Carbon supported PtNi nanoparticles were prepared by hydrazine reduction of Pt and Ni precursor salts under different conditions, namely by conventional heating (PtNi-1), by prolonged reaction at room temperature (PtNi-2) and by microwave assisted reduction (PtNi-3). The nanocomposites were characterized by XRD, EDX, XPS and TEM and used as electrocatalysts in direct methanol fuel cell (DMFC) reactions. Investigations into the mechanism of PtNi nanoparticle formation revealed that platinum nanoparticle seeding was essential for the formation of the bimetallic nanoparticles. The average particle size of PtNi prepared by microwave irradiation was the lowest, in the range of 2.9 – 5.8 nm. The relative rates of electrooxidation of methanol at room temperature as measured by cyclic voltammetry showed an inverse relationship between catalytic activity and particle size in the following order PtNi-1 < PtNi-2 < PtNi-3. / Singapore-MIT Alliance (SMA)

The current understanding of contaminant migration in fractured sedimentary rock aquifers is inadequate due to the difficulty in describing the geologic and hydrogeologic controls on contaminant fate and transport with appropriate detail. To address contamination at fractured rock sites, multiple methods focusing on different aspects of the hydrologic system are required, and particular emphasis needs to be placed on the rock matrix. This thesis shows the further development and utility of the decade-old rock core VOC method (i.e. CORETM), a rock matrix method, when used in conjunction with multiple high resolution datasets as it applies to a 100 m thick highly productive dolostone aquifer in Guelph, Ontario. The research site and surrounding area, located in the northwestern quadrant of the municipality of Guelph, was a productive zone for water supply until the early 1990s when the two closest municipal supply wells (Sacco, Smallfield) were shut down (1991, 1993 respectively) due to volatile organic compounds (VOCs) in the groundwater. Trichloroethene (TCE), a VOC, was used as a degreaser at the Guelph site and likely entered the groundwater more than 20 years ago. The thin overburden, shallow water table, relatively constant dolostone mineralogy, proximity to the UW analytical laboratory, relatively simple plume composition showing minimal degradation, and local importance make this an excellent study site for TCE fate and migration in fractured sedimentary rocks. This thesis is composed of four chapters. Chapter 1 provides a brief background to the rock core VOC method and gives the conceptual framework for the investigation. Chapter 2 focuses on the further development of the rock core VOC method by providing the field validation of a recently adapted extraction method for VOCs in rock core using microwave assisted extraction (MAE), demonstrating the importance of rapid field preservation of samples, and comparing to the industry standard purge and trap method for VOCs on solid matrices. Results indicate that the microwave assisted extraction (MAE) method typically provides equivalent or higher concentrations when compared with the shake-flask and purge and trap extraction methods, indicating more complete extraction or less loss during transfer and/or storage. The purge and trap method provided false negatives (i.e. non-detects) due to inadequate preservation, incomplete extraction, and the elevated detection limit for TCE. The necessity for field preservation was examined by comparing crushed rock samples preserved in methanol in the field to samples unpreserved in the field with a laboratory addition of methanol less than 12 hours later. Chapter 3 creates high resolution porosity and bulk density logs by using selected geophysical logging tools in combination with core derived physical properties for the purpose of calculating porewater concentrations from total contaminant mass concentrations obtained from the rock core VOC method and sample specific rock properties relevant to the conversion. This is beneficial because total mass estimates obtained from the rock core VOC method are not necessarily indicative of the groundwater concentrations given the presence of solid organic carbon controlled sorption. Chapter 4 is a demonstration of the discrete fracture network approach (Parker 2007) applied to the Guelph field site with emphasis on the insights gained through high resolution contaminant profiles generated from cored holes in or near the source area and along a transect. Together, these four chapters present a framework for investigating VOC contamination in fractured sedimentary rocks and with emphasis on evaluating recent advances in the rock core VOC methodology in a field site context.

