abstract: The object of this body of work is to study the properties and suitability of zinc oxide thin films with a view to engineering them for optoelectronics applications, making them a cheap and effective alternative to indium tin oxide (ITO), the most used transparent conducting oxides in the industry. Initially, a study was undertaken to examine the behavior of silver contacts to ZnO and ITO during thermal processing, a step frequently used in materials processing in optoelectronics. The second study involved an attempt to improve the conductivity of ZnO films by inserting a thin copper layer between two ZnO layers. The Hall resistivity of the films was as low as 6.9×10-5 -cm with a carrier concentration of 1.2×1022 cm-3 at the optimum copper layer thickness. The physics of conduction in the films has been examined. In order to improve the average visible transmittance, we replaced the copper layer with gold. The films were then found to undergo a seven orders of magnitude drop in effective resistivity from 200 -cm to 5.2×10-5 -cm The films have an average transmittance between 75% and 85% depending upon the gold thickness, and a peak transmittance of up to 93%. The best Haacke figure of merit was 15.1×10-3 . Finally, to test the multilayer transparent electrodes on a device, ZnO/Au/ZnO (ZAZ) electrodes were evaluated as transparent electrodes for organic light-emitting devices (OLEDs). The electrodes exhibited substantially enhanced conductivity (about 8×10-5 -cm) over conventional indium tin oxide (ITO) electrodes (about 3.2×10-5 -cm). OLEDs fabricated with the ZAZ electrodes showed reduced leakage compared to control OLEDs on ITO and reduced ohmic losses at high current densities. At a luminance of 25000 cd/m2, the lum/W efficiency of the ZAZ electrode based device improved by 5% compared to the device on ITO. A normalized intensity graph of the colour output from the green OLEDs shows that ZAZ electrodes allow for a broader spectral output in the green wavelength region of peak photopic sensitivity compared to ITO. The results have implications for electrode choice in display technology. / Dissertation/Thesis / Ph.D. Materials Science and Engineering 2010

Thesis (Master of Engineering in Mechanical Engineering)--Cape Peninsula University of Technology, 2017. / Transparent conductive oxides (TCOs), which are widely used in transparent electronics, possess a spectral selectivity that is suitable for a solar material absorber. TCO materials have a plasma wavelength in the infrared region. Consequently electromagnetic waves shorter than a plasma wavelength are transmitted through the material, while longer electromagnetic waves are reflected on the surface. In contrast to the opaque solar selective absorbers, the plasma wavelength in TCO materials can be easily tuned by controlling the heavy doping process to match the peak shift of thermal radiation at higher temperatures. Furthermore, the use of TCO in conjunction with a solar absorber relaxes the spectral selectivity of the latter and thus widens the selection of the solar absorber; subsequently the only requirement is a thermally stable black body. Aluminum doped Zinc Oxide (AZO) is a class of TCO materials which is cost effective to manufacture due to abundance ZnO, and Aluminum raw materials. This thesis is based on the synthesis of Al doped ZnO thin films nanostructure using radio frequency RF magnetron sputtering process. The influence of the deposition parameters, including argon working pressure and substrate temperature, on the structural and optical properties of the AZO thin films is investigated by means of X-ray diffraction (XRD) and optical spectroscopy (UV-VIS-NIR). The optical constants of AZO films are extracted from transmittance and reflectance spectra using a combination of Drude and Lorentz dielectric function model. A computer simulation is developed to calculate the radiative properties of Al doped ZnO thin films nanostructure. The thermal emittance and solar absorptance is predicted indirectly from optical reflectance and transmittance of AZO films by invoking Kirchhoff’s law. A Special attention has been paid to the parameters that influence the spectral properties of the AZO films including carrier’s mobility, Al doping concentration and film thickness. Carrier’s mobility turned out to have the most significant influence on the spectrally selective performance of AZO films.

