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Precursor-Mediated Synthesis of Shape-controlled Colloidal CsPbBr <sub/>3</sub> Perovskite Nanocrystals and their Nanofiber-Directed Self-assembly
摘要： Shape control is often necessary to tune the optical and electronic properties of nanocrystals (NCs) and is mostly achieved through manipulation of surface ligands and processing conditions. Here we present a versatile synthesis of colloidal CsPbBr3 perovskite NCs of various shapes (nanorods, nanocubes and nanoplatelets) from an inexpensive steroidal Cs precursor: cesium cholate (CsCh). Cesium cholate has several advantages over the most commonly used Cs-precursor (cesium oleate or Cs2CO3 or CsOAc) such as low-cost, non-hygroscopicity and better reproducibility in the perovskite synthesis. Due to the solubility of this Cs-precursor in polar solvents such as methanol, a miniscule polar environment is created during the nucleation and growth of the nanocrystals leading to the serendipitous formation of nanorods at 180 ℃, whereas using a biphasic mixture of 1-octadecene and methanol, the morphology changes to nanocubes. By lowering the reaction temperature (90 ℃), nanoplatelets with 8-9 monolayers thicknesses are formed. These colloidal NCs of variety of shapes are strongly luminescent with a green emission having narrow emission linewidths (16-17 nm) and high quantum yields (96% for nanocubes, 94% for nanoplatelets). Furthermore, hybrid materials of nanocubes and organogel of a dimeric bile acid-derived ester gelator are obtained through co-assembly in which nanocubes arrange along nanofibers with stable, sharp and bright green emission. This enables spatial ordering of nanocubes ranging from micron to centimeter scale in thin films, which is crucial for advanced optoelectronic applications. To date, there is no report in literature on the anisotropic organization of perovskite CsPbBr3 nanocubes triggered by supramolecular co-assembly involving organogel nanofibers.
关键词： nanocubes,organogel,Shape control,hybrid materials,nanorods,cesium cholate,nanoplatelets,supramolecular co-assembly,colloidal CsPbBr3 perovskite NCs
更新于2025-09-12 10:27:22
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ZnO@TiO2 Core Shell Nanorod Arrays with Tailored Structural, Electrical, and Optical Properties for Photovoltaic Application
摘要： ZnO has prominent electron transport and optical properties, beneficial for photovoltaic application, but its surface is prone to the formation of defects. To overcome this problem, we deposited nanostructured TiO2 thin film on ZnO nanorods to form a stable shell. ZnO nanorods synthesized by wet-chemistry are single crystals. Three different procedures for deposition of TiO2 were applied. The influence of preparation methods and parameters on the structure, morphology, electrical and optical properties were studied. Nanostructured TiO2 shells show different morphologies dependent on deposition methods: (1) separated nanoparticles (by pulsed laser deposition (PLD) in Ar), (2) a layer with nonhomogeneous thickness (by PLD in vacuum or DC reactive magnetron sputtering), and (3) a homogenous thin layer along the nanorods (by chemical deposition). Based on the structural study, we chose the preparation parameters to obtain an anatase structure of the TiO2 shell. Impedance spectroscopy shows pure electron conductivity that was considerably better in all the ZnO@TiO2 than in bare ZnO nanorods or TiO2 layers. The best conductivity among the studied samples and the lowest activation energy was observed for the sample with a chemically deposited TiO2 shell. Higher transparency in the visible part of spectrum was achieved for the sample with a homogenous TiO2 layer along the nanorods, then in the samples with a layer of varying thickness.
关键词： TiO2 thin film,optical properties,ZnO nanorods,chemical deposition,DC reactive magnetron sputtering,pulsed laser deposition,electrical properties,core–shell
更新于2025-09-12 10:27:22
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Nonlinear laser absorption over a dielectric embedded with nanorods
摘要： An analytical formalism of laser absorption in a nanorod embedded dielectric surface has been developed. Nanorods lie in the plane of the dielectric, in the form of a planar array. A laser, impinged on them with an electric field perpendicular to the lengths of the nanorods, imparts oscillatory velocity to nanorod electrons. As the free electrons of a nanorod are displaced, a space charge field is developed in the nanorod that exerts restoration force on the electrons and their drift velocity shows a resonance at v = vp/√2, where ωp denotes the plasma frequency of free electrons inside the nanorod. It is inhibited by collisions and nanorod expansion. At the resonance, the electrons are efficiently heated by the laser and laser energy is strongly absorbed, resulting in significant reduction in laser transmissivity. The transmissivity decreases with laser intensity.
