The overall research theme of this dissertation was the study of nanoparticle/polymer composites. Two types of nanoparticles were utilized: Single-Walled Carbon Nanotubes and quantum dots. Chapter 1 of this thesis comprises an extensive literature review on Carbon Nanotubes, which presents theoretical aspects relevant to the structure and properties of CNTs, methods of purifying and solubilizing CNTs in aqueous and organic solvents and selected applications. This literature review is followed by the study and comparison of the optical limiting performances of different Single-Walled Carbon Nanotubes/conjugated polymer dispersions (Chapter 2). The results obtained are discussed in terms of dispersion of the SWNTs in the polymer solutions and resulting SWNT bundle diameters. Chapter 3 presents the spontaneous assembly of dendrimer patterns induced by SWNTs. Finally, chapter 4 presents a new method for fabricating quantum dot/polymer composites, which uses the extraction of positively charged quantum dot into a hydrophobic liquid. The resulting solution is used as a compatible polymerization medium for poly(methylmethacrylate ) networks enabling the formation of transparent and fluorescent composites. / Ph. D.

Single walled carbon nanotubes (SWNTs) are considered potential biomedical materials because of their flexible structure, hollow interior for fluidic transport, propensity for functionalization of the exterior walls, and biocompatibility. Research into exploiting these properties has focused on SWNTs as building blocks for novel drug-delivery systems, dosage forms, and biomedical substrates. However, the use of the internal nanochannels as conduits for trans-membrane drug delivery has not been explored. This research was initially designed to explore the latter.<p> It is postulated that due to their mechanical strength and the presence of an internal conduit, SWNTs can be used for nanofluidic transport. Using a magnetic field, the magnetically responsive SWNT are driven into intact stratum corneum, creating nanochannels, for trans-membrane drug delivery. Initial studies showed however that a bottleneck is the aggregation of SWNTs on the surface of stratum corneum. To achieve trans-membrane nanofluidic delivery, the SWNTs have to be well dispersed in an appropriate pharmaceutical medium, and the SWNT have to be of high purity. Similarly, the presence of impurities in SWNTs, and the dispersion state of these materials in pharmaceutical solvents may give an insight into the discrepancies in toxicity that is reported.<p> The purity of five commercially available SWNTs (AP-SWNT and P2-SWNT, from Carbon Solutions Inc, HMS-SWNT from Helix Materials, and NA-SWNT from Nanostructured and Amorphous Materials Inc. and CT-SWNT from ChepTubes Inc.) were analyzed by raman and electron dispersive x-ray spectroscopy (EDS) spectroscopy. Secondly, the dispersion states of SWNTs in various pharmaceutical solvents were evaluated by ultraviolet (UV) spectroscopy, scanning electron microscopy (SEM), dynamic light scattering (DLS), zeta potential, and Raman spectroscopy to identify potential agents for exfoliation of SWNTs in selected pharmaceutical solution.<p> SWNTs were dispersed in various solvents (water, propylene glycol [PG], dimethylsulfoxide [DMSO], and ethanol) as well as in 0.1% w/v aqueous solutions of anionic, cationic and neutral surfactants at a SWNT concentration of 0.1 mg/mL. SWNT suspensions described as dispersed yielded an evenly coloured suspension with no visible precipitate. The most stable dispersions were obtained with the gemini surfactants, which were confirmed by SEM observation of exfoliated SWNTs. Zeta (î) potential measurements of the fully dispersed SWNTs showed typical values of greater than +30 mV, while non-dispersed samples were less than +20 mV. SEM images of the dispersed solution showed the presence of exfoliated SWNTs compared to the aggregated SWNT clusters observed in non-dispersed systems. Raman spectra of dispersed SWNTs showed G-band peak shifts (to higher wavelengths), confirming the presence of exfoliated SWNTs.<p> Even though the purity of SWNT did not correlate with amount of SWNT in dispersion, exfoliation of bundled SWNTs was accompanied by an increase in UV absorbance of the dispersion, with maximum exfoliation determined by a relatively stable UV absorbance.<p> As pharmaceutical excipients, we have demonstrated that gemini surfactants are suitable dispersing agents for SWNTs, and shown that the dispersion of SWNT for gemini surfactants (12-3-12) is achieved below the critical micelle concentration. The dispersion of SWNT bundles into individual strands is the first crucial step towards their use in biological systems as drug carriers.