Orientador: Neri Alves / Banca: Sidney Alves Lourenço / Banca: Edson Laureto / Banca: Lucas Fugikawa Santos / Banca: José Antonio Malmonge / Resumo: Transistores de filme fino de ZnO, cujo desempenho depende das condições de preparação da camada de ZnO e do dielétrico de gate, tem sido aplicados como sensores de radiação ultravioleta (UV), visando prevenir danos à saúde da pele. Este trabalho tem como objetivo a fabricação de transistores de ZnO/Al2O3, mediante o estudo simultâneo dos parâmetros relacionados à preparação das camadas de ZnO e Al2O3, bem como, o de transistores com dielétrico padrão (ZnO/SiO2) submetidos a diferentes condições de funcionamento. Estes estudos visam encontrar quais condições viabilizam as aplicações dos transistores como sensor UV. Os experimentos englobam a deposição de filmes de ZnO tanto por sputtering de um alvo de ZnO, quanto por spray pirolise de uma solução de acetato de zinco. O dielétrico SiO2 foi obtido comercialmente, enquanto que o Al2O3 foi crescido por anodização. Os transistores foram fabricados em diversas condições, as quais foram estabelecidas pelos métodos de planejamento experimental Taguchi e Plackett-Burman. As respostas das caracterizações foram interpretadas por técnicas de estatística (ANOVA). Os resultados demonstram que Al2O3 otimizado exibe correntes de fuga de até 10E-10 A e constante dielétrica de ~13. A identificação dos parâmetros mais importantes na preparação de filmes de ZnO por spray pirólise, permitiram produzir transistores de ZnO/Al2O3 com mobilidades de ~4,5 cm2/Vs. Os sensores UV, usando transistores de ZnO/SiO2 apresentaram mobilidades de 0,1 a 12 cm2... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: ZnO thin film transistors have been applied as ultraviolet (UV) radiation sensors in order to prevent damage to skin's health. However, the performance of ZnO transistor depends on the preparation conditions of both ZnO layer and gate dielectric. This work aims to produce and evaluate ZnO/Al2O3 transistors by studying simultaneously the parameters regarding the preparation of ZnO and Al2O3 layers, as well as the fabrication of ZnO transistors with a standard dielectric (ZnO/SiO2), under different conditions of working. It is intended to investigate the conditions to apply ZnO transistors as UV sensor. The experiments involve the deposition of ZnO films by sputter coating and spray pyrolysis of a solution of zinc acetate. SiO2 dielectric was commercially purchased, while Al2O3 was grown by anodization. The transistors were fabricated under different conditions, which were established by both experimental design Taguchi and Plackett-Burman methods. The responses from the characterization were interpreted by statistical techniques (ANOVA). The results showed that optimized Al2O3 films exhibit leakage current until 10E-10 A and dielectric constant of ~13. It was essential to identify the most important parameters regarding to preparation of ZnO films by pyrolysis spray in order to fabricate ZnO/Al2O3 transistors with mobilities of ~4,5 cm2/Vs. UV sensors based on ZnO/SiO2 transistors showed mobilities from 0,1 to 12 cm2/Vs and demonstrated that the sensitivity of the UV sensor de... (Complete abstract click electronic access below) / Doutor

Cu(In,Ga)(Se,S)2 (CIGS) solar cells have attracted a lot of attention due to their high performance and the prospect for lower manufacturing costs over conventional crystalline silicon solar cells. All recent record efficiency CIGS absorbers have been deposited using vacuum processing which introduces high manufacturing costs. CIGS can also be compatible with low cost, atmospheric processing which can significantly reduce manufacturing costs. Recently, there has been some progress in developing atmospheric solution-based processes for CIGS. Among different solution approaches, deposition of molecular precursors can be advantageous in terms of simplicity and straightforward compositional control. Nonetheless, the developed methodologies involve highly toxic reagents or large impurity content in the device, limiting the potential for commercialisation. This thesis describes the development of a novel solution-based approach for the deposition of CIGS absorber layers. Metal chalcogenides are used as the starting precursors, which are free from detrimental impurities. These compounds contain strong covalent bonds and, consequently, they are insoluble in common solvents. Until recently, hydrazine, which is highly toxic and explosive, was the only solvent to effectively dissolve these types of precursors, limiting the feasibility of this approach for industrial applications. In