Preparation And Application Of Novel Ratiometric Fluorescent Paper-based Chips

The ratiometric fluorescent molecular imprinted technology is a technology that combines ratiometric fluorescent signal changes with highly specific recognition sites for template molecules,making its results more accurate,and the changes in fluorescence can be recognized by the naked eye.This technology can effectively broaden the color change range of imprinted fluorescent sensors,making their application more convenient and fast.At the same time,it is conducive to the realization of visual detection,which can effectively solve the complex matrix of residual pesticide food samples,the time required for on-site detection,and the difficulty in operation.In view of this,this paper uses two different quantum dot materials,combined with the fluorescent dye NBD-Cl,to prepare a 2,4-D ratiometric fluorescent imprinted sensor and a difenoconazole ratiometric fluorescent imprinted sensor,and the fluorescence detection characteristics were examined in detail,and the high sensitivity and high selectivity of 2,4-D and difenoconazole in fruits,vegetables and lake water were detected.This paper uses cellulose paper as the base material and combines it with ratiometric fluorescent molecular imprinted technology.Since then,the micro fluidic technology was introduced into it,which lays the technical foundation for the construction of multi-channel visualization ratiometric fluorescent microfluidic paper chip.The main research contents and results are as follows:(1)Cellulose paper is used as a base material,and red CdTe quantum dots and green NBD-Cl fluorescent dye are grafted on the surface,A ratiometric molecularly imprinted fluorescence sensor based on the FRET fluorescence mechanism caused by fluorescence transfer was constructed for the detection of agricultural residues 2,4-D with high sensitivity and selectivity.The sensor exhibits excellent fluorescence characteristics and a satisfactory linear relationship in the range of 0.56-80 ?M,with detection limits as low as 90 nM.The sensor has been successfully applied to the detection of pesticide residues 2,4-D in bean sprout and lake water samples.and the recovery rate is 86.2-109.5%,and the accuracy is lower than 4.19%.The sensor combines ratiometric fluorescent technology and molecular imprinted technology for the first time and are modified on cellulose paper.It has specific selection and high sensitivity for the separation and detection of 2,4-D pesticide residues in actual samples.(2)The imprinted paper chip constructed in this research uses cellulose paper as the base material.The green non-toxic blue carbon quantum dot complex is chemically modified on its surface,and the conjugate NBD-APTES is also grafted on the surface of cellulose paper by coupling.Thus,a visualization ratiometric fluorescent imprinted paper chip based on single fluorescence quenching was constructed.When the difenoconazole solution was dripped on the imprinted paper chip,a strong charge transfer interaction occurred between the aromatic ring of the difenoconazole and the carbon quantum dot complex,resulting in the fluorescence quenching of the carbon quantum dot complex.And the conjugate NBD-APTES exists as a control fluorescence to achieve the rapid detection of difenoconazole.The fluorescence characteristics of the sensor shows satisfactory results.Its linear range is 0.3-60?M,the detection limit is 75 nM,and the sample detection shows high recovery and the range is between 102.1-111.2%.The accuracy is between 3.1-4.2%.This research can quickly and conveniently detect the pesticide residue difenoconazole in food samples,and has great application prospects in the field of rapid detection.The successful application of 2,4-D and difenoconazole ratiometric imprinted sensors provides theoretical and technical basis for the future multi-channel visual detection of pesticide residues,and also provides the possibility for the successful construction of new multi-channel sensors.