Self-assembly of catecholic ferrocene and electrochemical behavior of its monolayer

Abstract

Self-assembly of catecholic ferrocene was studied on different surfaces. The self-assembly kinetics of Fc-terminated (Fc-dopamine) self-assembled monolayers (SAMs) and their stability have been studied and characterized using atomic force microscopy (AFM) and cyclic voltammetry (CV), respectively. AFM images have revealed that the self-assembly process of Fc-dopamine molecules on a mica surface follows the systematic increase of surface coverage with assembly time until a closely packed density is reached. The redox behavior of the Fc-dopamine monolayer in NaClO₄ electrolyte solutions was characterized using CV, and the stability of the Fc-dopamine SAMs on an Au surface at different pH values and voltages was evaluated. CV results show that the Fc-dopamine SAMs are stable over a scan voltage range of −0.8–1.0 V under pH values lower than 11, but very rapidly destroyed above pH 11. Finally, the wetting behavior of the Fc-dopamine grafted on rough surfaces is tuned by a redox reaction of the Fc group in SAMs, which exhibits superhydrophobicity with a static water contact angle of 161° on anodized alumina surfaces, and hydrophilicity with a CA of 5° after Fc is oxidized. The work provides useful information for understanding the adhesion and deposition mechanisms of catecholic compounds on substrates.