Influence of polarization direction, incidence angle, and geometry on near-field enhancement in two-layered gold nanowires

The influences of polarization direction, incidence angle, and geometry on near-field enhancements in two-layered gold nanowires （TGNWs） have been investigated by using the vector wave function method. When the polarization direction is perpendicular to the incidence plane, the local field factor （LFF） in TGNW decreases first and then increases with the increase in the incidence angle. The minimum LFF is observed at an incidence angle of 41°. It is found that the increase in the dielectric constant of the inner core leads to a decrease in the LFF. With the increase in the inner core radius, the LFF in TGNW increases first and then decreases, and the maximum LFF is observed at an inner core radius of 27 nm. On the other hand, when the polarization direction is parallel to the incidence plane, the collective motions of the induced electrons are enhanced gradually with the decrease in the incidence angle, and hence the near-field enhancement is increased.

Synthesis and microwave absorption properties of graphene-oxide(GO)/polyaniline nanocomposite with gold nanoparticles

A composite of graphene/PANI/GAunano is synthesized using the co-blend method. The morphologies and microstructures of samples are examined by transition electron microscopy(TEM) and Fourier transform infrared spectroscopy(FTIR). Moreover, the microwave absorption properties of both graphene/PANI and GO/PANI/ GAunano composites are investigated in a microwave frequency band from 1 GHz to 18 GHz. The maximum reflection loss(RL) of GO/PANI/GAunano with a thickness of 2 mm is up to-24.61 d B at 15.45 GHz, and the bandwidth corresponding to RL at-10 d B can reach 4.08 GHz(from 13.92 GHz to 18.00 GHz) for a 2-mm-thick layer. The electromagnetic data demonstrate that GO/PANI/GAunano can be used as an attractive candidate for microwave absorbers.

Investigation of mechanical properties of twin gold crystal nanowires under uniaxial load by molecular dynamics method

Twin gold crystal nanowires, whose loading direction is parallel to the twin boundary orientation, are simulated.We calculate the nanowires under tensile or compressive loads, different length nanowires, and different twin boundary nanowires respectively. The Young modulus of nanowires under compressive load is about twice that under tensile load.The compressive properties of twin gold nanowires are superior to their tensile properties. For different length nanowires,there is a critical value of length with respect to the mechanical properties. When the length of nanowire is greater than the critical value, its mechanical properties are sensitive to length. The twin boundary spacing hardly affects the mechanical properties.

Electrochemical preparation and characterization of gold-polyaniline core-shell nanocomposites on highly oriented pyrolytic graphite

A simple electrochemical method for the in situ preparation of homogeneously dispersed gold-polyaniline core/shell nanocomposite particles with controlled size on the highly oriented pyrolytic graphite(HOPG)was demonstrated.The HOPG surface was modified preferentially by covalent bonding of a two-dimensional 4-aminophenyl monolayer employing diazonium chemistry.AuCl4 -ions were attached to the Ar-NH2 termination and reduced electrochemically.This results in the formation of Au nuclei that could be further grown into gold nanoparticles.The formation of polyaniline as the shell wrap of Au nanoparticle was established by localized electro-polymerization.These core-shell nanocomposites prepared were characterized by AFM and cyclic voltammetry.The results show that the gold-polyaniline core-shell composites on HOPG have a mean particle size of 100 nm in diameter and the polyaniline shell thickness is about 15 nm.

Highly active and sintering-resistant heteroepitaxy of Au nanoparticles on ZnO nanowires for CO oxidation

Gold was supported on commercial ZnO powders(P) and homemade ZnO nanowires(NWs) by a modified deposition–precipitation method. X-ray diffraction and transmission electron microscopy investigation indicated that the size of the Au nanoparticles(NPs) depended strongly on the calcination temperature.The Au NPs were highly dispersed(< 5 nm) on both supports with calcination temperatures < 400 °C.However, after calcination at 600 °C the Au NPs aggregated much more severely on ZnO P than on ZnO NWs. Gold NPs epitaxially grew into the {10–10} facets of the ZnO NWs after calcination at temperatures > 400 °C. Such unique anchoring mechanism accounts for the much better experimentally observed sintering resistance. X-ray photoelectron spectra showed that Au existed as both metallic Au0 and Auδ+species in all the synthesized catalysts with or without calcination treatment; the ratios of Auδ+/Au0,however, varied, depending on the treatment conditions. Catalytic tests showed that the activity for CO oxidation strongly depended on the size of the Au NPs. After calcination at 600 °C, the specific rate for CO oxidation at room temperature decreased about 30 times on Au/ZnO P but only about 4 times on Au/ZnO NW. Stability tests demonstrated that the Au/ZnO NW catalysts had better stability for CO oxidation.

