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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Investigation of the structure-property-processing relationships in paper and carbon nanotube composite materials

Muhlbauer, Rachel Lynn 21 September 2015 (has links)
In this research, multiwalled carbon nanotube (MWNT) and paper composite materials were fabricated by dropcasting aqueous dispersions containing MWNTs onto filter paper using vacuum filtration, a highly unidirectional drying technique. By varying the pore size of the paper backbone as well as the number of deposited MWNT layers, composites with distinct architectures and properties were created. This thesis provides numerous examples that show how the processing methodology used influences the location of the MWNTs, the amount of MWNTs deposited, and the interaction between the MWNTs and the paper backbone. These three factors work in tandem to form the structures and properties presented. Understanding how the structures and properties come about allows for the tailorability of these composites for different applications and devices. The pore size of the backbone material combined with the directionality of the drying methodology controlled the location of MWNT deposition. MWNT deposition occurred in three ways: on the paper surface only, within the paper material only, or combined surface and internal deposition. By varying the number of deposition steps, the properties of the composite could be altered in the location of deposition. Surface charge, dispersion concentration, paper pore size, drying methodology, MWNT length, the number of deposited MWNT layers, and post-processing techniques were all factors studied in this thesis which could successfully vary the interaction between the MWNTs and between the MWNT and paper materials and, ultimately, alter the properties of the composite. Regardless of the processing methodology employed and the starting materials used, structure and property evolutions in the composite materials were characterized using impedance spectroscopy, optical microscopy, scanning electron microscopy, and Current-AFM. Combining equivalent circuit fitting of the impedance data with the information obtained from the imaging techniques allowed for the elucidation of structural mechanisms which contribute to the electronic response measured for each composite. An overall equivalent circuit was built for each composite plane which could then be used to extract the electrical properties of the individual conduction mechanisms within the composite. In the in-plane, the electrical properties of the paper backbone, MWNT-MWNT junctions, MWNT bundles, and MWNT curved bundles could be determined. In the thru-plane, the electrical properties within the paper thickness, either paper-dominated or MWNT-dominated, could be measured. The resistance through the thickness of a bulk MWNT surface network could be also measured when the density of the MWNT network is sufficiently high.
2

Ballistic conduction in multiwalled carbon nanotubes

Yi, Yan 11 May 2004 (has links)
Multiwalled carbon nanotubes (MWNTs) are shown to be ballistic conductors at room temperature, with mean free paths of the order of tens of microns. The electrical transport measurements are performed both in air and in high vacuum in the transmission electron microscope on nanotubes pointing out of a nanotube-containing fiber that contact with a liquid metal. These measurements demonstrate that metallic MWNTs are one dimensional conductor that have quantized conductance nearly 1G0 (~{!V~}(12.9 K~{ and 8~})-1). The intrinsic resistance per unit length is found to be smaller than 100 ~{ and 8~}/~{ and L~}m, indicating a mean free path l> 65 ~{ and L~}m. The nanotube-metal contact resistances are in the range from 0.1 to 1 k~{ and 8 and L~}m. Contact scattering can explain why the measured conductances are about half of the expected theoretical value of 2G0. Current-to-voltage characteristic are in accord with the electronic structure. The nanotubes can survive high current (up to 1 mA, i.e., current density on the order of 109 A/cm2). In situ electron microscopy shows that a relative large fraction of the nanotubes do not conduct (even at high bias), consistent with the existence of semiconducting nanotubes. Discrepancies with other measurements are most likely due to damage caused to the outer layer(s) of the nanotubes during processing. The measured mean free path of clean, undamaged arc-produced MWNTs is several orders of magnitude greater than that for metals, making this perhaps the most significant property of carbon nanotubes.
3

Modulação da genotoxicidade do 1-Nitropireno por nanotubos de carbono de paredes múltiplas / Genotoxicity modulation of 1-Nitropyrene by multiwalled carbon nanotubes

