Construction and Multifunctional Applications of Visible-Light-Excited Multicolor Long Afterglow Carbon Dots/Boron Oxide Composites

Compared to ultraviolet light, visible light as an excitation light source has lower phototoxicity and deeper penetrability. This is of importance to explore the application of long afterglow materials with visible light as the excitation wavelength. In this work, multicolor long afterglow materials excited by visible light were prepared by embedding carbon dots (CDs) in boron oxide (B₂O₃) and the formation of carbon–boron bonds, and the glassy state of B₂O₃ during the heating process protected the triplet excitons from being quenched, thereby promoting the emission of long afterglow. In addition, some CDs/B₂O₃ composites show dual-mode afterglow emission with thermally activated delayed fluorescence (TADF) and room-temperature phosphorescence (RTP) at the same time. These as-designed multicolor CDs/B₂O₃ composites exhibit a long lifetime of 445.9 ms, a high afterglow quantum efficiency of 17.61%, and high stability. Meanwhile, the afterglow can be observed at room temperature by the naked eye and lasts for several seconds when the visible light is just switched off. These as-obtained CDs/B₂O₃ composites with visible-light-excited multicolor long afterglow emission have shown potential in reversible ratiometric temperature sensing, latent fingerprint identification, information anticounterfeiting, and encryption.