Construction Of Surface Imprinted-based Multiple-emission Fluorescence Sensor And Study On Rapid Visual Recognition Of Folic Acid In Food

Food safety involves multitudinous detection targets,such as natural toxins,pesticide residues,antibiotics,food additives,veterinary drugs,etc.,but their high toxicity,low content and complexity of food matrix require higher analysis methods.Hence,it is urgent to develop a novel rapid and simple detection technology.In this paper,integrating the specific selectivity of molecular imprinting technology and the excellent sensitivity of fluorescence analysis,two multi-emission molecularly imprinted-based fluorescence sensors were designed with different modified-CdTe QDs as the signal source based on surface imprinting,which effectively conquered external interference and made the rapid visual detection of folic acid possible.The main research contents are as follows:1.Facile approach to the synthesis of molecularly imprinted-based two-emission fluorescence nanosensor for the visual detection of folic acidBased on surface imprinting,the core-shell molecular imprinting fluorescence nanosensor with emission peaks at 449 nm and 619 nm was constructed for high-efficiency and visual detection of folic acid,with silica nanoparticles as the core,MPA-modified CdTe quantum dots as the signal source,and folic acid as the template.As the increasing FA,the fluorescence intensity of red-emission peak gradually declined and FA-induced blue fluorescence enhanced,resulting a profuse fluorescence color evolution with a window of red to pink to purple to final blue.A favorable linearity relationship between the fluorescence intensities ratio(I449/I619)and the FA concentration over 0.23-113?M was offered with a detection limit(LOD)of 48 nM.Furthermore,endogenous FA was detected in natural foodstuff and FA-fortified samples,and satisfactory spiked recoveries were obtained within 94.8-104.2%.2.Rational construction of a triple emission molecular imprinting sensor for accurate naked-eye readout of folic acidA multi-emission of blue,green and red based molecular imprinting sensor was constructed for fluorescence colorimetric visualization of a fluorescent analyte of folic acid by a flexible post-imprinting mixing strategy.That is,two kinds of folic acid-imprinted polymers were firstly synthesized via surface imprinting,which encapsulated green and red fluorescent quantum dots(g-QDs and r-QDs)individually on SiO2 cores,and then mixed at an appropriate ratio.The inherent blue fluorescence of folic acid,green and red fluorescence of QDs were gradually intensified,quenched and quenched at discrepant rate with increasing folic acid,respectively,causing a wider and more profuse fluorescence color evolution shifted from yellow to orange to red to purple to final blue.This excellent visualization capability contributed to the accurate naked-eye readout of folic acid concentration by a portable ultraviolet lamp.Under the optimal conditions,the ratiometric intensities of three emissions varied in a logistic function with 0.23-113?M of folic acid with the detection limit of 12 nM.Moreover,the MIPs sensor succeeded in folic acid determination of complicated food and pig serum samples with satisfactory recoveries of 99.5-108.0%.