Asfaltenos são constituídos de hidrocarbonetos policíclicos aromáticos que fazem parte de uma das classes de compostos químicos mais poluentes e carcinogênicos. São bem conhecidos por formarem inscrutações que obstruem tubulações, podendo até levar ao fechamento do poço. Estes podem constituir até 20% do petróleo, que ainda remanesce o principal recurso de energia usado em nosso planeta. Atualmente são convertidos em asfalto e coque durante o processo de refino, através de destilação destrutiva, exigindo altas temperaturas e emitindo compostos de enxofre na atmosfera. No entanto, sua conversão em matérias-primas mais valiosas e produtos menos poluentes, por exemplo, por craqueamento fotocatalítico ou oxidativo poderia ser uma opção mais limpa e econômica. A nanotecnologia vem sendo incorporada nas pesquisas com petróleo pelas contribuições positivas que acrescenta tanto do ponto de vista econômico como ambiental, assim como através do melhoramento e recuperação de óleos pesados. Os nanomateriais em geral possuem a vantagem de ter maior grau de dispersão e propriedades diferenciadas em relação ao bulk. Neste trabalho estudaram-se as interações entre os asfaltenos e diferentes nanomateriais com propriedades magnéticas, ópticas e eletrônicas extraordinárias, como as nanopartículas de óxido de ferro (Nmag), os híbridos de nanopartículas de ouro com óxido de grafeno reduzido (RGO@AuNP) e os nanobastões de ouro (AuNRs) respectivamente. As interações entre asfaltenos e Nmags com diferentes ligantes passivantes (C8H20O4Si e C6H17NO3Si) foram feitas através da construção de isotermas e experimentos de adsorção,revelando os tipos de ligação que ocorrem entre esses materiais, cobertura e a capacidade adsortiva. O recobrimento da nanopartícula e a concentração de asfalteno influenciam na adsorção, sendo a interação mais forte com as Nmags livres, indicando coordenação do ferro nos substituintes dos anéis aromáticos do asfalteno, tendo cobertura por monocamada. As Nmags funcionalizadas interagem por forças intermoleculares com os asfaltenos, apresentando cobertura por multicamadas. Em altas concentrações de asfalteno em tolueno, a adsorção foi mais efetiva para as Nmags funcionalizadas, pois a coordenação com o ferro é dificultada devido a formação de micela reversa, prevalecendo as interações hidrofóbicas. Houve uma drástica redução na temperatura de craqueamento dos asfaltenos na presença das Nmags, em mais de 100ºC, demonstrando seu potencial na catálise oxidativa de asfaltenos. As interações dos materiais RGO@AuNP e AuNR em filmes com asfalteno foram investigadas por microscopia hiperespectral de campo escuro. Como resultado observou-se o deslocamento e o alargamento da banda de espalhamento no espectro eletrônico, indicando a ocorrência de transferência de carga entre as espécies. A partir disso, realizaram-se fotocatálises com o RGO@AuNP à temperatura ambiente sob luz visível, utilizando o 9-antraldeído como composto modelo para o asfalteno. A reação levou à formação de endoperóxidos cíclicos, que sofreram clivagens com 90% de rendimento. Por ultimo, realizou-se um estudo mecanístico utilizando um sensor fluorogênico de espécies reativas de oxigênio (ROS) para avaliar a atividade fotocatalítica do RGO@AuNP. Mostrou-se que ocorrem transferências de elétrons fotoinduzidas da AuNP para o RGO em uma escala de tempo de ~11 fs, com eficiência quântica de ~35% e que radicais superóxidos (O2•-) podem ser gerados pelos efeitos sinérgicos da fotoexcitação do híbrido. / Asphaltenes are composed by polycyclic aromatic hydrocarbons that belong to one of the most polluting and carcinogenic chemical classes. They are well known for forming hard scales that obstruct pipelines and may even lead to the well shut down. They can constitute up to 20% of petroleum, which still remains the main source of energy used in our planet. At the present time, asphaltenes are converted into asphalt and coke by destructive distillation, in spite of the high cost and polluting technology involved, which employs high temperatures and releases sulfur compounds into the atmosphere. However, their conversion into more valuable raw materials, for instance, by photocatalytic or oxidative cracking using suitable catalysts, would be a better, more economic option. In recent years, nanotechnology has been incorporated into oil research, opening new economic and environmental perspectives, including the improvement and recovery of heavy oils. In general, nanomaterials have the advantage of being better dispersed and exhibiting differentiated properties in relation to the bulk. In this study the interactions between asphaltenes and different nanomaterials exhibiting remarkable magnetic, optical, and electronic properties, such as iron oxide nanoparticles (Nmag), hybrids of gold nanoparticles with reduced graphene oxide (RGO@AuNP) and the gold nanorods (AuNRs) respectively were investigated. The interactions between asphaltenes and Nmags with different surface-passivating ligands (C8H20O4Si and C6H17NO3Si) were made by performing isotherms curves and adsorption tests, revealing the types of binding between these materials, their coverage and the adsorptive capacity. The nanoparticle coating and the asphaltene concentration influence the adsorption. Theinteraction was stronger using the free Nmag, indicating coordination of the iron with the aromatic rings of the asphaltene, having a monolayer cover. Functionalized Nmags interact by intermolecular forces with asphaltenes, having a multilayer coverage. At high concentrations of asphaltene in toluene, the adsorption was more effective for the functionalized Nmags, since the coordination with the iron was hampered due to the formation of reverse micelle, prevailing the hydrophobic interactions. There was a drastic reduction in the asphaltene cracking temperature in the presence of Nmags, bigger than 100ºC, showing its potential on the oxidative catalysis of asphaltenes. The interactions of RGO@AuNP and AuNR materials with asphaltene films were investigated by dark field hyperspectral microscopy. As a result there was a shift and a broadening of the band in the electronic spectrum, indicating the occurrence of charge transfer between the species. From this, photocatalysis were performed with the RGO@AuNP, at room temperature, under visible light, using 9-antraldehyde (9-ATA) as a model compound for asphaltene. The reaction leads to the formation of cyclic endoperoxides that undergo further reactions, resulting in their cleavage, with 90% yield for the 9-ATA degradation. Finally, a mechanistic study was carried out using a fluorogenic sensor of reactive oxygen species to evaluate the photocatalytic activity of RGO@AuNP. It was showed that photoinduced electron transfer from AuNP to RGO can occur in ~11 fs time scale, with a quantum yield of ~35%, and superoxide radicals anions (O2•-) can be generated by synergistic effects after the hybrid photoexcitation.

