Yoshihiko Nishimori

Surface Junction Effects on the Electron Conduction of Molecular Wires

Surface junction effects on the electron conduction of p-phenylene-bridged bis(terpyridine)iron oligomers terminated with a ferrocene moiety were quantitatively analyzed by employing three different surface-anchoring terpyridine ligands. The dependence of the electron-transfer rate constant for oxidation of the ferrocene moiety, k(et), on the distance between the electrode surface and the ferrocene moiety, x, showed that the attenuation factor, beta(d), which indicates the degree of reduction of k(et) with x, was approximately 0.018 in all cases. However, the absolute k(et) value depended strongly on both electronic and steric factors of the surface-anchoring ligand.

Superior Electron-Transport Ability of π-Conjugated Redox Molecular Wires Prepared by the Stepwise Coordination Method on a Surface

Electronic conductivity of molecular wires is a critical fundamental issue in molecular electronics. pi-Conjugated redox molecular wires with the superior long-range electron-transport ability could be constructed on a gold surface through the stepwise ligand-metal coordination method. The beta(d) value, indicating the degree of decrease in the electron-transfer rate constant with distance along the molecular wire between the electrode and the redox active species at the terminal of the wire, were 0.008-0.07 A(-1) and 0.002-0.004 A(-1) for molecular wires of bis(terpyridine)iron and bis(terpyridine)cobalt complex oligomers, respectively. The influences on beta(d) by the chemical structure of molecular wires and the terminal redox units, temperature, electric field, and electrolyte concentration were clarified. The results indicate that facile sequential electron hopping between neighboring metal-complex units within the wire is responsible for the high electron-transport ability.

Observation of electrochemical single-electron-transfer events of gold nanoparticles in aqueous solution in the presence of both ammonium and sulfonate surface-active agents.

Metal nanoparticles (MNPs) behave as quantum dots and have attracted much attention in the fields of molecular electronics, catalysis, 3] and sensors. 4] Recently, biomaterials chemistry has employed MNPs intensively, and MNPattached proteins and DNAs have been used as DNA sensors, immunosensors, sugar sensors, HIV drugs, and photosensors, and thus the importance of the physical and chemical properties of MNPs in aqueous solution is increasing. It is known that MNPs smaller than 2.0 nm in diameter have a capacitance CCLU of less than one attofarad (1 aF) per nanoparticle in electrolyte solution, which enables observation of single-electron-transfer events even at room temperature. This phenomenon is called quantized double-layer (QDL) charging, and CCLU is given by Equation (1), where e is