Wet chemistry in organic solvents has proven highly efficient for the preparation of several types of metallic, metal-oxide, and semiconductor nanostructures. This Short Review focuses on the use of oleylamine (OAm) as a versatile reagent for the synthesis of various nanoparticle systems. We describe the ability of OAm to act as a surfactant, solvent, and reducing agent, as a function of other synthesis parameters. We also discuss the specific role of OAm either alone or in combination with other reactants, to form nanostructures using a variety of organic or inorganic compounds as precursors. In certain cases OAm can form complex compounds with the metal ions of the corresponding precursor, leading to metastable compounds that can act as secondary precursors and thus be decomposed in a controlled way to yield nanoparticles. We also point out that OAm-stabilized particles can often be dispersed in different organic solvents yielding solutions with enhanced colloidal stability over long times and the potential to find applications in a number of different fields.

A novel proton-conducting material, BaScO₂(OH) has been successfully fabricated. The known high-temperature proton conductors are typically perovskite-type oxides, in which the proton concentration is determined by hydration reaction of oxygen vacancies introduced by a small amount of acceptor dopant. On the other hand, the novel material BaScO₂(OH) is still associated with the A²⁺B⁴⁺O₃ perovskite structure but with the B-site cation fully consisting of an acceptor cation Sc³⁺, which facilitates to retain an appreciable amount of protonic defects. While it is difficult to obtain the material by simply hydrating the unhydrated form (Ba₂Sc₂O₅), a combination of a new low-temperature sol–gel synthesis and ultrahigh-pressure (4 GPa) compaction at room-temperature enables us to obtain the heavily hydrated phase BaScO₂(OH) due to on-synthesis hydration. The BaScO₂(OH) synthesized has been proved to be a pseudocubic perovskite phase with XRD and Raman analyses. The thermal dehydration analyses have verified the composition BaScO₂(OH) in terms of proton concentration, and their mobile nature has been observed with in situ FT-IR analysis. The protonic conductivity of the material is as high as 1.7 × 10^–2 S·cm^–1 at 500 °C, which is well higher than the total conductivity of the best proton-conducting perovskite oxides at intermediate temperature range.

Single layer boron-doped graphene layers have been grown on polycrystalline copper foils by chemical vapor deposition using methane and diborane as carbon and boron sources, respectively. Any attempt to deposit doped layers in one-step has been fruitless, the reason being the formation of very reactive boron species as a consequence of diborane decomposition on the Cu surface, which leads to disordered nonstoichiometric carbides. However, a two-step procedure has been optimized: as a first step, the surface is seeded with pure graphene islands, while the boron source is activated only in a second stage. In this case, the nonstochiometric boron carbides formed on the bare copper areas between preseeded graphene patches can be exploited to easily release boron, which diffuses from the peripheral areas inward of graphene islands. The effective substitutional doping (of the order of about 1%) has been demonstrated by Raman and photoemission experiments. The electronic properties of doped layers have been characterized by spatially resolved photoemission band mapping carried out on single domain graphene flakes using a photon beam with a spot size of 1 μm. The whole set of experiments allow us to clarify that boron is effective at promoting the anchoring carbon species on the surface. Taking the cue from this basic understanding, it is possible to envisage new strategies for the design of complex 2D graphene nanostructures with a spatially modulated doping.

A new cross-linked micelle pH nanosensor design was investigated. The nanosensor synthesis was based on self-assembly of an amphiphilic triblock copolymer, poly(ethylene glycol)-b-poly(2-amino ethyl methacrylate)-b-poly(coumarin methacrylate) (PEG-b-PAEMA-b-PCMA), which was synthesized by isolated macroinitiator atom transfer radical polymerization. Micelles were formed by PEG-b-PAEMA-b-PCMA self-assembly in water, giving micelles with an average diameter of 45 nm. The PCMA core was employed to utilize coumarin-based photoinduced cross-linking in the core of the micelles, which was performed by UV irradiation (320 nm < λ < 500 nm), and the progress of the cross-linking was monitored by UV spectroscopy. The formed cross-linked core–shell–corona micelle was converted into ratiometric pH nanosensors by binding the pH-sensitive fluorophores oregon green 488 and 2′,7′-bis-(2-carboxyethyl)-5-(and-6) carboxyfluorescein and a reference fluorophore Alexa 633 to the PAEMA shell region of the micelles. Fluorescence measurements show that these pH nanosensors are sensitive in a surprisingly broad pH range of 3.4–8.0, which is hypothesized to be due to small differences in the individual fluorophores’ local environement. It was found that the utilization of self-organization principles to form the nanoparticles, followed by cross-linking to ensure sensor integrity, provides a fast and highly flexible method that can be utilized in a broad range of nanosensor designs.

The synthesis of the first delaminated borosilicate layered zeolite precursor is described, along with its aluminosilicate analogue, which consists of Al-containing UCB-3 and B-containing UCB-4 from as-made SSZ-70. In addition, the delamination of PREFER (which is the precursor to ferrierite zeolite) under similar conditions yields delaminated layered zeolite precursors consisting of Al-containing UCB-5 and Ti-containing UCB-6. Multinuclear solid-state NMR spectroscopy (¹¹B and ²⁷Al), diffuse-reflectance UV-vis spectroscopy, and heteroatom/Si ratios measured via elemental analysis are consistent with a lack of heteroatom leaching from the framework following delamination. Such mild delamination conditions are achieved by swelling the zeolite precursor in a fluoride/chloride surfactant mixture in DMF solvent, followed by sonication. Powder X-ray diffraction, argon gas physisorption, and chemisorption of bulky base probes strongly suggest delamination, and demonstrate a 1.5-fold increase in the number density of external acid sites and surface area of calcined UCB-3, relative to calcined Al-SSZ-70. The synthesis of microporous pockets in materials UCB-3–UCB-5 suggests the possibility of interlayer porosity in SSZ-70, which is a layered zeolite precursor material whose structure remains currently unknown. The mildness of the delamination method presented here, as well as the lack of need for acidification in the synthesis procedure, enables the delamination of heteroatom-containing zeolites while preserving the framework integrity of labile heteroatoms, which could otherwise be leached under harsher conditions.

Superparamagnetic FeAs nanoparticles with a fairly high blocking temperature (T_B) have been synthesized through a hot injection precipitation technique. The synthesis involved usage of triphenylarsine (TPA) as the As precursor, which reacts with Fe(CO)₅ by ligand displacement at moderate temperatures (300 °C). Addition of a surfactant, hexadecylamine (HDA), assists in the formation of the nanoparticles, due to its coordinating ability and low melting point which provides a molten flux like condition making this synthesis a solventless method. Decomposition of the carbonaceous precursors, HDA, TPA and Fe(CO)₅, also produces the carbonaceous shell coating the FeAs nanoparticles. Magnetic characterization of these nanoparticles revealed the superparamagnetic nature of these nanoparticles with a perfect anhysteretic nature of the isothermal magnetization above T_B. The T_B observed in this system was indeed high (240 K) when compared with other superparamagnetic systems conventionally utilized for magnetic storage devices. It could be further increased by decreasing the strength of the applied magnetic field. The narrow hysteresis with low magnitude of coercivity at 5 K suggested soft ferromagnetic ordering in these nanoparticle ensembles. Mössbauer and XPS studies indicated that the Fe was present in +3 oxidation state and there was no signature of Fe(0) that could have been responsible for the increased magnetic moment and superparamagnetism. Typically for superparamagnetic nanoparticle ensemble, the need for isolation of the superparamagnetic domains (thereby inhibiting particle aggregation and enhancing the T_B) has been in constant limelight. Carbonaceous coating on these as-synthesized nanoparticles formed in situ provided the physical nonmagnetic barrier needed for such isolation. The high T_B and room temperature magnetic moment of these FeAs@C nanoparticles also make them potentially useful for applications in ferrofluids and magnetic refrigeration. In principle this method can be used as a general route toward synthesis of other arsenide nanostructures including the transition metal arsenide which show interesting magnetic and electronic properties (e.g., CoAs, MnAs) with finer control over morphology, composition and structure.

A major limitation of solid-state dye-sensitized solar cells is a short electron diffusion length, which is due to fast recombination between electrons in the TiO₂ electron-transporting layer and holes in the 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (Spiro-OMeTAD) hole-transporting layer. In this report, the sensitizing dye that separates the TiO₂ from the Spiro-OMeTAD was engineered to slow recombination and increase device performance. Through the synthesis and characterization of three new organic D-π-A sensitizing dyes (WN1, WN3, and WN3.1), the quantity and placement of alkyl chains on the sensitizing dye were found to play a significant role in the suppression of recombination. In solid-state devices using Spiro-OMeTAD as the hole-transport material, these dyes achieved the following efficiencies: 4.9% for WN1, 5.9% for WN3, and 6.3% for WN3.1, compared to 6.6% achieved with Y123 as a reference dye. Of the dyes investigated in this study, WN3.1 is shown to be the most effective at suppressing recombination in solid-state dye-sensitized solar cells, using transient photovoltage and photocurrent measurements.

Carbon-supported Pt (Pt/C) catalyst was selectively functionalized with thermally responsive poly(N-isopropylacrylamide) (PNIPAM) to improve water transport in the cathode of proton exchange membrane fuel cell (PEMFC). Amine-terminated PNIPAM selectively reacted with the functional group of −COOH on carbon surfaces of Pt/C via the amide reaction by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) as a catalyst. Pt surfaces of Pt/C were intact throughout the carbon surface functionalization, and the carbon surface property could be thermally changed. The PNIPAM-functionalized Pt/C was well-dispersed, because of its hydrophilic surface property at room temperature during the catalyst ink preparation. In sharp contrast, when PEMFC was operated at 70 °C, PNIPAM-coated carbon surface of Pt/C became hydrophobic, which resulted in a decrease in water flooding in the cathode electrode. Because of the switched wetting property of the carbon surface, PEMFC with PNIPAM-functionalized Pt/C catalyst in the cathode showed high performance in the high current density region. To explain the enhanced water transport, we proposed a simple index as the ratio of systematic pressure (driving force) and retention force. The synthetic method presented here will provide a new insight into various energy device applications using organic and inorganic composite materials and functional polymers.

