Morphological and Electrochemical Analysis of a Self-Assembled Monolayer of 3-Mercaptopropionic Acid on Gold Electrode

This paper investigates the morphology of a polycrystalline gold electrode modified with a monolayer of 3-MPA (Au/MPA) constructed in different immersion times and thiol concentrations, using the techniques of electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM).It was verified that both surface roughness as the capacitance of the Au/MPA are dependent on the concentration and the organization of the 3-MPA molecules adsorbed on the gold electrode surface.Voltammetric results demonstrated that the coverage is dependent on the immersion time and concentration of the 3-MPA solution.These results are in agreement with the EIS results which showed the increased in charge transfer resistance (Rct) as a function of the immersion time, due to increase of the electron transfer block caused by the monolayer.However, the Rct increased until 180 min.and higher immersion times did not show significant variations in resistance.