Development of the Instrument for UV-visible Electroreflectance Measurement for Analysing Redox Behavior of Adsorbed Monolayrs on Electrode Surfaces

研制了一种具有以下特点的紫外-可见电反射率（ER）测量新仪器。该仪器可应用于氧化形式的吸收光谱与还原形式的吸收光谱不同的测量系统，或吸附物质的量取决于电极电位的变化。该仪器灵敏度高（5mV电位调制时灵敏度为0.002%），稳定性好。此外，所有反射光线的电极材料均可用于该仪器。通过改变监测波长和电位调制频率，可以分别检测在相似电位范围内发生的多组分体系的电极反应。通过研究斯塔克效应，可以确定电极表面吸附分子的取向。分别检测了ER响应的实分量和虚分量，从而可以测量到高达10^5s^<-1>左右的电极反应速率。利用氙灯或氘灯作为光源，可以在200 ~ 900 nm宽波长范围内测量ER。利用所研制的仪器，得到了以下新的实验结果：测定了细胞色素c通过不同链长羧基端烷烃醇的电子转移反应速率。在较厚的硫醇层中，电子转移反应速率的对数与电子转移距离呈线性关系，而在较薄的硫醇层中，电子转移反应速率的对数与电子转移距离呈线性关系。四环烷化钴中四烷基（4-吡啶基）卟啉的内质网测量使我们能够阐明卟啉钴中心发生氧化还原反应。传统的伏安技术不能选择性地测量钴中心的信号。

The new instument for UV-visible electroreflectance (ER) measurement having the following characteristics was developed.1. The instrument can be applied to measurement systems where the absorption spectrum of the oxidized form is different from that of the reduced form or where the amount of adsorbed species changes depending on the electrode potential.2. The instument has high sensitivity (sensitivity of 0.002% at potential-modulation of 5mV) and high stability. In addition, all electrode materials which reflect light can be used for the instrument.3. The electrode reactions of multi-component systems which take place at similar potential range can be separately detected by changing the monitor wavelength and the frequency of potential modulation.4. By investigating the Stark effect, the orientation of adsorbed molecules on the electrode surfaces can be determined.5. Both the real component and the imaginary component of ER response are separately detected, so that the rate of electrode reactions up to around 10^5s^<-1> can be measured.6. The ER measurement in the wide wavelength region between 200 and 900 nm is possible by using a xenophoto lamp or adeuterium lamp as a light source.The following new experimental results were obtained by using the developed instrument.1. The electron transfer reaction rates of cytochrome c through COOH-terminated alkantiols with various chain lengths were measured. The linear relationship between the logarithm of the electron transfer reaction rate and the electron transfer distance was obtained in thick thiol layrs, while a deviation from the linear relation ship was observed in thinner thiol layrs.2. ER measurements of tetraruthenated cobalt meso-tetrakis (4-pyridyl) porphyrin enable us to elucidate that the redox reaction of the cobalt center of porphyrin occurs. Conventional voltammetric techniques could not measure the signal of the cobalt center selectively.