The purpose of this study was to investigate preservice science teachers&rsquo / mental models about the role and distribution of ozone layer and ozone layer depletion regarding their ontological orientation. This study was conducted with twenty four preservice science teachers who were enrolled in Elementary Science Education Program of Education Faculty of one public university located in Central Anatolia. From each grade level six preservice science teachers were selected / two from low achiever, two from middle achiever and two from high achiever. Moreover, in the study, data were collected by using semi structured interview and interview consists of eleven questions and with five questions having multiple parts. Interview recordings were transcribed and analyzed qualitatively. In the following steps of the analysis, researcher proceeded with the already formed and described codes in an easygoing way. The results revealed that preservice science teachers&rsquo / responses were mostly seen as skin cancer and sunburn as harmful effects of ultraviolet rays and preservice science teachers&rsquo / responses were mostly seen as activation vitamin D and photosynthesis of plants as beneficial effects of Sun&rsquo / s rays. Half of preservice science teachers thought that ozone layer exists in the atmosphere. Moreover, preservice science teachers&rsquo / responses were mostly seen as perfume, deodorant, car, and spray as harmful materials to ozone layer. Chlorofluorocarbon, carbon monoxide, and carbon-dioxide were the most seen responses as harmful chemicals to ozone layer. Similar misconceptions were identified when compared with past studies. Also, different misconceptions were found in the study. Ten distinct models were formed regarding role and distribution of ozone layer and five distinct models were formed regarding ozone layer depletion. Moreover, absorbing and reflecting surface was mostly seen ontological belief regarding role and distribution of ozone layer. Hole was mostly seen ontological belief regarding ozone layer depletion. Generally, achievement and grade level did not make difference among preservice science teachers forming which type of mental models and having ontological beliefs.

In this study, we introduce novel, truly non-ionic hydrogen-bonded layer-by-layer (LbL) coatings for cell surface engineering capable of long-term support of cell function. Utilizing the LbL technique imparts the ability to tailor membrane permeability, which is of particular importance for encapsulation of living cells as cell viability critically depends on the diffusion of nutrients through the artificial polymer membrane. Ultrathin, permeable polymer membranes are constructed on living cells without a cationic pre-layer, which is usually employed to increase the stability of LbL coatings. In the absence of the cytotoxic PEI pre-layer, viability of encapsulated cells drastically increases to 94%, as compared to 20-50% in electrostatically-bonded shells. Engineering surfaces of living cells with natural or synthetic compounds can mediate intercellular communication, render the cells less sensitive to environmental changes, and provide a protective barrier from hostile agents. Surface engineered cells show great potential for biomedical applications, including biomimetics, biosensing, enhancing biocompatibility of implantable materials, and may represent an important step toward construction of an artificial cell.

A challenge exists for understanding the origin of color for structurally colored, 3-dimensional bioorganic nanostructures, such as the scales of butterflies, beetles, and moths. Complex, hierarchical structures found within such scales create the overall scale appearance. The controlled alteration of color through material deposition and the addition of new optical functionalities to such structures are other areas of scientific interest. This dissertation addresses these challenges with a first-of-its-kind, systematic isolation (deconstruction) of scale component nanostructures, followed by evaluation of optical property/structure correlations. The additive deposition (constructive alteration) of emissive materials to structurally-colored templates complements this deconstructive approach towards understanding the origin of color in butterfly scales. Discoveries made through this work may help advance the bioinspired design of synthetic optical structures and subsequent color control through the addition of multilayered, emissive optical components.

