High-temperature annealing enabled iridium oxide nanofibers for both non-enzymatic glucose and solid-state pH sensing

As a new class of multifunctional material, high-temperature annealing enabled iridium oxide nanofibers (IrO₂ NFs) were synthesized and then employed as the sensing element to fabricate a novel dual glucose and pH sensor in this study. The as-prepared IrO₂ NFs were systematically characterized using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy, while the electrochemical and electrocatalytic performance of the IrO₂ NFs based dual sensor toward pH and glucose sensing were evaluated using open circuit potential, cyclic voltammetry and amperometric techniques, respectively. The IrO₂ NFs not only possess good and reversible pH sensitivity as expected, but also demonstrate the electrocatalytic activity toward glucose which was presumably attributed to the crystallinity enabled by high-temperature annealing effect during the preparation of IrO₂ NFs. This unique dual functionality enables us to develop a sensor which can be applied for both non-enzymatic glucose and solid-state pH sensing. The experiment results show that the IrO₂ NFs based dual sensor exhibits a Nernst constant close to a theoretical value with excellent reversibility in pH titration, while it also possesses a sensitivity of 22.22 μA mM^-1 cm⁻², a limit of detection of 2.9 μM (S/N = 3), and good selectivity against various interferents in non-enzymatic glucose detection. Its good accuracy for detecting glucose in human serum sample was also demonstrated by comparing to commercial glucose meter. All these features indicate that the high-temperature annealed IrO₂ NF is a promising multifunctional sensing material in the development of an integrated solid-state pH sensor and non-enzymatic glucose sensor.