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Nanopartículas de dióxido de titânio como aditivos em materiais híbridos orgânico-inogânico fotocrômicos baseados em fosfotungstatos; Titanium dioxide nanoparticles as an additive for photochromic hybrid organic-inorganic materials based on phosphotungstate

Gonçalves, Lidiane Patricia
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 04/02/2011 PT
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Nesse estudo procurou-se avaliar o impacto do aditivo dióxido de titânio, mistura anatase-rutila, no comportamento fotocrômico de nanocompósitos baseados em materiais híbridos do tipo silicatos orgânicos (Ormosis) contendo ácido fosfotúngstico, 'H IND.3'PW IND.12'O IND.40'. O material híbrido foi obtido via processo sol-gel tendo sido caracterizado quanto à sua morfologia por Microscopia óptica e Microscopia Eletrônica de Varredura (MEV), que mostrou que os filmes em geral são pouco rugosos e homogêneos. Estudos de Espectroscopia Vibracional (Espectroscopia de Absorção na Região do Infravermelho e Raman) confirmaram a integridade do heteropoliânion fosfotungstato e a formação de uma rede tridimensional de silicatos, assim como, permitiram identificar a abertura do anel oxirano para formar um poli(óxido de etileno) ramificado, caracterizando a formação de um material híbrido classe II. A Espectroscopia de absorção na região do Ultra-violeta visível (UV-vis) ou espectroscopia eletrônica, além de confirmar a integridade química da espécie fosfotungstato, permitiu acompanhar a formação de heteropoliazuis mono- e duplamente reduzidos de maneira quantitativa. A cristalinidade dos materiais foi avaliada por Difração de raios-x (DRX) e mostrando que o sólido resultante é amorfo. Os estudos espectroscópicos permitiram inferir que a interação entre os polioxometalatos e as nanopartículas de 'TI'O IND.2' deve ser fraca...

Desenvolvimento de materiais nanocompósitos e do processo de estereolitografia laser no infravermelho (CO2); Development of nanocomposite materials and the infrared laser stereolithography process

Maria Ingrid Rocha Barbosa
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 01/07/2010 PT
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A tendência atual na área de desenvolvimento de materiais aponta significantemente para o desenvolvimento de nanocompósitos. Várias pesquisas mostram que as características das propriedades que estes materiais apresentam ampliam de forma bastante promissora suas possíveis aplicações. Levando-se isso em consideração, este projeto tem como objetivo o estudo e desenvolvimento de materiais compósitos (polímero/carga) nanoestruturados para utilização no processo da Estereolitografia Laser no Infravermelho (CO2). Para tanto, o estudo envolve a mistura física de nanopartículas de sílica dispersas em uma matriz polimérica, composta por resina epóxi (diglicidil éter bisfenol A - DGEBA) e dietilenotriamina (DETA) como agente de cura. A determinação das propriedades térmicas e análise dos principais fenômenos e mecanismos gerais de cura do material nanocompósito foram realizadas utilizando a técnica de Calorimetria Exploratória Diferencial (DSC). Simulação computacional, utilizando um modelo matemático determinístico resolvido por volumes finitos através do programa ANSYS CFX®, foi realizada com o objetivo de avaliar os perfis da distribuição da temperatura espacial e temporal (análise térmica transiente)...

Development of Soft Nanocomposite Materials and Their Applications in Cell Culture and Tissue Engineering

Haraguchi, K
Fonte: Journal of Stem Cells and Regenerative Medicine Publicador: Journal of Stem Cells and Regenerative Medicine
Tipo: Artigo de Revista Científica
Publicado em 14/04/2012 EN
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Novel soft nanocomposite materials with unique organic/inorganic network structures have been developed by extending the strategy of “organic/inorganic nanocomposites” to the field of soft materials. The structures described here were synthesized by in-situ free-radical polymerization of various monomers in the presence of exfoliated clay (hectorite) in aqueous media. The nanocomposite hydrogels (NC gels) and soft nanocomposites (M-NCs) obtained were flexible and transparent soft materials, regardless of the clay content, that could be prepared in various shapes and surface forms, each consisting of individually different polymer/clay network structures. Owing to these unique network structures, both NC gels and M-NCs showed extraordinary mechanical properties such as ultrahigh elongation at break and widely controlled modulus and strength, which could overcome the problems (e.g., mechanical fragility, optical turbidity, poor processing ability) associated with conventional chemically crosslinked materials. In addition, the NC gels and M-NCs exhibited a number of new characteristics related to optical anisotropy, morphology, biocompatibility, stimulus sensitivity and cell culture. In the present review, we outline the novel features of these soft nanocomposites...

