Defect-engineered lignite-derived carbon/NiCo2O4 interfaces enable oxygen-vacancy-mediated nonenzymatic glucose sensing in serum samples

Abstract

The development of robust materials for nonenzymatic glucose sensing remains challenging due to material cost, instability, and limited mechanistic understanding. Moreover, many existing reports lack validation using real samples, making their real-world applicability uncertain. We report a novel defect-engineered interface composed of spinel nickel cobalt oxide and lignite-derived porous carbon (NCO/LC). The engineered carbon–oxide interface induces oxygen-vacancy-rich active sites, promoting rapid redox kinetics and electrocatalytic glucose oxidation. Initial electrochemical characterization was performed using a glassy carbon electrode (GCE) to establish the sensing mechanism, followed by successful translation to a screen-printed electrode (SPE) for practical validation and real sample analysis. The NCO/LC-modified GCE exhibited a high sensitivity of 2564.63 µA cm−2 mM−1 and a limit of detection (LOD) of 1.23 µM, while the NCO/LC-modified SPE yielded a sensitivity of 660.27 µA cm−2 mM−1 and a LOD of 9.6 µM. The enhanced performance is attributed to the synergistic coupling between mixed-valence Ni2+/Ni3+ and Co2+/Co3+ redox centers and the conductive, defect-rich carbon framework. Furthermore, the NCO/LC-modified SPE was evaluated for glucose quantification in rat blood serum, with the results highlighting the influence of the biological matrix on the analytical response. This work establishes a sustainable, waste-to-functional strategy for engineering defect-rich carbon–oxide nanozyme interfaces and demonstrates their potential for portable, point-of-care glucose sensing in complex biological matrices.