Colloque Electrochimie dans les Nanosciences 3

Electron Transport via Redox Molecules

NJ Tao

Center for Bioelectronics and Biosensors, Biodesign Institute,
Arizona State University, Tempe, AZ8528

Understanding and controlling charge transport in single molecules is a basic task in molecular electronics, and directly relevant to charge transfer in redox molecules, a phenomenon that plays critical roles in many chemical and biological processes. We have studied charge transport through single molecules attached to two electrodes in electrolytes. The molecules include benzene dithiol, perylene derivatives, and single layer graphene sheet, which share the same building block, aromatic ring. The HOMO-LUMO gap of the molecules decreases with the number of benzene rings and becomes zero in the case of graphene. We have measured the charge transport current through the molecules as a function of electrochemical gate voltage, which allows us to control the current by shifting the molecular energy levels relative to the Fermi levels of the electrodes. The gate effect is small in the case of benzene dithiol, but it can change the conductance of the perylene derivatives by 2-3 orders of magnitude. Graphene is highly conductive with a remarkably high mobility but the gate effect is relatively weak. We discuss the different charge transport mechanisms in these polycyclic aromatic hydrocarbons.