Ti-doped BiFeO₃ ceramics prepared by a mixed-oxide route were structurally characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM), giving evidence of the formation of an inner structure at the nanometric scale. The observed nanograins are separated by Ti-rich areas that originate due to the tendency of the titanium dopant to segregate from the perovskite lattice. Such a peculiar nanostructure is responsible for the changes produced in both the electrical and the magnetic properties of BiFeO₃ upon titanium doping: the Ti-rich interfaces act as resistive layers that increase the direct-current (dc) resistivity of the material, while the existence of structural domains in the scale of tens of nanometers causes a ferrimagnetic-like behavior with a huge coercive field (on the order of 20 kOe), even at room temperature.

A novel covalent triazine framework (CTF-0) was prepared by trimerization of 1,3,5-tricyanobenzene in molten ZnCl₂. The monomer/ZnCl₂ ratio, the reaction time, and temperature significantly influence the structure and porosity of such networks. XRD measurements revealed that crystalline frameworks can be formed with surface areas around 500 m²·g^–1 and high CO₂ uptakes. Increasing the reaction temperature yielded an amorphous material with an enlarged surface area of 2000 m²·g^–1. This material showed good catalytic activity for CO₂ cycloaddition.

Here, molten salt syntheses (MSS) are coupled with ultrasonic spray pyrolysis to yield single-crystalline Fe₂O₃ nano- and microparticles with controlled shapes and phases. It was previously demonstrated that aerosol-assisted MSS can produce single-crystalline nanoplates. Now, by selecting different molten salt flux components, various crystalline phases and particle shapes are accessed via the dissolution of Fe₂O₃ colloids, followed by precipitation of the iron oxide products from molten alkali carbonates that are spatially and temporally confined in the aerosol phase. This confinement limits crystal growth to the nanoscale and provides access to products at different stages of supersaturation. The resulting powders consist of hexagonal nanoplates (α- or γ-Fe₂O₃), rhombohedra (α-Fe₂O₃), or octahedra (LiFe₅O₈) depending on the selected molten salt flux. Significantly, this synthetic approach represents a continuous and potentially general route to the generation of shape- and phase-controlled nano- and microcrystals given the diversity of materials previously prepared by molten salt techniques.

Unexpected, excellent antisintering property of highly loaded AuNPs is observed when extra-large mesoporous silica EP-FDU-12 (cage size >25 nm) is used as the supports. The average particle size of the entrapped AuNPs after 550 °C calcination approaches 25.6 ± 5.2 nm at the gold loading amount of 5.0 wt %, but it greatly reduces into only 5.6 ± 1.2 nm as the metal loading reaches up to 26.1 wt %. It is demonstrated that the unique three-dimensional porous structure of EP-FDU-12 makes particle-migration difficult to occur and thus prevents direct particle–particle aggregation. This further allows two or more AuNPs to be encapsulated in every extra-large cage at high particle concentrations (10–35 wt %), which enables interparticle interactions via significant overlapping of the diffusion-spheres of AuNPs. As a result, atom-migration via vapor from cage to cage is largely shut off and local vapor-particle equilibrium within each cage is possible, leading to a successful stable AuNPs/mesoporous silica system.

A manganese oxide-based, thermochemical cycle for water splitting below 1000 °C has recently been reported. The cycle involves the shuttling of Na⁺ into and out of manganese oxides via the consumption and formation of sodium carbonate, respectively. Here, we explore the combinations of three spinel metal oxides and three alkali carbonates in thermochemical cycles for water splitting and CO₂ reduction. Hydrogen evolution and CO₂ reduction reactions of metal oxides with a given alkali carbonate occur in the following order of decreasing activity: Fe₃O₄ > Mn₃O₄ > Co₃O₄, whereas the reactivity of a given metal oxide with alkali carbonates declines as Li₂CO₃ > Na₂CO₃ > K₂CO₃. While hydrogen evolution and CO₂ reduction reactions occur at a lower temperature on the combinations with the more reactive metal oxide and alkali carbonate, higher thermal reduction temperatures and more difficult alkali ion extractions are observed for the combinations of the more reactive metal oxides and alkali carbonates. Thus, for a thermochemical cycle to be closed at low temperatures, all three reactions of hydrogen evolution (CO₂ reduction), alkali ion extraction, and thermal reduction must proceed within the specified temperature range. Of the systems investigated here, only the Na₂CO₃/Mn₃O₄ combination satisfies these criteria with a maximum operating temperature (850 °C) below 1000 °C.

We report the synthesis and characterization of thienylenevinylene-based donor–acceptor alternating copolymers (PTVPhI-Eh and PTVPhI-C12) as highly efficient ambipolar semiconductors in a thin film transistor. These polymers exhibit significantly improved hole and electron mobilities after thermal annealing. To determine the relationship between ambipolar charge transport and thermal annealing, we investigated these polymers using various analyses such as optical spectroscopy, Raman spectroscopy, computational quantum chemical calculation, X-ray diffraction, atomic force microscopy, and ambipolar charge mobility measurements. In pristine films, the polymer chains exhibited weak intra- and interchain ordering. However, when samples were annealed at sufficiently high temperatures, they exhibited a more ordered intra- and interchain conformation. As a result, we found a strong relationship between intra- and interchain conformational changes of the polymers and corresponding ambipolar charge transport properties during thermal annealing processes. Finally, we demonstrate complementary-like ambipolar inverters using a PTVPhI-Eh polymer. The largely shifted inverting voltage was improved for the thermally annealed inverters, which exhibited large voltage gains (∼40).

Highly ordered sulfonic acid functionalized mesoporous silica films with various pore sizes (2.2–3.9 nm) and acid densities (0.78–2.3 mmol g^–1) were successfully prepared by the Evaporation Induced Self-Assembly (EISA) process using tetramethoxysilane and 3-mercaptopropyltrimethoxysilane as starting materials. The relationship between the proton diffusivity and the water sorption process in the nanopores was clarified in detail by these mesoporous films. The proton conductivity of mesoporous films increased steeply according to the capillary condensation of water in the uniform mesopores. This steep increase of proton conductivity was controlled by the pore size and the acid density described by the Kelvin equation. Notably, the mesoporous electrolyte with the smallest pore size (2.2 nm) and the highest acid density (2.3 mmol g^–1) showed the highest proton conductivity at low relative humidity (RH) [e.g., 5.4 × 10^–3 S cm^–1 (25 °C) at 20% RH]. Furthermore, the proton diffusivity in the mesopores was enhanced by the high densification of sulfonic acid groups even at very small amounts of adsorbed water [λ(H₂O/SO₃H) = 2].

Adsorption and release of the biologically active nitric oxide (NO) was evaluated over a series of highly flexible iron(III) dicarboxylate MOFs of the MIL-88 structure type, bearing fumaric or terephthalic spacer functionalized or not by polar groups (NO₂, 2OH). As evidenced by ex situ X-ray powder diffraction and in situ IR spectroscopy, it appears that if the contracted dried forms of MIL-88 do not expand their structures in the presence of NO, the combination of very narrow pores and trimers of iron polyhedra leads to the adsorption of significant amounts of NO either physisorbed (very narrow pores) and/or chemisorbed [iron(II) or iron(III) coordinatively unsaturated metal sites (CUS)]. The delivery of NO under vapor of water or in simulated body fluid does not exceed 20% range of the total adsorbed amount probably due to a partial release that occurs between the adsorption/desorption setup and the chemiluminescence release tests. Some of these solids nevertheless exhibit a significant release at the biological levels over a long period of time (>16 h) that make these biocompatible and biodegradable MOFs of interest for the controlled release of NO.

The red long-lasting luminescence properties of the ZnGa₂O₄:Cr³⁺ spinel material are shown to be much improved when germanium or tin is substituted to the nominal composition. The resulting Zn_1+xGa_2–2x(Ge/Sn)_xO₄ (0 ≤ x ≤ 0.5) spinel solid solutions synthesized here by a classic solid state method have been structurally characterized by X-ray and neutron powder diffraction refinements coupled to ⁷¹Ga solid state NMR studies. In contrast to ZnGa₂O₄:Cr³⁺ for which long lasting luminescence properties have been reported to arise from tetrahedral positively charged defects resulting from the spinel inversion, our results show that a different mechanism occurs complementary for Zn_1+xGa_2–2x(Ge/Sn)_xO₄. Here, the great enhancement of the brightness and decay time of the long lasting luminescence properties is directly driven by the substitution mechanism which creates distorted octahedral sites surrounded by octahedral Ge and Sn positive substitutional defects which likely act as new efficient traps.