Honorio, Jaqueline Gonçalves, 1988- 20 August 2018 (has links)
Orientadores: Gisela de Aragão Umbuzeiro, Vitor Rafael Coluci / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Tecnologia / Made available in DSpace on 2018-08-20T12:15:06Z (GMT). No. of bitstreams: 1 Honorio_JaquelineGoncalves_M.pdf: 1809951 bytes, checksum: 7885a8cfa050d72f934edad04cce0f92 (MD5) Previous issue date: 2012 / Resumo: Nanomateriais, tais como nanotubos de carbono de paredes múltiplas (MWCNT) têm apresentado potencial para remediação de águas e solos poluídos por compostos orgânicos devido a sua área superficial elevada, que pode melhorar a capacidade dos NTC em adsorver compostos orgânicos. Embora o tratamento de MWCNT com ácido nítrico possa aumentar a capacidade de dispersão do material em água através da introdução de grupos oxigenados sobre a superfície dos NTC, como ácidos carboxílicos, a diminuição da capacidade de MWCNT de interagir com moléculas orgânicas pode ocorrer como consequência não intencional. Para investigar esta possibilidade, foi avaliada a capacidade de MWCNT tratados com ácido de adsorver um poluente ambiental comum, 1-Nitropireno (1-NP), que é um nitro-hidrocarboneto policíclico aromático altamente mutagênico e carcinogênico. Diferentes doses de MWCNTs caracterizados foram testadas com diferentes doses de 1-NP, e a detecção do 1-NP não adsorvido foi avaliada pelo ensaio de mutagenicidade Salmonella/microssoma, usando a linhagem TA98 que é altamente sensível a 1-NP. Assim, apenas 1-NP não adsorvido aos MWCNT são absorvidos pelas bactérias e causam mutagenicidade. Encontramos uma relação inversa entre a oxidação por tratamento ácido dos MWCNT e a mutagenicidade da mistura. Os dados obtidos sugerem que o tratamento ácido de MWCNT pode, de fato, reduzir a capacidade de poluentes orgânicos se ligarem a MWCNT, reduzindo a eficácia na remediação / Abstract: Nanomaterials, such as multi-wall carbon nanotubes (MWCNT) have been shown potential to remediate soil or water polluted with organic compounds because of their high specific-surface area, which can enhance the ability of the CNT to adsorb organics. Although treatment of MWCNT with nitric acid can increase the water solubility of MWCNT by introducing oxygenated groups such as carboxylic acids onto the surface, it may have the unintended consequence of decreasing the ability of MWCNT to interact with organic molecules. To investigate this possibility, we evaluated the ability of acid-treated MWCNT to absorb a common environmental pollutant, 1- nitropyrene (1-NP), which is a highly mutagenic and carcinogenic nitro-polycyclic aromatic hydrocarbon. Different doses of well-characterized MWCNTs were tested with different doses of 1-NP, and the detection of the non-adsorbed 1-NP was assessed by the Salmonella mutagenicity assay in strain TA98, which is highly sensitive to 1-NP. Thus, only free 1-NP not bound to the MWCNT was able to enter the bacteria and induce mutagenesis. We found an inverse association between the amount of oxidation by nitric-acid treatment of the MWCNT and the amount of mutagenicity of the reaction mixture. Our data suggest that acid treatment of MWCNT may, in fact, reduce the ability of MWCNT to bind organic pollutants, reducing their effectiveness for remediation / Mestrado / Tecnologia e Inovação / Mestre em Tecnologia
4

Manufacturing of High Performance Polymer Nanocomposites Containing Carbon Nanotubes And Carbon Nanofibers Using Ultrasound Assisted Extrusion Process

Kumar, Rishi 07 December 2010 (has links)
No description available.
5

Synthesis Of Various Carbon Nanostructures And The Transport Properties Of Carbon Nanotubes

