The possibility to manipulate electromagnetic radiation, as well as mechanical and acoustic waves has been an engaging topic since the beginning of the 20th century. Nowadays, thanks to the progress in technologies and the evolution of fabrication processes, realizing artificial materials that are able to interact with the environment in a desired fashion has become reality. The interest in micro/nanostructured metamaterials involves different field of research, ranging from optics to biology, through optoelectronics and photonics. Unfortunately, realizing experimentally these materials became highly challenging, since the size of the nanostructures are shrinking and the precision of the design became crucial for their effective operation. Disorder is, in fact, an intrinsic characteristic of fabrication processes and harnessing it by turning its unexpected effects in decisive advantages represents one of the ultimate frontiers in research. In this work we combine ab-initio FDTD simulations, fabrication process optimization and experimental results to show that, introducing disorder in metamaterials could constitute a key opportunity to enable many interesting capabilities otherwise locked. This could open up the way to novel applications in several fields, from smart network materials for solar cells and photo-electrochemical devices to all dielectric, highly-tunable structural colors.

Orientador: Maria Valnice Boldrin / Banca: Mário César Guerreiro / Banca: Luiz Henrique Dall'antonia / Resumo: O presente trabalho reporta os principais resultados obtidos na construção e caracterização de eletrodos de titânio recobertos com nanotubos de óxido de titânio modificados com nanopartículas de platina (TiO2/Pt) e eletrodos de cobre recobertos com nanopartículas de óxido de cobre (Cu/Cu2O) com vistas a sua aplicação na redução fotoeletrocatalítica de CO2 em meio aquoso e semicondutores em pó de CuNbO3-CuO, Cu0,85Zn0,15Nb2O6 e ZnNb2O6-Nb2O5 construídos e testados na redução fotocatalítica de CO2, com vistas a geração de produtos com maior valor agregado, tal como metanol. Os eletrodos TiO2/Pt e Cu/Cu2O foram construídos por meio de técnicas de eletroquímicas, enquanto que os semicondutores em pó CuNbO3-CuO, Cu0,85Zn0,15Nb2O6 e ZnNb2O6-Nb2O5 foram preparados utilizando a técnica de síntese por combustão e calcinação posterior. A redução fotoeletrocatalítica e fotocatalítica de CO2 não foi satisfatória sobre eletrodos de TiO2/Pt e semicondutor ZnNb2O6-Nb2O5, respectivamente. No entanto, o eletrodo de Cu/Cu2O apresentou grande eficiência na redução de CO2, atingindo 80% de remoção em meio de Na2CO3 0,3 mol L-1 pH 9 a +0,2 V, em solução tampão de NaHCO3/Na2CO3 0,1 mol L-1 pH 8, utilizando luz UV 125 W e potencial de +0,2 V mostrou uma reação praticamente seletiva para metanol, gerando 5,63 mmol L-1, correspondendo a 20% de conversão. Os semicondutores em pó CuNbO3-CuO e Cu0,85Zn0,15Nb2O6 também se mostraram bastante eficientes para a geração de metanol por redução de CO2 dissolvido em Na2CO3 0,1 mol L-1 pH8 utilizando luz visível de 450 W, chegando a formar 7,0 mmol L-1 e 3,2 mmol L-1 de metanol respectivamente. Os resultados obtidos neste trabalho mostram que ambas as técnicas podem ser empregadas para a redução do CO2, usando para isto os semicondutores Cu/Cu2O, CuNbO3-CuO e Cu0,85Zn0,15Nb2O6 e, poderia ser uma potencial alternativa para os problemas ambientais além de contribuir como fonte... / Abstract: This present work reports the main results obtained with the construction and characterization of TiO2 nanotubes modified by platinum nanoparticle electrode (TiO2/Pt) and copper covered by copper oxide nanoparticles electrode (Cu/Cu2O) for application in the photoelectrocatalytic reduction of dissolved CO2 and CuNbO3-CuO, Cu0,85Zn0,15Nb2O6 and ZnNb2O6-Nb2O5 powders semiconductors constructed and applied in the photocatalytic reduction of dissolved CO2 for the generation of products with higher added value. The TiO2/Pt and Cu/Cu2O electrodes were prepared by electrochemical techniques, whereas the CuNbO3-CuO, Cu0,85Zn0,15Nb2O6 and ZnNb2O6-Nb2O5 powder semiconductors were prepared using the combustion synthesis technique and submitted to annealed. The CO2 reduction by photoelectrocatalysis and photocatalysis were not satisfactory when using the TiO2/Pt electrode and the ZnNb2O6-Nb2O5 semiconductor, respectively. However, the Cu/Cu2O electrode shows a high efficiency in the CO2 reduction obtaining 80% of removal in 0.3 mol L-1 Na2CO3 pH 9 and +0.2 V, and, it showed a practically selective reaction to methanol (producing 5.63 mmol L-1), corresponding to 20% of conversion at ambient of 0.1 mol L-1 NaHCO3/Na2CO3 butter solution pH 8, using UV light of 125 W and +0,2 V. The CuNbO3-CuO and Cu0,85Zn0,15Nb2O6 powder semiconductors also showed a good efficiency to the methanol formation throughout dissolved CO2 reduction in 0.1 mol L-1 Na2CO3 pH 8 using visible light of 450 W, and forming 7 mmol L-1 and 3.2 mmol L-1 of methanol, respectively. The results obtained in this work show that both techniques can be employed for the CO2 reduction, using for this the Cu/Cu2O, CuNbO3-CuO and Cu0,85Zn0,15Nb2O6 semiconductors, and it could be a potential alternative to the environmental problems and contribute as raw material source for the production of fuels, for instance. / Mestre

