非晶SiO2纳米灯笼的制备和表征

在1000 ℃用活性炭把二氧化锡粉末还原成单质锡, 锡作为催化剂, 硅片作为硅源同时作为收集衬底, 在硅片上制备出了非晶SiO2纳米灯笼. 灯笼的一端连在硅片上, 另一端为一个锡球, 中间是一些圆弧状的SiO2纳米线把两端相连. 纳米灯笼具有良好的对称性. 利用扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)、选区电子衍射(SAED) 和HRTEM自带的能谱分析仪(EDS)对样品的表面形貌、微观结构和成分进行了分析研究. 结果表明, 灯笼中SiO2纳米线为非晶态, 结点是晶态锡, 结点表面覆盖一层非晶态的硅的氧化物. 结合实验条件对纳米灯笼的生长机理进行了讨论, 提出了纳米灯笼生长的一个模型.     

Progress on phthalocyanine-conjugated Ag and Au nanoparticles: Synthesis,characterization, and photo-physicochemical properties

Phthalocyanine (Pc) complexes are an important class of dyes with numerous (e.g., biological, photophysical, and analytical) applications. Among the methods used to improve the properties of these complexes, one should mention the introduction of different substituents, variation of the central metal ion, ligand exchange, and conjugation to nanomaterials (e.g., carbon-based nanomaterials and metal nanoparticles (NPs)). This work briefly reviews Pc complex conjugation to Ag and Au NPs, highlights the different NP shapes, and discusses the diversity of conjugation approaches. Moreover, the use of UV–Vis spectroscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, atomic force microscopy, dynamic light scattering and Fourier transform infrared spectroscopy to characterize Pc-NP hybrids is summarized. The effect of conjugation on Pc photo-physicochemical properties (fluorescence, singlet oxygen generation, triplet state formation, and optical limiting behavior) is discussed, and future perspectives for the synthesis and applications of new hybrids are provided.     

Amperometric Determination of lndole-3-acetic Acid Based on Platinum Nanowires and Carbon Nanotubes

Platinum nanowire （PtNW） can be grown by electrodeposition in polycarbonate membrane, with the average diameter of the nanowires about 250 nm. The PtNW and multiwalled carbon nanotubes （CNT） are then dispersed into chitosan （CHIT） solution. The resulting PtNW-CNT-CHIT material brings new capabilities for electrochemical devices by using the synergistic action of the electrocatalytic activity of PtNW and CNT. By dropping the PtNW-CNT-CHIT film onto the glassy carbon （GO） electrode surface, and after evaporation an amperometric sensor for the determination of indole-3-acetic acid （IAA） was developed. The oxidation current of IAA increased significantly at the PtNW-CNT-CHIT film coated GC electrode, in contrast to that at the CNT-CHIT modified GC. The linear response of the sensor is from 50 ng/ml to 50 μg/ml with a detection limit of 25 ng/mL.     

Vanadium-Substituted Dawson-Type Polyoxometalate–TiO2 Nanowire Composite Film as Advanced Cathode Material for Bifunctional Electrochromic Energy-Storage Devices

Polyoxometalates (POMs) demonstrate potential for application in the development of integrated smart energy devices based on bifunctional electrochromic (EC) optical modulation and electrochemical energy storage. Herein, a nanocomposite thin film composed of a vanadium-substituted Dawson-type POM, i.e., K₇[P₂W₁₇VO₆₂]·18H₂O, and TiO₂ nanowires were constructed via the combination of hydrothermal and layer-by-layer self-assembly methods. Through scanning electron microscopy and energy-dispersive spectroscopy characterisations, it was found that the TiO₂ nanowire substrate acts as a skeleton to adsorb POM nanoparticles, thereby avoiding the aggregation or stacking of POM particles. The unique three-dimensional core−shell structures of these nanocomposites with high specific surface areas increases the number of active sites during the reaction process and shortens the ion diffusion pathway, thereby improving the electrochemical activities and electrical conductivities. Compared with pure POM thin films, the composite films showed improved EC properties with a significant optical contrast (38.32% at 580 nm), a short response time (1.65 and 1.64 s for colouring and bleaching, respectively), an excellent colouration efficiency (116.5 cm² C⁻¹), and satisfactory energy-storage properties (volumetric capacitance = 297.1 F cm⁻³ at 0.2 mA cm⁻²). Finally, a solid-state electrochromic energy-storage (EES) device was fabricated using the composite film as the cathode. After charging, the constructed device was able to light up a single light-emitting diode for 20 s. These results highlight the promising features of POM-based EES devices and demonstrate their potential for use in a wide range of applications, such as smart windows, military camouflage, sensors, and intelligent systems.     

Influence of aspect ratio and anisotropy distribution in ordered CoNi nanowire arrays

The size effects on magnetic properties of nanowires arrays were studied varying the nanowires diameter and maintaining the same periodicity among them, for two different nominal compositions of Co and Ni in the alloy form. The competition among magnetocrystalline and shape anisotropies changes drastically from smallest to biggest diameters altering the easy axis direction. In the case of 75% of Co in alloy, experimental values of the effective anisotropy constant (K_eff) vary from positive to negative depending on the diameter, which means a reversal of the easy axis direction. For 50% of Co the shape anisotropy dominates over the magnetocrystalline for all studied diameters.     

