Editorial
What Is the Value of Publishing?
Warren Chan
This publication is free to access through this site. Learn More
In Nano
In Nano, Volume 12, Issue 7
Christen Brownlee
This publication is free to access through this site. Learn More
Perspectives
Small Meets Smaller: Effects of Nanomaterials on Microbial Biology, Pathology, and Ecology
Roland H. Stauber *- ,
Svenja Siemer - ,
Sven Becker - ,
Guo-Bin Ding - ,
Sebastian Strieth - , and
Shirley K. Knauer *
As functionalities and levels of complexity in nanomaterials have increased, unprecedented control over microbes has been enabled, as well. In addition to being pathogens and relevant to the human microbiome, microbes are key players for sustainable biotechnology. To overcome current constraints, mechanistic understanding of nanomaterials’ physicochemical characteristics and parameters at the nano–bio interface affecting nanomaterial–microbe crosstalk is required. In this Perspective, we describe key nanomaterial parameters and biological outputs that enable controllable microbe–nanomaterial interactions while minimizing design complexity. We discuss the role of biomolecule coronas, including the problem of nanoantibiotic resistance, and speculate on the effects of nanomaterial–microbe complex formation on the outcomes and fates of microbial pathogens. We close by summarizing our current knowledge and noting areas that require further exploration to overcome current limitations for next-generation practical applications of nanotechnology in medicine and agriculture.
Reviews
Assessing and Mitigating the Hazard Potential of Two-Dimensional Materials
Linda M. Guiney - ,
Xiang Wang - ,
Tian Xia - ,
André E. Nel - , and
Mark C. Hersam *
The family of two-dimensional (2D) materials is comprised of a continually expanding palette of unique compositions and properties with potential applications in electronics, optoelectronics, energy capture and storage, catalysis, and nanomedicine. To accelerate the implementation of 2D materials in widely disseminated technologies, human health and environmental implications need to be addressed. While extensive research has focused on assessing the toxicity and environmental fate of graphene and related carbon nanomaterials, the potential hazards of other 2D materials have only recently begun to be explored. Herein, the toxicity and environmental fate of postcarbon 2D materials, such as transition metal dichalcogenides, hexagonal boron nitride, and black phosphorus, are reviewed as a function of their preparation methods and surface functionalization. Specifically, we delineate how the hazard potential of 2D materials is directly related to structural parameters and physicochemical properties and how experimental design is critical to the accurate elucidation of the underlying toxicological mechanisms. Finally, a multidisciplinary approach for streamlining the hazard assessment of emerging 2D materials is outlined, thereby providing a pathway for accelerating their safe use in a range of technologically relevant contexts.
Articles
Multiscale Control of Nanocellulose Assembly: Transferring Remarkable Nanoscale Fibril Mechanics to Macroscale Fibers
Nitesh Mittal - ,
Farhan Ansari - ,
Krishne Gowda.V - ,
Christophe Brouzet - ,
Pan Chen - ,
Per Tomas Larsson - ,
Stephan V. Roth - ,
Fredrik Lundell - ,
Lars Wågberg - ,
Nicholas A. Kotov - , and
L. Daniel Söderberg *
This publication is Open Access under the license indicated. Learn More
ACS Editors' Choice® is a collection designed to feature scientific articles of broad public interest. Read the latest articles
Nanoscale building blocks of many materials exhibit extraordinary mechanical properties due to their defect-free molecular structure. Translation of these high mechanical properties to macroscopic materials represents a difficult materials engineering challenge due to the necessity to organize these building blocks into multiscale patterns and mitigate defects emerging at larger scales. Cellulose nanofibrils (CNFs), the most abundant structural element in living systems, has impressively high strength and stiffness, but natural or artificial cellulose composites are 3–15 times weaker than the CNFs. Here, we report the flow-assisted organization of CNFs into macroscale fibers with nearly perfect unidirectional alignment. Efficient stress transfer from macroscale to individual CNF due to cross-linking and high degree of order enables their Young’s modulus to reach up to 86 GPa and a tensile strength of 1.57 GPa, exceeding the mechanical properties of known natural or synthetic biopolymeric materials. The specific strength of our CNF fibers engineered at multiscale also exceeds that of metals, alloys, and glass fibers, enhancing the potential of sustainable lightweight high-performance materials with multiscale self-organization.
An Intestinal “Transformers”-like Nanocarrier System for Enhancing the Oral Bioavailability of Poorly Water-Soluble Drugs
Er-Yuan Chuang - ,
Kun-Ju Lin - ,
Tring-Yo Huang - ,
Hsin-Lung Chen - ,
Yang-Bao Miao - ,
Po-Yen Lin - ,
Chiung-Tong Chen - ,
Jyuhn-Huarng Juang *- , and
Hsing-Wen Sung *
Increasing the intestinal dissolution of orally administered poorly water-soluble drugs that have poor oral bioavailability to a therapeutically effective level has long been an elusive goal. In this work, an approach that can greatly enhance the oral bioavailability of a poorly water-soluble drug such as curcumin (CUR) is developed, using a “Transformers”-like nanocarrier system (TLNS) that can self-emulsify the drug molecules in the intestinal lumen to form nanoemulsions. Owing to its known anti-inflammation activity, the use of CUR in treating pancreatitis is evaluated herein. Structural changes of the TLNS in the intestinal environment to form the CUR-laden nanoemulsions are confirmed in vitro. The therapeutic efficacy of this TLNS is evaluated in rats with experimentally induced acute pancreatitis (AP). Notably, the CUR-laden nanoemulsions that are obtained using the proposed TLNS can passively target intestinal M cells, in which they are transcytosed and then transported into the pancreatic tissues via the intestinal lymphatic system. The pancreases in rats that are treated with the TLNS yield approximately 12 times stronger CUR signals than their counterparts receiving free CUR, potentially improving the recovery of AP. These findings demonstrate that the proposed TLNS can markedly increase the intestinal drug dissolution, making oral delivery a favorable noninvasive means of administering poorly water-soluble drugs.
“Minimalist” Nanovaccine Constituted from Near Whole Antigen for Cancer Immunotherapy
Kun Wang - ,
Shuman Wen - ,
Lianghua He - ,
Ang Li - ,
Yan Li - ,
Haiqing Dong - ,
Wei Li - ,
Tianbin Ren - ,
Donglu Shi - , and
Yongyong Li *
One of the major challenges in vaccine design has been the over dependence on incorporation of abundant adjuvants, which in fact is in violation of the “minimalist” principle. In the present study, a compact nanovaccine derived from a near whole antigen (up to 97 wt %) was developed. The nanovaccine structure was stabilized by free cysteines within each antigen (ovalbumin, OVA), which were tempospatially exposed and heat-driven to form an extensive intermolecular disulfide network. This process enables the engineering of a nanovaccine upon integration of the danger signal (CpG-SH) into the network during the synthetic process. The 50 nm-sized nanovaccine was developed comprising approximately 500 antigen molecules per nanoparticle. The nanovaccine prophylactically protected 70% of mice from tumorigenesis (0% for the control group) in murine B16-OVA melanoma. Significant tumor inhibition was achieved by strongly nanovaccine-induced cytotoxic T lymphocytes. This strategy can be adapted for the future design of vaccine for a minimalist composition in clinical settings.
Excitonics: A Set of Gates for Molecular Exciton Processing and Signaling
Nicolas P. D. Sawaya - ,
Dmitrij Rappoport - ,
Daniel P. Tabor - , and
Alán Aspuru-Guzik *
Regulating energy transfer pathways through materials is a central goal of nanotechnology, as a greater degree of control is crucial for developing sensing, spectroscopy, microscopy, and computing applications. Such control necessitates a toolbox of actuation methods that can direct energy transfer based on user input. Here we introduce a proposal for a molecular exciton gate, analogous to a traditional transistor, for regulating exciton flow in chromophoric systems. The gate may be activated with an input of light or an input flow of excitons. Our proposal relies on excitation migration via the second excited singlet (S2) state of the gate molecule. It exhibits the following features, only a subset of which are present in previous exciton switching schemes: picosecond time scale actuation, amplification/gain behavior, and a lack of molecular rearrangement. We demonstrate that the device can be used to produce universal binary logic or amplification of an exciton current, providing an excitonic platform with several potential uses, including signal processing for microscopy and spectroscopy methods that implement tunable exciton flux.
“Crypto-Display” in Dual-Mode Metasurfaces by Simultaneous Control of Phase and Spectral Responses
Gwanho Yoon - ,
Dasol Lee - ,
Ki Tae Nam - , and
Junsuk Rho *
Although conventional metasurfaces have demonstrated many promising functionalities in light control by tailoring either phase or spectral responses of subwavelength structures, simultaneous control of both responses has not been explored yet. Here, we propose a concept of dual-mode metasurfaces that enables simultaneous control of phase and spectral responses for two kinds of operation modes of transmission and reflection, respectively. In the transmission mode, the dual-mode metasurface acts as conventional metasurfaces by tailoring phase distribution of incident light. In the reflection mode, a reflected colored image is produced under white light illumination. We also experimentally demonstrate a crypto-display as one application of the dual-mode metasurface. The crypto-display looks a normal reflective display under white light illumination but generates a hologram that reveals the encrypted phase information under single-wavelength coherent light illumination. Because two operation modes do not affect each other, the crypto-display can have applications in security techniques.
Multivalent Flexible Nanogels Exhibit Broad-Spectrum Antiviral Activity by Blocking Virus Entry
Pradip Dey - ,
Tobias Bergmann - ,
Jose Luis Cuellar-Camacho - ,
Svenja Ehrmann - ,
Mohammad Suman Chowdhury - ,
Minze Zhang - ,
Ismail Dahmani - ,
Rainer Haag *- , and
Walid Azab *
The entry process of viruses into host cells is complex and involves stable but transient multivalent interactions with different cell surface receptors. The initial contact of several viruses begins with attachment to heparan sulfate (HS) proteoglycans on the cell surface, which results in a cascade of events that end up with virus entry. The development of antiviral agents based on multivalent interactions to shield virus particles and block initial interactions with cellular receptors has attracted attention in antiviral research. Here, we designed nanogels with different degrees of flexibility based on dendritic polyglycerol sulfate to mimic cellular HS. The designed nanogels are nontoxic and broad-spectrum, can multivalently interact with viral glycoproteins, shield virus surfaces, and efficiently block infection. We also visualized virus–nanogel interactions as well as the uptake of nanogels by the cells through clathrin-mediated endocytosis using confocal microscopy. As many human viruses attach to the cells through HS moieties, we introduce our flexible nanogels as robust inhibitors for these viruses.
Graphene Glass Inducing Multidomain Orientations in Cholesteric Liquid Crystal Devices toward Wide Viewing Angles
Huihui Wang - ,
Bingzhi Liu - ,
Ling Wang - ,
Xudong Chen - ,
Zhaolong Chen - ,
Yue Qi - ,
Guang Cui - ,
Huanhuan Xie - ,
Yanfeng Zhang *- , and
Zhongfan Liu *
The photonic reflection of a cholesteric liquid crystal (ChLC) device depends on the spatial distribution of the orientations of their helical axes, and many orientation techniques have been developed so far. In this study, we select the hybrids of graphene directly grown on quartz glass as platforms to construct ChLC-based devices. This special design makes graphene serve as both an alignment layer and a conductive layer, thus affording a more simplified device fabrication route. We reveal that multidomain structures can be evolved for ChLCs on polycrystalline monolayer graphene on quartz glass, as evidenced by polarized optical microscope characterizations. The disparate orientations of the helical axes of ChLCs and the formation of multidomain structures are proposed to be induced by the different domain orientations of graphene, leading to a wide viewing angle of the ChLC-based devices. Moreover, the pitch of ChLCs is also observed to play a key role in the relative orientations of ChLCs. A wide viewing angle of the ChLC-based device is also detected especially in the infrared spectrum region. Briefly, this work should provoke the application of graphene glass as a perfect transparent electrode in the fabrication of liquid-crystal-based devices showing broad application potentials in intelligent laser protection and energy-saving smart windows.
Identifying Few-Molecule Water Clusters with High Precision on Au(111) Surface
Anning Dong - ,
Lei Yan - ,
Lihuan Sun - ,
Shichao Yan - ,
Xinyan Shan - ,
Yang Guo - ,
Sheng Meng *- , and
Xinghua Lu *
Revealing the nature of a hydrogen-bond network in water structures is one of the imperative objectives of science. With the use of a low-temperature scanning tunneling microscope, water clusters on a Au(111) surface were directly imaged with molecular resolution by a functionalized tip. The internal structures of the water clusters as well as the geometry variations with the increase of size were identified. In contrast to a buckled water hexamer predicted by previous theoretical calculations, our results present deterministic evidence for a flat configuration of water hexamers on Au(111), corroborated by density functional theory calculations with properly implemented van der Waals corrections. The consistency between the experimental observations and improved theoretical calculations not only renders the internal structures of absorbed water clusters unambiguously, but also directly manifests the crucial role of van der Waals interactions in constructing water–solid interfaces.
Quantitative Assessment of Nanoparticle Biodistribution by Fluorescence Imaging, Revisited
Fanfei Meng - ,
Jianping Wang - ,
Qineng Ping - , and
Yoon Yeo *
Fluorescence-based whole-body imaging is widely used in the evaluation of nanoparticles (NPs) in small animals, often combined with quantitative analysis to indicate their spatiotemporal distribution following systemic administration. An underlying assumption is that the fluorescence label represents NPs and the intensity increases with the amount of NPs and/or the labeling dyes accumulated in the region of interest. We prepare DiR-loaded poly(lactic-co-glycolic acid) (PLGA) NPs with different surface layers (polyethylene glycol with and without folate terminus) and compare the distribution of fluorescence signals in a mouse model of folate-receptor-expressing tumors by near-infrared fluorescence whole-body imaging. Unexpectedly, we observe that fluorescence distribution patterns differ far more dramatically with DiR loading than with the surface ligand, reaching opposite conclusions with the same type of NPs (tumor-specific delivery vs predominant liver accumulation). Analysis of DiR-loaded PLGA NPs reveals that fluorescence quenching, dequenching, and signal saturation, which occur with the increasing dye content and local NP concentration, are responsible for the conflicting interpretations. This study highlights the critical need for validating fluorescence labeling of NPs in the quantitative analysis of whole-body imaging. In light of our observation, we make suggestions for future whole-body fluorescence imaging in the in vivo evaluation of NP behaviors.
Reducing Intestinal Digestion and Absorption of Fat Using a Nature-Derived Biopolymer: Interference of Triglyceride Hydrolysis by Nanocellulose
Glen M. DeLoid *- ,
Ikjot Singh Sohal - ,
Laura R. Lorente - ,
Ramon M. Molina - ,
Georgios Pyrgiotakis - ,
Ana Stevanovic - ,
Ruojie Zhang - ,
David Julian McClements - ,
Nicholas K. Geitner - ,
Douglas W. Bousfield - ,
Kee Woei Ng - ,
Say Chye Joachim Loo - ,
David C. Bell - ,
Joseph Brain - , and
Philip Demokritou *
Engineered nanomaterials are increasingly added to foods to improve quality, safety, or nutrition. Here we report the ability of ingested nanocellulose (NC) materials to reduce digestion and absorption of ingested fat. In the small intestinal phase of an acellular simulated gastrointestinal tract, the hydrolysis of free fatty acids (FFA) from triglycerides (TG) in a high-fat food model was reduced by 48.4% when NC was added at 0.75% w/w to the food, as quantified by pH stat titration, and by 40.1% as assessed by fluorometric FFA assay. Furthermore, translocation of TG and FFA across an in vitro cellular model of the intestinal epithelium was significantly reduced by the presence of 0.75% w/w NC in the food (TG by 52% and FFA by 32%). Finally, in in vivo experiments, the postprandial rise in serum TG 1 h after gavage with the high fat food model was reduced by 36% when 1.0% w/w NC was administered with the food. Scanning electron microscopy and molecular dynamics studies suggest two primary mechanisms for this effect: (1) coalescence of fat droplets on fibrillar NC (CNF) fibers, resulting in a reduction of available surface area for lipase binding and (2) sequestration of bile salts, causing impaired interfacial displacement of proteins at the lipid droplet surface and impaired solubilization of lipid digestion products. Together these findings suggest a potential use for NC, as a food additive or supplement, to reduce absorption of ingested fat and thereby assist in weight loss and the management of obesity.
Biocompatible Peptide-Coated Ultrasmall Superparamagnetic Iron Oxide Nanoparticles for In Vivo Contrast-Enhanced Magnetic Resonance Imaging
Heng Li Chee - ,
Ching Ruey R. Gan - ,
Michael Ng - ,
Lionel Low - ,
David G. Fernig - ,
Kishore K. Bhakoo - , and
David Paramelle *
The biocompatibility and performance of reagents for in vivo contrast-enhanced magnetic resonance imaging (MRI) are essential for their translation to the clinic. The quality of the surface coating of nanoparticle-based MRI contrast agents, such as ultrasmall superparamagnetic iron oxide nanoparticles (USPIONs), is critical to ensure high colloidal stability in biological environments, improved magnetic performance, and dispersion in circulatory fluids and tissues. Herein, we report the design of a library of 21 peptides and ligands and identify highly stable self-assembled monolayers on the USPIONs’ surface. A total of 86 different peptide-coated USPIONs are prepared and selected using several stringent criteria, such as stability against electrolyte-induced aggregation in physiological conditions, prevention of nonspecific binding to cells, and absence of cellular toxicity and contrast-enhanced in vivo MRI. The bisphosphorylated peptide 2PG-S*VVVT-PEG4-ol provides the highest biocompatibility and performance for USPIONs, with no detectable toxicity or adhesion to live cells. The 2PG-S*VVVT-PEG4-ol-coated USPIONs show enhanced magnetic resonance properties, r1 (2.4 mM–1·s–1) and r2 (217.8 mM–1·s–1) relaxivities, and greater r2/r1 relaxivity ratios (>90) when compared to those of commercially available MRI contrast agents. Furthermore, we demonstrate the utility of 2PG-S*VVVT-PEG4-ol-coated USPIONs as a T2 contrast agent for in vivo MRI applications. High contrast enhancement of the liver is achieved as well as detection of liver tumors, with significant improvement of the contrast-to-noise ratio of tumor-to-liver contrast. It is envisaged that the reported peptide-coated USPIONs have the potential to allow for the specific targeting of tumors and hence early detection of cancer by MRI.
Electron Transport Across Plasmonic Molecular Nanogaps Interrogated with Surface-Enhanced Raman Scattering
Li Lin - ,
Qiang Zhang - ,
Xiyao Li - ,
Meng Qiu - ,
Xin Jiang - ,
Wei Jin - ,
Hongchen Gu *- ,
Dang Yuan Lei *- , and
Jian Ye *
Charge transport plays an important role in defining both far-field and near-field optical response of a plasmonic nanostructure with an ultrasmall built-in nanogap. As the gap size of a gold core–shell nanomatryoshka approaches the sub-nanometer length scale, charge transport may occur and strongly alter the near-field enhancement within the molecule-filled nanogap. In this work, we utilize ultrasensitive surface-enhanced Raman spectroscopy (SERS) to investigate the plasmonic near-field variation induced by the molecular junction conductance-assisted electron transport in gold nanomatryoshkas, termed gap-enhanced Raman tags (GERTs). The GERTs, with interior gaps from 0.7 to 2 nm, are prepared with a wet chemistry method. Our experimental and theoretical studies suggest that the electron transport through the molecular junction influences both far-field and near-field optical properties of the GERTs. In the far-field extinction response, the low-energy gap mode predicted by a classical electromagnetic model (CEM) is strongly quenched and hence unobservable in the experiment, which can be well explained by a quantum-corrected model (QCM). In the near-field SERS response, the optimal gap size for maximum Raman enhancement at the excitation wavelength of 785 nm (633 nm) is about 1.35 nm (1.8 nm). Similarly, these near-field results do not tally with the CEM calculations but agree well with the QCM results where the molecular junction conductance in the nanogap is fully considered. Our study may improve understanding of charge-transport phenomena in ultrasmall plasmonic molecular nanogaps and promote the further development of molecular electronics-based plasmonic nanodevices.