Os polímeros tornaram-se relevantes em nossa vida cotidiana devido à variedade de utilidades que estes possuem. Ao observarmos a nossa volta percebemos que estamos imersos em um mundo cheio de materiais poliméricos. A grande demanda destes materiais exige o incremento da produção global de polímeros. Isto traz consigo um maior consumo de recursos fósseis, acelerando o esgotamento dos mesmos e aumentando a geração e poluentes ambientais. Neste sentido, a polimerização enzimática tem sido considerada uma alternativa importante às técnicas convencionais de polimerização química. Existem descritos na literatura uma variedade de polímeros que foram preparados por polimerização enzimática e em alguns casos usando monômeros de origem biológica comercialmente disponíveis. Na grande maioria dos casos, esses compostos (monômeros) possuem sua reatividade bem estabelecida na literatura. Este projeto teve como motivação o estudo e desenvolvimento de metodologia visando obter novas poliamidas mediante polimerização enzimática em condições de fluxo contínuo, usando monômeros sintetizados a partir da integração de reações fotocatalíticas e reações enzimáticas. Em um primeiro momento, decidiu-se preparar o primeiro intermediário sintético, o 3-carbamoiloctanoato de metila (I), a partir da reação radicalar de amidação do trans-2-octenoato de metila com a formamida. Este composto foi usado como bloco de construção de novos monômeros. O amido-éster I desejado foi obtido a partir de três metodologias: Método fotocatalítico em condições de fluxo contínuo, utilizando como fotoiniciadores acetona e benzofenona; Método fotocatalítico em batelada, usando como fotocatalisador decatungstato de tetrakis(tetrabutilamônio) e método redox catalisado por Fe(II) em presença de ácido viii sulfúrico e peróxido de hidrogênio. A melhor condição reacional avaliada forneceu o composto com 47% de rendimento. Visando obter os monômeros de amida, uma vez obtido o primeiro intermediário de síntese, iniciou-se o estudo da reação de aminólise catalisada enzimaticamente deste substrato com mono e diaminas, em batelada e em fluxo contínuo, para compreensão da reatividade deste tipo de composto. Não foi possível obter o monômero desejado, ao invés disso, foi isolado o produto resultante da reação de aminólise de 1 equivalente do 3-carbamoiloctanoato de metila (I) com a 1,6-hexanodiamina. Este produto foi obtido com 11 % de rendimento. Paralelamente, com o desejo de obter poliamidas a partir de monômeros de base biológica, foi realizado um estudo da reação de aminólise do anidrido itacônico e itaconato de dimetila, com aminas alifáticas catalisada enzimaticamente sob condições de fluxo contínuo. Não foram obtidos os produtos desejados, ao invés disso, foi obtida a lactama correspondente com 70% de rendimento. / Polymers have become relevant in our lives due to their wide variety of applications. As we look around we realize that we are immersed in a world full of polymeric materials. The high demand for these materials requires an increase in the overall production of polymers. As a consequence, a higher consumption of fossil resources and an increasing generation of environmental pollutants would be expected. In this sense, enzymatic polymerization has been considered an important alternative to the conventional chemical polymerization techniques. A wide variety of polymers have been described in the literature, which have been prepared by enzymatic polymerization and in some cases using commercially available monomers from biological sources. In most cases, these compounds (monomers) have their reactivities well established in the literature. This project had as motivation a study and development of methodology to obtain new polyamides by enzymatic polymerization under continuous flow conditions, using monomers synthesized from the integration of photocatalytic reactions and enzymatic reactions. Initially, it was decided to prepare the synthetic intermediate (amide-ester I), from the amidation reaction of methyl trans-2-octenoate with formamide. This compound will be the building block for the new monomers. The desired amide-ester I was obtained from three methodologies: Photocatalytic method under continuous flow conditions, using acetone and benzophenone as photoinitiators; photocatalytic method using tetrabutylammonium decatungstenate photocatalyst and Fe (II) catalyzed redox method in the presence of sulfuric acid and hydrogen peroxide. The best reaction condition provided the compound in 47% yield. x In order to obtain the amide monomers, we began a study to understand the reactivity of this type of compound in aminolysis reaction with mono and diamines catalyzed by lipase, under batch and continuous flow conditions. The desired monomer could not be obtained, instead the product resulting from the aminolysis reaction of 1 equivalent of the methyl 3-carbamoyloctanoate (I) with the 1,6-hexanediamine was isolated. This product was obtained in 11% yield. In parallel, also aiming to obtain polyamides from biologically based monomers, a study of aminolysis reaction of itaconic anhydride and dimethyl itaconate with aliphatic amines catalyzed by lipase was carried out under continuous flow conditions. The desired products were not obtained, instead, the corresponding lactam in 70% yield was obtained.

