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With a unique blend of power and energy densities, as well as long cycling lives, electrochemical supercapacitors are finding greater application in energy storage solutions. Among candidate materials for supercapacitors, MnO2 has garnered a great deal of attention. However, its low intrinsic electrical conductivity has proven to be a serious hindrance on performance when used in supercapacitor electrodes. Efficient use of conductive additives is a demonstrated, effective method to combat this problem, however there is still a great need for improvement. Two new colloidal processing techniques have been developed to mix chemically synthesized MnO2 and conductive multi-walled carbon nanotubes (MWCNT). The first strategy involved the linking of MnO2 and MWCNT through the formation of a Schiff base. 3,4-dihydroxybenzaldehyde (DB) was used to modify MnO2, while MWCNT were dispersed with the dye New Fuchsin (NF). These compounds were selected due to the presence of molecular features previously identified as conducive to strong adsorption and good colloidal dispersion, as well as the necessary functional groups required to form a Schiff base. The second involved the use of liquid-liquid extraction, primarily in an attempt to prevent post synthesis MnO2 particle agglomeration. Lauryl gallate (LG) was used as an extracting and dispersing agent for MnO2 synthesized via the reaction between aqueous potassium permanganate (KMnO4) and 1-butanol. LG facilitated the co-dispersion and mixing of both MnO2 and MWCNT in the 1-butanol phase. V2O3 was also investigated as a replacement for MnO2, as its high intrinsic electrical conductivity gives it a potential advantage over MnO2. In each of these three projects, electrodes were produced with exceptionally high areal normalized capacitances at high active mass loadings. The MnO2-MWCNT composites were used to fabricate full asymmetric supercapacitor devices that were able to deliver a useable amount of energy. / Thesis / Master of Applied Science (MASc) / The modern world has an insatiable appetite for energy and must have access to it for stationary and mobile applications. To meet this demand, it is of paramount importance to develop new, high performance energy storage technologies. The energy requirements for different applications, however, necessitate storage devices that have suitable properties. The energy stored in a large pool of hot water is not in a suitable form to power a cellphone. The key goal of this work was to further develop one particular energy storage technology, called electrochemical supercapacitors. Novel processing techniques were developed and new materials investigated with the aim of producing supercapacitor electrodes that would exceed the performance of what is already available today. The materials that were produced exhibited very high performance and offered new insight and direction for further research in this exciting field.

Yes / The effect of extruder screw configuration on the dispersion and properties of compatibilised polypropylene (PP)/multi‐walled carbon nanotube (MCNT) composite is investigated. Three principle screw designs with mainly conveying elements (medium intensity), kneading elements (high intensity), and folding elements (chaotic mixing) were used to prepare polypropylene nanocomposites containing 4wt% of maleic anhydride grafted polypropylene (MAH‐g‐PP) compatibilizer and different nanotube loadings. The effect of each screw configuration and nanotube loading on the tensile, rheological, and electrical properties of the nanocomposites were studied. The screw configurations were found to have a strong influence on the electrical resistivity while only slightly affected the tensile properties of the nanocomposites. Scanning electron microscopy examinations showed that the use of screw configuration consisting of kneading elements promoted the dispersion of nanotubes and resulted in a low electrical percolation at 2wt% of MCNT.

