Ligand exchange reactions on citrate-gold nanoparticles for a parallel colorimetric assay of six pesticides

In this study, we explore ligand exchange reactions on citrate-gold nanoparticles (citrate-Au NPs) for facile and rapid parallel colorimetric identification of six pesticides including three organophosphorus pesticides (acephate, phenthoate, and profenofos), neonicotinoid (acetamiprid), chloronitrile (chlorothalonil) and thiocarbamate (cartap) in water and vegetable samples. The citrate-Au NPs acted as probes for a parallel colorimetric assay of six pesticides based on the significant red-shifts in their surface plasmon resonance (SPR) bands, which was due to the aggregation of Au NPs via ligand exchange reactions. Under optical conditions, the probe exhibited good linearity in the micromolar concentration range for the six pesticides. Importantly, the sensing system showed lower detection limits at nanomolar range for the six pesticides and exhibited good selectivity in the presence of commonly found inorganic species. The potential of the method was assessed by analyzing six pesticides in spiked water and food samples, which suggested that this simple method exhibited good recoveries and can be practically applied in on-site and real-time parallel colorimetric sensing of the six pesticides.