Substantive equality and the challenge to affimative action as justification for unfair discrimination
- Authors: Delport, Petrus Jacobus
- Date: 2017
- Subjects: Discrimination in employment , Affirmative action programs , Equality
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: http://hdl.handle.net/10948/15467 , vital:28256
- Description: South Africa’s history as a nation is replete with examples of inequality and unfair discrimination. The working arena was no exception to the rule. In fact, it was one of the areas where inequality was most prevalent. Discriminatory legislation was promulgated under the Apartheid regime. These laws enforced differential treatment of employees along racial lines. After 1994, the newly democratic South Africa, through the Constitution of the Republic of South Africa Act 108 of 1996 (hereinafter referred to as the “Constitution”), regarded all people as equal before the law and entitled to equal benefit and protection under the law. National legislation was subsequently promulgated to give effect to this constitutional objective. The Employment Equity Act 55 of 1998 (hereinafter referred to as the “EEA”), specifically, gave effect to all employees’ constitutional right to equality in the workplace. Under the EEA, unfair discrimination was forbidden. The EEA also required employers to implement measures to eradicate the injustices of the past. Subsequent to the enactment of the EEA, the Courts reiterated two tests to determine whether unfair discrimination had taken place in the workplace. It also tested whether an affirmative action measure could justify such unfair discrimination. These two tests, referred to in Harksen v Lane NO and others (CCT9/97) [1997] ZACC 12 (11) BCLR 1489 (CC) (Hereinafter referred to as the “Harksen test”) and Minister of Finance v Van Heerden 2004 (11) BCLR 1125 (CC) (Hereinafter referred to as the “Van Heerden test”), were unfortunately applied by the Courts in an inconsistent manner. This created confusion about which test found application in specific circumstances. The Constitutional Court then clarified the confusion through the South African Police Service v Solidarity obo Barnard (2014) ZACC 23 (CC) (Hereinafter referred to as the “Barnard” decision”). It is important to note that this study does not seek to evaluate the correctness of the Barnard decision, nor does it consider the cases prior to the Barnard decision. Rather, this study considers the extent to which the Barnard decision informed later cases dealing with unfair discrimination and affirmative action. In the remaining chapters of this treatise the writer will attempt to answer this question as follows: In chapter two, the legislative framework applicable to issues of unfair discrimination and the application of affirmative action is discussed. Chapter three comprises of a detailed analysis of the Barnard decision. In chapters four and five the writer investigates how the Barnard decision informed four recent cases concerning affirmative action and unfair discrimination in the workplace. These discussions enabled the writer to, in the final chapter; conclude that all four cases were indeed informed by the Barnard decision. The Department of Correctional Services case, however, reiterated the Barnard decision to its fullest extent.
- Full Text:
- Date Issued: 2017
- Authors: Delport, Petrus Jacobus
- Date: 2017
- Subjects: Discrimination in employment , Affirmative action programs , Equality
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: http://hdl.handle.net/10948/15467 , vital:28256
- Description: South Africa’s history as a nation is replete with examples of inequality and unfair discrimination. The working arena was no exception to the rule. In fact, it was one of the areas where inequality was most prevalent. Discriminatory legislation was promulgated under the Apartheid regime. These laws enforced differential treatment of employees along racial lines. After 1994, the newly democratic South Africa, through the Constitution of the Republic of South Africa Act 108 of 1996 (hereinafter referred to as the “Constitution”), regarded all people as equal before the law and entitled to equal benefit and protection under the law. National legislation was subsequently promulgated to give effect to this constitutional objective. The Employment Equity Act 55 of 1998 (hereinafter referred to as the “EEA”), specifically, gave effect to all employees’ constitutional right to equality in the workplace. Under the EEA, unfair discrimination was forbidden. The EEA also required employers to implement measures to eradicate the injustices of the past. Subsequent to the enactment of the EEA, the Courts reiterated two tests to determine whether unfair discrimination had taken place in the workplace. It also tested whether an affirmative action measure could justify such unfair discrimination. These two tests, referred to in Harksen v Lane NO and others (CCT9/97) [1997] ZACC 12 (11) BCLR 1489 (CC) (Hereinafter referred to as the “Harksen test”) and Minister of Finance v Van Heerden 2004 (11) BCLR 1125 (CC) (Hereinafter referred to as the “Van Heerden test”), were unfortunately applied by the Courts in an inconsistent manner. This created confusion about which test found application in specific circumstances. The Constitutional Court then clarified the confusion through the South African Police Service v Solidarity obo Barnard (2014) ZACC 23 (CC) (Hereinafter referred to as the “Barnard” decision”). It is important to note that this study does not seek to evaluate the correctness of the Barnard decision, nor does it consider the cases prior to the Barnard decision. Rather, this study considers the extent to which the Barnard decision informed later cases dealing with unfair discrimination and affirmative action. In the remaining chapters of this treatise the writer will attempt to answer this question as follows: In chapter two, the legislative framework applicable to issues of unfair discrimination and the application of affirmative action is discussed. Chapter three comprises of a detailed analysis of the Barnard decision. In chapters four and five the writer investigates how the Barnard decision informed four recent cases concerning affirmative action and unfair discrimination in the workplace. These discussions enabled the writer to, in the final chapter; conclude that all four cases were indeed informed by the Barnard decision. The Department of Correctional Services case, however, reiterated the Barnard decision to its fullest extent.
- Full Text:
- Date Issued: 2017
Successful delivery of an online higher education course: a quantitative management framework
- Authors: Burger, Dimitri
- Date: 2017
- Subjects: Decision making -- Mathematical models Management -- Mathematical models , Management science Distance education -- South Africa -- Computer-assisted instruction Education, Higher
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/14785 , vital:27850
- Description: South Africa has been experiencing several challenges regarding access to higher education, quality of higher education, effectiveness of higher education course delivery, and funding for higher education. In the higher education sector, the bulk of the burden is placed on traditional higher education institutions, most notably universities, in providing higher education to a growing youth base in dire need of education that supports their individual learning needs. With these challenges facing traditional universities, online higher education provided by both public sector higher education institutions and private sector education providers can act as a valuable alternative and solution to access for some of the population. Online education and face-to-face education differ considerably in how they deliver courses to students. Many have argued that these differences are in some cases attributable to strengths in face-to-face education and drawbacks or limitations in online education, large enough that they should serve as the criteria for selecting the former over the latter as the better mode of delivery. While there have been examples of online programmes that have failed to deliver courses successfully by underutilising or misusing the tools and techniques available, there are positive examples where these programmes perform equally as well as face-to-face courses. The defining difference is ultimately and often the management of these courses’ resources, activities, people, processes, and practices. Considering the above, and with examination of the available literature, a conceptual and theoretical framework was constructed and a quantitative research study was undertaken to prove the significant correlational relationships between elements of course delivery and a management framework to govern those elements. The sample consisted of 115 students from a postgraduate degree programme presented in two formats, online and on-campus. The findings provide evidence of significant relationships between the core functions of management as well as between aspects of course delivery, such as opportunities for interaction, opportunities for feedback, and course content in achieving learning outcomes for students and contributing to engagement. The findings also indicate positive perceptions from students in relation to the delivery of the courses.
- Full Text:
- Date Issued: 2017
- Authors: Burger, Dimitri
- Date: 2017
- Subjects: Decision making -- Mathematical models Management -- Mathematical models , Management science Distance education -- South Africa -- Computer-assisted instruction Education, Higher
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/14785 , vital:27850
- Description: South Africa has been experiencing several challenges regarding access to higher education, quality of higher education, effectiveness of higher education course delivery, and funding for higher education. In the higher education sector, the bulk of the burden is placed on traditional higher education institutions, most notably universities, in providing higher education to a growing youth base in dire need of education that supports their individual learning needs. With these challenges facing traditional universities, online higher education provided by both public sector higher education institutions and private sector education providers can act as a valuable alternative and solution to access for some of the population. Online education and face-to-face education differ considerably in how they deliver courses to students. Many have argued that these differences are in some cases attributable to strengths in face-to-face education and drawbacks or limitations in online education, large enough that they should serve as the criteria for selecting the former over the latter as the better mode of delivery. While there have been examples of online programmes that have failed to deliver courses successfully by underutilising or misusing the tools and techniques available, there are positive examples where these programmes perform equally as well as face-to-face courses. The defining difference is ultimately and often the management of these courses’ resources, activities, people, processes, and practices. Considering the above, and with examination of the available literature, a conceptual and theoretical framework was constructed and a quantitative research study was undertaken to prove the significant correlational relationships between elements of course delivery and a management framework to govern those elements. The sample consisted of 115 students from a postgraduate degree programme presented in two formats, online and on-campus. The findings provide evidence of significant relationships between the core functions of management as well as between aspects of course delivery, such as opportunities for interaction, opportunities for feedback, and course content in achieving learning outcomes for students and contributing to engagement. The findings also indicate positive perceptions from students in relation to the delivery of the courses.
- Full Text:
- Date Issued: 2017
Supplier development for competitive advantage in manufacturing small medium enterprises
- Authors: Makumbila, Louis Boy
- Date: 2017
- Subjects: Competition -- South Africa Small business -- South Africa -- Management , Business planning -- South Africa Industrial management -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/18102 , vital:28576
- Description: Competitive advantage is crucial for a business to be sustainable, yet many small- and medium-sized enterprises are not engaging in supplier development in order to achieve a competitive advantage. This empirical study was conducted on a sample of 64 small- and medium-sized enterprises in the manufacturing industry in Kempton Park, Gauteng. The factors that influence engagement in supplier development were analysed to assess whether supplier development can lead to competitive advantage and other benefits. The findings indicate that supplier development can create and improve competitive advantage, as well as lead to other benefits. Four factors were found to have a relationship with supplier development, and therefore could influence the decision to take part in supplier development. Small- and medium-sized enterprises can use tools such as supplier development in order to be competitive and have an advantage over their competitors. The awareness of operational performance measures, competitive advantage, judgment of the absence or existence of trust, and a buyer’s relative power can all influence participation in supplier development.
