| With the development of science and technology, the materials with only one performance can not meet people's needs. At present, through complementing and optimizing the performance of two or more kinds of materials, composite materials with excellent properties can be synthesized. Composite materials have a wide application prospect. Nanocomposite materials are a relatively new class of materials, which come into being along with the development of the nanotechnology. Nanocomposite materials not only have the special properties of nanomaterials such as quantum size effect, surface effect and so on, but also have multifunctional properties including optical, electrical and magnetic properties. Therefore, nanocomposite materials have potential applications in many fields, such as biological medicine, chemical industry, environment, energy and so on. Surrounding the core/shell nanocomposite materials and organic-inorganic nanocomposite materials, this dissertation presents a systematic research about their synthesis and properties. The major achievement obtained is as follow:1. Magnetic Fe2O3 nanoparticles coated with SiO2 chemically doped with a Ru (II) complex were prepared using a simple solution based method. The obtained nanocomposite materials held strong magnetic response to a varying magnetic field, exhibited the bright red triplet metal-to-ligand charge transfer (3MLCT) emission, and its photoluminescent intensity was sensitive towards oxygen concentration. Compared with the Ru(II) complex in silica gels, the Ru(II) complex in the magnetic-optical-oxygen sensing nanocomposites demonstrated improved thermodynamic stability of emissions. Their magnetic, photoluminescent and oxygen sensing properties make them promising candidates for cell separation, biomarkers and optical oxygen sensor, which can measure the O2 concentration in the biologic bodies.2. A new type of multifunctional nanocomposites for biomedical applications, upconversion luminescent NaYF4:Yb3+, Tm3+ nanoparticles coated with Ru(II) complex chemically doped SiO2 has been developed by combining the useful functions of unconversion, oxygen-sensing, and bio-affinity properties into one nanoparticle. The obtained nanocomposites exhibited bright blue upconversion emission, and the luminescent emission intensity of Ru(II) complex in the nanocomposites was sensitive to oxygen. Compared with the simple mixture of Ru(II) complex and SiO2, the core-shell nanocomposites showed better linearity between emission intensity of Ru(II) complex and oxygen concentrations. These multifunctional nanocomposites may find applications in biochemical and biomedical fields, such as biolabels and optical oxygen sensors.3. Novel upconversion nanocomposites with nanoporous structure were presented in this paper. Silica-coated cubic NaYF4:Yb3+, Tm3+ nanoparticles were first prepared. After annealing, monodisperse cubic/hexagonal mixed phases NaYF4:Yb3+, Tm3+@SiO2 nanoparticles were obtained, and the NaYF4:Yb3+, Tm3+ cores became nanoporous. To the best of our knowledge, the nanoporous structure in NaYF4:Yb3+, Tm3+@SiO2 nanocomposites was observed for the first time. They demonstrate increased upconversion emission compared with unannealed dense NaYF4:Yb3+, Tm3+ nanoparticles due to the appearance of the hexagonal NaYF4:Yb3+, Tm3+. The silica shell not only makes the nanocomposites possess bio-affinity but also protects the NaYF4:Yb3+, Tm3+ cores from aggregating and growing up. Thus the upconversion, nanoporous and bio-affinity properties were combined into one single nanoparticle. These multifunctional nanocomposites are expected to find applications in biological fields, such as biolabels, drug storage and delivery.4. Inorganic-organic hybrid semiconductor (ZnSe)(N2H4)x(C5H5N)y nanosheets as well as (ZnSe)(C5H5N)y nanoparticles were first synthesized by a solvothermal method in a ternary solution. The morphology and composition of the products were largely influenced by the reaction temperature and the volume ratio of water. When the reaction temperature and the water content were lower, (ZnSe)(N2H4)x(C5H5N)y nanosheets were formed. As the reaction temperature or the content of water was high enough, (ZnSe)(C5H5N)y nanoparticles were formed. Pure hexagonal wurtzite ZnSe nanosheets or zinc blende ZnSe nanoparticles were obtained by extracting the corresponding hybrids. The bandgap absorption of ZnSe nanocrystals blue shifted in comparison with the bulk. The photoluminescent intensity of (ZnSe)(N2H4)x(C5H5N)y nanosheets was much stronger than that of (ZnSe)(C5H5N)y nanoparticles.5. One-dimensional composite nanomaterials, PVP (poly(vinylpyrrolidone)) fibers with diameters in the range of ~ 300?500 nm doped with RuL2(NCS)2 (L= 4,4'-Dicarboxy-2,2'-bipyridine) complex and TiO2 nanoparticles (NPs), were prepared by electrospinning technique. The morphology of the composite nanofibers was systemically studied when the diameters of TiO2 NPs, the concentrations of TiO2 NPs and RuL2(NCS)2 in the PVP matrix were changed. A new kind of organic-inorganic composite nanomaterials which combine the advantages of one-dimensional nanostructures, organic materials and inorganic materials was obtained and it is desirable for low-weight and flexible photovoltaic devices, especially for dye-sensitized TiO2 solar cells. |
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