Photocatalysis is an advanced oxidation process for the purification and remediation of contaminated waters and wastewaters, and is advantageous over conventional treatment technologies due to its ability to degrade emerging and recalcitrant pollutants. In addition, photocatalytic disinfection is less chemical-intensive than other methods such as chlorination, and can inactivate even highly resistant microorganisms with good efficacy. Process sustainability and cost-effectiveness may be improved by utilizing solar irradiation as the source of necessary photons for photocatalyst excitation. However, solar-induced activity of the traditionally-used titania is poor due to its inefficient visible light absorption, and recombination of photo-excited species is problematic. Additionally, mass transfer limitations and difficulties separating the catalyst from the post-treatment slurry hinder conversions and efficiencies obtainable in practice. In this research, various strategies were explored to address these issues using novel visible light active photocatalysts. Two classes of carbon-enhanced photocatalytic materials were studied: activated carbon adsorbent photocatalyst composites, and carbon-doped TiO2. Adsorbent photocatalyst composites based on activated carbon and plasmonic silver/silver chloride structures were synthesized, characterized, and experimentally investigated for their photocatalytic activity towards the degradation of model organic pollutants (methyl orange dye, phenol) and the inactivation of a model microorganism (Escherichia coli K-12) under visible light. The adsorptive behaviour of the composites towards methyl orange dye was also studied and described according to appropriate models. Photocatalytic bacterial inactivation induced by the prepared composites was investigated, and the inactivation mechanisms and roles of incorporated antimicrobial silver on disinfection were probed and discussed. These composites were extended towards magnetic removal strategies for post-use separation through the incorporation of magnetic nanoparticles to prepare Ag/AgCl-magnetic activated carbon composites, and the effect of nanoparticles addition on the properties and photoactivities of the resulting materials was explored. Another silver/silver halide adsorbent photocatalyst composite based on activated carbon and Ag/AgBr exhibiting visible light absorption due to both localized surface plasmon resonance and optical band gap absorption was synthesized and its photocatalytic activity towards organics degradation and microbial inactivation was studied. Carbon-doped mixed-phase titania was also prepared and experimentally investigated.

The scalable syntheses of functional, porous nanostructures with tunable three-dimensional morphologies is a significant challenge with potential applications in chemical, electrical, electrochemical, optical, photochemical, and biochemical devices. As a result, several bio-enabled and synthetic approaches are explored in this work (with an emphasis on peptide-enabled deposition) for the generation of aligned nanotubes of nanostructured titania for application as electrodes in dye-sensitized solar cells and biofuel cells. As part of this work, peptide-enabled deposition was used to deposit conformal titania coatings onto porous anodic alumina templates under ambient conditions and near-neutral pH to generate aligned, porous-wall titania nanotube arrays that can be integrated into dye-sensitized solar cells where the arrays displayed improved functional dye loading compared to sol-gel-derived nanotubes. A detailed comparison between synthetic and bioorganic polyamines with respect to titania film properties deposition rate provided valuable information for future titania coating experimental design given specific applications. The development of template-based approaches to single-wall titania nanotube arrays led to the development of a new synthetic method to create aligned, multi-walled titania nanotube arrays. Lastly, peptide-enabled deposition methods were extended beyond inorganic mineral and used for enzyme immobilization by cross-linking the peptide with the multicopper oxidase laccase. Peptide-laccase hybrid enzyme coatings improved both the amount of enzyme adsorbed onto carbon nanotube “buckypaper” and allowed the enzyme to retain more activity upon immobilization onto the surface.

