Carbon Dots/SiO₂ Fluorescent Photonic Crystals for Anti-Counterfeiting

Composite materials that combine quantum dots and photonic crystals can produce some complex anti-counterfeiting patterns, which solves the problems of simple encoded information and low anti-counterfeiting levels of monochromatic materials. Here, we prepared a type of carbon dots/silicon dioxide (CDs/SiO 2 ) fluorescent photonic crystal with both angle-dependent structural color and fluorescence properties. First, silica nanospheres of 220, 250, and 280 nm were prepared using the Stöber method by changing the ethanol amount. Then, monodispersed CDs/SiO 2 composite nanospheres were synthesized by the one-pot microwave hydrothermal method. The surface morphology, monodispersity, phase structure, and other properties of the nanospheres were explored. Experiments showed that the thin film formed after the natural deposition of composite microspheres had green fluorescence while retaining the original angle-dependent structural color. In addition, the fluorescence intensity of the composite nanospheres was significantly improved compared to the original CDs. This study provides a valuable experimental scheme for preparing multifunctional composite materials and ideas for expanding the application fields of fluorescent photonic crystals.