Oral mucositis is a painful and debilitating chronic inflammatory condition that can result from chemo and/or radiotherapy. While current treatment strategies which provide temporary relief exist, there is still an unmet clinical need for a robust long active barrier strategy which can simultaneously provide protection and release drug to enhance the wound healing response. It is proposed that an affinity based layer-by-layer self-assembled barrier administered as a series of mouth rinses can allow for wound specific drug delivery, providing an effective regenerative therapy. In this work, biotinylated poly(acrylic acid) is used to develop LBL assemblies based upon biotin-streptavidin affinity interactions. To explore the ability of developed LBL assemblies to resist the harsh intraoral environment, in vitro chemical and ex vivo mechanical tests are performed. The stability results demonstrate significant LBL barrier stability with wear resistance. From principal component regression analysis, factors such as polymer MW and number of layers in assemblies contributed significantly to chemical barrier stability. Also it is observed that the extent of biotin conjugation plays a significant role in LBL development and in mechanical stability. Thus, the proposed affinity based multilayered assemblies with their excellent barrier properties offer a modular treatment approach in oral mucosal injuries.

Ce projet s’inscrit dans la contribution à l’élaboration de tenues de protection vis-à-vis d’agents chimiques de guerre : les combinaisons actuelles ont un rôle de barrière, qui stoppent le contaminant sans le dégrader, conduisant à un risque de contamination croisée accru. L’idée novatrice est de recouvrir ces textiles avec une couche intelligente multifonctionnelle et transparent associant un composé actif (TiO2, capable de photo-oxyder les composés toxiques sous irradiation à température ambiante) à un composé passif (nanostructures carbonées, permettant de stocker temporairement les produits de réaction ou le contaminant en cas de manque de lumière ou de pic de contamination). L’étude a commencé sur surfaces modèles afin d’optimiser l’association par assemblages par la méthode Layer-by-Layer (LbL) des différents éléments à savoir, TiO2 à un polymère (PDDA), à du graphène, à du charbon actif ou encore à des nanodiamants. L’efficacité photocatalytique de cette couche sur la dégradation d’un simulant gazeux du gaz moutarde a été testée. Les meilleures revêtements ont ensuite été transférés sur textile et leur efficacité évaluée sur un simulant liquide du gaz Sarin. Des études plus spécifiques ont également été menées pour comprendre l’influence des différents constituants et de l’épaisseur sur l’efficacité photocatalytique du film. Le renforcement de ces textiles fonctionnels contre des contraintes d’abrasion et de lavage a aussi été étudié, ainsi que sa régénération après tests photocatalytiques. / This project is focused on the elaboration of protective suits against Chemical Warfare Agents. Indeed, the suits currently used mainly act as physical barriers, without any degradation of the toxic molecules, thus increasing cross-contamination risks.The original idea is to functionalise textile fibers with a multifunctional, multicomponent and transparent smart layer, combining active components (TiO2, for photo-oxidation of toxic agents under irradiation at room temperature) to passive components (carbon nanostructures, in order to temporary stock the reaction products or the contaminant in case of lack of irradiation or of high contamination level). The study begins on model surfaces, in order to optimise Layer-by-Layer (LbL) association of TiO2 with polymer, graphene, activated carbon, or nanodiamonds. The photocatalytic efficiency of the layer was evaluated towards the degradation of a gaseous mustard gas simulant. The best functionalisations were then transferred to textile and their photocatalytic efficiency were evaluated towards the degradation of a liquid simulant of Sarin gaz. Some detailed results were obtained in order to understand the impact of the different components and of the thickness of the films on the activity. Textiles reinforcement against abrasion and washing were also studied, as well as their regeneration after photocatalytic tests.