The research detailed in this dissertation is focused on the use of biomolecules (i.e., peptides and proteins) to form non-biologically produced materials under mild reaction conditions (i.e, neutral pH, aqueous solutions, and room temperature). The peptides utilized in the studies detailed in this dissertation were identified through the screening of single crystal rutile TiO2 substrates or Ge powder with a phage-displayed peptide library. Twenty-one peptides were identified which possessed an affinity for Ge. Those peptides possessing a basic isoelectric point as well as hydroxyl- and imidazole-containing amino acid residues were found to be the most effective in precipitating amorphous germania from an alkoxide precursor. The phage-displayed peptide library screening of TiO2 substrates yielded twenty peptides. The titania formation activity of these peptides was found to correlate with the number of positive charges they carried. The titania materials generated by the library-identified and designed peptides were found to be composed of amorphous titania as well as <10 nm anatase and/or monoclinic TiO2 crystallites. Four recombinant proteins, derived from the amino acid sequences of proteins (silaffins) associated with biosilicification in diatoms, were also investigated for titania precipitation activity. The two most basic of these recombinant silaffins, rSil1L and rSilC, were able to induce the formation of titania. The titania precipitates generated by rSil1L were found to be similar to those produced by the phage-displayed library identified peptides. The second recombinant silaffin, rSilC, was found to produce hollow spheres of titania, which, following dehydration, were observed to transform into larger, solid spheres composed of radially aligned columns of rutile TiO2. The highly repetitive nature of the rSilC s amino acid sequence is believed to be responsible for the differences in TiO2 polymorph generated by the different recombinant silaffins and peptides. This dissertation also details research conducted on the formation of titania utilizing rSilC conjugated to synthetic and biogenic silica surfaces. These silica surfaces were functionalized with a newly developed drendritic growth technique. The dendritic functional-group amplification process was demonstrated to increase the loading of hexahisitidine tagged proteins on silica surfaces by more than 40%, as compared to traditional immobilization procedures.

Bone response is one of the key determining factors in the overall success of biomaterials intended for bone regeneration and osseointegration. Understanding the formation of bone at an implant surface may lead to the improved design of biomaterials for the future. However, due to the inhomogeneity of bone tissue at an interface, two-dimensional images often lack detail on the interfacial complexity. Furthermore, the increasing use of nanotechnology in the design and production of biomaterials demands characterization techniques on a similar nano length scale. While current analysis methods, such as X-ray tomography, transmission electron microscopy, focused ion beam microscopy and scanning electron microscopy, provide a basis for analysing biomaterials and biointerfaces, they are incapable of doing so with both nanometre resolution and three-dimensional clarity. In contrast, electron tomography may be used to characterize the three-dimensional structure of biomaterials and their interfaces to bone with nanometre resolution. In this work, hydroxyapatite scaffolds, and laser-modified titanium and Ti6Al4V implants were studied in contact with human or rabbit bone. Z-contrast electron tomography revealed that the orientation of collagen in bone apposing hydroxyapatite, titanium and Ti6Al4V implants is consistently parallel to the implant surface, where the bioactive layer that precipitates on HA is oriented perpendicular to the implant surface. With this method, complete three-dimensional nanoscale osseointegration of titanium-based implants was also established. The extension of this technique from interfacial analyses to the design of biomaterials provided an understanding of the pore structure of mesoporous titania. In further investigations, the open three-dimensional pore network, as revealed by electron tomography, showed promise as a coating that improves implant osseointegration and enables site-specific drug-delivery from an implant surface. In summary, it was demonstrated that two-dimensional characterization techniques were insufficient for the investigation of nanostructured biomaterials, as well as their interfaces to bone. Visualizing biointerfaces and biomaterials with nanometre precision in three-dimensions can expose new fundamental information on materials properties and bone response, enabling better design of biomaterials for the future.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第13834号 / 工博第2938号 / 新制||工||1434(附属図書館) / 26050 / UT51-2008-C750 / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 井上 正志, 教授 江口 浩一, 教授 田中 庸裕 / 学位規則第4条第1項該当

