水溶液中TiO2纳米颗粒对化学吸附的多羟基醇和碳水化合物的高效快速单电子光氧化
Efficient, rapid one-electron photooxidation of chemisorbed polyhydroxyl alcohols and carbohydrates by TiO2 nanoparticles in an aqueous solution
摘要：
时间分辨瞬态吸收光谱已被用来研究纳秒和亚微秒的电子动力学在水溶性纳米粒子的存在下的空穴清除剂：化学吸附的多元醇和碳水化合物。这些多羟基化合物被空穴迅速氧化;这些空穴中的50-60%在355 nm激发激光脉冲的持续时间内被清除。清除效率随着锚定羟基的数量而迅速增加，并且随着碳水化合物结构的变化而变化很大。多元醇和碳水化合物的一个特定的结合位点的建议，涉及一个八面体钛原子螯合的聚-OH配体。这种模式的结合占耗尽的未配位的钛原子中观察到的XANES光谱的多元醇包覆的纳米粒子。我们认为，这些结合位点陷阱的空穴之前，后者下降到表面陷阱和/或重组与自由电子的相当一部分。由此产生的氧空穴中心迅速失去一个CH质子到环境中，产生一个亚稳态的C中心自由基。
英文摘要：
Time-resolved transient absorption spectroscopy has been used to study nanosecond and sub-microsecond electron dynamics in aqueous anatase nanoparticles in the presence of hole scavengers: chemisorbed polyols and carbohydrates. These polyhydroxylated compounds are rapidly oxidized by the holes; 50-60% of these holes are scavenged within the duration of 355 nm excitation laser pulse. The scavenging efficiency rapidly increases with the number of anchoring hydroxyl groups and varies considerably as a function of the carbohydrate structure. A specific binding site for the polyols and carbohydrates is suggested that involves an octahedral Ti atom chelated by the poly-OH ligand. This mode of binding accounts for the depletion of undercoordinated Ti atoms observed in the XANES spectra of polyol coated nanoparticles. We suggest that these binding sites trap a substantial fraction of holes before the latter descend to surface traps and/or recombine with free electrons. The resulting oxygen hole center rapidly loses a CH proton to the environment, yielding a metastable C-centered radical.
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