关键词： Dielectric surface,nanorods,laser absorption,plasma frequency
更新于2025-09-12 10:27:22
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Design of Nanoscaled Surface Morphology of TiO2–Ag2O Composite Nanorods through Sputtering Decoration Process and Their Low-Concentration NO2 Gas-Sensing Behaviors
摘要： TiO2–Ag2O composite nanorods with various Ag2O configurations were synthesized by a two-step process, in which the core TiO2 nanorods were prepared by the hydrothermal method and subsequently the Ag2O crystals were deposited by sputtering deposition. Two types of the TiO2–Ag2O composite nanorods were fabricated; specifically, discrete Ag2O particle-decorated TiO2 composite nanorods and layered Ag2O-encapsulated TiO2 core–shell nanorods were designed by controlling the sputtering duration of the Ag2O. The structural analysis revealed that the TiO2–Ag2O composite nanorods have high crystallinity. Moreover, precise control of the Ag2O sputtering duration realized the dispersive decoration of the Ag2O particles on the surfaces of the TiO2 nanorods. By contrast, aggregation of the massive Ag2O particles occurred with a prolonged Ag2O sputtering duration; this engendered a layered coverage of the Ag2O clusters on the surfaces of the TiO2 nanorods. The TiO2–Ag2O composite nanorods with different Ag2O coverage morphologies were used as chemoresistive sensors for the detection of trace amounts of NO2 gas. The NO2 gas-sensing performances of various TiO2–Ag2O composite nanorods were compared with that of pristine TiO2 nanorods. The underlying mechanisms for the enhanced sensing performance were also discussed.
关键词： composite nanorods,sputtering,nanostructured surface,surface decoration
更新于2025-09-12 10:27:22
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Plasmonic Cu Nanostructures in ZnO as Hyperbolic Metamaterial Thin Films
摘要： Plasmonic metals, such as Cu and Al, have been considered as potential low-loss alternatives for Au and Ag for photonic structures and devices. However challenges remain in the fabrication and applications of Cu nanostructures, due to its easy oxidation issues. In this work, a new metamaterial structure of plasmonic Cu nanostructures embedded in a dielectric ZnO matrix has been designed and successfully fabricated using a one-step thin film growth method. The Cu-ZnO hybrid thin films present excellent epitaxial quality and exotic optical properties, such as strong localized surface plasmon resonance in the visible regime, and, highly anisotropic and hyperbolic optical response, revealed by angular dependent and polarization resolved reflectivity measurements. This hyperbolic plasmonic metamaterial via the metal-in-oxide matrix form combining low loss plasmonic Cu nanostructures and extraordinary anisotropic optical properties could be used towards various nanophotonic applications, such as plasmonic solar energy devices and hyperlens.
关键词： anisotropic optical property,Cu nanorods,metamaterial,self-assembled,low-loss plasmonic metal
更新于2025-09-11 14:15:04
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Laser‐Directed Assembly of Nanorods of 2D Materials
摘要： Herein, the previously unrealized ability to grow nanorods and nanotubes of 2D materials using femtosecond laser irradiation is demonstrated. In as short as 20 min, nanorods of tungsten disulfide, molybdenum disulfide, graphene, and boron nitride are grown in solutions. The technique fragments nanoparticles of the 2D materials from bulk flakes and leverages molecular scale alignment by nonresonant intense laser pulses to direct their assembly into nanorods up to several micrometers in length. The laser treatment process is found to induce phase transformations in some of the materials, and also results in the modification of the nanorods with functional groups from the solvent atoms. Notably, the WS2 nanoparticles, which are ablated from semiconducting 2H WS2 crystallographic phase flakes, reassemble into nanorods consisting of the 1T metallic phase. Due to this transition, and the 1D nature of the fabricated nanorods, the WS2 nanorods display substantial improvements in electrical conductivity and optical transparency when employed as transparent conductors.
