Photoluminescence and Raman scattering from catalytically grown Zn(x)Cd(1-x)Se alloy nanowires

Zn(x)Cd(1-x)Se alloy nanowires, with composition x = 0, 0.2, 0.5, 0.7, and 1, have been successfully synthesized by a chemical vapor deposition (CVD) method assisted with laser ablation. The as-synthesized alloy nanowires, 60-150 nm in diameter and several tens of micrometers in length, complied with a typical vapor-liquid-solid (VLS) growth mechanism. The Zn(x)Cd(1-x)Se nanowires are single crystalline revealed from high-resolution transmission electron microscopic (HRTEM) images, selected area electron diffraction (SAED) patterns, and X-ray diffraction (XRD) measurement. Compositions of the alloy nanowires can be adjusted by varying the precursor ratios of the laser ablated target and the CVD deposition temperature. Crystalline structures of the Zn(x)Cd(1-x)Se nanowires are hexagonal wurtzite at x = 0, 0.2, and 0.5 with the [0 1 -1 0] growth direction and zinc blende at x = 0.7 and 1 with the [1 -1 1] growth direction. Energy gaps of the Zn(x)Cd(1-x)Se nanowires, determined from micro-photoluminescence (PL) measurements, change nonlinearly as a quadratic function of x with a bowing parameter of approximately 0.45 eV. Strong PL from the Zn(x)Cd(1-x)Se nanowires can be tuned from red (712 nm) to blue (463 nm) with x varying from 0 to 1 and has demonstrated that the alloy nanowires have potential applications in optical and sensory nanotechnology. Micro-Raman shifts of the longitudinal optical (LO) phonon mode observed in the Zn(x)Cd(1-x)Se nanowires show a one-mode behavior pattern following the prediction of a modified random element isodisplacement (MREI) model.     

Growth and luminescence of ternary semiconductor ZnCdSe nanowires by metalorganic chemical vapor deposition

ZnCdSe alloy nanowires were successfully grown on the GaAs (100) substrate by metalorganic chemical vapor deposition using Au as a catalyst. The nanowires display two distinct types of morphology. The majority of them are straight, uniform in diameter, and have a smooth surface. However, a significant portion of them contain one or two constrictions along their length. The alloy is found to be rich in Zn; its composition, as determined from X-ray diffraction and energy-dispersive X-ray microanalysis, is close to Zn(0.9)Cd(0.1)Se. The peak energy of its room temperature near-band-edge photoluminescence is also consistent with this composition. X-ray diffraction pattern and transmission electron microscopy find both types of nanowires to be single crystalline, have the metastable wurtzite structure, and a growth direction along 100. The presence of an Au-Cd-Zn alloy particle at the tip of the nanowires supports vapor-liquid-solid as the growth mechanism. The appearance of constrictions in some of the nanowires is found to be linked to the existence of structural defects, possibly stacking faults, during growth.     

Gold–platinum alloy nanowires as highly sensitive materials for electrochemical detection of hydrogen peroxide

The exploitation of the unique electrical properties of nanowires requires an effective assembly of nanowires as functional materials on a signal transduction platform. This paper describes a new strategy to assemble gold–platinum alloy nanowires on microelectrode devices and demonstrates the sensing characteristics to hydrogen peroxide. The alloy nanowires have been controllably electrodeposited on microelectrodes by applying an alternating current. The composition, morphology and alloying structures of the nanowires were characterized, revealing a single-phase alloy characteristic, highly monodispersed morphology, and controllable bimetallic compositions. The alloy nanowires were shown to exhibit electrocatalytic response characteristics for the detection of hydrogen peroxide, exhibiting a high sensitivity, low detection limit, and fast response time. The nanowire's response mechanism to hydrogen peroxide is also discussed in terms of the synergistic activity of the bimetallic binding sites, which has important implications for a better design of functional nanowires as sensing materials for a wide range of applications.     

电化学法制备Ni-W-P纳米线阵列电极及其催化析氢性能

采用二次氧化法制备了多孔阳极氧化铝(AAO)模板, 通过控制电位沉积技术在AAO模板内组装了Ni-W-P合金纳米线阵列. 在扫描电子显微镜(SEM)下观察到Ni-W-P纳米线表面光滑, 长约20 μm, 直径均匀(约为100 nm), 与AAO模板孔径基本一致. 阴极极化曲线和交流阻抗图谱(EIS)的测试结果表明, Ni-W-P合金纳米线阵列电极析氢反应(HER)电阻减小, 具有更高的催化析氢活性, 电流密度为10 mA·cm^-2时, 析氢极化电位较Ni-W-P合金电极正移约250 mV.     