Lanthanum lithium titanate (LLTO) is one of the most promising electrolyte materials for all-solid-state lithium-ion batteries. Despite numerous studies, the detailed crystal structure is still open to conjecture because of the difficulty of identifying precisely the positions of Li atoms and the distribution of intrinsic cation vacancies. Here we use subangstrom resolution scanning transmission electron microscopy (STEM) imaging methods and spatially resolved electron energy loss spectroscopy (EELS) analysis to examine the local atomic structure of LLTO. Direct annular bright-field (ABF) observations show Li locations on O4 window positions in Li-poor phase La_0.62Li_0.16TiO₃ and near to A-site positions in Li-rich phase La_0.56Li_0.33TiO₃. Local clustering of A-site vacancies results in aggregation of Li atoms, enhanced octahedral tilting and distortion, formation of O vacancies, and partial Ti⁴⁺ reduction. The results suggest local LLTO structures depend on a balance between the distribution of A-site vacancies and the need to maintain interlayer charge neutrality. The associated local clustering of A-site vacancies and aggregation of Li atoms is expected to affect the Li-ion migration pathways, which change from two-dimensional in Li-poor LLTO to three-dimensional in Li-rich LLTO. This study demonstrates how a combination of advanced STEM and EELS analysis can provide critical insights into the atomic structure and crystal chemistry of solid ionic conductors.

Iron pyrite (FeS₂) is a promising photovoltaic absorber because of its Earth abundance, high optical extinction, and infrared band gap (E_g = 0.95 eV), but its use has been hindered because of the difficulty of phase pure synthesis. Pyrite phase purity is a paramount concern, as other phases of iron sulfide have undesirable electronic properties. Here we report the synthesis of phase pure iron pyrite nanocrystals with cubic morphology and a mean dimension of 80 nm. Control over the nanocrystal shape was achieved using an unusual ligand, 1-hexadecanesulfonate. The particles were characterized via synchrotron X-ray spectroscopy, indicating an indirect band gap of 1.00 ± 0.11 eV and a valence bandwidth of nearly 1 eV. Transmission electron microscopy from early reaction stages suggests a nucleation and growth mechanism similar to solution precipitation syntheses typical of metal oxide nanocrystals, rather than the diffusion-limited growth process typical of hot-injection metal chalcogenide nanocrystal syntheses.

Dynamic structural changes during the first electrochemical charge and discharge cycle in the Li-excess layered oxide compound, Li[Li_1/5Ni_1/5Mn_3/5]O₂, are studied with synchrotron X-ray diffraction (SXRD), aberration corrected scanning transmission electron microscopy (a-S/TEM), and electron energy loss spectroscopy (EELS). At different states of charge, we carefully examined the crystal structures and electronic structures within the bulk and have found that increased microstrain is accompanied with the cation migration and a second phase formation which occurs during the first cycle voltage plateau as well as into the beginning of the discharge cycle. The evidence indicates that the oxygen vacancy formation and activation may facilitate cation migration and results in the formation of a second phase. The EELS results reveal a Mn valence change from 4+ to 3+ upon oxygen vacancy formation and recovers back to 4+ at the discharge. The oxygen vacancy formation and activation at the partially delithiated state leads to the generation of several crystal defects which are observed in TEM. Identification of the correlation between microstrain and oxygen vacancy formation during the first electrochemical cycle clarifies the complex intercalation mechanisms that accounts for the anomalous capacities exceeding 200 mAh/g in the Li-excess layered oxide compounds.

A series of novel porous polymer frameworks (PPFs) with [3 + 4] structure motif have been synthesized from readily accessible building blocks via imine condensation, and the dependence of gas adsorption properties on the building block dimensions and functionalities was studied. The resulting imine-linked frameworks exhibit high surface area: the Brunauer–Emmett–Teller (BET) specific surface area up to 1740 m² g^–1, and a Langmuir surface area up to 2157 m² g^–1. More importantly, the porous frameworks exhibit outstanding H₂ (up to 2.75 wt %, 77 K, 1 bar), CO₂ (up to 26.7 wt %, 273 K, 1 bar), CH₄ (up to 2.43 wt %, 273 K, 1 bar), and C₂H₂ (up to 17.9 wt %, 273 K, 1 bar) uptake, which are among the highest reported for organic porous materials. PPFs exhibit good ideal selectivities for CO₂/N₂ (14.5/1–20.4/1), and CO₂/CH₄ adsorption (8.6/1–11.0/1), and high thermal stabilities (up to 500 °C), thus showing a great potential in gas storage and separation applications.

Porous materials based on aluminum(III) 2-aminoterephthalate metal organic frameworks (MOFs NH₂MIL101(Al) and NH₂MIL53(Al)) and their composites with aluminum isopropoxide (Al-i-Pro) are studied as sorbents of vapors of volatile aldehydes and catalysts of acetaldehyde dimerization to ethyl acetate via the Tischenko reaction. MOF/Al-i-Pro composites obtained by simple impregnation of the MOFs with hydrocarbon solutions of Al-i-Pro are stable due to the formation of bonds between the MOF carbonyls and Al-i-Pro. The specific BET surface areas of the MOFs NH₂MIL101(Al) and NH₂MIL53(Al) ranged from 1650 to 1980 and 670–780 m²/g, respectively, and were lowered 6–12-fold by impregnation of Al-i-Pro into the MOF pores. However, the acetaldehyde and acrolein uptake by the MOF/Al-i-Pro composites from saturated vapor atmosphere is comparable to that of their respective parent MOFs and exceeds the aldehyde uptake of activated carbon or molecular sieves. Due of the propensity of the Al-i-Pro to catalyze dimerization of acetaldehyde to ethyl acetate, the latter is the main product of the reaction between acetaldehyde and MOF/Al-i-Pro materials, whereas crotonaldehyde is found in the products of the acetaldehyde self-condensation on the parent MOF NH₂MIL101(Al). The kinetics of acetaldehyde dimerization into ethyl acetate catalyzed by NH₂MIL101(Al)/Al-i-Pro in deuterated benzene at room temperature are measured over three consecutive cycles. The apparent second-order reaction rate is 5.2 × 10^–5 M^–1s^–1, which is of the same order as in the analogous reaction catalyzed by a homogeneous solution of Al-i-Pro. The MOF/Al-i-Pro materials are proven to be recyclable heterogeneous catalysts.

The evolution of the surface morphology of thermally annealed copper foils utilized for graphene growth by Chemical Vapor Deposition (CVD) has been studied by Scanning Tunneling Microscopy, Scanning Electron Microscopy, and optical microscopy to determine the effect of pretreatment and preannealing steps that aimed to increase grain size and reduce surface roughness for subsequent graphene growth. The results of the study show that (a) Fe(NO₃)₃ etch pretreatment leaves residue and etch quarries on the Cu surface even after thermal annealing, (b) certain preannealing processes yield a crust layer on the foil that can peel off, (c) graphene film can preserve an imprint of the Cu film grain structure after being transferred onto SiO₂ substrate, and (d) graphene/Cu surface height variations remain much larger than the diameter of the carbon atom over micrometer length scales. Nevertheless, good quality graphene can be grown on the rough Cu surface, and a layer of graphene on top of the copper reduces its apparent surface roughness.

The influence of clay-layer spacing on gas barrier thin films of sodium montmorillonite clay and polyelectrolytes, created via layer-by-layer assembly, is investigated. The alternate deposition of polymers and clay leads to the assembly of a nanobrick wall structure that is highly impermeable to gases. In an effort to tailor the thickness (or spacing) between clay layers, films with differing numbers of polymer layers between clay depositions were examined. Films analyzed for their thickness, clay concentration, transparency, nanostructure, and oxygen barrier as a function of layers (or spacing) between clay depositions reveal linear growth, optical clarity, and low OTR at 100 nm thick and containing only four clay layers. An optimal thickness between clay layers appears to exist for achieving the highest oxygen barrier LbL films (PO₂ < 1 × 10^–21 cc(STP)·cm/(cm²·s·Pa)). This knowledge can ultimately minimize deposition steps and lead to decreased thin film fabrication times.

Lithium fluoride is an interesting material because of its low refractive index and large band gap. Previously LiF thin films have been deposited mostly by physical methods. In this study a new way of depositing thin films of LiF using atomic layer deposition (ALD) is presented. Mg(thd)₂, TiF₄ and Lithd were used as precursors, and they produced crystalline LiF at a temperature range of 300–350 °C. The films were studied by UV–vis spectrometry, field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), atomic force microscopy (AFM), time-of-flight elastic recoil detection analysis (ToF-ERDA), and energy dispersive X-ray spectroscopy (EDX). In addition, film adhesion was tested by a Scotch tape test. This method results in LiF films with a growth rate of approximately 1.4 Å per cycle. According to the ToF-ERDA measurements, the films are pure LiF with very small Mg and Ti impurities, the largest impurity being hydrogen with contents below 1 atom %.

The chemical phase distribution in hydrothermally grown micrometric single crystals of LiFePO₄ following partial chemical delithiation was investigated. Full field and scanning X-ray microscopy were combined with X-ray absorption spectroscopy at the Fe and O K-edges, respectively, to produce maps with high chemical and spatial resolution. The resulting information was compared to morphological insight into the mechanics of the transformation by scanning transmission electron microscopy. This study revealed the interplay at the mesocale between microstructure and phase distribution during the redox process, as morphological defects were found to kinetically determine the progress of the reaction. Lithium deintercalation was also found to induce severe mechanical damage in the crystals, presumably due to the lattice mismatch between LiFePO₄ and FePO₄. Our results lead to the conclusion that rational design of intercalation-based electrode materials, such as LiFePO₄, with optimized utilization and life requires the tailoring of particles that minimize kinetic barriers and mechanical strain. Coupling TXM-XANES with TEM can provide unique insight into the behavior of electrode materials during operation, at scales spanning from nanoparticles to ensembles and complex architectures.