由於潔淨用水日漸短缺，科學家著力研究各種水淨化方法，其中以光催化技術作水淨化處理為可行的方法之一。光催化是以半導體光催化劑在光照射下所產生的活性物種（reactive oxidative species）進行消毒，其中的失活原理、各活性物種的作用和活性物種對細菌的攻擊方位，雖然已有廣範的研究，但當中仍有不清之處，比如說過氧化氫(H₂O₂)在光催化失活的作用便是其中之一，在光催化系統中所產生的H₂O₂濃度一般較低，因此其對細菌失活的效能仍然存有爭議。 / 本研究設計一種新的反應器去研究H₂O₂在連續供應模式中的失活動力學。在 8 mM 的H₂O₂下，10⁵的大腸桿菌(Escherichia coli)在8小時內完全失活。而在 2 mM 的H₂O₂ 下，並無出現顯著失活，由於該濃度遠遠高於一般光催化系統所產生的濃度（<50 μM），因此可以推斷，即使一般光催化系統所產生的H₂O₂是連續供應，也不會使細菌失活。然而在光照的情況下，其失活動力學大為不同，在強光照射(200 mW cm⁻²)下，H₂O₂的失活效率顯著增強，證明光照和過氧化氫之間存有協同效應。這現象亦出現於光預處理過(light pretreated)的大腸桿菌，進一步證實了光照改變細菌的生理機能，從而使其易於被H₂O₂失活。 / 其後我們使用RNA測序(RNA sequencing)去檢測的大腸桿菌的基因表達水平在光照下的變化，以便研究光照和H₂O₂之間的協同作用的機理。大多數涉及抵抗氧化的基因，包括過氧化氫酶(catalase, CAT)和超氧化物歧化酶(superoxide dismutase,SOD)的表達、DNA修復及細菌內的鐵含調控等等，其mRNA 水平沒有顯著的增加或減少，只有dps、fes和sodB有明顯的變化。此外，還有幾種調控細胞內的銅合量（cutA和cueR）和細胞膜組成（ompA、ompC、resx和gnsB）的基因在光照下產生顯著變化。 經RNA測序後，我們選定了10個目標基因，並選擇相對的大腸桿菌變異體(mutants)，對比他們和母體(E. coli BW25113)經過光預處理後被H₂O₂的失活效能。雖然這次研究並未找到相關基因，但研究結果表示，光照和H₂O₂的協同效應，應該是光照增加細胞膜的通透性和提高細菌內Fenton劑含量，使細菌內的羥基自由基(·OH)的濃度增加，因此加強對細菌DNA的損傷。 / 最後，我們亦比較了AgBr/Ag/Bi₂WO₆在不同的光源的照射下的對大腸桿菌的光催化失活效率。雖然發光二極管(light emitting diode)和熒光管都常用於室內照明，但AgBr/Ag/Bi₂WO₆的細菌失活效率在兩者的光照下表現出顯著的差異，而不同的發射波長下的細菌失活效率和AgBr/Ag/Bi₂WO₆光學吸收表現出良好的相關性。此外，相對其他顏色的發光二極管，綠色發光二極管照射下在犧牲劑研究(scavenger study)的結果大為不同，進一步表明了光照的發射波長(emissionwavelength)對光催化失活機制的影響。 / 本研究揭示了H₂O₂和光照在光催化失活中的重要性，並演示了H₂O₂和光照射之間的協同作用，也闡明了光照的屬性如何影響光催化下各活性物種的產生。本研究不僅提供了一個新的角度去探討的光照、H₂O₂和細菌的生理狀態在光催化失活中的重要性，也提供了新的方向和方法去研究光催化失活機制的。 / Due to the increasing concern for the need of clean drinking water, different methods for water purification have been developed. Photocatalysis, which makes use of semiconductor photocatalyst for the generation of reactive charged and oxidative species (ROSs) under light irradiation, is one of the most promising methods for water disinfection. The mechanisms of the photocatalytic inactivation have been extensively investigated. Different factors, including the roles of ROSs and the ROSs target site(s) of bacterial cell, were elaborated by different studies. However, there are still controversial issues on the role of H₂O₂ in photocatalytic inactivation. The effectiveness of the low concentration of H₂O₂ in the bacterial inactivation process is still under question. / This study designs a new reactor to study the kinetic of H₂O₂ inactivation in continuous supply mode. Complete inactivation of 5-log Escherichia coli within 8 h is achieved when 8 mM of H₂O₂ is applied. No significant inactivation was observed when 2 mM H₂O₂ is applied, this concentration of H₂O₂ is much higher than that detected in common photocatalytic system (< 50 μM). The results show that H₂O₂ produced by common photocatalytic system is not harmful to bacterial cell, even they are produced continuously. However, when light irradiation of 200 mW cm⁻² , using Xenon lamp as lighting source, was applied to the system, the inactivation efficiency of H₂O₂ was significantly enhanced, which demonstrate the synergistic effect between the light irradiation and H₂O₂. The enhancement of inactivation by H₂O₂ can also be observed with light pretreated E. coli K-12, further confirms that light irradiation alter the physiology of the bacterial cell which increases their sensitivity to H₂O₂. / In order to find out the mechanism(s) of the synergism between the light irradiation and H₂O₂, RNA sequencing (RNA-Seq) was used to reveal the change of gene expression level of the E. coli under light irradiation. The mRNA level of most of the genes involve in catalase (CAT) and superoxide dismutase (SOD) expression, DNA repairing and intracellular iron regulation did not have significant increase or decrease. Only dps, fes and sodB showed significantly changes. Moreover, some genes that related to regulation of intracellular copper (cutA and cueR) and membrane composition (ompA, ompC, resX and gnsB) also showed significantly changes under light irradiation. After the RNA-Seq, ten genes were chosen as the possible target genes that related to the mechanism(s). Then the inactivation of E. coli BW25113 (parental strain) and the isogenic deleted mutants by H₂O₂ with light pretreatment were conducted and compared. Although the gene(s) that directly involved in the mechanisms of the synergy between H₂O₂ and light irradiation are not identified in the study, the results show that genes that are important to bacterial defense of oxidative damages, such those responsible for CAT and SOD expression and DNA repairing, are not involved in the mechanism(s). Increase of cell permeability and intracellular Fenton’s reagent content should be the main causes for the enhancement of H₂O₂ under light irradiation. / Finally, the inactivation efficiency of E. coli K-12 using AgBr/Ag/Bi₂WO₆ under different lighting sources is compared. The results show that inactivation efficiency under different emission wavelength are highly correlated with the optical absorption of the AgBr/Ag/Bi₂WO₆. Photocatalytic inactivation under two indoor lighting sources, LED lamps and Fluorescence tubes, also showed significant difference. The result of scavenger study under green LED lamps is completely different from those under other colour of LED lamps, indicates that emission wavelength also has great influence in photocatalytic inactivation mechanisms. / This study reveals the roles of H₂O₂ and light irradiation in photocatalytic inactivation and demonstrates the synergism between the H₂O₂ and light irradiation. The influence of the properties of light irradiation, including the light intensity and major emission wavelength, on the ROSs production by photocatalyst is also reported as well. This study not only provides a new perspective to the importance of light irradiation, H₂O₂ and the physiology of bacteria in photocatalytic inactivation, but a new approach in the investigation of photocatalytic inactivation mechanisms as well. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Ng Tsz Wai. / Thesis (Ph.D.) Chinese University of Hong Kong, 2014. / Includes bibliographical references (leaves 111-131). / Abstracts also in Chinese.