Rationally Designed Polycationic Carriers for Potent Polymeric siRNA-Mediated Gene Silencing
Connie Wu - ,
Jiahe Li - ,
Wade Wang - , and
Paula T. Hammond *
The delivery of small interfering RNA (siRNA) remains a major hurdle for the clinical translation of RNA interference (RNAi) therapeutics. Because of its low valency and rigid nature, siRNA typically requires high excesses of cationic delivery materials to package it stably and deliver it to the cytoplasm of target cells, resulting in high toxicities and inefficient gene silencing in vivo. To address these challenges, we pair a polymeric form of siRNA, p-shRNA, with optimized biodegradable polycations to form stable complexes that induce far more potent gene silencing than with siRNA complexes. Furthermore, we unveil a set of design rules governing p-shRNA delivery, using degradable polycations containing hydrophobic and stabilizing polyethylene glycol domains that enable both stable condensation and efficient release inside cells. We demonstrate the therapeutic potential of this approach by silencing the oncogene STAT3 in a well-established B16F10 mouse melanoma model to significantly prolong survival. By blending nucleic acid engineering and polymer design, our system provides a potentially translatable platform for RNAi-based therapies.
Hidden Order and Haldane-Like Phase in Molecular Chains Assembled from Conformation-Switchable Molecules
Jialiang Deng - ,
Aidi Zhao *- ,
Ruiqi Zhang - ,
Huan Shan - ,
Bin Li *- ,
Jinlong Yang - , and
Bing Wang
Topological properties of matters have attracted tremendous interest in the past years due to the scientific and technological importance. It is of great interest to discover the analogs of topological phases in molecular architectures, if the key constituents of the phases are properly mimicked. Using scanning tunneling microscopy, we demonstrate that quasi-1D molecular chains assembled from conformation-switchable dibenzo[g,p]chrysene molecules show hidden antiparallel order analogous to the hidden antiferromagnetic order in the Haldane phase, a known topological phase of quantum spin-1 chains. This is realized by mimicking the spin degree of freedom with the intramolecular helicene chiral switches and by emulating the interspin antiferromagnetic coupling with intermolecular homochiral coupling. The discovery of the molecular analog of topological matters may inspire the search of molecular architectures with nontrivial topological properties.
Intracellular Biodegradation of Ag Nanoparticles, Storage in Ferritin, and Protection by a Au Shell for Enhanced Photothermal Therapy
Ana Espinosa - ,
Alberto Curcio - ,
Sonia Cabana - ,
Guillaume Radtke - ,
Matthieu Bugnet - ,
Jelena Kolosnjaj-Tabi - ,
Christine Péchoux - ,
Carmen Alvarez-Lorenzo - ,
Gianluigi A. Botton - ,
Amanda K. A. Silva - ,
Ali Abou-Hassan *- , and
Claire Wilhelm *
Despite their highly efficient plasmonic properties, gold nanoparticles are currently preferred to silver nanoparticles for biomedical applications such as photothermal therapy due to their high chemical stability in the biological environment. To confer protection while preserving their plasmonic properties, we allied the advantages of both materials and produced hybrid nanoparticles made of an anisotropic silver nanoplate core coated with a frame of gold. The efficiency of these hybrid nanoparticles (Ag@AuNPs) in photothermia was compared to monometallic silver nanoplates (AgNPs) or gold nanostars (AuNPs). The structural and functional properties of AuNPs, AgNPs, and Ag@AuNPs were investigated in environments of increasing complexity, in water suspensions, in cells, and in tumors in vivo. While AgNPs showed the greatest heating efficiency in suspension (followed by Ag@AuNPs and AuNPs), this trend was reversed intracellularly within a tissue-mimetic model. In this setup, AgNPs failed to provide consistent photothermal conversion over time, due to structural damage induced by the intracellular environment. Remarkably, the degraded Ag was found to be stored within the iron-storage ferritin protein. By contrast, the Au shell provided the Ag@AuNPs with total Ag biopersistence. As a result, photothermal therapy was successful with Ag@AuNPs in vivo in a mouse tumor model, providing the ultimate proof on Au shell’s capability to shield the Ag core from the harsh biological environment and preserve its excellent heating properties.
Mesenchymal Stem Cell/Red Blood Cell-Inspired Nanoparticle Therapy in Mice with Carbon Tetrachloride-Induced Acute Liver Failure
Hongxia Liang - ,
Ke Huang - ,
Teng Su - ,
Zhenhua Li - ,
Shiqi Hu - ,
Phuong-Uyen Dinh - ,
Emily A. Wrona - ,
Chen Shao - ,
Li Qiao - ,
Adam C. Vandergriff - ,
M. Taylor Hensley - ,
Jhon Cores - ,
Tyler Allen - ,
Hongyu Zhang - ,
Qinglei Zeng - ,
Jiyuan Xing - ,
Donald O. Freytes - ,
Deliang Shen - ,
Zujiang Yu *- , and
Ke Cheng *
Acute liver failure is a critical condition characterized by global hepatocyte death and often time needs a liver transplantation. Such treatment is largely limited by donor organ shortage. Stem cell therapy offers a promising option to patients with acute liver failure. Yet, therapeutic efficacy and feasibility are hindered by delivery route and storage instability of live cell products. We fabricated a nanoparticle that carries the beneficial regenerative factors from mesenchymal stem cells and further coated it with the membranes of red blood cells to increase blood stability. Unlike uncoated nanoparticles, these particles promote liver cell proliferation in vitro and have lower internalization by macrophage cells. After intravenous delivery, these artificial stem cell analogs are able to remain in the liver and mitigate carbon tetrachloride-induced liver failure in a mouse model, as gauged by histology and liver function test. Our technology provides an innovative and off-the-shelf strategy to treat liver failure.
Designing Optoelectronic Properties by On-Surface Synthesis: Formation and Electronic Structure of an Iron–Terpyridine Macromolecular Complex
Agustin Schiffrin - ,
Martina Capsoni - ,
Gelareh Farahi - ,
Chen-Guang Wang - ,
Cornelius Krull - ,
Marina Castelli - ,
Tanya Roussy - ,
Katherine A. Cochrane - ,
Yuefeng Yin - ,
Nikhil V. Medhekar - ,
Michael Fuhrer - ,
Adam Q. Shaw - ,
Wei Ji *- , and
Sarah A. Burke *
Supramolecular chemistry protocols applied on surfaces offer compelling avenues for atomic-scale control over organic–inorganic interface structures. In this approach, adsorbate–surface interactions and two-dimensional confinement can lead to morphologies and properties that differ dramatically from those achieved via conventional synthetic approaches. Here, we describe the bottom-up, on-surface synthesis of one-dimensional coordination nanostructures based on an iron (Fe)-terpyridine (tpy) interaction borrowed from functional metal–organic complexes used in photovoltaic and catalytic applications. Thermally activated diffusion of sequentially deposited ligands and metal atoms and intraligand conformational changes lead to Fe–tpy coordination and formation of these nanochains. We used low-temperature scanning tunneling microscopy and density functional theory to elucidate the atomic-scale morphology of the system, suggesting a linear tri-Fe linkage between facing, coplanar tpy groups. Scanning tunneling spectroscopy reveals the highest occupied orbitals, with dominant contributions from states located at the Fe node, and ligand states that mostly contribute to the lowest unoccupied orbitals. This electronic structure yields potential for hosting photoinduced metal-to-ligand charge transfer in the visible/near-infrared. The formation of this unusual tpy/tri-Fe/tpy coordination motif has not been observed for wet chemistry synthetic methods and is mediated by the bottom-up on-surface approach used here, offering pathways to engineer the optoelectronic properties and reactivity of metal–organic nanostructures.
Peptide-Programmable Nanoparticle Superstructures with Tailored Electrocatalytic Activity
Eun Sung Kang - ,
Yong-Tae Kim - ,
Young-Seon Ko - ,
Nam Hyeong Kim - ,
Geonhee Cho - ,
Yang Hoon Huh - ,
Ji-Hun Kim - ,
Jiyoung Nam - ,
Trung Thanh Thach - ,
David Youn - ,
Young Dok Kim - ,
Wan Soo Yun - ,
William F. DeGrado - ,
Sung Yeol Kim - ,
Paula T. Hammond - ,
Jaeyoung Lee - ,
Young-Uk Kwon - ,
Don-Hyung Ha *- , and
Yong Ho Kim *
Biomaterials derived via programmable supramolecular protein assembly provide a viable means of constructing precisely defined structures. Here, we present programmed superstructures of AuPt nanoparticles (NPs) on carbon nanotubes (CNTs) that exhibit distinct electrocatalytic activities with respect to the nanoparticle positions via rationally modulated peptide-mediated assembly. De novo designed peptides assemble into six-helix bundles along the CNT axis to form a suprahelical structure. Surface cysteine residues of the peptides create AuPt-specific nucleation site, which allow for precise positioning of NPs onto helical geometries, as confirmed by 3-D reconstruction using electron tomography. The electrocatalytic model system, i.e., AuPt for oxygen reduction, yields electrochemical response signals that reflect the controlled arrangement of NPs in the intended assemblies. Our design approach can be expanded to versatile fields to build sophisticated functional assemblies.
Eradication of Established Tumors by Chemically Self-Assembled Nanoring Labeled T Cells
Jacob R. Petersburg - ,
Jingjing Shen - ,
Clifford M. Csizmar - ,
Katherine A. Murphy - ,
Justin Spanier - ,
Kari Gabrielse - ,
Thomas S. Griffith - ,
Brian Fife - , and
Carston R. Wagner *
Our laboratory has developed chemically self-assembled nanorings (CSANs) as prosthetic antigen receptors (PARs) for the nongenetic modification of T cell surfaces. PARs have been successfully employed in vitro to activate T cells for the selective killing of leukemia cells. However, PAR efficacy has yet to be evaluated in vivo or against solid tumors. Therefore, we developed bispecific PARs that selectively target the human CD3 receptor and human epithelial cell adhesion molecule (EpCAM), which is overexpressed on multiple carcinomas and cancer stem cells. The αEpCAM/αCD3 PARs were found to stably bind T cells for >4 days, and treating EpCAM+ MCF-7 breast cancer cells with αEpCAM/αCD3 PAR-functionalized T cells resulted in the induction of IL-2, IFN-γ, and MCF-7 cytotoxicity. Furthermore, an orthotopic breast cancer model validated the ability of αEpCAM/αCD3 PAR therapy to direct T cell lytic activity toward EpCAM+ breast cancer cells in vivo, leading to tumor eradication. In vivo biodistribution studies demonstrated that PAR-T cells were formed in vivo and persist for over 48 h with rapid accumulation in tumor tissue. Following PAR treatment, the production of IL-2, IFN-γ, IL-6, and TNF-α could be significantly reduced by an infusion of clinically relevant concentrations of the FDA-approved antibiotic, trimethoprim, signaling pharmacologic PAR deactivation. Importantly, CSANs did not induce naïve T cell activation and thus exhibit a limited potential to induce naïve T cell anergy. In addition, murine immunogenicity studies demonstrated that CSANs do not induce a significant antibody response nor do they activate splenic cells. Collectively, our results demonstrate that bispecific CSANs are able to nongenetically generate reversibly modified T cells that are capable of eradicating targeted solid tumors.
Silicon Nanowire Field Effect Transistor Sensors with Minimal Sensor-to-Sensor Variations and Enhanced Sensing Characteristics
Sufi Zafar *- ,
Christopher D’Emic - ,
Ashish Jagtiani - ,
Ernst Kratschmer - ,
Xin Miao - ,
Yu Zhu - ,
Renee Mo - ,
Norma Sosa - ,
Hendrik Hamann - ,
Ghavam Shahidi - , and
Heike Riel
Silicon nanowire field effect transistor (FET) sensors have demonstrated their ability for rapid and label-free detection of proteins, nucleotide sequences, and viruses at ultralow concentrations with the potential to be a transformative diagnostic technology. Their nanoscale size gives them their ultralow detection ability but also makes their fabrication challenging with large sensor-to-sensor variations, thus limiting their commercial applications. In this work, a combined approach of nanofabrication, device simulation, materials, and electrical characterization is applied toward identifying and improving fabrication steps that induce sensor-to-sensor variations. An enhanced complementary metal-oxide-semiconductor-compatible process for fabricating silicon nanowire FET sensors on 8 in. silicon-on-insulator wafers is demonstrated. The fabricated nanowire (30 nm width) FETs with solution gates have a Nernst limit subthreshold swing (SS) of 60 ± 1 mV/decade with ∼1.7% variations, whereas literature values for SS are ≥80 mV/decade with larger (>10 times) variations. Also, their threshold voltage variations are significantly (∼3 times) reduced, compared to literature values. Furthermore, these improved FETs have significantly reduced drain current hysteresis (∼0.6 mV) and enhanced on-current to off-current ratios (∼106). These improvements resulted in nanowire FET sensors with the lowest (∼3%) reported sensor-to-sensor variations, compared to literature studies. Also, these improved nanowire sensors have the highest reported sensitivity and enhanced signal-to-noise ratio with the lowest reported defect density of 2.1 × 1018 eV–1 cm–3, in comparison to literature data. In summary, this work brings the nanowire sensor technology a step closer to commercial products for early diagnosis and monitoring of diseases.
Ultrafast Microscopy of Spin-Momentum-Locked Surface Plasmon Polaritons
Yanan Dai - ,
Maciej Dąbrowski - ,
Vartkess A. Apkarian - , and
Hrvoje Petek *
Using two-photon photoemission electron microscopy (2P-PEEM) we image the polarization dependence of coupling and propagation of surface plasmon polaritons (SPPs) launched from edges of a triangular, micrometer size, single-crystalline Ag crystal by linearly or circularly polarized light. 2P-PEEM records interferences between the optical excitation field and SPPs it creates with nanofemto space-time resolution. Both the linearly and circularly polarized femtosecond light pulses excite spatially asymmetric 2PP yield distributions, which are imaged. We attribute the asymmetry for linearly polarized light to the relative alignments of the laser polarization and triangle edges, which affect the efficiency of excitation of the longitudinal component of the SPP field. For circular polarization, the asymmetry is caused by matching of the spin angular momenta (SAM) of light and the transverse SAM of SPPs. Moreover, we show that the interference patterns recorded in the 2P-PEEM images are cast by phase shifts and amplitudes for coupling of light into the longitudinal and transverse components of SPP fields. While the interference patterns depend on the excitation polarization, nanofemto movies show that the phase and group velocities of SPPs are independent of SAM of light in time-reversal invariant media. Simulations of the wave interference reproduce the polarization and spin-dependent coupling of optical pulses into SPPs.
Vascular Interventional Radiology-Guided Photothermal Therapy of Colorectal Cancer Liver Metastasis with Theranostic Gold Nanorods
Abdul Kareem Parchur - ,
Gayatri Sharma - ,
Jaidip M. Jagtap - ,
Venkateswara Rao Gogineni - ,
Peter S. LaViolette - ,
Michael J. Flister - ,
Sarah Beth White - , and
Amit Joshi *
We report sub-100 nm optical/magnetic resonance (MR)/X-ray contrast-bearing theranostic nanoparticles (TNPs) for interventional image-guided photothermal therapy (PTT) of solid tumors. TNPs were composed of Au@Gd2O3:Ln (Ln = Yb/Er) with X-ray contrast (∼486 HU; 1014 NPs/mL, 0.167 nM) and MR contrast (∼1.1 × 108 mM–1 S–1 at 9.4 T field strength). Although TNPs are deposited in tumors following systemic administration via enhanced permeation and retention effect, the delivered dose to tumors is typically low; this can adversely impact the efficacy of PTT. To overcome this limitation, we investigated the feasibility of site-selective hepatic image-guided delivery of TNPs in rats bearing colorectal liver metastasis (CRLM). The mesenteric vein of tumor-bearing rats was catheterized, and TNPs were infused into the liver by accessing the portal vein for site-selective delivery. The uptake of TNPs with hepatic delivery was compared with systemic administration. MR imaging confirmed that delivery via the hepatic portal vein can double the CRLM tumor-to-liver contrast compared with systemic administration. Photothermal ablation was performed by inserting a 100 μm fiber-optic carrying 808 nm light via a JB1, 3-French catheter for 3 min under DynaCT image guidance. Histological analysis revealed that the thermal damage was largely confined to the tumor region with minimal damage to the adjacent liver tissue. Transmission electron microscopy imaging validated the stability of core–shell structure of TNPs in vivo pre- and post-PTT. TNPs comprising Gd-shell-coated Au nanorods can be effectively employed for the site-directed PTT of CRLM by leveraging interventional radiology methods.
Determination of Polypeptide Conformation with Nanoscale Resolution in Water
Georg Ramer - ,
Francesco Simone Ruggeri - ,
Aviad Levin - ,
Tuomas P. J. Knowles - , and
Andrea Centrone *
The folding and acquisition of proteins native structure is central to all biological processes of life. By contrast, protein misfolding can lead to toxic amyloid aggregates formation, linked to the onset of neurodegenerative disorders. To shed light on the molecular basis of protein function and malfunction, it is crucial to access structural information on single protein assemblies and aggregates under native conditions. Yet, current conformation-sensitive spectroscopic methods lack the spatial resolution and sensitivity necessary for characterizing heterogeneous protein aggregates in solution. To overcome this limitation, here we use photothermal-induced resonance to demonstrate that it is possible to acquire nanoscale infrared spectra in water with high signal-to-noise ratio (SNR). Using this approach, we probe supramolecular aggregates of diphenylalanine, the core recognition module of the Alzheimer’s β-amyloid peptide, and its derivative Boc-diphenylalanine. We achieve nanoscale resolved IR spectra and maps in air and water with comparable SNR and lateral resolution, thus enabling accurate identification of the chemical and structural state of morphologically similar networks at the single aggregate (i.e., fibril) level.
Reversibly Stabilized Polycation Nanoparticles for Combination Treatment of Early- and Late-Stage Metastatic Breast Cancer
Gang Chen - ,
Yixin Wang - ,
Pengkai Wu - ,
Yiwen Zhou - ,
Fei Yu - ,
Chenfei Zhu - ,
Zhaoting Li - ,
Yu Hang - ,
Kaikai Wang - ,
Jing Li - ,
Minjie Sun *- , and
David Oupicky *
Metastatic breast cancer is a major cause of cancer-related female mortality worldwide. The signal transducer and activator of transcription 3 (STAT3) and the chemokine receptor CXCR4 are involved in the metastatic spread of breast cancer. The goal of this study was to develop nanomedicine treatment based on combined inhibition of STAT3 and CXCR4. We synthesized a library of CXCR4-inhibiting polymers with a combination of beneficial features that included PEGylation, fluorination, and bioreducibility to achieve systemic delivery of siRNA to silence STAT3 expression in the tumors. An in vivo structure–activity relationship study in an experimental lung metastasis model revealed superior antimetastatic activity of bioreducible fluorinated polyplexes when compared with nonreducible controls despite similar CXCR4 antagonism and the ability to inhibit in vitro cancer cell invasion. When compared with nonreducible and nonfluorinated polyplexes, improved siRNA delivery was observed with the bioreducible fluorinated polyplexes. The improvement was ascribed to a combination of enhanced physical stability, decreased serum destabilization, and improved intracellular trafficking. Pharmacokinetic analysis showed that fluorination decreased the rate of renal clearance of the polyplexes and contributed to enhanced accumulation in the tumors. Therapeutic efficacy of the polyplexes with STAT3 siRNA was assessed in early stage breast cancer and late-stage metastatic breast cancer with primary tumor resection. Strong inhibition of the primary tumor growth and pronounced antimetastatic effects were observed in both models of metastatic breast cancer. Mechanistic studies revealed multifaceted mechanism of action of the combined STAT3 and CXCR4 inhibition by the developed polyplexes relying both on local and systemic effects.
