Electrochemical analysis at nanometer-scaled electrodes

该方案的目的是研究氧化还原反应在超微电极上的异常电化学行为，当反应区域为纳米级时。这种反常行为表现为化学平衡常数、反应速率常数随电极尺寸的明显变化。这种行为已经在纳米尺度的材料上观察到，例如金属纳米颗粒、纳米薄膜和纳米团簇。电化学分析有利于这一研究，因为超微电极提供了纳米级的环境，并且可以在纳米尺度上进行检测。以往关于氧化还原反应速率常数与电极尺寸的关系的数据是，随着电极半径的减小，Fe(II)(CN)6和Fe(III)(CN)6的半波电位发生了移动。有人批评说，络合物可能会被吸附，因此氧化还原行为应该是不寻常的行为。为了规避这一批评，我们努力寻找其他氧化还原体系和制备纳米电极。目前，我们得到了二茂铁在二氯乙炔溶液中和TCNQ在乙腈溶液中的极大的传递系数。较大的系数对应于反应速率的提高，定量地支持了较高的活化度和较少的原料。为了消除电极几何形状的模糊性，对实验数据进行了理论分析。提出了一些模型来解释反应速率的提高。作者认为，这种增强是由于低估了电极半径而造成的。

The aim of this proposal was to investigate abnormal electrochemical behavior of redox reactions at ultramicroelectrodes when reaction domains are on nanometer scale. The abnormal behavior is exemplified by apparent variation of chemical equilibrium constants, reaction rate constants with electrode size. This behavior has been observed at namometer-scaled materials such as metal nanoparticles, nanometered thin films, and nano-clusters. The electrochemical analysis is favorable for this research in that the ultramicroelectrodes provides nano-meter circumstances as well as their detection on the nanometered scale.The previous data of the relation between redox reaction rate constants and the electrode size were the shift of halfwave potentials of Fe(II)(CN)_6 and Fe(III)(CN)_6 with a decrease in the electrode radii. A criticism was presented in that the complexes might be adsorbed so that the redox behavior should be out of the ordinary behavior. In order to circumvent this criticism, we made efforts of searching other redox systems and fabricating nanometer electrodes. At present, we got extremely large transfer coefficients of ferrocene in dichloroethyne solution and TCNQ in acetonitrile. The large coefficient corresponds to enhancement of reaction rates, supporting quantitatively the higher activation with a decrease in material. In order to remove ambiguity of electrode geometry, theoretical work has been made for the analysis of experimental data. The some models have been presented for explaining the enhancement of the reaction rates. The authors think the enhancement is artially due to under estimation of the electrode radii.