SERS and electrochemical dual-detection method based on gold-conjugated magnetic nanoparticles for the detection of Methyl Parathion insecticide: Experimental and theoretical approaches

Methyl parathion (MP), a class I (extremely toxic) organophosphorus pesticide, has been banned in several countries, including the European Union, but remains in use in others, highlighting the importance of its monitoring to ensure environmental and public health safety. Here, we explore magneto-plasmonic nanoparticles addressing dual-function, SERS (surface-enhanced Raman scattering), and electrochemical sensing of MP. We have anchored gold nanoparticles to magnetite, creating gold-conjugated magnetic nanoparticles (AuMNP). Using a neodymium magnet, we investigated the effect of the magnetic concentration of AuMNP conjugates to detect MP. A theoretical investigation was performed to elucidate MP’s Raman and SERS spectra. In both techniques, the signal depends on the analyte’s adsorption mechanism to the AuMNP conjugates, which followed the Langmuir model. For SERS, the magnetic concentration contributes to increasing the number of hotspots and concentrating the analyte in the laser path. For electrochemistry, the magnetic concentration transports the analyte to the vicinity of the working electrode surface and counts with the electrocatalytic effect of AuMNP conjugates. The limits of detection for MP were calculated as 1.9 × 10−6 mol L −1 and 1.4 × 10−6 mol L −1 by SERS and differential pulse voltammetry (DPV), respectively. Since the maximum amount of residue of MP on crops used as food established by the United States Food and Drug Administration is 0.1 to 1 ppm (0.38 μmol L −1 to 3.8 μmol L −1), the developed methodologies are suitable for MP quantification in some food crops.