Time-dependent phosphorescence color from P-doped carbon dots for advanced anti-counterfeiting and information encryption
Biomass-derived room-temperature phosphorescence (RTP) carbon dots (CDs) hold great promise for anti-counterfeiting and information encryption. However, achieving solid-state matrix-free long-lived CDs with time-dependent phosphorescence colors (TDPC) remains challenging due to aggregation-induced quenching. Here, solid-state matrix-free RTP phosphorus-doped CDs (P-CDs) are developed via one-step hydrothermal treatment of feather powder and phytic acid. The resulting P-CDs powder exhibits bright blue fluorescence under UV illumination and unprecedented TDPC shifting from yellow to green after UV removal, with afterglow lasting 12 s (average lifetime 1.15 s). Enhanced RTP is attributed to increased triplet-state excitons via spin-orbit coupling induced by P-doping. A dual-mode luminescent ink formulated by combining P-CDs with polyvinyl alcohol (PVA) is successfully applied to commercial A4 paper, showing pronounced TDPC (light-yellow to green) with improved RTP lifetime (1.31 s) after ceasing UV irradiation. The P-CDs/PVA ink demonstrates excellent anti-counterfeiting and information encryption capabilities, outstanding luminescent durability, and broad practicability on cellulosic substrates including fabric and paper. These findings provide a strategy for exploiting matrix-free solid-state RTP P-CDs with distinctive TDPC properties and offer a sustainable route to converting feather wastes into high-value materials.