In this study, a novel polyimide (PI) film, consisting of multiwall carbon nanotubes (MWCNTs) dispersed in an Ionic Liquid (IL), were demonstrated to be high shielding effectiveness (SE). The film was potentially useful for screening electromagnetic interference(EMI) in an optical transceiver module. The experimental results showed MWCNT-PI composite dispersed well in IL exhibits a high far-field SE of 38 ~ 45 dB within the frequency range of 1 ~ 3 GHz. It was also demonstrated the MWCNT-PI composite prepared with IL dispersed process have higher SE and lower weight percentage of MWCNTs than those with non-IL-dispersed process. Their intermolecular forces were carefully examined in order to understand dispersion mechanisms among MWCNTs. The aggregation phenomenon of MWCNTs was known, resulting from van der Waals forces. In our study, IL was employed to disperse MWCNTs. A proposal reason was that the attractive force between cation of the IL and £k electrons of MWCNTs is greater than the van der Waals forces among MWCNTs. From conductivity measurement, percolation threshold of the IL-dispersed MWCNT-PI composite was 5.2 wt%; percolation threshold of the non-IL-dispersed MWCNT-PI composite was 11.5 wt%. Given the lower percolation threshold ,we demonstrated the successful dispersion of MWCNT by adding IL. From the results of Raman spectrometer analyses, the IL dispersion was proved to be a physical interaction. Furthermore, the IL-dispersed MWCNT-PI composite was used as package material in monopole antenna and got a near-field SE of 37dB within the frequency of 2.8 GHz. It implied that the IL-dispersed MWCNT-PI composite has an excellent EMI performance.The IL-dispersed MWCNT-PI composite is suitable for packaging low-cost and high-performance optical transceiver modules in the application of the fiber-to-the-home (FTTH) lightwave transmission systems.

Lead-tin solder has been widely used as interconnection material in electronics packaging for a long time. In response to environmental legislation, the lead-tin alloys are being replaced with lead-free alloys and electrically conductive adhesives in consumer electronics. Lead-free solder usually require higher reflow temperatures than the traditional lead-tin alloys, which can cause die crack and board warpage in assembly process, thereby impacting the assembly yields. The high tin content in lead-free solder forms tin whiskers, which has the potential to cause short circuits failure. Conductive adhesives are an alternative to solder reflow processing, however, conductive adhesives require up to 80 wt% metal filler to ensure electrical and thermal conductivity. The high loading content degrades the mechanical properties of the polymer matrix and reduces the reliability and assembly yields when compared to soldered assemblies. Carbon nanotubes (CNTs) have ultra high aspect ratio as well as many novel properties. The high aspect ratio of CNTs makes them easy to form percolation at low loading and together with other novel properties make it possible to provide electrical and thermal conductivity for the polymer matrix while maintaining or even reinforcing the mechanical properties. Replacing the metal particles with CNTs in conductive adhesive compositions has the potential benefits of being lead free, low process temperature, corrosion resistant, electrically/thermally conductive, high mechanical strength and lightweight. In this paper, multiwall nanotubes (MWNTs) with different dimensions are mixed with epoxy. The relationships among MWNTs dimension, volume resistivity and thermal conductivity of the composite are characterized. Different loadings of CNTs, additives and mixing methods were used to achieve satisfying electrical and mechanical properties and pot life. Different assembly technologies such as pressure dispensing, screen and stencil printing are used to simplify the processing method and raise the assembly yields. Contact resistance, volume resistivity, high frequency performance, thermal conductivity and mechanical properties were measured and compared with metal filled conductive adhesive and traditional solder paste.

Studies on charge transport properties in carbon nanotubes (CNTs) have been a subject of great interest for a long time not only as an important topic in fundamental science, but also as a basic requirement for the application of CNTs for nanoelectronics. CNTs show a wide range of transport behavior that varies from ballistic to hopping regime, depending on the dimensionality and nature of disorder in the system. Minute variations in disorder can lead from weak to strong localization, and this yields complex and intriguing features in the analysis of transport data. It is particularly important to carry out such a study for multiwall carbon nanotubes (MWCNTs), in which both dimensionality and disorder play an important role and the nature of localization is non-trivial as wave functions are extended along the tube or bundle of tubes. A proper understanding of the mechanisms of charge transport and their quantitative knowledge is an essential requirement for any possible application of CNTs in nanodevices. Such studies not only yield information on the transport parameters crucial for applications but can also provide a test for any possible microscopic theories of transport. Main focus of the current thesis is to understand the mechanism of charge transport in iron-embedded MWCNTs and to gain more knowledge on the transport behavior. Magnetically functionalized CNTs, in particular the CNTs filled with ferromagnetic materials are of profound interest for the basic scientific research as well as for technological application. Iron-embedded MWCNTs are synthesized by one step pyrolysis method. This method gives a proper route to synthesize the magnetic particles encapsulated CNTs. Beyond the geometrical advantage of a cylinder-shaped nanostructure design, the carbon shells provide an effective protection against oxidation of magnetic nanoparticles. The iron-embedded MWCNTs exhibit excellent magnetic properties like the uniaxial magnetic anisotropy, and the high coercivity, which is larger than the coercivity of bulk iron. Thus, they have significant potential for data storage devices and biomedical applications. Vertical alignment of CNTs is an important issue for device applications such as field electron emitters and flat-panel displays. Vertically aligned MWCNTs are grown on various substrates in the present work and the role of catalyst particles in vertical alignment is discussed. This thesis also reports the investigations on the magnetic properties including magnetotransport studies. The thesis is organized in seven chapters and a brief summary of each chapter is given below. Chapter 1 presents an introduction of the CNTs and its structural and electronic properties. Charge transport in CNTs is then discussed in terms of the fundamental aspects of conduction regimes and transport length scales. The synthesis and characterization of iron-embedded MWCNTs is described in chapter 2. It is important to get good quality CNTs in a scalable way. The various methods available for CNT synthesis are arc discharge, laser ablation, chemical vapor deposition etc. A one-step thermally assisted pyrolysis method employed