by Fong Wai-lan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 138-152). / Text in English; abstracts in English and Chinese. / by Fong Wai-lan. / Acknowledgements --- p.i / Abstracts --- p.ii / Contents --- p.vi / List of figures --- p.xii / List of Plates --- p.xviii / List of tables --- p.xix / Abbreviations --- p.xxi / Chemical equations --- p.xxiii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Pentachlorophenol --- p.1 / Chapter 1.1.1 --- Characteristics of pentachlorophenol --- p.1 / Chapter 1.1.2 --- Use of pentachlorophenol --- p.4 / Chapter 1.1.3 --- Annual consumption and regulations for the use of pentachlorophenol --- p.4 / Chapter 1.1.4 --- Pentachlorophenol in the environment --- p.4 / Chapter 1.1.5 --- Toxicity of pentachlorophenol --- p.5 / Chapter I. --- Mechanism --- p.5 / Chapter II. --- Toxicity towards plant and animals --- p.7 / Chapter III. --- Toxicity towards human --- p.7 / Chapter 1.2 --- Treatments of pollutant --- p.9 / Chapter 1.2.1 --- Physical treatment --- p.9 / Chapter 1.2.2 --- Chemical treatment --- p.9 / Chapter 1.2.3 --- Biological treatment --- p.12 / Chapter 1.2.4 --- Advanced Oxidation Processes (AOPs) --- p.14 / Chapter Chapter 2 --- Objectives --- p.28 / Chapter 3 --- Materials and methods --- p.29 / Chapter 3.1 --- Chemical reagents --- p.29 / Chapter 3.2 --- Photocatalytic reactor --- p.29 / Chapter 3.3 --- Determination of pentachlorophenol concentration --- p.31 / Chapter 3.4 --- Optimization of reaction conditions for UV-PCO --- p.34 / Chapter 3.4.1 --- Batch system --- p.34 / Chapter 3.4.1.1 --- Effect of initial hydrogen peroxide concentration --- p.34 / Chapter 3.4.1.2 --- "Effect of initial titanium dioxide concentration, light intensity and initial pH" --- p.34 / Chapter 3.4.1.3 --- Effect of initial pentachlorophenol concentration and irradiation time & determination of total organic carbon (TOC) removal during UV-PCO --- p.36 / Chapter 3.4.2 --- Continuous system --- p.36 / Chapter 3.5 --- Optimization of reaction conditions for VL-PCO --- p.38 / Chapter 3.5.1 --- "Effect of VL source, initial hydrogen peroxide, titanium dioxide concentration，light intensity, pH and reaction volume" --- p.38 / Chapter 3.5.2 --- Effect of initial pentachlorophenol concentration and irradiation time & determination of total organic carbon (TOC) removal during VL-PCO --- p.39 / Chapter 3.6 --- Optimization of reaction conditions for S-PCO --- p.39 / Chapter 3.6.1 --- "Effect of initial hydrogen peroxide, titanium dioxide concentration，light intensity and pH" --- p.39 / Chapter 3.6.2 --- Effect of irradiation time & determination of total organic carbon (TOC) removal during S-PCO --- p.41 / Chapter 3.7 --- Modification of photocatalytic oxidation --- p.41 / Chapter 3.7.1 --- Buffering system --- p.41 / Chapter 3.7.2 --- Immobilized titanium dioxide system --- p.41 / Chapter 3.7.2.1 --- Preparation of titanium dioxide coated spiral column --- p.41 / Chapter 3.7.2.2 --- Effect of flow rate for the UV-PCO (continuos- buffering/immobilized titanium dioxide) system --- p.43 / Chapter 3.8 --- Estimation of pentachlorophenol degradation pathway by photocatalytic oxidation --- p.43 / Chapter 3.9 --- Evaluation for the toxicity change of pentachlorophenol during the degradation process --- p.43 / Chapter 3.9.1 --- Microtox® test --- p.43 / Chapter 3.9.2 --- Amphipod survival test --- p.45 / Chapter Chapter 4 --- Results --- p.47 / Chapter 4.1 --- Determination of pentachlorophenol concentration --- p.47 / Chapter 4.2 --- Optimization of reaction conditions for UV-PCO --- p.47 / Chapter 4.2.1 --- Batch system --- p.47 / Chapter 4.2.1.1 --- Effect of initial hydrogen peroxide concentration --- p.47 / Chapter 4.2.1.2 --- Effect of initial titanium dioxide concentration --- p.54 / Chapter 4.2.1.3 --- Effect of light intensity --- p.54 / Chapter 4.2.1.4 --- Effect of initial pH --- p.54 / Chapter 4.2.1.5 --- Effect of initial pentachlorophenol concentration and irradiation time & determination of total organic carbon (TOC) removal during UV-PCO --- p.61 / Chapter 4.2.2 --- Continuous system --- p.61 / Chapter 4.3 --- Optimization of reaction conditions for VL-PCO --- p.69 / Chapter 4.3.1 --- Effect of VL source --- p.69 / Chapter 4.3.2 --- Effect of initial hydrogen peroxide concentration --- p.69 / Chapter 4.3.3 --- Effect of initial titanium dioxide concentration --- p.69 / Chapter 4.3.4 --- Effect of light intensity --- p.76 / Chapter 4.3.5 --- Effect of initial pH --- p.76 / Chapter 4.3.6 --- Effect of reaction volume --- p.76 / Chapter 4.3.7 --- Effect of initial pentachlorophenol concentration and irradiation time & determination of total organic carbon (TOC) removal during VL-PCO --- p.83 / Chapter 4.4 --- Optimization of reaction conditions for S-PCO --- p.83 / Chapter 4.4.1 --- Effect of initial hydrogen peroxide concentration --- p.83 / Chapter 4.4.2 --- Effect of initial titanium dioxide concentration --- p.90 / Chapter 4.4.3 --- Effect of initial pH --- p.90 / Chapter 4.4.4 --- Effect of irradiation time & determination of total organic carbon (TOC) removal during S-PCO --- p.90 / Chapter 4.5 --- Modification of photocatalytic oxidation --- p.96 / Chapter 4.5.1 --- Buffering system --- p.96 / Chapter 4.5.2 --- Immobilized titanium dioxide system --- p.104 / Chapter 4.6 --- Estimation of pentachlorophenol degradation pathway by photocatalytic oxidation --- p.104 / Chapter 4.7 --- Evaluation of the toxicity change of pentachlorophenol during photocatalytic oxidation --- p.104 / Chapter 4.7.1 --- Microtox® test --- p.104 / Chapter 4.7.2 --- Amphipod survival test --- p.112 / Chapter Chapter 5 --- Discussion --- p.116 / Chapter 5.1 --- Determination of pentachlorophenol concentration --- p.116 / Chapter 5.2 --- Optimization of reaction conditions for UV-PCO --- p.116 / Chapter 5.2.1 --- Batch system --- p.116 / Chapter 5.2.1.1 --- Effect of initial hydrogen peroxide concentration --- p.116 / Chapter 5.2.1.2 --- Effect of initial titanium dioxide concentration --- p.117 / Chapter 5.2.1.3 --- Effect of light intensity --- p.119 / Chapter 5.2.1.4 --- Effect of initial pH --- p.119 / Chapter 5.2.1.5 --- Effect of initial pentachlorophenol concentration and irradiation time & determination of total organic carbon (TOC) removal during UV-PCO --- p.120 / Chapter 5.2.2 --- Continuous system --- p.120 / Chapter 5.3 --- Optimization of reaction conditions for VL-PCO --- p.121 / Chapter 5.3.1 --- Effect of visible light (VL) source --- p.121 / Chapter 5.3.2 --- Effect of initial hydrogen peroxide concentration --- p.121 / Chapter 5.3.3 --- Effect of initial titanium dioxide concentration --- p.122 / Chapter 5.3.4 --- Effect of light intensity --- p.123 / Chapter 5.3.5 --- Effect of initial pH --- p.124 / Chapter 5.3.6 --- Effect of reaction volume --- p.124 / Chapter 5.3.7 --- Effect of initial pentachlorophenol concentration and irradiation time & determination of total organic carbon (TOC) removal during VL-PCO --- p.124 / Chapter 5.4 --- Optimization of reaction conditions for S-PCO --- p.125 / Chapter 5.4.1 --- Effect of initial hydrogen peroxide concentration --- p.125 / Chapter 5.4.2 --- Effect of initial titanium dioxide concentration --- p.126 / Chapter 5.4.3 --- Effect of initial pH --- p.127 / Chapter 5.4.4 --- Effect of irradiation time & determination of total organic carbon (TOC) removal during S-PCO --- p.127 / Chapter 5.5 --- Modification of photocatalytic oxidation --- p.128 / Chapter 5.5.1 --- Buffering system --- p.128 / Chapter 5.5.2 --- Effect of flow rate on removal efficiency for the UV-PCO (continuos-buffering/immobilized titanium dioxide) system --- p.129 / Chapter 5.6 --- Estimation of pentachlorophenol degradation pathway by photocatalytic oxidation --- p.130 / Chapter 5.7 --- Evaluation for the toxicity change of pentachlorophenol during photocatalytic oxidation --- p.132 / Chapter 5.7.1 --- Microtox® test --- p.132 / Chapter 5.7.2 --- Amphipod survival test --- p.133 / Chapter Chapter 6 --- Conclusions --- p.135 / Chapter Chapter 7 --- References --- p.138 / Appendix i --- p.153 / Appendix ii --- p.154 / Appendix iii --- p.154

Tang Hung Yuk. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 71-79). / Abstracts in English and Chinese. / ABSTRACT --- p.i / DECLARATION --- p.iii / ACKNOWLEDGEMENT --- p.iv / TABLE OF CONTENTS --- p.v / LIST OF TABLES --- p.viii / LIST OF FIGURES --- p.ix / Chapter CHAPTER ONE: --- INTRODUCTION --- p.1 / Chapter 1.1 --- Fundamentals of TiO2 --- p.1 / Chapter 1.2 --- Application of TiO2 --- p.5 / Chapter 1.3 --- Scope of Work --- p.11 / Chapter CHAPTER TWO: --- DISINFECTION BY UV IRRADIATED TiO2 --- p.14 / Chapter 2.1 --- Introduction --- p.14 / Chapter 2.2 --- Experimental --- p.19 / Chapter 2.2.1 --- Materials --- p.19 / Chapter 2.2.2 --- Preparation of TiO2 films --- p.19 / Chapter 2.2.3 --- Culture of microorganisms --- p.20 / Chapter 2.2.4 --- Bactericidal activities --- p.21 / Chapter 2.2.5 --- Photocatalytic experiment to degrade acetone in gas phase --- p.21 / Chapter 2.2.6 --- Photocatalytic experiment to degrade rhodamine B in aqueous phase --- p.22 / Chapter 2.2.7 --- Characterization --- p.23 / Chapter 2.3 --- Results and Discussions --- p.25 / Chapter 2.3.1 --- Bactericidal activity --- p.25 / Chapter 2.3.2 --- Photocatalytic activity --- p.34 / Chapter 2.3.3 --- Thickness and transmittance of Ti〇2 films --- p.37 / Chapter 2.3.4 --- Surface morphology and roughness of thin films --- p.40 / Chapter 2.3.5 --- Crystalline phase and crystallite size of thin films --- p.42 / Chapter 2.3.6 --- XPS study --- p.43 / Chapter CHAPTER THREE: --- DISINFECTION BY VISIBLE IRRADIATED TiO2 --- p.47 / Chapter 3.1 --- Introduction --- p.47 / Chapter 3.2 --- Experimental --- p.58 / Chapter 3.2.1 --- Materials --- p.58 / Chapter 3.2.2 --- Preparation of TiO2 films --- p.58 / Chapter 3.2.3 --- Culture of microorganisms --- p.59 / Chapter 3.2.4 --- Bactericidal activity --- p.60 / Chapter 3.3 --- Results and discussions --- p.61 / Chapter 3.3.1 --- Dye adsorbed TiO2 film stability --- p.61 / Chapter 3.3.2 --- Bactericidal activity of the dye-sensitized TiO2 films --- p.62 / Chapter 3.3.3 --- Bactericidal mechanism of the films under irradiation --- p.64 / Chapter CHAPTER FOUR: --- CONSLUSIONS --- p.68 / REFERENCES --- p.71

by Wong Kin-hang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 99-127). / Text in English; abstracts in English and Chinese. / by Wong Kin-hang. / Acknowledgements --- p.i / Abstracts --- p.ii / Contents --- p.vi / List of Figures --- p.ix / List of Tables --- p.x / Abbreviations --- p.xi / Chemical Equations --- p.xii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Poly chlorinated biphenyls --- p.1 / Chapter 1.1.1 --- Characteristics of polychlorinated biphenyls (PCBs) --- p.1 / Chapter 1.1.2 --- Use of polychlorinated biphenyls --- p.3 / Chapter 1.1.3 --- World-wide production of polychlorinated biphenyls --- p.7 / Chapter 1.1.4 --- Polychlorinated biphenyls in the environment --- p.8 / Chapter 1.1.5 --- Toxicity of polychlorinated biphenyls --- p.12 / Chapter I. --- Mechanism --- p.12 / Chapter II. --- Toxicity towards plant and animals --- p.13 / Chapter III. --- Toxicity towards human --- p.14 / Chapter IV. --- Enzymatic induction by PCBs --- p.14 / Chapter V. --- Carcinogenicity of PCBs --- p.18 / Chapter 1.2 --- Treatments of pollutant --- p.19 / Chapter 1.2.1 --- Physical treatment --- p.19 / Chapter 1.2.2 --- Chemical treatment --- p.20 / Chapter 1.2.3 --- Biological treatment --- p.22 / Chapter 1.2.4 --- Photocatalytic oxidation (PCO) --- p.25 / Chapter Chapter 2 --- Objectives --- p.35 / Chapter Chapter 3 --- Materials and methods --- p.36 / Chapter 3.1 --- Chemical reagents --- p.36 / Chapter 3.2 --- Photocatalytic oxidation reactor --- p.36 / Chapter 3.3 --- Separation and determination of eight PCB congeners --- p.39 / Chapter 3.4 --- Determination of tetra-CB concentration --- p.40 / Chapter 3.5 --- Determination of PCO intermediates and products --- p.41 / Chapter 3.6 --- Optimisation of reaction conditions for UV-PCO in batch system --- p.44 / Chapter 3.6.1 --- Control experiments and effect of initial titanium dioxide concentration --- p.44 / Chapter 3.6.2 --- Effect of initial hydrogen dioxide concentration and UV intensity --- p.44 / Chapter 3.6.3 --- Effect of initial titanium dioxide concentration and initial pH --- p.45 / Chapter 3.7 --- Estimation of tetra-CB degradation pathway by photocatalytic oxidation --- p.45 / Chapter 3.8 --- Evaluation for the toxicity of hydrogen peroxide and toxicity change of tetra-CB during PCO by Microtox® test --- p.45 / Chapter 3.9 --- Determination of H202 concentration after PCO --- p.47 / Chapter Chapter 4 --- Results --- p.50 / Chapter 4.1 --- Separation and determination of eight PCB congeners --- p.50 / Chapter 4.2 --- Photocatalytic oxidation of mono-CB --- p.50 / Chapter 4.3 --- Determination of tetra-CB --- p.55 / Chapter 4.4 --- Optimisation of reaction conditions for UV-PCO in batch system --- p.56 / Chapter 4.4.1 --- Control experiments and effects of initial titanium dioxide concentration --- p.56 / Chapter 4.4.2 --- Effect of initial hydrogen peroxide concentration and UV intensity --- p.56 / Chapter 4.4.3 --- Effect of initial titanium dioxide concentration and initial pH --- p.60 / Chapter 4.5 --- Estimation of tetra-CB degradation pathway by photocatalytic oxidation --- p.71 / Chapter 4.6 --- Evaluation for the toxicity of hydrogen peroxide and toxicity change of tetra-CB by Microtox® test --- p.72 / Chapter 4.7 --- Determination of H202 concentration after PCO --- p.72 / Chapter Chapter 5 --- Discussion --- p.89 / Chapter 5.1 --- Separation and determination of eight PCB congeners --- p.89 / Chapter 5.2 --- Photocatalytic oxidation of mono-CB --- p.89 / Chapter 5.3 --- Determination of tetra-CB --- p.90 / Chapter 5.4 --- Optimisation of reaction conditions for UV-PCO in batch system --- p.90 / Chapter 5.4.1 --- Control experiments and effects of initial titanium dioxide concentration --- p.91 / Chapter 5.4.2 --- Effect of initial hydrogen peroxide concentration and UV intensity --- p.91 / Chapter 5.4.3 --- Effect of initial titanium dioxide concentration and initial pH --- p.93 / Chapter 5.5 --- Estimation of tetra-CB degradation pathway by photocatalytic oxidation --- p.95 / Chapter 5.6 --- Evaluation for the toxicity of hydrogen peroxide and toxicity change of tetra-CB by Microtox® test --- p.96 / Chapter 5.7 --- Determination of H202 concentration after PCO --- p.97 / Chapter Chapter 6 --- Conclusions --- p.98 / Chapter Chapter 7 --- References --- p.99

Semiconductor photocatalysis has received extensive attention due to its wide applications in water and indoor air purification, solar fuel production, etc. Charge carrier separation is a crucial step in semiconductor photocatalysis and influences the overall efficiency. It has been demonstrated that internal depolarisiation field of ferroelectric materials can drive spatial separation of charge carriers, which results in spatial separation of reduction and oxidation reactions, and improved charge carrier separation. In this thesis, ferroelectric barium titanate was chosen and its photocatalytic performance in decolourisation of organic dye molecules was investigated. Photodeposition method was adopted to deposite silver nanoparticles on the surface of barium titanate. Silver modified barium titanate showed increased photodecolourisation rate compared with bare barium titanate due to its role of electron traps and hindered charge carrier recombination. A simple thermal treatment was used to alter the phase composition of the as-received barium titanate. Samples which contained more ferroelectric tetragonal phase were found to possess higher photocatalytic activity compared with non-ferroelectric samples. This was associated with stronger ferroelectricity after thermal treatment, which enhanced dye molecule adsorption and aid charge carrier separation. The mechanism and intermediates generated in photodegradation of Rhodamine B with silver modified ferroelectric barium titanate were studied. Cleavage of chromophore was demonstrated to dominate in the initial process. Benzoic acid was identified as the main intermediate and no siginificant discrepancy in intermediates distribution between ferroelectric photocatalytic system and non-ferroelectric system was observed. The influence of ferroelectric dipole of barium titanate on photocatalytic activity of heterostructured barium titanate/hematite was also studied. The synthesised heterostructured barium titanate/hematite showed higher photodcolourisation rate than both barium titanate and hematite. This phenomenon was attributed to the improved charge carrier separation and extended charge carrier lifetime arising from heterojunction and an interaction between the ferroelectric dipole and the carriers in the hematite.

