Atualmente, a nanociência e nanotecnologia são consideradas como um campo emergente onde, continuamente, as barreiras entre as disciplinas são rompidas. Seu principal foco de estudo consiste em buscar o controle estrutural ao nível molecular, arranjando os átomos de modo a se conseguir um entendimento e controle das propriedades fundamentais da matéria. Neste estudo foram propostas modificações moleculares e, consequentemente, na morfologia, propriedades ópticas e cristalinas em filmes finos de TiO2 com o objetivo de aumentar sua eficiência fotônica. Os filmes finos de TiO2 foram preparados pelo processo sol-gel avaliando a influência de diferentes ácidos e agente direcionador para a obtenção dos arranjos nanoestruturados. A seguir, os filmes que apresentaram maior eficiência fotônica foram incorporados com nanopartículas metálicas (Au, Ag, Pd e Pt) com objetivo de minimizar os processos de recombinação eletrônica do par lacuna/elétron. Das diversas rotas estudadas, os filmes finos de TiO2 preparados com ácido acético obtiveram maior eficiência fotônica devido à pouca aglomeração dos grãos de titânia, o que pode ter favorecido uma maior exposição dos sítios fotocatalíticos. A presença do agente direcionador na formulação teve pouco efeito na eficiência fotônica, possivelmente devido à maior aglomeração dos grãos nos filmes finos de TiO2. Com a adição de nanopartículas metálicas, os filmes finos de TiO2 com nanopartículas de platina e ouro apresentaram maior eficiência fotônica. A presença de hexamina nos filmes finos de TiO2 com nanopartículas metálicas teve pouca influência na eficiência fotônica, exceto com nanopartículas de platina e ouro. A melhora da eficiência fotônica, nestes casos, pode ser atribuída a uma possível diminuição da velocidade de recombinação do par lacuna/elétron. Dessa forma, com o presente trabalho pôde-se comprovar a grande influência das condições de preparação do TiO2 nas propriedades ópticas, morfológicas e na eficiência fotônica. Futuramente, com o maior entendimento do mecanismo desta influência poder-se-ão delinear de forma mais precisas a morfologia e eficiência fotônica destes filmes finos de TiO2, conforme a aplicação a qual serão destinados. / Currently, nanoscience and nanotechnology are considered an emerging field and continuously breaking the barrier among various disciplines. The main focus of study involves controlling structures at molecular level, arranging the atoms in order to achieve an understanding and controlling the fundamental properties of matter. In this study, molecular changes on the basis of morphology, optical and crystalline properties of TiO2 thin films in order to increase their photon efficiency were proposed. The TiO2 thin films were prepared by solgel process evaluating the influence of different acids and templates to obtain the nanostructured arrangements. Then, metal nanoparticles like Au, Ag, Pd and Pt were incorporated on TiO2 thin films. This incorporation might minimize the electron-hole recombination, so it could improve the photon efficiency. From the several routes studied, the TiO2 thin films prepared with acetic acid showed the best performance by the reason of low agglomeration of TiO2 grains, which favors the exposure of the photoactive sites. The presence of template in the formulation had a slightly effect on photon efficiency, possible due to the higher agglomeration of the grains on the TiO2 thin films. The addition of Pt and Au nanoparticles on TiO2 thin films showed superior photon efficiency. The TiO2 thin films with hexamine and metallic nanoparticles did not show the improvement on photon efficiency except for Pt and Au nanoparticles. On these situations, the improvement on photon efficiency is might be due to a possible decrease at the electron-hole recombinations velocity. Thus, the present work demonstrates the great influence of preparation conditions on the optical, morphological properties and the photon efficiency. In the future, with greater understanding of the mechanism of this influence, the properties of TiO2 thin films will be able tailoring depending on the application.

