Single Molecular Electrochemistry within an STM

Abstract

This chapter focuses on single molecule electrical measurements under electrochemical conditions. It describes experimental methods suitable for determining the electrical properties of molecules in an electrochemical configuration. The chapter provides an overview of electron transfer mechanisms for single molecules in a scanning tunneling microscopy (STM) nanogap configuration. Single molecule electrical measurements made using an electrochemical STM are then reviewed. The first use of electrochemical STM to explicitly study electron transfer at the single molecule level at the electrode-electrolyte interface was by Tao. The first electrochemical single molecule conductance measurements were performed on viologen derivatives. Osmium and cobalt transition metal complexes attached to Au(111) or Pt(111) single-crystal electrodes have proven to be very rich systems for studies of electron transfer using the in situ electrochemical STM. The different metal centers provide notably differing electron transfer rates as determined from electrochemical measurements.