Fluorescent structured color pigments based on CB@SiO2/CQDs core-shell nanospheres for solvent/UV dual-responsive anti-counterfeiting coating

Since traditional anti-counterfeiting technology with a single decryption mode is easy to be cracked and imitated, the development of new anti-counterfeiting technology with complex response modes has significance. Here, we propose a preparation method for solvent/ultraviolet (UV) dual-responsive anti-counterfeiting coating based on fluorescent structural color pigments. The fluorescent non-iridescent structural color pigments based on CB@SiO 2 /CQDs core-shell nanospheres were prepared by carbon black (CB) as the core, and SiO 2 loaded with carbon quantum dots (CQDs) as the shell. The structural design of CB as the core can enhance the structural color saturation and enhance the chromatic stability. In addition, the CQDs embedded in SiO2 shells impart fluorescence function to structural color pigments, while effectively avoiding fluorescence quenching caused by agglomeration. Eventually, the solvent/UV dual-responsive photonic crystal anti-counterfeiting coatings were prepared by alternating spraying and superhydrophobic modification, consisting of structurally colored CB@SiO2, CB@SiO2/CQDs nanospheres and SiO 2 nanospheres. The top SiO 2 layer became transparent when the coatings were exposed to water. The underlying CB@SiO 2 and CB@SiO 2 /CQDs composite coatings were impervious to water infiltration, owing to the superhydrophobic properties. The structural color and fluorescent pattern information can be observed under natural light and UV illumination, respectively, after the SiO 2 layer became transparent. The solvent/UV dual-responsive anti-counterfeiting technology independent of large refractive index contrast was achieved by the above method, and this dual-responsive anti-counterfeiting strategy of fluorescence and structural color combination has a broad prospect in the field of anti-counterfeiting and information encryption.