Visible-Light-Excited Room-Temperature Phosphorescent Carbon Dots via Surface Amination in a Microreactor for Multimode Anticounterfeiting

Carbon dots (CDs) with a long-lifetime room-temperature phosphorescence (RTP) have received considerable attention but still remain a great challenge, especially for synthesizing visible-light-excited RTP CDs. Until now, most studies have applied isolated and chromophorous reactants to achieve visible-light-excited RTP CDs. Therefore, those strategies to modulate the excitation wavelength are not referential or reproducible. Herein, surface amination and combination with boric acid (BA, H 3 BO 3 ) of CDs are applied to build long-lifetime RTP, which drives excitation light from the ultraviolet (UV) area to the visible area and gives out excitation-related afterglow. Meanwhile, surface amination promotes the intersystem crossing process, increasing the quantum yield to 18.63%. After removal of excitation light, the afterglow time visible to naked eyes can reach 10 s, with a phosphorescence lifetime of 453 ms. Furthermore, time-dependent density functional theory (TDDFT) explained the differentiated influence of surface amination on the triplet state and singlet state, which benefits the idea of realizing a wider region for excitation. Based on the above features, CDs@BA are applied in encryption with different excitation wavelengths in the advanced anticounterfeiting security field.