Numerical quadrature of oscillatory and non-oscillatory integrals
- Dukuza, Kenneth Njengele https://orcid.org/0000-0002-4525-7390
- Authors: Dukuza, Kenneth Njengele https://orcid.org/0000-0002-4525-7390
- Date: 2009
- Subjects: Oscillations , Numerical integration , Numerical analysis
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24304 , vital:62600
- Description: In this dissertation we develop efficient new methods and techniques to numerically evaluate integrals of both oscillatory and non oscillatory kind. We have done a comprehensive literature review on the existing methods and made some modifications to them so as to cope with difficulties such as oscillations and strong singularities. In the numerical algorithms we have used mainly the MATLAB source code. Our results have been compared with well known methods by renowned authors in this field. , Thesis (MSc) -- Faculty of Science and Agriculture, 2009
- Full Text:
- Date Issued: 2009
- Authors: Dukuza, Kenneth Njengele https://orcid.org/0000-0002-4525-7390
- Date: 2009
- Subjects: Oscillations , Numerical integration , Numerical analysis
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24304 , vital:62600
- Description: In this dissertation we develop efficient new methods and techniques to numerically evaluate integrals of both oscillatory and non oscillatory kind. We have done a comprehensive literature review on the existing methods and made some modifications to them so as to cope with difficulties such as oscillations and strong singularities. In the numerical algorithms we have used mainly the MATLAB source code. Our results have been compared with well known methods by renowned authors in this field. , Thesis (MSc) -- Faculty of Science and Agriculture, 2009
- Full Text:
- Date Issued: 2009
On Moving House
- Authors: Krueger, Anton
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229785 , vital:49710 , xlink:href="https://hdl.handle.net/10520/EJC47812"
- Full Text:
- Date Issued: 2009
- Authors: Krueger, Anton
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229785 , vital:49710 , xlink:href="https://hdl.handle.net/10520/EJC47812"
- Full Text:
- Date Issued: 2009
Opposing responses elicited by positively charged phthalocyanines in the presence of CdTe quantum dots
- Moeno, Sharon, Nyokong, Tebello
- Authors: Moeno, Sharon , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264506 , vital:53740 , xlink:href="https://doi.org/10.1016/j.jphotochem.2008.10.027"
- Description: Tetrapositively charged phthalocyanines and CdTe quantum dots (QDs) capped with thioglycolic acid (TGA) and mercaptopropionic acid (MPA) were synthesized. The response of the tetrapositively charged zinc phthalocyanines in the presence of quantum dots was studied. Aggregation and charge transfer were observed for [tetramethyl-2,(3)-[tetra-(2-mercaptopyridinephthalocyaninato)]zinc(II)]4+ (TmTMPyZnPc), however aggregation proved to be the more prominent process of the two. Fluorescence resonance energy transfer (FRET) was observed with [tetramethyl-2,(3)-[tetra-(2- pyridyloxyphthalocyaninato)]zinc(II)]4+ (TmTPyZnPc). In the FRET study the efficiency of FRET with TmTPyZnPc was determined to be 21% for both MPA and TGA capped CdTe QDs. For the charge transfer study the fluorescence of the quantum dots was quenched by the TmTMPyZnPc used, and from these quenching studies the quenching constants, binding constants and number of binding sites on the quantum dots were determined.
- Full Text:
- Date Issued: 2009
- Authors: Moeno, Sharon , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264506 , vital:53740 , xlink:href="https://doi.org/10.1016/j.jphotochem.2008.10.027"
- Description: Tetrapositively charged phthalocyanines and CdTe quantum dots (QDs) capped with thioglycolic acid (TGA) and mercaptopropionic acid (MPA) were synthesized. The response of the tetrapositively charged zinc phthalocyanines in the presence of quantum dots was studied. Aggregation and charge transfer were observed for [tetramethyl-2,(3)-[tetra-(2-mercaptopyridinephthalocyaninato)]zinc(II)]4+ (TmTMPyZnPc), however aggregation proved to be the more prominent process of the two. Fluorescence resonance energy transfer (FRET) was observed with [tetramethyl-2,(3)-[tetra-(2- pyridyloxyphthalocyaninato)]zinc(II)]4+ (TmTPyZnPc). In the FRET study the efficiency of FRET with TmTPyZnPc was determined to be 21% for both MPA and TGA capped CdTe QDs. For the charge transfer study the fluorescence of the quantum dots was quenched by the TmTMPyZnPc used, and from these quenching studies the quenching constants, binding constants and number of binding sites on the quantum dots were determined.