this work, metal chalcogenides are dissolved in a safer solvent combination of 1,2-ethanedithiol and 1,2-ethylenediamine, completely eliminating hydrazine from the process. By using this solvent system, optically transparent solutions are formed which exhibit long-term stability. The precursor solutions are decomposed cleanly and they are converted to single phase CIGS upon selenisation. CuIn(S,Se)2 solar cells with power conversion efficiencies up to 8.0% were successfully fabricated by spray depositing the precursor solution, followed by a selenisation step. This progress has been made by continuously optimising the deposition, drying, and especially the selenisation configuration. Among other parameters, the working pressure during selenisation was found to have a dramatic effect on the material crystalline quality. Rapid thermal processing was also explored as an alternative selenisation configuration to tube furnace annealing and it was shown to improve the back contact/absorber interface. It has been demonstrated that Ga can easily be incorporated in the absorber for band-gap tuning and, consequently, for VOC enhancement of the solar cells. The structural properties of the films were investigated with Ga content, as well as the opto-electronic characteristics of the corresponding solar cells. The band-gap of the material was conveniently varied by simply adjusting the precursor ratio, allowing for fine compositional control. By using this technique, Cu(In,Ga)(Se,S)2 solar cells with conversion efficiencies of up to 9.8% were obtained. The solar cell performance in this work is limited by the porosity of the absorber and the back contact quality. Despite a significant improvement during the course of this work, the remaining porosity of the absorber causes selenium to diffuse towards the back forming a thick MoSe2 layer and causing a high series resistance in the device. A low cost, solution-based technique was also developed for the deposition of aluminium-doped zinc oxide films that can be used as the transparent conductive oxide layer in thin film solar cells. This methodology involves the use of an ultrasonic spray pyrolysis system, which is a very versatile and easily controlled deposition technique. Although the presence of oxygen makes the film closer to stoichiometric (fewer oxygen vacancies) good electronic and optical properties have been obtained by process optimisation. Films deposited with optimum conditions exhibited a sheet resistance of 23 Ω/sq, which can be further reduced by increasing the thickness with minimal transmittance losses. The simplicity, low toxicity and straightforward control make the proposed methodologies extremely potential for low cost and scalable deposition of thin film solar cells.

Ag thin film growth on ZnO substrates has been investigated theoretically using multi-timescale simulation methods. The models are based on an atomistic approach where the interactions between atoms are treated classically using a mixture of fixed and variable charge potential energy functions. After some preliminary tests it was found that existing fixed charge potential functions were unreliable for surface growth simulations. This resulted in the development of a ReaxFF variable charge potential fitted to Ag/ZnO surface interactions. Ab initio models of simple crystal structures and surface configurations were used for potential fitting and testing. The dynamic interaction of the Ag atoms with the ZnO surface was first investigated using single point depositions, via molecular dynamics, whereby the Ag impacted various points on an irreducible symmetry zone of the ZnO surface at a range of energies. This enabled the determination of the relative numbers of atoms that could penetrate, reflect or bond to the surface as a function of incident energy. The results showed that at an energy of up to 10 eV, most atoms deposited adsorbed on top of the surface layer. The second part of the dynamic interaction involved a multi-timescale technique whereby molecular dynamics (MD) was used in the initial stages followed by an adaptive kinetic Monte Carlo (AKMC) approach to model the diffusion over the surface between impacts. An impact energy of 3 eV was chosen for this investigation. Ag was grown on various ZnO surfaces including perfect polar, O-deficient and surfaces with step edges. Initial growth suggests that Ag prefers to be spread out across a perfect surface until large clusters are forced to form. After further first layer growth, subsequent Ag atoms begin to deposit on the existing Ag clusters and are unlikely to join the first layer. Ag island