Single walled carbon nanotubes (SWNTs) are considered potential biomedical materials because of their flexible structure, hollow interior for fluidic transport, propensity for functionalization of the exterior walls, and biocompatibility. Research into exploiting these properties has focused on SWNTs as building blocks for novel drug-delivery systems, dosage forms, and biomedical substrates. However, the use of the internal nanochannels as conduits for trans-membrane drug delivery has not been explored. This research was initially designed to explore the latter.<p> It is postulated that due to their mechanical strength and the presence of an internal conduit, SWNTs can be used for nanofluidic transport. Using a magnetic field, the magnetically responsive SWNT are driven into intact stratum corneum, creating nanochannels, for trans-membrane drug delivery. Initial studies showed however that a bottleneck is the aggregation of SWNTs on the surface of stratum corneum. To achieve trans-membrane nanofluidic delivery, the SWNTs have to be well dispersed in an appropriate pharmaceutical medium, and the SWNT have to be of high purity. Similarly, the presence of impurities in SWNTs, and the dispersion state of these materials in pharmaceutical solvents may give an insight into the discrepancies in toxicity that is reported.<p> The purity of five commercially available SWNTs (AP-SWNT and P2-SWNT, from Carbon Solutions Inc, HMS-SWNT from Helix Materials, and NA-SWNT from Nanostructured and Amorphous Materials Inc. and CT-SWNT from ChepTubes Inc.) were analyzed by raman and electron dispersive x-ray spectroscopy (EDS) spectroscopy. Secondly, the dispersion states of SWNTs in various pharmaceutical solvents were evaluated by ultraviolet (UV) spectroscopy, scanning electron microscopy (SEM), dynamic light scattering (DLS), zeta potential, and Raman spectroscopy to identify potential agents for exfoliation of SWNTs in selected pharmaceutical solution.<p> SWNTs were dispersed in various solvents (water, propylene glycol [PG], dimethylsulfoxide [DMSO], and ethanol) as well as in 0.1% w/v aqueous solutions of anionic, cationic and neutral surfactants at a SWNT concentration of 0.1 mg/mL. SWNT suspensions described as dispersed yielded an evenly coloured suspension with no visible precipitate. The most stable dispersions were obtained with the gemini surfactants, which were confirmed by SEM observation of exfoliated SWNTs. Zeta (î) potential measurements of the fully dispersed SWNTs showed typical values of greater than +30 mV, while non-dispersed samples were less than +20 mV. SEM images of the dispersed solution showed the presence of exfoliated SWNTs compared to the aggregated SWNT clusters observed in non-dispersed systems. Raman spectra of dispersed SWNTs showed G-band peak shifts (to higher wavelengths), confirming the presence of exfoliated SWNTs.<p> Even though the purity of SWNT did not correlate with amount of SWNT in dispersion, exfoliation of bundled SWNTs was accompanied by an increase in UV absorbance of the dispersion, with maximum exfoliation determined by a relatively stable UV absorbance.<p> As pharmaceutical excipients, we have demonstrated that gemini surfactants are suitable dispersing agents for SWNTs, and shown that the dispersion of SWNT for gemini surfactants (12-3-12) is achieved below the critical micelle concentration. The dispersion of SWNT bundles into individual strands is the first crucial step towards their use in biological systems as drug carriers.

