Effect of solution composition on the desorption behavior of self-assembled monolayers of alkanethiols with different terminal groups

Voltammetry and chronoamperometry are used to study the effect of the composition of a solution on the desorption behavior of self-assembled monolayers (SAMs) of alkanethiols with approximately the same chain length but different end groups of thiols (R: –CH3, –CH2OH, and –NH2). The hydrophilic properties of terminal groups for the studied thiols increase in the –CH3 –NH2 ≤ –CH2OH series. It has been found that the anion and cation compositions of electrolyte significantly affect the electrochemical stability and blocking ability of SAMs of thiols with different terminal groups. It has been established that the electrochemical stability and blocking ability of SAMs decrease in the Li+, Na+, K+ series in basic solutions regardless of the thiol terminal group. The cation nature in perchlorate and chloride solutions is manifested only for thiol with terminal group-NH2. The shape of cathode voltammograms changes for this thiol when passing from basic to ClO4– and Сl– medium, possibly owing to a change in the degree of protonation of the amino group.