Synthesis Of Fluorescence Sensor Based On Surface Molecular Imprinted Polymers Capped Quantum Dots For Selective Identification And Detection Of Food Contaminants

The food pollution issue has become even worse with the development of modern industry,which can be a great threat to human health,making the detection and supervision on food pollutes more and more important.However,traditional detection methods cannot meet the demand of speedy,simple and accurate detection of food pollutes in terms of complicated,tedious and time-consuming pre-treatment and detection procedures.In addition,due to the complexed components and low concentration of such pollutes,the separation and concentrating process are required.Thus,it is of great importance and urgency to develop a highly selective,recognizable and sensitive detection method towards to food pollutes.Molecular imprinted fluorescence probe,which combines the merits of both molecular imprinting technology and fluorescent detection,can be applied to concentrate and recognize particular component in complexed mixtures as well as detect its accurate concentration according to the fluorescence change.Making use of the strength of surface imprinting technology and fluorescent properties of quantum dots,this article aims at preparing selective surface molecular imprinted fluorescence probe based on GO or mesoporous silica materials,which possess well-designed morphology and higher selectivity towards particular food pollutes.Besides,several effective measures were taken to characterize the microstructures and functional groups of the surface molecular imprinted fluorescence probe,along with investigating their recognizable and selective ability to microscale food pollutes.Moreover,Standard addition recovery experiments were carried out in real samples to evaluate the practicability of the surface molecular imprinted fluorescence probe.The main research contents and results are listed below:?1?By using propanamide?PAM?as Pseudo template,methylacrylic acid?MAA?as functional monomer,the complex of Mn doped ZnS quantum dots and GO as substrates,a novel virtual fluorescent surface molecularly imprinted sensor?AM-MIP?was prepared by free radical polymerization for acrylamide detection in deep-fried food.When analyzing the microstructure and morphology of AM-MIP,a uniform imprinted layer coated on GO surface was observed.Through static adsorption experiment,the timescale needed for reaching adsorption equilibrium of AM-MIP was investigated,demonstrating a high speed recognizable PAM sensor prepared successfully.The stability when exposed to different p H condition,detection range and fluorescentstability of AM-MIP were further studied,suggesting higher fluorescent stability and wider linear range.The obtained AM-MIP sensor was applied to trace amount AM detection in fried food,proving the practicability of AM-MIP sensor.?2?By using sol-gel method and P123 served as pore-foaming agent,Zn O quantum dots were coated with SiO₂,obtaining a stable SiO₂@Zn O mesoporous fluorescent substrate material.Using melamine?MEL?as template,acrylic acid as functional monomer,a fluorescent molecular imprinted probe?MEL-MIP?was synthesized,which can be utilized in MEL adsorption.The MEL-MIP was characterized by TEM,PL,FT-IR,etc.to study its structure.When investigating its adsorption ability,pH,sample concentration,adsorption equilibrium as well as recognition capability were taken into consideration,demonstrating MEL-MIP was a stable and speedy fluorescent sensor.The lower detection limit and wider linear range were proved by linearly fluorescence quenching,being applied to MEL detection in milk.?3?By taking SBA-15 as microreactor and furfuryl alcohol?FA?as precursor carbon resource,graphene was successfully prepared in the internal channel wall of SBA-15 by high temperature carbonization.The uniform graphene quantum dots?GQDs?were obtained subsequently by oxidative cleavage graphene with nitric acid vapor.Next,selecting bisphenol A?BPA?as template,MAA as well as MAP phenylalanine methyl ester?MAP?as functional monomers,the polymerization occurred on the modified GO surface with GQDs added in during the polymerization,gaining a novel fluorescent surface imprinted sensor towards BPA?BPA-MIP?.It was observed that BPA-MIP possessed selectivity and sensibility towards BPA in complex mixtures.The wider linear range and good recovery rate of BPA-MIP towards BPA in soft drinks were proved by conducting fluorescence detection,in which the fluorescence of BPA-MIP quenched with raising BPA concentration.?4?Water-soluble N-doped carbon quantum dots?NCQDs?was prepared by hydrothermal process with citric acid amine and ethanediamine as precursor.Then,a unique fluorescent imprinted polymer?4-NP-MIP?,which possess selective absorption capability towards 4-NP,was prepared by using MAA as functional monomer and 4-nitrophenol as template to prepared NCQDs doped imprinted polymer based on GO.The structure and morphology of 4-NP-MIP was characterized,proving homogeneous imprinted microspheres grasped on 2D GO sheets.The static adsorption experiments were performed,finding out the best adsorption condition with minimumadsorption time was at pH 7.0.4-NP-MIP was turned out to be with high selectivity and recovery rate when detecting 4-NP in vegetables.