for synthesizing MWCNTs is a simple and cost-effective method. Benzene is used as a precursor and ferrocene as a catalyst in the present case. Good quality CNTs are obtained from this method, which are of multiwall in nature (outer diameter in the range of 10-25 nm). Vertically aligned mats of MWCNTs are also obtained on the quartz substrate. The thickness of the mats is several tens of microns. The prepared MWCNTs are characterized by electron microscopic studies for its structure and surface morphology. Many iron particles are seen inside the tubes. Energy dispersive x-ray (EDX) spectra taken from the small region of the sample under TEM show the presence of iron. Raman spectra of the sample suggest good quality of the tubes. Prominent G-peak in this spectrum shows that the sample is of well-graphitic nature. X-ray diffraction pattern of MWCNT material shows the presence of -Fe and Fe3C apart from the graphitic peak. Chapter 3 describes the growth of vertically aligned MWCNTs (v-MWCNTs) on various substrates and role of catalyst particles in the alignment. The v-MWCNTs are grown on sapphire, quartz and thermally oxidized silicon substrates without pre-deposition of any catalyst. The grown MWCNT mats had a thickness of several tens of microns. Surface elemental analysis shows the presence of catalyst particles on the substrate which is essential for vertical alignment of the tubes. It is found that the order in which the precursor and the catalyst were introduced during chemical vapor deposition determines the orientation of the nanotubes. When there were no catalyst particles on the substrate in the beginning, random alignment of CNTs took place instead of vertical alignment. Base growth mode of CNTs is proposed in the present case from the results obtained. Chapter 4 deals with the magnetic properties of the as-synthesized MWCNTs. The CNTs in pristine form are of diamagnetic in nature. The ferromagnetic-like behavior arises from the iron particles embedded in MWCNTs. These ferromagnetic particles are retained in the MWCNTs automatically, as the catalyst in this case contains iron. MWCNTs of different iron weight percentage are prepared by taking different amount of ferrocene as a precursor. These particles exhibit a magnetic moment up to 98 emu/g and coercivity in the range of 500–2000 Oe. Reduced magnetization is attributed to the formation of surface shell with spin disorder and to the presence of Fe3C phase. Large coercivity compared to the bulk vale of few orested is due to the complex state of interactions, which can create strong pinning centers for the core moments during the demagnetization. In addition the observed dependence of the magnetoresistance on the direction of applied field, is correlated with the shape anisotropy of the Fe particles. The trend of saturation of magnetization at higher fields suggests that exchange coupling in the present case is one-dimensional. The charge transport properties of MWCNT mats are discussed in chapter 5. Many of the transport parameters are often affected by the presence of magnetic field. In order to gain a deeper insight into the conduction mechanism, the study of the electrical transport in presence of magnetic field is highly useful. The temperature and magnetic field dependence of the conductivity of MWCNT mat is studied in the temperature range of 1.4-150 K in the magnetic field up to 10 T. The charge transport in the system is governed by Mott’s variable-range hopping (VRH) of three-dimensional type in the higher temperature range and two-dimensional type in the lower temperature range. Mott’s various parameters like localization length, hopping length, hopping energy, and density of states at the Fermi level are deduced from the VRH fit. The hopping length decreases from 13.2 to 12.2 nm, as temperature increases from 110 to 150 K. The obtained value of hopping length around ~13 nm is within the range of nanotube diameters of 10 to 25 nm. This is the main component of the hopping length, which indicates that VRH takes place on the tube scale. The localization lengths observed in the case of 3D VRH and 2D VRH conduction are well within the range of outer diameter of MWCNTs, which indicates that the localization takes place at the tube scale along the boundaries of the tubes. If the charges are localized at the tube boundaries, then the localization length gives an average diameter of the tubes and the results obtained supports this argument. It is also important to note that the defects present in the nanotubes in the form of structural defects and bad matching of chirality gives rise to localization. There are not many reports on the effect of a magnetic field on the VRH process for MWCNT systems. The resistance of the sample decreases with the magnetic field in the direction of tube axis of the nanotubes. The magnetic field gives rise to delocalization of states as evident from the values of localization lengths at different fields. The application of magnetic field lowers the crossover temperature, at which three-dimensional VRH turns to two-dimensional VRH. The conductivity at the lower temperature side is governed by the weak localization (WL) give rise to positive magnetoconductance (MC). Here a phase diagram with temperature and magnetic field is proposed, showing different regions for different kind of transport mechanisms. This may be applicable for other class of disordered material as well. Chapter 6 deals with the magnetotransport studies on disordered MWCNT mat. The electrical conductivity and MC data are analyzed in the temperature range of 1.4-150 K and in the magnetic fields up to 11 T. The system is in the critical regime obeying conductivity of metallic systems as suggested in weak localization-electron electron interaction model. The MC is positive for the whole temperature range except at temperature below 4.2 K. Results are analyzed in the terms of weak localization, electron-electron interaction and VRH. The H 2 dependence at lower magnetic fields and H dependence at higher magnetic fields is found supporting weak localization. Inelastic scattering lengths are also deduced from the low temperature MC data and its temperature dependence shows that the dominant dephasing mechanism in the present case is inelastic electron-electron scattering in the dirty limit. Chapter 7 describes measurements on individual MWCNTs and subsequent charge transport studies. After many trials a suitable method was devised to isolate single tubes and to put contacts on it for the four probe measurement. For electrical measurements on isolated single tube, it is found that the joule heating due to excess current is an important issue. A current of the order of few µA burns the sample immediately. I-V characteristics of the MWCNTs show that the electrical contacts are ohmic and the resistance is few k. Initial electrical measurements show that there is slight decrease in resistance with increase of temperature and MR is approximately negative. This behavior suggests that signature of weak localization is present in the sample. Further studies are required in order to gain the insight into the transport mechanism for individual MWCNT. Finally, the thesis concludes with a general conclusion and future directions for this work.

