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Leung Cheuk-wan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract --- p.i / Abstract (Chinese) --- p.ii / Acknowledgement --- p.iii / Table of Contents --- p.v / Lists of Tables --- p.ix / Lists of Figures --- p.x / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- TiO2 Photocatalysis --- p.1 / Chapter 1.1.1 --- Mechanisms of TiO2 Photocatalysis --- p.1 / Chapter 1.2 --- Visible Light Photocatalyst --- p.4 / Chapter 1.2.1 --- Preparation of Visible Light Ti02 Photocatalysts --- p.5 / Chapter 1.2.1.1 --- Dye Sensitization --- p.5 / Chapter 1.2.1.2 --- Metal Doping --- p.6 / Chapter 1.2.1.3 --- Coupling of Semiconductors --- p.6 / Chapter 1.2.1.4 --- Nonmetal Doping --- p.7 / Chapter 1.3 --- Enhanced TiO2 Photocatalytic Activity under UV Light --- p.8 / Chapter 1.3.1 --- Preparation of TiO2 Photocatalyst with Enhanced Activity in UV Light --- p.8 / Chapter 1.3.1.1 --- Loading of Metal --- p.8 / Chapter 1.3.1.2 --- Impurity Co-doping --- p.9 / Chapter 1.3.1.3 --- Morphological Control --- p.10 / Chapter 1.3.1.4 --- Increasing Surface Area --- p.10 / Chapter 1.4 --- Summary --- p.11 / Chapter 1.6 --- Aim of This Research and its Significance --- p.12 / Chapter 1.7 --- References --- p.13 / Chapter Chapter 2 --- Preparation of N-doped TiO2 with Enhanced Surface Area: A Detailed Characterization and Mechanism --- p.19 / Chapter 2.1 --- Introduction --- p.19 / Chapter 2.2 --- Experimental --- p.21 / Chapter 2.2.1 --- Materials and Catalyst Preparation --- p.21 / Chapter 2.2.2 --- Characterization --- p.21 / Chapter 2.2.3 --- Photocatalytic Activity --- p.23 / Chapter 2.3 --- Results and Discussion --- p.24 / Chapter 2.3.1 --- XRD Analysis --- p.24 / Chapter 2.3.2 --- UV-Vis Absorption Spectroscopy and Bandgap Energies --- p.27 / Chapter 2.3.3 --- N2 Sorption Analysis --- p.29 / Chapter 2.3.4 --- SEM Analysis --- p.33 / Chapter 2.3.5 --- TEM Analysis --- p.35 / Chapter 2.3.6 --- FT-IR Spectroscopy --- p.36 / Chapter 2.3.7 --- Raman Spectroscopy --- p.39 / Chapter 2.3.8 --- XPS Studies --- p.44 / Chapter 2.3.9 --- PL Measurements --- p.49 / Chapter 2.3.10 --- Photocatalytic Activity Measurements --- p.50 / Chapter 2.3.11 --- Advantages of Using Urea as a N-doping Source --- p.54 / Chapter 2.3.12 --- Mechanisms for N-doping --- p.56 / Chapter 2.4 --- Conclusions --- p.58 / Chapter 2.5 --- References --- p.59 / Chapter Chapter 3 --- Preparation of Nanoporous Interstitial B-doped TiCO2 with Enhanced Photocatalytic Activity --- p.63 / Chapter 3.1 --- Introduction --- p.63 / Chapter 3.2 --- Experimental --- p.65 / Chapter 3.2.1 --- Materials and Catalyst Preparation --- p.65 / Chapter 3.2.2 --- Characterization --- p.66 / Chapter 3.2.3 --- Photocatalytic Activity --- p.67 / Chapter 3.3 --- Results and Discussion --- p.68 / Chapter 3.3.1 --- XRD Analysis --- p.68 / Chapter 3.3.2 --- UV-Vis Absorption Spectroscopy and Bandgap Energies --- p.71 / Chapter 3.3.3 --- N2 Sorption Analysis --- p.73 / Chapter 3.3.4 --- SEM and TEM --- p.76 / Chapter 3.3.5 --- FT-IR Spectroscopy --- p.80 / Chapter 3.3.6 --- Raman Spectroscopy --- p.82 / Chapter 3.3.7 --- PL Measurements --- p.84 / Chapter 3.3.8 --- XPS Studies --- p.85 / Chapter 3.3.9 --- Photocatalytic Activity Measurements --- p.89 / Chapter 3.3.10 --- State and Form of Boron in TiO2 Lattice and its Effects --- p.91 / Chapter 3.4 --- Conclusions --- p.93 / Chapter 3.5 --- References --- p.94 / Chapter Chapter 4 --- Conclusions --- p.97

by Lin Jun. / "Nov. 28, 2000." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2000. / 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.

