Preparation of MulticolorRoom-Temperature PhosphorescenceCarbon Dots by Changing the Conjugation Degree of Precursors for InformationEncryption

Room temperature phosphorescence (RTP) materials have attracted considerable attention, because of their outstanding properties and a wide array of potential applications. However, achieving control over the emission color of RTP materials still presents certain challenges. In this article, carbon dots (CDs) of three distinct colors were synthesized through a simple host–guest doping strategy. Blue CDs (B-CDs) were obtained by using phenylboronic acid as guest phosphors and B₂O₃ as host protect matrix, achieving an ultralong lifetime (up to 1.597 s). Under 254 nm light excitation, blue RTP for 14 s of B-CDs can be visually observed. By increasing the conjugation degree of the precursor molecules and introducing 4-(1-naphthyl) naphthalene-1-boronic acid and pyren-1-ylboronic acid as guest phosphors, green CDs (G-CDs) and red CDs (R-CDs) were obtained, respectively. Theoretical calculations and band gap analyses suggest that larger conjugated structures can reduce the HOMO–LUMO energy level difference, thereby causing a redshift in emission wavelength. Last, these multicolor CDs composite were applied for information encryption.