The interwall spacing of multi-walled carbon nanotubes has an effect on their physical and chemical properties. Tubes with larger interwall spacing - compared to the spacing where the carbon atoms are in their natural distance to each other - are for instance expected to be mechanically less stable. Considering the MWCNT interwall spacing’s dependence on the tube size, three interesting previous studies with slightly different conclusions can be found. All of them conclude an increase of the interwall spacing with a decreasing tube size. We describe their analysis procedure, compare them to each other and to our own measured data. In the beginning of our analyses, we determine the expected inaccuracy for measured distances out of TEM images being up to 10 % and we show the impacts of the TEM’s defocus, a powerful setting in TEM imaging. Finally, we suppose that the interwall spacings are not as strongly varying as one previous study concludes, but our analyses are relatively in harmony with the two other studies. The interwall spacings from tubes with an inner diameter larger than 5 nm are relatively constant within the whole tube. Furthermore, it appears that the middle spacings (excluding the outer- and innermost ones) show values that are most consistent with the interlayer spacings of turbostratic graphite. In underfocused images, the outer- and innermost spacings tend to have values being slightly smaller than the middle ones from the same tube.

A área das Ciências Farmacêuticas busca constantemente por tratamentos mais eficientes, direcionados para alvos específicos, com diminuição da dose necessária e com a minimização dos efeitos adversos. Neste contexto, a área de Nanotecnologia Farmacêutica apresenta grande potencial de aplicabilidade, com resultados bastante promissores para o tratamento de diversas doenças. Os sistemas nanoestruturados têm sido avaliados para a incorporação de fármacos já utilizados em tratamentos administrados formas farmacêuticas convencionais que apresentam problemas farmacocinéticos ou farmacodinâmicos quando administrados. E, também, para a incorporação de novas moléculas com potencial para o tratamento de determinada doença. Neste trabalho de tese, nanocápsulas de núcleo lipídico versáteis contendo metotrexato na forma ácida e éster, bromelina, etanercept e infliximab foram desenvolvidas buscando contornar as limitações e aumentar a eficácia terapêutica desses fármacos. Inicialmente, as propriedades anti-inflamatórias de nanocápsulas de núcleo lipídico revestidas por micelas de polissorbato 80 contendo metotrexato encapsulado foram avaliadas em experimentos in vitro e in vivo, em células mononucleares obtidas a partir do líquido sinovial de pacientes com artrite reumatoide e em ratos Lewis com artrite induzida por adjuvante completo de Freund, respectivamente. As nanocápsulas de núcleo lipídico demonstraram serem altamente eficazes no controle da inflamação, sendo que os efeitos anti-inflamatórios in vivo foram alcançados em doses 75% menores que o metotrexato em solução. Na sequência, o tratamento in vitro da linhagem de células de carcinoma de mama humano, MCF-7, com nanocápsulas de núcleo lipídico multiparede funcionalizadas com bromelina demonstrou uma redução de 160 vezes na concentração necessária para obter o mesmo efeito quando comparada a uma solução de bromelina. A influência das pseudofases aniônicas e catiônicas no mecanismo de distribuição da indometacina, tacrolimus, aciclovir, metotrexato e éster etílico de metotrexato, foram avaliadas aplicando um algoritmo desenvolvido para nanocápsulas de núcleo lipídico. Verificou-se que somente a indometacina sofreu influência da presença de cargas, aumentando a afinidade pela fase dispersa das formulações. Formulações de nanocápsulas de núcleo lipídico multiparede contendo metotrexato na forma ácida e éster encapsulados e/ou funcionalizando a superfície das nanocápsulas foram desenvolvidas e testadas in vitro em linhagens de células tumorais (MCF-7) e em linhagens de células sadias (HaCaT). Essas formulações demonstraram atividade antiproliferativa maior para as MCF-7 (com redução em mais de 50% na viabilidade celular) em comparação com as soluções de metotrexato e éster etílico de metotrexato e esta atividade foi maior para as formulações em que as moléculas foram funcionalizadas na superfície das nanopartículas. A captação das nanopartículas pelas células também foi maior para as formulações funcionalizadas com metotrexato ou éster etílico de metotrexato em comparação com a formulação em que o éster de metotrexato está encapsulado. As três formulações contendo metotrexato na forma ácida ou éster não demonstraram ação antiproliferativa em linhagens de células sadias (HaCaT). Devido à baixa expressão de receptores de folato nessas células, não houve aumento da captação celular em comparação à formulação sem fármaco. Por último, foram desenvolvidas satisfatoriamente formulações de nanocápsulas de núcleo lipídico multiparede funcionalizadas com os anticorpos monoclonais infliximab e etanercept, e contendo éster etílico de metotrexato encapsulado, demonstrando que são adequadas para futuros estudos visando o tratamento da artrite reumatoide. Esse conjunto de resultados demonstra que as nanocápsulas de núcleo lipídico com funcionalização de superfície versátil, sejam revestidas com polissorbato 80 ou multiparede funcionalizadas são um sistema bastante promissor para a administração de fármacos de modo a aumentar sua especificidade e eficácia. / The Pharmaceutical Sciences field is constantly searching for more effective treatments, aiming specific targets, with dose reduction and minimization of side effects. In this context, the Pharmaceutical Nanotechnology field presents great applicability potential, with highly promising results for the treatment of several diseases. Nanostructured systems have been evaluated for the encapsulation of drugs approved for use in conventional pharmaceutical dosage forms that, however, exhibit pharmacokinetic or pharmacodynamics problems when administered, and for the encapsulation of novel molecules with potential to treat a determined disease. In the present thesis, versatile