La chimie d'interface du diazonium a progressé au cours des dernières années et s'est pratiquement impliquée dans tous les domaines de la science et technologie des matériaux. L’utilisation des sels de diazonium est justifiée par le fait qu’ils adhèrent aux surfaces avec de fortes énergies de liaison, en particulier sur le carbone sp², ce qui en fait d’excellents agents de couplage pour les polymères aux surfaces. Dans ce contexte, nous avons travaillé sur deux types de nanohybrides de nanotubes de carbone (NTC) : NTC-polytriazole (NTC-PTAz) et NTC-colorant. Le nanohybride NTC-PTAz a été synthétisé par polymérisation « click » en surface. Pour ce faire, les NTCs ont été greffés de groupes 4-azidophényle à partir du sel de diazonium correspondant. Le NTC modifié (NTC-N3) a servi de support pour une polymérisation confinée en surface de type polyaddition générant ainsi le nanohybride NTC-PTAz. Ce matériau a été caractérisé par ATG, XPS, IR et Raman. Ses applications potentielles sont dans le développent d’adsorbants de métaux lourds, l’immobilisation de nanocatalyseurs ou pour le stockage des gaz. La seconde partie de la thèse est plus étoffée et porte sur les nanotubes de carbone greffés de colorants diazotés Rouge Neutre (NR), Azure A (AA) et Rouge Congo (CR). L’analyse fine de ces matériaux a révélé une très forte adhésion des colorants aux NTCs et les couches superficielles ont des épaisseurs de 2 à 6 nm, sont homogènes et continues. Les NTC-colorant ont été incorporés dans des matrices élastomères de type EVA pour la réalisation d’actionneurs opto-thermiques implantés dans des pads pour non-voyant. Dans les matrices EVA, les NTCs greffés de colorants servent à capter la lumière et induire un changement de forme dans le pad qui soit palpable par le non voyant (250 µm). Les matrices EVA renforcées de nos nanotubes greffés de colorants ont été réalisées et testées par analyse mécanique dynamique. Les composites NTC/colorant-EVA sont flexibles et prometteurs pour le développement de nouveaux types des pads tactiles pour les non-voyants. Les nanohybrides NTC-NR ont servi comme capteurs chémo-résistifs pour la reconnaissance moléculaire de l’acétone.Dans une dernière application, le nanohybride CNT-CR a été étudié en tant qu’électrocatalyseur pour l’oxydation directe du méthanol. Des résultats intéressants ont été obtenus avec ces nanohybrides mais des améliorations significatives (rapport 3) des propriétés électrocatalytiques ont été obtenues avec des CNT-CR décorés avec des nanoparticules d'or. Le système électrocatalytique nouvellement conçu pourrait être considéré pour différentes applications prometteuses, notamment les capteurs, les biocapteurs, les catalyseurs hétérogènes pour les piles à combustible. Pour résumer, les nanohybrides à base de CNT nouvellement conçus présentent des performances uniques attribuées à la polyvalence de la chimie d'interface du diazonium pour la fixation efficace de couches moléculaires et macromoléculaires fonctionnelles. Les nanohybrides novateurs servent de blocs de construction pour la conception de matériaux nanocomposites à hautes performances potentiellement utiles dans les nouveaux défis socio-économiques tels que l’environnement, la biomédecine et l’énergie / Diazonium interface chemistry has progressed over the last few years and practically involved in all areas of materials science and engineering. The rationale for employing diazonium salts is that they attach to surfaces with remarkable bond energies, particularly on sp² carbon materials, making them an ideal coupling agent for polymers to surfaces In this context, novel CNT-polytriazole (CNT-PTAz) and CNT-dye nanohybrids were designed and thoroughly characterized. First, CNT-PTAz nanohybrid was prepared by click polymerization: multiwalled carbon nanotubes (CNTs) were modified with azidophenyl groups (CNT-N3) from 4-azidobenzenediazonium precursor and served as nanoscale platform for the surface confined polyaddition. The CNT-PTAz nanohybrid was characterized by TGA, XPS, IR, and Raman. The robust CNT-PTAz is robust and has potential in developing heavy metal adsorbents, nanosupport for catalysts or for gas storage. In the second major part, we grafted CNT with diazotized Neutral red (NR), Azure A (AA) and Congo Red (CR) dyes by simple, spontaneous reaction of the diazonium salts and CNTs in water, at RT. A thorough investigation of the nanohybrids showed that the adhesion is strong (CNT-dye C-C bond energy higher than 150 kJ/mol), and the layer is uniform. These nanohybrids further served to reinforce ethylene-vinyl acetate (EVA) an elastomeric matrix. The reinforced matrix is flexible and serves as optothermal actuators where the grafted dye catches the light to induce mechanical changes in the matrix monitored by dynamic mechanical analysis. CNT/dye-reinforced EVA is a promising flexible composite for developing new types of visual-aid tablet for visually impaired people. The versatile CNT-dye nanohybrids are also unique chemiresistive gas sensors for the molecular recognition of acetone vapours. In a final application, CNT-CR nanohybrid was investigated as an electrocatalyst for the Direct Oxidation of Methanol. Interesting results were obtained with these nanohybrids but significant improvements (3-fold) of the electrocatalytic properties were achieved with CNT-CR decorated with gold nanoparticles. The newly designed electrocatalytic system could be regarded for different promising applications most likely as for sensors, biosensors, heterogeneous catalysts for fuel cells and for nanotechnology To summarize, newly designed CNT-based nanohybrids have unique performances ascribed to the versatility of the diazonium interface chemistry in efficiently attaching functional molecular and macromolecular layers. The novel nanohybrids serve as building blocks for designing high performance nanocomposite materials relevant to challenging timely social economic issues, namely environment, biomedicine and energy