formation (as mentioned within the literature) can then occur via this growth mechanism. O-deficient regions of ZnO surfaces result in unfavourable Ag adsorption sites and cause cluster formation to occur away from O-vacancies. In contrast, ZnO step edges attract deposited Ag atoms and result in the migration of surface Ag atoms to under-coordinated O atoms in the step edge. Various improvements have been made to the existing methodology in which transitions are determined. A new method for determining defects within a system, by considering the coordination number of atoms, is shown to increase the number of transitions found during single ended search methods such as the relaxation and translation (RAT) algorithm. A super-basin approach based on the mean rate method is also introduced as a method of accelerating a simulation when small energy barriers dominate. This method effectively combines states connected by small energy barriers into a single large basin and calculates the mean time to escape such basin. To accelerate growth simulations further and allow larger systems to be considered, a lattice based adaptive kinetic Monte Carlo (LatAKMC) method is developed. As off-lattice AKMC and MD results suggest Ag resides in highly symmetric adsorption sites and that low energy deposition events lead to no penetrating Ag atoms or surface deformation, the on-lattice based approach is used to grow Ag on larger perfect polar ZnO surfaces. Results from the LatAKMC approach agree with off-lattice AKMC findings and predict Ag island formation. Critical island sizes of Ag on ZnO are also approximated using a mean rate approach. Single Ag atoms are placed above an existing Ag cluster and all transition states are treated as belonging to a single large super-basin . Results indicate that small Ag clusters on the perfect ZnO surface grow in the surface plane until a critical island size of around 500 atoms is reached. Once a critical island size is reached, multiple Ag ad-atoms will deposit on the island before existing Ag atoms join the cluster layer and hence islands will grow upwards. A marked difference is seen for second layer critical island sizes; second layer Ag islands are predicted to be two orders of magnitude smaller (< 7 atoms). This analysis suggests that Ag on ZnO (0001) may exhibit Stranski-Krastanov (layer plus island) growth.

Orientador: Dayse Iara dos Santos / Banca: Manuel Henrique Leite / Banca: Alejandra Hortencia Miranda González / Resumo: Materiais nanoestruturados vêm sendo amplamente estudados pela comunidade científica, devido às suas propriedades únicas obtidas com o controle da síntese dos materiais. Por meio do controle experimental, esses materiais podem ser utilizados em numerosas áreas, tais como na eletrônica e na fotônica. Dentre os vários métodos químicos, o processo poliol vem sendo utilizado devido à fácil obtenção de nanopartículas de óxidos e metais na sua forma elementar. O presente trabalho teve como objetivo a síntese do óxido de zinco nanoestruturado por meio do método poliol. Diferentes precursores metálicos, tais como acetato de zinco dihidratado, nitrato de zinco hexahidratado, sulfato de zinco monohidratado e cloreto de zinco anidro e diferentes tempos de permanência da síntese foram utilizados para verificar possíveis interferências dos ânions precursores na síntese e na morfologia do óxido de zinco quando obtido. Os materiais obtidos das sínteses foram caracterizados por difração de raios X (DRX), análises térmicas (TG/DTA), medidas de adsorção de gás nitrogênio, microscopia eletrônica de varredura (MEV), microscopia eletrônica de varredura de alta resolução (MEV-FEG) e cronopotenciometria. Por meio destas técnias mostrou-se a viabilidade da obtenção do óxido de zinco nanoestruturado dd maneira direta a partir do acetato de zinco, através de refluxo em etilenoglicol por 2, 4 e 8 horas seguido de lavagem e centrifugação. A menor nanoestrutura encontrada apresentou partículas com dimensão de aproximadamente 25 nm e formato poliédrico, as quais foram observadas pelo FEG. A técnica de cronopotenciometria, representada por meio das curvas de carga/descarga mostraram que a utilização do compósito contendo o óxido de zinco sintetizado apresenta melhores resultados quando comparados ao uso... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Nanostructered materials have been extensively studied by the scientific community due to their unique properties obtained by controlled synthesis of materials. By means of the control of parameters, this new materials can be used in a number of applications in electronic and photonic technology. Among the several methods to obtain nanoparticles or nanostructured materials, the polyol method has been applied because it shows easy procedures to produce nanostructured oxides and elemental metals. The aim of this work is the synthesis of nanostructured zinc oxide, one of the most multifunctional oxides, by the polyol method. Different precursors salts like zinc acetate dihydrate, zinc nitrate hexahydrate, zinc sulfate monohydrate and zinc chloride anhydrate, as well as several times of reflux, were used to investigate the influence of the precursos anions on the synthesis and on the morphology of the crystals of zinc oxide whenever produced. The obtained powders were characterized by X-ray diffraction (DRX), thermal analyses (TG/DTA), and measurements of 'N IND. 2' gas adsorption, scanning electronic and field emission microscopy (MEV and FEG) and chronopotentiometry. These techniques showed the possibility of producing nanostructured zinc oxide in direct way from the reflux in etylenglycol for 2, 4 and 8 hours, followed by washing and centrifugation. The smallest nanostructure observed by FEG presented around 25 nm polyhedral particles. The chronopotentiometry, present charge/discharge curves showing better results for the electrode made of polimer composite containing ZnO nanoparticles than the obtaining results for the oxide alone. The best results showed reversibility of the lithium-ion cell upon 20 cycles, applying 3 μΑ electric current and showing a charge potential up to 4.2 V. / 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 / Mestre

Orientador: Dayse Iara dos Santos / Banca: Alejandra Hortencia Miranda González / Banca: Marcela Mohallem Oliveira / Resumo: O campo dos nanomateriais tem se expandido enormemente nas últimas décadas principalmente devido às suas propriedades especiais. As experiências descritas na literatura em grande gama de aplicações mostram propriedades elétricas, magnéticas, ópticas e outras, extremamente aperfeiçoadas com relação aos sisstemas macroscópios. A ciência e tecnologia trabalham atualmente com inúmeras técnicas químicas para a obtenção de óxidos e dentre elas destaca-se o Método Poliol por ser vantajoso e adequado na preparação de nanopartículas com variadas morfologias, dimensões e crisalinidade. Entretanto, poucos estudos foram realizados sobre a síntese e a caracterização de compósitos com o propósito de investigar as propriedades resultantes da possível sinergia obtida a partir da interação entre dois óxidos nanoestruturados. Este trabalho teve como objetivo a síntese e a caracterização de compósito nanoestruturado formado de dois óxidos multifuncionais: o óxido de zinco e o dióxido de titânio. Para a síntese foram utilizados o acetato de zinco dihidratado e o isopropóxido de titânio para a obtenção do ZnO e do TiO2, respectivamente. o compósito foi obtido pelo Método Poliol a partir da interrupção momentânea da síntese dos óxidos isolados seguido da mistura das soluções. O compósito, assim como os óxidos sintetizados isoladamente, foram caracterizados po9r difração de raios X (DRX), análise térmicas (TG/DTA), medidas de adsorção de gás nitrogênio (BET), microscopia eletrônica de varredura (MEV), espectroscopia de adsorção de luz na região do ultravioleta, visível e infravermelho, espectroscopia Raman. O compósito formado pelo Método Poliol apresentou o ZnO na forma aglomerado, porém nanoestruturado, e o TiO2 após tratamento térmico de 400º C. Foi verificada ainda a presença de resíduos orgânicos nos materiais como... (Resumo completo, clicar acesso / Abstract: The field of nanomaterials has expanded greatly in recent decades mainly due to its special propoerties. The experiments described in the literature in a wide variety of applications show electrical properties, magnetic, optical and others, extremely improvement properties with respect to macroscopic systems. Science a technology are currently working with numerous chemical techniques to achieve oxides and them stands out the Polyol Method to be advantageous and appropriate in the preparation of nanoparticles with various morphologies, size and crystallinity. However, few studies have been done on the synthesis and characterization of composites in order to investigate the resultants properties from possible synergy obtained from the interaction between two nanoestructured oxides. This work aimed to the synthesis and characterization nanostructured composites formed by two multifunctional oxides, zinc oxide and titanium dioxide. For the synthesis were used zinc acetate dihydrate and titanium isopropoxide to obtain the ZnO and TiO2, respectively. The composite was obtained