关键词： laser assembly,graphene,nanorods,transition metal dichalcogenides
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Mobile Based in Situ Detection of Live/Dead and Antibiotic Resistant Bacteria by Silver Nanorods Array Sensor Fabricated by Glancing Angle Deposition
摘要： The rapid in-situ detection of viability of bacteria is essential for human health and environmental care. It has become one of the biggest needs in biological and medical sciences to prevent infections and diseases, which usually occur in hospitals and field clinics. Nowadays, antibiotic resistance (ABR) has been grown as one of the world’s acutest public health problems, which requires a quick and efficient solution. Here, we demonstrate an easy, sensitive, user-friendly, portable, cost effective and time saving approach for detection of live, dead and drug resistant bacteria. Most of the organisms are found to produce H2S gas by their metabolism system. The endogenous H2S evolution was targeted to differentiate between live and dead as well as ABR bacteria. The silver nanorods (AgNRs) arrays sensors were fabricated by glancing angle deposition technique. The colorimetric and water wettability (contact angle) features of as-synthesized AgNRs were found to be highly sensitive and selective for hydrogen sulfide (H2S) gas. E.coli, P. aeruginosa, B. subtilis and S. aureus were used as the model organisms for this study. A drastic visible change in color as well as wetting properties of AgNRs array was observed. To make it easy, a user friendly and field deployable android based mobile app ‘Colorimetric Detector’ was developed. This dual mode detection is facile, inexpensive and can be easily scaled-up in the field of disease diagnosis.
关键词： mobile app,colorimetric detection,silver nanorods,antibiotic resistance,bacteria detection,H2S gas
更新于2025-09-11 14:15:04
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Synthesis, characterization and modeling of self-assembled porphyrin nanorods
摘要： Porphyrin nanorods were prepared by ion-association between free-base meso 5,10,15,20-tetrakis-(4-N-methylpyridinium)porphyrin cations and tetraphenylborate anions. The nanorods have variable lengths (up to a few micrometers long) and diameters (~50–500 nm). Their structure at the molecular level was elucidated by combining multinuclear solid state NMR spectroscopy, synchrotron X-ray powder diffraction and DFT calculations.
关键词： DFT modeling,solid state NMR,NMR crystallography,nanorods,porphyrin,self-assembly
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting - Atlanta, GA, USA (2019.7.7-2019.7.12)] 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting - Generalized Tensor FDTD Method for Sloped Plasmonic Interfaces
摘要： A tensor finite-difference time-domain (FDTD) method for sloped interfaces is generalized to dispersive media and applied to the study of plasmonic periodic structures formed by silver nanorods. Conventional staircased FDTD exhibits poor convergence properties in this situation, as plasmonic fields are strongly localized right where staircasing errors occur, namely at the air-silver interface. Alternative methods that have been proposed for this problem include the use of a triangular mesh or effective permittivity models that lead to a fourth-order auxiliary differential equation (ADE) connecting D and E at the interface. The proposed approach offers high accuracy, still employing a rectangular FDTD mesh, thus striking a very appealing balance between accuracy and computational efficiency.
关键词： numerical techniques,plasmonic interfaces,tensor FDTD,silver nanorods,dispersive media
更新于2025-09-11 14:15:04
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Efficiency Improvement of TiO <sub/>2</sub> Nanorods Electron Transport Layer Based Perovskite Solar Cells by Solvothermal Etching
摘要： The efficiency improvement of perovskite solar cells (PSCs) by solvothermal etching and/or TiCl4 treatment of TiO2 nanorod arrays (NRAs) based electron transport layer (ETL) is reported in this article. The TiO2 NRAs are explore for the ETL because of their better direct carrier transportation over other TiO2 nanostructures. The solvothermal etching of TiO2 NRAs enhances the surface-to-volume ratio of the ETL, which, in turn, enhances the power conversion efficiency (PCE) of the PSCs. All the measurements are performed at room temperature and high humid (with ～65% humidity) conditions to demonstrate the performance of the PSCs under normal environmental conditions. A noteworthy efficiency of 15.16% with an improved fill factor and short circuit current density (JSC) is achieved in the proposed PSCs under this article. The performance of the PSC is shown to improve further by exploring TiCl4 treatment of the solvothermally etched TiO2 NRs as the ETL in the device.
关键词： solar cell,solvothermal etching,TiO2 nanorods,perovskite,Hydrothermal process
更新于2025-09-11 14:15:04