Singh, Laishram Tomba 11 1900 (has links) (PDF)
Different carbon nanostructures have different properties and different applications. It is needed to synthesize good quality and also on large scale. From the point of industrial applications, highly productive and low cost synthesis method is very essential. Research has been done extensively on the intrinsic and individual properties of both single walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWC-NTs) in the range of nanometer to micrometer length scale. The important question is how the properties change beyond this length scale and if they are used in group in the form of an array instead of the individual carbon nanotubes (CNTs). Some applications require large current output, large energy production etc. For such kind of applications, it becomes essential to use CNTs in large number in the form of arrays or array, instead of using large numbers of CNTs in individual level. Future nanotechnology scope requires large scale application using the very rich intrinsic properties of the CNTs and nanomaterials. Keeping these problems and challenges in front, this thesis work is devoted to the research of the large scale synthesis of mm long MWCNTs, having different morphology and studies on various physical properties of MWCNTs in the form of arrays. Synthesis of mm long aligned and buckled MWCNTs have been reported for the first time. Generally buckled CNTs were obtained by compressing the straight CNTs. Apart from this, different morphologies like, aligned straight, helical or coiled CNTs are also synthesized. Resistance of the individual CNT increases with the increase in length. Resistance versus length of an array of CNT also shows similar behaviour. The thermal conductivity of CNT array is observed to decrease with the increase of array diameter (diameter �100 µm). There are few reports of the similar behaviour with the experiments done on small diameter CNT arrays (diameter �100 nm). From these observations, it seems that in the arrays of CNT, their intrinsic individual property is preserved though the magnitudes are different. The conductance measurements done on buckled CNT array by compressing it to apply uniaxial strain, shows the conductance oscillation. This conductance oscillation seems to be originating from the band gap change due to strain when the CNTs bend during compression. Recent research focuses on the arrays of CNT as they can carry large current of the order of several milliamperes that make the arrays suitable in nanoscale electronics and in controlling macroscopic devices such as light emitting diodes and electromotors. Regarding this aspect, a part of this thesis work is devoted on the application of CNT array to field effect transistor (FET) and study of thermoelectric power generation using CNT arrays. The entire thesis is based on the works discussed above. It has been organized as follows: Chapter 1 deals with introduction about the different carbon nanostructures and different synthesis methods. A brief introduction about the different current-voltage (IV) characteristics of SWCNTs and MWCNTs, length and diameter dependence and effect of the mode of contacts, are given. Some applications of the array of CNTs like buckling effect on compression, stretching of CNT into the form of rope, and conduction change on compression are discussed. Application of CNT as FET, as a thermometer, and thermoelectric effect of CNT are discussed. The electromechanical effect of CNT is also discussed briefly. Chapter 2 deals with experimental setup for synthesis of different morphologies of carbon nanostructures. The samples are characterized using common characterization techniques like, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. A brief introduction about Raman Spectroscopy of CNT is given. Chapter 3 reports the unusual IV characteristics and breakdown of long CNT arrays. The current carrying ability and the threshold voltage as a function of array diameter are reported. The effect of the ambient like temperature and pressure are discussed. Chapter 4 deals with theoretical models to analyze the IV characteristics reported in Chapter 3. It has been shown that a set of classical equations are applicable to quantum structures and the band gap can be evaluated. Chapter 5 describes with application of CNT arrays as temperature sensors. It has been shown that CNT arrays of suitable diameters are used as temperature sensors after calibration. Chapter 6 reports the high current FET application of CNT arrays. Effects of temperature and ambient pressure are discussed. The type of the majority charge carrier is determined. Chapter 7 deals with application of CNT arrays as thermoelectric power generator to get large thermoelectric current. Effects of different array diameter are discussed. Modulation of thermoemf with gate voltage is discussed. The type of the majority charge carrier is determined. Chapter 8 reports the effect of compressive strain on buckled MWCNT arrays. Conductance is measured during the compression of the array. Quantum electromechanical conductance oscillation is observed. The structural changes are observed with SEM. Raman spectroscopic study supports the explanation of the effect. Chapter 9 provides the conclusion and overall summary of the thesis.
6

Microstructure of Fe-based and NiFe nanowires encapsulated by multiwalled carbon nanotube radial structures