We report synthesis, characterization, and properties of a multifunctional oxalate framework, {KDy(C₂O₄)₂(H₂O)₄}_n (1) (C₂O₄^2– = oxalate dianion) composed of two absolutely different metal ions in terms of their size, charge, and electronic configuration. Dehydrated framework (1′) exhibits permanent porosity and interesting solvent (H₂O, MeOH, CH₃CN, and EtOH) vapor sorption characteristics based on specific interactions with unsaturated alkali metal sites on the pore surface. Compound 1 shows solvent responsive bimodal magnetic and luminescence properties related to the Dy^III center. Compound 1 exhibits reversible ferromagnetic to antiferromagnetric phase transition upon dehydration and rehydration, hitherto unknown for any lanthanide based coordination polymer or metal–organic frameworks. Both the compounds 1 and 1′ exhibit slow magnetic relaxation with very high anisotropic barrier (417 ± 9 K for 1 and 418 ± 7 K for 1′) which has been ascribed to the single ion magnetic anisotropy of the Dy^III centers. Nevertheless, compound 1 shows a metal based luminescence property in the visible region and H₂O molecules exhibit the strongest quenching effect compared to other solvents MeOH, MeCN, and EtOH, evoking 1′ as a potential H₂O sensor.

Yeelimite, Ca₄[Al₆O₁₂]SO₄, is outstanding as an aluminate sodalite, being the framework of these type of materials flexible and dependent on ion sizes and anion ordering/disordering. On the other hand, yeelimite is also important from an applied perspective as it is the most important phase in calcium sulfoaluminate cements. However, its crystal structure is not well studied. Here, we characterize the room temperature crystal structure of stoichiometric yeelimite through joint Rietveld refinement using neutron and X-ray powder diffraction data coupled with chemical soft-constraints. Our structural study shows that yeelimite has a lower symmetry than that of the previously reported tetragonal system, which we establish to likely be the acentric orthorhombic space group Pcc2, with a √2a × √2a × a superstructure based on the cubic sodalite structure. Final unit cell values were a = 13.0356(7) Å, b = 13.0350(7) Å, and c = 9.1677(2) Å. We determine several structures using density functional theory calculations, with the lowest energy structure being Pcc2 in agreement with our experimental result. Yeelimite undergoes a reversible phase transition to a higher-symmetry phase which has been characterized to occur at 470 °C by thermodiffractometry. The higher-symmetry phase is likely cubic or pseudocubic possessing an incommensurate superstructure, as suggested by our theoretical calculations which show a phase transition from an orthorhombic to a tetragonal structure. Our theoretical study also predicts a pressure-induced phase transition to a cubic structure of space group I43m. Finally, we show that our reported crystal structure of yeelimite enables better mineralogical phase analysis of commercial calcium sulfoaluminate cements, as shown by R_F values for this phase, 6.9% and 4.8% for the previously published orthorhombic structure and for the one reported in this study, respectively.

We examined the effects of changing the central bridging atom identity from carbon (d-CDT(PTTh₂)₂) to silicon (d-DTS(PTTh₂)₂) in the cyclopentadithiophene unit in a small molecule donor material. The substitution left the optical and electrical properties largely unchanged but significantly modified the melting/crystallization behavior and the formation of crystalline domains in thin film blends with PC₇₁BM. Solar cells made with the d-CDT(PTTh₂)₂:PC₇₁BM had efficiencies less than 1%, while thermally annealed solar cells made with d-DTS(PTTh₂)₂:PC₇₁BM achieved efficiencies up to 3.4%. Morphological analyses of the active layer film morphology were done with polarized optical microscopy, grazing incidence wide-angle X-ray scattering, and transmission electron microscopy and showed that large (micrometer scale) crystals formed in the d-CDT(PTTh₂)₂ based films while smaller (25 to 50 nm) crystals formed in the d-DTS(PTTh₂)₂, largely explaining the difference in device performance. Thermally activated photocurrent was observed in devices suggest that the additional current at elevated temperatures results from thermally activated charge generation. Charge transfer excitons were also investigated using external quantum efficiency measurements. Sharper band tails for the small molecule donors suggest less disorder than in P3HT:PCBM and other polymer systems.

A layered sulfide, Na_0.5NbS₂ (space group: P6₃/mmc), was synthesized by a conventional solid-state reaction as an electrode material for a Na-ion battery. Galvanostatic Na insertion/extraction was performed to characterize the system Na_xNbS₂ (0 ≤ x ≤ 1.0) operating on the Nb(IV)/Nb(III) redox couple. Although the system shows a high specific capacity of 143.6 mAh g^–1, the voltage profile is not suitable with a signature of Na/vacancy ordering at x = 0.5. First-principles calculation was applied to reveal possible structures of Na_xNbS₂ and describe the corresponding electrochemical properties. The calculated Na binding energies and voltages are in good agreement with experimental charge/discharge voltages. We also found a possible atomic arrangement of Na/vacancy ordering in Na_0.5NbS₂. Although layered NaMS₂ systems allow full sodium intercalation, the strong Na⁺–Na⁺ intralayer interaction induces layer gliding and Na⁺-ion ordering that create undesirable steps in the voltage profile.

The mechanisms of growth of TiO₂ thin films by atomic layer deposition (ALD) using either acetic acid or ozone as the oxygen source and titanium isopropoxide as the metal source are investigated by in situ Fourier transform infrared spectroscopy (FTIR) and ex situ X-ray photoelectron spectroscopy. The FTIR study of the acetic acid-based process clearly shows a ligand exchange leading to the formation of surface acetate species (vibrational bands at 1527 and 1440 cm^–1) during the acetic acid pulse. Their removal during the metal alkoxide pulse takes place via the elimination of an ester and the formation of Ti–O–Ti bonds. These findings confirm the expected ester elimination condensation mechanism and demonstrate that the reaction proceeds without intermediate surface hydroxyl species. The in situ FTIR study of the O₃-based ALD process demonstrates similarities with the process described above, with formation of surface formate and/or carbonate species upon exposure of the surface titanium alkoxide species to ozone. These surface species are removed by the subsequent titanium isopropoxide pulse, leading to the formation of Ti–O–Ti bonds.

Indoline dyes exhibit impressive short-circuit photocurrent (J_SC) but show generally low open-circuit voltage (V_OC) in dye-sensitized solar cells (DSCs). To retard charge recombination in DSCs, four indoline dyes (XS41, XS42, XS43, and XS44) featuring, respectively, dipropylfluorene, hexyloxybenzene, tert-butylbenzene, and hexapropyltruxene electron donors, have been engineered. The incorporation of bulky rigid groups (i.e., dipropylfluorene and hexapropyltruxene unit) can notably retard the charge recombination at the titania/electrolyte interface. Moreover, we have developed two organic dyes (TC1 and TC2) as alternative coadsorbents to chenodeoxycholic acid (CDCA). Interestingly, it is found that regardless of the dye selection coadsorption with TC2 shows an improved V_OC as well as J_SC in comparison with its TC1 analogues. Dependence of photovoltage on the structure of TC1/TC2 was also investigated. The results suggest that the change in V_OC is likely correlated with the molecular matching between the dyes and the coadsorbents. Combining the two contributions, high V_OC in indoline-based DSCs can be realized. The results of XS41, upon coadsorption with TC2, produce a J_SC of 16.1 mA cm^–2, a V_OC of 770 mV, and a fill factor of 0.66, corresponding to a power conversion efficiency of 8.18% under simulated AM1.5G solar light (100 mW cm^–2). These findings pave a new way to achieve further efficiency enhancement of indoline dyes.

Solid-state nuclear magnetic resonance (NMR) of paramagnetic samples has the potential to provide a detailed insight into the environments and processes occurring in a wide range of technologically-relevant phases, but the acquisition and interpretation of spectra is typically not straightforward. Structural complexity and/or the occurrence of charge or orbital ordering further compound such difficulties. In response to such challenges, the present article outlines how the total Fermi contact (FC) shifts of NMR observed centers (OCs) may be decomposed into sets of pairwise metal–OC bond pathway contributions via solid-state hybrid density functional theory calculations. A generally applicable “spin flipping” approach is outlined wherein bond pathway contributions are obtained by the reversal of spin moments at selected metal sites. The applications of such pathway contributions in interpreting the NMR spectra of structurally and electronically complex phases are demonstrated in a range of paramagnetic Li-ion battery positive electrodes comprising layered LiNiO₂, LiNi_0.125Co_0.875O₂, and LiCr_0.125Co_0.875O₂ oxides; and olivine-type LiMPO₄ and MPO₄ (M = Mn, Fe, and Co) phosphates. The FC NMR shifts of all ^6/7Li and ³¹P sites are decomposed, providing unambiguous NMR-based proof of the existence of local Ni³⁺-centered Jahn–Teller distortions in LiNiO₂ and LiNi_0.125Co_0.875O₂, and showing that the presence of M²⁺/M³⁺ solid solutions and/or M/M′ isovalent transition metal (TM) mixtures in the olivine-type electrodes should lead to broad and potentially interpretable NMR spectra. Clear evidence for the presence of a dynamic Jahn–Teller distortion is obtained for LiNi_xCo_1–xO₂. The results emphasize the utility of solid-state NMR in application to TM-containing battery materials and to paramagnetic samples in general.

