With the rapid proliferation of carbon nanotube technologies and consumer products comes a need to research the toxicological and ecotoxicological effects of these materials. This research attempted to develop a baseline knowledge of the effects of bulk, unmodified multi-walled carbon nanotubes on commonly studied soil toxicology test organisms: earthworms, springtails, and agricultural plants. In order to minimize confounding factors in the study, a slurry composed of bulk multi-walled carbon nanotubes, silica sand, and water was used to amend test soil without the use of surfactants or functionalization. Analysis of data produced by these experiments showed no significant trends resulting from the exposure of the test organisms to artificial soil amended by the multi- walled carbon nanotube slurry. It was observed, however that carbon nanotubes accumulated in the gut of the earthworm Eisenia andrei and were expelled as castings in the test soil.

This research work focuses on single wall carbon nanotube (SWNT)/polymer composites and novel structured electrospun polymer materials. Poly (methyl methacrylate) (PMMA) is used as polymer matrix. Obtaining SWNT/PMMA composite with enhanced mechanical and electrical properties is one of the research goals. The first important step is to figure out a method for achieving uniform SWNT dispersion in PMMA. Eight different solvents were used to disperse SWNT in PMMA. It is found that the polar component of the solubility parameter (£_p) of the solvent affects SWNT dispersion in PMMA. SWNT dispersion in PMMA improves with increasing solvent Ôp value, and the most uniform dispersion is obtained in nitromethane, which is the most polar solvent employed in this study. SWNT/PMMA composite films at various SWNT concentrations were processed employing nitromethane as the solvent. Mechanical and electrical property enhancements are observed. Processing, structure, morphology, and properties of these composites are discussed. A comparison between reinforcement efficiency of SWNT, multiwall carbon nanotubes (MWNT), and vapor grown carbon nano fibers (VGCNF) in PMMA is also discussed. In order to electrospin SWNT/PMMA/nitromethane solution into composite nanofibers successfully, first PMMA was electrospun. With increasing solution concentration, morphology of the electrospun polymer changed from particles to fibers. At relatively low solution concentrations, micro- and nano-structured polymer particles, and at higher solution concentrations, porous and solid nanofibers are observed. SWNT/PMMA/nitromethane solution was electrospun into polymer shell-SWNT core nanofibers. Solvent characteristics play an important role on particle or fiber mat morphology. The qualitative relationship between solvent properties (evaporation rate, dielectric constant, surface tension, and viscosity) and particle morphologies is discussed. By tailoring solution properties and electrospinning conditions, one can produce particles or fibers with controlled morphology for specific applications.

Thesis--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 235-246).

Thesis (M.S.)--Rochester Institute of Technology, 2009. / Typescript. Includes bibliographical references (leaves 115-120).

Η βασική ιδέα της μεταπτυχιακής εργασίας είναι η παρασκευή νανοσυνθέτων υλικών πολυμερικής μήτρας νανοσωλήνων άνθρακα και ο προσδιορισμός των μηχανικών τους ιδιοτήτων. Ως συνιστώσα ενίσχυσης, χρησιμοποιήθηκαν λεπτές μεμβράνες νανοσωλήνων άνθρακα (buckypapers) που αποτελούν δίκτυα υψηλού πορώδους. Παρασκευάζονται μέσω διήθησης αιωρημάτων νανοσωλήνων άνθρακα από φίλτρα με μικρό μέγεθος πόρων (< 1 μm), παρουσία κενού. Οι τελικές ιδιότητες των buckypapers επηρεάζονται από ποικίλες παραμέτρους, όπως η χημική οξείδωση των νανοσωλήνων, ο χρόνος διασποράς, το μέγεθος του κενού και το είδος του διαλύτη. Στην εργασία αυτή παρασκευάστηκαν buckypapers από νανοσωλήνες άνθρακα πολλαπλού τοιχώματος, οξειδωμένων είτε με νιτρικό οξύ είτε με υπερμαγγανικό