Mechanical property and deformation mechanism of gold nanowire with non-uniform distribution of twinned boundaries:A molecular dynamics simulation study

The mechanical property and deformation mechanism of twinned gold nanowire with non-uniform distribution of twinned boundaries(TBs)are studied by the molecular dynamics(MD)method.It is found that the twin boundary spacing(TBS)has a great effect on the strength and plasticity of the nanowires with uniform distribution of TBs.And the strength enhances with the decrease of TBS,while its plasticity declines.For the nanowires with non-uniform distribution of TBs,the differences in distribution among different TBSs have little effect on the Young's modulus or strength,and the compromise in strength appears.But the differences have a remarkable effect on the plasticity of twinned gold nanowire.The twinned gold nanowire with higher local symmetry ratio has better plasticity.The initial dislocations always form in the largest TBS and the fracture always appears at or near the twin boundaries adjacent to the smallest TBS.Some simulation results are consistent with the experimental results.

Role of Chromium Intermediate Thin-Film on the Growth of Silicon Oxide (SiO_x) Nanowires

In the present work, one-dimensional nanostructures of silicon oxide (SiOx) have been synthesized by thermal annealing method with and without chromium thin film on silicon substrate. The synthesis was carried out at different process temperatures ranging from 1000°C to 1100°C by using gold/chromium (Au/Cr) catalysts stack layer on the Si substrate in nitrogen (N2) ambience. The as-synthesized SiOx nanostructures have tetragonal rutile structure and show polycrystalline nature. The SEM images reveal wire-like nanostructures on the substrate with and without chromium thin film. Under the catalytic reaction of the gold/chromium metal, the density of SiOx nanowires is enhanced, since the Cr layer serves as a diffusion barrier for the diffusion of the gold downwards into the Si substrate. The vapor-liquid solid (VLS) growth mechanism is found to be dominant in the growth of SiOx nanowires. Furthermore, X-Ray diffraction microscopy (XRD) and Photoluminescence spectroscopy (PL) analysis conclude the defect free growth of the SiOx nanowires on gold/chrome/silicon substrate.

3-9 Molecular Dynamics Study of Point Defects Evolution in Self Irradiated Gold Nanowire

Due to the large surface-to-volume ratio, nanowires are proposed to be more radiation tolerant than traditional bulk materials. In recent years, many works are published which are trying to find the response of nanowires under radiation damage[1;2].In this work, we use molecular dynamics simulation package LAMMPS[3] to simulate ion irradiation of gold nanowire.

PEG4000/聚苯胺形状稳定复合相变材料的制备及其储热性能

以聚苯胺气凝胶(PANI)为支撑骨架,聚乙二醇4000(PEG4000)为相变材料,银纳米线(AgNWs)为导热增强填料,采用低温氧化聚合法和真空浸渍法制备得到具有良好形状和循环稳定性的定形相变复合材料PEG4000@Ag/PANI.聚苯胺气凝胶的高孔隙率及PEG4000与基体材料间的氢键作用和毛细作用,使得相变复合材料的最高负载率能够达到94.17%(熔融焓为165.17 J·g^(–1),凝固焓为152.77 J·g^(–1));加入AgNWs与PANI气凝胶共同搭建导热通路,提高了相变复合材料的导热性能(热导率最高为0.45 W·m^(–1)·K^(–1),比纯PEG4000提高80%);借助Ag NWs和聚苯胺优异的光吸收能力,相变复合材料的光–热转换效率达到90.61%.高储能密度、高光热转换能力和高热导率定形相变复合材料的成功制备为新型相变复合材料的合成提供了新思路,为太阳能光–热转换和储能应用提供了新材料,实现对太阳能的高效利用.