Pd-Ag合金纳米线的可见光辅助简易合成及其对乙醇的电催化氧化

以硝酸钯和硝酸银为金属前驱体,乙醇和柠檬酸钠作为还原剂,聚乙烯吡咯烷酮作为稳定剂和导向剂,以普通市售白炽灯作为光源,采用简易可见光辅助液相法合成了Pd-Ag合金纳米线。通过FESEM、TEM、HRTEM、PXRD和UV-Vis等技术对样品的形貌、晶体结构和光学性质进行了表征,并通过循环伏安法和计时电流法研究了Pd-Ag合金纳米线修饰玻碳电极对乙醇的电催化氧化。与相同条件下制备的纳米钯材料相比,Pd-Ag合金纳米线具有更好的电催化活性、抗中毒性和稳定性。     

Pd-Ag合金纳米线的可见光辅助简易合成及其对乙醇的电催化氧化

以硝酸钯和硝酸银为金属前驱体,乙醇和柠檬酸钠作为还原剂,聚乙烯吡咯烷酮作为稳定剂和导向剂,以普通市售白炽灯作为光源,采用简易可见光辅助液相法合成了Pd-Ag合金纳米线。通过FESEM、TEM、HRTEM、PXRD和UV-Vis等技术对样品的形貌、晶体结构和光学性质进行了表征,并通过循环伏安法和计时电流法研究了Pd-Ag合金纳米线修饰玻碳电极对乙醇的电催化氧化。与相同条件下制备的纳米钯材料相比,Pd-Ag合金纳米线具有更好的电催化活性、抗中毒性和稳定性。     

Preparation and characterization of straight and zigzag AlN nanowires

Hexagonal single-crystal AlN nanowires with straight or zigzag morphologies were successfully synthesized by the reaction of aluminum alloy in an ammonia/nitrogen atmosphere at 1100 degrees C. It is found that the crystal tropism of the nanowires is along [0001], whereas the growth directions of the zigzag nanowires shift between [2111] and [2111].     

化学沉积法制备Ni-P纳米线与纳米管有序阵列

以多孔氧化铝膜为模板, 在室温下的酸性化学镀镍槽中通过化学沉积法生长出纳米线与纳米管有序阵列. 分别用X射线衍射仪(XRD)与透射电子显微镜(TEM)对纳米线、纳米管阵列进行表征. 并通过对纳米线与纳米管的生长方式进行分析比较, 系统地研究了多孔氧化铝模板的前处理对纳米阵列生长的影响. 结果表明, 生成的纳米线与纳米管均为非晶态的镍磷合金. 室温下镍纳米管的生成主要取决于敏化、活化过程, 而当纳米管的厚度达到一定程度后就不再随时间变化.     

Structural, magnetic, and magnetoresistive properties of electrodeposited Ni5Zn21 alloy nanowires

Ni5Zn21 alloy nanowires were fabricated through template-assisted electrochemical deposition method. The morphology and microstructures of as-deposited nanowires were determined by field-emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), electron diffraction (ED), and electron probe microanalysis (EPMA). The accurate composition was measured via induced coupling plasma atomic emission spectroscopy. SEM results show that Ni5Zn21 nanowires are deposited in most of the nanopores of the template, and they are continuous and dense throughout the whole length. The XRD result demonstrates that the nanowires are mainly composed of a cubic gamma phase Ni5Zn21 alloy, but there also exists a trace of Zn-rich eta phase. HRTEM and ED reveal that the alloy nanowires are polycrystalline with the crystallite size of several tens of nanometers. EPMA of a single nanowire illustrates that there exist Ni-rich microzones in as-deposited nanowires. Subsequent magnetic measurements of the array also confirmed the existence of them. In addition, it can be further inferred that the shape of Ni-rich microzones is probably barlike or disklike, from the anisotropy of zero field cooling/field cooling (ZFC/FC) curves as well as the vortex magnetization behavior of the Ni5Zn21 nanowire array. The low-temperature magnetoresistance of the Ni5Zn21 nanowire array was also measured. Giant magnetoresistance instead of anisotropic magnetoresistance is suggested to be responsible for contributing to the magnetoresistance.     

