural design elements such as composition, chain length, and cross-linking. (34,35) Functional polymers can respond to external stimuli (e.g., temperature, (36,37) pH, (38,39) light, (40,41) and ultrasound (42−46)), creating design space for post-assembly modulation of the constructed nanoarchitecture.
Here, we present an innovative approach for 2D/3D isomerization of PMs by post-engineering HB polymer linkages. Using HB-interacting polymer-functionalized AuNPs, we assembled ABN-type PMs in the colloidal form. The interconnecting polymer bundles (i.e., the PM bonds) formed between A- and B-type NPs somewhat mimic σ-bond formation from atomic orbital hybridization. Post-ultrasonication significantly enhances HB cross-linking within the polymer bundles by facilitating the ejection of solvent molecules. This stimulus transitions PM bonds from soft to rigid efficiently, which further results in distinct 2D or 3D configurations of PMs during drop-casting on the substrate. Notably, the structural stiffness of PMs directly correlates with the interparticle distance between A- and B-NPs, analogous to molecular bonds where shorter lengths correspond to higher energies. We have studied several PM isomers, including AB4, AB6, AB8, and AB12, and have gained insights into their transformations in both colloidal and solid states. This study combines experimental observations with optical simulations to explain the mechanisms driving these transitions, setting the foundation for a deeper discussion of the implications and applications of our findings.

Results and Discussion

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Isomerization of PMs by Post-ultrasonication

As illustrated in Figure 1B, a thiol-terminated random copolymer of styrene and hydroxystyrene (P(St0.7-r-HSt0.3)m) is utilized for its HB donating ability via the phenol group. This copolymer is synthesized via reversible addition–fragmentation chain-transfer (RAFT) polymerization, followed by hydrolyzation and reduction steps (Figure S1). Commercial thiol-terminated poly(ethylene glycol) methyl ether (PEGn) of varying chain length is used for its ether group as HB-acceptors (m and n are both repeating units). Cetyltrimethylammonium chloride (CTAC)-stabilized AuNPs are synthesized by seed-mediated growth methods with diameters of 22, 28, 30, and 34 nm. These two types of polymers are grafted onto the surface of AuNPs via a ligand exchange process, forming a covalent thiol–gold bond (Figures S14–18, and Table S1). The high Au–S binding strength (170 kJ/mol) (47) ensures robust anchoring of the polymer brushes on the Au surface (Figure S23), preventing detachment during ultrasonication. HB-acceptor NPs (i.e., A-NPs, with a PEGn shell) and HB-donor NPs (i.e., B-NPs, carrying a P(St0.7-r-HSt0.3)m shell) were then prepared as stock colloids serving as the building blocks for the subsequent PM assembly process (Figure 1A).

Figure 1

Figure 1. Schematic of self-assembly and isomerization of PMs via HB interaction. (A) Building blocks: PEGn (HB acceptor) and P(St0.7-r-HSt0.3)m (HB donor) grafted onto AuNPs. m and n refer to the number of repeating units. (B) HB-donor and -acceptor polymer design and their interaction when grafted onto the AuNPs. (C) Mixing A- and B-NPs forms colloidal PMs (AB4-α) by forming polymer bundles (PM bonds). (D) Scanning electron microscopy (SEM) image: AB4-α colloid transfers to a 2D square planar on a substrate. (E) Upon post-ultrasonication, AB4-α changes to the AB4-ω state in the colloid. Polymer bundles shrink, and the polymer chains entangle tightly. This results in a decrease in the PM bond length and an increase in the structural stiffness. (F) SEM image: drop-casting AB4-ω achieves a tetrahedral isomer due to increased stiffness. (G) Ultrasonication ejects solvent molecules, forming new HB linkages and transitioning from ABN-α to ABN-ω.

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The self-assembly process is performed by mixing the A- and B-NPs in predetermined ratios under optimized conditions. (26) Samples are then taken after different conditions (ultrasonication and incubation time) for UV–vis spectroscopy and dynamic light scattering (DLS) analysis to monitor changes in the colloidal states. After drop-casting onto a substrate, SEM measurements are conducted to determine the assemblies’ geometry in their dried state. A binary solvent mixture of tetrahydrofuran (THF, a moderate HB donor (48,49)) and chloroform (CHCl3, a weak HB acceptor (48,49)) is used to provide an appropriate level of solvation for each HB moiety.
The initial mixing requires only 15 s of ultrasonication to form stable ABN-clusters. This condition enables interconnecting multidentate HB interaction to form polymer bundles between the central A-NP and each individual adjacent B-NP, akin to covalent bond formation in molecules. The resulting PM bonds also possess characteristics such as “bond length”, i.e., the interparticle distance between A- and B-NPs (dA–B), and “bond strength” correlating with the ratio of connected/unconnected HB pairs. When the freshly prepared PM colloid (Figure 1C) is drop-cast onto a substrate and left to dry, 2D PMs form (Figures 1D and 2A), being separated and with well-controlled coordination numbers N. The mechanism for such a 2D structure formation is illustrated in Figure 1C,D and thoroughly discussed in our recent study. (26) Briefly, the capillary force between the central A-NP and the substrate surface pulls surrounding B-NPs toward the substrate. Concurrently, steric and electrostatic repulsive forces from the bulky polymer bundles ensure that high symmetry is maintained even after 2D rearrangement. For example, AB4 PM transforms from a tetrahedral geometry in the colloidal state into a square planar configuration upon drying.

Figure 2

Figure 2. PMs with different coordination numbers and configurations on the substrate. (A) SEM images of ABN PMs in 2D configurations for N = 4, 6, 8, and 12 prepared by drop-casting ABN-α colloid on a silicon wafer. Insert illustrations show the spatial arrangement on the substrate schematically. The A-NPs used are PEG136-grafted 22 nm A-NPs for N = 4, PEG227-grafted 28 nm A-NPs for N = 6 and 8, and PEG454-grafted 30 nm A-NPs for N = 12. All samples utilize 34 nm B-NPs grafted with P(St0.7-r-HSt0.3)420. (B) SEM images of ABN PMs in 3D configurations, prepared using ABN-ω colloid, which underwent post-ultrasonication from the corresponding ABN-α colloid. Inset illustrations show the typical schematic spatial arrangement on the substrate. (C) Statistical distribution of N values for AB4, AB6, AB8, and AB12 samples. Detailed sample conditions and additional SEM images are provided in the Supporting Information (Table S2 and Figures S3–S10). Scale bars are 100 nm.

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The PM’s colloidal structure should avoid the aforementioned 3D to 2D transition to create a stable tetrahedral isomer on the substrate. Therefore, the structural stiffness must be increased to prevent the collapse of the 3D geometry under capillary forces during the drying process. For this task, we aim to decrease the PM bond length and concurrently increase the bond strength to stabilize the PM structure. Experimentally, we found, to our surprise, that an additional ultrasonication step significantly changes the structure of the colloidal PMs: We will refer to the just-assembled colloid as the ABN-α state while to the ultrasound-treated as the ABN-ω state. In the AB4 sample, after post-ultrasonication for a few minutes (continuously) at room temperature and following incubation, the colloid’s color changes from red to violet (Figure 3C), indicating a drastically enhanced plasmonic coupling between the AuNPs (15) within the colloidal PMs. DLS results further indicate a drastic reduction in the hydrodynamic diameter (Dh) from 114 to 70 nm when going from the AB4-α to the -ω state (Figure 3B). This change is particularly impressive compared to the Dh of B-NPs, which is 68 nm and thus nearly identical to that of AB4-ω.

Figure 3

Figure 3. DLS and UV–vis results demonstrate the distinct colloidal behavior between ABN-α and ABN-ω and the significant effect of ultrasonication treatment. These colloids correspond to the samples used for preparing 2D/3D PMs’ isomers on substrates in Figure 2. (A) DLS measurements indicate that after post-ultrasonication, the hydrodynamic diameter (Dh) of the PMs in the colloid is significantly reduced for all samples. (B) Schematic illustrations showing the changes in Dh from AB4-α to AB4-ω: after ultrasonication treatment, the Dh decreases from 114 to 70 nm, which is comparable with the size of pure B-NPs in the same solvent condition (68 nm). (C) Photograph of the AB4-α and AB4-ω colloids. The color shift from red to violet indicates strong plasmonic coupling due to the significantly decreased dA–B within a cluster. (D) UV–vis spectra of ABN-α and ABN-ω for N = 4, 6, 8, and 12, compared with the spectra of A- and B-NPs under the same solvent conditions.

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This dramatic state change in the colloidal PMs results from the altered interactions among HB-donor polymers, HB-acceptor polymers, and solvent molecules. Ultrasonication, acting as a high-frequency mechanical wave, clearly can impact the HB interaction, (42,43,50) and Figure 1G shows a rational explanation for our case: In the ABN-α state, most HB moieties on the polymer are solvated with a few bonded to each other. The ultrasonication cleaves the bound solvent molecules from the corresponding HB moieties, temporarily causing desolvation and thus promoting new HB binding sites between polymers. Similar ultrasonication-induced desolvation phenomena have also been reported by Rahimzadeh et al. They observed that poly(N-isopropylacrylamide) exhibits an exceptionally high ultrasonication-responsiveness to dehydration at certain frequencies through the breakage of HB with water molecules. This effect occurs at a speed that even surpasses the well-known temperature-responsiveness of poly(N-isopropylacrylamide). (42,43) In our case, a bath-type sonicator provides (by accident) the appropriate sonication conditions for our polymer/solvent system. Ultrasonication accelerates the PMs from the α state (more solvent–polymer HB) toward the ω state (more polymer–polymer HB). (Preliminary experiments with specialized ultrasound generators at different frequencies and power levels did not yield improved results; this will be the subject of future studies). Moreover, as the interchain linkages increase, the PMs become more rigid and the PM bond strength increases. Similar phenomena can be extensively found in studies where ultrasound stimuli are utilized for gelation by inducing cross-linking from HB and other noncovalent interactions. (51−54) Consequently, the stabilized AB4-ω PM is able to maintain its tetrahedron structure when transferred from the colloid to substrate (Figure 1F).
Following solvent loss and a higher PM’s bond strength, the polymer bundles shrink, and the polymer chains entangle tightly, pulling the adjacent B-NPs toward the A-NP (Figure 1E). Consequently, the Dh decreases and stronger plasmonic coupling occurs.
Notably, the proportions of 2D or 3D isomer are 100% for each substrate sample, indicating that ultrasound facilitates a 100% yield of the α–ω transition and ensures the consistent evolution of each PM bond.
In short, the α–ω transition changes the properties of the PM from several perspectives, including the PM bond length, bond strength, and isomerization capability during drop-casting. Interestingly, these three properties are also decisive parameters for a real molecule. The relationship in which a short PM bond corresponds to a stronger bond strength parallels that seen in chemical bond systems. Although the mechanism of PM and molecular bond is fundamentally different, both systems share similarities for the formation of defined symmetry within an interacting ABN ensemble. (55−57)

2D/3D Isomerization of PMs with Varied Coordination Numbers

With an understanding of the impact of ultrasound on the α–ω transition and the dynamic structural change of PMs on solid substrates, we aim to generalize the structural isomerization across a broad spectrum of coordination numbers. In addition to AB4, we choose N = 6, 8, and 12 due to their high symmetry in 3D configurations. PMs with target N number are successfully fabricated using our model of solvent-competing self-assembly, (26) where we found that in a THF/CHCl3 mixture with x(THF) of 7.0–12.5%, the self-assembly of PMs proceeds in a controlled fashion. Within this concentration window, the P(St0.7-r-HSt0.3)m polymer chains on B-NPs gradually collapse as the x(THF) decreases, causing more B-NPs to be able to pair with one A-NPs. As such, a single set of A-/B-NP can span several N values in assembling PMs by only slightly changing the solvent composition in 1–2% increments. Further variation can be introduced by altering the ratio of total phenol to ether groups, by changing either the polymer chain length or the particle size. (26)
For demonstration, we fixed the polymer length at m = 420 and the AuNP’s size at 34 nm on B-NPs and varied the polymer length or AuNPs’ sizes on A-NPs, with variations in the solvent ratio to obtain all targeted PMs. Specifically, PEG136-capped 22 nm A-NPs are used for AB4 (x(THF) = 10.0%); PEG227-capped 28 nm A-NPs are used for AB6 and AB8 (x(THF) = 10.0% and 7.5% respectively); PEG454-capped 30 nm A-NPs are used for AB12 (x(THF) = 7.0%). Detailed conditions are summarized in Table S2.
For all ABN discussed herein, the ABN-α and ABN-ω states were produced using the above-mentioned method. These colloidal states were analyzed by using DLS (Figure 3A) and UV–vis spectroscopy (Figure 3D). Structural isomerization of these states on the substrate was examined by SEM (Figures 2 and S3–S10).
Figure 2C and Table S2 demonstrate that samples meet the target N-value. Figure 2A,B shows the successful formation of 2D/3D PMs’ isomers from their respective ABN-α and ABN-ω states without losing any adjacent B-NPs upon ultrasonication (statistical comparison for AB4 samples is shown in Figure S21 and Table S2). Analogue to the planar square/tetrahedron isomerization for AB4, AB6 features a hexagonal configuration for 2D and a nearly octahedral one for 3D. AB8’s 2D form appears as a deformed octagon as the circumference of A-NP is insufficient to accommodate all 8 B-NPs. Its 3D form predominantly exhibits a square antiprismatic geometry, where the upper four B-NPs are situated in the gaps of the lower layers, indicating a minor effect of capillary forces (with a few exceptions forming cubes). The AB12 samples exhibit the most extreme geometry change: The 2D form of AB12 visually shows a “splash” of B-NPs, including some B-NPs located on the second layer while remaining attached to the A-NPs. This supports the assumption that the PM bonds are extended in the colloidal ABN-α state. The structure exhibits high plasticity, allowing for the elongation of polymer bundles to the outermost B-NPs. As the PM bond length shortens and the overall structural stiffness increases, the AB12-ω state leads to a densely packed globular (3D) structure on the substrate. Notably, a perfect icosahedron with hcp stacking is formed when N is exactly 12.
DLS results (Figure 3A) confirm the significant reduction of Dh for all ABN samples, indicating that all PMs undergo a similar degree of α–ω transition under ultrasonication. The UV–vis spectra provide clearer evidence of PM formation as well as changes in PM bond length (Figure 3D): The plasmonic resonance peak of the ABN-α colloid is close to that of single A-/B-NPs. A slight red shift here can be attributed to the increased surrounding refractive index due to self-assembly as the NPs come closer. The decreased dA–B induced by ultrasonication leads to the ABN-ω state, which shows two characteristic resonance modes: one at 540–570 nm (λ1) and a new mode at 640–720 nm (λ2). For the low coordination numbers (N = 4, 6), λ1 can be associated with the resonance mode of a single AuNP. (15) It shares the same position as that seen in the α state. The significant red shift of λ2 from the resonance mode of AuNPs can be attributed to the localized surface plasmon coupling between A- and B-NPs, where the A-NPs induce oppositely directed dipoles in the B-NPs. (15,58) This hybridized mode suggests that the PM bonds are considerably shortened, as the degree of red shift in λ2 correlates with dA–B─the shorter the distance, the stronger the shift. (58) We will further discuss this in the next section in greater detail. The influence of coupling between B-NPs in these cases is negligible due to the wide distance between B-NPs (detailed explanation, see Figure S19). For N = 8 and 12, as the distance between B-NPs significantly decreases, the B–B coupling begins to take effect, as evidenced via the simulation where the central A-NP is removed (Figure S20). This hybridization forms a bright superradiant collective mode and a dark subradiant collective mode (Fano resonance). (17,59) Thus, the spectra of PMs are seen as a broad and continuous bright mode separated by a distinct dip from the dark mode due to destructive interference. As a result, this leads to a red-shift of the λ1 peak maximum and a broadening of the overall peaks, particularly evident in AB12 PMs.

Spectroscopic Study of Ultrasonication Altered PMs’ Bond Lengths and Simulations

This section focuses on studying how ultrasonication affects the PM’s bond lengths and how these changes are reflected in spectroscopic results. We designed a series of experiments with a step-by-step (SBS) treatment to shorten the PM bond length gradually. This involved pausing between each ultrasonication session to record changes in the hydrodynamic diameter and absorption spectra. Simulations were also conducted to generate theoretical spectra with different dA–B. Comparing experimental and simulation results gives insights into the structural changes during the α–ω transition.
For these experiments, we selected the AB6 structure for demonstration. Both A-NPs and B-NPs were chosen with the same diameter (34 nm) to simplify the system and mitigate the effects caused by differences in the NP size. This series of samples is referred to as AB6SBS to distinguish it from the previous AB6 samples.
As shown in Figure 4A–C, the fresh assembled sample (AB6SBS-α) was first recorded and then left to incubate overnight before recording again (AB6SBS(tUS = 0)) prior to ultrasonication steps. Each ultrasonication step lasted 1–3 min, with tUS representing the cumulative ultrasonication duration (AB6SBS(tUS = 1–26 min)). These steps were repeated, until only minor changes were observed in the UV–vis spectra. After 10 ultrasonication steps, the sample was incubated overnight again for the final recording (AB6SBS-ω).

Figure 4

Figure 4. Experimental and simulation results of step-by-step ultrasonication on AB6SBS colloid. (A–C) Experiment: (A) UV–vis spectra for B-NPs (gray dashed) and AB6SBS colloid (red to blue) at each step. (B) Photographs showing color changes. (C) Relationship between λ2 peak position and hydrodynamic diameter (measured by DLS) with red-shift indicating PM shrinkage. Gray and red dashed lines show resonance modes of pure B-NPs and λ1, respectively. (D–F) Simulation: (D) simulated absorption spectra for AB6 structures with decreasing dA–B. The gray dashed curve is the spectrum of a single 34 nm AuNP multiplied by seven. (E) Schematic of dA–B changes. (F) Relationship between λ2 wavelength and dA–B, with a fitted curve for dA–B = 2–30 nm. Gray and red dashed lines indicate resonance modes of 34 nm AuNP and λ1, respectively.

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Inspection of UV–vis spectra (Figure 4A) reveals the gradual evolution of two peaks: λ1, consistently located at 541 nm, predominantly originates from the resonance mode of AuNPs; λ2, which separates from λ1, exhibits red-shifting and increased intensity after each step. This behavior aligns well with the previous discussion, suggesting that λ2 is a hybrid mode enhanced by stronger plasmonic coupling due to the decreased dA–B. These spectral shifts correspond to the visual color changes in the sample, as depicted in Figure 4B: The colloid initially transitions from red to purple, attributed to the λ2 band moving to around 650 nm; then, it takes on a pink-red color as this hybrid mode further transitions toward a lower energy region (around 700 nm). The consistent shifting of λ2 while maintaining a narrow bandwidth, alongside apparent color changes, allows us to infer that the PM bond length changes are uniform across all of the PMs in the samples.
DLS measurements (Figure 4C) reveal a consistent decrease in Dh after each ultrasonication step, directly correlating with the shift of λ2. This affirms the fact that the PM’s shrinkage and spectroscopic evolution proceed simultaneously. This relationship persists across individual experiments with the same pattern (Figure S2B). We have repeated this sequential treatment of AB6SBS PM with a 4-fold diluted particle concentration and observed the same trend but faster α–ω evolution under the same ultrasonication power condition (Figure S2A).
To further clarify the α–ω evolution, we incorporated two incubation phases (each about 16 h) before and after the experimental sequence of ultrasonication steps. Both UV–vis and DLS results indicate that the PMs also evolve slightly during these phases, albeit several magnitudes slower than when applying ultrasonication. This suggests that the ω state is thermodynamically more favored than the α state. Ultrasonication likely accelerates this process by overcoming the activation energy needed for solvent dissociation and the formation of new HB between polymers.
Furthermore, we have utilized our expertise in electromagnetic modeling via finite-difference time-domain (FDTD) simulation methods (60,61) to determine the impact of changes in the PM’s bond length on spectral variations (Figure 4D–F) and field enhancement (Figure 5) under different PM bond length conditions. The simulation model (Figure S13) closely replicates the experimental conditions of the AB6SBS series, that is, an AB6 structure with 34 nm A-NPs and B-NPs covered with the corresponding polymer shell, configured in octahedral coordination and aligned with the XYZ axes of the coordinate system. The dA-B is defined as the edge-to-edge distance between the gold surface of A- and B-NPs (Figure 4E) and varies from 30 to 0 nm.

Figure 5

Figure 5. Electric field profiles at resonance modes for the dA–B = 14 and 2 nm, displayed in both xy and yz planes for a colloidal AB6 PM (same model as in Figure 4). (A) Electric field profile for dA–B = 14 nm at λ = 555 nm (spectral maximum), with a calculated enhancement factor of 16. (B,C) Electric field profiles for dA–B = 2 nm at λ1 = 552 nm (B) and λ2 = 696 nm (C), with calculated enhancement factors of 21 and 251, respectively.

