Boric acid-derived rigid matrix confined synthesis of m-phenylenediamine-based ultralong room-temperature phosphorescent carbon dots for dynamic information anti-counterfeiting

Room-temperature phosphorescent carbon dots (RTP-CDs) exhibit exceptional biocompatibility and tunable luminescence but are limited by short lifetimes and exciton quenching. Herein, we develop a one-step pyrolysis strategy using m-phenylenediamine and boric acid to fabricate boron-doped RTP-CDs (M-CDs) with ultralong green afterglow (16 s) and extended lifetime (37.03 ms). The rigid polycrystalline boron oxide matrix effectively confines molecular motion, isolates quenchers, and stabilizes triplet excitons, while boron doping reduces the singlet-triplet energy gap (ΔE ST  = 0.206 eV) to promote intersystem crossing (ISC). Further heavy-atom doping (Cl/Br) enhances spin-orbit coupling, boosting afterglow to 18 s and lifetime to 41.16 ms, whereas iodine disrupts the matrix. Leveraging tunable afterglow dynamics, we demonstrate dynamic information encryption with visible/UV-switchable patterns. This work provides a cost-effective route to high-performance RTP-CDs and clarifies synergistic regulation mechanisms for advanced optoelectronic applications.