Este trabalho apresenta o estudo do desempenho de catalisadores nanoestruturados de dióxido de titânio, TiO2, dopados com nitrogênio, visando melhorar sua atividade fotocatalítica sob radiação visível. Os nanotubos de TiO2 foram preparados pelo método hidrotérmico, onde partículas de TiO2 reagem com NaOH a temperatura e pressão elevadas. Em seguida o material é tratado, através de uma lavagem ácida e calcinação, de modo a apresentar as características desejáveis para a aplicação como fotocatalisador. Foram determinadas as melhores condições de obtenção dos nanotubos avaliando-se sua atividade fotocatalítica, variando-se o pH da solução de lavagem e temperatura de calcinação. Determinadas essas condições, buscou-se em três compostos nitrogenados o melhor desempenho para dopagem de nanotubos. Foram eles: amônia, uréia e tiouréia. A reação de degradação do corante rodamina B foi utilizada para avaliar a atividade fotocatalítica dos catalisadores. Os experimentos foram realizados em um reator batelada agitado, com o catalisador em suspensão e na presença de aeração, sob radiação UV e visível. Avaliaram-se inicialmente as condições de reação, como concentração de catalisador e de corante, com o catalisador comercial e precursor de Ti, P25 Degussa. Além da determinação da atividade fotocatalítica, foram feitas as seguintes análises para caracterização dos materiais: difração de raios X (DRX), espectroscopia de refletância difusa (ERD), microscopia eletrônica de transmissão (MET) e determinação da área específica e volume de poros. A partir dos ensaios fotocatalíticos observou-se que os tratamentos a que foram submetidos os materiais tiveram grande influência na sua atividade catalítica. Sob radiação UV nenhum catalisador foi mais ativo que o P 25. Sob radiação visível, as amostras dopadas com tiouréia (NTT-4-500/TiouréiaI) e amônia (NTT-7-600/NH3I) apresentaram os melhores resultados, com um aumento na fotodegradação de 16 e 30 % em relação às amostras não dopadas, respectivamente. / This work presents the study of the catalytic performance of nanostructured titanium oxide, TiO2, doped with nitrogen in order to improve its photocatalytic activity under visible light. TiO2 nanotubes were prepared by hydrothermal method, where TiO2 particles react with NaOH at high temperature and pressure. Then the material was handled through an acid wash and calcination, in order to produce desirable characteristics for the photocatalyst applications. The best conditions for titania nanotubes preparation were determined by varying the pH of the wash water and calcination temperature. Established these conditions, the research focused on obtaining among three nitrogen doping the one that provided best performance of nanotubes. They were: ammonium hydroxide, urea and thiourea. The degradation reaction of rhodamine B dye was used to evaluate the photocatalytic activity of catalyst. The experiments were performed in a stirred batch reactor, with the catalyst in suspension and in the presence of aeration, in the presence of UV and visible radiations. Initially the reaction conditions, such as catalyst and dye concentrations, were determined with the commercial catalyst and Ti precursor, P25 Degussa. In addition to determining the photocatalytic activity, the material characterization was made by X-ray diffraction (XRD), diffusive reflectance spectroscopy (DRS), transmission electron microscopy (TEM) and determination of specific area and pore volume by N2 absorption isotherms. The photocatalytic tests showed that the acid washed and calcination had a strong influence on its photocatalytic activity. No synthesized catalyst presented a larger photodegradation activity under UV light than P25. Under visible light, the samples doped with thiourea (NTT-4-500/TiouréiaI), and ammonia (NTT-7-600/NH3I) showed the best results with an increase in the photodegradation activity of 16 and 30% compared to the undoped samples, respectively.

No presente trabalho foi realizado o estudo do desempenho de catalisadores nanoestruturados de dióxido de titânio, TiO2, dopados com diferentes metais (prata, ouro, cobre, paládio e zinco), a fim de promover um aumento da atividade fotocatalítica sob radiação visível. Os experimentos foram realizados em um reator batelada de vidro, com controle de temperatura e catalisador em suspensão, sob radiação UV e visível, usando-se rodamina B (RhB) como molécula teste. Além disso, foram avaliadas as condições de reação, como as concentrações de catalisador e de corante, e do catalisador comercial P-25 Degussa. Para síntese dos nanotubos de TiO2 utilizou-se o método hidrotérmico, que consiste na reação de partículas de TiO2 com uma solução aquosa de NaOH sob temperatura e pressão elevadas, seguida de lavagem ácida e calcinação. Foram determinadas as melhores condições de obtenção dos nanotubos, variando-se o pH da solução de lavagem e temperatura de calcinação, antes da dopagem com metais. Além da avaliação da atividade fotocatalítica, a difração de raios X (DRX), espectroscopia de reflectância difusa (ERD), microscopia eletrônica de transmissão (MET) e a determinação da área específica e volume de poros foram utilizadas para caracterização dos fotocatalisadores dopados e dos nanotubos de TiO2 (NTTs). Pelos ensaios fotocatalíticos observou-se que os tratamentos a que foram submetidos os materiais tiveram grande influência na sua atividade catalítica. Sob radiação UV apenas o catalisador dopado com paládio foi mais ativo que o P 25, com uma degradação de 93%. Sob radiação visível, as amostras dopadas com prata (NTT-4-600/Ag+UV e NTT-4-600/Ag+escuro), paládio (NTT-4-500/Pd) e ouro (NTT-4-500/AuI) apresentaram os melhores resultados, em relação às amostras não dopadas, com degradação de 19%, 11%, 17% e 16% respectivamente. / The performance of nanostructured titanium dioxide catalysts doped with different metals was studied (silver, gold, copper, palladium and zinc), in order to promote an increase in the