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The simulated absorption cross-section spectra (Figure 4D) exhibit consistency with the experimental spectra: (1) λ1 slightly red-shifts from the single AuNPs and stabilizes at 552 nm across all dA–B values. Minor deviations from the experimental data (541 nm) are likely due to approximations in the polymer shells modeling. (2) λ2 is near absent at dA–B = 30 nm and then begins to appear as a peak broadening at dA–B = 14 nm. It continues red-shifting and increases in intensity, moving to 696 nm at dA–B = 2 nm (close to the position of the AB6SBS-ω sample). If dA–B is shortened to 0 nm, λ2 reaches its theoretically highest shift to 722 nm. More quantitatively, the wavelength of λ2 shows a near-exponential decay with distance (Figure 4F), in line with the universal scaling behavior of surface plasmon coupling in dimers, (58,62) and can be described with an empirical surface plasmon ruler equation
λ2=243exp(−dA−B3.54)+552nm,fordA−B=2−30nm
The electric field profiles (Figure 5) further confirm the origins of the λ1 and λ2 modes. For λ1, no significant coupling or changes in the field enhancement factor are observed, even as dA–B decreases to 2 nm, indicating its derivation predominantly from AuNPs (Figure 5A,B). In contrast, λ2 = 696 nm exhibits significant “hot spots” between A-NPs and B-NPs, with an enhancement factor reaching 251 at dA–B = 2 nm (Figure 5C). This illustrates its dependence on strong plasmonic coupling between A- and B-NPs.
From the experimental and simulation findings, we have pinpointed that the spectra for dA–B at 14 and 2 nm align most closely with the AB6SBS-α and AB6SBS-ω states, respectively (Figure 4A,D). Despite some deviations, we can still infer that transitioning from the α state to the ω state requires a reduction of >10 nm in dA–B and that ultrasonication facilitates a significant shrinkage down to a few-nm interparticle distances. This fact strongly supports our interpretation and gives a comprehensive visualization of the significant change in PM bond properties during α–ω evolution. The predicted plasmonic hot spots also reveal a strong potential to apply ω-PM for sensing and optical applications.

Conclusions

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In summary, we developed an HB-based platform for the self-assembly of polymer-grafted AuNPs into a series of colloidal PMs. The coordination number of these PMs can be tailored by adjusting the polymeric building blocks, the nanoparticle dimensions, and the self-assembly conditions. Ultrasonication is found to be an exceptionally effective and controllable stimulus that transforms colloidal PMs from an α-state with long and flexible bonds to an ω-state with short bonds and a rigid structure, as evidenced by SEM, UV–vis spectra, and DLS results. The colloidal state of the PM decides its configuration on a solid substrate after casting: α-state PMs are arranged in 2D isomers, while ω-state PMs form 3D isomers. Unlike the current methods in the literature that require complex redesigns of assembly pathways, our method overcomes this by using a simple ultrasonication process. Additionally, step-by-step ultrasonication experiments and FDTD simulations detail the progressive α–ω transition by bridging spectroscopic behaviors with the gradual change in the bond length, dA–B. From the calculated plasmon ruler from the simulations, the dA–B for α- and ω-states can be well estimated as 14 and 2 nm. Our approach offers a rational design and the tailored construction of nanoarchitectures. The tunable optical behavior of the PMs that may be dialed up by easily controlling their bond lengths provides great potential for the fabrication of optical devices and sensors.

Experimental Section

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Synthesis of Thiol-Terminated P(St0.7-r-HSt0.3)m

The synthesis of thiol-terminated P(St0.7-r-HSt0.3)m followed previously reported procedures. (26) As shown in the synthetic route (Figure S1A), this two-step process begins with the synthesis of a benzodithioate-terminated random copolymer of styrene and 4-acetoxystyrene, P(St0.7-r-ASt0.3)m, through RAFT polymerization. Subsequently, the polymer was hydrolyzed to form thiol-terminated P(St0.7-r-HSt0.3)m.
In brief, benzyl benzodithioate (3.4 mg, 0.014 mmol), styrene (1.46 g, 14.0 mmol), and 4-acetoxystyrene (973 mg, 6.00 mmol) were combined in a glass vial. The mixture was purged with argon for 15 min to ensure an inert environment. The reaction was performed at 110 °C for 18 h and then quenched by exposing the mixture to air and rapidly cooling it in an ice bath. The polymer was purified through four cycles, each consisting of precipitation with methanol, collection by centrifugation, and redispersion in THF. The obtained benzodithioate-terminated P(St0.7-r-ASt0.3)m was dried in a vacuum at 100 °C overnight. For hydrolysis, 1 g of the as-obtained intermediate polymer was dissolved in 20 mL of dioxane in a glass vial, which was then purged with argon. After hydrazine (2 mL) was injected, the mixture was shaken overnight. The polymer underwent three cycles of purification, each involving precipitation in hexane, centrifugation, and redispersion in THF. Finally, the thiol-terminated P(St0.7-r-HSt0.3)m was dried in a vacuum oven at 130 °C overnight.
From the SEC measurement (Figure S1B), the average molecular weight M̅n of benzodithioate-terminated P(St0.7-r-ASt0.3)m was determined to be 50.7 kg/mol with a dispersity D̵ = 1.2. 1H NMR was used to determine the polymer composition (ratio between St/ASt, and St/HSt) and confirmed that the hydrolysis process is complete (Figure S1C). From these characterizations, the degree of polymerization was calculated to be m = 420.

Synthesis of AuNPs

CTAC-stabilized spherical AuNPs were prepared using the method reported by Xia’s group, (63) with an up-scaling of the feed ratio. This method involves first preparing cetyltrimethylammonium bromide (CTAB)-stabilized single crystal Au-clusters followed by two subsequent growth steps: the first to ∼10 nm to form CTAC-stabilized seeds and the second to achieve the final size of the AuNPs. Briefly, the cluster was prepared by rapidly adding a NaBH4 aqueous solution (0.6 mL, 10 mM, freshly dissolved) to a mixture of HAuCl4 (5 mL, 0.5 mM) and CTAB (5 mL, 200 mM) under vigorous stirring. The mixture was stirred for another 15 min at 27 °C and left undisturbed at 27 °C for 3 h. The ∼10 nm seed is prepared by rapidly adding a solution of HAuCl4 (50 mL, 0.5 mM) into the mixture of CTAC (50 mL, 200 mM), ascorbic acid (37.5 mL, 100 mM), and 1.25 mL cluster at 27 °C. After stirring for another 15 min, the seeds were collected and washed once with water through ultracentrifugation at 105 g and redispersed in 22.5 mL of 20 mM CTAC for the next step. For the second growth step, CTAC (1040 mL, 100 mM), ascorbic acid (67.6 mL, 10 mM), and the as-prepared ∼10 nm seeds were mixed in a container. The final size of the AuNPs is controlled by the amount of the seeds. A syringe pump system was used to continuously add a HAuCl4 aqueous solution (1040 mL in total, 0.5 mM) into the mixture with an injection rate of 1040 mL/h while stirring. After the injection was completed, the mixture was stirred for an additional 15 min to ensure the completion of the reaction. The AuNP product was collected and washed twice with 1 mM CTAC and finally redispersed in 1 mM CTAC as a stock dispersion with an approximate concentration of 8 mg[Au0]/mL.

Preparing A-NPs and B-NPs by Polymer Functionalization on AuNPs

The polymer functionalization on AuNPs followed the procedure previously reported, (26) with some modifications. Typically, 1 mL of a stock dispersion of CTAC-stabilized 34.3 nm AuNPs was rapidly added to a polymer solution of P(St0.7-r-HSt0.3)420 in THF under sonication. The sonication continued for 30 min, after which the mixture was left undisturbed overnight before purification. The excess polymer was removed through 13 cycles of centrifugation/redispersion in THF. Notably, these multiple washing cycles are crucial for removing any trace amounts of unbound polymer, which can disturb the self-assembly result. Finally, the P(St0.7-r-HSt0.3)420-functionalized AuNPs were redispersed in 1 mL of THF as a stock dispersion, with an approximate concentration of 8 mg[Au0]/mL. All A-NPs and B-NP used in this work, along with the specific conditions for each sample, are summarized in Table S1.

Assembling A- and B-NPs into ABN-α State of PMs

For assembling ABN-α (N = 4, 6, 8, 12) PMs, the stock colloid of B-NPs (10 μL, in THF) was diluted to 300 μL (B-sol) in a 2 mL glass vial. The stock colloid of A-NPs (predetermined amount, in THF) was diluted into 100 μL (A-sol) in a polypropylene vial. Both A-sol and B-sol were adjusted during the dilution with the necessary volumes of THF and CHCl3 to achieve the required solvent compositions. For the sample that was used later for the AB6SBS experiment series, a 4-fold scale was used. The initial mixing process involved adding A-sol to the B-sol under bath sonication, with the mixture sonicated for 15 s (Movie S1). For the ABN-α state, DLS measurements, UV–vis spectroscopy, and sample preparation for SEM measurements were conducted with the freshly prepared PMs colloid. The sample colloid can be stored in a perfluoroalkoxy alkane vial to avoid the loss of PMs through adsorption onto the glass surface. The detailed information on all PMs used in this work is summarized in Table S2.
Post-ultrasonication for transitioning ABN-α to ABN-ω PMs for 3D structures on the substrate. To convert ABN-α PMs (where N = 4, 6, 8, 12) into ABN-ω PMs for 3D structures formation on the substrate, 100 μL of the overnight-incubated PMs colloid was placed in a 2 mL glass vial. This vial was then positioned at the center of an ultrasonication bath (Figure S22 and Movie S2). The ultrasonication process was continued until the hydrodynamic diameter of the PMs was reduced by about 20–25 nm. It is important to note that ultrasonication efficiency is highly dependent on diverse factors, including the colloid volume and concentration. For the given volume and concentration, sonication duration of 5, 5, 2, and 3.5 min was found to be the optimal condition for AB4, AB6, AB8, and AB12 samples, respectively. Then, the colloid was transferred into a PFA vial and left undisturbed overnight to allow for the complete formation of ABN-ω PMs. DLS measurements and UV–vis spectroscopy were performed on ABN-ω PMs to obtain their hydrodynamic diameter and absorption spectra in colloids. For visualizing their 3D geometry on the substrate, sample colloids were drop-cast onto a silicon substrate and used for SEM measurements.
Step-by-step ultrasonication experiments were performed with AB6 structures (AB6SBS series). The AB6SBS sample was used for the step-by-step ultrasonication experiment, which consisted of A-NPs and B-NPs with the same diameter of 34.3 nm. After the initial mixing of the A-NPs and B-NPs (AB6SBS-α), the colloid was incubated overnight prior to ultrasonication experiments. For the ultrasonication experiments, 700 μL of the overnight-incubated colloid was placed in a 7 mL glass vial (⌀ 16 mm) positioned at the center of the sonication bath. The sonication process began with a 1 min session for the first step, followed by 3 min for each subsequent step, accumulating a total sonication time of 26 min. After each sonication session, the colloid was left undisturbed for about 30 min to allow for the shrinking of the structure. DLS measurements, UV–vis spectroscopy, and photographs were taken before proceeding to the next ultrasonication step. This series of ultrasonication was continued until the changes observed in the hydrodynamic diameter and the absorption spectra were minor. The sample was incubated overnight to form AB6SBS-ω before the last measurements. In a separate individual experiment series, 700 μL of a 4-fold diluted colloid was used. This series involved 10 ultrasonication steps, totaling 11 min of accumulated sonication time, to achieve the same level of sonication efficiency as described above. The DLS results and UV–vis spectra from this series are shown in Figure S2.

FDTD Analysis

FDTD-based simulations are carried out using a commercial-grade electromagnetic solver (64) (Ansys Lumerical FDTD: 3D Electromagnetic Simulator, version 8.16). To reproduce the Mie scattering-based optical responses of the 3D PMs (ABN; N = 6) immersed in organic solvent (9% THF/91% CHCl3), “total-field scattered-field” (TFSF) sources are implemented with PML boundary conditions along the X, Y, and Z coordinates with an FDTD background refractive index of 1.4429. According to the experimental conditions of the AB6SBS series, the diameters of the spherical AuNPs are considered to be 34.3 nm, with an additional polymer shell of 2 nm for both A-NP and B-NPs. The corresponding modeling is shown in Figure S13. The dielectric characteristics of gold are modeled using a six-coefficient data fit from Johnson and Christy, (65) with an RMS error of 0.2. Additionally, the refractive index of the PEG shell for the A-NP is assumed to be constant, with values of 1.467. The refractive index of P(St0.7-r-HSt0.3)420 was approximated at 1.59 using the values for polystyrene. The absorption cross sections are calculated using the “analysis group”, placed inside the TFSF source, by considering the net power flow into the PM. To investigate the influence of the interparticle distance on the optical characteristics, the edge-to-edge distance between the gold surfaces of A- and B-NP (dA–B) is varied in discrete steps. Furthermore, to ensure the effect of plasmonic coupling, electric field profiles for the resonant modes are achieved by placing “frequency domain field and power” monitors across the diametric cross-section of the PM. An additional mesh grid with dimensions dx = 1 nm, dy = 1 nm, and dz = 1 nm is applied throughout all of the calculations for enhanced precision. Additional simulations for AB6, AB8, and AB12 are also carried out to investigate the effect of B–B coupling through the removal of central A-NP (Figures S19 and S20).

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsnano.4c10912.

  • Details of chemicals, characterization methods, and equipment; detailed polymer functionalization conditions for each A-NP and B-NP sample; detailed self-assembly conditions for each PM sample; coordination number statistics; synthesis route, SEC results, and 1H NMR spectra of the synthesized polymer; UV–vis and DLS results from an additional AB6SBS experimental series; additional SEM images; modeling used for FDTD-based simulations; TEM images of A-NPs and B-NPs; additional simulation results; ultrasonication setup; and thermogravimetric analysis results (PDF)

  • Initial ultrasonication process to assemble A- and B-NPs into PMs (AVI)

  • Post-ultrasonication process (AVI)

Terms & Conditions

Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

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  • Corresponding Author
  • Authors
    • Swagato Sarkar - Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany
    • Yuwen Peng - Institut für Physikalische Chemie, Georg-August-Universität Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
    • Tobias A. F. König - Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany;  Center for Advancing Electronics Dresden (cfaed), Technische Universität Dresden, Helmholtzstraße 18, 01069 Dresden, Germany;  Faculty of Chemistry and Food Chemistry, Technische Universität Dresden, Bergstraße 66, 01069 Dresden, Germany;  Orcidhttps://orcid.org/0000-0002-8852-8752
    • Philipp Vana - Institut für Physikalische Chemie, Georg-August-Universität Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany;  Orcidhttps://orcid.org/0000-0001-6032-3854
  • Author Contributions

    YC conceived and directed the project, performed the experiments, and wrote the manuscript; SS performed the simulations; YP synthesized the gold nanoparticles; TK and PV supervised and revised the manuscript. All authors have approved the final version of the manuscript.

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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We are grateful to Dr. Amin Rahimzadeh from Technische Universität Darmstadt and Dr. Holger Gibhardt from Georg-August-Universität Göttingen for their helpful and inspiring discussion about the ultrasonication mechanism. The Volkswagen Foundation financially supported this project through a Freigeist Fellowship to T.K.

Abbreviations

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NP(s)

nanoparticle(s)

AuNP(s)

gold nanoparticle(s)

PM(s)

plasmonic molecule(s)

HB

hydrogen bond(ing)