Este estudo propôs uma avaliação do papel dos três principais parâmetros clássicos da síntese do nitreto de carbono grafítico: temperatura final, tempo de permanência na temperatura final e taxa de aquecimento. Realizou-se a otimização da síntese, via metodologia de superfície de resposta, usando-se como variável-resposta a degradação fotocatalítica de um poluente-modelo (tartrazina). A significância estatística dos fatores foi confirmada, com 95% de confiança. Em seguida, um modelo de segunda ordem foi ajustado às melhores respostas e, no ponto de máxima degradação, as condições foram: 605oC por 183 min, com taxa de aquecimento de 5oC min-1. A taxa de degradação com o fotocatalisador sintetizado foi aproximadamente três vezes maior que a da fotólise. As amostras da região de melhores respostas foram analisadas em uma série de experimentos de caracterização, sendo eles: difratometria de raios X, espectroscopia na região do infravermelho médio, área superficial específica, microscopias de varredura (MEV e MEV-FEG), potencial zeta e espectroscopia de reflectância difusa na região do ultravioleta-visível. O fotocatalisador com maior atividade apresentou menor energia de band gap e maior área superficial especifica do que as relatadas na literatura (2,59 eV e 29,5 m2 g-1, respectivamente). Foram criadas heteroestruturas entre o fotocatalisador sintetizado e o trióxido de tungstênio. A partir de uma série de caracterizações básicas, confirmou-se a formação da heteroestrutura. Com essa heteroestrutura, a taxa de degradação foi aproximadamente cinco vezes maior que a com o nitreto de carbono grafítico. / This study proposed an assessment of the role of the three major classical parameters for synthesizing graphitic carbon nitride: final temperature, residence time at the final temperature and heating rate. The synthesis was optimized, via response surface methodology, using the photocatalytic degradation of a model pollutant (tatrazine) as the response-variable. The statistical significance of the factors was confirmed, within 95% confidence level. Afterwards, a second-order model was adjusted to the better responses and, at the maximum degradation point, the conditions were: 605oC for 183 min, with heating rate of 5oC min-1. The degradation rate with the synthetized photocatalyst was approximately three times greater than the photolytic one. The samples from the better response region were analyzed in a series of characterization experiments: X ray diffractometry, mid-infrared spectrometry, specific surface area, scanning electron microscopy (SEM and FEG-SEM), zeta potential, and ultraviolet-visible diffuse reflectance spectroscopy. The most active photocatalyst showed smaller band gap energy and greater specific surface area than the ones reported in literature (2.59 eV and 29.5 m2 g-1, respectively). Heterostructures were formed between the synthetized photocatalyst and tungsten trioxide. A series of basic characterization techniques confirmed the heterostructure formation. Using this heterostructure, the degradation rate was approximately five times greater than the one with graphitic carbon nitride.

O presente trabalho estuda a degradação fotocatalítica da nicotina em solução aquosa, um alcaloide altamente tóxico que tem sido detectado em efluentes, águas subterrâneas e água mineral. Os experimentos foram realizados em um reator batelada sob irradiação ultravioleta, tendo sido avaliadas três principais variáveis: concentração inicial do contaminante, concentração de catalisador e pH inicial da solução. Foram realizados dois planejamentos de experimentos para os catalisadores comerciais ZnO e TiO2, com o objetivo de encontrar a melhor condição para promover a degradação da nicotina em água. Outros catalisadores, preparados a partir de resíduos industriais e laboratoriais, foram testados nas condições otimizadas. O método analítico empregado para quantificar a nicotina nas amostras foi a cromatografia líquida de alta eficiência, o que permitiu registrar a formação de intermediários e subprodutos de reação. Os resultados experimentais demostraram que a degradação da nicotina por fotocatálise heterogênea é um processo bastante eficiente. Em ambos os planejamentos, o pH foi a variável que exerceu o maior efeito sobre a degradação, sendo este fortemente positivo. Já a concentração inicial de nicotina exerceu efeito negativo sobre a resposta e a concentração de catalisador em suspensão exibiu um ponto ótimo, que correspondeu a 0,91 g.L-1 para o ZnO, e 1,20 g.L-1 para o TiO2. Ensaios foram realizados nas condições otimizadas encontradas, onde cerca de 98% da molécula foi degradada utilizando ZnO em suspensão e 88% empregando TiO2, em uma hora de reação. A degradação fotocatalítica da nicotina demonstrou seguir uma cinética de pseudoprimeira ordem dentro do tempo de reação de 60 minutos, para os dois catalisadores comerciais. Entre os catalisadores não convencionais que foram testados, aquele que demonstrou o maior percentual de degradação foi obtido a partir de resíduo de uma indústria petroquímica, cerca de 43%. / The present work studies the photocatalytic degradation of nicotine in aqueous solution. This alkaloid is highly toxic and it has been detected in wastewater, groundwater and mineral water. The experiments were performed in a batch reactor under ultraviolet radiation. Three main variables of process were evaluated: initial concentration of pollutant, catalyst concentration and initial pH of the solution. Two experimental designs were performed for commercial catalysts ZnO and TiO2. The purpose was to find the best condition to promote the nicotine degradation in water. Other catalysts prepared from industrial and laboratory waste were tested under the optimized conditions. Analytical method used to quantify nicotine and its degradation products in all samples was high performance liquid chromatography. Experimental results showed that nicotine degradation by heterogeneous photocatalysis is a very efficient process. In both designs, initial pH was the most significant variable which has a strong positive effect. Initial nicotine concentration showed a negative effect, and catalyst concentration exhibited an optimal value for both commercial catalysts: 0,91 g.L-1 using ZnO, and 1,20 g.L-1 with TiO2. At the best conditions, about 98% of the molecule was degraded using ZnO and 88% with TiO2. Photocatalytic nicotine degradation followed a pseudo first order kinetic until 60 minutes of reaction for both commercial catalysts. Among the non-conventional catalysts tested, the one prepared from a petrochemical industry residue exhibited the highest photocatalytic degradation, about 43%.

