Preparation Of Lanthanide MOF Functional Nanoparticles And Their Applications In Sensing And Catalysis

As newly organic-inorganic hybrid materials, metal-organic framework (MOF) show tremendous prospect in gas separation and storage, catalysis, chemical sensing, luminescent materials and nanomedicine due to their flexible structures and unique characters such as light, electricity and magnetism. In recent years, designing and preparing functional materials based on MOF have become a research hotspot. Because of the unique fluorescence properties, fluorescent probes based on lanthanide are widely applied in bioassays because their long emission lifetimes can be utilized to eliminate short-lived autofluorescence of biosamples through time-resolved techniques. However, the luminescence of lanthanide ions is weak because of their low molar absorptivity. Thus, they usually need antenna ligands to enhance the fluorescence of themselves. Taking advantage of the component and structural flexibility of MOF, we used Tb3+ as central ion to design and prepare three new types of lanthanide MOF functional nanoparticles. And then we used them to construct new fluorescent scavenger or sensors which are used for sensing in aqueous solution. The main research works are summarized as follows:(1) Nitrite plays an important role in nitrogen cycling of organisms and environment. At the same time, due to its possible carcinogenicity, nitrite is also a substance relating to the safety and health of human beings. Based on the structure platform of MOF, we designed and prepared a kind of MOF nanoparticles U-Tb-OBBA which can selectivity determine NO2-and light-indicate the degree of NO2- removal. We used Tb3+ as luminous ion, 4,4'-oxybis(benzoic acid) (OBBA) as an antennarnolecule, and 5-fluorouracil (U) as an auxiliary ligand to prepare the MOF nanoparticles by solvothermal method. U-Tb-OBBA MOF nanoparticles are able to selectivity fluorescent-determine and remove NO2- in aqueous solution. The minimum detectable concentration of NO2- in drinking water and human urine are 300 nM and 800 nM, respectively. The removal capacity is about 4.44 mg of NO2- per gram of particles, which is satisfied with the elimination of NO2- in drinking water. We did a research to reveal the mechanism why U-Tb-OBBA nanoparticles response to NO2-specifically. The MOF nanoparticles U-Tb-OBBA designed and prepared by us is the first scavenger nanoparticles with light-indicating function.(2) Traditional methods for the determination of pH such as indicator method and glass electrode method are not suitable for the determination of pH in organism. The fluorescent probe is available for the determination of pH, but the majority of pH fluorescent sensors reported at present were only applied to the determination of pH in weakly acid or alkaline circumstances, while the fluorescent sensors for determining lower pH almost haven't been reported. Based on the structure platform of MOF, we designed and prepared a kind of fluorescent sensor—MOF nanoparticles DMF-Tb-Phen for the determination of pH in strong acid environment. We used Tb3+ as luminous ion, DMF and Phen as functional ligands to prepare the MOF nanoparticles by solvothermal method. Based on ICT and PET effects, DMF-Tb-Phen MOF nanoparticles can linearly response the change of concentration of H+ with the reange of pH from 1.03 to 3.50, showing good selectivity and stability. In addition, DMF-Tb-Phen was successfully used to determine pH in artificial gastric juices. DMF-Tb-Phen MOF nanoparticles prepared by us show a bright application prospect in the determination of pH in lysosome, acidophilic cells and gastric juice.(3) H2O2 is a catalytic by-product of almost all oxidases, and we can determine biological molecules such glucose, cholesterol and uric acid indirectly through the determination of H2O2. Thus, the determination of hydrogen peroxide is of great significance in many aspects such as food safety, environmental protection, disease diagnosis and biomedicine. Based on the structure platform of MOF, we designed and prepared a kind of luminous MOF catalyst PA-Tb-Cu which can catalyze the reaction involving H2O2. We used Tb3+ as luminous ion, Cu2+ as catalytic ion, and m-phthalic acid (PA) as organic ligand to prepare the MOF nanoparticles by solvothermal method. We found that PA-Tb-Cu can efficiently catalyze the reaction of AA and H2O2 and the catalytic efficiency is about 16 times of Cu2+ which is a commonly used catalyst. PA-Tb-Cu also can light-indicate the extent of the reaction upon catalyzing the reaction and then can determine H2O2. The result showed that this fluorescent menthod had high sensitivity with the detection limit of 0.2 ?M. Because of the utilization of Tb3+, this method is particularly suitable for the determiantion of biological samples with background fluorescence. It may be the first time to design and prepare a catalyst with light-indicating function. What's more, we researched the light-catalyze mechanism.