Adsorptive interaction of bisphenol A with mesoporous titanosilicate/reduced graphene oxide nanocomposite materials: FT-IR and Raman analyses

Nguyen-Huy, Chinh; Kim, Nayoung; Nguyen-Phan, Thuy-Duong; Yoo, Ik-Keun; Shin, Eun Woo
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 03/09/2014 EN
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Nanocomposite materials containing graphene oxide have attracted tremendous interest as catalysts and adsorbents for water purification. In this study, mesoporous titanosilicate/reduced graphene oxide composite materials with different Ti contents were employed as adsorbents for removing bisphenol A (BPA) from water systems. The adsorptive interaction between BPA and adsorption sites on the composite materials was investigated by Fourier transform infrared (FT-IR) and Raman spectroscopy. Adsorption capacities of BPA at equilibrium, q e (mg/g), decreased with increasing Ti contents, proportional to the surface area of the composite materials. FT-IR observations for fresh and spent adsorbents indicated that BPA adsorbed onto the composite materials by the electrostatic interaction between OH functional groups contained in BPA and on the adsorbents. The electrostatic adsorption sites on the adsorbents were categorized into three hydroxyl groups: Si-OH, Ti-OH, and graphene-OH. In Raman spectra, the intensity ratios of D to G band were decreased after the adsorption of BPA, implying adsorptive interaction of benzene rings of BPA with the sp2 hybrid structure of the reduced graphene oxide.

Polyelectrolyte multilayers : nanofabricated architectures for bio-interface materials

Mendelsohn, Jonas Daniel, 1975-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 135 p.; 14268994 bytes; 14268753 bytes; application/pdf; application/pdf
ENG
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The layer-by-layer process, whereby aqueous solutions of oppositely charged polymers are alternately and repeatedly deposited onto a substrate, has emerged in recent years as a promising approach for creating thin films with nanoscale control of structure, composition, and surface properties. Applications ranging from surface modification to optical and electronic devices have arisen from the versatility of this nanocomposite fabrication technique. The additional ability to assemble into films a wide variety of biological entities, such as enzymes and DNA, has expanded the use of polyelectrolyte multilayers for biosensor and other biomaterials applications. This thesis further explores the rationale of using multilayers as biomaterials, with particularly emphasis on the importance of the underlying molecular architecture. Many of the results presented here concern films assembled from weak polyions, i.e., ones with pH-dependent charge densities, including poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH). Using weak polyions enables the creation of thin films with chemical and structural properties controlled with nanoscale precision by simply adjusting the pH of the polymer solutions. Under certain assembly conditions...

Ballistic characterization of nanostructured composite materials for aerospace applications

PASTORE, ROBERTO
Fonte: La Sapienza Universidade de Roma Publicador: La Sapienza Universidade de Roma
Tipo: Tese de Doutorado
EN
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The manuscript is arranged in three main parts. In the first chapter the nanocomposite manufacturing is described. As far as the CNTfilled polymeric composites are concerned, a carbon nanotube functionalization process by thermal and chemical treatments has been performed, and Scanning Electron Microscopy (SEM) analysis, as well as Raman and FT-IR spectroscopies were used to verify the surface modifications of the CNTs by the added radical groups. Then, the manufacturing of the CNT-reinforced epoxy composite has been carried out, and Differential Scanning Calorimetry (DSC) was used to analyze the polymerization process for the nano-reinforced thermosetting polymer systems. SEM investigations were also performed to assess the nanocomposites quality in terms of nanoparticle dispersion and material homogeneity. Regarding the STF-reinforced materials, STFs have been synthesized in a single step reaction through high power ultrasound technique, and characterized in terms of their rheological properties. The shear thickening fluid is prepared by ultrasound irradiation of silica nanoparticles dispersed in liquid polyethylene glycol polymer. Then, STF-reinforced fabrics have been realized by soaking layers of several types of Kevlar in STF/ethanol solution; the morphology of the as-realized fabrics...