A formação de nanocompósitos de nanotubos de carbono e certos materiais tais como óxidos e polímeros abre a possibilidade de melhorar as propriedades mecânicas e eletrônicas dos seus constituintes, tornando-os candidatos para as mais diferentes aplicações. O preparo desses nanocompósitos com propriedades desejadas requer o conhecimento do tipo de interação entre os dois materiais. Atualmente, a espectroscopia Raman é considerada uma das principais técnicas utilizadas na caracterização de compósitos contendo os nanotubos. Este trabalho tem como objetivo o estudo espectroscópico, em conjunto com outras técnicas de caracterização, na investigação de evidências de interação de compósitos envolvendo nanotubos de carbono de parede única e nanotubos de carbono de paredes múltiplas formados com o semicondutor nanoestruturado, dióxido de titânio, como também com o polímero polipirrol. Todos os compósitos foram preparados a partir dos nanotubos oxidados em ácido nítrico. Essa etapa é bastante importante, pois além de influenciar sua solubilidade, possibilita gerar grupos funcionais oxigenados nas superfícies dos tubos capazes de formar ligações com outros materiais. Através dos espectros Raman foi possível obter evidência de interação entre os constituintes do compósito, através inversão da razão das intensidades relativas das bandas D e G. No caso dos nanotubos de carbono de parede única, sugerimos a formação do nanomaterial ligado nos nanotubos externos dos feixes e as bandas Raman D e G observadas nos espectros dos compósitos são originadas dos tubos internos dos feixes de nanotubos em ressonância com a energia do laser. Considerando os nanotubos de carbono de paredes múltiplas, a presença do material de tamanho nanométrico faz com que as paredes mais externas desses nanotubos percam sua identidade como nanotubo de carbono. Assim, as características das bandas Raman D e G observadas no espectro são originadas dos tubos mais internos que são semelhantes ao nanotubo pristina. Pelo estudo Raman ressonante dos compósitos de nanotubos de carbono de parede única e polipirrol foi verificada a transferência de carga do polímero em direção ao nanotubo através das modificações tanto nas características espectrais do nanotubo quanto do polímero. Foram observados também, processos de transferência eletrônica do dióxido de titânio para os nanotubos de carbono de parede única através dos deslocamentos das frequências Raman. Foi realizado ainda um estudo comparativo dos processos de degradação do corante verde de Janus B em suspensão de dióxido de titânio e em uma mistura de dióxido de titânio e nanotubos de carbono de paredes múltiplas em diferentes valores de pH iniciais do corante. Foi observado o aumento significativo na eficiência da degradação do corante na presença do nanotubo no sistema fotocatalítico. Além disso, a investigação dos intermediários formados nos sistemas de catalisadores foi realizada através dos espectros SERS das soluções degradadas e FT-Raman dos catalisadores sólidos / The formation of nanocomposites of carbon nanotubes and certain materials such as oxides and polymers opens the possibility of improving the mechanical and electronic properties of its constituents, making them candidates for a wide range of applications. The preparation of these nanocomposites with desired properties requires the knowledge of the type of interaction between the two materials. Currently, Raman spectroscopy is considered one of the main techniques in the characterization of composites containing nanotubes. This work aims the spectroscopic study combined with other characterization techniques in investigating evidences of interaction in composites involving single-wall nanotubes and multi-wall nanotubes with the nanostructured semiconductor, titanium dioxide, as well as with the polymer polypyrrole. All composites were prepared from the oxidized nanotubes in nitric acid. This step is very important since it influences nanotubes solubility, and enables the generation of oxygenated functional groups on the surfaces of tubes, allowing further functionalization with other materials. Through the Raman spectra, it was possible to obtain evidences of interaction between the constituents of the investigated composites through the inversion in the ratio of the relative intensities of D and G bands. In the case of single-wall nanotubes, it is suggested that the formation of the nanomaterial occurs on the external nanotube bundles, and D and G Raman bands observed in the spectrum are derived from the inner tubes in the bundles in resonance with the laser energy. Considering the multi-wall nanotubes, the presence of nanosized material causes the outer walls of these nanotubes to lose their identity as carbon nanotubes. Thus, the characteristics of the Raman D and G bands observed in the spectrum are derived from innermost tubes, which are similar to pristine nanotube. The resonance Raman study of single-wall nanotubes and polypyrrole composite revealed charge transfer of the polymer into the nanotube through modifications in the spectral characteristics of the nanotube and the polymer as well. Were also observed, electron-transfer process of titanium dioxide to the single-wall nanotubes through the downshift of the characteristic nanotube Raman frequencies. A comparative study of the degradation processes Janus green B dye in titanium dioxide suspension and mixture of multi-wall nanotubes and titanium dioxide was carried out at different pH values. We observed a significant increase in the degradation efficiency of the dye in the presence of nanotubes on the photocatalytic system. Furthermore, the investigation of the intermediates formed in the catalyst systems were performed using SERS spectra of the degraded solutions and FT-Raman of solid catalysts.