Ibrar, Muhammad January 2018 (has links)
The crystalline iron-based nanowires encapsulated by multiwalled carbon nanotubes have been the subject of numerous studies owing to the range of potential applications. The presence of a-Fe (bcc)/y -Fe(fcc) junctions o ers the possibility of exploitation of the exchange bias effect, an interfacial magnetic phenomenon that plays a major role in magnetocaloric cooling, spintronic and high-density magnetic storage devices. This work is concerned with the synthesis and microstructural characterization of Fe-based and NiFe nanowires encapsulated by multiwall carbon nanotube radial structures. The known attributes of these structures are well matched to the magnetocaloric application. The primary aim of this work was to determine the unknown microstructural details of the encapsulated nanowire that are of relevance to the magnetocaloric application (junction types, location and orientation relative to the nanotube axis). The secondary aim was to explore the modi cation of the synthesis route to promote desirable attributes. This is the first report of a-Fe/y -Fe sequential junctions and a-Fe/Fe3C concentric junctions in encapsulated Fe-based nanowires. The presence of a-Fe/y -Fe junctions was inferred from the observation of a-Fe nanowires terminated by a ~100 nm length y-Fe crystallites of larger diameter. The a-Fe/Fe3C junctions exhibit the Bagaryatski orientation relationship: [110 ]bcck[100 ]orth. The degree of substrate roughness was found to be a means of tailoring details of the structure and composition of the encapsulated nanowires. NiFe encapsulated nanowires were found to contain crystallites of a-NiFe, y-NiFe and Ni3Fe and the sequential junctions -NiFe/Ni3Fe and a-NiFe/y-NiFe junctions.
7

Characterization and Applications of Multiwalled Carbon Nanotubes

Hilding, Jenny Marie 01 January 2004 (has links)
Multiwalled carbon nanotubes (MWNTs) have attracted great interest during thelast decade due to their possession of a unique set of properties. In addition totheir strength, MWNTs have well defined morphologies, with large aspect ratiosand pores in the meso range, and intriguing transport properties, such as highelectrical and thermal conductivity.We are interested in how variations in the MWNT morphology affect areas ofpossible engineering applications. We have identified morphology as a criticalelement for the performance of MWNTs in engineering applications. Specificareas studied and reported here spans from surface adsorption and capillarycondensation, to dispersion and dispersion processes, and transport propertiesin relation to MWNT aspect ratio. This wide range of exploration is typicallyneeded for evaluating opportunities for new materials.MWNTs can be used in different types of adsorption systems and it should bepossible to tailor the MWNT morphology to suit a specific adsorption process.We found that the major part of butane, our model gas, adsorbs on the externalMWNT and only a small fraction ends up in the pores.The unusually large aspect ratio makes MWNTs ideal as fillers in polymermatrixes. Since MWNTs are electrically conductive, it is possible to align theMWNTs in the matrix before curing. We investigated the effect of AC-fields onaqueous MWNT dispersions and the possibility to align MWNTs in an electricalfield.It is also necessary to develop suitable dispersion methods, to enable theproduction of homogeneous dispersions and composites. We studied a numberof different mechanical dispersion methods and their effect on the MWNTmorphology.
8

Nanocompositos elastomericos baseados em MWCNTs : preparação, caracterização, e aplicações / Elastomeric nanocomposites based on MWCNTs : preparation, characterization, and applications