photocatalytic activity under visible light. The experiments were performed in a glass batch reactor with controlled temperature and catalyst in suspension under UV and visible radiation for rhodamine B (RhB) degradation. In addition, was evaluated the reaction conditions such as catalyst and dye concentration, and the performance of the commercial catalyst TiO2 Degussa P-25. TiO2 nanotubes were synthesized by hydrothermal method, which consists of the reaction of TiO2 particles with aqueous NaOH solution under elevated temperature and pressure, followed by acid washing and calcining. Before the doping metals were determined the best conditions for to obtain nanotubes, by varying the pH of the wash and calcination temperature. In addition to the evaluation of photocatalytic activity, the X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM) and determine the specific area and pore volume were the techniques used for characterization of doped photocatalysts and TiO2 nanotubes (NTTs). The photocatalytic tests showed that the treatments had a great influence on its catalytic activity. Under UV radiation only doped with palladium catalyst was more active than the P 25, with a 93% degradation. Under visible light, the samples doped with silver (NTT-4-600/Ag+UV e NTT-4-600/Ag+dark), palladium (NTT-4-500/Pd) and gold (NTT-4-500/ AuI) showed the best results, with a degradation 19%, 11%, 17% e 16% respectively.

Esta tese investigou o efeito da taxa de resfriamento em partículas de Al2O3, Al2O3 - TiO2, e Al2TiO5 aspergidas por pistola a plasma e submetidas a diferentes taxas de resfriamento (alta: aspersão contra um substrato metálico a 100 mm de distância da pistola de plasma, e baixa: contra uma superfície de água, a 300 mm de distância). Os resultados foram avaliados por microscopia eletrônica de varredura (com EDX) e por difração de raio X para a caracterização de fases e cálculo de tamanho de cristalito por Single Line. O óxido Al2TiO5 na forma de pó quase amorfo com composição estequiométrica de tialita (tialita*) aspergido foi obtido por coprecipitação, a partir dos precursores TiCl4 e Al(NO4)3, tratado termicamente a 400, 600, 800, 900, 1000, 1200, 1300 e 1400 °C, com 6 h de patamar. Nos tratamentos térmicos com 6 horas de patamar a 800 °C e mais nitidamente a 900 °C, é identificada a formação parcial da fase tialita; desta forma, foram realizados tratamentos térmicos a 900, 1000 e 1100 °C, porém com 30 minutos de patamar. A Al2O3-a com tamanho de cristalito micrométrico foi obtida para menores taxas de resfriamento. Com o aumento da taxa de resfriamento, predominaram nanocristalitos de alumina Al2O3-g, coexistindo com fase amorfa. Já para a titânia, a fase rutilo pode ser obtida mesmo com altas taxas de resfriamento. Quando a tialita* foi submetida à alta taxa de resfriamento, levou exclusivamente à formação da fase metaestável tialita b como estrutura cristalina. No entanto, o mesmo pó, a taxas de resfriamento não tão altas, resultou na obtenção de tialita b, Al2O3-a e rutilo. Tratamentos térmicos da tialita* propiciaram a formação de tialita b, e incipientemente anatásio, com tamanho de cristalito muito pequeno (abaixo de 30 nm). À medida que a temperatura de tratamento térmico aumentou, surgiram simultaneamente as fases Al2O3-a, rutilo e tialita b. A obtenção de fases metaestáveis só foi possível quando o tamanho de cristalito era pequeno – abaixo de 100 nm, o que evidenciou a importância do número de átomos na superfície, como fator de estabilização (ou metaestabilização) de fases obtidas foras do equilíbrio. / This thesis investigated the effect of cooling rate of Al2O3, Al2O3 - TiO2 and Al2TiO5 particles plasma sprayed and subjected to different cooling rates (high: to spray against a metal substrate to 100 mm away from the plasma gun, and low: against a surface of water, 300 milimeters away). The results were evaluated by scanning electron microscope (with EDX) and X ray diffraction to characterize phases and crystallite size through Single Line. The sprayed Al2TiO5 oxide was a quasi-amorphous powder with stoichiometric composition of tialite (tialita*) obtained by co-precipitation from precursors TiCl4 and Al(NO4)3, heat treated at 400, 600, 800, 900, 1000, 1200, 1300 and 1400 °C with 6 hours of dwell. In the heat treatments with 6 hour of dwell at 800 ° C and more explicitly at 900 °C, is identified partial formation of tialite phase; then, heat treatments were performed at 900, 1000 and 1100 ° C, but with 30 minutes of dwell. Basically, a-Al2O3 with micrometer crystallite size was obtained for smaller cooling rates. By increasing the cooling rate, there were predominantly g-Al2O3 nanocrystallites coexisting with amorphous phase. However, for the titania, the rutile phase could be obtained even with high cooling rates. When tialita* was subjected to high cooling rate, exclusively, metastable b tialite was observed as crystalline phase. However, the same powder, with cooling rates not so high, resulted in b tialite, a-Al2O3 and rutile. Heat treatments of tialita* provided the formation of b tialite, and incipiently anatase with crystallite size very small (below 30 nm). As the heating treatment temperature was increased, there were simultaneously a-Al2O3, rutile and b tialite phases. Metastable phases were obtained only when the crystallite size was small - less than 100 nm. This highlighted the importance of the number of atoms on the surface as a stabilizing factor (or metastabilization) to produce phases out of equilibrium.

