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Carbon-carbon and carbon-nitrogen bond forming events are essential in chemistry. Although numerous stoichiometric/catalytic methods provided elegant and powerful solutions enabling those processes, the use of scarce/toxic reagents and harsh conditions is still ubiquitous in this field. As a result, extensive research has been conducted in the development of environmentally benign and inexpensive reagents for such transformations, however, general solutions remain a challenge. In this context, one of the focuses of our lab is to enable those processes in a more practical and sustainable fashion by using hypervalent iodine reagents. In this dissertation we demonstrate the synthetic applications of λ3-iodane reagents towards the formation of challenging carbon-carbon and carbon-nitrogen bonds in a complementary way to the methods already reported. Chapter 1 of this dissertation outlines the general electronic structure, geometry, synthesis and reactivity of λ3-iodanes as serves and background regarding these reagents. Chapter 2 highlights the applications of λ3-iodanes to access high-oxidation state transition metals until the year of 2017. This literature review provides detailed information about how λ3-iodanes can be applied to access 1st, 2nd and 3rd row high-oxidation complexes, as well as mechanistic details and synthetic utility of high-valent transition metals. Chapter 3 demonstrates our efforts to generate selective carbon-nitrogen and carbon-carbon products from a high-valent nickel complex. This led to important information of this mechanism adopted by the reaction and how the choice of oxidant can impact 1e- versus 2e- oxidative pathways on “hard” nickel pincer scaffolds. Chapter 4 describes our efforts towards the selective formation of α-C(sp2)-C(sp2) bonds at the α-position of enones via a reductive Iodonium-Claisen rearrangement. We demonstrate the utility of β-pyridinium silyl enol ethers as a platform for direct α-arylation, and how the 2-iodo-aryl-α-arylated enones can be used to access diverse heterocyclic structures. Chapter 5 demonstrates our initial efforts towards the selective C2 or C3 carbon-nitrogen bond formation on indoles. By exposing different indoles to (bis)cationic nitrogen-ligated HVI (N-HVI) reagents we found that selective C2 or C3 C-H indole-pyridinium salts can be formed in good to excellent yield. Although, this project is not finished yet, we anticipate the indole-pyridinium salts generated could serve as platform for accessing diverse piperidines, pyridones and primary amines through straightforward procedures. The combined chapters of this dissertation highlight the applications of λ3-iodanes towards transition metals and emphasize the applications of these reagents to enable challenging C–C and C–N bond formation events. More importantly, this dissertation serves as a guide for future development of the hypervalent iodine field. / Chemistry

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Carbon nanotubes have now been a subject of intense research for approaching two decades. Although a short time relative to most conventional materials, much hype about the intrinsic properties of this material has now been substantiated by experiment. The results are conclusive that carbon nanotubes are truly phenomenal materials with highly desirable mechanical, electrical and thermal properties. Furthermore, multiwall carbon nanotubes (MWNTs) have emerged as the most economically viable and abundant form of carbon nanotubes, and therefore the most likely candidate for application. The key materials engineering challenge remains in effectively transferring their properties to macro-scale materials in the form of composites. It is here that research merges with application. This dissertation has therefore been directed to focus on carbon nanotube composites in an applied sense. Here, the state of the art is reviewed, and experimental results of carefully selected composite systems, studied in detail for (1) mechanical, (2) electrical and (3) thermal properties, are presented and discussed. In terms of mechanical properties, the effects of MWNTs for augmentation of the tensile properties of PAN-based carbon fiber, and fatigue performance of poly(methyl methacrylate) are investigated and reported. In MWNT composite PAN-based carbon fiber, the formation of an ordered interphase layer sheathing the nanotubes was observed in fracture surfaces, which indicated a clear importance of their function to template the growth of carbon formation in the PAN-based matrix fiber. These structures open up a route to nano-scale tailorability of the crystallographic morphology of the composite fibers. Large improvements in fatigue performance were observed in MWNT/PMMA composites compared to MWNT/chopped carbon fiber composites, and attributed to the nanometer scale dimensions of the MWNTs enabling them to mitigate submicron damage such as polymer crazing. In terms of electrical and thermal properties, MWNT/epoxy composites were superior to MWNT/carbon black composites. Furthermore, extremely large improvements in the thermal conductivity of epoxy were observed for epoxy-infiltrated aligned MWNT arrays. The alignment of the MWNTs was shown to play a dominant role in enabling the improvement. Finally, these results, in concert with the literature are discussed in terms of the application of carbon nanotubes in engineering materials.

