Polyethylene glycol (PEG) stabilized silver nanoparticles as colorimetric nano-sensor for diazinon detection in water

In this study, Polyethylene glycol (PEG₄₀₀) stabilized silver nanoparticles (PEG-AgNPs) were used as a colorimetric nanosensor to detect diazinon selectively. Highly stable PEG-AgNPs were synthesized through the one-pot two-phase procedure. The characterization of nano-sensor was performed via UV–vis spectroscopy, scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), atomic force microscopy (AFM), and dynamic light scattering (DLS). After adding the analyte to the PEG-AgNPs solution, the color of the PEG-AgNPs changed from yellow to pinkish-red, followed by a redshift of the Localized Surface Plasmon (LSPR) absorption band in the UV–Vis range. This behavior was only seen with diazinon molecules due to the presence of π-conjugated pyrimidine nitrogen and sulfur moieties, and the unique orientation of diazinon molecules facilitated non-covalent interactions with PEG-AgNPs. Synthesized nanosensor was able to detect and quantify diazinon in a linear range of (5–90 µM) 0.001–0.03 gL⁻¹ with a lower limit of detection of 0.006 gL⁻¹. The prepared nanosensor successfully identified diazinon in the presence of various interfering pesticides and displayed great potential for detection in water.