Influence of composition and size on the thermodynamic stability and structural evolution of CuAlNi nanoclusters

The heating process for CuAlNi nanoclusters with cuboctahedral structure was studied by molecular dynamics simulation with the embedded atom method. A diffusionless martensitic transformation from the cuboctahedral (CO) to the icosahedral (ICO) structure before the melting point was found in some CuAlNi nanoclusters. The effects of element composition and cluster size on the thermodynamic stability and structural transformation of trimetallic nanoclusters were investigated. The results show that the CO–ICO transformation temperature was size-dependent and occurred only for small clusters. It was also observed that the CO–ICO transformation temperature firstly dropped and then raised as Al concentration increased, which may be strongly related to the release of excess energy. Furthermore, the surface segregation phenomenon was also observed that the lower surface energy components, such as Al and Cu atoms, segregated to the surface of CuAlNi nanoclusters. The changes in the melting points of CuAlNi nanoclusters with different alloy compositions and cluster sizes were also studied. And furthermore, the physical basis of structural transition of CuAlNi nanoclusters was discussed.     

纳米团簇晶体的制备和结构研究

利用表面调制“幻数团簇”的方法制备出Al、Ga和In的纳米团簇人造晶体。这种方法是用Si(111) 7× 7表面作为“模板”生长尺寸相同和分布有序的纳米团簇。通过扫描隧道显微镜 (STM )原位分析结合第一性原理计算确定了金属纳米团簇的原子结构以及这些结构的形成机理。我们的研究表明对生长动力学的精确控制是制备团簇晶体的关键所在。此外 ,这种方法并不局限于制备某一种金属团簇。人造纳米团簇具有高的热稳定性和独特的结构使它们有希望在实际中得到广泛的应用。     

纳米团簇淀积过程的分形聚集特征

采用惰性气体凝聚法获得非金属团簇淀积体。透射电子显微分析及动力学模拟结果表明：纳米团簇淀积体的生长、聚集过程对构成团簇的原子的热力学性质、团簇制备中的蒸发率和惰性气体气压及淀积温度等参数极为敏感。在团簇的淀积体中，随生长条件不同，将会出现不同的聚集结构。因此可在一定程度上定量控制团簇淀积体的聚集状态，获得特定的纳米结构图案。     

纳米GeO_2在空芯光纤中的化学气相沉积

采用调节高温区与冷却区距离的方法，使多晶GeO2介质膜的颗粒度降低到0.1m左右，提高了光纤的传输能力，将光纤的传输损耗降低到0.8dB/m以下。     

银纳米团簇颗粒局域表面等离激元增强荧光

采用基于磁控等离子体团簇束流源的低能团簇束流沉积在石英衬底上制备了银纳米团簇颗粒,并测量了其透射光谱.将二氧化硅荧光纳米球分别分散在裸石英片和有银纳米团簇颗粒的石英片上,用波长为410 nm的激光激发,结果表明有银钠米团簇颗粒的荧光发射强度与没有银纳米团簇颗粒的荧光发射强度相比,增强倍数达5.3倍.最后,用Mie散射理论数值计算单个银纳米球颗粒在其表面等离激元共振位置处的电场强度分布,据此对实验结果进行了合理的解释.     

A novel method for preparing platinized counter electrode of nanocrystalline dye-sensitized solar cells

The platinized FTO glass counter electrode was prepared by employing techniques of colloid preparation, Langmuir-Blodgett film and serf-assembly. The present electrode had very low platinum loading, high catalytic activity for iodine/triiodide reduction reaction. Compared with the conventional counter electrodes used in nanocrystalline dye-sensitized solar cells, the present electrode had provided a much higher catalytic performance which was attributed to the structure of platinum nanoclusters distributed homogeneously on the electrode.