Pedroni, Lucas Gomes 13 August 2018 (has links)
Orientadores: Ana Flavia Nogueira, Maria Isabel Felisberti / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-13T13:37:27Z (GMT). No. of bitstreams: 1 Pedroni_LucasGomes_M.pdf: 2275674 bytes, checksum: 3829c2b15fd56db6cd84d632bf86508b (MD5) Previous issue date: 2009 / Resumo: Nanocompósitos poliméricos baseados em nanotubos de carbono possuem um dos mais elevados potenciais tecnológicos devido à possibilidade de produção de materiais com destacadas propriedades mecânicas, alta condutividade elétrica em baixos teores (baixos limites de percolação), e boa processabilidade. São sistemas versáteis que podem apresentar propriedades excepcionais, as quais podem ser controladas pela alteração na proporção de seus componentes, permitindo que sejam moldados para atender à aplicação exigida. Nesse trabalho, nanocompósitos de nanotubos de carbono de paredes múltiplas (MWCNTs) e um elastômero comercial (Kraton-D®), que é um copolímero em bloco de estireno-butadieno-estireno (SBS), foram preparados por extrusão e pela técnica de evaporação de solvente (casting). As propriedades térmicas, mecânicas, e elétricas desses materiais foram comparadas. A caracterização foi realizada através de medidas de condutividade elétrica (método de Coleman), microscopias eletrônicas de varredura e de transmissão (caracterização morfológica), termogravimetria (determinação do teor de cargas e estabilidade térmica), ensaios de tração e análise dinâmico-mecânica (propriedades mecânicas). Além disso, o potencial de aplicação dos compósitos em células solares de TiO2/corante (DSSC) e como materiais absorvedores de radiação (MAR) foi avaliado. Os resultados evidenciaram uma forte influência da metodologia de preparo nas propriedades finais dos compósitos, a qual é creditada a mudanças de morfologia do sistema em função das condições de preparação utilizadas. As amostras preparadas por casting apresentaram condutividades elétricas mais elevadas, enquanto as propriedades mecânicas foram superiores para os filmes extrudados, e ambas tiveram melhoria da estabilidade térmica. Os compósitos se mostraram promissores quanto ao uso em DSSC e como MAR, mas muitos estudos ainda são necessários para aprimorar sua eficiência nesses campos / Abstract: Polymeric nanocomposites based on carbon nanotubes (CNTs) have one of the highest technological potential due to the possibility of produce materials with improved mechanical properties, high electrical conductivity at low loadings (low percolation threshold), and good processability. These systems are versatile, may present astonishing properties, and are allowed to control them by changing the proportion of their components, being able to tailor these materials to suit a desired application. In this work, nanocomposites of multiwalled carbon nanotubes (MWCNTs) and a commercial elastomer (Kraton-D®), which is a block copolymer of styrenebutadiene- styrene (SBS), were prepared by extrusion and by casting. The thermal, mechanical, and electrical properties presented by these materials were compared. The characterization was performed by measurement of the electrical conductivity (Coleman¿s method), scanning and transmission electron microscopy (for morphologic characterization), thermogravimetry (for thermal stability and determination of the loading of filler), stress-strain tests and dynamic mechanical analysis (for the mechanical properties). Furthermore, the potential of application of the extruded composites in dye-sensitized solar cells (DSSC) and as radiation absorbing materials (RAM) was tested. The results showed a strong influence of the methodology of preparation upon the final properties of composites, which was attributed to changes in the morphology of the system with conditions used to prepare the samples. Composites made by casting showed a higher electrical conductivity than the extruded ones, although the latter presented better mechanical properties than the former ones. Despite the requirement of further studies to improve their efficiency in DSSC and as RAM, the composites were promising for these applications / Mestrado / Quimica Inorganica / Mestre em Química
9

Kinetika i mehanizam uklanjanja odabranih metala iz vode adsorpcijom na aminofunkcionalizovanom ugljeničnom nanomaterijalu / The kinetics and mechanism of removal of selected metals from water by adsorption on amino functionalized carbon nanomaterials

