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

A facile, economic, and portable test kit based on target-responsive hydrogel with smartphone detection was 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 (645 nm) was dynamically quenched by Cu2+ while that of CDs (490 nm) were non-response for Cu2+, em erging a typical 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 the test kit, which was recorded by smartphone's camera, was transduced by ImageJ software into the color parameter that was linearly proportional to the logarithm of dichlorvos concentration. This portable test kit showed wide linear range of 1 to 40 ppb and low detection limit of 0.38 ppb for dichlorvos. This test kit exhibited rapid sample-to-answer detection time (50 min) 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%.

Automated summary

A portable test kit based on target-responsive hydrogel with smartphone detection was developed for accurate determination of dichlorvos in tap water and food samples. The kit showed wide linear range and low detection limit for dichlorvos, with rapid sample-to-answer detection time and high recoveries.