Single-walled carbon nanotubes (SWNTs) are one of the leading candidate materials to realize novel nanoscale photonic devices. In order to assess their performance characteristics as optoelectronic materials, it is crucial to examine their optical properties in highly non-equilibrium situations such as high magnetic fields, low temperatures, and under high photoexcitation. Therefore, we present our latest result on the magnetic susceptibility anisotropy of metallic carbon nanotubes due to the Aharonov-Bohm effect. Here, we performed magnetic linear dichroism on a metallic-enriched HiPco SWNT sample utilizing a 35 T Hybrid Magnet to measure absorption with light polarization both perpendicular and parallel to the magnetic field. By relating these values with the nematic order parameter for alignment, we found that the metallic carbon nanotubes do not follow a strict diameter dependence across the 7 chiralities present in our sample. In addition to the studying the absorption properties exhibited at high magnetic field, we performed temperature-dependent (300 K to 11 K) photoluminescence (PL) on HiPco SWNTs embedded in an ι -carrageenan matrix utilizing intense fs pulses from a wavelength-tunable optical parametric amplifier. We found that for each temperature the PL intensity saturates as a function of pump fluence and the saturation intensity increases from 300 K to a moderate temperature around 100-150 K. Within the framework of diffusion-limited exciton-exciton annihilation (EEA), we successfully estimated the density of 1D excitons in SWNTs as a function of temperature and chirality. These results coupled with our results of magnetic brightening, or an increase in PL intensity as a function of magnetic flux through each SWNT due to the Aharonov-Bohm effect, yield great promise that in the presence of a high magnetic field the density of excitons can be further increased.

Well dispersed aqueous suspensions containing single-walled carbon nanotubes (SWCNTs) from bulk powders were prepared with surfactant and without surfactant by acid functionalization. SWCNT coated electrodes were then prepared from the SWCNT aqueous suspensions using various methods to create uniform nanoporous networks of SWCNTs on various substrates and stainless steel (SST) current collectors for use as ultracapacitor electrodes. Drop coating, high voltage electro-spraying (HVES), inkjet printing, and electrophoretic deposition (EPD) methods were evaluated. Optical and scanning electron microscope images were used to evaluate the SWCNT dispersion quality of the various electrodes. Ultimately an EPD process was established which reliably produced uniform SWCNT nanoporous networks on SST substrates. The prepared SWCNT coated electrodes were characterized using cyclic voltammetry and their capacitance was determined. A correlation between extended EPD processing times, EPD processing temperatures, and electrode capacitance was quantified. Optimum EPD processing occurs where linear capacitance gains were observed for processing times less than 10 minutes. At processing times between 10 – 60 minutes a non-linear relationship demonstrated diminishing capacitance gains with extended EPD processing times. Likewise, optimum EPD processing occurs when the processing temperature of the SWCNT suspension is raised above room temperature. At processing temperatures from 45°C to 60°C an increase in capacitance was observed over the room temperature (22°C) electrodes processed for the same durations. Conversely, for processing temperatures less than room temperature, at 5°C, a decrease in capacitance was observed. It was also observed that SWCNT electrodes processed at 60°C processing temperatures resulted in 4 times the capacitance of 5°C electrodes for the same processing times, when the durations were 8 minutes or less. For samples with raised processing temperatures the time dependent capacitance gains were observed to be significantly diminished beyond 10 minute processing times. The SWCNT network thickness was also correlated to EPD processing temperature and capacitance. A linear relationship was identified between the SWCNT network thickness and the capacitance of the electrode. It was also observed that elevated processing temperatures increase the EPD deposition rate of SWCNTs, produce thicker SWCNT networks, and thus create electrodes with higher capacitance than electrodes processed at lower EPD processing temperatures. EPD of SWCNTs was demonstrated in this work to be an effective method for the fabrication of SWCNT ultracapacitor electrodes. Characterization of the process determined that optimal EPD processing occurs within the first 10 minutes of processing time and that elevated processing temperatures yield higher SWCNT deposition rates and higher capacitance values. In this work the addition of SWCNT nanoporous networks to SST electrodes resulted in increases in capacitance of up to 398 times the capacitance of the uncoated SST electrodes yielding a single 1cm2 electrode with a capacitance of 91mF and representing an estimated specific capacitance for the processed SWCNT material of 45.78F/g.

