Facile approach to the synthesis of molecularly imprinted ratiometric fluorescence nanosensor for the visual detection of folic acid.

A core-shell molecular imprinting fluorescence nanosensor was developed for the ratiometric fluorescence and visual detection of folic acid (FA). The nanosensor was prepared by anchoring imprinting shell on the silica nanoparticles, and embedding the CdTe quantum dots in imprinted shell to provide FA-dependent fluorescence signals. Under the optimum conditions, a favorable linearity relationship between the fluorescence intensities ratio (I449/I619) and the FA concentration over 0.23-113 μM was offered with a detection limit (LOD) of 48 nM. The visual detection for FA was realized by evaluating profuse fluorescence color change from red to pink to purple to final blue. The proposed sensor possessed excellent sensing performances of rapid response, high precision, super sensitivity and selective recognition. Furthermore, endogenous FA was detected in real samples ranging from 37.4 to 265.8 μg/100 g; satisfactory spiked recoveries were obtained within 94.8-104.2%, which conformed to the measurement results by HPLC-UV.