Orientador: Carlos José Leopoldo Constantino / Banca: Aldo Eloizo Job / Banca: Patrícia Alexandra Antunes / Banca: Neri Alves / O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp / Resumo: Esta dissertação apresenta o estudo do crescimento (em escala nanométrica) e morfológica (em escala micrométrica) de filmes finos fabricados segundo a técnica Layer-by-Layer (LbL) contendo ftalocianina tetrasulfonada de níquel, polímeros condutores, o polímero poli(alilamina hidroclorada) (PAH), e gomas naturais. Três sistemas foram investigados: i) filmes LbL de NiTsPc e PAH; ii) filme LbL de NiTsPc, PAH e gomas naturais e iii) filmes LbL dos polímeros condutores polianilina (PANI) e poli(o-metoxianilina) (POMA) com gomas naturais. As gomas utilizadas neste trabalho foram extraídas das árvores cajueiro (Anacardium occidentale), chichá (Sterculia striata), caraia (Sterculia urens) e angico (Anadenanthera macrocarpa Benth). As caracterizações destes filmes foram realizadas por meio das técnicas de espectroscopia eletrônica utilizando absorção na região do ultravioleta-visível (UV-vis), espectroscopia vibracional por espalhamento micro-Raman e por absorção na região do infravermelho (IV) com transformada de Fourier (FTIR). Os resultados deste trabalho mostraram que, somente os filmes de NiTsPc e PAH em pH 8,5 e os filmes de NiTsPc, PAH e gomas naturais apresentaram crescimento controlado, uniformidade morfológica e química. / Abstract: This dissertation presents the study of growth (in nano-scale thickness) and morphology (micrometric scale) of thin films produced using the Layer-by-Layer technique (LbL) containing nickel tetrasulfonated phthalocyanine, conducting polymers, the polymer poly(allylamine hydrochloride) (PAH), and natural gums. Three systems were investigated: i) LbL films of NiTsPc and PAH; ii) LbL films of NiTsPc, PAH and natural gums and iii) LbL films of the conducting polymers polyaniline (PANI) and poly (o-methoxyaniline) (POMA) with natural gums. The gums used in this work were obtained from the cashew (Anacardium occidentale), chicha (Sterculia striata), caraia (Sterculia urens) and angico (Anadenanthera macrocarpa Benth) trees. The characterizations of the LbL films were made using the ultraviolet-visible (UV-vis) absorption spectroscopy, vibrational spectroscopy through micro-Raman scattering and Fourier Transform infrared (FTIR) absorption. The results showed that only the LbL films of NiTsPc and PAH at pH 8.5 and the LbL films of NiTsPc, PAH and natural gums present controlled growth and morphological and chemical uniformity. / Mestre

Made available in DSpace on 2016-06-02T20:36:10Z (GMT). No. of bitstreams: 1 DissFTS.pdf: 2833638 bytes, checksum: 674f7848802feac6027a9471c4dcc7e0 (MD5) Previous issue date: 2003-05-19 / Universidade Federal de Minas Gerais / In this work, the electrochemical characterization of a self-assembled film containing two conductive polymers, poly(o-methoxyanilina)(POMA) and poly(3- thiophene acetic acid)(PTAA), is presented. The technique that allows to obtain these films is known as layer-by-layer (LBL) deposition. It consists in a spontaneous adsorption of species with opposite charges. The technique used for the electrochemical characterization was cyclic voltammetry coupled with mass variation using an electrochemical quartz crystal microbalance (EQCM), which allows the characterization of the LBL film mass/charge transport during the redox process. Electroacoustic impedance experiments of the LBL films with different number of bilayers show that the viscoelastic and mechanic tension properties do not change significantly in the potential range studied. Therefore, allowing the use of the Sauerbrey equation for converting the frequency values in mass values. The charge compensation mechanism was determined using the species flux (ions+solvent molecules) compared with POMA those casting films. The POMA-PTAA LBL film presents a charge compensation mechanism due to simultaneous intercalation of cations and anions. This behavior suggests the existence of a pseudo-self-doping mechanism related to carboxilic lateral groups interactions through the alternating layers structure of POMA-PTAA. The charge in the deprotonated carboxilic groups neutralize the charge generation of the imina groups present in the POMA backbone, which gives a decrease of the total mass change of the film. In this sense, the LBL