Página 1 dos resultados de 551 itens digitais encontrados em 0.012 segundos

Tyrosinase biosensor based on a glassy carbon electrode modified with multi-walled carbon nanotubes and 1-butyl-3-methylimidazolium chloride within a dihexadecylphosphate film

Vicentini, Fernando Campanhã; Janegitz, Bruno C.; Brett, Christopher M. A.; Fatibello-Filho, Orlando
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
126.4%
A glassy carbon electrode modified with functionalized multi-walled carbon nanotubes (MWCNT), 1-butyl-3-methylimidazolium chloride (ionic liquid = IL) and tyrosinase (Tyr) within a dihexadecylphosphate (DHP) film for the development of a biosensor is proposed. MWCNT, IL and Tyr were efficiently immobilized in the film using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS) as crosslinking agents, and which was characterized by cyclic voltammetry (CV) in the presence of catechol. The IL-MWCNT nanocomposite showed good conductivity and biocompatibility with Tyr enzyme, since the biosensor presented biocatalytic activity toward the oxidation of catechol to o-quinone which was electrochemically reduced to catechol at a potential of 0.04 V. The analytical curve ranged from 4.9 × 10−6 to 1.1 × 10−3 mol L−1 with a detection limit of 5.8 × 10−7 mol L−1. The developed Tyr-IL-MWCNT-DHP/GCE biosensor showed a wide linear range, good reproducibility, sensitivity and stability and the biosensor was successfully applied to the determination of catechol in natural water samples, with satisfactory results compared with a spectrophotometric method, at the 95% confidence level.

The electrochemical effect of acid functionalisation of carbon nanotubes to be used in sensors development

MORAES, F. C.; CABRAL, M. F.; MASCARO, L. H.; MACHADO, S. A. S.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
106.37%
The electrochemical behaviour of multi-walled carbon nanotubes was compared with that of glassy carbon, and the differences were investigated by cyclic voltammetry and electrochemical impedance spectroscopy before and after acid pre-treatment. The electrochemical techniques showed that acid functionalisation significantly improves the electrocatalytic properties of carbon nanotubes. These electrocatalytic properties enhance the analytical signal, shift the oxidation peak potential to a less positive value, and the charge-transfers rate increase of both dopamine and K(4)[Fe(CN)(6)]. The functionalisation step and the resulting appearance of edge planes covered with different chemical groups were confirmed by FTIR measurements. Carbon nanotubes after acid pre-treatment are a potentially powerful analytical tool for sensor development. (C) 2010 Elsevier B.V. All rights reserved.; CNPq; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); CAPES[0316083]

Nanostructured films from phthalocyanine and carbon nanotubes: Surface morphology and electrical characterization

Brito, Jackeline B.; Gomes, Douglas J. C.; Justina, Vanessa D.; Lima, Aline M. F.; Olivati, Clarissa A.; Silva, Josmary R.; de Souza, Nara C.
Fonte: Academic Press Inc. Elsevier B.V. Publicador: Academic Press Inc. Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 467-471
ENG
Relevância na Pesquisa
106.41%
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); We report on the investigation of the surface morphology and DC conductivity of nanostructured layer-by-layer (LbL) films from nickel tetrasulfonated phthalocyanine (NiTsPc) alternated with either multi-walled carbon nanotubes (MWNTs/NiTsPc) or multi-walled carbon nanotubes dispersed in chitosan (MWNTs + Ch/NiTsPc). We have explored the surface morphology of the films by using fractal concepts and dynamic scale laws. The MWNTs/NiTsPc LbL films were found to have a fractal dimension of ca. 2, indicating a quasi Euclidean surface. MWNTs + Ch/NiTsPc LbL films are described by the Lai-Das Sarma-Villain (LDV) model, which predicts the deposition of particles and their subsequent relaxation. An increase in the wetting contact angle of MWNTs + Ch/NiTsPc LbL films was observed, as compared with MWNTs/NiTsPc LbL films, which presented an increase in the fractal dimension of the first system. Room temperature conductivities were found be ca. 0.45 S/cm for MWNTs/NiTsPc and 1.35 S/cm for MWNTs + Ch/NiTsPc. (C) 2011 Elsevier B.V. All rights reserved.