Murine and Non-Human Primate Dendritic Cell Targeting Nanoparticles for in Vivo Generation of Regulatory T-Cells
Sebastian O. Sterling - ,
Svjetlana Kireta - ,
Steve J. P. McInnes - ,
Francis D. Kette - ,
Kisha N. Sivanathan - ,
Juewan Kim - ,
Eduardo J. Cueto-Diaz - ,
Frederique Cunin - ,
Jean-Olivier Durand - ,
Christopher J. Drogemuller - ,
Robert P. Carroll - ,
Nicolas H. Voelcker *- , and
Patrick T. Coates *
Porous silicon nanoparticles (pSiNP), modified to target dendritic cells (DC), provide an alternate strategy for the delivery of immunosuppressive drugs. Here, we aimed to develop a DC-targeting pSiNP displaying c-type lectin, dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN), and CD11c monoclonal antibodies. The in vivo tracking of these fluorescent DC-targeting nanoparticles was assessed in both C57BL/6 mice and common marmosets (Callithrix jacchus) by intravenous injection (20 mg/kg). Rapamycin and ovalbumin (OVA)323–339 peptide loaded pSiNP were employed to evaluate their ability to generate murine CD4+CD25+FoxP3+ regulatory T-cells in vivo within OVA sensitized mice. In vivo, pSiNP migrated to the liver, kidneys, lungs, and spleen in both mice and marmosets. Flow cytometry confirmed pSiNP uptake by splenic and peripheral blood DC when functionalized with targeting antibodies. C57BL/6 OVA sensitized mice injected with CD11c-pSiNP loaded with rapamycin + OVA323–339 produced a 5-fold higher number of splenic regulatory T-cells compared to control mice, at 40 days post-pSiNP injection. These results demonstrate the importance of the immobilized targeting antibodies to enhance cellular uptake and enable the in vivo generation of splenic regulatory T-cells.
Selective Laser-Assisted Synthesis of Tubular van der Waals Heterostructures of Single-Layered PbI2 within Carbon Nanotubes Exhibiting Carrier Photogeneration
Stefania Sandoval - ,
Dejan Kepić - ,
Ángel Pérez del Pino *- ,
Enikö György - ,
Andrés Gómez - ,
Martin Pfannmoeller - ,
Gustaaf Van Tendeloo - ,
Belén Ballesteros *- , and
Gerard Tobias *
The electronic and optical properties of two-dimensional layered materials allow the miniaturization of nanoelectronic and optoelectronic devices in a competitive manner. Even larger opportunities arise when two or more layers of different materials are combined. Here, we report on an ultrafast energy efficient strategy, using laser irradiation, which allows bulk synthesis of crystalline single-layered lead iodide in the cavities of carbon nanotubes by forming cylindrical van der Waals heterostructures. In contrast to the filling of van der Waals solids into carbon nanotubes by conventional thermal annealing, which favors the formation of inorganic nanowires, the present strategy is highly selective toward the growth of monolayers forming lead iodide nanotubes. The irradiated bulk material bearing the nanotubes reveals a decrease of the resistivity as well as a significant increase in the current flow upon illumination. Both effects are attributed to the presence of single-walled lead iodide nanotubes in the cavities of carbon nanotubes, which dominate the properties of the whole matrix. The present study brings in a simple, ultrafast and energy efficient strategy for the tailored synthesis of rolled-up single-layers of lead iodide (i.e., single-walled PbI2 nanotubes), which we believe could be expanded to other two-dimensional (2D) van der Waals solids. In fact, initial tests with ZnI2 already reveal the formation of single-walled ZnI2 nanotubes, thus proving the versatility of the approach.
High Aspect Ratio Nanostructures Kill Bacteria via Storage and Release of Mechanical Energy
Denver P. Linklater - ,
Michael De Volder - ,
Vladimir A. Baulin - ,
Marco Werner - ,
Sarah Jessl - ,
Mehdi Golozar - ,
Laura Maggini - ,
Sergey Rubanov - ,
Eric Hanssen - ,
Saulius Juodkazis - , and
Elena P. Ivanova *
The threat of a global rise in the number of untreatable infections caused by antibiotic-resistant bacteria calls for the design and fabrication of a new generation of bactericidal materials. Here, we report a concept for the design of antibacterial surfaces, whereby cell death results from the ability of the nanofeatures to deflect when in contact with attaching cells. We show, using three-dimensional transmission electron microscopy, that the exceptionally high aspect ratio (100–3000) of vertically aligned carbon nanotubes (VACNTs) imparts extreme flexibility, which enhances the elastic energy storage in CNTs as they bend in contact with bacteria. Our experimental and theoretical analyses demonstrate that, for high aspect ratio structures, the bending energy stored in the CNTs is a substantial factor for the physical rupturing of both Gram-positive and Gram-negative bacteria. The highest bactericidal rates (99.3% for Pseudomonas aeruginosa and 84.9% for Staphylococcus aureus) were obtained by modifying the length of the VACNTs, allowing us to identify the optimal substratum properties to kill different types of bacteria efficiently. This work highlights that the bactericidal activity of high aspect ratio nanofeatures can outperform both natural bactericidal surfaces and other synthetic nanostructured multifunctional surfaces reported in previous studies. The present systems exhibit the highest bactericidal activity of a CNT-based substratum against a Gram-negative bacterium reported to date, suggesting the possibility of achieving close to 100% bacterial inactivation on VACNT-based substrata.
Flexible Guidance of Microengines by Dynamic Topographical Pathways in Ferrofluids
Fan Yang - ,
Fangzhi Mou *- ,
Yuzhou Jiang - ,
Ming Luo - ,
Leilei Xu - ,
Huiru Ma - , and
Jianguo Guan *
In this work, we demonstrate a simple, versatile, and real-time motion guidance strategy for artificial microengines and motile microorganisms in a ferrofluid by dynamic topographical pathways (DTPs), which are assembled from superparamagnetic nanoparticles in response to external magnetic field (H). In this general strategy, the DTPs can exert anisotropic resistance forces on autonomously moving microengines and thus regulate their orientation. As the DTPs with different directions and lengths can be reversibly and swiftly assembled in response to the applied H, the microengines in the ferrofluid can be guided on demand with controlled motion directions and trajectories, including circular, elliptical, straight-line, semi-sine, and sinusoidal trajectories. The as-demonstrated control strategy obviates reliance on the customized responses of micromotors and applies to autonomously propelling agents swimming both in bulk and near substrate walls. Furthermore, the microengines (or motile microorganisms) in a ferrofluid can be considered as an integrated system, and it may inspire the development of intelligent systems with cooperative functions for biomedical and environmental applications.
Aqueous Ion Trapping and Transport in Graphene-Embedded 18-Crown-6 Ether Pores
Alex Smolyanitsky *- ,
Eugene Paulechka - , and
Kenneth Kroenlein
Using extensive room-temperature molecular dynamics simulations, we investigate selective aqueous cation trapping and permeation in graphene-embedded 18-crown-6 ether pores. We show that in the presence of suspended water-immersed crown-porous graphene, K+ ions rapidly organize and trap stably within the pores, in contrast with Na+ ions. As a result, significant qualitative differences in permeation between ionic species arise. The trapped ion occupancy and permeation behaviors are shown to be highly voltage-tunable. Interestingly, we demonstrate the possibility of performing conceptually straightforward ion-based logical operations resulting from controllable membrane charging by the trapped ions. In addition, we show that ionic transistors based on crown-porous graphene are possible, suggesting utility in cascaded ion-based logic circuitry. Our results indicate that in addition to numerous possible applications of graphene-embedded crown ether nanopores, including deionization, ion sensing/sieving, and energy storage, simple ion-based logical elements may prove promising as building blocks for reliable nanofluidic computational devices.
Locally Deployable Nanofiber Patch for Sequential Drug Delivery in Treatment of Primary and Advanced Orthotopic Hepatomas
Jiannan Li - ,
Weiguo Xu - ,
Di Li - ,
Tongjun Liu - ,
Yu Shrike Zhang *- ,
Jianxun Ding *- , and
Xuesi Chen *
With unsatisfactory effects of systemic chemotherapy for treatment of unresectable or advanced hepatoma, local and sustained delivery of chemotherapeutic agents is becoming a promising solution. The in situ administered platforms increase the drug concentrations in tumor regions, decrease the side effects to organs, prevent the damage to vascular endothelium, and reduce the frequency of drug administration. The prevalent strategy based on minimally invasive transarterial chemoembolization oftentimes induces upper gastrointestinal hemorrhage, liver failure, and liver abscess. In addition, integrating various antitumor drugs in one platform, especially the drugs with different hydrophilic/hydrophobic properties, and achieving sustained and/or sequential release profiles to synergistically inhibit cancer progression remain challenging. In this study, a local drug delivery system made of an emulsion-electrospun polymer patch was developed, which contained hydrophobic 10-hydroxycamptothecin (HCPT) and hydrophilic tea polyphenols (TP) in the shell and core of the nanofiber, respectively. Due to this core–sheath structure, HCPT and TP exhibited sustained and sequential releases first with HCPT followed by TP. HCPT was used to suppress the proliferation and malignant transformation of hepatoma, whereas TP was aimed to decrease the levels of oxygen free radicals and further prevent the invasion and metastasis of tumor cells. Our study presented the potential superiority of this class of core–sheath structured nanofiber membranes in localized treatment of both primary and advanced orthotopic hepatomas.
Ferroelectric Field-Effect Transistors Based on MoS2 and CuInP2S6 Two-Dimensional van der Waals Heterostructure
Mengwei Si - ,
Pai-Ying Liao - ,
Gang Qiu - ,
Yuqin Duan - , and
Peide D. Ye *
We demonstrate room-temperature ferroelectric field-effect transistors (Fe-FETs) with MoS2 and CuInP2S6 two-dimensional (2D) van der Waals heterostructure. The ferroelectric CuInP2S6 is a 2D ferroelectric insulator, integrated on top of MoS2 channel providing a 2D/2D semiconductor/insulator interface without dangling bonds. The MoS2- and CuInP2S6-based 2D van der Waals heterostructure Fe-FETs exhibit a clear counterclockwise hysteresis loop in transfer characteristics, demonstrating their ferroelectric properties. This stable nonvolatile memory property can also be modulated by the back-gate bias of the MoS2 transistors because of the tuning of capacitance matching between the MoS2 channel and the ferroelectric CuInP2S6, leading to the enhancement of the on/off current ratio. Meanwhile, the CuInP2S6 thin film also shows resistive switching characteristics with more than four orders of on/off ratio between low- and high-resistance states, which is also promising for resistive random-access memory applications.
Atomic Scale Photodetection Enabled by a Memristive Junction
Alexandros Emboras *- ,
Alessandro Alabastri - ,
Fabian Ducry - ,
Bojun Cheng - ,
Yannick Salamin - ,
Ping Ma - ,
Samuel Andermatt - ,
Benedikt Baeuerle - ,
Arne Josten - ,
Christian Hafner - ,
Mathieu Luisier - ,
Peter Nordlander - , and
Juerg Leuthold *
The optical control of atomic relocations in a metallic quantum point contact is of great interest because it addresses the fundamental limit of “CMOS scaling”. Here, by developing a platform for combined electronics and photonics on the atomic scale, we demonstrate an optically controlled electronic switch based on the relocation of atoms. It is shown through experiments and simulations how the interplay between electrical, optical, and light-induced thermal forces can reversibly relocate a few atoms and enable atomic photodetection with a digital electronic response, a high resistance extinction ratio (70 dB), and a low OFF-state current (10 pA) at room temperature. Additionally, the device introduced here displays an optically induced pinched hysteretic current (optical memristor). The photodetector has been tested in an experiment with real optical data at 0.5 Gbit/s, from which an eye diagram visualizing millions of detection cycles could be produced. This demonstrates the durability of the realized atomic scale devices and establishes them as alternatives to traditional photodetectors.
Homeotropic Self-Alignment of Discotic Liquid Crystals for Nanoporous Polymer Films
Jody A. M. Lugger - ,
Dirk J. Mulder - ,
Subham Bhattacharjee - , and
Rint P. Sijbesma *
This publication is Open Access under the license indicated. Learn More
Nanostructured polymer films with continuous, membrane-spanning pores from polymerizable hexagonal columnar discotic liquid crystals (LCs) were fabricated. A robust alignment method was developed to obtain homeotropic alignment of columns between glass surfaces by adding a small amount of a tri(ethylene glycol) modified analogue of the mesogen as a dopant that preferentially wets glass. The homeotropic LC alignment was fixated via a photoinitiated free radical copolymerization of a high-temperature tolerant trisallyl mesogen with a divinyl ester. Removal of the hydrogen-bonded template from the aligned columns afforded a nanoporous network with pores of nearly 1 nm in diameter perpendicular to the surface, and without noticeable collapse of the nanopores. The effect of pore orientation was demonstrated by an adsorption experiment in which homeotropic film showed a threefold increase in the initial uptake rate of methylene blue compared to planarly aligned films.
Bacteria-Activated Janus Particles Driven by Chemotaxis
Zihan Huang - ,
Pengyu Chen - ,
Guolong Zhu - ,
Ye Yang - ,
Ziyang Xu - , and
Li-Tang Yan *
In the development of biocompatible nano-/micromotors for drug and cargo delivery, motile bacteria represent an excellent energy source for biomedical applications. Despite intense research of the fabrication of bacteria-based motors, how to effectively utilize the instinctive responses of bacteria to environmental stimuli in the fabrication process, particularly, chemotaxis, remains an urgent and critical issue. Here, by developing a molecular-dynamics model of bacterial chemotaxis, we present an investigation of the transport of a bacteria-activated Janus particle driven by chemotaxis. Upon increasing the stimuli intensity, we find that the transport of the Janus particle undergoes an intriguing second-order state transition: from a composite random walk, combining power-law-distributed truncated Lévy flights with Brownian jiggling, to an enhanced directional transport with size-dependent reversal of locomotion. A state diagram of Janus-particle transport depending on the stimuli intensity and particle size is presented, which allows approaches to realize controllable and predictable propulsion directions. The physical mechanism of these transport behaviors is revealed by performing a theoretical modeling based on the bacterial noise and Janus geometries. Our findings could provide a fundamental insight into the physics underlying the transport of anisotropic particles driven by microorganisms and highlight stimulus-response techniques and asymmetrical design as a versatile strategy to possess a wide array of potential applications for future biocompatible nano-/microdevices.
Force-Induced Unravelling of DNA Origami
Megan C. Engel *- ,
David M. Smith - ,
Markus A. Jobst - ,
Martin Sajfutdinow - ,
Tim Liedl - ,
Flavio Romano - ,
Lorenzo Rovigatti - ,
Ard A. Louis - , and
Jonathan P. K. Doye
The mechanical properties of DNA nanostructures are of widespread interest as applications that exploit their stability under constant or intermittent external forces become increasingly common. We explore the force response of DNA origami in comprehensive detail by combining AFM single molecule force spectroscopy experiments with simulations using oxDNA, a coarse-grained model of DNA at the nucleotide level, to study the unravelling of an iconic origami system: the Rothemund tile. We contrast the force-induced melting of the tile with simulations of an origami 10-helix bundle. Finally, we simulate a recently proposed origami biosensor, whose function takes advantage of origami behavior under tension. We observe characteristic stick–slip unfolding dynamics in our force–extension curves for both the Rothemund tile and the helix bundle and reasonable agreement with experimentally observed rupture forces for these systems. Our results highlight the effect of design on force response: we observe regular, modular unfolding for the Rothemund tile that contrasts with strain-softening of the 10-helix bundle which leads to catastropic failure under monotonically increasing force. Further, unravelling occurs straightforwardly from the scaffold ends inward for the Rothemund tile, while the helix bundle unfolds more nonlinearly. The detailed visualization of the yielding events provided by simulation allows preferred pathways through the complex unfolding free-energy landscape to be mapped, as a key factor in determining relative barrier heights is the extensional release per base pair broken. We shed light on two important questions: how stable DNA nanostructures are under external forces and what design principles can be applied to enhance stability.
Enhanced Performance of Ge Photodiodes via Monolithic Antireflection Texturing and α-Ge Self-Passivation by Inverse Metal-Assisted Chemical Etching
Munho Kim - ,
Soongyu Yi - ,
Jeong Dong Kim - ,
Xin Yin - ,
Jun Li - ,
Jihye Bong - ,
Dong Liu - ,
Shih-Chia Liu - ,
Alexander Kvit - ,
Weidong Zhou - ,
Xudong Wang - ,
Zongfu Yu - ,
Zhenqiang Ma - , and
Xiuling Li *
Surface antireflection micro and nanostructures, normally formed by conventional reactive ion etching, offer advantages in photovoltaic and optoelectronic applications, including wider spectral wavelength ranges and acceptance angles. One challenge in incorporating these structures into devices is that optimal optical properties do not always translate into electrical performance due to surface damage, which significantly increases surface recombination. Here, we present a simple approach for fabricating antireflection structures, with self-passivated amorphous Ge (α-Ge) surfaces, on single crystalline Ge (c-Ge) surface using the inverse metal-assisted chemical etching technology (I-MacEtch). Vertical Schottky Ge photodiodes fabricated with surface structures involving arrays of pyramids or periodic nano-indentations show clear improvements not only in responsivity, due to enhanced optical absorption, but also in dark current. The dark current reduction is attributed to the Schottky barrier height increase and self-passivation effect of the i-MacEtch induced α-Ge layer formed on top of the c-Ge surface. The results demonstrated in this work show that MacEtch can be a viable technology for advanced light trapping and surface engineering in Ge and other semiconductor based optoelectronic devices.
On-Demand Drug Release from Gold Nanoturf for a Thermo- and Chemotherapeutic Esophageal Stent
Sori Lee - ,
Gyoyeon Hwang - ,
Tae Hee Kim - ,
S. Joon Kwon - ,
Jong Uk Kim - ,
Kyongbeom Koh - ,
Byeonghak Park - ,
Haeleen Hong - ,
Ki Jun Yu - ,
Heeyeop Chae - ,
Youngmee Jung *- ,
Jiyeon Lee *- , and
Tae-il Kim *
Stimuli-responsive delivery systems for cancer therapy have been increasingly used to promote the on-demand therapeutic efficacy of anticancer drugs and, in some cases, simultaneously generate heat in response to a stimulus, resulting in hyperthermia. However, their application is still limited due to the systemic drawbacks of intravenous delivery, such as rapid clearance from the bloodstream and the repeat injections required for sustained safe dosage, which can cause overdosing. Here, we propose a gold (Au)-coated nanoturf structure as an implantable therapeutic interface for near-infrared (NIR)-mediated on-demand hyperthermia chemotherapy. The Au nanoturf possessed long-lasting doxorubicin (DOX) duration, which helps facilitate drug release in a sustained and prolonged manner. Moreover, the Au-coated nanoturf provides reproducible hyperthermia induced by localized surface plasmon resonances under NIR irradiation. Simultaneously, the NIR-mediated temperature increase can promote on-demand drug release at desired time points. For in vivo analysis, the Au nanoturf structure was applied on an esophageal stent, which needs sustained anticancer treatment to prevent tumor recurrence on the implanted surface. This thermo- and chemo-esophageal stent induced significant cancer cell death with released drug and hyperthermia. These phenomena were also confirmed by theoretical analysis. The proposed strategy provides a solution to achieve enhanced thermo-/chemotherapy and has broad applications in sustained cancer treatments.
Electrically Driven Reversible Magnetic Rotation in Nanoscale Multiferroic Heterostructures
Junxiang Yao - ,
Xiao Song - ,
Xingsen Gao *- ,
Guo Tian - ,
Peilian Li - ,
Hua Fan - ,
Zhifeng Huang - ,
Wenda Yang - ,
Deyang Chen - ,
Zhen Fan - ,
Min Zeng - , and
Jun-Ming Liu *
Electrically driven magnetic switching (EDMS) is highly demanded for next-generation advanced memories or spintronic devices. The key challenge is to achieve repeatable and reversible EDMS at sufficiently small scale. In this work, we reported an experimental realization of room-temperature, electrically driven, reversible, and robust 120° magnetic state rotation in nanoscale multiferroic heterostructures consisting of a triangular Co nanomagnet array on tetragonal BiFeO3 films, which can be directly monitored by magnetic force microscope (MFM) imaging. The observed reversible magnetic switching in an individual nanomagnet can be triggered by a small electric pulse within 10 V with an ultrashort time of ∼10 ns, which also demonstrates sufficient switching cycling and months-long retention lifetime. A mechanism based on synergic effects of interfacial strain and exchange coupling plus shape anisotropy was also proposed, which was also verified by micromagnetic simulations. Our results create an avenue to engineer the nanoscale EDMS for low-power-consumption, high-density, nonvolatile magnetoelectric memories and beyond.
