Residual-dye-derived carbon dots from wastewater for anti-counterfeiting and information encryption

With the development of resource recycling awareness, the number of research on the synthesis and utilization of carbon dots (CDs) from natural wastes continues to grow. Meanwhile, the little -studied synthesis of CDs originating from industrial waste has also become more relevant. In this work, reactive yellow 95 (Y95) molecules in exhausted dyeing wastewater were used as carbon source. By a simple one-step hydrothermal method, the CDs with stimuli -responsive fluorescent chromotropic properties were obtained. With the addition of hydrochloric acid to the CDs solution, the emission of the CDs was red -shifted from 470 nm to 514 nm, and the fluorescence changed from blue to green. The phenomenon was attributed to the synergistic effect of more C - - O defects on the surface of CDs and the protonation of the carbonyl groups after adding acid. Based on acid -induced fluorescent chromotropic performance, we designed anti -counterfeiting labels for textiles and a double -switching information encryption anti -counterfeiting ink. This work synthesized responsive fluorescent CDs using waste dyes and showed great potential in the field of resource recycling.