Real Time Monitoring of Electron Transfer Dynamics at Solid/liquid Interfaces by Non-linear Spectroscopy

为了理解固/液界面上的电子传递动力学机制，电极/电解质界面上的分子结构信息，包括界面上的短寿命中间体和溶剂的结构信息是必不可少的。然而，传统的表面振动技术很难确定中间体和溶剂的界面结构，因为与大分子相比，分子数量少。利用红外吸附和表面比和频率产生（SFG）技术监测了电子激发引起的振动模式的时间振动。我们利用这些光谱方法研究了界面结构与反应动力学之间的关系。固/液界面吸附过程的SFG光谱观察与动力学采用可见泵浦SFG探针测量了Pt电极上吸附CO的动力学。在2064cm- 1处，铂的顶部位置吸附了CO，形成SFG峰。此外，该峰的强度在激发后迅速下降，并在10秒内恢复。在800cm -l处观察到一个新的宽峰，对应于多重位点的CO吸附，表明激发后的位点交换。结果表明，回收率与电位有关。时间分辨可见泵浦可见光和红外探针技术，分别将极短的紫外或可见脉冲激发与延迟的超快可见光和中红外吸收相结合，是监测光激发后电子和分子结构变化的有力工具。在本研究中，(1)构建了一个允许这两种测量的系统，(2)应用可见泵浦红外探针技术研究了尺寸和表面处理对CdS载流子动力学的影响，(3)应用可见泵浦可见光和红外探针技术研究了三钌配合物[Ru_3(O)(CH_3CO2)_6(CO)L_2]的光诱导分子内电荷转移，其中L=配体，含有强红外活性配体CO，作为金属中心电子密度的直接红外探针。生物材料表面水结构的表征许多生物系统如蛋白质和酶在没有水的情况下是无活性的。为了全面了解这些系统的功能，水的结构和动力学信息是必不可少的。我们研究了几种生物材料表面的水结构。例如，在不同压力下，我们利用SFG光谱监测了水-聚合物凝胶/固体界面水的结构。弱氢键水在SFG谱中的贡献随压力的增加而增加，表明弱氢键水对聚合物凝胶/固体界面的低摩擦性能起重要作用。少

To understand the mechanism of electron transfer dynamics at solid/liquid interfaces, information of structures of molecules at electrode/electrolyte interface including short-lived intermediates and solvent at the interface is essential. The determination of the interfacial structures of the intermediate and solvent is, however, difficult by conventional surface vibrational techniques because of small number of molecules compared to bulk molecules. Temporal vibration of vibrational modes induced by electronic excitation is monitored by IR adsorption and surface-specific sum frequecy generation (SFG) techniques. We investigated the relations between interfacial structures and reaction dynamics by using these spectroscopic methods.1. Observation and dynamics of adsorbates at solid/liquid interfaces by SFG spectroscopyDynamics of adsorbed CO on Pt electrode was followed by visible pump SFG probe measurements. An SFG peak due to adsorbed CO at on-top site of Pt was observed at 2064cm-l. T … More he intensity of this peak decreased quickly upon excitation and recovered within few ten of os. A new broad peak was observed at 1980cm-l corresponding to adsorbed CO at multi-fold site, suggesting the site exchange upon excitation. The recovery rate was found to be dependent on potential.2. Carrier and charge transfer dynamics by visible pump-visible and IR techniqueTime-resolved visible-pump visible and infrared-probe techniques, in which very short UV or visible pulse excitation is combined with delayed ultrafast visible and mid-IR absorption, respectively, are powerful tools to monitor the changes in electronic and molecular structure, respectively, as after the photoexcitation. In the present study, (1) a system, which allows these two measurements, was constructed, (2) visible-pump infrared-probe technique was applied to study the effect of size and surface treatment on the carrier dynamics of CdS, and (3) visible-pump visible and infrared-probe techniques were applied to study the photo-induced intra-molecular charge transfer with a triruthenium complex [Ru_3(O)(CH_3CO2)_6(CO)L_2], where L=ligands, containing a strongly IR active ligand, CO, which act as a direct IR probe of the electron density at the metal center.3. Characterization of water structure at biomaterial surfacesMany biological systems such as proteins and enzymes are inactive without water. For a complete understanding of the function of such systems, information of the structure and dynamics of the water is essential. We incestigated the structure of water at several biomaterial surfaces. For example, we monitored the structure of interfacial water at hydro-polymer gel/solid interface by SFG spectroscopy under various pressures. The contribution of weakly hydorogen bonded water in SFG spectra increased with pressure, suggesting the inportant role of weakly hydorogen bonded water to the low friction properties at the hydro-polymer gel/solid interfaces. Less