In order to find/design porous materials that could be used in practical applications involving adsorption, it is important to investigate the basic properties (i.e. isosteric heat, specific surface area, binding energy, pore size, pore volume, etc.) of each material. With this aim in mind we have looked at three different types of materials: single-walled carbon nanotubes (prepared by the HiPco and laser methods), single-walled nanohorns (dahlia-like and bud-like) and metal-organic frameworks (Cu-BTC and RPM-1). For these substrates we have measured volumetric adsorption isotherms using several gases such as neon, argon, tetrafluoromethane (CF4), xenon, and methane (not all gases for all substrates). Experimental adsorption isotherms were measured using methane, argon, xenon, and neon gases on unpurified single-walled carbon nanotubes prepared by the HiPco method. The main idea behind these experiments was to investigate, using different size gas molecules, the sites available for adsorption on this type of porous material. We found that surface area occupied by these adsorbates on the sample is the same, regardless of their size. This means that all the gases have access to the same group of adsorption sites. Since the biggest adsorbate in this experiment was Xe, and since it is unlikely that it could penetrate the interstitial channels in the nanotube bundles, we conclude that none of the gases, including the smallest one - Ne, are able to adsorb in the interstitial channels in bundles of single-walled carbon nanotubes. For the case of argon on laser produced single-walled carbon nanotubes we measured 21 adsorption isotherms using argon gas temperatures between 40 and 153 K that were used to determine the isosteric heat of adsorption for this system. Our experimental results were compared to the ones from computer simulations performed by J. K. Johnson (from the University of Pittsburgh) for the same gas on heterogeneous and homogenous bundles. It was observed that the isosteric heat data matches better with data computed for heterogeneous nanotube bundles. This indicates that at the lowest pressure and coverages argon might be adsorbing in the defect-induced interstitial channels. We studied Cu3(Benzene-1,3,5-tricarboxylate)2(H2O)3 (abbreviated as Cu-BTC) metal-organic framework with argon to determine the sites available for adsorption on this material. Volumetric adsorption isotherms were measured at temperatures between 66 and 143 K. We found two substeps in the isotherm data, indicating that there are two types of pores present in the material: tetrahedrally-shaped side pockets and the main channels. Our experimental results were compared with data from simulations conducted using the Grand Canonical Monte Carlo method. We determined that the theoretical results match reasonably well with ours if the coverage is scaled down by a factor of 1.6. We explored the potential of two different metal-organic framework materials (Cu-BTC and RPM-1) for gas separation application. We used argon and tetrafluoromethane (CF4) gases to check if this can be achieved through kinetic and steric mechanisms. We found that Cu-BTC has excellent potential in gas separation using a steric mechanism, since argon easily adsorbs into the small pores present in the sample, while CF4 is excluded from them. Adsorption properties of RPM-1 showed that it could be employed in gas separation using a kinetic mechanism - argon gas adsorbs and reaches equilibrium in the pores of the sample more than the order of magnitude faster than CF4. Closed-ended dahlia-like nanohorns were studied with neon and tetrafluoromethane gases. In the first layer of neon and tetrafluoromethane adsorbed on dahlia-like nanohorns we found two substeps. These results were compared with results of computer simulations performed by Prof. M. Calbi. We determined, after comparison with the simulation isotherms, that the lower pressure substeps correspond to adsorption of Ne and CF4 in the narrowest parts of interstitial channels of the aggregates. Surface area calculated from neon isotherms was found to be higher than the one obtained using CF4, meaning that the smaller Ne molecule has the access to the parts of the interstitial channels that are not accessible for the bigger CF4 molecule. Features that appeared in neon adsorption isotherms on bud-like nanohorn aggregates were quite different from the ones on dahlia-like aggregates. We measured neon adsorption isotherms on this type of sample at temperatures between 22 and 49 K. In the monolayer regime we observed one single substep whose origin we can not definitely identify, because the structure of the bud-like nanohorns is not well-known. The binding energy value that was calculated from the isotherm data was lower than the value for neon adsorbed in the grooves of nanotube bundles but higher than for neon on graphite.