- Full Text:
- Date Issued: 2017
- Authors: Makumbila, Louis Boy
- Date: 2017
- Subjects: Competition -- South Africa Small business -- South Africa -- Management , Business planning -- South Africa Industrial management -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/18102 , vital:28576
- Description: Competitive advantage is crucial for a business to be sustainable, yet many small- and medium-sized enterprises are not engaging in supplier development in order to achieve a competitive advantage. This empirical study was conducted on a sample of 64 small- and medium-sized enterprises in the manufacturing industry in Kempton Park, Gauteng. The factors that influence engagement in supplier development were analysed to assess whether supplier development can lead to competitive advantage and other benefits. The findings indicate that supplier development can create and improve competitive advantage, as well as lead to other benefits. Four factors were found to have a relationship with supplier development, and therefore could influence the decision to take part in supplier development. Small- and medium-sized enterprises can use tools such as supplier development in order to be competitive and have an advantage over their competitors. The awareness of operational performance measures, competitive advantage, judgment of the absence or existence of trust, and a buyer’s relative power can all influence participation in supplier development.
- Full Text:
- Date Issued: 2017
Supportive supervision: the experiences of social workers in the field of child protection
- Authors: Vetfuti, Nkosinathi Oscar
- Date: 2017
- Subjects: Social workers -- Supervision of -- South Africa -- Nelson Mandela Bay Municipality Child welfare -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/14433 , vital:27595
- Description: Supervision in social work is composed of educational, administrative and supportive functions. Supportive supervision is particularly important for child protection social workers, given their work with vulnerable children. Supportive supervision facilitates the child protection social worker’s reflection on practice issues with a designated supervisor who, through this process, addresses their personal and professional development as well as their emotional needs; this, in turn, contributes to sound ethical practice. The sparse literature available on the topic and practice observations pointing to the lack of supportive function in the area of Child Protection Services gave rise to this study. The purpose of this qualitative, exploratory, descriptive and contextual study was thus toenhance an understanding of the experiences of social workers in Child Protection Services in respect of supportive function of supervision within the public sector in the Nelson Mandela Bay region. A non-probability purposive sampling strategy was used to identify social workers working in the field of child protection for an uninterrupted minimum period of three years. The final sample consisted of ten child protection social workers. Data was collected through semi-structured, in-depth, individual, face-to-face interviews, which were guided by an interview schedule. The data was analysed using Tesch’s (1990) model as outlined in Creswell (2014:198). The trustworthiness of the research process and the findings was enhanced by using a range of data verification techniques. The main themes that emerged from the process of data analysis are: 1) Social workers’ experiences of working in Child Protection Services; 2) Social workers’ perceptions and experiences of social work supervision in general and supportive supervision in particular; and 3) Social workers’ recommendations on how supportive supervision needs can be addressed. The findings of this study yielded valuable scholarly knowledge in respect of the supportive supervision function in Child Protection Services.
- Full Text:
- Date Issued: 2017
- Authors: Vetfuti, Nkosinathi Oscar
- Date: 2017
- Subjects: Social workers -- Supervision of -- South Africa -- Nelson Mandela Bay Municipality Child welfare -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/14433 , vital:27595
- Description: Supervision in social work is composed of educational, administrative and supportive functions. Supportive supervision is particularly important for child protection social workers, given their work with vulnerable children. Supportive supervision facilitates the child protection social worker’s reflection on practice issues with a designated supervisor who, through this process, addresses their personal and professional development as well as their emotional needs; this, in turn, contributes to sound ethical practice. The sparse literature available on the topic and practice observations pointing to the lack of supportive function in the area of Child Protection Services gave rise to this study. The purpose of this qualitative, exploratory, descriptive and contextual study was thus toenhance an understanding of the experiences of social workers in Child Protection Services in respect of supportive function of supervision within the public sector in the Nelson Mandela Bay region. A non-probability purposive sampling strategy was used to identify social workers working in the field of child protection for an uninterrupted minimum period of three years. The final sample consisted of ten child protection social workers. Data was collected through semi-structured, in-depth, individual, face-to-face interviews, which were guided by an interview schedule. The data was analysed using Tesch’s (1990) model as outlined in Creswell (2014:198). The trustworthiness of the research process and the findings was enhanced by using a range of data verification techniques. The main themes that emerged from the process of data analysis are: 1) Social workers’ experiences of working in Child Protection Services; 2) Social workers’ perceptions and experiences of social work supervision in general and supportive supervision in particular; and 3) Social workers’ recommendations on how supportive supervision needs can be addressed. The findings of this study yielded valuable scholarly knowledge in respect of the supportive supervision function in Child Protection Services.
- Full Text:
- Date Issued: 2017
Surgical counting practices of registered nurses in private operating rooms in the Eastern Cape region
- Authors: Lines, Ina-Mari Adele'
- Date: 2017
- Subjects: Surgical instruments and apparatus -- Safety measures Operating room nursing
- Language: English
- Type: Thesis , Masters , MCur
- Identifier: http://hdl.handle.net/10948/45377 , vital:38603
- Description: The study aim was to explore and describe surgical counting practices of registered nurses in private operating rooms in the Eastern Cape region. A quantitative, explorative, descriptive, and contextual research design was implemented to reach the objective of the study. The research population consisted of 84 registered nurses working in six different private Hospitals. All-inclusive sampling was used. A structured questionnaire was used to collect data. Face and content validity of the questionnaire were ensured by making use of a statistician and an expert in the field. The collected data was analysed by making use of a statistician and Statistical version 12. The research results indicated that registered nurses who work in private hospitals in the Eastern Cape region generally abide by the recommended practice guidelines of WHO. The results were documented and presented by means of graphs and tables. Recommendations were made at the end of the study.
- Full Text:
- Date Issued: 2017
- Authors: Lines, Ina-Mari Adele'
- Date: 2017
- Subjects: Surgical instruments and apparatus -- Safety measures Operating room nursing
- Language: English
- Type: Thesis , Masters , MCur
- Identifier: http://hdl.handle.net/10948/45377 , vital:38603
- Description: The study aim was to explore and describe surgical counting practices of registered nurses in private operating rooms in the Eastern Cape region. A quantitative, explorative, descriptive, and contextual research design was implemented to reach the objective of the study. The research population consisted of 84 registered nurses working in six different private Hospitals. All-inclusive sampling was used. A structured questionnaire was used to collect data. Face and content validity of the questionnaire were ensured by making use of a statistician and an expert in the field. The collected data was analysed by making use of a statistician and Statistical version 12. The research results indicated that registered nurses who work in private hospitals in the Eastern Cape region generally abide by the recommended practice guidelines of WHO. The results were documented and presented by means of graphs and tables. Recommendations were made at the end of the study.
- Full Text:
- Date Issued: 2017
Sustainable livelihoods, employment and poverty alleviation: the case of the Good News Ark Project
- Authors: Nkwakwa, Bandlakazi Beira
- Date: 2017
- Subjects: Sustainable development -- South Africa Rural development -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/19784 , vital:28965
- Description: Income generating projects play a significant role in the lives of rural people and make a significant contribution to rural development in South Africa. Although, income generating projects play a major contribution to rural development, problems of funding for such projects and the high levels of unskilled personnel to run those projects is still a challenge in most, if not all rural areas of South Africa. Therefore this study has undertaken with the objectives of assessing income generating projects in relation to its contribution to rural development in the study area. The sustainable livelihoods and basic needs approaches were used to assess the contribution of income generating projects in poverty alleviation in rural areas. Such approaches to rural development can help in reducing the poverty gap that exists in society and at the same time help achieve sustainable rural development. Findings show that there are a number of challenges and constraints that are experienced by the Thaba Nchu community, like poverty and unemployment. However, the main findings of the research study suggested that the contribution made by the Good News Ark Project toward poverty alleviation and community development is to empower the project members and casual workers. To have a successful rural development, there is need for the government to support these projects in the form of skills training programmes and finance. The study recommends that intervention should occur and the coordination between the relevant stakeholders should be strengthened as the development of the rural poor depends on both social development and food production.
- Full Text:
- Date Issued: 2017
- Authors: Nkwakwa, Bandlakazi Beira
- Date: 2017
- Subjects: Sustainable development -- South Africa Rural development -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/19784 , vital:28965
- Description: Income generating projects play a significant role in the lives of rural people and make a significant contribution to rural development in South Africa. Although, income generating projects play a major contribution to rural development, problems of funding for such projects and the high levels of unskilled personnel to run those projects is still a challenge in most, if not all rural areas of South Africa. Therefore this study has undertaken with the objectives of assessing income generating projects in relation to its contribution to rural development in the study area. The sustainable livelihoods and basic needs approaches were used to assess the contribution of income generating projects in poverty alleviation in rural areas. Such approaches to rural development can help in reducing the poverty gap that exists in society and at the same time help achieve sustainable rural development. Findings show that there are a number of challenges and constraints that are experienced by the Thaba Nchu community, like poverty and unemployment. However, the main findings of the research study suggested that the contribution made by the Good News Ark Project toward poverty alleviation and community development is to empower the project members and casual workers. To have a successful rural development, there is need for the government to support these projects in the form of skills training programmes and finance. The study recommends that intervention should occur and the coordination between the relevant stakeholders should be strengthened as the development of the rural poor depends on both social development and food production.
- Full Text:
- Date Issued: 2017
Sustainable tourism opportunities for Mauritius
- Authors: Ternel, Maeva
- Date: 2017
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10962/6118 , vital:21046
- Description: Sustainable Tourism (ST) integrates governance, economic, socio-cultural and environmental dimensions of tourism in tourism development and management. Growing Environmental, Social and Governance (ESG) concerns suggest that traditionally, tourism tends to corrupt the very resources it needs to thrive, and thus its sustainability over the long haul has become of general concern. However, despite the vast and extensive literature dedicated to ST, including preeminent journals providing both a theoretical base and reliable empirical evidence to the subject, the concept of sustainability in tourism remains somehow at its embryonic stage, especially in the case of a small island developing state (SIDS). The research occurred within the context of the destination (Mauritius), with however, a focus on five sizeable Mauritian hotel groups. With tourism being one of the pillars of the Mauritian economy, this research intended to explore the different repercussions of such an industry. The aim of the research was to determine to what extent tourism’s operations and development, was appropriately managed in Mauritius by assessing the country’s current tourism situation relating to sustainability and identifying priority areas for intervention. This, was done using different tools, including the United Nations World Tourism Organisation's framework, the Global Sustainable Tourism Council's guidelines and the Sustainable Tourism Attitude Scale. The contribution this research intended to make was to suggest sustainable tourism opportunities and make recommendations for the tourism sector and its stakeholders for the island of Mauritius. Overall, the research concluded that despite the increased importance of ST, the need for Managed Tourism (MT) and the formulation of general principles and guidelines, tourism governance; poverty reduction; and the sustainability of the natural and cultural environment were identified as areas of particular need and should be considered with high priority for intervention/action.