RAFT

reversible addition–fragmentation chain-transfer

P(St0.7-r-HSt0.3)m

random copolymer of styrene and hydroxystyrene

PEGn

poly(ethylene glycol) methyl ether

CTAC

cetyltrimethylammonium chloride

CTAB

cetyltrimethylammonium bromide

DLS

dynamic light scattering

SEM

scanning electron microscopy

THF

tetrahydrofuran

Dh

hydrodynamic diameter

ABN-α

just-assembled PMs in colloid

ABN-ω

ultrasound-treated PMs in colloid

N

coordination number

dA–B

the interparticle distance between A-NP and B-NP in a PM

SBS

step-by-step

FDTD

finite-difference time-domain

P(St0.7-r-ASt0.3)m

a random copolymer of styrene and 4-acetoxystyrene

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    ACS Nano (2017), 11 (3), 2917-2927CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)
    The authors explore the evolution of plasmonic modes in 2-dimensional nanocrystal oligomer metamols. as the no. of nanocrystals is systematically varied. Precise, hexagonally ordered Au nanocrystal oligomers with 1-31 members are assembled via capillary forces into polygonal topog. templates defined using electron-beam lithog. The visible and near-IR scattering response of individual oligomers is measured by spatially resolved, polarized darkfield scattering spectroscopy. The response is highly sensitive to in-plane vs. out-of-plane incident polarization, and the authors observe an exponentially satg. red shift in plasmon resonance wavelength as the no. of nanocrystals per oligomer increases, in agreement with theor. predictions. Simulations further elucidate the modes supported by the oligomers, including elec. dipole and magnetic dipole resonances and their Fano interference. The single-oligomer sensitivity of the measurements also reveals the role of positional disorder in detg. the wavelength and character of the plasmonic response. The progression of oligomer metamol. structures studied here advances the understanding of fundamental plasmonic interactions in the transition regime between few-member plasmonic clusters and extended 2-dimensional arrays.
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  12. 12
    Fan, J. A.; He, Y.; Bao, K.; Wu, C.; Bao, J.; Schade, N. B.; Manoharan, V. N.; Shvets, G.; Nordlander, P.; Liu, D. R.; Capasso, F. DNA-Enabled Self-Assembly of Plasmonic Nanoclusters. Nano Lett. 2011, 11, 4859– 4864,  DOI: 10.1021/nl203194m
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    12
    DNA-Enabled Self-Assembly of Plasmonic Nanoclusters
    Fan, Jonathan A.; He, Yu; Bao, Kui; Wu, Chihhui; Bao, Jiming; Schade, Nicholas B.; Manoharan, Vinothan N.; Shvets, Gennady; Nordlander, Peter; Liu, David R.; Capasso, Federico
    Nano Letters (2011), 11 (11), 4859-4864CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
    DNA nanotechnol. provides a versatile foundation for the chem. assembly of nanostructures. Plasmonic nanoparticle assemblies are of particular interest because they can be tailored to exhibit a broad range of electromagnetic phenomena. In this Letter, the authors report the assembly of DNA-functionalized nanoparticles into heteropentamer clusters, which consist of a smaller gold sphere surrounded by a ring of four larger spheres. Magnetic and Fano-like resonances are obsd. in individual clusters. The DNA plays a dual role: it selectively assembles the clusters in soln. and functions as an insulating spacer between the conductive nanoparticles. These particle assemblies can be generalized to a new class of DNA-enabled plasmonic heterostructures that comprise various active and passive materials and other forms of DNA scaffolding.
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  13. 13
    Chuntonov, L.; Haran, G. Trimeric Plasmonic Molecules: The Role of Symmetry. Nano Lett. 2011, 11, 2440– 2445,  DOI: 10.1021/nl2008532
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    13
    Trimeric Plasmonic Molecules: The Role of Symmetry
    Chuntonov, Lev; Haran, Gilad
    Nano Letters (2011), 11 (6), 2440-2445CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
    Artificial plasmonic mols. possess excitation modes that are defined by their symmetry and obey group theory rules, just like conventional mols. The evolution of surface-plasmon spectra of plasmonic trimers, assembled from equal-sized silver nanoparticles, as gradual geometric changes break their symmetry was analyzed. The spectral modes of an equilateral triangle, the most sym. structure of a trimer, are degenerate. This degeneracy is lifted as the symmetry is lowered when one of the vertex angles in opened, which also leads to a subtle transition between bright and dark modes. The exptl. results are quant. explained using numerical simulations and plasmon hybridization theory.
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  14. 14
    Park, K. J.; Huh, J.-H.; Jung, D.-W.; Park, J.-S.; Choi, G. H.; Lee, G.; Yoo, P. J.; Park, H.-G.; Yi, G.-R.; Lee, S. Assembly of "3D" Plasmonic Clusters By "2D" AFM Nanomanipulation of Highly Uniform and Smooth Gold Nanospheres. Sci. Rep. 2017, 7, 6045– 6110,  DOI: 10.1038/s41598-017-06456-w
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    There is no corresponding record for this reference.
  15. 15
    Rossner, C.; König, T. A. F.; Fery, A. Plasmonic Properties of Colloidal Assemblies. Adv. Opt. Mater. 2021, 9, 2001869,  DOI: 10.1002/adom.202001869
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    15
    Plasmonic Properties of Colloidal Assemblies
    Rossner, Christian; Koenig, Tobias A. F.; Fery, Andreas
    Advanced Optical Materials (2021), 9 (8), 2001869CODEN: AOMDAX; ISSN:2195-1071. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A review. The assembly of metal nanoparticles into supracolloidal structures unlocks optical features, which can go beyond synergistic combinations of the properties of their primary building units. This is due to inter-particle plasmonic coupling effects, which give rise to emergent properties. The motivation for this progress report is twofold: First, it is described how simulation approaches can be used to predict and understand the optical properties of supracolloidal metal clusters. These simulations may form the basis for the rational design of plasmonic assembly architectures, based on the desired functional cluster properties, and they may also spark novel material designs. Second, selected scalable state-of-the-art preparative strategies based on synthetic polymers to guide the supracolloidal assembly are discussed. These routes also allow for equipping the assembly structures with adaptive properties, which in turn enables (inter-)active control over the cluster optical properties.
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  16. 16
    Bautista, G.; Dreser, C.; Zang, X.; Kern, D. P.; Kauranen, M.; Fleischer, M. Collective Effects in Second-Harmonic Generation from Plasmonic Oligomers. Nano Lett. 2018, 18, 2571– 2580,  DOI: 10.1021/acs.nanolett.8b00308
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    16
    Collective Effects in Second-Harmonic Generation from Plasmonic Oligomers
    Bautista, Godofredo; Dreser, Christoph; Zang, Xiaorun; Kern, Dieter P.; Kauranen, Martti; Fleischer, Monika
    Nano Letters (2018), 18 (4), 2571-2580CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
    The authors study collective effects in plasmonic oligomers of different symmetries using 2nd-harmonic generation (SHG) microscopy with cylindrical vector beams (CVBs). The oligomers consist of Au nanorods that have a longitudinal plasmon resonance close to the fundamental wavelength that is used for SHG excitation and whose long axes are arranged locally such that they follow the distribution of the transverse component of the elec. field of radially or azimuthally polarized CVBs in the focal plane. SHG from such rotationally sym. oligomers is strongly modified by the interplay between the polarization properties of the CVB and interparticle coupling. The oligomers with radially oriented nanorods exhibit small coupling effects. But the oligomers with azimuthally oriented nanorods exhibit large coupling effects that lead to silencing of SHG from the whole structure. The exptl. results are in very good agreement with numerical calcns. based on the boundary element method. The work describes a new route for studying coupling effects in complex arrangements of nano-objects and thereby for tailoring the efficiency of nonlinear optical effects in such structures.
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  17. 17
    Hentschel, M.; Saliba, M.; Vogelgesang, R.; Giessen, H.; Alivisatos, A. P.; Liu, N. Transition from Isolated to Collective Modes in Plasmonic Oligomers. Nano Lett. 2010, 10, 2721– 2726,  DOI: 10.1021/nl101938p
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    17
    Transition from Isolated to Collective Modes in Plasmonic Oligomers
    Hentschel, Mario; Saliba, Michael; Vogelgesang, Ralf; Giessen, Harald; Alivisatos, A. Paul; Liu, Na
    Nano Letters (2010), 10 (7), 2721-2726CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
    The transition from isolated to collective optical modes in plasmonic oligomers is demonstrated. The resonant behavior of planar plasmonic hexamers and heptamers with gradually decreasing the interparticle gap sepn. was studied. A pronounced Fano resonance is obsd. in the plasmonic heptamer for sepns. <60 nm. The spectral characteristics change drastically upon removal of the central nanoparticle. The work paves the road toward complex hierarchical plasmonic oligomers with tailored optical properties.
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  18. 18
    Yan, W.; Xu, L.; Xu, C.; Ma, W.; Kuang, H.; Wang, L.; Kotov, N. A. Self-Assembly of Chiral Nanoparticle Pyramids with Strong R/S Optical Activity. J. Am. Chem. Soc. 2012, 134, 15114– 15121,  DOI: 10.1021/ja3066336
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    18
    Self-Assembly of Chiral Nanoparticle Pyramids with Strong R/S Optical Activity
    Yan, Wenjing; Xu, Liguang; Xu, Chuanlai; Ma, Wei; Kuang, Hua; Wang, Libing; Kotov, Nicholas A.
    Journal of the American Chemical Society (2012), 134 (36), 15114-15121CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Chirality at the nanometer scale represents one of the most rapidly developing areas of research. Self-assembly of DNA-nanoparticle (NP) hybrids enables geometrically precise assembly of chiral isomers. The concept of a discrete chiral nanostructure of tetrahedral shape and topol. fabricated from 4 different NPs located in the corners of the pyramid is fundamental to the field. While the 1st observations of optical activity of mixed pyramidal assemblies were made in 2009 (Chen, W.; Nano Lett.2009, , 2153-2159), further studies are difficult without finely resolved optical data for precisely organized NP pyramidal enantiomers. Here the authors describe the prepn. of a family of self-assembled chiral pyramids made from multiple metal and/or semiconductor NPs with a yield ≤80%. Purposefully made R- and S-enantiomers of chiral pyramids with 4 different NPs from 3 different materials displayed strong chiroptical activity, with anisotropy g-factors ≤1.9 × 10-2 in the visible spectral range. Importantly, all NP constituents contribute to the chiroptical activity of the R/S pyramids. The authors were able to observe 3 different CD signals at 350-550 nm simultaneously. They correspond to the plasmonic oscillations of Au, Ag, and bandgap transitions of quantum dots. Tunability of chiroptical bands related to these transitions is essential from fundamental and practical points of view. The predictability of optical properties of pyramids, the simplicity of their self-assembly in comparison with lithog., and the possibility for polymerase chain reaction-based automation of their synthesis are expected to facilitate their future applications.
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  19. 19
    Wang, P.; Huh, J.-H.; Lee, J.; Kim, K.; Park, K. J.; Lee, S.; Ke, Y. Magnetic Plasmon Networks Programmed by Molecular Self-Assembly. Adv. Mater. 2019, 31, 1901364,  DOI: 10.1002/adma.201901364
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    There is no corresponding record for this reference.
  20. 20
    Hanske, C.; González-Rubio, G.; Hamon, C.; Formentın, P.; Modin, E.; Chuvilin, A.; Guerrero-Martınez, A.; Marsal, L. F.; Liz-Marzán, L. M. Large-Scale Plasmonic Pyramidal Supercrystals via Templated Self-Assembly of Monodisperse Gold Nanospheres. J. Phys. Chem. C 2017, 121, 10899– 10906,  DOI: 10.1021/acs.jpcc.6b12161
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    20
    Large-Scale Plasmonic Pyramidal Supercrystals via Templated Self-Assembly of Monodisperse Gold Nanospheres
    Hanske, Christoph; Gonzalez-Rubio, Guillermo; Hamon, Cyrille; Formentin, Pilar; Modin, Evgeny; Chuvilin, Andrey; Guerrero-Martinez, Andres; Marsal, Lluis F.; Liz-Marzan, Luis M.
    Journal of Physical Chemistry C (2017), 121 (20), 10899-10906CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    Plasmonic nanoparticle three-dimensional supercrystals are a novel class of materials with exciting applications in technologies such as light harvesting or meta-materials; however, their realization relies on extraordinarily regular colloidal building blocks and accurate self-assembly methods. A simple, up-scalable protocol to synthesize smooth Au nanospheres with high mono-dispersity in size and sphericity is described. The synthesis involves rapid growth up to the desired size and subsequent removal of surface roughness using an efficient etching step, so nanospheres with 10-110 μm diam. can be obtained in large quantities. Upon functionalization with thiolated polyethylene glycol and low surfactant concn., Au nanospheres were used as building blocks to produce uniform arrays of micron-sized, three-dimensional pyramidal supercrystals over large areas, by a template-assisted approach. Focused ion beam cutting and SEM characterization showed a face-centered cubic lattice within individual pyramidal supercrystals.
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  21. 21
    Molet, P.; Passarelli, N.; Pérez, L. A.; Scarabelli, L.; Mihi, A. Engineering Plasmonic Colloidal Meta-Molecules for Tunable Photonic Supercrystals. Adv. Opt. Mater. 2021, 9, 2100761,  DOI: 10.1002/adom.202100761
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    21
    Engineering Plasmonic Colloidal Meta-Molecules for Tunable Photonic Supercrystals
    Molet, Pau; Passarelli, Nicolas; Perez, Luis A.; Scarabelli, Leonardo; Mihi, Agustin
    Advanced Optical Materials (2021), 9 (20), 2100761CODEN: AOMDAX; ISSN:2195-1071. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Ordered arrays of metal nanoparticles offer new opportunities to engineer light-matter interactions through the hybridization of Rayleigh anomalies and localized surface plasmons. The generated surface lattice resonances exhibit much higher quality factors compared to those obsd. in isolated metal nanostructures. Template-induced colloidal self-assembly has already shown a great potential for the scalable fabrication of 2D plasmonic meta-mol. arrays, but the exptl. challenge of controlling optical losses within the repeating units has so far prevented this approach to compete with more std. fabrication methods in the prodn. of high-quality factor resonances. In this manuscript, the optical properties of plasmonic arrays are investigated by varying the lattice parameter (between 200 and 600 nm) as well as the diam. of the gold colloidal building-blocks (between 11 ± 1 and 98 ± 6 nm). It is systematically studied how the internal architecture of the repeating gold-nanoparticle meta-mols. influences the optical response of the plasmonic supercrystals. Combining both exptl. measurements and simulations, it is demonstrated how, reducing the size of the gold nanoparticles it is possible to switch from strong near-field plasmonic architectures to high-quality factors (>60) for lattice plasmon resonances located in the visible spectral range.
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  22. 22
    Santos, P. J.; Gabrys, P. A.; Zornberg, L. Z.; Lee, M. S.; Macfarlane, R. J. Macroscopic Materials Assembled from Nanoparticle Superlattices. Nature 2021, 591, 586– 591,  DOI: 10.1038/s41586-021-03355-z
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    22
    Macroscopic materials assembled from nanoparticle superlattices
    Santos, Peter J.; Gabrys, Paul A.; Zornberg, Leonardo Z.; Lee, Margaret S.; Macfarlane, Robert J.
    Nature (London, United Kingdom) (2021), 591 (7851), 586-591CODEN: NATUAS; ISSN:0028-0836. (Nature Research)
    Nanoparticle assembly has been proposed as an ideal means to program the hierarchical organization of a material by using a selection of nanoscale components to build the entire material from the bottom up. Multiscale structural control is highly desirable because chem. compn., nanoscale ordering, microstructure and macroscopic form all affect phys. properties1,2. However, the chem. interactions that typically dictate nanoparticle ordering3-5 do not inherently provide any means to manipulate structure at larger length scales6-9. Nanoparticle-based materials development therefore requires processing strategies to tailor micro- and macrostructure without sacrificing their self-assembled nanoscale arrangements. Here we demonstrate methods to rapidly assemble gram-scale quantities of faceted nanoparticle superlattice crystallites that can be further shaped into macroscopic objects in a manner analogous to the sintering of bulk solids. The key advance of this method is that the chem. interactions that govern nanoparticle assembly remain active during the subsequent processing steps, which enables the local nanoscale ordering of the particles to be preserved as the macroscopic materials are formed. The nano- and microstructure of the bulk solids can be tuned as a function of the size, chem. makeup and crystallog. symmetry of the superlattice crystallites, and the micro- and macrostructures can be controlled via subsequent processing steps. This work therefore provides a versatile method to simultaneously control structural organization across the mol. to macroscopic length scales.
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  23. 23
    Kastilani, R.; Wong, R.; Pozzo, L. D. Efficient Electrosteric Assembly of Nanoparticle Heterodimers and Linear Heteroassemblies. Langmuir 2018, 34, 826– 836,  DOI: 10.1021/acs.langmuir.7b01323
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    23
    Efficient Electrosteric Assembly of Nanoparticle Heterodimers and Linear Heteroassemblies
    Kastilani, Ryan; Wong, Ryan; Pozzo, Lilo D.
    Langmuir (2018), 34 (3), 826-836CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)
    A method of self-assembly of nanoparticles into controlled heteroaggregates is reported. The technique relies on carefully balancing attractive electrostatic forces with repulsive steric hindrance that is provided by surface-grafted polyethylene glycol (PEG). Two different-sized gold nanoparticles (GNPs) were used as a model system: 13 nm GNPs were functionalized with PEG-thiol and mercapto dodecanoic acid, while 7 nm GNPs were functionalized with PEG-thiol and (11- Mercaptoundecyl)trimethylammonium bromide. When mixed together, these oppositely charged particles self-assemble into stable colloidal structures (i.e., nanoclusters) whose structure depends strongly on the surface concn. of PEG. Smaller structures are obtained as the PEG surface concn. increases because steric hindrance dominates and prevents uncontrolled aggregation. In particular, under the right conditions, the authors were able to selectively synthesize heterodimers (which are effectively Janus particles) and linear heteroassemblies. This method is scalable, and it provides a step forward in bottom-up synthesis of nanomaterials.
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    Duan, H.; Jia, Z.; Liaqat, M.; Mellor, M. D.; Tan, H.; Nieh, M.-P.; Lin, Y.; Link, S.; Landes, C. F.; He, J. Site-Specific Chemistry on Gold Nanorods: Curvature-Guided Surface Dewetting and Supracolloidal Polymerization. ACS Nano 2023, 17, 12788– 12797,  DOI: 10.1021/acsnano.3c03929
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    24
    Site-Specific Chemistry on Gold Nanorods: Curvature-Guided Surface Dewetting and Supracolloidal Polymerization
    Duan, Hanyi; Jia, Zhenyang; Liaqat, Maham; Mellor, Matthew D.; Tan, Haiyan; Nieh, Mu-Ping; Lin, Yao; Link, Stephan; Landes, Christy F.; He, Jie
    ACS Nano (2023), 17 (13), 12788-12797CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)
    Control of interparticle interactions in terms of their direction and strength highly relies on the use of anisotropic ligand grafting on nanoparticle (NP) building blocks. We report a deficient ligand exchange strategy to achieve site-specific polymer grafting of gold nanorods (AuNRs). Patchy AuNRs with controllable surface coverage can be yielded during ligand exchange with a hydrophobic polystyrene ligand and an amphiphilic surfactant while adjusting the ligand concn. (CPS) and solvent condition (Cwater in dimethylformamide). At a low grafting d. of ≤ 0.08 chains/nm2, dumbbell-like AuNRs with two polymer domains capped at the two ends can be synthesized through surface dewetting with a high purity of > 94%. These site-specifically modified AuNRs exhibit great colloidal stability in aq. soln. Dumbbell-like AuNRs can further undergo supracolloidal polymn. upon thermal annealing to form one-dimensional plasmon chains of AuNRs. Such supracolloidal polymn. follows the temp.-solvent superposition principle as revealed by kinetic studies. Using the copolymn. of two AuNRs with different aspect ratios, we demonstrate the design of chain architectures by varying the reactivity of nanorod building blocks. Our results provide insights into the postsynthetic design of anisotropic NPs that potentially serve as units for polymer-guided supracolloidal self-assembly.
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    Yi, C.; Liu, H.; Zhang, S.; Yang, Y.; Zhang, Y.; Lu, Z.; Kumacheva, E.; Nie, Z. Self-Limiting Directional Nanoparticle Bonding Governed by Reaction Stoichiometry. Science 2020, 369, 1369– 1374,  DOI: 10.1126/science.aba8653
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    25
    Self-limiting directional nanoparticle bonding governed by reaction stoichiometry
    Yi, Chenglin; Liu, Hong; Zhang, Shaoyi; Yang, Yiqun; Zhang, Yan; Lu, Zhongyuan; Kumacheva, Eugenia; Nie, Zhihong
    Science (Washington, DC, United States) (2020), 369 (6509), 1369-1374CODEN: SCIEAS; ISSN:1095-9203. (American Association for the Advancement of Science)
    Nanoparticle clusters with mol.-like configurations are an emerging class of colloidal materials. Particles decorated with attractive surface patches acting as analogs of functional groups are used to assemble colloidal mols. (CMs); however, high-yield generation of patchy nanoparticles remains a challenge. We show that for nanoparticles capped with complementary reactive polymers, a stoichiometric reaction leads to reorganization of the uniform ligand shell and self-limiting nanoparticle bonding, whereas electrostatic repulsion between colloidal bonds governs CM symmetry. This mechanism enables high-yield CM generation and their programmable organization in hierarchical nanostructures. Our work bridges the gap between covalent bonding taking place at an at. level and colloidal bonding occurring at the length scale two orders of magnitude larger and broadens the methods for nanomaterial fabrication.
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    Cai, Y.; Vana, P. 2D Plasmonic Molecules via Hydrogen Bond Interaction between Polymer-Grafted Nanoparticles. Angew. Chem., Int. Ed. 2023, 62, e202309798  DOI: 10.1002/anie.202309798
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    There is no corresponding record for this reference.
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    Lin, X.; Ye, S.; Kong, C.; Webb, K.; Yi, C.; Zhang, S.; Zhang, Q.; Fourkas, J. T.; Nie, Z. Polymeric Ligand-Mediated Regioselective Bonding of Plasmonic Nanoplates and Nanospheres. J. Am. Chem. Soc. 2020, 142, 17282– 17286,  DOI: 10.1021/jacs.0c08135
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    27
    Polymeric Ligand-Mediated Regioselective Bonding of Plasmonic Nanoplates and Nanospheres
    Lin, Xiaoying; Ye, Shunsheng; Kong, Chuncai; Webb, Kyle; Yi, Chenglin; Zhang, Shaoyi; Zhang, Qian; Fourkas, John T.; Nie, Zhihong
    Journal of the American Chemical Society (2020), 142 (41), 17282-17286CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Nanoparticle (NP) clusters are attractive for many applications, but controllable and regioselective assembly of clusters remains challenging. This communication reports a strategy to precisely assemble Ag nanoplates (NP-As) and Au nanospheres (NP-Bs) grafted with copolymer ligands into defined ABx clusters with controlled coordination no. (x) and orientation of the NPs. The directional bonding of shaped NPs relies on the stoichiometric reaction of complementary reactive groups on copolymer ligands. The x value of NP clusters can be tuned from 1 to 4 by varying the no. ratio of reactive groups on single NP-Bs to NP-As. The regioselective bonding of nanospheres to the edge or face of a central nanoplate is governed by the steric hindrance of copolymeric ligands on the nanoplate. The clusters exhibit distinctive plasmonic properties that are dependent on the bonding modes of NPs. This study paves a route to fabricating nanostructures with high precision and complexity for applications in plasmonics, catalysis, and sensing.
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  28. 28
    Kuttner, C.; Höller, R. P. M.; Quintanilla, M.; Schnepf, M. J.; Dulle, M.; Fery, A.; Liz-Marzán, L. M. SERS and Plasmonic Heating Efficiency from Anisotropic Core/Satellite Superstructures. Nanoscale 2019, 11, 17655– 17663,  DOI: 10.1039/c9nr06102a
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    28
    SERS and plasmonic heating efficiency from anisotropic core/satellite superstructures
    Kuttner, Christian; Holler, Roland P. M.; Quintanilla, Marta; Schnepf, Max J.; Dulle, Martin; Fery, Andreas; Liz-Marzan, Luis M.
    Nanoscale (2019), 11 (38), 17655-17663CODEN: NANOHL; ISSN:2040-3372. (Royal Society of Chemistry)
    The optical properties of nanoparticle assemblies can be tailored via hybridization of plasmon modes. Isotropic core/satellite superstructures made of spherical nanoparticles are known to exhibit coupled modes with a strongly scattering (radiative) character, and provide hot spots yielding high activity in surface-enhanced Raman scattering (SERS). However, to complement this functionality with plasmonic heating, addnl. absorbing (non-radiative) modes are required. We introduce herein anisotropic superstructures formed by decorating a central nanorod with spherical satellite nanoparticles, which feature two coupled modes that allow application for both SERS and heating. On the basis of diffuse reflectance spectroscopy, small-angle X-ray scattering (SAXS), and electromagnetic simulations, the origin of the coupled modes is disclosed and thus serves as a basis toward alternative designs of functional superstructures. This work represents a proof-of-principle for the combination of high SERS efficiency with efficient plasmonic heating by near-IR irradn.
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  29. 29
    Höller, R. P. M.; Dulle, M.; Thomä, S.; Mayer, M.; Steiner, A. M.; Förster, S.; Fery, A.; Kuttner, C.; Chanana, M. Protein-Assisted Assembly of Modular 3D Plasmonic Raspberry-like Core/Satellite Nanoclusters: Correlation of Structure and Optical Properties. ACS Nano 2016, 10, 5740– 5750,  DOI: 10.1021/acsnano.5b07533
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    29
    Protein-Assisted Assembly of Modular 3D Plasmonic Raspberry-like Core/Satellite Nanoclusters: Correlation of Structure and Optical Properties
    Holler Roland P M; Thoma Sabrina; Fery Andreas; Kuttner Christian; Chanana Munish; Holler Roland P M; Mayer Martin; Steiner Anja Maria; Fery Andreas; Kuttner Christian; Dulle Martin; Forster Stephan; Fery Andreas; Fery Andreas; Kuttner Christian; Chanana Munish
