Engineered IrO₂@NiO Core-Shell Nanowires for Sensitive Non-enzymatic Detection of Trace Glucose in Saliva

Hierarchical core-shell IrO₂@NiO nanowires (NWs) have been designed through two simple steps, which combined electrospinning of IrO₂ conductive core and chemical bath deposition growth of ultracontinuous NiO nanoflakes. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray spectrometry mapping, and X-ray photoelectron spectroscopy were employed to characterize the morphologies and structures of the as-prepared samples, and the results were also carefully compared with that of pure NiO nanoflowers and IrO₂ NWs. Electrochemical studies indicate that the as-prepared core-shell IrO₂@NiO NWs exhibited excellent nonenzymatic detection ability to glucose. At 0.35 V, it offered a sensitivity of 1439.4 μA mM^-1 cm^-2 (one order higher than pure NiO) with a wider linear range from 0.5 μM to 2.5 mM, a low detection limit of 0.31 μM (signal-to-noise ratio = 3, and moreover, good resolution in low glucose concentration, reproducibility, and long-term performance stability. Owing to the high sensitivity and performance, application of the proposed sensor in monitoring saliva glucose was also demonstrated; the results indicated that the sensor can effectively distinguish the diabetes from the healthy people and even the varying degrees of diabetic.