Lifetime-Engineered Phosphorescent Carbon Dots-in-Zeolite Composites for Naked-Eye Visible Multiplexing

Lifetime-coded optical multiplexing has attracted wide attention due to avoiding spectral overlap and background interference. At present, most of the materials used for lifetime-coded multiplexing involve rare-earth metal ions with their lifetime domains in the microsecond range, thus greatly limiting their application scope. Herein, nine kinds of green, room-temperature phosphorescent (RTP) carbon dots-in-zeolite (CDs@zeolite) composites with engineered lifetimes from 0.38 to 2.1 s are thermally prepared under solvent-free conditions by systematically adjusting the reaction conditions and host–guest interactions. The regulation mechanism of various reaction factors of RTP lifetime has been elucidated. Varying crystallization temperature and time or introducing different amounts of C=O, C=N, or N-H bonds through CDs precursors would tune intersystem crossing rate (K_ISC) and nonradiative decay rate (K_nr) of CDs@zeolite composites. In addition, changing zeolite matrices would generate different host-guest interactions, then result in variable K_nr, thus giving tunable RTP lifetimes. In view of the second-level lifetime tunability of as-made CDs@zeolite composites, naked-eye visible multiplexing by lifetime coding has been demonstrated, realizing portrait encryption. This work opens a new opportunity for the application of CDs-based materials in optical multiplexing.