Na presente tese de doutorado, foram exploradas possibilidades para a aplicação de nanopartículas (NPs) metálicas plasmônicas (fenômenos ópticos intensificados) em processos de fotocatálise e em células solares de Si. Estratégias foram exploradas para a imobilização das NPs plasmônicas em TiO2 Degussa P25 (mistura anatase:rutila 4:1) para captação da radiação eletromagnética UV/visível e somente visível em processos fotocatalíticos; e de NPs de Cu em células solares de Si para processos de fotoconversão, contribuindo com a compreensão dos fenômenos de intensificação local de energia mediados pelas NPs, o qual ainda está em debate no cenário científico. Compósitos de P25+NPs Ag de diferentes arquiteturas (fios, esferas e fotorreduzidas), de P25+NPs Ag recoberta com uma camada de SiO2 e de P25+NPs Au foram desenvolvidos. A caracterização dos materiais foi realizada por meio de técnicas de espectroscopia UV-VIS, IR e Raman, área superficial, DRX e de microscopia eletrônica de varredura e de transmissão. Os efeitos das propriedades plasmônicas dessas nanopartículas foram avaliados na eficiência de fotodegradação de três corantes (alizarina vermelha S, vermelho do Congo e fenossafranina) e de fenol. Todos os materiais plasmônicos apresentaram bom desempenho catalítico, aumentando consideravelmente a velocidade e a porcentagem de fotodegradação sob radiação UV/visível, mas principalmente sob radiação visível (onde a fotodegradação catalisada por P25 é limitada). A comparação entre a fotodegradação de fenol pelo compósito P25+NPs Ag esferas e P25+NPs Ag@SiO2 permitiu concluir que a transferência de carga não é o fenômeno que governa o aumento da eficiência catalítica em comparação à fotodegradação catalisada por P25. O fenômeno de intensificação de radiação eletromagnética localizada por meio de LSPR foi observado também em células solares de silício de primeira geração (wafer) contendo NPs de Cu imobilizadas em sua superfície. Aumentos na densidade de corrente de curto-circuito de cerca de 8 % na região acima de 750 nm e de até 16% na potência destas células solares foram observados. / In this thesis, we explored possibilities for the application of metallic plasmonic nanoparticles (NPs) resulting in intensified optical phenomena processes in photocatalysis and Si solar cell. Different strategies were explored for the immobilization of plasmonic NPs on TiO2 Degussa P25 (mixture anatase: rutile 4:1) to capture electromagnetic radiation UV / visible and visible only in photocatalytic processes; and Cu NPs in Si solar cell for photoconversion processes, contributing with the understanding of the phenomena related to the localized ressonance energy mediated by NPs, which is still under debate in the scientific field. Composites of P25+Ag NPs of various architectures (wires, spheres and photoreduced) P25+Ag NPs coated with a layer of SiO2 and P25+Au NPs were developed. The material characterization was performed by means of UV-VIS, IR and Raman spectroscopies, BET surface area, XRD and scanning and transmission electron microscopy. The effects of plasmonic nanoparticles properties were evaluated in the photodegradation efficiency of three textile dyes (Alizarin Red S, Congo red and phenosafranine) and phenol. All plasmonic materials showed good catalytic performance, greatly increasing the kinetic and percentage of photodegradation under UV/visible, but mostly under visible light (where the photodegradation catalyzed by P25 is limited). The comparison between the photodegradation of phenol by P25+Ag sphere NPs and P25+Ag@SiO2 composite showed that the charge transfer is not the phenomenon that governs the increase in catalytic efficiency when compared to the photodegradation catalyzed by P25. The phenomenon of near field intensification through LSPR was also observed in first generation Si solar cells (wafer) containing Cu NPs immobilized on its surface. Increases in the short-circuit current density of about 8% in the region above 750 nm and up to 16% in the power of these solar cells were observed.

水資源缺乏引起的一系列問題在世界上已建得到廣泛關注，因此，確保提供潔淨衛生的水在保護人類健康和環境方面起著重要作用。近來，光催化作為頗有前景的替代方法被廣泛應用殺菌除污。二氧化鈦是目前研究最多應用最廣的光催化劑。基於紫外光譜照射，催化劑表面產生活性氧化物種，這些物種具有強氧化性能殺滅細胞。 / 本文首次研究了母體菌種大腸桿菌BW25113和它的同源單基因缺陷變異體對光催化殺菌的靈敏度差異。母體菌種和變異菌種表現出不同的耐受性。基於此，能幫助發掘出重要的變種。通過生物化學方法，可以檢測出不同菌種的生理性特徵。結合其他方法，可以進一步揭示光催化殺菌的生理性機理。 / 首先，我們篩選出了兩種重要的變異體。一種是大腸桿菌JW1081，即脂肪酸變異體，該菌種缺乏脂肪酸合成調節的關鍵基因。一種是大腸桿菌JW3942，即乙酰輔酶A變異體，該菌種缺乏乙酰輔酶A合成調控得到關鍵激酶。我們發現脂肪酸變異體對光催化處理的耐受性稍低，而乙酰輔酶A變異體則耐受性較高。 同時發現，溫度可以調節細胞膜的不飽和酸和飽和酸的比例。因此，我們提出脂肪酸和乙酰輔酶A是光催化殺菌中的重要影響因子。 / 更進一步研究發掘了細胞內酶和光催化產生的活性氧物種間的關係。大腸桿菌JW3914，即過氧化氫酶變異體，是發現的另一個重要的變異體。通過對母體和變異體的淬滅劑實驗，主要的殺菌活性氧物種是光催化產生的雙氧水，而不是羥基自由基。細胞體內的過氧化氫酶誘導在母體菌體內發現，而未在變異體內檢測到。 / 本課題採用母體/單基因變異體的研究方法，為全面深刻理解光催化殺菌的深層機理提供一種全新的研究思路。 / Many problems associated with the lack of clean, fresh water worldwide are well known. Developing countries will particularly be affected by water availability problems and there will be further pressure on water demand resulting from economic development and population growth. Therefore, the provision of safe and clean water plays a key role in protecting human health and the environment. Recently, photocatalytic oxidation (PCO) has been widely accepted as a promising alternative method of water disinfection. Titanium dioxide (TiO₂) has been investigated extensively and is the most widely used photocatalyst. Upon the irradiation of UVA lamp, reactive charged and oxidative species are generated on TiO₂ surface and can inactive the bacterial cells. / In this study, the photocatalytic performances of a parental strain (E.coli BW25113) and its isogenic single-gene deletion mutant strains have been investigated for the first time. These bacterial strains exhibited different sensitivies towards photocalytic inactivation. Based on this, it can help reveal some important mechanism from the mutations. Biotic factors were confirmed by physiological biochemical measurement. / Firstly, we screened out the potential mutation fabF⁻ mutant (E. coli JW1081, carrying the mutation of fabF759(del)::kan) and coaA⁻ mutant (E. coli JW3942, carrying the mutation of coaA755(del)::kan). The isogenic fabF⁻ mutant is slightly more susceptible, and coaA⁻ mutant is less susceptible to photocatalytic inactivation. Through conditioning temperature, it adjusts the ratio of unsaturated to saturated fatty acid (FA) of cell membrane. We propose that FA profile and coenzyme A level significantly affect photocatalytic inactivation of bacteria. Moreover, we show photogenerated electrons (e⁻) can directly inactivate the cells of E. coli. / Furthermore, we report the relationship between the bacterial intracellular enzyme and the reactive charged and oxidative species (ROSs) generated during photocataltic inactivation. The katG⁻ mutant, E. coli JW3914, carrying the mutation of katG729(del)::kan is another important mutation. The parental and katG⁻ mutant strains reveal that photogenerated H₂O₂ but not OH[subscript free] is another important reactive oxygen species to inactivate bacteria. The inducible catalase (CAT) corresponding to H₂O₂can be detected in parental strain but not in katG⁻ mutant. / The research methodology using parental/single-gene deletion mutant strains is expected to shed light on fully understanding of the fundamental mechanism of photocatalytic inactivation of E. coli. / 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. / Gao, Minghui. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 130-177). / 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.v / Table of contents --- p.ix / List of Figures --- p.xiii / List of Plates --- p.xvii / List of Tables --- p.xviii / List of Equations --- p.xix / Abbreviations --- p.xxi / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Water crisis --- p.1 / Chapter 1.2 --- Traditional disinfection methods --- p.3 / Chapter 1.2.1 --- Chlorination --- p.4 / Chapter 1.2.2 --- Ozonation --- p.6 / Chapter 1.2.3 --- Ultraviolet irradiation --- p.8 / Chapter 1.2.4 --- Multiple disinfectants --- p.10 / Chapter 1.3 --- Advanced oxidation process (AOPs) --- p.10 / Chapter 1.3.1 --- Hydrogen Peroxide/Ozone (H₂O₂/O₃) --- p.11 / Chapter 1.3.2 --- Ozone/Ultraviolet Irradiation (O₃/UV) --- p.12 / Chapter 1.3.3 --- Hydrogen Peroxide/ Ultraviolet Irradiation (H₂O₂/UV) --- p.12 / Chapter 1.3.4 --- Fenton's --- p.Reaction / Chapter 1.4 --- Solar photocatalytic disinfection (SPC-DIS) --- p.14 / Chapter 1.4.1 --- Photocatalyst-TiO₂ --- p.31 / Chapter 1.4.2 --- Irradiation sources --- p.35 / Chapter 1.4.3 --- TiO₂ photocatalytic process --- p.35 / Chapter 1.4.4 --- The role of photogenerated reactive charged and oxidative species (ROSs) --- p.38 / Chapter 1.5 --- Bacteria --- p.40 / Chapter 1.5.1 --- E. coli BW25113 --- p.40 / Chapter 1.5.2 --- E. coli Keio Collection --- p.41 / Chapter 1.5.3 --- Bacterial defense mechanism towards oxidative stresses --- p.44 / Chapter 1.6 --- Photocalytic applications --- p.53 / Chapter 1.7 --- Significance of the project --- p.55 / Chapter 2. --- Objectives --- p.58 / Chapter 3. --- Genetic studies of the roles of fatty acid and coenzyme A in photocatalytic inactivation of Escherichia coli --- p.61 / Chapter 3.1 --- Introduction --- p.61 / Chapter 3.2 --- Materials and methods --- p.65 / Chapter 3.2.1 --- Photocatalyst --- p.65 / Chapter 3.2.2 --- Bacterial nutrient --- p.66 / Chapter 3.2.3 --- Bacterial strains --- p.67 / Chapter 3.2.4 --- Photocatalytic inactivation --- p.69 / Chapter 3.2.5 --- Fatty acid profile --- p.72 / Chapter 3.2.6 --- Fluorescent measurement of bacterial coenzyme A content --- p.74 / Chapter 3.2.7 --- The role of photogenerated electrons (e⁻) to bacterial inactivation --- p.74 / Chapter 3.2.8 --- Transmission Electron Microscopic (TEM) --- p.75 / Chapter 3.2.9 --- Photoelectrochemical measurement --- p.77 / Chapter 3.3 --- Results --- p.77 / Chapter 3.3.1 --- Photocatalytic inactivation --- p.77 / Chapter 3.3.2 --- Effects of pre-incubation at different temperatures --- p.80 / Chapter 3.3.3 --- Fatty acid profile --- p.83 / Chapter 3.3.4 --- Fluorescent measurement of bacterial coenzyme A content --- p.84 / Chapter 3.3.5 --- The role of electron (e⁻) in photocataytic inactivation --- p.84 / Chapter 3.3.6 --- Transmission electron microscopy (TEM) --- p.89 / Chapter 3.3.7 --- Photocurrent measurement --- p.90 / Chapter 3.4 --- Discussion --- p.90 / Chapter 3.5 --- Conclusions --- p.96 / Chapter 4 --- Genetic and physiological studies of the role of Catalase and H₂O₂ in photocatalytic inactivation of E. coli --- p.98 / Chapter 4.1 --- Introduction --- p.98 / Chapter 4.2 --- Materials and methods --- p.101 / Chapter 4.2.1 --- Bacterial strains --- p.101 / Chapter 4.2.2 --- Photocatalytic performance --- p.102 / Chapter 4.2.3 --- Scavenger studies --- p.103 / Chapter 4.2.4 --- Effects of different pHs on photocatalytic inactivation --- p.104 / Chapter 4.2.5 --- Measurement of bacterial catalase activity and H₂O₂ --- p.104 / Chapter 4.2.6 --- Transmission electron microscopy (TEM) --- p.105 / Chapter 4.2.7 --- Atomic absorption spectrophotometer (AAS) --- p.105 / Chapter 4.3 --- Results and discussion --- p.106 / Chapter 4.3.1 --- Photocatalytic performance --- p.106 / Chapter 4.3.2 --- Scavenger studies --- p.108 / Chapter 4.3.3 --- Contribution of hydrogen peroxide (H₂O₂) --- p.111 / Chapter 4.3.4 --- Effects of different pHs on photocatalytic inactivation --- p.114 / Chapter 4.3.5 --- Bacterial catalase (CAT) activity --- p.116 / Chapter 4.3.6 --- Destruction model of bacterial cells --- p.118 / Chapter 4.4 --- Conclusions --- p.120 / Chapter 5. --- General conclusions --- p.122 / Chapter 6. --- Prospectives --- p.125 / Chapter 7. --- Appendix --- p.127 / Chapter 8. --- References --- p.130

The photocatalytic properties of titanium dioxide have been widely studied over recent decades since the discovery in 1972 of water photolysis by TiO2 electrodes. There are a number of different TiO2 polymorphs. Rutile and anatase are the most studied due to their chemo-physical properties. Under ultraviolet light, TiO2 is able to absorb photons, creating a charge separation on the surface, an electron and a positive “hole”. This electron-hole pair then reacts with water and oxygen, generating radicals, very unstable and reactive species which show great potential for neutralisation of pollutants. In the introduction the state of art of photocatalysis; chemo-physical principles, applications and current analysis are described. A number of protocols to test photoactivity are discussed with particular emphasis on the importance of gas phase reactions. The development of a novel system to study gas phase reactions by mass spectrometry was explored, detailing the conditions and parameters that were optimised. This instrument was used to analyse photocatalytic properties of TiO2 powders and photocatalytic coatings under different UV light conditions. The results showed how TiO2 in the form of anatase and rutile removed nitrogen and carbon dioxide under different UV light sources, with anatase being more effective. A comprehensive study of several commercially available TiO2 powders and coatings was performed to identify the differences between photocatalytic properties, using electron microscopy, Raman and UV-vis diffusive spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. An important question that was answered in this thesis is whether the physical properties of nanoparticles or their electronic properties are critical for their photocatalytic behaviour. Results for anatase powders of different particle size and surface area showed how the positioning of their electronic band gap with the wavelength of the UV light source was fundamental for an effective photocatalyic process. In order to improve the photocatalytic process, “self-doping” TiO2 was investigated. Different reduction temperatures were studied to generate the best ratio of Ti3+-Ti4+ that stabilised the charge distribution process to maximize the electron-hole pairs