Influence of mesoporous defect induced mixed-valent NiO (Ni^2+/Ni³⁺)-TiO₂ nanocomposite for non-enzymatic glucose biosensors

An extraordinary sensitive and selective non-enzymatic glucose sensor has been demonstrated based on the electrochemically highly stable NiO-TiO₂ mixed oxide comprising the defect induced mesoporous TiO₂ nanoparticles with Ni²⁺ and Ni³⁺ ions scattered on the surface. The defects on TiO₂ nanoparticles have been successfully introduced using NiO to investigate the interfacial properties between NiO and TiO₂. This defect induced interfacial behavior was characterized using X-ray diffraction, X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy analyses. The obtained mixed oxide NiO-TiO₂ nanocomposite dispersion was drop casted on glassy carbon electrode to form a NiO-TiO₂/GCE modified electrode for non-enzymatic glucose sensor. The defects along with high surface area of mixed oxide enabled excellent electrocatalytic activity for glucose oxidation with sensitivity of 24.85 μA mM⁻¹ cm⁻² and detection limit of 0.7 μM (S/N = 3). The Ni ions scattered on the surface of TiO₂ nanoparticles, enabling effective charge transfer process, circumventing the agglomeration during prolonged detection, and resulting the unprecedented long-term stability and sensitivity. Thus, this defect induced mesoporous metal oxide nanocomposite is an outstanding candidate for application as redox active material in electrochemical biosensors.