The current understanding of contaminant migration in fractured sedimentary rock aquifers is inadequate due to the difficulty in describing the geologic and hydrogeologic controls on contaminant fate and transport with appropriate detail. To address contamination at fractured rock sites, multiple methods focusing on different aspects of the hydrologic system are required, and particular emphasis needs to be placed on the rock matrix. This thesis shows the further development and utility of the decade-old rock core VOC method (i.e. CORETM), a rock matrix method, when used in conjunction with multiple high resolution datasets as it applies to a 100 m thick highly productive dolostone aquifer in Guelph, Ontario. The research site and surrounding area, located in the northwestern quadrant of the municipality of Guelph, was a productive zone for water supply until the early 1990s when the two closest municipal supply wells (Sacco, Smallfield) were shut down (1991, 1993 respectively) due to volatile organic compounds (VOCs) in the groundwater. Trichloroethene (TCE), a VOC, was used as a degreaser at the Guelph site and likely entered the groundwater more than 20 years ago. The thin overburden, shallow water table, relatively constant dolostone mineralogy, proximity to the UW analytical laboratory, relatively simple plume composition showing minimal degradation, and local importance make this an excellent study site for TCE fate and migration in fractured sedimentary rocks. This thesis is composed of four chapters. Chapter 1 provides a brief background to the rock core VOC method and gives the conceptual framework for the investigation. Chapter 2 focuses on the further development of the rock core VOC method by providing the field validation of a recently adapted extraction method for VOCs in rock core using microwave assisted extraction (MAE), demonstrating the importance of rapid field preservation of samples, and comparing to the industry standard purge and trap method for VOCs on solid matrices. Results indicate that the microwave assisted extraction (MAE) method typically provides equivalent or higher concentrations when compared with the shake-flask and purge and trap extraction methods, indicating more complete extraction or less loss during transfer and/or storage. The purge and trap method provided false negatives (i.e. non-detects) due to inadequate preservation, incomplete extraction, and the elevated detection limit for TCE. The necessity for field preservation was examined by comparing crushed rock samples preserved in methanol in the field to samples unpreserved in the field with a laboratory addition of methanol less than 12 hours later. Chapter 3 creates high resolution porosity and bulk density logs by using selected geophysical logging tools in combination with core derived physical properties for the purpose of calculating porewater concentrations from total contaminant mass concentrations obtained from the rock core VOC method and sample specific rock properties relevant to the conversion. This is beneficial because total mass estimates obtained from the rock core VOC method are not necessarily indicative of the groundwater concentrations given the presence of solid organic carbon controlled sorption. Chapter 4 is a demonstration of the discrete fracture network approach (Parker 2007) applied to the Guelph field site with emphasis on the insights gained through high resolution contaminant profiles generated from cored holes in or near the source area and along a transect. Together, these four chapters present a framework for investigating VOC contamination in fractured sedimentary rocks and with emphasis on evaluating recent advances in the rock core VOC methodology in a field site context.

The objective of this study was to compare microwave assisted extraction (MAE) and conventional extraction methods for the extraction of total phenolic compounds (TPC) from tomato and sour cherry pomace. Antiradical efficiency (AE) of the extracts and also the concentration of phenolic compounds were determined. In MAE, the effects of microwave power (400 and 700 W), solvent type (water, ethanol and ethanol-water mixture at 1:1 v/v), extraction time (8-20 min) and solvent to solid ratio (10, 20 and 30 ml/g) were studied to observe the change of TPC and AE of the extracts. Conventional extraction was conducted for 6 h using different solvent to solid ratios (10, 20 and 30 ml/g) and solvent types (water, ethanol and ethanol-water mixture at 1:1 v/v). When the power increased from 400 W to 700 W, TPC and AE values increased. In MAE, maximum TPC and AE values were obtained at a solvent to solid ratio of 20 ml/g. The highest TPC and AE values were obtained when the ethanol-water mixture was used for both MAE and conventional extraction. The highest TPC and AE of tomato pomace extracts was determined as 3.76 mg gallic acid equivalent, GAE/g sample and 4.84 mg 1,1-diphenyl-2-picrylhydrazyl, DPPH/g sample, respectively in MAE using power level of 700 W, ethanol-water mixture, solvent to solid ratio of 20 ml/g and extraction time of 14 min. The major phenolic acids detected in tomato pomace extract were gentisic acid and vannilic acid. For sour cherry pomace extracts, the highest TPC and AE was found as 14.14 mg GAE/g sample and 28.32 mg DPPH/g sample, respectively in MAE using power level of 700 W, solvent to solid ratio of 20 ml/g, ethanol-water mixture and extraction time of 12 min. Epicatechin was found to be the major phenolic acid in sour cherry pomace. There was no significant difference in different extraction methods in terms of TPC. On the other hand, AE value and concentration of major phenolic acids of tomato and sour cherry pomace increased when MAE was used.

