Photophysicochemical properties and surface-enhanced Raman scattering of phthalocyanine-nanoparticle conjugates
- Authors: Nwahara, Nnamdi
- Date: 2019
- Subjects: Boron compounds , Electrochemistry , Phthalocyanines , Nanoparticles , Bioconjugates , Raman effect
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/71647 , vital:29928
- Description: This work presents the synthesis, photophysical and photochemical characterization of a series of metallophthalocyanines (MPcs) and boron dipyrromethene (BODIPY) and their conjugates with either gold or silver nanoparticles (AuNPs or AgNPs) or graphene quantum dots (GQDs). The rich π-electron systems of GQDs and MPcs employed in this work enabled the coordination of MPcs to GQDs (either as pristine or modified) via the non-covalent (π-π stacking) method. GQDs, AuNPs and AgNPs were also functionalized with L-glutathione (GSH) in order to assist coupling to the Pcs or BODIPY dye. Spectroscopic and microscopic studies confirmed the formation of the respective nanoparticles (NPs) as well as the conjugates which exhibited enhanced photophysicochemical properties in comparison to the phthalocyanines (Pcs) or BODIPY alone. This work also shows that the incorporation of folic acid (FA) into Pcs-NPs composites leads to further enhancements in the singlet oxygen generation capabilities of the resulting conjugates, and so experimentally demonstrates for the first time, a synergy between FA and the respective nanoparticles (GQDs, AuNPs and AgNPs) in affecting the photophysical properties of Pcs complexes. GQDs and Pcs/GQDs hybrids were also herein decorated with AuNPs – metallic nanostructures that employ localized surface plasmon resonances to capture or radiate electromagnetic waves at optical frequencies. These nanostructures herein reported, have been shown to possess enhanced light-matter properties, enabling unique surface-enhanced Raman scattering (SERS) behaviours, with unprecedented enhancement factors of up to 30-fold. This work therefore, reports on the fabrication of Pc/GQDs/AuNPs hybrids and experimentally demonstrates their incredible potential as novel Raman-active PDT agents.
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- Date Issued: 2019
Template ecological analsyis of the narratives of partner’s and family member’s of women who consumed alcohol in pregnancy
- Authors: Tsetse, Agrinette Nontozamo
- Date: 2019
- Subjects: Pregnant women -- Alcohol use -- Social aspects , Substance abuse in pregnancy , Fetus -- Effect of drugs on , Pregnancy -- Psychological aspects , Pregnant women -- Substance use , Substance abuse -- Social aspects , Ecological Systems Theory
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/114905 , vital:34055
- Description: Although there is increasing research on alcohol in South Africa, most of this work has an epidemiological focus. Very little research has explored alcohol use during pregnancy specifically from the perspective of the woman’s partner or family member or focused on contextual risk factors beyond the pregnant woman. This information is important to ensure that interventions are formulated based on the social contexts within which drinking in pregnancy takes place and in guiding interventions that aim to prevent prenatal alcohol use, thereby preventing the occurrence of FASDs. This study was guided by Bronfenbrenner’s Ecological Systems Theory to understand partners’ and family members’ perspectives of prenatal exposure within the actual environments in which alcohol use takes place. According to this theory, an individual exists within layers of social relationships: the family, intimate partners, friendships, and healthcare workers (microsystems), interactions among these microsystems, for example, interaction between healthcare workers and intimate partner and family and social workers (mesosystem), accessibility of alcohol in the neighbourhoods (exosystems), religion, culture and society (macro-systems) and changes of the individual and socio-historical context (chronosystem). The data were collected using a biographic narrative interpretive method of interviewing. Thirteen narratives interviews were conducted with partners and family members in a disadvantaged community in Buffalo City, Eastern Cape Province. The interviews were analysed using Template Analysis within the Ecological Systems Theory to interrogate the stories of partners and family members. According to participants, some of the reasons women consumed alcohol in pregnancy are: drinking habits before pregnancy that were difficult to break in pregnancy; women drank during the first trimester of their pregnancy because of unplanned pregnancy; women continued drinking throughout their pregnancies to cope with the emotional upset caused by the trauma of rape and losing loved ones, stress, receiving HIV-diagnosis in pregnancy, intimate partner violence, infidelity, rejection and denial of pregnancy from partners. After birth, some women continued drinking. Consequently, their children were taken away from them by social workers and family members because the parents were unable to care for the child due to alcohol use. There was lack of compliance of shebeens with liquor regulations, heavy drinking, high rates of alcohol use in pregnancy, and easy accessibility of alcohol within this study community. Pregnant women used religious coping beliefs to cope with their circumstances such as changes in their health, relationships and finances. Drinking during pregnancy is a complex problem that stems from multiple social and structural issues and interventions should therefore not only focus on the individual, but also on social networks and communities.