- Full Text:
- Date Issued: 2009
Paper recycling patterns and potential interventions in the education sector: A case study of paper streams at Rhodes University, South Africa
- Amutenya, N, Shackleton, Charlie M, Whittington-Jones, Kevin J
- Authors: Amutenya, N , Shackleton, Charlie M , Whittington-Jones, Kevin J
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181180 , vital:43705 , xlink:href="https://doi.org/10.1016/j.resconrec.2008.12.001"
- Description: This paper considers the use of paper by academics and student computer laboratories at Rhodes University as a basis for identifying areas to reduce the amounts used and increase rates of recycling. A sample of 50 academic staff monitored the volume and purpose of the paper they used over 5 months, and the procurement officers in all the academic departments were interviewed regarding the total amount of paper used per academic department. Mean use was 34 ± 20 new sheets of paper per working day, of which 3% were trashed, 15% were kept for later use (as scrap or printed on the opposite side) and 79% were given out as notes to students, filed as records or posted out as mail to other departments or institutions. There was a significant relationship between number of students served by a department and the overall demand for paper, as well the number of staff per department and the number of recycling bins. The university could save approximately US$ 7000 per year for every 10% reduction in current use of paper (12,784 reams/year). Reduction in paper usage could be achieved through an increase in re-use of paper, printing handouts for students on both sides of each sheet of paper and by investing in printers that are capable of printing on both sides of a sheet of paper. Double-sided printers are only 20–25% more expensive than single-sided ones, but will potentially reduce paper usage by half. A 40% reduction would save the university approximately US $ 20,000 per year in direct costs, and more in reduced waste streams, as well as help promote the environmental image of the university. On a per unit basis, the higher costs for a double-sided printer in offices would be repaid in 9 months or less through reduced paper use.
- Full Text:
- Date Issued: 2009
- Authors: Amutenya, N , Shackleton, Charlie M , Whittington-Jones, Kevin J
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181180 , vital:43705 , xlink:href="https://doi.org/10.1016/j.resconrec.2008.12.001"
- Description: This paper considers the use of paper by academics and student computer laboratories at Rhodes University as a basis for identifying areas to reduce the amounts used and increase rates of recycling. A sample of 50 academic staff monitored the volume and purpose of the paper they used over 5 months, and the procurement officers in all the academic departments were interviewed regarding the total amount of paper used per academic department. Mean use was 34 ± 20 new sheets of paper per working day, of which 3% were trashed, 15% were kept for later use (as scrap or printed on the opposite side) and 79% were given out as notes to students, filed as records or posted out as mail to other departments or institutions. There was a significant relationship between number of students served by a department and the overall demand for paper, as well the number of staff per department and the number of recycling bins. The university could save approximately US$ 7000 per year for every 10% reduction in current use of paper (12,784 reams/year). Reduction in paper usage could be achieved through an increase in re-use of paper, printing handouts for students on both sides of each sheet of paper and by investing in printers that are capable of printing on both sides of a sheet of paper. Double-sided printers are only 20–25% more expensive than single-sided ones, but will potentially reduce paper usage by half. A 40% reduction would save the university approximately US $ 20,000 per year in direct costs, and more in reduced waste streams, as well as help promote the environmental image of the university. On a per unit basis, the higher costs for a double-sided printer in offices would be repaid in 9 months or less through reduced paper use.
