The Preparation And Properties Of Metal-containing Multifunctional Nanomaterials

With the development of science and technology, multifunctional nanomaterialsattracted more and more attention of scientists and they have been widely used inions detection, catalysis and biological imaging. Existing functional materials arefluorescent, magnetic, and electrical function. However, nanomaterials with singlefunction can not be suitable for practical applications. Multifunctional hybridmaterials, especially magnetic and fluorescent hybrid materials become one ofresearch focus. Therefore, based on the point of view of basic research andapplications, exploring novel synthesis method and property of magnetic andfluorescent nano-materials as well as further preparing the multifunctional hybridmaterials will undoubtedly have important practical significance. In my PhD paper,around metal-containing multifunctional nanomaterials, we carry out the follow fourparts of work:In Chapter2, we develop reduction method with weak amine to preparefluorescent nanoclusters （NCs）. Using hydrazine hydrate （N2H4.2H2O） as reducingagent and glutathione （GSH） as stabling agent, fluorescent Ag NCs were synthesizedat room temperature. As-prepared Ag NCs exhibited red fluorescence with amaximum emission at620nm, and had good stability, water-soluble and uniformsize. Using presynthesized and size-specific controlled Ag nanodots （Ag NDs） astemplates, the galvanic exchange reaction was used to prepare fluorescent goldnanodots （GNDs）. As-prepared GNDs with the size of2.9nm lead to propensities ofstrong fluorescence （quantum yields¹0%）, high stability and surface-bioactivity.The PL of resultant GNDs showed high photo-, time-, metal-and pH-stability. In pHvalues ranged from1to11, the solution of high salt concentration, exposed under450W Xenon （Xe） lamp for3h and storing under normal condition for three months,the PL of GNDs hardly changed, which were attributed to the protective surface layer of glutathione （GSH） and the presence of Au（I）-S complex on the surface ofthe gold core.. Moreover, this glutathione, as a stabilizer makes GNDs have gooddispersion in aqueous solution and low biological toxicity. In this study, the CAL-27and MC3T3-E1cells are used as a model to evaluate the fluorescence imaging ofGNDs.Next in Chapter3, we study the novel near-infrared （NIR） NCs. In vivoapplication the NIR nanomaterials have the advantages of the deep light penetrationand weak light scattering. Using GSH as capping reagent and sulfur-hydrazinehydrate complex as S^2-source, NIR Ag₂S NCs were prepared. The resultant Ag₂SNCs showed tunable luminescence from visible red （624nm） to NIR （724nm）corresponding to increasing the size from1.6nm to4.5nm. GSH is a kind of smallbiomolecules with several functional groups, including carboxyl and amino groupsthat suggested resultant Ag₂S NCs had good dispersion in aqueous solution and lowbiological toxicity. These advantages made as-prepared Ag₂S NCs possess potentialapplications in biological labeling as well. At last, MC3T3-EI cells are choosed toconfirm as-prepared NIR Ag₂S NCs have good application in the field of cellimaging.In Chapter4, we use similar amine reducing approach to prepare magnetic andfluorescent dual functional EuSe nanocrystals. Using EuCl3（H2O）6and elemental Seas Eu and Se sources, and using the alkyl amines （OLA） and alkyl acids （OA） asstabilizing agent, one-step was developed to prepare divalent EuSe nanocrystals. Theresultant EuSe nanocrystals with spherical morphology and the size of20nm showblue emission （peaking at403nm with2.8%quantum yield） and magnetic propertywith coercively （Hc） of80.2Oe at room temperature. Controlling experimentalconditions, the morphologis of EuSe nanocrystals could be tunable and nanorods,nanobelts, spherical and hollow nanoparticles can be prepared. These EuSenanocrystals with various morphologies also have fluorescent and magneticpreporties. In our approach, the amine also behaves as a reducing agent. Note thatour ready approach is highly reproducible and suitable for large-scale production, facilitating the potential in various applications including opto-magnetic devices,optical isolators, optical catalysis, and photo magnetic memories. By F127, EuSenanocrystals could be transferred to aqueous phase, which suggested the EuSenanocrystals had a broader range of applications in the field of cell imaging andmagnetic imaging.Finally, in Chapter5, the layer by layer assembly method is used to preparefluorescent NCs and magnetic nanopartlcles （NPs） hybrid nanomaterials. Using UVreduction method, PAA, the anionic polyelectrolyte, stabilized fluorescent Ag NCswere synthesized. As-prepared PAA-Ag NCs with the size of1.5nm showfluorescence property with emission at570nm. Then, through the help of PAH, thecationic electrolyte, magnetic Fe₃O₄NPs and fluorescent PAA-Ag NCs hybridnanomaterials are prepared by layer by layer assembly. As-prepared hybridnanomaterials have the core of Fe₃O₄and the outermost layer of fluorescent PAA-AgNCs. Hence as-prepared hybrid nanomaterials show magnetic and fluorescentproperties of Fe₃O₄NPs and Ag NCs. Then, we use similar layer by layer assemblymethod to prepare paramagnetic, up and down dual model fluorescent AgNCs-NaGdF₄: Yb/Tm NPs hybrid nanomaterials. The magnetic and fluorescentmultifunctional hybrid nanomaterials could be applied in the field of biologicalimaging and magnetic resonance imaging.