technique could be an alternative method to prepare conducting polymer films modifying their electrochemistry properties. / Este trabalho tem como objetivo a caracterização dos processos eletroquímicos em filmes automontados contendo dois polímeros condutores, a poli (o-metoxianilina)(POMA) e o poli(ácido-3-tiofeno acético)(PTAA). A técnica que permite a obtenção destes filme é conhecida como layer by layer (LBL) e consiste na adsorção espontânea de espécies carregadas com cargas espaciais opostas. A caracterização eletroquímica foi realizada utilizando a técnica de voltametria cíclica acoplada à microbalança de cristal de quartzo eletroquímica (MCQE). Através dela foi possível analisar os processos de transferência de massa e carga que ocorrem nos filmes LBL durante o processo redox. Além disso, medidas de impedância eletroacústica revelaram que os filmes LBL com diferente número de multicamadas não apresentam variações consideráveis em suas propriedades viscoelásticas e mecânicas, justificando o uso da Equação de Sauerbrey. As espécies que participam do mecanismo de compensação de carga puderam ser determinadas com o auxílio das curvas de fluxo de espécies (íons+moléculas do solvente), permitindo a comparação com filmes de poli(o-metoxianilina) obtidos por evaporação do solvente. O filme LBL de POMA-PTAA apresentou um mecanismo de compensação de carga diferente do observado em filme de POMA obtido por evaporação do solvente. Neste caso, o mecanismo de compensação de carga no filme LBL apresentou uma participação simultânea de espécies catiônicas e aniônicas durante o processo redox. Este comportamento sugere a presença de uma pseudo-autodopagem relacionada com as interações dos grupos carboxílcos laterais através da estrutura das multicamadas alternadas de POMA-PTAA. A carga presente nos grupos carboxilatos auxiliam na compensação de cargas geradas nos grupos imina da POMA, proporcionando uma diminuição da massa transportada da solução para manter a condição de eletroneutralidade. Os resultados obtidos demonstraram que a técnica de automontagem pode ser um método alternativo na fabricação de filmes de polímeros condutores com modificações em suas propriedades eletroquímicas.

La technique d'auto-assemblage couche par couche de polyélectrolytes, permettant de construire des films appelés « multicouches », s'est grandement développée au cours des deux dernières décennies. Cette technique permet non seulement de modifier des surfaces de matériaux mais également d'élaborer des membranes auto-supportées. Dans cette thèse, j'ai étudié la croissance de deux systèmes multicouches assemblés dans des conditions extrêmes de pH pour accélérer leur croissance. Les films à base de poly(ethylene imine) et d'acide poly(acrylique) ont été utilisés pour réaliser, d'une part, des membranes possédant une capacité à répondre à l'humidité, et d'autre part, des membranes asymétriques présentant des propriétés anti-bactériennes. Les films à base de poly(L-lysine) et de hyaluronane ont été réalisé par croissance amplifiée par le pH, et l'effet du poids moléculaire du HA sur la croissance et les propriétés interne des films a été étudié. Ces films ont servi de réservoir pour le piégeage de précurseurs métalliques, qui ont ensuite été réduit in situ par irradiation UV, afin de former des nanoparticules. Ainsi, des films nanocomposites contenant des particules d'argent et des particules d'or ont été synthétisés. / Layer-by-layer assembly has witnessed great development during the two last decades and has expanded its application from surface modification to membrane construction. In this thesis, I studied the buildup of layer-by-layer films assembled at extreme pH (i.e. pH-amplified). I first focused on the fabrication of free-standing film made of poly(ethylene imine) and poly(acrylic acid). An application was to use these films as humidity sensors and a second one was to load silver ions in the films to create anti-bacterial membranes. Then, I worked on poly(L-lysine)/hyaluronan films and I investigated the effect of HA molecular weight on film growth and internal properties. Finally, nanocomposites were made via in situ synthesis of metal NPs in (PLL/HA) films: silver NP loaded (PLL/HA) free-standing films were constructed and their mechanical properties were tested; well dispersed gold NPs with sizes ranging from ~2 nm to ~9 nm were synthesized in (PLL/HA) films.