Esta tese investigou o efeito da taxa de resfriamento em partículas de Al2O3, Al2O3 - TiO2, e Al2TiO5 aspergidas por pistola a plasma e submetidas a diferentes taxas de resfriamento (alta: aspersão contra um substrato metálico a 100 mm de distância da pistola de plasma, e baixa: contra uma superfície de água, a 300 mm de distância). Os resultados foram avaliados por microscopia eletrônica de varredura (com EDX) e por difração de raio X para a caracterização de fases e cálculo de tamanho de cristalito por Single Line. O óxido Al2TiO5 na forma de pó quase amorfo com composição estequiométrica de tialita (tialita*) aspergido foi obtido por coprecipitação, a partir dos precursores TiCl4 e Al(NO4)3, tratado termicamente a 400, 600, 800, 900, 1000, 1200, 1300 e 1400 °C, com 6 h de patamar. Nos tratamentos térmicos com 6 horas de patamar a 800 °C e mais nitidamente a 900 °C, é identificada a formação parcial da fase tialita; desta forma, foram realizados tratamentos térmicos a 900, 1000 e 1100 °C, porém com 30 minutos de patamar. A Al2O3-a com tamanho de cristalito micrométrico foi obtida para menores taxas de resfriamento. Com o aumento da taxa de resfriamento, predominaram nanocristalitos de alumina Al2O3-g, coexistindo com fase amorfa. Já para a titânia, a fase rutilo pode ser obtida mesmo com altas taxas de resfriamento. Quando a tialita* foi submetida à alta taxa de resfriamento, levou exclusivamente à formação da fase metaestável tialita b como estrutura cristalina. No entanto, o mesmo pó, a taxas de resfriamento não tão altas, resultou na obtenção de tialita b, Al2O3-a e rutilo. Tratamentos térmicos da tialita* propiciaram a formação de tialita b, e incipientemente anatásio, com tamanho de cristalito muito pequeno (abaixo de 30 nm). À medida que a temperatura de tratamento térmico aumentou, surgiram simultaneamente as fases Al2O3-a, rutilo e tialita b. A obtenção de fases metaestáveis só foi possível quando o tamanho de cristalito era pequeno – abaixo de 100 nm, o que evidenciou a importância do número de átomos na superfície, como fator de estabilização (ou metaestabilização) de fases obtidas foras do equilíbrio. / This thesis investigated the effect of cooling rate of Al2O3, Al2O3 - TiO2 and Al2TiO5 particles plasma sprayed and subjected to different cooling rates (high: to spray against a metal substrate to 100 mm away from the plasma gun, and low: against a surface of water, 300 milimeters away). The results were evaluated by scanning electron microscope (with EDX) and X ray diffraction to characterize phases and crystallite size through Single Line. The sprayed Al2TiO5 oxide was a quasi-amorphous powder with stoichiometric composition of tialite (tialita*) obtained by co-precipitation from precursors TiCl4 and Al(NO4)3, heat treated at 400, 600, 800, 900, 1000, 1200, 1300 and 1400 °C with 6 hours of dwell. In the heat treatments with 6 hour of dwell at 800 ° C and more explicitly at 900 °C, is identified partial formation of tialite phase; then, heat treatments were performed at 900, 1000 and 1100 ° C, but with 30 minutes of dwell. Basically, a-Al2O3 with micrometer crystallite size was obtained for smaller cooling rates. By increasing the cooling rate, there were predominantly g-Al2O3 nanocrystallites coexisting with amorphous phase. However, for the titania, the rutile phase could be obtained even with high cooling rates. When tialita* was subjected to high cooling rate, exclusively, metastable b tialite was observed as crystalline phase. However, the same powder, with cooling rates not so high, resulted in b tialite, a-Al2O3 and rutile. Heat treatments of tialita* provided the formation of b tialite, and incipiently anatase with crystallite size very small (below 30 nm). As the heating treatment temperature was increased, there were simultaneously a-Al2O3, rutile and b tialite phases. Metastable phases were obtained only when the crystallite size was small - less than 100 nm. This highlighted the importance of the number of atoms on the surface as a stabilizing factor (or metastabilization) to produce phases out of equilibrium.

