Rapid Preparation of Long-Wavelength Emissive Carbon Dots for Information Encryption Using the Microwave-Assisted Method

Threetypes of long-wavelength emissive fluorescent carbondots, yellow, orange, and red, were rapidly prepared using the microwave-assistedmethod and successfully used for information encryption. The synthesis of long-wavelengthemission fluorescent carbon dotsis not common, and it is even more difficult to quickly synthesizewithin 10 min. In this experiment, yellow, orange, and red B, N codopedfluorescent carbon dots were successfully synthesized using a microwave-assistedmethod with o-phenylenediamine as the carbon-nitrogensource, boric acid as the boron source, and potassium chloride asthe catalyst in just 7 min. Based on the different contents of B,N element doping, there are differences in their surface structures,resulting in differences in the luminescence properties of the synthesizedcarbon dots. Long-wavelength carbon dots can avoid interference fromthe blue fluorescence of filter papers and have a clearer displayin information encryption. Therefore, three types of carbon dots weremixed with PVP to produce fluorescent inks, and anticounterfeitingand encryption patterns were designed on the filter paper, displayingdifferent fluorescence information under sunlight and UV light. Inaddition, the rich fluorescent colors were combined ingeniously toenable secondary encryption of information in the form of binary codesthat increase the difficulty of decoding. These indicate that thethree synthesized long-wavelength carbon dots have good applicationprospects in information encryption.