- Full Text:
- Date Issued: 2017
- Authors: Ternel, Maeva
- Date: 2017
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10962/6118 , vital:21046
- Description: Sustainable Tourism (ST) integrates governance, economic, socio-cultural and environmental dimensions of tourism in tourism development and management. Growing Environmental, Social and Governance (ESG) concerns suggest that traditionally, tourism tends to corrupt the very resources it needs to thrive, and thus its sustainability over the long haul has become of general concern. However, despite the vast and extensive literature dedicated to ST, including preeminent journals providing both a theoretical base and reliable empirical evidence to the subject, the concept of sustainability in tourism remains somehow at its embryonic stage, especially in the case of a small island developing state (SIDS). The research occurred within the context of the destination (Mauritius), with however, a focus on five sizeable Mauritian hotel groups. With tourism being one of the pillars of the Mauritian economy, this research intended to explore the different repercussions of such an industry. The aim of the research was to determine to what extent tourism’s operations and development, was appropriately managed in Mauritius by assessing the country’s current tourism situation relating to sustainability and identifying priority areas for intervention. This, was done using different tools, including the United Nations World Tourism Organisation's framework, the Global Sustainable Tourism Council's guidelines and the Sustainable Tourism Attitude Scale. The contribution this research intended to make was to suggest sustainable tourism opportunities and make recommendations for the tourism sector and its stakeholders for the island of Mauritius. Overall, the research concluded that despite the increased importance of ST, the need for Managed Tourism (MT) and the formulation of general principles and guidelines, tourism governance; poverty reduction; and the sustainability of the natural and cultural environment were identified as areas of particular need and should be considered with high priority for intervention/action.
- Full Text:
- Date Issued: 2017
Synergistic interactions of selected medicinal plants traditionally used to treat meningitis
- Kamwamba, Thokozani Edson, Zondie, Leyli
- Authors: Kamwamba, Thokozani Edson , Zondie, Leyli
- Date: 2017
- Subjects: Medicinal plants -- Biotechnology Meningitis -- Treatment
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/18816 , vital:28729
- Description: The antibacterial and antifungal activities of aqueous, methanol and acetone extracts of the leaves of Geranium incanum, Mangifera indica, Bidens pilosa, Ricinus communis, Carica papaya and fruit pulp of Adansonia digitata as well as activity of their combined preparation were evaluated against selected meningitis causing pathogens. The microorganisms under study were methicillin and oxacillin resistant Staphylococcus aureus (ATCC 43300), Pseudomonas aeruginosa (ATCC 27853), Salmonella typhimurium (ATCC 49416), Escherichia coli (ATCC 35218), Candida albicans (ATCC 10231) and Cryptococcus neoformans (clinical strain). The screening of antimicrobial activities were assessed using an agar well diffusion technique for the different plant extractions. The individual and combined plant extracts that demonstrated antimicrobial effects were further studied using the INT microtitre plate technique to determine the minimum inhibitory concentration. The sum of fractional inhibitory concentration indices were calculated and used to assess the type of antimicrobial interaction. The medicinal plants exerted antimicrobial effects independently and in combination on the bacterial and fungal organisms under study. The antimicrobial activities depended on the test organism and extracting solvents used. In the combination studies, the medicinal plants under study were combined in the ratio of 1:1. Antimicrobial interactions ranging from synergistic to antagonistic effects were noted. Methanol extracts of combinations B. pilosa: M. indica, R. communins: M. indica and C. papaya: M. indica had synergistic effects against P. aeruginosa. On the other hand, aqueous extracts of a mixture of C. papaya: B. pilosa exerted synergistic effects on E. coli and S. typhimurium. Acetone extracts of a mixture of A. digitata: G. incanum, G. incanum: M. indica as well as methanol extract of the combination of C. papaya: G. incanum exhibited synergistic effects against C. albicans. The aqueous extract combination of G. incanum: M. indica displayed the most noteworthy synergistic activity against C. neoformans. In addition, aqueous extracts of the combinations of A. digitata: B. pilosa and R. communis: G. incanum exhibited synergistic effects against C. neoformans. The results validate the traditional healing practices which utilise combinations of different species of plants for treatment of predisposing factors of meningitis.
- Full Text:
- Date Issued: 2017
- Authors: Kamwamba, Thokozani Edson , Zondie, Leyli
- Date: 2017
- Subjects: Medicinal plants -- Biotechnology Meningitis -- Treatment
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/18816 , vital:28729
- Description: The antibacterial and antifungal activities of aqueous, methanol and acetone extracts of the leaves of Geranium incanum, Mangifera indica, Bidens pilosa, Ricinus communis, Carica papaya and fruit pulp of Adansonia digitata as well as activity of their combined preparation were evaluated against selected meningitis causing pathogens. The microorganisms under study were methicillin and oxacillin resistant Staphylococcus aureus (ATCC 43300), Pseudomonas aeruginosa (ATCC 27853), Salmonella typhimurium (ATCC 49416), Escherichia coli (ATCC 35218), Candida albicans (ATCC 10231) and Cryptococcus neoformans (clinical strain). The screening of antimicrobial activities were assessed using an agar well diffusion technique for the different plant extractions. The individual and combined plant extracts that demonstrated antimicrobial effects were further studied using the INT microtitre plate technique to determine the minimum inhibitory concentration. The sum of fractional inhibitory concentration indices were calculated and used to assess the type of antimicrobial interaction. The medicinal plants exerted antimicrobial effects independently and in combination on the bacterial and fungal organisms under study. The antimicrobial activities depended on the test organism and extracting solvents used. In the combination studies, the medicinal plants under study were combined in the ratio of 1:1. Antimicrobial interactions ranging from synergistic to antagonistic effects were noted. Methanol extracts of combinations B. pilosa: M. indica, R. communins: M. indica and C. papaya: M. indica had synergistic effects against P. aeruginosa. On the other hand, aqueous extracts of a mixture of C. papaya: B. pilosa exerted synergistic effects on E. coli and S. typhimurium. Acetone extracts of a mixture of A. digitata: G. incanum, G. incanum: M. indica as well as methanol extract of the combination of C. papaya: G. incanum exhibited synergistic effects against C. albicans. The aqueous extract combination of G. incanum: M. indica displayed the most noteworthy synergistic activity against C. neoformans. In addition, aqueous extracts of the combinations of A. digitata: B. pilosa and R. communis: G. incanum exhibited synergistic effects against C. neoformans. The results validate the traditional healing practices which utilise combinations of different species of plants for treatment of predisposing factors of meningitis.
- Full Text:
- Date Issued: 2017
Synthesis and bioassay of rationally designed DXR inhibitors as potential antimalarial lead compounds
- Authors: Nokalipa, Iviwe Cwaita
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4888 , vital:20740
- Description: Globally, the eradication of malaria has been challenging due to the problem of resistance that past and currently available drugs exhibit. This is exacerbated by the inherent need for anti-malarial drugs to be affordable to the poverty-stricken majority that is primarily affected by this burden. This research has focused on the development of potential inhibitors of 1-deoxy-D- xylulose-5 phosphate reductoisomerase (DXR), an essential enzyme in the mevalonate- independent pathway for the biosynthesis of isoprenoids in Plasmodium falciparum. DXR mediates the isomerisation and reduction of 1-deoxy-D-xylulose-5-phosphate into 2-C- methyl-D-erithrytol 4-phosphate. This enzyme has been determined to be a target for the development of novel antimalarial agents and extensive molecular modelling has been undertaken to develop inhibitors that fit into the DXR active site. The in silico docking data have been used to inform the design and synthesis of various N-benzyl-substituted phosphoramidate ligands that were determined to have potential as novel substrate mimics of fosmidomycin, a known DXR inhibitor. Synthesis of the N-benzyl-substituted phosphoramidate ligands involved a nine-step sequence commencing from diethyl phosphoramidate. In all, some 40 compounds have been prepared, some of them new, and were fully characterized using NMR. Attention has also been given to the mass spectrometric fragmentation patterns exhibited by selected intermediates. Four of the final products were evaluated for in vitro antimalarial activity using a PLDH assay and exhibited IC50 values < 100 µM.
- Full Text:
- Date Issued: 2017
- Authors: Nokalipa, Iviwe Cwaita
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4888 , vital:20740
- Description: Globally, the eradication of malaria has been challenging due to the problem of resistance that past and currently available drugs exhibit. This is exacerbated by the inherent need for anti-malarial drugs to be affordable to the poverty-stricken majority that is primarily affected by this burden. This research has focused on the development of potential inhibitors of 1-deoxy-D- xylulose-5 phosphate reductoisomerase (DXR), an essential enzyme in the mevalonate- independent pathway for the biosynthesis of isoprenoids in Plasmodium falciparum. DXR mediates the isomerisation and reduction of 1-deoxy-D-xylulose-5-phosphate into 2-C- methyl-D-erithrytol 4-phosphate. This enzyme has been determined to be a target for the development of novel antimalarial agents and extensive molecular modelling has been undertaken to develop inhibitors that fit into the DXR active site. The in silico docking data have been used to inform the design and synthesis of various N-benzyl-substituted phosphoramidate ligands that were determined to have potential as novel substrate mimics of fosmidomycin, a known DXR inhibitor. Synthesis of the N-benzyl-substituted phosphoramidate ligands involved a nine-step sequence commencing from diethyl phosphoramidate. In all, some 40 compounds have been prepared, some of them new, and were fully characterized using NMR. Attention has also been given to the mass spectrometric fragmentation patterns exhibited by selected intermediates. Four of the final products were evaluated for in vitro antimalarial activity using a PLDH assay and exhibited IC50 values < 100 µM.
