Gold-nanoparticle-based fluorescent "turn-on" sensor for selective and sensitive detection of dimethoate

A simple approach to fabricate a highly selective and sensitive dimethoate probe was developed based on Rhodamine B (RB)-functionalized gold nanoparticles (AuNPs). The quenching of RB fluorescence in the presence of AuNPs in the solution, mediated by fluorescence resonance energy transfer, was observed. In the presence of dimethoate, the fluorescence intensity of the RB-AuNP solution is gradually recovered when dimethoate molecules displace RB molecules on the surface of the AuNPs, which significantly increased the fluorescence intensity of RB. Fluorescence is proportional to the dimethoate concentration in the range of 0.005-1.0 ppm (R² = 0.989), and the LOD was 0.004 ppm. The recoveries of dimethoate in water and fruit samples were 86-116% with a good RSD (< 9.3%). Because of its high sensitivity, excellent selectivity, and convenient fabrication process, this method is a promising candidate for dimethoate screening.