Functionalized Ru(II) polypyridines and phthalocyanines: Potential dyes for dye-sensitized solar cells(DSSCs)
- Authors: Adeloye, Adewale Olufunsho https://orcid.org/0000-0003-1736-5738
- Date: 2011-01
- Subjects: Phthalocyanines , Dye-sensitized solar cells
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/24365 , vital:62645
- Description: This study describes the design, synthesis, characterization and preliminary investigation of the solar-to-electrical energy conversion efficiency of ruthenium(II) functionalized polypyridine and phthalocyanine complexes with extended π-conjugation. Polypyridinyl functionalized with anthracene, 2,3-dimethylacrylic acid and 1-methoxy-1-buten-3-yne were synthesized and characterized by infrared, UV-Vis, photoluminescence, 1H and 13C NMR and elemental analysis. The functionalized polypyridine molecules were used to synthesize various ruthenium(II) homoleptic/heteroleptic and/or heteronuclear complexes and their photophysical and electrochemical properties evaluated. The preliminary results of the solar-to-electrical conversion efficiencies of some synthesized Ru(II) polypyridyl complexes were presented in chapter 5. It was found out as expected that the ruthenium(II) polypyridine complexes containing either heteronuclear polypyridine ligands or their thiocyanate analogues of the types [Ru(L1)2L2(PF6)2], [RuL1(L2)2(PF6)2] and [RuL1L2(NCS)2], showed better photophysical properties (red-shifted metal-to-ligand charge-transfer (MLCT) transitions concomitant with enhanced molar extinction coefficients), luminescence and interesting electrochemical redox properties than those containing homonuclear ligand types [Ru(L1)3(PF6)2]. The ruthenium(II) anthracenyl functionalized phthalocyanine complexes which were obtained by electrophilic aromatic substitution reactions in the peripheral positions gave good solubility properties in various organic solvents and also showed interesting near infrared absorption and electroredox characteristics. Cyclic and square wave voltammetries of these complexes revealed major redox processes and the numbers of electron(s) transfer were determined by chronocoulometry. It was established that a mono- and/or multi-electronic transfer reactions can occur in the various ruthenium(II) complexes. The photophysical properties of some complexes showed them to be better and promising candidates in the design of chemosensors, organic light emitting diodes (OLEDs) and as photosensitizers, while their redox-active natures make them potential mediators in electron-transfer for various photochemical processes. However, due to low surface concentration and/or adsorption of some tested complexes on TiO2 semiconductor nanocrystalline particle, low currents were generated and the highest solar-to- electrical conversion efficiency recorded in this study was 0.10 percent. , Thesis (PhD) -- Faculty of Science and Agriculture, 2011
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Functionalized Ru(II) polypyridines and phthalocyanines: Potential dyes for dye-sensitized solar cells(DSSCs)
- Authors: Adeloye, Adewale Olufunsho https://orcid.org/0000-0003-1736-5738
- Date: 2011-01
- Subjects: Phthalocyanines , Dye-sensitized solar cells
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/24343 , vital:62638
- Description: This study describes the design, synthesis, characterization and preliminary investigation of the solar-to-electrical energy conversion efficiency of ruthenium(II) functionalized polypyridine and phthalocyanine complexes with extended π-conjugation. Polypyridinyl functionalized with anthracene, 2,3-dimethylacrylic acid and 1-methoxy-1-buten-3-yne were synthesized and characterized by infrared, UV-Vis, photoluminescence, 1H and 13C NMR and elemental analysis. The functionalized polypyridine molecules were used to synthesize various ruthenium(II) homoleptic/heteroleptic and/or heteronuclear complexes and their photophysical and electrochemical properties evaluated. The preliminary results of the solar-to-electrical conversion efficiencies of some synthesized Ru(II) polypyridyl complexes were presented in chapter 5. It was found out as expected that the ruthenium(II) polypyridine complexes containing either heteronuclear polypyridine ligands or their thiocyanate analogues of the types [Ru(L1)2L2(PF6)2], [RuL1(L2)2(PF6)2] and [RuL1L2(NCS)2], showed better photophysical properties (red-shifted metal-to-ligand charge-transfer (MLCT) transitions concomitant with enhanced molar extinction coefficients), luminescence and interesting electrochemical redox properties than those containing homonuclear ligand types [Ru(L1)3(PF6)2]. The ruthenium(II) anthracenyl functionalized phthalocyanine complexes which were obtained by electrophilic aromatic substitution reactions in the peripheral positions gave good solubility properties in various organic solvents and also showed interesting near infrared absorption and electroredox characteristics. Cyclic and square wave voltammetries of these complexes revealed major redox processes and the numbers of electron(s) transfer were determined by chronocoulometry. It was established that a mono- and/or multi-electronic transfer reactions can occur in the various ruthenium(II) complexes. The photophysical properties of some complexes showed them to be better and promising candidates in the design of chemosensors, organic light emitting diodes (OLEDs) and as photosensitizers, while their redox-active natures make them potential mediators in electron-transfer for various photochemical processes. However, due to low surface concentration and/or adsorption of some tested complexes on TiO2 semiconductor nanocrystalline particle, low currents were generated and the highest solar-to-electrical conversion efficiency recorded in this study was 0.10 percent. , Thesis (PhD) -- Faculty of Science and Agriculture, 2011
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The role of the Department of Education in addressing the education of children living and working in the street in the Eastern Cape:
- Authors: Mawisa, Nompumelelo Mavis
- Date: 2011-01
- Subjects: Street children , Social Conditions , Education
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/23337 , vital:57354
