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Im Rahmen der vorliegenden Arbeit wurden Dibortetrahalogenide dargestellt, deren Eigenschaften strukturell sowie spektroskopisch analysiert und deren Reaktivität gegenüber Lewis-basischen Hauptgruppenelementverbindungen untersucht. Durch anschließende Reaktivitätsstudien konnten unter anderem neuartige Diborene dargestellt und analysiert werden. Weiterhin wurde die Verbindungsklasse der Elementhalogenide der Gruppe 13 in der Oxidationsstufe +2 (B, Ga, In) und +3 (In) bezüglich ihrer Reaktivität gegenüber Übergangsmetall Lewis-Basen untersucht. Die gebildeten, neuartigen Bindungsmodi der Gruppe 13 Elemente am Übergangsmetall wurden strukturell, spektroskopisch sowie quantenchemisch analysiert. / As a part of the present work diborontetrahalides were synthesized, analyzed and their reactivity was investigated towards Lewis-basic main group compounds. Subsequent reactivity studies were performed and novel Diborenes were synthesized and analyzed. Furthermore the reactivity of group 13 elemental halides in the oxidation state +2 (B, Ga, In) and +3 (In) was investigated towards Lewis-basic transition metal complexes. The novel bonding motifs of the group 13 elements at the metal center were investigated structurally, spectroscopically and by quantum chemical calculations.

Indium tin oxide is a transparent conductive oxide electrode which is widely used for organic electronics. Morphology of ITO plays an important role in the performance of organic electronics. To understand the influence of the substrate morphology in device performance, a controllable route for producing periodic and aperiodic roughness of ITO surfaces are necessary. In this thesis, this was attempted by using various approaches to forming ITO nanostructures. Initially, ITO was deposited by a traditional sputtering procedure. However, the roughness distribution of the sputtered ITO resulted in a s Gaussian distribution, unsuitable to further studies of roughness. ITO nanostructures can also be formed by depositing ITO nanoparticles on an ITO sub- strates. Using acetate and chloride precursors, ITO films were produced from solution and formed into nanoparticles using the reverse micelles deposition approach. The acetate route (InAc+SnCl2+ethanol), was the most successful prior to the nanoparticle formation, showing high quality ITO with bixbyte crystal structure and Sn percentages of 20%, low enough to form a conductive film. Nanoparticles were fabricated with diblock copolymer reverse micelles(PS-b-P2VP). Reverse micelles were found to act as a nano reactor, restricting the size of nanoparticles by having hydrophilic reactants undergo chemical reactions inside the micelles. However, nanoparticles from the reverse micelles revealed Sn percentages much above 20%. This was attributed to the solubility difference of the precursors leading to displacing or preventing of pre- cursor loading into the reverse micelles. The change of the stirring time, the micelles concentration, the sequence of precursors loading, and the weight of precursors were not found to affect the Sn concentration; moreover, large variations in Sn concentrations were observed. From quantitative nano mechanical testing of the micelles, a maximum load amount for the precursors was observed, confirming that the high concentration of Sn was likely due to the solubility differences between the precursors and their ability to penetrate the micelle. By manipulating the nanoparticles distribution through spin coating speeds, micelles concentration, and deposited volume, several degrees of order were obtained, though hexagonal packing was not observed. In general, even though Sn concentration were found to be above 20%, nanoparticles were successfully fabricated with reverse micelles, confirming that the reverse micelle technique is a good strategy for future studies of roughness. / Thesis / Master of Applied Science (MASc)

<p> The atomic beam magnetic resonance technique with radioactive detection has been used to investigate the hyperfine structure of In^117m. The present research is based on the work done by Cameron (1962) who could not obtain accurate values for the hyperfine interaction constants due to the low neutron flux at the time in the McMaster reactor.</p> <p> This thesis is an account of an attempt to complete that experiment by observing the field independent direct hyperfine transitions. The theory of the experiment, the apparatus and techniques, and the method of data analysis are described. Because of the counting errors, the data are not as conclusive as had been hoped. If the resonances have, in fact, been seen, then the results are: a1/2 = -932.996 ± 0.012 Mc/sec a3/2 = -99.005 ± 0.005 Mc/sec μI = -0.25146 ± 0.00003 nuclear magnetons.</p> / Thesis / Master of Science (MSc)

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Thesis (M.Sc. (Physics)) -- University of Limpopo, 2017 / The undoped ZnO nanoparticles, In or Co single doped ZnO nanoparticles and the In and Co combinational doped ZnO nanoparticles were synthesised through sol-gel technique. The samples were characterised using XRD, TEM, FTIR, Raman spectroscopy, UV-Vis, PL and also tested for the gas sensing applications. XRD patterns revealed that the synthesised samples were of ZnO hexagonal wurtzite structure. The lattice parameters and the bond length of all the undoped and doped ZnO samples were determined and found to be similar to that of the Bulk ZnO. The average particle size of the undoped and doped ZnO nanoparticles were calculated and found to reduce with an introduction of dopants while increasing with an increase in temperature. The strain of all the prepared samples were also determined and observed to be in an inverse relation to the particle size. TEM images showed that the synthesised samples were spherically shaped and that was in agreement with XRD results, while the EDS results showed that In and Co were successfully doped into the ZnO nanoparticles. Raman and FTIR spectroscopy indicated that the prepared samples were indeed ZnO nanoparticles which confirmed the XRD results. The UV-Vis results showed a red-shift in the energy band gap with an introduction of dopants and that was related to the reduction of the particle size, this results were consistent with the PL results. Gas sensing results showed that doping Co and In into the ZnO nanoparticles has an effect into ZnO properties. Combinational-doping of In and Co was found to increase the response to the gases CH4, CO, NH3 and H2 as compared to the undoped and singly doped ZnO nanoparticle sensors. The response\recovery time was found to be affected with introduction of In and Co. Improvements were also observed in the operating temperature and the selectivity of the single doped and co-doped ZnO nanoparticles towards different gases used in this study. / University of Limpopo IBSA National Research Foundation (NRF)