- Full Text:
- Date Issued: 2017
Synthesis and characterisation of lanthanide complexes with O,O-donor ligands: towards a new generation of hydrophosphonylation catalysts
- Authors: Mkwakwi, Kwakhanya
- Date: 2017
- Subjects: Rare earth metals Catalysts
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/11986 , vital:27016
- Description: This study investigates the coordination behaviour of potentially bi- and tridentate O,O- and O,N,O-donor Schiff base ligands with trivalent lanthanide ions. The reactions of lanthanide nitrates with 2-((E)-(tert-butylimino)methyl)-6-methoxyphenol (HL1) have yielded five complexes that are described by the general formula [Ln(HL1)2(NO3)3] (Ln = Ce, Nd, Gd, Ho and Er) and were characterised using physico-chemical techniques including single-crystal X-ray diffraction spectroscopy. The cerium complex crystallised in a triclinic (P-1) space group, while the rest of the complexes crystallised in the monoclinic (P21/c) space group. All the complexes are ten-coordinate adopting a tetradecahedron geometry with two HL1 molecules coordinated through the phenolic and methoxy oxygen atoms. The coordination sphere is completed by six oxygen atoms from three bidentately coordinated nitrate ligands. Electronic data reveals that only the neodymium, holmium and erbium complexes exhibit weak f-f transitions in the visible region. The redox behaviour of the complexes was also investigated and reported. Five novel complexes were prepared by reacting 2-((E)-(tert-butylimino)methyl)phenol (HL2) with [Ln(NO3)3∙xH2O] (Ln = Gd and Dy ; x = 5 or 6) and [LnCl3∙6H2O] (Ln = Nd, Gd and Dy). The crystal structures of the former two complexes are isostructural and the coordination sphere is composed of three HL2 ligands bonded to the metal centre through the phenolic oxygen atom and three nitrate ions coordinated in a bidentate fashion. Both complexes are nine-coordinate and SHAPE analysis reveals that they adopted a muffin geometry. The average Ln-Onitrate and Ln-Ophenolate bond lengths are 2.5078 and 2.2814 Å, respectively. The complexes derived from the chloride salts exhibited an octahedral geometry with four monodentate ligands [Ln-Ophenolate distances range from 2.224(4) to 2.2797(17) Å] coordinating in the equatorial positions and two chloride ions [average Ln-Cl bond length is 2.6527 Å, and average Cl-Ln-Cl angles is 180o] in axial positions. The ligand coordinated through the phenolic oxygen with the phenolic proton migrating to the imino nitrogen to give a zwitterionic form of the ligand. There are weak C-H∙∙∙Cl interactions present and O-H∙∙∙N hydrogen bonds are also observed in the crystal packing. The synthesis of lanthanide complexes with methoxy-6-((E)-(phenylimino)methyl)phenol (HL3) was carried out in methanol to yield two mononuclear complexes with the formulae [Nd(HL3)2(NO3)3] and [Ho(HL3)(NO3)3(DMF)(H2O)]. Single-crystal crystallographic studies shows that the neodymium complex contains two HL3 ligands coordinated bidentately through its methoxide and phenolic oxygen atoms, with three nitrate ions also bonded to the metal in a bidentate manner. The coordination geometry in the holmium complex is composed of only oxygen atoms from the various ligands. Both complexes are ten-coordinate and exhibit a tetradecahedron geometry.
- Full Text:
- Date Issued: 2017
- Authors: Mkwakwi, Kwakhanya
- Date: 2017
- Subjects: Rare earth metals Catalysts
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/11986 , vital:27016
- Description: This study investigates the coordination behaviour of potentially bi- and tridentate O,O- and O,N,O-donor Schiff base ligands with trivalent lanthanide ions. The reactions of lanthanide nitrates with 2-((E)-(tert-butylimino)methyl)-6-methoxyphenol (HL1) have yielded five complexes that are described by the general formula [Ln(HL1)2(NO3)3] (Ln = Ce, Nd, Gd, Ho and Er) and were characterised using physico-chemical techniques including single-crystal X-ray diffraction spectroscopy. The cerium complex crystallised in a triclinic (P-1) space group, while the rest of the complexes crystallised in the monoclinic (P21/c) space group. All the complexes are ten-coordinate adopting a tetradecahedron geometry with two HL1 molecules coordinated through the phenolic and methoxy oxygen atoms. The coordination sphere is completed by six oxygen atoms from three bidentately coordinated nitrate ligands. Electronic data reveals that only the neodymium, holmium and erbium complexes exhibit weak f-f transitions in the visible region. The redox behaviour of the complexes was also investigated and reported. Five novel complexes were prepared by reacting 2-((E)-(tert-butylimino)methyl)phenol (HL2) with [Ln(NO3)3∙xH2O] (Ln = Gd and Dy ; x = 5 or 6) and [LnCl3∙6H2O] (Ln = Nd, Gd and Dy). The crystal structures of the former two complexes are isostructural and the coordination sphere is composed of three HL2 ligands bonded to the metal centre through the phenolic oxygen atom and three nitrate ions coordinated in a bidentate fashion. Both complexes are nine-coordinate and SHAPE analysis reveals that they adopted a muffin geometry. The average Ln-Onitrate and Ln-Ophenolate bond lengths are 2.5078 and 2.2814 Å, respectively. The complexes derived from the chloride salts exhibited an octahedral geometry with four monodentate ligands [Ln-Ophenolate distances range from 2.224(4) to 2.2797(17) Å] coordinating in the equatorial positions and two chloride ions [average Ln-Cl bond length is 2.6527 Å, and average Cl-Ln-Cl angles is 180o] in axial positions. The ligand coordinated through the phenolic oxygen with the phenolic proton migrating to the imino nitrogen to give a zwitterionic form of the ligand. There are weak C-H∙∙∙Cl interactions present and O-H∙∙∙N hydrogen bonds are also observed in the crystal packing. The synthesis of lanthanide complexes with methoxy-6-((E)-(phenylimino)methyl)phenol (HL3) was carried out in methanol to yield two mononuclear complexes with the formulae [Nd(HL3)2(NO3)3] and [Ho(HL3)(NO3)3(DMF)(H2O)]. Single-crystal crystallographic studies shows that the neodymium complex contains two HL3 ligands coordinated bidentately through its methoxide and phenolic oxygen atoms, with three nitrate ions also bonded to the metal in a bidentate manner. The coordination geometry in the holmium complex is composed of only oxygen atoms from the various ligands. Both complexes are ten-coordinate and exhibit a tetradecahedron geometry.
- Full Text:
- Date Issued: 2017
Synthesis and characterization of CdSe quantum dots for solar cell application
- Authors: Makinana, Sinovuyo
- Date: 2017
- Subjects: Quantum dots Quantum dots -- Optical properties Renewable energy sources
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/5994 , vital:29466
- Description: This study shows a detailed report on the morphological, structural and optical properties of CdSe QDs synthesised by the hot injection method. Cadmium acetate dihydrate and Se powder were used as cadmium and selenide precursors, respectively. Various QD sizes were achieved by synthesizing in temperature range of 150ºC, 175ºC, 200ºC, 225ºC, 250ºC, 275ºC and 300ºC, respectively. The as synthesized QDs by the hot injection method were cross-examined for their morphological, structural and optical using HRTEM, FTIR, XRD, RS, and UV-Vis spectroscopy techniques respectively. FTIR analysis has revealed vibrations at 738, 738, 738, 738, 735, 735 and 733 cm-1 for the QDs synthesized at various temperatures of 150, 175, 200, 225, 250, 275, and 300℃, respectively. The presence of the above mentioned peaks confirms the presence of Cd-Se bond in our samples. XRD analysis of CdSe QDs revealed diffraction peaks at 2 angles of 16.66 , 25.20 , 34.77 , 40.9 , 45.39 and 49.1 for 150 17.4 , 25.22 , 34.85 , 41.7 , 44.45 and 47.5 for the QDs synthesized at various temperatures of 175 17.07 , 25.19 , 34.85 , 41.34 , 44.41 and 48.86 for 200 ; 16.34 , 25.20 , 34.76 , 40.6 , 44.74 and 49.48 for 225 ; 17.44 , 25.17 , 34.19 , 41.7 , 44.45 , 49.24 for 250 ; 16.70 , 25.16 , 34.85 , 40.32 , 45.1 and 49.1 7 for 275 ;and 17.35 , 25.18 , 35.13 , 41.63 , 45.7 , 49.48 for 300 . These XRD peaks relate to crystal planes of (100), (002), (102), (220), (103) and (112) which belong to hexagonal Wurtzite CdSe crystal structure. Additionally XRD analysis has revealed a general peak shift to higher 2 values was observed for CdSe QDs. HRTEM analysis showed that the synthesised CdSe QDs have a spherical shape and are monodispersed. Moreover, HRTEM analysis has revealed CdSe QDs modal crystallite size of 1.79 nm, 1.81 nm, 2.06 nm, 2.08 nm, 2.11 nm, 3.10 nm and 3.12 nm for the QDs synthesized at various temperatures of 150ºC, 175ºC, 200ºC, 225ºC, 250ºC, 275ºC and 300ºC, respectively. HRTEM results were in mutual agreement with XRD results. Additionally, the SAED images showed intense electron diffraction rings, which confirmed that the as-synthesised CdSe QDs have a Wurtzite crystal structure. RS analysis showed that CdSe QDs have LO and 2LO vibrational modes which are characteristic peaks for CdSe. The presence of these peaks in Raman spectra further supports our previous observation from XRD analysis and HRTEM analysis that the synthesized CdSe QDs have a Wurtzite crystal structure. The effect of synthesis temperature Raman peak shift, FHWH and peak intensity has been cross examined in this work, Moreover, the effect of increasing temperature on the peak shift, FWHM and peak intensity is discussed in detail below. UV-Vis analysis revealed an absorbance of CdSe QDs in higher wavelengths as temperature was increased. Furthermore, the Yu et al 2003 relation was used to calculate QD size and band gap energy of CdSe QDs. The results showed that QD size increases with increasing synthesis temperature, which is in agreement with HRTEM and XRD results.
