Synthesis, characterization and evaluation of the structural, electronic and antioxidant properties of biogenic carbon nitride nanoparticles

This study reports the green synthesis of biogenic carbon nitride nanoparticles (CN) derived from seed coat of Lablab purpureus and evaluates their antioxidant and neuroprotective potential. The synthesized CN were characterized for their structural and surface properties using UV–vis, XRD, FTIR, SEM-EDS, DLS and XPS techniques. The nanoparticles were spherical in morphology with sizes in the range of 90–120 nm, and exhibited enhanced antioxidant activity of IC 50 at 43.92 ± 0.8 ug/ml. Assessment of invitro cytotoxicity on SH-SY5Y cells showed minimal cytotoxicity with a cell viability of 86.54 ± 2% at 125 µg/ml. Furthermore, treatment with CN nanoparticles significantly protected oxidatively stressed SH-SY5Y cells, with cell viability of 79.05 ± 1.16% at 3.125 µg/ml. To gain mechanistic insights of the radical-quenching activity of the novel CN, density functional theory (DFT) calculations were employed on heptazine, and their hydroxylated fragments representing the novel CN structure. The hydroxylated model, M2 displayed comparatively favorable electronic characteristics. It showed the maximum Highest Occupied Molecular Orbital (HOMO) value of −6.21 eV and the minimum HOMO-LUMO gap of 4.63 eV, indicating enhanced electron donating ability. These computational results agree with characterization results confirming the formation of defect rich, hydroxyl-functionalized carbon nitride nanoparticles. Overall, the combined experimental and computational findings show that novel nanoparticle have the potential to mitigate neuronal oxidative stress. Schematic representation of green synthesis of hydroxyl functionalized novel biogenic carbon nitride nanoparticles which exhibit enhanced antioxidant activity. DFT studies of the heptazine based functionalised models reveal reduced band gap and enhanced electron donation, efficient ROS scavenging capacity, thus explaining its antioxidant property and neuroprotective potential in SH-SY5Y cells under H 2 O 2 induced oxidative stress. • Green synthesis of biogenic carbon nitride nanoparticles from Lablab purpureus seed coat. • Structural and electronic characterization confirming hydroxyl-functionalized g-CN framework. • Strong antioxidant activity with IC₅₀ of 43.92 ± 0.8 µg/ml. • DFT analysis reveals enhanced electron donation and reduced band gap in functionalized models. • Cytoprotective effects against H₂O₂-induced oxidative stress in SH-SY5Y cells.