Dynamic Afterglow Crossover in Triple-Doped Carbon Dots for Dynamic Encryption and Bioimaging

High Resolution Image Download MS PowerPoint Slide Nanomaterials with multimode afterglow are highly valuable for advanced dynamic encryption, as their persistent photoluminescence with time-varying chromaticity enhances decryption complexity. Here, we report the hydrothermal synthesis of dual-mode afterglow carbon dots (CDs) using dansylamide as the carbon source and hydrochloric acid as the catalytic agent. Chemical and morphological analyses revealed that the resulting CDs (CD-DSA) are triple-doped with nitrogen, sulfur, and chlorine. Thermal analysis showed that CD-DSA exhibits persistent photoluminescence even in liquid media, where thermally activated delayed fluorescence (TADF) occurs due to the small energy gap between triplet and singlet excited states. When applied as an aqueous ink on paper, CD-DSA exhibits persistent emission with the emergence of room-temperature phosphorescence (RTP). Our results demonstrate a dynamic crossover from TADF to RTP as the dominant afterglow mechanism, characterizing a thermochromic luminescence exploitable for high-level security encryption. Moreover, live-cell staining showed preferential accumulation in intranuclear foci without compromising cell viability, highlighting the potential of CD-DSA as a bioimaging probe.