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- Date Issued: 2019
My madam: same race, different class: living and working conditions of undocumented, migrant BaSotho domestic workers employed in black middle class houshold
- Authors: Madonsela, Koketso Njabulo Gosiame
- Date: 2017
- Subjects: Black women household empoyees -- South Africa , Black employers -- South Africa , Women household employees -- South Africa , Women, Sotho -- Employment -- South Africa , Businesspeople, Black -- South Africa , Migrant labor -- South Africa , Illegal aliens -- South Africa , Master and servant -- South Africa , Women, Black -- Employment -- South Africa , Industrial relations -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/35166 , vital:24337
- Description: Jacklyn Cock’s Maids and Madams is a study on domestic work in the Eastern Cape which places a focus on black domestic workers who work in white families. Cock’s study was ground-breaking research within labour development in South Africa (with regards to domestic service). The apartheid system regarded domestic work as that of social reproduction: domestic workers left their families to replenish and reproduce the labour power of white families, whose members were employed in a formal workplace. The contribution to this system, according to Cock (1989), was unbreakable because they did not earn enough money to disrupt the system. The respondents of this thesis are undocumented migrant Basotho domestic workers. These domestic workers have much in common with Cock’s respondents. For one, they leave their homes and families to replenish the labour power of black middle class families, whose members are employed in a formal workplace. The difference between this thesis and Cock’s study is that the respondents’ employers are members of the black middle class. Furthermore, the employees are undocumented Basotho domestic workers. Undocumented, migrant, Basotho domestic workers are in a similarly vulnerable position to that of Cock’s respondents. This dissertation engages with the extent to which Maids and Madams is still relevant to the living and working conditions of a new vulnerable workforce in the domestic sector: undocumented, female, Basotho domestic workers employed in black, middle-class households in Gauteng. The dissertation also finds that the relationship between the black migrant domestic worker and the black middle class employer is influenced cultural aspects of what domestic chores represent in black families, and the element of respect from employers (particularly to elderly domestic workers) or lack thereof. This dissertation underlines that the term “ousi” makes the Basotho domestic workers a collective, and not individuals. Thus the term “ousi” can be viewed as the term that takes away the identity of the domestic worker. The theoretical framework of the research is labour process theory (LPT). The new wave of labour process theorists are much more focused on the service industry. LPT is significant to this research because its focus is on the subjective experiences of the workers. This is the core purpose of the thesis. The focus of the new wave LPT involves a shift from understanding workers at a macro level to understanding the subjective experiences of the workers (in the service industry) at a micro level. This provides an appropriate framework to study the subjective working and living experiences of undocumented, migrant, Basotho domestic workers. The research design is based on qualitative research. The research made use of in-depth and semi-structured interviews. The selection of respondents was done through purposive sampling. They findings of this research highlighted the central themes in the relevant literature. However, the key findings of this research also reveal tensions and contradictions that are not explored in detail in the existing literature. For example, the relationship between the black middle class employer and the black domestic worker has tensions which originate from a cultural context. The respondents of this dissertation and their employers are of the same race, yet are of a different class.