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In an effort to lower atmospheric carbon dioxide (C02) levels, a number of sequestration methods, including geological storage, ocean storage and mineral carbonation of CO2 have been proposed for British Columbia. The selection of a suitable sink depends largely on the geology available for a given region. A methodology for assessment of suitable raw material for the mineral carbonation process has been proposed. The Tulameen ultramafic complex is selected as a promising site for providing the raw feed for mineral C02 sequestration and representative dunites have been collected and examined. Carbonation tests of these dunites took place at the Albany Research Center in Oregon and C02 analyses in reaction products (up to 29.4 wt%) suggest 48-56% conversion to magnesite and silica for the dunites, and 18% conversion for a serpentinized dunite. Based on these results, one tonne of Tulameen dunite could potentially sequester up to 0.4 tomes of C02.

Carbon monoxide (CO) poisoning represents a global health threat responsible for hundreds of thousands of hospital visits and tens of thousands of deaths annually. Oxygen therapy is the only current approved treatment for CO poisoning. Previous work published in the 1970’s and research conducted in the VCURES lab group has indicated that a reduced form of vitamin B12, hydroxocobalamin (B12r), can potentially serve as an antidote for CO poisoning by converting CO bound to hemoglobin to carbon dioxide (CO2) and mitigating the deleterious neurological effects of CO poisoning. For the first time in documented literature we successfully used a Clark-type polarographic oxygen-sensitive electrode to demonstrate CO-induced decreases in brain tissue oxygen tension in anesthetized rats. Additionally, we demonstrated that B12r is capable of rescuing this CO-induced hypoxia and hypotension within 15 minutes of intraperitoneal administration with no adverse effects on blood chemistry.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. / A comprehensive experimental study on alternating current (AC) electrical transport in the three forms of carbon nanotubes (CNTs) and nanodiamond films is presented. It is termed dynamic electrical transport to differentiate it from direct current measurements, which may be referred as static transport. The results and analysis are based on the scattering parameter measurements of a few horizontally aligned single, double, multi-walled carbon nanotubes and nanodiamond films. Which were measured in the frequency range 10 MHz to 65 GHz, at room and cryogenic temperatures using a vector network analyser. The work is motivated by the fact that AC transport in 1D systems has not been fully studied and is not well understood. From direct current measurements, it is known that one dimensional (1D) electrical transport is very different from its two or three dimensional counterpart. This is because adding an electron to a 1D system tends to affect the whole system in ways which to date cannot be fully explained theoretically. CNTs present an ideal platform to study the AC or dynamic transport behaviour of 1D systems because of the high mobility and electrical conductivity at nano-scale. Therefore from the AC complex impedance and conductance, this work demonstrates quantum effects of collectively excited strongly interacting electrons (Luttinger Liquid), which had been predicted theoretically but not observed experimentally using this technique. Ballistic transport at room temperature is also demonstrated by setting the stimulus frequency higher than the scattering rate in the CNTs. A crossover from capacitive to inductive behaviour in the imaginary component of impedance has been shown by improving the CNT-electrode coupling. Furthermore the effect of metal contacts on microwave/ radio frequency transmission is also demonstrated. The results are consolidated by RF simulations, as strong conclusions are drawn. Studies on the dynamic transport in nanodiamond films revealed a crossover from the insulating to semi-metallic regime by nitrogen incorporation. The crossover is explained by considering the changes of the grain boundary morphology. This work shows that AC transport in polycrystalline nanodiamond films is similar to DC transport.