- Full Text:
- Date Issued: 2017
- Authors: Makinana, Sinovuyo
- Date: 2017
- Subjects: Quantum dots Quantum dots -- Optical properties Renewable energy sources
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/5994 , vital:29466
- Description: This study shows a detailed report on the morphological, structural and optical properties of CdSe QDs synthesised by the hot injection method. Cadmium acetate dihydrate and Se powder were used as cadmium and selenide precursors, respectively. Various QD sizes were achieved by synthesizing in temperature range of 150ºC, 175ºC, 200ºC, 225ºC, 250ºC, 275ºC and 300ºC, respectively. The as synthesized QDs by the hot injection method were cross-examined for their morphological, structural and optical using HRTEM, FTIR, XRD, RS, and UV-Vis spectroscopy techniques respectively. FTIR analysis has revealed vibrations at 738, 738, 738, 738, 735, 735 and 733 cm-1 for the QDs synthesized at various temperatures of 150, 175, 200, 225, 250, 275, and 300℃, respectively. The presence of the above mentioned peaks confirms the presence of Cd-Se bond in our samples. XRD analysis of CdSe QDs revealed diffraction peaks at 2 angles of 16.66 , 25.20 , 34.77 , 40.9 , 45.39 and 49.1 for 150 17.4 , 25.22 , 34.85 , 41.7 , 44.45 and 47.5 for the QDs synthesized at various temperatures of 175 17.07 , 25.19 , 34.85 , 41.34 , 44.41 and 48.86 for 200 ; 16.34 , 25.20 , 34.76 , 40.6 , 44.74 and 49.48 for 225 ; 17.44 , 25.17 , 34.19 , 41.7 , 44.45 , 49.24 for 250 ; 16.70 , 25.16 , 34.85 , 40.32 , 45.1 and 49.1 7 for 275 ;and 17.35 , 25.18 , 35.13 , 41.63 , 45.7 , 49.48 for 300 . These XRD peaks relate to crystal planes of (100), (002), (102), (220), (103) and (112) which belong to hexagonal Wurtzite CdSe crystal structure. Additionally XRD analysis has revealed a general peak shift to higher 2 values was observed for CdSe QDs. HRTEM analysis showed that the synthesised CdSe QDs have a spherical shape and are monodispersed. Moreover, HRTEM analysis has revealed CdSe QDs modal crystallite size of 1.79 nm, 1.81 nm, 2.06 nm, 2.08 nm, 2.11 nm, 3.10 nm and 3.12 nm for the QDs synthesized at various temperatures of 150ºC, 175ºC, 200ºC, 225ºC, 250ºC, 275ºC and 300ºC, respectively. HRTEM results were in mutual agreement with XRD results. Additionally, the SAED images showed intense electron diffraction rings, which confirmed that the as-synthesised CdSe QDs have a Wurtzite crystal structure. RS analysis showed that CdSe QDs have LO and 2LO vibrational modes which are characteristic peaks for CdSe. The presence of these peaks in Raman spectra further supports our previous observation from XRD analysis and HRTEM analysis that the synthesized CdSe QDs have a Wurtzite crystal structure. The effect of synthesis temperature Raman peak shift, FHWH and peak intensity has been cross examined in this work, Moreover, the effect of increasing temperature on the peak shift, FWHM and peak intensity is discussed in detail below. UV-Vis analysis revealed an absorbance of CdSe QDs in higher wavelengths as temperature was increased. Furthermore, the Yu et al 2003 relation was used to calculate QD size and band gap energy of CdSe QDs. The results showed that QD size increases with increasing synthesis temperature, which is in agreement with HRTEM and XRD results.
- Full Text:
- Date Issued: 2017
Synthesis and characterization of titanium dioxide nanotubes using electrochemical anodization technique for solar cell applications
- Authors: Lupiwana, Mpheleki
- Date: 2017
- Subjects: Titanium dioxide Nanostructured materials Nanotubes
- Language: English
- Type: Thesis , Masters , Chemistry
- Identifier: http://hdl.handle.net/10353/11795 , vital:39107
- Description: High demand on energy conversion in dye-sensitized solar solar cells (DSSCs), requires development of well-organized TiO2 nanotube (TNT) structures because of their large surface area-to-volume ratio, superior lifetime and provision of optimal pathways for electron percolation. In this work TiO2 nanotube membranes with an average length of 2.40 μm and average pore diameter of 41.08 nm have been fabricated using electrochemical anodisation employing an organic electrolyte consisting of 0.5wt.percent NH4F + 3 vol percent H2O + Glycerol at an applied voltage of 60 V for 12 hours. The fabricated TNTs were annealed at different annealing temperatures. Scanning Electron Microscopy (SEM) showed that anodisation at these conditions yields nanotubes with periodic rings which present the roughness of the walls. Surface SEM images have revealed the presence of porous structures on the fabricated TNT membranes. Also evident from SEM cross-sectional images are multi-layered TiO2 nanotubes with top and bottom layers. The effect of annealing temperature on the structural, morphological and topographical has been investigated for TNTs. Surface SEM morphological analyses have revealed that the surface morphology of the annealed TNTs membranes changes with an increase in annealing temperature from 350°C to 650°C. The surface SEM analysis has revealed that as the annealing temperature increases the fabricated nanotubes deforms and collapses at annealing temperatures above 550°C. The TNTs annealed at 350°C have a modal pore size of 34.56 nm which is somewhat smaller compared to the TNTs annealed at 650°C with a modal pore size of 31.05 nm. Atomic Force Microscopy (AFM) topographical measurements have confirmed the presence of porous structure on the surface of the as-annealed TNTs with a modal pore diameter decreasing with increasing in annealing temperature. SEM-EDS analysis have revealed the presence of Ti, O and C and no other additional impurities. The presence of Ti and O confirms the successful electro-anodization of titanium metal sheets to TNTs. C must be due to glycerol electrolyte that got absorbed onto the TNTs structured during electro anodization. Structure investigation through X-Ray Diffraction (XRD) analysis has revealed that as-anodised TNTs have peaks at 2Ɵ positions 35.62°, 39.02°, 40.76°, 53.55°, 63.49°, 71.14°, and 76.71° belonging to the amorphous phase of TiO2. Additionally XRD analysis has revealed that for the annealed samples in the temperature range from 350°C to 450°C have peaks at 24.66° (101), 27.11° (110) belonging Anatase and Rutile phase of TiO2 respectively. Confocal Raman Spectroscopy (CRM) image analysis through a large area scan, and Raman depth profiling have also been used to evaluate the phase changes in TNTs annealed at different temperatures. CRM large area scan and depth profiling has revealed the presence of Anatase phase of TiO2 with Raman vibration modes at 142.37 cm-1, 199.04 cm-1, 394.67 cm-1,516.16 cm-1 and 639.29 cm-1 and the presence of some Rutile phase of TiO2 peaks with Raman vibration modes at 445.26 cm-1 and 612.07 cm-1. These findings were correlated to the XRD analysis, SEM analysis as well as AFM. In XRD the transformation of Anatase to Rutile phase was observed as the annealing temperature increased, that was also supported by SEM analysis whereby nanotube structures collapsed and deformed as annealing temperature increased due to phase transformation. In AFM pore diameter decreased as annealing temperature increases, which was also due to the effect of phase transformation observed in XRD and CRM. These findings showed that TiO2 nanotube membranes were successfully fabricated, which may have wide applications in the development of electronic materials for the solar devices.
- Full Text:
- Date Issued: 2017
- Authors: Lupiwana, Mpheleki
- Date: 2017
- Subjects: Titanium dioxide Nanostructured materials Nanotubes
- Language: English
- Type: Thesis , Masters , Chemistry
- Identifier: http://hdl.handle.net/10353/11795 , vital:39107
- Description: High demand on energy conversion in dye-sensitized solar solar cells (DSSCs), requires development of well-organized TiO2 nanotube (TNT) structures because of their large surface area-to-volume ratio, superior lifetime and provision of optimal pathways for electron percolation. In this work TiO2 nanotube membranes with an average length of 2.40 μm and average pore diameter of 41.08 nm have been fabricated using electrochemical anodisation employing an organic electrolyte consisting of 0.5wt.percent NH4F + 3 vol percent H2O + Glycerol at an applied voltage of 60 V for 12 hours. The fabricated TNTs were annealed at different annealing temperatures. Scanning Electron Microscopy (SEM) showed that anodisation at these conditions yields nanotubes with periodic rings which present the roughness of the walls. Surface SEM images have revealed the presence of porous structures on the fabricated TNT membranes. Also evident from SEM cross-sectional images are multi-layered TiO2 nanotubes with top and bottom layers. The effect of annealing temperature on the structural, morphological and topographical has been investigated for TNTs. Surface SEM morphological analyses have revealed that the surface morphology of the annealed TNTs membranes changes with an increase in annealing temperature from 350°C to 650°C. The surface SEM analysis has revealed that as the annealing temperature increases the fabricated nanotubes deforms and collapses at annealing temperatures above 550°C. The TNTs annealed at 350°C have a modal pore size of 34.56 nm which is somewhat smaller compared to the TNTs annealed at 650°C with a modal pore size of 31.05 nm. Atomic Force Microscopy (AFM) topographical measurements have confirmed the presence of porous structure on the surface of the as-annealed TNTs with a modal pore diameter decreasing with increasing in annealing temperature. SEM-EDS analysis have revealed the presence of Ti, O and C and no other additional impurities. The presence of Ti and O confirms the successful electro-anodization of titanium metal sheets to TNTs. C must be due to glycerol electrolyte that got absorbed onto the TNTs structured during electro anodization. Structure investigation through X-Ray Diffraction (XRD) analysis has revealed that as-anodised TNTs have peaks at 2Ɵ positions 35.62°, 39.02°, 40.76°, 53.55°, 63.49°, 71.14°, and 76.71° belonging to the amorphous phase of TiO2. Additionally XRD analysis has revealed that for the annealed samples in the temperature range from 350°C to 450°C have peaks at 24.66° (101), 27.11° (110) belonging Anatase and Rutile phase of TiO2 respectively. Confocal Raman Spectroscopy (CRM) image analysis through a large area scan, and Raman depth profiling have also been used to evaluate the phase changes in TNTs annealed at different temperatures. CRM large area scan and depth profiling has revealed the presence of Anatase phase of TiO2 with Raman vibration modes at 142.37 cm-1, 199.04 cm-1, 394.67 cm-1,516.16 cm-1 and 639.29 cm-1 and the presence of some Rutile phase of TiO2 peaks with Raman vibration modes at 445.26 cm-1 and 612.07 cm-1. These findings were correlated to the XRD analysis, SEM analysis as well as AFM. In XRD the transformation of Anatase to Rutile phase was observed as the annealing temperature increased, that was also supported by SEM analysis whereby nanotube structures collapsed and deformed as annealing temperature increased due to phase transformation. In AFM pore diameter decreased as annealing temperature increases, which was also due to the effect of phase transformation observed in XRD and CRM. These findings showed that TiO2 nanotube membranes were successfully fabricated, which may have wide applications in the development of electronic materials for the solar devices.
