Construction of redox- and photo-functional molecular systems on electrode surface for application to molecular devices

Two systems using bottom-up fabrication of molecular wires on an electrode surface are described. The first system involves films composed of linear and branched wires of metal complex oligomers, which were prepared using stepwise complexation of metal ions with bis- and tris-tpy (tpy = 2,2 ':6 ',2 ''-terpyridine) ligands, respectively, on tpy-terminated SAM on gold. This method allows the formation of desired numbers of polymer units and of desired sequences of hetero-metal structures in the polymer chain. The electron transport mechanism and kinetics for the redox reaction of the films of linear and branched oligomer wires analyzed by potential step chronoamperometry indicate that electron conduction occurs by successive electron hopping between neighboring redox sites within a molecular wire. The second system is an assembly of bio-conjugated materials to achieve the output of electrons directly from photosystem I ( PSI) of thermophilic cyanobacteria to a gold nanoparticle on the gate of a field-effect transistor (FET) by bypassing the electron flow via a molecular wire. Photo-electrons generated by the irradiation of reconstituted PSI on the gate with 670-680 nm light were found to control the FET performance, which is sufficiently stable for use exceeding a period of 1 year. (C) 2007 Elsevier B. V. All rights reserved.