We report the successful multifunctional colloids that enable reversible phase transfer between organic and aqueous phases via layer-by-layer (LbL) assembly. These colloids exhibited a high level of dispersion stability in a variety of solvents ranging from nonpolar to aqueous media, based on the type of outermost layer adsorbed onto the colloids. Hydrophobic nanoparticles (NPs) synthesized using carboxylic acid or ammonium moiety-based ligands (i.e., oleic acid or tetraoctylammonium) in a nonpolar solvent (toluene, hexane, or chloroform) were directly deposited onto dendrimer-coated SiO₂ colloids via ligand exchange between the hydrophobic ligands and the amine-functionalized dendrimers in the same organic solvent. Additionally, these hydrophobic NPs were adsorbed onto the colloids forming the densely packed layer structure that could not be easily achieved by conventional electrostatic LbL assembly. The subsequent adsorption of amine-functionalized dendrimers onto hydrophobic NP-coated colloids led to well-dispersed colloids in aqueous media as well as alcohol solvent and possibly induced the deposition of electrostatic LbL-assembled films, such as (cationic Au_NP/anionic polyelectrolyte (PE))_n or (cationic PE/anionic enzyme)_n multilayers. Furthermore, the additional deposition of ligand exchange-induced multilayers (i.e., (dendrimer/hydrophobic NP)_n) onto electrostatic multilayer-coated colloids produced colloids with highly dispersible properties in organic media. Given that previous approaches to the reversible phase transfer of colloids have depended on the physicochemical properties of selective ligands under limited and specific conditions, our approach may provide a basis for the design and exploitation of high-performance colloids with tailored functionality in a variety of solvents.

Transition metal dichalcogenides, TSe₂ with T = V, Ti, and Ta, were synthesized through self-assembly of designed amorphous precursors. All three compounds formed with the expected layered transition metal dichalcogenide structure with highly preferred orientation of the TSe₂ layers aligned parallel with the substrate surface. VSe₂ and TiSe₂ self-assembled as the 1T polytype, which is the only known polytype found in the bulk form, while TaSe₂ self-assembled into a new turbostratically disordered polytype. This turbostratic disorder is common among compounds made by self-assembly of designed amorphous precursors, also known as the modulated elemental reactant synthetic approach. The data obtained in this study on the formation of transition metal dichalcogenides suggest that templated nucleation at interfaces is the self-assembly growth mechanism that produces crystallographic alignment between structural units. If there is only one potential low energy orientation for the templated nucleation of the next layer, then a crystalline polytype is formed. If there is more than one low energy orientation for the templated nucleation of the next layer, a disordered polytype, referred to as a ferecrystal, is formed.

All three polymorphs of LiVOPO₄ have been synthesized, for the first time, by a microwave-assisted solvothermal (MW-ST) method by adjusting the reaction media and conditions. The triclinic polymorph (α-LiVOPO₄) was obtained as the most stable and stoichiometric product and was thus chosen for optimization. Varying solvent mixtures consisting of water and alcohols/glycols proved to have significant effects on the particle size/morphology, with the water and glycol mixtures generally producing smaller particles. Particle size was also reduced with decreasing reaction time, decreasing reactant concentration, and CTAB surfactant addition. The electrochemical performance was analyzed in two potential ranges: 3.0–4.5 V corresponding to the insertion/extraction of one lithium and 2.0–4.5 V corresponding to the insertion/extraction of two lithium into/from the LiVOPO₄ structure. Synthesis in a mixture of water and ethylene glycol in particular led to a high capacity of 134 mAh/g during the first cycle in the 3.0–4.5 V region. Initial attempts at coating the particles with PEDOT:PSS improved the cycling performance.

Integration of other functional materials onto the surfaces or into the matrixes of metal–organic frameworks (MOFs) is a new strategy to acquire multifunctionality for MOFs. Herein, we report a novel means that can integrate ultrafine metal (Au or Ag) nanoparticles onto designated crystallographic planes of zeolitic imidazolate framework (i.e., ZIF-8). The key challenge herein is to determine appropriate surfactants that can help to generate the interaction between the incorporated metal nanoparticles and ZIF-8 phase. In our current work, single-layered metal nanoparticles have been added onto exterior surfaces and/or into interior bulk matrixes of ZIF-8 by forming coordination bonds. Such bonding is actually attained through the coordinative interaction between the surfactants of metal nanoparticles and partially coordinated Zn²⁺ions on the exterior surface of ZIF-8 crystals. Additional epitaxial growth of ZIF-8 can also be carried out, which turns the surface metal nanoparticles into ZIF-8 bulk phase. Adequate synthetic flexibility has been attained for complex architectures of metal–MOFs hybrid nanocomposites for the first time. Our Au-containing ZIF-8 also shows high catalytic activity for 4-nitrophenol reduction.

Plasma-assisted atomic layer deposition (ALD) processes were developed for the deposition of platinum films at room temperature. High-quality, virtually pure films with a resistivity of 18–24 μΩ cm were obtained for processes consisting of MeCpPtMe₃ dosing, O₂ plasma exposure, and H₂ gas or H₂ plasma exposure. The H₂ pulses were used to reduce the PtO_x that is otherwise deposited at low substrate temperatures. It is shown that the processes enable the deposition of Pt on polymer, textile, and paper substrates, which is a significant result as it demonstrates the broad application range of Pt ALD, including applications involving temperature-sensitive materials.

A synthesis route to rock salt zinc oxide (rs-ZnO), high-pressure phase metastable at ambient conditions, has been developed. High-purity bulk nanocrystalline rs-ZnO has been synthesized from wurtzite (w) ZnO nanopowders at 7.7 GPa and 770–820 K and, for the first time, recovered at normal conditions. Structure, phase composition, and thermal phase stability of recovered rs-ZnO have been studied by synchrotron X-ray powder diffraction and X-ray absorption spectroscopy (XANES and EXAFS) at ambient pressure. Phase purity of rs-ZnO was achieved by usage of w-ZnO nanoparticles with a narrow size distribution as a pristine material synthesized by various chemical methods. At ambient pressure, rs-ZnO could be stable up to 360 K. The optical properties of rs-ZnO have been studied by conventional cathodoluminescence in high vacuum at room and liquid-nitrogen temperatures. The nanocrystalline rs-ZnO at 300 and 77 K has shown bright blue luminescence at 2.42 and 2.56 eV, respectively.

A simple process for preparing mesoporous chromium nitride (CrN) by the ammonolysis of a bulk ternary oxide (K₂Cr₂O₇) is reported. The products were characterized by Rietveld refinement of powder X-ray diffraction patterns, scanning electron microscopy (SEM), and nitrogen adsorption/desorption analysis. Pore sizes ranging from 10 to 20 nm are easily accessible. The conductivity of mesoporous CrN powder compressed at 35 bar is 54 S/cm. A Pt/CrN catalyst prepared from the mesoporous CrN shows a negative onset potential for methanol electrooxidation (0.20 V vs SCE) similar to that of Pt/C (0.22 V vs SCE). The electrochemically active specific surface area (ECSA) of the Pt/CrN catalyst (82 m²/g) was only slightly higher than that of Pt/C (75 m²/g). More importantly, the Pt/CrN catalyst demonstrates high tolerance to corrosion and is a candidate to replace carbon black, which is known to corrode under high potentials, as a support for fuel cell catalysts. This work provides an efficient method for preparing mesoporous metal nitrides that are promising supports for the oxidation of small organic molecules in fuel cells.

We report a new synthetic pathway for growing monodisperse colloidal indium antimonide nanocrystals. We propose that highly reactive element-nitrogen bonded precursors, such as In and Sb amides, may provide required nucleation and growth kinetics for the formation of uniform colloidal nanocrystals of InSb. Size-dependent absorption and emission spectra of InSb nanocrystals in the near-infrared region of 1500–2000 nm point to semiconductor behavior with quantum confinement. Furthermore, we demonstrate zinc blende/wurzite polymorphism and polytypism of InSb nanocrystals, conveniently controlled by the In/Sb molar ratio of precursors. This amide-based synthesis route may open new opportunities for designing near- and mid-IR active III–V semiconductor nanostructures.

Ruthenium was deposited on SiO₂/Si(001) substrates at 473 K by chemical vapor deposition (CVD) using triruthenium dodecacarbonyl with and without an overpressure of CO. Carbon monoxide was employed to inhibit the growth of previously nucleated islands to allow the formation of additional nuclei. Carbon monoxide also competed with the precursor for free hydroxyl sites on SiO₂ sites where precursor adsorption and decomposition is favored. Total pressure was maintained at 84 mTorr, and CO was introduced at partial pressures of 2.5 and 8.4 mTorr at various intervals during 15 min growth runs. The nucleation density decreases with increasing CO overpressure when CO and precursor are injected simultaneously from the beginning; in this case, CO blocks the free hydroxyls where the Ru precursor dissociates. When 8.4 mTorr CO is introduced for 5 min to the CVD chamber after a 10 min period of deposition without CO, the maximum nucleation density was achieved (16.4 × 10¹¹/cm²), which is twice as much as the Ru particle density found for 15 min deposition without added CO. After 10 min of growth, hydroxyl groups have mostly reacted and the injected CO adsorbs on Ru nanoparticles, inhibiting growth and forcing additional Ru nucleation on the SiO₂ substrate. Growth was extended to 2 h to explore the influence of CO on ultrathin Ru film characteristics. The film grown without CO for 10 min and then with 8.4 mTorr CO for 1 h 50 min was thinner and smoother than the film grown without CO for 2 h because CO adsorption on the Ru surface slows the Ru islands/film growth rate.

Reaction of the anion-deficient, cation-ordered perovskite phase Ba₂YFeO₅ with 80 atm of oxygen pressure at 410 °C results in the formation of the Fe⁴⁺ phase Ba₂YFeO_5.5. The topochemical insertion of oxide ions lifts the inversion symmetry of the centrosymmetric host phase, Ba₂YFeO₅ (space group P2₁/n), to yield a noncentrosymmetric (NCS) phase Ba₂YFeO_5.5 (space group Pb2₁m (No. 26), a = 12.1320(2) Å, b = 6.0606(1) Å, c = 8.0956(1) Å, V = 595.257(2) ų) confirmed by the observation of second-harmonic generation. Dielectric and PUND ferroelectric measurements, however, show no evidence for a switchable ferroelectric polarization, limiting the material to pyroelectric behavior. Magnetization and low-temperature neutron diffraction data indicate that Ba₂YFeO_5.5 undergoes a magnetic transition at 20 K to adopt a state which exhibits a combination of ferromagnetic and antiferromagnetic order. The symmetry breaking from centrosymmetric to polar noncentrosymmetric, which occurs during the topochemical oxidation process is discussed on the basis of induced lattice strain and an electronic instability and represents a new strategy for the preparation of NCS materials that readily incorporate paramagnetic transition metal centers.

