Electric field induced proton transfer at α,ω-mercaptoalkanecarboxylic acids self-assembled monolayers of different chain length

A comprehensive experimental investigation of the influence of the chain length on the electric field induced proton transfer at α,ω-mercaptoalkanecarboxylic acids self-assembled monolayers (SAMs) is conducted by means of voltammetric and electrochemical impedance spectroscopic measurements. The chain length has a significant impact on the total protonation/deprotonation charge and on the kinetics of the phenomenon. The results are discussed in light of existing theoretical models describing this electric field driven protonation/deprotonation process. Characteristic proton transfer frequencies were independently determined by impedance spectroscopy and by scan rate dependent voltammetric analyses. The two types of measurements are in mutual agreement and show that the protonation/deprotonation slows down as the chain length increases.