水溶性TiO2纳米粒子的空穴清除和光刺激电子-空穴对
Hole Scavenging and Photo-Stimulated Recombination of Electron-Hole Pairs in Aqueous TiO2 Nanoparticles
摘要：
结果表明，532 nm和1064 nm激光光激发由355 nm光解水性二氧化钛（TiO 2）纳米颗粒产生的俘获电子，导致其在可见光和近红外吸收带的快速光漂白。这种光漂白发生在激光脉冲的持续时间内（3 ns FWHM）;它是由光诱导电子脱陷，然后快速重组所产生的自由电子和陷阱空穴。电子光漂白的量子产率约为0.001。0.28对于532 nm和ca. 0.024对于1064 nm光激发。使用甘油作为选择性的空穴清除剂，证明了从捕获的电子和空穴的光谱贡献的完全分离。当将甘油添加到溶液中时，一些光吸收空穴在355 nm光激发脉冲的持续时间内被迅速清除，一些在355 nm脉冲之后的前200 ns内以较慢的速率被清除，并且其余的不被清除，即使在高浓度的清除剂（> 10体积%）下也是如此。与化学和物理吸附的甘油的反应将分别解释空穴的快速和缓慢衰减。这些结果的影响进行了讨论。
英文摘要：
It is shown that 532 nm and 1064 nm laser photoexcitation of trapped electrons generated by 355 nm photolysis of aqueous titania (TiO2) nanoparticles causes rapid photobleaching of their absorbance band in the visible and near IR. This photobleaching occurs within the duration of the laser pulse (3 ns FWHM); it is caused by photoinduced electron detrapping followed by rapid recombination of the resulting free electron and a trapped hole. The quantum yield for the electron photobleaching is ca. 0.28 for 532 nm and ca. 0.024 for 1064 nm photoexcitation. Complete separation of the spectral contributions from trapped electron and hole is demonstrated using glycerol as a selective hole scavenger. When glycerol is added to the solution, some light-absorbing holes are scavenged promptly within the duration of the 355 nm photoexcitation pulse, some are scavenged at a slower rate over the first 200 ns after the 355 nm pulse, and the rest are not scavenged, even at high concentration of the scavenger (> 10 vol %). A reaction with chemi- and physi- sorbed glycerol would account for the prompt and the slow hole decay, respectively. The implications of these results are discussed.
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