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- Date Issued: 2017
Systematics and biogeography of forest snails, chondrocyclus (mollusca: gastropoda: caenogastropoda: cyclophoridae) in Southern Africa
- Authors: Cole, Mary Louise
- Date: 2017
- Subjects: Chondrocyclus , Mollusks -- South Africa , Cyclophoridae -- South Africa
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/4356 , vital:20651
- Description: This study presents a molecular phylogeny and systematic revision of Chondrocyclus, the major South African group of the large family of operculate terrestrial molluscs, the Cyclophoridae. Chondrocyclus snails are small gastropods found in forest and moist thicket throughout South Africa. This is the first detailed systematic treatment of a group of Cyclophoridae in mainland Africa and the first to provide molecular data. This study complements regional studies on the systematics of the family in Asia and provides comparative data for studies of higher level relationships within the Cyclophoridae. Phylogenetic reconstruction by BI and ML methods of combined and single gene datasets of 16S and CO 1 all showed Chondrocyclus to be monophyletic and recovered five well-supported clades that corresponded to groups of populations identifiable on the basis of combinations of morphological characters. Species were diagnosed morphologically and were shown to be genetically distinct lineages. Informative morphological features include shell dimensions, protoconch, periostracum, operculum, radula and penis. Two species in Afromontane regions of Zimbabwe and Malawi respectively are excluded from Chondrocyclus based on morphology and tentatively placed in Cyathopoma. Diversity recognised within the genus more than doubled, from a previous seven South African species to seventeen. Re-descriptions of established species and descriptions of new species are provided, together with photographs of morphological characteristics. New taxon names and nomenclatural acts within it are disclaimed and are therefore not available in the sense of the International Code of Zoological Nomenclature until validly published elsewhere. Several cryptic species within previously widespread “species” and unrecorded narrowly endemic species were documented. The clade consisting of populations of “Chondrocyclus isipingoensis”, now considered to be a species complex, was sister to a group containing the other four clades. The “Isipingoensis” clade occurs widely in Afromontane regions, along the Great Escarpment, and on the south-east coast. The other four clades occur from Zululand to the Cape Peninsula with a pattern of east-west lineage turnover. The biogeography of Chondrocyclus is interpreted by comparison with concordant patterns in other terrestrial molluscs and unrelated taxa with poor dispersal ability. This study complements other research on composition, spatial distribution and phylogenetic diversity of low-vagility invertebrates and expands the data available for biodiversity conservation in South Africa.
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- Date Issued: 2017
Development of MgZnO-grown MOCVD for UV Photonic applications
- Authors: Talla, Kharouna
- Date: 2011
- Subjects: Photoluminescence , Photonics , Zinc oxide
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10537 , http://hdl.handle.net/10948/d1012585 , Photoluminescence , Photonics , Zinc oxide
- Description: MgxZn1-xO has emerged as a material of great technological importance. Having a direct energy band gap that is tunable throughout much of the ultraviolet (UV) region of the spectrum from the near-UV (~370 nm) to the deep-UV (~176 nm), this compound is of interest for a variety of optoelectronic devices operating in this part of the electromagnetic spectrum. MgxZn1-xO offers advantages over the more mature compound semiconductor AlGaN which stem mainly from the unusually high exciton binding energy (60 meV in ZnO). In this study the growth of ZnO and MgxZn1-xO thin films using metal organic chemical vapour deposition (MOCVD) is systematically investigated. The films are mainly grown on c-Al2O3 and Si (100) and characterized using various techniques, such as photoluminescence (PL), x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and auger electron spectroscopy (AES). The optical and the structural properties are essentially inspected in order to improve their quality. In this thesis the optimisation of ZnO grown using oxygen gas as a new oxidant in our reactor is investigated. The growth temperature and VI/II ratio are varied in order to find optimum parameters giving high quality layers. The effects of Si (100), Si (111), c- and r-sapphire, glass, GaAs and ZnO substrates on the optical, structural and morphological properties of ZnO thin films grown with tert-butanol (TBOH) is examined. Similar morphologies are observed for all substrates, with the films comprising hexagonal columns having cone shaped ends. The photoluminescence spectra are similar, but the various transitions have different relative intensities. It is clear that the different substrates influence neither the orientation of the films, nor the surface morphology, significantly. The photoluminescence hints at larger stacking fault densities in films grown on silicon and glass, however, as evidenced by stronger basal plane stacking fault-related luminescence at ~3.319 eV in the relevant low temperature photoluminescence spectra. The morphology changes with Mg incorporation, from hexagonal columnar structures to cubic faceted columns. From PL, the full with at half maximum is found to gradually increase with Mg content due to alloy broadening. The deep level emission (DLE) is observed to shift with Mg content. By changing the Mg content, the band gap of MgxZn1-xO film is tuned by ~450 meV, which provides an excellent opportunity for band gap engineering for optoelectronic applications. The c-lattice constant of ZnO (5.205 Å) decreases by only 0.6% when the Mg content reaches x=0.39. The introduction of Mg into ZnO is shown to increase the relative PL intensity of stacking fault-related transitions (at 3.314 eV for ZnO). This becomes the dominant near band edge emission. Using TEM a thin Mg rich layer is observed at the interface between the film and the Si or Al2O3. Temperature dependent PL measurements on layers with low Mg concentration (x=0.05 and 0.1) show that the main bound exciton peak exhibits an “s-shaped” temperature dependence, characteristic of localization in a disordered alloy. The origin of the PL line broadening of MgxZn1-xO (x≤0.04) is also analyzed with respect to alloy broadening, taking into account a random cation distribution and alloy clustering. The influence of various MOCVD growth parameters such as growth temperature and VI/II ratio is studied. Varying the temperature from 280 ˚C to 580 ˚C reveals strong morphological changes and optical degradation of the films. Low (<280 ˚C) and high (>580 ˚C) growth temperatures reduce the Mg incorporation. High VI/II ratios also decrease the Mg incorporation, as evidenced by the red-shift of the donor bound exciton (D°X) line. This is ascribed to a stronger premature reaction between (MeCp)2Mg and the oxidant or a preferential heterogeneous interaction between the Mg and oxygen species on the growth front. For both oxidizing agents (O2 and TBOH), the growth at 420 ˚C and a VI-II ratio of 60 on c-Al2O3 gave optimal quality layers in terms of their optical and structural quality. A comparison of films grown using TBOH and O2 gas as oxidizing agent shows no major difference in terms of Mg incorporation. The effect of annealing, the inclusion of a buffer layer and the influence of growth rate on the properties MgxZn1-xO thin films are also reported.
