Methionine-assisted electrodeposition of porous copper cobalt bi-metallic hetero-nanostructures on an indium tin oxide electrode: a disposable and stable electrode for non-enzymatic glucose sensing

Abstract

Herein, we present the biomolecule-assisted electrodeposition of copper–cobalt bimetallic hetero-nanostructures (h-NSs) on an indium tin oxide (ITO) electrode as a highly sensitive and disposable glucose-sensing electrode. Generally, transition metal-based hydroxide/oxy-hydroxide films electrodeposited on ITO electrodes are unstable and easily peel off from the electrode surface during electrocatalysis. To address this issue, especially for ITO and FTO (fluorine-doped tin oxide) like glass-based electrodes (smooth-surfaced), post-electrodeposition high-temperature calcination is the main strategy to form stable modified electrodes. However, in the present work, we found a very facile method to make extremely stable electrodeposited films on the ITO electrodes using the thiol-functionalized amino acid methionine without any high-temperature heat treatment or external binder. Methionine was found to play multiple roles such as a structure directing agent, stabilizing agent and mainly tuning the composition of electrodeposited films. The mechanism for methionine's role in composition tuning is discussed in detail. Further, the prepared binder-free electrodes were successfully utilized for glucose electrooxidation and sensing. The designed glucose sensor showed very high sensitivity (1418 μA mM⁻¹ cm⁻²) and selectivity towards glucose with the lowest detection limit of 9.1 μM and a detection range of 20 to 1640 μM. Notably, the glucose electrode exhibits excellent reproducibility, repeatability, long-term stability and practical applicability. Its electroanalytical performances are superior/comparable to many previously reported results. Importantly, this work opens a new route for the direct and stable fabrication of ITO-based modified electrodes at room temperature for photo-electrocatalysis, electrocatalysis and other electrode applications.