Synergistic boric acid crosslinking and silane engineering enable time-programmable multicolor afterglow in carbon...

Carbon dots (CDs) have emerged as promising room-temperature phosphorescence (RTP) materials for advanced anti-counterfeiting and encryption applications owing to their tunable emission and favorable biocompatibility. However, the simultaneous realization of multicolor phosphorescence, long lifetime, and dynamic color modulation within a single CDs-based system remains a significant challenge. Herein, a boric acid-crosslinked and silane-confined CDs system was constructed to investigate the roles of rigid-network confinement and the rhodamine B (RhB)-regulated phosphorescence Förster resonance energy transfer (P-FRET) in governing dynamic multicolor afterglow. Compared with the conventional aminopropyl silane (APTES)-derived network, the long-chain diamine silane (DAMO)-derived network provided additional amino sites and a rigid-flexible confinement environment, which enhanced n-π* transition processes and promoted intersystem crossing, thereby extending the phosphorescence lifetime from 106.37 to 448.87 ms. Phosphorescence spectroscopic analysis revealed that increasing the RhB content introduced low-energy acceptor centers, which enhanced the P-FRET process from CDs to RhB-related acceptors and enabled tunable afterglow emission from blue (480 nm) to red (595 nm). The shortened donor lifetime, time-resolved emission evolution, and reduced energy gap revealed by density functional theory (DFT) calculations collectively supported the T₁-S₁ P-FRET process from CD donors to RhB related acceptors. The resulting time-dependent afterglow color evolution was further demonstrated in dynamic digital encryption, multicolor QR codes, and time-resolved logic-gate anti-counterfeiting. This work provides a rational strategy for designing dynamic CDs-based RTP materials through rigid-network confinement and energy-transfer engineering.