Layer-by-Layer Films Based on Carbon Nanotubes and Polyaniline for Detecting 2-Chlorophenol

Silva, Juliana S.; Barros, Anerise de; Constantino, Carlos J. L.; Simoes, Fabio R.; Ferreira, Marystela
Fonte: Amer Scientific Publishers Publicador: Amer Scientific Publishers
Tipo: Artigo de Revista Científica Formato: 6586-6592
ENG
Relevância na Pesquisa
106.31%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Electrochemical sensors made with layer-by-layer (LbL) films of functionalized multi-walled carbon nanotubes (MWCNT5-COO-) and polyaniline (PAni) deposited onto ITO substrates were used to detect 2-chlorophenol. Concentrations down to ppm level could be detected with square wave voltammetry (SWV), owing to synergistic effects between PAni and nanotubes, whose molecular-level interactions in the LbL films were inferred using FTIR and Raman spectroscopy. Significantly, the Raman spectra of MWCNTs-COO-/PAni LbL films indicated that the conducting properties of PAni were preserved upon adsorption on the ITO substrates, with homogeneous nanocomposites being formed according to Scanning Electron Microscopy (SEM) images.

Fabrication, characterization and analytical performance of the hydroxylamine sensor based on an oracet blue multi-walled carbon nanotubes film deposited on an electrode surface

Zare,Hamid R.; Nasirizadeh,Navid
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
Relevância na Pesquisa
126.38%
In this work, the electrocatalytic oxidation of hydroxylamine on a glassy carbon electrode modified with oracet blue and multi-walled carbon nanotubes (OBMWCNT-GCE) has been studied. The peak potential of hydroxylamine at OBMWCNT-GCE surface shifts by about 320 and 335mV toward negative values compared with those at a MWCNT and activated GCE surface. Kinetic parameters for the oxidation of hydroxylamine at the modified electrode surface were determined by cyclic voltammetry measurements. The amperometric detection of hydroxylamine was carried out at 170 mV in a 0.1 mol L-1 phosphate buffer solution (pH 7.0) resulting in two linear response ranges of 4.0-102.4 µmol L-1 and 102.4-5820.9 µmol L-1 and the limit of detection of 0.7 µmol L-1. The amperometric response for hydroxylamine determination proved to be repeatable, fast and stable. Finally, OBMWCNT-GCE was successfully applied to the hydroxylamine determination in two water natural samples.

Surface properties of oxidized and aminated multi-walled carbon nanotubes

Silva,Wellington M.; Ribeiro,Hélio; Seara,Luciana M.; Calado,Hállen D. R.; Ferlauto,André S.; Paniago,Roberto M.; Leite,Cristiano F.; Silva,Glaura G.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
Relevância na Pesquisa
126.41%
The influence of chemical modification by acid treatment followed by triethylenetetramine (TETA) functionalization on the surface of multi-walled carbon nanotubes (MWCNT) was evaluated, both qualitative and quantitatively. Thermogravimetric analysis (TGA) showed that, in the case of amine-functionalized nanotubes, 29% of mass loss can be attributed to -C(=O)TETA and residual oxygen-containing functional groups. X-ray photoelectron spectroscopy (XPS) was used to observe the oxygenated and aminated functions covalently linked to the nanotube surface. Electric force microscopy (EFM) images indicated that the nanotubes with diverse surface chemistry showed distinct responses to the tip potential in the presence of air. Shifts in EFM phase images decreased when the nanotube surface was modified with oxygen and amine-containing functional groups. In dry and inert N2 atmosphere, however, the three different surfaces showed the same response to EFM. In addition, the hydrophilic character of the buckypapers increased in the order MWCNT < aminated-MWCNT < oxidized-MWCNT.

