Thioglycolic acid-modified AuNPs as a colorimetric sensor for the rapid determination of the pesticide chlorpyrifos

Herein, we report the preparation of a gold nanoparticle-thioglycolic acid (TGA@AuNP) suspension for the label-free colorimetric detection of the organophosphorus pesticide chlorpyrifos. This colorimetric sensor was synthesized by a one-pot method, providing thioglycolic acid (TGA)-modified gold nanoparticles with a negatively charged surface. The formation of TGA@AuNPs was confirmed by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and dynamic light scattering (DLS). In addition, chlorpyrifos was quantitatively determined by UV-vis spectrophotometry. The modification time, TGA concentration, pH, incubation time, temperature, ionic strength, and interference of other pesticides were also investigated. The synthesized TGA@AuNP colorimetric sensor possesses a detection limit as low as 20 μg L-1 and a selective sensing response, and the detection time is less than 2 minutes. In addition, this method can also be applied to detect various practical samples in life, such as environmental water samples and tea.