The invention of catalytic processes that convert feedstock chemicals into pharmacologically-privileged amines is a landmark challenge in organic synthesis. This thesis describes the development of three novel transition-metal catalyzed processes for the synthesis of alkylamines that attempts to meet this challenge. The first Pd-catalyzed methylene β-C−H carbonylation of alkylamines to form substituted β-lactams is reported. Through the synergistic use of a Pd-catalyst and Xanpthos ligand, secondary amines underwent exclusive methylene β-C−H activation in high yields and diastereoselectivities. Subsequently, the development of a remarkably selective methylene β-C−H carbonylation of α-tertiary amines (ATAs), is detailed. This methodology enables the C−H carbonylation of methylene C−H bonds over traditionally more reactive methyl and C(sp2)−H bonds. Importantly, a range of functional groups previously incompatible with C−H technologies were tolerated in good yields. Finally, the development of a novel multicomponent synthesis of tertiary amines is described. The novel photocatalytic single-electron reduction of alkyl iminium ions furnishes -amino radicals that engage alkenes forming a new C-C bond. The reaction exhibits broad functional group tolerance and enables the synthesis of amines not readily accessible by existing methods.

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.

Dans le cadre de cette thèse, nous avons étudié plusieurs processus radicalaires et en particulier l'addition de radicaux libres sur des systèmes insaturés tels que les alcènes et les hétérocycles aromatiques. Nous avons ainsi montré la réactivité unique des radicaux carbamoyles, issus de la décarboxylation des acides oxamiques. La carbamoylation "sans métal" photocatalysée des hétérocycles a donc été réalisée en présence d'un réactif iodé hypervalent, conduisant à des bases hétéroaromatiques fonctionnalisées, généralement avec de bons rendements. Le processus a été étendu aux acides oxamiques préparés à partir d'acides aminés homochiraux, la réaction se déroulant sans racémisation du substrat initial.Dans la recherche d'un groupe fonctionnel équivalent à un aldéhyde et compatible avec les groupes fonctionnels résidents, nous avons mis au point un nouveau procédé de carbo-cyanation des oléfines par voie radicalaire, permettant l'incorporation, sur un squelette oléfinique, d'un fragment portant un groupe électroattracteur et un groupe cyano. Des conditions photochimiques ont également été développées afin d'éviter l'utilisation d'amorçeurs coûteux tels que le di-tert-butyl hyponitrite (DTBHN). Cette réaction clé a ensuite été utilisée afin de construire, en seulement 4 étapes, un modèle du squelette bicyclique de l’alcaloïde leuconoxine.Enfin, dans la dernière partie de la thèse, nous avons décrit une synthèse simple de naphthalénones, portant un stéréocentre quaternaire benzylique tout carboné. La réaction entre un halogénure de phénacyle et un cyclopropène substitué se déroule sous photocatalyse en utilisant un catalyseur à l'iridium et de la lumière visible. Une carbo-arylation du cyclopropène est ainsi réalisée conduisant au cyclopropane correspondant, lequel s’ouvre dans les conditions de la réaction pour conduire à la naphthalénone souhaitée avec des rendements modérés, mais avec rétention de la chiralité du cyclopropène homochiral initial. / In the context of this thesis we studied several radical processes and in particular the addition of free-radicals onto unsaturated systems such as alkenes and aromatic heterocycles. We have thus shown the unique reactivity of carbamoyl radicals, issued from the decarboxylation of oxamic acids. Photocatalyzed “metal-free” carbamoylation of heterocycles was thus performed in the presence of an hypervalent iodine reagent, leading to -functionalized heteroaromatic bases, generally in good yields. The process was extended to oxamic acids prepared from homochiral amino acids and was shown to proceed without