Integrating target-responsive CD-CdTe QD-based ratiometric fluorescence hydrogel with smartphone for visual and on-site determination of dichlorvos.

Abstract

A facile, economic, and portable test kit based on target-responsive hydrogel with smartphone detectionwas fabricated for the accurate determination of dichlorvos in tap water and food samples. Carbon dots (CDs) and CdTe quantum dots (QDs) embedded hydrogel were employed as indicator, and fluorescence of CdTe QDs (645nm) was dynamically quenched by Cu2+ while that of CDs (490nm) were non-response for Cu2+, em erging atypical ratiometric fluorescence signal. Acetylcholinesterase hydrolyzed acetylthiocholine to generate thiocholine that bound with Cu2+ strongly via S-Cu-S bond. Dichlorvos as competitive inhibitor for acetylcholinesterase prevented the generation of thiocholine, which blocked the formation of Cu-thiocholine complex and changed the ratiometric fluorescence signal. The signal of thetest kit, which was recorded by smartphone's camera, was transduced byImageJ software into the color parameter that was linearly proportional to the logarithm ofdichlorvos concentration. This portable test kit showed wide linear range of 1 to 40ppb and low detection limit of 0.38ppb for dichlorvos. This test kit exhibited rapid sample-to-answer detection time (50min) of dichlorvos in tap water and food samples, and the recoveries were in the range 81.3 to 111% with relative standard deviations of less than 9.1%. A facile and economic portable test kit based on CD-CdTe QD target-responsive hydrogel with smartphone was innovatively fabricated for the accurate determination of organophosphorus pesticides. This portable test kit showed low detection limit of 0.38ppb for dichlorvos and rapid sample-to-answer detection time (50min) in tap water and food samples, which offered a new sight for portable monitoring of environmental pollution and food safety.