This thesis research investigates the adhesion mechanisms of protein molecules to surfaces of biomaterials. New understanding in such adhesion mechanisms will lead to materials design and surface engineering in order to extend the lifespan of implants. The present research evaluates and analyzes the adhesive strength of proteins on pure High Density Polyethylene (HDPE), Single Wall Carbon Nanotube (SWCNT) enhanced HDPE composites, Ti-C:H coating and Ti6Al4V alloys (grade 2). The adhesive strength was studied through fluid shear stress and the interactions between the fluid and material surfaces. The adhesive strength of protein molecules was measured through the critical shear strength that resulted through the fluid shear stress. The effects of surface and material properties, such as roughness, topography, contact angle, surface conductivity, and concentration of carbon nanotubes on adhesion were analyzed. Research results showed that the surface roughness dominated the adhesion. Protein was sensitive to micro-scale surface roughness and especially favored the nano-porous surface feature. Results indicated that the unpurified SWCNTs influenced crystallization of HDPE and resulted in a nano-porous structure, which enhanced the adhesion of the protein onto a surface. Titanium hydrocarbon coating on silicon substrate also had a porous topography which enhanced its adhesion with protein, making it superior to Ti6Al4V.

<p>Single-walled carbon nanotubes (SWNT) are highly ordered filamentous nanocarbon structures. As their commercial and industrial use becomes more widespread, it is anticipated that SWNT will enter the environment through waste streams and product degradation. Because of their highly hydrophobic nature, SWNT aggregate and settle out of aqueous environments, especially in saline environments such as estuaries. Therefore, sediments are a likely environmental sink for SWNT once released. It is important to understand how these materials will impact benthic estuarine systems since they are the probable target area for SWNT exposure in addition to containing many lower trophic level organisms whose survvial and contaminant body burdens can have a large impact on the overall ecosystem. Disruptions in lower trophic level organism survival can have negative consequences for higher trophic levels, impacting the overall health of the ecosystem. It is also important to consider contaminant bioaccumulation, trophic transfer and biomagnification. If SWNT are taken up by benthic invertebrates, there is the possibility for trophic transfer, increasing the exposure of SWNT to higher trophic level organisms that otherwise would not have been exposed. If this type of transfer occurs in environmentally important species, the potential for human exposure may increase. My research aims to determine the magnitude of the toxicity and bioaccumulation of SWNT in benthic estuarine systems, as well as determine how they interact with other contaminants in the environment. This research will contribute to the knowledge base necessary for performing environmental risk assessments by providing information on the effects of SWNT to benthic estuarine systems. </p><p> Before investigating the environmental effects of SWNT, it is imperative that a measurement method is established to detect and quantify SWNT once they enter the environment. This research utilized pristine, semiconducting SWNT to develop extraction and measurement methods to detect and quantify these specific materials in environmental media using near infrared fluorescence (NIRF) spectroscopy. Semiconducting SWNT fluoresce in the near infrared (NIR) spectrum when excited with visible&ndashNIR light. This unique optical property can be used to selectively measure SWNT in complex media. </p><p> The fate, bioavailability, bioaccumulation and toxicity of SWNT have not been extensively studied to date. Pristine SWNT are highly hydrophobic and have been shown to strongly associate with natural particulate matter in aquatic environments. In light of this, I have focused my research to examine the influence of sediment and food exposure routes on bioavailability, bioaccumulation, and toxicity of structurally diverse SWNT in several ecologically-important marine invertebrate species. No significant mortality was observed in any organism at concentrations up to 1000 mg/kg. Evidence of biouptake after ingestion was observed for pristine semiconducting SWNT using NIRF spectroscopy and for oxidized <super>14</super>C&ndashSWNT using liquid scintillation counting. After a 24 hour depuration period, the pristine semiconducting SWNT were eliminated from organisms to below the method detection limit (5 &mug/mL), and the <super>14</super>C&ndashSWNT body burden was decreased by an order of magnitude to a bioaccumulation factor (BAF) of <0.01. Neither pristine SWNT nor oxidized <super>14</super>C&ndashSWNT caused environmentally relevant toxicity or bioaccumulation in benthic invertebrates. Overall, the SWNT were not bioavailable and appear to associate with the sediment.