racemization.In the search for a functional group equivalent to an aldehyde and compatible with resident functional groups, we have devised a new free-radical olefin carbo-cyanation process, allowing the incorporation, on an olefin backbone, of a fragment bearing an electron-withdrawing group and a cyano group. Photochemical conditions have also been developed in order to avoid the use of costly initiators such as the di-tert-butyl hyponitrite (DTBHN). This key reaction was then used to construct, in only 4 steps, a bicyclic skeleton model for the alkaloid leuconoxine.Finally, in the last part of the thesis, we have described a straightforward synthesis of naphthalenones, bearing an all-carbon benzylic quaternary stereocenter. The reaction between a phenacyl halide and a substituted cyclopropene proceeds under photocatalysis using an iridium catalyst and visible light. A carbo-arylation of the cyclopropene is thus carried out leading to the corresponding cyclopropane, which is opened under the reaction conditions to afford the desired naphthalenone in moderate yields, with retention of the chirality of the starting homochiral cyclopropene.

L'apparition d’un développement cancérigène est souvent caractéristique des tumeurs de la région de la tête et du cou. En raison des altérations prémalignes et malignes fréquentes, il n'est souvent pas possible de supprimer complètement la tumeur par chirurgie.Il en résulte un risque élevé de récidive tumorale. Par conséquent, cette recherche de doctorat vise à développer des nanoparticules photocatalytiques (NPs) qui seront utilisées localement en complément de la thérapie tumorale traditionnelle. Ces NPs, une fois absorbées par les cellules tumorales induiront la mort des cellules photocatalytiques par activation de lumière UV. Des NPs de TiO2 ayant des propriétés photocatalytiques et une taille moyenne inférieure à 20 nm étaient donc synthétisées. La biocompatibilité des NPs, leur absorption dans les cellules et un ciblage tumoral efficace devraient être garantis par une modification de surface des particules avec des molécules organiques dendritiques permettant un contrôle précis de la charge de surface des particules ainsi que la possibilité de couplage avec des anticorps. Un autre objectif était la combinaison de propriétés thérapeutiques et diagnostiques dans le système de NPs par exemple réalisé par incorporation d'agent luminescent. Cette recherche était menée à l'Université de Bordeaux (synthèse des molécules organiques pour la fonctionnalisation des particules) en coopération avec l'Institut Fraunhofer de recherche en silicate ISC à Würzburg, Allemagne (synthèse des nanoparticules). / The occurrence of field cancerization is characteristic for tumours of the head and neck region. Due to these widespread premalignant and malignant alterations, it is frequently not possible to entirely remove the tumour by surgery. This results in a high risk of tumour recurrence. Therefore, this PhD research aimed to develop photocatalytic nanoparticles (NPs) as completion of the traditional tumour therapy. These NPs are supposed to be incorporated by tumour cells and to induce photocatalytic cell death by UV light activation. TiO2 with convincing photocatalytic properties and an average size smaller than 20 nm should therefore be synthesized. NP biocompatibility, their uptake into cells and an efficient tumour targeting should be guaranteed by surface modification of the particles with dendritic organic molecules that allow a precise control of the surface charge of the particles as well as antibody coupling.A further objective was the combination of therapeutic and diagnostic properties within the NPsystem realized for example via introduction of a luminescent dye. This research was carried out at the University of Bordeaux (synthesis of organic molecules for particle functionalization) in cooperation with the Fraunhofer Institute for Silicate Research ISC in Würzburg, Germany (nanoparticle synthesis).