generated per photon in the gas phase. From a wide range of reduction temperatures, titanium sub-oxime reduced at 400 oC showed the best performance in removing carbon dioxide. In the application of TiO2 for the built environment, the best commercially available TiO2 powder, anatase P25 was applied with two different techniques. Electrophoretic deposition has the potential to scale up the process for prefabricated panels in construction. Solvent, iv deposition time, voltage and substrate were optimised. The resulting photoactivity of the coatings was evaluated showing a higher efficiency than a compressed pellet of anatase P25. The final part of the thesis was dedicated to the formulation and application of a photocatalytic enhanced lime based coatings for the built heritage. The use of calcium hydroxide dispersions is widely used in the conservation and restoration community, reinforcing limestone when it carbonates. Anatase P25, was added to improve the performance in polluted atmospheres, acting as a sacrificial barrier. Results showed that by adding anatase to the formulation, calcium hydroxide reacted preferentially with sulphur dioxide over carbon dioxide. The final product in the formulation with anatase was calcium sulphate, whereas the final product for the calcium hydroxide formulation was calcium sulphite. Finally, a general discussion of the results is presented and the conclusions of this research are drawn. Recommendations for further work are presented in the last chapter.

Ce travail de thèse examine une nouvelle méthode prometteuse pour la dépollution efficace des eaux contaminées par des polluants organiques insolubles de type toluène, 1-méthylnaphtalène, nitrobenzène,…. Cette méthode d’oxydation avancée repose sur la photocatalyse hétérogène dans des émulsions de Pickering. Dans ce type d’émulsions, les tensioactifs stabilisants des gouttelettes huileuses sont remplacés par des nanoparticules solides à propriétés photocatalytiques élevées. Par ailleurs, ces nanoparticules solides doivent remplir les conditions de mouillabilité partielle dans les deux phases aqueuse et huileuse grâce à un équilibre hydrophile-hydrophobe à leur surface. Pour cette raison, le dioxyde de titane (TiO2) anatase a été préparé par la méthode sol-gel puis modifié par fluoration pour obtenir le catalyseur TiO2-F. L’objectif est de formuler des émulsions de Pickering de type huile dans l’eau (H/E) à partir de polluants organiques de faible solubilité dans l’eau. Les catalyseurs synthétisés ont été caractérisés par XRD, BET, SEM, DRS, XPS, et TG-TD-MS. Il a été montré que la fluoration apporte des changements importants dans les propriétés optiques du TiO2 et a amélioré l’équilibre hydrophile/hydrophobe à sa surface de façon significative. Par ailleurs, les résultats obtenus indiquent que des émulsions de Pickering stables peuvent être formulées en utilisant des particules de TiO2 ou TiO2-F de taille nanométrique. Le type et la stabilité des émulsions dépendent de la mouillabilité des nanoparticules stabilisantes évaluées par des mesures d'angle de contact. La mouillabilité des nanoparticules a été trouvée fortement dépendante du type d’huile en raison des contributions de la polarité et des interactions spécifiques avec les polluants. L'étude des émulsions de Pickering par conductivité électrique, microscopie optique et diffusion de la lumière a montré qu'une stabilité élevée a été obtenue dans des conditions de mouillage partiel : angle de contact dans l'eau compris entre 70 et 110°. L’évolution de la taille des gouttelettes d'huiles avec le rapport de masse huile/photocatalyseur a confirmé une forte adsorption des nanoparticules de catalyseur sur les gouttelettes d'huiles. Finalement, les émulsions jugées stables ont été photodégradées sous rayonnement UV. La cinétique de photodégradation des polluants organiques mesurée par HPLC a montré que la dégradation a été intensifiée en utilisant les émulsions de Pickering par rapport aux systèmes non émulsionnés. Ces résultats ont prouvé que l’utilisation des émulsions de Pickering stabilisées par des nanoparticules de dioxyde de titane constituait un moyen efficace et innovateur pour intensifier la dégradation photocatalytique des polluants organiques / This thesis examines a promising new method for the effective depollution of water contaminated by insoluble organic pollutants such as toluene, 1-methylnaphthalene, nitrobenzene, etc. This advanced oxidation method is based on heterogeneous photocatalysis in Pickering emulsions. In this type of emulsion, the stabilizing surfactants of the oily droplets are replaced by solid nanoparticles having high photocatalytic properties. Moreover, these solid nanoparticles must fulfill the conditions of partial wettability in both aqueous and oily phases thanks to a hydrophilic-hydrophobic balance on their surface. For this reason, the titanium dioxide (TiO2) anatase was prepared by the sol-gel method and then modified by fluorination to obtain the TiO2-F catalyst. The objective is to formulate Pickering oil-in-water (O/W) emulsions from organic pollutants of low water solubility. The synthesized catalysts were characterized by XRD, BET, SEM, DRS, XPS, and TG-TD-MS. It has been shown that fluorination brings about important changes in the optical properties of TiO2 (change in band gap) and improves the hydrophilic / hydrophobic balance at its surface significantly. Moreover, the obtained results indicate that stable Pickering emulsions can be formulated using TiO2 or TiO2-F nanoparticles. The type and stability of the emulsions depend on the wettability of the stabilizing nanoparticles evaluated by contact angle measurements. The wettability of the nanoparticles has been found to be highly dependent on the type of oil due to the contributions of polarity and specific interactions with pollutants. The study of Pickering emulsions by electrical conductivity, optical microscopy and light scattering showed that high stability was obtained under partial wetting conditions: contact angle in water between 70 and 110°. The change in the size of the oil droplets with the oil/photocatalyst mass ratio confirmed a strong adsorption of the catalyst nanoparticles on the oil droplets. Finally, the judged stable emulsions were photodegraded under UV radiation. The photodegradation kinetics of organic pollutants measured by HPLC showed that degradation was intensified using Pickering emulsions compared to non-emulsified systems. These results have shown that the use of Pickering emulsions stabilized by titanium dioxide nanoparticles is an effective and innovative way to intensify the photocatalytic degradation of organic pollutants