</p><p> In addition to investigating the toxicity and bioaccumulation of SWNT as an independent toxicant, it is important to consider how they will interact with other contaminants in the environment (i.e., increase or decrease toxicity and bioaccumulation of co&ndashcontaminants, alter the environmental transport of co&ndashcontaminants, induce degradation of co&ndashcontaminants, etc.). I wanted to investigate the effects of SWNT on a complex mixture of contaminants already present in a natural system. New Bedford Harbor (NBH) sediment, which is contaminated with polychlorinated biphenyls (PCBs), was amended with pristine SWNT to determine if the presence of SWNT would mitigate the toxicity and bioaccumulation of the PCBs in deposit-feeding invertebrates. A dilution series of the NBH sediment was created using uncontaminated Long Island Sound (LIS) sediment to test 25% NBH sediment, 50% NBH sediment, 75% NBH sediment, and 100% NBH sediment. The results of this work showed increased organism survival and decreased bioaccumulation of PCBs in treatments amended with SWNT, with the greatest reduction observed in the 25% NBH sediment treatment group amended with 10 mg SWNT/g dry sediment. Polyethylene (PE) passive samplers indicated a reduction of interstitial water (ITW) PCB concentration of greater than 90% in the 25% NBH sediment + 10 mg SWNT/g dry sediment amendment. The ITW concentration was reduced because PCBs were not desorbing from the SWNT. Lower bioavailability leads to reduced potential for toxic effects, supporting the observation of increased survival and decreased bioaccumulation. Once in the sediment, not only are SWNT not bioavailable, they act as a highly sorptive phase, such as black carbon (BC), into which hydrophobic organic contaminants (HOCs), such as PCBS and polycyclic aromatic hydrocarbons (PAHs), can partition, thereby reducing the toxicity and bioavailability of co-occurring HOCs.</p><p> To more fully understand the impact of SWNT in this environment, their biodegradability also needs to be investigated. Biodegradation of SWNT could lead to release and/or transformation of sorbed HOCs as well as a change in the inherent transport, toxicity, and bioaccumulation of SWNT in the estuarine environment. Because the persistence of SWNT will be a primary determinant of the fate of these materials in the environment, I conducted experiments to determine if the fungus <italic>Trametes versicolor</italic>, the natural bacterial communities present in NBH sediment, and municipal wastewater treatment plant sludge could degrade or mineralize oxidized <super>14</super>C&ndashSWNT. Over a six month time period, no significant degradation or mineralization was observed. In all treatments, approximately 99% of the 14C-SWNT remained associated with the solid phase, with only approximately 0.8% of added <super>14</super>C present as dissolved species and only 0.1% present as <super>14</super>CO₂. These small pools of non-SWNT <super>14</super>C were likely due to trace impurities, as no differences in production were observed between treatments and abiotic (killed) controls.</p> / Dissertation

The successful fabrication and characterization of two chemiresistive platforms for biomolecule detection was demonstrated by this work. The Si/Silica based single walled nanotube thin film (SWNTTF) platform was developed to understand the effect of device geometry on pH and M13 bacteriophage sensing capabilities as well as the underlying mechanisms governing SWNTTF chemiresistive biosensors. The dominant mechanism of sensing switched from direct chemical doping to electrostatic gating when the target analyte changed from H+/OH- ions in pH testing to whole viruses. The experimental limit of detection for M13 for this platform was 0.5pM and an increased sensitivity as well as variability was observed in devices with smaller channel widths. Preliminary device calibration was completed in order to correlate a resistance response to a bulk M13 concentration. The polyethylene terephthalate (PET) based SWNTTF platform was developed to demonstrate the commercial potential of SWNTTF chemiresistive biosensors by detecting relevant concentrations of brain natriuretic peptide (BNP) on economically viable substrates. The pH response of these chemiresistors confirmed that chemical doping was the cause for resistance change in the SWNTTFs. The preliminary results demonstrated successful BNP detection at 50pg/mL using both aptamers and antibodies as recognition elements. Using SWNTTFs as the transducing element of chemiresistors allowed for further understanding of electrical mechanisms of sensing as well as achieving sensitive, real-time and reproducible electrical virus and biomolecule detection. Although these platforms do not achieve ultrasensitive limits of detection, they demonstrate the commercial potential of platforms using SWNTTFs as the transducing element of electrical biomolecule sensors.

