UV/visible light dual-mode excitable multicolor room-temperature afterglow of carbon dots embedded in matrixes

Host-guest systems of carbon dots (CDs) embedding in matrix with room-temperature afterglow (RTA) are of great importance for various applications, but so far rather limited due to relaying on high-energy ultraviolet (UV) excitation, monochromatic afterglow emission, or harsh synthesis. Herein, PTA materials (PASP@BA) with UV/visible light dual-mode excitation are prepared via one-step heat treatment of polyaspartic acid (PASP) and boric acid (BA). The RTA colors of PASP@BA display a significant bathochromic shift from blue to yellow as the excitation wavelength increases from 254 to 420 nm under ambient condition. Impressively, the visible-light-activated ultralong RTA can last for about 7 s by naked eye under ambient conditions. By correlating photophysical properties with structural characterization results, it is concluded that the polycrystalline boron oxide matrix and covalent B–C bonds can effectively suppress non-radiative transitions and stabilize the triplet excited state of CDs by restricting molecular motion and isolating environmental quenchers, thus facilitating the generation of long afterglow. More interestingly, the afterglow color can be also tuned by dynamic varying in B–C bond density and CDs dimensions. Finally, practical applications of such photo-responsive systems in multi-level information anti-counterfeiting and encryption are further demonstrated.