lipid-core nanocapsules containing methotrexate in the acid and ester forms, bromelain, etanercept and infliximab were developed, seeking to circumvent the limitations and increase the therapeutic efficacy of these drugs. Initially, the anti-inflammatory properties of methotrexate-loaded lipid-core nanocapsules coated with polysorbate 80 micelles were evaluated in in vitro and in vivo experiments, using mononuclear cells obtained from the synovial fluid of rheumatoid arthritis patients and Lewis rats with Freund complete adjuvant-induced arthritis. Lipid-core nanocapsules demonstrated to be highly effective in the control of inflammation, and the in vivo anti-inflammatory effects were reached in a dose 75% lower than the methotrexate in solution. In the sequence, the in vitro treatment of a human breast cancer cell line, MCF-7, with bromelina-functionalized multiple-wall lipid-core nanocapsules demonstrated a 160-fold reduction of the concentration required to obtain the same effect when compared with a bromelain solution. The influence of the anionic and cationic pseudo-phases in the distribution mechanism of indomethacin, tacrolimus, acyclovir, methotrexate and methotrexate ethyl ester was evaluated through an algorithm developed for lipid-core nanocapsules. It was verified that only indomethacin underwent influence in the presence of charge, increasing the affinity by the disperse phase of the formulations. Multiple-wall lipid-core nanocapsules formulations containing methotrexate in the acid and ester forms encapsulated and/or functionalizing the surface of the nanoparticles were developed and tested in vitro in tumour MCF-7 cells and in a healthy cell line (HaCaT). These formulations demonstrated higher anti-proliferative activity for the MCF-7 cells (reduction of over 50 % in cellular viability) in comparison with the methotrexate and methotrexate ethyl ester solutions and this activity was higher for the formulations in which the molecules were functionalized in the surface of the nanoparticles. A higher cellular uptake was observed for the formulations functionalized with methotrexate or methotrexate ethyl ester in comparison with the formulations in which the methotrexate ester is encapsulated. The three formulations containing methotrexate in the acid or ester form did not demonstrate anti-proliferative activity in non-tumour cell lines (HaCaT). Since these cells have a small expression of folate receptors, the uptake was not increased in comparison with the formulation without drug. Lastly, formulations of methotrexate ethyl ester-loaded multiwall lipid core nanocapsules functionalized with monoclonal antibodies infliximab and etanercept were successfully developed demonstrating suitability for future studies aiming the treatment of rheumatoid arthritis. These groups of results demonstrate that versatile lipid core nanocapsules, either coated with polysorbate 80 or multiwalled functionalized are a very promising system for the administration of drugs aiming their specificity and efficacy.

A área das Ciências Farmacêuticas busca constantemente por tratamentos mais eficientes, direcionados para alvos específicos, com diminuição da dose necessária e com a minimização dos efeitos adversos. Neste contexto, a área de Nanotecnologia Farmacêutica apresenta grande potencial de aplicabilidade, com resultados bastante promissores para o tratamento de diversas doenças. Os sistemas nanoestruturados têm sido avaliados para a incorporação de fármacos já utilizados em tratamentos administrados formas farmacêuticas convencionais que apresentam problemas farmacocinéticos ou farmacodinâmicos quando administrados. E, também, para a incorporação de novas moléculas com potencial para o tratamento de determinada doença. Neste trabalho de tese, nanocápsulas de núcleo lipídico versáteis contendo metotrexato na forma ácida e éster, bromelina, etanercept e infliximab foram desenvolvidas buscando contornar as limitações e aumentar a eficácia terapêutica desses fármacos. Inicialmente, as propriedades anti-inflamatórias de nanocápsulas de núcleo lipídico revestidas por micelas de polissorbato 80 contendo metotrexato encapsulado foram avaliadas em experimentos in vitro e in vivo, em células mononucleares obtidas a partir do líquido sinovial de pacientes com artrite reumatoide e em ratos Lewis com artrite induzida por adjuvante completo de Freund, respectivamente. As nanocápsulas de núcleo lipídico demonstraram serem altamente eficazes no controle da inflamação, sendo que os efeitos anti-inflamatórios in vivo foram alcançados em doses 75% menores que o metotrexato em solução. Na sequência, o tratamento in vitro da linhagem de células de carcinoma de mama humano, MCF-7, com nanocápsulas de núcleo lipídico multiparede funcionalizadas com bromelina demonstrou uma redução de 160 vezes na concentração necessária para obter o mesmo efeito quando comparada a uma solução de bromelina. A influência das pseudofases aniônicas e catiônicas no mecanismo de distribuição da indometacina, tacrolimus, aciclovir, metotrexato e éster etílico de metotrexato, foram avaliadas aplicando um algoritmo desenvolvido para nanocápsulas de núcleo lipídico. Verificou-se que somente a indometacina sofreu influência da presença de cargas, aumentando a afinidade pela fase dispersa das formulações. Formulações de nanocápsulas de núcleo lipídico multiparede contendo metotrexato na forma ácida e éster encapsulados e/ou funcionalizando a superfície das nanocápsulas foram desenvolvidas e testadas in vitro em linhagens de células tumorais (MCF-7) e em linhagens de células sadias (HaCaT). Essas formulações demonstraram atividade antiproliferativa maior para as MCF-7 (com redução em mais de 50% na viabilidade celular) em comparação com as soluções de metotrexato e éster etílico de metotrexato e esta atividade foi maior para as formulações em que as moléculas foram funcionalizadas na superfície das nanopartículas. A captação das nanopartículas pelas células também foi maior para as formulações funcionalizadas com metotrexato ou éster etílico de metotrexato em comparação com a formulação em que o éster de metotrexato está encapsulado. As três formulações contendo