金属辅助化学刻蚀法制备硅纳米线及应用

金属辅助化学刻蚀是近些年发展起来的一种各向异性湿法刻蚀,利用该方法可以制备出高长径比的半导体一维纳米结构。 本文综述了金属辅助化学刻蚀法可控制备硅纳米线的最新进展,简要概述了刻蚀的基本过程与机制,重点阐述了基于不同模板的金属辅助化学刻蚀可控制备高度有序、高长径比的硅纳米线阵列的具体流程与工艺,并介绍了其在锂离子电池、太阳能电池、气体传感检测和仿生超疏水等方面的潜在应用,探讨了目前存在的问题及其今后的研究发展方向。     

Vapor phase synthesis of tungsten nanowires

A concept is presented for synthesizing metal nanowires directly from the vapor phase using chemical vapor transport to temperatures higher than the corresponding metal oxide decomposition temperature. Specifically, this concept is demonstrated with the synthesis of tungsten metal nanowires with sizes ranging from 70 to 40 nm by increasing the condensation temperature. The simultaneous condensation and decomposition of the tungsten oxide species during nucleation and growth is suggested for 1-D growth of metallic tungsten nanowires. This synthesis concept could potentially be extended to the vapor phase synthesis of metal nanowires of several other nonvolatile and refractory metals. The tungsten nanowires could find potential applications in gas sensors and as electron sources in electron microscopes.     

金属纳米线的合成与组装

金属纳米线以它独特的光学和电学性质以及在纳米级电子线路中的应用潜力,受到人们越来越多的关注。本文介绍了金属纳米线的合成方法及其二维有序组装体系研究的最新进展,展望了纳米材料未来的研究方向和发展趋势。     

Accelerating electrochemistry with metal nanowires

Scalable, solution-phase syntheses of metal nanowires are enabling their increased use in electrochemical processes. This review highlights recent results demonstrating how metal nanowires can exhibit better durability and higher activity than traditional metal nanoparticle electrocatalysts on carbon supports. Metal nanowires can also form interconnected two-dimensional and three-dimensional (3D) networks that eliminate the need for a carbon support, thus eliminating the detrimental effects of carbon corrosion. Porous 3D networks of nanowires can be used as flow-through electrodes with the highest specific surface areas and mass transport coefficients obtained to date, enabling dramatic increases in the productivity of electrochemical reactions. Nanowire networks are also serving as 3D current collectors that improve the capacity of batteries. The tunable surface structure and dimensions of metal nanowires offer researchers a new opportunity to create electrodes that are tailored from the atomic scale to the microscale to improve electrochemical performance.     

Template electrodeposition of metals. Review

The works devoted to the electrodeposition of metals, alloys, and semiconductors onto the substrates through the templates of various non-conducting materials with pores of various shapes and sizes are reviewed. The composite materials, nanowires, metal foams, and the parts with nanostructured surface obtained by this method are promising materials for the electrocatalysis, electroanalysis of media, development of various sensors, modern miniature magnetic memory devices, optoelectronics, power sources, etc.     

Flow‐Enabled Self‐Assembly of Large‐Scale Aligned Nanowires

One‐dimensional nanowires enable the realization of optical and electronic nanodevices that may find applications in energy conversion and storage systems. Herein, large‐scale aligned DNA nanowires were crafted by flow‐enabled self‐assembly (FESA). The highly oriented and continuous DNA nanowires were then capitalized on either as a template to form metallic nanowires by exposing DNA nanowires that had been preloaded with metal salts to an oxygen plasma or as a scaffold to direct the positioning and alignment of metal nanoparticles and nanorods. The FESA strategy is simple and easy to implement and thus a promising new method for the low‐cost synthesis of large‐scale one‐dimensional nanostructures for nanodevices.     

Depositional characteristics of metal coating on single-crystal TiO2 nanowires

Ultralong single-crystalline TiO(2) nanowires were prepared by a simple, low-cost solvothermal process. Silver nitrate, neodymium chloride, ceric nitrate, stannic chloride hydrate, and cadmium chloride were used as metal sources and deposited by reduction on the surface of TiO(2) nanowires. The composites were subsequently characterized by transmission electron microscopy, and their coverage was compared. The nature of the coatings on the TiO(2) nanowires varies from metal to metal. A novel approach on modified one-dimensional nanostructures with metal coating was developed, which has great potential applications in catalysts, sensors, and nanoscale devices.     

Nanotubes and nanowires

Synthesis and characterization of nanotubes and nanowires constitute an important part of nanoscience since these materials are essential building units for several devices. We have prepared aligned carbon nanotube bundles and Y-junction nanotubes by the pyrolysis of appropriate organic precursors. The aligned bundles are useful for field emission display while the Y-junction nanotubes are likely to be useful as nanochips since they exhibit diode properties at the junction. By making use of carbon nanotubes, nanowires of metals, metal oxides and GaN have been obtained. Both the oxide and GaN nanowires are single crystalline. Gold nanowires exhibit plasmon bands varying markedly with the aspect ratio. GaN nanowires show excellent photoluminescence characteristics. It has been possible to synthesise nanotubes and nanowires of metal chalcogenides by employing different strategies.     

