Water-Unquenchable Ultralong Room-Temperature Phosphorescent CDs@SiO2 Composites for Information Encryption and Anticounterfeiting Applications

• • Aqueous dispersion lifetime of 2.38 s with 22% absolute quantum yield—exceeding the <1 s benchmark of conventional RTP materials by >2.3×, enabling stable liquid-phase encryption inks. • • Solid-state average lifetime of 3.04 s, the highest reported for carbon-based RTP systems, attributed to Si–O–C covalent bonds and Si–O–Si rigid networks that reduce nonradiative decay rates by an order of magnitude. • • Water-responsive structural color combined with blue fluorescence and cyan RTP provides three independent optical security channels, raising forgery complexity beyond single-mode fluorescent labels. • • Ex-situ covalent coupling yields composites with reversible and stable optical properties under ambient conditions, supporting roll-to-roll integration for anticounterfeiting labels and information encryption.