metotrexato na forma ácida ou éster não demonstraram ação antiproliferativa em linhagens de células sadias (HaCaT). Devido à baixa expressão de receptores de folato nessas células, não houve aumento da captação celular em comparação à formulação sem fármaco. Por último, foram desenvolvidas satisfatoriamente formulações de nanocápsulas de núcleo lipídico multiparede funcionalizadas com os anticorpos monoclonais infliximab e etanercept, e contendo éster etílico de metotrexato encapsulado, demonstrando que são adequadas para futuros estudos visando o tratamento da artrite reumatoide. Esse conjunto de resultados demonstra que as nanocápsulas de núcleo lipídico com funcionalização de superfície versátil, sejam revestidas com polissorbato 80 ou multiparede funcionalizadas são um sistema bastante promissor para a administração de fármacos de modo a aumentar sua especificidade e eficácia. / The Pharmaceutical Sciences field is constantly searching for more effective treatments, aiming specific targets, with dose reduction and minimization of side effects. In this context, the Pharmaceutical Nanotechnology field presents great applicability potential, with highly promising results for the treatment of several diseases. Nanostructured systems have been evaluated for the encapsulation of drugs approved for use in conventional pharmaceutical dosage forms that, however, exhibit pharmacokinetic or pharmacodynamics problems when administered, and for the encapsulation of novel molecules with potential to treat a determined disease. In the present thesis, versatile lipid-core nanocapsules containing methotrexate in the acid and ester forms, bromelain, etanercept and infliximab were developed, seeking to circumvent the limitations and increase the therapeutic efficacy of these drugs. Initially, the anti-inflammatory properties of methotrexate-loaded lipid-core nanocapsules coated with polysorbate 80 micelles were evaluated in in vitro and in vivo experiments, using mononuclear cells obtained from the synovial fluid of rheumatoid arthritis patients and Lewis rats with Freund complete adjuvant-induced arthritis. Lipid-core nanocapsules demonstrated to be highly effective in the control of inflammation, and the in vivo anti-inflammatory effects were reached in a dose 75% lower than the methotrexate in solution. In the sequence, the in vitro treatment of a human breast cancer cell line, MCF-7, with bromelina-functionalized multiple-wall lipid-core nanocapsules demonstrated a 160-fold reduction of the concentration required to obtain the same effect when compared with a bromelain solution. The influence of the anionic and cationic pseudo-phases in the distribution mechanism of indomethacin, tacrolimus, acyclovir, methotrexate and methotrexate ethyl ester was evaluated through an algorithm developed for lipid-core nanocapsules. It was verified that only indomethacin underwent influence in the presence of charge, increasing the affinity by the disperse phase of the formulations. Multiple-wall lipid-core nanocapsules formulations containing methotrexate in the acid and ester forms encapsulated and/or functionalizing the surface of the nanoparticles were developed and tested in vitro in tumour MCF-7 cells and in a healthy cell line (HaCaT). These formulations demonstrated higher anti-proliferative activity for the MCF-7 cells (reduction of over 50 % in cellular viability) in comparison with the methotrexate and methotrexate ethyl ester solutions and this activity was higher for the formulations in which the molecules were functionalized in the surface of the nanoparticles. A higher cellular uptake was observed for the formulations functionalized with methotrexate or methotrexate ethyl ester in comparison with the formulations in which the methotrexate ester is encapsulated. The three formulations containing methotrexate in the acid or ester form did not demonstrate anti-proliferative activity in non-tumour cell lines (HaCaT). Since these cells have a small expression of folate receptors, the uptake was not increased in comparison with the formulation without drug. Lastly, formulations of methotrexate ethyl ester-loaded multiwall lipid core nanocapsules functionalized with monoclonal antibodies infliximab and etanercept were successfully developed demonstrating suitability for future studies aiming the treatment of rheumatoid arthritis. These groups of results demonstrate that versatile lipid core nanocapsules, either coated with polysorbate 80 or multiwalled functionalized are a very promising system for the administration of drugs aiming their specificity and efficacy.

A área das Ciências Farmacêuticas busca constantemente por tratamentos mais eficientes, direcionados para alvos específicos, com diminuição da dose necessária e com a minimização dos efeitos adversos. Neste contexto, a área de Nanotecnologia Farmacêutica apresenta grande potencial de aplicabilidade, com resultados bastante promissores para o tratamento de diversas doenças. Os sistemas nanoestruturados têm sido avaliados para a incorporação de fármacos já utilizados em tratamentos administrados formas farmacêuticas convencionais que apresentam problemas farmacocinéticos ou farmacodinâmicos quando administrados. E, também, para a incorporação de novas moléculas com potencial para o tratamento de determinada doença. Neste trabalho de tese, nanocápsulas de núcleo lipídico versáteis contendo metotrexato na forma ácida e éster, bromelina, etanercept e infliximab foram desenvolvidas buscando contornar as limitações e aumentar a eficácia terapêutica desses fármacos. Inicialmente, as propriedades anti-inflamatórias de nanocápsulas de núcleo lipídico revestidas por micelas de polissorbato 80 contendo metotrexato encapsulado foram avaliadas em experimentos in vitro e in vivo, em células mononucleares obtidas a partir do líquido sinovial de pacientes com artrite reumatoide e em ratos Lewis com artrite induzida por adjuvante completo de Freund, respectivamente. As nanocápsulas de núcleo lipídico demonstraram serem altamente eficazes no controle da inflamação, sendo que os efeitos anti-inflamatórios in vivo foram alcançados em doses 75% menores que o metotrexato em