Šućurović Aleksandra 27 September 2017 (has links)
<p>Predmet istraživanja ove doktorske disertacije bio je ispitivanje adsorpcionog pona&scaron;anja As(III) i odabranih metala (Cu(II), Cd(II), Pb(II), Cr(VI)) na amino- funkcionalizovanim vi&scaron;eslojnim ugljeničnim nanocevima, MWCNT-NH<sub>2 </sub>, na četiri odabrane pH vrednosti (3; 4,5; 6 i 11) i pri različitim sastavima vodenog rastvora (prisustvo hlorida, nitrata, sulfata i fosfata), a u cilju ispitivanja mogućnosti primene MWCNT-NH<sub>2</sub> za uklanjanje arsena i jona metala iz vodenih rastvora u oblasti relativno niskih koncentracija (0,01-3 mg L <sup>-1</sup> ). Fokus ove doktorske disertacije<br />je bio na utvrđivanju mehanizma procesa adsorpcije u ispitivanim uslovima.&nbsp;&nbsp; Adsorpciju arsena i metala na MWCNT-NH<sub>2</sub> najbolje je opisao reakcioni model pseudo-drugog reda &scaron;to&nbsp; znači da adsorpcija može biti pripisana uspostavljanju hemijskih interakcija između adsorbata i vezivnih grupa na povr&scaron;ini adsorbenta. Modelovanje brzine Weber Morris-ovim difuzionim modelom ukazalo je&nbsp; na to da unutarčestična difuzija, iako sporiji korak&nbsp; od eksterne difuzije, nije jedini ograničavajući korak u procesu adsorpcije, već su za to odgovorne i interakcije ispitivanih jona sa vezivnim mestima na povr&scaron;ini adsorbenta.&nbsp; U ravnotežnim uslovima, na različitim pH vrednostima, adsorpcija se mogla opisati&nbsp; Langmuir-ovim i Freundlich-ovim adsorpcionim modelima. Kapacitet i afinitet adsorbenta, kao i sam mehanizam adsorpcije, značajno su bili uslovljeni pH vredno&scaron;ću rastvora, kako zbog karakteristika povr&scaron;ine ispitivanog adsorbenta uslovljenih pH vredno&scaron;ću, tako i zbog uticaja pH vrednosti rastvora na pojavne hemijske oblike u kojima se arsen i metali nalaze. Ispitivanje uticaja anjona pokazalo je da je prisustvo hlorida povećalo afinitet povr&scaron;ine MWCNT-NH<sub>2 </sub>ka jonima arsena i svih metala u oblasti niskih<br />koncentracija, dok je prisustvo hlorida, nitrata, sulfata i fosfata pozitivno uticalo na afinitet povr&scaron;ine (od 2 do 8 puta veći u odnosu na dejonizovanu vodu) MWCNT-NH<sub>2</sub><br />ka Cu(II) u oblasti vi&scaron;ih koncentracija. Najmanji uticaj anjona na afinitet povr&scaron;ine ka vezivanju metala primećen je kod hroma. Pretpostavljeni&nbsp; mehanizmi uklanjanja arsena i odabranih metala u prisustvu anjona ukljuĉuju reakcije građenja različitih vrsta spolja&scaron;nje-&nbsp; i unutra&scaron;nje-sfernih kompleksa, jonske izmene, kao i&nbsp; elektrostatičke interakcije koje se ostvaruju između pozitivno naelektrisane povr&scaron;ine MWCNT-NH<sub><span style="font-size: 8.33333px;">2</span></sub>&nbsp;i anjona, na pH vrednostima manjim od 6,4, a koje menjaju afinitet<br />povr&scaron;ine ka jonima arsena i metala. Rezultati ove doktorske disertacije pokazuju da se ispitivani adsorbent, MWCNT-NH<sub>2 </sub>,&nbsp; može koristiti za uklanjanje arsena i te&scaron;kih metala iz vode u prisustvu različitih anjona i da, svojim adsorpcionim karakteristikama, može konkurisati komercijalnim i&nbsp; ekonomski pristupačnim adsorbentima.</p> / <p>The subject of this doctoral thesis was the examination of the adsorption behaviour of As(III), and selected metals (Cu(II), Cd(II), Pb(II), Cr(VI)) on the amino-functionalized multiwalled carbon nanotubes, MWCNT-NH<sub>2</sub>, at four pH values (3, 4.5, 6, and 11) with different compositions of aqueous solutions (in the presence of chlorides, nitrates, sulphates and phosphates), in order to examine the possibilities of applying MWCNT-NH<sub>2</sub> in removal of arsenic and metal ions from aqueous solutions in relatively low concentration (0,01- 3mg L<sup>-1</sup>). The focus of this doctoral thesis was to establish the mechanism of adsorption process in given conditions. Arsenic and metal adsorption on MWCNT-NH<sub>2</sub> were best described with the pseudo-second order kinetic model, which assumes that adsorption can be attributed to the establishment of chemical reactions between the adsorbate, and the binding groups at the surface of adsorbent. The Weber - Morris diffusion model indicated that intercellular diffusion, although being a slower step than external diffusion, is not the only limiting step in the adsorption process, but also that the interactions of ions with the adsorbent surface binding sites, are responsible. In equilibrium, at different pH values, the adsorption could be described by the Langmuir and Freundlich adsorption models. The capacity and affinity of the adsorbent, and adsorption mechanism, were considerably determined by the pH value of the solution, either because of the characteristics of the surface of the investigated adsorbent depending on pH value, or the effect of the solution&rsquo;s pH value on the chemical forms of arsenic and other metals. Investigation of the influence of the anion showed that the presence of chloride increased affinity of the surface of MWCNT-NH<sub>2</sub> to arsenic ions and to all metals in low concentration ranges, while presence of chlorides, nitrates, sulphates and phosphates had a positive impact on the affinity of the surface (2 or 8 times greater than for deionized water) MWCNT-NH<sub>2</sub> for Cu(II) in high concentration ranges. The smallest impact of anions to affinity of the surface to bond metals was noticed for chromium. The assumed mechanisms of removing arsenic and selected metals in the presence of anions include reactions of forming various kinds of outer- and inner-spheric complexes, ionic exchange, as well as electrostatic interaction which occur between positively charged surface of MWCNT-NH<sub>2</sub> and anions, for pH &lt; 6.4, and which change affinity of the surface towards arsenic and metal ions. Results of this doctoral thesis show that the investigated adsorbent, MWCNT-NH<sub>2</sub>, can be used for the removal of arsenic and heavy metals from water, in the presence of different anions, and that with its adsorbent characteristic it can compete with commercially, and economically more affordable adsorbents.</p>
10

