Formation of Nanoparticle Ensemble and its Electronic Structure : From Fractal Cluster to Particle Crystal

在预定的时间内，我们开发了一种制备技术，可以使用高密度纳米胶体在石英或HOPG衬底上铸造薄膜，并通过STM/AFM观察其结构。在过去的一年里，我们把精力集中在金纳米颗粒薄膜的形成以及隔离颗粒大小的确定上。在原有物理法制备方法的基础上，又尝试了新的胶体化学法制备方法。结果表明，以硫代酸盐为粒径控制剂，可制得最小粒径为1um的颗粒。通过有机还原法制得粒径大于10nm的颗粒，发现粒径分布宽度窄至15%。采用各种物理化学方法测定了该硫酸盐修饰颗粒的精确表面状态。为了达到颗粒晶体形成的目的，我们采用巯基表面修饰的方法进行了g量级的大规模合成。在实验的最后阶段，使用Au-MSA修饰的纳米颗粒来测试颗粒晶体的形成。测试的调节参数为：水/有机溶剂含量、一种溶剂（甲醇、乙醇、2-丙醇）、盐浓度、一种盐（硫酸铵、氯化铵）、结晶温度。使用在蛋白质化学领域著名的微电镀方法测试了数百种不同的条件。不幸的是，大尺寸的晶体形成被认为不适合x射线分析。粒度分离技术如色谱法或粒度选择沉淀法仍有待进一步研究，以形成三维大粒度晶体。

During a scheduled period, we have developed a preparation technique enables casting film on quartz or HOPG substrate using high density nanocolloids and observed their structure by STM/AFM which is incorporated in our laboratory. In the last year, we have focused our effort on the formation of gold nanoparticle film together with the confirmation of the size of isolated particles.In addition to the previous preparation method using physical process, a new colloid chemical method was also attempted. It was found that a particle with the smallest size of 1um was prepared when using thiolate as a size controller. A particle whose size is larger than 10nm was formed by the organic reduction method and was fount that the size distribution width is narrow as 15%. The precise surface state of this thiolate-modified particles was determined using various physico-chemical method. In order to aim the particle crystal formation, we have developed a large scale amount synthesis in the order of g using thiol surface modified method. This amount is far from that by the physical dry process in the order of mg. In the final stage of the experiment, particle crystal formation was tested using Au-MSA modified nanoparticles. The regulation parameters tested were content of water/organic solvent, a kind of solvent (methanol, ethanol, 2-propanol),salt concentration, a kind of salt (ammonium sulfate, ammonium chloride), and crystallization temperature. More than several hundreds different conditions were tested using a micro-plating method, well-known in the field of protein chemistry. Unfortunately, a large size crystal formation was not perceived appropriate for the X-ray analysis.The size separation technique such as chromatography or the size-selected precipitation method was remained in a future study to form a three dimensional large size crystal.