Controllable Afterglow Emission of Single-Mode to Dual-Mode Carbon Dot Composites through Matrix Ratio Adjustment

Room temperature afterglow materials have received widespread attention and application in anti-counterfeiting, imaging, and other fields, but the many shortcomings of traditional afterglow materials in terms of cost, environment, and synthesis methods have limited their development. In contrast, carbon dot materials have attracted more and more research due to their numerous advantages and great potential for development. However, the preparation of carbon dot materials with phosphorescence and delayed fluorescence afterglow emission capabilities remains a difficult task. In this study, a series of long life afterglow carbon dot composites with single-mode and dual-mode afterglow emission were successfully prepared by inserting carbon dots synthesized from glucose and glycine into boric acid matrix through a two-step hydrothermal method. This series of carbon dot composites has achieved a transformation from single-mode phosphorescent emission to unique dual-mode afterglow emission, allowing for efficient environmental response color modulation. The composites display different afterglow emissions dominated by either phosphorescent or delayed fluorescence at different temperatures. Based on their excellent temperature sensitivity, a single-mode long phosphorescence with a lifetime of 1.62 seconds was achieved at low temperature. In summary, we have discovered a convenient and efficient method to achieve dual-mode emission by adjusting the matrix proportion. A two-step hydrothermal method synthesized dual-mode afterglow carbon dots (CDs) from glucose, glycine, and boric acid. Varying the CDs to matrix ratio achieved a shift from green phosphorescence (261.2 ms lifetime) to cyan phosphorescence (525 nm) and blue delayed fluorescence (440 nm), with a 249.16 ms lifetime, offering a strategy for dual-mode emission tuning. image