Dual-Functional Nitrogen-Doped Carbon Dot/Copper Oxide Nanocomposites for 2 Electrochemical Sensing of Ascorbic Acid and Antimicrobial Applications

Antimicrobial resistance poses a growing threat to effective infection treatment, while imbalances in ascorbic acid (AA) levels are linked to various health issues. Nanotechnology offers innovative solutions, with carbon dot-based nanocomposites emerging as promising materials for both antimicrobial applications and sensitive detection of biomolecules. This study aimed to synthesize nitrogen-doped carbon dots (NCDs), copper oxide nanoparticles (CuO NPs), and their nanocomposites (CuO-NCDs), and to evaluate their electrochemical sensing of AA and antimicrobial activity. NCDs were prepared via pyrolysis of citric acid and urea, and CuO NPs by precipitation of copper nitrate. Characterization by UV-Vis, FT-IR, XRD, and SEM confirmed their optical properties, functional groups, crystallinity, and morphology. The CuO-NCD nanocomposite exhibited enhanced optical absorption with a reduced energy band gap (2.6 eV) compared to individual components. Electrochemical tests revealed a detection limit of 2.56 μM for AA and increased electrode surface area, indicating improved sensitivity and selectivity. Antimicrobial assays showed significant activity against Staphylococcus aureus, with a 24 mm inhibition zone at 200 mg/mL after 24 hours. These results demonstrate that CuO-NCD nanocomposites hold potential as dual-function materials for effective AA detection and combating microbial infections.