Cost-effective smartphone-integrated colorimetric sensor for the detection of ethion using gold nanoparticles

Gold nanoparticles capped with citrate were prepared and characterized using particle size measurements, FT-IR, and an HR-TEM study. The prepared particles were evaluated for their ability to detect pesticides in water samples. A color change visible to the naked eye was witnessed in a solution containing ethion. Other pesticides did not produce a similar change in color. The recognition of ethion using AuNPs was also witnessed through UV-vis analysis. The color change was exploited to develop a smartphone-aided system for the detection of pesticides in aqueous samples. A good limit of detection value (0.060 ± 0.002 µM) was witnessed using UV-vis spectroscopy, while the red color component and grayscale pixel intensity provided a limit of detection value of 0.052 ± 0.003 µM and 0.055 ± 0.008 µM, respectively. The ethion concentration was also determined in a spiked tap water and soil samples using both smartphone-aided technique and UV-vis spectroscopy. The particle size measurements using Dynamic Light Scattering (DLS) and High-resolution Transmission Electron Microscopy (HR-TEM) analysis indicated aggregation of AuNPs on interaction with ethion.