基于银纳米线/聚苯胺纳米复合材料的电致变色薄膜及器件的制备与性能

以质量比分别为1:5,1:15,1:25的银纳米线(AgNWs)和苯胺为原料,采用化学氧化聚合法制备了银纳米线/聚苯胺(AgNWs/PANI)纳米复合材料,喷涂在氧化铟锡(ITO)导电玻璃上得到AgNWs/PANI电致变色薄膜,将喷涂AgNWs/PANI(质量比为1:15)和聚(3,4-乙烯二氧噻吩)(PEDOT)电致变色薄膜的ITO基电极组装得到分层式电致变色器件,研究了AgNWs/PANI电致变色薄膜和电致变色器件的微观形貌和电致变色性能。结果表明:AgNWs/PANI电致变色薄膜中PANI均匀包覆在AgNWs上形成线性核壳结构,当AgNWs和苯胺质量比为1:5时薄膜中有很多AgNWs暴露在外,当质量比为1:25时AgNWs暴露缺陷较少但形成的导电通路连续性差,当质量比为1:15时AgNWs被PANI完美包覆且导电通路连续均匀;与纯PANI电致变色薄膜相比,AgNWs/PANI电致变色薄膜的峰值电流密度、离子扩散速率和光学对比度增大,电荷传递阻抗减小,变色效果明显,电致变色性能提升,AgNWs和苯胺质量比为1:15时电致变色性能最佳;电致变色器件的最大光学对比度为65.2%,着色和褪色过程响应时间分别仅为6.5,4.9 s,经历1 000次恒电位跃迁后光学对比度保留率高达97.7%,着色效率高达124.6 cm^(2)·C^(-1)。

基于共振能量转移策略的电化学发光免疫传感器及肌红蛋白灵敏检测

基于硫化镉纳米线(CdS NWs)与金纳米粒子(Au NPs)之间的共振能量转移(RET)效应,构建了一种简单、高效的夹心型电化学发光(ECL)免疫传感器,用于肌红蛋白(Myo)的灵敏检测。由于CdS NWs的ECL发射光谱与Au NPs的紫外-可见吸收光谱可产生完美重叠,二者可发生高效的RET,从而猝灭CdS NWs的ECL信号,实现Myo含量的灵敏检测。在优化条件下,测得Myo的线性范围为1.0×10^(-12)~1.0×10^(-7)g/mL,检出限为8.8×10^(-13)g/mL。将该传感器用于人血清样品中Myo含量的测定,检测结果与医院提供的参考值相吻合,相对误差不超过7.5%,具有潜在的实际应用能力。

Modulating the alloying mode in the doping-induced synthesis of Au-Pd nanowires

Heterogeneous doping is one effective strategy for synthesizing metal alloy nanowires.Herein,the heterogeneous doping processes of Pd on the ultrathin Au nanowires were systematically modulated and investigated.Au-Pd alloy nanowires with various morphologies and lattice structures can be obtained by adjusting the morphology of the precursor Au nanowires and the kinetics of the heterogeneous doping processes.The effects of the rate of Pd reduction and the concentration of the ligand oleylamine(OAm)on the Pd deposition and alloying mode were articulated.Generally,as the Pd deposition rate decreases,the Pd deposition and alloying mode switches from the island-forming Stransky–Krastanov(SK)mode to the epitaxial Frank-van der Merwe(FM)mode,and eventually to an unconventional twisting alloying mode,where the interdiffusion of Pd and Au causes drastic rearrangement of the lattice structure and formation of helical structures.The kinetics-related variation of alloying mode could also be observed in the Au-Ag nanowires,demonstrating a general design principle for the synthesis of alloy nanostructures.In addition,the electrocatalytic performance of various Au-Pd nanowires was evaluated,and the alloy nanowire formed via the SK mode was found to be an excellent electrocatalyst for oxygen reduction and ethanol oxidation.

多孔泡沫炭/聚吡咯负载金纳米线催化剂的制备及催化应用研究

三维多孔泡沫碳是一种重要的催化剂载体材料,如何开发新型的泡沫炭基复合催化剂材料具有重要意义。首先采用高温热解法将三聚氰胺泡沫制成泡沫碳;然后通过原位聚合法制备泡沫碳/聚吡咯复合载体;进一步采用氨基硅烷偶联剂修饰CF@PPy,并通过浸泡法在其表面修饰金种子,制备泡沫碳/聚吡咯负载金纳米粒子催化剂;最后,通过化学还原法制备出多孔泡沫碳/聚吡咯负载金纳米线催化剂。采用扫描电镜对复合催化剂的形貌进行表征。结果表明:聚吡咯均匀地生长在泡沫碳上,金纳米线均匀地负载在泡沫碳/聚吡咯上面。利用紫外-可见光谱分别研究该催化剂在水相和油水乳液中对4-硝基苯酚的催化还原效果。实验得出:CF@PPy@AuNWs比CF@PPy@AuNPs具有更优的催化还原效果,且循环使用5次后的催化效率仍大于90%。本方法制备过程简单,催化性能良好,具有重要的科学意义和较大的潜在应用价值。

