One-step growth of gold nanorods using a β-diketone reducing agent

The synthesis and characterisation of gold nanorods have been carried out by reduction of the gold salt HAuCl₄. This has been done using a single reducing agent, acetylacetone, rather than the two reducing agents, sodium borohydride and ascorbic acid, normally required by standard wet chemistry methods of gold nanorod formation. Using this novel method, the nanorods were synthesised at several different pH values which were found to greatly affect both the rate at which the nanorods form and their physical dimensions. The concentrations of acetylacetone and silver nitrate used relative to the gold salt were found to alter the aspect ratio of the nanorods formed. Rods with an average length of 42 nm and an aspect ratio of 4.6 can be easily and reproducibly formed at pH 10 using this method. Nanorods formed under optimum conditions were investigated using TEM. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Study of magnetic properties of ZnO nanoparticles codoped with Co and Cu

Here, we report on systematic studies of the magnetic properties of Co and Cu codoped ZnO nanoparticles prepared by sol–gel technique. The effect of hydrogenation and shape on the magnetic properties of Zn_0.93Co_0.05Cu_0.02O nanoparticles is presented. The Zn_0.93Co_0.05Cu_0.02O nanoparticles and well-aligned Zn_0.93Co_0.05Cu_0.02O nanorod array display ferromagnetic behavior at room temperature. Our results demonstrate the influence of shape and hydrogenation on the ferromagnetic properties of Zn_0.93Co_0.05Cu_0.02O nanoparticles at room temperature.     

Electrostatically Controlled Nematic and Smectic Assembly of Gold Nanorods

The assembly of gold nanorods(GNRs) into different liquid crystalline structures can be controlled by tuning their surface electric potential. After mildly removing excess surfactants in the GNRs solution, the electrostatic interaction between GNRs can be tuned by adjusting counter ion concentration. Specifically, nematic and smectic structures formed after solvent evaporation at low and high bromide concentrations, respectively. These results could be helpful for fabricating anisotropy enabled devices composed of metal and semiconductor nanorods.     

纳米硫化镉在对氨基苯硫酚自组装单层修饰金电极上的电化学合成

采用电流脉冲法在自组装了对氨基苯硫酚单层的金电极(PATP/Au)上电沉积硫化镉(CdS)纳米薄膜,运用扫描电子显微镜(SEM)和X射线衍射谱(XRD)对其形貌和结构进行了表征,发现得到的是垂直基底生长的CdS纳米棒有序阵列.研究电沉积中电流脉冲参数的影响时发现:随着电流脉冲宽度增大,CdS纳米棒的尺寸增大,有序性降低;脉冲幅度增大,则纳米棒尺寸增大,覆盖度也随之增大.因此通过调节脉冲宽度和脉冲幅度,可对所制备的CdS纳米薄膜的形貌和尺寸进行调控.运用循环伏安法和计时电位法对电沉积机理进行了探究.根据实验结果我们认为Au电极自组装PATP单分子层后,PATP分子中的-NH2与溶液中Cd2+相互作用,使沉积时的电子通过表面的PATP分子链进行传递.并进一步提出纳米CdS在PATP/Au电极上电化学合成的生长机理.     

磷酸铋纳米棒的可控合成及其光催化性能

采用水热法合成了形貌可控的磷酸铋纳米棒光催化剂,并以亚甲基蓝(MB)为探针研究了其光催化活性.利用粉末X射线衍射(XRD),透射电镜(TEM)和紫外-可见漫反射光谱(UV-VisDRS)对产物进行了表征.研究发现甘油含量、水热时间、水热温度及前驱体浓度会影响磷酸铋纳米棒的形貌及结构.甘油含量和前驱体浓度主要影响产物形貌.随着甘油含量的增加,产物的长径比先增大后减小.前驱体浓度越低,所得BiPO4纳米棒的尺寸越小,长径比越大.水热时间短时,产物结晶度差,且为六方相,时间延长后转化为单斜相.水热温度过低或过高均不利于完美晶体的形成,160°C时产物的结晶度最高.实验结果表明:BiPO4纳米棒在紫外光下具有良好的光催化性能,其光催化活性受长径比和尺寸大小影响的总体趋势是长径比越大,尺寸越小,其光催化活性越强.结晶度对BiPO4的光催化性能影响较大,结晶度越高,其光催化活性越好.单斜相BiPO4的光催化活性较六方相的强.     