Electrochemical reduction of the mycotoxin citrinin at bare and modified with multi-walled carbon nanotubes glassy carbon electrodes in a non-aqueous reaction medium

Zachetti,Vanessa G. L.; Granero,Adrian M.; Robledo,Sebastian N.; Zon,María A.; Rosa,Carlos A. DaRocha; Fernández,Héctor
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
Relevância na Pesquisa
116.35%
Electrochemical reduction mechanism of citrinin in acetonitrile plus 0.1 mol L-1 (C4H9)4NClO4 at both bare and modified with multi-walled carbon nanotube glassy carbon (GC) electrodes was investigated by cyclic voltammetry and controlled potential electrolysis. Results allowed to infer a complex electroreduction mechanism with chemical and electrochemical steps coupled to the initial electron transfer reaction. Citrinin shows a single cathodic peak that corresponds at least to two electron reduction steps and two homogeneous chemical reactions, conforming to an ECEC (electron-transfer coupled with proton acceptance) self-protonation mechanism. The chemical reactions are originated in the intermolecular proton transfers from the substrate to its basic reduction intermediates, featuring a self-protonation mechanism. Kinetics analysis by simulation procedures of voltammetric results permitted a fully characterization of the mechanism of citrinin heterogeneous reduction.

Developing a sensor for the simultaneous determination of dopamine, acetaminophen and tryptophan in pharmaceutical samples using a multi-walled carbon nanotube and oxadiazole modified glassy carbon electrode

Nasirizadeh,Navid; Shekari,Zahra; Zare,Hamid R.; Ardakani,Seied A. Y.; Ahmar,Hamid
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/11/2013 EN
Relevância na Pesquisa
116.36%
The present study describes the electrochemical characteristics of an electrodeposited oxadiazole derivative on multi-walled carbon nanotubes glassy carbon electrode (OMWCNT-GCE) and its role as highly sensitive electrochemical sensor for the electrocatalytic oxidation of dopamine (DA). The surface charge transfer rate constant (k s) and the charge transfer coefficient (α) for the electron transfer between GCE and electrodeposited oxadiazole were calculated. OMWCNT-GCE exhibited suitable electrocatalytic properties for DA oxidation in a phosphate buffer (pH 7.0) solution. The modified electrode exhibited low limit of detection (0.12 µmol L-1) for DA. In differential pulse voltammetry (DPV) measurements, OMWCNT-GCE could separate the oxidation peak potentials of DA, acetaminophen (AC) e tryptophan (Trp) present in the same solution, while the bare GCE gave two broad responses. The analytical performance of this sensor was evaluated to determine DA and AC in real samples.

Ag ion decoration for surface modifications of multi-walled carbon nanotubes

Travessa,Dilermando N.; Silva,Fábio S. da; Cristovan,Fernando H.; Jorge Jr.,Alberto M.; Cardoso,Kátia Regina
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2014 EN
Relevância na Pesquisa
106.33%
The production of high performance metal matrix composites depends on a proper design of the surface of the reinforcing phase, ensuring a good contact with a metal phase. In the present work, two Ag decorating procedures to modify the surface of multi-walled carbon nanotubes (MWCNT) were evaluated for further production of aluminum matrix composites. The procedures consisted in a two steps route based on acid oxidation of carbon nanotubes (CNT) followed by suspension in an Ag ion solution; and a single step route, based on the effect of n-dimethylformamide (DMF) as an activation agent of CNT surface, in presence of Ag ions. Transmission and scanning-transmission electron microscopy, Raman and Fourier-transformed infrared spectroscopy were employed in order to characterize the results. The two steps route resulted in Ag nano-particles homogeneously deposited over the CNT surface. The mechanism for the deposition is based on carboxyl and probably hydroxyl functional groups formed in the first step, acting as nucleation sites for Ag precipitation in the second step. The single step route resulted in the formation of sub-micrometric Ag particles heterogeneously mixed to CNT bundles.