κάλιο και μελετήθηκε η επίδραση του διαφορετικού μέσου οξείδωσης και διαφορών στη διαδικασία παραγωγής. Τα ξηραμένα buckypapers που παρασκευάστηκαν αποδείχτηκε ότι ήταν ομογενή, ομαλά και χωρίς ατέλειες, επιδεικνύοντας εξαιρετική δομική ακεραιότητα. Η ομογενή και πυκνή μορφολογία παρατηρήθηκε όχι μόνο στις επιφάνειες, αλλά και στο εσωτερικό των buckypaper. Νανοσύνθετα υλικά υψηλής περιεκτικότητας σε νανοσωλήνες άνθρακα παρήχθησαν με δύο διαφορετικές μεθόδους – απλή εμβάπτιση των φιλμ σε διάλυμα ρητίνης και εμποτισμός με φιλμ ρητίνης σε αυτόκλειστο φούρνο (Resin Film Infusion, RFI). Και στις δύο περιπτώσεις παρατηρήθηκε πλήρης διαβροχή του δικτύου των νανοσωλήνων με πολυμερές. Τα υλικά μελετήθηκαν ως προς τις μηχανικές τους ιδιότητες. Κάτω από συγκεκριμένες συνθήκες, τα σύνθετα υλικά επέδειξαν βελτιωμένη μηχανική συμπεριφορά σε σχέση με αυτήν της πολυμερικής μήτρας. / The basic concept of this master thesis is the preparation of nanocomposite materials of polymeric matrices and buckypapers and the determination of their mechanical properties. Buckypapers are thin sheets of entangled carbon nanotubes (CNTs), which are highly porous networks. They are prepared by vacuum filtration of well-dispersed CNT suspension. Final properties of buckypapers can be affected with various factors, such as chemical oxidation of nanotubes, sonication time, vacuum pressure and solvent. Buckypapers from MWCNTs oxidized by either nitric acid or potassium permanganate were prepared. The effect of different oxidation treatment of MWCNTs and different procedure conditions on the mechanical properties of buckypapers is studied. Dry buckypapers prepared by vacuum filtration of well-dispersed CNT - water solution were uniform, smooth and crack-free disks exhibiting significant structural integrity. Homogeneous and dense morphology is achieved not only on the surface but also through the thickness of the buckypapers. High-volume fraction CNT composites were produced by two different techniques – simple soaking with resin solution or autoclave resin film infusion (RFI). In both cases, full impregnation of CNT network with polymer was observed. The materials were tested to determine their mechanical properties. Some of prepared buckypapers-composites showed significant improved mechanical performance.

Ο σχεδιασμός καινοτόμων νανοδομημένων μεμβρανών αποτελεί μία πολλά υποσχόμενη λύση για την αποτελεσματική και χαμηλού κόστους επεξεργασία των λυμάτων. Συνεπώς, η επιλογή των κατάλληλων υλικών και η βελτιστοποίηση των ιδιοτήτων διαπερατότητας τους αποτελούν βασικά ζητήματα. Οι νανοσωλήνες άνθρακα αποτελούν μία πολύ ελκυστική επιλογή λόγω της ικανότητας απόρριψης οργανικών ρύπων χαμηλού μοριακού βάρους. Γι’ αυτό το λόγο, η διεξαγωγή μοριακών προσομοιώσεων είναι πολύ σημαντική, όσον αναφορά τη μελέτη της ρόφησης και της μεταφοράς των μορίων αυτών, έτσι ώστε να επιτευχθεί καλύτερος σχεδιασμός των υλικών. Στην παρούσα εργασία μελετήθηκε η αυτό-οργάνωση και η διάχυση μορίων χαμηλού μοριακού βάρους εντός νανοσωλήνων άνθρακα σε σχέση με τη διάμετρο των πόρων του. Αρχικά, με τη βοήθεια ενός ατομιστικού αλγορίθμου Monte Carlo, κατέστη δυνατή η μελέτη της ρόφησης και της δομής των μορίων νερού εντός των νανοσωλήνων άνθρακα, σε συνάρτηση με τη διάμετρο τους, ενώ ο αλγόριθμος μπορεί να επεκταθεί έτσι ώστε να μελετηθεί η αυτό-οργάνωση και άλλων μικρών μορίων. Στην περίπτωση μας, παρατηρήθηκε ισχυρή εξάρτηση της δομής του εγκλεισμένου νερού από τη διάμετρο των υδροφοβικών νανοπόρων. Ο δεύτερος ατομιστικός αλγόριθμος που αναπτύχθηκε βασίζεται στη μέθοδο της Μοριακής Δυναμικής (MD) και μας επιτρέπει να υπολογίσουμε τις δυναμικές ιδιότητες των μορίων που ροφώνται εντός του νανοσωλήνα άνθρακα, ως συνάρτηση πάλι της διαμέτρου του. Η εφαρμογή και των δύο αλγορίθμων (MC και MD) είναι πολύ σημαντική, καθώς αρχικά με την υλοποίηση του αλγόριθμου Monte Carlo (MC), χρησιμοποιώντας μια σειρά από δραστικές κινήσεις, μπορούν να μελετηθούν οι δομικές ιδιότητες του συστήματος που μας