The transport properties of Tl_xCr₅Se₈ pseudo-hollandite have been investigated, from 2 up to 800 K. A semiconducting behavior is observed from 200 down to 2 K, with a transition observed at T ∼ 43 K, at the antiferromagnetic transition. Above 200 K, small values of ρ are obtained, close to 10 mΩ·cm at 800 K. The Seebeck coefficient continuously increases in this range of temperature, reaching 300 μV/K at 800 K. Moreover, the thermal conductivity of this low dimensional structure is small, leading to a figure of merit ZT = S²T/(ρκ) = 0.5 at 800 K. All the electronic transport properties can be fitted by a standard Boltzmann equation, with a large scattering parameter (r = 3/2, characteristic of diffusion by ionized impurities). The combination of small thermal conductivity, large scattering parameter, and low concentration of carriers (4.5 × 10¹⁹ cm^–3) is at the origin of this large ZT.

Silicon and germanium nanowires are grown in high density directly from a tin layer evaporated on stainless steel. The nanowires are formed in low cost glassware apparatus using the vapor phase of a high boiling point organic solvent as the growth medium. HRTEM, DFSTEM, EELS, and EDX analysis show the NWs are single crystalline with predominant ⟨111⟩ growth directions. Investigation of the seed/nanowire interface shows that in the case of Si an amorphous carbon interlayer occurs that can be removed by modifying the growth conditions. Electrochemical data shows that both the tin metal catalyst and the semiconductor nanowire reversibly cycle with lithium when the interface between the crystalline phases of the metal and semiconductor is abrupt. The dually active nanowire arrays were shown to exhibit capacities greater than 1000 mAh g^–1 after 50 charge/discharge cycles.

The rich phase behavior of 5,11-bis(triethylsilylethynyl) anthradithiophene (TES ADT) – one of the most promising, solution-processable small-molecular organic semiconductors – is analyzed, revealing the highest performing polymorph among four solid-state phases, opening pathways toward the reliable fabrication of high-performance bottom-gate/bottom-contact transistors.

The neutral complexes [GaCl₃(EⁿBu₂)] (E = Se or Te), [(GaCl₃)₂{ⁿBuE(CH₂)_nEⁿBu}] (E = Se, n = 2; E = Te, n = 3), and [(GaCl₃)₂{^tBuTe(CH₂)₃Te^tBu}] are conveniently prepared by reaction of GaCl₃ with the neutral EⁿBu₂ in a 1:1 ratio or with ⁿBuE(CH₂)_nEⁿBu or ^tBuTe(CH₂)₃Te^tBu in a 2:1 ratio and characterized by IR/Raman and multinuclear (¹H, ⁷¹Ga, ⁷⁷Se{¹H}, and ¹²⁵Te{¹H}) NMR spectroscopy, respectively, all of which indicate distorted tetrahedral coordination at Ga. The tribromide analog, [GaBr₃(SeⁿBu₂)], was prepared and characterized similarly. A crystal structure determination on [(GaCl₃)₂{^tBuTe(CH₂)₃Te^tBu}] confirms this geometry with each pyramidal GaCl₃ fragment coordinated to one Te donor atom of the bridging ditelluroether, Ga–Te = 2.6356(13) and 2.6378(14) Å. The ⁿBu-substituted ligand complexes serve as convenient and very useful single source precursors for low pressure chemical vapor deposition (LPCVD) of single phase gallium telluride and gallium selenide, Ga₂E₃, films onto SiO₂ and TiN substrates. The composition and morphology were confirmed by SEM, EDX, and Raman spectroscopy, while XRD shows the films are crystalline, consistent with cubic Ga₂Te₃ (F4̅3m) and monoclinic Ga₂Se₃ (Cc), respectively. Hall measurements on films grown on SiO₂ show the Ga₂Te₃ is a p-type semiconductor with a resistivity of 195 ± 10 Ω cm and a carrier density of 5 × 10¹⁵ cm^–3, indicative of a close to stoichiometric compound. The Ga₂Se₃ is also p-type with a resistivity of (9 ± 1) × 10³ Ω cm, a carrier density of 2 × 10¹³ cm^–3, and a mobility of 20–80 cm²/V·s. Competitive deposition of Ga₂Te₃ onto a photolithographically patterned SiO₂/TiN substrate indicates that film growth onto the conducting and more hydrophobic TiN is preferred.

The investigation of poly(3,4-ethylenedioxythiophene) (PEDOT) exposed to several example amines has shown that they bind to the conducting polymer through a nucleophilic attack on the positively charged carbon atoms. The PEDOT films were polymerized using the vacuum vapor phase polymerization (VPP) technique, and their electrical and optical properties subsequently modified by adsorbing aniline, ammonia or urea. Analysis of the surface chemistry shows that the reversibility of the binding depends on the nature of the amine, although a portion is chemisorbed to the PEDOT. This mechanism allows the polymer surface to be decorated with biomolecules or nanoparticles, as demonstrated by attachment of poly(allylamine) coated silica nanoparticles to the PEDOT. This understanding provides the opportunity to control PEDOT properties, and opens the pathway to extend the utility of these electroactive, optoactive, and bioactive materials.

Mineralization of alkaline-earth carbonates in silica-rich media at high pH leads to fascinating crystal morphologies that strongly resemble products from biomineralization, despite the absence of any organic matter. Recent work has demonstrated that elaborate CaCO₃ structures can be grown in such systems even at high supersaturation, as nanoparticles of amorphous calcium carbonate (ACC) were spontaneously coated by skins of silica and thus served as temporary storage depots continuously supplying growth units for the formation of crystalline calcite. In the present study, we have precipitated barium carbonate under similar conditions and found surprisingly different behavior. At low silica concentrations, there was no evidence for an amorphous carbonate precursor phase and crystallization occurred immediately, resulting in elongated crystals that showed progressive self-similar branching due to the poisoning influence of silicate oligomers on the growth process. Above a certain threshold in the silica content, rapid crystallization was in turn prevented and amorphous nanoparticles were stabilized in solution. However, in contrast to previous observations made for CaCO₃, the particles were found to be hybrids consisting of a silica core that was surrounded by a layer of amorphous barium carbonate, which was then again covered by a an outer shell of silica. These self-assembled core–shell–shell nanoparticles were characterized by different techniques, including high-resolution transmission electron microscopy and elemental analyses at the nanoscale. Time-dependent studies further evidence that the carbonate component in the particles can either be permanently trapped in an amorphous state (high silica concentrations, leading to impervious outer silica skins), or be released gradually from the interstitial layers into the surrounding medium (intermediate concentrations, giving porous external shells). In the latter case, enhanced particle aggregation induces segregation of silica hydrogel with embedded amorphous BaCO₃ precursors, which later crystallize in the matrix to yield complex ultrastructures consisting of uniform silica-coated nanorods. The spontaneous formation of core–shell–shell nanoparticles and their subsequent development in the system is discussed on the basis of local pH gradients and inverse pH-dependent trends in the solubility of carbonate and silica, which link their chemistry in solution and provoke coupled mineralization events. Our findings depict a promising strategy for the production of multilayered nanostructures via a facile one-pot route, which is based on self-organization of simple components and may be exploited for the design of novel advanced materials.

SrSi₂O₂N₂:Eu²⁺ is an outstanding yellow emitting phosphor material with practical relevance for application in high power phosphor-converted light-emitting diodes. The triclinic compound exhibits high thermal and chemical stability and quantum efficiency above 90% and can be excited by GaN-based UV to blue LEDs efficiently. We have now discovered a hitherto unknown monoclinic polymorph of SrSi₂O₂N₂, synthesized by solid-state reaction, which is characterized by an alternating stacking sequence of silicate layers made up of condensed SiON₃ tetrahedra and metal-ion layers. As proven by single-crystal X-ray diffraction, the arrangement of the silicate layers is significantly different from the triclinic polymorph. The translation period along the stacking direction is doubled in the monoclinic modification (P2₁, Z = 8, a = 7.1036(14), b = 14.078(3), c = 7.2833(15) Å, β = 95.23(3)°, V = 725.3(3) ų). TEM investigations in combination with HRTEM-image simulations confirm the structure model. The powder X-ray diffraction pattern shows that the volume fractions of the monoclinic and triclinic modifications are approximately equal in the corresponding powder sample. The emission wavelength of 532 nm (fwhm ∼2600 cm^–1) as determined by single-crystal luminescence measurements of the monoclinic phase exhibits a shift to smaller wavelengths by ∼5 nm compared to the triclinic polymorph. Differences of the luminescence properties between the monoclinic and triclinic phase are interpreted with respect to the differing coordination of Eu²⁺ in both phases. The new monoclinic SrSi₂O₂N₂:Eu²⁺ polymorph is a very attractive phosphor material for the enhancement of color rendition of white-light pc-LEDs.