Lithium-ion batteries play a crucial role in portable electronics, but require further innovation for electric vehicle and grid storage applications. To meet this demand, significant emphasis has been placed on developing safe, inexpensive, high energy density cathode materials. LiFePO₄ is a candidate cathode material for electric vehicle and grid storage applications. Vanadium-doped LiFePO₄ cathodes of the form [chemical formula] (0 ≤ x ≤ 0.25) were synthesized here by a facile, low-temperature microwave-assisted solvothermal (MW-ST) method. Such an approach offers manufacturing-energy and cost savings compared to conventional synthesis. Additionally, although [chemical formula] has been synthesized previously by conventional methods, it is shown here that the MW-ST method allows much higher doping levels than can be achieved at conventional temperatures, indicating that metastable phases can be isolated through the low-temperature microwave-assisted synthesis. LiFePO₄ suffers from poor ionic conductivity, but this limitation can be minimized by microwave-assisted synthesis through a tuning of the particle size, allowing for decreased Li⁺ diffusion paths. LiVOPO₄ is another polyanion material with higher energy density than LiFePO₄, but similar ionic conductivity limitations. It has not been previously synthesized by MW-ST. Thus, a MW-ST method was developed here to prepare LiVOPO₄. By varying reaction conditions, three polymorphic modifications of LiVOPO₄ were accessed and the electrochemical performance was optimized. LiVOPO₄ can be further discharged to Li₂VOPO₄, which has been suggested in the literature, but the structural transformation that accompanies this process has not been detailed. To this end, the delithiation process was studied by ex situ XRD measurements to better understand how the second lithium is accommodated. Finally, MW-ST has also been exploited to grow thin films of anatase TiO₂ phase on indium tin oxide (ITO)-coated glass substrates. The microwave field is selectively absorbed by the conductive ITO layer on the glass substrates, leading to ohmic heating. The resulting heated ITO layer acts as a favorable site for nucleation and growth. TiO₂ thin films have widespread applications in the energy and electronics sectors. Such selective microwave-assisted ohmic heating of solid materials within a growth solution represents a promising new avenue for microwave synthesis, which has been minimally explored in the literature. / text

Lithium-ion batteries are being intensely pursued as energy storage devices because they provide higher energy and power densities compared to other battery systems such as lead-acid and nickel-metal hydride batteries. This dissertation (i) explores the use of a low-temperature microwave-assisted synthesis process to obtain aliovalently-doped lithium transition-metal phosphates and lower-valent vanadium oxide spinels, some of which are difficult to obtain by conventional high-temperature processes, and (ii) presents an investigation of the electrochemical properties of the aliovantly-doped phosphate cathodes and doped lithium manganese oxide and oxyfluoride spinel cathodes in lithium-ion batteries. Following the introduction and general experimental procedures, respectively, in Chapters 1 and 2, Chapter 3 first focuses on understanding of how the inductive effect and structural features in lithium transition-metal borate, silicate, and phosphate cathodes affect the M²⁺ʹ³⁺redox energies. It is found that the magnitude of the voltages delivered by the polyanion cathodes can be predicted based simply on the coordination of the transition-metal ion. Furthermore, the differences in the voltages delivered by the phosphates and pyrophosphates are explained by considering the resonance structures and their contribution to the covalency of the polyanion. Chapter 4 presents a low-temperature microwave-assisted solvothermal process to substitute 20 atom % V³⁺ for Mn²⁺ in LiMnPO₄. It is shown that the solubility of vanadium in LiMnPO₄ decreases upon heating the doped samples to ≥ 575 °C, demonstrating the importance of employing a low-temperature process to achieve aliovalent doping in LiMnPO₄. It is further demonstrated that by increasing the vanadium content in the material, the discharge capacity in the first cycle could be increased without any additional carbon coating. Subsequent X-ray absorption spectroscopy data reveal that the better performance is