Artificial photosynthesis utilises solar-light for clean fuel H2 production and is emerging as a potential solution for renewable energy generation. Photocatalytic systems that combine a light harvester and catalysts in one-pot reactor are promising strategies towards this direction. Yet, most of the reported systems function by consuming excess amount of expensive sacrificial reagents, preventing commercial development. In this thesis, carbon nitrides (CNx) have been selected as non-toxic, stable and low-cost photocatalysts. CNx are first introduced as efficient light harvesters, to couple alcohol oxidation with proton reduction, in the presence of a Ni-based molecular catalyst. This system operated in a single compartment while the oxidation and reduction products were collected in the solution and gaseous phases, respectively, demonstrating a closed redox system. In the presence of an organic substrate and absence of a proton reduction catalyst, photoexcited CNx was found to accumulate long-lived "trapped-electrons", which enables decoupling oxidation and reduction reactions temporarily and spatially. This allows solar H2 generation in the dark, following light exposure, replication light and dark cycle of natural photosynthesis in an artificial set-up. The stability of the designed system was found to be limited by the Ni-based molecular catalyst, and the spectroscopic studies revealed electron transfer from CNx to catalyst as the kinetic bottleneck. Graphene based conductive scaffolds were introduced to the CNx-Ni system, to accelerate the rate of electron transfer from CNx to the Ni catalyst. Time-resolved spectroscopic techniques revealed that introducing these conductive binders enabled better electronic communication between CNx and Ni, resulting in significantly enhanced photocatalytic activity. To improve the solar-light utilisation and the photocatalytic performance of bulk CNx, a straightforward ultra-sonication approach was introduced. This pre-treatment was found to break aggregates of bulk CNx, and the resulting activated CNx had significantly improved activity. The activated CNx showed record activities per gram of the material used, for H2 evolution with a molecular Ni catalyst. The use of abundant waste sources instead of organic substrates was investigated in the presence of activated CNx. The system demonstrated to photoreform purified and raw lignocellulose samples into H2 in the presence of various H2 evolution catalysts over a wide range of pH.

Um dos fatores críticos nos processos de fotocatálise, que inviabiliza sua utilização em larga escala, é a necessidade de operações unitárias para a separação entre fotocatalisador e efluente. Uma solução para este problema é o uso do catalisador imobilizado em suportes. Assim, neste trabalho, o dióxido de titânio foi fixado em tecido de algodão, pelo uso de ácidos policarboxílicos (ácido succínico, cítrico e maleico) como ligantes, através do método deposição-enxugamento-cura. Foram usados planejamentos de experimentos para estabelecer as condições mais adequadas de concentração do ligante, tempo e temperatura de cura. Além disso, foram avaliados a massa de catalisador depositada, pelo método gravimétrico e a morfologia resultante nos materiais formados, pela Microscopia Eletrônica de Varredura. A melhor condição de tratamento, para cada um dos ligantes, foi utilizada para preparação de amostras que foram expostas ao UV, à vazão de água e ao borbulhamento de ar por 24 h, comparando-se a atividade e a estabilidade dos materiais obtidos. Os testes fotocatalíticos foram realizados adaptando-se uma metodologia existente na literatura para imobilização em vidro. Nesta, a partir da formulação de uma tinta indicadora de atividade e dispositivos de coleta e avaliação de imagem, é possível acompanhar o andamento da reação fotocatalítica. Os resultados mostraram que a atividade fotocatalítica e a massa depositada aumentam, dentro dos limites do planejamento, com a elevação da temperatura de cura, variável significativa estatisticamente para todos os ligantes testados. Contudo, o aumento na massa de fotocatalisador depositada não é sempre acompanhado pelo aumento na atividade fotocatalítica, indicando que a distribuição das partículas de fotocatalisador na matriz têxtil também é de grande importância para a eficiência fotocatalítica. Os resultados para o comportamento das variáveis na atividade fotocatalítica obtidos para o ligante ácido maleico diferenciam-se dos resultados obtidos para os outros ligantes, o que possivelmente pode ser explicado pela interação do mesmo com o catalisador NaH2PO2 e pelas diferenças na reação de reticulação da celulose. Além disso, imagens de MEV evidenciaram a deposição do catalisador de forma heterogênea, característica de superfícies irregulares como as dos têxteis. A avaliação dos resultados e de fatores econômicos e ambientais sugere que o ácido cítrico seja o agente mais promissor no processo de imobilização de dióxido de titânio em tecidos de algodão. / A critical factor in photocatalytic processes, which prevents its large scale usage, is the need for unit operations in order to remove the photocatalyst from the effluent. One possible solution to this problem is the use of photocatalyst immobilized on supports. In this work, titanium dioxide was immobilized into cotton textile by polycarboxylic acids binders (succinic, citric and maleic acid), through deposition-pad-cure method. Experimental design tests were performed to establish the most appropriate conditions of each binder concentration, curing time and temperature. In addition, the photocatalyst deposited mass was evaluated by gravimetric method and the resulting material morphology by Scanning Electron Microscopy (SEM). The optimum conditions of treatment for each binder was used to prepare samples that were exposed to UV, water flow and aeration for 24 h, in pursuance of comparing the materials activity and stability. The photocatalytic tests were performed by adapting an existing literature method for glass substrates. From a photoactivity indicator ink formulation and image capture and evaluation devices, it is possible to follow the photocatalytic reaction progress. The results showed an increase on the photocatalytic activity and deposited mass, within the experimental design limits, by raising curing temperature, variable statistically significant for all tested binders. However, the increase in photocatalyst mass deposition is not always followed by an increase in photocatalytic activity, indicating that photocatalyst particles distribution in the textile matrix is also of great importance for the photocatalytic efficiency. The results of variables behavior on photocatalytic activity for maleic acid binder are different from results obtained for other binders, which can possibly be explained by its interaction with the catalyst NaH2PO2 and differences in the cellulose crosslinking reaction. Moreover, SEM images showed heterogeneous photocatalyst deposition, characteristic of uneven surfaces such as textiles. The evaluation of these results and the economic and environmental factors suggests that citric acid is the most promising binder for titanium dioxide immobilization process into cotton fabrics.