solução. Na sequência, o tratamento in vitro da linhagem de células de carcinoma de mama humano, MCF-7, com nanocápsulas de núcleo lipídico multiparede funcionalizadas com bromelina demonstrou uma redução de 160 vezes na concentração necessária para obter o mesmo efeito quando comparada a uma solução de bromelina. A influência das pseudofases aniônicas e catiônicas no mecanismo de distribuição da indometacina, tacrolimus, aciclovir, metotrexato e éster etílico de metotrexato, foram avaliadas aplicando um algoritmo desenvolvido para nanocápsulas de núcleo lipídico. Verificou-se que somente a indometacina sofreu influência da presença de cargas, aumentando a afinidade pela fase dispersa das formulações. Formulações de nanocápsulas de núcleo lipídico multiparede contendo metotrexato na forma ácida e éster encapsulados e/ou funcionalizando a superfície das nanocápsulas foram desenvolvidas e testadas in vitro em linhagens de células tumorais (MCF-7) e em linhagens de células sadias (HaCaT). Essas formulações demonstraram atividade antiproliferativa maior para as MCF-7 (com redução em mais de 50% na viabilidade celular) em comparação com as soluções de metotrexato e éster etílico de metotrexato e esta atividade foi maior para as formulações em que as moléculas foram funcionalizadas na superfície das nanopartículas. A captação das nanopartículas pelas células também foi maior para as formulações funcionalizadas com metotrexato ou éster etílico de metotrexato em comparação com a formulação em que o éster de metotrexato está encapsulado. As três formulações contendo metotrexato na forma ácida ou éster não demonstraram ação antiproliferativa em linhagens de células sadias (HaCaT). Devido à baixa expressão de receptores de folato nessas células, não houve aumento da captação celular em comparação à formulação sem fármaco. Por último, foram desenvolvidas satisfatoriamente formulações de nanocápsulas de núcleo lipídico multiparede funcionalizadas com os anticorpos monoclonais infliximab e etanercept, e contendo éster etílico de metotrexato encapsulado, demonstrando que são adequadas para futuros estudos visando o tratamento da artrite reumatoide. Esse conjunto de resultados demonstra que as nanocápsulas de núcleo lipídico com funcionalização de superfície versátil, sejam revestidas com polissorbato 80 ou multiparede funcionalizadas são um sistema bastante promissor para a administração de fármacos de modo a aumentar sua especificidade e eficácia. / The Pharmaceutical Sciences field is constantly searching for more effective treatments, aiming specific targets, with dose reduction and minimization of side effects. In this context, the Pharmaceutical Nanotechnology field presents great applicability potential, with highly promising results for the treatment of several diseases. Nanostructured systems have been evaluated for the encapsulation of drugs approved for use in conventional pharmaceutical dosage forms that, however, exhibit pharmacokinetic or pharmacodynamics problems when administered, and for the encapsulation of novel molecules with potential to treat a determined disease. In the present thesis, versatile lipid-core nanocapsules containing methotrexate in the acid and ester forms, bromelain, etanercept and infliximab were developed, seeking to circumvent the limitations and increase the therapeutic efficacy of these drugs. Initially, the anti-inflammatory properties of methotrexate-loaded lipid-core nanocapsules coated with polysorbate 80 micelles were evaluated in in vitro and in vivo experiments, using mononuclear cells obtained from the synovial fluid of rheumatoid arthritis patients and Lewis rats with Freund complete adjuvant-induced arthritis. Lipid-core nanocapsules demonstrated to be highly effective in the control of inflammation, and the in vivo anti-inflammatory effects were reached in a dose 75% lower than the methotrexate in solution. In the sequence, the in vitro treatment of a human breast cancer cell line, MCF-7, with bromelina-functionalized multiple-wall lipid-core nanocapsules demonstrated a 160-fold reduction of the concentration required to obtain the same effect when compared with a bromelain solution. The influence of the anionic and cationic pseudo-phases in the distribution mechanism of indomethacin, tacrolimus, acyclovir, methotrexate and methotrexate ethyl ester was evaluated through an algorithm developed for lipid-core nanocapsules. It was verified that only indomethacin underwent influence in the presence of charge, increasing the affinity by the disperse phase of the formulations. Multiple-wall lipid-core nanocapsules formulations containing methotrexate in the acid and ester forms encapsulated and/or functionalizing the surface of the nanoparticles were developed and tested in vitro in tumour MCF-7 cells and in a healthy cell line (HaCaT). These formulations demonstrated higher anti-proliferative activity for the MCF-7 cells (reduction of over 50 % in cellular viability) in comparison with the methotrexate and methotrexate ethyl ester solutions and this activity was higher for the formulations in which the molecules were functionalized in the surface of the nanoparticles. A higher cellular uptake was observed for the formulations functionalized with methotrexate or methotrexate ethyl ester in comparison with the formulations in which the methotrexate ester is encapsulated. The three formulations containing methotrexate in the acid or ester form did not demonstrate anti-proliferative activity in non-tumour cell lines (HaCaT). Since these cells have a small expression of folate receptors, the uptake was not increased in comparison with the formulation without drug. Lastly, formulations of methotrexate ethyl ester-loaded multiwall lipid core nanocapsules functionalized with monoclonal antibodies infliximab and etanercept were successfully developed demonstrating suitability for future studies aiming the treatment of rheumatoid arthritis. These groups of results demonstrate that versatile lipid core nanocapsules, either coated with polysorbate 80 or multiwalled functionalized are a very promising system for the administration of drugs aiming their specificity and efficacy.