Submitted by Livia Mello (liviacmello@yahoo.com.br) on 2016-09-13T12:30:44Z No. of bitstreams: 1 DissRNS.pdf: 2358374 bytes, checksum: bd765e801c40083c7519f443a638ca3d (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-15T13:27:29Z (GMT) No. of bitstreams: 1 DissRNS.pdf: 2358374 bytes, checksum: bd765e801c40083c7519f443a638ca3d (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-15T13:27:40Z (GMT) No. of bitstreams: 1 DissRNS.pdf: 2358374 bytes, checksum: bd765e801c40083c7519f443a638ca3d (MD5) / Made available in DSpace on 2016-09-15T13:27:50Z (GMT). No. of bitstreams: 1 DissRNS.pdf: 2358374 bytes, checksum: bd765e801c40083c7519f443a638ca3d (MD5) Previous issue date: 2016-01-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / The great interest in supramolecular assemblies between porphyrins and phthalocyanines has growing lately due to the enhancement on chemical and physical properties compared to individual units. Ionic assemblies with metalloporphyrins and metallophthalocyanines grafted with ionic substituents of opposite charges stand out due to favorable formation and electronic density coupling between the macrocycles rings in a face-to-face array. Most of the reports in the literature on these kinds of arrangements is limited to its solution behavior. The main goal of this work were to synthesize and isolate heterocomplexes of 4,4’,4’’,4’’’- irontetracarboxyphthalocyanine (FeTcPc), or 4,4’,4’’,4’’’- irontetrasulfophthalocyanine (FeTsPc), with irontetrakis(n-metil-4-pyridyl)porphyrin (FeTMPyP). Three tetrapyrrolic macrocycles precursors were synthesized and characterized, and the heterocomplex formation was investigated by spectroscopic titration of FeTMPyP aqueous solution with FeTsPc or FeTcPc. The heterocomplex stoichiometry was determined by Job’s method. The stoichiometry of the heterocomplexes was not affected by the substituents and dyads FeTsPc/FeTMPyP and FeTcPc/FeTMPyP were obtained in both cases. For the first time, dyads were isolated from solution, and characterized by infrared (IR) and ultraviolet-visible (UV-Vis) spectroscopies, thermal analysis, and cyclic voltammetry. A significant change in the macrocycles electronic levels were observed due to the electronic coupling in a face-to- face arrangement. FeTsPc/FeTMPyP dyad presented an extensive orbital mixing, higher than FeTcPc/FeTMPyP dyad. IR analysis showed an additional interaction through coordination of bridged ligand between the metallic centers. Thermogravimetric analysis of the heterocomplexes showed a different degradation profile of the macrocycles in each dyad, which indicated that interaction between the macrocycles in each heterocomplex might be different. Electrostatic Layer-by-Layer technique (LbL) was applied and thin films of macrocycle precursors, mixed films (by intercalating precursor layers), and dyads were obtained. FeTcPc, FeTsPc, and FeTMPyP macrocycles exhibited a linear transfer up to 48 bilayers. The mixed film between FeTsPc and FeTMPyP showed similar spectral properties to FeTsPc/FeTMPyP dyad in solution indicating that similar macrocycles array in the mixed films over the deposition. The cyclic voltammetry of the macrocycles and dyads in solution showed that, in both cases, metallic centers electronic densities were affected by dyad formation, but macrocyclic redox processes was more affected in FeTcPc/FeTMPyP. The immobilization shifted the electrochemical redox process for cathodic potentials. The results indicated that interaction between the macrocycles