Color-changing Fluorescent Carbon Dots Synthesized by Simple Hydrothermal Method for Anti-counterfeiting Pattern Study

Abstract A simple hydrothermal method was employed to synthesize the carbon dots with dopamine hydrochloride used as the mainly carbon source and o-phenylenediamine as the nitrogen source. In the study, the fluorescent carbon dots which have good water solubility and alcohol solubility showed visible pink under daylight and orange under UV after purification by column chromatography, and dichloromethane: methanol (v: v =20:1) was selected as the separation solvents. Meanwhile, the pink fluorescent carbon dots (λmax =595 nm under 577 nm excitation) was observed that it can be changed to bright yellow (λmax =530 nm under 442 nm excitation), the conditions of different stocked solvents and time were explored in detail. The IR spectra for the pink carbon dots indicated its color-changing property due to the unsatisfaction group of its chemical structure. For UV and fluorescence characterization, the quantum yield of pink carbon dots is ∼11.0%. In addition, the application of color-changing carbon dots as anti-counterfeiting ink for high-quality anti-counterfeit patterns on paper was investigated, and the preliminary results showed good potential of the prepared carbon dots as effective and eco-friendly anti-counterfeiting materials.