An Ultrasensitive Diagnostic Biochip Based on Biomimetic Periodic Nanostructure-Assisted Rolling Circle Amplification
Qian Yao - ,
Yingqian Wang - ,
Jie Wang - ,
Shaomin Chen - ,
Haoyang Liu - ,
Zhuoran Jiang - ,
Xiaoe Zhang - ,
Songmei Liu - ,
Quan Yuan *- , and
Xiang Zhou *
Developing portable and sensitive devices for point of care detection of low abundance bioactive molecules is highly valuable in early diagnosis of disease. Herein, an ultrasensitive photonic crystals-assisted rolling circle amplification (PCs-RCA) biochip was constructed and further applied to circulating microRNAs (miRNAs) detection in serum. The biochip integrated the optical signal enhancement capability of biomimetic PCs surface with the thousand-fold signal amplification feature of RCA. The biomimetic PCs displayed periodic dielectric nanostructure and significantly enhanced the signal intensity of RCA reaction, leading to efficient improvement of detection sensitivity. A limit of detection (LOD) as low as 0.7 aM was obtained on the PCs-RCA biochip, and the LOD was 7 orders of magnitude lower than that of standard RCA. Moreover, the PCs-RCA biochip could discriminate a single base variation in miRNAs. Accurate quantification of ultralow-abundance circulating miRNAs in clinical serum samples was further achieved with the PCs-RCA biochip, and patients with the nonsmall cell lung carcinoma were successfully distinguished from healthy donors. The PCs-RCA biochip can detect bioactive molecules with ultrahigh sensitivity and good specificity, making it valuable in clinical disease diagnosis and health assessment.
Synthesis of Highly Uniform Nickel Multipods with Tunable Aspect Ratio by Microwave Power Control
Parth N. Vakil - ,
David A. Hardy - , and
Geoffrey F. Strouse *
As the importance of anisotropic nanostructures and the role of surfaces continues to rise in applications including catalysis, magneto-optics, and electromagnetic interference shielding, there is a need for efficient and economical synthesis routes for such nanostructures. The article describes the application of cycled microwave power for the rapid synthesis of highly branched pure-phase face-centered cubic crystalline nickel multipod nanostructures with >99% multipod population. By controlling the power delivery to the reaction mixture through cycling, superior control is achieved over the growth kinetics of the metallic nanostructures, allowing formation of multipods consisting of arms with different aspect ratios. The multipod structures are formed under ambient conditions in a simple reaction system composed of nickel acetylacetonate (Ni(acac)2), oleylamine (OAm), and oleic acid (OAc) in a matter of minutes by selective heating at the (111) overgrowth corners on Ni nanoseeds. The selective heating at the corners leads to accelerated autocatalytic growth along the ⟨111⟩ direction through a “lightning rod” effect. The length is proprtional to the length and number of microwave (MW)-on cycles, whereas the core size is controlled by continuous MW power delivery. The roles of heating mode (cycling versus variable power versus convective heating) during synthesis of the materials is explored, allowing a mechanism into how cycled microwave energy may allow fast multipod evolution to be proposed.
Simultaneous Blood–Brain Barrier Crossing and Protection for Stroke Treatment Based on Edaravone-Loaded Ceria Nanoparticles
Qunqun Bao - ,
Ping Hu *- ,
Yingying Xu - ,
Tiansheng Cheng - ,
Chenyang Wei - ,
Limin Pan *- , and
Jianlin Shi *
Cerebral vasculature and neuronal networks will be largely destroyed due to the oxidative damage by overproduced reactive oxygen species (ROS) during a stroke, accompanied by the symptoms of ischemic injury and blood–brain barrier (BBB) disruption. Ceria nanoparticles, acting as an effective and recyclable ROS scavenger, have been shown to be highly effective in neuroprotection. However, the brain access of nanoparticles can only be achieved by targeting the damaged area of BBB, leading to the disrupted BBB being unprotected and to turbulence of the microenvironment in the brain. Nevertheless, the integrity of the BBB will cause very limited accumulation of therapeutic nanoparticles in brain lesions. This dilemma is a great challenge in the development of efficient stroke nanotherapeutics. Herein, we have developed an effective stroke treatment agent based on monodisperse ceria nanoparticles, which are loaded with edaravone and modified with Angiopep-2 and poly(ethylene glycol) on their surface (E-A/P-CeO2). The as-designed E-A/P-CeO2 features highly effective BBB crossing via receptor-mediated transcytosis to access brain tissues and synergistic elimination of ROS by both the loaded edaravone and ceria nanoparticles. As a result, the E-A/P-CeO2 with low toxicity and excellent hemo/histocompatibility can be used to effectively treat strokes due to great intracephalic uptake enhancement and, in the meantime, effectively protect the BBB, holding great potentials in stroke therapy with much mitigated harmful side effects and sequelae.
Enhanced Intracellular Ca2+ Nanogenerator for Tumor-Specific Synergistic Therapy via Disruption of Mitochondrial Ca2+ Homeostasis and Photothermal Therapy
Lihua Xu - ,
Guihua Tong - ,
Qiaoli Song - ,
Chunyu Zhu - ,
Hongling Zhang - ,
Jinjin Shi *- , and
Zhenzhong Zhang *
Breast cancer therapy has always been a hard but urgent issue. Disruption of mitochondrial Ca2+ homeostasis has been reported as an effective antitumor strategy, while how to contribute to mitochondrial Ca2+ overload effectively is a critical issue. To solve this issue, we designed and engineered a dual enhanced Ca2+ nanogenerator (DECaNG), which can induce elevation of intracellular Ca2+ through the following three ways: Calcium phosphate (CaP)-doped hollow mesoporous copper sulfide was the basic Ca2+ nanogenerator to generate Ca2+ directly and persistently in the lysosomes (low pH). Near-infrared light radiation (NIR, such as 808 nm laser) can accelerate Ca2+ generation from the basic Ca2+ nanogenerator by disturbing the crystal lattice of hollow mesoporous copper sulfide via NIR-induced heat. Curcumin can facilitate Ca2+ release from the endoplasmic reticulum to cytoplasm and inhibit expelling of Ca2+ in cytoplasm through the cytoplasmic membrane. The in vitro study showed that DECaNG could produce a large amount of Ca2+ directly and persistently to flow to mitochondria, leading to upregulation of Caspase-3, cytochrome c, and downregulation of Bcl-2 and ATP followed by cell apoptosis. In addition, DECaNG had an outstanding photothermal effect. Interestingly, it was found that DECaNG exerted a stronger photothermal effect at lower pH due to the super small nanoparticles effect, thus enhancing photothermal therapy. In the in vivo study, the nanoplatform had good tumor targeting and treatment efficacy via a combination of disruption of mitochondrial Ca2+ homeostasis and photothermal therapy. The metabolism of CaNG was sped up through disintegration of CaNG into smaller nanoparticles, reducing the retention time of the nanoplatform in vivo. Therefore, DECaNG can be a promising drug delivery system for breast cancer therapy.
Oxide–Carbon Nanofibrous Composite Support for a Highly Active and Stable Polymer Electrolyte Membrane Fuel-Cell Catalyst
Yukwon Jeon - ,
Yunseong Ji - ,
Yong Il Cho - ,
Chanmin Lee - ,
Dae-Hwan Park - , and
Yong-Gun Shul *
Well-designed electronic configurations and structural properties of electrocatalyst alter the activity, stability, and mass transport for enhanced catalytic reactions. We introduce a nanofibrous oxide–carbon composite by an in situ method of carbon nanofiber (CNF) growth by highly dispersed Ni nanoparticles that are exsoluted from a NiTiO3 surface. The nanofibrous feature has a 3D web structure with improved mass-transfer properties at the electrode. In addition, the design of the CNF/TiO2 support allows for complex properties for excellent stability and activity from the TiO2 oxide support and high electric conductivity through the connected CNF, respectively. Developed CNF/TiO2–Pt nanofibrous catalyst displays exemplary oxygen-reduction reaction (ORR) activity with significant improvement of the electrochemical surface area. Moreover, exceptional resistance to carbon corrosion and Pt dissolution is proven by durability-test protocols based on the Department of Energy. These results are well-reflected to the single-cell tests with even-better performance at the kinetic zone compared to the commercial Pt/C under different operation conditions. CNF/TiO2–Pt displays an enhanced active state due to the strong synergetic interactions, which decrease the Pt d-band vacancy by electron transfer from the oxide–carbon support. A distinct reaction mechanism is also proposed and eventually demonstrates a promising example of an ORR electrocatalyst design.
Modification of Extracellular Vesicles by Fusion with Liposomes for the Design of Personalized Biogenic Drug Delivery Systems
Max Piffoux - ,
Amanda K. A. Silva - ,
Claire Wilhelm - ,
Florence Gazeau *- , and
David Tareste *
Extracellular vesicles (EVs) are recognized as nature’s own carriers to transport macromolecules throughout the body. Hijacking this endogenous communication system represents an attractive strategy for advanced drug delivery. However, efficient and reproducible loading of EVs with therapeutic or imaging agents still represents a bottleneck for their use as a drug delivery system. Here, we developed a method for modifying cell-derived EVs through their fusion with liposomes containing both membrane and soluble cargoes. The fusion of EVs with functionalized liposomes was triggered by polyethylene glycol (PEG) to create smart biosynthetic hybrid vectors. This versatile method proved to be efficient to enrich EVs with exogenous lipophilic or hydrophilic compounds, while preserving their intrinsic content and biological properties. Hybrid EVs improved cellular delivery efficiency of a chemotherapeutic compound by a factor of 3–4, as compared to the free drug or the drug-loaded liposome precursor. On one side, this method allows the biocamouflage of liposomes by enriching their lipid bilayer and inner compartment with biogenic molecules. On the other side, the proposed fusion strategy enables efficient EV loading, and the pharmaceutical development of EVs with adaptable activity and drug delivery property.
Perfect Strain Relaxation in Metamorphic Epitaxial Aluminum on Silicon through Primary and Secondary Interface Misfit Dislocation Arrays
Xiang-Yang Liu - ,
Ilke Arslan - ,
Bruce W. Arey - ,
Justin Hackley - ,
Vincenzo Lordi - , and
Christopher J. K. Richardson *
Understanding the atomically precise arrangement of atoms at epitaxial interfaces is important for emerging technologies such as quantum materials that have function and performance dictated by bonds and defects that are energetically active on the micro-electronvolt scale. A combination of atomistic modeling and dislocation theory analysis describes both primary and secondary dislocation networks at the metamorphic Al/Si (111) interface, which is experimentally validated by atomic resolution scanning transmission electron microscopy. The electron microscopy images show primary misfit dislocations for the majority of the strain relief and evidence of a secondary structure allowing for complete relaxation of the Al–Si misfit strain. This study demonstrates the equilibrium interface that represents the lowest energy structure of a highly mismatched and semicoherent single-crystal interface with complete strain relief in an atomically abrupt structure.
Cross-Linked Fluorescent Supramolecular Nanoparticles for Intradermal Controlled Release of Antifungal Drug—A Therapeutic Approach for Onychomycosis
Fang Wang - ,
Peng Yang - ,
Jin-sil Choi - ,
Petar Antovski - ,
Yazhen Zhu - ,
Xiaobin Xu - ,
Ting-Hao Kuo - ,
Li-En Lin - ,
Diane N. H. Kim - ,
Pin-Cheng Huang - ,
Haoxiang Xu - ,
Chin-Fa Lee - ,
Changchun Wang *- ,
Cheng-Chih Hsu *- ,
Kai Chen *- ,
Paul S. Weiss *- , and
Hsian-Rong Tseng *
The existing approaches to onychomycosis demonstrate limited success since the commonly used oral administration and topical cream only achieve temporary effective drug concentration at the fungal infection sites. An ideal therapeutic approach for onychomycosis should have (i) the ability to introduce antifungal drugs directly to the infected sites; (ii) finite intradermal sustainable release to maintain effective drug levels over prolonged time; (iii) a reporter system for monitoring maintenance of drug level; and (iv) minimum level of inflammatory responses at or around the fungal infection sites. To meet these expectations, we introduced ketoconazole-encapsulated cross-linked fluorescent supramolecular nanoparticles (KTZ⊂c-FSMNPs) as an intradermal controlled release solution for treating onychomycosis. A two-step synthetic approach was adopted to prepare a variety of KTZ⊂c-FSMNPs. Initial characterization revealed that 4800 nm KTZ⊂c-FSMNPs exhibited high KTZ encapsulation efficiency/capacity, optimal fluorescent property, and sustained KTZ release profile. Subsequently, 4800 nm KTZ⊂c-FSMNPs were chosen for in vivo studies using a mouse model, wherein the KTZ⊂c-FSMNPs were deposited intradermally via tattoo. The results obtained from (i) in vivo fluorescence imaging, (ii) high-performance liquid chromatography quantification of residual KTZ, (iii) matrix-assisted laser desorption/ionization mass spectrometry imaging mapping of KTZ distribution in intradermal regions around the tattoo site, and (iv) histology for assessment of local inflammatory responses and biocompatibility, suggest that 4800 nm KTZ⊂c-FSMNPs can serve as an effective treatment for onychomycosis.
Self-Assembled Chiral Photonic Crystals from a Colloidal Helix Racemate
Qun-li Lei - ,
Ran Ni *- , and
Yu-qiang Ma *
Chiral crystals consisting of microhelices have many optical properties, while presently available fabrication processes limit their large-scale applications in photonic devices. Here, by using a simplified simulation method, we investigate a bottom-up self-assembly route to build up helical crystals from the smectic monolayer of a colloidal helix racemate. With increasing the density, the system undergoes an entropy-driven cocrystallization by forming crystals of various symmetries with different helical shapes. In particular, we identify two crystals of helices arranged in binary honeycomb and square lattices, which are essentially composed of two sets of opposite-handed chiral crystals. Photonic calculations show that these chiral structures can have large complete photonic band gaps. In addition, in the self-assembled chiral square crystal, we also find dual polarization band gaps that selectively forbid the propagation of circularly polarized light of a specific handedness along the helical axis direction. The self-assembly process in our proposed system is robust, suggesting possibilities of using chiral colloids to assemble photonic metamaterials.
A Monolayer of Hexagonal Boron Nitride on Ir(111) as a Template for Cluster Superlattices
Moritz Will *- ,
Nicolae Atodiresei *- ,
Vasile Caciuc - ,
Philipp Valerius - ,
Charlotte Herbig - , and
Thomas Michely
The moiré of a monolayer of hexagonal boron nitride on Ir(111) is found to be a template for Ir, C, and Au cluster superlattices. Using scanning tunneling microscopy, the cluster structure and epitaxial relation to the substrate, the cluster binding site, the role of defects, as well as the thermal stability of the cluster lattice are investigated. The Ir and C cluster superlattices display a high thermal stability, before they decay by intercalation and Smoluchowski ripening. Ab initio calculations explain the extraordinarily strong Ir cluster binding through selective sp3 rehybridization of boron nitride involving B-Ir cluster bonds and a strengthening of the nitrogen bonds to the Ir substrate in a specific, initially only chemisorbed valley area within the moiré.
Diameter-Dependent Optical Absorption and Excitation Energy Transfer from Encapsulated Dye Molecules toward Single-Walled Carbon Nanotubes
Stein van Bezouw - ,
Dylan H. Arias - ,
Rachelle Ihly - ,
Sofie Cambré - ,
Andrew J. Ferguson - ,
Jochen Campo - ,
Justin C. Johnson - ,
Joeri Defillet - ,
Wim Wenseleers *- , and
Jeffrey L. Blackburn *
This publication is Open Access under the license indicated. Learn More
The hollow cores and well-defined diameters of single-walled carbon nanotubes (SWCNTs) allow for creation of one-dimensional hybrid structures by encapsulation of various molecules. Absorption and near-infrared photoluminescence-excitation (PLE) spectroscopy reveal that the absorption spectrum of encapsulated 1,3-bis[4-(dimethylamino)phenyl]-squaraine dye molecules inside SWCNTs is modulated by the SWCNT diameter, as observed through excitation energy transfer (EET) from the encapsulated molecules to the SWCNTs, implying a strongly diameter-dependent stacking of the molecules inside the SWCNTs. Transient absorption spectroscopy, simultaneously probing the encapsulated dyes and the host SWCNTs, demonstrates this EET, which can be used as a route to diameter-dependent photosensitization, to be fast (sub-picosecond). A wide series of SWCNT samples is systematically characterized by absorption, PLE, and resonant Raman scattering (RRS), also identifying the critical diameter for squaraine filling. In addition, we find that SWCNT filling does not limit the selectivity of subsequent separation protocols (including polyfluorene polymers for isolating only semiconducting SWCNTs and aqueous two-phase separation for enrichment of specific SWCNT chiralities). The design of these functional hybrid systems, with tunable dye absorption, fast and efficient EET, and the ability to remove all metallic SWCNTs by subsequent separation, demonstrates potential for implementation in photoconversion devices.
Electrochromic-Tuned Plasmonics for Photothermal Sterile Window
Jingwen Xu - ,
Yong Zhang - ,
Ting-Ting Zhai - ,
Zeyu Kuang - ,
Jian Li - ,
Yongmei Wang - ,
Zhida Gao - ,
Yan-Yan Song *- , and
Xing-Hua Xia *
Electrochromic materials are widely used in smart windows. An ideal future electrochromic window would be able to control visible light transmission, tune building’s heat conversion of near-infrared (NIR) solar radiation, and reduce attacks by microorganisms. To date, most of the reports have primarily focused on visible-light transmission modulation using electrochromic materials. Herein, we report the fabrication of an electrochromic-photothermal film by integrating electrochromic WO3 with plasmonic Au nanostructures and demonstrate its adjustability during optical transmission and photothermal conversion of visible and NIR lights. The localized surface plasmon resonance (LSPR) of Au nanostructures and the broadband nonradiative plasmon decay are proposed to be tunable using both the electric field and the WO3 substrate. Further enhanced photothermal conversion is achieved in colored state, which is attributed to coupling of traditional visible-band optical switching with NIR-LSPR extinction. The resulted electrochromic-photothermal film can also effectively reduce the numbers of attacking microorganisms, thus promising for use as a sterile smart window for advanced applications.
Nanoparticle-Assisted Transcutaneous Delivery of a Signal Transducer and Activator of Transcription 3-Inhibiting Peptide Ameliorates Psoriasis-like Skin Inflammation
Jin Yong Kim - ,
Jinhyo Ahn - ,
Jinjoo Kim - ,
Minsuk Choi - ,
Hyungsu Jeon - ,
Kibaek Choe - ,
Dong Yun Lee - ,
Pilhan Kim - , and
Sangyong Jon *
Signal transducer and activator of transcription 3 (STAT3) is constitutively activated in psoriatic skin inflammation and acts as a key player in the pathogenesis and progression of this autoimmune disease. Although numerous inhibitors that intervene in STAT3-associated pathways have been tested, an effective, highly specific inhibitor of STAT3 has yet to be identified. Here, we evaluated the in vitro and in vivo biological activity and therapeutic efficacy of a high-affinity peptide specific for STAT3 (APTstat3) after topical treatment via intradermal and transcutaneous delivery. Using a preclinical model of psoriasis, we show that intradermal injection of APTstat3 tagged with a 9-arginine cell-penetrating peptide (APTstat3-9R) reduced disease progression and modulated psoriasis-related cytokine signaling through inhibition of STAT3 phosphorylation. Furthermore, by complexing APTstat3-9R with specific lipid formulations led to formation of discoidal lipid nanoparticles (DLNPs), we were able to achieve efficient skin penetration of the STAT3-inhibiting peptide after transcutaneous administration, thereby effectively inhibiting psoriatic skin inflammation. Collectively, these findings suggest that DLNP-assisted transcutaneous delivery of a STAT3-inhibiting peptide could be a promising strategy for treating psoriatic skin inflammation without causing adverse systemic events. Moreover, the DLNP system could be used for transdermal delivery of other therapeutic peptides.