ενδιαφέρει. Στη συνέχεια, μπορούν να πραγματοποιηθούν προσομοιώσεις MD χρησιμοποιώντας ως αρχική απεικόνιση μία διαμόρφωση από το MC η οποία θα βρίσκεται σε κατάσταση θερμοδυναμικής ισορροπίας. Το γεγονός αυτό καθίσταται πολύ σημαντικό για αρκετά μεγάλα μόρια, των οποίων η προσομοίωση MD απαιτεί τεράστιο υπολογιστικό χρόνο, καθώς η ρόφηση εντός των νανοσωλήνων άνθρακα μπορεί να είναι αρκετά χρονοβόρα. Αντίθετα για μικρά μόρια, οι προσομοιώσεις Μοριακής Δυναμικής μπορούν να προβλέψουν αξιόπιστα τα χαρακτηριστικά της ρόφησης σε εύλογο χρονικό υπολογιστικό διάστημα. Μέχρι τώρα, έχουν υλοποιηθεί προσομοιώσεις MD για να προβλεφθεί η αυτό-οργάνωση και η υδροδυναμική συμπεριφορά όχι μόνο του νερού αλλά και άλλων μορίων (όπως η τυροσόλη, το βανιλλικό οξύ και το π-κουμαρικό οξύ) για πολυθρονικούς μονοφλοιικούς νανοσωλήνες άνθρακα, με τα αποτελέσματα να εμφανίζουν μεγάλη εξάρτηση από τη διάμετρο των πόρων των νανοσωλήνων. / The rejection of organic pollutants with low molecular weight, as well as the membrane fouling, should be considered fundamental aspects for the design of innovative nanostructured membranes for waste water treatment. The selection of the appropriate materials for the manufacturing of new membranes and the optimization of their permeability properties constitute key issues that one has to address for new, improved, and integrated separation processes. Carbon nanotubes (CNTs) exhibit the unique capability to reject low molecular weight solutes which renders them a very attractive alternative to conventional separation membranes. Their ability to transport or store fluids, particularly aqueous solutions at the nanoscale is a key parameter that one has to explore in terms of science and technological aspect. Therefore, a thorough understanding of the molecular distribution and the transport mechanisms of small molecules within CNTs is essential. Molecular simulations have proven to be a versatile tool for studying fluid characteristics within CNTs. In the present study, we have carried out detailed atomistic Grand Canonical μVT Monte Carlo (GCMC) and Molecular dynamics (MD) simulations of low-molecular weight compounds inside smooth single-wall carbon nanotubes (SWNTs) and studied their structural and dynamic properties as a function of the CNT diameter. The GCMC code is capable of probing the CNT loading of water molecules and their self-organization inside the tube as a function of its diameter, while the MD algorithm allowed us to compute also the dynamics of the absorbed molecules inside the CNT, again as a function of its diameter. For the case of water molecules, the results for the thermodynamic and structural properties obtained by both methods (Grand canonical MC and MD) were identical and demonstrated a highly ordered, hydrogen-bonded structure which depends strongly on the diameter of the nanotube. Ideally, the two methods should be used in a hierarchical way: first, with the help of the MC algorithm, and by making use of a set of drastic MC moves, one can study the nano-sorption properties of the compound of interest for a given CNT diameter. Then, MD simulations can be carried out using as initial configuration one obtained from the MC runs at the state of thermodynamic equilibrium. This is very important for rather large molecules whose sorption inside CNTs with a rather small diameter might take too long to complete in a brute-force MD simulation because it might require times longer than the few microseconds that can be accessed today on the most powerful supercomputers. But for small compounds, the MD simulations can reliably predict their nano-soprtion characteristics within reasonable CPU time. Therefore, MD simulations were employed to compute the sorption and structural properties not only of water but also of other molecules (such as hexane, decane, tyrosol, and vanilic acid) in arm-chair CNTs with several diameters. All of the results have been found to depend strongly on the diameter of the nanotube.

