Diazonium Electrografting vs. Physical Adsorption of Azure A at Carbon Nanotubes for Mediated Glucose Oxidation with FAD‐GDH

Abstract The electrochemical reduction of aryldiazonium salts is a versatile and direct route to obtain robust covalently modified electrodes. We report here a comparative study of Azure A modified carbon nanotube electrodes prepared by diazonium electrografting and by physical adsorption for bioelectrocatalytic glucose oxidation with fungal FAD‐glucose dehydrogenase from Aspergillus sp . The electrografted and adsorbed electrodes exhibited different reversible electroactivity consistent with polymer‐type and monomer‐type phenothiazine surface assemblies, respectively. The electrografted Azure A electrodes exhibited superior mediated bioelectrocatalysis compared to the adsorbed Azure A electrodes. A more than 10‐fold higher catalytic current up to 2 mA cm −2 at 0.2 V vs . Ag/AgCl together with a similarly low onset potential of −0.05 V vs . Ag/AgCl was observed at the electrografted electrodes. Faster estimated electron transfer kinetics and a +200 mV potential shift for the polymer‐type redox couple vs . the adsorbed monomer‐type couple underlines the favourable driving force for mediated electron transfer with the buried FAD active site for the diazonium‐derived bioelectrode.