Synergistic Effect of Copper oxide Nanoparticles and Diazonium-Modified Carbon Nanotubes for Colorimetric Detection of Dimethoate Residues in Food Products

Dimethoate (DMT) is one of the most used organophosphate compounds for plants protection against pests. Because of its toxicity, its trace presence in ecosystems constitutes a threat to the environment. Thus, it becomes more than necessary to develop highly sensitive methods for monitoring dimethoate in food products. On this, a new sensor based on carbon nanotubes modified by diazonium and decorated with copper oxide nanoparticles (f-CNTs@CuO) was chosen for the quantitative detection by Uv–vis spectrophotometry and, at the same time, for the colorimetric recognition of dimethoate. This sensor was characterized using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS). and X-ray Photoelectron Spectroscopy (XPS), which confirmed the formation of f-CNTs@CuO. The presence of copper nanoparticles improves sensitivity and is responsible for the color change during detection. Formal evidence of naked eye detection was confirmed by digital photo images. This sensor presents a unique response and very high selectivity for the analysis of dimethoate compared to other potentially competitive compounds such as malathion, parathion, glucose and calcium ions. The detection limits with the naked eye and by experimental calculation are equal to 50 ppb and 26.1 ppb respectively, and are well below the maximum limit authorized by the EU and China. The applicability of the sensor was successfully verified in cabbage samples with recoveries of 67.8–104.6%. This study provides a new material for the analysis of organophosphate pesticides in food samples.