No description available.

Anthony Chi Heng Ng. / "January 2002." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Energy harvesting directly from sunlight has attracted tremendous attention owing to its great potential for low-cost and clean hydrogen production. However, the current photoconversion efficiency from nanostructured metal oxides remains low due to a number of factors, such as low surface area, limited light absorption, poor electron mobility and high electron-hole recombination. In this research, a number of approaches have been carried out to overcome these difficulties. Firstly, changing the morphology of nanomaterials will help to increase the effective surface area of the photoanodes. ZnO nanotubes were prepared and the photoelectrochemical measurements revealed an efficiency of 3 times higher than their nanorod counterparts. In addition, the combination of ZnO nanorods with a 3D metal substrate, stainless steel mesh, showed a further enhancement in the water splitting efficiency by two-fold when compared with that on a planar substrate. Secondly, the hybridisation of two different metal oxides was studied by creating a heterojunction to improve the charge separation, extending the light absorption and increasing the total surface area of the electrode. In this work, both urchin-like ZnO nanorod arrays on TiO2 hollow hemispheres and 1D BiVO4/ZnO nanorod films displayed synergistic enhancement in photoelectrochemical water splitting efficiency. Thirdly, doped ZnO nanostructures with different optical and/or electrical properties were tailored for photoelectrochemical water splitting and gas ionisation sensing applications. The photoelectrochemical water splitting performances of the doped ZnO nanostructures was improved by at least 27% due to increased light absorption. Conductive Y-doped ZnO nanorods were prepared and applied in gas ionisation sensor application. The measurements revealed that both the selectivity and sensitivity of Y-doped ZnO nanorods were enhanced with respect to undoped ZnO nanorods. Furthermore, the effect of UV illumination on gas sensitivity was also investigated. In summary, different approaches and namomaterials have been adapted and demonstrated in this thesis, for the design of specific photoanodes/electrodes for specific applications.

1 / Bing Shan

"October 2002" / Includes bibliographical references (leaves 180-191) / v, 191 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemistry, 2003

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

No description available.

Columbia River sediment was irradiated with ultraviolet light to determine if organic material could be removed without altering the sorptive properties of the hydrous oxides of iron and manganese. A laboratory preparation of Zn-65 spiked hydrous ferric oxide was subjected to ultraviolet irradiation in order to assess the photochemical effect upon Zn-65 release. The photochemically induced release of Mn-54 present on the Columbia River sediment was used to assess the effect on the hydrous oxides of manganese. The ultraviolet irradiation proved effective in removing up to 68% of the sedimentary organic material in 17 hours without causing release of Zn-65 or Sc-46. While the ultraviolet irradiation had no effect upon Zn-65 release from laboratory preparations of hydrous ferric oxides and Zn-65 spiked montmorillonite, a significant release of Mn-54 resulted from the photolysis treatment. The removal of Mn-54 was not accompanied by the release of sorbed Zn-65 or Sc-46 (nuclides expected to be sorbed by hydrous oxides), nor did there appear to be any permanent change in the nature of the Mn-54 on the sediment. Although it is possible that the hydrous oxides of manganese are affected by the ultraviolet treatment, it is likely that another species, such as the carbonate, is the species involved. Photo-oxidation appears to provide a method of obtaining sediments with substantially reduced organic content without affecting the sorptive properties of hydrous oxides or clay minerals. This result should allow the use of uptake studies to determine the importance of organic material in trace metal sorption by sediments. / Graduation date: 1972

Graduation date: 2000

Graduation date: 1997