Transition metal oxide nanoparticle-graphene oxide composites as potential sensors for commercially formulated pesticides.

The binding interactions of organic molecules with carbon-based materials or nanoparticles have already been studied; however, understanding the preferred binding affinity towards any of these components is difficult, involving time-consuming and expensive procedures. In this work, we investigated a new and simple method to identify the preferred interactions of commercial formulations of three pesticides, i.e., λ-cyhalothrin, imidacloprid, and metsulfuron-methyl, with transition metal oxide nanoparticles (t-MONPs, Fe3O4, CoO, NiO, CuO, and ZnO) or graphene oxide (GO) by using their composites. Fluorescence spectroscopy was performed to study the sensing potential of these composites through Stern-Volmer plots, and dynamic light scattering/zeta potential measurements were carried out to investigate the preferred binding affinity of the pesticides towards either graphene oxide or transition metal oxide nanoparticles. The linear regression analysis of Stern-Volmer plots revealed that the detection limit is in the micromolar range for these composites, indicating their satisfactory sensing performance. The binding constants, limit of detection, and limit of quantification were calculated for these composites.