Citric acid-coated gold nanoparticles for visual colorimetric recognition of pesticide dimethoate

A colorimetric chemo-sensor based on citric acid-coated gold NPs (C-GNP) showed a linear increase in fluorescence intensity with increasing concentration of pesticide dimethoate (DM). The limit of detection was found to be between similar to 8.25 +/- 0.3 and 20 +/- 9.5 ppm. The increase in fluorescence intensity was suggested to have originated from the soft-soft interaction between C-GNPs and DM via sulfur group which is absent in pesticide dicofol (DF). Similar studies with citric acid-coated silver NPs (C-SNPs) did not result any change in the fluorescence intensity. The microscopic studies suggested aggregation of C-GNPs in the presence of DM but not in case of DF.