Slow surface charge trapping kinetics on irradiated TiO2
Slow surface charge trapping kinetics on irradiated TiO2
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DOI：
10.1021/jp004244h
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发表时间：
2002-03-21
影响因子：
3.3
通讯作者：
Hoffmann, MR
中科院分区：
文献类型：
--
作者：
Szczepankiewicz, SH;Moss, JA;Hoffmann, MR
用漫反射红外光谱(DRIFTS)表征了多晶二氧化钛禁带辐照后的自由载流子和俘获载流子。全光谱吸收信号与λ(1.7)成正比(lambda=波长/微米)，表明晶格中存在自由导带电子与声学声子耦合。自由电子似乎按照饱和动力学衰减。拟合的参数显示了有限数量的陷阱态。这些状态的浓度似乎通过连续的紫外线处理而减少。随着样品的脱水，自由载流子衰减寿命延长，这表明在电子捕获过程中发生了激发态弛豫事件。光生自由电子相当于从表面结合的发色团注入的导带电子，这些电子的寿命可以延长几个数量级。中心位于3380 cm(-1)的宽红外吸收峰归因于导带下方0.42 eV被占据的表面电子陷阱的电子跃迁。
Free and trapped charge carriers in polycrystalline TiO2 following band gap irradiation are characterized by diffuse reflectance IR spectroscopy (DRIFTS). A spectrum-wide absorption signal proportional to lambda(1.7) (lambda = wavelength/mum) indicates the presence of free conduction band electrons coupled with acoustic phonons in the lattice. Free electrons appear to decay according to saturation kinetics. The fitted parameters indicate a limited number of trapping states. The concentration of these states appears to be diminished by sequential UV treatments. The free carrier decay lifetime is lengthened as the samples are dehydrated, which suggests an excited-state relaxation event during electron trapping. Photogenerated free electrons are comparable to conduction band electrons injected from surface-bound chromophores, and the lifetime of these electrons can be extended across several orders of magnitude. A broad IR absorption peak centered at 3380 cm(-1) is attributed to an electronic transition from an occupied surface electron trap 0.42 eV below the conduction band.