    ACS nano (2016), 10 (6), 5740-50 ISSN:.
    We present a bottom-up assembly route for a large-scale organization of plasmonic nanoparticles (NPs) into three-dimensional (3D) modular assemblies with core/satellite structure. The protein-assisted assembly of small spherical gold or silver NPs with a hydrophilic protein shell (as satellites) onto larger metal NPs (as cores) offers high modularity in sizes and composition at high satellite coverage (close to the jamming limit). The resulting dispersions of metal/metal nanoclusters exhibit high colloidal stability and therefore allow for high concentrations and a precise characterization of the nanocluster architecture in dispersion by small-angle X-ray scattering (SAXS). Strong near-field coupling between the building blocks results in distinct regimes of dominant satellite-to-satellite and core-to-satellite coupling. High robustness against satellite disorder was proved by UV/vis diffuse reflectance (integrating sphere) measurements. Generalized multiparticle Mie theory (GMMT) simulations were employed to describe the electromagnetic coupling within the nanoclusters. The close correlation of structure and optical property allows for the rational design of core/satellite nanoclusters with tailored plasmonics and well-defined near-field enhancement, with perspectives for applications such as surface-enhanced spectroscopies.
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  30. 30
    Cai, Y.; Peng, W.; Vana, P. Gold Nanoparticle Ring Arrays from Core–Satellite Nanostructures Made To Order by Hydrogen Bond Interactions. Nanoscale Adv. 2022, 4, 2787– 2793,  DOI: 10.1039/D2NA00204C
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    Xia, Y.; Nguyen, T. D.; Yang, M.; Lee, B.; Santos, A.; Podsiadlo, P.; Tang, Z.; Glotzer, S. C.; Kotov, N. A. Self-Assembly of Self-Limiting Monodisperse Supraparticles from Polydisperse Nanoparticles. Nat. Nanotechnol. 2011, 6, 580– 587,  DOI: 10.1038/nnano.2011.121
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    Self-assembly of self-limiting monodisperse supraparticles from polydisperse nanoparticles
    Xia, Yunsheng; Nguyen, Trung Dac; Yang, Ming; Lee, Byeongdu; Santos, Aaron; Podsiadlo, Paul; Tang, Zhiyong; Glotzer, Sharon C.; Kotov, Nicholas A.
    Nature Nanotechnology (2011), 6 (9), 580-587CODEN: NNAABX; ISSN:1748-3387. (Nature Publishing Group)
    Nanoparticles are known to self-assemble into larger structures through growth processes that typically occur continuously and depend on the uniformity of the individual nanoparticles. Here, we show that inorg. nanoparticles with non-uniform size distributions can spontaneously assemble into uniformly sized supraparticles with core-shell morphologies. This self-limiting growth process is governed by a balance between electrostatic repulsion and van der Waals attraction, which is aided by the broad polydispersity of the nanoparticles. The generic nature of the interactions creates flexibility in the compn., size and shape of the constituent nanoparticles, and leads to a large family of self-assembled structures, including hierarchically organized colloidal crystals.
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    Wang, Y.; Chen, G.; Yang, M.; Silber, G.; Xing, S.; Tan, L. H.; Wang, F.; Feng, Y.; Liu, X.; Li, S.; Chen, H. A systems Approach Towards the Stoichiometry-Controlled Hetero-Assembly of Nanoparticles. Nat. Commun. 2010, 1, 87,  DOI: 10.1038/ncomms1089
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    A systems approach towards the stoichiometry-controlled hetero-assembly of nanoparticles
    Wang Yong; Chen Gang; Yang Miaoxin; Silber Georg; Xing Shuangxi; Tan Li Huey; Wang Feng; Feng Yuhua; Liu Xiaogang; Li Shuzhou; Chen Hongyu
    Nature communications (2010), 1 (), 87 ISSN:.
    A central theme in nanotechnology is to advance the fundamental understanding of nanoscale component assembly, thereby allowing rational structural design that may lead to materials with novel properties and functions. Nanoparticles (NPs) are often regarded as 'artificial atoms', but their 'reactions' are not readily controllable. Here, we demonstrate a complete nanoreaction system whereby colloidal NPs are rationally assembled and purified. Two types of functionalized gold NPs (A and B) are bonded to give specific products AB, AB(2), AB(3) and AB(4). The stoichiometry control is realized by fine-tuning the charge repulsion among the B-NPs. The products are protected by a polymer, which allows their isolation in high purity. The integration of hetero-assembly, stoichiometry control, protection scheme and separation method may provide a scalable way to fabricate sophisticated nanostructures.
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    Larson-Smith, K.; Pozzo, D. C. Scalable Synthesis of Self-Assembling Nanoparticle Clusters Based on Controlled Steric Interactions. Soft Matter 2011, 7, 5339– 5347,  DOI: 10.1039/c0sm01497d
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    Scalable synthesis of self-assembling nanoparticle clusters based on controlled steric interactions
    Larson-Smith, Kjersta; Pozzo, Danilo C.
    Soft Matter (2011), 7 (11), 5339-5347CODEN: SMOABF; ISSN:1744-683X. (Royal Society of Chemistry)
    A simple one-pot method is presented for the synthesis of amphiphilic gold nanoparticles that can spontaneously self-assemble into stable clusters with controllable geometry. The technique is based on the control of colloidal interactions through sequential functionalization of the surfaces with long polyethylene glycol (PEG) chains followed by short alkane-thiol mols. This process renders the gold nanoparticles amphiphilic and initiates the self-assembly of stable clusters in the dispersion. It is shown that the dominant structures and sizes of the clusters (i.e. singlets, doublets, triplets and others) are directly and reproducibly controlled by the concn. of PEG chains that are linked to the particle surface. Changes in the structure of the clusters are systematically characterized by small angle X-ray scattering (SAXS), dynamic light scattering (DLS) and transmission electron microscopy (TEM). Systematic shifts in the plasmon resonance peak of the gold nanoparticle clusters demonstrate that this new method for self-assembly can be effectively used to tune optical properties with great precision. With this new approach, we show that it is possible to fabricate large nos. of amphiphilic nanoparticles and clusters with controllable structure by manipulating the repulsive steric forces that are imparted by surface bound polymers and the attractive interactions of the hydrophobic alkane-thiols. The major advantage of this technique lies in its simplicity, versatility and potential for scalable prodn. of self-assembled colloidal mols.'.
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    Peng, W.; Cai, Y.; Fanslau, L.; Vana, P. Nanoengineering with RAFT Polymers: from Nanocomposite Design to Applications. Polym. Chem. 2021, 12, 6198– 6229,  DOI: 10.1039/D1PY01172C
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    Nanoengineering with RAFT polymers: from nanocomposite design to applications
    Peng, Wentao; Cai, Yingying; Fanslau, Luise; Vana, Philipp
    Polymer Chemistry (2021), 12 (43), 6198-6229CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)
    A review. Reversible addn.-fragmentation chain-transfer (RAFT) polymn. is a powerful tool for the precise formation of macromol. building blocks that can be used for the construction of well-defined nanocomposites. Esp. when combining RAFT polymers with uniform inorg./metallic nanoparticles, a vast variety of complex nanocomposites become available that may find applications esp. in the field of life sciences, e.g., bio-imaging, drug delivery or cancer-therapy, but also in areas such as energy conversion or catalysis. RAFT polymn. not only provides the possibility to control the size and the macromol. architecture of the polymer building blocks, but inherently delivers highly functional end-groups that can often directly be employed as linker-sites for installing the polymeric components into the final nanocomposites. This review describes recent advances in this vivid field and concs. on innovations in the fabrication method and design strategies for polymer/inorg. nanohybrids. The methodol. of synthesizing RAFT polymer with the aim of surface functionalization and the design options for anchoring RAFT polymer on surfaces are covered. A series of core-shell nanostructures with the focus on novel functionalities brought by RAFT polymer brushes will be reviewed with focus on the detailed macromol. design for each specific application's scenario. Examples of ordered nano-assemblies using RAFT polymer linkers will be reviewed in order to demonstrate the advantages of RAFT polymer for introducing different morphologies, interactions and chirality to the final functional nanostructures.
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    Song, P.; Wang, H. High-Performance Polymeric Materials through Hydrogen-Bond Cross-linking. Adv. Mater. 2020, 32, 1901244,  DOI: 10.1002/adma.201901244
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    High-Performance Polymeric Materials through Hydrogen-Bond Cross-Linking
    Song, Pingan; Wang, Hao
    Advanced Materials (Weinheim, Germany) (2020), 32 (18), 1901244CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A review. It has always been crit. to develop high-performance polymeric materials with exceptional mech. strength and toughness, thermal stability, and even healable properties for meeting performance requirements in industry. Conventional chem. crosslinking leads to enhanced mech. strength and thermostability at the expense of extensibility due to mutually exclusive mechanisms. Such major challenges have recently been addressed by using noncovalent crosslinking of reversible multiple hydrogen-bonds (H-bonds) that widely exist in biol. materials, such as silk and muscle. Recent decades have witnessed the development of many tailor-made high-performance H-bond crosslinked polymeric materials. Here, recent advances in H-bond crosslinking strategies are reviewed for creating high-performance polymeric materials. H-bond crosslinking of polymers can be realized via (i) self-assocn. of interchain multiple H-bonding interactions or specific H-bond crosslinking motifs, such as 2-ureido-4-pyrimidone units with self-complementary quadruple H-bonds and (ii) addn. of external crosslinkers, including small mols., nanoparticles, and polymer aggregates. The resultant crosslinked polymers normally exhibit tunable high strength, large extensibility, improved thermostability, and healable capability. Such performance portfolios enable these advanced polymers to find many significant cutting-edge applications. Major challenges facing existing H-bond crosslinking strategies are discussed, and some promising approaches for designing H-bond crosslinked polymeric materials in the future are also proposed.
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    Jancke, S.; Liu, C.; Wang, R.; Sarkar, S.; Besford, Q. A.; König, T. A. F.; Popp, J.; Cialla-May, D.; Rossner, C. Turning on Hotspots: Supracolloidal SERS Probes Made Brilliant by an External Activation Mechanism. Nanoscale 2023, 15, 18687– 18695,  DOI: 10.1039/D3NR05121H
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    Jochum, F. D.; Theato, P. Temperature- and Light-Responsive Smart Polymer Materials. Chem. Soc. Rev. 2013, 42, 7468– 7483,  DOI: 10.1039/C2CS35191A
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    Temperature- and light-responsive smart polymer materials
    Jochum, Florian D.; Theato, Patrick
    Chemical Society Reviews (2013), 42 (17), 7468-7483CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
    A review. Stimuli-responsive polymers have been attracting great interest within the scientific community for several decades. The unique feature to respond to small changes in the environmental conditions has made this class of materials very promising for several applications in the field of nanoscience, nanotechnol. and nanomedicine. So far, several different chem., phys. or biochem. stimuli have been investigated within natural or synthetic polymers. Very interesting and appealing seems to be the combination of several stimuli to tune the properties of these materials in manifold ways. Within this present review, we want to highlight the recent progress in the field of synthetic stimuli-responsive polymers combining temp. and light responsiveness.
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    Kocak, G.; Tuncer, C.; Bütün, V. pH-Responsive Polymers. Polym. Chem. 2017, 8, 144– 176,  DOI: 10.1039/c6py01872f
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    pH-Responsive polymers
    Kocak, G.; Tuncer, C.; Butun, V.
    Polymer Chemistry (2017), 8 (1), 144-176CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)
    A review. In this review, we provide an anal. of some of the recent literature reports on the synthesis and applications of pH-responsive polymers. Depending on the soln. pH, such copolymers can self-assemble and form various nanosized structures including core-shell micellar structures, micelles/reverse micelles, hollow spheres, vesicle structures, adsorbed species at the water-air interface, and more complex architectures. Their self-assembly behaviors open the door for the prodn. of various novel nanostructures including shell/core cross-linked micelles, hollow spheres, hydrogels, microgels, layer-by-layer (LbL) nanofilms, controlled releasing systems, drug carrier systems, etc. The review consists of various major parts including types of pH-responsive polymers, synthetic methods for their synthesis and their soln. behaviors, their nanostructures in aq. media, applications as LbL nanofilms, delivery devices, controlled release systems, sensors, stabilizers, solubilizers, etc. In the last two decades, there have been great developments in synthetic methods and strategies for the prepn. of novel pH-responsive polymers or polymeric materials providing possible materials for various applications including biotechnol., nanotechnol., colloid and surface science, materials science, etc.
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  39. 39
    Ranneh, A.-H.; Takemoto, H.; Sakuma, S.; Awaad, A.; Nomoto, T.; Mochida, Y.; Matsui, M.; Tomoda, K.; Naito, M.; Nishiyama, N. An Ethylenediamine-based Switch to Render the Polyzwitterion Cationic at Tumorous pH for Effective Tumor Accumulation of Coated Nanomaterials. Angew. Chem., Int. Ed. 2018, 57, 5057– 5061,  DOI: 10.1002/anie.201801641
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    An Ethylenediamine-based Switch to Render the Polyzwitterion Cationic at Tumorous pH for Effective Tumor Accumulation of Coated Nanomaterials
    Ranneh, Abdul-Hackam; Takemoto, Hiroyasu; Sakuma, Shunya; Awaad, Aziz; Nomoto, Takahiro; Mochida, Yuki; Matsui, Makoto; Tomoda, Keishiro; Naito, Mitsuru; Nishiyama, Nobuhiro
    Angewandte Chemie, International Edition (2018), 57 (18), 5057-5061CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Polyzwitterions are employed as coating polymers for biomaterials to induce an antifouling property on the surface. Fine-tuning the betaine structure switches the antifouling property to be interactive with anionic tissue constituents in response to a tumorous pH gradient. The ethylenediamine moiety in the carboxybetaine enabled stepwise protonation and initiated the di-protonation process around tumorous pH (6.5). The net charge of the developed polyzwitterion (PGlu(DET-Car)) was thus neutral at pH 7.4 for antifouling, but was cationic at pH 6.5 for interaction with anionic constituents. Quantum dots coated with PGlu(DET-Car) exhibited comparable stealth and enhanced tumor accumulation relative to the PEG system. The present study provides a novel design of smart switchable polyzwitterion based on a precise control of the net charge.
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    Chen, Y.; Wang, Z.; He, Y.; Yoon, Y. J.; Jung, J.; Zhang, G.; Lin, Z. Light-Enabled Reversible Self-Assembly and Tunable Optical Properties of Stable Hairy Nanoparticles. Proc. Natl. Acad. Sci. U.S.A. 2018, 115, E1391– E1400,  DOI: 10.1073/pnas.1714748115
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    Light-enabled reversible self-assembly and tunable optical properties of stable hairy nanoparticles
    Chen, Yihuang; Wang, Zewei; He, Yanjie; Yoon, Young Jun; Jung, Jaehan; Zhang, Guangzhao; Lin, Zhiqun
    Proceedings of the National Academy of Sciences of the United States of America (2018), 115 (7), E1391-E1400CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
    The ability to dynamically organize functional nanoparticles (NPs) via the use of environmental triggers (temp., pH, light, or solvent polarity) opens up important perspectives for rapid and convenient construction of a rich variety of complex assemblies and materials with new structures and functionalities. Here, we report an unconventional strategy for crafting stable hairy NPs with light-enabled reversible and reliable self-assembly and tunable optical properties. Central to our strategy is to judiciously design amphiphilic star-like diblock copolymers comprising inner hydrophilic blocks and outer hydrophobic photoresponsive blocks as nanoreactors to direct the synthesis of monodisperse plasmonic NPs intimately and permanently capped with photoresponsive polymers. The size and shape of hairy NPs can be precisely tailored by modulating the length of inner hydrophilic block of star-like diblock copolymers. The perpetual anchoring of photoresponsive polymers on the NP surface renders the attractive feature of self-assembly and disassembly of NPs on demand using light of different wavelengths, as revealed by tunable surface plasmon resonance absorption of NPs and the reversible transformation of NPs between their dispersed and aggregated states. The dye encapsulation/release studies manifested that such photoresponsive NPs may be exploited as smart guest mol. nanocarriers. By extension, the star-like block copolymer strategy enables the crafting of a family of stable stimuli-responsive NPs (e.g., temp.- or pH-sensitive polymer-capped magnetic, ferroelec., upconversion, or semiconducting NPs) and their assemblies for fundamental research in self-assembly and crystn. kinetics of NPs as well as potential applications in optics, optoelectronics, magnetic technologies, sensory materials and devices, catalysis, nanotechnol., and biotechnol.
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    Huebner, D.; Rossner, C.; Vana, P. Light-induced self-assembly of gold nanoparticles with a photoresponsive polymer shell. Polymer 2016, 107, 503– 508,  DOI: 10.1016/j.polymer.2016.05.073
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    Light-induced self-assembly of gold nanoparticles with a photoresponsive polymer shell
    Huebner, Dennis; Rossner, Christian; Vana, Philipp
    Polymer (2016), 107 (), 503-508CODEN: POLMAG; ISSN:0032-3861. (Elsevier Ltd.)
    The light-induced self-assembly of gold nanoparticles was studied systematically. A methacrylate type monomer with an azobenzene sidechain was polymd. in a reversible addn.-fragmentation chain transfer (RAFT) polymn. The resulting light responsive polymer was grafted to gold nanoparticles via the RAFT group. UV-light induced trans to cis isomerization of the azobenzene moieties triggers the aggregation of the polymer-gold hybrid particles in toluene dispersion. The thermally induced cis to trans relaxation was found to be significantly slower than for small mols. at gold surfaces. The self-assembly was followed by dynamic light scattering (DLS), UV/vis spectroscopy and transmission electron microscopy (TEM). The d. of primary gold particles within the self-assembled aggregates can be tuned by varying the molar mass of the grafted polymer.
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    Rahimzadeh, A.; Rutsch, M.; Kupnik, M.; Klitzing, R. v. Visualization of Acoustic Energy Absorption in Confined Aqueous Solutions by PNIPAM Microgels: Effects of Bulk Viscosity. Langmuir 2021, 37, 5854– 5863,  DOI: 10.1021/acs.langmuir.1c00235
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    Stock, S.; Mirau, L.; Rutsch, M.; Wismath, S.; Kupnik, M.; von Klitzing, R.; Rahimzadeh, A. Ultrasound-Induced Adsorption of Acousto-Responsive Microgels at Water–Oil Interface. Adv. Sci. 2024, 11, 2305395,  DOI: 10.1002/advs.202305395
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    Wei, P.; Cornel, E. J.; Du, J. Ultrasound-Responsive Polymer-Based Drug Delivery Systems. Drug Delivery Transl. Res. 2021, 11, 1323– 1339,  DOI: 10.1007/s13346-021-00963-0
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    Ultrasound-responsive polymer-based drug delivery systems
    Wei, Ping; Cornel, Erik Jan; Du, Jianzhong
    Drug Delivery and Translational Research (2021), 11 (4), 1323-1339CODEN: DDTRCY; ISSN:2190-3948. (Springer)
    Abstr.: Ultrasound-responsive polymeric materials have received a tremendous amt. of attention from scientists for several decades. Compared to other stimuli-responsive materials (such as UV-, thermal-, and pH-responsive materials), these smart materials are more applicable since they allow more efficient drug delivery and targeted treatment by fairly non-invasive means. This review describes the recent advances of such ultrasound-responsive polymer-based drug delivery systems and illustrates various applications. More specifically, the mechanism of ultrasound-induced drug delivery, typical formulations, and biomedical applications (tumor therapy, disruption of blood-brain barrier, fighting infectious diseases, transdermal drug delivery, and enhanced thrombolysis) are summarized. Finally, a perspective on the future research directions for the development of ultrasound-responsive polymeric materials to facilitate a clin. translation is given.
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    Wei, P.; Sun, M.; Yang, B.; Xiao, J.; Du, J. Ultrasound-Responsive Polymersomes Capable of Endosomal Escape for Efficient Cancer Therapy. J. Controlled Release 2020, 322, 81– 94,  DOI: 10.1016/j.jconrel.2020.03.013
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    Ultrasound-responsive polymersomes capable of endosomal escape for efficient cancer therapy
    Wei, Ping; Sun, Min; Yang, Bo; Xiao, Jiangang; Du, Jianzhong
    Journal of Controlled Release (2020), 322 (), 81-94CODEN: JCREEC; ISSN:0168-3659. (Elsevier B.V.)
    Stimuli-responsive anticancer drug delivery vehicles have attracted increasing attention in nanomedicine. However, controlled drug release in vivo is still an important challenge, as traditional stimuli lack maneuverability. To solve this problem, we designed an ultrasound and pH-responsive polymersome by self-assembly of poly(ethylene oxide)-block-poly(2-(diethylamino)ethyl methacrylate)-stat-poly(methoxyethyl methacrylate) [PEO-b-P(DEA-stat-MEMA)], where PEO acts as the corona-forming block, DEA acts as the endosomal escape segment, and MEMA acts as the ultrasound-responsive segment. This strategy combines the advantages of noninvasive ultrasonic stimulus which can be applied from outside to any organ regardless of depth, and the weakly acidic microenvironment of tumor tissue. In vitro expts. confirmed excellent endosomal escape ability, on-demand drug release behavior, low cytotoxicity, and high intracellular delivery efficiency of polymersomes. In vivo antitumor tests revealed that in the presence of sonication, the anticancer drug was released at an accelerated rate from these ultrasound-responsive polymersomes, and the DOX-loaded polymersomes + sonication group significantly inhibited tumor growth (95% redn. in tumor mass) without any side effects. Overall, this ultrasound-responsive polymersome provides us with a fresh insight into designing next-generation stimuli-responsive drug carriers with better maneuverability and higher chemotherapeutic efficiency.
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    Huebsch, N.; Kearney, C. J.; Zhao, X.; Kim, J.; Cezar, C. A.; Suo, Z.; Mooney, D. J. Ultrasound-Triggered Disruption and Self-Healing of Reversibly Cross-linked Hydrogels for Drug Delivery and Enhanced Chemotherapy. Proc. Natl. Acad. Sci. U.S.A. 2014, 111, 9762– 9767,  DOI: 10.1073/pnas.1405469111
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    Ultrasound-triggered disruption and self-healing of reversibly cross-linked hydrogels for drug delivery and enhanced chemotherapy
    Huebsch, Nathaniel; Kearney, Cathal J.; Zhao, Xuanhe; Kim, Jaeyun; Cezar, Christine A.; Suo, Zhigang; Mooney, David J.
    Proceedings of the National Academy of Sciences of the United States of America (2014), 111 (27), 9762-9767CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
    Biol. systems are exquisitely sensitive to the location and timing of physiol. cues and drugs. This spatiotemporal sensitivity presents opportunities for developing new therapeutic approaches. Polymer-based delivery systems are used extensively for attaining localized, sustained release of bioactive mols. However, these devices typically are designed to achieve a const. rate of release. We hypothesized that it would be possible to create digital drug release, which could be accelerated and then switched back off, on demand, by applying ultrasound to disrupt ionically crosslinked hydrogels. We demonstrated that ultrasound does not permanently damage these materials but enables nearly digital release of small mols., proteins, and condensed oligonucleotides. Parallel in vitro studies demonstrated that the concept of applying temporally short, high-dose "bursts" of drug exposure could be applied to enhance the toxicity of mitoxantrone toward breast cancer cells. We thus used the hydrogel system in vivo to treat xenograft tumors with mitoxantrone, and found that daily ultrasound-stimulated drug release substantially reduced tumor growth compared with sustained drug release alone. This approach of digital drug release likely will be applicable to a broad variety of polymers and bioactive mols., and is a potentially useful tool for studying how the timing of factor delivery controls cell fate in vivo.
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    Xue, Y.; Li, X.; Li, H.; Zhang, W. Quantifying Thiol-Gold Interactions Towards the Efficient Strength Control. Nat. Commun. 2014, 5, 4348– 4349,  DOI: 10.1038/ncomms5348
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    Quantifying thiol-gold interactions towards the efficient strength control
    Xue, Yurui; Li, Xun; Li, Hongbin; Zhang, Wenke
    Nature Communications (2014), 5 (), 4348CODEN: NCAOBW; ISSN:2041-1723. (Nature Publishing Group)
    The strength of the thiol-gold interactions provides the basis to fabricate robust self-assembled monolayers for diverse applications. Investigation on the stability of thiol-gold interactions has thus become a hot topic. Here we use at. force microscopy to quantify the stability of individual thiol-gold contacts formed both by isolated single thiols and in self-assembled monolayers on gold surface. Our results show that the oxidized gold surface can enhance greatly the stability of gold-thiol contacts. In addn., the shift of binding modes from a coordinate bond to a covalent bond with the change in environmental pH and interaction time has been obsd. exptl. Furthermore, isolated thiol-gold contact is found to be more stable than that in self-assembled monolayers. Our findings revealed mechanisms to control the strength of thiol-gold contacts and will help guide the design of thiol-gold contacts for a variety of practical applications.
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  1. Christian Rossner. Polymer‐Grafted Gold Colloids and Supracolloids: From Mechanisms of Formation to Dynamic Soft Matter. Macromolecular Rapid Communications 2025, 35 https://doi.org/10.1002/marc.202400851
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  • Abstract

