Single-molecule conductance of dipyridines binding to Ag electrodes measured by electrochemical scanning tunneling microscopy break junction

We have measured the conductance of three pyridyl-terminated molecules binding to Ag electrodes by using electrochemical jump-to-contact scanning tunneling microscopy break junction approach (ECSTM-BJ). Three molecules, including 4,4'-bipyridine (BPY), 1,2-di(pyridin-4-yl)ethene (BPY-EE), and 1,2-di(pyridin-4-yl)ethane (BPY-EA), contacting with Ag electrodes show three sets of conductance values, which follow the order of BPY > BPY-EE > BPY-EA. These values are smaller than those of molecules with Au electrodes, but larger than those of molecules with Cu electrodes. The difference may attribute to the different electronic coupling efficiencies between the molecules and electrodes. Moreover, the influence of the electrochemical potential on the Fermi level of electrodes is also discussed.