Carbon nanomaterials have attracted significant attention in the past decades for their unique properties and potential applications in many areas. This dissertation addresses the preparation, functionalization and potential biomedical applications of various carbonaceous nanomaterials. Trimetallic nitride template endohedral metallofullerenes (TNT-EMFs, M₃N@C₈₀, M = Gd, Lu, etc.) are some of the most promising materials for biomedical applications. Water-soluble Gd₃N@C₈₀ was prepared by the functionalization with poly(ethylene glycol) (PEG) and hydroxyl groups (Gd₃N@C₈₀[DiPEG(OH)ₓ]). The length of the PEG chain was tuned by changing the molecular weight of the PEG from 350 to 5000. The 1H magnetic resonance relaxivities of the materials were studied at 0.35 T, 2.4 T and 9.4 T. Their relaxivities were found to increase as the molecular weight of the PEG decreased, which is attributed to the increasing aggregate size. The aggregate sizes were confirmed by dynamic light scattering. In vivo study suggested that Gd3N@C₈₀[DiPEG(OH)x] was a good candidate for magnetic resonance imaging (MRI) contrast agents. Another facile method was also developed to functinalize Gd₃N@C₈₀ with both carboxyl and hydroxyl groups by reaction with succinic acyl peroxide and sodium hydroxide thereafter. The product was determined to be Gd₃N@C₈₀(OH)~₂₆(CH₂CH₂COOM)~₁₆ (M = Na, H) by X-ray photoelectron spectrometry. The Gd₃N@C₈₀(OH)~₂₆(CH₂CH₂COOM)~₁₆ also exhibited high relaxivity, and aggregates in water. The research on both pegylated and carboxylated Gd₃N@C₈₀ suggests that aggregation and rotational correlation time plays an important role in relaxation, and the relaxivities and aggregation of the water-soluble metallofullerenes can be tuned by varying the molecular weight of the functionality. TNT-EMFs can be encapsulated inside single-walled carbon nanotubes (SWNTs) to form "peapod" structures by heating the mixture of TNT-EMFs and SWNTs in a vacuum. The peapods were characterized by Raman spectrometry and transmission electron microscopy (TEM). The peapods were then functionalized with hydroxyl groups by a high speed vibration milling (HSVM) method in the presence of KOH. The functionalized Gd-doped peapods exhibited high relaxivites and had an additional advantage of "double carbon wall" protection of the toxic Gd atoms from possible leaking. The HSVM method was modified by using succinic acyl peroxide. The modified HSVM method could functionalize multi-walled carbon nanotubes (MWNT) and single-walled carbon nanohorns (SWNHs) with carboxyl groups. In the presence of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC), carboxylate MWNTs and SWNHs could be conjugated with CdSe/ZnS quantum dots (QDs). TNT-EMFs were also encapsulated inside SWNHs to form SWNH peapods. SWNH peapods were functionalized by the modified HSVM method and then were conjugated with CdSe/ZnS QDs. The peapods were characterized by TEM. In vitro and in vivo studies indicated that SWNH peapods could serve as a multimodal diagnostic agent: MRI contrast agent (Gd₃N@C₈₀ encapsulated), radio-active therapeutic agent (Lu₃N@C₈₀ encapsulated) and optical imaging agent (QDs). / Ph. D.

This thesis examines the effects of cold forming on the material properties of steel and stainless steel structural members. Extensive research has been carried out over many years on both of these materials as they are used to manufacture structural sections to various design specifications which exist in many different countries. However, to date, no design code exists in the UK for cold formed stainless steel structural members. A significant amount of research has focused on the localised effect of cold forming on material properties such as the yield and ultimate tensile strengths, particularly of steel, and this is discussed at length in Chapter 1- Literature Review. Less attention has been placed on stainless steel, but over the last 20 years with the advent of design specifications particularly in the USA, stainless steel has gained popularity for cold forming. Chapter 1 describes the research that has been carried out on stainless steel, with particular emphasis on localised forming effects. Chapter 2 gives a general introduction to Thin-Walled Structures since cold-formed structural sections are commonly used as thin-walled members. The deformation and properties of metallic materials are described in Chapter 3 showing the particular relevance to the cold forming process. This chapter is extended into Chapter 4 where the strengthening, forming and properties of metallic materials are discussed in detail, with particular attention given to the cold forming processes. Chapter 