聚苯胺纳米线复合材料的制备与储能性分析

针对软、硬模板法制备纳米线的缺陷,提出一种步骤简单、快速且低成本的方法来获得直径均匀的PANI纳米线复合材料,并对所制备出的PANI纳米线复合材料进行表征和电化学性能研究。首先,采用阳极氧化剥离法,分别在硝酸体系、磷酸还原体系及硫酸体系中对表面光滑的石墨板进行电化学剥离处理。随后,在经过电化学剥离后的粗糙石墨表面上进行电聚合,从而得到PANI纳米线复合材料。表征分析发现,经电化学剥离处理的石墨纸表面分别生成具有大量活性点的石墨烯和氧化石墨烯,与PANI结合显著提高了PANI的导电性。其中硝酸体系制备的聚苯胺复合材料(PANI/GO)微观为纳米线组成的三维网状结构;磷酸还原体系制备的聚苯胺复合材料(PANI/GR1)微观是纳米线和纳米片层混合结构;硫酸体系制备的聚苯胺复合材料(PANI/GR2)的微观结构介于二者之间。以镁合金和上述三种PANI复合材料为电极,制备出简易的海水电池。使其在电流密度为3.75 mA·cm^(−2)下放电至0.9 V时止。三种电池的比能量分别为540、228和363 mWh·g^(−1),结果表明PANI/GO的储能性最优。随后进行的Tafel曲线分析和交流阻抗分析表明,PANI/GO复合电极的导电性和稳定性优异、比表面积大,有利于与电解液充分接触,促进离子在其上的传输和扩散,因而电池反应的极化小,电化学性能最优,有望应用于电池正极材料。

Polyaniline-poly(vinylidene fluoride) blend microfiltration membrane and its spontaneous gold recovery application

Structural regular polyaniline was synthesized via a modified-chemical oxidative polymerization reaction. Highly hydrophilic polyaniline(PANi) and polyaniline-poly(vinylidene fluoride) blend(PANi-PVDF) membranes were prepared by solution casting and phase inversion techniques. Both of the mechanical and filtration properties of the membranes depend on the polymer composition and doping level of the blends. The elasticity of the membrane is greatly improved upon introducing poly(vinylidene fluoride) into the blend. The water permeability of the blend membranes is further enhanced when the membranes are doped with hydrochloric acid. The PANi-PVDF blend membranes are capable of recovering metallic gold from the acid/halide leaching streams spontaneous and sustainably, and are promising candidates for wastewater treatments in electronic industries.

In situ atomic-scale analysis of Rayleigh instability in ultrathin gold nanowires

Comprehensive understanding of the structural/morphology stability of ultrathin （diameter 〈 10 nm） gold nanowires under real service conditions （such as under Joule heating） is a prerequisite for the reliable implementation of these emerging building blocks into functional nanoelectronics and mechatronics systems. Here, by using the in situ transmission electron microscopy （TEM） technique, we discovered that the Rayleigh instability phenomenon exists in ultrathin gold nanowires upon moderate heating. Through the controlled electron beam irradiation-induced heating mechanism （with 〈 100 ~C temperature rise）, we further quantified the effect of electron beam intensity and its dependence on Rayleigh instability in altering the geometry and morphology of the ultrathin gold nanowires. Moreover, in situ high-resolution TEM （HRTEM） observations revealed surface atomic diffusion process to be the dominating mechanism for the morphology evolution processes. Our results, with unprecedented details on the atomic-scale picture of Rayleigh instability and its underlying physics, provide critical insights on the thermal/structural stability of gold nanostructures down to a sub-10 nm level which may pave the way for their interconnect applications in future ultra- large-scale integrated ciroaits.

基于铂@金纳米线作为信号放大物的电化学适体传感器检测黄曲霉毒素

目的:为了满足食品质量安全并快速检测食品中黄曲霉毒素B1(AFB1)的含量,构建基于铂@金纳米线(Pt@AuNWs)作为信号放大物的电化学适配体传感器用于花生中AFB1的高灵敏、高选择性检测。方法:首先在玻碳电极(GC)表面修饰纳米金颗粒(Au NPs)构建Au NPs/GC电极,增强基底电极的电催化性能并通过Au﹣S键将互补链(cDNA)固定于Au NPs/GC,其次通过模板法合成Pt@AuNWs使其与适配体结合构建信号探针(记为Pt@AuNWs-apt),最后基于碱基互补配对作用构建电化学适配传感器。当AFB1存在时,其和c DNA竞争结合适配体,导致电极表面的Pt@AuNWs-apt信号探针部分脱落,使电化学适配体传感器催化H_(2)O_(2)产生的电流信号降低,从而间接定量检测AFB1。结果:该传感器在0.25 nmol/L cDNA、apt与c DNA孵育40 min、10 mmol/L H_(2)O_(2)、0.1 mol/L磷酸盐浓度pH7.0的测试条件下具有最优的分析性能。该方法具有较宽的线性范围(1~100 ng/mL),检出限为0.41 ng/mL,具有良好的选择性、重现性和稳定性,将该传感器应用于花生样品中进行加标回收实验,结果表明回收率在85.1%~88.0%。结论:构建的电化学适配体传感器可应用于花生中AFB1的检测,在快速检测中具有较好的应用价值。

