Department of Chemistry, Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, Israel.
Photochem Photobiol. 2012 Jan-Feb;88(1):14-20. doi: 10.1111/j.1751-1097.2011.01015.x. Epub 2011 Nov 3.
Photoexcited TiO(2) has been found to generate reactive oxygen species, yet the precise mechanism and chemical nature of the generated oxy species especially regarding the different crystal phases remain to be elucidated. Visible light-induced reactions of a suspension of titanium dioxide (TiO(2)) in water were investigated using electron paramagnetic resonance (EPR) coupled with the spin-trapping technique. Increased levels of both hydroxyl (˙OH) and superoxide anion (˙O(2)(-)) radicals were detected in TiO(2) rutile and anatase nanoparticles (50 nm). The intensity of signals assigned to the ˙OH and ˙O(2)(-) radicals was larger for the anatase phase than that originating from rutile. Moreover, illumination with visible (nonUV) light enhanced ˙O(2)(-) formation in the rutile phase. Singlet oxygen was not detected in water suspension of TiO(2) neither in rutile nor in anatase nanoparticles, but irradiation of the rutile phase with visible light revealed a signal, which could be attributed to singlet oxygen formation. The blue part of visible spectrum (400-500 nm) was found to be responsible for the light-induced ROS in TiO(2) nanoparticles. The characterization of the mechanism of visible light-induced oxy radicals formation by TiO(2) nanoparticles could contribute to its use as a sterilization agent.
光激发的 TiO(2) 已被发现会产生活性氧物种，但确切的机制和生成氧物种的化学性质，特别是关于不同的晶体相，仍有待阐明。使用电子顺磁共振 (EPR) 结合自旋捕获技术，研究了二氧化钛 (TiO(2)) 在水中悬浮液的可见光诱导反应。在 TiO(2) 金红石和锐钛矿纳米粒子 (50nm) 中检测到羟基 (˙OH) 和超氧阴离子 (˙O(2)(-)) 自由基的水平增加。来自锐钛矿相的信号强度大于来自金红石相的信号强度，分配给 ˙OH 和 ˙O(2)(-) 自由基的信号。此外，可见光 (非 UV) 光照射增强了金红石相中 ˙O(2)(-) 的形成。在 TiO(2) 金红石和锐钛矿纳米粒子的水悬浮液中均未检测到单线态氧，但用可见光照射金红石相时，发现了一个信号，可归因于单线态氧的形成。可见光谱的蓝色部分 (400-500nm) 被发现负责 TiO(2) 纳米粒子中光诱导的 ROS。TiO(2) 纳米粒子可见光诱导产生氧自由基的机制的表征有助于将其用作杀菌剂。
