Innovation in printer ink based on Carbon Quantum Dots (CQDs) derived from styrofoam waste for anti-counterfeiting document technology

In response to the dual challenges of the environmental plastic pollution and the rise of document forgery, this study presents a novel fluorescent printer ink based on nitrogen and boron co-doped carbon quantum dots (N,B- -codoped CQDs) derived from styrofoam waste. The CQDs were synthesized using a microwave-assisted green synthesis approach, and their photoluminescent properties were tailored via co-doping with urea and boric acid. The resulting ink formulation not only exhibited strong dual-colour fluorescence under 365 and 532 nm excitation but also demonstrated effective printability and stability on standard paper substrates. Characterization techniques, including UV– –Vis spectrophotometry, fluorescence emission, Fourier-transform infrared spectroscopy and high-resolution transmission electron microscopy confirmed the successful incorporation of heteroatoms and the formation of nanoscale amorphous CQDs with rich surface functionality. Compared to the commercial printer ink, the N,B-codoped CQDs printer ink offered superior anti-counterfeiting features through fluorescence activation, albeit with a slightly lower ink absorption rate (0.47±0.14 vs. 0.74±0.06 cm/min). This study introduces a low- -cost, eco-friendly and scalable strategy for producing smart ink with potential applications in secure printing and sustainable nanomaterial development.