| In recent years, the strategy to fabricate nanomaterials with particular structures and morphologies like hollow spheres and core-shell composite spheres with metallic nanoshells is of burgeoning interest. Hollow spheres as new advanced functional materials are becoming one focused research field, principally because of their novel properties, such as low density, high specific surface areas and infiltration ability. Composite spheres with metallic nanoshells can display novel and enhanced properties (e.g. mechanical, chemical, electrical, rheological, magnetic and optical and so on),which is due to plasmon resonances excitation from metal nanoparticles and their enhancement of the electromagnetic field around metal naoparticles.In this study, inorganic hollow spheres SiO2, ZnO were prepared via a facile method in the same media respectively, and SiO2/Ag composite spheres were prepared by the aid of reducing and stabilizing function of polyvinylpyrrolidone (PVP). In addition, the photocatalytic, catalytic and surface-enhanced Raman scattering (SERS) performances of these spheres were investigated respectively. All the research contents and results are shown as follows:(1) In the first chapter, based on the method of preparation of the micro-size hollow spheres reported by our group, monodisperse hollow silica spheres with small sizes were further prepared via one-step method using around 260nm PS as template particles, which were synthesized via emulsifier-free emulsion polymerization usingα,α'-azodiisobutyramidine dihydrochloride (AIBA) as a initiator and polyvinylpyrrolidone (PVP) as a stabilizer. In this approach, the obtained polystyrene suspension was dialyzed in ethanol using cellulose membrane and the solid content of polystyrene suspension was tailored through the addition of ethanol. Then hydrolysis and condensation of TEOS was carried out in aqueous ammoniacal alcohol medium at 50℃, in which PS particles were "dissolved" subsequently even synchronously in the same medium to form hollow silica spheres. And the morphology and thickness of hollow silica spheres could be adjusted through the concentration of ammonia and TEOS in the formulation respectively. Neither additional dissolution nor calcination process was needed to remove the polystyrene cores.(2) In the second chapter, ZnO hollow spheres were further prepared via a facile method. Monodisperse PS spheres were first prepared by dispersion polymerization and then sulfonated by concentrated sulfuric acid. The formed sulfonated polystyrene core-shell spheres were used as template spheres, when Zn(Ac)2·2H2O was added into the ethanol dispersion of the template spheres, zinc ions were first adsorbed onto the surfaces of template spheres via electrostatic interaction. The NaOH solution was added into the mixture and reacted with zinc ions to form ZnO crystal nucleus which was followed by the growth step to form ZnO nanoshells.During the formation of ZnO nanoshells or later on, the sulfonated polystyrene core-shell spheres were "dissolved" in the same media to obtain ZnO hollow spheres directly. Neither additional dissolution nor calcination process was needed to remove the template cores, and reaction condition was mild, neither high temperature nor long time was needed. TEM, SEM, XPS and XRD were used to investigate the morphology, surface composition and crystalline structure of the ZnO hollow spheres, respectively. UV-visible spectra show these ZnO hollow spheres had very good photocatalytic activity.(3) In the last chapter, we described a novel method for fabrication of SiO2/Ag composite spheres by the aid of reducing and stabilizing function of polyvinylpyrrolidone (PVP). In this approach, [Ag(NH3)2]+ ions were first adsorbed onto the surfaces of silica spheres via electrostatic attraction between the silanol groups and ions, these [Ag(NH3)2]+ ions adsorbed on silica spheres were then reduced and protected by PVP to obtain SiO2/Ag composite spheres. Neither additional reducing agent nor the core surface modification was needed, the particle size and the coverage degree of silver nanoparticles on the silica spheres could be easily tuned through altering the concentration of the precursor-[Ag(NH3)2]+ ions. UV-visible spectrometer analysis showed these composite spheres had very good catalytic property; Raman spectrometer measurement displayed that these composite spheres occupied excellent surface-enhanced Raman scattering (SERS) performance.
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