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    Figure 1

    Figure 1. Schematic of self-assembly and isomerization of PMs via HB interaction. (A) Building blocks: PEGn (HB acceptor) and P(St0.7-r-HSt0.3)m (HB donor) grafted onto AuNPs. m and n refer to the number of repeating units. (B) HB-donor and -acceptor polymer design and their interaction when grafted onto the AuNPs. (C) Mixing A- and B-NPs forms colloidal PMs (AB4-α) by forming polymer bundles (PM bonds). (D) Scanning electron microscopy (SEM) image: AB4-α colloid transfers to a 2D square planar on a substrate. (E) Upon post-ultrasonication, AB4-α changes to the AB4-ω state in the colloid. Polymer bundles shrink, and the polymer chains entangle tightly. This results in a decrease in the PM bond length and an increase in the structural stiffness. (F) SEM image: drop-casting AB4-ω achieves a tetrahedral isomer due to increased stiffness. (G) Ultrasonication ejects solvent molecules, forming new HB linkages and transitioning from ABN-α to ABN-ω.

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    Figure 2

    Figure 2. PMs with different coordination numbers and configurations on the substrate. (A) SEM images of ABN PMs in 2D configurations for N = 4, 6, 8, and 12 prepared by drop-casting ABN-α colloid on a silicon wafer. Insert illustrations show the spatial arrangement on the substrate schematically. The A-NPs used are PEG136-grafted 22 nm A-NPs for N = 4, PEG227-grafted 28 nm A-NPs for N = 6 and 8, and PEG454-grafted 30 nm A-NPs for N = 12. All samples utilize 34 nm B-NPs grafted with P(St0.7-r-HSt0.3)420. (B) SEM images of ABN PMs in 3D configurations, prepared using ABN-ω colloid, which underwent post-ultrasonication from the corresponding ABN-α colloid. Inset illustrations show the typical schematic spatial arrangement on the substrate. (C) Statistical distribution of N values for AB4, AB6, AB8, and AB12 samples. Detailed sample conditions and additional SEM images are provided in the Supporting Information (Table S2 and Figures S3–S10). Scale bars are 100 nm.

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    Figure 3

    Figure 3. DLS and UV–vis results demonstrate the distinct colloidal behavior between ABN-α and ABN-ω and the significant effect of ultrasonication treatment. These colloids correspond to the samples used for preparing 2D/3D PMs’ isomers on substrates in Figure 2. (A) DLS measurements indicate that after post-ultrasonication, the hydrodynamic diameter (Dh) of the PMs in the colloid is significantly reduced for all samples. (B) Schematic illustrations showing the changes in Dh from AB4-α to AB4-ω: after ultrasonication treatment, the Dh decreases from 114 to 70 nm, which is comparable with the size of pure B-NPs in the same solvent condition (68 nm). (C) Photograph of the AB4-α and AB4-ω colloids. The color shift from red to violet indicates strong plasmonic coupling due to the significantly decreased dA–B within a cluster. (D) UV–vis spectra of ABN-α and ABN-ω for N = 4, 6, 8, and 12, compared with the spectra of A- and B-NPs under the same solvent conditions.

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    Figure 4

    Figure 4. Experimental and simulation results of step-by-step ultrasonication on AB6SBS colloid. (A–C) Experiment: (A) UV–vis spectra for B-NPs (gray dashed) and AB6SBS colloid (red to blue) at each step. (B) Photographs showing color changes. (C) Relationship between λ2 peak position and hydrodynamic diameter (measured by DLS) with red-shift indicating PM shrinkage. Gray and red dashed lines show resonance modes of pure B-NPs and λ1, respectively. (D–F) Simulation: (D) simulated absorption spectra for AB6 structures with decreasing dA–B. The gray dashed curve is the spectrum of a single 34 nm AuNP multiplied by seven. (E) Schematic of dA–B changes. (F) Relationship between λ2 wavelength and dA–B, with a fitted curve for dA–B = 2–30 nm. Gray and red dashed lines indicate resonance modes of 34 nm AuNP and λ1, respectively.

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    Figure 5

    Figure 5. Electric field profiles at resonance modes for the dA–B = 14 and 2 nm, displayed in both xy and yz planes for a colloidal AB6 PM (same model as in Figure 4). (A) Electric field profile for dA–B = 14 nm at λ = 555 nm (spectral maximum), with a calculated enhancement factor of 16. (B,C) Electric field profiles for dA–B = 2 nm at λ1 = 552 nm (B) and λ2 = 696 nm (C), with calculated enhancement factors of 21 and 251, respectively.

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  • References

    This article references 65 other publications.