Field emission is the emission of electrons from a solid under an intense electric field, of the order of 109 V/m. Emission occurs by the quantum mechanical tunneling of electrons through a potential barrier to vacuum. Field emission sources offer several attractive features such as instantaneous response to field variation, resistance to temperature fluctuation and radiation, a high degree of focusing ability in electron optics, good on/off ratio, ballistic transport, and a nonlinear current-voltage relationship. Carbon nanotubes (CNTs) are potential candidates as field emitters since they possess high aspect ratio and are chemically inert to poisoning, and physically inert to sputtering during field emission. They can carry a very high current density and do not suffer field-induced tip sharpening like metallic tips. In addition, the CNT field emitters have the advantage of charge transport through 1D channels and electron emission at the sharp tips due to large enhancement. But the injection of electrons from the back contact remains a technical challenge which requires binding of CNT emitters to metallic substrate. Also, detachment of the CNT from the substrate tends to occur with time. The electrically conducting mixtures of CNTs and polymer can provide an alternative route to address these issues in the field emission of CNTs. The composites can be casted on any substrate in desired shape and the polymer matrix provides necessary support. The research work reported in this thesis includes the preparation of high quality multiwall carbon nanotubes (MWCNTs), MWCNT-polystyrene (PS) composites, and experimental investigation on field emission properties of MWCNT¬PS composites in two different configurations. Electrical conductivity and percolation threshold of the MWCNT-PS composites are also investigated to ensure their high quality prior to the field emission studies. The study has been further extended to reduced graphene oxide (rGO) coated on polymer substrate. The main results obtained in present work are briefly summarized below. This thesis contains eight chapters. Chapter 1 provides an overview of basics of field emission, and the potential of CNT and CNT-polymer composites as field emitters. Chapter 2 deals with the concise introduction of various structural characterization tools and experimental techniques employed in this study. Chapter 3 describes the synthesis of MWCNTs and characterization by using electron microscopy and Raman spectroscopy. MWCNTs are synthesized by chemical vapor deposition (CVD) of toluene [(C6H5) CH3] and ferrocene [(C5H5)2 Fe] mixture at 980 °C. Here toluene acts as carbon source material and ferrocene provides catalytic iron (Fe) particles. The MWCNT formation is based on the thermal decomposition of the precursor mixture. Scanning electron microscopy (SEM) characterization shows that the MWCNTs are closely packed and quite aligned in one direction. The average length of MWCNTs is about 200 μm and outer diameter lies in the range of 50-80 nm. The high quality of as-prepared MWCNT sample is confirmed by Raman spectroscopy. The as-grown MWCNTs are encapsulated with catalytic Fe nanoparticles, revealed by transmission electron microscopy. The Fe nanoparticles trapped within the MWCNT serve as fantastic system for studying the magnetic properties. Three types of MWCNT samples filled with Fe nanoparticles of different aspect ratio (~10, 5 and 2) are synthesized by varying the amount of ferrocene in the precursor material, and their magnetic properties are investigated. Enhanced values of coercivity (Hc) are observed for all samples, Hc being maximum (~2.6 kOe) at 10 K. The enhancement in Hc values is attributed to the strong shape anisotropy of Fe nanoparticles and significant dipolar interactions between Fe nanoparticles. Chapter 4 deals with the field emission studies of MWCNT-PS composites in the parallel configuration. By incorporating as-prepared MWCNTs in PS matrix in a specific ratio, composites with varying loading from 0.01-0.45 weight (wt.) fraction are prepared using solution mixing and casting. High degree of dispersion of MWCNTs in PS matrix without employing any surfactant is achieved by ultrasonication. Low percolation threshold (~0.0025 wt. fraction) in the MWCNT-PS composites ensures the good connectivity of filler in the fabricated samples. Field emission of MWCNT¬PS composites is studied in two different configurations: along the top surface of the film (parallel configuration) and along the cross section of the sample (perpendicular configuration). In this chapter field emission results of the MWCNT-PS composites in parallel configuration are presented. The effect of charge transport in limiting the field emission of MWCNT-PS composite is discussed. Field emission results of MWCNT-PS composites in parallel configuration indicate that the emission performance can be maximized at moderate wt. fraction of MWCNT (0.15). The obtained current densities are ~10 µA/cm2 in the parallel configuration. Chapter 5 presents the study of field emission characteristics of MWCNT¬PS composites of various wt. fractions in the perpendicular configuration. Till date most studies using nanotube composites tend to have the nanotubes lying in two dimensional plane, perpendicular to the applied electric field. In the perpendicular configuration, the nanotubes are nearly aligned parallel to the direction of the applied electric field which results in high field enhancement, and electron emission at lower applied fields. SEM micrographs in cross-sectional view reveal that MWCNTs are homogeneously distributed across the thickness and the density of protruding tubes can be scaled with wt. fraction of the composite film. Field emission from composites has been observed to vary considerably with density of MWCNTs in the polymer matrix. High emission current density of 100 mA/cm2 is achieved at a field of 2.2 V/µm for 0.15 wt. fraction. The field emission is observed to follow the Fowler– Nordheim tunneling mechanism, however, electrostatic screening plays a role in limiting the current density at higher wt. fractions. Chapter 6 highlights the field emission response of rGO coated on a flexible PS film. Field emission of rGO coated PS film along the cross section of the sample is studied in addition to the top film surface of the film. The effect of geometry on the improved field emission efficiency of rGO coated polymer film is demonstrated. The emission characteristics are analyzed by Fowler–Nordheim tunneling for field emission. Low turn-on field (~0.6 V/µm) and high emission current (~200 mA/cm2) in the perpendicular configuration ensure that rGO can be a potential field emitter. Furthermore, stability and repeatability of the field emission characteristics are also presented. Chapter 7 deals with the synthesis, characterization, and field emission of two different kinds of hybrid materials: (1) MWCNT coated with zinc oxide (ZnO) nanoparticles (2) ZnO/graphitic carbon (g-C) core-shell nanowires. The field emission from the bucky paper is improved by anchoring ZnO nanoparticles on the surface of MWCNT. A shift in turn on field from 3.5 V/µm (bucky paper) to 1.0 V/µm is observed by increasing the ZnO nanoparticle loading on the surface of MWCNT with an increase in enhancement factor from 1921 to 4894. Field emission properties of a new type of field emitter ZnO/g-C core-shell nanowires are also presented in this chapter. ZnO/g-C core/shell nanowires are synthesized by CVD of zinc acetate at 1300 °C. Overcoming the problems of ZnO nanowire field emitters, which in general possess high turn on fields and low current densities, the core-shell nanowires exhibit excellent field emission performance with low turn on field of 2.75 V/µm and high current density of 1 mA/cm2. Chapter 8 presents a brief summary of the important results and future perspectives of the work reported in the thesis.