Effect of different microwave-based treatments on multi-walled carbon nanotubes

Hojati-Talemi, P.; Cervini, R.; Simon, G.P.
Fonte: Springer Netherlands Publicador: Springer Netherlands
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
Relevância na Pesquisa
106.39%
Three new methods for the functionalization of multi-walled carbon nanotubes (MWCNTs) are reported using microwave (MW) energy and water as a mild chemical agent. In the first method we reported the effect of MW irradiation on a dispersion of MWCNTs in deionized water, in the second method we studied the exposing of MWCNT to microwave irradiation in the presence of steam, and in the third method we used microwave oven-generated plasma for the functionalization of MWCNTs. We also performed thermal oxidation and acid treatment as two conventional methods for oxidative functionalization of carbon nanotubes, to compare their effect with our results. Transmission electron microscopy (TEM) and Raman spectroscopy results showed that although these microwave methods introduced some defects to the carbon nanotubes, the damage was less severe than conventional treatments. X-ray photoelectron spectroscopy (XPS) measurements confirmed that the functionalization of carbon nanotubes by these methods favored hydroxyl groups, which are useful when further functionalization is required.; Pejman Hojati-Talemi, Raoul Cervini, George P. Simon

Multi-walled carbon nanotubes modified screen-printed electrodes for cisplatin detection

Materon, Elsa M.; Wong, Ademar; Klein, Stanlei I.; Liu, Juewen; Sotomayor, Maria D. P. T.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 271-276
ENG
Relevância na Pesquisa
126.36%
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); A screen printed electrode functionalized with multi-walled carbon nanotubes and factory modified with carboxyl groups (MWCNT-COOH/SPCEs) was characterized by cyclic voltammetry and differential pulse voltammetry in a NaCl (0.1 mol L-1, pH 7) solution containing 800 mu mol L-1 sodium dodecyl sulfate (SDS). The MWCNT-COOH/SDS/SPCEs sensor was tested for the detection and quantification of cisplatin. For solutions of cisplatin, the electrochemical analysis showed a linear correlation coefficient of 0.9974 to cisplatin at concentrations between 1.45 x 10(-5) and 1.0 x 10(-4) mol L-1, a sensitivity of 4.4 x 10(4) (+/- 1.0 x 10(3)) mu A L mol(-1), and detection and quantification limits of 4.6 x 10(-6) and 1.4 x 10(-5) mol L-1, respectively. The reproducibility of the sensor response evaluated by the analysis of three replicates, indicated a RSD of 3.91%. The excellent response of the MWCNT-COOH/SDS/SPCEs cisplatin sensor allowed it to be tested in samples of human blood serum whose levels of added cisplatin were monitored by the HPLC. The average error % (sensor/HPLC) of 3.4 indicates that the combined methodology of MWCNT-COOH modified SPCE and the addition of a surfactant such as dodecyl sulfate is a convenient alternative for the use of HPLC for cisplatin determination in biological samples. The methodology cannot be applied to non-ionizable antitumor drugs carboplatin...

COMPOSITES OF MULTI-WALLED CARBON NANOTUBES WITH POLYPROPYLENE AND THERMOPLASTIC OLEFIN BLENDS PREPARED BY MELT COMPOUNDING

