The Applications Of Metal-organic Frameworks In The Photochemical Detection Of Lead,Methyl Parathion And Curcumin In Food

Metal-Organic Frameworks?MOFs?are porous crystalline materials composed of metal ions or metal clusters and organic ligands coordinated by self-assembly.Owing to the advantages of high porosity,adjustable pore structure,and modifiable metal sites,MOFs showed potential applications in gas adsorption and separation,drug loading,electrochemical sensing,and energy storage.For the applications,first,MOF-5 was used as a phosphorescent probe to achieve highly selective and sensitive detection of Pb???.Second,Fe₃O₄@ZIF-8 was used to catalyze H₂O₂ to oxidize TMB thus generated a color reaction.Methyl parathion?MP?can inhibit the activity of acetylcholinesterase to produce H₂O₂,thus developed the rapid detection of MP.Third,a ratiometric fluorescence sensor for curcumin?Cur?in condiments was developed by using carbon dots?CDs?@MOF-5@rhodamine-6G?Rh-6G?composite.The thesis is devied into four parts:1.The development,synthesis methods,and applications in sensing,gas storage,catalysis,and drug delivery of MOFs are briefly introduced.The research progress in detecting Pb???,MP,and Cur in food is elaborated.2.A novel,rapid,and“turn-on”phosphorescent sensor was developed to monitor Pb???using metal-organic framework-5?MOF-5,Zn₄O?TPA?₃,TPA:terephthalic acid?as a highly selective and sensitive luminescent probe.A mechanism describing the leaching of Zn?II?from Zn₄O complexes and self-assembly of TPA after Pb???coordination is proposed for the MOF-5-Pb???system.Using enhanced phosphorescence,the sensor displays a wide linear detection range of0.01-10?mol/L and a low detection limit of 2 nmol/L for the determination of Pb???.Moreover,it is noteworthy that when immobilized in a polyethylene glycol?PEG?film,the MOF-5 probe exhibited a visually distinct color change at 1.0?mol/L Pb???under 365 nm UV light.From these results,a test strip was prepared for semi-quantitative analysis of Pb???content.Finally,the proposed phosphorescent sensor was successfully utilized to detect Pb???content in mussel.3.A colormetric sensor for MP was fabricated by using Fe₃O₄@ZIF-8 as the mimetic enzyme.Fe₃O₄ nanoparticles were prepared by hydrothermal method,and then wrapped with ZIF-8 to obtain core-shell structural Fe₃O₄@ZIF-8 nanocomposite.The as-synthesized Fe₃O₄@ZIF-8 has mimetic properties thus can catalyze the oxidation of TMB by H₂O₂ to make the solution color change from transparent to blue.It is well-known that AChE is able to generate H₂O₂ under the reaction of ATCl and CHOx,and MP has a inhibitory effect on AChE.Based on these observations,a simple and rapid colorimetric method was proposed to detectMP.Under the optimal conditions,the MP concentration in a range of 10-200?g/L has a good linear relationship with the absorbance,and the detection limit is 6.3?g/L.Finally,the as-proposed method was successfully applied in the detection of MP in cabbage.4.A new ratiometric fluorescence sensor based on CDs@MOF-5@Rh-6G composite was established and used to detect Cur in condiments.Using Zn?NO₃?₂·6H₂O,CDs,and TPA as precursors,CDs@MOF-5 was prepared by hydrothermal method,and then CDs@MOF-5@Rh-6G composite was prepared by further adsorption of Rh-6G on the surface of CDs@MOF-5.Our study found that the CDs@MOF-5@Rh-6G reveals a cubic shape with a particle size of about 100?m.Under excitation at 335 nm,the as-prepared CDs@MOF-5@Rh-6G showed two distinct emission peaks at 435 nm and 560 nm.After adding Cur,based on the internal filtering effect and dynamic quenching effect,the fluorescence of CDs at 435 nm is absorbed by Cur with an absorption range of 300-500 nm,thus the fluorescence peak intensity(F₄₃₅)is quenched,while the emission of Rh-6G is at 560 nm remained unchanged.Under optimal conditions,the Cur concentration in the range of 0.1-5?mol/L has a good linear relationship with the ratio of F₄₃₅/F₅₆₀,and the detection limit is 15 nmol/L?S/N=3?.Finally,the established method was successfully applied to the detection of Cur in the condiment.