Efficient reconfigurable antennas are highly sought after in all communication applications for the ability to reduce space cost while maintaining the ability to control the frequency, gain, and polarization. The ability to control these parameters allows a single antenna to maximize its performance in a wide range of scenarios to satisfy changing operating requirements. This thesis will describe reconfigurable antennas using liquid-metal alloys that give the system this ability by injecting or retracting the liquid metal from various channels. After simulations were performed in an electromagnetic simulation software, proof-of-concept models were built, tested, and compared to the simulations to verify the results. / Master of Science / Antennas that can change the tuned center frequency and/or the direction they are pointing are needed in many different applications. Antenna adaptability allows the system to maximize the physical dimensions of the antenna to satisfy a wide range of situations without losing performance. This thesis describes antennas using a liquid-metal alloy that can make physical adaptations for the need at hand. After simulations were performed using computer software, proof-of-concept models were constructed and empirically validated to verify the simulation models.

Jusqu’à tout récemment, la plupart des travaux effectués pour l’exaltation de la fluorescence moléculaire avaient comme substrat l’argent ou l’or sous forme de nanoparticules. Toutefois, ces deux métaux ne sont pas tout à fait adaptés pour l’exaltation de la fluorescence dans l’UV avec leur maximum plasmonique situé aux environs de 400 nm pour l’argent et aux environs de 530 nm pour l’or. L’intérêt de l’UV vient principalement de visées biomédicales considérant qu’une majorité de biomolécules absorbent et émettent dans cette région. Dans le cadre de ce projet, les biomolécules d’intérêt sont l’ADN qui fluorescence grâce aux bases azotées et les trois acides aminés aromatiques, le tryptophane, la tyrosine et la phénylalanine, qui sont quant à eux responsables de la fluorescence des protéines. Le but de ce projet est de développer un système nanoparticulaire permettant l’exaltation de la fluorescence dans l’UV. Le métal choisi est l’indium puisque ce dernier fait partie du groupe du bore (Al, Ga, In, Tl) et que ceux-ci sont caractérisés par de faibles pertes par absorption, mais également pour leur forte bande plasmonique vers 300 nm. L’indium possède donc toutes les qualités requises pour permettre l’exaltation de la fluorescence dans l’UV. Dans ce projet, des nanoparticules sphériques d’indium ont été développées avec une taille modulable entre 60 et 80 nm. Le plasmon de ces nanoparticules se situe vers 310 nm. Par la suite, ces mêmes cœurs d’indium ont été recouverts d’une couche diélectrique protectrice de silice. L’avantage d’une coquille de silice est la facilité avec laquelle l’épaisseur peut en être modifiée. La taille des coquilles synthétisées varie entre 5 et 50 nm. Une fois cette couche synthétisée, différentes avenues ont été envisagées pour le greffage des fluorophores en surface. Le choix final s’est arrêté sur l’incorporation des fluorophores à l’intérieur même d’une couche de silice. Les fluorophores sont préalablement modifiés pour faire en sorte qu’ils se lient de manière covalente à la silice. Le choix des fluorophores principaux s’est arrêté sur le Carbostyril 124, en tant que fluorophore modèle, et sur le tryptophane puisqu’il s’agit de l’acide aminé le plus fluorescent. Des facteurs d’exaltation de fluorescence de l’ordre de 3 et 7 ont respectivement été obtenus pour le Carbostyril 124 et le tryptophane. D’autres tests préliminaires ont également été menés sur les autres acides aminés, la tyrosine et la phénylalanine, ainsi que sur l’ADN. / Until recently, most of the work done on metal-enhanced fluorescence of molecular fluorophores employed silver and gold nanoparticles as the substrate. However, these metals are not perfectly suit for fluorescence enhancement in the UV region of the spectrum as their maximum plasmonic bands are centered at approximately 400 nm and 530 nm for silver and gold, respectively. The interest in the UV region is mostly due to biomedical studies as most of the biomolecules absorb and emit in this region. In this project, the focus is on DNA, which is fluorescent via the nucleobases, en even more so on proteins which owe their intrinsic fluorescence to the three aromatic amino acids, tryptophan, tyrosine and phenylalanine. The main goal of this project is to develop a nanostructure able to support metal-enhanced fluorescence in the UV. Indium seems to be the perfect metal to work with as it is part of the boron group (Al, Ga, In, Tl) which is characterized by low absorption losses, but also by its strong plasmonic band centered at approximately 300 nm making it suitable for metal-enhanced fluorescence studies in the UV. In this project, indium nanoparticles with a size ranging from 60 to 80 nm were developed with a plasmon approximately centered at 310 nm. Then, a protective dielectric layer of silica was synthesized on the indium core. The thickness of the silica layer is easily tunable; it is used to find the optimal distance to observe a maximal fluorescence enhancement. Silica shells between 5 and 50 nm were used. Different strategies were considered for the grafting of the fluorophores on the surface of indium-silica nanoparticles. Incorporation of the fluorophore into a silica layer was chosen as it allows for covalent bonding between the fluorophore and the silica layer. Two different fluorophores were used. The first one is Carbostyril 124, acting as a model fluorophore, and the second one is tryptophan as it is the most fluorescent amino acid. Enhancement factors of up to 3 and 7 were obtained for Carbostyril 124 and tryptophan, respectively. Others preliminary tests have been made on tyrosine and phenylalanine, the two other fluorescent amino acids, and on DNA.