Les capteurs sont des dispositifs ayant montré une utilisation répandue, allant de la détection des molécules en phase gazeuse au suivi de signaux chimiques dans les cellules biologiques. En général, un capteur est réalisé à partir d’un élément actif de détection et d’un signal transducteur produisant un signal de sortie qui peut être électrique, optique, thermique ou magnétique. Les électrodes à base de nanotubes de carbone à simple paroi et les électrodes à base de graphène se sont révélées être un matériau excellent pour le développement des biocapteurs électrochimiques, puisqu’ils montrent des propriétés électroniques remarquables et la capacité de se comporter en tant que nano-électrodes individuelles, un excellent transport de porteur de charge à faible dimension, et permettent de l’électrocatalyse de surface. Le travail présenté vise à la préparation et à l’étude d’électrodes de nanotubes de carbone à simple paroi et d’électrodes de graphène modifiées par voie électrochimique pour des applications dans le domaine des biocapteurs. Nous avons d’abord étudié les films de nanotubes de carbone à simple paroi et nous nous sommes intéressés à leur topographie, à leur composition de surface, et leurs propriétés électriques et optiques. Nous montrons que ces films sont homogènes avec une conductivité d’environ 200-300 Ω/□, et une transparence d’environ 40%. En parallèle aux nanotubes de carbone à simple paroi, des films de graphène ont été étudiés. Des valeurs de résistance plus élevées en comparaison avec les films de nanotubes ont été obtenues. La modification de surface par voie électrochimique des deux types d'électrodes a été étudiée en suivant deux voies, (i) l’électro-greffage de sels d’aryl diazonium, et (ii) l’addition électrophile de 1, 3- benzodithiolilyumtetrafluoroborate (BDYT). Les caractéristiques qualitatives et quantitatives de la surface modifiée des électrodes ont été étudiées, comme le degré de fonctionnalisation et la composition de surface. La combinaison de spectroscopie Raman, et de photoelectrons X- (XPS) de microscopie à force atomique (AFM),d'électrochimie et d’autres techniques, a montré que des précurseurs particuliers peuvent être ancrés de façon covalente à la surface des électrodes de nanotubes etde graphène, grâce à la formation de nouvelles liaisons carbone-carbone. Dans le premier cas (i), leur post-modification par des réactions de « clickchemistry» mène finalement à l’immobilisation sur la surface de l’électrode des groupes fonctionnels souhaités, comme des sondes/shuttles redox (e.g., un groupeferrocenyl) ou des groupements catalytiques (e.g., une enzyme). L'enzyme HRP(horse-radish peroxidase) a été, par exemple, immobilisée sur des surfaces de nanotubes de carbones à simple paroi modifiées par un groupe aryl, et l'étude voltammétrique a montré une réponse catalytique avec l’augmentation de la concentration de peroxyde d’hydrogène en solution, en suivant le « shuttle » redoxhydroquinone/benzoquinone à la surface de l’électrode. Dans le second cas (ii), l’addition électrophile de radicaux BDYT électro-générés a été étudiée pour la première fois sur des électrodes de nanotubes de carbone à simple paroi ou sur les électrodes de graphène. La combinaison de différentes techniques complémentaires a montré l’attachement covalent de BDYT aux électrodes de nanotubes de carbone à paroi simple. Une telle modification mène à la formation de rubans torsadés qui ont pu être observés et analysés par AFM et parmicroscopie électronique à balayage. Aucune preuve de la formation de rubans torsadés n’a pu être mise en évidence pour les électrodes modifiées à base de graphène. / Sensors are devices that have shown wide spread use, from the detection of gas molecules to the tracking of chemical signals in biological cells. In general, a sensor is made of an active sensing element and a signal transducer producing an electrical,optical, thermal or magnetic output signal. Single walled carbon nanotube (SWCNT) and graphene based electrodes have demonstrated to be an excellent material for the development of electrochemical biosensors as they display remarkable electronic properties and the ability to act as individual nanoelectrodes, display an excellent low-dimensional charge carrier transport, and promote surface electrocatalysis. The present work aims at the preparation and investigation of electrochemically modified SWCNT and graphene-based electrodes for applications in the field of biosensors. We initially studied SWCNT