Afterglow of carbon dots regulated by the solvent effect for temperature sensing and anti-counterfeiting

Afterglow carbon dots have attracted a lot of attention due to their unique advantageous properties, such as high sensitivity and resistance to interference from background light. However, achieving dual-mode afterglow emission from the single-mode afterglow of carbon dots remains a challenge. Here, we achieved the induction of a carbon dot afterglow emission mode through solvent effects. In this method, boric acid is used to construct a rigid plane to suppress the non-radiative transition of triplet excitons, and the afterglow of carbon dots can be changed from dual-mode emission, to single-mode emission to no afterglow emission under H₂O, DMF and MeOH environments during the synthesis. Notably, the solvent contains different hybrid forms of the nitrogen element, which have different effects on the delayed fluorescence: sp² hybrid nitrogen causes the delayed fluorescence to disappear and sp hybrid nitrogen induces a slight increase in delayed fluorescence. Meanwhile, doping with N effectively improves the quantum yield of CDs@BA. Finally, carbon dots with different afterglow properties were obtained in different solvent environments and applied in temperature sensing and anti-counterfeiting. This work provides a design idea and a feasible strategy to construct carbon dots with different afterglow properties.