Cucurbit[8]uril (CB[8]) has attracted great interest in the cucurbit[n]uril (CB[\textit{n}]) family on account of its capability to simultaneously accommodate two guests inside its cavity, to form strong yet dynamic ternary complexes. Owing to the photo-induced \textit{trans} to \textit{cis} isomerisation property, azobenzene (Azo) derivatives have been widely employed in several host-guest systems, leading to various light-responsive materials. This thesis focuses on CB[8]-based ternary complexes, especially those involving Azo derivatives. These systems can be exploited as a platform to hierarchically fabricate supramolecular constructs, including crystalline structures and composite materials. Specifically, novel morphology-controlled (1D needle-like, 2D sheet-like) crystals have been prepared by adjusting the assembly of Azo-CB[8] complexes, which can be further developed to oriented macroscopic free-standing crystalline pillars grown from a glass surface. Next, a composite micelle-nanoparticle complex has been prepared utilising Azo-CB[8] assemblies, which demonstrates $\sim$90$\%$ efficiency in surfactant recycling. Finally, an organic CB[8]-mediated hydrogel reinforced by inorganic nanowires has been prepared. This hybrid structure shows increased stiffness due to various supramolecular interactions. Chapter 1 gives a brief introduction to CB[\textit{n}] host-guest chemistry with emphasis on CB[\textit{n}]-based crystalline structures and CB[8] ternary complexes. Recent progress of Azo-based host-guest chemistry is then reviewed. In addition, shape-controlled crystals formed \textit{via} supramolecular interactions are discussed at the end of the chapter. Chapter 2 focuses on the crystalline structure of the 1:2 homoternary complex formed between CB[8] and a methyl orange (MO) guest, which is the fastest CB[8]-based crystallisation to date. As a commonly used pH indicator, MO possesses an azobenzene moiety with both an electronically positive amino group and an anionic sulfonate group. At low pH values, formation of the homoternary complex 2MO@CB[8] occurs, serving as a 'tectonic' building block, which rapidly stacks into a herringbone arrangement. The intermolecular and intercomplex interactions inside 2MO@CB[8] crystals are discussed, whereby the CB[8] macrocycle orients the electrostatic charges on MO guests resulting in the repulsive interactions being shielded; this in turn leads to fast electrostatically-driven crystal growth. The 2MO@CB[8] system provides a promising approach for designing ultrarapid crystallisation systems derived from CB[\textit{n}] host-guest complexes. Moreover, the host-guest chemistry between CB[8] and a variety of Azo derivatives with different functional groups is discussed, demonstrating the influence of guest structures on their crystalline behaviours. Chapter 3 further explores the mechanism of 2MO@CB[8] crystallisation through a series of experimental and computational methods. Control over the crystal shape, length and growth rate can be achieved in a facile manner whilst maintaining the same (internal) unit cell. Therefore, the properties of the macro-scale crystals can be tuned at the molecular level through adjusting the assembly of 2MO@CB[8] building blocks. For example, tuning the ionic strength of the solution enables a second growth dimension, yielding 2D crystals with sheet-like and more complex morphologies. Furthermore, our understanding of oriented electrostatics provided by the homoternary tecton can then be exploited to prepare oriented macroscopic free-standing crystalline pillars grown from a glass surface at room temperature. Next, CB[8] ternary complexes have been employed as 'bridges' to link (organic) soft and (inorganic) hard materials together, resulting in composite materials. In chapter 4, a micelle-nanoparticle complex (\textbf{MNC}) structure has been assembled \textit{via} host-guest interactions between Azo-functionalised, cargo-loaded micelles and magnetic SiO$_2$ nanoparticles (NPs) functionalised with CB[8] catenanes. Owing to the photo-responsive and magnetic properties, \textbf{MNCs} can be exploited to recycle detergents (micelles) from aqueous solution. This is followed by the controlled release of the encapsulated hydrophobic molecules inside the micelle cavity. In this process, both the micelles and NPs can be recycled efficiently. The novel \textbf{MNC} structure provides a promising approach to recycle versatile drug carriers through host-guest chemistry. Chapter 5 introduces a CB[8]-based hydrogel in which inorganic nanowires (NWs) are employed to enhance the gel stiffness. The supramolecular hydrogel is comprised of methylviologen-functionalised poly(vinyl alcohol) (PVA-MV), hydroxyethyl cellulose with naphthyl moieties (HEC-Np) and CB[8]. The gel structure is effectively enhanced by the framework supporting effects of CePO$_4$ NWs and additional hydrogen bonding interactions between NWs and PVA-MV/HEC-Np polymers. The high aspect ratio NWs serve as a 'skeleton' for the network, providing extra physical crosslinks. This results in a single continuous phase hybrid supramolecular network with improved strength, showcasing a general approach to reinforce soft materials. Finally, this thesis closes with a summary and perspective chapter, concluding the present work and highlighting an insight towards future work. Utilising CB[8] ternary complexes, various supramolecular constructs can be prepared through hierarchical self-assemblies, leading to a wide variety of composite systems and functional materials in the future.