films and focused on their topography and surface composition, electrical and optical properties. We show that these films are homogeneous with thickness around 6̴ 0-70 nm, resistance values around 2̴ 00-300Ω/□, and transparency around 4̴ 0%. Parallel to SWCNTs, graphene films were investigated. Higher resistance values were obtained in comparison with nanotubes films.The electrochemical surface modification of both electrodes was investigated following two routes (i) the electrografting of aryl diazonium salts, and (ii) the electrophylic addition of 1, 3-benzodithiolylium tetrafluoroborate (BDYT). Both the qualitative and quantitative characteristics of the modified electrode surfaces were studied such as the degree of functionalization and their surface composition. The combination of Raman, X-ray photoelectron spectroscopy, atomic force microscopy, electrochemistry and other techniques, has demonstrated that selected precursors could be covalently anchored to the nanotubes and graphene-based electrode surfaces through novel carbon-carbon formation. In route (i), their post-modification by click-chemistry reactions finally leads to the immobilization at the electrode surface of desired functional groups, such as redoxprobes/shuttles (e.g., a ferrocenyl group) or catalytic moieties (e.g., an enzyme).HRP has been for instance immobilized on SWCNT-aryl-modified surfaces, and its voltammetric study showed catalytic response with the increasing concentration of hydrogen peroxide in solution upon monitoring the redox shuttlehydroquinone/benzoquinone at the electrode surface. In route (ii), the electrophylic addition of electrogenerated BDYT radicals was investigated for the first time at either SWCNT- or graphene-based electrodes. The combination of different techniques has demonstrated the covalent attachment of BDYT to SWCNT-based electrodes. Such modification leads to the formation of twisted ropes observed and analyzed by AFM and scanning electron microscopy. No evidence of twisted ropes formation was instead observed for modified graphene based electrodes.

The design and performance of an instrument is presented whose purpose is the extraction of samples highly enriched in one species of single-walled carbon nanotubes from density gradient ultracentrifugation. This instrument extracts high purity samples which are characterized by various optical studies. The samples are found to be enriched in just a few species of nanotubes, with the major limitation to enrichment being the separation, rather than extraction. The samples are then used in optical and microscopic studies which attempt to determine the first absorption coefficient (S1) of the (6,5) species of nanotube. Initial experiments give a value of 9.2 ± 2.6 cm2 C atom-1. Future work is proposed to improve upon the experiment in an attempt to reduce possible errors

Carbon nanotubes, and particularly single wall carbon nanotubes (SWNTs) have attracted much attention for their unique structure, as well as for their excellent mechanical, electrical and thermal properties. Most properties of carbon nanotubs are closely related with its anisotropic structure and geometry factor. Characterization of carbon nanotube length is critical for understanding their behavior in solutions as well as in polymer composites. Microscopy, particularly atomic force microscopy, has been used for their length measurement. Microscopy, though straightforward, is quite laborious, particularly for statistically meaningful sampling. Light scattering can be used to measure particle dimensions. In this study, light scattering has been used to study polyvinyl pyrrolidone (PVP) wrapped SWNTs surfactant assisted aqueous dispersion and SWNT dispersion in oleum. To determine the length of SWNTs, Stokes - Mueller formalism was used, which is a universal model for particles with any size and shape. The Mueller matrix for an ensemble of long, thin cylinders proposed by McClain et al. was used in this study. This Mueller matrix includes the information of size (length and radius) and optical constants (refractive index and extinction coefficient) of cylinders. In this matrix, extinction coefficient, radius and length of SWNTs are unknown. By normalizing scattering intensity I(theta) (theta from 30 to 155 degree) to that at 30degree , the effects of radius and extinction coefficient were cancelled out. Thus, the effect of SWNT length on scattering intensity could be studied independently. A series of curves of normalized scattering intensity of SWNTs (I(theta) /I(30degree)) with varied length as a function of wave vector were predicted. A curve of normalized scattering intensity of SWNT as a function of wave vector was also obtained experimentally. By comparing experimental and predicted curves, average SWNT length in the dispersion has been determined. Scattering intensity at a given angle initially increases with concentration, and then reaches a critical concentration(C*), above which the scattering intensity decreases. This phenomenon has been attributed to the competition between scattering and absorption of light by the presence of SWNT. By using Beer-Lambert law, this phenomenon has been used to determine the molar absorption coefficient of SWNTs.

