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

•A RB-AuNPs-based fluorescent turn-on nanosensor for dimethoate analysis was developed.•The method shows wide linear range and good recoveries.•The methods was applied successful for dimethoate determination in water and fruit samples. 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 (