High Color Stability Blue-to-Violet Room Temperature Phosphorescent Carbon Dot Composites with Ultralong Lifetime for Information Encryption

Ultralong room temperature phosphorescent (RTP) materials have a wide range of applications in information encryption, bio-imaging, optoelectronics, and display and illumination. Among them, blue-emitting RTP materials with high quantum yield (QY) and ultralong luminescence have been a challenge in the field of RTP materials. Herein, we prepared blue-to-violet RTP carbon dot (CD) composites with high color stability by mixing boric acid with pyromellitic acid, trimesic acid, and terephthalic acid, separately, and pyrolyzing them at identical temperature conditions, leading to CD composites with emission peaks at 440, 407, and 430 nm, respectively. This strategy enables the precursors to effectively suppress the deactivation of the triplet state through covalent bonding (B–C bond) and hydrogen bonding interactions and confinement in a highly rigid B2O3 polycrystalline network, thereby successfully producing blue-to-violet CD composites with high QY (49, 64, and 78%, meanwhile, their phosphorescence QY can reach 47, 57, and 65%), ultralong lifetime (0.633, 1.882, and 2.332 s, respectively), and high color stability. Owing to the unique properties, the CD composites show great potential for application in the field of anti-counterfeiting and information encryption.