Modified Magnesium Hydroxide Nanoparticles Inhibit the Inflammatory Response to Biodegradable Poly(lactide-co-glycolide) Implants
Eugene Lih - ,
Chang Hun Kum - ,
Wooram Park - ,
So Young Chun - ,
Youngjin Cho - ,
Yoon Ki Joung - ,
Kwang-Sook Park - ,
Young Joon Hong - ,
Dong June Ahn - ,
Byung-Soo Kim - ,
Tae Gyun Kwon - ,
Myung Ho Jeong - ,
Jeffrey A. Hubbell *- , and
Dong Keun Han *
Biodegradable polymers have been extensively used in biomedical applications, ranging from regenerative medicine to medical devices. However, the acidic byproducts resulting from degradation can generate vigorous inflammatory reactions, often leading to clinical failure. We present an approach to prevent acid-induced inflammatory responses associated with biodegradable polymers, here poly(lactide-co-glycolide), by using oligo(lactide)-grafted magnesium hydroxide (Mg(OH)2) nanoparticles, which neutralize the acidic environment. In particular, we demonstrated that incorporating the modified Mg(OH)2 nanoparticles within degradable coatings on drug-eluting arterial stents efficiently attenuates the inflammatory response and in-stent intimal thickening by more than 97 and 60%, respectively, in the porcine coronary artery, compared with that of drug-eluting stent control. We also observed that decreased inflammation allows better reconstruction of mouse renal glomeruli in a kidney tissue regeneration model. Such modified Mg(OH)2 nanoparticles may be useful to extend the applicability and improve clinical success of biodegradable devices used in various biomedical fields.
Dynamics of Cellulose Nanocrystal Alignment during 3D Printing
Michael K. Hausmann - ,
Patrick A. Rühs *- ,
Gilberto Siqueira *- ,
Jörg Läuger - ,
Rafael Libanori - ,
Tanja Zimmermann - , and
André R. Studart *
The alignment of anisotropic particles during ink deposition directly affects the microstructure and properties of materials manufactured by extrusion-based 3D printing. Although particle alignment in diluted suspensions is well described by analytical and numerical models, the dynamics of particle orientation in the highly concentrated inks typically used for printing via direct ink writing (DIW) remains poorly understood. Using cellulose nanocrystals (CNCs) as model building blocks of increasing technological relevance, we study the dynamics of particle alignment under the shear stresses applied to concentrated inks during DIW. With the help of in situ polarization rheology, we find that the time period needed for particle alignment scales inversely with the applied shear rate and directly with the particle concentration. Such dependences can be quantitatively described by a simple scaling relation and qualitatively interpreted in terms of steric and hydrodynamic interactions between particles at high shear rates and particle concentrations. Our understanding of the alignment dynamics is then utilized to estimate the effect of shear stresses on the orientation of particles during the printing process. Finally, proof-of-concept experiments show that the combination of shear and extensional flow in 3D printing nozzles of different geometries provides an effective means to tune the orientation of CNCs from fully aligned to core–shell architectures. These findings offer powerful quantitative guidelines for the digital manufacturing of composite materials with programmed particle orientations and properties.
Fluorinated Gold Nanoparticles for Nanostructure Imaging Mass Spectrometry
Amelia Palermo - ,
Erica M. Forsberg - ,
Benedikt Warth - ,
Aries E. Aisporna - ,
Elizabeth Billings - ,
Ellen Kuang - ,
H. Paul Benton - ,
David Berry - , and
Gary Siuzdak *
Nanostructure imaging mass spectrometry (NIMS) with fluorinated gold nanoparticles (f-AuNPs) is a nanoparticle assisted laser desorption/ionization approach that requires low laser energy and has demonstrated high sensitivity. Here we describe NIMS with f-AuNPs for the comprehensive analysis of metabolites in biological tissues. F-AuNPs assist in desorption/ionization by laser-induced release of the fluorocarbon chains with minimal background noise. Since the energy barrier required to release the fluorocarbons from the AuNPs is minimal, the energy of the laser is maintained in the low μJ/pulse range, thus limiting metabolite in-source fragmentation. Electron microscopy analysis of tissue samples after f-AuNP NIMS shows a distinct “raising” of the surface as compared to matrix assisted laser desorption ionization ablation, indicative of a gentle desorption mechanism aiding in the generation of intact molecular ions. Moreover, the use of perfluorohexane to distribute the f-AuNPs on the tissue creates a hydrophobic environment minimizing metabolite solubilization and spatial dislocation. The transfer of the energy from the incident laser to the analytes through the release of the fluorocarbon chains similarly enhances the desorption/ionization of metabolites of different chemical nature, resulting in heterogeneous metabolome coverage. We performed the approach in a comparative study of the colon of mice exposed to three different diets. F-AuNP NIMS allows the direct detection of carbohydrates, lipids, bile acids, sulfur metabolites, amino acids, nucleotide precursors as well as other small molecules of varied biological origins. Ultimately, the diversified molecular coverage obtained provides a broad picture of a tissue’s metabolic organization.
Transmission Electron Microscope Nanosculpting of Topological Insulator Bismuth Selenide
Sarah E. Friedensen - ,
William M. Parkin - ,
Jerome T. Mlack - , and
Marija Drndić *
We present a process for sculpting Bi2Se3 nanoflakes into application-relevant geometries using a high-resolution transmission electron microscope. This process takes several minutes to sculpt small areas and can be used to cut the Bi2Se3 into wires and rings, to thin areas of the Bi2Se3, and to drill circular holes and lines. We determined that this method allows for sub 10 nm features and results in clean edges along the drilled regions. Using in situ high-resolution imaging, selected area diffraction, and atomic force microscopy, we found that this lithography process preserves the crystal structure of Bi2Se3. TEM sculpting is more precise and potentially results in cleaner edges than does ion-beam modification; therefore, the promise of this method for thermoelectric and topological devices calls for further study into the transport properties of such structures.
Understanding the Interplay between Self-Assembling Peptides and Solution Ions for Tunable Protein Nanoparticle Formation
Bhuvana K. Shanbhag - ,
Chang Liu - ,
Victoria S. Haritos - , and
Lizhong He *
Protein-based nanomaterials are gaining importance in biomedical and biosensor applications where tunability of the protein particle size is highly desirable. Rationally designed proteins and peptides offer control over molecular interactions between monomeric protein units to modulate their self-assembly and thus particle formation. Here, using an example enzyme–peptide system produced as a single construct by bacterial expression, we explore how solution conditions affect the formation and size of protein nanoparticles. We found two independent routes to particle formation, one facilitated by charge interactions between protein–peptide and peptide–peptide exemplified by pH change or the presence of NO3– or NH4+ and the second route via metal-ion coordination (e.g., Mg2+) within peptides. We further demonstrate that the two independent factors of pH and Mg2+ ions can be combined to regulate nanoparticle size. Charge interactions between protein–peptide monomers play a key role in either promoting or suppressing protein assembly; the intermolecular contact points within protein–peptide monomers involved in nanoparticle formation were identified by chemical cross-linking mass spectrometry. Importantly, the protein nanoparticles retain their catalytic activities, suggesting that their native structures are unaffected. Once formed, protein nanoparticles remain stable over long periods of storage or with changed solution conditions. Nevertheless, formation of nanoparticles is also reversible—they can be disassembled by desalting the buffer to remove complexing agents (e.g., Mg2+). This study defines the factors controlling formation of protein nanoparticles driven by self-assembly peptides and an understanding of complex ion–peptide interactions involved within, offering a convenient approach to tailor protein nanoparticles without changing amino acid sequence.
Tensan Silk-Inspired Hierarchical Fibers for Smart Textile Applications
Wenwen Zhang - ,
Chao Ye - ,
Ke Zheng - ,
Jiajia Zhong - ,
Yuzhao Tang - ,
Yimin Fan *- ,
Markus J. Buehler *- ,
Shengjie Ling *- , and
David L. Kaplan *
Tensan silk, a natural fiber produced by the Japanese oak silk moth (Antherea yamamai, abbreviated to A. yamamai), features superior characteristics, such as compressive elasticity and chemical resistance, when compared to the more common silk produced from the domesticated silkworm, Bombyx mori (B. mori). In this study, the “structure-property” relationships within A. yamamai silk are disclosed from the different structural hierarchies, confirming the outstanding toughness as dominated by the distinct mesoscale fibrillar architectures. Inspired by this hierarchical construction, we fabricated A. yamamai silk-like regenerated B. mori silk fibers (RBSFs) with mechanical properties (extensibility and modulus) comparable to natural A. yamamai silk. These RBSFs were further functionalized to form conductive RBSFs that were sensitive to force and temperature stimuli for applications in smart textiles. This study provides a blueprint in exploiting rational designs from A. yamanmai, which is rare and expensive in comparison to the common and cost-effective B. mori silk to empower enhanced material properties.
Roll-to-Roll Gravure Printed Electrochemical Sensors for Wearable and Medical Devices
Mallika Bariya - ,
Ziba Shahpar - ,
Hyejin Park - ,
Junfeng Sun - ,
Younsu Jung - ,
Wei Gao - ,
Hnin Yin Yin Nyein - ,
Tiffany Sun Liaw - ,
Li-Chia Tai - ,
Quynh P. Ngo - ,
Minghan Chao - ,
Yingbo Zhao - ,
Mark Hettick - ,
Gyoujin Cho *- , and
Ali Javey *
As recent developments in noninvasive biosensors spearhead the thrust toward personalized health and fitness monitoring, there is a need for high throughput, cost-effective fabrication of flexible sensing components. Toward this goal, we present roll-to-roll (R2R) gravure printed electrodes that are robust under a range of electrochemical sensing applications. We use inks and electrode morphologies designed for electrochemical and mechanical stability, achieving devices with uniform redox kinetics printed on 150 m flexible substrate rolls. We show that these electrodes can be functionalized into consistently high performing sensors for detecting ions, metabolites, heavy metals, and other small molecules in noninvasively accessed biofluids, including sensors for real-time, in situ perspiration monitoring during exercise. This development of robust and versatile R2R gravure printed electrodes represents a key translational step in enabling large-scale, low-cost fabrication of disposable wearable sensors for personalized health monitoring applications.
Low-Fouling and Biodegradable Protein-Based Particles for Thrombus Imaging
Thomas Bonnard - ,
Anand Jayapadman - ,
Jasmine A. Putri - ,
Jiwei Cui - ,
Yi Ju - ,
Catherine Carmichael - ,
Thomas A. Angelovich - ,
Stephen H. Cody - ,
Shauna French - ,
Karline Pascaud - ,
Hannah A. Pearce - ,
Shweta Jagdale - ,
Frank Caruso - , and
Christoph E. Hagemeyer *
Nanomedicine holds great promise for vascular disease diagnosis and specific therapy, yet rapid sequestration by the mononuclear phagocytic system limits the efficacy of particle-based agents. The use of low-fouling polymers, such as poly(ethylene glycol), efficiently reduces this immune recognition, but these nondegradable polymers can accumulate in the human body and may cause adverse effects after prolonged use. Thus, new particle formulations combining stealth, low immunogenicity and biocompatible features are required to enable clinical use. Here, a low-fouling particle platform is described using exclusively protein material. A recombinant protein with superior hydrophilic characteristics provided by the amino acid repeat proline, alanine, and serine (PAS) is designed and cross-linked into particles with lysine (K) and polyglutamic acid (E) using mesoporous silica templating. The obtained PASKE particles have low-fouling behavior, have a prolonged circulation time compared to albumin-based particles, and are rapidly degraded in the cell’s lysosomal compartment. When labeled with near-infrared fluorescent molecules and functionalized with an anti-glycoprotein IIb/IIIa single-chain antibody targeting activated platelets, the particles show potential as a noninvasive molecular imaging tool in a mouse model of carotid artery thrombosis. The PASKE particles constitute a promising biodegradable and versatile platform for molecular imaging of vascular diseases.
Morphology-Controlled Synthesis of Rhodium Nanoparticles for Cancer Phototherapy
Seounghun Kang - ,
Woojun Shin - ,
Myung-Ho Choi - ,
Minchul Ahn - ,
Young-Kwan Kim - ,
Seongchan Kim - ,
Dal-Hee Min *- , and
Hongje Jang *
Rhodium nanoparticles are promising transition metal nanocatalysts for electrochemical and synthetic organic chemistry applications. However, notwithstanding their potential, to date, Rh nanoparticles have not been utilized for biological applications; there has been no cytotoxicity study of Rh reported in the literature. In this regard, the absence of a facile and controllable synthetic strategy of Rh nanostructures with various sizes and morphologies might be responsible for the lack of progress in this field. Herein, we have developed a synthetic strategy for Rh nanostructures with controllable morphology through an inverse-directional galvanic replacement reaction. Three types of Rh-based nanostructures—nanoshells, nanoframes, and porous nanoplates—were successfully synthesized. A plausible synthetic mechanism based on thermodynamic considerations has also been proposed. The cytotoxicity, surface functionalization, and photothermal therapeutic effect of manufactured Rh nanostructures were systematically investigated to reveal their potential for in vitro and in vivo biological applications. Considering the comparable behavior of porous Rh nanoplates to that of gold nanostructures that are widely used in nanomedicine, the present study introduces Rh-based nanostructures into the field of biological research.
Metasurfaces Leveraging Solar Energy for Icephobicity
Efstratios Mitridis - ,
Thomas M. Schutzius *- ,
Alba Sicher - ,
Claudio U. Hail - ,
Hadi Eghlidi *- , and
Dimos Poulikakos *
Inhibiting ice accumulation on surfaces is an energy-intensive task and is of significant importance in nature and technology where it has found applications in windshields, automobiles, aviation, renewable energy generation, and infrastructure. Existing methods rely on on-site electrical heat generation, chemicals, or mechanical removal, with drawbacks ranging from financial costs to disruptive technical interventions and environmental incompatibility. Here we focus on applications where surface transparency is desirable and propose metasurfaces with embedded plasmonically enhanced light absorption heating, using ultrathin hybrid metal–dielectric coatings, as a passive, viable approach for de-icing and anti-icing, in which the sole heat source is renewable solar energy. The balancing of transparency and absorption is achieved with rationally nanoengineered coatings consisting of gold nanoparticle inclusions in a dielectric (titanium dioxide), concentrating broadband absorbed solar energy into a small volume. This causes a > 10 °C temperature increase with respect to ambient at the air–solid interface, where ice is most likely to form, delaying freezing, reducing ice adhesion, when it occurs, to negligible levels (de-icing) and inhibiting frost formation (anti-icing). Our results illustrate an effective unexplored pathway toward environmentally compatible, solar-energy-driven icephobicity, enabled by respectively tailored plasmonic metasurfaces, with the ability to design the balance of transparency and light absorption.
Cross-Linking Hollow Carbon Sheet Encapsulated CuP2 Nanocomposites for High Energy Density Sodium-Ion Batteries
Shuangqiang Chen - ,
Feixiang Wu - ,
Laifa Shen - ,
Yuanye Huang - ,
Shyam Kanta Sinha - ,
Vesna Srot - ,
Peter A. van Aken - ,
Joachim Maier - , and
Yan Yu *
Sodium-ion batteries (SIB) are regarded as the most promising competitors to lithium-ion batteries in spite of expected electrochemical disadvantages. Here a “cross-linking” strategy is proposed to mitigate the typical SIB problems. We present a SIB full battery that exhibits a working potential of 3.3 V and an energy density of 180 Wh kg–1 with good cycle life. The anode is composed of cross-linking hollow carbon sheet encapsulated CuP2 nanoparticles (CHCS-CuP2) and a cathode of carbon coated Na3V2(PO4)2F3 (C-NVPF). For the preparation of the CHCS-CuP2 nanocomposites, we develop an in situ phosphorization approach, which is superior to mechanical mixing. Such CHCS-CuP2 nanocomposites deliver a high reversible capacity of 451 mAh g–1 at 80 mA g–1, showing an excellent capacity retention ratio of 91% in 200 cycles together with good rate capability and stable cycling performance. Post mortem analysis reveals that the cross-linking hollow carbon sheet structure as well as the initially formed SEI layers are well preserved. Moreover, the inner electrochemical resistances do not significantly change. We believe that the presented battery system provides significant progress regarding practical application of SIB.
Cellulose Nanofiber–Graphene Oxide Biohybrids: Disclosing the Self-Assembly and Copper-Ion Adsorption Using Advanced Microscopy and ReaxFF Simulations
Chuantao Zhu - ,
Susanna Monti - , and
Aji P. Mathew *
The self-assembly of nanocellulose and graphene oxide into highly porous biohybrid materials has inspired the design and synthesis of multifunctional membranes for removing water pollutants. The mechanisms of self-assembly, metal ion capture, and cluster formation on the biohybrids at the nano- and molecular scales are quite complex. Their elucidation requires evidence from the synergistic combination of experimental data and computational models. The AFM-based microscopy studies of (2,2,6,6-tetramethylpiperidine-1-oxylradical)-mediated oxidized cellulose nanofibers (TOCNFs), graphene oxide (GO), and their biohybrid membranes provide strong, direct evidence of self-assembly; small GO nanoparticles first attach and accumulate along a single TOCNF fiber, while the long, flexible TOCNF filaments wrap around the flat, wide GO planes, thus forming an amorphous and porous biohybrid network. The layered structure of the TOCNFs and GO membrane, derived from the self-assembly and its surface properties before and after the adsorption of Cu(II), is investigated by advanced microscopy techniques and is further clarified by the ReaxFF molecular dynamics (MD) simulations. The dynamics of the Cu(II)-ion capture by the TOCNF and GO membranes in solution and the ion cluster formation during drying are confirmed by the MD simulations. The results of this multidisciplinary investigation move the research one step forward by disclosing specific aspects of the self-assembly behavior of biospecies and suggesting effective design strategies to control the pore size and robust materials for industrial applications.
Doping-Free Complementary Logic Gates Enabled by Two-Dimensional Polarity-Controllable Transistors
Giovanni V. Resta *- ,
Yashwanth Balaji - ,
Dennis Lin - ,
Iuliana P. Radu *- ,
Francky Catthoor - ,
Pierre-Emmanuel Gaillardon *- , and
Giovanni De Micheli
This publication is Open Access under the license indicated. Learn More
Atomically thin two-dimensional (2D) materials belonging to transition metal dichalcogenides, due to their physical and electrical properties, are an exceptional vector for the exploration of next-generation semiconductor devices. Among them, due to the possibility of ambipolar conduction, tungsten diselenide (WSe2) provides a platform for the efficient implementation of polarity-controllable transistors. These transistors use an additional gate, named polarity gate, that, due to the electrostatic doping of the Schottky junctions, provides a device-level dynamic control of their polarity, that is, n- or p-type. Here, we experimentally demonstrate a complete doping-free standard cell library realized on WSe2 without the use of either chemical or physical doping. We show a functionally complete family of complementary logic gates (INV, NAND, NOR, 2-input XOR, 3-input XOR, and MAJ) and, due to the reconfigurable capabilities of the single devices, achieve the realization of highly expressive logic gates, such as exclusive-OR (XOR) and majority (MAJ), with fewer transistors than possible in conventional complementary metal-oxide-semiconductor logic. Our work shows a path to enable doping-free low-power electronics on 2D semiconductors, going beyond the concept of unipolar physically doped devices, while suggesting a road to achieve higher computational densities in two-dimensional electronics.
Mapping the Conductance of Electronically Decoupled Graphene Nanoribbons
Peter H. Jacobse - ,
Mark J. J. Mangnus - ,
Stephan J. M. Zevenhuizen - , and
Ingmar Swart *
With the advent of atomically precise synthesis and consequent precise tailoring of their electronic properties, graphene nanoribbons (GNRs) have emerged as promising building blocks for nanoelectronics. Before being applied as such, it is imperative that their charge transport properties are investigated. Recently, formation of a molecular junction through the controlled attachment of nanoribbons to the probe of a scanning tunneling microscope (STM) and subsequent lifting allowed for the first conductance measurements. Drawbacks are the perturbation of the intrinsic electronic properties through interaction with the metal surface, as well as the risk of current-induced defect formation which largely restricts the measurements to low bias voltages. Here, we show that resonant transport—essential for device applications—can be measured by lifting electronically decoupled GNRs from an ultrathin layer of NaCl. By varying the applied voltage and tip–sample distance, we can probe resonant transport through frontier orbitals and its dependence on junction length. This technique is used for two distinct types of GNRs: the 7 atom wide armchair GNR and the 3,1-chiral GNR. The features in the conductance maps can be understood and modeled in terms of the intrinsic electronic properties of the ribbons as well as capacitive coupling to tip and substrate. We demonstrate that we can simultaneously measure the current decay with increasing junction length and bias voltage by using a double modulation spectroscopy technique. The strategy described in this work is widely applicable and will lead to a better understanding of electronic transport through molecular junctions in general.
