Water-soluble long afterglow carbon dots/silica composites for dual-channel detection of alkaline phosphatase and multi-level information anti-counterfeiting

Water-soluble carbon dots/silica (CDs/SiO2) composites with an ultra-long lifetime of 846.9 ms and an ultra-high afterglow quantum yield of 12.1% were successfully obtained by incorporating CDs into a SiO2 network. Within the aqueous solution, the SiO2 layer isolates CDs from the surrounding oxygen. Meanwhile, hydrogen bonds and covalent bonds are formed between the CDs and SiO2, and these bonds restrict the movement and vibration of the CDs. Accordingly, the non-radiative inactivation rate of the triplet excitons of the CDs is reduced, thereby enhancing the room-temperature phosphorescence of the CDs and triggering thermally activated delayed fluorescence. The multiple properties of the material effectively protect the CDs from the external environment, making CDs/SiO2 emit a long afterglow in the solid and liquid phases. The prepared CDs/SiO2 composites have exceptional stability against strong oxidants, acids, bases, and polar solvents. The composites were successfully used in the dual-optical mode detection of alkaline phosphatase, as an anti-counterfeiting ink, and in multi-level information anti-counterfeiting and encryption.