Efficient DNA-assisted synthesis of trans-membrane gold nanowires

Whereas electric circuits and surface-based(bio)chemical sensors are mostly constructed in-plane due to ease of manufacturing,3D microscale and nanoscale structures allow denser integration of electronic components and improved mass transport of the analyte to(bio)chemical sensor surfaces.This work reports the first out-of-plane metallic nanowire formation based on stretching of DNA through a porous membrane.We use rolling circle amplification(RCA)to generate long single-stranded DNA concatemers with one end anchored to the surface.The DNA strands are stretched through the pores in the membrane during liquid removal by forced convection.Because the liquid–air interface movement across the membrane occurs in every pore,DNA stretching across the membrane is highly efficient.The stretched DNA molecules are transformed into trans-membrane gold nanowires through gold nanoparticle hybridization and gold enhancement chemistry.A 50 fM oligonucleotide concentration,a value two orders of magnitude lower than previously reported for flat surface-based nanowire formation,was sufficient for nanowire formation.We observed nanowires in up to 2.7% of the membrane pores,leading to an across-membrane electrical conductivity reduction from open circuit to <20Ω.The simple electrical read-out offers a high signal-to-noise ratio and can also be extended for use as a biosensor due to the high specificity and scope for multiplexing offered by RCA.

Enhanced electroactive β-phase formation in electrospun poly(vinylidene fluoride-co-hexafluoropropylene)nanowires with gold nanoparticles

As a representative piezoelectric polymer,poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP)has been widely used in sensors transducers and actuators.In this paper,gold nanoparticles(AuNPs)are prepared and doped into the PVDF-HFP solution to enhance the piezoelectric property of electrospun PVDF-HFP nanowires.The results indicate that proper amounts of AuNPs within the nanowires can improve the piezoelectric phase in PVDF-HFP.Then,a nanogenerator was prepared using the PVDF-HFP/Au nanowires to verify the increase in piezoelectric performance.Experimental results show that compared with PVDF-HFP n anoge nerator without AuNPs doping,the output voltage is in creased by about two times,while the output current is doubled for the PVDF-HFP/Au nano generator.Furthermore,systematic molecular dyn amics(MD)simulations are conducted to elucidate the physical mechanism of AuNPs enhanced β-phase formation in PVDF-HFP.Our results show that the adsorption and electrostatic interaction between the AuNPs and the PVDF chains promote the electroactive β-phase formation,and also significa ntly in crease the ten sion and poling effect during electrospin ning process,which is the origin of the enhanced elec-troactive phase formation in electrospun PVDF-HFP nanowires.

Boosting electrocatalytic selectivity in carbon dioxide reduction:The fundamental role of dispersing gold nanoparticles on silicon nanowires

Carbon dioxide electrochemical reduction(CO_(2)RR)has been recognized as an efficient way to mitigate CO_(2)emissions and alleviate the pressure on global warming and associated environmental consequences.Gold(Au)is reported as stable and active electrocatalysts to convert CO_(2)to CO at low overpotential due to its moderate adsorption strength of^(*)COOH and^(*)CO.The request for improved catalytic performance,however,is motivated by current unsatisfied catalytic selectivity because of the side hydrogen evolution reaction.In this context,the design of Au based binary catalysts that can boost CO selectivity is of great interest.In the present work,we report that Au nanoparticles can be feasibly dispersed and anchored on silicon nanowires to form Au-Si binary nanomaterials.The Au-Si may stably drive CO_(2)RR with a CO Faraday efficiency of 95.6%at−0.6 V vs.RHE in 0.5 mol/L KHCO_(3)solution.Such selectivity outperforms Au particles by up to 61%.Controlled experiments illustrate that such catalytic enhancement can chiefly be ascribed to electronic effects of binary catalysts.Theoretical calculations reveal that spontaneously produced silicon oxide may not only inhibit hydrogen evolution reaction,but also stabilize the key intermediate^(*)COOH in CO formation.