Bio-inspired conjugation inheritance of ultra-narrow bandgap carbon quantum dots for efficient surface photothermal conversion and triple-synergistic interfacial antibacterial therapy

The disordered carbon skeletons and broad bandgaps of conventional carbon quantum dots (CQDs) severely restrict their near-infrared (NIR) harvesting and surface energy conversion efficiencies. Inspired by tea polyphenols “oxidative polymerization gradient”, a “conjugation inheritance” strategy was proposed, which could atomic-level tune the energy band structure of CQDs via precursor conjugated degree. The results indicate that CQDs prepared from highly polymerized tea theabrownins (TB-CQDs) effectively retain the large conjugated system of the precursor, exhibiting a highly quasi-graphitic surface structure and an ultra-narrow band gap (0.835 eV). This optimized electronic structure endowed TB-CQDs with outstanding near-infrared absorption, achieving 66.4% photothermal conversion efficiency and enhanced reactive oxygen species generation at the nanoscale interface. The complete elimination of S. aureus and Escherichia coli was achieved through the triple synergy mechanism of “chemical - photothermal – photodynamic”. Leveraging their amphiphilic surface properties, TB-CQDs functioned as a highly versatile phototherapeutic platform across diverse interfaces. It facilitated the formulation of a solvent-free aqueous nano-coating for the preservation of abiotic fruits, and acted as a biosafe agent promoting tissue regeneration in skin infection without systemic toxicity. This study provided deep insights into how precursors dictate the final surface electronic states, bandgap and interfacial photothermal performance of carbon nanomaterials.