facilitated by enhanced Mn-O hybridization upon incorporating vanadium into the lattice. Chapter 5 explores the influence of various factors, such as the oxidation state of Mn, electronegativity of the dopant cation Mn+, and the dissociation energy of M-O bond, on the electrochemical properties of cation-doped oxide and oxyfluoride spinel cathodes. As an extension, Chapter 6 presents the effect of processing conditions on the surface concentration of the dopant cation Mn+. Chapter 7 presents an extension of the low-temperature microwave-assisted synthesis process to obtain AV₂O₄ (Mg, Fe, Mn, and Co) spinel oxides. The method is remarkably effective in reducing the synthesis time and energy use due to the efficiency of dielectric heating compared to conventional heating. The ability to access V³⁺ is facilitated by the relative positions of the energy levels of the cations in solution, which is lower than that in the solid, and the use of a strong reducing solvent like TEG. Finally, Chapter 8 provides a summary of the salient findings in this dissertation. / text

A celulose das árvores do gênero Eucalyptus é um dos principais elementos de interesse econômico desse vegetal. Suas folhas, apesar de conter óleo essencial (OE), caracterizam-se como um subproduto da indústria de processamento de papel e celulose. Assim, pesquisas com relação à recuperação dessa biomassa tornam-se importantes, principalmente, do ponto de vista ambiental e econômico. Tradicionalmente, a extração de OEs ocorre pelo processo de hidrodestilação (HD), o qual necessita de longos tempos de extração. Visando superar essa restrição, a tecnologia de extração assistida por micro-ondas (Microwave Assisted Extraction - MAE) vem sendo desenvolvida e aplicada. O objetivo principal deste estudo foi avaliar o processo de extração de OE de folhas de eucalipto, empregando os métodos de extração HD e MAE. Para esse processo em escala de bancada, desenvolveu-se um aparato de extração por meio da adaptação de um forno micro-ondas doméstico. Inicialmente, analisou-se o rendimento de OE das matrizes de subprodutos de folhas de eucalipto das espécies Eucalyptus saligna, E. urohpylla e E. urophylla x globulus geradas a partir de uma indústria de celulose. Os resultados apontaram que a espécie E. urophylla x globulus apresentou maior teor de OE (2,16±0,02%), sendo a espécie escolhida para a aplicação da tecnologia MAE. Na segunda etapa do estudo, fez-se uma avaliação dos efeitos dos fatores do processo MAE, avaliando os fatores razão sólido:solvente (1:1; 1:1,5 e 1:2), potência do micro-ondas (680, 850 e 1.020 W) e tempo de extração total (20, 40, 60 min) no rendimento de OE. Desse modo, as condições ideais do processo foram determinadas como: razão sólido:solvente de 1:2, potência de 680 W e tempo de extração total de 60 minutos. Para essas condições, realizou-se o estudo cinético e modelagem matemática com a avaliação dos modelos de primeira ordem, segunda ordem, Peleg e Patricelli. No estudo cinético, o tempo total do processo MAE para a obtenção do rendimento de 1,8±0,1% foi apenas 60 minutos, tempo 57% inferior ao observado no método HD para igual rendimento (140 minutos). Dentre os modelos cinéticos estudados, o modelo de Patricelli foi o que apresentou melhor ajuste aos dados experimentais da extração HD (R² igual 0,9904 e RMSE igual 0,0016) e da extração MAE (R² igual 0,9962 e RMSE igual 0,0006). Por fim, as análises energéticas e de impacto ambiental também indicaram o método MAE como uma tecnologia mais ambientalmente amigável do que a HD, tornando-se atrativa para o setor industrial. Com base nos resultados obtidos, pode-se concluir que a extração de OE da matriz estudada proporcionou a reutilização de um subproduto industrial, sugerindo uma alternativa de exploração e agregando valor ao mesmo. / The cellulose from trees of the genus Eucalyptus is the main industrial product of this species. Its leaves, although containing essential oil (EO), are characterized as a by-product from the pulp and paper processing industry. Thus, researches about the recovery of this biomass are important, mainly from the environmental and ecological point of view. Traditionally, the extraction of EO occurs by hydrodistillation (HD), process that requires long extraction times. In order to overcome this restriction, microwave assisted extraction (MAE) has been developed and applied. The main objective of this study was to evaluate the extraction process of