by Polyol from the interruption of the synthesis of single oxides followed by mixing the solutions. The composite, as weell as oxides separately synthesized, were characterized by X-ray diffraction (XRD), thermal analysis (TG/DTA), meassurements of nitrogen gas adsorption (BET), scanning electron microscopy (SEM), YV-VIS and IR absorption spectroscopy and Raman spectroscopy. The composite obtained by the Polyol Method presented ZnO as agglomerate, however nanostructured, and TiO2 after heat treatment of 400ºC. It was also verified the presence of organic waste in the materials as synthesized and titanium glycolate as an intermediate in the reaction of titanium dioxide. A comparison of optical behavior, as synthesized composite formed by ZnO and titanium... (Complete abstract click electronic access below) / Mestre

Magister Scientiae - MSc (Chemistry) / Pulmonary Tuberculosis (TB) a disease second to HIV/AIDS is a global health problem that arises in two states; as an active state and as a latent state. Diagnosis of active TB is tedious and requires expensive procedures since there is no recognizable method for the sole detection of active TB. The current diagnosis consists of chest X-rays and multiple sputum cultures used for acid-fast bacilli detection. The TB diagnosis of children is particularly difficult which further complicates the diagnosis. Thus, rapid identification of this pathogen is important for the treatment and control of this infection to allow effective and timely therapy. In an effort to solve this issue, this study reports the development of immunosensors constructed with electroactive layers of amino groups functionalized graphene oxide (GO) doped respectively with green synthesized zinc oxide (ZnO NPs) nanoparticles and silver (Ag NPs) nanoparticles on glassy carbon electrodes. The surface morphology of GO, ZnO NPs, Ag NPs and their composites was revealed by employing High-Resolution Transmission Electron Microscopy (HR-TEM) and High-Resolution Scanning Electron Microscopy (HR-SEM) while the composition and structure of these materials were studied using Fourier Transform Infra-Red Spectroscopy (FTIR). The resultant graphene oxide-metallic composites were covalently attached with CFP-10 and/or ESAT-6 antibodies to achieve the electrochemical detection. The immunosensor was then used for the impedimetric and amperometric detection of anti-CFP-10 and/or anti-ESAT-6 antigens in standard solutions.

Nanofios semicondutores de óxido metálico apresentam enorme potencial em aplicações de nano-sensoriamento de diferentes gases e substâncias químicas e biológicas, bem como na aplicação a detectores UV-visível. Neste trabalho, desenvolvemos e aperfeiçoamos a síntese de nanofios de ZnO em substratos de safira (001), silício (111) e silício (100) sob diferentes concentrações de oxigênio usando o processo de transporte de vapor-liquido-sólido (VLS). No presente trabalho, investigamos a influência da concentração de oxigênio no crescimento de nanofios de ZnO por Espectroscopia de Fotoluminescência a temperatura variável com a finalidade de estudo da mudança na concentração de defeitos. Apresentamos, ainda, caracterizações elétricas (IxV e Ixt) de nanoestruturas de ZnO sob diferentes pressões com o objetivo de estudar os defeitos envolvidos nos processos de transportes eletrônicos. Por último, propomos o desenvolvimento de micro-contatos através da técnica de microfeixe iônico e através de nanolitografia por feixe de elétrons com a finalidade de aplicações a sensores químicos, gasosos e fotodetectores. / Metal oxide nanowires semiconductors have enormous potential in high-sensitive, fast and selective sensing applications. It may be used to selectively detect different gases, chemical and biological substances and also in UV-visible photodetectors. The described processes involve the synthesis as well as the characterization of ZnO nanowires grown on sapphire (001), silicon (100) e silicon (111) substrates by the Vapor-liquid-solid transport method. In the present work, we describe the influence of oxygen concentration introduced in the growth step measured by photoluminescence at variable temperature to demonstrate the change in defect levels emission (DLE). Furthermore, we have shown electrical characterization (IxV and Ixt) in order to study the ambient effect for transport mechanisms in ZnO nanowires. We also report the development of crucial steps in the fabrication for an upcoming ZnO nanowire sensor device (gas, chemical and photodetector) using lithography techniques such as ion micro-beam and electron beam with the purpose of fabricating metallic micro-pads.

