Inorganic Salt Incorporated Solvothermal Synthesis of Multicolor Carbon Dots, Emission Mechanism, and Antibacterial Study

Enriching the synthetic routes of functionalized carbon dots (C dots) and expanding their application are necessary for promoting research into carbon-based nanomaterials. In this study, we develop a one-step and efficient method to prepare excitation-dependent multicolor emissive carbon dots (M-C dots) with quaternary ammonium functional groups via a solvothermal reaction of chloroform, diethylamine, and ammonium carbonate. Through detailed structural characterizations and further reactions of surface functional groups (such as reduction, oxidation, and hydrolysis) on M-C dots, the excitation-dependent tunable photoluminescence behaviors are proposed to come from the multiple emission domains on the surface. The prepared M-C dots possess antibacterial activity against Gram-positive bacteria and Gram-negative bacteria. And the antibacterial effects of M-C dots were investigated by destroying the bacterial cell walls/membranes via strongly electrostatic interactions between positively charged M-C dots and negatively charged bacteria. This study provides a novel strategy to prepare functionalized C dots and reveals the nature of intrinsic multicolor emission of C dots.