Wrinkling and Growth Mechanism of CuO Nanowires in Thermal Oxidation of Copper Foil

We report a systematic study on wrinkling and CuO nanowires （NWs） growth in the thermal oxidation of copper foil. Copper foils with thickness of 0.5 mm were thermally oxidized in air at 500℃ for 0.5-10 h. It is found that all the samples have wrinkles and the size of the wrinkles increases with the oxidation time increasing. CuO NWs can grow on both the sidehill and hilltop of wrinkle. The CuO NWs on sidehill are longer and denser than those on hilltop. The growth direction of the CuO NWs on sidehill is not vertical to the substrate but vertical to their growth surfaces. The process of wrinkling and CuO NWs growth can be divided into three stages： undulating, voiding, and cracking. The CuO NWs on both sidehill and hilltop grow at the undulating stage. However, only the CuO NWs on sidehill grow and those on hilltop stop growing at the voiding and cracking stages because of the void in hilltop. The local electric field in a wrinkle at undulating stage was calculated, and it is found that the difference of local electric field strengths between hilltop and sidehill is small, which indicates that the predominant driving force for the diffusion of Cu ion during CuO NWs growth is internal stress.     

Spatially‐resolved and polarized Raman scattering from a single Si nanowire

We report spatially‐resolved and polarized Raman scattering results from a single Si nanowire (NW). Transmission electron microscope images show that the surface morphology of the Si NW varies from smooth to rough along the long axis. As the NW grows, the smooth surface becomes rough because of Au diffusion to the surface, resulting in the formation of facets and stacking faults. Spatially‐resolved Raman spectra along the NW long axis reveal variations in tensile strain related to the morphological changes in NW surface. The tensile strain in the top segment of the NW with a smooth surface is greater than that in the bottom segment with a rough surface. Despite the formation of facets and stacking faults, polarized Raman scattering results both from the top and bottom segments of the NW are consistent with the Raman polarization selection rules expected for a cubic crystal. Copyright © 2015 John Wiley & Sons, Ltd.     

Evanescent Wave-Guided Growth of an Organic Supramolecular Nanowire Array

The ordered assembly of molecules within a specific space of nanoscale, such as a surface, holds great promise in advanced micro-/nanostructure fabrication for various applications. Herein, we demonstrate the evanescent wave (EW)-guided organization of small molecules into a long-range ordered nanowire (NW) array. Experiment and simulation revealed that the orientation and periodicity of the NW array were feasibly regulated by altering the propagation direction and the wavelength of EW. The generality of this approach was demonstrated by using different molecule precursors. While existing studies on EW often took advantages of its near-field property for optical sensing, this work demonstrated the photochemical power of EW in the guided-assembly of small molecules for the first time. It also provides an enlightening avenue to periodic structure with fluorescence, promising for super-resolution microscopy and important devices applicable to optical and bio-related fields.     

不同孪晶界密度银纳米线拉伸形变行为的分子动力学模拟

采用分子动力学方法模拟了不同孪晶界密度银纳米线的拉伸形变行为, 分析了孪晶界密度对多晶银纳米线屈服强度、弹性模量和塑性变形机理的影响. 在弹性形变区域, 孪晶界的存在对杨氏模量变化的作用不明显. 在塑性形变阶段, 首先从表面边缘开始产生位错成核, 然后延伸并受阻于孪晶界. 在进一步拉伸载荷作用下, 孪晶界将作为位错源产生新的位错. 模拟结果表明, 银纳米线的强度与孪晶界和晶粒的尺寸有关. 孪晶界密度较小(即晶粒的长径比大于1)时, 此纳米线的屈服应力比单晶纳米线还要小, 只有当孪晶界密度较大时(即晶粒的长径比小于1), 孪晶界使得纳米线得到强化. 综合分析了孪晶界和晶粒尺寸对银纳米线的影响, 为构建高强度金属纳米线打下基础. 最后讨论了温度和拉伸速度对孪晶纳米线屈服应力所产生的影响, 随着温度的升高, 孪晶纳米线与单晶纳米线的屈服应力差先升高后趋于稳定; 当拉伸速度逐渐增大, 孪晶纳米线与单晶纳米线的屈服应力差先稳定后增大.     

化学还原法制备多形貌银纳米材料

银纳米材料因具有导热导电性能好、光电性能优良及抗菌能力强等优点而引起广泛关注,近年来其制备方法得到广泛研究。已报道的制备方法可分为化学法、物理法和生物法等,其中化学还原法可以通过使用不同的还原剂、包裹试剂及助剂,实现不同形貌及粒径的银纳米材料的快速制备。本文综述了化学还原法制备颗粒状、线形、片状、立方体及其它形貌的银纳米材料的原理及应用,并展望了银纳米材料工业化制备及应用研究的发展趋势。可控制备多形貌银纳米材料对于电子行业、医药生物以及传感器等相关领域的发展具有重要意义。