Presentation: 2025 ND EPSCoR Annual conference 

October 21, 2025, NDSU Memorial Union, Fargo, North Dakota

IRON AND NITROGEN CO-DOPED GRAPHENE QUANTUM DOTS AS FLUORESCENT NANOZYMES FOR NADPH DETECTION

Nanozymes are nanomaterials that mimic enzymatic functions, offering benefits like low cost, high stability, and ease of surface modification. Among these, graphene quantum dots (GQDs) are particularly promising for sensing applications due to their unique optical and electronic properties. Herein, we report on a novel GQD-based nanozyme, Fe-N4-GQDs, designed for the sensitive detection of NADPH, a crucial high-energy electron carrier. The Fe-N4-GQDs were synthesized from a hydrophilic polyethyleneimine (PEI) precursor doped with hemin under hydrothermal conditions, resulting in nanoparticles with an average hydrodynamic size of 7.1 ± 1.5 nm. Characterization including EDS, XPS and spectroscopic techniques confirmed the successful incorporation of iron and nitrogen, which is essential for its catalytic activity. The nanozyme’s ability to detect NADPH is based on a fluorescence quenching mechanism. It exhibited a high quantum yield of 60%, surpassing the quinine sulfate control. Biocompatibility studies in mouse-brain-derived microvascular endothelial cells (BMVECs) confirmed its suitability for use in both normal and metabolically distressed conditions, demonstrating strong potential for targeted applications in metabolic disease research.