Regulation of Multicolored Reed-Based Carbon Dots and their Application for Anti-Counterfeiting and Cell Imaging.

Biobased fluorescent carbon dots (CDs) with their advantages of being environmentally friendly, renewable, easy to modify, superior water solubility, luminescence stability, and biocompatibility have attracted extensive attention. In this study, agricultural waste reed is used to controllably prepare multicolor (cyan, green, and yellow) CDs (C-CDs, G-CDs, and Y-CDs) by using the one-step hydrothermal method, regulating the types of nitrogen sources. The result showed that the average particle sizes for C-CDs, G-CDs, and Y-CDs were 2.58 nm, 5.31 nm, and 6.80 nm, respectively. The redshift is explained by doping different nitrogen sources, which leads to increased particle size of CDs, and the deepening of the graphitization degree of CDs leads to increased sp² hybridization degree. The fluorescence quantum yields (QY) for C-CDs, G-CDs, and Y-CDs were 15.45%, 39.07%, and 7.87%. These CDs exhibit good salt resistance, photobleaching resistance, and chemical stability, A multi-dimensional anti-counterfeiting system has been successfully constructed, displaying specific fluorescence patterns under ultraviolet excitation. In addition, the cytotoxicity test Cell Counting Kit-8 (CCK-8) showed that the survival rate of reed-based CDs to HeLa cells remained above 98% even at 0-250 µg/mL, showing good biocompatibility and nontoxicity. So, the CDs can be utilized in anti-counterfeiting fluorescent ink and cell imaging. It is particularly noteworthy that using agricultural waste as raw material to prepare CDs not only conforms to green chemistry, low cost, and sustainable development but also realizes the high-value utilization of waste resources.