Construction And Property Of Containing Rare Earth Elements Polyoxometalates/Organic Small Molecules Assemblies

Supramoleculear self-assembly utilizes the non-covalent bond weak interactions and synergistic effects between various building blocks to build ordered aggregates with functional organic,inorganic or biological small molecules as basic assembly units.Ion self-assembly(ISA),whose main driven force is electrostatic interaction,exhibits strong designability and is easy to construct aggregates of hierarchical structures.Polyoxometalates(POMs)are metal clusters formed of transition metal atoms by bridging oxygen bonds.The structure and properties of POMs make them the preferred building blocks in supramolecular chemistry.Especially,the POMs containing rare earth elements have excellent optical,electrical and magnetic properties.The combination of POMs and organic components based on the ISA method not only fully exerts the functionality of POMs,but also achieves supramolecular synergistic effects.The functional supramolecular materials prepared by self-assembly of POMs have rich application value and important academic research significance.The main research content of this dissertation is made up of four parts as following:Part ?,the introduction of the research background.The concepts of supramolecular chemistry,supramolecular self-assembly,and ionic self-assembly based on electrostatic interaction are introduced;the structure types,properties and applications of POMs are presented,especially the POMs containing rare earth elements.The self-assembly methods of POMs and the research status of organic molecules and POMs composites is reviewed.The application of functional materials of POMs self-assembly is summarized.Finally,the objective and significance of this dissertation are presented.Part ?,nanoflowers formed by self-assembly of Weakley-type polyoxometalate EuW10 and alkylamine and their catalytic properties.The morphologies and sizes of the nanostructures could be simply controlled by varying the molecular weights and concentrations of alkylamines.The fluorescent color of EuW10 and tetraethylenepentamine(TEPA)nanoflowers changed compared with that of EuW10 owing to the varied symmetry degree of europium coordination in EuW10/TEPA nanoflowers.FT-IR?XRD?UV-vis,TGA and other characterizations demonstrated that this effective self-assembly occurs mainly though the hydrogen bond and electrostatic interaction between EuW10 and TEPA.What's more,the EuW10/TEPA nanoflowers after calcining showed recyclable decomposition efficiency toward methylene blue dyes.Part ?,the EuW10/TbW10/TEPA fluorescent nanoflowers prepared through ion self-assembly and its functional applications were studied.The shape and petal size of the nanoflower as well as its fluorescent behaviors can be tuned through varying the ratio of EuW10/TbW10 while fixed the concentration of TEPA.It's worth noting that the EuW10/TEPA composites displayed good stability toward temperatures above 180 K while the fluorescent emissions of TbW10/TEPA composites decreased linearly with an increase in temperature in the range of 100-260 K,which may be used as luminescent ratiometric thermometers.Moreover,after being mixed with polydimethylsiloxane(PDMS),the as-formed hybrid films showed stable fluorescence along with good transparency.The robustness of the hybrid films was also demonstrated by corrosion resistance upon treatment with strong acid and alkali,and the hybrid films have fluorescence responsiveness to toluene which can be used as fluorescent sensors for the recyclable detection of toluene.Part ?,the system built by tetra-n-alkyl ammonium(TA)and anion cluster POMs(EuW10)with enhanced fluorescent properties have been studied using ionic self-assembly technique.The factors of alkyl chain length,amimo group,and inorganic salt concentration have influences to morphology and fluorescent properties of the system.The results indicated that the fluorescent intensity of EuW10/tetramethylammonium bromide(TMAB)composite increased about 14 times,whereas the extent of increase of fluorescence for EuW10/tetraethylammonium bromide(TEAB)and EuW10/tetrabutylammonium bromide(TBAB)composites gradually decrease due to the bulkier steric hindrance of the longer alkyl chain.The luminescence of EuW10/TMAB nanoparticles is pH responsive,and the reversibility of their structures and luminescence can be realized upon the addition of NaOH/HCl.Moreover,the EuW10/TMAB system also shows great fluorescence-sensing behavior,which could detect Cu2+ with a detection limit of 0.15 ?M.Our work provides a facile construction strategy for a functional fluorescent complex via POMs-based supramolecular self-assembly in aqueous solution,which will be further used in photoelectricity and sensors.