Ascorbic acid functionalized gold nanoparticles as a probe for colorimetric and visual read-out determination of dichlorvos in environmental samples

We report a facile, rapid, selective and sensitive colorimetric method for the detection of dichlorvos based on the aggregation of ascorbic acid (AA) capped gold nanoparticles (Au NPs) induced by dichlorvos. The influence of AA concentration on the UV-visible absorption spectra and the color of AA-Au NPs was investigated. In the presence of dichlorvos, the UV-visible spectrum of AA-Au NPs was red-shifted from 525 nm to 620 nm, indicating that the aggregation of AA-Au NPs was induced by dichlorvos via hydrogen-bonding between AA-Au NPs and dichlorvos, which results in a change in color from cherry red to purple that can be monitored by UV-visible spectrophotometer or the naked eye. The limit of detection was found to be 42.94 mu M, and good recoveries in the range of 90.0-101.2% with relative standard deviation (RSD) of <0.85%. The method was successfully applied to detect dichlorvos in water (tap, river and canal), apple and wheat samples.