Made available in DSpace on 2014-06-11T19:27:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-14Bitstream added on 2014-06-13T20:55:49Z : No. of bitstreams: 1 ribeiro_b_me_guara.pdf: 3513331 bytes, checksum: c356674974d9d1db4ef22d6a6637cd7d (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A incorporação de nanotubos de carbono (CNT) em matrizes poliméricas pode originar materiais com propriedades superiores aos compósitos tradicionais, principalmente quando são consideradas propriedades térmicas, elétricas e tribológicas. Nesse sentido, o presente trabalho tem como objetivo o estudo das cinéticas de cristalização e de degradação de compósitos nanoestruturados de PA 6,6/ CNT. A obtenção dos compósitos nanoestruturados utilizados neste estudo foi realizada a partir da técnica de mistura em solução, onde foram obtidos filmes contendo poliamida 6,6 (PA 6,6) reforçada com CNT em quantidades de 0,1, 0,5, e 1,0% em massa. As análises por microscopia eletrônica de varredura e difração de raios-X foram utilizadas com o intuito de avaliar a qualidade da dispersão dos CNTs na matriz polimérica, bem como as propriedades cristalográficas do compósito nanoestruturado obtido. O estudo cinético de cristalização dos compósitos nanoestruturados foi realizado por meio da técnica de calorimetria exploratória diferencial (DSC) sob condições isotérmicas e não-isotérmicas (dinâmicas). Já o estudo da degradação térmica dos compósitos nanoestruturados de PA 6,6/CNT foi realizado utilizando-se de análises termogravimétricas em atmosfera de nitrogênio a diferentes taxas de aquecimento. Os resultados mostram que a adição de nanotubos de carbono na poliamida reduz o expoente de Avrami, afetando o processo de cristalização do material. A partir das curvas de TGA obtidas, foi utilizado o modelamento matemático de Ozawa-Wall-Flynn para a determinação dos parâmetros cinéticos de degradação. Neste estudo, os resultados mostram que a adição de CNTs em até 0,5% em massa aumentou a estabilidade térmica da poliamida / The carbon nanotubes incorporation into polymeric matrices can generate materials with superior properties when compared to the traditional composites, mainly when are considered thermal, electrical and tribological properties. In this way, this work presents as aim the PA 6.6/CNT nanostructured composites crystallization and degradation kinetics study. The mixing solution technique was used to obtain the nanostructured composites studied in this work. Thus, PA films were produced with amounts of 0.1, 0.5, and 1.0 wt% CNT. Analyses by using scanning electron microscopy and X-ray diffraction were performed in order to evaluate the CNTs dispersion quality in polymeric matrix, as well as the obtained nanostructured composite crystallographic properties. The nanostructured composites crystallization kinetic study was performed using the differential scanning calorimetry (DSC) under isothermal and non-isothermal (dynamic) conditions. The study of thermal degradation for PA 6.6/CNT nanostructured composites was performed by thermogravimetric analysis in nitrogen atmosphere at different heating rates. The results have showed that the addition of carbon nanotubes in polyamide reduces the Avrami exponent, affecting the crystallization process of the material. O-Z-W mathematical modeling was applied to the TGA results in order to calculate the degradation kinetic parameters. In this study, the results show that the CNTs addition in up to 0.5wt% increased the thermal stability of polyamide

Innate immune cells, such as macrophages, are trained by the unique microenvironment of the tissue they occupy. This tissue influence can include the extracellular matrix, the presence of inflammatory stimuli or signals and, in some tissues, the microbiota. Most studies, however, have examined such tissue specific training in health whereas little is known about the possibility of immune re-training in the lung following acute inflammation. The lung extracellular matrix is important for mechanical stability and structural support, as well as influencing inflammation via altering cell adhesion, migration, survival, proliferation and differentiation. Matrix alterations are a feature of a number of significant chronic respiratory diseases that carry high clinical unmet need. These include idiopathic pulmonary fibrosis, cystic fibrosis and chronic obstructive pulmonary disease (COPD). On the other hand, the impact on matrix after acute inflammation and whether it is returned to its pre-infection state is relatively unexplored. In murine models, macroscopic examination of the lung following acute inflammation implies a return to a reasonable homeostatic state. However, using more sensitive techniques, we now show that this is not the case. In this thesis we test the premise that a more thorough interrogation of lung extracellular matrix by mass spectrometry will reveal long term alterations that are not visible by histology. After influenza virus infection, we demonstrate that heightened extracellular matrix persists in the lung tissue, often forming structures that were not present in health. Furthermore, basement membrane components, for example collagen IV and laminin, are reduced. In vitro investigations show that individual extracellular matrix components affect lung macrophage activity. For example, hyaluronan and fibronectin alter macrophage expression of microRNA species known to influence toll-like receptor responsiveness and fibrosis. We also describe an alteration in microRNA species in response to influenza virus infection as well as a non-infectious model of pulmonary inflammation using carbon nanotubes. Collectively, this implies that altered matrix composition impacts on the inflammatory tone of the lung innate immune system. It is therefore feasible that such changes following severe lung inflammation could be overcome by targeting abnormal matrix production or degradation.

