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 solution composition on the desorption behavior of self-assembled monolayers of alkanethiols with approximately the same chain length but different terminal groups of thiols (R: –CH₃, –CH₂OH, and –NH₂). The hydrophilic properties of the terminal groups for the studied thiols increased in the –CH₃ \( \ll \) –NH₂ ≤ –CH₂OH series. It is found that the anionic and cationic composition of electrolyte affected significantly the electrochemical stability and blocking ability of self-assembled monolayers of thiols with different terminal groups. It is established that the electrochemical stability and blocking ability of the self-assembled monolayers decreased in the Li⁺, Na⁺, K⁺ series in alkaline solutions regardless of the thiol terminal group. The cation nature in perchlorate and chloride solutions manifested itself only for thiol with the –NH₂ terminal group. The shape of cathodic voltammograms changed for this thiol when passing from alkaline to \({\text{ClO}}_{4}^{ - }\) and Сl^– medium, possibly owing to a change in the amino group protonation degree.