- Full Text:
- Date Issued: 2009
Photophysical, photochemical and electrochemical properties of water soluble silicon, titanium and zinc phthalocyanines
- Masilela, Nkosiphile, Idowu, Mopelola A I, Nyokong, Tebello
- Authors: Masilela, Nkosiphile , Idowu, Mopelola A I , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264496 , vital:53739 , xlink:href="https://doi.org/10.1016/j.jphotochem.2008.10.009"
- Description: The photophysical, and photochemical properties of titanium, silicon and zinc octacarboxy phthalocyanine (OTiOCPc, (OH)2SiOCPc and ZnOCPc) and their tetrasulfonated counterparts (OTiTSPc, (OH)2SiTSPc and ZnTSPc) in phosphate-buffer solution (PBS), pH 10 were studied. The tetrasulfonated derivatives were also studied in the presence of a surfactant, cremophore EL (CEL) due to their high aggregation tendency in aqueous solutions. Triplet quantum yields ranged from 0.20 to 0.48 for MOCPcs and 0.32–0.65 for MTSPcs in the presence of CEL and in pH 10. High triplet lifetimes were observed for ZnTSPc (270 μs, in the presence of CEL) or ZnOCPc (130 μs) compared to values ranging from 50 to 70 μs for the rest of the complexes.
- Full Text:
- Date Issued: 2009
- Authors: Masilela, Nkosiphile , Idowu, Mopelola A I , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264496 , vital:53739 , xlink:href="https://doi.org/10.1016/j.jphotochem.2008.10.009"
- Description: The photophysical, and photochemical properties of titanium, silicon and zinc octacarboxy phthalocyanine (OTiOCPc, (OH)2SiOCPc and ZnOCPc) and their tetrasulfonated counterparts (OTiTSPc, (OH)2SiTSPc and ZnTSPc) in phosphate-buffer solution (PBS), pH 10 were studied. The tetrasulfonated derivatives were also studied in the presence of a surfactant, cremophore EL (CEL) due to their high aggregation tendency in aqueous solutions. Triplet quantum yields ranged from 0.20 to 0.48 for MOCPcs and 0.32–0.65 for MTSPcs in the presence of CEL and in pH 10. High triplet lifetimes were observed for ZnTSPc (270 μs, in the presence of CEL) or ZnOCPc (130 μs) compared to values ranging from 50 to 70 μs for the rest of the complexes.
- Full Text:
- Date Issued: 2009
Photophysicochemical and fluorescence quenching studies of tetra-and octa-carboxy substituted silicon and germanium phthalocyanines
- Idowu, Mopelola A I, Nyokong, Tebello
- Authors: Idowu, Mopelola A I , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263500 , vital:53633 , xlink:href="https://doi.org/10.1016/j.jphotochem.2009.02.002"
- Description: Spectral, photophysical and photochemical properties of tetra- and octa-carboxy substituted metallophthalocyanines containing silicon and germanium as central metals ((OH)2GeTCPc, (OH)2SiTCPc, (OH)2GeOCPc and (OH)2SiOCPc) have been studied in dimethylsulfoxide (DMSO) and the trends in triplet, fluorescence, singlet oxygen quantum yields and triplet lifetimes are described for these compounds. The GePc derivatives exhibited high triplet quantum yields (ΦT = 0.79 for (OH)2GeOCPc and 0.82 for (OH)2GeTCPc compared to ΦT = 0.66 for (OH)2SiTCPc and 0.48 for (OH)2SiOCPc) due to the spin–orbit coupling induced by Ge(IV). The triplet lifetimes were higher for MOCPc (τT = 760 μs for (OH)2SiOCPc and 480 μs for (OH)2GeOCPc compared to τT = 210 μs for (OH)2SiTCPc and 260 μs for (OH)2GeTCPc). The fluorescent states of the metallophthalocyanine (MPc) complexes were effectively quenched by benzoquinone (BQ) and the quenching course was found to follow a diffusion-controlled (dynamic) bimolecular mechanism. Theoretical values of bimolecular rate constant for the interaction of the complexes with BQ were determined using the Stokes–Einstein–Smoluchowski model, and values together with the Stern–Volmer quenching constants were used in calculating the fluorescence lifetimes of the complexes.