Modern day engineering systems research presently lacks techniques to exploit the unique properties of many nanomaterials; coupled with this challenge exists the need to interface these nanomaterials with microscale and macroscale platforms. A nanomaterial of particular interest is the carbon nanotube (CNT), due to its enhanced physical properties. In addition to varied electrical properties, the CNT has demonstrated high thermal conductivity and tensile strength compared to conventional fiber materials. CNTs are beginning to see commercial applications in areas in which sufficient study has been dedicated. While a large part of the worldwide focus of CNT research has been in synthesis, an equally important area of research lies in CNT integration processes. The unique and useful properties of many nanostructured materials will never be realized in mainstream manufacturing processes and commercial applications without the proper exploration of integration methods such as those detailed in this thesis. The primary motivation for the research detailed in this thesis has been to develop CNT synthesis processing techniques that allow for novel interfacing methods between carbon nanotubes and eventual applications. In this study, an investigation was performed to look at several approaches to integrating CNTs into micro-electromechanical systems (MEMS). Synthesis of CNTs was studied in two different settings. Synthesis was first performed, directly on the microsystem, via a global scale chemical vapor deposition (CVD) process. Secondly, synthesis was performed directly onto a microsystem device via localized resistive heating. Following synthesis, the application of atomically layered, protective coatings was then investigated. Integration methods were then investigated to allow for CNT transfer to microsystem applications incapable of withstanding synthesis temperatures. The developed integration methods were evaluated by creating functional microscale electrical circuits in flexible substrates via hot emboss imprint lithography. Lastly, post synthesis processing methods were used to create micropatterned cell guidance substrates as well as neuronal stimulating substrates.

This dissertation explores the electrochemical behavior of enzymes and their cofactors at carbon nanotube (CNT) and nitrogen-doped carbon nanotube (N-CNT) electrodes. Two common types of oxidoreductases are considered: flavin adenine dinucleotide (FAD)-dependent oxidases and nicotinamide adenine dinucleotide-dependent (NAD⁺)-dehydrogenases. Chapter 1 presents the oxygen reduction reaction (ORR) at N-CNT electrodes as a way to electrochemically measure enzymatic turnover at the electrode surface. The unique peroxide pathway at N-CNT electrodes, which catalytically disproportionates hydrogen peroxide (H₂O₂) back into oxygen, provides an increased ORR current directly proportional to the rate of enzymatic turnover for H₂O₂ producing enzymes, even in an oxygen saturated solution. Biosensing of L-lactate using the increased ORR current is demonstrated using L-lactate oxidase. Chapter 2 explores the surface bound electrochemical signal of FAD when FAD-dependent enzyme or free FAD is allowed to spontaneously adsorb onto the CNT/N-CNT surface. Specifically, the origin of the enzymatically generated FAD signal and the rate constant of the electron transfer are elucidated. Chapter 3 continues the discussion of the cofactor FAD by demonstrating its use as an informative surface specific redox probe for graphitic carbon surfaces. Primarily, FAD can be used to determine the electroactive surface area and the relative hydrophobicity/hydrophilicity of graphitic surfaces. Chapter 4 changes gears to NAD⁺-dependent dehydrogenases by investigating the electrocatalytic oxidation of NADH at N-CNTs in comparison with conventional carbon electrodes or nondoped CNTs. Biosensing of glucose through the oxidation of NADH is demonstrated using glucose dehydrogenase adsorbed onto the N-CNT surface. Chapter 5 continues the discussion of NAD⁺-dependent dehydrogenases by addressing the reaction kinetics of NADH oxidation at N-CNTs as a tool to measure the enzymatic reduction of NAD⁺.