Monte Carlo simulation of nanowires of different metals and two-metal alloys

Nanowires of different metals and two-metal alloys have been studied by means of canonical Monte Carlo simulations and the embedded atom method for the interatomic potentials. For nanowires of gold, a relatively stable three-atom-wide chain was observed. The presence of one-atom-wide linear atomic chains is not stable in any case. For two-metal alloy nanowires, the metal with a higher surface energy tends to locate in the inner region of the nanowire.     

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.     

Formation of Pd/Au nanostructures from Pd nanowires via galvanic replacement reaction

Bimetallic nanostructures with non-random metal atoms distribution are very important for various applications. To synthesize such structures via benign wet chemistry approach remains challenging. This paper reports a synthesis of a Au/Pd alloy nanostructure through the galvanic replacement reaction between Pd ultrathin nanowires (2.4 +/- 0.2 nm in width, over 30 nm in length) and AuCl3 in toluene. Both morphological and structural changes were monitored during the reaction up to 10 h. Continuous changes of chemical composition and crystalline structure from Pd nanowires to Pd68Au32 and Pd45Au55 alloys, and to Au nanoparticles were observed. More interestingly, by using combined techniques such as high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), energy dispersive X-ray spectrometry (EDS), UV-vis absorption, and extended X-ray absorption fine structure (EXAFS) spectroscopy, we found the formation of Pd68Au32 non-random alloy with Au-rich core and Pd-rich shell, and random Pd45Au55 alloy with uniformly mixed Pd and Au atom inside the nanoparticles, respectively. Density functional theory (DFT) calculations indicated that alkylamine will strongly stabilize Pd to the surface, resulting in diffusion of Au atoms into the core region to form a non-random alloy. We believe such benign synthetic techniques can also enable the large scale preparation of various types of non-random alloys for several technically important catalysis applications.     

Spatial bandgap engineering along single alloy nanowires

Bandgap engineering of semiconductor nanowires is important in designing nanoscale multifunctional optoelectronic devices. Here, we report a facile thermal evaporation method, and realize the spatial bandgap engineering in single CdS(1-x)Se(x) alloy nanowires. Along the length of these achieved nanowires, the composition can be continuously tuned from x = 0 (CdS) at one end to x = 1 (CdSe) at the other end, resulting in the corresponding bandgap (light emission wavelength) being modulated gradually from 2.44 eV (507 nm, green light) to 1.74 eV (710 nm, red light). In spite of the existing composition (crystal lattice) transition along the length, these multicolor nanowires still possess high-quality crystallization. These bandgap engineered nanowires will have promising applications in such as multicolor display and lighting, high-efficiency solar cells, ultrabroadly spectral detectors, and biotechnology.     

Synthesis of CdS and ZnS nanowires using single-source molecular precursors

Single-source molecular precursors were used to synthesize II-VI compound semiconductor nanowires for the first time. Cadmium sulfide and zinc sulfide nanowires were prepared using cadmium diethyldithiocarbamate, Cd(S2CNEt2)2, and zinc diethyldithiocarbamate, Zn(S2CNEt2)2, respectively, as precursors in a gold nanocluster-catalyzed vapor-liquid-solid growth process. High-resolution transmission electron microscopy studies show that the CdS and ZnS nanowires are single-crystal wurtzite structures with stoichiometric compositions. In addition, photoluminescence measurements demonstrate that these nanowires exhibit high-quality optical properties. The applicability of our approach to the synthesis of other compound and alloy semiconductors nanowires as well as nanowire heterostructures of these materials is discussed.     

PtRu纳米线的合成及其在直接甲醇燃料电池阳极中的催化活性

 分别以SBA-15和MCM-41介孔分子筛作模板剂,采用浸渍还原法制备了纵横比及合金度不同的双组元PtRu纳米线和纳米棒电催化剂. 透射电镜、 X射线衍射表征和电化学测试结果表明, PtRu纳米线具有较高的合金度和较大的纵横比,在甲醇硫酸溶液中表现出更好的电催化活性. 初步探讨了PtRu纳米线催化剂的合金度和纵横比对其电催化活性和电极性能的影响.     

