Experimental and theoretical study of natural carbon dots as fluorescence sensor for hexythiazox detection

• Carbon dots are synthesized by a simple and fast hydrothermal method using Tomato as a precursor • The synthesized CDs are spherical particles and show high fluorescence properties • The CDs are used as a simple optical probe to determination of hexythiazox pesticide • The interaction between synthesized CDs and some pesticides was discussed using DFT calculations . Water is the most significant chemical material that affects various aspects of life, including social, environmental, economic and even political things. With the advancement of industry, and excessive use of hazardous materials, water pollution has become a big problem. Water pollution by heavy metals and agricultural pesticides, due to the high toxicity of these substances, is a growing threat to the environment and human health. There are various methods for detecting these pollutants. Among them, the fluorescence method, especially the fluorescence based on carbon quantum dots, has received much attention due to its high sensitivity, easy operation and wide application. In this study, carbon quantum dot (CDs) was synthesized by hydrothermal method using tomato as carbon source and doped by cysteine as sulfur source. Then, the synthesized CDs was used as a fluorescence probe to detect hexythiazox pesticide. The linear range was obtained 2.50 to 10.00 μM with the detection limit of 0.83 μM. This study showed that the use of natural, available and cheap sources for carbon quantum dot synthesis is a fast, practical and environmentally friendly method. In parallel the geometry of CDs, functionalized CDs and different pesticides were optimized using DFT method in solvent phase. According to calculated results the structure and reactivity of CDs after being doped with L-Cys change significantly. Moreover, the interaction between functionalized CDs and pesticides were investigated from thermodynamic point of view. .