Room Temperature Detection of Chlorpyrifos Using Thermally Oxidized Manganese and Copper Thin Films

Abstract

The usage of pesticides has increased rapidly over the past three decades to boost crop production and meet the global food demand. According to UN FAO, about 66% of the countries have reported an average increase in pesticide consumption of about 1.85 kg hectare−1 between 1990 and 2019. Chlorpyrifos is a widely used but hazardous pesticide, popular for domestic and agricultural applications. Real-time monitoring of Chlorpyrifos is necessary for its safe application due to its toxicity, even at the residue level. In this work, an attempt has been carried out to detect chlorpyrifos at room temperature using thermally oxidized manganese and copper thin films. Thermal oxidation of thin films has been carried out under air ambient at different temperatures ranging from 400 °C to 550 °C for manganese and 500 °C to 800 °C for copper thin films. Morphological investigation depicts nanobar-like morphology and irregular-sized clusters for various oxidation temperatures of manganese oxide thin films, and granular-like morphology with an increase in grain size has been observed for increasing oxidation temperature. Structural investigation using the XRD technique depicts the evolution of various phases of manganese oxide thin film and a single monoclinic phase for copper oxide thin film. Further, the RMS roughness of the manganese and copper film was found to vary differently with the rise in oxidation temperature. Copper oxide thin films have shown higher chlorpyrifos sensing response with sensitivity than thermally oxidized manganese thin films better sensing response towards chlorpyrifos. The sensitivity at room temperature is found to be around 30 and 250 for manganese oxide and copper oxide thin films, respectively.