Gold Fusion: From Au25(SR)18 to Au38(SR)24, the Most Unexpected Transformation of a Very Stable Nanocluster
Tiziano Dainese *- ,
Sabrina Antonello - ,
Sara Bogialli - ,
Wenwen Fei - ,
Alfonso Venzo - , and
Flavio Maran *
The study of the molecular cluster Au25(SR)18 has provided a wealth of fundamental insights into the properties of clusters protected by thiolated ligands (SR). This is also because this cluster has been particularly stable under a number of experimental conditions. Very unexpectedly, we found that paramagnetic Au25(SR)180 undergoes a spontaneous bimolecular fusion to form another benchmark gold nanocluster, Au38(SR)24. We tested this reaction with a series of Au25 clusters. The fusion was confirmed and characterized by UV–vis absorption spectroscopy, ESI mass spectrometry, 1H and 13C NMR spectroscopy, and electrochemistry. NMR evidences the presence of four types of ligand and, for the same proton type, double signals caused by the diastereotopicity arising from the chirality of the capping shell. This effect propagates up to the third carbon atom along the ligand chain. Electrochemistry provides a particularly convenient way to study the evolution process and determine the fusion rate constant, which decreases as the ligand length increases. No reaction is observed for the anionic clusters, whereas the radical nature of Au25(SR)180 appears to play an important role. This transformation of a stable cluster into a larger stable cluster without addition of any co-reagent also features the bottom-up assembly of the Au13 building block in solution. This very unexpected result could modify our view of the relative stability of molecular gold nanoclusters.
Recognition Tunneling of Canonical and Modified RNA Nucleotides for Their Identification with the Aid of Machine Learning
JongOne Im - ,
Suman Sen - ,
Stuart Lindsay *- , and
Peiming Zhang *
In the present study, we demonstrate a tunneling nanogap technique to identify individual RNA nucleotides, which can be used as a mechanism to read the nucleobases for direct sequencing of RNA in a solid-state nanopore. The tunneling nanogap is composed of two electrodes separated by a distance of <3 nm and functionalized with a recognition molecule. When a chemical entity is captured in the gap, it generates electron tunneling currents, a process we call recognition tunneling (RT). Using RT nanogaps created in a scanning tunneling microscope (STM), we acquired the electron tunneling signals for the canonical and two modified RNA nucleotides. To call the individual RNA nucleotides from the RT data, we adopted a machine learning algorithm, support vector machine (SVM), for the data analysis. Through the SVM, we were able to identify the individual RNA nucleotides and distinguish them from their DNA counterparts with reasonably high accuracy. Since each RNA nucleoside contains a hydroxyl group at the 2′-position of its sugar ring in an RNA strand, it allows for the formation of a tunneling junction at a larger nanogap compared to the DNA nucleoside in a DNA strand, which lacks the 2′ hydroxyl group. It also proves advantageous for the manufacture of RT devices. This study is a proof-of-principle demonstration for the development of an RT nanopore device for directly sequencing single RNA molecules, including those bearing modifications.
Hierarchical Order in Dewetted Block Copolymer Thin Films on Chemically Patterned Surfaces
Federico Ferrarese Lupi *- ,
Tommaso Jacopo Giammaria - ,
Andrea Miti - ,
Giampaolo Zuccheri - ,
Stefano Carignano - ,
Katia Sparnacci - ,
Gabriele Seguini - ,
Natascia De Leo - ,
Luca Boarino - ,
Michele Perego *- , and
Michele Laus *
We investigated the dewetting process on flat and chemically patterned surfaces of ultrathin films (thickness between 2 and 15 nm) of a cylinder forming polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) spin coated on poly(styrene-r-methyl methacrylate) random copolymers (RCPs). When the PS-b-PMMA film dewets on a 2 nm-thick RCP layer, the ordering of the hexagonally packed PMMA cylinders in the dewetted structures extends over distances far exceeding the correlation length obtained in continuous block copolymer (BCP) films. As a result, micrometer-sized circular droplets featuring defectless single grains of self-assembled PS-b-PMMA with PMMA cylinders perpendicularly oriented with respect to the substrate are generated and randomly distributed on the substrate. Additionally, alignment of the droplets along micrometric lines was achieved by performing the dewetting process on large-scale chemically patterned stripes of 2 nm thick RCP films by laser lithography. By properly adjusting the periodicity of the chemical pattern, it was possible to tune and select the geometrical characteristics of the dewetted droplets in terms of maximum thickness, contact angle and diameter while maintaining the defectless single grain perpendicular cylinder morphology of the circular droplets.
Photocarrier Transfer across Monolayer MoS2–MoSe2 Lateral Heterojunctions
Matthew Z. Bellus - ,
Masoud Mahjouri-Samani - ,
Samuel D. Lane - ,
Akinola D. Oyedele - ,
Xufan Li - ,
Alexander A. Puretzky - ,
David Geohegan - ,
Kai Xiao - , and
Hui Zhao *
In-plane heterojuctions formed from two monolayer semiconductors represent the finest control of electrons in condensed matter and have attracted significant interest. Various device studies have shown the effectiveness of such structures to control electronic processes, illustrating their potentials for electronic and optoelectronic applications. However, information about the physical mechanisms of charge carrier transfer across the junctions is still rare, mainly due to the lack of adequate experimental techniques. Here we show that transient absorption measurements with high spatial and temporal resolution can be used to directly monitor such transfer processes. We studied MoS2–MoSe2 in-plane heterostructures fabricated by chemical vapor deposition and lithographic patterning followed by laser-generated vapor sulfurization. Transient absorption measurements in reflection geometry revealed evidence of exciton transfer from MoS2 to MoSe2. By comparing the experimental data with a simulation, we extracted an exciton transfer velocity of 104 m s–1. These results provide valuable information for understanding and controlling in-plane carrier transfer in two-dimensional lateral heterostructures for their electronic and optoelectronic applications.
Programming Chemical Reaction Networks Using Intramolecular Conformational Motions of DNA
Wei Lai - ,
Lei Ren - ,
Qian Tang - ,
Xiangmeng Qu - ,
Jiang Li - ,
Lihua Wang - ,
Li Li - ,
Chunhai Fan - , and
Hao Pei *
The programmable regulation of chemical reaction networks (CRNs) represents a major challenge toward the development of complex molecular devices performing sophisticated motions and functions. Nevertheless, regulation of artificial CRNs is generally energy- and time-intensive as compared to natural regulation. Inspired by allosteric regulation in biological CRNs, we herein develop an intramolecular conformational motion strategy (InCMS) for programmable regulation of DNA CRNs. We design a DNA switch as the regulatory element to program the distance between the toehold and branch migration domain. The presence of multiple conformational transitions leads to wide-range kinetic regulation spanning over 4 orders of magnitude. Furthermore, the process of energy-cost-free strand exchange accompanied by conformational change discriminates single base mismatches. Our strategy thus provides a simple yet effective approach for dynamic programming of complex CRNs.
Paper-Based Surface-Enhanced Raman Spectroscopy for Diagnosing Prenatal Diseases in Women
Wansun Kim - ,
Soo Hyun Lee - ,
Jin Hwi Kim - ,
Yong Jin Ahn - ,
Yeon-Hee Kim *- ,
Jae Su Yu *- , and
Samjin Choi *
We report the development of a surface-enhanced Raman spectroscopy sensor chip by decorating gold nanoparticles (AuNPs) on ZnO nanorod (ZnO NR) arrays vertically grown on cellulose paper (C). We show that these chips can enhance the Raman signal by 1.25 × 107 with an excellent reproducibility of <6%. We show that we can measure trace amounts of human amniotic fluids of patients with subclinical intra-amniotic infection (IAI) and preterm delivery (PTD) using the chip in combination with a multivariate statistics-derived machine-learning-trained bioclassification method. We can detect the presence of prenatal diseases and identify the types of diseases from amniotic fluids with >92% clinical sensitivity and specificity. Our technology has the potential to be used for the early detection of prenatal diseases and can be adapted for point-of-care applications.
Two-Dimensional Thickness-Dependent Avalanche Breakdown Phenomena in MoS2 Field-Effect Transistors under High Electric Fields
Jinsu Pak - ,
Yeonsik Jang - ,
Junghwan Byun - ,
Kyungjune Cho - ,
Tae-Young Kim - ,
Jae-Keun Kim - ,
Barbara Yuri Choi - ,
Jiwon Shin - ,
Yongtaek Hong - ,
Seungjun Chung *- , and
Takhee Lee *
As two-dimensional (2D) transition metal dichalcogenides electronic devices are scaled down to the sub-micrometer regime, the active layers of these materials are exposed to high lateral electric fields, resulting in electrical breakdown. In this regard, understanding the intrinsic nature in layer-stacked 2D semiconducting materials under high lateral electric fields is necessary for the reliable applications of their field-effect transistors. Here, we explore the electrical breakdown phenomena originating from avalanche multiplication in MoS2 field-effect transistors with different layer thicknesses and channel lengths. Modulating the band structure and bandgap energy in MoS2 allows the avalanche multiplication to be controlled by adjusting the number of stacking layers. This phenomenon could be observed in transition metal dichalcogenide semiconducting systems due to its quantum confinement effect on the band structure. The relationship between the critical electric field for avalanche breakdown and bandgap energy is well fitted to a power law curve in both monolayer and multilayer MoS2.
Tunable Nonthermal Distribution of Hot Electrons in a Semiconductor Injected from a Plasmonic Gold Nanostructure
Scott Kevin Cushing - ,
Chih-Jung Chen - ,
Chung Li Dong - ,
Xiang-Tian Kong - ,
Alexander O. Govorov - ,
Ru-Shi Liu *- , and
Nianqiang Wu *
For semiconductors photosensitized with organic dyes or quantum dots, transferred electrons are usually considered thermalized at the conduction band edge. This study suggests that the electrons injected from a plasmonic metal into a thin semiconductor shell can be nonthermal with energy up to the plasmon frequency. In other words, the electrons injected into the semiconductor are still hot carriers. Photomodulated X-ray absorption measurements of the Ti L2,3 edge are compared before and after excitation of the plasmon in Au@TiO2 core–shell nanoparticles. Comparison with theoretical predictions of the X-ray absorption, which include the heating and state-filling effects from injected hot carriers, suggests that the electrons transferred from the plasmon remain nonthermal in the ∼10 nm TiO2 shell, due in part to a slow trapping in defect states. By repeating the measurements for spherical, rod-like, and star-like metal nanoparticles, the magnitude of the nonthermal distribution, peak energy, and number of injected hot electrons are confirmed to be tuned by the plasmon frequency and the sharp corners of the plasmonic nanostructure. The results suggest that plasmonic photosensitizers can not only extend the sunlight absorption spectral range of semiconductor-based devices but could also result in increased open circuit voltages and elevated thermodynamic driving forces for solar fuel generation in photoelectrochemical cells.
Anomalous Pressure Characteristics of Defects in Hexagonal Boron Nitride Flakes
Yongzhou Xue - ,
Hui Wang - ,
Qinghai Tan - ,
Jun Zhang - ,
Tongjun Yu - ,
Kun Ding - ,
Desheng Jiang - ,
Xiuming Dou *- ,
Jun-jie Shi *- , and
Bao-quan Sun *
Research on hexagonal boron nitride (hBN) has been intensified recently due to the application of hBN as a promising system of single-photon emitters. To date, the single photon origin remains under debate even though many experiments and theoretical calculations have been performed. We have measured the pressure-dependent photoluminescence (PL) spectra of hBN flakes at low temperatures by using a diamond anvil cell device. The absolute values of the pressure coefficients of discrete PL emission lines are all below 15 meV/GPa, which is much lower than the pressure-induced 36 meV/GPa redshift rate of the hBN bandgap. These PL emission lines originate from atom-like localized defect levels confined within the bandgap of the hBN flakes. Interestingly, the experimental results of the pressure-dependent PL emission lines present three different types of pressure responses corresponding to a redshift (negative pressure coefficient), a blueshift (positive pressure coefficient), or even a sign change from negative to positive. Density functional theory calculations indicate the existence of competition between the intralayer and interlayer interaction contributions, which leads to the different pressure-dependent behaviors of the PL peak shift.
Acceptor Percolation Determines How Electron-Accepting Additives Modify Transport of Ambipolar Polymer Organic Field-Effect Transistors
Michael J. Ford *- ,
Ming Wang - ,
Karen C. Bustillo - ,
Jianyu Yuan - ,
Thuc-Quyen Nguyen - , and
Guillermo C. Bazan *
Organic field-effect transistors (OFETs) that utilize ambipolar polymer semiconductors can benefit from the ability of both electron and hole conduction, which is necessary for complementary circuits. However, simultaneous hole and electron transport in organic field-effect transistors result in poor ON/OFF ratios, limiting potential applications. Solution processing methods have been developed to control charge transport properties and transform ambipolar conduction to hole-only conduction. The electron-acceptor phenyl-C61-butyric acid methyl ester (PC61BM), when mixed in solution with an ambipolar semiconducting polymer, can reduce electron conduction. Unipolar p-type OFETs with high, well-defined ON/OFF ratios and without detrimental effects on hole conduction are achieved for a wide range of blend compositions, from 95:5 to 5:95 wt % semiconductor polymer:PC61BM. When introducing the alternative acceptor N,N′-bis(1-ethylpropyl)-3,4:9,10-perylenediimide (PDI), high ON/OFF ratios are achieved for 95:5 wt % semiconductor polymer:PDI; however, electron conduction increases for 50:50 and 5:95 wt % semiconductor polymer:PDI. As described within, we show that electron conduction is practically eliminated when additive domains do not percolate across the OFET channel, that is, electrons are “morphologically trapped”. Morphologies were characterized by optical, electron, and atomic force microscopy as well as X-ray scattering techniques. PC61BM was substituted with an endohedral Lu3N fullerene, which enhanced contrast in electron microscopy and allowed for more detailed insight into the blend morphologies. Blends with alternative, nonfullerene acceptors further emphasize the importance of morphology and acceptor percolation, providing insights for such blends that control ambipolar transport and ON/OFF ratios.
Proton-Gradient-Driven Oriented Motion of Nanodiamonds Grafted to Graphene by Dynamic Covalent Bonds
Petr Kovaříček *- ,
Marek Cebecauer - ,
Jitka Neburková - ,
Jan Bartoň - ,
Michaela Fridrichová - ,
Karolina A. Drogowska - ,
Petr Cigler - ,
Jean-Marie Lehn *- , and
Martin Kalbac
Manipulating nanoscopic objects by external stimuli is the cornerstone of nanoscience. Here, we report the implementation of dynamic covalent chemistry in the reversible binding and directional motion of fluorescent nanodiamond particles at a functionalized graphene surface via imine linkages. The dynamic connections allow for controlling the formation and rupture of these linkages by external stimuli. By introduction of pH gradients, the nanoparticles are driven to move along the gradient due to the different rates of the imine condensation and hydrolysis in the two environments. The multivalent nature of the particle-to-surface connection ensures that particles remain attached to the surface, whereas its dynamic character allows for exchange reaction, thus leading to displacement yet bound behavior in two-dimensional space. These results open a pathway for thermodynamically controlled manipulation of objects on the nanoscale.
Epigenetic Optical Mapping of 5-Hydroxymethylcytosine in Nanochannel Arrays
Tslil Gabrieli - ,
Hila Sharim - ,
Gil Nifker - ,
Jonathan Jeffet - ,
Tamar Shahal - ,
Rani Arielly - ,
Michal Levi-Sakin - ,
Lily Hoch - ,
Nissim Arbib - ,
Yael Michaeli *- , and
Yuval Ebenstein *
This publication is Open Access under the license indicated. Learn More
The epigenetic mark 5-hydroxymethylcytosine (5-hmC) is a distinct product of active DNA demethylation that is linked to gene regulation, development, and disease. In particular, 5-hmC levels dramatically decline in many cancers, potentially serving as an epigenetic biomarker. The noise associated with next-generation 5-hmC sequencing hinders reliable analysis of low 5-hmC containing tissues such as blood and malignant tumors. Additionally, genome-wide 5-hmC profiles generated by short-read sequencing are limited in providing long-range epigenetic information relevant to highly variable genomic regions, such as the 3.7 Mbp disease-related Human Leukocyte Antigen (HLA) region. We present a long-read, highly sensitive single-molecule mapping technology that generates hybrid genetic/epigenetic profiles of native chromosomal DNA. The genome-wide distribution of 5-hmC in human peripheral blood cells correlates well with 5-hmC DNA immunoprecipitation (hMeDIP) sequencing. However, the long single-molecule read-length of 100 kbp to 1 Mbp produces 5-hmC profiles across variable genomic regions that failed to show up in the sequencing data. In addition, optical 5-hmC mapping shows a strong correlation between the 5-hmC density in gene bodies and the corresponding level of gene expression. The single-molecule concept provides information on the distribution and coexistence of 5-hmC signals at multiple genomic loci on the same genomic DNA molecule, revealing long-range correlations and cell-to-cell epigenetic variation.
Nanoscale Control of Oxygen Defects and Metal–Insulator Transition in Epitaxial Vanadium Dioxides
Yogesh Sharma - ,
Janakiraman Balachandran - ,
Changhee Sohn - ,
Jaron T. Krogel - ,
Panchapakesan Ganesh - ,
Liam Collins - ,
Anton V. Ievlev - ,
Qian Li - ,
Xiang Gao - ,
Nina Balke - ,
Olga S. Ovchinnikova - ,
Sergei V. Kalinin - ,
Olle Heinonen - , and
Ho Nyung Lee *
Strongly correlated vanadium dioxide (VO2) is one of the most promising materials that exhibits a temperature-driven, metal–insulator transition (MIT) near room temperature. The ability to manipulate the MIT at nanoscale offers both insight into understanding the energetics of phase transition and a promising potential for nanoelectronic devices. In this work, we study nanoscale electrochemical modifications of the MIT in epitaxial VO2 thin films using a combined approach with scanning probe microscopy (SPM) and theoretical calculations. We find that applying electric voltages of different polarity through an SPM tip locally changes the contact potential difference and conductivity on the surface of VO2 by modulating the oxygen stoichiometry. We observed nearly 2 orders of magnitude change in resistance between positive and negative biased-tip written areas of the film, demonstrating the electric field modulated MIT behavior at the nanoscale. Density functional theory calculations, benchmarked against more accurate many-body quantum Monte Carlo calculations, provide information on the formation energetics of oxygen defects that can be further manipulated by strain. This study highlights the crucial role of oxygen vacancies in controlling the MIT in epitaxial VO2 thin films, useful for developing advanced electronic and iontronic devices.
Low-Voltage Control of (Co/Pt)x Perpendicular Magnetic Anisotropy Heterostructure for Flexible Spintronics
Shishun Zhao - ,
Ziyao Zhou *- ,
Chunlei Li - ,
Bin Peng - ,
Zhongqiang Hu - , and
Ming Liu *
The trend of mobile Internet requires portable and wearable devices as bio-device interfaces. Electric field control of magnetism is a promising approach to achieve compact, light-weight, and energy-efficient wearable devices. Within a flexible sandwich heterostructure, perpendicular magnetic anisotropy switching was achieved via low-voltage gating control of an ionic gel in mica/Ta/(Pt/Co)x/Pt/ionic gel/Pt, where (Pt/Co)x acted as a functional layer. By conducting in situ VSM, EPR, and MOKE measurements, a 1098 Oe magnetic anisotropy field change was determined at the bending state with tensile strain, corresponding to a magnetic anisotropy energy change of 3.16 × 105 J/m3 and a giant voltage tunability coefficient of 0.79 × 105 J/m3·V. The low voltage and strain dual control of magnetism on mica substrates enables tunable flexible spintronic devices with an increased degree of manipulation.
