Monolayer of microgel particles based on poly(acrylic acid) modified with dopamine for electrochemical pH sensing

A novel electroactive and pH-responsive microgel was successfully synthesized. The obtained microgel was based on acrylic acid, dopamine methacrylamide and N,N′-bis(acryloyl)cystamine as the crosslinker. Using the distillation precipitation polymerization method, spherical, smooth-surface microgel particles of ca. 400 nm in diameter were obtained. The presence of dopamine groups in the polymer network was confirmed with cyclic voltammetry and NMR spectroscopy. The dependence of microgel hydrodynamic diameter on pH was investigated using the DLS technique. The presence of -SS- groups in the microgel particle was used to modify the Au electrode surface by chemisorption. The attachment was monitored with the QCM-D technique. The obtained microgel was successfully anchored to the Au regular- and microelectrode surfaces. The electrochemical properties of the modified electrodes were promising. It was found that modified electrodes exhibited potentially useful pH-sensing properties. Modification of Au microelectrode surface with the environmentally sensitive and electroactive microgel monolayer is a novel, innovative approach.