- Full Text:
- Date Issued: 2009
- Authors: Idowu, Mopelola A I , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263500 , vital:53633 , xlink:href="https://doi.org/10.1016/j.jphotochem.2009.02.002"
- Description: Spectral, photophysical and photochemical properties of tetra- and octa-carboxy substituted metallophthalocyanines containing silicon and germanium as central metals ((OH)2GeTCPc, (OH)2SiTCPc, (OH)2GeOCPc and (OH)2SiOCPc) have been studied in dimethylsulfoxide (DMSO) and the trends in triplet, fluorescence, singlet oxygen quantum yields and triplet lifetimes are described for these compounds. The GePc derivatives exhibited high triplet quantum yields (ΦT = 0.79 for (OH)2GeOCPc and 0.82 for (OH)2GeTCPc compared to ΦT = 0.66 for (OH)2SiTCPc and 0.48 for (OH)2SiOCPc) due to the spin–orbit coupling induced by Ge(IV). The triplet lifetimes were higher for MOCPc (τT = 760 μs for (OH)2SiOCPc and 480 μs for (OH)2GeOCPc compared to τT = 210 μs for (OH)2SiTCPc and 260 μs for (OH)2GeTCPc). The fluorescent states of the metallophthalocyanine (MPc) complexes were effectively quenched by benzoquinone (BQ) and the quenching course was found to follow a diffusion-controlled (dynamic) bimolecular mechanism. Theoretical values of bimolecular rate constant for the interaction of the complexes with BQ were determined using the Stokes–Einstein–Smoluchowski model, and values together with the Stern–Volmer quenching constants were used in calculating the fluorescence lifetimes of the complexes.
- Full Text:
- Date Issued: 2009
Plankton trophodynamics at the subtropical convergence, Southern Ocean
- Richoux, Nicole B, Froneman, P William
- Authors: Richoux, Nicole B , Froneman, P William
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457967 , vital:75704 , xlink:href="https://doi.org/10.1093/plankt/fbp054"
- Description: Stable isotope signatures (δ13C, δ15N) in zooplankton tissues and particulate organic matter (POM) were determined to assess regional differences in the trophodynamics of zooplankton communities between 38 and 43°S, where the cool nutrient-rich subantarctic waters of the Southern Ocean meet the warm nutrient-poor subtropical waters of the southwest Indian Ocean at the subtropical convergence (STC). Significantly enriched values of δ15N were noted in populations of all major zooplankton groups inhabiting the warm and saline water mass north of the STC (maximum surface temperature 21°C), including the euphausiids, salps, amphipods, copepods, ostracods, pyrosomes, pteropods and chaetognaths, compared with those in the cool, less saline southern water mass (minimum surface temperature 11°C). Similar patterns of δ15N in POM collected throughout the region suggest that the large changes in zooplankton δ15N values across the frontal region are driven by variations in the phytoplankton communities. The differing trophodynamics in communities north and south of the STC provide compelling evidence of distinct bottom-up effects on planktonic food webs which have important implications in the determination of trophic positions and motility of plankton and higher consumers using δ15N signatures. Although expected, similar latitudinal variations in δ13C signatures were not found.
- Full Text:
- Date Issued: 2009
- Authors: Richoux, Nicole B , Froneman, P William
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457967 , vital:75704 , xlink:href="https://doi.org/10.1093/plankt/fbp054"
- Description: Stable isotope signatures (δ13C, δ15N) in zooplankton tissues and particulate organic matter (POM) were determined to assess regional differences in the trophodynamics of zooplankton communities between 38 and 43°S, where the cool nutrient-rich subantarctic waters of the Southern Ocean meet the warm nutrient-poor subtropical waters of the southwest Indian Ocean at the subtropical convergence (STC). Significantly enriched values of δ15N were noted in populations of all major zooplankton groups inhabiting the warm and saline water mass north of the STC (maximum surface temperature 21°C), including the euphausiids, salps, amphipods, copepods, ostracods, pyrosomes, pteropods and chaetognaths, compared with those in the cool, less saline southern water mass (minimum surface temperature 11°C). Similar patterns of δ15N in POM collected throughout the region suggest that the large changes in zooplankton δ15N values across the frontal region are driven by variations in the phytoplankton communities. The differing trophodynamics in communities north and south of the STC provide compelling evidence of distinct bottom-up effects on planktonic food webs which have important implications in the determination of trophic positions and motility of plankton and higher consumers using δ15N signatures. Although expected, similar latitudinal variations in δ13C signatures were not found.