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      The authors present a simple and intuitive picture, an electromagnetic analog of MO theory, that describes the plasmon response of complex nanostructures of arbitrary shape. The authors' model can be understood as the interaction or hybridization of elementary plasmons supported by nanostructures of elementary geometries. As an example, the approach is applied to the important case of a four-layer concentric nanoshell, where the hybridization of the plasmons of the inner and outer nanoshells dets. the resonant frequencies of the multilayer nanostructure.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXjtVWjtb8%253D&md5=ea84018ef7760e1f23687ba25aaab488
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      Wu, X.; Hao, C.; Kumar, J.; Kuang, H.; Kotov, N. A.; Liz-Marzán, L. M.; Xu, C. Environmentally Responsive Plasmonic Nanoassemblies For Biosensing. Chem. Soc. Rev. 2018, 47, 4677– 4696,  DOI: 10.1039/C7CS00894E
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      Environmentally responsive plasmonic nanoassemblies for biosensing
      Wu, Xiaoling; Hao, Changlong; Kumar, Jatish; Kuang, Hua; Kotov, Nicholas A.; Liz-Marzan, Luis M.; Xu, Chuanlai
      Chemical Society Reviews (2018), 47 (13), 4677-4696CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      A review. Assemblies of plasmonic nanoparticles enable new modalities for biosensing. Engineered superstructures from metal nanoparticles can enhance the plasmon resonances and chiroptical activity of nanoscale dispersions. Such phenomena are keys to the fabrication of highly sensitive, selective and fast-responding detection platforms, making them promising candidates for clin. applications. This tutorial review summarizes and discusses recent advances in this area. The topics covered in the review include the basic strategies adopted for assembly and engineering of plasmonic nanoparticles, optical properties of the assembled nanostructures and their applications to both in vitro and in vivo detection of biol. compds. We also offer our vision of the future prospects of this field of research. Among emerging applications in this area are novel nanosensors and platforms, for food safety, environmental monitoring, health safeguarding, as well as biodefense.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXptVaks70%253D&md5=2f77fb63cbd570ca08e314354af40772
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      Matricardi, C.; Hanske, C.; Garcia-Pomar, J. L.; Langer, J.; Mihi, A.; Liz-Marzán, L. M. Gold Nanoparticle Plasmonic Superlattices as Surface-Enhanced Raman Spectroscopy Substrates. ACS Nano 2018, 12, 8531– 8539,  DOI: 10.1021/acsnano.8b04073
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      Gold Nanoparticle Plasmonic Superlattices as Surface-Enhanced Raman Spectroscopy Substrates
      Matricardi, Cristiano; Hanske, Christoph; Garcia-Pomar, Juan Luis; Langer, Judith; Mihi, Agustin; Liz-Marzan, Luis M.
      ACS Nano (2018), 12 (8), 8531-8539CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)
      Metal colloids are of great interest in the field of nanophotonics, mainly due to their morphol.-dependent optical properties, but also because they are high-quality building blocks for complex plasmonic architectures. Close-packed colloidal supercrystals not only serve for investigating the rich plasmonic resonances arising in strongly coupled arrangements but also enable tailoring the optical response, on both the nano- and the macroscale. Bridging these vastly different length scales at reasonable fabrication costs has remained fundamentally challenging, but is essential for applications in sensing, photovoltaics or optoelectronics, among other fields. We present here a scalable approach to engineer plasmonic supercrystal arrays, based on the template-assisted assembly of gold nanospheres with topog. patterned polydimethylsiloxane molds. Regular square arrays of hexagonally packed supercrystals were achieved, reaching periodicities down to 400 nm and feature sizes around 200 nm, over areas up to 0.5 cm2. These two-dimensional supercrystals exhibit well-defined collective plasmon modes that can be tuned from the visible through the near-IR by simple variation of the lattice parameter. We present electromagnetic modeling of the phys. origin of the underlying hybrid modes and demonstrate the application of superlattice arrays as surface-enhanced Raman scattering (SERS) spectroscopy substrates which can be tailored for a specific probe laser. We therefore investigated the influence of the lattice parameter, local degree of order, and cluster architecture to identify the optimal configuration for highly efficient SERS of a nonresonant Raman probe with 785 nm excitation.
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      Fang, Z.; Liu, Z.; Wang, Y.; Ajayan, P. M.; Nordlander, P.; Halas, N. J. Graphene-Antenna Sandwich Photodetector. Nano Lett. 2012, 12, 3808– 3813,  DOI: 10.1021/nl301774e
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      Graphene-Antenna Sandwich Photodetector
      Fang, Zheyu; Liu, Zheng; Wang, Yumin; Ajayan, Pulickel M.; Nordlander, Peter; Halas, Naomi J.
      Nano Letters (2012), 12 (7), 3808-3813CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
      Nanoscale antennas sandwiched between 2 graphene monolayers yield a photodetector that efficiently converts visible and near-IR photons into electrons with an 800% enhancement of the photocurrent relative to the antennaless graphene device. The antenna contributes to the photocurrent in 2 ways: by the transfer of hot electrons generated in the antenna structure upon plasmon decay, as well as by direct plasmon-enhanced excitation of intrinsic graphene electrons due to the antenna near field. This results in a graphene-based photodetector achieving up to 20% internal quantum efficiency in the visible and near-IR regions of the spectrum. This device can serve as a model for merging the light-harvesting characteristics of optical frequency antennas with the highly attractive transport properties of graphene in new optoelectronic devices.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xoslamtro%253D&md5=5e45495ad4e3cf56259d694a8f364643
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      Zhang, J.; Wang, Y.; Li, D.; Sun, Y.; Jiang, L. Engineering Surface Plasmons in Metal/Nonmetal Structures for Highly Desirable Plasmonic Photodetectors. ACS Mater. Lett. 2022, 4, 343– 355,  DOI: 10.1021/acsmaterialslett.1c00768
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      Engineering Surface Plasmons in Metal/Nonmetal Structures for Highly Desirable Plasmonic Photodetectors
      Zhang, Junchang; Wang, Yawen; Li, Dong; Sun, Yinghui; Jiang, Lin
      ACS Materials Letters (2022), 4 (2), 343-355CODEN: AMLCEF; ISSN:2639-4979. (American Chemical Society)
      A review. Recently, small-size photodetectors have attracted considerable attention, because of their promising potential for superintegrated circuits in the photoelec. sensor system. However, the small size may disable the photodetectors or result in low photoelec. conversion efficiency, because of the optical diffraction limit and the inefficient light absorption. Encouragingly, plasmonic nanostructures take excellent advantage of light-confinement effect and elec. fields enhancement at the nanoscale, providing huge opportunities to achieve small-size photodetectors while maintaining high device performance (broad photodetection range, high photoresponsivity, and fast response speed). This Review highlights the state-of-the art progress in the development of photodetectors based on various plasmonic structures. Since surface plasmons are well-controlled by the shape, size, and component of nanostructures, special emphasis will be put on the rational regulation of plasmonic nanostructures including metal nanostructures, doped semiconductors, and graphene to achieve high-performance photodetectors. In addn., the underlying enhanced mechanism is also discussed. Finally, we highlight the challenges that require deeper insights into the underlying plasmon enhanced mechanism, develop inexpensive plasmonic nanostructures for practical application, and need more research on plasmonic photodetectors based on nonmetal nanostructures and provide perspectives for future research. This Review may provide guidance for rational design of plasmonic nanostructures for small-size photodetectors with high performance.
      >> More from SciFinder ®
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      Lee, J.; Huh, J.-H.; Kim, K.; Lee, S. DNA Origami-Guided Assembly of the Roundest 60–100 nm Gold Nanospheres into Plasmonic Metamolecules. Adv. Funct. Mater. 2018, 28, 1707309,  DOI: 10.1002/adfm.201707309
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    11. 11
      Greybush, N. J.; Liberal, I.; Malassis, L.; Kikkawa, J. M.; Engheta, N.; Murray, C. B.; Kagan, C. R. Plasmon Resonances in Self-Assembled Two-Dimensional Au Nanocrystal Metamolecules. ACS Nano 2017, 11, 2917– 2927,  DOI: 10.1021/acsnano.6b08189
      11
      Plasmon Resonances in Self-Assembled Two-Dimensional Au Nanocrystal Metamolecules
      Greybush, Nicholas J.; Liberal, Inigo; Malassis, Ludivine; Kikkawa, James M.; Engheta, Nader; Murray, Christopher B.; Kagan, Cherie R.
      ACS Nano (2017), 11 (3), 2917-2927CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)
      The authors explore the evolution of plasmonic modes in 2-dimensional nanocrystal oligomer metamols. as the no. of nanocrystals is systematically varied. Precise, hexagonally ordered Au nanocrystal oligomers with 1-31 members are assembled via capillary forces into polygonal topog. templates defined using electron-beam lithog. The visible and near-IR scattering response of individual oligomers is measured by spatially resolved, polarized darkfield scattering spectroscopy. The response is highly sensitive to in-plane vs. out-of-plane incident polarization, and the authors observe an exponentially satg. red shift in plasmon resonance wavelength as the no. of nanocrystals per oligomer increases, in agreement with theor. predictions. Simulations further elucidate the modes supported by the oligomers, including elec. dipole and magnetic dipole resonances and their Fano interference. The single-oligomer sensitivity of the measurements also reveals the role of positional disorder in detg. the wavelength and character of the plasmonic response. The progression of oligomer metamol. structures studied here advances the understanding of fundamental plasmonic interactions in the transition regime between few-member plasmonic clusters and extended 2-dimensional arrays.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXisVOqsbg%253D&md5=0a7de3030b355f7d971a6e93adca8ac7
    12. 12
      Fan, J. A.; He, Y.; Bao, K.; Wu, C.; Bao, J.; Schade, N. B.; Manoharan, V. N.; Shvets, G.; Nordlander, P.; Liu, D. R.; Capasso, F. DNA-Enabled Self-Assembly of Plasmonic Nanoclusters. Nano Lett. 2011, 11, 4859– 4864,  DOI: 10.1021/nl203194m
      12
      DNA-Enabled Self-Assembly of Plasmonic Nanoclusters
      Fan, Jonathan A.; He, Yu; Bao, Kui; Wu, Chihhui; Bao, Jiming; Schade, Nicholas B.; Manoharan, Vinothan N.; Shvets, Gennady; Nordlander, Peter; Liu, David R.; Capasso, Federico
      Nano Letters (2011), 11 (11), 4859-4864CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
      DNA nanotechnol. provides a versatile foundation for the chem. assembly of nanostructures. Plasmonic nanoparticle assemblies are of particular interest because they can be tailored to exhibit a broad range of electromagnetic phenomena. In this Letter, the authors report the assembly of DNA-functionalized nanoparticles into heteropentamer clusters, which consist of a smaller gold sphere surrounded by a ring of four larger spheres. Magnetic and Fano-like resonances are obsd. in individual clusters. The DNA plays a dual role: it selectively assembles the clusters in soln. and functions as an insulating spacer between the conductive nanoparticles. These particle assemblies can be generalized to a new class of DNA-enabled plasmonic heterostructures that comprise various active and passive materials and other forms of DNA scaffolding.
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    13. 13
      Chuntonov, L.; Haran, G. Trimeric Plasmonic Molecules: The Role of Symmetry. Nano Lett. 2011, 11, 2440– 2445,  DOI: 10.1021/nl2008532
      13
      Trimeric Plasmonic Molecules: The Role of Symmetry
      Chuntonov, Lev; Haran, Gilad
      Nano Letters (2011), 11 (6), 2440-2445CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
      Artificial plasmonic mols. possess excitation modes that are defined by their symmetry and obey group theory rules, just like conventional mols. The evolution of surface-plasmon spectra of plasmonic trimers, assembled from equal-sized silver nanoparticles, as gradual geometric changes break their symmetry was analyzed. The spectral modes of an equilateral triangle, the most sym. structure of a trimer, are degenerate. This degeneracy is lifted as the symmetry is lowered when one of the vertex angles in opened, which also leads to a subtle transition between bright and dark modes. The exptl. results are quant. explained using numerical simulations and plasmon hybridization theory.
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    14. 14
      Park, K. J.; Huh, J.-H.; Jung, D.-W.; Park, J.-S.; Choi, G. H.; Lee, G.; Yoo, P. J.; Park, H.-G.; Yi, G.-R.; Lee, S. Assembly of "3D" Plasmonic Clusters By "2D" AFM Nanomanipulation of Highly Uniform and Smooth Gold Nanospheres. Sci. Rep. 2017, 7, 6045– 6110,  DOI: 10.1038/s41598-017-06456-w
      There is no corresponding record for this reference.
    15. 15
      Rossner, C.; König, T. A. F.; Fery, A. Plasmonic Properties of Colloidal Assemblies. Adv. Opt. Mater. 2021, 9, 2001869,  DOI: 10.1002/adom.202001869
      15
      Plasmonic Properties of Colloidal Assemblies
      Rossner, Christian; Koenig, Tobias A. F.; Fery, Andreas
      Advanced Optical Materials (2021), 9 (8), 2001869CODEN: AOMDAX; ISSN:2195-1071. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A review. The assembly of metal nanoparticles into supracolloidal structures unlocks optical features, which can go beyond synergistic combinations of the properties of their primary building units. This is due to inter-particle plasmonic coupling effects, which give rise to emergent properties. The motivation for this progress report is twofold: First, it is described how simulation approaches can be used to predict and understand the optical properties of supracolloidal metal clusters. These simulations may form the basis for the rational design of plasmonic assembly architectures, based on the desired functional cluster properties, and they may also spark novel material designs. Second, selected scalable state-of-the-art preparative strategies based on synthetic polymers to guide the supracolloidal assembly are discussed. These routes also allow for equipping the assembly structures with adaptive properties, which in turn enables (inter-)active control over the cluster optical properties.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXjvVegtLk%253D&md5=9cab7e429eacd1bd2a3369efec7a8a44
    16. 16
      Bautista, G.; Dreser, C.; Zang, X.; Kern, D. P.; Kauranen, M.; Fleischer, M. Collective Effects in Second-Harmonic Generation from Plasmonic Oligomers. Nano Lett. 2018, 18, 2571– 2580,  DOI: 10.1021/acs.nanolett.8b00308
      16
      Collective Effects in Second-Harmonic Generation from Plasmonic Oligomers
      Bautista, Godofredo; Dreser, Christoph; Zang, Xiaorun; Kern, Dieter P.; Kauranen, Martti; Fleischer, Monika
      Nano Letters (2018), 18 (4), 2571-2580CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
      The authors study collective effects in plasmonic oligomers of different symmetries using 2nd-harmonic generation (SHG) microscopy with cylindrical vector beams (CVBs). The oligomers consist of Au nanorods that have a longitudinal plasmon resonance close to the fundamental wavelength that is used for SHG excitation and whose long axes are arranged locally such that they follow the distribution of the transverse component of the elec. field of radially or azimuthally polarized CVBs in the focal plane. SHG from such rotationally sym. oligomers is strongly modified by the interplay between the polarization properties of the CVB and interparticle coupling. The oligomers with radially oriented nanorods exhibit small coupling effects. But the oligomers with azimuthally oriented nanorods exhibit large coupling effects that lead to silencing of SHG from the whole structure. The exptl. results are in very good agreement with numerical calcns. based on the boundary element method. The work describes a new route for studying coupling effects in complex arrangements of nano-objects and thereby for tailoring the efficiency of nonlinear optical effects in such structures.
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    17. 17
      Hentschel, M.; Saliba, M.; Vogelgesang, R.; Giessen, H.; Alivisatos, A. P.; Liu, N. Transition from Isolated to Collective Modes in Plasmonic Oligomers. Nano Lett. 2010, 10, 2721– 2726,  DOI: 10.1021/nl101938p
      17
      Transition from Isolated to Collective Modes in Plasmonic Oligomers
      Hentschel, Mario; Saliba, Michael; Vogelgesang, Ralf; Giessen, Harald; Alivisatos, A. Paul; Liu, Na
      Nano Letters (2010), 10 (7), 2721-2726CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
      The transition from isolated to collective optical modes in plasmonic oligomers is demonstrated. The resonant behavior of planar plasmonic hexamers and heptamers with gradually decreasing the interparticle gap sepn. was studied. A pronounced Fano resonance is obsd. in the plasmonic heptamer for sepns. <60 nm. The spectral characteristics change drastically upon removal of the central nanoparticle. The work paves the road toward complex hierarchical plasmonic oligomers with tailored optical properties.
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    18. 18
      Yan, W.; Xu, L.; Xu, C.; Ma, W.; Kuang, H.; Wang, L.; Kotov, N. A. Self-Assembly of Chiral Nanoparticle Pyramids with Strong R/S Optical Activity. J. Am. Chem. Soc. 2012, 134, 15114– 15121,  DOI: 10.1021/ja3066336
      18
      Self-Assembly of Chiral Nanoparticle Pyramids with Strong R/S Optical Activity
      Yan, Wenjing; Xu, Liguang; Xu, Chuanlai; Ma, Wei; Kuang, Hua; Wang, Libing; Kotov, Nicholas A.
      Journal of the American Chemical Society (2012), 134 (36), 15114-15121CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Chirality at the nanometer scale represents one of the most rapidly developing areas of research. Self-assembly of DNA-nanoparticle (NP) hybrids enables geometrically precise assembly of chiral isomers. The concept of a discrete chiral nanostructure of tetrahedral shape and topol. fabricated from 4 different NPs located in the corners of the pyramid is fundamental to the field. While the 1st observations of optical activity of mixed pyramidal assemblies were made in 2009 (Chen, W.; Nano Lett.2009, , 2153-2159), further studies are difficult without finely resolved optical data for precisely organized NP pyramidal enantiomers. Here the authors describe the prepn. of a family of self-assembled chiral pyramids made from multiple metal and/or semiconductor NPs with a yield ≤80%. Purposefully made R- and S-enantiomers of chiral pyramids with 4 different NPs from 3 different materials displayed strong chiroptical activity, with anisotropy g-factors ≤1.9 × 10-2 in the visible spectral range. Importantly, all NP constituents contribute to the chiroptical activity of the R/S pyramids. The authors were able to observe 3 different CD signals at 350-550 nm simultaneously. They correspond to the plasmonic oscillations of Au, Ag, and bandgap transitions of quantum dots. Tunability of chiroptical bands related to these transitions is essential from fundamental and practical points of view. The predictability of optical properties of pyramids, the simplicity of their self-assembly in comparison with lithog., and the possibility for polymerase chain reaction-based automation of their synthesis are expected to facilitate their future applications.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xht1Wqu7%252FK&md5=add449bb3cf3c3e1e01749ba801e8473
    19. 19
      Wang, P.; Huh, J.-H.; Lee, J.; Kim, K.; Park, K. J.; Lee, S.; Ke, Y. Magnetic Plasmon Networks Programmed by Molecular Self-Assembly. Adv. Mater. 2019, 31, 1901364,  DOI: 10.1002/adma.201901364
      There is no corresponding record for this reference.
    20. 20
      Hanske, C.; González-Rubio, G.; Hamon, C.; Formentın, P.; Modin, E.; Chuvilin, A.; Guerrero-Martınez, A.; Marsal, L. F.; Liz-Marzán, L. M. Large-Scale Plasmonic Pyramidal Supercrystals via Templated Self-Assembly of Monodisperse Gold Nanospheres. J. Phys. Chem. C 2017, 121, 10899– 10906,  DOI: 10.1021/acs.jpcc.6b12161
      20
      Large-Scale Plasmonic Pyramidal Supercrystals via Templated Self-Assembly of Monodisperse Gold Nanospheres
      Hanske, Christoph; Gonzalez-Rubio, Guillermo; Hamon, Cyrille; Formentin, Pilar; Modin, Evgeny; Chuvilin, Andrey; Guerrero-Martinez, Andres; Marsal, Lluis F.; Liz-Marzan, Luis M.
      Journal of Physical Chemistry C (2017), 121 (20), 10899-10906CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      Plasmonic nanoparticle three-dimensional supercrystals are a novel class of materials with exciting applications in technologies such as light harvesting or meta-materials; however, their realization relies on extraordinarily regular colloidal building blocks and accurate self-assembly methods. A simple, up-scalable protocol to synthesize smooth Au nanospheres with high mono-dispersity in size and sphericity is described. The synthesis involves rapid growth up to the desired size and subsequent removal of surface roughness using an efficient etching step, so nanospheres with 10-110 μm diam. can be obtained in large quantities. Upon functionalization with thiolated polyethylene glycol and low surfactant concn., Au nanospheres were used as building blocks to produce uniform arrays of micron-sized, three-dimensional pyramidal supercrystals over large areas, by a template-assisted approach. Focused ion beam cutting and SEM characterization showed a face-centered cubic lattice within individual pyramidal supercrystals.
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    21. 21
      Molet, P.; Passarelli, N.; Pérez, L. A.; Scarabelli, L.; Mihi, A. Engineering Plasmonic Colloidal Meta-Molecules for Tunable Photonic Supercrystals. Adv. Opt. Mater. 2021, 9, 2100761,  DOI: 10.1002/adom.202100761
      21
      Engineering Plasmonic Colloidal Meta-Molecules for Tunable Photonic Supercrystals
      Molet, Pau; Passarelli, Nicolas; Perez, Luis A.; Scarabelli, Leonardo; Mihi, Agustin
      Advanced Optical Materials (2021), 9 (20), 2100761CODEN: AOMDAX; ISSN:2195-1071. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Ordered arrays of metal nanoparticles offer new opportunities to engineer light-matter interactions through the hybridization of Rayleigh anomalies and localized surface plasmons. The generated surface lattice resonances exhibit much higher quality factors compared to those obsd. in isolated metal nanostructures. Template-induced colloidal self-assembly has already shown a great potential for the scalable fabrication of 2D plasmonic meta-mol. arrays, but the exptl. challenge of controlling optical losses within the repeating units has so far prevented this approach to compete with more std. fabrication methods in the prodn. of high-quality factor resonances. In this manuscript, the optical properties of plasmonic arrays are investigated by varying the lattice parameter (between 200 and 600 nm) as well as the diam. of the gold colloidal building-blocks (between 11 ± 1 and 98 ± 6 nm). It is systematically studied how the internal architecture of the repeating gold-nanoparticle meta-mols. influences the optical response of the plasmonic supercrystals. Combining both exptl. measurements and simulations, it is demonstrated how, reducing the size of the gold nanoparticles it is possible to switch from strong near-field plasmonic architectures to high-quality factors (>60) for lattice plasmon resonances located in the visible spectral range.
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    22. 22
      Santos, P. J.; Gabrys, P. A.; Zornberg, L. Z.; Lee, M. S.; Macfarlane, R. J. Macroscopic Materials Assembled from Nanoparticle Superlattices. Nature 2021, 591, 586– 591,  DOI: 10.1038/s41586-021-03355-z
      22
      Macroscopic materials assembled from nanoparticle superlattices
      Santos, Peter J.; Gabrys, Paul A.; Zornberg, Leonardo Z.; Lee, Margaret S.; Macfarlane, Robert J.
      Nature (London, United Kingdom) (2021), 591 (7851), 586-591CODEN: NATUAS; ISSN:0028-0836. (Nature Research)
      Nanoparticle assembly has been proposed as an ideal means to program the hierarchical organization of a material by using a selection of nanoscale components to build the entire material from the bottom up. Multiscale structural control is highly desirable because chem. compn., nanoscale ordering, microstructure and macroscopic form all affect phys. properties1,2. However, the chem. interactions that typically dictate nanoparticle ordering3-5 do not inherently provide any means to manipulate structure at larger length scales6-9. Nanoparticle-based materials development therefore requires processing strategies to tailor micro- and macrostructure without sacrificing their self-assembled nanoscale arrangements. Here we demonstrate methods to rapidly assemble gram-scale quantities of faceted nanoparticle superlattice crystallites that can be further shaped into macroscopic objects in a manner analogous to the sintering of bulk solids. The key advance of this method is that the chem. interactions that govern nanoparticle assembly remain active during the subsequent processing steps, which enables the local nanoscale ordering of the particles to be preserved as the macroscopic materials are formed. The nano- and microstructure of the bulk solids can be tuned as a function of the size, chem. makeup and crystallog. symmetry of the superlattice crystallites, and the micro- and macrostructures can be controlled via subsequent processing steps. This work therefore provides a versatile method to simultaneously control structural organization across the mol. to macroscopic length scales.
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    23. 23
      Kastilani, R.; Wong, R.; Pozzo, L. D. Efficient Electrosteric Assembly of Nanoparticle Heterodimers and Linear Heteroassemblies. Langmuir 2018, 34, 826– 836,  DOI: 10.1021/acs.langmuir.7b01323
      23
      Efficient Electrosteric Assembly of Nanoparticle Heterodimers and Linear Heteroassemblies
      Kastilani, Ryan; Wong, Ryan; Pozzo, Lilo D.
      Langmuir (2018), 34 (3), 826-836CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)
      A method of self-assembly of nanoparticles into controlled heteroaggregates is reported. The technique relies on carefully balancing attractive electrostatic forces with repulsive steric hindrance that is provided by surface-grafted polyethylene glycol (PEG). Two different-sized gold nanoparticles (GNPs) were used as a model system: 13 nm GNPs were functionalized with PEG-thiol and mercapto dodecanoic acid, while 7 nm GNPs were functionalized with PEG-thiol and (11- Mercaptoundecyl)trimethylammonium bromide. When mixed together, these oppositely charged particles self-assemble into stable colloidal structures (i.e., nanoclusters) whose structure depends strongly on the surface concn. of PEG. Smaller structures are obtained as the PEG surface concn. increases because steric hindrance dominates and prevents uncontrolled aggregation. In particular, under the right conditions, the authors were able to selectively synthesize heterodimers (which are effectively Janus particles) and linear heteroassemblies. This method is scalable, and it provides a step forward in bottom-up synthesis of nanomaterials.
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    24. 24
      Duan, H.; Jia, Z.; Liaqat, M.; Mellor, M. D.; Tan, H.; Nieh, M.-P.; Lin, Y.; Link, S.; Landes, C. F.; He, J. Site-Specific Chemistry on Gold Nanorods: Curvature-Guided Surface Dewetting and Supracolloidal Polymerization. ACS Nano 2023, 17, 12788– 12797,  DOI: 10.1021/acsnano.3c03929
      24
      Site-Specific Chemistry on Gold Nanorods: Curvature-Guided Surface Dewetting and Supracolloidal Polymerization