- Full Text:
- Date Issued: 2017
Synthesis and evaluation of arylpyrrole-chalcone hybrids as antiplasmodial and antitrypanosomal agents
- Authors: Zulu, Ayanda Ignatia
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65268 , vital:28716
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2017
- Authors: Zulu, Ayanda Ignatia
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65268 , vital:28716
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2017
Synthesis and photophysical studies of crown ether-bodipy dyes and the fabrication of bodipy embedded fluorescent nanofibers
- Authors: Stone, Justin
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4953 , vital:20746
- Description: This study has three major objectives: 1) to synthesize a series of structurally related BODIPY dyes, 2) to fabricate BODIPY embedded electrospun nanofibers, and 3) to investigate and characterize the photophysical properties of all synthesized BODIPY dyes with a special focus on their ability to generate singlet oxygen. This thesis first explores the acid catalysed condensation reaction to produce two structurally analogous meso-substituted BODIPY dyes based on cuminaldehyde and 4-dimethylaminobenzaldehdye. In order to enhance the rate of ISC and promote the generation of reactive oxygen species bromine atoms were then attached to the BODIPY 2,6-positions. These BODIPY dyes were then embedded in a polystyrene solution and electrospun into nanofibers. The resulting nanofibers were found to be highly fluorescent, but were no longer able to generate singlet oxygen. Ion-sensitive BODIPYs were prepared from the dibrominated BODIPY dyes by employing a modified Knoevenagel condensation reaction to form a styryl bond with 4’-formylbenzo-15-crown-5 at the 3,5-position of the BODIPY core. Changes in the morphology and position of the absorption and emission spectra of these crown ether-styryl BODIPY dyes were observed in the presence of sodium ions. These results imply that crown ether-substituted BODIPY dyes could function as ion sensors.
- Full Text:
- Date Issued: 2017
- Authors: Stone, Justin
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4953 , vital:20746
- Description: This study has three major objectives: 1) to synthesize a series of structurally related BODIPY dyes, 2) to fabricate BODIPY embedded electrospun nanofibers, and 3) to investigate and characterize the photophysical properties of all synthesized BODIPY dyes with a special focus on their ability to generate singlet oxygen. This thesis first explores the acid catalysed condensation reaction to produce two structurally analogous meso-substituted BODIPY dyes based on cuminaldehyde and 4-dimethylaminobenzaldehdye. In order to enhance the rate of ISC and promote the generation of reactive oxygen species bromine atoms were then attached to the BODIPY 2,6-positions. These BODIPY dyes were then embedded in a polystyrene solution and electrospun into nanofibers. The resulting nanofibers were found to be highly fluorescent, but were no longer able to generate singlet oxygen. Ion-sensitive BODIPYs were prepared from the dibrominated BODIPY dyes by employing a modified Knoevenagel condensation reaction to form a styryl bond with 4’-formylbenzo-15-crown-5 at the 3,5-position of the BODIPY core. Changes in the morphology and position of the absorption and emission spectra of these crown ether-styryl BODIPY dyes were observed in the presence of sodium ions. These results imply that crown ether-substituted BODIPY dyes could function as ion sensors.
- Full Text:
- Date Issued: 2017
Synthesis and physicochemical evaluation of a series of boron dipyrromethene dye derivatives for potential utility in antimicrobial photodynamic therapy and nonlinear optics
- Authors: Kubheka, Gugu Patience
- Date: 2017
- Subjects: Dyes and dyeing -- Chemistry , Photochemotherapy , Cancer -- Photochemotherapy , Anti-infective agents , Nonlinear optics , BODIPY
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4776 , vital:20723
- Description: A series of new BODIPY dye derivatives have been synthesized and characterized using various characterization tools such as 1H-NMR, MALDI-TOF mass spectrometry, FT-IR, UV-visible spectrophotometry and elemental analysis. The aniline-substituted BODIPY derivative was further coordinated with gold nanorods and the characterization was achieved by transmission electron microscopy (TEM), X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS).In addition to this dye, quaternized BODIPY dyes were also synthesized and investigated for their potential utility as photosentitizers in antimicrobial photodynamic therapy (APDT).BODIPY dyes with pyrene substituted styryl groups were embedded in polymer thin film using poly(bisphenol A carbonate) (PBC) to study their optical limiting properties. The optical limiting values of these BODIPY dyes once embedded in thin films were found to be greatly improved and the limiting intensityof each film was well below the maximum threshold which is set to be 0.95 J.cm-². The physicochemical properties and NLO parameters of all of the synthesized dyes were investigated.
- Full Text:
- Date Issued: 2017
- Authors: Kubheka, Gugu Patience
- Date: 2017
- Subjects: Dyes and dyeing -- Chemistry , Photochemotherapy , Cancer -- Photochemotherapy , Anti-infective agents , Nonlinear optics , BODIPY
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4776 , vital:20723
- Description: A series of new BODIPY dye derivatives have been synthesized and characterized using various characterization tools such as 1H-NMR, MALDI-TOF mass spectrometry, FT-IR, UV-visible spectrophotometry and elemental analysis. The aniline-substituted BODIPY derivative was further coordinated with gold nanorods and the characterization was achieved by transmission electron microscopy (TEM), X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS).In addition to this dye, quaternized BODIPY dyes were also synthesized and investigated for their potential utility as photosentitizers in antimicrobial photodynamic therapy (APDT).BODIPY dyes with pyrene substituted styryl groups were embedded in polymer thin film using poly(bisphenol A carbonate) (PBC) to study their optical limiting properties. The optical limiting values of these BODIPY dyes once embedded in thin films were found to be greatly improved and the limiting intensityof each film was well below the maximum threshold which is set to be 0.95 J.cm-². The physicochemical properties and NLO parameters of all of the synthesized dyes were investigated.
- Full Text:
- Date Issued: 2017
Synthesis of L-menthyl glyoxylate, an important intermediate in the manufacture of ARVS, using flow chemistry technology
- Authors: Moyo, McQuillan
- Date: 2017
- Subjects: Chemistry , Pharmaceutical chemistry , Organic compounds -- Synthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/12019 , vital:27018
- Description: Herein an alternative approach to the conventional batch synthesis of L-menthyl glyoxylate hydrate (MGH), an important intermediate in the synthesis of drugs of importance is reported, through flow chemistry technology. MGH was initially synthesized in batch and various reaction parameters optimized. It was found to proceed to completion after 6 hours of esterifying glyoxylic acid with excess alcohol (L-menthol) in the presence of a catalyst, ideally amberlyst-15 (an ion exchange resin) at 105 °C giving a yield of 72 %. The batch reaction conditions were adopted in a continuous flow synthesis setup, using the Labtrix Start system, in which reaction conditions were optimized. The optimization of glyoxylic acid conversion (92 %) in the Labtrix Start system gave reaction conditions that resulted in low MGH selectivity (25 %) whereas the optimization for MGH selectivity (100 %) gave a conversion a poor glyoxylic acid conversion (15 %). The FlowSyn system fitted with a column reactor gave the best results, in which the optimum conditions were an excess of L-menthol (1.5 M, 6.0 equiv.), temperature (80 °C) and a residence time of 2.5 minutes with a high selectivity (77 %) and average conversion (50 %). The optimized reaction conditions for conversion and selectivity on the different flow systems did not vary significantly and similar trends were observed for the systems. It was shown that an increase in temperature, mole equivalents and residence time led to an increase in MGH conversion in all flow systems. The scale up of the esterification reaction from the Labtrix Start system (19 μL microreactor) to the FlowSyn system fitted with a 2 mL reactor chip, showed that the reaction proceeds with a slight drop in selectivity from 100 % to 92 % while conversion dropped from 15 to 12 %. On the contrary, a significant drop in conversion and selectivity were observed when the FlowSyn column reactor was up-scaled to the Elite-tubular furnace, owing to the poor mixing in the larger channel size reactor.
- Full Text:
- Date Issued: 2017
- Authors: Moyo, McQuillan
- Date: 2017
- Subjects: Chemistry , Pharmaceutical chemistry , Organic compounds -- Synthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/12019 , vital:27018
- Description: Herein an alternative approach to the conventional batch synthesis of L-menthyl glyoxylate hydrate (MGH), an important intermediate in the synthesis of drugs of importance is reported, through flow chemistry technology. MGH was initially synthesized in batch and various reaction parameters optimized. It was found to proceed to completion after 6 hours of esterifying glyoxylic acid with excess alcohol (L-menthol) in the presence of a catalyst, ideally amberlyst-15 (an ion exchange resin) at 105 °C giving a yield of 72 %. The batch reaction conditions were adopted in a continuous flow synthesis setup, using the Labtrix Start system, in which reaction conditions were optimized. The optimization of glyoxylic acid conversion (92 %) in the Labtrix Start system gave reaction conditions that resulted in low MGH selectivity (25 %) whereas the optimization for MGH selectivity (100 %) gave a conversion a poor glyoxylic acid conversion (15 %). The FlowSyn system fitted with a column reactor gave the best results, in which the optimum conditions were an excess of L-menthol (1.5 M, 6.0 equiv.), temperature (80 °C) and a residence time of 2.5 minutes with a high selectivity (77 %) and average conversion (50 %). The optimized reaction conditions for conversion and selectivity on the different flow systems did not vary significantly and similar trends were observed for the systems. It was shown that an increase in temperature, mole equivalents and residence time led to an increase in MGH conversion in all flow systems. The scale up of the esterification reaction from the Labtrix Start system (19 μL microreactor) to the FlowSyn system fitted with a 2 mL reactor chip, showed that the reaction proceeds with a slight drop in selectivity from 100 % to 92 % while conversion dropped from 15 to 12 %. On the contrary, a significant drop in conversion and selectivity were observed when the FlowSyn column reactor was up-scaled to the Elite-tubular furnace, owing to the poor mixing in the larger channel size reactor.