Orientador: Alexandre Fontes da Fonseca / Banca: Fernando Sato / Banca: Francisco Carlos Lavarda / 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 / Resumo: As propriedades especiais dos nanotubos de carbono (CNTs) inspiraram pesquisadores em diversas aplicações tecnológicas. Diversos produtos macroscópicos que são feitos ou contém nanotubos de carbono já existem como raquetes de tênis, tacos de beisebol, quadros de bicicletas, pás de turbinas eólicas e cascos de embarcações. A fim de de obter mais conhecimento sobre o comportamento desses produtos e materiais, seja para o desenvolvimento de novas aplicações ou melhorar as já existentes, é importante continuar investigação das propriedades físicas individuais dos nanotubos de carbono. Neste trabalho, utilizando ferramentas de simulação de dinâmica molecular, apresentamos os resultados para o coeficiente de expansão térmica de três nanotubos de carbono de duas camadas (DWCNTs "Double Walled (CNTs") (5,5)@(10,10), sem e com defeitos. Os defeitos considerados nesse estudo são de dois tipos: átomos de carbono intersticial e ligações do tipo sp entre as camadas. Validamos nossos métodos calculando o coeficiente de expansão térmica do nanotubo de carbono de uma camada (SWCNT "Single Walled CNT") (10,10) e comparando os resultados com os presentes na literatura. Nós mostramos que os defeitos reduzem, em módulo, o coeficiente de expansão térmica do (5,5)@(10,10) DWCNT. Discutimos esse resultado em comparação com o valor do coeficiente de expansão térmica do diamante / Abstract: The special properties of carbon nanotubes (NTs) have inspired researchers in many technological applications. Examples of macroscopic products that contain or are made of CNTs are tennis rackets, baseball bats, bicycle frames, ligthweiht wind turbine blades and boat hulls. In order to get more knowledge about the behavior of these products and materials, either to develop new applications or improve the actual ones, it is important to investigate the physical properties of individual CNTs in diverse situations. In this work, using tools of molecular dynamics simulations, we present three results for the coefficient of thermal expansion of the Double Walled CNTs (DWCNTs) (5.5)@(10,10) with and without defects. The types of defects considered here are carbon atoms at interstitial sites and sp connections between the walls of the (5,5)@(10,10) DWCNT. Our methods are, first, validate by the calculation of the coefficient of thermal expansion of the Single Walled CNT (SWCNT) (10,10) and the camparison of the result with that from the literature. We show that the coefficient of thermal expansion of the (5,5)@(10,10) DWCNT. This result is discussed in terms of the coefficient of thermal expansion of the diamond / Mestre

SILVEIRA, José Valdenir da. Microrreatores e sensores de gases baseados em nanotubos de carbono. 2014. 138 f. Tese (Doutorado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2014. / Submitted by Edvander Pires (edvanderpires@gmail.com) on 2014-09-12T20:16:40Z No. of bitstreams: 1 2014_tese_jvsilveira.pdf: 17216086 bytes, checksum: b751845b2b9448eb6e67f9368f248e62 (MD5) / Approved for entry into archive by Edvander Pires(edvanderpires@gmail.com) on 2014-09-12T20:22:36Z (GMT) No. of bitstreams: 1 2014_tese_jvsilveira.pdf: 17216086 bytes, checksum: b751845b2b9448eb6e67f9368f248e62 (MD5) / Made available in DSpace on 2014-09-12T20:22:36Z (GMT). No. of bitstreams: 1 2014_tese_jvsilveira.pdf: 17216086 bytes, checksum: b751845b2b9448eb6e67f9368f248e62 (MD5) Previous issue date: 2014 / This work exploits the fabrication, setup and tests of the micro-reactors and gas sensors based on carbon nanotubes. The configuration of the gas sensors was designed to allow the use of multi-walled carbon nanotubes - as commercially acquired, oxidized or decorated with nanoparticles – as sensor elements which have similar behavior to a sensor element formed of a single-walled carbon nanotube with large diameter (~ 20 nm). In this configuration, the nanotubes were deposited using dielectrophoresis technique with their ends supported on the edges of the electrodes and the central part suspended (bridged) over a gap ~ 1 m wide and ~5 m deep, in order to connect the ends of pre-produced standard metal electrodes. A new approach