5 describes existing analytical and design code approaches to determine the increase in strength of cold formed steel structural sections, along with an empirically derived relationship to calculate the increased yield strength of stainless steel sections. Chapter 6 describes the recommendations provided by various design specifications on evaluation of the axial compression capacity of short struts subject to varying degrees of cold forming. This chapter also describes the recommendations provided by various design specifications on evaluation of both the axial compression and the combined bending and axial compression load capacities of cold formed lipped channel section stainless steel columns of short-to-medium length. The results obtained from Chapters 5 and 6 are compared to the results obtained from an extensive experimental approach as described in Chapter 7. A finite element non-linear analysis using the ANSYS finite element software package is presented in Chapter 8 which models the behaviour of cold formed stainless steel lipped channel section columns of short-to-medium length subject to pure axial compression loading and also combined bending and axial compression loading. Chapter 9 presents the experimental findings showing the relationship between material hardness and material yield strength for cold-formed areas. The results are then compared to the theoretical results from Chapter 6 to determine their accuracy in prediction of the structural behaviour of full cold formed structural member cross-sections. The load capacity obtained for axially compressed steel and stainless steel struts from experiments are compared to those obtained from the various design code predictions described in Chapter 6. Also presented are the experimental findings, design code recommendations and finite element predictions for the load capacity of stainless steel columns. Chapter 10 concludes on the work by discussing the various issues arising from the experiments, from the design code recommendations and from finite element analysis 11 M. Macdonald

Lai, Kim Fung = 幼樑之振動與力學特性 / 黎劍鋒. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 99-102). / Abstracts in English and Chinese. / Lai, Kim Fung = You liang zhi zhen dong yu li xue te xing / Li, Jianfeng. / Chapter I --- Vibrations of Timoshenko Beams --- p.1 / Chapter 1 --- Introduction --- p.2 / Chapter 1.1 --- Overview --- p.2 / Chapter 1.2 --- Simple theory of static beam bending --- p.6 / Chapter 1.3 --- Foundation of problem --- p.7 / Chapter 1.4 --- Literature review --- p.12 / Chapter 1.4.1 --- Euler-Bernoulli Beam Theory (EBBT) --- p.12 / Chapter 1.4.2 --- Timoshenko Beam Theory (TBT) --- p.16 / Chapter 1.5 --- Preview of our results --- p.20 / Chapter 2 --- 3-D problem --- p.22 / Chapter 2.1 --- Elastic theory --- p.23 / Chapter 2.2 --- Boundary conditions --- p.24 / Chapter 2.3 --- Plane waves in uniform thin beams --- p.25 / Chapter 2.4 --- Solving order-by-order analytically --- p.26 / Chapter 2.5 --- Minimization approach --- p.36 / Chapter 3 --- 2-D problem --- p.50 / Chapter 3.1 --- Boundary conditions and effective moduli --- p.51 / Chapter 3.2 --- Expansion for thin beams --- p.54 / Chapter 3.3 --- Plane waves in uniform thin beam --- p.56 / Chapter 3.4 --- Boundary conditions --- p.57 / Chapter 3.5 --- Truncation --- p.58 / Chapter 3.6 --- Numerical solution --- p.58 / Chapter 3.7 --- Analytic results for soft mode --- p.60 / Chapter 3.8 --- EBBT and TBT for 2-D problem --- p.62 / Chapter 3.9 --- Analytic results for hard mode at q = 0 --- p.64 / Chapter 3.10 --- Higher-order corrections for hard mode --- p.66 / Chapter 4 --- Summary --- p.71 / Chapter II --- Vibrations of Single-Walled Carbon nanotubes --- p.73 / Chapter 5 --- Introduction --- p.74 / Chapter 5.1 --- General properties --- p.74 / Chapter 5.2 --- Graphene sheet --- p.76 / Chapter 5.3 --- Rolling up a graphene sheet --- p.78 / Chapter 5.4 --- Foundation of problem --- p.79 / Chapter 5.5 --- Literature review --- p.79 / Chapter 5.6 --- Preview of our results --- p.80 / Chapter 6 --- Structure and strain energy under zero stress --- p.81 / Chapter 6.1 --- Description of the structure --- p.81 / Chapter 6.2 --- Description of the strain energy --- p.83 / Chapter 6.3 --- Minimization of energy --- p.86 / Chapter 7 --- SWCNT under strain --- p.89 / Chapter 7.1 --- Subject to an axial strain --- p.89 / Chapter 7.2 --- Subject to a radial strain --- p.94 / Chapter 7.3 --- Subject to a torsional strain --- p.95 / Chapter 8 --- Summary --- p.98 / Bibliography --- p.99 / Chapter A --- "Expressing elastic moduli G, λ and M in terms of Y andv" --- p.103 / Chapter B --- Simplification of the functional E to a neat expression --- p.105 / Chapter C --- Expressing effective elastic moduli G' and M' in terms of Y' and v' --- p.106 / Chapter D --- Illustration of the lowest non-trivial truncation --- p.107 / Chapter E --- The proof of Self-adjointness of H(q) --- p.109 / Chapter F --- Proof of the identity KeVec= KeVel --- p.112

