Thesis (M.S.)--University of Missouri-Columbia, 2005. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (July 13, 2006) Includes bibliographical references.

Thesis (M.Sc.)--City University of Hong Kong, 2005. / At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Aug. 31, 2006) Includes bibliographical references.

Thesis (M.Sc.)--City University of Hong Kong, 2005. / At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 1, 2006) Includes bibliographical references.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2008. / Title from title screen (site viewed Feb. 17, 2009). PDF text: xiii, 110 p. : ill. ; 3 Mb. UMI publication number: AAT 3326861. Includes bibliographical references. Also available in microfilm and microfiche formats.

It has been found that by combining various borocations or neutral electrophilic boranes with a multitude of alkynes, interesting and often highly selective borylation reactivity is observed. The reactions can be loosely categorised as de-(elemento)boration of the alkyne, haloboration and carboboration. Direct alkyne de-(elemento)boration was achieved as both dehydroboration and desilylboration, generating a selection of borylated alkynes. Other examples of more complicated alkyne borylation were also observed, such as the boroamination of TMS-ethylene. Upon discovering that 2-N,N-dimethylaminopyridine ligated dichloro-boronium salt underwent selective 1,2-haloboration with a range of terminal alkynes, and that the dibromo-analogue could haloborate a limited number of internal alkynes, the more Lewis acidic borenium salt [Cl2B(2,6-lutidine)][AlCl4] was synthesised and reacted with a series of internal alkynes to give haloborated products. These included dialkyl and diaryl internal alkynes containing a range of functional groups including thioether, methoxyphenyl, vinyl and halide. Each proceeded with excellent stereo- and regio-selectivity, with the boron and the halide added mutually cis, and the regioselectivity determined by the electronically most stable form of the carbocation intermediate. The initial dihalovinyl borane products were esterified in-situ to provide the more stable pinacol boronate esters. The elementoboration method was expanded via modification of the borocations to include different transfer groups that, upon reaction with trimethylsilyl-substituted alkynes, underwent 1,1-carboboration, with migration of the TMS-group. This method also provided access to a small selection of borylated dienes, resulting from reactions with excess alkyne. It was also shown that some neutral boranes reacted analogously with certain TMS-alkynes, albeit with limitations on scope. In addition to this, two types of 1,2-carboboration were discovered. The first involved intercepting products from alkyne haloboration with a TMS-alkyne, undergoing a vinylboration to produce 1-boradiene products. The second was an example of an intermolecular trans carboboration, where the initially formed vinyl carbocation is intercepted by a thiophene.

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Methods for the determination of boron are reviewed. A thorough investigation of the curcumin method was undertaken. Factors such as spectral absorption, boron volatilisation and the effects of pH, the stability of reagents and colour solutions, the drying of reaction products and the interference from certain elements, were investigated. A study of the efficiency of extracting boron from plant material using an ashing procedure is presented. The modified curcumin method for the determination of boron in plant material is described. The statistical accuracy and precision of the modified method is presented. The modified method was used to determine the boron content in citrus and pineapple leaf samples obtained from various parts of the Eastern Cape.

Graphene and monoatomic boron nitride as members of the new class of two dimensional materials are discussed in this thesis. Since the discovery of graphene in 2004, various aspects of this one atom thick material have been studied with previously unexpected results. Out of many outstanding amazing properties of graphene, its elastic properties are remarkable as graphene can bear strain up to 20% of its actual size without breaking. This is the record value amongst all known materials. In this work experiments were conducted to study the mechanical behaviour of graphene under compression and tension. For this purpose graphene monolayers were prepared on top of polymer (PMMA) substrates. They were then successfully subjected to uniaxial deformation (tension- compression) using a micromechanical technique known as cantilever beam analysis. The mechanical response of graphene was monitored by Raman spectroscopy. A nonlinear behaviour of the graphene G and 2D Raman bands was observed under uniaxial deformation of the graphene monolayers. Furthermore the buckling strength of graphene monolayers embedded in the Polymer was determined. The critical buckling strain as the moment of the final failure of the graphene was found to be dependent on the size and the geometry of the graphene monolayer flakes. Classical Euler analysis show that graphene monolayers embedded in the polymer provide higher values of the critical buckling strain as compared to the suspended graphene monolayers. From these studies we find that the lateral support provided by the polymer substrate enhances the buckling strain more than 6 orders of magnitude as compared to the suspended graphene. This property of bearing stress more than any other material can be utilized in different applications including graphene polymer nanocomposites and strain engineering on graphene based devices. The second part of the thesis focuses on a two dimensional insulator, single layer boron nitride. These novel two dimensional crystals have been successfully isolated and thoroughly characterized. Large area boron nitride layers were prepared by mechanical exfoliation from bulk boron nitride onto an oxidized silicon wafer. For their detection, it is described that how varying the thickness of SiO2 and using optical filters improves the low optical contrast of ultrathin boron nitride layers. Raman spectroscopy studies are presented showing how this technique allows to identify the number of boron nitride layers. The Raman frequency shift and intensity of the characteristic Raman peak of boron nitride layers of different thickness was analyzed for this purpose. Monolayer boron nitride shows an upward shift as compared to the other thicknesses up to bulk boron nitride. The Raman intensity decreases as the number of boron nitride layers decreases. Complementary studies have been carried out using atomic force microscopy. With the achieved results it is now possible to successfully employ ultrathin boron nitride crystals for precise fabrication of artificial heterostrutures such as graphene-boron nitride heterostrutures.

An experimental investigation of the spins of the 2.14 (Jɪ) and 5.03 (J) Mev levels in B¹¹ has been made using the B¹º(dp)B¹¹ reaction to populate the 5.03 Mev level in B¹¹ and then studying pɣ and pɣɣ angular correlations to determine the values of J and Jɪ . The theoretical analysis of the angular correlation data is based on a method in which the dp reaction mechanism is represented by a relatively small number of experimentally determined parameters and therefore the resulting spin assignments are not open to the usual criticisms of the use of (sometimes doubtful) nuclear reaction theories for the positive determination of nuclear spins. Using the information gained from this experiment and previous experimental information on the statistical distribution of M1 to E2 multipole mixing ratios it was possible to assign an overwhelming statistical probability in favour of the J = ³⁄₂, Jɪ = ½ spin assignment. These spin assignments are in agreement with previous tentative ones and with the theoretical shell model calculations of Cohen and Kurath. The parameters, determined by this experiment, describing the dp reaction are compared with those calculated using stripping theory and are shown to be in disagreement with both the Butler Plane Wave and Distorted Wave Born approximation calculations. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This work was undertaken to verify the results of Pennington and Petch. They studied the effect of quadrupole perturbation on the n. m .r. spectrum of B¹¹ in inderite and from these studies found the values of quadrupole coupling constants and asymmetry parameters of the crystalline electrostatic fields for different sites of B¹¹. This data has been used in the present work to predict the "pure" quadrupole resonance frequencies. The resonance frequency for the M site has been experimentally measured. The result is within 1% of the predicted value. The improvements made in the spectrometers are discussed. / Science, Faculty of / Physics and Astronomy, Department of / Graduate