Controllable assembly of aligned ZnO nanowires/belts arrays

We describe a simple method to assemble ZnO nanowires/belts into highly ordered arrays. ZnCu(2) alloy was used as the Zn source, which reacted with water vapor to generate ZnO nanocrystals. The reaction was performed in a mild way, which facilitated the easy control of the reaction conditions. By simply controlling the water bath temperature and carrier gas flux in our experiments, we obtained ZnO nanowires/belts aligned to form ordered arrays. The highly ordered nature of the ZnO arrays is suggested to be related both with the polarities of the H(2)O molecule and the ZnO (0001) surface. Photoluminescence (PL) microscopy revealed that the comblike structures had waveguide properties, where green light enhancement was observed at the tips of the branches. The light enhancement property reveals their promising applications as light source arrays.     

Co、Ni及其合金纳米线阵列的制备及磁性研究

采用交流电化学沉积法,在多孔阳极氧化铝(AAO）模板孔洞中成功组装了铁磁性金属Co、Ni、CoNi合金纳米线阵列并采用扫描电子显微镜(SEM）、X射线衍射(XRD）等对样品进行表征。结果表明,Co、Ni及CoNi合金阵列体系中纳米线均匀有序,形状各向异性较大(长径比达30以上）,有显著的结晶择优取向。对Co、Ni、CoNi合金纳米线阵列体系进行磁性分析,振动样品磁强计(VSM）测试结果显示,纳米线有明显的磁各向异性,适合用作垂直磁记录介质。纳米线阵列退火后沿纳米线方向矫顽力和矩形比减小,样品的垂直磁各向异     

电化学阶边精饰法制备钯镍合金纳米线的研究

运用连续恒电势三脉冲的电化学阶边精饰法在高定向石墨(HOPG)上制备钯镍合金纳米线阵列， 并研究了合金成分的影响因素. 结果表明，改变镀液组成可以调整钯镍合金成分，调整生长时间和生长电势来控制钯镍合金纳米线的直径. 用7 mmol•L^-1 PdCl2,3 mmo•L^-1 NiSO₄, 0.2 mol•L^-1 NH₄Cl，pH 8.5的混合溶液，控制脉冲电势-2.0 V形核0.2 s，在脉冲电势－0.4 V生长1 h，可以获得平均直径为200 nm, 长度约400 μm的钯镍合金纳米线阵列, 纳米线的合金成分中镍含量为12.4%(质量分数,w).     

Alpha-CuV2O6 nanowires: hydrothermal synthesis and primary lithium battery application

We report on the synthesis, characterization, and electrochemical lithium intercalation of alpha-CuV2O6 nanowires, mesowires, and microrods that were prepared through a facile hydrothermal route. The diameters of the as-synthesized alpha-CuV2O6 nanowires, mesowires, and microrods were about 100 nm, 400 nm, and 1 microm, respectively. It was found that by simply controlling the hydrothermal reaction parameters, such as the reagent concentration and the dwell time, the transformation of microrods to nanowires was readily achieved via a "ripening-splitting" mechanism. Electrochemical measurements revealed that the as-prepared alpha-CuV2O6 nanowires and mesowires displayed high discharge capacities (447-514 mAh/g at 20 mA/g and 37 degrees C) and excellent high-rate capability. In particular, the alpha-CuV2O6 nanowires showed capacities much higher than those of alpha-CuV2O6 mesowires, microrods, and bulk particles. The mechanisms for the electrochemical lithium intercalation into the alpha-CuV2O6 nanowires were also discussed. From the Arrhenius plot of lithium intercalation into alpha-CuV2O6 nanowires, the activation energies were calculated to be 39.3 kJ/mol at 2.8 V (low lithium uptake) and 35.7 kJ/mol at 2.3 V (high lithium uptake). This result indicates that the alpha-CuV2O6 nanowires are promising cathode candidates for primary lithium batteries used in long-term implantable cardioverter defibrillators (ICD).     

Single-crystalline, size, and orientation controllable nanowires and ultralong microwires of organic semiconductor with strong photoswitching property

Single-crystalline, precise size-controlled nanowires and ultralong microwires with lengths reaching several millimeters of organic semiconductor 1 were prepared in large scale by cast assembly. The size and density of the nanowires and microwires could be controlled by simply adjusting the concentration of 1 in casting solutions. More importantly, the formation of these nanowires and microwires showed no substrate and solvent dependence and was orientation controllable. Highly reproducible and sensitive photo response characteristics were observed in these nanowires and microwires. Fast and reversible photoswitchers based on multiple or individual single-crystal microwires were fabricated via "multi times gold wire mask moving" technique with switch ratio over 100.