Carbon nanotubes (CNTs) have been recognized as potential candidates for mainstream device fabrication and technologies. CNTs have become a topic of interest worldwide due to their unique mechanical and electrical properties. In addition, CNTs possess high aspect ratio and low density that make them an important material for various technological applications. The field of carbon nanotube devices is rapidly evolving and attempts have been made to use CNTs in the fabrication of devices like field emitters, gas sensors, flow meters, batteries, CNT-field effect transistors etc. These molecular nanostructures are proposed to be an efficient hydrogen storage material. CNT cylindrical membranes are reported to be used as filters for the elimination of multiple components of heavy hydrocarbons from petroleum and for the filtration of bacterial contaminants of size less than 25 nm from water. Recently, CNT bundles have been proposed to be a good material for low-temperature sensing. CNTs have also been considered as promising filler materials due to extraordinary characteristics mentioned above. Fabrication of nanocomposites using CNTs as reinforcing material has completely renewed the research interest in polymer composites. The conductive and absorptive properties of insulating polymer doped with conducting filler are sensitive to the exposure to gas vapors and hence they can be used in monitoring various gases. The application of fiibre reinforced polymer composites in aeronautic industry are well known due to their high mechanical strength and light weight. Also, the conductive composite materials can be used for electromagnetic shielding. Desired properties in CNT-composites can be attained by adding small amount of CNTs in comparison to traditional filler materials. Due to high aspect ratio and low density of CNTs, percolation threshold in CNT-polymer composites can be achieved at 0.1 vol % as compared to ~16 vol. % in case of carbon particles. The research work ׽0.1 vol. %, as compared to reported in this thesis includes the preparation of multiwall carbon nanotube (MWNTs) and MWNT-polystyrene composites, experimental investigations on low temperature charge transport, and magnetic properties in these systems. This thesis contains 7 chapters. Chapter 1 provides an overview of CNTs and CNT-polymer composites. This chapter briefly describes the methods for synthesizing CNTs and fabricating CNT-polymer composites, charge transport mechanisms in CNTs and composites, and their magnetic properties as well. Chapter 2 deals with the concise introduction of various structural characterization tools and experimental techniques employed in the present work. An adequate knowledge of the strengths and limitations of experimental equipment can help in gathering necessary information about the sample, which helps in studying and interpreting its physical properties correctly. Chapter 3 describes the synthesis of MWNTs and their use as filler material for the fabrication of composites with polystyrene (PS). The characterization results of as-prepared MWNT and composites show that MWNTs possess high aspect ratio (~4000), and are well dispersed in the composite samples (thickness ~50-70 µm). The composite samples are prepared by varying the MWNT concentration from 0.1 to 15 wt %. The as¬fabricated composites are electrically conductive and expected to display novel magnetic properties since MWNTs are embedded with iron (Fe) nanoparticles. Chapter 4 presents the study of charge transport properties of aligned and random MWNTs in the temperature range 300-1.4 K. The low temperature electrical conductivity follows the weak localization (WL) and electron-electron (e-e) interaction model in both samples. The dominance of WL and e-e interaction is further verified by magneto-conductance (MC) measurements in the perpendicular magnetic field up to 11 T at low temperatures. The MC data of these samples consists of both positive and negative contributions, which originates from WL (at lower fields and higher temperatures) and e-e interaction (at higher fields and lower temperatures). Chapter 5 contains the results of charge transport studies in MWNT-PS composite near the percolation threshold (~0.4 wt %) at low temperatures down to 1.4 K. Metallic-like transport behavior is observed in composite sample of 0.4 wt %, which is quite unusual. In general, the usual activated transport is observed for systems near the percolation threshold. The unusual weak temperature dependence of conductivity in MWNT-PS sample at percolation threshold is further verified from the negligible frequency dependence of conductivity, in the temperature range from 300 to 5 K. Chapter 6 accounts on the experimental results of magnetization studies of MWNTs and MWNT-PS composites. The observation of maxima in coercivity and squareness ratio at 1 wt % of Fe-MWNT in a polymer matrix show the dominance of dipolar interactions among the encapsulated Fe-nanorods within MWNTs. The hysteresis loop of 0.1 wt % sample shows anomalous narrowing at low temperatures, which is due to significant contribution from shape anisotropy of Fe-nanorods. Chapter 7 presents brief summary and future perspectives of the research work reported in the thesis.

Ever since their discovery, Carbon nanotubes (CNTs) have been renowned to be potential candidates for a variety of applications. Nevertheless, the difficulties accompanied with their dispersion and poor solubility in various solvents have hindered CNTs potential applications. As a result, studies have been developed to address the dispersion problem. The solution is in modifying the surfaces of the nanotubes covalently or non-covalently with a desired dispersant. Various materials have been employed for this purpose out of which polymers are the most common. Non-covalent functionalization of CNTs via polymer wrapping represents an attractive method to obtain a stable and homogenous CNTs dispersion. This method is able to change the surface properties of the nanotubes without destroying their intrinsic structure and preserving their properties. This thesis explores and studies the surface modification and solublization of pristine single and multiwalled carbon nanotubes via a simple solution mixing technique through non-covalent interactions of CNTs with various anionic and cationic conjugated polyelectrolytes (CPEs). The work includes studying the interaction of various poly(phenylene ethynylene) electrolytes with MWCNTs and an imidazolium functionalized poly(3-hexylthiophene) with SWCNTs. Our work here focuses on the noncovalent modifications of carbon nanotubes using novel CPEs in order to use these resulting CPE/CNT complexes in various applications. Upon modifying the CNTs with the CPEs, the resulting CPE/CNT complex has been proven to be easily dispersed in various organic and aqueous solution with excellent homogeneity and stability for several months. This complex was then used as a nanofiller and was dispersed in another polymer matrix (poly(methyl methacrylate), PMMA). The PMMA/CPE/CNT composite materials were cast or electrospun depending on their desired application. The presence of the CPE modified CNTs in the polymer matrix has been proven to enhance the composites thermal, mechanical and electrical properties compared to pristine CNTs. Various spectroscopic and microscopic techniques such as UV-vis, fluorescence, TEM, AFM and SEM were used to study and characterize the CPE/CNT complexes. Also, TGA, DSC and DMA were used to study the thermal and mechanical properties of the composite materials. Our current work represents a fundamental study on the non-covalent interactions between CNTs and CPEs on one hand and gives a real life example on the CPE/CNT application in composite materials and electronics.