Carbon nanostructures have been extensively used in different applications; ranging from electronic and optoelectronic devices to energy conversion. The interest stems from the fact that covalently bonded carbon atoms can form a wide variety of structures with zero-, one- and two-dimensional configuration with different physical properties. For instance, while fullerene molecules (zero-dimensional carbon structures) realize semiconductor behavior, two-dimensional graphene shows metallic behavior with exceptional electron mobility. Moreover the possibility to even further tune these fascinating properties by means of doping, chemical modification and combining carbon based sub-classes into new hybrid structures make the carbon nanostructure even more interesting for practical application.  This thesis focuses on synthesizing SWCNT and different C60 one-dimensional structures as well as tuning their properties by means of different chemical and structural modification. The purpose of the study is to have better understanding of the synthesis and modification techniques, which opens for better control over the properties of the product for desired applications. In this thesis carbon nanotubes (CNTs) are grown by chemical vapor deposition (CVD) on iron/cobalt catalyst particles. The effect of catalyst particle size on the diameter of the grown CNTs is systematically studied and in the case of SWCNTs it is shown that the chirality distribution of the grown SWCNTs can be tuned by altering the catalyst particle composition. In further experiments, incorporation of the nitrogen atoms in SWCNTs structures is examined. A correlation between experimental characterization techniques and theoretical calculation enable for precise analysis of different types of nitrogen configuration in SWCNTs structure and in particular their effect on growth termination and electronic properties of SWCNTs are studied. C60 one-dimensional structures are grown through a solution based method known as Liquid-liquid interfacial precipitation (LLIP). By controlling the crystal seed formation at the early stage of the growth the morphology and size of the grown C60 one-dimensional structures where tuned from nanorods to large diameter rods and tubes. We further introduce a facile solution-based method to photo-polymerize the as-grown C60 nanorods, and show that such a method crates a polymeric C60 shell around the nanorods. The polymeric C60 shell exhibits high stability against common hydrophobic C60 solvents, which makes the photo-polymerized nanorods ideal for further solution-based processing. This is practically shown by decoration of both as grown and photo-polymerized nanorods by palladium nanoparticles and comparison between their electrochemical activities. The electrical properties of the C60 nanorods are also examined by utilizing a field effect transistor geometry comprising different C60 nanorods. In the last part of the study a variant of CNT is synthesized in which large diameter, few-walled CNTs spontaneously transform to a collapsed ribbon shape structure, the so called collapsed carbon nanotube (CCNT). By inserting C60 molecules into the duct edges of CCNT a new hybrid structure comprising C60 molecules and CCNT is synthesized and characterized. A further C60 insertion lead to reinflation of CCNTs, which eventually form few-walled CNT completely filled with C60 molecules.

