Structure of semiconductor nanoparticles supporting noble metals and their catalysis induced by gamma-ray irradiation measured with labeled compounds

通过测量不同颗粒材料的产氢率，研究了伽玛射线辐照下分散在水溶液中的纳米颗粒的析氢过程。使用^<60>Co γ源在封闭的小瓶中照射样品溶液后，通过气相色谱系统检测氢气。辐照在室温下进行。结果表明，作为高光催化材料的二氧化钛颗粒的析氢产率较低，仅略高于水辐射析氢的背景产率，而氧化铝、BaTiO_2和β - sic的收率要高得多。部分析氢机理可以理解为光催化机理的外推，其中光子产生的空穴和电子分别作为氧化和还原物种在粒子表面电解水。然而，由于伽马光子的能量远高于普通光催化所涉及的能量，因此应考虑许多其他过程，如电子从粒子中移出并入射到粒子中，辐射分解形成自由基等。

Hydrogen gas evolution induced by gamma-ray irradiation of nanoparticles dispersed in aqueous solution was investigated by surveying hydrogen yields of various kinds of particle materials. Hydrogen gas was detected by a gas chromatography system after an irradiation of the sample solution in a closed vial using a ^<60>Co gamma-source. The irradiation was performed at room temperature. It was found that the titania particles known as a highly photo-catalytic material has a low evolution yield just slightly higher than the back ground hydrogen evolution due to water radiolysis, while alumina, BaTiO_2 and beta-SiC showed a much higher yield. A part of mechanism of the hydrogen evolution may be understood as an extrapolation of that of the photo-catalysis, in which holes and electrons created by photons play roles as respectively oxidizing and reducing apecies to electrolyze water on the particle surface. However, since the gamma-photon has an energy far higher than those involved in the ordinary photo-catalysis, many other processes should be taken into account, such as electron removal from and incident to the particle, radicals formation from the radiolysis, etc.