Defect Engineering via Aggregation: Unlocking Hour-Long Afterglow and UV Thermoluminescence in Self-Embedded Carbon Nitride Quantum Dots.

Carbon nitride quantum dots (CNQDs) exhibiting aggregation-induced visible long persistent luminescence (LPL), ultraviolet (UV) high-temperature afterglow (HTA), and thermoluminescence (TL) are reported for the first time. The CNQDs are synthesized via a facile solvent-free thermolysis of biuret and display a blue LPL lasting over 1.5 h under ambient conditions. Upon heating to 150°C, intense UV HTA and TL emissions are generated. Mechanistic studies reveal that aggregation-associated π-π stacking stabilizes triplet excitons, while aggregation-stabilized defect-related paramagnetic centers promote carrier capture and long-term energy storage, with deeper traps serving as reservoirs for thermally activated release. Reverse intersystem crossing further transfers de-trapped carriers from triplet to singlet excited states, resulting in a pronounced blue-shift of the HTA and TL emissions into the UV region. Owing to the stability of the aggregates and their protective effect on excited states and trapped charges, the luminescence remains robust in aqueous dispersions, while the invisible UV TL signals remain clearly detectable after more than 15 days under ambient conditions. Leveraging these characteristics, we demonstrate applications in highly concealed information storage and high-contrast bioimaging. This work establishes an aggregation-induced defect-engineering strategy for energy-storage luminescent materials and opens a new pathway toward self-embedded LPL/TL systems.