Electron transport characteristics were studied in redox molecule-modified tunneling junctions Au(111) | 6-thiohexanoylferrocene (Fc6) | solution gap | Au STM tip employing an electro­chemical STM setup. We observed transistor- and diode-like current−voltage responses accounted for by the redox process at the ferrocene moiety. We discovered as a unique feature the formation of uniform (~2.4 nm) gold nanoparticles, upon multiple oxidation/reduction cycles of the Fc6 adlayer. For the Fc6 tunneling junctions modified by the immobilized nanoparticles we observed single-electron Coulomb charging signatures with up to seven narrow and equally spaced energy states upon electrochemical gating.
Our results demonstrate the power of the electrochemical approach in molecular electronics and offer a new perspective toward two-state and multistate electronic switching in condensed media at room temperature.

This work was carried out in the group of Prof. Thomas Wandlowski.

References:

• Z. Li, Y. Liu, S. F. L. Mertens, I. V. Pobelov and T. Wandlowski;
  "From Redox Gating to Quantized Charging"
  J. Am. Chem. Soc., 132, 8187–8193, (2010); doi:10.1021/ja102754n.