No presente trabalho foi realizado o estudo do desempenho de catalisadores nanoestruturados de dióxido de titânio, TiO2, dopados com diferentes metais (prata, ouro, cobre, paládio e zinco), a fim de promover um aumento da atividade fotocatalítica sob radiação visível. Os experimentos foram realizados em um reator batelada de vidro, com controle de temperatura e catalisador em suspensão, sob radiação UV e visível, usando-se rodamina B (RhB) como molécula teste. Além disso, foram avaliadas as condições de reação, como as concentrações de catalisador e de corante, e do catalisador comercial P-25 Degussa. Para síntese dos nanotubos de TiO2 utilizou-se o método hidrotérmico, que consiste na reação de partículas de TiO2 com uma solução aquosa de NaOH sob temperatura e pressão elevadas, seguida de lavagem ácida e calcinação. Foram determinadas as melhores condições de obtenção dos nanotubos, variando-se o pH da solução de lavagem e temperatura de calcinação, antes da dopagem com metais. Além da avaliação da atividade fotocatalítica, a difração de raios X (DRX), espectroscopia de reflectância difusa (ERD), microscopia eletrônica de transmissão (MET) e a determinação da área específica e volume de poros foram utilizadas para caracterização dos fotocatalisadores dopados e dos nanotubos de TiO2 (NTTs). Pelos ensaios fotocatalíticos observou-se que os tratamentos a que foram submetidos os materiais tiveram grande influência na sua atividade catalítica. Sob radiação UV apenas o catalisador dopado com paládio foi mais ativo que o P 25, com uma degradação de 93%. Sob radiação visível, as amostras dopadas com prata (NTT-4-600/Ag+UV e NTT-4-600/Ag+escuro), paládio (NTT-4-500/Pd) e ouro (NTT-4-500/AuI) apresentaram os melhores resultados, em relação às amostras não dopadas, com degradação de 19%, 11%, 17% e 16% respectivamente. / The performance of nanostructured titanium dioxide catalysts doped with different metals was studied (silver, gold, copper, palladium and zinc), in order to promote an increase in the photocatalytic activity under visible light. The experiments were performed in a glass batch reactor with controlled temperature and catalyst in suspension under UV and visible radiation for rhodamine B (RhB) degradation. In addition, was evaluated the reaction conditions such as catalyst and dye concentration, and the performance of the commercial catalyst TiO2 Degussa P-25. TiO2 nanotubes were synthesized by hydrothermal method, which consists of the reaction of TiO2 particles with aqueous NaOH solution under elevated temperature and pressure, followed by acid washing and calcining. Before the doping metals were determined the best conditions for to obtain nanotubes, by varying the pH of the wash and calcination temperature. In addition to the evaluation of photocatalytic activity, the X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM) and determine the specific area and pore volume were the techniques used for characterization of doped photocatalysts and TiO2 nanotubes (NTTs). The photocatalytic tests showed that the treatments had a great influence on its catalytic activity. Under UV radiation only doped with palladium catalyst was more active than the P 25, with a 93% degradation. Under visible light, the samples doped with silver (NTT-4-600/Ag+UV e NTT-4-600/Ag+dark), palladium (NTT-4-500/Pd) and gold (NTT-4-500/ AuI) showed the best results, with a degradation 19%, 11%, 17% e 16% respectively.