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.