Achieving efficient phosphorescence of carbon dots via a synergistic enhancement strategy for bright field anti-counterfeiting

Abstract

Phosphorescent materials that exhibit high efficiency and intensity are crucial for practical applications. In this study, we devised a novel strategy to enhance carbon dots (CDs) phosphorescence based on a crosslink-enhanced emission (CEE) and layer-by-layer self-assembly (LBL) synergistic enhancement design. The seed CDs are initially functionalized with cationic polymers on their surfaces, followed by assembly with negatively charged matrices to enhance their phosphorescence. This leads to a significant phosphorescence intensity enhancement by a factor of more than 88, enabling visual readability even in bright fields. Their lifetime is prolonged from 0.13 to 0.41 s and the maximum phosphorescence quantum yield reached up to 27.2 %. Detailed investigations revealed that CEE and LBL significantly inhibited molecular vibrations and protected the triplet excitons of CDs from oxygen quenching, enhancing phosphorescence emission. The loading capacity of the CDs in the matrix was significantly enhanced owing to the uniform dispersion induced by the electrostatic interactions between CDs and the substrate. Furthermore, we envision potential applications of these CDs for anti-counterfeiting and crack detection in bright fields.