Physical Sciences and Mathematics Commons^™

X-Ray Absorption Spectroscopy, X-Ray Diffraction And Optical Luminescence Studies Of Phase Transition Of Titania Nanotubes, Lu Yao

Electronic Thesis and Dissertation Repository

The one-dimensional (1D) TiO₂ nanotubes (NTs) and their derivatives have been extensively studied due to their wide applications, such as photocatalysts, solar cell, paints and so on. Since TiO₂ has a wide band gap (~3.0 eV), its photo-absorption as the photocatalyst only occurs in the UV region that wastes mostly solar energy. Therefore, the solution to higher photocatalytic efficiency has been sought for some time. This thesis presents a study of the size-dependent phase transitions of TiO₂ NTs using synchrotron-based X-ray techniques. The chemical environment including local symmetry and the luminescence origin of the TiO₂ NTs …

X-Ray Absorption And Emission Studies Of Anodic Titania Nanostructures, Jun Li

Electronic Thesis and Dissertation Repository

One-dimensional (1D) TiO₂ nanomaterials with ordered structure have been extensively applied in various fields, such as photocatalysts, solar cells, supercapacitors and rechargeable batteries, due to the unique structural and functional properties compared to the disordered nanoparticulate forms. Nevertheless, intrinsic disadvantages of TiO₂, such as its large band gap (~3 eV), fast recombination rate of photoexcited electron–hole pairs and insufficient ionic conductivity, severely limit the development of 1D TiO₂ nanomaterials for practical applications. To address the above issues, the scope of this thesis focus on the fundamental understandings of the electronic structure of highly ordered TiO_{2 …}

Optical Properties, Electronic Structures And High Pressure Study Of Nanostructured One Dimensional Titanium Dioxide By Synchrotron Radiation And Spectroscopy, Ankang Zhao

Electronic Thesis and Dissertation Repository

One dimensional (1D) titanium dioxide (TiO₂) nanomaterials have been extensively studied in recent years due to their superior electrical, optical mechanical and chemical properties compared with their bulk counterparts. Two different kinds of 1D TiO₂ nanomaterials, TiO₂ nanowires (TiO₂ NW) and TiO₂ nanotubes (TiO₂ NT), are studied in this thesis by using various techniques.

In one study, TiO₂ NW synthesized by hydrothermal method and a series of calcinated TiO₂ NW were investigated by using absorption near edge structures (XANES), X-ray diffraction (XRD) and X-ray excited optical luminescence (XEOL). It is found …

X-Ray Absorption Fine Structure And X-Ray Excited Optical Luminescence Studies Of Gallium Nitride - Zinc Oxide Solid Solution Nanostructures, Matthew J. Ward

Electronic Thesis and Dissertation Repository

Gallium nitride – zinc oxide (GaN-ZnO) solid solutions have been realized as potential photocatalysts for overall water splitting due to a narrowing of the band-gap into the visible region of the solar spectrum. Although there has been much experimental and theoretical work on this novel class of semiconductors many questions about the nature of their electronic and chemical properties remain unanswered. In particular the mechanism of band-gap reduction in these materials is not clearly understood. It is also unclear what the local chemical environment of gallium, zinc, nitrogen, and oxygen is in both the surface and bulk of these solid …

X-Ray Absorption Fine Structure And X-Ray Excited Optical Luminescence Studies Of One-Dimensional Nanomaterials, Lijia Liu

Electronic Thesis and Dissertation Repository

One dimensional nanomaterials have attracted extensive attention in recent years due to their superior electrical, optical, mechanical and chemical properties compared to their bulk counterparts. In this thesis, electronic structure and optical properties of three types of nanomaterials are investigated using synchrotron based X-ray absorption spectroscopy: X-ray absorption fine structure (XAFS) and X-ray excited optical luminescence (XEOL).

Si nanowire arrays are synthesized using electroless chemical etching, and coated with platinum and gold nanoparticles. The interaction between metal nanoparticles and the nanowire substrate is investigated using X-ray absorption near-edge structure (XANES). The luminescence properties of thermally oxidized Si nanostructures, such as …