Functionalization of Silver Nanoparticles with Carbohydrate Derivative for Colorimetric Assay of Thiram

The surface of silver nanoparticles (Ag NPs) was functionalized with a carbohydrate derivative (glutathione-lactose, GSH-Lac) to form GSH-Lac-Ag NPs for sensing of thiram in real samples with a rapid and sensitive visual readout. This colorimetric assay of thiram relies on the change in the surface plasmon resonance (SPR) band of the GSH-Lac-Ag NPs, resulting in their aggregation by thiram, which leads to a visual change of the GSH-Lac-Ag NPs from yellow to reddish brown. As a result, the SPR band of GSH-Lac-Ag NPs red-shifts from 406 nm to 458 nm, showing good linearity in the range of 0.01 mu M to 3.00 mu M (R-2 = 0.9841) with a limit of detection (LOD) of 3.00 nM. Addition of other pesticides did not show a remarkable red-shift of the SPR band of the GSH-Lac-Ag NPs, indicating their high selectivity as a colorimetric sensor. This method enables a facile and portable analytical platform for on-site detection of thiram in real samples with minimum volume.