Pesticides are natural or synthetic substances, which are meant to prevent, destroy, or control pathogens, pests, and weeds, for reducing crop yield losses and improving food quality. In fact, the small portion (1% of the used pesticide approximately) can reach to the target. However, the rest enters the environment gratuitously, causing the environmental pollution and poisoning to human beings and animals. Therefore, it is important to monitor the presence of pesticides and regulate their levels. With the development of nanotechnology, nanomaterials have attracted substantial interest because of their unique optical, electrical, thermal and catalytic properties. These properties originating from quantum-size dimensions could change with their sizes and shapes. Recently, graphene-based nanomaterials such as graphene quantum dots (GQDs) have gained interest in various fields of research, especially agri-food industry. GQD is a chemically inert, water soluble, low toxicity, and low cost nanomaterial compared to other nanomaterials. The objective of this research is to determine three pesticides residues (imidacloprid, penconazole, and infinito) in water samples using GQDs functionalized with Alizarin Red S during pyrolysis procedure and different active metals (Sn2+, Co2+, Fe3+, Ca2+, and Cr3+). Both colorimetric and fluorimetric measurements have been done in pH=0.5, 3, 7, and 12. The results showed that all pesticides can be distinguished from each other at pH=3 in both colorimetric and fluorimetric sensing without using any active metal. The limits of detection (LOD) for imidacloprid, penconazole, and infinito are 0.01, 0.1, and 1 ppm according to the UV-Vis spectra, respectively. Moreover, after adding Cr3+ to the pesticides solutions at pH=0.5, the results were satisfactory in comparison to the rest of active metals with LODs of 100, 10, and 0.01 ppm for imidacloprid, penconazole, and infinito, respectively.
