Temperature response TADF/ RTP dual mode afterglow of carbon dots and flake C3N4 composites for information encryption and advanced lighting

TADF emission based on CD materials has inspired extensive attention in recent years. Herein, CD composites with afterglow color temperature-responsive were prepared by confining BCDs/ BPCDs in a g-C3N4 matrix. The covalent bonds extensively protect the triplet states and promote the ISC process, and the small △EST is sufficient to encourage the RISC process. At room temperature, the BCD composite exhibits a deep blue TADF emission, and the BPCD composite shows two TADF emission peaks in the blue-green region. BCD/ BPCD composites exhibit RTP emission at lower temperatures, and the competition between TADF and RTP leads to the color temperature-responsive properties in these composites. A simple concept of information encryption was developed to demonstrate the great potential of these composites in advanced security applications. Based on the high overall quantum yields (44 %) and broad full width at half maximum (over 140 nm) at the visible region of the BPCD composites, they are successfully applied to develop the single component fluorescence/ TADF dual-emission delay WLED with CIE coordinates and CRI of (0.32, 0.34) and 92. This work provides a new strategy for producing CDs-based TADF materials and may motivate CDs TADF materials applied in information encryption and advanced lighting application.