Preparation and microstructure control of metal/oxide nano-composite thin films utilizing porous structure of oxide gels

以正硅酸乙酯-水-乙醇-盐酸-氯金酸四水溶液为原料，对凝胶膜进行热处理，制得了含分散金纳米颗粒的二氧化硅涂层。研究发现，通过控制溶液反应时间和起始溶液中的水量，可以控制金粒子的大小和形状。此外，由纤维状拟薄水铝石颗粒组成的涂层中可以析出取向的、拉长的金纳米粒子。研究发现，当金属颗粒引入二氧化钛光阳极后，在可见光区出现光响应。研究了金纳米粒子的引入对染料敏化二氧化钛薄膜光阳极光电化学性能的影响。金纳米颗粒的引入降低了染料在可见光区的光响应，但当金颗粒与染料的光吸收重叠较大时，这种光响应较小。这表明金颗粒和染料分子之间确实存在偶极-偶极耦合，增强了电极表面发生的光化学过程。综上所述，已经证明可以通过控制凝胶基质的微观结构来控制金属纳米颗粒的尺寸和形状，其中细长的金属纳米颗粒也是可能的。还探讨了开发具有高能量转换效率的新型光电极的可能性。

Silica coating films containing dispersed gold nanoporticles have been prepared by heat-treating the gel films obtained from tetraethoxysilane-water-ethanol-hydrochloric acid-chloroauric acid tetrahydrate solutions. It was found that the size and shape of the gold particles can be controlled by controlling the solution reaction time and amount of water in the starting solutions. In addition, aligned, elongated gold nenoparticles could be precipitated in coating films consisting of fibrous pseudoboehmite particles.Titania film electrodes containing dispersed gold or silver nanoparticles have been prepared by sol-gel method. It was found that photoresponse emerges in visible region when the metal particles are introduced to the titania photoanodes. The effect of the introduction of gold nanoparticles on the photoelectrochemical properties of dye-sensitized titania film photoanodes was also studied. The introduction of gold nanoparticles decreased the dye-induced photoresponse in the visible region, which was, however, found to be less when the overlap of the optical absorption of the gold particles and dyes was larger. This indicates that the dipole-dipole coupling between the gold particles and dye molecules dose exist, enhancing the photochemical processes occurring at the surface of the electrodes.In summary, it has been demonstrated that the size and shape of the metal nanoparticles can be controlled by controlling the microstructure of the gel matrices, where alignment of elongated metal nanoparticles is also possible. Possibility of development of new photoelectrodes with high energy conversion efficiencies was also investigated.