- Full Text:
- Date Issued: 2009
Sigtuna think piece 6: A case of exploring learning interactions in rural farming communities of practice in Manicaland, Zimbabwe
- Authors: Pesanayi, Tichaona V
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386427 , vital:68140 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122802"
- Description: Food insecurity is one of the major threats to sustainable development in Africa, and particularly southern Africa. Climate change is increasingly having negative impacts on food production, further increasing the vulnerability of resource-poor communities. This paper outlines a research study conducted in two Zimbabwean smallholder communities of practice, with the aim of understanding learning interactions taking place within the community of practice that influence its choice of cultivated food plants. This would hopefully inform capability-centred teaching and learning. The study was conducted in the context of vulnerability to environment risk, socio-political pressures and a market-oriented agro-based economy in recession. Various causal mechanisms influencing plant-food choice were identified using critical realist ontological analysis. These included mixed messages from external influences in conflict with local knowledge due to power knowledge relationships. A number of learning interactions were found to be important in promoting the adaptive capacity of the farmers to chronic drought, which included inter-generational knowledge sharing; farmer to farmer exchange and reflective dialogue; experiential learning; farmers ‘passing on’ part of their harvests to other farmers; farming communities learning from risk and responding to risk; and learning from trying things out. The implications for capability-centred social learning processes were that it is important to understand the causal mechanisms that influence choices; and to confront tensions, while reducing ambivalence. A focus on more sustainable alternatives, feasible and practical for farmers, was recommended. These findings, in the context of one case study, create research questions to be examined in other case contexts in environmental education research focusing on climate change learning and adaptation.
- Full Text:
- Date Issued: 2009
- Authors: Pesanayi, Tichaona V
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386427 , vital:68140 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122802"
- Description: Food insecurity is one of the major threats to sustainable development in Africa, and particularly southern Africa. Climate change is increasingly having negative impacts on food production, further increasing the vulnerability of resource-poor communities. This paper outlines a research study conducted in two Zimbabwean smallholder communities of practice, with the aim of understanding learning interactions taking place within the community of practice that influence its choice of cultivated food plants. This would hopefully inform capability-centred teaching and learning. The study was conducted in the context of vulnerability to environment risk, socio-political pressures and a market-oriented agro-based economy in recession. Various causal mechanisms influencing plant-food choice were identified using critical realist ontological analysis. These included mixed messages from external influences in conflict with local knowledge due to power knowledge relationships. A number of learning interactions were found to be important in promoting the adaptive capacity of the farmers to chronic drought, which included inter-generational knowledge sharing; farmer to farmer exchange and reflective dialogue; experiential learning; farmers ‘passing on’ part of their harvests to other farmers; farming communities learning from risk and responding to risk; and learning from trying things out. The implications for capability-centred social learning processes were that it is important to understand the causal mechanisms that influence choices; and to confront tensions, while reducing ambivalence. A focus on more sustainable alternatives, feasible and practical for farmers, was recommended. These findings, in the context of one case study, create research questions to be examined in other case contexts in environmental education research focusing on climate change learning and adaptation.
- Full Text:
- Date Issued: 2009
Solvent and central metal effects on the photophysical and photochemical properties of peripherally tetra mercaptopyridine substituted metallophthalocyanines
- Moeno, Sharon, Nyokong, Tebello
- Authors: Moeno, Sharon , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263522 , vital:53635 , xlink:href="https://doi.org/10.1016/j.jphotochem.2009.01.021"
- Description: The synthesis of peripherally tetra 2-mercaptopyridine substituted phthalocyanines containing Si, Ga, Sn and In as central metal ions is reported for the first time in this study. Photophysical and photochemical studies were carried out on these compounds in order to determine the potential of the complexes as photosensitizers for use in photodynamic therapy. Fluorescence quantum yields (ΦF) ranged from 0.012 to 0.2 and triplet quantum yields (ΦT) from 0.54 to 0.89 in dimethylformamide (DMF) and from 0.65 to 0.93 in dimethylsulfoxide (DMSO). The triplet lifetimes ranged from 20 to 130 μs, the low values are due to the heavy atom effects of the central metal. The triplet lifetimes were larger in DMSO when compared with DMF.
