Preparation Of Transition And Lanthanide Metal Coordination Polymers And Their Fluorescence Sensing Analysis Of Ions And Organics

Metal-organic coordination polymers are porous organic-inorganic hybrid materials formed by coordination of organic ligands with metal ions or metal clusters.Due to its large specific surface area,good thermal stability,diverse and designable structure,and many active sites,it has attracted extensive attention of many researchers in recent years.In particular,luminescent metal-organic coordination polymers possess rich responses of host and guest due to their special luminescent properties,which have important application potential in the field of fluorescence sensing.In this thesis,several luminescent metal-organic coordination polymers were constructed by encapsulating nanoparticles,modifying ligands and introducing rare earth ions,etc.,and they were successfully applied to the efficient detection of heavy metal ions,anions,pesticides,anthrax spore.The main works in the thesis are as follows:(1)Lys-Au NPs@ZIF-8 nanocomposite was synthesized by ZIF-8 encapsulating the gold nanoparticles for sensitive detection of Hg²⁺in aqueous solution.Scanning electron microscopy(SEM)shows that the particle size of the nanocomposite is between 300 nm and 500 nm,and it has good dispersibility in water.The fluorescence emission peak of Au NPs at 640 nm decreased with the increase of Hg²⁺concentration,while the fluorescence emission peak of Lys at 430 nm remained basically unchanged.Therefore,a ratio fluorescence sensor for detecting Hg²⁺(Lys-Au NPs@ZIF-8)was successfully constructed.The linear range of Hg²⁺is 24-450 nm,and the detection limit is 7.5 nm based on a 3d/slope.(2)A novel sensing platform for highly selective and sensitive detection of Fe³⁺in aqueous solution was proposed based on 2,5-dihydroxyterephthalic acid(DOBDC)-Zn²⁺MOFs(Zn MOF-74).The as-prepared Zn MOF-74 exhibited uniform clavicorn nanostructures and high day-to-day stability in acidic aqueous solution(p H4.0).Because of the special response of phenolic hydroxyl groups of DOBDC with Fe³⁺,the cation exchange between Fe³⁺and Zn²⁺occurred,which caused collapse of the skeleton and formed a blue weak-fluorescent iron(III)-phenol salt complex(Fe-DOBDC),which led to the effective fluorescence quenching of Zn MOF-74.Zn MOF-74 was used as a probe for detection of Fe³⁺under relatively acidic condition with a good linear range of 0.1-100?M and a low detection limit of 40 n M.The fluorescence probe was also applied to determine Fe³⁺in real river water and human serum with good recovery and accuracy.This work provided a good Fe³⁺sensor based on Zn MOF-74 due to high affinity between phenolic hydroxyl group and Fe³⁺.(3)A luminescent hydroxyl-functionalized MIL-53(Al)(OH-MIL-53(Al))was prepared by one-step solvent thermal method for multiresponsive fluorescence sensor.The OH-MIL-53(Al)exhibited uniform nanospheres with average diameter of 150±20nm,flexible three-dimensional frameworks,and good dispersion in water.The OH-MIL-53(Al)emitted green fluorescence with a maximum wavelength of 515 nm which showed good fluorescence quenching response for sensing F^-and fluoresce fluorescence enhancement response for water,with good day-to-day stability.The mechanism was based on protonation/deprotonation of hydroxyl group located on OH-MIL-53(Al).Good linear relationship could be found between the luminescence intensity of 515 nm and F^-concentrations in the range of 0.2-60?M with a determination limit of 70 n M.At the concentrations from 0.3%to 100%,the fitting curve for water content was in good agreement with the linear equation,and the detection limit was 0.10%.OH-MIL-53(Al)demonstrated excellent fluorescence sensing performance,indicating that it could be used as a multiresponsive sensor to practical application.(4)A luminescent Tb³⁺-pyromellitic acid(H₄L=pyromellitic acid)coordination polymer(Tb-H₄L CP,Tb L_0.5(H₂L)_0.5(H₂O)DMF)was prepared for multiresponsive fluorescence sensor.The Tb-H₄L CP exhibits uniform nanospheres with average diameter of 220±20 nm,good crystalline structure,and good dispersion in water.The Tb-H₄L CP emitted the characteristic green fluorescence through antenna effect from H₄L which was an excellent antenna molecule when excited at 270 nm and could be used to selectively determine Fe³⁺and polychlorinated benzenes based on fluorescence quenching effect.The coordination between Fe³⁺and carboxylic oxygen of Tb-H₄L to damage the antenna effect and polychlorinated benzenes absorb the excitation light to result the inner-filter effect of fluorescence,which quenched the fluorescence of Tb-H₄L CP.The linear range for Fe³⁺was 2.0-100?M with a detection limit of 0.7?M and for 1,3,5-trichlorobenzene was 0.26-0.44×10³ ppm with a detection limit of 0.087 ppm.The Tb-H₄L CP demonstrates excellent fluorescence sensing performances,indicating that it can be used as a multi-response sensor to effectively measure toxic and harmful substances.(5)We proposed a new strategy for ratiometric fluorescence detection of DPA based on microporous Ln/melamine-terephthaladehyde Schiff base networks(Ln/MTSNW)complex for the first time.The microporous MTSNW was prepared by amine-aldehyde condensation between melamine and terephthaladehyde and presented lamellar and octahedral structure.Lanthanide ions,Eu³⁺or Tb³⁺were coordinated with N atoms of MTSNW to form Ln/MTSNW complex.The microporous Ln/MTSNW complex not only provided large surface area to improve the sensitivity of DPA detection,but also constructed ratiometric fluorescence sensors to eliminate environmental effects and instrument fluctuation.DPA was a highly efficient antenna molecule for Eu³⁺and Tb³⁺and transferred the energy to Eu³⁺or Tb³⁺to sensitize their fluorescence.The Ln/MTSNW complex were uniformly and stably dispersed in aqueous solution for DPA detection with a linear range from 15n M to 7?M and low detection limit of 5.2 n M for Eu/MTSNW and a linear range from 4 n M to 2.5?M and low detection limit of 1.4 n M for Tb/MTSNW.Due to the simple preparation of Ln/MTSNW complex and low technical requirement,the ratiometric fluorescence DPA sensor based on Ln/MTSNW complex might show great potential in practical applications.