Current research in the field of nano-electronics is directed towards device miniaturization in order to find ways to increase the speed of electronic devices. The work presented in this dissertation is on the electronic transport properties of single walled carbon nanotube (SWNT) ropes synthesized by laser ablation. The measurements were performed on devices with different geometries; namely SWNT mats, metal incorporated (aligned individual and bundled) SWNTs and lastly on aligned pure SWNTs from low temperatures up to room temperature. The work was performed so as to gain an understanding on how best to utilize SWNTs in the semiconductor industry towards miniaturization. Such an understanding would ultimately highlight if SWNTs can be considered as a viable alternative to the current silicon-based technology, which seems to be approaching its physical limit. For a mat of SWNTs, 3D-Variable range hopping is the principal conduction mechanism from 2 K – 300 K. The magneto-resistance was found to be predominantly negative with a parabolic nature which converts to a linear nature as the temperature is increased. The negative MR is a consequence of quantum interference and the positive upturn is attributed to wave function shrinkage at low temperatures as described by the Efros-Shklovskii model. The hopping ranges of the electrons for a SWNT mat increases as the temperature decreases due to manifestation of quantum effects and reduced scattering. It was also found that metal incorporation does not alter the properties of the SWNT significantly. SWNT ropes aligned by di-electrophoresis across a 1 micron gap between gold micro-electrodes, exhibit Tomonaga-Luttinger liquid (TLL) like behaviour, within the 80 K – 300 K temperature range. The effects of confinement and electron-electron interaction unique to one dimension were identified in electronic transport as a non-universal power law dependence of the differential conductance on temperature and source-drain voltage. Ballistic conductance at room temperature was confirmed from the high frequency transport of the SWNT devices. The complex impedance showed some oscillatory behaviour in the frequency range 6 to 30 GHz, as has been predicted theoretically in the Tomonaga-Luttinger Liquid model. The observation of Luttinger Liquid behaviour demonstrates the outstanding nature of these one-dimensional molecular systems. In these devices the charging Coulomb energy of a single particle played a critical role in the overall device performance. This study can be used to understand the nature of dynamics of plasmons which are the charge carriers in a TLL system and how Coulomb interactions can be used to design highly tuneable systems for fabrication of single molecule devices. The incorporation of metal onto individual SWNT ropes does not alter its electronic properties significantly but the properties of the bundled metal incorporated SWNT ropes are altered. This study has found that under optimized conditions SWNTs might be a viable option for incorporation in nano electronics devices. Individual SWNT ropes promise better devices compared to SWNT mats and further work should be done on individual SWNTs.

Thermoelectric generators are solid state machines used to convert temperature gradients into electrical energy. They are formed by several thermoelectric units connected electrically in series and thermally in parallel. These units are made by creating a junction between a p-type and an n-type conductor. This investigation documents the characterisation of the thermoelectric properties of carbon nanotube (CNT) films and the fabrication process of carbon nanotube-based thermoelectric devices. The Seebeck coefficient is a intrinsic property of a thermoelectric material that correlates the voltage produced by a conductor and the temperature gradient applied to it. To measure the Seebeck coefficient of films, an experimental set-up was fabricated and calibrated using constantan as standard material. CNT films of aligned nanotubes fabricated using a chemical vapour deposition method were analysed. The Seebeck coefficient along and across the samples did not show significant variations, with values between 40$\mu$V/K and 80$\mu$V/K. Using these CNT films, thermoelectric cells were fabricated with the CNT as the p-type conductor and constantan as the n-type. As a proof of concept, two hand-made thermoelectric generators were assembled by connecting hundreds of these thermoelectric cells. These devices were subjected to a temperature gradient of $\approx$200K, which was enough to produce enough power to light an LED. Other analytical techniques were used to characterise the materials used in this work. Electrical conductivity measurements, thermogravimetric analysis, Raman spectroscopy and scanning electron microscopy were performed. Using a deposition technique, films of nanotubes were produced from a liquid phase. The impact of the production method on their properties was evaluated. Characterisation equipment was developed to measure the Seebeck coefficient and thermal conductivity. Thermoelectric devices made with the carbon nanotube films were fabricated and characterised. The values of thermal conductivity of the CNT films analysed in this work are between 0.86Wm$^{-1}$K$^{-1}$. The electrical conductivity of these materials is between 3500Sm$^{-1}$ and 14100Sm$^{-1}$. The maximum figure of merit of the carbon nanotube thermoelectric devices fabricated in this work is $ZT$=0.35.