Preparation Of Mn Doped ZnS Quantum Dot-molecular Imprinted Polymer And Its Application In Biochemical Analysis

The combination of molecular imprinted polymer and nanometer materials in the biochemical analysis and separation has great application prospect.As a kind of nano-structure crystal,the quantum dots(QDs)not only allows them as a fluorescence signal source,but also be available as a multi-functional substances binding with various analytes and biological macromolecules.Using QDs as substances,preparation of Mn-doped ZnS quantum dot-molecularly imprinted polymer composites(ZnS:Mn QDs@MIP)by molecular imprinting,has the ability as chemical/biological biomimetic sensor,which can be used in recognition and detection of specific component in complex samples.This biochemical biomimetic sensor combine the high selectivity of molecular imprinting polymer and optical properties of quantum dots in one system,not only increases the specific recognition ability for the target molecules,but also improves the detection sensitivity,which has a great advantage in analysis of specific components in complex sample analysis.In this paper,we combined the water soluble zinc sulfide quantum dots with the molecularly imprinted materials,choosing two typical compounds: lysozyme and bisphenol A as template molecule,preparing Mn:ZnS QDs@MIP fluorescent composites as fluorescence artificial receptors for target analyte,and evaluated their practical application ability in real samples.The main content is as follows:Chapter 1: First,the introduction reviewed the principle of molecular imprinting technique,classification and the polymerization technology.Secondly,overviewed the properties of quantum dots,the principle and preparation technology.Finally,summarized the technical route of preparation of QDs@MIP composites,and discussing its research significance and their application in the field of biochemical analysis.Chapter 2: Successfully synthesized 3-Mercaptopropyltriethoxysilane(MPTS)modified ZnS: Mn QDs.The QDs are close to spherical morphology,with diameters ranging from 4 to 5nm,and has strong orange fluorescence emission.The preparation of QDs@MIP fluorescent composites was using MPTS modified QDs as support,bisphenol A as template molecule,3-aminopropyltriethoxysilane and tetraethoxysilane as functional monomer and cross-linker.The QDs@MIP can specific binding BPA,result in obviously fluorescence quench.The fluorescence quenching of QDs@MIP composites is proportional to the concentration of the BPA,therefore,the QDs@MIP can as fluorescent sensors for detection of BPA.The fluorescent sensors had a rapidly absorb kinetics for BPA,reached the adsorption equilibrium after 30 min,and the limit of detection was 35.22 nm.The QDs@MIP composites can specific recognition of a target molecule BPA,and the imprinting factor(IF)for BPA was 4.58.Moreover,the proposed fluorescent receptor was satisfactorily applied to the determination of BPA in real samples,with recoveries of 92 to 106% for bisphenol A.The study shows that the preparation of bisphenol A imprinted-QDs composite can be used as a fluorescent sensor for specific recognition bisphenol A.The proposed method is simple,quickly,stability and low-cost,provides the theoretical basis and reference for analysis of trace BPA in water samples.Chapter 3: This section demonstrates a new strategy for producing fluorescent QD embedded molecularly imprinted membranes(QD-MIMs)for specific recognition of a target molecule.The MPTS modified Mn-doped ZnS QDs entrapped in polyacrylamide gel crosslinking network polymer matrix for fabricating QD-MIMs by molecular imprinting procedure on a silylanized glass plate.The atomic force microscopy(AFM)shows that in the QDs were successfully embedded in polymer network structure,and uniform dispersion.When the target molecule was capture by the MIMs,the fluorescence intensity of MIMs was quenched due to the activated by the electron transfer between the QDs and bisphenol A.The quenched fluorescence emission intensity was proportional to the concentration of bisphenol A.Hence,based on the efficient quenching mechanism,a simple and rapid procedure was developed for directly fluorescent detecting trace levels of specific component in complex samples.The QD-embedded MIMs can be used as a fluorescent sensor for specific recognition BPA.The adsorption equilibrium of MIMs was reached after 7 min and the limit of detectionwas 0.0019 μM,had more rapidly absorbed kinetics compare and better LOD compared to the QDs@MIP.The QD-MIMs has a higher selectivity for target molecule BPA,and the imprinting factor(IF)is 8.98,which was higher than that of analogs of bisphenol A.However,the non-imprinted composites were not obviously response to the BPA and its analogs.Moreover,the proposed fluorescent MIMs receptor was satisfactorily applied to the determination of BPA in real samples,the recoveries of BPA was 92% to 108%.The experiment results shows that the QD-MIMs can be use as fluorescent sensors for detection of target analyte,which has a many advantages such as high selectivity,good sensitivity,fast absorption kinetics,convenient to operation,and low-cost.This proposed method has great potential applications in the field of fast detection.Chapter 3: This section demonstrated a new method for preparing fluorescent artificial receptor of lysozyme by coating molecular imprinted polymer layer on the surface of L-cysteine modified Mn-doped ZnS QDs via the surface molecular imprinting process.As a kind of nontoxic material,L-cysteine was used to modify the surface of QDs by the ligand competition.This process reduced cytotoxicity,increased the water dispersion ability and stability of QDs.The QDs@MIP composites were synthesized using L-cysteine capped ZnS:Mn QDs as support,acrylamide as a functional monomer,N,Nmethylenediacrylamide as a cross-linker and lysozyme as template molecule via a facile surfaceimprinting process.These MIP-based QDs composites combined the advantages of MIPs with the optical properties of the QDs,which could be a potential as fluorescent biochemical sensors for recognizing and detecting.The fluorescent artificial receptor can be used as a fluorescent sensor for specific recognition Lyz with a rapidly absorb kinetics,the adsorption equilibrium was reached after 21 min,the limit of detection was 25.2 μM,and the optimum solution pH value was found to be pH 6.0.The fluorescent artificial receptor has a high selectivity for Lyz,and the imprinting factor(IF)is 4.65,which was higher than that of the reference proteins.As the control,the non-imprinted composites were not obviously response to the Lyz and its analogs.The proposed fluorescent receptor was satisfactorily applied to the determination of Lyz in real samples.Moreover,as a fluorescent sensor,the QDs@MIP composites could accurately determined lysozyme with good regeneration and stability.The experiment results suggest that the MIP-based fluorescent artificial receptor provides a direct,high selectivity and sensitivity approach for fluorescence detecting of target protein in complex biologic samples.