This dissertation is related to the understanding of catalytic reactions of metal oxides. For several decades, the surfaces and bulk of materials have been probed to determine additional properties that relate to photocatalytic applications. This investigation furthers these efforts by the (a) modification of a metal oxide surface to isolate known influences of chemical properties and (b) proposing and utilizing a novel methodology for attribution of photocatalytic activity to a discernable influence. For the first effort, by effectively utilizing a known technique for a new application on a metal oxide, such isolations can be made despite unfavorable states. For the second effort, a reduction in the influence of surface states for metal oxides is effectively performed, providing the isolation of influences originating from the bulk. The challenge with such a proposal is verifying such bulk states have been adequately isolated as external influences would obviously distort any conclusions. Thus, techniques to both create such bulk states and eliminate unwanted combinations thereof are additionally required and must be provided for. Lastly, a determination of the photocatalytic activity is made to these states and results are provided.

TiO2 photocatalysis is been widely studied for air and water purification applications; titanium dioxide is the most used semiconductor principally because its low cost, stability and chemical properties. However it only utilizes the UV portion of the solar spectrum as an energy source (less than 4% of the total sunlight energy). This behavior is due to its high band gap value of 3.2 eV. The modification of light harvesting properties of TiO2 by doping has become an important research topic to achieve an efficient operating range under UV and visible light. In addition, the structure and surface properties of photocatalysts play an important role. This thesis explores the effects of Zn doped TiO2, prepared by the sol-gel method, on its photocatalytic activity to decompose organics and the characterization of the doped samples. Since this study is part of a collaborative initiative, the samples were synthesized and provided by Dr. A. R. Phani from the Department of Physics, University of L'Aquila. Preliminary examination revealed a relatively low photocatalytic efficiency of the samples. The objective is to modify/improve its properties by high energy ball milling which is expected to generate accumulations of defects, particle size reduction and an increase in the active surface area. The characterization of doped and mechanochemically treated materials will be analyzed by optical diffuse reflectance measurements and optical absorption calculations using the Kubelka-Munk approach. The phase structure and particle size of the materials will be determined using X-ray diffraction (XRD). The BET surface area of the samples will be obtained using an Autosorb instrument. The photocatalytic properties will be studied by the analysis of decomposition of Methyl Orange in an aqueous solution. An aqueous photocatalytic tubular reactor with capability of operation using UV and/or fluorescent light will be designed and built.