eucalyptus EO, using the HD and MAE methods. For this laboratory-scale process, an extraction apparatus was developed through the adaption of a domestic microwave oven. Initially, the yield of EO by-products of eucalyptus leaves of the species Eucalyptus saligna, E. urophylla and E. urophylla x globulus from a cellulose industry were analyzed. The results showed that the species E. urophylla x globulus presented the highest EO content (2.16 ± 0.02%), being the species chosen for the application of the MAE technology. In the second stage of the study, an evaluation of the effects of MAE process factors was performed, analyzing the factors ratio solid:solvent (1:1, 1:1,5 and 1:2), microwave power (680, 850 and 1.020 W) and total extraction time (20, 40, 60 min) in the EO yield. Thus, the ideal process conditions were determined as: ratio solid:solvent of 1:2, power of 680 W and total extraction time of 60 minutes. For these conditions, a kinetic study and a mathematical modeling were performed evaluating the first-order, second-order, Peleg and Patricelli models. In the kinetic study, the total time of the MAE process to obtain the yield of 1.8 ± 0.1% was only 60 minutes, 57% lower than the HD method for the same yield (140 min). Among the kinetic models studied, the Patricelli model presented the best fit to the experimental data of the HD extraction (R² equal to 0.9904 and RMSE equal to 0.0016) and MAE extraction (R² equal to 0.9962 and RMSE equal to 0.0006). Finally, the energy and environmental impact analyzes also indicated the MAE method more environmentally friendly than HD, being attractive for the industrial sector. Based on the results, it is possible to conclude that the extraction of EO from the studied matrix provided the reuse of an industrial by-product, suggesting an exploration alternative adding value to this residue.

Doctor of Philosophy / Department of Chemistry / Emily McLaurin / Semiconductors are materials whose conductivity is between metals and insulators. Semiconductor nanocrystals (NCs) have sizes in the range 2 to 10 nm. Because of their unique optical properties like tunable emission wavelength, narrow emission peak, and stability over dyes, they have potential applications in displays. Indium phosphide (InP) is considered a less toxic alternative to commercially used cadmium-based semiconductor NCs. Microwave-assisted (MA) methods using ionic liquids (ILs) afford fast reaction heating rates because of the good MW absorbing capacity of ILs. For tuning size and surface, which are some of the important problems associated with the InP NCs, new synthetic methods are reported herein. In MAIL etching HF generated in the microwave reaction etches the InP NCs surface. Pyridinium and imidazolium based ILs containing tetrafluoroborate (BF₄⁻) and hexafluorophosphate (PF₆⁻) ions yield luminescent NCs. In a silicon carbide (SiC) reaction vessel, which blocks most of the microwaves penetrating into the reaction, bigger NCs form than those from a Pyrex reaction vessel because of the higher reaction temperatures in the SiC vessel. By changing microwave set-power (SP), different reaction times can be achieved. Though a small degree of change in average NC diameter of the NCs is observed at different SPs and reaction temperatures, addition of dodecylamine (DDA) yields NCs with average sizes between 3.2 to 4.2 nm with a broad size distribution. At lower SPs smaller NCs form and at higher SPs bigger NCs form. NC luminescence can be tuned from green (545 nm) to red (630 nm) in the visible region with quantum yields as high as 30%. Rapid heating and InP precursor activation might be responsible for the larger change in NC size. The effect of DDA on NC size is also verified by microwave reactions in SiC vessels. ILs containing PF₆⁻ ions at 280 °C will modify the surface of the NCs so the NC dispersibility changes from non-polar (toluene) to polar (DMSO) as the amount of IL increases. This is due to ligand stripping, which is the removal of large palmitic ligands from the NC surface. These NCs have broad absorption features and emission peaks with QYs of up to 30%. Fourier transform infrared spectroscopy indicates the absence of palmitic acid ligands on the NC surface and zeta potential measurements indicate the presence of anions on the NC surface. From X-ray photoelectron spectroscopy and nuclear magnetic resonance spectroscopy, the inorganic ion PO₂F₂⁻ is identified on the NCs surface.