      Duan, Hanyi; Jia, Zhenyang; Liaqat, Maham; Mellor, Matthew D.; Tan, Haiyan; Nieh, Mu-Ping; Lin, Yao; Link, Stephan; Landes, Christy F.; He, Jie
      ACS Nano (2023), 17 (13), 12788-12797CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)
      Control of interparticle interactions in terms of their direction and strength highly relies on the use of anisotropic ligand grafting on nanoparticle (NP) building blocks. We report a deficient ligand exchange strategy to achieve site-specific polymer grafting of gold nanorods (AuNRs). Patchy AuNRs with controllable surface coverage can be yielded during ligand exchange with a hydrophobic polystyrene ligand and an amphiphilic surfactant while adjusting the ligand concn. (CPS) and solvent condition (Cwater in dimethylformamide). At a low grafting d. of ≤ 0.08 chains/nm2, dumbbell-like AuNRs with two polymer domains capped at the two ends can be synthesized through surface dewetting with a high purity of > 94%. These site-specifically modified AuNRs exhibit great colloidal stability in aq. soln. Dumbbell-like AuNRs can further undergo supracolloidal polymn. upon thermal annealing to form one-dimensional plasmon chains of AuNRs. Such supracolloidal polymn. follows the temp.-solvent superposition principle as revealed by kinetic studies. Using the copolymn. of two AuNRs with different aspect ratios, we demonstrate the design of chain architectures by varying the reactivity of nanorod building blocks. Our results provide insights into the postsynthetic design of anisotropic NPs that potentially serve as units for polymer-guided supracolloidal self-assembly.
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    25. 25
      Yi, C.; Liu, H.; Zhang, S.; Yang, Y.; Zhang, Y.; Lu, Z.; Kumacheva, E.; Nie, Z. Self-Limiting Directional Nanoparticle Bonding Governed by Reaction Stoichiometry. Science 2020, 369, 1369– 1374,  DOI: 10.1126/science.aba8653
      25
      Self-limiting directional nanoparticle bonding governed by reaction stoichiometry
      Yi, Chenglin; Liu, Hong; Zhang, Shaoyi; Yang, Yiqun; Zhang, Yan; Lu, Zhongyuan; Kumacheva, Eugenia; Nie, Zhihong
      Science (Washington, DC, United States) (2020), 369 (6509), 1369-1374CODEN: SCIEAS; ISSN:1095-9203. (American Association for the Advancement of Science)
      Nanoparticle clusters with mol.-like configurations are an emerging class of colloidal materials. Particles decorated with attractive surface patches acting as analogs of functional groups are used to assemble colloidal mols. (CMs); however, high-yield generation of patchy nanoparticles remains a challenge. We show that for nanoparticles capped with complementary reactive polymers, a stoichiometric reaction leads to reorganization of the uniform ligand shell and self-limiting nanoparticle bonding, whereas electrostatic repulsion between colloidal bonds governs CM symmetry. This mechanism enables high-yield CM generation and their programmable organization in hierarchical nanostructures. Our work bridges the gap between covalent bonding taking place at an at. level and colloidal bonding occurring at the length scale two orders of magnitude larger and broadens the methods for nanomaterial fabrication.
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    26. 26
      Cai, Y.; Vana, P. 2D Plasmonic Molecules via Hydrogen Bond Interaction between Polymer-Grafted Nanoparticles. Angew. Chem., Int. Ed. 2023, 62, e202309798  DOI: 10.1002/anie.202309798
      There is no corresponding record for this reference.
    27. 27
      Lin, X.; Ye, S.; Kong, C.; Webb, K.; Yi, C.; Zhang, S.; Zhang, Q.; Fourkas, J. T.; Nie, Z. Polymeric Ligand-Mediated Regioselective Bonding of Plasmonic Nanoplates and Nanospheres. J. Am. Chem. Soc. 2020, 142, 17282– 17286,  DOI: 10.1021/jacs.0c08135
      27
      Polymeric Ligand-Mediated Regioselective Bonding of Plasmonic Nanoplates and Nanospheres
      Lin, Xiaoying; Ye, Shunsheng; Kong, Chuncai; Webb, Kyle; Yi, Chenglin; Zhang, Shaoyi; Zhang, Qian; Fourkas, John T.; Nie, Zhihong
      Journal of the American Chemical Society (2020), 142 (41), 17282-17286CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Nanoparticle (NP) clusters are attractive for many applications, but controllable and regioselective assembly of clusters remains challenging. This communication reports a strategy to precisely assemble Ag nanoplates (NP-As) and Au nanospheres (NP-Bs) grafted with copolymer ligands into defined ABx clusters with controlled coordination no. (x) and orientation of the NPs. The directional bonding of shaped NPs relies on the stoichiometric reaction of complementary reactive groups on copolymer ligands. The x value of NP clusters can be tuned from 1 to 4 by varying the no. ratio of reactive groups on single NP-Bs to NP-As. The regioselective bonding of nanospheres to the edge or face of a central nanoplate is governed by the steric hindrance of copolymeric ligands on the nanoplate. The clusters exhibit distinctive plasmonic properties that are dependent on the bonding modes of NPs. This study paves a route to fabricating nanostructures with high precision and complexity for applications in plasmonics, catalysis, and sensing.
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    28. 28
      Kuttner, C.; Höller, R. P. M.; Quintanilla, M.; Schnepf, M. J.; Dulle, M.; Fery, A.; Liz-Marzán, L. M. SERS and Plasmonic Heating Efficiency from Anisotropic Core/Satellite Superstructures. Nanoscale 2019, 11, 17655– 17663,  DOI: 10.1039/c9nr06102a
      28
      SERS and plasmonic heating efficiency from anisotropic core/satellite superstructures
      Kuttner, Christian; Holler, Roland P. M.; Quintanilla, Marta; Schnepf, Max J.; Dulle, Martin; Fery, Andreas; Liz-Marzan, Luis M.
      Nanoscale (2019), 11 (38), 17655-17663CODEN: NANOHL; ISSN:2040-3372. (Royal Society of Chemistry)
      The optical properties of nanoparticle assemblies can be tailored via hybridization of plasmon modes. Isotropic core/satellite superstructures made of spherical nanoparticles are known to exhibit coupled modes with a strongly scattering (radiative) character, and provide hot spots yielding high activity in surface-enhanced Raman scattering (SERS). However, to complement this functionality with plasmonic heating, addnl. absorbing (non-radiative) modes are required. We introduce herein anisotropic superstructures formed by decorating a central nanorod with spherical satellite nanoparticles, which feature two coupled modes that allow application for both SERS and heating. On the basis of diffuse reflectance spectroscopy, small-angle X-ray scattering (SAXS), and electromagnetic simulations, the origin of the coupled modes is disclosed and thus serves as a basis toward alternative designs of functional superstructures. This work represents a proof-of-principle for the combination of high SERS efficiency with efficient plasmonic heating by near-IR irradn.
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    29. 29
      Höller, R. P. M.; Dulle, M.; Thomä, S.; Mayer, M.; Steiner, A. M.; Förster, S.; Fery, A.; Kuttner, C.; Chanana, M. Protein-Assisted Assembly of Modular 3D Plasmonic Raspberry-like Core/Satellite Nanoclusters: Correlation of Structure and Optical Properties. ACS Nano 2016, 10, 5740– 5750,  DOI: 10.1021/acsnano.5b07533
      29
      Protein-Assisted Assembly of Modular 3D Plasmonic Raspberry-like Core/Satellite Nanoclusters: Correlation of Structure and Optical Properties
      Holler Roland P M; Thoma Sabrina; Fery Andreas; Kuttner Christian; Chanana Munish; Holler Roland P M; Mayer Martin; Steiner Anja Maria; Fery Andreas; Kuttner Christian; Dulle Martin; Forster Stephan; Fery Andreas; Fery Andreas; Kuttner Christian; Chanana Munish
      ACS nano (2016), 10 (6), 5740-50 ISSN:.
      We present a bottom-up assembly route for a large-scale organization of plasmonic nanoparticles (NPs) into three-dimensional (3D) modular assemblies with core/satellite structure. The protein-assisted assembly of small spherical gold or silver NPs with a hydrophilic protein shell (as satellites) onto larger metal NPs (as cores) offers high modularity in sizes and composition at high satellite coverage (close to the jamming limit). The resulting dispersions of metal/metal nanoclusters exhibit high colloidal stability and therefore allow for high concentrations and a precise characterization of the nanocluster architecture in dispersion by small-angle X-ray scattering (SAXS). Strong near-field coupling between the building blocks results in distinct regimes of dominant satellite-to-satellite and core-to-satellite coupling. High robustness against satellite disorder was proved by UV/vis diffuse reflectance (integrating sphere) measurements. Generalized multiparticle Mie theory (GMMT) simulations were employed to describe the electromagnetic coupling within the nanoclusters. The close correlation of structure and optical property allows for the rational design of core/satellite nanoclusters with tailored plasmonics and well-defined near-field enhancement, with perspectives for applications such as surface-enhanced spectroscopies.
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    30. 30
      Cai, Y.; Peng, W.; Vana, P. Gold Nanoparticle Ring Arrays from Core–Satellite Nanostructures Made To Order by Hydrogen Bond Interactions. Nanoscale Adv. 2022, 4, 2787– 2793,  DOI: 10.1039/D2NA00204C
      There is no corresponding record for this reference.
    31. 31
      Xia, Y.; Nguyen, T. D.; Yang, M.; Lee, B.; Santos, A.; Podsiadlo, P.; Tang, Z.; Glotzer, S. C.; Kotov, N. A. Self-Assembly of Self-Limiting Monodisperse Supraparticles from Polydisperse Nanoparticles. Nat. Nanotechnol. 2011, 6, 580– 587,  DOI: 10.1038/nnano.2011.121
      31
      Self-assembly of self-limiting monodisperse supraparticles from polydisperse nanoparticles
      Xia, Yunsheng; Nguyen, Trung Dac; Yang, Ming; Lee, Byeongdu; Santos, Aaron; Podsiadlo, Paul; Tang, Zhiyong; Glotzer, Sharon C.; Kotov, Nicholas A.
      Nature Nanotechnology (2011), 6 (9), 580-587CODEN: NNAABX; ISSN:1748-3387. (Nature Publishing Group)
      Nanoparticles are known to self-assemble into larger structures through growth processes that typically occur continuously and depend on the uniformity of the individual nanoparticles. Here, we show that inorg. nanoparticles with non-uniform size distributions can spontaneously assemble into uniformly sized supraparticles with core-shell morphologies. This self-limiting growth process is governed by a balance between electrostatic repulsion and van der Waals attraction, which is aided by the broad polydispersity of the nanoparticles. The generic nature of the interactions creates flexibility in the compn., size and shape of the constituent nanoparticles, and leads to a large family of self-assembled structures, including hierarchically organized colloidal crystals.
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    32. 32
      Wang, Y.; Chen, G.; Yang, M.; Silber, G.; Xing, S.; Tan, L. H.; Wang, F.; Feng, Y.; Liu, X.; Li, S.; Chen, H. A systems Approach Towards the Stoichiometry-Controlled Hetero-Assembly of Nanoparticles. Nat. Commun. 2010, 1, 87,  DOI: 10.1038/ncomms1089
      32
      A systems approach towards the stoichiometry-controlled hetero-assembly of nanoparticles
      Wang Yong; Chen Gang; Yang Miaoxin; Silber Georg; Xing Shuangxi; Tan Li Huey; Wang Feng; Feng Yuhua; Liu Xiaogang; Li Shuzhou; Chen Hongyu
      Nature communications (2010), 1 (), 87 ISSN:.
      A central theme in nanotechnology is to advance the fundamental understanding of nanoscale component assembly, thereby allowing rational structural design that may lead to materials with novel properties and functions. Nanoparticles (NPs) are often regarded as 'artificial atoms', but their 'reactions' are not readily controllable. Here, we demonstrate a complete nanoreaction system whereby colloidal NPs are rationally assembled and purified. Two types of functionalized gold NPs (A and B) are bonded to give specific products AB, AB(2), AB(3) and AB(4). The stoichiometry control is realized by fine-tuning the charge repulsion among the B-NPs. The products are protected by a polymer, which allows their isolation in high purity. The integration of hetero-assembly, stoichiometry control, protection scheme and separation method may provide a scalable way to fabricate sophisticated nanostructures.
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    33. 33
      Larson-Smith, K.; Pozzo, D. C. Scalable Synthesis of Self-Assembling Nanoparticle Clusters Based on Controlled Steric Interactions. Soft Matter 2011, 7, 5339– 5347,  DOI: 10.1039/c0sm01497d
      33
      Scalable synthesis of self-assembling nanoparticle clusters based on controlled steric interactions
      Larson-Smith, Kjersta; Pozzo, Danilo C.
      Soft Matter (2011), 7 (11), 5339-5347CODEN: SMOABF; ISSN:1744-683X. (Royal Society of Chemistry)
      A simple one-pot method is presented for the synthesis of amphiphilic gold nanoparticles that can spontaneously self-assemble into stable clusters with controllable geometry. The technique is based on the control of colloidal interactions through sequential functionalization of the surfaces with long polyethylene glycol (PEG) chains followed by short alkane-thiol mols. This process renders the gold nanoparticles amphiphilic and initiates the self-assembly of stable clusters in the dispersion. It is shown that the dominant structures and sizes of the clusters (i.e. singlets, doublets, triplets and others) are directly and reproducibly controlled by the concn. of PEG chains that are linked to the particle surface. Changes in the structure of the clusters are systematically characterized by small angle X-ray scattering (SAXS), dynamic light scattering (DLS) and transmission electron microscopy (TEM). Systematic shifts in the plasmon resonance peak of the gold nanoparticle clusters demonstrate that this new method for self-assembly can be effectively used to tune optical properties with great precision. With this new approach, we show that it is possible to fabricate large nos. of amphiphilic nanoparticles and clusters with controllable structure by manipulating the repulsive steric forces that are imparted by surface bound polymers and the attractive interactions of the hydrophobic alkane-thiols. The major advantage of this technique lies in its simplicity, versatility and potential for scalable prodn. of self-assembled colloidal mols.'.
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    34. 34
      Peng, W.; Cai, Y.; Fanslau, L.; Vana, P. Nanoengineering with RAFT Polymers: from Nanocomposite Design to Applications. Polym. Chem. 2021, 12, 6198– 6229,  DOI: 10.1039/D1PY01172C
      34
      Nanoengineering with RAFT polymers: from nanocomposite design to applications
      Peng, Wentao; Cai, Yingying; Fanslau, Luise; Vana, Philipp
      Polymer Chemistry (2021), 12 (43), 6198-6229CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)
      A review. Reversible addn.-fragmentation chain-transfer (RAFT) polymn. is a powerful tool for the precise formation of macromol. building blocks that can be used for the construction of well-defined nanocomposites. Esp. when combining RAFT polymers with uniform inorg./metallic nanoparticles, a vast variety of complex nanocomposites become available that may find applications esp. in the field of life sciences, e.g., bio-imaging, drug delivery or cancer-therapy, but also in areas such as energy conversion or catalysis. RAFT polymn. not only provides the possibility to control the size and the macromol. architecture of the polymer building blocks, but inherently delivers highly functional end-groups that can often directly be employed as linker-sites for installing the polymeric components into the final nanocomposites. This review describes recent advances in this vivid field and concs. on innovations in the fabrication method and design strategies for polymer/inorg. nanohybrids. The methodol. of synthesizing RAFT polymer with the aim of surface functionalization and the design options for anchoring RAFT polymer on surfaces are covered. A series of core-shell nanostructures with the focus on novel functionalities brought by RAFT polymer brushes will be reviewed with focus on the detailed macromol. design for each specific application's scenario. Examples of ordered nano-assemblies using RAFT polymer linkers will be reviewed in order to demonstrate the advantages of RAFT polymer for introducing different morphologies, interactions and chirality to the final functional nanostructures.
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    35. 35
      Song, P.; Wang, H. High-Performance Polymeric Materials through Hydrogen-Bond Cross-linking. Adv. Mater. 2020, 32, 1901244,  DOI: 10.1002/adma.201901244
      35
      High-Performance Polymeric Materials through Hydrogen-Bond Cross-Linking
      Song, Pingan; Wang, Hao
      Advanced Materials (Weinheim, Germany) (2020), 32 (18), 1901244CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A review. It has always been crit. to develop high-performance polymeric materials with exceptional mech. strength and toughness, thermal stability, and even healable properties for meeting performance requirements in industry. Conventional chem. crosslinking leads to enhanced mech. strength and thermostability at the expense of extensibility due to mutually exclusive mechanisms. Such major challenges have recently been addressed by using noncovalent crosslinking of reversible multiple hydrogen-bonds (H-bonds) that widely exist in biol. materials, such as silk and muscle. Recent decades have witnessed the development of many tailor-made high-performance H-bond crosslinked polymeric materials. Here, recent advances in H-bond crosslinking strategies are reviewed for creating high-performance polymeric materials. H-bond crosslinking of polymers can be realized via (i) self-assocn. of interchain multiple H-bonding interactions or specific H-bond crosslinking motifs, such as 2-ureido-4-pyrimidone units with self-complementary quadruple H-bonds and (ii) addn. of external crosslinkers, including small mols., nanoparticles, and polymer aggregates. The resultant crosslinked polymers normally exhibit tunable high strength, large extensibility, improved thermostability, and healable capability. Such performance portfolios enable these advanced polymers to find many significant cutting-edge applications. Major challenges facing existing H-bond crosslinking strategies are discussed, and some promising approaches for designing H-bond crosslinked polymeric materials in the future are also proposed.
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    36. 36
      Jancke, S.; Liu, C.; Wang, R.; Sarkar, S.; Besford, Q. A.; König, T. A. F.; Popp, J.; Cialla-May, D.; Rossner, C. Turning on Hotspots: Supracolloidal SERS Probes Made Brilliant by an External Activation Mechanism. Nanoscale 2023, 15, 18687– 18695,  DOI: 10.1039/D3NR05121H
      There is no corresponding record for this reference.
    37. 37
      Jochum, F. D.; Theato, P. Temperature- and Light-Responsive Smart Polymer Materials. Chem. Soc. Rev. 2013, 42, 7468– 7483,  DOI: 10.1039/C2CS35191A
      37
      Temperature- and light-responsive smart polymer materials
      Jochum, Florian D.; Theato, Patrick
      Chemical Society Reviews (2013), 42 (17), 7468-7483CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      A review. Stimuli-responsive polymers have been attracting great interest within the scientific community for several decades. The unique feature to respond to small changes in the environmental conditions has made this class of materials very promising for several applications in the field of nanoscience, nanotechnol. and nanomedicine. So far, several different chem., phys. or biochem. stimuli have been investigated within natural or synthetic polymers. Very interesting and appealing seems to be the combination of several stimuli to tune the properties of these materials in manifold ways. Within this present review, we want to highlight the recent progress in the field of synthetic stimuli-responsive polymers combining temp. and light responsiveness.
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    38. 38
      Kocak, G.; Tuncer, C.; Bütün, V. pH-Responsive Polymers. Polym. Chem. 2017, 8, 144– 176,  DOI: 10.1039/c6py01872f
      38
      pH-Responsive polymers
      Kocak, G.; Tuncer, C.; Butun, V.
      Polymer Chemistry (2017), 8 (1), 144-176CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)
      A review. In this review, we provide an anal. of some of the recent literature reports on the synthesis and applications of pH-responsive polymers. Depending on the soln. pH, such copolymers can self-assemble and form various nanosized structures including core-shell micellar structures, micelles/reverse micelles, hollow spheres, vesicle structures, adsorbed species at the water-air interface, and more complex architectures. Their self-assembly behaviors open the door for the prodn. of various novel nanostructures including shell/core cross-linked micelles, hollow spheres, hydrogels, microgels, layer-by-layer (LbL) nanofilms, controlled releasing systems, drug carrier systems, etc. The review consists of various major parts including types of pH-responsive polymers, synthetic methods for their synthesis and their soln. behaviors, their nanostructures in aq. media, applications as LbL nanofilms, delivery devices, controlled release systems, sensors, stabilizers, solubilizers, etc. In the last two decades, there have been great developments in synthetic methods and strategies for the prepn. of novel pH-responsive polymers or polymeric materials providing possible materials for various applications including biotechnol., nanotechnol., colloid and surface science, materials science, etc.
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    39. 39
      Ranneh, A.-H.; Takemoto, H.; Sakuma, S.; Awaad, A.; Nomoto, T.; Mochida, Y.; Matsui, M.; Tomoda, K.; Naito, M.; Nishiyama, N. An Ethylenediamine-based Switch to Render the Polyzwitterion Cationic at Tumorous pH for Effective Tumor Accumulation of Coated Nanomaterials. Angew. Chem., Int. Ed. 2018, 57, 5057– 5061,  DOI: 10.1002/anie.201801641
      39
      An Ethylenediamine-based Switch to Render the Polyzwitterion Cationic at Tumorous pH for Effective Tumor Accumulation of Coated Nanomaterials
      Ranneh, Abdul-Hackam; Takemoto, Hiroyasu; Sakuma, Shunya; Awaad, Aziz; Nomoto, Takahiro; Mochida, Yuki; Matsui, Makoto; Tomoda, Keishiro; Naito, Mitsuru; Nishiyama, Nobuhiro
      Angewandte Chemie, International Edition (2018), 57 (18), 5057-5061CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Polyzwitterions are employed as coating polymers for biomaterials to induce an antifouling property on the surface. Fine-tuning the betaine structure switches the antifouling property to be interactive with anionic tissue constituents in response to a tumorous pH gradient. The ethylenediamine moiety in the carboxybetaine enabled stepwise protonation and initiated the di-protonation process around tumorous pH (6.5). The net charge of the developed polyzwitterion (PGlu(DET-Car)) was thus neutral at pH 7.4 for antifouling, but was cationic at pH 6.5 for interaction with anionic constituents. Quantum dots coated with PGlu(DET-Car) exhibited comparable stealth and enhanced tumor accumulation relative to the PEG system. The present study provides a novel design of smart switchable polyzwitterion based on a precise control of the net charge.
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    40. 40
      Chen, Y.; Wang, Z.; He, Y.; Yoon, Y. J.; Jung, J.; Zhang, G.; Lin, Z. Light-Enabled Reversible Self-Assembly and Tunable Optical Properties of Stable Hairy Nanoparticles. Proc. Natl. Acad. Sci. U.S.A. 2018, 115, E1391– E1400,  DOI: 10.1073/pnas.1714748115
      40
      Light-enabled reversible self-assembly and tunable optical properties of stable hairy nanoparticles
      Chen, Yihuang; Wang, Zewei; He, Yanjie; Yoon, Young Jun; Jung, Jaehan; Zhang, Guangzhao; Lin, Zhiqun
      Proceedings of the National Academy of Sciences of the United States of America (2018), 115 (7), E1391-E1400CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
      The ability to dynamically organize functional nanoparticles (NPs) via the use of environmental triggers (temp., pH, light, or solvent polarity) opens up important perspectives for rapid and convenient construction of a rich variety of complex assemblies and materials with new structures and functionalities. Here, we report an unconventional strategy for crafting stable hairy NPs with light-enabled reversible and reliable self-assembly and tunable optical properties. Central to our strategy is to judiciously design amphiphilic star-like diblock copolymers comprising inner hydrophilic blocks and outer hydrophobic photoresponsive blocks as nanoreactors to direct the synthesis of monodisperse plasmonic NPs intimately and permanently capped with photoresponsive polymers. The size and shape of hairy NPs can be precisely tailored by modulating the length of inner hydrophilic block of star-like diblock copolymers. The perpetual anchoring of photoresponsive polymers on the NP surface renders the attractive feature of self-assembly and disassembly of NPs on demand using light of different wavelengths, as revealed by tunable surface plasmon resonance absorption of NPs and the reversible transformation of NPs between their dispersed and aggregated states. The dye encapsulation/release studies manifested that such photoresponsive NPs may be exploited as smart guest mol. nanocarriers. By extension, the star-like block copolymer strategy enables the crafting of a family of stable stimuli-responsive NPs (e.g., temp.- or pH-sensitive polymer-capped magnetic, ferroelec., upconversion, or semiconducting NPs) and their assemblies for fundamental research in self-assembly and crystn. kinetics of NPs as well as potential applications in optics, optoelectronics, magnetic technologies, sensory materials and devices, catalysis, nanotechnol., and biotechnol.
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    41. 41
      Huebner, D.; Rossner, C.; Vana, P. Light-induced self-assembly of gold nanoparticles with a photoresponsive polymer shell. Polymer 2016, 107, 503– 508,  DOI: 10.1016/j.polymer.2016.05.073
      41
      Light-induced self-assembly of gold nanoparticles with a photoresponsive polymer shell
      Huebner, Dennis; Rossner, Christian; Vana, Philipp
      Polymer (2016), 107 (), 503-508CODEN: POLMAG; ISSN:0032-3861. (Elsevier Ltd.)
      The light-induced self-assembly of gold nanoparticles was studied systematically. A methacrylate type monomer with an azobenzene sidechain was polymd. in a reversible addn.-fragmentation chain transfer (RAFT) polymn. The resulting light responsive polymer was grafted to gold nanoparticles via the RAFT group. UV-light induced trans to cis isomerization of the azobenzene moieties triggers the aggregation of the polymer-gold hybrid particles in toluene dispersion. The thermally induced cis to trans relaxation was found to be significantly slower than for small mols. at gold surfaces. The self-assembly was followed by dynamic light scattering (DLS), UV/vis spectroscopy and transmission electron microscopy (TEM). The d. of primary gold particles within the self-assembled aggregates can be tuned by varying the molar mass of the grafted polymer.
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    42. 42
      Rahimzadeh, A.; Rutsch, M.; Kupnik, M.; Klitzing, R. v. Visualization of Acoustic Energy Absorption in Confined Aqueous Solutions by PNIPAM Microgels: Effects of Bulk Viscosity. Langmuir 2021, 37, 5854– 5863,  DOI: 10.1021/acs.langmuir.1c00235
      There is no corresponding record for this reference.
    43. 43
      Stock, S.; Mirau, L.; Rutsch, M.; Wismath, S.; Kupnik, M.; von Klitzing, R.; Rahimzadeh, A. Ultrasound-Induced Adsorption of Acousto-Responsive Microgels at Water–Oil Interface. Adv. Sci. 2024, 11, 2305395,  DOI: 10.1002/advs.202305395
      There is no corresponding record for this reference.
    44. 44
      Wei, P.; Cornel, E. J.; Du, J. Ultrasound-Responsive Polymer-Based Drug Delivery Systems. Drug Delivery Transl. Res. 2021, 11, 1323– 1339,  DOI: 10.1007/s13346-021-00963-0
      44
      Ultrasound-responsive polymer-based drug delivery systems
      Wei, Ping; Cornel, Erik Jan; Du, Jianzhong
      Drug Delivery and Translational Research (2021), 11 (4), 1323-1339CODEN: DDTRCY; ISSN:2190-3948. (Springer)