- Full Text:
- Date Issued: 2009
- Authors: Moeno, Sharon , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263522 , vital:53635 , xlink:href="https://doi.org/10.1016/j.jphotochem.2009.01.021"
- Description: The synthesis of peripherally tetra 2-mercaptopyridine substituted phthalocyanines containing Si, Ga, Sn and In as central metal ions is reported for the first time in this study. Photophysical and photochemical studies were carried out on these compounds in order to determine the potential of the complexes as photosensitizers for use in photodynamic therapy. Fluorescence quantum yields (ΦF) ranged from 0.012 to 0.2 and triplet quantum yields (ΦT) from 0.54 to 0.89 in dimethylformamide (DMF) and from 0.65 to 0.93 in dimethylsulfoxide (DMSO). The triplet lifetimes ranged from 20 to 130 μs, the low values are due to the heavy atom effects of the central metal. The triplet lifetimes were larger in DMSO when compared with DMF.
- Full Text:
- Date Issued: 2009
St. Petersburg
- Authors: Krueger, Anton
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229818 , vital:49713 , xlink:href="https://hdl.handle.net/10520/EJC47812"
- Full Text:
- Date Issued: 2009
- Authors: Krueger, Anton
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229818 , vital:49713 , xlink:href="https://hdl.handle.net/10520/EJC47812"
- Full Text:
- Date Issued: 2009
Students as Agents of Social Change-Student Initiatives at Rhodes University, South Africa
- Authors: Togo, Muchaiteyi
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386561 , vital:68151 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122830"
- Description: Rhodes University has a diversity of sustainable development initiatives meant for students and in a range of cases activities are initiated by students themselves with the support of the university. Results of a sustainability assessment revealed the involvement of students in environmental societies, environmental awareness campaigns, campus sustainability initiatives and community sustainability projects. Though most of the projects are still in their infancy and some challenges are yet to be overcome, the sustainability initiatives are gaining momentum and have contributed to improving the overall picture of sustainability at the university. Based on the results of the Rhodes University case study, the underpinning viewpoint in this paper is that university students are not merely recipients of Education for Sustainable Development but have the capacity to become agents for social change.
- Full Text:
- Date Issued: 2009
- Authors: Togo, Muchaiteyi
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386561 , vital:68151 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122830"
- Description: Rhodes University has a diversity of sustainable development initiatives meant for students and in a range of cases activities are initiated by students themselves with the support of the university. Results of a sustainability assessment revealed the involvement of students in environmental societies, environmental awareness campaigns, campus sustainability initiatives and community sustainability projects. Though most of the projects are still in their infancy and some challenges are yet to be overcome, the sustainability initiatives are gaining momentum and have contributed to improving the overall picture of sustainability at the university. Based on the results of the Rhodes University case study, the underpinning viewpoint in this paper is that university students are not merely recipients of Education for Sustainable Development but have the capacity to become agents for social change.
- Full Text:
- Date Issued: 2009
Study of the photophysical behavior of tetrasulfonated metallophthalocyanines in the presence of CdTe quantum dots
- Idowu, Mopelola A I, Nyokong, Tebello
- Authors: Idowu, Mopelola A I , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264138 , vital:53701 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.02.040"
- Description: Förster resonance energy transfer (FRET) studies were carried out with CdTe quantum dots (QDs) synthesized in aqueous phase and various tetrasulfonated metallophthalocyanines (MPcS4, M = aluminum ((OH)AlPcS4), zinc (ZnPcS4), silicon ((OH)2SiPcS4) and germanium ((OH)2GePcS4) in a H2O:MeOH (1:1) solvent mixture. The QDs studied were capped with thioglycolic acid (TGA) or mercaptopropionic acid (MPA) with sizes ranging from 2.3 to 3.7 nm. Non-radiative energy transfer from QDs emission to MPcS4 complexes was observed. Study of the photophysics of the MPcs in the presence of the QDs revealed high triplet state quantum yields (ΦT, ranging from 0.41 to 0.85 in the presence of QDs), with corresponding long triplet state lifetimes (τT, which ranged from 140 to 610 μs in the presence of QDs) to allow for photosensitized reactions to occur. The efficiency of energy transfer and the donor–acceptor distance between the MPcs and the QDs were also evaluated.
