Synthesis and enhancement of carbon quantum dots from Mopan persimmons for Fe3+ sensing and anti-counterfeiting applications

The utilization of biomass is an important approach to supplying sustainable carbon sources for green chemistry, by which the product could be more environmentally friendly and lower toxicity. In this work, the local fruit Mopan persimmons were used to be a carbon source to prepare carbon quantum dots (MP-CQDs) via the hydrothermal method. A series of characteristics were applied to the carbon dots to study the structural and optical properties. The results demonstrated that the MP-CQDs were well synthesized and coated by N, O-related surface functional groups. The PL of MP-CQDs showed an excitation-dependent behavior, whose peak shifted from 446 nm to 545 nm under the excitation wavelength from 350 nm to 450 nm. After a selectivity study on different metal ions, we found that MP-CQDs were sensitive to Fe3+ ions, and the limit of detection (LOD) was determined as 0.324 mu M with the 3 sigma rule. Further, by mixing MP-CQDs with sugar, we successfully applied MP-CQDs to the anti-counterfeiting field by painting anti-counterfeiting patterns with the combination of commercial fluorescent ink (CFI) and MP-CQDs@sugar ink (MPI). The pattern can present different fluorescent properties under 365 nm, 395 nm, and 450 nm respectively. The results revealed that biomass-derived MP-CQDs were a promising candidate for Fe3+ ions detection and anti-counterfeiting application.