Multicolor Fluorescent Inks Based on Boron and Nitrogen Codoped Carbon Nanodots for High-Security Anticounterfeiting and Information Encryption.

The growing sophistication of counterfeit technologies necessitates the development of innovative security materials with enhanced protection capabilities. This study presents a one-pot solvothermal synthesis of multicolor fluorescent inks based on boron and nitrogen codoped carbon nanodots (B, N-CDs) with blue, green, and yellow emissions. The emission wavelengths are modulated through precursor selection and reaction condition optimization, resulting in emissions at 440, 520, and 540 nm, respectively. Detailed structural and optical analyses reveal that the fluorescence shift is related to doping levels and particle size, as confirmed by XPS, FTIR, TEM, and PL lifetime analysis. The synthesized B, N-CDs were formulated into inks suitable for both handwriting and screen-printing applications. Under ambient light, the patterns are nearly invisible but exhibit strong multicolored fluorescence when illuminated with ultraviolet (UV) light at 365 nm. Practical demonstrations such as QR code printing, product authentication tags for luxury goods, and Morse code encryption confirmed the potential of these inks for secure labeling and information encryption. Additionally, the inks exhibited excellent stability under various environmental stresses including UV radiation, mechanical abrasion, humidity, solvents, and temperature fluctuations. These features position B, N-CD-based fluorescent inks as a cost-effective and robust solution with strong potential for scalable production in advanced anticounterfeiting and information encryption technologies.