钴的表面增强拉曼散射中的电磁增强因子计算

本文初步探讨了钴电极的表面增强拉曼散射机理。采用二维阵列理论模型在 0 .5～ 4.0eV的光子能量范围对钴纳米椭球阵列的表面增强拉曼散射 (SERS)现象进行了理论分析。有关计算表明 ,经过合适的表面粗糙化的钴金属电极能产生较弱的表面增强效应 (SERS增强因子约 1 0 2 ～ 1 0 4 ) ,制备出具有高纵横比的纳米粒子阵列是得到钴体系较大的SERS增强因子的关键     

Preparation and Photoluminescence of ZnO Nanorods Arrays

A high-density well-aligned Zinc Oxide nanorod array was synthesized on Si (100) substrate by a simplevapor deposition under normal pressure using neither a catalyst and nor pre-deposition of ZnO film. Various different morphologies were obtained in different deposition regions. Si substrate put over the Zn source was the key factor in getting a well-aligned sample. Field emission scanning electron microscope (FESEM) observations and X-ray diffraction were carried out to characterize the surface morphology and crystalline quality of the samples. The growth mechanism is discussed. The photoluminescence properties of the ZnO samples were also investigated. It is suggested that the green band is related to oxygen vacancies and thekinetic process involving transition from shallow donor to deep acceptor level.     

Effect of carbon source on the carbothermal reduction for the fabrication of ZnO nanostructure

Surface area effect of carbon source on the carbothermal reduction for the fabrication of ZnO nanostructure was investigated. For a systematic comparison, graphite and three kinds of carbon black powder were used as source materials for the carbothermal reduction. Depending on the surface area, the carbothermal reduction at 800 °C for 30 min resulted in Zn-silicate island or ZnO nanorod at the same experimental condition. These structures were characterized with a scanning electron microscopy, a transmission electron microscopy, an energy dispersive spectroscopy and an X-ray photoelectron spectroscopy. The results show that the reducing power of ZnO_(s) source into Zn_(g) vapor is strongly dependent on the surface area of carbon source, and that the fabrication of ZnO nanostructure can be performed more efficiently by using carbon source with large surface area.     

Effect of boehmite nanorods on the properties of glycidoxypropyl-trimethoxysilane (GPTS) hybrid coatings

AlOOH boehmite nanorods, synthesized by a solid-based process, were incorporated into a sol–gel coating in which GPTS was used as a precursor. Transparent composite coatings with nanorod content up to 40 wt% were obtained by spin coating the sol–gel mixture on glass substrates. Nanorods in the coating were found be aligned parallel to the substrate surface. Mechanical properties, such as modulus and hardness of the nanorod filled coating, were slightly lower than coatings of the same composition but filled with commercially available nanosized boehmite particles. However, crack toughness was greatly improved, as supported by nanoindentation test results. The improvement in crack toughness was attributed to the high aspect ratio of the rigid nanorods, in addition to the fact that the nanorods were aligned within the composite parallel to the surface.     

The control of the diameter of the nanorods prepared by dc reactive magnetron sputtering and the applications for DSSC

The TiO₂ nanorod arrays, with about 1.8 μm lengths, have been deposited on ITO substrates by dc reactive magnetron sputtering at different target-substrate distances. The average diameter of these nanorods can be modified from about 45 to 85 nm by adjusting the target-substrate distance from 90 to 50 mm. These nanorods are highly ordered and perpendicular to the substrate. Both XRD and Raman measurements show that the nanorods prepared at different target-substrate distances have only an anatase TiO₂ phase. The nanorods prepared at the target-substrate distance less than 80 mm have a preferred orientation along the (2 2 0) direction. However, this preferred orientation disappears as the target-substrate distance is more than 80 mm. These TiO₂ nanorods have been used as the electrodes for dye-sensitized solar cells (DSSCs). The highest conversion efficiency, about 4.78%, has been achieved for TiO₂ nanorods prepared at 80 mm target-substrate distance.