Nitrogen and Boron Co-Doped Graphene Oxide Quantum Dots: Top-Down Fabrication, Comprehensive Characterization and...

Herein, we present the synthesis of three types of graphene oxide quantum dots (GOQDs) having different dopants, namely, nitrogen and boron. Doped GOQDs were successfully synthesized via a one-step top-down hydrothermal treatment of graphene oxide in the presence of H₂O₂ and appropriate dopant precursors. The nanoparticles were characterized using TEM, XPS, UV-vis, and photoluminescence spectroscopy. The applied strategy provides a reproducible route to anisotropic nanoparticles with heights in the range of 1.0-1.5 nm and lateral sizes in the range of 7-10 nm, with a well-defined graphenic structure of the core and defined compositional and optical characteristics, highlighting the advantages of top-down approaches over bottom-up methodologies for systematic structure-property investigations. XPS analysis demonstrated nitrogen incorporation into the graphenic lattice of all studied GOQDs, primarily in pyrrolic and graphitic forms, whereas the introduction of boron through boric acid or 3-aminophenylboronic acid predominantly affected edge functionalities. Biological evaluation revealed a pronounced dependence of antibacterial activity on GOQD composition. Among the three materials, nitrogen-doped GOQDs exhibited broad-spectrum bactericidal activity against the ESKAPE-(E) panel, with a particularly low MBC of 8 μg/mL against Staphylococcus aureus. Boron- and nitrogen-co-doped GOQDs exhibited pronounced bacteriostatic activity against S. aureus within the concentration range of 100-4 μg/mL. Cytotoxicity assays using HaCaT keratinocytes demonstrated that N-GOQDs combine effective antibacterial performance with excellent cytocompatibility, achieving bacterial eradication at concentrations that remain entirely nontoxic to human skin cells. The results provide clear structure-activity insights and position N-GOQDs as a promising platform for developing next-generation antibacterial nanomaterials targeting multidrug-resistant ESKAPE pathogens.