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- Date Issued: 2011
Failure rather than success : conflict management and resolution in the Democratic Republic of Congo, 1996-1999
- Authors: Munyae, Isaac Muinde
- Date: 2001
- Subjects: Conflict management -- Congo (Democratic Republic) , Dispute resolution (Law) -- Congo (Democratic Republic). , Congo (Democratic Republic) -- History -- 1997-
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2856 , http://hdl.handle.net/10962/d1007427 , Conflict management -- Congo (Democratic Republic) , Dispute resolution (Law) -- Congo (Democratic Republic). , Congo (Democratic Republic) -- History -- 1997-
- Description: History has proven time and time again that conflict is an inevitable aspect of any given society. The seemingly long-standing nature of conflicts in Africa has been changing over time and these conflicts have been either inter-state or intra-state. However, sometimes intrastate wars have escalated into regional conflicts. These scenarios can be seen in the Great Lakes region of Africa where you have the civil war of 1996-7 and the rebellion, which began in 1998 in the Democratic Republic of Congo (DRC). In the DRC there have been at least four stages of conflict. The first is against the Belgians and secondly, the civil strife of the early 1960s. Third, is the civil strife against Mobutu and fourthly, currently against Kabila. The expanding nature of conflict is characterised by power struggles, politicisation of ethnicity, and the impact of external forces. It is noted that the expanding nature of conflict calls for a change in the methods of conflict management and resolution. Initially conflicts were resolved through military intervention. but with the complexity of African wars it has become apparent that peaceful methods are more prudent. With reference to Africa it can be assumed that conflicts need to be increasingly resolved through political means, such as the use of the diplomatic process. The conflict in Chad between 1968 and 1984 is a good example in which military intervention was used but failed, giving way to mediation and negotiation through the use of diplomacy. Both the DRC and Chadian conflicts are similar because they witnessed the influence of external forces (neighbouring countries and non-African states such as France and the US) and African states attempting to find solutions to their own problems. The conflict in the DRC provides a unique example of the changing nature of intra-state conflict in Africa. Thus, the study aims to trace the characteristics of conflict in the DRC and attempts made at conflict management and resolution. The study uses the period bet ween 1996 and 1999 because it highlights this change in the nature and character of conflict.
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- Date Issued: 2001
The Patchway Gold Mine : a mineragraphic and petrographic examination of ore from the Patchway Gold Mine, Rhodesia, and an appraisal of the relationship between gold mineralisation and geological structure
- Authors: Ward, J H W
- Date: 1969
- Subjects: Gold ores -- Geology -- Zimbabwe , Petrology -- Zimbabwe , Geology -- Zimbabwe , Ores -- Zimbabwe , Gold mines and mining -- Zimbabwe
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5069 , http://hdl.handle.net/10962/d1013471
- Description: A remarkable correlation between hydrothermal gold mineralisation and geological structure is discussed. The mineralisation occurs in vein quartz which occupies a fissure in Archaean greenstones of the Basement Complex in Rhodesia, It has been determined that gold which is silver-rich is typical of low-grade ore, and is associated in space with sulphides that crystallised early in paragenesis. Silver-poor gold is characteristic of highgrade ore which is concentrated along the crestal zone of anticlinal warps in the fissure. It is suggested that the local pattern of fracturing and folding is related to fundamental wrench faulting.
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- Date Issued: 1969