Facial preparation of electrochemically stable NiO/ZnO hybrid electrode exhibiting excellent redox activity for enhanced glucose detection

Abstract

A composite structure of three-dimensional NiO over the ZnO nanorod/Ni foam scaffold was fabricated via hydrothermal synthesis and rare-gas calcination. The strong bonding of NiO with high electron mobility ZnO improved its electrochemical activity and stability. The heterojunction's excellent redox activity attributed to the band-edge potentials of ZnO (CB: −0.72 eV and VB: 2.36 eV) and NiO (CB: −1.136 eV and VB: 2.54 eV). The heterostructure exhibited wide detection range (0.01–5.6 mM), outstanding sensitivity (1382 µA∙mM−1∙cm−2), low detection limit (28 µM), and fast response (4 s) as a glucose-sensing electrode. The built-in electric field at the heterojunction facilitated the charge transfer process from NiO to the electrode, while the large electrochemically active surface area (44.32 cm2) enabled greater availability of active sites, resulting in faster response and higher sensitivity. The heterostructure showed excellent selectivity towards glucose and effectively responded to the glucose concentration in saliva, establishing its suitability for noninvasive glucose monitoring.