Water-unquenchable ultralong room-temperature phosphorescent CDs@SiO2 composites for information encryption and anticounterfeiting applications

Abstract

Room-temperature phosphorescence (RTP) materials play a vital role in security domain due to their unique optical properties. However, most average lifetimes of available RTP materials remain less than 1 s in aqueous-phase media, which is unfavorable to practical applications. Herein, an ex-situ covalent coupling strategy is proposed to fabricate liquid-phase long-lived RTP materials by combining SiO₂ microspheres with the feather-derived carbon dots (CDs). Astonishingly, the aqueous dispersion of the resulting CDs@SiO₂ microspheres exhibits a lifetime of up to 2.38 s with an absolute quantum yield of 22%. Moreover, the average lifetime of the solid CDs@SiO₂ is as long as 3.04 s, which is superior to that of existing RTP carbon-based materials. The striking enhancements in the RTP of the CDs@SiO₂ composites are mainly attributed to the immobilization of the formed Si–O–C covalent bonds and Si–O–Si rigid networks. The CDs@SiO₂ composites were subsequently applied in the fields of information encryption and anti-fake. Interestingly, the CDs@SiO₂ composites possess intriguing, reversible and stable optical properties, including water-responsive structural colors, blue fluorescence and cyan RTP, exhibiting excellent covert performance in applications of information encryption and decryption, and high-level anticounterfeiting. These findings provide not only a straightforward strategy for developing multiresponsive optical materials but also a more secure anticounterfeiting technology.