Zinc oxide (ZnO) nanostructures, especially nanowires, have been one of the most important semiconductive materials used for photocatalysis due to their unique material properties and remarkable performance. In this project, vertically-aligned ZnO nanowires on glass substrate have been synthesized by using the facile hydrothermal methods with the help of pre-coated ZnO seeding layer. The crystalline structure, morphology and UV-Vis transmission spectra of the as-synthesized sample were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and Ultra-violet Visible (UV-Vis) Spectrophotometer. The photocatalytic activity of the sample was examined for the photocatalytic degradation of methyl orange (MO) as the test dye in aqueous solution under UV-A irradiation. The extent of direct hydrolysis of the MO dye under UV light without the photocatalysts was first measured to eliminate the possible contribution from the undesired variables to the overall efficiency. The effects of pH and initial concentration of the MO solution, as well as the nanowire growth time, on the photocatalytic efficiency have been investigated, in order to determine the optimal conditions for photocatalytic applications of ZnO nanowires in the industry. Furthermore, the reproducibility of the experimental methods used in this project was tested to ensure the reliability of the experimental results obtained; and the reusability of the prepared ZnO nanowire arrays were also evaluated to investigate the stability of the products for photocatalytic applications in a large scale. In addition, a micro-chamber based microfluidic device with integrated ZnO nanowire arrays has been fabricated and used for photodegradation studies of MO solution under continuous-flow conditions. As expected, the micro-chamber based approach exhibited much improved photodegradation efficiency as compared to the conventional method using bulk dye solution. The effects of the flow rate and chamber height of the microfluidic device have also been investigated in order to determine the optimal experimental conditions for photodegradation reactions in microfluidic devices.

Silver (Ag) was loaded to three different kinds (P-25, NT-22, and TiO(OH)2) of titanium dioxide (TiO2) powders through adding three different quantities (4.6, 9.2, and 13.8 ml) of silver nitrate (AgNO3) solution by mechanical ball milling process. X-Ray diffraction analysis suggested that Ag was loaded on the TiO2 powders in the form of silver oxide (AgO). SEM, particle size, and BET surface area analyses revealed that TiO2 particles agglomerated after ball milling, resulting in the decrease of specific surface area of the TiO2 powders. Powders P-25, NT-22, and TiO(OH)2 degraded 94 %, 46 %, and 26 %, respectively of MO solution under 1 h UV irradiation. Increasing amount of Ag loading enhanced photocatalytic activity of TiO2 powders under UV irradiation. The best photocatalytic performance was achieved by 13.8 ml AgNO3 solution added NT-22 powders. Percent methyl orange (MO) degradation of 13.8 ml AgNO3 solution added P-25, NT-22, and TiO(OH)2 powders under 1 h UV irradiation was 85 %, 96 %, and 67 %, respectively. Contact angle measurements revealed that hydrophilic properties of TiO2 powders were also improved by Ag loading. Moreover, TiO2 powders gained antibacterial prospect after Ag addition. Ag loaded TiO2 powders could be used effectively for the applications requiring better photocatalytic activity and antibacterial effect.

The photocatalytic activity of semiconductor metal oxides can be improved by the addition of sensitizer which enhances the band gap by considerable red shift of the absorption edge of semiconductor. In the present study, the effect of ascorbic acid as sensitizer on the photocatalytic activity of titania-silica binary mixtures was studied. The SiO2-TiO2 mixtures having 50wt%Ti:Si composition were prepared with sol-gel method. The surface area and porosity of the samples were modified by using various amounts of polyethylene glycol (PEG) as template. The thin films of the samples were obtained by dip coating of glass plates to colloidal solutions. The samples were characterized by methylene blue adsorption method and UV-Vis spectrophotometry. The photocatalytic activities of the samples were measured with methylene blue degradation, methyl orange degradation and direct water splitting in the presence and absence of ascorbic acid. Increase in the surface area and reaction rate with increasing PEG addition until a threshold value was observed. Highest methylene blue degradation activity was observed for 27g PEG added sol-gel derived film and surface area of this film is measured as 44m2/m2. Ascorbic acid presence shows a significant increase in the photocatalytic degradation activity of methyl orange. The sensitization effect of ascorbic acid was also compared with the effect of EDTA. It was found that the effect of ascorbic acid on the methyl orange degradation rate is significantly higher than the effect of EDTA. However, the effect of EDTA is more pronounced in water splitting reaction.

