Gaseous Diffusion of Active Oxygen Species Generated at Photocatalyst and its Applications

TiO_2光催化剂在紫外光照射下具有很强的氧化能力，可以氧化大多数有机物。有机物的氧化分解一般只发生在TiO_2表面。然而，我们最近发现活性氧物种不仅存在于TiO_2表面，而且还通过气相扩散并氧化远离TiO_2的有机物种。硅、金刚石、银和铜也可以通过这种现象被氧化，即远程氧化。将使用光掩模的各种目标的远程氧化与芬顿和光芬顿反应进行比较。结果表明，直接氧化底物的活性物种很可能是羟基自由基。在10 ~ 100 μm的范围内改变TiO_2光掩模与基片之间的距离，基片上的图案相似。在此基础上，提出了反应机理：在TiO_2表面生成的H_2O_2通过空气扩散到靶上，H_2O_2在靶上被光活化并分解为羟基自由基，羟基自由基氧化靶。基于远距离氧化效应，研制了分辨率为1.5 μm的光催化光刻技术.

TiO_2 photocatalysts have been known to exhibit strong oxidizing abilities under UV light, which could oxidize most organic species. It has been believed that the oxidative decomposition of organic species takes place only at the TiO_2 surface. However, we have recently found that active oxygen species not only exist on the TiO_2 surface, but also diffuse through the gas phase and oxidize organic species placed apart from the TiO_2. Silicon, diamond, silver, and copper could also be oxidized by this phenomenon, remote oxidation. Remote oxidation of various targets using photomask was compared to Fenton and photo-Fenton reactions. The results suggested that the active species directly oxidizeing substrates was most likely hydroxyl radical. Varying the distance between the TiO_2-coated photomask and substrates from 10 to 100 μm showed similar patterns on the substrate. Based on these results, the mechanism of the reaction was proposed that hydrogen peroxide generated at the TiO_2 surface diffuses to targets through air, where the hydrogen peroxide is photoactivated and then decomposed to hydroxyl radical, which, in turn, oxidizes the targets. Photocatalytic lithography was developed based on the remote oxidation effect with resolution of 〜5 μm.