in the dyads occur via two mechanisms, by ligand bridged interaction between the metallic centers, and by electrostatic attraction of the peripheral substituents. / Arranjos supramoleculares mistos contendo porfirinas e ftalocianinas tem despertado interesse devido a possibilidade de que os arranjos mistos apresentem propriedades superiores àquelas das unidades individuais. Neste contexto, arranjos iônicos entre metaloporfirinas e metaloftalocianinas se destacam devido a simplicidade de síntese e possibilidade do acoplamento das densidades eletrônicas dos macrociclos no arranjo face-a-face. Na literatura, pouco é abordado sobre arranjos deste tipo, sendo os estudos limitados ao comportamento em solução. Portanto, os objetivos principais deste trabalho foram sintetizar e isolar heterocomplexos formados pela combinação da 4,4’,4’’,4’’’- tetracarboxiftalocianina de ferro(FeTcPc) ou da 4,4’,4’’,4’’’-tetrassulfoftalocianina de ferro (FeTsPc) com a tetrakis(N-metil-4-piridil)porfirina de ferro(FeTMPyP), e investigar como o substituinte periférico pode afetar a formação e as propriedades do heterocomplexo. Para tal, foram sintetizados e caracterizados os três complexos precursores e a formação de heterocomplexos investigada através de titulações espectroscópicas, utilizando soluções aquosas da porfirina (FeTMPyP) e de uma das ftalocianinas (FeTsPc ou FeTcPc). A estequiometria dos heterocomplexos foi determinada utilizando o método de Job. A formação das díades FeTsPc/FeTMPyP e FeTcPc/FeTMPyP demonstrou que o substituinte periférico não afetou diretamente a estequiometria do heterocomplexo. As díades foram isoladas da solução, pela primeira vez, e caracterizadas por espectroscopia de absorção na região do infravermelho (i.v) e do UV-Vis, análise térmica e voltametria cíclica. Observou-se uma mudança significativa dos níveis eletrônicos dos macrociclos devido a interação entre as densidades eletrônicas no arranjo face-a-face. A díade FeTsPc/FeTMPyP apresentou uma maior perturbação dos níveis eletrônicos do que a FeTcPc/FeTMPyP, indicando um maior acoplamento entre as densidades eletrônicas. A análise por espectroscopia no i.v. mostrou que, além da interação eletrostática, existe uma interação adicional via ligante em ponte, que parece possuir maior participação no contato entre os complexos nas díades. Análises termogravimétricas dos heterocomplexos foram realizadas mostrando um perfil de degradação diferenciado dos precursores individuais para cada díade, indicando que a interação existente entre os macrociclos em cada heterocomplexo pode ser diferente. Filmes finos utilizando a técnica Layer-by-Layer foram montados para os complexos precursores, para filmes mistos, ao intercalar camadas dos precursores, e para as díades. Os complexos metálicos FeTcPc, FeTsPc e FeTMPyP se mostraram bons polieletrólitos, com deposição linear até 48 bicamadas. O filme misto entre FeTsPc e a FeTMPyP, apresentou propriedades semelhantes a díade FeTsPc/FeTMPyP em solução, indicando que os complexos adotam um arranjo similar no filme misto. As medidas de voltametria cíclica dos complexos e das díades em solução apresentaram processos do macrociclo e do centro metálico, e a resposta eletroquímica foi modificada com a imobilização nos filmes finos. Os resultados, de maneira geral, indicam que a interação entre os complexos precursores nas díades ocorre por dois mecanismos, através de uma ligação em ponte entre os centros metálicos e através da atração eletrostática dos substituintes periféricos.

CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Devido o contínuo desenvolvimento tecnológico e o crescimento populacional, o consumo de energia vem sendo cada vez maior ao longo dos anos. Neste aspecto, a fotocatálise atrai grande interesse devido seu potencial no aproveitamento da energia solar. No cenário nacional, os niobatos lamelares são materiais interessantes para atuarem como fotocatalisadores, uma vez que o Brasil detém 98% das reservas de nióbio no mundo. Dentro deste contexto, o presente trabalho apresenta as possibilidades do K4Nb6O17 como fotocatalisador tanto na forma em pó como imobilizado em filmes finos. O K4Nb6O17 foi preparado a partir da reação em estado sólido do Nb2O5 com K3CO2 e esfoliado em solução de hidróxido de tetrabutilamônio. O niobato esfoliado foi então modificado com platina, comparando-se dois diferentes precursores H2PtCl6 e [Pt(NH3)4]Cl2, e também combinado à nanopartículas de ouro. As amostras foram caracterizadas por diferentes técnicas e o desempenho fotocatalítico avaliado tanto para fotodegradação de azul de metileno e metanol como para a produção de H2. Na fotodegradação do corante, o niobato esfoliado sem qualquer co-catalisador apresentou a maior eficiência fotônica (ξ = 2,1%). Em contraste, para a fotodegradação de metanol e para a produção fotocatalítica de H2, as amostras modificadas apresentaram maior desempenho fotocatalítico em relação ao niobato esfoliado. Na produção de H2, foram obtidas eficiências fotônicas próximas a 0,2% para as amostras contendo tanto Pt como Au. Já na fotodegradação de metanol, as amostras de niobato e Pt resultaram em eficiências próximas a 4,0% e a modificada com ouro, 7,0%. A fabricação de filmes pode melhorar a aplicação dos fotocatalisadores por facilitar sua recuperação, prevenir perdas e diminuir a aglomeração de material. Os filmes de niobato e niobato com Pt foram montados utilizando a técnica Layer-by-Layer (LbL) devido sua facilidade e versatilidade. Os filmes foram caracterizados quanto às suas propriedades morfológicas, fotocatalíticas e fotoeletroquímicas. Na fotodegradação de azul de metileno, ambos os filmes resultaram em eficiências fotônicas semelhantes (ξ = 0,1%). Em contrapartida, para a produção fotocatalítica de H2, a presença da Pt nos filmes resultou em uma eficiência duas vezes maior (ξ = 1,2%) em relação ao filme de niobato (ξ = 0,6%). O aumento do número de bicamadas ocasionou o aumentou linear da velocidade de produção de H2, indicando que a imobilização do material não ocasionou a perda de sítios ativos. / As the technological development and population growth continuously increases, energy consumption is becoming higher over the years. In this aspect, photocatalysis attracts great interest due to its potential to harvest and convert solar energy. In a national scenario, layered niobates are interesting materials to act as photocatalysts, since Brazil accounts for 98% of the world’s niobium reserves. In this work application of K4Nb6O17 as a photocatalyst both, in powder form and immobilized as thin films, was investigated. K4Nb6O17 was prepared by the solid state reaction between Nb2O5 and K2CO3 and then it was exfoliated in tetrabutylammonium hydroxide solution. The exfoliated niobate was modified with platinum using two different precursors, H2PtCl6 and [Pt(NH3)4]Cl2, and it was also combined with gold nanoparticles. The samples were characterized by different techniques and the photocatalytic performance was evaluated for methylene blue and methanol oxidation and for H2 production. In the dye photodegradation, the unmodified exfoliated niobate exhibited the highest photonic efficieny (ξ = 2.1%). In contrast, for the methanol photodegradation and H2 evolution, the modified samples presented higher photocatalytic performance than the exfoliated niobate. For H2 evolution, photonic efficiencies close to 0.2% were obtained for samples modified by Pt and Au. For methanol photodegradation, the Pt-niobate composites exhibited photonic efficiencies close to 4.0% and the Au-niobate 7.0%. The assembly of thin films can favor the application as photocatalysts due to ease of recovering, smaller losses and reduced material agglomeration. The bare niobate and the Pt-niobate films were assembled by the Layer-by-Layer (LbL) technique because of its easiness and versatility. The films were characterized towards their morphology, photocatalytic and photoelectrochemical properties. For methylene blue photodegradation, both films resulted in similar photonic efficiencies (ξ = 0.1%). In contrast, for the H2 photocatalytic production, the presence of Pt in the films resulted in a photonic efficiency twice higher (ξ = 1.2%) than the bare niobate film (ξ = 0.6%). The increase in the bilayers number caused a linear increase of the H2 evolution rate, indicating that the material immobilization did not lead to the active sites losses. / Dissertação (Mestrado)