Titanium Dioxide (TiO 2) has been considered an ideal photocatalyst due to factors such as its photocatalytic properties, chemical stability, impact on the environment and cost. However, its application has been primarily limited to ultraviolet (UV) environments due to its high band gap (3.2 eV). This high band gap limits the harvesting of photons to approximately 4% of sunlight radiation. Research today is focused on lowering this gap by doping or coupling TiO 2 with other semiconductors, transition metals and non-metal anions, thereby expanding its effectiveness well into the visible range. This thesis explores the effects of thermal and thermochemical ammonia treatment of nano-particulated TiO 2. The objective is to synthesize a photocatalytic activity in the visible range while at the same time retaining its photocatalytic properties in the UV range. Specifically, this study utilizes pure commercial nano-particulated TiO 2 powder (Degussa P-25), and uses this untreated TiO2 as a baseline to investigate the effects of thermal and thermochemical treatments. Nitrogen-doping is carried out by gas phase impregnation using anhydrous ammonia as the nitrogen source and a tube furnace reactor. The effects of temperature, time duration and gas flow rate on the effectiveness of thermally and thermochemically treated TiO 2 are examined. Thermally treated TiO 2 was calcinated in a dry inert nitrogen (N2) atmosphere and the effects of temperature and treatment duration are investigated. The band gap of the thermally treated and thermochemically ammonia treated TiO 2 have been measured and calculated using an optical spectrometer. The photocatalytic properties of all materials have been investigated by the degradation of methyl orange (MO) in an aqueous solution using both visible simulated solar spectrum (VSSS) and simulated solar spectrum (SSS) halogen light sources. Methyl orange degradation has been measured and calculated using an optical spectrometer. The phase structure and particle size of the materials is determined using x-ray diffraction (XRD). The BET surface area of the samples has been obtained using an Autosorb. Surface or microstructure characterization has also been obtained by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

Zinc oxide (ZnO) nanostructures, especially nanowires, have been one of the most important semiconductive materials used for photocatalysis due to their unique material properties and remarkable performance. In this project, vertically-aligned ZnO nanowires on glass substrate have been synthesized by using the facile hydrothermal methods with the help of pre-coated ZnO seeding layer. The crystalline structure, morphology and UV-Vis transmission spectra of the as-synthesized sample were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and Ultra-violet Visible (UV-Vis) Spectrophotometer. The photocatalytic activity of the sample was examined for the photocatalytic degradation of methyl orange (MO) as the test dye in aqueous solution under UV-A irradiation. The extent of direct hydrolysis of the MO dye under UV light without the photocatalysts was first measured to eliminate the possible contribution from the undesired variables to the overall efficiency. The effects of pH and initial concentration of the MO solution, as well as the nanowire growth time, on the photocatalytic efficiency have been investigated, in order to determine the optimal conditions for photocatalytic applications of ZnO nanowires in the industry. Furthermore, the reproducibility of the experimental methods used in this project was tested to ensure the reliability of the experimental results obtained; and the reusability of the prepared ZnO nanowire arrays were also evaluated to investigate the stability of the products for photocatalytic applications in a large scale. In addition, a micro-chamber based microfluidic device with integrated ZnO nanowire arrays has been fabricated and used for photodegradation studies of MO solution under continuous-flow conditions. As expected, the micro-chamber based approach exhibited much improved photodegradation efficiency as compared to the conventional method using bulk dye solution. The effects of the flow rate and chamber height of the microfluidic device have also been investigated in order to determine the optimal experimental conditions for photodegradation reactions in microfluidic devices.