Preparation Of Surface Molecularly Imprinted Ratiometric Fluorescence Sensors And Their Application In The Detection Of Tetrabromobisphenol A

Molecularly imprinted polymer(MIP)has imprinted cavities that are complementary to the size and structure of the target analyte,which enables them to recognize the target molecule specifically in the presence of interfering compounds.Because of the specific recognition properties of MIP,it is usually combined with other analytical methods and used for the detection of target compounds in complex matrix.Compared with the traditional chromatographicbased detection methods,the molecularly imprinted ratiometric fluorescence sensors have the advantages of rapid,accurate,and visual detection of the target molecule.In this thesis,a series of molecularly imprinted ratiometric fluorescent sensors were prepared by combining the advantages of surface molecularly imprinted polymer and fluorescent material and used for the visual detection of tetrabromobisphenol A(TBBPA)in water.The specific research contents are as follows:(1)A molecularly imprinted ratiometric fluorescence sensor CQDs@SiO2/yCdTe@MIP was constructed using silica-coated blue fluorescent carbon quantum dots(CQDs@SiO2)as an external fluorescence reference signal and yellow fluorescent CdTe quantum dots(y-CdTe QDs)as a fluorescence response signal for the visual detection of TBBPA.Firstly,blue fluorescent CQDs were synthesized by the hydrothermal method and then coated with silica by the reverse microemulsion method to obtain an external fluorescence reference signal CQDs@SiO2.At the same time,SiO2 was used as the imprinting carrier,and the imprinted polymer y-CdTe@MIP was obtained by co-condensation on the surface of SiO2 in the presence of the response signal y-CdTe QDs,the functional monomer 3-aminopropyltriethoxysilane(APTES)and crosslinking agent tetraethoxysilane(TEOS).The synthesized materials were characterized by a series of characterization methods.The ratiometric fluorescent sensor CQDs@Si02/y-CdTe@MIP was constructed by mixing the solution of blue fluorescent CQDs@SiO2 and yellow fluorescent y-CdTe@MIP in proportion.under the optimized conditions,the hybrid sensor has a good linear relationship between the fluorescence intensity ratio and TBBPA concentration in the range of 0.2 to 15 μm with a detection limit of 10.4 nM.The change of the fluorescence intensity ratio in the detection process makes the color of the mixed sensor change from yellow to blue,and the visual detection of TBBPA is realized.In addition,the hybrid sensor was used for the detection of TBBPA in a real sample.The recoveries were 97.47-102.17%,and the relative standard deviations were less than 3.8%.(2)A molecularly imprinted ratiometric fluorescence sensor C-MIP was constructed by using CQDs@SiO2 as the imprinted carrier and red fluorescent CdTe quantum dots as the fluorescence response signal for visual detection of TBBPA.Firstly,CQDs containing amino and carboxyl groups were prepared by the hydrothermal method,and then SiO2 was coated on the surface of CQDs to obtain a stable built-in reference signal CQDs＠SiO2.Then,the red fluorescent CdTe quantum dots were introduced into the imprinted layer by the sol-gel method to prepare the ratiometric fluorescence sensor C-MIP with CQDs@SiO2 as the carrier.In the presence of TBBPA,the fluorescence intensity of CQDs as a reference signal remained stable,while the fluorescence intensity of CdTe quantum dots as a response signal was effectively quenched.The change of fluorescence intensity ratio makes the fluorescence color of the sensor changed from red to blue,achieving the purpose of visual detection of TBBPA.The sensor has a good linear relationship between the fluorescence intensity ratio and TBBPA concentration in the range of 0.1-10 μM with a detection limit of 3.8 nM.At the same time,a fluorescent test strip for the visual detection of TBBPA was prepared by combining MIP with filter paper.The test strip has the advantages of simple operation and intuitive data display,which makes it very suitable for offline visual detection of target molecules.(3)A molecularly imprinted ratiometric fluorescence sensor FMIP was prepared by using mesoporous silica nanoparticles as the imprinted carrier and green fluorescent organic monomer as the fluorescence response signal for high selectivity and sensitivity detection of TBBPA.Firstly,blue fluorescent CQDs were prepared by the hydrothermal method and were coated with SiO2 by the reverse microemulsion method to obtain CQDs@SiO2.Then,mesoporous silica was coated on the surface of CQDs@SiO2 by an oil-water two-phase method.After removing the template molecule,mesoporous silica nanoparticles CQDs@mSiO2 were obtained.The vinyl was modified on the surface of mesoporous silica nanoparticles to obtain vinyl-modified mesoporous silica nanoparticles CQDs@mSiO2-KH570.The molecularly imprinted ratiometric fluorescence sensor FMIP based on the mesoporous carrier was prepared by using CQDs@mSiO2-KH570 as the carrier and initiating the polymerization of organic fluorescent monomer in the presence of the functional monomer,template molecule,and crosslinking agent.Under optimal conditions,the sensor has a good linear relationship between the fluorescence intensity ratio and TBBPA concentration in the range of 0.05-10 μM with the detection limit of 2.5 nM.In addition,the sensor was also used for the determination of TBBPA in real samples,with recoveries of 97.70-102.70%and relative standard deviations of 0.94-2.33%.