Eco-Friendly Carbon Dots Exhibiting Aqueous-Stable Room-Temperature Phosphorescence for Anti-Forgery and Information Hiding

Carbon dots (CDs) with room-temperature phosphorescence (RTP) characteristics have drawn considerable attention because of their broad applications in various area. However, achieving water-soluble RTP CDs remains highly challenging owing to the severe phosphorescence quenching effect caused by dissolved oxygen in aqueous solutions. Herein, a realizable strategy of attaining long-lifetime and high stability RTP CDs-based composites in aqueous solutions is proposed via constructing a rigid hydrogen-bonded network. The synthesized composites display an ultra-long phosphorescence lifetime of 1.38 s in solid state and 316 ms in aqueous phase. Moreover, the RTP emission remains visible to naked eye for up to 10 s even under strongly acidic or alkaline conditions. TEM, XRD, FT-IR, and XPS analyses confirmed the successful conjugation of cyanuric acid (CA) with carbon dots (CDs) which the rigid CA framework effectively restricted the chromophore vibrations and rotations, minimizing non-radiative recombination of triplet excitons. Finally, applications of CDs in screen printing, anti-counterfeiting and information protection were explored.