Desenvolvimento de um sensor amperométrico baseado em ftalocianina de ferro, nanotubo de carbono oxidado e óxido de grafeno para determinação de isoniazida / Development of an amperometric sensor based on iron phthalocyanine, oxidized carbon nanotube and graphene oxide for determination of isoniazid

Spindola, Rolff Ferreira 25 July 2016 (has links)
Submitted by Rosivalda Pereira (mrs.pereira@ufma.br) on 2017-06-02T19:09:40Z No. of bitstreams: 1 RolffSpindola.pdf: 1912678 bytes, checksum: 00839e9b1b8a2b01a86770dd2561ec07 (MD5) / Made available in DSpace on 2017-06-02T19:09:40Z (GMT). No. of bitstreams: 1 RolffSpindola.pdf: 1912678 bytes, checksum: 00839e9b1b8a2b01a86770dd2561ec07 (MD5) Previous issue date: 2016-07-25 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ) / Fundação de Amparo à Pesquisa e ao Desenvolvimento Científico e Tecnológico do Maranhão (FAPEMA) / A novel platform for electroanalysis of isoniazid based on multi-walled carbon nanotube oxide and graphene oxide composite as support to iron phthalocyanine (MWCNTO-GO/FePc) has been developed. The FePc/MWCNTO-GO modified electrode is sensible for isoniazid, decreasing substantially its oxidation potential to + 200 mV vs. Ag/AgCl. Electrochemical and electroanalytical properties of the FePc/MWCNTO-GO modified electrode were investigated by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electrochemical microscopy, and amperometry. The sensor presents better performance in 0,1 mol L-1 phosphate buffer at pH 7,4. Under optimized conditions, a linear response range from 5 μmol L-1 to 476 µmol L-1 was obtained with a sensitivity of 0,0225 μA L μmol-1. The limits of detection and quantification for isoniazid determination were 0,56 μmol L-1 and 1,88 μmol L-1, respectively. The relative standard deviation for 10 determinations of 100 μmol L-1 isoniazid was 2,5%. The sensor was successfully applied for isoniazid determination in artificial body fluids. / No presente trabalho é apresentado o desenvolvimento de uma nova plataforma para eletroanálise de isoniazida baseada em (MWCNTO-GO/FePc). O eletrodo modificado com FePc/MWCNTO-GO diminuiu sensivelmente o potencial de oxidação da isoniazida para +200 mV vs. Ag/AgCl. As propriedades eletroquímicas e eletroanalíticas do eletrodo modificado com FePc/MWCNTO-GO foram investigadas por voltametria cíclica, espectroscopia de impedância eletroquímica, microscopia eletroquímica de varredura, e amperometria. O sensor apresentou melhor desempenho em tampão fosfato 0,1 mol L-1 com pH 7,4. Sob condições otimizadas uma faixa de resposta linear de 5 μmol L-1 a 476 µmol L-1 foi obtida com uma sensibilidade de 0,0225 μA L μmol-1. O limite de detecção e quantificação para a isoniazida foram determinados como sendo 0,56 μmol L-1 e 1,88 μmol L-1, respectivamente. O desvio padrão relativo para 10 determinações de 100 μmol L-1 de isoniazida foi de 2,5%. O sensor foi aplicado com sucesso para determinação de isoniazida em fluidos corporais artificiais.

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