Surface modification using redox-active units is one of the important subjects in molecular electrochemistry. During the past two decades, many functional nanostructures with redox activity have been prepared and examined the new functionalities. Based on the solution chemistry of protonresponsive ruthenium complexes containing benzimidazole derivates, I have developed the coordination LbL growth of redox-active Ru complexes toward molecular functional devices. To control the molecular orientation of the redox-active complexes on a transparent conductive ITO surface, tetrapod phosphonic acid anchor groups have been introduced in the rod-shaped ruthenium dinuclear complexes, resulting in the formation of well-ordered surface coordination network structures in a nanometer scale. Electrochemical functions of the nanostructures such as molecular switches, diodes, and memories have been achieved.

In this review, a summary of electrochemical studies by our research group is described. These studies started from the research of anodic stripping voltammetry using a hanging mercury drop electrode, followed by adsorptive stripping voltammetry at the modified carbon paste electrode. The preparation of ligand labeled with an electroactive compound enabled the electrochemical binding assay using avidin-biotin and lectin-sugar interactions. This method was applied to the screening of endocrine disrupting chemicals. The electrochemical detection at the immobilized DNA and CNT electrodes was also investigated.

An electrochemical reaction at an interface between electrode and electrolyte is one of the central problems in electrochemistry. The history of theoretical and computational approaches devoted to this problem has been reviewed. We paid particular attention to the detail of a series of simulation technique based on the effective screening medium method, which is a core part of the comprehensive simulation platform for electrochemical reactions. The simulation platform enables us to understand and clarify the detail of the reactions quantitatively.

On the complex plane, an impedance of a Randles-type equivalent circuit, which is commonly used for the analysis of an electrochemical impedance, traces a semicircle originated from the parallel connection of the charge-transfer resistance (R_ct) and the double-layer capacitance (C_dl), and a 45-degree line originated from the Warburg element (Z_W). It is often mentioned that there is an “overlap” between the semicircle and the extrapolation of the 45-degree line, and mathematically it has a length of 2⋅σ ²⋅C_dl. Although this is correct, to emphasize the existence of such an “overlap” may mislead the analysis, since its magnitude is extremely small compared with the size of the semicircle, when the figures of the semicircle and line are visibly separated from each other.