Synthesis And Characterization Of CaTiO₃Nanoparticles And Composites Based On CaTiO₃

In this dissertation, a modified polyacrylamide gel method was used to fabricate CaTiO3nanoparticles, CaTiO3@graphene and CaTiO3@Ag nanocomposites, and their properties were investigated systematically. The main points obtained are summarized as follows:(1) A polyacrylamide gel route was used to prepare CaTiO3nanoparticles. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), ultraviolet-visible diffuse reflectance spectroscopy. The results show single-phase CaTiO3nanoparticles can be prepared separately using ethylenediamine-tetraacetic acid (EDTA), acetic acid, tartaric acid and citrate acid as the chelating agent at a calcining temperature of600℃and calcining time of6h. The four as-prepared samples have regular spherical particle shapes and uniform particle sizes with an average diameter of25nm,33nm,36nm and75nm, respectively. The bandgap energy of the four samples is measured to be3.66-3.59eV by ultraviolet-visible diffuse reflectance spectroscopy. The photocatalytic activity of nanoparticles CaTiO3by ultraviolet (UV) radiation degrade methyl orange (MO) to examine. Hydroxyl radicals are revealed, by the photoluminescence technique using terephthalic acid as a probe molecule, to be produced on the irradiated CaTiO3nanoparticles and suggested to be the primary active species toward the dye degradation. The photocatalytic mechanism involved was discussed in detail.(2) CaTiO3@graphene nanocomposites were fabricated by mixing CaTiO3nanoparticles and graphene into absolute ethanol solution followed by thermal drying. TEM observation shows that CaTiO3nanoparticles are well assembled onto graphene sheets. The photocatalytic activity of prepared samples was evaluated by degrading MO under irradiation of UV. It is revealed that CaTiO3@graphene nanocomposites exhibit significantly enhanced photocatalytic activity compared to bare CaTiO3nanoparticles. Hydroxyl radicals are revealed, by the photoluminescence technique using terephthalic acid as a probe molecule, to be produced on the irradiated CaTiO3@graphene and suggested to be the primary active species toward the dye degradation. The photocatalytic mechanism involved was discussed in detail.(3) CaTiO3@Ag nanocomposites were fabricated by photochemical reduction method. The prepared samples were characterized by XRD, TEM, energy dispersive X-ray spectroscopy (EDX), ultraviolet-visible diffuse reflectance spectroscopy. TEM observation shows that Ag nanoparticles are well assembled onto CaTiO3nanocomposites surface. The photocatalytic activity of prepared samples was evaluated by MO under irradiation of UV. It is revealed that CaTiO3@Ag nanocomposites exhibit significantly enhanced photocatalytic activity compared to bare CaTiO3nanoparticles. This can be attributed to the fact that photogenerated electrons from CaTiO3are transferred to Ag nanoparticles, leading to an increased availability of holes for the photocatalytic reaction.·OH radicals are found to be produced over the UV light irradiated CaTiO3and CaTiO3@Ag, and an enhanced yield is observed for the latter. In addition, the addition of ethanol results in a dramatic decrease in the photocatalytic efficiency as well as the quenching of·OH radicals. This indicates that·OH radicals are the dominant active species responsible for the degradation reaction. The photocatalytic mechanism involved was discussed in detail.