High Thermoelectric Performance in Crystallographically Textured n-Type Bi2Te3–xSex Produced from Asymmetric Colloidal Nanocrystals
Yu Liu - ,
Yu Zhang - ,
Khak Ho Lim - ,
Maria Ibáñez - ,
Silvia Ortega - ,
Mengyao Li - ,
Jérémy David - ,
Sara Martí-Sánchez - ,
Ka Ming Ng - ,
Jordi Arbiol - ,
Maksym V. Kovalenko - ,
Doris Cadavid *- , and
Andreu Cabot *
In the present work, we demonstrate crystallographically textured n-type Bi2Te3–xSex nanomaterials with exceptional thermoelectric figures of merit produced by consolidating disk-shaped Bi2Te3–xSex colloidal nanocrystals (NCs). Crystallographic texture was achieved by hot pressing the asymmetric NCs in the presence of an excess of tellurium. During the hot press, tellurium acted both as lubricant to facilitate the rotation of NCs lying close to normal to the pressure axis and as solvent to dissolve the NCs approximately aligned with the pressing direction, which afterward recrystallize with a preferential orientation. NC-based Bi2Te3–xSex nanomaterials showed very high electrical conductivities associated with large charge carrier concentrations, n. We hypothesize that such large n resulted from the presence of an excess of tellurium during processing, which introduced a high density of donor TeBi antisites. Additionally, the presence in between grains of traces of elemental Te, a narrow band gap semiconductor with a work function well below Bi2Te3–xSex, might further contribute to increase n through spillover of electrons, while at the same time blocking phonon propagation and hole transport through the nanomaterial. NC-based Bi2Te3–xSex nanomaterials were characterized by very low thermal conductivities in the pressing direction, which resulted in ZT values up to 1.31 at 438 K in this direction. This corresponds to a ca. 40% ZT enhancement from commercial ingots. Additionally, high ZT values were extended over wider temperature ranges due to reduced bipolar contribution to the Seebeck coefficient and the thermal conductivity. Average ZT values up to 1.15 over a wide temperature range, 320 to 500 K, were measured, which corresponds to a ca. 50% increase over commercial materials in the same temperature range. Contrary to most previous works, highest ZT values were obtained in the pressing direction, corresponding to the c crystallographic axis, due to the predominance of the thermal conductivity reduction over the electrical conductivity difference when comparing the two crystal directions.
Inducing Strong Superconductivity in WTe2 by a Proximity Effect
Ce Huang - ,
Awadhesh Narayan - ,
Enze Zhang - ,
Yanwen Liu - ,
Xiao Yan - ,
Jiaxiang Wang - ,
Cheng Zhang - ,
Weiyi Wang - ,
Tong Zhou - ,
Changjiang Yi - ,
Shanshan Liu - ,
Jiwei Ling - ,
Huiqin Zhang - ,
Ran Liu - ,
Raman Sankar - ,
Fangcheng Chou - ,
Yihua Wang - ,
Youguo Shi - ,
Kam Tuen Law - ,
Stefano Sanvito - ,
Peng Zhou *- ,
Zheng Han *- , and
Faxian Xiu *
The search for proximity-induced superconductivity in topological materials has generated widespread interest in the condensed matter physics community. The superconducting states inheriting nontrivial topology at interfaces are expected to exhibit exotic phenomena such as topological superconductivity and Majorana zero modes, which hold promise for applications in quantum computation. However, a practical realization of such hybrid structures based on topological semimetals and superconductors has hitherto been limited. Here, we report the strong proximity-induced superconductivity in type-II Weyl semimetal WTe2, in a van der Waals hybrid structure obtained by mechanically transferring NbSe2 onto various thicknesses of WTe2. When the WTe2 thickness (tWTe2) reaches 21 nm, the superconducting transition occurs around the critical temperature (Tc) of NbSe2 with a gap amplitude (Δp) of 0.38 meV and an unexpected ultralong proximity length (lp) up to 7 μm. With the thicker 42 nm WTe2 layer, however, the proximity effect yields Tc ≈ 1.2 K, Δp = 0.07 meV, and a short lp of less than 1 μm. Our theoretical calculations, based on the Bogoliubov–de Gennes equations in the clean limit, predict that the induced superconducting gap is a sizable fraction of the NbSe2 superconducting one when tWTe2 is less than 30 nm and then decreases quickly as tWTe2 increases. This agrees qualitatively well with the experiments. Such observations form a basis in the search for superconducting phases in topological semimetals.
In Situ Atomic-Scale Observation of Surface-Tension-Induced Structural Transformation of Ag-NiPx Core–Shell Nanocrystals
Xing Huang *- ,
Zhongqiang Liu - ,
Marie-Mathilde Millet - ,
Jichen Dong - ,
Milivoj Plodine - ,
Feng Ding *- ,
Robert Schlögl - , and
Marc-Georg Willinger *
The properties of nanocrystals are highly dependent on their morphology, composition, and structure. Tailored synthesis over these parameters is successfully applied for the production of nanocrystals with desired properties for specific applications. However, in order to obtain full control over the properties, the behavior of nanocrystals under external stimuli and application conditions needs to be understood. Herein, using Ag-NiPx nanocrystals as a model system, we investigate the structural evolution upon thermal treatment by in situ aberration-corrected scanning transmission electron microscopy. A combination of real-time imaging with elemental analysis enables the observation of the transformation from a Ag-NiPx core–shell configuration to a Janus structure at the atomic scale. The transformation occurs through dewetting and crystallization of the NiPx shell and is accompanied by surface segregation of Ag. Further temperature increase leads to a complete sublimation of Ag and formation of individual Ni12P5 nanocrystals. The transformation is rationalized by theoretical modeling based on density functional theory calculations. Our model suggests that the transformation is driven by changes of the surface energy of NiPx and the interfacial energy between NiPx and Ag. The direct observation of atomistic dynamics during thermal-treatment-induced structural modification will help to understand more complex transformations that are induced by aging over time or the interaction with a reactive gas phase in applications such as catalysis.
Fast Charge Extraction in Perovskite-Based Core–Shell Nanowires
Michael J. Ashley - ,
Edward J. Kluender - , and
Chad A. Mirkin *
Realizing nanostructured interfaces with precise architectural control enables one to access properties unattainable using bulk materials. In particular, a nanostructured interface (e.g., a core–shell nanowire) between two semiconductors leads to a short charge separation distance, such that photoexcited charge carriers can be more quickly and efficiently collected. While vapor-phase growth methods are used to synthesize uniform core–shell nanowire arrays of semiconductors such as Si and InP, more general strategies are required to produce related structures composed of a broader range of materials. Herein, we employ anodic aluminum oxide templates to synthesize CH3NH3PbI3 perovskite core–copper thiocyanate shell nanowire arrays employing a combination of electrodeposition and solution casting methods. Using scanning electron microscopy, powder X-ray diffraction, and time-resolved photoluminescence spectroscopy, we confirm the target structure and show that adopting a core–shell nanowire architecture accelerates the rate of charge quenching by nearly 3 orders of magnitude compared to samples with only an axial junction. Subsequently, we fit decay curves to a triexponential function to attribute fast quenching in core–shell nanowires to charge extraction by the copper thiocyanate nanotubes, as opposed to recombination within the perovskite nanowires. Dramatic improvements to charge extraction speed and efficiency result from the substantially reduced charge separation distance and increased interfacial area achieved via the core–shell nanowire array architecture.
Cycling of Rational Hybridization Chain Reaction To Enable Enzyme-Free DNA-Based Clinical Diagnosis
Gaolian Xu - ,
Hang Zhao - ,
Julien Reboud - , and
Jonathan M. Cooper *
This publication is Open Access under the license indicated. Learn More
In order to combat the growing threat of global infectious diseases, there is a need for rapid diagnostic technologies that are sensitive and that can provide species specific information (as might be needed to direct therapy as resistant strains of microbes emerge). Here, we present a convenient, enzyme-free amplification mechanism for a rational hybridization chain reaction, which is implemented in a simple format for isothermal amplification and sensing, applied to the DNA-based diagnosis of hepatitis B virus (HBV) in 54 patients. During the cycled amplification process, DNA monomers self-assemble in an organized and controllable way only when a specific target HBV sequence is present. This mechanism is confirmed using super-resolution stochastic optical reconstruction microscopy. The enabled format is designed in a manner analogous to an enzyme-linked immunosorbent assay, generating colored products with distinct tonality and with a limit of detection of ca. five copies/reaction. This routine assay also showed excellent sensitivity (>97%) in clinical samples demonstrating the potential of this convenient, low cost, enzyme-free method for use in low resource settings.
Cobalt Disulfide Nanoparticles Embedded in Porous Carbonaceous Micro-Polyhedrons Interlinked by Carbon Nanotubes for Superior Lithium and Sodium Storage
Yuan Ma - ,
Yanjiao Ma - ,
Dominic Bresser - ,
Yuanchun Ji - ,
Dorin Geiger - ,
Ute Kaiser - ,
Carsten Streb - ,
Alberto Varzi *- , and
Stefano Passerini *
Transition metal sulfides are appealing electrode materials for lithium and sodium batteries owing to their high theoretical capacity. However, they are commonly characterized by rather poor cycling stability and low rate capability. Herein, we investigate CoS2, serving as a model compound. We synthesized a porous CoS2/C micro-polyhedron composite entangled in a carbon-nanotube-based network (CoS2-C/CNT), starting from zeolitic imidazolate frameworks-67 as a single precursor. Following an efficient two-step synthesis strategy, the obtained CoS2 nanoparticles are uniformly embedded in porous carbonaceous micro-polyhedrons, interwoven with CNTs to ensure high electronic conductivity. The CoS2-C/CNT nanocomposite provides excellent bifunctional energy storage performance, delivering 1030 mAh g–1 after 120 cycles and 403 mAh g–1 after 200 cycles (at 100 mA g–1) as electrode for lithium-ion (LIBs) and sodium-ion batteries (SIBs), respectively. In addition to these high capacities, the electrodes show outstanding rate capability and excellent long-term cycling stability with a capacity retention of 80% after 500 cycles for LIBs and 90% after 200 cycles for SIBs. In situ X-ray diffraction reveals a significant contribution of the partially graphitized carbon to the lithium and at least in part also for the sodium storage and the report of a two-step conversion reaction mechanism of CoS2, eventually forming metallic Co and Li2S/Na2S. Particularly the lithium storage capability at elevated (dis-)charge rates, however, appears to be substantially pseudocapacitive, thus benefiting from the highly porous nature of the nanocomposite.
Mechanism of Ligand-Controlled Emission in Silicon Nanoparticles
Woong Young So - ,
Qi Li - ,
Christian M. Legaspi - ,
Brendan Redler - ,
Krystle M. Koe - ,
Rongchao Jin - , and
Linda A. Peteanu *
Although bulk silicon (Si) is known to be a poor emitter, Si nanoparticles (NPs) exhibit size-dependent photoluminescence in the red or near-infrared due to quantum confinement. Recently, it has been shown that surface modification of Si NPs with nitrogen-capped ligands results in bluer emission wavelengths and quantum yields of up to 90%. However, the emission mechanism operating in these surface-modified Si NPs and the factors that determine their emission maxima are still unclear. Here, the emission in these species is shown to arise from a charge-transfer state between the Si surface and the ligand. The energy of this state is linearly correlated to the calculated ground-state dipole moment of the free ligand. This trend can be used in a predictive fashion for the design and synthesis of Si NPs with a broader range of emission wavelengths.
High-Performance Near-Infrared Photodetectors Based on p-Type SnX (X = S, Se) Nanowires Grown via Chemical Vapor Deposition
Dingshan Zheng - ,
Hehai Fang - ,
Mingsheng Long *- ,
Feng Wu - ,
Peng Wang - ,
Fan Gong - ,
Xing Wu - ,
Johnny C. Ho - ,
Lei Liao *- , and
Weida Hu *
Because of the distinct electronic properties and strong interaction with light, quasi-one-dimensional nanowires (NWs) with semiconducting property have been demonstrated with tremendous potential for various technological applications, especially electronics and optoelectronics. However, until now, most of the state-of-the-art NW photodetectors are predominantly based on the n-type NW channel. Here, we successfully synthesized p-type SnSe and SnS NWs via the chemical vapor deposition method and fabricated high-performance single SnSe and SnS NW photodetectors. Importantly, these two NW devices exhibit an impressive photodetection performance with a high photoconductive gain of 1.5 × 104 (2.8 × 104), good responsivity of 1.0 × 104 A W–1 (1.6 × 104 A W–1), and excellent detectivity of 3.3 × 1012 Jones (2.4 × 1012 Jones) under near-infrared illumination at a bias of 3 V for the SnSe NW (SnS NW) channel. The rise and fall times can be as efficient as 460 and 520 μs (1.2 and 15.1 ms), respectively, for the SnSe NW (SnS NW) device. Moreover, the spatially resolved photocurrent mapping of the devices further reveals the bias-dependent photocurrent generation. All these results evidently demonstrate that the p-type SnSe and SnS NWs have great potential to be applied in next-generation high-performance optoelectronic devices.
A Reduction in Particle Size Generally Causes Body-Centered-Cubic Metals to Expand but Face-Centered-Cubic Metals to Contract
Dhani Nafday - ,
Subhrangsu Sarkar - ,
Pushan Ayyub *- , and
Tanusri Saha-Dasgupta *
From a careful analysis of existing data as well as new measurements, we show that the size dependence of the lattice parameters in metal nanoparticles with face-centered cubic (fcc) and body-centered cubic (bcc) symmetries display opposite trends: nanoparticles with fcc structure generally contract with decreasing particle size, while those with bcc structure expand. We present a microscopic explanation for this apparently puzzling behavior based on first-principles simulations. Our results, obtained from a comparison of density functional theory calculations with experimental data, indicate that the nanoparticles are capped by a surface monolayer of oxygen atoms, which is routinely detected by surface-sensitive techniques. The bcc- and fcc-based nanoparticles respond in contrasting fashion to the presence of the oxygen capping layer, and this dictates whether the corresponding lattice parameter would increase or decrease with size reduction. The metal–oxygen bonds at the surface, being shorter and stronger than typical metal–metal bonds, pull the surface metal atoms outward. This outward movement of surface atoms influences the core regions to a larger extent in the relatively open bcc geometry, producing a rather large overall expansion of the cluster, compared to the bulk. In case of fcc clusters, on the other hand, the outward movement of surface metal atoms does not percolate too far inside, resulting in either a smaller net expansion or contraction of the cluster depending on the extent of surface oxygen coverage. Our study therefore provides a convincing physicochemical basis for the correlation between the underlying geometry and the nature of change of the lattice parameters under size reduction.
Solution-Synthesized High-Mobility Tellurium Nanoflakes for Short-Wave Infrared Photodetectors
Matin Amani - ,
Chaoliang Tan - ,
George Zhang - ,
Chunsong Zhao - ,
James Bullock - ,
Xiaohui Song - ,
Hyungjin Kim - ,
Vivek Raj Shrestha - ,
Yang Gao - ,
Kenneth B. Crozier - ,
Mary Scott - , and
Ali Javey *
Two-dimensional (2D) materials, particularly black phosphorus (bP), have demonstrated themselves to be excellent candidates for high-performance infrared photodetectors and transistors. However, high-quality bP can be obtained only via mechanical exfoliation from high-temperature- and high-pressure-grown bulk crystals and degrades rapidly when exposed to ambient conditions. Here, we report solution-synthesized and air-stable quasi-2D tellurium (Te) nanoflakes for short-wave infrared (SWIR) photodetectors. We perform comprehensive optical characterization via polarization-resolved transmission and reflection measurements and report the absorbance and complex refractive index of Te crystals. It is found that this material is an indirect semiconductor with a band gap of 0.31 eV. From temperature-dependent electrical measurements, we confirm this band-gap value and find that 12 nm thick Te nanoflakes show high hole mobilities of 450 and 1430 cm2 V–1 s–1 at 300 and 77 K, respectively. Finally, we demonstrate that despite its indirect band gap, Te can be utilized for high-performance SWIR photodetectors by employing optical cavity substrates consisting of Au/Al2O3 to dramatically increase the absorption in the semiconductor. By changing the thickness of the Al2O3 cavity, the peak responsivity of Te photoconductors can be tuned from 1.4 μm (13 A/W) to 2.4 μm (8 A/W) with a cutoff wavelength of 3.4 μm, fully capturing the SWIR band. An optimized room-temperature specific detectivity (D*) of 2 × 109 cm Hz1/2 W–1 is obtained at a wavelength of 1.7 μm.
Fast and Sensitive Colloidal Quantum Dot Mid-Wave Infrared Photodetectors
Matthew M. Ackerman - ,
Xin Tang - , and
Philippe Guyot-Sionnest *
Colloidal quantum dots (CQDs) with a band gap tunable in the mid-wave infrared (MWIR) region provide a cheap alternative to epitaxial commercial photodetectors such as HgCdTe (MCT) and InSb. Photoconductive HgTe CQD devices have demonstrated the potential of CQDs for MWIR photodetection but face limitations in speed and sensitivity. Recently, a proof-of-concept HgTe photovoltaic (PV) detector was realized, achieving background-limited infrared photodetection at cryogenic temperatures. Using a modified PV device architecture, we report up to 2 orders of magnitude improvement in the sensitivity of the HgTe CQD photodetectors. A solid-state cation exchange method was introduced during device fabrication to chemically modify the interface potential, leading to an order of magnitude improvement of external quantum efficiency at room temperature. At 230 K, the HgTe CQD photodetectors reported here achieve a sensitivity of 109 Jones with a cutoff wavelength between 4 and 5 μm, which is comparable to that of commercial photodetectors. In addition to the chemical treatment, a thin-film interference structure was devised using an optical spacer to achieve near unity internal quantum efficiency upon reducing the operating temperature. The enhanced sensitivity of the HgTe CQD photodetectors reported here should motivate interest in a cheap, solution-processed MWIR photodetector for applications extending beyond research and military defense.
Tailoring Platinum(IV) Amphiphiles for Self-Targeting All-in-One Assemblies as Precise Multimodal Theranostic Nanomedicine
Shasha He - ,
Chan Li - ,
Qingfei Zhang - ,
Jianxun Ding - ,
Xing-Jie Liang - ,
Xuesi Chen - ,
Haihua Xiao *- ,
Xiaoyuan Chen *- ,
Dongfang Zhou *- , and
Yubin Huang
Drug, targeting ligand, and imaging agent are the three essential components in a nanoparticle-based drug delivery system. However, tremendous batch-to-batch variation of composition and drug content typically accompany the current approaches of building these components together. Herein, we report the design of photoactivatable platinum(IV) (Pt(IV)) amphiphiles containing one or two hydrophilic lactose targeting ligands per hydrophobic Pt(IV) prodrug for an all-in-one precise nanomedicine. Self-assembly of these Pt(IV) amphiphiles results in either micelle or vesicle formation with a fixed Pt/targeting moiety ratio and a constantly high content of Pt. The micelles and vesicles are capable of hepatoma cell-targeting, fluorescence/Pt-based CT imaging and have shown effective anticancer efficacy under laser irradiation in vitro and in vivo. This photoactivatable, active self-targeting, and multimodal theranostic amphiphile strategy shows great potential in constructing precise nanomedicine.
Directed Flow of Micromotors through Alignment Interactions with Micropatterned Ratchets
Jaideep Katuri - ,
David Caballero - ,
Raphael Voituriez - ,
Josep Samitier - , and
Samuel Sanchez *
To achieve control over naturally diffusive, out-of-equilibrium systems composed of self-propelled particles, such as cells or self-phoretic colloids, is a long-standing challenge in active matter physics. The inherently random motion of these active particles can be rectified in the presence of local and periodic asymmetric cues given that a nontrivial interaction exists between the self-propelled particle and the cues. Here, we exploit the phoretic and hydrodynamic interactions of synthetic micromotors with local topographical features to break the time-reversal symmetry of particle trajectories and to direct a macroscopic flow of micromotors. We show that the orientational alignment induced on the micromotors by the topographical features, together with their geometrical asymmetry, is crucial in generating directional particle flow. We also show that our system can be used to concentrate micromotors in confined spaces and identify the interactions leading to this effect. Finally, we develop a minimal model, which identifies the key parameters of the system responsible for the observed rectification. Overall, our system allows for robust control over both temporal and spatial distribution of synthetic micromotors.
Evolution of Nanoparticle Protein Corona across the Blood–Brain Barrier
Alysia Cox *- ,
Patrizia Andreozzi - ,
Roberta Dal Magro - ,
Fabio Fiordaliso - ,
Alessandro Corbelli - ,
Laura Talamini - ,
Clizia Chinello - ,
Francesca Raimondo - ,
Fulvio Magni - ,
Maria Tringali - ,
Silke Krol - ,
Paulo Jacob Silva - ,
Francesco Stellacci - ,
Massimo Masserini - , and
Francesca Re
This publication is Open Access under the license indicated. Learn More
Engineered nanoparticles offer the chance to improve drug transport and delivery through biological barriers, exploiting the possibility to leave the blood circulation and traverse the endothelial vascular bed, blood–brain barrier (BBB) included, to reach their target. It is known that nanoparticles gather molecules on their surface upon contact with biological fluids, forming the “protein corona”, which can affect their fate and therapeutic/diagnostic performance, yet no information on the corona’s evolution across the barrier has been gathered so far. Using a cellular model of the BBB and gold nanoparticles, we show that the composition of the corona undergoes dramatic quantitative and qualitative molecular modifications during passage from the “blood” to the “brain” side, while it is stable once beyond the BBB. Thus, we demonstrate that the nanoparticle corona dynamically and drastically evolves upon crossing the BBB and that its initial composition is not predictive of nanoparticle fate and performance once beyond the barrier at the target organ.
