Center for Photochemical Sciences, Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, USA.
J Am Chem Soc. 2010 Feb 17;132(6):1999-2004. doi: 10.1021/ja909168e.
The inhomogeneous interfacial electron transfer (IET) dynamics of 9-phenyl-2,3,7-trihydroxy-6-fluorone (PF)-sensitized TiO(2) nanoparticles (NPs) has been probed by a single-molecule photon-stamping technique as well as ensemble-averaged femtosecond transient absorption spectroscopy. The forward electron transfer (FET) time shows a broad distribution at the single-molecule level, indicating the inhomogeneous interactions and ET reactivity of the PF/TiO(2) NP system. The broad distribution of the FET time is measured to be 0.4 +/- 0.1 ps in the transient absorption and picoseconds to nanoseconds in the photon-stamping measurements. The charge recombination time, having a broad distribution at the single-molecule level, clearly shows a biexponential dynamic behavior in the transient absorption: a fast component of 3.0 +/- 0.1 ps and a slow component of 11.5 +/- 0.5 ns. We suggest that both strong and weak interactions between PF and TiO(2) coexist, and we have proposed two mechanisms to interpret the observed IET dynamics. A single-molecule photon-stamping technique and ensemble-averaged transient absorption spectroscopy provide efficient "zoom-in" and "zoom-out" approaches for probing the IET dynamics. The physical nature of the observed multiexponential or stretched-exponential ET dynamics in the ensemble-averaged experiments, often associated with dynamic and static inhomogeneous ET dynamics, can be identified and analyzed by single-molecule spectroscopy measurements.
通过单分子光子标记技术以及平均体相飞秒瞬态吸收光谱，研究了 9-苯基-2,3,7-三羟基-6-氟酮（PF）敏化的 TiO2 纳米颗粒（NP）的不均匀界面电子转移（IET）动力学。在单分子水平上，正向电子转移（FET）时间呈现出广泛的分布，表明 PF/TiO2 NP 体系的不均匀相互作用和 ET 反应性。FET 时间的宽分布在瞬态吸收中测量为 0.4 ± 0.1 ps，在光子标记测量中测量为皮秒到纳秒。在单分子水平上具有广泛分布的电荷复合时间在瞬态吸收中清楚地显示出双指数动态行为：快速组件为 3.0 ± 0.1 ps，慢速组件为 11.5 ± 0.5 ns。我们认为 PF 和 TiO2 之间存在强相互作用和弱相互作用，并且我们提出了两种机制来解释观察到的 IET 动力学。单分子光子标记技术和平均体相瞬态吸收光谱为探测 IET 动力学提供了有效的“放大”和“缩小”方法。通过单分子光谱测量，可以识别和分析通常与动态和静态不均匀 ET 动力学相关的平均体相实验中观察到的多指数或扩展指数 ET 动力学的物理性质。