- Description: A UNICEF report on the drastic effects of child labour in developing countries indicates there are 4040 million children under the age of 18 not attending school (1977). Many are street and working children who deserve the chance, but face parental neglect and poverty to attend school and become conscious and productive citizens. Non-formal education has been identified as an alternative to traditional schooling, in which children learn vocational trades or academic subjects, aimed at enhancing their lives. This alternative approach is considered non-formal education because it is typically short–term and non – degree granting. Though non-formal education can be used for rehabilitation purposes, it cannot replace ultimate schooling. All children want to graduate and compete in the job market. The main aim of this study is to determine the role of the Department of Education in addressing the education of children working and living in the street in the Eastern Cape. The children working and living in the street phenomenon is a major development problem that is experienced all over the developing world. A major cause of this problem in the Eastern Cape is drop–outs due to parental negligence and poverty. To assist children working and living in the street and those in conflict with the law, child and youth care centres in East London, King William’s Town and Queenstown have been established. However, they have not had a very noticeable impact on the magnitude of the problem. Potential for such an impact seems to lie in the domain of collaboration with other non-governmental organisations, other departments and education providers. This study evaluated the quality of education of child and youth care centres and non-formal education programmes in providing education to children working and living in the street, with a view to highlighting the difference that formal education in mainstream schools has, in relation to these centres. The descriptive survey design was used in this study. The sample comprised ten children working and living in the street three child and youth care centres in East London, King William’s Town and Queenstown, ten children working and living in the street in East London, three managers from these centres, and two managers from the Department of Education and the Department of Social Development. The study employed the purposive sampling technique. Data to answer the research questions were collected mainly through questionnaires and interviews. The following conclusions were drawn from this study regarding empowering of children who are working and living in the street: (1) children were acutely cognisant of their impoverished positions in society but were unable to alleviate their economic burdens due to poverty. (2) The lack of teacher training strongly impacted on the children’s self concept to achieve empowerment (3) Non-formal education programmes should be used temporary whilst children working and living in the street are being rehabilitated. Thereafter children should join mainstream schools where they can obtain certificates on completion of their studies. The age factor should be considered when administering non-formal education. (4) Parents were the most important stakeholders in facilitating the enrolment of children in schools and monitoring their attendance. (5) Collaboration of all relevant stakeholders in the education of children working and living in the street is key to their education. , Thesis (PHD) -- Faculty of Social Sciences and Humanities, 2011
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ZIMBABWE’S LIBERATION STRUGGLE: A CRITICAL DECADE OF THE ZIMBABWE AFRICAN NATIONAL UNION (ZANU)’S GUERRILLA WAR, 1970-1980
- Authors: Dzimbanhete, Jephias Andrew (https://orcid.org/0000-0002-7648-8722)
- Date: 2011-01
- Subjects: National Liberation Movements -- Zimbabwe , Guerillas , Zimbabwe -- History -- Chimurenga
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/23315 , vital:57048
- Description: This study offers a comprehensive examination of the Zimbabwean war of independence depicting the mobilisation of forces of liberation against an intransigent colonial Rhodesian settler state during a critical decade of the 1970s. Its introductory outline presents a broad historical context to the decolonisation processes in Africa. It also introduces the two liberation movements that drove the war of independence, and these revolved around the Zimbabwe African People’s Union (ZAPU) and the Zimbabwe African National Union (ZANU). The empirical chapters of the thesis narrow the focus to the main research subject, that explain the ZANU’s guerrilla warfare and how that was launched under the military wing of the Zimbabwe African National Liberation Army (ZANLA). The study looks, particularly on how and why that formation assembled groundswell support and generated pervasive intelligence to operate relentlessly against the Rhodesian colonial government resulting in a compromised independence in 1980. In addition to a wide-ranging survey of literature that deals with the Zimbabwean war of independence, the production of this thesis is thoroughly grounded on empirical methods that hinge on archival research and oral testimonies. The study breaks new ground in outlining the various facets and different phases of the Zimbabwean liberation war. It reveals that the liberation fighters were not merely provided with arms and deployed to fight the Rhodesian army. Rather they underwent a methodical process, which comprised recruitment, extensive training and fundamental political education. This re-represents an alternative narrative or even eccentric paradigm to that persistently presented within the conventional Zimbabwean liberation war historiography. The thesis breaks further new ground in discussing the complex nature of how intelligence gathering and propaganda uses were also centrally linked to the cooperation of or assistance from the various segments of the colonial African society. Its empirical chapters outline the various actions undertaken by the various groups and individuals, the language they adopted in expressing themselves and the convivial connections between them and the guerrilla fighters in the countryside as the war front expanded within the home boundaries. Chapters also explore in greater detail how the liberation movement bred the complex relation and contestation between the political formation of ZANU and its military wing, ZANLA. The uneven power relations between these two formations somehow dictated the course and the outcome of the liberation war. As a result a constitutional settlement or military victory became the two options by which the Rhodesian question could be resolved in the later 1970s. As it turned out, attempts to seek a constitutional solution became a feature of diplomatic dimensions of the postcolonial Rhodesian political landscape. The study concludes with the latter point. , Thesis (PHD) -- Faculty of Social Sciences and Humanities, 2011
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