The design and performance of an instrument is presented whose purpose is the extraction of samples highly enriched in one species of single-walled carbon nanotubes from density gradient ultracentrifugation. This instrument extracts high purity samples which are characterized by various optical studies. The samples are found to be enriched in just a few species of nanotubes, with the major limitation to enrichment being the separation, rather than extraction. The samples are then used in optical and microscopic studies which attempt to determine the first absorption coefficient (S1) of the (6,5) species of nanotube. Initial experiments give a value of 9.2 ± 2.6 cm2 C atom-1. Future work is proposed to improve upon the experiment in an attempt to reduce possible errors

As pointed out more and more frequently in the literature, there is a pressing need for research into the health and environmental impact of nanoparticles. This work represents a joint effort between scientists in nanotechnology, chemistry and biology to answer this call and to investigate the environmental effects of carbon nantoubes (CNTs) from a brand new aspect. The results showed clearly the dose-dependent effects of single-walled carbon nanotubes (SWNTs) on the ingestion and digestion of bacteria by Tetrahymena thermophila, a ciliated protozoan, propagated to its prey bacteria, Escherichia coli. Investigated by confocal microscopy Tetrahymena were able to internalize large quantities of SWNTs and then excrete SWNTs and undigested bacteria in aggregates. Inhibition of ciliate bacterivory measured by Ciliate Bacterivory assay was evident at far below lethal concentrations. At high tube concentrations (above 6.8 μg∙ml-1), cell viability was affected. In addition, explored by fluorescence microscopy and scanning electron microscopy, SWNTs stimulated Tetrahymena to abnormally egest viable bacteria inside membrane protected structures, which enhanced bacterial survival during antimicrobial treatments, bacteriostatic or bacteriocidal. This phenomenon may have important implications to public health. In general, research on toxicity of nanoparticles is in a very early stage with most studies on direct fatality (kill or not to kill) of a single organism or certain type of cells. This work is believed to be among the first few investigating extrapolated effects. Hopefully, this wok will stimulate a line of research towards better understanding of the effects of nanomaterials on diverse organisms, and stimulate not only toxicology but also ecotoxicology studies.

As pointed out more and more frequently in the literature, there is a pressing need for research into the health and environmental impact of nanoparticles. This work represents a joint effort between scientists in nanotechnology, chemistry and biology to answer this call and to investigate the environmental effects of carbon nantoubes (CNTs) from a brand new aspect. The results showed clearly the dose-dependent effects of single-walled carbon nanotubes (SWNTs) on the ingestion and digestion of bacteria by Tetrahymena thermophila, a ciliated protozoan, propagated to its prey bacteria, Escherichia coli. Investigated by confocal microscopy Tetrahymena were able to internalize large quantities of SWNTs and then excrete SWNTs and undigested bacteria in aggregates. Inhibition of ciliate bacterivory measured by Ciliate Bacterivory assay was evident at far below lethal concentrations. At high tube concentrations (above 6.8 μg∙ml-1), cell viability was affected. In addition, explored by fluorescence microscopy and scanning electron microscopy, SWNTs stimulated Tetrahymena to abnormally egest viable bacteria inside membrane protected structures, which enhanced bacterial survival during antimicrobial treatments, bacteriostatic or bacteriocidal. This phenomenon may have important implications to public health. In general, research on toxicity of nanoparticles is in a very early stage with most studies on direct fatality (kill or not to kill) of a single organism or certain type of cells. This work is believed to be among the first few investigating extrapolated effects. Hopefully, this wok will stimulate a line of research towards better understanding of the effects of nanomaterials on diverse organisms, and stimulate not only toxicology but also ecotoxicology studies.