Another study was to prepare hierarchically mesoporous titania materials with well-defined grape-like morphology in the presence of a triblock copolymer using bubbling-mediated hydrolysis approach. The effects of bubbling time and calcination temperature on both physicochemical and photocatalytic properties were investigated. / Furthermore, thermally stable ordered mesoporous CeO2/TiO 2 visible photocatalysts were prepared by the evaporation-induced self-assembly method. Introducing highly dispersed CeO2 species into the mesoporous TiO2 framework could effectively extend the response of TiO 2 to visible light region and improve the thermal stability of the mesoporous TiO2. / In addition, visible-light-driven mesoporous TiO2-xN x photocatalysts were developed via in-situ pyrolysis of the product from a chelation reaction between TiCl4 and ethylenediamine under sonication. The effects of ultrasound bombardment on the physicochemical properties and photoactivity of mesoporous TiO2-xNx were discussed. / Part I. Ordered and well crystallized cubic Im 3¯ m mesoporous Cr-TiO2 photocatalysts were fabricated through EISA (evaporation induced self assembly) process. The as prepared photoactalysts exhibited very strong photoactivity in the degradation of methylene blue under visible light irradiation owing to the excitation of 3d electron of Cr3+ to the conduction band of TiO2. / Part II. New approaches have been developed for the fabrication of visible light photocatalysts, BiVO4 and Bi 2WO6. In the case of BiVO4, ordered mesoporous bismuth vanadate (BiVO4) crystals were synthesized via nanocasting method. Compared to the conventional BiVO4, the product exhibited superior photocatalytic performance in the photochemical degradation of methylene blue and photocatalytic oxidation of NO gas in air under visible-light irradiation. In addition, hierarchical flower-like Bi2WO6 was synthesized via microwave-assisted route. Compared to the samples prepared by the hydrothermal method, the products exhibited excellent photocatalytic activities of degrading methylene blue and photocatalytic oxidation of NO gas in air under visible light irradiation. The effects of microwave irradiation on both physicochemical and photocatalytic properties of the as prepared products were investigated. / Two different types of porous visible light photocatalysts were studied in this thesis. The first part reports on the improvement of photocatalytic performance of porous TiO2 through metal/nonmetal doping and morphology controlling. The second part describes the fabrication of porous non-TiO2 photocatalysts including BiVO4 and Bi2WO6. / . / Adviser: Jimmy C. Yu. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3527. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

本论文主要研究了各种可见光光催化剂的合成。包括了Cu₂S，CuO/ZnO复合物以及钒酸根掺杂的磷酸银材料。论文讨论了这些光催化剂的性质与光催化活性，机理同应用也在本文中进行了探讨。 / 首先，发现并合成了硫化亚铜十四面体纳米粒子。研究中发现三正辛基膦对硫化亚铜多面体的形成是必需的。得到的硫化亚铜多面体具有暴露的罕见的面。通过对其光电活性的研究发现，相对于常见的硫化亚铜六边形片状纳米粒子，这种多面体具有5倍以上的活性。 / 其次，异质结构的CuO/ZnO复合材料通过光化学沉积合成。在这两种半导体的接触面形成了p-n结，促进了电子在两者间的传递。在荧光谱图中发现，因电子空穴淬灭引发的荧光峰消失了。这代表由于异质节的形成电荷分离的效率大大提高，从而光催化的效率也得到了很好的提高。 / 最后，含氧根离子作为一种新型的掺杂材料被用于提高磷酸银的性质。磷酸银光解水的能力经过掺杂后得到了显著提高。同时，其在可见光下的稳定性也获得了很大的提高。含氧根离子掺杂物对于磷酸银材料的性质改变及机理在文中都进行了探讨。 / This thesis focuses primarily on the development of visible-light-driven photocatalysts. These include Cu₂S, CuO/ZnO composites and vanadate doped Ag₃PO₄. The property and activity of the materials were studied. The application and mechanism of the enhancement were also explored. / Firstly, 14-facet polyhedra Chalcocite Cu₂S Nanocrystals were synthesized utilizing solvothermal method. It was found that the presence of trio-n-octylphosphine was essential for the exposure of unconventional faces. Studies of the photoelectrochemical performance have indicated that the polyhedra bounded by facets exhibit much higher activities than Cu₂S hexagonal plates with only facets. / Secondly, a heterostructure of CuO/ZnO was fabricated via photochemical deposition. The formation of p-n junction improved the visible light absorption property of ZnO. Photoluminescence spectra showed diminished peaks caused by recombination of excited electrons and holes in the semiconductor which demonstrated that the heterostructure facilitated the charge separation and thus enhanced the photocatalytic activity. / Thirdly, an oxoanion doping method was employed to improve the properties of Ag₃PO₄. The water oxidation ability was found to be higher than the pure Ag₃PO₄. The doping method was proven to be effective in both improving activity and durability. The mechanism of the doping method was also discussed. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Li, Yecheng. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 71-77). / Abstracts also in Chinese. / Abstract (Chinese) --- p.i / Abstract --- p.ii / Acknowledgement --- p.iii / List of Figures --- p.v / Table of Contents --- p.viii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1. --- Basic Principles of Photocatalysis --- p.1 / Chapter 1.2. --- Strategies to Develop Visible-light-driven Photocatalysts --- p.4 / Chapter 1.2.1. --- Native visible-light-driven photocatalysts --- p.4 / Chapter 1.2.2. --- Ion substitution (doping) --- p.6 / Chapter 1.2.3. --- Solid solution photocatalysts --- p.10 / Chapter 1.2.4. --- Dye sensitization to harvest visible light --- p.13 / Chapter 1.3. --- Strategies to Enhance Photocatalytic Activity --- p.15 / Chapter 1.3.1. --- Interface engineering --- p.15 / Chapter 1.3.2. --- Band gap engineering (Tuning distribution of dopants) --- p.17 / Chapter 1.3.3. --- Crystal structure and morphology engineering --- p.19 / Chapter 1.3.4. --- Cocatalyst loading --- p.23 / Chapter 1.4. --- Summary --- p.25 / Chapter 1.5. --- Objective of the Thesis --- p.25 / Chapter Chapter 2 --- Facet Effect of Copper(I) Sulfide Nanocrystals on Photoelectrochemical Properties --- p.28 / Chapter 2.1. --- Introduction --- p.28 / Chapter 2.2. --- Experimental --- p.30 / Chapter 2.2.1. --- Synthesis --- p.30 / Chapter 2.2.2. --- Characterization --- p.30 / Chapter 2.2.3. --- Photoelectrochemical performance analysis --- p.31 / Chapter 2.3. --- Results and Discussion --- p.32 / Chapter 2.4. --- Conclusions --- p.40 / Chapter Chapter 3 --- CuO-ZnO Composites for Enhanced Photoelectrochemical Performance --- p.41 / Chapter 3.1. --- Introduction --- p.41 / Chapter 3.2. --- Experimental --- p.42 / Chapter 3.2.1. --- Synthesis --- p.42 / Chapter 3.2.2. --- Characterization --- p.43 / Chapter 3.2.3. --- Photoelectrochemical performance analysis --- p.44 / Chapter 3.3. --- Results and Discussion --- p.45 / Chapter 3.4. --- Conclusions --- p.56 / Chapter Chapter 4 --- Vanadate Doped Ag₃PO₄ and Its Enhanced Photoactivity and Durability --- p.57 / Chapter 4.1. --- Introduction --- p.57 / Chapter 4.2. --- Experimental --- p.59 / Chapter 4.2.1. --- Synthesis --- p.59 / Chapter 4.2.2. --- Characterization --- p.59 / Chapter 4.2.3. --- Oxygen evolution tests --- p.60 / Chapter 4.3. --- Results and Discussion --- p.61 / Chapter 4.4. --- Conclusions --- p.68 / Chapter Chapter 5 --- Summary --- p.69 / Reference --- p.71

Orientador: José Humberto Dias Da Silva / Banca: Marcio Medeiros Soares / Banca: Antonio Ricardo Zanatta / Banca:José Roberto Ribeiro Bortoleto / Banca: Andre Luis de Jesus Pereira / Resumo: A motivação para este trabalho foi buscar uma melhor compreensão sobre o processo de crescimento dos filmes de óxido de cobalto pela técnica de DC magnetron sputtering reativo. Os filmes de interesse foram depositados sobre substratos de sílica amorfa (a -SiO2 ), aluminato de lantânio (LaAlO3 ) e safira - c (Al2O3- c) usando diferentes valores de potência de deposição e fluxo de oxigênio . As condições de crescimento dos filmes foram analisadas utilizando simulação computacional do processo de sputtering reativo baseada no modelo de Depla, medidas da emissão óptica das espécies presentes no plasma e monitor amento da taxa de crescimento através de uma microbalança de quartzo. Os resultados de difração de raios X mostraram que em baixa potência é obtida a fase Co3O4 espinélio, enquanto que em alta potência os filmes apresentaram a fase CoO cúbica . A s simulações computacionais do processo de sputtering reativo indicaram que, quando as potências de deposição são baixas, o processo de crescimento dos filmes ocorre com o alvo no regime "envenenado" . Em contraste, altas potencias favorece m o regime metálico do alvo. Medidas de emissão do plasma de deposição mostraram que em baixa potência de deposição a intensidade da linha de emissão do oxigênio é alta, porém com o aumento da potência sua intensidade diminui e a d a linha do cobalto aumenta. O s filmes de Co 3 O 4 depositados sobre substratos cristalinos apresentaram resultados promissores . Medidas de difração de raios X de... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The motivation for this work was to obtain a better understanding of the growth process of cobalt oxides by the DC magnetron reactive sputtering technique. The films were dep osited on amorphous silica (a-SiO2), lanthanum aluminate (LaAlO3) and sapphire-c (c-Al2O3) substrates using different values of deposition power and oxygen flow. The conditions of growth of the films were analyzed using the optical analysis of the species present in the plasma and the monitoring of the growth rate through a quartz microbalance. The X-ray diffraction results showed that at lower powers the Co3O4 phase was obtained, while at high er power s the films presented the CoO cubic phase. The computational simulations of the reactive sputtering process indicated that, at low deposition power, the gro wth process of the films occurs with the target in the "poisoned" regime, while in high powers it favors the metallic regime of the target. Plasma emission measurements showed that at low deposition power the oxygen intensity is high while at high power it s intensity decreases and that of cobalt increases. The Co 3 O 4 films deposited on crystalline substrates showed promising results. High - resolution X-ray diffraction measurements using synchrotron radiation indicated that the deposition of Co3O4 on c-Al2O3 resulted in epitaxial growth, in which the direction [111] is perpendicular to the surface of the c - sapphire (0001) substrates. However, the deposition on LaAlO 3 resulted in growth with str... (Complete abstract click electronic access below) / Doutor

Titanium dioxide (TiO2) photocatalysis, which can oxidise or reduce organic and inorganic pollutants, is a developing technology for water and wastewater treatment. The current work investigates the photocatalytic reduction of cadmium and selenium species as the presence of these elements in water are of environmental concern. Although TiO2 has been widely used for the photocatalytic process, its light absorption is limited to the UV region of the solar spectrum. Hence, the current project also explores the possibility to deposit cadmium selenide (CdSe) onto TiO2 to extend the photoresponse to the visible region. This study demonstrated that cadmium (Cd(II)) could be reduced to its metallic form by photocatalysis. The choice of hole scavengers and reaction pH are of importance in determining whether the photocatalytic reduction reaction will occur. It is also essential that both Cd(II) and organic additives are adsorbed on the surface of TiO2. A mechanism for cadmium photoreduction in the presence of formate as the hole scavenger was proposed. The current investigation elucidated the mechanism for the photoreduction of selenite (Se(IV)). Selenite was found to be photoreduced to its elemental form (Se(0)) as films, by direct photoreduction of Se(IV), and as discrete particles, by the reaction between Se(IV) and selenide (Se(2-)) ions. The Se(2-) ions are believed to have been generated from the 6 electron photoreduction of Se(IV) and/or the further photoreduction of the Se(0) deposits. Photocatalytic reduction reactions of Se(IV) and selenate (Se(VI)) using different commercial TiO2 materials was also studied. The current work also successfully deposited CdSe by photocatalysis using Se-TiO2 obtained from the photoreduction of Se(IV) and Se(VI). The mechanism for CdSe deposition was clarified and attributed to the reaction of Cd(II) present in the system and the Se(2-) released from the reduction of Se(0) upon further illumination. The Se??TiO2 photocatalysts obtained from the photoreduction of different selenium precursors (Se(IV) and Se(VI)) resulted in the dominance of different morphologies of the CdSe particles. This suggests a new approach to manipulate the properties of CdSe during its formation, and hence control over electrical and optical properties of this semiconductor.