A crescente urbanização e modernização leva a população a passar cada vez mais tempo em ambientes fechados e com climatização artificial. Estes ambientes são propícios para o desenvolvimento de contaminantes, como compostos orgânicos voláteis e microrganismos, os quais estão diretamente relacionados a problemas de saúde. Neste trabalho, propõe-se o uso de fotocatálise heterogênea para remoção de poluentes orgânicos presentes no ar. O semicondutor escolhido como fotocatalisador para este trabalho foi o óxido de zinco, que possui uma grande capacidade de absorção de luz UV. Inicialmente um estudo sistemático das condições de síntese de microestruturas de ZnO imobilizadas sobre diferentes substratos foi realizado com base em um planejamento de experimentos composto central circunscrito. Foram avaliadas as razões molares dos reagentes NaOH e D-frutose em relação à quantidade de Zn2+ presente no meio reacional, o tempo e a temperatura de síntese. A variável de resposta do sistema foi a porcentagem de degradação de rodamina B sob irradiação de luz ultravioleta por uma hora. Este corante é comumente usado como molécula alvo em ensaios de degradação fotocatalítica servindo de padrão para avaliação da eficiência do catalisador. Os materiais utilizados como substratos para o crescimento das microestruturas foram vidro, cobre e zinco. Os testes realizados permitiram concluir que, dentre os materiais estudados, substrato de zinco é o mais promissor, apresentando uma porcentagem de degradação máxima de 80%. Em relação às condições de síntese, os gráficos de contorno permitem identificar uma região de máxima resposta para o substrato zinco. As variáveis mais significativas do modelo estudado foram a quantidade de NaOH e a temperatura de síntese. Para a segunda etapa desta pesquisa, dois compostos facilmente encontrados em ambientes fechados – limoneno e acetona – foram utilizados como moléculas alvo de compostos orgânicos voláteis. Foram utilizados três reatores com configurações diferentes e três fotocatalisadores para o estudo de degradação fotocatalítica – TiO2 P25, ZnO Merck e nanobastões de ZnO sintetizados em laboratório. Os resultados indicam que o TiO2 apresenta uma maior facilidade de degradação de limoneno do que ZnO, totalizando uma remoção de 70% e 45%, respectivamente. O oposto acontece para acetona, onde ZnO apresentou uma degradação total de 61% e TiO2 48%. Nanobastões de ZnO foram responsáveis pela remoção de menos de 10% de limoneno. Estes resultados indicam a relação da atividade fotocatalítica com a interação entre estrutura do fotocatalisador/molécula alvo. / The increasing urbanization and modernization have led people to spend more and more time indoors and with artificial air conditioning. Such environments are conducive to the development of contaminants, such as volatile organic compounds and microorganisms, which are directly related to health issues. In this work, we propose the use of heterogeneous photocatalysis for organic pollutants removal in air. The semiconductor chosen as photocatalyst for this study was zinc oxide, a material with great UV light absorption capacity. Initially a systematic study of the ZnO microstructures synthesis conditions immobilized on different substrates was performed. In order to do so, a circumscribed central composite design of experiments was developed for each substrate. The reactants molar ratio – NaOH/Zn and Zn/Fructose –, time and temperature of synthesis were evaluated. The response variable was rhodamine B (RhB) degradation percentage using UV light for one hour. This dye is commonly used as a target molecule, been referred as standard test to evaluate the photocatalyst efficiency. The materials used as substrates for microstructures growth were glass, copper and zinc. The experiments shoed that, among the studied materials, zinc substrate is the most promising, with a maximum (RhB) degradation of 80%. Regarding the synthesis condition, the contour plots allow the identification of a maximum response region for the zinc substrate. The most significant variables from the studied model were the molar ratio NaOH/Zn and synthesis temperature. For the following step in this work, two compounds easily found indoors – limonene and acetone – were used as target molecules of volatile organic compounds (VOCs). Three reactors with different configurations, and three photocatalysts – TiO2 P25, ZnO Merck and synthesized ZnO nanorods – were used for the study of photocatalytic degradation. The results indicate that TiO2 has a greater ease of limonene degradation than ZnO, with a total removal of 70% e 45%, respectively. The opposite happens to acetone, where ZnO showed an overall degradation of 61 e 48%, respectively. ZnO nanorods were responsible for less than 10% of limonene removal. This results indicate a relation between photocatalytic activity and photocatalyst structure/target molecule.