Simple methods for preparation of a well-defined 4-pyridinethiol modified surface on Au(111) electrodes for cytochrome c electrochemistry

A very small amount of sulfide impurity in 4-pyridinethiol (4-PySH) modifier solution was found to interfere with the proper formation of the 4-PySH modified surface for cytochrome c electrochemistry on an Au(111) electrode. When the modification was conducted in an alkaline (e.g. 0.1 M KOH) solution, in aqueous solutions under applying a potential more positive than 0.3 V vs. Ag/AgCl, or at a low modifier concentration (e.g. 20 μM), the proper 4-PySH modified surface was obtained even using 4-PySH as received, which contained a small amount of sulfide. The selective adsorption of 4-PySH in the presence of a small amount of sulfide under these conditions was due to the rapid formation of proper 4-PySH modified surface, which prevented the sulfide from reacting with the electrode surface.