Nitrogen-Enriched Sulfur-Functionalized Reduced Graphene Oxide Nanosheets for Non-Enzymatic Uric Acid Sensing and Supercapacitor Application

Abstract Reduced graphene oxide (RGO) was functionalized with nitrogen-enriched sulfur-containing groups via a facile and cost-effective hydrothermal approach to enhance the electrochemical performance of RGO nanosheets. The crystallinity, morphology, and chemical composition of obtained nitrogen-enriched sulfur-functionalized reduced graphene oxide (NESRGO) was investigated using X-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy, and X-ray photoelectron spectroscopy. The electrochemical investigation of NESRGO with higher electronegativity and improved electrical conductivity yielded a superior oxidation current of 52 µA towards uric acid (UA) than nitrogen sulfur-functionalized reduced graphene oxide (NSRGO) (30 µA) and RGO (21 µA). The NESRGO-modified electrode showed high sensitivity (826.25 µA mM-1 cm-2), a detection limit of 4 µM, and good stability (relative standard deviation of 3.69%). Moreover, the high selectivity of the developed UA sensor in the presence of other electroactive interferents and excellent recovery rates between 99.29% and 110.40% in human serum demonstrated the applicability of the sensor in clinical diagnosis. Finally, the NESRGO-modified carbon cloth electrode applied as a supercapacitor exhibited a specific capacitance of 70.23 F g-1 and excellent cycle stability, with 109.7% retention over 2,500 cycles. The results highlight the NESRGO's potential in UA sensing and energy storage devices.