Development of time-resolved and two-dimensional infrared spectroscopy for dynamic studies of solid/liquid interfaces

我们开发了一种新的红外光谱技术，可以实时监测固/液界面的反应和动力学。该技术采用了三种先进的红外技术，即表面增强红外吸收光谱（SEIRAS）、时间分辨FT-IR和二维相关分析（2D-IR）。SEIRAS以非常高的灵敏度探测界面，而不受体溶液的干扰。由于SEIRAS的高灵敏度，快速扫描和步进扫描FT-IR干涉测量的高速光谱测量成为可能。我们首次成功地以微秒到毫秒的时间分辨率监测电化学反应。由于时间分辨光谱测量的成功，从光谱中获得的分子信息与从常规电化学测量中获得的动力学信息直接相关。由于反应物和生成物的吸收带重叠，在反应过程中收集的时间分辨光谱往往比较复杂。为了利用其特有的随时间变化的行为来区分物种的光谱特征，采用了二维相关分析技术。二维红外的基本概念有点类似于核磁共振中使用的二维相关技术。发现2D-IR强调了在一维时间分辨光谱中不易看到的某些动态信息。2D-IR的一个重要特征是可以确定不同物种产生的波段强度变化的时间序列。这个特性在研究反应过程中是很有用的。我们已经通过几个电化学反应的研究证明了该技术的实用性。该项目最重要的成果之一是对“双层”结构的成功分析。我们发现水分子在Au（111）电极表面根据表面电荷重新定向。所得结果与近年来双分子层的分子动力学模拟结果一致。少

We have developed a novel infrared spectroscopy technique that enables real-time monitoring of reactions and dynamics at solid/liquid interfaces. This technique uses three advanced infrared technologies, surface-enhanced infrared absorption spectroscopy (SEIRAS), time-resolved FT-IR,and two-dimensional correlation analysis (2D-IR).SEIRAS probes the interface without the interference from the bulk solution at a very high sensitivity. Owing to the high sensitivity of SEIRAS,high-speed spectral measurements with rapid-scan and step-scan FT-IR inferferometry becomes possible. We have succeeded for the first time to monitor electrochemical reactions with time-resolutions ranging from microseconds to milliseconds. By the success of the time-resolved spectra measurements, the molecular information obtained from the spectra became to be directly correlated with the kinetic information obtained from conventional electrochemical measurements.The time-resolved spectra collected during reactions a … More re often complex due to the overlapping of absorption bands of reactants and products. To differentiate spectral features of the species by using their characteristic time-dependent behaviors, 2D correlation analysis technique was employed. The basic concept of 2D-IR is somewhat analogous to that of 2D correlation technique used in NMR.It was found that 2D-IR accentuates certain dynamic information that is not readily seen in the one-dimensional time-resolved spectra. One of the important characters of 2D-IR is that the time-sequence of the intensity changes of the bands arising from different species can be determined. This character is very useful in the studies of reaction processes.We have demonstrated the utilities of the developed technique through studies of several electrochemical reactions. One of the most significant achievements in this project is the success in the analysis of the "double-layr" structure. We found that water molecules reorient at the Au (111) electrode surface depending upon the surface charge. The results are in good agreement with recent molecular dynamics simulations of the double-layr. Less