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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Real-Time Observation of Photoinduced Adiabatic Electron Transfer in Strongly Coupled Dye/Semiconductor Colloidal Systems with a 6 fs Time Constant
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Real-Time Observation of Photoinduced Adiabatic Electron Transfer in Strongly Coupled Dye/Semiconductor Colloidal Systems with a 6 fs Time Constant

机译：时间常数为6 fs的强耦合染料/半导体胶体系统中光诱导绝热电子转移的实时观察

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摘要

Electron transfer from organic dye molecules to semiconductor-colloidal systems is among the fastest reported charge-separation reactions. We present investigations on alizarin complexing the surface of TiO_2 semiconductor colloids in solution. Because of the very strong electronic coupling between the sensitizer and the semiconductor in the alizarin/TiO_2 system, very fast electron injection from the photoexcited dye to the conduction band of TiO_2 occurs. The real-time observation of the injection process is achieved by transient absorption spectroscopy using a 19-fs excitation pulse provided by a pump pulse from a noncollinear optical parametric amplifier and a probe pulse from a quasi-chirp-free supercontinuum. An injection time τ_(inj) of 6 fs can be unambiguously derived in three different ways from the experimental data: (i) analysis of individual transients at spectral positions without contributions from subsequent reactions (relaxation, recombination); (ii) global fitting procedure for 31 wavelengths over a wide spectral range; and (iii) calculation of the S~* state and comparison to the "nonreactive" system alizarin/ZrO_2. The spectral signature of the 6-fs kinetic component can be assigned to electron transfer from the excited dye molecule to the TiO_2 colloid. Even for this strongly coupled system, we propose a localized excitation with a subsequent adiabatic electron transfer reaction that is, to our knowledge, the fastest electron-transfer reaction that has been directly measured by transient spectroscopy.
机译：从有机染料分子到半导体胶体系统的电子转移是报道最快的电荷分离反应之一。我们目前对茜素在溶液中络合TiO_2半导体胶体表面的研究。由于茜素/ TiO_2系统中敏化剂和半导体之间的电子耦合非常强，因此发生了从光激发染料到TiO_2导带的非常快速的电子注入。注入过程的实时观察是通过瞬态吸收光谱法实现的，其中使用了一个19-fs激发脉冲，该激发脉冲由来自非共线光学参量放大器的泵浦脉冲和来自准无chi的超连续谱的探测脉冲提供。可以以三种不同的方式从实验数据中明确得出6 fs的注入时间τ_（inj）：（i）分析频谱位置处的单个瞬变，而没有后续反应（松弛，重组）的影响; （ii）在宽光谱范围内对31个波长的全局拟合程序; （iii）计算S *状态并与“非反应性”系统茜素/ ZrO 2比较。 6-fs动力学成分的光谱特征可以分配给从激发的染料分子到TiO_2胶体的电子转移。即使对于这种强耦合系统，我们也提出了局部激发和随后的绝热电子转移反应，据我们所知，这是通过瞬态光谱法直接测量的最快的电子转移反应。

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