Time-resolved spectroscopic characterization of ballistic impact events in polymer and nanocomposite materials

Saini, Gagan
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 95 p.
ENG
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A detailed understanding of how materials respond to ballistic shock-loading is critical for the design and development of new protective materials. However, the nonlinear viscoelastic deformation present in polymers and nanocomposites during and immediately following a ballistic impact event is not currently well understood. The dynamic mechanical responses of materials experiencing ballistic shock-loading conditions are quite complex, with large amplitude compressions resulting in strain rates in excess of 106 s-1 and pressures exceeding several GPa. Historically, if one wants to study materials under ballistic shock loading conditions, a gas gun apparatus is necessary to generate appropriate high strain rate events. However, advances in high power ultra-fast laser amplifier systems have opened the possibility of optically generating ballistic shocks which are comparable to a shock wave generated by gas gun apparatus. Time-resolved mechanical property information, such as elastic modulus, bulk modulus, shear modulus, and Poisson's ratio are measured using impulsive stimulated thermal scattering, a laser-based photoacoustic technique.; (cont.) A series of polymeric and polymer based nanocomposite material systems are studied, including multilayered thin films of alternating layers of polymer and hard nanoparticles...

Synthesis of titanate nanofibers co-sensitized with ZnS and Bi2S3 nanocrystallites and their application on pollutants removal

Entradas, T. J.; Cabrita, J. C.; Barrocas, B.; Nunes, M. R.; Silvestre, A. J.; Monteiro, O. C.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 30/03/2015
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The synthesis of nanocomposite materials combining titanate nanofibers (TNF) with nanocrystalline ZnS and Bi2S3 semiconductors is described in this work. The TNF were produced via hydrothermal synthesis and sensitized with the semiconductor nanoparticles, through a single-source precursor decomposition method. ZnS and Bi2S3 nanoparticles were successfully grown onto the TNF's surface and Bi2S3-ZnS/TNF nanocomposite materials with different layouts were obtained using either a layer-by-layer or a co-sensitization approach. The samples' photocatalytic performance was first evaluated through the production of the hydroxyl radical using terephthalic acid as probe molecule. All the tested samples show photocatalytic ability for the production of this oxidizing species. Afterwards, the samples were investigated for the removal of methylene blue. The nanocomposite materials with best adsorption ability for the organic dye were the ZnS/TNF and Bi2S3ZnS/TNF. The removal of the methylene blue was systematically studied, and the most promising results were obtained considering a sequential combination of an adsorption-photocatalytic degradation process using the Bi2S3ZnS/TNF powder as a highly adsorbent and photocatalyst material.; Comment: 26 pages...

Ni(OH)2 Nanoplates Grown on Graphene as Advanced Electrochemical Pseudocapacitor Materials

Wang, Hailiang; Casalongue, Hernan Sanchez; Liang, Yongye; Dai, Hongjie
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 05/05/2010
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Ni(OH)2 nanocrystals grown on graphene sheets with various degrees of oxidation are investigated as electrochemical pseudocapacitor materials for potential energy storage applications. Single-crystalline Ni(OH)2 hexagonal nanoplates directly grown on lightly-oxidized, electrically-conducting graphene sheets (GS) exhibit a high specific capacitance of ~1335F/g at a charge and discharge current density of 2.8A/g and ~953F/g at 45.7A/g with excellent cycling ability. The high specific capacitance and remarkable rate capability are promising for applications in supercapacitors with both high energy and power densities. Simple physical mixture of pre-synthesized Ni(OH)2 nanoplates and graphene sheets show lower specific capacitance, highlighting the importance of direct growth of nanomaterials on graphene to impart intimate interactions and efficient charge transport between the active nanomaterials and the conducting graphene network. Single-crystalline Ni(OH)2 nanoplates directly grown on graphene sheets also significantly outperform small Ni(OH)2 nanoparticles grown on heavily-oxidized, electrically-insulating graphite oxide (GO), suggesting that the electrochemical performance of these composites are dependent on the quality of graphene substrates and the morphology and crystallinity of the nanomaterials grown on top. These results suggest the importance of rational design and synthesis of graphene-based nanocomposite materials for high-performance energy applications.; Comment: Published in JACS