Petrie, Kyle
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
106.35%
Composites of multi-walled carbon nanotubes (MWCNTs) with polypropylene (PP) and thermoplastic olefins (TPOs) were prepared by melt compounding. Two non-covalent functionalization methods were employed to improve nanotube dispersion and the resulting composite properties are reported. The first functionalization approach involved partial coating of the surface of the nanotubes with a hyperbranched polyethylene (HBPE). MWCNT functionalization with HBPE was only moderately successful in breaking up the large aggregates that formed upon melt mixing with PP. In spite of the formation of large aggregates, the samples were conductive above a percolation threshold of 7.3 wt%. MWCNT functionalization did not disrupt the electrical conductivity of the nanotubes. The composite strength was improved with addition of nanotubes, but ductility was severely compromised because of the existence of aggregates. The second method involved PP matrix functionalization with aromatic moieties capable of π-π interaction with MWCNT sidewalls. Various microscopy techniques revealed the addition of only 25 wt% of PP-g-pyridine (Py) to the neat PP was capable of drastically reducing nanotube aggregate size and amount. Raman spectroscopy confirmed improved polymer/nanotube interaction with the PP-g-Py matrix. Electrical percolation threshold was obtained at a MWCNT loading of approximately 1.2 wt%. Electrical conductivity on the order of 10-2 S/m was achieved...

Administração de nanotubos de carbono "multiwalled" in vivo ativa citotoxicidade tumor-específica de linfócitos T CD8+; In vivo administration of "multi-walled" carbon nanotubes activates the tumor-specific cytotoxic CD8+ T lymphocytes

Adriel dos Santos Moraes
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 27/02/2012 PT
Relevância na Pesquisa
106.44%
A administração "in vivo" de nanotubos de carbono "multi-walled" (MWCNT's), mesmo sem serem funcionalizados, estimula o aparecimento de uma reposta imune em camundongos normais. Nesse trabalho nós fornecemos evidências de que essas nanopartículas de carbono também estimulam a resposta imune em camundongos portadores de tumor. Os MWCNT's (100 ?g) diluídos em PBS contendo 0,1 % de Pluronic 127 foram inoculados sistemicamente em camundongos portando tumores cujos tamanhos atingiram 5 milímetros (mm) e a resposta imune foi avaliada nos linfonodos desses animais. Observamos que os tumores de animais que receberam as nanopartículas não cresceram como os tumores dos animais não tratados. A discreta inibição do crescimento do carcinoma pulmonar de Lewis (LLC) foi acompanhada pela ativação de linfócitos T CD8+ tanto em número quanto em função. A ativação da função citotóxica dos linfócitos T CD8+ pode ser explicada pelo aumento da expressão de citocinas pertencentes à família da IL-12, principalmente IL-27, que é descrita como a citocina envolvida na estimulação da citotoxicidade de linfócitos T CD8+. Nossos dados demonstraram que nanotubos de carbono "multi-walled", mesmo sem funcionalização estimula resposta imunológica antitumoral.; The "in vivo" administration of multi walled carbon nanotubes (MWCNT's) even without functionalization stimulates the immune response of naïve mice. Here we provide evidence that these carbon nanoparticles also stimulated the immune response of tumor-bearing mice. The MWCNT's (100 ?g) diluted in PBS with 0...

Electrooxidation of DNA at glassy carbon electrodes modified with multi-walled carbon nanotubes with different oxidation degree

Bollo Dragnic, Soledad; Cañete Rosales, Paulina; Álvarez Lueje, Alejandro Francisco
Fonte: Sociedad Chilena de Química Publicador: Sociedad Chilena de Química
Tipo: Artículo de revista
EN
Relevância na Pesquisa
106.35%
Artículo de publicación SciELO; For the first time, the study of the effect of length and degree of oxidation of multi-walled carbon nanotubes (CNTs) on the electroanalytical DNA sensing properties of modified glassy carbon electrodes (GCEs) is reported. GCE/CNT electrodes were prepared using chitosan (CHI) as a dispersing agent. Short (S-NCs) and long (L-NCs) carbon nanotubes, as well as unoxidized and 3 or 6 hour oxidized samples were used. Cyclic voltammetry indicated that S-NCs exhibited larger capacitance values than L-NCs, and that these values increased when the CNTs were oxidized. Using Scanning Electrochemical Microscopy (SECM), an increase in the surface homogeneity was determined when oxidized CNTs were used as electrode modifiers. dsDNA electrooxidation showed the highest response using GCEs/CHI-L-NCs, and a clear decrease in the current intensity was observed when the oxidation time was increased. This result correlates with the higher BET surface area of L-NCs. In conclusion, the electrochemical performance of GCE/CNT electrodes against DNA increase when the length of CNTs is higher and decrease at higher oxidation state.; Financial support from the Fondecyt-CHILE (Grant 1120246) is gratefully acknowledged. P.C. acknowledges CONICYT scholarships for PhD studies in Chile...