Well dispersed aqueous suspensions containing single-walled carbon nanotubes (SWCNTs) from bulk powders were prepared with surfactant and without surfactant by acid functionalization. SWCNT coated electrodes were then prepared from the SWCNT aqueous suspensions using various methods to create uniform nanoporous networks of SWCNTs on various substrates and stainless steel (SST) current collectors for use as ultracapacitor electrodes. Drop coating, high voltage electro-spraying (HVES), inkjet printing, and electrophoretic deposition (EPD) methods were evaluated. Optical and scanning electron microscope images were used to evaluate the SWCNT dispersion quality of the various electrodes. Ultimately an EPD process was established which reliably produced uniform SWCNT nanoporous networks on SST substrates. The prepared SWCNT coated electrodes were characterized using cyclic voltammetry and their capacitance was determined. A correlation between extended EPD processing times, EPD processing temperatures, and electrode capacitance was quantified. Optimum EPD processing occurs where linear capacitance gains were observed for processing times less than 10 minutes. At processing times between 10 – 60 minutes a non-linear relationship demonstrated diminishing capacitance gains with extended EPD processing times. Likewise, optimum EPD processing occurs when the processing temperature of the SWCNT suspension is raised above room temperature. At processing temperatures from 45°C to 60°C an increase in capacitance was observed over the room temperature (22°C) electrodes processed for the same durations. Conversely, for processing temperatures less than room temperature, at 5°C, a decrease in capacitance was observed. It was also observed that SWCNT electrodes processed at 60°C processing temperatures resulted in 4 times the capacitance of 5°C electrodes for the same processing times, when the durations were 8 minutes or less. For samples with raised processing temperatures the time dependent capacitance gains were observed to be significantly diminished beyond 10 minute processing times. The SWCNT network thickness was also correlated to EPD processing temperature and capacitance. A linear relationship was identified between the SWCNT network thickness and the capacitance of the electrode. It was also observed that elevated processing temperatures increase the EPD deposition rate of SWCNTs, produce thicker SWCNT networks, and thus create electrodes with higher capacitance than electrodes processed at lower EPD processing temperatures. EPD of SWCNTs was demonstrated in this work to be an effective method for the fabrication of SWCNT ultracapacitor electrodes. Characterization of the process determined that optimal EPD processing occurs within the first 10 minutes of processing time and that elevated processing temperatures yield higher SWCNT deposition rates and higher capacitance values. In this work the addition of SWCNT nanoporous networks to SST electrodes resulted in increases in capacitance of up to 398 times the capacitance of the uncoated SST electrodes yielding a single 1cm2 electrode with a capacitance of 91mF and representing an estimated specific capacitance for the processed SWCNT material of 45.78F/g.

Orientador: Oswaldo Luiz Alves / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-13T13:25:05Z (GMT). No. of bitstreams: 1 Otubo_Larissa_D.pdf: 20335674 bytes, checksum: e95a782705baee771821f94a195ba7d0 (MD5) Previous issue date: 2009 / Resumo: Neste trabalho foram feitas preparações de nanopartículas de ouro passivadas com diferentes moléculas orgânicas (4,4'-tiobisbenzenotiol, benzenotiol, aminotiofenol e tiocolesterol). Tais moléculas possuem cadeias aromáticas mono ou difuncionalizadas, tendo tióis e aminas como grupamentos terminais. Foram estudados parâmetros como tamanho, estabilidade frente à agregação e coalescência, formação de blocos de agregados de nanopartículas conectadas por moléculas bifuncionais, variações das absorções no UV-Vis frente à sua formação e agregação, mostrando a importância das moléculas passivadoras nas propriedades das nanopartículas. Foram estudados também os efeitos causados pelo tratamento hidrotérmico sobre os agregados de nanopartículas passivadas com mono e ditióis. Tal estudo reforçou a importância das moléculas passivadoras na estabilidade das nanopartículas, sendo que o ditiol utilizado foi capaz de impedir o crescimento e coalescência das nanopartículas. Na segunda parte desta Tese, foram feitas as purificação e modificação química de nanotubos de carbono de parede simples com grupamentos oxigenados, tióis e aminas, visando a