- Full Text:
- Date Issued: 2017
Synthesis of modified zinc oxide nanoparticles using pneumatic spray pyrolysis for solar cell application
- Authors: Ntozakhe, Luyolo
- Date: 2017
- Subjects: Zinc oxide -- Synthesis Nanoparticles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/5862 , vital:29408
- Description: In this work, the pneumatic spray pyrolysis was used to synthesize un-doped and carbon doped zinc oxide (ZnO) nanoparticles. The zinc acetate, tetrabutylammonium bromide and ethanol were used as starting materials for the desired ZnO nanoparticles and the prepared samples were annealed at 400 oC in the furnace. The as synthesized un-doped and carbon doped ZnO NPs were evaluated using X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive x-ray spectroscopy (EDX), High-resolution transmission electron microscopy (HRTEM), Raman spectroscopy (RS) and Ultraviolet-visible spectroscopy (UV-Vis). XRD analysis of the synthesized NPs revealed peaks at 31.90°, 34.50°, 36.34°, 47.73°, 56.88°, 63.04°, 68.20°, and 77.33° belonging to the hexagonal Wurtzite ZnO crystal structure. The incorporation of C species into ZnO lattice was cross examined by monitoring the peak positions of the (100), (002) and (001) planes. These three main peaks of C-ZnO NPs show a peak shift to higher 2θ values which indicates substitutional carbon doping in ZnO NPs. SEM analysis has revealed that the as synthesized NPs have spherical shape and the morphology of the NPs change as the concentration of carbon increases. The EDX spectra of both un-doped and doped ZnO nanoparticles have revealed prominent peaks at 0.51 keV, 1.01 keV, 1.49 keV, 8.87 keV and 9.86 keV. Peaks at, X-ray energies of 0.51 keV and 1.01 keV respectively represent the emissions from the K-shell of oxygen and L-shell of zinc. The L-shell emission at 1.01 keV is considered as convolution of Zn 2p3/2 and Zn 2p1/2 photoelectron energies. The occurrence of these peaks in the EDX endorses the existence of Zn and O atoms in the PSP prepared samples. HRTEM analysis has revealed NPs size modal range from 6.65-14.21 nm for the PSP synthesized samples which is in mutual agreement with the XRD data calculated values. More over the selected area diffraction images displaying the fact that only the diffraction planes of (101), (002) and (100) are responsible for the diffraction pattern belonging to Wurtzite ZnO. RS analysis has revealed that the un-doped ZnO and doped ZnO samples have characteristic Raman vibration modes at 325 cm-1, and 434 cm-1 belonging to Wurtzite ZnO structure. Moreover, the prominent peak at 434 cm-1 which is the characteristic peak of E2(2) (high) mode of the Wurtzite ZnO and the E2(2) (high) has been red shifted by 4 cm-1, as compared to that found in the bulk ZnO. Additionally, the effect of carbon doping through Raman spectroscopy peak shifts of the E2(2) (high) mode, A1(LO) mode and multi-phonon has also been considered and discussed in detail. UV-Vis diffuse reflectance spectroscopy has revealed a red shift of the absorption edge with increase in C doping. Finally, the effect of nano-crystallite size and gradual prominence of C into ZnO lattice due to increase in C doping concentration in the PSP prepared nanoparticles was meticulously elaborated through Raman Spectroscopy analysis.
- Full Text:
- Date Issued: 2017
- Authors: Ntozakhe, Luyolo
- Date: 2017
- Subjects: Zinc oxide -- Synthesis Nanoparticles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/5862 , vital:29408
- Description: In this work, the pneumatic spray pyrolysis was used to synthesize un-doped and carbon doped zinc oxide (ZnO) nanoparticles. The zinc acetate, tetrabutylammonium bromide and ethanol were used as starting materials for the desired ZnO nanoparticles and the prepared samples were annealed at 400 oC in the furnace. The as synthesized un-doped and carbon doped ZnO NPs were evaluated using X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive x-ray spectroscopy (EDX), High-resolution transmission electron microscopy (HRTEM), Raman spectroscopy (RS) and Ultraviolet-visible spectroscopy (UV-Vis). XRD analysis of the synthesized NPs revealed peaks at 31.90°, 34.50°, 36.34°, 47.73°, 56.88°, 63.04°, 68.20°, and 77.33° belonging to the hexagonal Wurtzite ZnO crystal structure. The incorporation of C species into ZnO lattice was cross examined by monitoring the peak positions of the (100), (002) and (001) planes. These three main peaks of C-ZnO NPs show a peak shift to higher 2θ values which indicates substitutional carbon doping in ZnO NPs. SEM analysis has revealed that the as synthesized NPs have spherical shape and the morphology of the NPs change as the concentration of carbon increases. The EDX spectra of both un-doped and doped ZnO nanoparticles have revealed prominent peaks at 0.51 keV, 1.01 keV, 1.49 keV, 8.87 keV and 9.86 keV. Peaks at, X-ray energies of 0.51 keV and 1.01 keV respectively represent the emissions from the K-shell of oxygen and L-shell of zinc. The L-shell emission at 1.01 keV is considered as convolution of Zn 2p3/2 and Zn 2p1/2 photoelectron energies. The occurrence of these peaks in the EDX endorses the existence of Zn and O atoms in the PSP prepared samples. HRTEM analysis has revealed NPs size modal range from 6.65-14.21 nm for the PSP synthesized samples which is in mutual agreement with the XRD data calculated values. More over the selected area diffraction images displaying the fact that only the diffraction planes of (101), (002) and (100) are responsible for the diffraction pattern belonging to Wurtzite ZnO. RS analysis has revealed that the un-doped ZnO and doped ZnO samples have characteristic Raman vibration modes at 325 cm-1, and 434 cm-1 belonging to Wurtzite ZnO structure. Moreover, the prominent peak at 434 cm-1 which is the characteristic peak of E2(2) (high) mode of the Wurtzite ZnO and the E2(2) (high) has been red shifted by 4 cm-1, as compared to that found in the bulk ZnO. Additionally, the effect of carbon doping through Raman spectroscopy peak shifts of the E2(2) (high) mode, A1(LO) mode and multi-phonon has also been considered and discussed in detail. UV-Vis diffuse reflectance spectroscopy has revealed a red shift of the absorption edge with increase in C doping. Finally, the effect of nano-crystallite size and gradual prominence of C into ZnO lattice due to increase in C doping concentration in the PSP prepared nanoparticles was meticulously elaborated through Raman Spectroscopy analysis.
- Full Text:
- Date Issued: 2017
Synthesis, characterisation and evaluation of novel ferrocene-thiazole derivatives as antiplasmodial agents
- Authors: Hakizimana, Emmanuel Victor
- Date: 2017
- Subjects: Plasmodium , Malaria -- Chemotherapy , Plasmodium falciparum , Plasmodium -- Inhibitors , Drug resistance in microorganisms , Thiaszoles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/5304 , vital:20807
- Description: Malaria is mosquito-transmitted disease which continues to pose threat to humanity, despite the efforts undertaken by the scientific community, government entities and international organizations. The major problem is that Plasmodium species have developed resistance against available drugs. In order to counter this problem, antimalarial drugs that are efficacious and with novel mode of action are of great necessity. Thiazole derivatives, in particular aminomethylthiazole analogues, have been shown to exhibit promising antimalarial activity against Plasmodium falciparum strains. Previous studies reported the hit compound MMV010539, which showed good antimalarial activity against both K1 (CQ and multidrug resistant strains) and NF54 (CQ sensitive strain). In this study, MMV010539 was deemed to be as an attractive compound to generate novel analogues by addition of ferrocenyl organometallic unit. The ferrocene based compounds have shown biological activity; and with ferroquine currently in clinical trials there has been increasing research into identifying new ferrocenyl-containing molecules as potential antimalarial agents. Herein, thiazole ferrocene based molecules 3.22a-e were synthesised in low to good yields. Their structural identities were confirmed using conventional spectroscopic techniques (¹H and ¹³C NMR, FT-IR spectroscopy and mass spectrometry). The cell cytotoxicity assay of all final compounds confirmed that all ferrocene-thiazole blends 3.22a-e were non-toxic against HeLa cell lines. However, the in vitro biological assay revealed that despite the absence of cell cytotoxicity these compounds poorly inhibited the growth of Plasmodium falciparum parasite. As the aim was to expand further the structure-activity relationship (SAR) of MMV010539, this study confirmed the previous findings that there is a limited structural modification that could be accommodated as indicated in Figure 3.3 (Panel C). Moreover, the combination of ferrocenyl moiety and various alkylamines resulted in compounds with poor antiplasmodial potency, further suggesting that the free amine (Panel A, Figure 3.3) is important for activity.
- Full Text:
- Date Issued: 2017
- Authors: Hakizimana, Emmanuel Victor
- Date: 2017
- Subjects: Plasmodium , Malaria -- Chemotherapy , Plasmodium falciparum , Plasmodium -- Inhibitors , Drug resistance in microorganisms , Thiaszoles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/5304 , vital:20807
- Description: Malaria is mosquito-transmitted disease which continues to pose threat to humanity, despite the efforts undertaken by the scientific community, government entities and international organizations. The major problem is that Plasmodium species have developed resistance against available drugs. In order to counter this problem, antimalarial drugs that are efficacious and with novel mode of action are of great necessity. Thiazole derivatives, in particular aminomethylthiazole analogues, have been shown to exhibit promising antimalarial activity against Plasmodium falciparum strains. Previous studies reported the hit compound MMV010539, which showed good antimalarial activity against both K1 (CQ and multidrug resistant strains) and NF54 (CQ sensitive strain). In this study, MMV010539 was deemed to be as an attractive compound to generate novel analogues by addition of ferrocenyl organometallic unit. The ferrocene based compounds have shown biological activity; and with ferroquine currently in clinical trials there has been increasing research into identifying new ferrocenyl-containing molecules as potential antimalarial agents. Herein, thiazole ferrocene based molecules 3.22a-e were synthesised in low to good yields. Their structural identities were confirmed using conventional spectroscopic techniques (¹H and ¹³C NMR, FT-IR spectroscopy and mass spectrometry). The cell cytotoxicity assay of all final compounds confirmed that all ferrocene-thiazole blends 3.22a-e were non-toxic against HeLa cell lines. However, the in vitro biological assay revealed that despite the absence of cell cytotoxicity these compounds poorly inhibited the growth of Plasmodium falciparum parasite. As the aim was to expand further the structure-activity relationship (SAR) of MMV010539, this study confirmed the previous findings that there is a limited structural modification that could be accommodated as indicated in Figure 3.3 (Panel C). Moreover, the combination of ferrocenyl moiety and various alkylamines resulted in compounds with poor antiplasmodial potency, further suggesting that the free amine (Panel A, Figure 3.3) is important for activity.
