Preparation Of Fluorescent Probes Based On CdTe Quantum Dots Coated With Molecularly Imprinted Polymers And Their Applications In The Detection Of Malachite Green And Lecuomalachite Green In Aquatic Products

As an industrial dye,malachite green?MG?has been once applied in aquaculture for disease treatment caused by bacteria and fungus.Many studies confirmed that more than 80%of MG in organisms would be metabolized and transformed into liposoluble leucomalachite green?LMG?,and resulted in serious carcinogenicity,teratogenicity and mutagenicity to human body.At present,the most common detections of MG and LMG in aquatic products depend on large apparatus such as HPLC and MS,which show some disadvantages,such as fussy pre-treatment process,expensive instruments and long detection period.In this work,fluorescent probes based on CdTe QDs coated with molecularly imprinted polymers were fabricated for rapid detection of MG and LMG in aquatic products based on fluorescence quenching.The dissertation mainly inclueds the following parts:Section 1,a fluorescent probe based on PS@CdTe coated with molecularly imprinted polymers was fabricated for rapid detection of MG.After activization with PDDA,PS could combine with CdTe QDs on account of electrostatic interaction.Molecularly imprinted polymers?MIP?was fabricated through the precipitation polymerization using PS@CdTe as the core,MG as the template,acrylamide?AM?as the functional monomer,ethylene dimethacrylate?EGDMA?as the cross-linking agent,2,2'-Azobis?2-methylpropionitrile??AIBN?as the initiator and ethylalcohol as the solvent.The optimization results indicated that the molar ratio of MG,AM and EGDMA was 1:8:20,the amounts of PS@CdTe was 28 mg,the volume of ethylalcohol was30 mL,and the polymerization time was 3 h.The adsorption capacity of MIP@PS@CdTe toward MG was 15.3 mg g^-11 and the adsorption equilibrium time was 3 min.Based on normal fluorescence quenching,the as-prepared MIP@PS@CdTe was applied to detect MG in aquatic products.The linearity concentrations ranged from 0.01 to 20?mol L^-1with a detection limit of4.7 nmol L^-1,and the spiked recoveries of MG ranged from 87.6%to 105.4%.Section 2,MIP-coated QDs was fabricated through the precipitation polymerization using CdTe QDs as the core,LMG as the template,AM as the functional monomer,EGDMA as the cross-linking agent,AIBN as the initiator,acetonitrile as the solvent,and was used to detect LMG in aquatic products.The preparation condition of MIP-coated QDs were optimized and the approximate partical size was 67 nm.The adsorption capacity of MIP-coated QDs toward LMG was 52?g g^-11 and the adsorption equilibrium time was 10 min.Based on synchronous fluorescence quenching,the as-prepared MIP-coated QDs was applied to detect LMG in fish samples.The linearity concentrations ranged from 0.1 to 20?mol L^-1with a detection limit of 30nmol L^-1,and the spiked recoveries of LMG ranged from 94.0%to 107.8%.Section 3,MIP-coated QDs was prepared via a reverse microemulsion method using mixture of cyclohexane,n-hexanol and triton X-100 as microemulsion system,CdTe QDs as the core,LMG as the template,?3-aminopropyl?triethoxysilane?APTES?as the functional monomer,tetraethyl orthosilicate?TEOS?as the cross-linking agent,ammonium hydroxide as the initiator.The optimization results indicated that the molar ratio of LMG,APTES and TEOS was 1:3:10,the amounts of CdTe QDs was 5 mg.The partical size of MIP-coated QDs was around 50 nm.The adsorption capacity of MIP-coated QDs toward LMG was 73?g g^-11 and the adsorption equilibrium time was 7 min.Based on synchronous fluorescence quenching,the as-prepared MIP-coated QDs was applied to detect LMG in fish samples.The linearity concentrations ranged from 0.1 to 20?mol L^-11 with a detection limit of 23 nmol L^-1,and the spiked recoveries of LMG ranged from 96.2%to 104.9%.Section 4,The dual templates molecularly imprinted fluorescent probe was prepared via a reverse microemulsion method using MG and LMG as the dual templates.In the process of fluorescence detection,the amounts of MG in mixture could be accurately measured based on normal fluorescence quenching,the total amounts of MG and LMG could be measured based on synchronous fluorescence quenching,and the amounts of LMG could be abtained.So CdTe@MIP could simultaneously detect MG and LMG in mixture.Under optimal conditions,The detection limit of MG and LMG were 17 nmol L^-11 and 28 nmol L^-1,respectively.The spiked recoveries of MG and LMG ranged from 92.0%to 107.0%and 91.0%to 108.0%,respectively.The results demonstrated that the as-prepared fluorescent probes based on CdTe QDs coated with molecularly imprinted polymers could detect MG and LMG in aquatic products with accuracy and sensitivity.