Several studies have demonstrated the efficiency and speed of using redox-induced ion-pairing interactions to deposit charged (macro)molecules and colloidal particles from aqueous solution onto ferrocene-terminated self-assembled monolayers (SAMs) on gold electrodes. Depending on the chemical system, the deposition can be reversible or irreversible. The relative roles of the molecular scaffold and the charged functional group in controlling the reversibility of the surface assemblies are unclear. To address the role of specific ion effects, we investigate the interfacial electrochemistry of ferrocenylalkanethiolate SAMs in aqueous solutions of sodium salts of anionic surfactant amphiphiles with a fixed decyl chain and different headgroups: sulfate, sulfonate, carboxylate, and phosphonate. Pairing of the surfactant anions with the electrogenerated ferrocenium-terminated SAM surface and their aggregation at the SAM/aqueous interface was followed in situ by electrochemical surface plasmon resonance (ESPR). Ex situ atomic force microscopy (AFM) imaging was used to verify the presence of irreversibly adsorbed surfactant on the SAM surface after removal of the applied potential and rinsing the SAM surface with deionized–distilled water. Binary SAMs composed of ferrocenylalkanethiolate and hydroxyl- or methyl-terminated alkanethiolate were used to investigate the influence of surface hydrophobicity on surfactant deposition. The findings of this work identify factors that influence the reversibility of the redox-controlled interfacial deposition of materials and inform the rational design of temporary versus stable surface assemblies.
Guérin et al. (Fri,) studied this question.