TiO2 is a fascinating material proving its usefulness in a wide range of applications. In photocatalytic and gas sensitization applications, it has been utilized as a stable semiconductor for the organic matter of waste water cleaning and impetus on environmental consciousness the need for highly efficient combustion engines, controlled industrial processes and monitoring the hazardous gas level in the environment. Nanocrystalline TiO2 modified with Nb incorporation has been produced by LPD technique that deposited at 40 oC with (NH4)2TiF6 for 0.2 M, and 0.6 M for boric acid and a few mount of Nb solution. The deposition rate can be controlled perfectly about 40-50 nm/h. The addition of Nb stabilizes the anatase phase and retards the grain growth during high temperature annealing. XRD and RAMAN spectra of undoped and Nb doped samples show that the undoped one has converted to rutile at 900 oC, meanwhile the doped one remains anatase phase. Nanocrystalline films stabilize at 800 oC with grain size of about 7 nm have successfully been synthesized by the additives of Nb, which appear to be an adequate dopant to improve the photocatalytic and gas sensor performances. The ability of niobium introduction is of retarding the anatase to rutile transformation and hindering its grain growth.

Metal oxides are important materials that are being developed for use in research and health-related applications. In particular, TiO2 and ZnO nanomaterials for applications in antibacterial coatings, pollutant purification, and photovoltaic devices have been extensively studied. The photocatalytic performances are highly dependent on morphology and crystal structure. However, there are few studies are comparing pollutant purification and antibacterial behavior of different TiO2 nanostructures and less studies of antibacterial activity related to fundamental properties of ZnO. In this study, the details of proposed mechanism and principle of antibacterial mechanisms of metal oxide nanostructures has been examined. Different TiO2 nanostructures (nanotubes, nanorods) have been successfully synthesized and their photocatalytic properties have been studied. In addition, studies of basic properties of commercial ZnO nanoparticles related to antibacterial activity have been performed. / published_or_final_version / Physics / Master / Master of Philosophy

Titanium dioxide (TiO2) photocatalysis, which can oxidise or reduce organic and inorganic pollutants, is a developing technology for water and wastewater treatment. The current work investigates the photocatalytic reduction of cadmium and selenium species as the presence of these elements in water are of environmental concern. Although TiO2 has been widely used for the photocatalytic process, its light absorption is limited to the UV region of the solar spectrum. Hence, the current project also explores the possibility to deposit cadmium selenide (CdSe) onto TiO2 to extend the photoresponse to the visible region. This study demonstrated that cadmium (Cd(II)) could be reduced to its metallic form by photocatalysis. The choice of hole scavengers and reaction pH are of importance in determining whether the photocatalytic reduction reaction will occur. It is also essential that both Cd(II) and organic additives are adsorbed on the surface of TiO2. A mechanism for cadmium photoreduction in the presence of formate as the hole scavenger was proposed. The current investigation elucidated the mechanism for the photoreduction of selenite (Se(IV)). Selenite was found to be photoreduced to its elemental form (Se(0)) as films, by direct photoreduction of Se(IV), and as discrete particles, by the reaction between Se(IV) and selenide (Se(2-)) ions. The Se(2-) ions are believed to have been generated from the 6 electron photoreduction of Se(IV) and/or the further photoreduction of the Se(0) deposits. Photocatalytic reduction reactions of Se(IV) and selenate (Se(VI)) using different commercial TiO2 materials was also studied. The current work also successfully deposited CdSe by photocatalysis using Se-TiO2 obtained from the photoreduction of Se(IV) and Se(VI). The mechanism for CdSe deposition was clarified and attributed to the reaction of Cd(II) present in the system and the Se(2-) released from the reduction of Se(0) upon further illumination. The Se??TiO2 photocatalysts obtained from the photoreduction of different selenium precursors (Se(IV) and Se(VI)) resulted in the dominance of different morphologies of the CdSe particles. This suggests a new approach to manipulate the properties of CdSe during its formation, and hence control over electrical and optical properties of this semiconductor.