在過去的幾十年中，人們越來越關心由致病微生物引起的水傳播疾病的爆發。作為一種綠色技術，太陽能光催化在不引起二次污染的殺滅各種致病微生物方面引起了廣泛關注。但是，目前最廣泛應用的TiO₂光催化劑僅在紫外光激發範圍內有效，而紫外光僅占太陽光譜的4%。因為太陽光譜中有45%是可見光，所以新型可見光催化劑的開發是現今光催化技術亟待解決的問題。另一方面，目前對於光催化殺菌機理的研究報導非常稀少而且主要集中于紫外-TiO₂光催化系統中，而對於可見光催化系統中的殺菌機理研究還鮮有報導。 / 本研究介紹三種新型可見光催化劑的殺菌性能。它們是B,Ni共摻TiO₂微米球（BNT），BiVO₄納米管（BV-NT）和CdIn₂S₄微米球（CIS）。其中一種是修飾的TiO₂催化劑，另兩種是新型的非TiO₂基催化劑。採用加入各種湮滅劑結合一種分離裝置的研究方法系統研究了三種催化劑的可見光殺菌機理。首先，研究發現當用BNT作為光催化劑的時候，可見光催化降解染料和殺菌之間存在巨大的差異。對於光催化降解染料，光催化反應主要發生在催化劑的表面，是由表面活性物質如h⁺, ・OHs和・O₂⁻參與，而細菌可以被擴散物種如・OH[subscript b]和H₂O₂，以不直接接觸催化劑表面的方式被殺死。可擴散的H₂O₂在這種殺菌過程中起了最重要的作用，而它可以在催化劑價帶以・OH[subscript b]溶液體相耦合和・OH[subscript s]催化劑表面耦合兩種方式產生。 / 其次，在用BV-NT作為光催化劑可見光殺滅大腸桿菌的過程中，光生空穴（h⁺）以及由空穴產生的氧化物種，如・OH[subscript s], H₂O₂和・HO₂/・O₂⁻，是主要的活性物種。但是這個殺菌過程只有很少量的H₂O₂可以擴散到溶液中，導致有效殺菌需要細菌和光催化表面直接接觸。研究還發現，細菌本身可以捕獲光生電子（e⁻）來降低空穴-電子複合率，這個作用在無氧氣參與的殺菌過程中尤為明顯。透射電鏡顯示，細菌的破壞是由細胞壁開始從外到內的被破壞。研究認為，表面羥基・OH[subscript s]比溶液體相羥基・OH[subscript b]更加重要，並且很難從BV-NT表面擴散進容易中。 / 最後，研究還發現CIS也具有不接觸細菌而有效可見光催化殺滅大腸桿菌的能力，這也歸結為可擴散H₂O₂，而不是・OH的作用。H₂O₂可以通過・O₂⁻從催化劑導帶和價帶同時產生。本研究提供了幾種具有應用前景的高效可見光催化殺菌催化劑，並對其光催化機理提出了新的思路，指出可見光催化殺菌機理與使用的光催化劑是密切相關的。更重要的是，本研究建立了一種簡便易行的研究方法，可用於對其他各種可見光催化殺菌系統進行深入的機理研究。 / During the last few decades, there has been an increasing public concern related to the outbreak of waterborne diseases caused by pathogenic microorganisms. As a green technology, solar photocatalysis has attracted much attention for the disinfection of various microorganisms without secondary pollution. However, the most commonly used TiO₂ photocatalyst is only active under UV irradiation which accounts for only 4% of the solar spectrum. Therefore, new types of photocatalysts that can be excited by visible light (VL) are highly needed, as 45% of the solar spectrum is covered by VL. In addition, existing reports on the mechanisms of photocatalytic bacterial disinfection are rather limited and mostly based on TiO₂-UV irradiated systems, thus the mechanisms in visible-light-driven (VLD) photocatalystic disinfection systems are far from fully understandable. / In this study, three different kinds of VLD photocatalysts were discovered for the photocatalytic bacterial disinfection. They were B-Ni-codoped TiO₂ microsphere (BNT), bismuth vanadate nanotube (BV-NT), and cadmium indium sulfide (CIS). One was modified TiO₂-based photocatalyst, and the other two were new types of non-TiO₂ based photocatalyst. The mechanisms of VLD photocatalytic disinfection were investigated by multiple scavenging studies combined with a partition system. Firstly, significant differences between VLD photocatalytic dye decolorization and bacterial disinfection were found in the case of BNT as the photocatalyst. For photocatalytic dye decolorization, the reaction mainly occurred on the photocatalyst surface with the aid of surface-bounded reactive species (h⁺, ・OH[subscript s] and ・O₂⁻), while bacterial cell could be inactivated by diffusing reactive oxidative species such as ・OH[subscript b] and H₂O₂ without the direct contact with the photocatalyst. The diffusing H₂O₂ played the most important role in the photocatalytic disinfection, which could be produced both by the coupling of ・OH[subscript b] in bulk solution and ・OH[subscript s] on the surface of photocatalyst at the valence band. / Secondly, when using BV-NT as the photocatalyst for Escherichia coli K-12 inactivation, the photogenerated h⁺ and reactive oxidative species derived from h⁺, such as ・OH[subscript s], H₂O₂ and ・HO₂/・O₂⁻, were the major reactive species. However, the inactivation requires close contact between the BV-NT and bacterial cells, as only a limited amount of H₂O₂ can diffuse into the solution to cause the inactivation. The bacterial cells can trap e⁻ in order to minimize e⁻-h⁺ recombination, especially under anaerobic condition. Transmission electron microscopic study indicated the destruction process of bacterial cell began from the cell wall to other cellular components. The ・OH[subscript s] was postulated to be more important than ・OH[subscript b] and was not supposed to be released very easily from BV-NT surface. / Finally, it was found that E. coli cells could be effectively inactivated without the direct contact with CIS, which was attributed to the function of diffusing H₂O₂ rather than ・OH. H₂O₂ was produced from both conduction and valance bands with the involvement of ・O₂⁻, which were detected by ESR spin-trap with DMPO trapping technology. While this study provided promising candidates of efficient VLD photocatalysts for water disinfection as well as deep insights into the disinfection mechanisms, it was notable that the photocatalytic disinfection mechanisms were quite dependent on the selected photocatalysts. Nevertheless, the research methodology established in this study was proved to be facile and versatile for the in-depth investigation of mechanisms in different VLD photocatalyst systems. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Wang, Wanjun. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 140-170). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Acknowledgements --- p.i / Abstract --- p.vi / List of Figures --- p.xvi / List of Plates --- p.xxiii / List of Tables --- p.xxiv / List of Equations --- p.xxv / Abbreviations --- p.xxvii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Water disinfection --- p.1 / Chapter 1.2 --- Traditional water disinfection methods --- p.2 / Chapter 1.2.1 --- Chlorination --- p.2 / Chapter 1.2.2 --- Ozonation --- p.3 / Chapter 1.2.3 --- UV irradiation --- p.4 / Chapter 1.3 --- Advanced oxidation process --- p.5 / Chapter 1.4 --- Photocatalysis --- p.6 / Chapter 1.4.1 --- Fundamental mechanism for TiO₂ photocatalysis --- p.7 / Chapter 1.4.2 --- Photocatalytic water disinfection --- p.12 / Chapter 1.5 --- Visible-light-driven photocatalysts for water disinfection --- p.16 / Chapter 1.5.1 --- Modified TiO₂ photocatalysts --- p.16 / Chapter 1.5.1.1 --- Surface modication of TiO₂ by noble metals --- p.16 / Chapter 1.5.1.2 --- Ion doped TiO₂ --- p.18 / Chapter 1.5.1.3 --- Dye-sensitized TiO₂ --- p.19 / Chapter 1.5.1.4 --- Composite TiO₂ --- p.20 / Chapter 1.5.2 --- Non-TiO₂ based photocatalysts --- p.22 / Chapter 1.5.2.1 --- Metal oxides --- p.22 / Chapter 1.5.2.2 --- Metal sulfides --- p.24 / Chapter 1.5.2.3 --- Bismuth metallates --- p.25 / Chapter 1.6 --- Photocatalystic disinfection mechanisms --- p.27 / Chapter 2 --- Objectives --- p.30 / Chapter 3 --- Comparative Study of Visible-light-driven Photocatalytic Mechanisms of Dye Decolorization and Bacterial Disinfection by B-Ni-codoped TiO₂ Microspheres --- p.32 / Chapter 3.1 --- Introduction --- p.32 / Chapter 3.2 --- Experimental --- p.35 / Chapter 3.2.1 --- Materials --- p.35 / Chapter 3.2.2 --- Characterizations --- p.36 / Chapter 3.2.3 --- Photocatalytic decolorization of RhB --- p.36 / Chapter 3.2.4 --- Photocatalytic disinfection of E. coli K-12 --- p.37 / Chapter 3.2.5 --- Partition system --- p.40 / Chapter 3.2.6 --- Scavenging study --- p.41 / Chapter 3.2.7 --- Analysis of ・OH and ・O₂⁻ --- p.42 / Chapter 3.2.8 --- Analysis of H₂O₂ --- p.43 / Chapter 3.3 --- Results and Discussion --- p.44 / Chapter 3.3.1 --- XRD and SEM images --- p.44 / Chapter 3.3.2 --- Photocatalytic decolorization of RhB --- p.46 / Chapter 3.3.2.1 --- Role of reactive species --- p.46 / Chapter 3.3.2.2 --- Partition system for dye decolorization --- p.49 / Chapter 3.3.3 --- Photocatalytic bacterial disinfection --- p.51 / Chapter 3.3.3.1 --- Role of reactive species --- p.51 / Chapter 3.3.3.2 --- Partition system for bacterial disinfection --- p.54 / Chapter 3.3.3.3 --- pH effects --- p.58 / Chapter 3.3.3.4 --- Role of H₂O₂ --- p.60 / Chapter 3.3.4 --- Role of ・O₂⁻ in RhB decolorization and bacterial disinfection --- p.67 / Chapter 3.4 --- Conclusions --- p.75 / Chapter 4. --- Visible-light-driven Photocatalytic Inactivation of E. coli K-12 by Bismuth Vanadate Nanotubes: Bactericidal Performance and Mechanism --- p.76 / Chapter 4.1 --- Introduction --- p.76 / Chapter 4.2 --- Experimental --- p.78 / Chapter 4.2.1 --- Materials --- p.78 / Chapter 4.2.2 --- Photocatalytic bacterial inactivation --- p.80 / Chapter 4.2.3 --- Bacterial regrowth ability test --- p.82 / Chapter 4.2.4 --- Analysis of reactive species --- p.82 / Chapter 4.2.5 --- Preparation procedure for bacterial TEM study --- p.83 / Chapter 4.2.6 --- Analysis of bacterial catalase activity --- p.84 / Chapter 4.2.7 --- Analysis of potassium ion leakage --- p.84 / Chapter 4.3 --- Results and Discussion --- p.85 / Chapter 4.3.1 --- Photocatalytic bacterial inactivation --- p.85 / Chapter 4.3.2 --- Mechanism of photocatalytic inactivation --- p.87 / Chapter 4.3.2.1 --- Role of primary reactive species --- p.87 / Chapter 4.3.2.2 --- Role of direct contact effect --- p.96 / Chapter 4.3.3 --- Destruction model of bacterial cells --- p.98 / Chapter 4.3.4 --- Analysis of radical production --- p.104 / Chapter 4.4 --- Conclusions --- p.109 / Chapter 5 --- CdIn₂S₄ Microsphere as an Efficient Visible-light-driven Photocatalyst for Bacterial Inactivation: Synthesis, Characterizations and Photocatalytic Inactivation Mechanisms --- p.111 / Chapter 5.1 --- Introduction --- p.111 / Chapter 5.2 --- Experimental --- p.113 / Chapter 5.2.1 --- Synthesis --- p.113 / Chapter 5.2.2 --- Characterizations --- p.114 / Chapter 5.2.3 --- Photocatalytic bacterial inactivation --- p.116 / Chapter 5.3 --- Results and Discussion --- p.117 / Chapter 5.3.1 --- Characterizations of Photocatalyst --- p.117 / Chapter 5.3.2 --- Photocatalytic bacterial inactivation and mechanism --- p.121 / Chapter 5.3.3 --- Destruction process of bacterial cell --- p.128 / Chapter 5.3.4 --- Analysis of radical generation --- p.131 / Chapter 5.4 --- Conclusions --- p.133 / Chapter 6 --- General Conclusions --- p.135 / Chapter 7 --- References --- p.140

The development of nanostructured materials for environmental applications has received considerable attention in recent years. The properties of nanoparticles or nanostructured materials, such as large surface areas or high aspect ratios, translate into large improvements in the performance of existing devices and in the discovery of novel applications. On the other hand, photocatalysis is an attractive technology for the elimination of organic pollutants in water due to its simplicity, ease of implementation and reasonable cost compared to other advanced oxidation processes. A key disadvantage of many photocatalysts is their use in powder form which makes their recovery from treated water costly. In addition, incomplete removal can lead to accumulation over time with adverse effects to the environment. As a result significant effort has been placed in immobilizing photocatalytic materials on different substrates. The immobilization of