Design and optimization of plasmonic-based metal-dielectric nanocomposite materials for energy applications

Trice, J.; Favazza, C.; Garcia, H.; Sureshkumar, R.; Kalyanaraman, R.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 18/01/2010
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Metallic nanoparticles embedded in dielectrics permit enhanced capture of light at specific wavelengths through excitation of plasmons, i.e. the quanta of coherent and collective oscillations of large concentrations of nearly free electrons. In order to maximize the potential of such enhanced absorption in useful tasks, such as the generation of carriers in photocatalysts and semiconductors, it is important to be able to predict and design plasmonic nanocomposites with desired wavelength-dependent optical absorption. Recently, a mixing approach formulated by Garcia and co-workers [Phys. Rev. B, 75, 045439 (2007)] has been successfully applied to model the experimentally measured broadband optical absorption for ternary nanocomposites containing alloys or mixtures of two metals (from Ag, Au or Cu) in SiO dielectric. In this work we present the broadband optical behavior of important optical coating dielectrics (SiN and SiO) and photocatalyst (TiO) containing various configuration of nanoparticles of Al, Au, Ag, or Cu. The spectral behavior of various combinations of the metallic species in the dielectrics was optimized to show either broadband solar absorption or strong multiple plasmonic absorption peaks. The applications of such nanocomposite materials in solar energy harvesting and spectral sensing are also presented and discussed.; Comment: 14 pages...

In-Situ Synthesis of Polypyrrole-MnO2−x Nanocomposite Hybrids

Cuentas Gallegos, A. K.; Gómez-Romero, P.
Fonte: Ecole polytechnique (Montréal, Québec) Publicador: Ecole polytechnique (Montréal, Québec)
Tipo: Artículo Formato: 344581 bytes; application/pdf
ENG
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This work centers on hybrid materials based on MnO2-x and conducting polymers and their possible application as electrodes in rechargeable lithium batteries. We approached the study of these hybrids as an alternative to crystalline manganese oxides, which capacity is frequently limited by irreversible phase transitions. We followed the approach of forming simultaneously the organic and inorganic components in an attempt to get nanocomposite materials. PPy/MnO2-x nanocomposite hybrids were prepared by direct one-pot reaction of pyrrole and potassium permanganate, obtaining hybrids with different amounts of the inorganic phase. The results on the chemical, spectroscopic and electrochemical characterization of the PPy/MnO2-x hybrids indicated that as the MnO2-x content increases, so does the initial specific charge in lithium rechargeable cells, reaching values as high as 134 Ah/Kg.5; Partial financial support from the Ministry of Science and Technology (Spain) (GrantMAT2002-04529-C03) and from CONACYT (México) (fellowship to A.K. Cuentas-Gallegos) are gratefully acknowledged; Peer reviewed

Polyoxometalates: from inorganic chemistry to materials science

Gómez-Romero, P.; Casañ Pastor, Nieves
Fonte: Frontiers in Bioscience Publications Publicador: Frontiers in Bioscience Publications
Tipo: Artículo Formato: 579917 bytes; image/jpeg
ENG
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Full-text available Open Access at: http://www.cienciateca.com/POMs%20Frontiers%20in%20Bioscience2004.pdf; Polyoxometalates have been traditionally the subject of study of molecular inorganic chemistry. Yet, these polynuclear molecules, reminiscent of oxide clusters, present a wide range of structures and with them ideal frameworks for the deployment of a plethora of useful magnetic, electroionic, catalytic, bioactive and photochemical properties. With this in mind, a new trend towards the application of these remarkable species in materials science is beginning to develop. In this review we analyze this trend and discuss two main lines of thought for the application of polyoxometalates as materials. On the one hand, there is their use as clusters with inherently useful properties on themselves, a line which has produced fundamental studies of their magnetic, electronic or photoelectrochemical properties and has shown these clusters as models for quantum-sized oxides. On the other hand, the encapsulation or integration of polyoxometalates into organic, polymeric or inorganic matrices or substrates opens a whole new field within the area of hybrid materials for harnessing the multifunctional properties of these versatile species in a wide variety of applications...

