Biomass-Derived Boron-Doped Carbon Quantum Dots with Tunable Electronic Structure and Enhanced Bioactivity: A...

Boron-doped carbon quantum dots (B-CQDs) have been synthesized via a sustainable hydrothermal method using banana peel biomass and boric acid as precursors. Uniform spherical dots with an average size of 2 nm after doping have been revealed through an electron microscope. Optical studies showed a red shift in absorption and photoluminescence peaks. Tauc's plot revealed band gap reduction from 2.73 eV (CQDs) to 2.33 eV (B-CQDs) after boron incorporation due to the modification in the electronic structure. The doped CQDs exhibit enhanced electrochemical capacitance (78 F g-1 at 0.5 A g-1) and improved antibacterial efficiency against Escherichia coli with MIC values of 3.0 mg mL-1. They also maintained excellent cytocompatibility, with over 90% cell viability in the 3T3-L1 fibroblast cell line. DFT simulations supported the experimental findings by revealing that asymmetric boron doping introduces defect states near the Fermi level, thereby reducing the HOMO-LUMO gap. Both experimental and theoretical analysis indicate that boron incorporation alters the electronic configuration. The synergy between green hydrothermal synthesis and electronic modification highlights B-CQDs as eco-friendly nanomaterials for bioelectronic and antimicrobial applications.