to improve the electrical and thermal contact between multi-walled carbon nanotubes deposited by dielectrophoresis and metal electrodes was developed by using heating spatially localized, through the use of laser radiation in the microRaman setup. Subsequent to deposition, the nanotubes were directly heated in the ambient atmosphere by a focused laser beam. The Raman signal of the nanotubes was used to determine the temperature reached in the process and this method has been used to improve the electrical contact with different electrodes (W, Ti and Au). The reduction in electrical resistance was up to three orders of magnitude, resulting in contact resistivity as low as ~ 0,1-1 kΩ.μm2, with the lowest values obtained for Au. A new method of simultaneous deposition of nanotubes and decoration with gold nanoparticles grown by electrochemical method is also presented. The method enables the production of hybrid structures with high potential for application in opto-electronic devices such as gas sensors, biosensors or photodetectors. The structural and morphological characterization of each sensor element used in this work was mainly made by scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, Raman spectroscopy and electrical measurements. Sensing elements with different combinations of nanostructured materials (MWCNTs as commercially acquired, oxidized, or decorated with metal nanoparticles) were tested in inert (Ar or N2) and oxidant (O2) atmosphere. Crucial parameters for the proper functioning of gas sensors (specific response time/recovery, sensitivity, stability, reproducibility, etc.) were investigated based on the obtained experimental data. / O presente trabalho explora a fabricação, montagem e testes de micro-reatores e de sensores de gás baseados em nanotubos de carbono. A configuração dos sensores de gases foi planejada de modo a permitir o uso de nanotubos de carbono de muitas paredes – como adquiridos comercialmente, oxidados ou decorados com nanopartículas - como elementos sensores de comportamento semelhante a um elemento sensor formado por nanotubos de carbono de uma única parede e com grandes diâmetros (~20 nm). Nesta configuração, os nanotubos foram depositados utilizando a técnica dieletroforese com as pontas apoiadas sobre as bordas dos eletrodos e com a parte central suspensa (em ponte) sobre um gap de ~1 m de largura por ~5 m de profundidade, de modo a ligar as extremidades de eletrodos metálicos padronizados pré-produzidos. Uma nova abordagem para melhorar o contato elétrico e térmico entre nanotubos de carbono de múltiplas paredes depositados por dieletroforese e eletrodos de metal foi desenvolvida, usando aquecimento espacialmente localizado, através do uso de laser. Subsequentemente à deposição, os nanotubos foram diretamente aquecidos, em atmosfera ambiente, por um feixe de laser focado. O sinal Raman dos nanotubos foi usado para determinar a temperatura atingida no processo e este método foi utilizado para melhorar o contato elétrico com diferentes eletrodos (W, Ti e Au). A redução na resistência elétrica foi de até três ordens de magnitude, resultando em resistividade de contato tão baixa quanto ~ 0,1-1 kΩ.μm2, com os menores valores obtidos para Au. Um novo método de deposição de nanotubos com simultânea decoração por nanopartículas de ouro crescidas pelo método eletroquímico também é apresentado. O método possibilita obtenção de estruturas híbridas com alto potencial de aplicação em dispositivos opto-eletrônicos, tais como sensores de gases, biossensores ou fotodetectores. A caracterização estrutural e morfológica de cada elemento sensor usado neste trabalho foi feita principalmente por microscopia eletrônica de varredura, microscopia eletrônica de transmissão, espectroscopia de energia dispersiva, espectroscopia Raman e medidas elétricas. Foram usados elementos sensores com diferentes combinações de materiais nanoestruturados (MWCNTs como adquiridos comencialmente, oxidados, ou decorados com nanopartículas metálicas), testados em atmosferas inertes (N2 ou Ar) e oxidante (O2). Parâmetros determinantes para um bom funcionamento dos sensores de gás (tempos específicos de resposta/recuperação, sensibilidade, estabilidade, reprodutibilidade, etc) foram investigados com base nos dados experimentais obtidos.