A fluorescent probe of quantum dot-embedded imprinted polymer used with a portable smartphone-assisted color analysis...

A fluorescent probe was successfully developed using nitrogen-doped graphene quantum dots (N-GQDs) decorated porous zinc oxide (ZnO) embedded in a molecularly imprinted polymer (MIP). The ZnO∗N-GQDs∗MIP sensing probe was synthesized via the sol-gel polymerization method and exhibited a strong fluorescence emission at 403 nm. Applied to detect trace levels of diuron determined by spectrophotometry, the fluorescent sensor exhibited a good linear response within the range of 0.10-50.0 μg L^-1 with a coefficient of determination of 0.9997. The limit of detection was 0.07 μg L^-1. Coupled with a smartphone-assisted fluorescence color analysis platform, the probe produced linearity in the range of 5.0-50.0 μg L^-1, with an R² of 0.9986 and a limit of detection of 2.5 μg L^-1. Both developed methods successfully determined diuron in radish, tomato, cucumber and green tea. Recoveries were between 90.5 and 107.3 % with RSDs <8.0 % for the fluorescent sensor coupled with spectrophotometry and 91.5-105.3 % with an RSD of <7 % for the smartphone-assisted method. The reliability and accuracy of both methods were confirmed by comparison with high-performance liquid chromatography. The proposed fluorescent probe coupled with the smartphone-assisted color analysis platform provided high sensitivity and good selectivity while being simple, convenient, rapid and inexpensive. The method has several application possibilities for on-site detection of trace diuron.