Materiais nanoestruturados são caracterizados por terem tamanho de cristalito inferior a 100 nm e apresentarem propriedades diferenciadas em relação aos materiais convencionais. A intensificação da nanotecnologia como uma área de pesquisa vem gerando grandes expectativas na ciência de materiais, tendo em vista a vasta gama de novas propriedades físicas e químicas e as potencialidades tecnológicas decorrentes dos materiais nanoestruturados. O óxido de zinco (ZnO) encontra importantes aplicações tecnológicas em borrachas e tintas industriais. As propriedades químicas e microestruturais desse óxido, por sua vez, dependem do método de síntese empregado. Este trabalho teve como objetivo principal a síntese de óxido de zinco nanoestruturado através do método de combustão em solução e sua caracterização quanto às suas características microestruturais e atividade fotocatalítica. Como combustível utilizou-se o ácido cítrico. Para tanto, foram definidas as razões combustível/oxidante a partir de cálculo termodinâmico.Os produtos da reação de síntese foram caracterizados por difração de raios X (fases cristalinas presentes e tamanho de cristalito por single line), por microscopia eletrônica de varredura (análise morfológica), pelo método Branauer, Emmet e Teller - BET (área superficial), por análises térmicas (perda de massa e endo- ou exotermia sob aquecimento), por análise granulométrica (diâmetro médio do grão);Os resultados obtidos indicam que é possível obter ZnO nanoestruturado via síntese por combustão em solução utilizando ácido cítrico como combustível nas razões combustível/oxidante investigadas. Os produtos da síntese apresentaram características microestruturais e atividade fotocatalítica diferentes em função da quantidade de combustível utilizado no processo de combustão. Verificou-se a discordância do efeito da razão combustível/oxidante observado com o que é relatado na literatura para determinadas características dos produtos de reação.O tratamento térmico dos produtos da síntese influenciou diretamente na atividade catalítica de algumas amostras, conferindo-lhe aumento da cristalinidade. / Nanostructured materials are characterized by a crystallite size below 100 nm and display different properties compared to conventional materials. The intensification of nanotechnology as a research area has generated great expectations in materials science, taking into account the wide range of new physical and chemical properties and technological potential of the resulting nanostructured materials. Zinc oxide has important technological applications in rubber and industrial paints. The chemical properties and microstructure of ZnO powder depends on the synthesis method employed. This work aimed to the synthesis of nanostructured zinc oxide by combustion method and their mircrosctrucutural characterization and photocatalytic activity. As fuel was used the citric acid. To do so, the reasons were defined fuel / oxidizer from thermodynamic calculation.The products of the reaction of synthesis were characterized by diffraction of rays-X (present crystalline phases and size of cristallite by single line), by electronic microscopy of scan (morphological analysis), by the approach Branauer, Emmet and Teller - BET (superficial area), by thermal analyses (weight loss and endo- or exotermia under heating), by granulometric analysis (medium diameter of the grain). The results obtained indicate that is possible obtain ZnO nanostructured by synthesis Combustion in solution utilizing citric acid as fuel in the reasons fuel/oxidized investigated.The products of the synthesis presented characteristics microstructured and activity photocatalytic different in function of the quantity of fuel utilized in the porcedure of combustion. There was the disagreement of the effect of the reason fuel/oxidant observed with what is related in the literature for determined characteristics of the products of reaction.The thermal treatment of the synthesis directly influenced in the catalytic activity of some samples, giving it increased crystallinity.