An Ultrasensitive Sensing of Carbaryl by Changing Catalytic Activity of AuNPs on Fehling Reaction-Resonance Scattering Spectroscopy

Acetylcholinesterase (AChE) can catalyze the hydrolysis of acetylthiocholine iodide (S-ACh-I) to produce thiocholine, which can crosslink with gold nanoparticles (AuNPs) by Au-S covalent bond and trigger AuNPs aggregation. The catalytic ability of aggregation of AuNPs is less than dispersed AuNPs. In the presence of carbaryl, which can inhibit the catalysis activity of AChE, therefore, the production amounts of thiocholine and aggregation degree were decreased. In the Fehling reaction, low aggregation degree AuNPs was used to catalyze the reduction of Cu2+ by glucose to form large size Cu2O particle. Large Cu2O particle has high resonance scattering signal intensities, which is negative correlated with carbaryl concentration. The developed assay was applied to detect the carbaryl in aqueous solutions, and two excellent linear relationships were obtained in the range of 0.03–3.31 nM and 26.50–265.05 nM. The limit of detection (LOD) of carbaryl was down to 17.49 pM. The proposed method was successfully used to determine the concentration of spiked carbaryl in the apple matrix, and satisfactory recovery and repeatability were obtained.