Hybrid Nanocomposite Materials

Gómez-Romero, P.; Lira-Cantú, Monica
Fonte: John Wiley & Sons Publicador: John Wiley & Sons
Tipo: Capítulo de libro Formato: 579917 bytes; image/jpeg
ENG
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In: Kirk-Othmer Encyclopedia of Chemical Technology; Hybrid organic–inorganic materials constitute a fast-growing field that has already led to a very large variety of materials and applications. These nanocomposite materials abound both with organic or inorganic matrices and represent oportunities to design eclectic materials by taking advantage of the best properties of their components. But the hybrid concept can even go beyond this approach by creating materials with novel structures or supramolecular architectures, with synergic properties, or even with activities impossible for the isolated components. This article is a general review of the field, discussing the different categories of materials according to their chemical nature and their applications as structural or functional materials. A variety of hybrids with organic matrics (most commonly polymers) are distinguished from these in which the dominating phase is inorganic (polymeric or extended in nature). To the category of silicon-based hybrids that predominated in the early literature a larger variety of hybrids has followed which includes, among many others, inorganic molecular species intergrated in organic polymers, perovskites built with organic and inorganic building blocks or polymer-inserted inorganic phases. All of them are categorized and discussed with emphasis on their many different applications and commercial developments.; Peer reviewed

Hybrid Organic-Inorganic Materials - In Search of Synergic Activity

Gómez-Romero, P.
Fonte: John Wiley & Sons Publicador: John Wiley & Sons
Tipo: Artículo Formato: 579917 bytes; image/jpeg
ENG
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Full-text available Open Access at: http://www.cienciateca.com/PGR_Review_Hybrids_AdvMat2001.pdf; This review surveys the work developed in the field of functional hybrid materials, especially those containing conducting organic polymers (COPs), in combination with a variety of inorganic species, from molecular to extended phases, including clusters and nano-sized inorganic particles. Depending on the dominating structural matrix, we distinguish and analyze organic-inorganic (OI) hybrids, nanocomposite materials, and inorganic-organic (IO) phases. These materials have been used in a wide variety of applications, including energy-storage applications, electrocatalysis, the harnessing of electrochromic and photoelectrochromic properties, application in display devices, photovoltaics, and novel energy-conversion systems, proton-pump electrodes, sensors, or chemiresistive detectors, which work as artificial noses.; Peer reviewed

Hybrid nanocomposite materials for energy storage and conversion applications

Gómez-Romero, P.; Cuentas Gallegos, A. K.; Lira-Cantú, Monica; Casañ Pastor, Nieves
Fonte: Springer Publicador: Springer
Tipo: Artículo Formato: 579917 bytes; image/jpeg
ENG
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Functional Hybrid materials based on conducting polymers and inorganic photo-electroactive species provide a wealth of opportunities for the development of novel materials with improved properties. Polyoxometalates are one type of well-known inorganic species with most interesting photo-electrochemical activity. They are perfect models for nanometer-sized oxide quantum-dots both concerning structure, topology and electrochemical and photochemical properties. Yet, they have not been applied as materials because of their molecular nature (i.e., soluble in most solvents or electrolytes). In our group we have recently developed a research line dealing with the integration of these fascinating clusters in conducting polymer matrices to yield functional hybrid materials. Our past emphasis was on electroactivity for energy-storage applications but these materials can also be used, as it is shown here, for photoelectrochemical applications.; The authors acknowledge partial financial support from the Ministry of Science and Technology (Spain) (Grant MAT2002-04529-C03) and express his deep gratitude for the total dedication of his Ph.D. students; Peer reviewed