photocatalyst results in a decrease in photocatalytic performance mainly due to reduction of surface area; therefore, research is now focusing on developing nanostructured materials which combine the attributes of nanotechnology and photocatalysis. In the present thesis, a systematic study of the relationship between properties of supported ZnO nanostructures and their photocatalytic activity was performed. Analysis was carried out by producing ZnO nanostructured films via anodization. The effects of voltage, temperature, reaction time and type of electrolyte on the morphology of ZnO nanostructures was studied. Results show that the type of electrolyte and its concentration determine the morphology and size of the nanostructures. Voltage, time and temperature affect the distribution and density of the nanostructures along the surface and affect the crystal size of the ZnO. The band gaps of the films were in the range of 3.27 and 3.50 eV. Although ZnO is a hydrophilic material, some of the films displayed hydrophobic and super-hydrophobic behaviour. The results obtained in this study and some data already published in the literature were correlated to the synthesis parameters, and were used to devise design guidelines to obtain ZnO films with specific nanostructures and macroscopic properties by controlling the anodization parameters. The photocatalytic activity of the ZnO nanostructured films (ZnO-NFs) were studied using three different photocatalytic reactors, (i) a thermo-stated batch reactor, (ii) a recirculating flat plate reactor, and (iii) a recirculating tubular annular reactor. Phenol and methyl orange (MO) were used as a model compounds. It was found that crystal size does not affect the photocatalytic performance of the films while morphology has an important impact on the degradation of phenol. The stability of the ZnO nanostructures was tested under different levels of oxygen, degradation of phenol occurred even at anoxic conditions following the Mars-van Krevelen mechanism. The formation of new nanostructures produced during the photocatalytic reaction was studied and a mechanism of formation was proposed. The study of the photocatalytic performance in the flat plate reactor showed that there was a mass transfer limitation in the process. ZnO nanostructures showed higher photocatalytic activity and morphology stability in the tubular annular reactor. Degradation of MO and phenol was produced in darkness by the nanostructures supported in Zn foil. It was also demonstrated that oxygen plasma post-treatment enhances the photocatalytic activity of the ZnO-NF by 36% while making the photocatalyst more stable for the photocatalytic degradation of phenol compared to those treated with heat. An electrical current was applied to the photocatalyst in the tubular annular reactor, which improved the degradation of phenol and participated in the formation of nanostructures in the Zn wire surface.

The development of mesoporous titania (meso-TiO2) films is a considerable research goal in the field of mesoporous material development due to their proven applicability in solar cells and phtocatalysts. In this work, the meso-TiO2 films were fabricated through different methods and these home-made titania structures were applied in DSSCs and photocatalysts. Meso-TiO2 powders were first prepared from ethanol/water or ethanol solvent. The meso-TiO2 made from the ethanol/water solvent did not have an ordered mesostructure, but that made from ethanol solvent had 2D-hexagonal mesostructure. Films were prepared by adding ordered meso-TiO2 particles into paste formulations of P25 nanoparticles with weight proportion ranging from 0 to 100%. These were used to form films by doctor blading, and the influence of paste composition on film structure, morphology, porosity, optical properties and cell performance were investigated. Secondly, ordered meso-TiO2 films were fabricated by dip coating from aqueous or ethanol solvent. Both films had cubic mesostructures, but the film coated from aqueous solvent was not uniform. The film formed from ethanol solvent was doped with sulphur. The effects of doping on the mesostructure, morphology, structure, optical properties and photocatalytic activity were studied. The thickness of films was increased by repeated coating. The number of layers had an influence on the mesostructure, morphology, optical properties and cell performance when these films were applied in DSSCs Finally, a novel method was adopted to prepared meso-TiO2 films. Molecular titania precursors or titania colloidal seeds were used as the titania source. Both of them can be used to prepare free-standing hybrid films at air-water interface by a self-assembly method, however the one synthesised from the molecular titania precursor did not contain very much titania and became a powder after calcination. In contrast, after calcination, the films formed from the colloidal titania solution remained intact, and were composed of mixtures of TiO2 nanoparticles and nanowires with mesopores arising from interparticle porosity. These films were applied in DSSCs. This interfacial method was also successfully extended to prepare free-standing ZnO films from a molecular precursor. After calcination, the free-standing ZnO films were found to be composed of rough spheres formed by flocculation of smaller nanoparticles.