pH-Switchable Redox Reactions and Bioelectrocatalytic Processes Using Au Nanoparticles-Modified Electrodes

Boronate ester complexes generated between methylene blue (MB⁺)-functionalized Au nanoparticles (NPs) and electrode surfaces are implemented to stimulate the bioelectrocatalyzed reduction of H₂O₂ in the presence of horseradish peroxidase (HRP). Two kinds of Au NPs are prepared: Class I includes MB⁺/phenylboronic acid as a modifying layer, whereas Class II includes MB⁺/dithiothreitol as a mixed capping layer. The Class I or II NPs form boronate ester complexes with a dithiothreitol- or phenylboronic acid-functionalized Au electrodes, respectively. By the cyclic loading of the NPs on the electrodes (pH8.1), and the removal of the NPs (pH1.5), switchable bioelectrocatalyzed reduction of H₂O₂ is demonstrated.