sua interação com nanopartículas de ouro. Foram abordados dois métodos de interação dos nanotubos com as nanopartículas de ouro: o in situ e o ex situ. Tais métodos estão relacionados com a redução do ouro e formação das nanopartículas em presença ou não dos nanotubos modificados, respectivamente. Foi observado que o tipo de grupamento na superfície dos nanotubos e o método de interação influenciaram tanto na quantidade de nanopartículas aderidas aos nanotubos, dado as diferenças de afinidade, quanto na distribuição de tamanho / Abstract: In this Thesis, passivated gold nanoparticles were prepared with different types of organic molecules (4,4'-thiobisbenzenethiol, benzenethiol, aminethiophenol e thiocolesterol). These molecules have aromatic chains, mono or difunctionalized, with thiols and amines as terminal groups. Some aspects were studied: size, stability against aggregation and coalescence, formation of blocks of nanoparticles, connected through bifuntional molecules, variations of UV-Vis absorption during aggregation, wich showed the importance of the passivating molecules on the final properties of the nanoparticles. Hydrothermal treatments were also carried out on the nanoparticles aggregates.Such study reinforced the importance of the passivating molecules on the nanoparticles' stabilization, once the dithiol showed to be capable of preventing the growing and coalescence of the nanoparticles. In the second part of this work, single-walled carbon nanotubes were purified and chemically modified. The chemical modification on the surface of the carbon nanotubes were done resulting in oxygenated, thiol and amine groups, aiming their interaction with gold nanoparticles. Two methods of interaction of the carbon nanotubes with gold nanoparticles were used: in situ and ex situ. Such methods are related with the reduction of gold and formation of the nanoparticles in presence or not of the modified nanotubes, respectively. It was observed that the type of surface modification of the nanotubes and the method of interaction influenced not only in the amount of nanoparticles on the surface of the nanotubes, due to different affinity, but also the size distribution / Doutorado / Quimica Inorganica / Doutor em Ciências

No description available.

Carbon nanotubes are appealing materials for nanofabrication due to their unique properties and structures. However, for carbon nanotubes to be used in mass-fabricated devices, precise control of nanotube orientation and location on surfaces is critical. I have developed a technique to align single-walled carbon nanotubes (SWNTs) on surfaces from a droplet of nanotube suspension under gas flow. Fluid motion studies indicate that alignment is likely due to circulation of SWNTs in the droplet. My work provides a facile method for generating oriented nanotubes for nanodevice applications. I have also devised an approach for localizing SWNTs onto 1-pyrenemethylamine-decorated DNA on surfaces. I found that 63% of SWNTs on surfaces were anchored along DNA, and these nanotubes covered ~5% of the total DNA length. This technique was an initial demonstration of DNA-templated SWNT localization. In an improved method to localize SWNTs on DNA templates, dodecyltrimethylammonium bromide was utilized to suspend SWNTs in aqueous media and localize them on DNA electrostatically. SWNT positioning was controlled by the surface DNA arrangement, and the extent of deposition was influenced by the SWNT concentration and number of treatments. Under optimized conditions, 83% of the length of surface DNAs was covered with SWNTs, and 76% of the deposited SWNTs were on DNA. In some regions, nearly continuous SWNT assemblies were formed. This approach should be useful for the fabrication of nanotube nanowires in nanoelectronic circuits. Using my improved procedures, I have localized SWNTs on DNA templates across electrodes and measured the electrical properties of DNA-templated SWNT assemblies. When a DNA-templated SWNT was deposited on top of and bridging electrodes, the measured conductance was comparable to literature values. In contrast, SWNTs with end-on contacts to the sides of electrodes had conductances hundreds of times lower than literature values, probably due to gaps between the SWNT ends and the electrodes. This work provides a novel approach for localizing SWNTs across contacts in a controlled manner. These results may be useful in the fabrication of nanoelectronic devices such as transistors with SWNTs as active components. Moreover, this approach could be valuable in arranging SWNTs as electrical interconnects for nanoelectronics applications.