Time-dependent phosphorescence color from P-doped carbon dots for advanced anti-counterfeiting and information encryption

• • Solid-state P-CDs exhibit TDPC from yellow to green with afterglow lasting 12 s and average lifetime 1.15 s, enabling dynamic multi-level anti-counterfeiting without matrix encapsulation. • • P-doping induces spin-orbit coupling, increasing triplet-state excitons, which is the mechanistic basis for enhanced RTP; this design principle can be extended to other heteroatom-doped carbon dots. • • P-CDs/PVA ink on commercial A4 paper shows improved RTP lifetime of 1.31 s, demonstrating practical utility on flexible cellulosic substrates for security printing. • • The one-step hydrothermal synthesis from feather powder and phytic acid offers a sustainable, low-cost route to valorize biomass waste, addressing both environmental and economic concerns in luminescent material production.