- Full Text:
- Date Issued: 2017
Synthesis, characterisation and evaluation of novel ferrocene-thiazole derivatives as antiplasmodial agents
- Authors: Hakizimana, Emmanuel Victor
- Date: 2017
- Subjects: Plasmodium , Malaria -- Chemotherapy , Plasmodium falciparum , Plasmodium -- Inhibitors , Drug resistance in microorganisms , Thiaszoles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/96068 , vital:31232
- Description: Malaria is mosquito-transmitted disease which continues to pose threat to humanity, despite the efforts undertaken by the scientific community, government entities and international organizations. The major problem is that Plasmodium species have developed resistance against available drugs. In order to counter this problem, antimalarial drugs that are efficacious and with novel mode of action are of great necessity. Thiazole derivatives, in particular aminomethylthiazole analogues, have been shown to exhibit promising antimalarial activity against Plasmodium falciparum strains. Previous studies reported the hit compound MMV010539, which showed good antimalarial activity against both K1 (CQ and multidrug resistant strains) and NF54 (CQ sensitive strain). In this study, MMV010539 was deemed to be as an attractive compound to generate novel analogues by addition of ferrocenyl organometallic unit. The ferrocene based compounds have shown biological activity; and with ferroquine currently in clinical trials there has been increasing research into identifying new ferrocenyl-containing molecules as potential antimalarial agents. Herein, thiazole ferrocene based molecules 3.22a-e were synthesised in low to good yields. Their structural identities were confirmed using conventional spectroscopic techniques (¹H and ¹³C NMR, FT-IR spectroscopy and mass spectrometry). The cell cytotoxicity assay of all final compounds confirmed that all ferrocene-thiazole blends 3.22a-e were non-toxic against HeLa cell lines. However, the in vitro biological assay revealed that despite the absence of cell cytotoxicity these compounds poorly inhibited the growth of Plasmodium falciparum parasite. As the aim was to expand further the structure-activity relationship (SAR) of MMV010539, this study confirmed the previous findings that there is a limited structural modification that could be accommodated as indicated in Figure 3.3 (Panel C). Moreover, the combination of ferrocenyl moiety and various alkylamines resulted in compounds with poor antiplasmodial potency, further suggesting that the free amine (Panel A, Figure 3.3) is important for activity.
- Full Text:
- Date Issued: 2017
- Authors: Hakizimana, Emmanuel Victor
- Date: 2017
- Subjects: Plasmodium , Malaria -- Chemotherapy , Plasmodium falciparum , Plasmodium -- Inhibitors , Drug resistance in microorganisms , Thiaszoles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/96068 , vital:31232
- Description: Malaria is mosquito-transmitted disease which continues to pose threat to humanity, despite the efforts undertaken by the scientific community, government entities and international organizations. The major problem is that Plasmodium species have developed resistance against available drugs. In order to counter this problem, antimalarial drugs that are efficacious and with novel mode of action are of great necessity. Thiazole derivatives, in particular aminomethylthiazole analogues, have been shown to exhibit promising antimalarial activity against Plasmodium falciparum strains. Previous studies reported the hit compound MMV010539, which showed good antimalarial activity against both K1 (CQ and multidrug resistant strains) and NF54 (CQ sensitive strain). In this study, MMV010539 was deemed to be as an attractive compound to generate novel analogues by addition of ferrocenyl organometallic unit. The ferrocene based compounds have shown biological activity; and with ferroquine currently in clinical trials there has been increasing research into identifying new ferrocenyl-containing molecules as potential antimalarial agents. Herein, thiazole ferrocene based molecules 3.22a-e were synthesised in low to good yields. Their structural identities were confirmed using conventional spectroscopic techniques (¹H and ¹³C NMR, FT-IR spectroscopy and mass spectrometry). The cell cytotoxicity assay of all final compounds confirmed that all ferrocene-thiazole blends 3.22a-e were non-toxic against HeLa cell lines. However, the in vitro biological assay revealed that despite the absence of cell cytotoxicity these compounds poorly inhibited the growth of Plasmodium falciparum parasite. As the aim was to expand further the structure-activity relationship (SAR) of MMV010539, this study confirmed the previous findings that there is a limited structural modification that could be accommodated as indicated in Figure 3.3 (Panel C). Moreover, the combination of ferrocenyl moiety and various alkylamines resulted in compounds with poor antiplasmodial potency, further suggesting that the free amine (Panel A, Figure 3.3) is important for activity.
- Full Text:
- Date Issued: 2017
Synthesis, crystal structures and molecular modelling of rare earth complexes with bis(2-pyridylmethyl)amine: aim topological analysis and ligand conformation search
- Authors: Matthews, Cameron
- Date: 2017
- Subjects: Rare earths , Ligands , Complex compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/8230 , vital:26229
- Description: Eight rare earth complexes with bis(2-pyridylmethyl)amine (DPA) were synthesised and recrystallised, under air-sensitive or low moisture conditions. The crystal structures were successfully determined, via SC-XRD, and the asymmetric units of five complexes (1, 3, 5, 6 and 7) were submitted for DFT molecular modelling calculations, which involved geometry optimisation and frequency calculations. The neutral complexes obtained were bis(bis(2-pyridylmethyl)amine)-trichloro-lanthanum(III) [LaCl3(DPA)2] (1), bis(bis(2-pyridylmethyl)amine)-trichloro-cerium(III)) [CeCl3(DPA)2] (2), bis(μ2-chloro)-diaqua-tetrachloro-bis(bis(2-pyridylmethyl)amine)-di-praseodymium(III) [PrCl2(μ-Cl)(DPA)(OH2)]2 (3) and bis(μ2-methoxo)-bis(bis(2-pyridylmethyl)amine)- tetrachloro-di-dysprosium(III) [DyCl2(μ-OCH3)(DPA)]2 (4). The cationic complexes obtained in this study were dichloro-bis(bis(2-pyridylmethyl)amine)- neodymium(III) chloride methanol solvate [NdCl2(DPA)2]Cl·CH3OH (5), dichloro-bis(bis(2- pyridylmethyl)amine)-dysprosium(III) chloride methanol solvate [DyCl2(DPA)2]Cl·CH3OH (6), dichloro-bis(bis(2-pyridylmethyl)amine)-yttrium(III) chloride methanol solvate [YCl2(DPA)2]Cl·CH3OH (7) and dichloro-bis(bis(2-pyridylmethyl)amine)-lutetium(III) chloride methanol solvate [LuCl2(DPA)2]Cl·CH3OH (8). The ‘Quantum theory of atoms in molecules’ approach was used to investigate the electron density topology, primarily in order to investigate the hydrogen and coordination bonds for three of the eight complexes. Two of the neutral complexes contain the ‘early’ rare earth elements lanthanum and praseodymium and one cationic complex contains the ‘late’ lanthanide element dysprosium. Noncovalent interaction analysis was also performed on the aforementioned complexes in order to gain a deeper understanding of the intra-molecular stereo-electronic interactions. Spin density analysis was used to investigate the distribution of unpaired electron density at and around the metal centres of the aforementioned paramagnetic Pr- and Dy-complexes. A ligand conformation search for DPA was undertaken and 32 low energy conformers were identified and their relative energies were determined using two DFT functionals, namely M06 and M06-2X.
- Full Text:
- Date Issued: 2017
- Authors: Matthews, Cameron
- Date: 2017
- Subjects: Rare earths , Ligands , Complex compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/8230 , vital:26229
- Description: Eight rare earth complexes with bis(2-pyridylmethyl)amine (DPA) were synthesised and recrystallised, under air-sensitive or low moisture conditions. The crystal structures were successfully determined, via SC-XRD, and the asymmetric units of five complexes (1, 3, 5, 6 and 7) were submitted for DFT molecular modelling calculations, which involved geometry optimisation and frequency calculations. The neutral complexes obtained were bis(bis(2-pyridylmethyl)amine)-trichloro-lanthanum(III) [LaCl3(DPA)2] (1), bis(bis(2-pyridylmethyl)amine)-trichloro-cerium(III)) [CeCl3(DPA)2] (2), bis(μ2-chloro)-diaqua-tetrachloro-bis(bis(2-pyridylmethyl)amine)-di-praseodymium(III) [PrCl2(μ-Cl)(DPA)(OH2)]2 (3) and bis(μ2-methoxo)-bis(bis(2-pyridylmethyl)amine)- tetrachloro-di-dysprosium(III) [DyCl2(μ-OCH3)(DPA)]2 (4). The cationic complexes obtained in this study were dichloro-bis(bis(2-pyridylmethyl)amine)- neodymium(III) chloride methanol solvate [NdCl2(DPA)2]Cl·CH3OH (5), dichloro-bis(bis(2- pyridylmethyl)amine)-dysprosium(III) chloride methanol solvate [DyCl2(DPA)2]Cl·CH3OH (6), dichloro-bis(bis(2-pyridylmethyl)amine)-yttrium(III) chloride methanol solvate [YCl2(DPA)2]Cl·CH3OH (7) and dichloro-bis(bis(2-pyridylmethyl)amine)-lutetium(III) chloride methanol solvate [LuCl2(DPA)2]Cl·CH3OH (8). The ‘Quantum theory of atoms in molecules’ approach was used to investigate the electron density topology, primarily in order to investigate the hydrogen and coordination bonds for three of the eight complexes. Two of the neutral complexes contain the ‘early’ rare earth elements lanthanum and praseodymium and one cationic complex contains the ‘late’ lanthanide element dysprosium. Noncovalent interaction analysis was also performed on the aforementioned complexes in order to gain a deeper understanding of the intra-molecular stereo-electronic interactions. Spin density analysis was used to investigate the distribution of unpaired electron density at and around the metal centres of the aforementioned paramagnetic Pr- and Dy-complexes. A ligand conformation search for DPA was undertaken and 32 low energy conformers were identified and their relative energies were determined using two DFT functionals, namely M06 and M06-2X.
- Full Text:
- Date Issued: 2017