152 f. / Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2013-04-04T15:44:44Z No. of bitstreams: 1 TESE COMPLETA_SONILDA TEIXEIRA.pdf: 3246757 bytes, checksum: c41c8741042ef35b54690019e768753b (MD5) / Approved for entry into archive by Ana Hilda Fonseca(anahilda@ufba.br) on 2013-05-09T16:28:03Z (GMT) No. of bitstreams: 1 TESE COMPLETA_SONILDA TEIXEIRA.pdf: 3246757 bytes, checksum: c41c8741042ef35b54690019e768753b (MD5) / Made available in DSpace on 2013-05-09T16:28:03Z (GMT). No. of bitstreams: 1 TESE COMPLETA_SONILDA TEIXEIRA.pdf: 3246757 bytes, checksum: c41c8741042ef35b54690019e768753b (MD5) Previous issue date: 2009 / CAPES / Amostras de material particulado (PM10) foram coletadas no Recôncavo Baiano (RB) e em uma estação controle (Arembepe), de Agosto de 2007 a Abril de 2008, utilizando um amostrador de grandes volumes. Foram medidas as concentrações dos 16 HPAs classificados como poluentes prioritários pela Agência de Proteção Ambiental dos Estados Unidos (US-EPA), em duas campanhas de amostragem intensivas, nas estações chuvosa e seca, pelo período de 24 h durante 5-6 dias consecutivos, nos três sítios localizados na parte norte e nordeste da Baía de Todos os Santos (BTS) e em Arembepe (litoral norte da Bahia) tomado como sítio controle. Os filtros de fibra de vidro foram extraídos por microondas (MAE) utilizando um protocolo otimizado no qual a extração ocorreu em 10 min e consumiu 20 mL de DCM/acetona (1:1) antes da análise por cromatografia a gás/espectrometria de massas com detector de massas (GC/MS/MS). O somatório das concentrações médias dos 16 HPAs variou de 0,036 ng m-3 (Arembepe) a 108 ng m-3 (próximo a refinaria de petróleo e indústria de eletrodos de Carbono), apresentando uma variação sazonal (razão inverno/verão) na faixa de 0,2-306. Os HPAs potencialmente carcinogênicos representaram 53-74% da concentração total nos sítios do RB. Os HPAs predominantes foram os de alta massa molecular, do Fluoranteno ao Benzo(ghi)perileno, representando 90-99 % do total de HPAs no RB. Em Candeias as concentrações elevadas encontradas no inverno foram provavelmente causadas por emissões locais de fontes estacionárias. Para facilitar a identificação das fontes de HPAs no PM10 foi aplicada a análise de componentes principais (PCA) juntamente com o estudo das razões diagnósticas entre HPAs específicos. Na região estudada as emissões veiculares e industriais foram as principais contribuintes para os HPAs associados ao PM10. As concentrações de benzo(a)pireno equivalente (BaPeq) foram estimadas usando a relação de fatores de equivalência tóxica (TEFs) com valores de 0,1 a 22 ng m-3. Concentrações elevadas de BaPeq para os HPAs de 5 a 6 anéis no ar ambiente alertam para uma situação de aumento de riscos para a saúde humana e para a qualidade ambiental na região do RB, principalmente em Candeias e Madre de Deus / Salvador

Dióxido de titânio com alta área superficial específica na fase anatase é considerado um material promissor para aplicações ambientais. Neste trabalho, TiO2 com boa aplicabilidade em processos fotocatalíticos e na produção de hidrogênio foi obtido pelo método com baixo consumo de energia baseado na rota dos peróxidos oxidantes combinado com tratamento solvotermal assistido por microondas. Para preparar o material, propóxido de titânio, peróxido de hidrogênio e álcool isopropílico foram utilizados. A influência do tempo, do pH e da temperatura durante a etapa solvotermal nas propriedades como morfologia, cristalinidade, composição de fase, área superficial específica e comportamento fotocatalítico foram investigados. As amostras foram caracterizadas por difração de raios X (DRX), microscopia eletrônica de varredura (MEV), microscopia eletrônica de transmissão (MET), análise termogravimétrica (ATG), teoria Brunauer-Emmett-Teller (BET), reflectância difusa e espectroscopia por emissão fluorescente. A fotoatividade foi determinada usando o método de decomposição do corante alaranjado de metila em luz UV-A e a produção de hidrogênio foi realizada em água usando etanol como agente de sacrifício. Com o aumento da temperatura durante a etapa solvotermal, as propriedades fotocatalíticas foram melhoradas. As nanoestruturas de TiO2 sintetizadas a 200°C e 30 min a partir deste método mostraram atividade fotocatalítica comparável ao do TiO2 P25 comercial Aeroxide©. Isso pode ser atribuído ao fato de que a energia associada a esta temperatura tenha sido suficiente para