The alkaline stability of imidazolium salts and imidazolium-based alkaline anion-exchange membranes (AEMs) was investigated in this work. C2-substituted (with methyl, isopropyl or phenyl groups) imidazolium salts, 3-ethyl-1,2-dimethyl imidazolium bromine ([EDMIm][Br]), 3-ethyl-2-isopropyl-1-methylimidazolium bromine ([EIMIm][Br]), and 3-ethyl-1-methyl-2-phenyl- imidazolium bromine ([EMPhIm][Br]), were synthesized and characterized. The effect of the C2-substitution on the alkaline stability of imidazolium salts was investigated by ¹H and ¹³C NMR spectroscopy. Compared with the C2-unsubstituted imidazolium salt, 3-ethyl-1-methylimidazolium bromine ([EMIm][Br]), the alkaline stability of C2-substituted imidazolium salts is significantly enhanced at elevated temperatures, probably due to the steric hindrance of the substituents, which protected the imidazolium cations against the hydroxide attack. Moreover, the higher LUMO energies may also improve the alkaline stability of imidazolium salts. The alkaline stability of C2-substituted imidazolium salts was found to be in the order [EDMIm][Br] > [EIMIm][Br] > [EMPhIm][Br]. This work provides a feasible approach for enhancing the chemical stability of C2-substituted imidazolium salts, which has potential applications for alkaline anion-exchange membranes.

Modification of nanoparticle surfaces by adsorption or grafting of polymers allows fine control of hybrid materials properties for diverse applications. To obtain such a control, it is of paramount importance to understand the impact of the polymer structure on the nature and strength of its interaction with the nanoparticle. We investigated here a simple model of hybrid materials made of poly(N-isopropylacrylamide) of different molar masses and end groups interacting with gold surfaces. A series of poly(N-isopropylacrylamide) with number-average molar masses ranging from 3700 to 10000 g·mol^–1 were synthesized by reversible addition–fragmentation chain transfer/macromolecular design by interchange of xanthates (RAFT/MADIX). The terminal xanthate group was then reduced into either a thiol or a hydrogen group. Quartz crystal microbalance adsorption/desorption experiments demonstrated that the polymer termini have a strong impact on the mechanism of polymer adsorption on flat gold surfaces. These differences in polymer structure have, in return, a strong influence on the colloidal stability and growth mechanism of nanoparticles when directly synthesized in polymer solution. For those properties, the effect of xanthate group compared very favorably to the conventional thiol moiety. Interestingly, the properties of nanohybrids were poorly affected by the molar mass of the polymer.

By employing ³¹P multiple-quantum coherence-based solid-state nuclear magnetic resonance spectroscopy, we present the first comprehensive experimental assessment of the nature of the orthophosphate-ion distributions in silicate-based bioactive glasses (BGs). Results are provided both from melt-prepared BG and evaporation-induced self-assembly-derived mesoporous bioactive glass (MBG) structures of distinct compositions. The phosphate species are randomly dispersed in melt-derived BGs (comprising 44–55 mol % SiO₂) of the Na₂O–CaO–SiO₂–P₂O₅ system, whereas a Si-rich (86 mol % SiO₂) and Ca-poor ordered MBG structure exhibits nanometer-sized amorphous calcium phosphate clusters, conservatively estimated to comprise at least nine orthophosphate groups. A Ca-richer MBG (58 mol % SiO₂) reveals a less pronounced phosphate clustering. We rationalize the variable structural role of P in these amorphous biomaterials.

Colloidal hybrid nanoparticles contain multiple domains that are directly fused together through a solid–solid interface, which facilitates synergistic interactions between the components that can lead to enhanced properties, as well as multifunctionality in a single particle. By nucleating one nanoparticle on the surface of another, a growing number of these hybrid nanoparticles can be synthesized. However, to rapidly expand the materials diversity of such systems, alternative routes to heterogeneous seeded nucleation are needed. Here, we show that solution-mediated chemical transformation reactions, which are well established for pseudomorphically transforming colloidal metal nanoparticles into derivative metal-containing phases, can also be applied to colloidal hybrid nanoparticles. Specifically, we show that Pt–Fe₃O₄ heterodimers react with Pb(acac)₂ and Sn(acac)₂ at 180–200 °C in a mixture of benzyl ether, oleylamine, oleic acid, and tert-butylamine borane to form PtPb–Fe₃O₄ and Pt₃Sn–Fe₃O₄ heterodimers, respectively. This chemical transformation reaction introduces intermetallic and alloy components into the heterodimers, proceeds with morphological retention, and preserves the solid–solid interface that characterizes these hybrid nanoparticle systems. In addition, the PtPb–Fe₃O₄ heterodimers spontaneously aggregate to form colloidally stable (PtPb–Fe₃O₄)_n nanoflowers via a process that is conceptually analogous to a molecular condensation reaction. These reactions add to the growing toolbox of predictable manipulations of colloidal hybrid nanoparticles, ultimately expanding their materials diversity and range of potential applications.

In this work, nitrogen-rich carbon nanodots (CNDs) are prepared by the emulsion-templated carbonization of polyacrylamide. The formation mechanism and chemical structure are investigated by infrared, nuclear magnetic resonance, and X-ray photoelectron spectroscopies. Transmission electron microscopy also reveals that the obtained CNDs have well-developed graphitic structure and narrow size distribution without any size selection procedure. We vary the molecular weight of the polymer to control the size of the CNDs and finally obtain the CNDs rendering bright visible light under UV illumination with a high quantum yield of 40%. Given that the CNDs are worth utilizing in phosphor applications, we fabricate large-scale (20 × 20 cm) freestanding luminescent films of the CNDs based on a poly(methyl methacrylate) matrix. The polymer matrix can not only provide mechanical support but also disperse the CNDs to prevent solid-state quenching. For practical application, we demonstrate white LEDs consisting of the films as color-converting phosphors and InGaN blue LEDs as illuminators. Such white LEDs exhibit no temporal degradation in the emission spectrum under practical operation conditions. This study would suggest a promising way to exploit the luminescence from solid-state CNDs and offer strong potential for future CND-based solid-state lighting systems.

Materials with the cubic ReO₃-type structure are, in principle, excellent candidates for negative thermal expansion (NTE). However, many such materials, including TaO₂F, do not display NTE. It is proposed that local distortions away from the ideal structure, associated with the need to accommodate the different bonding requirements of the disordered O/F, contribute to the occurrence of near zero thermal expansion rather than NTE. The local structure of TaO₂F is poorly described by an ideal cubic ReO₃-type model with O and F randomly distributed over the available anion sites. A supercell model featuring −Ta–O–Ta–O–Ta–F– chains along ⟨1 0 0⟩, with different Ta–O and Ta–F distances and O/F off-axis displacements, gives much better agreement with pair distribution functions (PDFs) derived from total X-ray scattering data for small separations (<8 Å). Analyses of PDFs derived from variable temperature measurements (80 to 487 K), over different length scales, indicate an average linear expansion coefficient of close to zero with similar contributions from the geometrically distinct Ta–O—Ta and Ta–F—Ta links in TaO₂F.

Control of the nucleation behavior during atomic layer deposition (ALD) of metals is of great importance for the deposition of metallic thin films and nanoparticles, and for nanopatterning applications. In this work it is established for Pt ALD, that the exposure to O₂ during the O₂ pulse of the ALD process is the key parameter controlling the nucleation behavior. The O₂ dependence of the Pt nucleation is explained by the enhanced diffusion of Pt species in the presence of oxygen, and the resulting faster aggregation of Pt atoms in metal clusters that catalyze the surface reactions of ALD growth. Moreover, it is demonstrated that the O₂ exposure can be used as the parameter to tune the nucleation to enable (i) deposition of ultrathin films with minimal nucleation delay, (ii) preparation of single element or core/shell nanoparticles, and (iii) nanopatterning of metallic structures based on area-selective deposition.

Upconversion (UC) is a promising option to enhance the efficiency of solar cells by conversion of sub-bandgap infrared photons to higher energy photons that can be utilized by the solar cell. The UC quantum yield is a key parameter for a successful application. Here the UC luminescence properties of Er³⁺-doped Gd₂O₂S are investigated by means of luminescence spectroscopy, quantum yield measurements, and excited state dynamics experiments. Excitation into the maximum of the ⁴I_15/2 → ⁴I_13/2 Er³⁺ absorption band around 1500 nm induces very efficient UC emission from different Er³⁺ excited states with energies above the silicon bandgap, in particular, the emission originating from the ⁴I_11/2 state around 1000 nm. Concentration dependent studies reveal that the highest UC quantum yield is realized for a 10% Er³⁺-doping concentration. The UC luminescence is compared to the well-known Er³⁺-doped β-NaYF₄ UC material for which the highest UC quantum yield has been reported for 25% Er³⁺. The UC internal quantum yields were measured in this work for Gd₂O₂S: 10%Er³⁺ and β-NaYF₄: 25%Er³⁺ to be 12 ± 1% and 8.9 ± 0.7%, respectively, under monochromatic excitation around 1500 nm at a power of 700 W/m². The UC quantum yield reported here for Gd₂O₂S: 10%Er³⁺ is the highest value achieved so far under monochromatic excitation into the ⁴I_13/2 Er³⁺ level. Power dependence and lifetime measurements were performed to understand the mechanisms responsible for the efficient UC luminescence. We show that the main process yielding ⁴I_11/2 UC emission is energy transfer UC.

Films of β-Co(OH)₂ with a dense microcone morphology are electrodeposited at room temperature by reducing tris(ethylenediamine)cobalt(III) in alkaline solution. The synthesis exploits the fact that the kinetically inert Co(III) complex of ethylenediamine (en) is 35 orders of magnitude more stable than the kinetically labile Co(II) complex. [Co(en)₃]³⁺ is therefore stable in alkaline solution, but [Co(en)₃]²⁺ reacts with excess hydroxide ion to produce β-Co(OH)₂. The electrodeposited β-Co(OH)₂ is an active catalyst for the oxygen evolution reaction. Raman spectroscopy suggests that the surface of β-Co(OH)₂ is converted to CoOOH at the potentials at which oxygen evolution occurs.