Dedoping of Lead Halide Perovskites Incorporating Monovalent Cations
Mojtaba Abdi-Jalebi *- ,
Meysam Pazoki - ,
Bertrand Philippe - ,
M. Ibrahim Dar - ,
Mejd Alsari - ,
Aditya Sadhanala - ,
Giorgio Divitini - ,
Roghayeh Imani - ,
Samuele Lilliu - ,
Jolla Kullgren - ,
Håkan Rensmo - ,
Michael Grätzel - , and
Richard H. Friend
This publication is Open Access under the license indicated. Learn More
We report significant improvements in the optoelectronic properties of lead halide perovskites with the addition of monovalent ions with ionic radii close to Pb2+. We investigate the chemical distribution and electronic structure of solution processed CH3NH3PbI3 perovskite structures containing Na+, Cu+, and Ag+, which are lower valence metal ions than Pb2+ but have similar ionic radii. Synchrotron X-ray diffraction reveals a pronounced shift in the main perovskite peaks for the monovalent cation-based films, suggesting incorporation of these cations into the perovskite lattice as well as a preferential crystal growth in Ag+ containing perovskite structures. Furthermore, the synchrotron X-ray photoelectron measurements show a significant change in the valence band position for Cu- and Ag-doped films, although the perovskite bandgap remains the same, indicating a shift in the Fermi level position toward the middle of the bandgap. Such a shift infers that incorporation of these monovalent cations dedope the n-type perovskite films when formed without added cations. This dedoping effect leads to cleaner bandgaps as reflected by the lower energetic disorder in the monovalent cation-doped perovskite thin films as compared to pristine films. We also find that in contrast to Ag+ and Cu+, Na+ locates mainly at the grain boundaries and surfaces. Our theoretical calculations confirm the observed shifts in X-ray diffraction peaks and Fermi level as well as absence of intrabandgap states upon energetically favorable doping of perovskite lattice by the monovalent cations. We also model a significant change in the local structure, chemical bonding of metal-halide, and the electronic structure in the doped perovskites. In summary, our work highlights the local chemistry and influence of monovalent cation dopants on crystallization and the electronic structure in the doped perovskite thin films.
Ultrasound Triggered Conversion of Porphyrin/Camptothecin-Fluoroxyuridine Triad Microbubbles into Nanoparticles Overcomes Multidrug Resistance in Colorectal Cancer
Min Chen - ,
Xiaolong Liang - ,
Chuang Gao - ,
Ranran Zhao - ,
Nisi Zhang - ,
Shumin Wang - ,
Wen Chen - ,
Bo Zhao - ,
Jinrui Wang - , and
Zhifei Dai *
Multidrug resistance remains one of the main obstacles to efficient chemotherapy of colorectal cancer. Herein, an efficient combination therapeutic strategy is proposed based on porphyrin/camptothecin-floxuridine triad microbubbles (PCF-MBs) with high drug loading contents, which own highly stable co-delivery drug combinations and no premature release. The triad PCF-MBs can act not only as a contrast agent for ultrasound (US)/fluorescence bimodal imaging but also a multimodal therapeutic agent for synergistic chemo-photodynamic combination therapy. Upon local ultrasound exposure under the guidance of ultrasound imaging, in situ conversion of PCF-MBs into porphyrin/camptothecin-floxuridine nanoparticles (PCF-NPs) leads to high accumulation of chemo-drugs and photosensitizer in tumors due to the induced high permeability of the capillary wall and cell membrane temporarily via sonoporation effect, greatly reducing the risk of systemic exposure. Most importantly, it was found that the PCF-MB-mediated photodynamic therapy could significantly reduce the expression of adenosine-triphosphate (ATP)-binding cassette subfamily G member 2 (ABCG2), which is responsible for the drug resistance in chemotherapy, resulting in a prominent intracellular camptothecin increase. In vivo experiments revealed that the PCF-MBs in combination with ultrasound and laser irradiation could achieve a 90% tumor inhibition rate of HT-29 cancer with no recurrence. Therefore, such triad PCF-MB-based combination therapeutic strategy shows great promise for overcoming drug resistance of colorectal cancer and other cancers.
Tailored Emission Properties of ZnTe/ZnTe:O/ZnO Core–Shell Nanowires Coupled with an Al Plasmonic Bowtie Antenna Array
Kui-Ying Nie - ,
Xuecou Tu - ,
Jing Li - ,
Xuanhu Chen - ,
Fang-Fang Ren *- ,
Guo-Gang Zhang *- ,
Lin Kang - ,
Shulin Gu - ,
Rong Zhang - ,
Peiheng Wu - ,
Youdou Zheng - ,
Hark Hoe Tan - ,
Chennupati Jagadish - , and
Jiandong Ye *
The ability to manipulate light–matter interaction in semiconducting nanostructures is fascinating for implementing functionalities in advanced optoelectronic devices. Here, we report the tailoring of radiative emissions in a ZnTe/ZnTe:O/ZnO core–shell single nanowire coupled with a one-dimensional aluminum bowtie antenna array. The plasmonic antenna enables changes in the excitation and emission processes, leading to an obvious enhancement of near band edge emission (2.2 eV) and subgap excitonic emission (1.7 eV) bound to intermediate band states in a ZnTe/ZnTe:O/ZnO core–shell nanowire as well as surface-enhanced Raman scattering at room temperature. The increase of emission decay rate in the nanowire/antenna system, probed by time-resolved photoluminescence spectroscopy, yields an observable enhancement of quantum efficiency induced by local surface plasmon resonance. Electromagnetic simulations agree well with the experimental observations, revealing a combined effect of enhanced electric near-field intensity and the improvement of quantum efficiency in the ZnTe/ZnTe:O/ZnO nanowire/antenna system. The capability of tailoring light–matter interaction in low-efficient emitters may provide an alternative platform for designing advanced optoelectronic and sensing devices with precisely controlled response.
In Situ Observation of Resistive Switching in an Asymmetric Graphene Oxide Bilayer Structure
Sungkyu Kim - ,
Hee Joon Jung - ,
Jong Chan Kim - ,
Kyung-Sun Lee - ,
Sung Soo Park - ,
Vinayak P. Dravid *- ,
Kai He *- , and
Hu Young Jeong *
Graphene oxide decorated with oxygen functional groups is a promising candidate as an active layer in resistive switching devices due to its controllable physical-chemical properties, high flexibility, and transparency. However, the origin of conductive channels and their growth dynamics remain a major challenge. We use in situ transmission electron microscopy techniques to demonstrate that nanoscale graphene oxide sheets bonded with oxygen dynamically change their physical and chemical structures upon an applied electric field. Artificially engineered bilayer reduced graphene oxide films with asymmetric oxygen content exhibit nonvolatile write-once-read-many memory behaviors without experiencing the bubble destruction due to the efficient migration of oxygen ions. We clearly observe that a conductive graphitic channel with a conical shape evolves from the upper oxygen-rich region to the lower oxygen-poor region. These findings provide fundamental guidance for understanding the oxygen motions of oxygen-containing carbon materials for future carbon-based nanoelectronics.
Controlling Disorder by Electric-Field-Directed Reconfiguration of Nanowires To Tune Random Lasing
Philip P. Donahue - ,
Chenji Zhang - ,
Nicholas Nye - ,
Jennifer Miller - ,
Cheng-Yu Wang - ,
Rong Tang - ,
Demetrios Christodoulides *- ,
Christine D. Keating *- , and
Zhiwen Liu *
Top-down fabrication is commonly used to provide positioning control of optical structures; yet, it places stringent limitations on component materials, and oftentimes, dynamic reconfigurability is challenging to realize. Here, we present a reconfigurable nanoparticle platform that can integrate heterogeneous particle assembly of different shapes, sizes, and chemical compositions. We demonstrate dynamic control of disorder in this platform and use it to tune random laser emission characteristics for a suspension of titanium dioxide nanowires in a dye solution. Using an alternating current electric field, we control the nanowire orientation to dynamically engineer the collective scattering of the sample. Our theoretical model indicates that a change of up to 22% in scattering coefficient can be achieved for the experimentally determined nanowire length distribution upon alignment. Dependence of light confinement on anisotropic particle alignment provides a means to reversibly tune random laser characteristics; a nearly 20-fold increase in lasing intensity was observed with aligned particle orientation. We illustrate the generality of the approach by demonstrating enhanced lasing for aligned nanowires of other materials including gold, mixed gold/dielectric, and vanadium oxide.
Aligned Carbon Nanotube Synaptic Transistors for Large-Scale Neuromorphic Computing
Ivan Sanchez Esqueda *- ,
Xiaodong Yan - ,
Chris Rutherglen - ,
Alex Kane - ,
Tyler Cain - ,
Phil Marsh - ,
Qingzhou Liu - ,
Kosmas Galatsis *- ,
Han Wang *- , and
Chongwu Zhou *
This paper presents aligned carbon nanotube (CNT) synaptic transistors for large-scale neuromorphic computing systems. The synaptic behavior of these devices is achieved via charge-trapping effects, commonly observed in carbon-based nanoelectronics. In this work, charge trapping in the high-k dielectric layer of top-gated CNT field-effect transistors (FETs) enables the gradual analog programmability of the CNT channel conductance with a large dynamic range (i.e., large on/off ratio). Aligned CNT synaptic devices present significant improvements over conventional memristor technologies (e.g., RRAM), which suffer from abrupt transitions in the conductance modulation and/or a small dynamic range. Here, we demonstrate exceptional uniformity of aligned CNT FET synaptic behavior, as well as significant robustness and nonvolatility via pulsed experiments, establishing their suitability for neural network implementations. Additionally, this technology is based on a wafer-level technique for constructing highly aligned arrays of CNTs with high semiconducting purity and is fully CMOS compatible, ensuring the practicality of large-scale CNT+CMOS neuromorphic systems. We also demonstrate fine-tunability of the aligned CNT synaptic behavior and discuss its application to adaptive online learning schemes and to homeostatic regulation of artificial neuron firing rates. We simulate the implementation of unsupervised learning for pattern recognition using a spike-timing-dependent-plasticity scheme, indicate system-level performance (as indicated by the recognition accuracy), and demonstrate improvements in the learning rate resulting from tuning the synaptic characteristics of aligned CNT devices.
Thermal Imaging with Plasmon Resonance Enhanced HgTe Colloidal Quantum Dot Photovoltaic Devices
Xin Tang - ,
Matthew M. Ackerman - , and
Philippe Guyot-Sionnest *
Thermal imaging in the midwave infrared plays an important role for numerous applications. The key functionality is imaging devices in the atmospheric window between 3 and 5 μm, where disturbance from fog, dust, and other atmospheric influence could be avoided. Here, we demonstrate sensitive thermal imaging with HgTe colloidal quantum dot (CQD) photovoltaic detectors by integrating the HgTe CQDs with plasmonic structures. The responsivity at 5 μm is enhanced 2- to 3-fold over a wide range of operating temperatures from 295 to 85 K. A detectivity of 4 × 1011 Jones is achieved at cryogenic temperature. The noise equivalent temperature difference is 14 mK at an acquisition rate of 1 kHz for a 200 μm pixel. Thermal images are captured with a single-pixel scanning imaging system.
Dynamic Structure Evolution of Composition Segregated Iridium-Nickel Rhombic Dodecahedra toward Efficient Oxygen Evolution Electrocatalysis
Yecan Pi - ,
Qi Shao - ,
Xing Zhu - , and
Xiaoqing Huang *
The anodic oxygen evolution reaction (OER) is central to various energy conversion devices, but the investigation of the dynamic evolution of catalysts in different OER conditions remains quite limited, which is unfavorable for the understanding of the actual structure–activity relationship and catalyst optimization. Herein, we constructed monodispersed IrNix nanoparticles (NPs) with distinct composition-segregated features and captured their structural evolution in various OER environments. We decoded the interesting self-reconstruction of IrNix NPs during the OER, in which an Ir-skin framework is generated in an acidic electrolyte, while a Ni-rich surface layer is observed in an alkaline electrolyte owing to Ni migration. Benefiting from such self-reconstruction, considerable OER enhancements are achieved under both acidic and alkaline conditions. For comparison, IrNix nanoframes with Ir skins prepared by chemical etching show a similar structural evolution result in the acidic electrolyte, but a total different phenomenon in the alkaline electrolyte. By tracking the structural evolution of IrNix catalysts and correlating them with OER activity trajectories, the present work provides a significant understanding for designing efficient OER catalysts with controlled compositional distributions.
Nanoporous Red Phosphorus on Reduced Graphene Oxide as Superior Anode for Sodium-Ion Batteries
Shuai Liu - ,
Hui Xu - ,
Xiufang Bian *- ,
Jinkui Feng *- ,
Jie Liu - ,
Yinghui Yang - ,
Chao Yuan - ,
Yongling An - ,
Runhua Fan - , and
Lijie Ci
As a potential alternative to lithium-ion batteries, sodium-ion batteries (SIBs) have attracted more and more attention due to the lower cost of sodium than lithium. Red phosphorus (RP) is an especially promising anode for SIBs with the highest theoretical capacity of 2596 mAh g–1, which faces the challenges of large volume change and low conductivity. Herein, we develop a nanoporous RP on reduced graphene oxide (NPRP@RGO) as a high-performance anode for SIBs through boiling. Its nanoporous structure could accommodate the volume change and minimize the ion diffusion length, and the high electronic conductive network built on RGO sheets facilitates the fast electron and ion transportation. As a result, NPRP@RGO exhibits a superhigh capacity (1249.7 mAh gcomposite–1 after 150 cycles at 173.26 mA gcomposite–1), superior rate capability (656.9 mAh gcomposite–1 at 3465.28 mA gcomposite–1), and ultralong cycle life at 5.12 A gRP–1 for RP-based electrodes (775.3 mAh gRP–1 after 1500 cycles). The successful synthesis of NPRP@RGO marks a significant enhanced performance for RP-based SIB anodes, providing a scalable synthesis route for nanoporous structures.
Tracking Metal Electrodeposition Dynamics from Nucleation and Growth of a Single Atom to a Crystalline Nanoparticle
Haytham E. M. Hussein - ,
Reinhard J. Maurer - ,
Houari Amari - ,
Jonathan J. P. Peters - ,
Lingcong Meng - ,
Richard Beanland - ,
Mark E. Newton - , and
Julie V. Macpherson *
In electrodeposition the key challenge is to obtain better control over nanostructure morphology. Currently, a lack of understanding exists concerning the initial stages of nucleation and growth, which ultimately impact the physicochemical properties of the resulting entities. Using identical location scanning transmission electron microscopy (STEM), with boron-doped diamond (BDD) serving as both an electron-transparent TEM substrate and electrode, we follow this process, from the formation of an individual metal atom through to a crystalline metal nanoparticle, under potential pulsed conditions. In doing so, we reveal the importance of electrochemically driven atom transport, atom cluster formation, cluster progression to a nanoparticle, and the mechanism by which neighboring particles interact during growth. Such information will help formulate improved nucleation and growth models and promote wider uptake of electrodeposited structures in a wide range of societally important applications. This type of measurement is possible in the TEM because the BDD possesses inherent stability, has an extremely high thermal conductivity, is electron beam transparent, is free from contamination, and is robust enough for multiple deposition and imaging cycles. Moreover, the platform can be operated under conditions such that we have confidence that the dynamic atom events we image are truly due to electrochemically driven deposition and no other factors, such as electron-beam-induced movement.
Vapor-Infiltration Approach toward Selenium/Reduced Graphene Oxide Composites Enabling Stable and High-Capacity Sodium Storage
Xuming Yang - ,
Jinkai Wang - ,
Shuo Wang - ,
Hongkang Wang - ,
Ondrej Tomanec - ,
Chunyi Zhi - ,
Radek Zboril - ,
Denis Y. W. Yu *- , and
Andrey Rogach *
Emerging sodium–selenium batteries suffer from volume expansion of the selenium cathode and shuttling effects of soluble intermediates. Confining selenium within the carbon matrix is the most adopted strategy to address these two issues, which is generally realized via a melt-infusion method. Herein, we developed a vapor-infiltration method to fabricate selenium/carbon composites that are advantageous over the melt-infusion route in terms of several aspects: it relieves the requirement of intensive mechanical mixing and simplifies the ratio optimization between selenium and carbon; it avoids selenium aggregation and makes it possible to utilize all of the surface and pores of the carbon host. Utilizing this method, we fabricated a selenium/graphene composite from thermally reduced graphene oxide with a selenium loading equal to 71 wt %, thus approaching the record value. The obtained composite achieved the highest reported to date initial Coulombic efficiency of 88% among various selenium cathodes, with superior rate and cycle performance (410 and 367 mA h g–1 at 0.1 and 1 A g–1; capacity decay <10% after 800 cycles at 2 A g–1) enabled by the supporting graphene framework and the use of the ether electrolyte. In view of the distinct advantages of the vapor-infiltration method and the significant influence of the ether electrolyte on both initial Coulombic efficiency and cyclability of the batteries, we believe the introduced approach will be frequently adopted to incorporate selenium into various host materials, and the ether electrolyte will be widely considered for selenium-based electrodes.
Stereocomplex Prodrugs of Oligo(lactic acid)n-Gemcitabine in Poly(ethylene glycol)-block-poly(d,l-lactic acid) Micelles for Improved Physical Stability and Enhanced Antitumor Efficacy
Yu Tong Tam - ,
Chengbin Huang - ,
Michael Poellmann - , and
Glen S. Kwon *
Herein we demonstrate the formation of stereocomplex prodrugs of oligo(l-lactic acid)n-gemcitabine (o(LLA)n-GEM) and oligo(d-lactic acid)n-gemcitabine (o(DLA)n-GEM) for stable incorporation in poly(ethylene glycol)-block-poly(d,l-lactic acid) (PEG-b-PLA) micelles. O(LLA)n or o(DLA)n was attached at the amino group (4-(N)) of GEM via an amide linkage. When n = 10, a 1:1 mixture of o(LLA)10-GEM and o(DLA)10-GEM (o(L+DLA)10-GEM) was able to form a stereocomplex with a distinctive crystalline pattern. Degradation of o(L+DLA)10-GEM was driven by both backbiting conversion and esterase contribution, generating primarily o(L+DLA)1-GEM and GEM. O(L+DLA)10-GEM stably loaded in PEG-b-PLA micelles in the size range of 140–200 nm with an unexpected elongated morphology. The resulting micelles showed improved physical stability in aqueous media and inhibited backbiting conversion of o(L+DLA)10-GEM within micelles. Release of o(L+DLA)10-GEM from micelles was relatively slow, with a t1/2 at ca. 60 h. Furthermore, weekly administration of o(L+DLA)10-GEM micelles i.v. displayed potent antitumor activity in an A549 human non-small-cell lung carcinoma xenograft model. Thus, stereocomplexation of isotactic o(LLA)n and o(DLA)n acts as a potential prodrug strategy for improved stability and sustained drug release in PEG-b-PLA micelles.
Additions and Corrections
Correction to Twists and Turns of Orbiting and Spinning Metallic Microparticles Powered by Megahertz Ultrasound
Chao Zhou - ,
Leilei Zhao - ,
Mengshi Wei - , and
Wei Wang *
This publication is free to access through this site. Learn More
Correction to Nanocrystalline Titanium Metal–Organic Frameworks for Highly Efficient and Flexible Perovskite Solar Cells
UnJin Ryu - ,
Seohyeon Jee - ,
Joon-Suh Park - ,
Il Ki Han - ,
Ju Ho Lee - ,
Minwoo Park *- , and
Kyung Min Choi *
This publication is free to access through this site. Learn More
Mastheads
Issue Editorial Masthead
This publication is free to access through this site. Learn More
Issue Publication Information
This publication is free to access through this site. Learn More