The dissertation is split into two parts. The first part will be focused on changes in material properties found at the nanoscale, as miscibility and electronic structure can change significantly with size. The formation of classically-immiscible bimetallic nanoparticles (BNPs) becomes favorable at the nanoscale and novel catalytic properties can emerge from the bimetallic alloying. The formation of alloyed and non-alloyed BNPs is achieved through pulse laser ablation (PLA) and a significant increase in catalytic activity is observed for both. Recently discovered, the increased activity in the non-alloyed BNPs, deemed multicomponent photocatalysis, is examined and the proposed mechanism discussed. The second part of the talk will focus on thermal barrier coatings (TBCs), which are advanced, multi-layered coatings used to protect materials in high temperature environments. MCrAlY (M=Ni, Co) bond coats deposited via atmospheric plasma spray (APS) are intrinsically rough and initially the roughness provides a high surface area platform for the mechanical interlocking of the yttria stabilized zirconia (YSZ) top coat, which provides the bulk of the thermal insulation. After high temperature exposure, a protective oxide scale forms at the top coat/bond coat interface however the convex asperities of the bond coat can grow non-α-Al2O3 type oxides that can be detrimental for coating lifetime. A surface modification technique that removes the asperities while leaving intact the concavities is used to examine the role that roughness distribution has on 1100°C APS coating lifetime. Lastly, recent work validating a modelling strategy for evaluating 900°C TBC lifetimes, which can typically surpass 25 kh, is presented. Differences in coating-substrate interdiffusion behavior over 5-20 kh of 900°C exposure are discussed and reproduced with Thermo- Calc/DICTRA for three superalloys (1483, 247, X4) deposited with high velocity oxy fuel (HVOF) NiCoCrAlY coatings.

Metal oxides in the atmosphere emitted from various natural and anthropogenic processes alter the chemical balance of the Earth's atmosphere due to heterogeneous and photochemical processes with atmospheric trace gases. Therefore, understanding the heterogeneous chemistry and heterogeneous photochemistry of atmospheric trace gases on these oxide surfaces has become vital to precisely predict the effect of mineral dust loading on the Earth's atmosphere. Among the various components of mineral dust, light absorbing oxides play a significantly important role during the daytime. The work reported herein has focused mainly on TiO2 and Α-Fe2O3. These are light adsorbing components found in atmospheric mineral dust. Apart from being a component of mineral dust, TiO2 is heavily used in a number of industrial applications ranging from uses in self-cleaning, water purification to cosmetics. These applications have led to their presence in the atmosphere as anthropogenic dust particles and in contact with the atmosphere as a stationary phase. Iron-containing particles are transferred to the atmosphere mainly from wind and volcanic activities in the form of iron-containing mineral dust and volcanic ash aerosols. Α-Fe2O3 is the most stable iron containing compound found in the Earths' crust which constitutes in significant amounts in mineral dust. The presence of these oxide surfaces in the atmosphere can play a major role in heterogeneous chemistry and photochemistry. In this dissertation research, transmission FTIR spectroscopy and X-ray photoelectron spectroscopy are used to probe the details of heterogeneous chemistry and photochemistry of CO2, SO2, NO2, HCOOH, and HNO3 on titanium dioxide and hematite surfaces. Adsorption sites, surface speciation and surface species stability have been determined from analysis of FTIR and XPS spectra. Isotope labeling experiments were also carried out in order to obtain mechanistic information about the details of surface hydroxyl group reactivity on these oxide particle surfaces. Furthermore, heterogeneous photochemical reactions of adsorbates from atmospheric trace gas adsorption on TiO2 and Α-Fe2O3 were investigated under the conditions pertinent to troposphere. The role of adsorbed water on the stability of adsorbed species that form as a result of heterogeneous reactions and the effect of relative humidity on photochemistry on these oxide particles surfaces has also been investigated due to its important implications in the atmospheric chemistry of oxide surfaces. The research adds to our overall scientific understanding of the molecular level details of heterogeneous chemistry and photochemistry of light absorbing components in the atmosphere.