吡啶在几种金属纳米线阵列上的表面增强喇曼光谱

近20多年来利用表面增强喇曼光谱（SERS）的研究还仅限于Ag,Au,Cu这三种具有强SERS效应的金属,最近,田中群等利用合适的表面处理方法和共焦曼光谱技术成功地获得了许多无机离子和有机小分子吸附在一系列的过渡金属（如Pt,Ni,Fe,Pd,Rh,Co,Ru等）上的SERS光谱,拓宽了SERS的应用范围,但这些表面处理方法对基底进行处理时存在着较大的随机性,从而导致对所得SERS信号的解释困难。近年来通过自组装膜、模板合成等技术可得比较有序具有强SERS效应的或表面,例如Nie等最近发现尺寸分布狭窄的Ag溶胶粒子（约80－100nm）能诱导出巨大的SERS增强;Freeman和C tffumj m jf rbutb uqf At A 体微粒组装在聚合物基底上,制得高活性的SERS基底,以上工作都表明制备有序纳米级金属颗粒表面将推动SERS的应用和机理研究,迄今,3半导体纳米线阵列上的喇曼光谱已有报道,而利用金属纳米线阵列作为SERS基底除半于样模合成法制备的Ag纳米线阵列上的SERS之外,尚未见其它相关报道,本文主要研究样模合成法制备金属纳米线的过程,并以此为基底研究吡啶吸附的SERS光谱。     

On-wire conversion chemistry: engineering solid-state complexity into striped metal nanowires using solution chemistry reactions

Multisegment template-grown metal nanowires have become important one-dimensional materials for a variety of applications in chemistry, physics, engineering, biology, and medicine. Segmented nanowires are traditionally fabricated in anodic alumina membranes using electrodeposition, and this technique is applicable to a range of metals, alloys, and semiconductors. Here we report an alternative and simple solution chemistry strategy for incorporating multimetal components of controllable length and composition into template-grown metal nanowires. By reacting membrane-confined nanowires with metal salt solutions under reducing conditions, site-specific diffusion occurs to convert one or both nanowire tips or the entire nanowire into a variety of multimetal phases. Platinum-based intermetallic compounds were chosen as targets for demonstrating the feasibility of the on-wire conversion chemistry.     

Electric field-directed assembly of gold and platinum nanowires from an electrolysis process

Gold and platinum nanowires have been grown on a silicon dioxide surface between two microfabricated electrodes from an electrolysis process under an AC signal with a DC offset. In the process, the anode electrode acted as a sacrificing layer and oxidized to metal ions. The metal ions were reduced to particles and aligned along the electric field forming nanowires connected with the cathode. Greater than 10 V and 12 V DC offset were required for growing gold and platinum nanowires, respectively. Other factors affecting the growth of the nanowires include frequency of applied bias and gap between the electrodes.     

Controllable CVD route to CoS and MnS single-crystal nanowires

CoS and MnS nanowires were prepared through a simple chemical vapor deposition process. The adopted synthetic route is expected to be applicable for the synthesis of other metal sulfide semiconductor nanowires.     

Iron–cobalt and iron–cobalt–nickel nanowires deposited by means of cyclic voltammetry and pulse-reverse electroplating

Metal nanowires composed of Fe–Co and Fe–Co–Ni alloys were successfully prepared by means of cyclic voltammetry (CV) and pulse-reverse (PR) electroplating techniques from acidic metal chloride solutions. The anodic dissolution process in the CVs or in the reverse electroplating period was found to be the key factor influencing the formation of metal nanowires. The addition of nickel into the Fe–Co alloy was found to extend the diameter of these nanowires. The morphology and crystalline information of these alloy deposits prepared by CV and PR deposition techniques were obtained from the field-emission scanning electron microscopic (FE-SEM) photographs and X-ray diffraction (XRD) patterns, respectively.     

Au nanowire fabrication from sequenced histidine-rich peptide

A new biological approach to fabricate Au nanowires was examined by using sequenced histidine-rich peptide nanowires as templates. The sequenced histidine-rich peptide molecules were assembled as nanowires, and the biological recognition of the sequenced peptide toward Au lead to efficient Au coating on the nanowires. Monodisperse Au nanocrystals were uniformly coated on the histidine peptide nanowires with the high-density coverage, and the crystalline phases of the Au nanocrystals were observed as (111) and (220). The uniformity of the Au coating on the nanowires without contamination of precipitated Au aggregates is advantageous for the fabrication of electronics and sensor devices when the nanowires are used as the building blocks. We believe this simple metal nanowire fabrication method can be applied to various metals and semiconductors with peptides whose sequences are known to mineralize specific ions.     

