A Universal Strategy for Preparing Carbon Quantum Dots Based Composites with Blue and Green Afterglow Luminescence

Afterglow materials, such as room temperature phosphorescence (RTP) or delayed fluorescence (DF) materials, have been paid more attention for its unique optical properties and great potential applications. However, most afterglow materials currently studied such as metal-containing composite luminescent material have certain biological toxicity. Carbon quantum dots (CQDs), with excellent optoelectronic and tunable optical properties have become a kind of environmental-friendly nano luminescent materials because of low toxicity and good biocompatibility. Recently, the afterglow properties of CQDs have attracted significant interest. Nevertheless, afterglow CQDs still face challenges such as color-tunable afterglow and easy quenching in aqueous environments. Here, we have proposed a universal strategy for dispersing CQDs into cyanuric acid (CA) to prepare CQDs-CA composites, which simultaneously exhibit dark-blue DF and blue RTP (after 254 nm excitation), and green RTP (after 365 nm excitation). The afterglow lifetimes exceed 1s. Even in extreme conditions (pH=1 or 14), the afterglow in the aqueous solution still persists. The excellent afterglow properties and good stability make CQDs-CA a promising material for fingerprints and advanced anti-counterfeiting.