- Full Text:
- Date Issued: 2009
- Authors: Idowu, Mopelola A I , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264138 , vital:53701 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.02.040"
- Description: Förster resonance energy transfer (FRET) studies were carried out with CdTe quantum dots (QDs) synthesized in aqueous phase and various tetrasulfonated metallophthalocyanines (MPcS4, M = aluminum ((OH)AlPcS4), zinc (ZnPcS4), silicon ((OH)2SiPcS4) and germanium ((OH)2GePcS4) in a H2O:MeOH (1:1) solvent mixture. The QDs studied were capped with thioglycolic acid (TGA) or mercaptopropionic acid (MPA) with sizes ranging from 2.3 to 3.7 nm. Non-radiative energy transfer from QDs emission to MPcS4 complexes was observed. Study of the photophysics of the MPcs in the presence of the QDs revealed high triplet state quantum yields (ΦT, ranging from 0.41 to 0.85 in the presence of QDs), with corresponding long triplet state lifetimes (τT, which ranged from 140 to 610 μs in the presence of QDs) to allow for photosensitized reactions to occur. The efficiency of energy transfer and the donor–acceptor distance between the MPcs and the QDs were also evaluated.
- Full Text:
- Date Issued: 2009
Study South Africa
- International Education Association of South Africa (IEASA), Jooste, Nico
- Authors: International Education Association of South Africa (IEASA) , Jooste, Nico
- Date: 2009
- Subjects: Education, Higher -- South Africa , Universities and colleges -- South Africa , Technical Institutes -- South Africa , Vocational guidance -- South Africa
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/64983 , vital:28642 , ISBN 9780620448161
- Description: [Extract from message from Minister of Higher Education and Training, Hon. Dr BE Nzimande]: It gives me pleasure to provide support to the International Education Association of South Africa’s (IEASA) 9th edition of the Study South Africa publication. The focus of this edition, which is Higher Education and Development in South Africa, is most appropriate today as South Africa continuously strives to ensure that higher education remains relevant and responsive to the developmental needs of the country. To this end, we always have to bear in mind that South Africa is a developing country, and as such still confronts challenges such as poverty and under-development. These challenges are characteristic of most developing countries, particularly in sub-Saharan Africa. Thus, our higher education sector, through its core functions of teaching, research, and community engagement, should seek to address these issues especially as they affect the poor and other vulnerable members of our society. Since we became a democratic state in 1994, South Africa has gone a long way to transform and restructure our higher education system to ensure amongst others equity with regard to the demographics of our staff and student population. The gender and racial profile of our students has improved significantly over the years to the extent that we now have black and female students constituting the majority at our institutions, especially at undergraduate level. It is also pleasing to note that our institutions enjoy good international standing. South African researchers and institutions continue to engage in research collaborations with their peers and counterparts around the world, and thus, are integral parts of research programmes and networks. With respect to student mobility, our higher education institutions continue to attract large numbers of international students, particularly from other parts of Africa. In 2007 the number of international students enrolled at our institutions was counted at 59 209, a significant increase from 44 439 in 2000. About 85% of these students originate from the African continent, more specifically the Southern African Development Community (SADC) region. Several factors account for the increase in the number of international students coming to South Africa. These include the country’s natural and ecological resources, rich and diverse cultural heritage, and the stable socio-political conditions. The consistent growth in the number of international students seeking to study in South Africa is a positive affirmation on the quality of the country’s institutions and the international reputation of their academics and qualifications. As a country, we see this growth as a positive development as it provides us with the opportunity not only to impart or relate our experiences, but also, to learn from others, and by so doing further enhance the international standing of our higher education system. , 9th Edition
- Full Text:
- Date Issued: 2009
- Authors: International Education Association of South Africa (IEASA) , Jooste, Nico
- Date: 2009
- Subjects: Education, Higher -- South Africa , Universities and colleges -- South Africa , Technical Institutes -- South Africa , Vocational guidance -- South Africa
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/64983 , vital:28642 , ISBN 9780620448161