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-07-11T13:13:10Z No. of bitstreams: 1 JOÃO FERNANDES DUARTE NETO - DISSERTAÇÃO (PPGCEMat) 2015.pdf: 2295774 bytes, checksum: d73166400ea15685ca449c373a12dc20 (MD5) / Made available in DSpace on 2018-07-11T13:13:10Z (GMT). No. of bitstreams: 1 JOÃO FERNANDES DUARTE NETO - DISSERTAÇÃO (PPGCEMat) 2015.pdf: 2295774 bytes, checksum: d73166400ea15685ca449c373a12dc20 (MD5) Previous issue date: 2015-02-24 / Este trabalho investigou o processo de adsorção, equilibrio e cinética de argilas esmectíticas da cidade de Boa Vista (Paraíba), usadas como adsorventes de corantes com comportamentos químicos distintos - rodamina B (RB), catiônico, e alaranjado de metila (AL), aniônico - em meio aquoso. Essas argilas foram escolhidas devido às suas propriedades características do argilomineral esmectítico, que possui sítios quimicamente ativos, provocado pela substituição isomórfica e interação das arestas, tornando-o atrativo sua aplicação para fins adsortivos. As argilas utilizadas são conhecidas como bentonita chocolate e bentonita chocobofe. Esses materiais foram utilizados na forma natural e após tratamento com carbonato de sódio, ácido clorídrico e organofilização (sal quaternário de amônio PRAEPAGEN). Todos os adsorventes foram caracterizados por fluorescência de raios X, difração de raios X, análises térmicas (TG, DTG e DTA) e determinação de tamanho de partícula. Os ensaios de adsorção dos corantes foram examinados por sistema de bateladas, alterando tempo de contato, quantidade de adsorvente, concentração dos corantes e pH inicial. Para a análise do comportamento de adsorção foi utilizado espectrofotometria UV-VIS. O modelo de isoterma de Freundlich foi o que melhor se ajustou aos dados experimentais das argilas naturais e modificadas. Porém nos processos adsortivos envolvendo as argilas organofilizadas, na interação com RB, tanto o modelo de Langmuir como o de Freundlich apresentaram um bom ajuste aos dados experimentais. Os dados cinéticos de adsorção foram ajustados ao modelo de pseudo-segunda ordem (R2>0,9). Os testes de capacidades de adsorção permitiram concluir que a maior eficiência em remover a RB ocorre quando as argilas são tratadas com ácido clorídrico. A maior eficiência na remoção do AL ocorre quando as argilas estudadas foram as organofilizadas. De modo geral, as argilas esmectíticas estudadas se mostraram adsorventes adequados para a remoção do corante RB, sendo, no entanto, necessário tratamentos específicos para maximizar ou melhorar a capacidade de adsorção dos corantes RB e AL. / This study investigated the process of adsorption, equilibrium and kinetics, of smectite clays from Boa Vista of Paraíba used as chemical adsorbents of dyes with different ionic behavior in aqueous media. Smectite clays known as chocolate and chocobofe and the dyes Rhodamine B (RB) (cationic) and Methyl Orange (AL), (anionic) were used in this study. The adsorbents were characterized by X-ray fluorescence, X-ray diffraction, thermal analysis (TG, DTA and DTG) and determination of particle size. Clays have been used in natural form and after treatment with sodium carbonate, acid and organophilization (quaternary ammonium salt – PRAEPAGEN). The dye adsorption was examined by a batch system, changing: contact time, amount of adsorbent, dye concentration and initial pH. UVVIS spectrophotometry was used for the analysis of the adsorption behavior. The clays were characterized as smectite clays and the efficiency of the treatments was confirmed by X-ray fluorescence and X-ray diffraction. The model of Freundlich isotherm presented the best fit to the experimental data of natural clays. However, in the adsorptive processes involving clays organophilizated both the Langmuir model and the Freundlich model showed good fitting to the experimental data. The kinetic adsorption data were fitted to the model of pseudo-second order (R2> 0.9). The adsorption capacities test showed that the highest efficiency in removing RB occurs when the clays are treated with hydrochloric acid. The highest efficiency of the removal of AL occurs when the clays are organophilizated. In general, the smectite clays were suitable adsorbent for the removal of the dye RB. However, special treatment is necessary to maximize or improve the adsorption ability of the dyes AL and RB.

V této práci byl popsán princip fotokatalýzy. Práce se soustřeďuje na kovové oxidy, které mají široké využití ve fotokatalytických aplikacích. Bylo také popsáno různé použití fotokatalytických materiálů. Tato práce se zaměřuje zejména na využití fotokatalytických materiálů pro rozklad organických vodu znečisťujících látek. Popsaný fotokatalyzátor je oxid měďný, který má velmi dobré vlastnosti pro rozklad organických látek pomocí fotokatalýzy. Schopnost rozkladu organických látek oxidu měďného byla popsána na rozkladu organického barviva methylová oranž.