Influence of size and oxidative treatments of multi-walled carbon nanotubes on their electrocatalytic properties

Álvarez Lueje, Alejandro Francisco; Bollo Dragnic, Soledad; Martínez, María Teresa; Ansón, Alejandro; Ortega, Valeria; González, Mónica; Cañete Rosales, Paulina
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo de revista
EN
Relevância na Pesquisa
106.33%
The influence of chemical oxidation on the electrochemical behavior against hydrogen peroxide of long and short multi-walled carbon nanotubes (MWCNT) has been investigated. Different degrees of oxidation with a sulfo-nitric mixture and with nitric acid were used and a complete physical and oxygen functional group characterization was performed by Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), acid group titration, transmission and scanning electron microscopies (TEM/SEM), elemental analysis, thermogravimetric analysis (TGA), nitrogen adsorption isotherms and cyclic voltammetry. The results revealed that electrodes modified using pristine short CNT (s-NC) present higher amperometric response against hydrogen peroxide than that obtained using long CNT (l-NC), which correlates with the greater degree of packing observed for l-NC by SEM and the long and thin structures observed in s-NC. On the other hand, the chemical oxidation process increases slightly the sensitivity of resulting electrodes, in about 25%, for both s-NC and l-NC indicating that for hydrogen peroxide oxidation the metal catalyst impurities, that are removed in the oxidation process, are not as relevant in the electrocatalysis as the increase in the capacitance values observed in the oxidized CNTs. The presence of oxygen groups introduces (a) new sites for redox reaction (pseudocapacitance) and (b) strong polar sites that would adsorb water molecules favoring double-layer formation (double-layer capacitance).; Fondecyt- CHILE (Grant 1080526)...

Buckling and Postbuckling Analysis of Multi-/Walled Carbon Nanotubes Based on the Continuum Shell Model

He, Xiaoqiao; Qu, Chuan-Yong; Qin, Qing Hua; Wang, C.M.
Fonte: World Scientific Publishing Company Publicador: World Scientific Publishing Company
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
106.33%
Buckling and postbuckling behaviors of multi-walled carbon nanotubes (MWCNTs) under a compressive force are studied. MWCNTs are modeled by Donnell's shallow shell nonlinear theory with the allowance of van der Waals (vdW) interaction between the walls. It

Growth and characterization of multi-walled carbon nanotubes at NASA Glenn Research Center

Harris, Jerry; Hepp, Aloysius; Raffaelle, Ryne; Gennett, Thomas; Vander Wal, Randy; Landi, Brian; Luo, Yu; Scherson, Daniel
Fonte: American Institute of Aeronautics and Astronautics Publicador: American Institute of Aeronautics and Astronautics
Tipo: Abstract Formato: 38350 bytes; application/pdf
EN_US
Relevância na Pesquisa
106.63%
Aligned multi-walled carbon nanotubes were prepared by the injection chemical vapor deposition (CVD) method using an iron-based organometallic compound as the catalyst source and toluene as the solvent. The concentration of the catalyst precursor was found to influence both the growth habit of the nanotubes, as well as the amount of iron in the deposited material. As deposited, the multi-walled carbon nanotubes contained as little as 2.8% iron by weight. The material was characterized by scanning electron microscopy, tunneling electron microscopy, Raman spectroscopy and thermogravimetric analysis. Using a second synthetic method, multi-walled carbon nanotubes were grown directly onto Co-coated stainless steel (SS) metal supports. Coulometric analysis of the cyclic voltammograms obtained for the carbon nanotube coated electrodes yielded lithium ion storage capacities as high as those observed for more conventional carbon materials, providing evidence that all the multi-walled carbon nanotubes within the entire ensemble are electrochemically active.; "Growth and characterization of multi-walled carbon nanotubes at NASA Glenn Research Center," Proceedings of the First International Energy Conversion Engineering Conference. The American Institute of Aeronautics and Astronautics. Held in Portsmouth...