The influence of alkyl side chains on the crystallinity of semiconducting copolymer films and their sub-bandgap density-of-states (DOS), the latter being closely related to the stability and the device performance of organic field-effect transistors (OFETs), is investigated. Three different poly(hexathiophene-alt-bithiazole) (PHTBTz) based polymer semiconductors, with identical backbones but different side chain positions and lengths, were synthesized. The crystallinity examined by grazing incidence X-ray diffraction (GIXRD) strongly depends on the number, position, and length of each type of alkyl side chain attached to the thiophene and thiazole copolymer backbones. Also, the sub-bandgap trap DOS distributions were extracted by performing multiple-frequency capacitance–voltage (MF-CV) spectroscopy on the field effect devices. The relationship between film crystallinity and trap DOS in the field-effect transistors can be interpreted in terms of the complex interplay between the number, position, and length of each alkyl side chain for efficient π–π stacking. In particular, the number and position of the alkyl side chain attached to the polymer backbone significantly affects the device performance. Poly(tetryloctylhexathiophene-alt-dioctylbithiazole) (PHTBTz-C8) exhibits the best electrical performance among the different semiconductors synthesized, with a relatively low bulk trap density of ∼2.0 × 10²⁰ cm^–3 eV^–1 as well as reasonable hole mobility of ∼0.25 cm² V^–1 s^–1. The microstructural analyses of this organic material strongly suggest that the short π–π stacking distance induces strong interaction between adjacent polymer backbones, which in turn results in enhanced electrical properties.

To gain insight into the role of crystallinity and morphology on proton transport through solid polymer electrolytes, we synthesized graft copolymers, poly(vinylidene difluoride-co-chlorotrifluoroethylene)-g-polystyrene [P(VDF-co-CTFE)-g-PS], consisting of a hydrophobic, fluorous backbone and styrenic graft chain of varied length (DP_styrene = 39, 62, and 79), by graft atom transfer radical polymerization (ATRP). The polystyrene graft chains were subsequently sulfonated to different degrees to provide three series of polymers with controlled ion exchange capacity (IEC). The crystallinity and morphology of solution-cast membranes were examined by XRD and TEM, respectively. The grafting of the parent side chain is found to hinder crystallization of the fluorous backbone and the impact of the degree of sulfonation of the side chain on the crystallinity of the polymer is dependent on the graft length: No impact is found for medium and long graft lengths, but for short graft length copolymers (PS₃₉), the degree of crystallinity in the sulfonated membranes is twice that of the unsulfonated membrane. A phase-separated morphology consisting of 2–5 (±1) nm ion-rich domains is observed for all of the graft copolymers. These graft copolymers allow access to very high IEC membranes (>3 mmol/g), which are insoluble in water. The shorter graft length series, P(VDF-co-CTFE)-g-SPS₃₉, swells less in the intermediate IEC range (<3.0 mmol/g) because of its higher degree of crystallinity and lower PS to VDF ratio, and provides membranes with exceptionally high proton conductivity. Two graft series possessing similar weight fraction of PS but different graft density were also examined in order to evaluate the effect of graft density. It was found that lower graft density copolymers possess higher crystallinity and more contiguous PVDF domains, which allow high IEC membranes to be prepared that swell to lower extents.

Hierarchical clinoptilolite and L zeolites are prepared using optimized tandem dealumination–desilication treatments. The main challenge in the postsynthetic modification of these zeolites is the high Al content, requiring a tailored dealumination prior to the desilication step. For natural clinoptilolite, sequential acid treatments using aqueous HCl solutions were applied, while for L a controlled dealumination using ammonium hexafluorosilicate is required. Subsequent desilication by NaOH treatment yields mesopore surfaces of up to 4-fold (clinoptilolite, 64 m² g^–1; L, 135 m² g^–1) relative to the parent zeolite (clinoptilolite, 15 m² g^–1; L, 45 m² g^–1). A thorough characterization sheds light on the composition, crystallinity, porosity, morphology, coordination, and acidity of the modified clinoptilolite and L zeolites. It is elaborated that, besides the degree of dealumination, the resulting Al distribution is a critical precondition for the following mesopore formation by desilication. Adsorption experiments of Cu²⁺ and methylene blue from aqueous solutions and the catalytic evaluation in alkylations and Knoevenagel condensation evidence the superiority of the hierarchical zeolites, as compared to their purely microporous counterparts. Finally, the postsynthetic routes for clinoptilolite and L are generalized with other recently reported modification strategies, and presented in a comprehensive overview.

Single crystals of Li₁₇Si₄ were synthesized from melts Li_xSi_100–x (x > 85) at various temperatures and isolated by isothermal centrifugation. Li₁₇Si₄ crystallizes in the space group F4̅3m (a = 18.7259(1) Å, Z = 20). The highly air and moisture sensitive compound is isotypic with Li₁₇Sn₄. Li₁₇Si₄ represents a new compound and thus the lithium-richest phase in the binary system Li–Si superseding known Li₂₁Si₅ (Li_16.8Si₄). As previously shown Li₂₂Si₅ (Li_17.6Si₄) has been determined incorrectly. The findings are supported by theoretical calculations of the electronic structure, total energies, and structural optimizations using first-principles methods. Results from melt equilibration experiments and differential scanning calorimetry investigations suggest that Li₁₇Si₄ decomposes peritectically at 481 ± 2 °C to “Li₄Si” and melt. In addition a detailed investigation of the Li–Si phase system at the Li-rich side by thermal analysis using differential scanning calorimetry is given.

Mesoporous silica nanoparticles have the capacity to load and deliver therapeutic cargo and incorporate imaging modalities, making them prominent candidates for theranostic devices. One of the most widespread imaging agents utilized in this and other theranostic platforms is nanoscale superparamagnetic iron oxide. Although several core–shell magnetic mesoporous silica nanoparticles presented in the literature have provided high T₂ contrast in vitro and in vivo, there is ambiguity surrounding which parameters lead to enhanced contrast. Additionally, there is a need to understand the behavior of these imaging agents over time in biologically relevant environments. Herein, we present a systematic analysis of how the transverse relaxivity (r₂) of magnetic mesoporous silica nanoparticles is influenced by nanoparticle diameter, iron oxide nanoparticle core synthesis, and use of a hydrothermal treatment. This work demonstrates that samples which did not undergo a hydrothermal treatment experienced a drop in r₂ (75% of original r₂ within 8 days of water storage), while samples with hydrothermal treatment maintained roughly the same r₂ for over 30 days in water. Our results suggest that iron oxide oxidation is the cause of r₂ loss, and this oxidation can be prevented during both synthesis and storage by use of deoxygenated conditions during nanoparticle synthesis. Hydrothermal treatment also provides colloidal stability, even in acidic and highly salted solutions, and a resistance against acid degradation of the iron oxide nanoparticle core. Results of this study show the promise of multifunctional mesoporous silica nanoparticles but will also likely inspire further investigation into multiple types of theranostic devices, taking into consideration their behavior over time and in relevant biological environments.

To develop various strategies to prevent the aggregation, sintering, or leaching of noble metal nanoparticles (NPs) represents a crucial issue for efficient synthesis and utilization of supported noble metal NPs with highly active and stable catalytic performance. Here, we report a facile synthesis approach to obtain a Pd@hCeO₂ hollow core–shell nanocomposite that is composed of tiny Pd nanoparticles cores encapsulated within CeO₂ hollow shells. The core–shell strategy efficiently prevents the aggregation of Pd NPs in the high temperature calcination process and the leaching of Pd NPs for the catalytic reaction in a liquid phase. This anti-aggregation and anti-leaching behavior is not able to be achieved for traditional supported Pd/CeO₂ catalyst. Such a Pd@hCeO₂ composite can serve as an efficient multifunctional nanocatalyst in both heterogeneous thermocatalytic and photocatalytic selective reduction of aromatic nitro compounds in water under ambient conditions. Each component, namely Pd metal core or semiconductor CeO₂ shell, makes a necessary but totally dissimilar reactive contribution to achieving the same end product during these two different catalytic processes. Importantly, Pd@hCeO₂ exhibits an excellent reusable and much higher catalytic performance than supported Pd/CeO₂. This work provides a generic concept example on inhibiting aggregation of noble metal NPs during high temperature calcination and leaching of noble metal nanoparticles into solution via a hollow core–shell strategy and, more significantly, on sufficiently harnessing the specific metal core or semiconductor shell function integrated in a core–shell nanoarchitecture toward a multifunctional catalytic use in both thermocatalytic and photocatalytic selective green transformation in water.

We present a study in which the intrawall porosity and primary mesoporosity of SBA-15 are independently controlled by modifying the strength of the molecular interaction that governs the formation of the material. The interactions are targeted at specific times during the process of formation, which results in selective tuning of the porosity, while other characteristics of the SBA-15 material are retained. We show that the intrawall porosity can be considerably reduced by addition of NaI, but not NaCl, and that the shape of the primary mesopores can be influenced by a decrease in temperature, while the two-dimensional hexagonal structure and the particle morphology and size remain unchanged. The timing of the “tuning event” is imperative. We show that a decrease in intrawall porosity by addition of NaI is generic to Pluronic-based mesoporous silica syntheses. This work demonstrates that the material characteristic of mesoporous silica is not necessarily restricted by the initial synthesis conditions as the material properties can be tuned by “actions” taken upon the ongoing synthesis. The triblock copolymer Pluronic P104 was used as a structure director and tetramethyl orthosilicate as a silica source. The materials have been characterized primarily with nitrogen sorption and small-angle X-ray diffraction.