Biocompatible Ti-based metallic glasses and nanocomposite materials

Hynowska, Anna
Fonte: [Barcelona] : Universitat Autònoma de Barcelona, Publicador: [Barcelona] : Universitat Autònoma de Barcelona,
Tipo: Tesis i dissertacions electròniques; info:eu-repo/semantics/doctoralThesis; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2014 ENG
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Aquesta Tesi comprèn la síntesi i caracterització d'aliatges de base Ti amorfs i nanoestructurats. Així, s'han estudiat diversos aliatges amb composició Ti-44.3Nb- 8.7Zr12.3Ta, Ti-31.0Fe-9.0Sn, Ti40Zr20Hf20Fe20, Ti45Zr15Pd35-xSi5Nbx (x = 0, 5%) com a exemples d'aliatges de base Ti nanoestructurats, i el vidre amorf massís Ti40Zr10Cu38Pd12. Aquests materials es van escollir tenint en compte les seves potencials aplicacions com a implants ortopèdics. La primera part d'aquesta Tesi va consistir en la síntesi i caracterització d'aquests aliatges bo i fent especial èmfasi en les correlacions existents en el triangle microestructura – comportament mecànic – biocompatibilitat. En la segona part es van dur a terme tractaments d'irradiació amb feixos d'ions del vidre amorf com a estratègia per modificar les seves propietats superficials i, de retruc, incrementar-ne la compatibilitat biomecànica. Totes les mostres es van sintetitzar per fusió d'arc i posterior emmotllament. Es va dur a terme una caracterització exhaustiva de tipus tèrmic i estructural de les mostres anteriorment mencionades mitjançant calorimetria diferencial d'escombrat (DSC), difracció de raigs X (XRD) i microscòpia electrònica de rastreig i transmissió (SEM...

Advanced amperometric nanocomposite sensors based on carbon nanotubes and graphene: characterization, optimization, functionalization and applications

Muñoz Martín, Jose María
Fonte: [Barcelona] : Universitat Autònoma de Barcelona, Publicador: [Barcelona] : Universitat Autònoma de Barcelona,
Tipo: Tesis i dissertacions electròniques; info:eu-repo/semantics/doctoralThesis; info:eu-repo/semantics/publishedVersion
Publicado em //2015 ENG
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Dins de l'amplia gama de nanocompòsits, la incorporació de materials conductors de carboni nanoestructurats, entre els quals s'hi troben els nanotubs de carboni (NTCs) i el grafè, a dins d'una matriu polimèrica aïllant, és una forma molt atractiva de combinar les propietats mecàniques i elèctriques úniques del material de farciment amb els atributs dels plàstics. Concretament, els materials nanocompòsits basats en carboni han jugat un gran lideratge en el camp de l'electroquímica analítica, sobre tot en el desenvolupament de dispositius (bio)sensors, degut a les seves interessants avantatges respecte a un material conductor pur. Aquestes avantatges els hi proporcionen un alt valor afegit, com versatilitat, durabilitat, una fàcil regeneració de la superfície i integració, simplicitat a l'hora d'incorporar diferents (bio)modificadors o una baixa corrent de fons, entre d'altres. En aquest sentit, aquesta tesi aborda el desenvolupament de sensors nanocompòsits avançats de tipus amperomètrics que, havent sigut optimitzada la seva relació carboni/polímer, poden ser modificats amb un ampli ventall de nanopartícules (NPs) per millorar-ne la seva eficiència electroanalítica. Les propietats elèctriques d'aquests nanocompòsits i...

Carbon Xerogel nanocomposite materials for electrochemical devices: application to heavy metal detection

