Investigation of Electron-Transfer Process on Photoexcited Heterogeneous Interface and Its New Application

研究光激发半导体上的反应机理具有重要意义。在这项研究中，我们采用了STM（扫描隧道显微镜）和动态电位脉冲技术作为新的方法。取得了以下结果。(1)我们建立了一个专门设计用于观察纳米粒子-溶液界面的STM仪器。初步的观察给出了HOPG的原子图像。用扫描隧道显微镜也获得了MoS_2的高质量图像。(2)采用动态电位脉冲技术研究了半导体/电解质结电荷转移机制的控制因素。在各种氧化还原电解质中，将纳秒量级的电位脉冲施加到n-SiC单晶电极。(3)采用一种新的光电化学方法获得了异质界面的高分辨率图像。(4)半导体光激发表面的光化学反应活性被用来杀死癌细胞。HeLa细胞是一种典型的癌细胞，光激发的TiO_2超微粒子能杀死HeLa细胞。血卟啉修饰的TiO_2粒子也表现出良好的活性。

It is important to investigate the mechanism of reactions on photoexited semiconductor. In this study, we have employed STM (scanning tunneling microscopy) and a dynamic potential pulse technique as new methods. The following results have been obtained. (1) We built a STM instrument specially designed for observation of semicondoctor-solution interface. A preliminary observation gave an atomic image of HOPG. High-quality images Of MoS_2 was also obtained by STM. (2) A dynamic potential pulse technique has been used to explore the controlling factors of the charge transfer mechanism at semiconductor/electrolyte junction. Potential pulses were applied in the order of nanoseconds to a n-SiC single crystal electrode in various redox electrolytes. (3) High resolution images were obtained on heterogenious interface by a new method of photoelectro chemistry. (4) Activity of photochemical reaction on the photoexcited surface of a semiconductor was applied to kill cancer cells. A typical cancer cell, HeLa cell was killed by photoexcited TiO_2 ultrafine particles. TiO_2 particles modified by hematoporphyrine also showed a good activity.