A Universal Strategy for Activating the Multicolor Room-Temperature Afterglow of Carbon Dots in a Boric Acid Matrix

Carbon dots (CDs) have attracted attention in metal-free afterglow materials, but most CDs were heteroatom-containing and the afterglow emissions are still limited to the short-wavelength region. A universal approach to activate the room-temperature phosphorescence (RTP) of both heteroatom-free and heteroatom-containing CDs was developed by one-step heat treatment of CDs and boric acid (BA). The introduction of an electron-withdrawing boron atom in composites can greatly reduce the energy gap between the singlet and triplet state; the formed glassy state can effectively protect the excited triplet states of CDs from nonradiative deactivation. A universal host for embedding CDs to achieve long-lifetime and multi-color (blue, green, green-yellow and orange) RTP via a low cost, quick and facile process was developed. Based on their distinctive RTP performances, the applications of these CD-based RTP materials in information encryption and decryption are also proposed and demonstrated.