Long organic persistent luminescence triggered by photo-induced charge-separation for water-resistant information encryption

The long persistent luminescence (LPL) phenomenon in the water environment presents us with a broad blueprint to struggle for a new generation of optical materials. However, the realization of water-resistant LPL remains a formidable challenge due to severe quenching of triplet excitons inflowing media. Here, an electron donor–acceptor system is designed based on a B2O3 host and carbon dot (CD) guest, which exhibits deep-blue LPL with a lasting time of about 21 s to the naked eye. The average LPL lifetime is over 2 s, and the LPL quantum yield is 10.78%. This host–guest system possesses charge-separated states and charge-transferred states triggered by an optical source, which is the foundation for LPL. Importantly, in water environments (HCl, NaOH, electrolyte NaCl, and H2O), the LPL of as-obtained CDs@B2O3 can still remain due to high environmental stability of B₂O₃. Based on the excellent LPL with ultra-long lifetime and water-resistant feature, the CDs@B₂O₃ successfully applies in water-resistant information encryption.