converter a maioria dos precursores em produtos cristalinos e pouca fase amorfa está presente. Foi possível produzir, com sucesso, nanoestruturas de TiO2, via método dos peróxidos oxidantes e tratamento solvotermal assistido por microondas em diferentes pHs. O material tratado em pH 1 exibiu melhor comportamento fotocatalítico na degradação da solução contendo alaranjado de metila. Aparentemente, o pH do meio não afetou significativamente a microestrutura das amostras. Foi observado uma diminuição na intensidade fotoluminescente da amostra preparada em pH ácido. Isso ocorre provavelmente porque as modificações ácidas em TiO2 favorecem eficientemente a separação das cargas, que está também relacionada com o comportamento dessa amostra durante o processo de degradação. Em relação à produção de hidrogênio, foi possível observar que a razão aumentou com o aumento do pH da solução. Isso pode ser atribuído ao aumento da concentração de OH- fisisorvidos, os quais podem participar dos processos de trapeamento das lacunas e nas reações de transferência de cargas. Por último, esses resultados foram notáveis porque foi utilizado um método de preparação com baixo consumo de energia onde apenas precursores orgânicos e baixas temperaturas foram empregados. Além disso, calcinação ou dopagem não foram necessários para alcançar tal desempenho, uma vez que, os catalisadores assim preparados exibiram boa atividade fotocatalítica na remoção de poluentes da água como o alaranjado de metila e na produção de hidrogênio. / Titanium dioxide with high specific surface area in the crystalline anatase phase is a promising material for environmental applications. In this work, TiO2 with good applicability for photocatalytic processes and hydrogen production has been obtained using the low energy consumption synthesis based on oxidant peroxide method combined with microwave-assisted low temperature solvothermal treatment. To prepare the material, titanium propoxide, hydrogen peroxide, and isopropyl alcohol were used. The influence of time, pH and temperature during the solvothermal step on properties like, morphology, crystallinity, phase composition, specific surface area, and photocatalytic behavior were investigated. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), scanning electron transmission (TEM), thermal gravimetric analysis (TGA), Brunauer- Emmett-Teller theory (BET), UV–Vis diffuse reflectance and fluorescence emission spectroscopy. Photoactivity was determined using the methyl orange decomposition method in UV-A light and hydrogen production was performed in water using ethanol as sacrificial agent. Increasing temperature during solvothermal step, photocatalytic properties could be improved. The nanostructured TiO2 particles synthesized at 200ºC and 30 min with this method showed photocatalytic activity comparable to commercial Aeroxide® TiO2 P25. This can be attributed to the fact that the energy associated with this temperature has been sufficient to convert most of precursors into crystalline products and small amount of amorphous phase is present. We successfully produced nanostructured TiO2 via the oxidant peroxide method and microwave-assisted solvothermal treatment at different pHs. The material that we treated at pH 1 exhibited better photocatalytic performance on the degradation of methyl orange solutions. It appears that the pH of the medium does not significantly affect the microstructure of the samples. It was observed a decrease in the photoluminescence intensity of the sample prepared at acidic pH. This finding likely occurred because the acidic modification of TiO2 favors efficiently separating the charge carriers, which is also related to the behavior of this sample during the degradation process. Related to hydrogen production, it was possible to observe that the rate increases with increasing solution pH. This has been attributed to the increased concentrations of physisorbed OH− groups at basic solutions, which participate in hole trapping processes and charge transfer reactions. Lastly, these results are remarkable because of the low energy consumption preparation method: only organic-metalic compounds and low temperatures were employed. Furthermore, calcination or doping was not necessary to achieve such performance, since the asprepared catalysts exhibited good photocatalytic activity on removal of pollutants from water as the methyl orange and on hydrogen production.