Side-Wall Functionalization of Multi-Walled Carbon Nanotubes with t-Butyl Diazoacetate

Rogel-Hernández,Eduardo; Alonso-Nuñez,Gabriel; Camarena,Juan P.; Espinoza-Gómez,Heriberto; Aguirre,Gerardo; Paraguay-Delgado,Francisco; Somanathan,Ratnasamy
Fonte: Sociedad Química de México A.C. Publicador: Sociedad Química de México A.C.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2011 EN
Relevância na Pesquisa
106.43%
The covalent functionalization of multiwall carbon nanotubes (MWCNT) and its characterization techniques are reported. MWCNT were functionalized with tert-butyldiazoacetate to give methano-bridged ester group. Functionalized carbon nanotube by ester and its hydrolyzed carboxylic acid were characterized by high resolution electron microscope techniques, scanning electron microscopy (SEM), transmission electron microscopy (TEM) to study the shape a structure and fast Fourier transform infrared (FT-IR) to evaluate types of binding.

The Electrocatalysis of Multi-walled Carbon Nanotubes (MWCNTs) for Oxygen Reduction Reaction (ORR) in Room Temperature Ionic Liquids (RTILs)

Ding,Keqiang
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
Relevância na Pesquisa
126.36%
Oxygen reduction reaction (ORR) was investigated on a multi-walled carbon nanotubes (MWCNTs)-modified edge plane pyrolytic graphite (EPPG) electrode using cyclic voltammetry (CV) in three kinds of room temperature ionic liquids (RTILs), i.e., 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4), 1-n-propyl-3-methylimida-zolium tetrafluoroborate (PMIBF4), and 1-n-butyl-3-methylimidazolium tetrafluoro-borate (BMIBF4). The results demonstrated that, after being modified by MWCNTs on the EPPG electrode, both the reduction peak current of oxygen and the oxidation peak current of superoxide anion were all dramatically increased, and the values of standard rate constant, κs, corresponding to ORR, were greatly enhanced. Under the same condition, in PMIBF4, MWCNTs-modified EPPG electrode exhibited the most satisfied electrocatalysis for ORR, in which standard rate constant, κs, was improved from 2.9 × 10-3 cm s-1 on a EPPG electrode, to 10.4 × 10-3 cm s-1. While in EMIBF4 and BMIBF4, after being modified by MWCNTs, the value of κs was increased from 4.3 × 10-3 to 8.3 × 10-3 and 2.3 × 10-3 to 4.2 × 10-3 cm s-1, respectively. For the catalysis of MWCNTs-modified EPPG electrode towards ORR, the enhanced surface area of electrode and the increased amount of “defect” sites on electrode were thought to be the main reasons for our obtained results.

Decoration of multi-walled carbon nanotubes by metal nanoparticles and metal oxides using chemical evaporation method

Masipa,Pheladi M.; Magadzu,Takalani; Mkhondo,Bridget
Fonte: South African Journal of Chemistry Publicador: South African Journal of Chemistry
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2013 EN
Relevância na Pesquisa
126.36%
The powder patterns of the as-prepared and acid treated MWCNTs are shown by the XRD spectra. The TEM results show the microstructure of the multi-walled carbon nanotubes well decorated with metal nanoparticles (Cu, Fe, Ni) and metal oxides (CuO, Fe2O3 NiO), while the SEM show the surface morphology.