Niu, Pengfei; Casas Duocastella, Lluís
Fonte: [Barcelona] : Universitat Autònoma de Barcelona, Publicador: [Barcelona] : Universitat Autònoma de Barcelona,
Tipo: Tesis i dissertacions electròniques; info:eu-repo/semantics/doctoralThesis; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2015 ENG
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En aquesta Tesi es descriu la fabricació d'elèctrodes nanocompòsits de carboni porós en forma de capa prima i capa gruixuda i la seva aplicació en l'anàlisi de metalls pesants en aigües. Aquests nanocompòsits de carboni es van preparar a partir de la piròlisi de materials obtinguts per química sol-gel, concretament de gels de resorcinol-formaldehid i de resorcinol-formaldehid amb sílice, que contenien precursors de bismut. Els gels pirolitzats presenten una estructura de carbó porós amb porositat oberta que conté nanopartícules de bismut ben distribuïdes. Aquests materials es van moldre fins a obtenir una pols de granulometria adequada per fer elèctrodes de pasta de carboni per ser estudiats al laboratori i elèctrodes serigrafiats de capa gruixuda de tipus comercial. Aquests elèctrodes presenten una resposta molt bona en l'anàlisi de metalls pesats en aigües. Els límits de detecció de Pb(II), Cd(II) i Ni(II) obtinguts amb aquest elèctrodes estan molt per sota de la concentracions màximes d'aquests metalls contemplades en les normatives d'aigua per al consum de la Unió Europea i els Estats Units (US-EPA). Es va dur a terme l'anàlisi de Pb(II), Cd(II), Ni(II), Zn(II) i Cu(II) en aigües reals de diferent origen i complexitat i es va veure que en la majoria de casos s'obtenien resultats que estaven d'acord amb les mesures fetes per espectroscòpia de masses. També es van estudiar les limitacions dels sensors desenvolupats i interferències entre els diferents analits. Pel que fa als elèctrodes en capa prima...

Organic/Inorganic Hybrid Nanocomposite Infrared Photodetection by Intraband Absorption

Lantz, Kevin Richard
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2011
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The ability to detect infrared radiation is vital for a host of applications that include optical communication, medical diagnosis, thermal imaging, atmospheric monitoring, and space science. The need to actively cool infrared photon detectors increases their operation cost and weight, and the focus of much recent research has been to limit the dark current and create room-temperature infrared photodetectors appropriate for mid-to-long-wave infrared detection. Quantum dot infrared photodetectors (QDIPs) provide electron quantum confinement in three dimensions and have been shown to demonstrate high temperature operation (T>150 K) due to lower dark currents. However, these inorganic devices have not achieved sensitivity comparable to state-of-the-art photon detectors, due in large part to the inability to control the uniformity (size and shape) of QDs during strained-layer epitaxy.

The purpose of this dissertation research was to investigate the feasibility of room-temperature infrared photodetection that could overcome the shortfalls of QDIPs by using chemically synthesized inorganic colloidal quantum dots (CQDs). CQDs are coated with organic molecules known as surface ligands that prevent the agglomeration of dots while in solution. When CQDs are suspended in a semiconducting organic polymer...

Carbon nanotube macrofilm-based nanocomposite electrodes for energy applications

Cao, Zeyuan
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
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Wei, Bingqing; Finding new electrode materials for energy conversion and storage devices have been the focus of recent research in the fields of science and engineering. Suffering from poor electronic conductivity, chemical and mechanical stability, active electrode materials are usually coupled with different carbon nanostructured materials to form nanocomposite electrodes, showing promising electrochemical performance. Among the carbon nanostructured materials, carbon nanotube (CNT) macrofilms draw great attention owing to their extraordinary properties, such as a large specific surface area, exceptionally high conductivity, porous structure, flexibility, mechanical robustness, and adhesion. They could effectively enhance the electrochemical performance of the incorporated active materials in the nanocomposites. In this dissertation, CNT macrofilm-based nanocomposites are investigated for rechargeable lithium-ion batteries, supercapacitors, and electrocatalysts of fuel cells. The progressive research developed various nanocomposites from cathode materials to anode materials followed by a general nanocomposite solution due to the unique adhesive property of the fragmented CNT macrofilms. The in-situ synthesis strategy are explored to in-situ deposit unlithiated cathode materials V2 O5 and lithiated cathode materials LiMn2 O4 nanocrystals in the matrix of the CNT macrofilms as nanocomposites to be paired with metallic lithium in half cells. The presence of oxygen-containing functional groups on the surface of the CNT macrofilms after purification can enhance the association with the active materials to enable the facilitated transport of solvated ions to the electrolyte/electrode interfaces and increase the diffusion kinetics...