Neste trabalho é reportado o estudo de degradação do fenol via processo de fotocatálise heterogênea pelo uso de radiação eletromagnética visível em duas classes de fotocatalisadores: os baseados no TiO2 e os baseados na Ag. Os materiais baseados no TiO2 foram modificados com Ag2O e Ag3PO4 e foram preparados por meio do tratamento hidrotérmico de TiO2 comercial em meio altamente alcalino. Já os materiais baseados na Ag foram obtidos via reações de precipitação química, tendo sido preparados os seguintes compostos: Ag2O, Ag2CO3, Ag3PO4 e Ag2CrO4. A caracterização dos fotocatalisadores obtidos foi feita por meio das técnicas de microscopia eletrônica de varredura (MEV), difração de raios &#8722;X, DRX, fisissorção de N2, espectroscopias no ultravioleta &#8722; visível por refletância difusa, UV-Vis e no infravermelho, IV. Os resultados mostraram a obtenção de estruturas com morfologia associada a fios de TiO2 anatase modificados superficialmente com partículas esféricas de Ag2O e Ag3PO4, com elevado grau de cristalinidade e pureza de fase. O estudo fotocatalítico revelou que os materiais modificados com Ag2O e Ag3PO4 apresentaram melhor desempenho na fotodegradação do fenol em comparação com TiO2 puro, com eficiência de 60% de degradação em 5 horas de irradiação de fótons na região do visível. Em relação aos fotocatalisadores a base de Ag, foram obtidas partículas com boa distribuição de tamanho e morfologias associadas a cristais octaédricos de Ag2O, bastões de Ag2CO3, poliedros de Ag3PO4, bem como partículas multifacetas de Ag2CrO4. Os resultados indicaram que estes fotocatalisadores apresentaram elevada eficiência na fotodecomposição do fenol. Dentre eles, o Ag2O e o Ag3PO4 foram mais efetivos na remoção do poluente, com eficiência de 90% em apenas 2 horas de tratamento. Adicionalmente, avaliou-se a formação de radicais hidroxila durante a reação de oxidação, por meio da técnica da fotoluminescência utilizando a cumarina (COU) como uma molécula sonda. Como resultado foi observado que, com exceção do TiO2 puro,não houve formação da 7-hidroxicumarina (7HC) como produto fluorescente da reação da cumarina com os radicais &#8226;OH. Além disso, estes fotocatalisadores foram avaliados em relação à estabilidade e desempenho catalítico no reuso. A análise dos resultados obtidos por DRX e MEV dos fotocatalisadores após o uso em estudo fotocatalítico de degradação mostrou que houve a formação de prata metálica na estrutura dos mesmos. No entanto, os fotocatalisadores Ag2O e Ag2CO3 revelaram um aumento na atividade fotocatalítica após o reciclo catalítico, sugerindo que a modificação da estrutura contribuiu positivamente na eficiência da degradação do fenol. / In this, work it is reported the study of phenol degradation by heterogeneous photocatalysis process using TiO2-based and Ag-based photocatalysts materials, irradiated by visible light. TiO2-based catalysts were modified with Ag2O and Ag3PO4 and prepared by the alkaline hydrothermal treatment of commercial TiO2, while the Ag-based materials were obtained by chemical precipitation. It was prepared the following compounds: Ag2O, Ag2CO3</sub, Ag3PO4 and Ag2CrO4. Photocatalysts characterization was made by microscopy electron scanning (SEM), x ray diffraction (XRD), physisorption N2 method, UV-Vis diffuse reflectance spectroscopy and infrared spectroscopy (FT-IR). Anatase TiO2 materials showed wire-like morphology superficially modified with spherical particles of Ag2O or Ag3PO4, with high crystallinity and phase purity. The photocatalytic study found that the materials modified by Ag2O and Ag3PO4 showed better performance in phenol photodegradation than pure TiO2, with a degradation of 60% after 5 hours of irradiation by visible light. On the other hand, Ag-based catalysts exhibited particles with morphology associated to: Ag2O octahedrons crystals, Ag2CO3</sub rods, Ag3PO4 polyhedrons, and Ag2CrO4 multifaceted particles. Ag-based photocatalysts showed high efficiency in the phenol photocatalytic degradation by visible light. Among them, Ag2O and Ag3PO4 were the most effective, with 90% of pollutant degradation after only 2 hours of treatment. Moreover, the hydroxyl radicals production/role during the oxidative process was investigated by the photoluminescence technique (PL) using coumarin (COU) as a probe molecule. It was found that there was no formation of 7-hydroxycoumarin (7HC) as fluorescent product of the reaction of COU with radicals &#8226;OH, except using pure TiO2. Furthermore, the stability and catalytic performance during the reuse of these photocatalysts were evaluated. XRD and SEM analysis after catalyst use in the phenol photodegradation showed that metallic silver formation at their structures surface. Ag2O and Ag2CO3 photocatalysts showed an increase in photocatalytic activity after therecycle, suggesting that the structure modifications could contribute positively for phenol photodegradation efficiency.