      Abstr.: Ultrasound-responsive polymeric materials have received a tremendous amt. of attention from scientists for several decades. Compared to other stimuli-responsive materials (such as UV-, thermal-, and pH-responsive materials), these smart materials are more applicable since they allow more efficient drug delivery and targeted treatment by fairly non-invasive means. This review describes the recent advances of such ultrasound-responsive polymer-based drug delivery systems and illustrates various applications. More specifically, the mechanism of ultrasound-induced drug delivery, typical formulations, and biomedical applications (tumor therapy, disruption of blood-brain barrier, fighting infectious diseases, transdermal drug delivery, and enhanced thrombolysis) are summarized. Finally, a perspective on the future research directions for the development of ultrasound-responsive polymeric materials to facilitate a clin. translation is given.
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    45. 45
      Wei, P.; Sun, M.; Yang, B.; Xiao, J.; Du, J. Ultrasound-Responsive Polymersomes Capable of Endosomal Escape for Efficient Cancer Therapy. J. Controlled Release 2020, 322, 81– 94,  DOI: 10.1016/j.jconrel.2020.03.013
      45
      Ultrasound-responsive polymersomes capable of endosomal escape for efficient cancer therapy
      Wei, Ping; Sun, Min; Yang, Bo; Xiao, Jiangang; Du, Jianzhong
      Journal of Controlled Release (2020), 322 (), 81-94CODEN: JCREEC; ISSN:0168-3659. (Elsevier B.V.)
      Stimuli-responsive anticancer drug delivery vehicles have attracted increasing attention in nanomedicine. However, controlled drug release in vivo is still an important challenge, as traditional stimuli lack maneuverability. To solve this problem, we designed an ultrasound and pH-responsive polymersome by self-assembly of poly(ethylene oxide)-block-poly(2-(diethylamino)ethyl methacrylate)-stat-poly(methoxyethyl methacrylate) [PEO-b-P(DEA-stat-MEMA)], where PEO acts as the corona-forming block, DEA acts as the endosomal escape segment, and MEMA acts as the ultrasound-responsive segment. This strategy combines the advantages of noninvasive ultrasonic stimulus which can be applied from outside to any organ regardless of depth, and the weakly acidic microenvironment of tumor tissue. In vitro expts. confirmed excellent endosomal escape ability, on-demand drug release behavior, low cytotoxicity, and high intracellular delivery efficiency of polymersomes. In vivo antitumor tests revealed that in the presence of sonication, the anticancer drug was released at an accelerated rate from these ultrasound-responsive polymersomes, and the DOX-loaded polymersomes + sonication group significantly inhibited tumor growth (95% redn. in tumor mass) without any side effects. Overall, this ultrasound-responsive polymersome provides us with a fresh insight into designing next-generation stimuli-responsive drug carriers with better maneuverability and higher chemotherapeutic efficiency.
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    46. 46
      Huebsch, N.; Kearney, C. J.; Zhao, X.; Kim, J.; Cezar, C. A.; Suo, Z.; Mooney, D. J. Ultrasound-Triggered Disruption and Self-Healing of Reversibly Cross-linked Hydrogels for Drug Delivery and Enhanced Chemotherapy. Proc. Natl. Acad. Sci. U.S.A. 2014, 111, 9762– 9767,  DOI: 10.1073/pnas.1405469111
      46
      Ultrasound-triggered disruption and self-healing of reversibly cross-linked hydrogels for drug delivery and enhanced chemotherapy
      Huebsch, Nathaniel; Kearney, Cathal J.; Zhao, Xuanhe; Kim, Jaeyun; Cezar, Christine A.; Suo, Zhigang; Mooney, David J.
      Proceedings of the National Academy of Sciences of the United States of America (2014), 111 (27), 9762-9767CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
      Biol. systems are exquisitely sensitive to the location and timing of physiol. cues and drugs. This spatiotemporal sensitivity presents opportunities for developing new therapeutic approaches. Polymer-based delivery systems are used extensively for attaining localized, sustained release of bioactive mols. However, these devices typically are designed to achieve a const. rate of release. We hypothesized that it would be possible to create digital drug release, which could be accelerated and then switched back off, on demand, by applying ultrasound to disrupt ionically crosslinked hydrogels. We demonstrated that ultrasound does not permanently damage these materials but enables nearly digital release of small mols., proteins, and condensed oligonucleotides. Parallel in vitro studies demonstrated that the concept of applying temporally short, high-dose "bursts" of drug exposure could be applied to enhance the toxicity of mitoxantrone toward breast cancer cells. We thus used the hydrogel system in vivo to treat xenograft tumors with mitoxantrone, and found that daily ultrasound-stimulated drug release substantially reduced tumor growth compared with sustained drug release alone. This approach of digital drug release likely will be applicable to a broad variety of polymers and bioactive mols., and is a potentially useful tool for studying how the timing of factor delivery controls cell fate in vivo.
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    47. 47
      Xue, Y.; Li, X.; Li, H.; Zhang, W. Quantifying Thiol-Gold Interactions Towards the Efficient Strength Control. Nat. Commun. 2014, 5, 4348– 4349,  DOI: 10.1038/ncomms5348
      47
      Quantifying thiol-gold interactions towards the efficient strength control
      Xue, Yurui; Li, Xun; Li, Hongbin; Zhang, Wenke
      Nature Communications (2014), 5 (), 4348CODEN: NCAOBW; ISSN:2041-1723. (Nature Publishing Group)
      The strength of the thiol-gold interactions provides the basis to fabricate robust self-assembled monolayers for diverse applications. Investigation on the stability of thiol-gold interactions has thus become a hot topic. Here we use at. force microscopy to quantify the stability of individual thiol-gold contacts formed both by isolated single thiols and in self-assembled monolayers on gold surface. Our results show that the oxidized gold surface can enhance greatly the stability of gold-thiol contacts. In addn., the shift of binding modes from a coordinate bond to a covalent bond with the change in environmental pH and interaction time has been obsd. exptl. Furthermore, isolated thiol-gold contact is found to be more stable than that in self-assembled monolayers. Our findings revealed mechanisms to control the strength of thiol-gold contacts and will help guide the design of thiol-gold contacts for a variety of practical applications.
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    48. 48
      Cook, J. L.; Hunter, C. A.; Low, C. M. R.; Perez-Velasco, A.; Vinter, J. G. Preferential Solvation and Hydrogen Bonding in Mixed Solvents. Angew. Chem., Int. Ed. 2008, 47, 6275– 6277,  DOI: 10.1002/anie.200801349
      There is no corresponding record for this reference.
    49. 49
      Driver, M. D.; Williamson, M. J.; Cook, J. L.; Hunter, C. A. Functional Group Interaction Profiles: A General Treatment of Solvent Effects on Non-Covalent Interactions. Chem. Sci. 2020, 11, 4456– 4466,  DOI: 10.1039/D0SC01288B
      49
      Functional group interaction profiles: a general treatment of solvent effects on non-covalent interactions
      Driver, Mark D.; Williamson, Mark J.; Cook, Joanne L.; Hunter, Christopher A.
      Chemical Science (2020), 11 (17), 4456-4466CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
      Solvation has profound effects on the behavior of supramol. systems, but the effects can be difficult to predict even at a qual. level. Functional group interaction profiles (FGIPs) provide a simple visual method for understanding how solvent affects the free energy contribution due to a single point interaction, such as a hydrogen bond, between two solute functional groups. A generalised theor. approach has been developed, which allows calcn. of FGIPs for any solvent or solvent mixt., and FGIPs for 300 different solvents have been produced, providing a comprehensive description of solvent effects on non-covalent chem. The free energy calcns. have been validated using exptl. measurements of assocn. consts. for hydrogen bonded complexes in multiple solvent mixts. The calcd. FGIPs provide good descriptions of the solvation of polar solutes, solvophobic interactions between non-polar solutes in polar solvents like water, and preferential solvation in solvent mixts. Applications are explored of the use of FGIPs in drug design, for optimizing receptor-ligand interactions, and in enantioselective catalysis for solvent selection to optimize selectivity.
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    50. 50
      Zhang, L.; Wang, X.; Wang, T.; Liu, M. Tuning Soft Nanostructures in Self-assembled Supramolecular Gels: From Morphology Control to Morphology-Dependent Functions. Small 2015, 11, 1025– 1038,  DOI: 10.1002/smll.201402075
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      Tuning Soft Nanostructures in Self-assembled Supramolecular Gels: From Morphology Control to Morphology-Dependent Functions
      Zhang, Li; Wang, Xiufeng; Wang, Tianyu; Liu, Minghua
      Small (2015), 11 (9-10), 1025-1038CODEN: SMALBC; ISSN:1613-6810. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A review. Supramol. gels are one kind of important soft material, in which small low-mol. wt. compds. self-assemble into various nanostructures through non-covalent interactions to immobilize the solvents. While there are many important fundamental issues related to the gelation process, such as the design of the gelator, synergism of various non-covalent interactions between gelators, gelator-solvents, the balances between gelation and crystn. and so on, the self-assembled nanostructures forming during gelation are very interesting. These nanostructures have many unique features, such as the flexibility to respond to external stimuli, morphol. diversity, ease of fabrication in large quantities, and so on. This review highlights some important features in tuning the nanostructures in the supramol. gels from their morphol. diversity, morphol. control, morphol. conversion, and morphol.-depended functions.
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    51. 51
      Isozaki, K.; Takaya, H.; Naota, T. Ultrasound-Induced Gelation of Organic Fluids with Metalated Peptides. Angew. Chem., Int. Ed. 2007, 46, 2855– 2857,  DOI: 10.1002/anie.200605067
      51
      Ultrasound-induced gelation of organic fluids with metalated peptides
      Isozaki, Katsuhiro; Takaya, Hikaru; Naota, Takeshi
      Angewandte Chemie, International Edition (2007), 46 (16), 2855-2857, S2855/1-S2855/31CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Stable solns. of a palladium ortho-metalated N-dipeptidyl benzaldimine complexes undergo reversible gelation after brief ultrasound irradn.; the sol state may be restored by heating. Palladium complexes [LXPd-1,2-C6H4CH:N-κN-(CH2)nOCOCH2CH2CH(NHFmoc)CONHCH(CONHBu)CH2CH2COO(CH2)nN:CHC6H4-1,2-PdXL] (L = PPh3; 1a X = Cl, n = 2; 1b X = NCS, n = 2; 1c X = Cl, n = 5), Fmoc[NHCHYCONH]mBu (Y = CH2CH2CO2CH2CH2N:CH-1,2-C6H4PdLCl; 2-4; m = 1-4) undergo ultrasound-induced gelation, tentatively explained by extensive H-bond formation. This is the first case of a reversible, remotely controlled, and rapid sol-gel transition by H-bonding aggregates. By adjusting the sonication time, the gelation rates and heat-resistant properties of the aggregates can be controlled.
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    52. 52
      Wang, Y.; Zhan, C.; Fu, H.; Li, X.; Sheng, X.; Zhao, Y.; Xiao, D.; Ma, Y.; Ma, J. S.; Yao, J. Switch from Intra- to Intermolecular H-Bonds by Ultrasound: Induced Gelation and Distinct Nanoscale Morphologies. Langmuir 2008, 24, 7635– 7638,  DOI: 10.1021/la801499y
      52
      Switch from Intra- to Intermolecular H-Bonds by Ultrasound: Induced Gelation and Distinct Nanoscale Morphologies
      Wang, Yaobing; Zhan, Chuanlang; Fu, Hongbing; Li, Xiao; Sheng, Xiaohai; Zhao, Yongsheng; Xiao, Debao; Ma, Ying; Ma, Jin Shi; Yao, Jiannian
      Langmuir (2008), 24 (15), 7635-7638CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)
      During cooling of the (R)-N-Fmoc-Octylglycine (Fmoc-OG)/cyclohexane soln., gelation is obsd. exclusively when ultrasound is used as an external stimulus, while deposit is obtained without sonication. The xerogel consists of entangled fibrous network made by interconnected nanofibers, while the deposit comprises large nos. of unbranched nanowires. It is found that the Fmoc-OG mols. form bilayer structures in both the deposit and the gel. However, the ratio (R) between the Fmoc-OG mols. in a stable intramol. H-bonding conformation and those in a metastable intermol. H-bonding conformation can be tuned by the ultrasound, R (deposit) > R (gel). The increased population of the intermol. H-bonding Fmoc-OG mols. induced by the ultrasonication facilitates to the interconnection of nanofibers for the formation of the fibrous network, and therefore gelation. The alteration in the morphologies and properties of the obtained nanomaterials induced by the ultrasound wave demonstrates a potential method for smart controlling of the functions of nanomaterials from the mol. level.
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    53. 53
      Nele, V.; Wojciechowski, J. P.; Armstrong, J. P. K.; Stevens, M. M. Tailoring Gelation Mechanisms for Advanced Hydrogel Applications. Adv. Funct. Mater. 2020, 30, 2002759,  DOI: 10.1002/adfm.202002759
      53
      Tailoring Gelation Mechanisms for Advanced Hydrogel Applications
      Nele, Valeria; Wojciechowski, Jonathan P.; Armstrong, James P. K.; Stevens, Molly M.
      Advanced Functional Materials (2020), 30 (42), 2002759CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A review. Hydrogels are one of the most commonly explored classes of biomaterials. Their chem. and structural versatility has enabled their use across a wide range of applications, including tissue engineering, drug delivery, and cell culture. Hydrogels form upon a sol-gel transition, which can be elicited by different triggers designed to enable precise control over hydrogelation kinetics and hydrogel structure. The chosen hydrogelation trigger and chem. can have a profound effect on the success of the targeted application. In this Progress Report, a crit. overview of recent advances in hydrogel design is presented, with a focus on the available strategies used to trigger the formation of hydrogel networks (e.g., temp., light, ultrasound). These triggers are presented within a new classification system, and their suitability for six key hydrogel-based applications is assessed. This Progress Report is intended to guide trigger selection for new hydrogel applications and inspire the rational design of new hydrogelation trigger mechanisms.
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    54. 54
      Yu, X.; Chen, L.; Zhang, M.; Yi, T. Low-Molecular-Mass Gels Responding to Ultrasound and Mechanical Stress: Towards Self-Healing Materials. Chem. Soc. Rev. 2014, 43, 5346– 5371,  DOI: 10.1039/C4CS00066H
      54
      Low-molecular-mass gels responding to ultrasound and mechanical stress: towards self-healing materials
      Yu, Xudong; Chen, Liming; Zhang, Mingming; Yi, Tao
      Chemical Society Reviews (2014), 43 (15), 5346-5371CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      A review. In this review, we focus on the types of smart supramol. gels whose self-assembly processes are affected or even triggered by phys. forces including sonication and mech. stress (mech. force). The types of gels that are responsive to sonication and mech. stress are examd. and summarised. The gels exhibit non-covalent interactions among the gelator mols. and show dynamic and reversible properties controlled by the stimuli. Upon stimulation, the gelators cause instant and in situ gelation of org. solvents or water with different modes and outcomes of self-assembly. On the other hand, sonication and mech. stress, as external factors, can give rise to dynamic changes in microscopic morphol., optical properties, etc. Certain thixotropic supramol. gels exhibit perfect self-healing characteristics. The driving forces and the mechanism of the self-assembly process and the responsive outcome of morphol. and spectroscopic changes are discussed. Those supramol. gels responding to sonication and mech. stress offer a wide range of applications in fields such as smart and adaptive materials, switches, drug control and release, and tissue engineering.
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    55. 55
      Hueckel, T.; Hocky, G. M.; Sacanna, S. Total Synthesis of Colloidal Matter. Nat. Rev. Mater. 2021, 6, 1053– 1069,  DOI: 10.1038/s41578-021-00323-x
      55
      Total synthesis of colloidal matter
      Hueckel, Theodore; Hocky, Glen M.; Sacanna, Stefano
      Nature Reviews Materials (2021), 6 (11), 1053-1069CODEN: NRMADL; ISSN:2058-8437. (Nature Portfolio)
      A review. Atoms serve as an inspiration for colloidal self-assembly, whereby building blocks can combine and confer endless functionality using a few design principles, including directionality, valence and reversible binding. Tetrahedral structures inspired by the bonding of carbon atoms have long been targeted as candidates for metamaterials and are now becoming accessible through mol. mimetic colloidal building blocks. Beyond carbon mimics, increasingly complex particles are being synthesized that can be arranged in their own periodic table and used to generate forms of matter unique to colloidal systems. This Review presents a framework to describe the synthesis of these micrometer-scale colloids, in which the fundamental constituents are either combined through interparticle reactions or transformed through intraparticle reactions, in analogy to mols. in traditional synthetic chem. We build on this framework to illustrate how unique particle shape and surface chem. leads to diverse assembly routes for these colloidal building blocks.
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      Poon, W. Colloids as Big Atoms. Science 2004, 304, 830– 831,  DOI: 10.1126/science.1097964
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      Physics: Colloids as big atoms
      Poon, Wilson
      Science (Washington, DC, United States) (2004), 304 (5672), 830-831CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      A review. Colloid science is important for applications ranging from drugs to dairy products. Less well known is that it can also illuminate basic physics questions, because in certain crucial respects, colloids behave as 'big atoms'.
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      van Blaaderen, A. CHEMISTRY: Colloidal Molecules and Beyond. Science 2003, 301, 470– 471,  DOI: 10.1126/science.1087140
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      Chemistry: Colloidal molecules and beyond
      van Blaaderen, Alfons
      Science (Washington, DC, United States) (2003), 301 (5632), 470-471CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      A polemic in response to (V. N. Manoharan, M. T. Elsesser, D. J. Pine, Science 301, 483, 2003).
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      Yoon, J. H.; Lim, J.; Yoon, S. Controlled Assembly and Plasmonic Properties of Asymmetric Core–Satellite Nanoassemblies. ACS Nano 2012, 6, 7199– 7208,  DOI: 10.1021/nn302264f
      58
      Controlled Assembly and Plasmonic Properties of Asymmetric Core-Satellite Nanoassemblies
      Yoon, Jun Hee; Lim, Jonghui; Yoon, Sangwoon
      ACS Nano (2012), 6 (8), 7199-7208CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)
      The assembly of noble metal nanoparticles offers an appealing means to control and enhance the plasmonic properties of nanostructures. However, making nanoassemblies with easily modifiable gap distances with high efficiency was challenging. Here, the authors report a novel strategy to assemble Au nanoparticles (AuNPs) into Janus-type asym. core-satellite nanostructures. Markedly different desorption efficiency between large and small AuNPs in EtOH allows one to prep. the asym. core-satellite nanoassemblies in a dispersed colloidal state with near 100% purity. The resulting nanoassemblies have well-defined structures in which a core AuNP (51 nm) is covered by an av. of 13 ± 3 satellite AuNPs (13 nm) with part of the core surfaces left unoccupied. Strong surface plasmon coupling is obsd. from these nanoassemblies as a result of the close proximity between the core and the satellites, which appears significantly red-shifted from the surface plasmon resonance frequencies of the constituting nanoparticles. The dependence of the surface plasmon coupling on a gap distance of <3 nm is systematically studied by varying the length of the alkanedithiol linkers. The asym. core-satellite nanoassemblies also serve as an excellent surface-enhanced Raman scattering substrate with an enhancement factor of ∼106. Finally, the presented assembly method is extendible to the prepn. of compositionally heterogeneous core-satellite nanoassemblies.
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      Hentschel, M.; Dregely, D.; Vogelgesang, R.; Giessen, H.; Liu, N. Plasmonic Oligomers: The Role of Individual Particles in Collective Behavior. ACS Nano 2011, 5, 2042– 2050,  DOI: 10.1021/nn103172t
      59
      Plasmonic Oligomers: The Role of Individual Particles in Collective Behavior
      Hentschel, Mario; Dregely, Daniel; Vogelgesang, Ralf; Giessen, Harald; Liu, Na
      ACS Nano (2011), 5 (3), 2042-2050CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)
      A comprehensive exptl. study is presented of the optical properties of plasmonic oligomers. Both the constitution and configuration of plasmonic oligomers have a large influence on their resonant behavior, which draws a compelling analogy to mol. theory in chem. To elucidate the constitution influence, the size of individual nanoparticles were varied and the role identified of the target nanoparticle from the spectral change. To illustrate the configuration influence, the positions and nos. of nanoparticles in a plasmonic oligomer was varied. A large spectral red shift at the transition from displaced nanoparticles to touching ones was demonstrate exptl. The oligomeric design strategy opens up a rich pathway for the implementation of optimized optical properties into complex plasmonic nanostructures for specific applications.
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    60. 60
      Guo, Z.; Sarkar, S.; Liu, R.; Zhang, Y.; Sheng, Q.-T.; Chen, G.; König, T. A. F.; Ye, C. Dynamic Tunable Chiral Plasmonic Properties via Self-Assembly on Helical Threads. Adv. Opt. Mater. 2024, 12, 2302728,  DOI: 10.1002/adom.202302728
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      Kumar, L.; Nandan, B.; Sarkar, S.; König, T. A.; Pohl, D.; Tsuda, T.; Zainuddin, M. S. B.; Humenik, M.; Scheibel, T.; Horechyy, A. Enhanced photocatalytic performance of coaxially electrospun titania nanofibers comprising yolk-shell particles. J. Colloid Interface Sci. 2024, 674, 560– 575,  DOI: 10.1016/j.jcis.2024.06.133
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      Jain, P. K.; Huang, W.; El-Sayed, M. A. On the Universal Scaling Behavior of the Distance Decay of Plasmon Coupling in Metal Nanoparticle Pairs: A Plasmon Ruler Equation. Nano Lett. 2007, 7, 2080– 2088,  DOI: 10.1021/nl071008a
      62
      On the Universal Scaling Behavior of the Distance Decay of Plasmon Coupling in Metal Nanoparticle Pairs: A Plasmon Ruler Equation
      Jain, Prashant K.; Huang, Wenyu; El-Sayed, Mostafa A.
      Nano Letters (2007), 7 (7), 2080-2088CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
      Localized surface plasmon resonances (LSPR) in lithog. fabricated Au nanodisc pairs are studied using microabsorption spectroscopy and electrodynamic simulations. In agreement with previous work, the fractional plasmon wavelength shift for polarization along the interparticle axis decays nearly exponentially with the interparticle gap. The decay length is roughly ∼0.2 in units of the particle size for different nanoparticle size, shape, metal type, or medium dielec. const. The near-exponential distance decay and the interesting universal scaling behavior of interparticle plasmon coupling can be qual. explained from a dipolar-coupling model as being due to the interplay of 2 factors: the direct dependence of the single-particle polarizability on the cubic power of the particle dimension and the decay of the plasmonic near-field as the cubic power of the inverse distance. Using this universal scaling behavior, the authors are able to derive a plasmon ruler equation that ests. the interparticle sepn. between Au nanospheres in a biol. system from the obsd. fractional shift of the plasmon band. Agreement was found of the interparticle sepns. estd. using this equation with the exptl. observations of Reinhard et al. (2005).
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      Zheng, Y.; Zhong, X.; Li, Z.; Xia, Y. Successive Seed-Mediated Growth for the Synthesis of Single-Crystal Gold Nanospheres with Uniform Diameters Controlled in the Range of 5–150 nm. Part. Part. Syst. Char. 2014, 31, 266– 273,  DOI: 10.1002/ppsc.201300256
      63
      Successive, Seed-Mediated Growth for the Synthesis of Single-Crystal Gold Nanospheres with Uniform Diameters Controlled in the Range of 5-150 nm
      Zheng, Yiqun; Zhong, Xiaolan; Li, Zhiyuan; Xia, Younan
      Particle & Particle Systems Characterization (2014), 31 (2), 266-273CODEN: PPCHEZ; ISSN:1521-4117. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A simple and robust route is described to the synthesis of single-crystal Au nanospheres with diams. controlled in the range 5-150 nm. The success of this synthesis relies on the use of single-crystal Au spheres with different diams. as the seeds for successive growth and the use of a slow injection rate for the precursor to enable surface diffusion for the atoms added onto the surface of a seed. The diams. could be precisely controlled by varying the size and/or no. of the seeds. The products exhibit excellent uniformity in terms of both size and shape and they are expected to find widespread use in a no. of applications, including self-assembly, fabrication of metallodielec. photonic crystals, plasmonics, and biomedical research.
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      There is no corresponding record for this reference.
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      Johnson, P. B.; Christy, R. W. Optical Constants of the Noble Metals. Phys. Rev. B: Solid State 1972, 6, 4370– 4379,  DOI: 10.1103/PhysRevB.6.4370
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      Optical constants of the noble metals
      Johnson, P. B.; Christy, R. W.
      Physical Review B: Solid State (1972), 6 (12), 4370-9CODEN: PLRBAQ; ISSN:0556-2805.
      The optical consts. n and k were obtained for Cu, Ag, and Au from reflection and transmission measurements on vacuum-evapd. thin films at room temp., in the spectral range 0.5-6.5 eV. The film-thickness range was 185-500 Å. Three optical measurements were inverted to obtain the film thickness d as well as n and k. The estd. error in d was ±2 Å, and that in n, k was <0.02 over most of the spectral range. The results in the film-thickness range 250-500 Å were independent of thickness, and were unchanged after vacuum annealing or aging in air. The free-electron optical effective masses and relaxation times derived from the results in the near ir agreed satisfactorily with previous values. The interband contribution to the imaginary part of the dielec. const. was obtained by subtracting the free-electron contribution. Some recent theor. calcns. were compared with the results for Cu and Au. In addn., some other recent expts. are crit. compared with the present results.
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  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsnano.4c10912.

    • Details of chemicals, characterization methods, and equipment; detailed polymer functionalization conditions for each A-NP and B-NP sample; detailed self-assembly conditions for each PM sample; coordination number statistics; synthesis route, SEC results, and 1H NMR spectra of the synthesized polymer; UV–vis and DLS results from an additional AB6SBS experimental series; additional SEM images; modeling used for FDTD-based simulations; TEM images of A-NPs and B-NPs; additional simulation results; ultrasonication setup; and thermogravimetric analysis results (PDF)

    • Initial ultrasonication process to assemble A- and B-NPs into PMs (AVI)

    • Post-ultrasonication process (AVI)


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