Photocatalytic activity of silicon nanowires under UV and visible light irradiation

The communication reports on the high performance of hydrogen-terminated silicon nanowires and silicon nanowires coated with metal (Ag, Cu) nanostructures for the photodegradation of rhodamine B under UV and visible light irradiation.     

Coordinated organogel templated fabrication of silver/polypyrrole composite nanowires

A new method to fabricate metal/conducting polymer composite nanowires is presented by taking silver/polypyrrole composite nanowires as an example.A silver(Ⅰ)-coordinated organogel as template was prepared firstly,and redox-polymerization of pyrrole took place on the gel fiber,giving product of silver/polypyrrole nanowires.The silver/polypyrrole nanowires were characterized by multiple techniques.This strategy could be carried out in one-step procedure at room temperature,and it proves the utility of coordinated organogels in template synthesis of polymer nanostructures.     

The role of vortices in the process of impurity nanoparticles coalescence in liquid helium

The process of condensation of metal atoms in superfluid helium was shown to occur mainly in the quantized vortices. Firstly the spherical nanocrystals were grown there. At low metal content in liquid they fused then into long cylindrical nanowires. At higher metal content the spherical microparticles were formed instead with their size terminated by mutual repulsion arisen in vortex core. Small number of zigzag-shaped nanowires was found to be formed in usual vortices of normal liquid helium as well. The production of ideal 1-D structures such as long polymer chains was predicted for non-metallic material condensation in superfluid helium.     

Facile Synthesis,Crystal Structure,and Adsorption Property of Small Titanate Nanowires

Small titanate nanowires with NaTi_2O_4(OH) formulation were directly synthesized via the hydrothermal reaction of amorphous titanate particles with concentrated Na OH solution.The average width of these nanowires is smaller than 20 nm,and the surface area is higher than 200 m~2/g.Compared with the larger nanowires obtained by the hydrothermal treatment of crystalline titania in alkaline solution,these small nanowires exhibit larger adsorption capacities and faster adsorption rate in the removal of both heavy metal ions and dyes.     

Preparation and electrical properties of ultrafine Ga2O3 nanowires

Uniform and well-crystallized beta-Ga2O3 nanowires are prepared by reacting metal Ga with water vapor based on the vapor-liquid-solid (VLS) mechanism. Electron microscopy studies show that the nanowires have diameters ranging from 10 to 40 nm and lengths up to tens of micrometers. The contact properties of individual Ga2O3 nanowires with Pt or Au/Ti electrodes are studied, respectively, finding that Pt can form Schottky-barrier junctions and Au/Ti is advantageous to fabricate ohmic contacts with individual Ga2O3 nanowires. In ambient air, the conductivity of the Ga2O3 nanowires is about 1 (Omega.m)-1, while with adsorption of NH3 (or NO2) molecules, the conductivity can increase (or decrease) dramatically at room temperature. The as-grown Ga2O3 nanowires have the properties of an n-type semiconductor.     

Understanding the Metal-Directed Growth of Single-Crystal M-TCNQF(4) Organic Nanowires with Time-Resolved, in Situ X-ray Diffraction and First-Principles Theoretical Studies

The deterministic growth of oriented crystalline organic nanowires (CONs) from the vapor-solid chemical reaction (VSCR) between small-molecule reactants and metal nanoparticles has been demonstrated in several studies to date; however, the growth mechanism has not yet been conclusively understood. Here, the VSCR growth of M-TCNQF(4) (where M is Cu- or Ag-) nanowires is investigated both experimentally and theoretically with time-resolved, in situ X-ray diffraction (XRD) and first-principles atomistic calculations, respectively, to understand how metals (M) direct the assembly of small molecules into CONs, and what determines the selectivity of a metal for an organic vapor reactant in the growth process. Analysis of the real-time growth kinetics data using a modified Avrami model indicates that the formation of CONs from VSCR follows a one-dimensional ion diffusion-controlled tip growth mechanism wherein metal ions diffuse from a metal film through the nanowire to its tip where they react with small molecules to continue growth. The experimental data and theoretical calculations indicate that the selectivity of different metals to induce nanowire growth depends strongly upon effective charge transfer between the organic molecules and the metal. Specifically, the experimental finding that Cu ions can exchange and replace Ag ions in Ag-TCNQF(4) to form Cu-TCNQF(4) nanowires is explained by the significantly stronger chemical bond between Cu and TCNQF(4) molecules than for Ag, due to the strong electronic contribution of Cu d-orbitals near the Fermi level. Understanding how to control the VSCR growth process may enable the synthesis of novel organic nanowires with axial or coaxial p/n junctions for organic nanoelectronics and solar energy harvesting.