- Description: [Extract from message from Minister of Higher Education and Training, Hon. Dr BE Nzimande]: It gives me pleasure to provide support to the International Education Association of South Africa’s (IEASA) 9th edition of the Study South Africa publication. The focus of this edition, which is Higher Education and Development in South Africa, is most appropriate today as South Africa continuously strives to ensure that higher education remains relevant and responsive to the developmental needs of the country. To this end, we always have to bear in mind that South Africa is a developing country, and as such still confronts challenges such as poverty and under-development. These challenges are characteristic of most developing countries, particularly in sub-Saharan Africa. Thus, our higher education sector, through its core functions of teaching, research, and community engagement, should seek to address these issues especially as they affect the poor and other vulnerable members of our society. Since we became a democratic state in 1994, South Africa has gone a long way to transform and restructure our higher education system to ensure amongst others equity with regard to the demographics of our staff and student population. The gender and racial profile of our students has improved significantly over the years to the extent that we now have black and female students constituting the majority at our institutions, especially at undergraduate level. It is also pleasing to note that our institutions enjoy good international standing. South African researchers and institutions continue to engage in research collaborations with their peers and counterparts around the world, and thus, are integral parts of research programmes and networks. With respect to student mobility, our higher education institutions continue to attract large numbers of international students, particularly from other parts of Africa. In 2007 the number of international students enrolled at our institutions was counted at 59 209, a significant increase from 44 439 in 2000. About 85% of these students originate from the African continent, more specifically the Southern African Development Community (SADC) region. Several factors account for the increase in the number of international students coming to South Africa. These include the country’s natural and ecological resources, rich and diverse cultural heritage, and the stable socio-political conditions. The consistent growth in the number of international students seeking to study in South Africa is a positive affirmation on the quality of the country’s institutions and the international reputation of their academics and qualifications. As a country, we see this growth as a positive development as it provides us with the opportunity not only to impart or relate our experiences, but also, to learn from others, and by so doing further enhance the international standing of our higher education system. , 9th Edition
- Full Text:
- Date Issued: 2009
Synthesis and characterization of electrocatalytic conjugates of tetraamino cobalt (II) phthalocyanine and single wall carbon nanotubes
- Mugadza, Tawanda, Nyokong, Tebello
- Authors: Mugadza, Tawanda , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263341 , vital:53619 , xlink:href="https://doi.org/10.1016/j.electacta.2009.05.074"
- Description: In this paper we report on the synthesis and characterization of electrocatalytic conjugates of tetraamino cobalt (II) phthalocyanine and single walled carbon nanotubes (CoTAPc–SWCNT-linked) for use as electrode surface modifiers. FTIR, UV–vis and Raman spectroscopies were used to ascertain the chemical linkage between CoTAPc and SWCNT while cyclic voltammetry and rotating disk electrode voltammetry were used to assess the electrocatalytic efficiency of the linked product towards the oxidation of 2-mercaptoethanol. The CoTAPc–SWCNT-linked-GCE demonstrated very good catalytic efficiency relative to CoTAPc–SWCNT-mixed-GCE, CoTAPc-GCE and f-SWCNTs-GCE (functionalised SWCNT). CoTAPc–SWCNT-linked-GCE gave a sensitivity of 0.2 μA/μM and a limit of detection (LOD) of 1.2 × 10−7 M for 2-mercaptoethanol (2-ME) at pH 4.
- Full Text:
- Date Issued: 2009
- Authors: Mugadza, Tawanda , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263341 , vital:53619 , xlink:href="https://doi.org/10.1016/j.electacta.2009.05.074"
- Description: In this paper we report on the synthesis and characterization of electrocatalytic conjugates of tetraamino cobalt (II) phthalocyanine and single walled carbon nanotubes (CoTAPc–SWCNT-linked) for use as electrode surface modifiers. FTIR, UV–vis and Raman spectroscopies were used to ascertain the chemical linkage between CoTAPc and SWCNT while cyclic voltammetry and rotating disk electrode voltammetry were used to assess the electrocatalytic efficiency of the linked product towards the oxidation of 2-mercaptoethanol. The CoTAPc–SWCNT-linked-GCE demonstrated very good catalytic efficiency relative to CoTAPc–SWCNT-mixed-GCE, CoTAPc-GCE and f-SWCNTs-GCE (functionalised SWCNT). CoTAPc–SWCNT-linked-GCE gave a sensitivity of 0.2 μA/μM and a limit of detection (LOD) of 1.2 × 10−7 M for 2-mercaptoethanol (2-ME) at pH 4.
- Full Text:
- Date Issued: 2009
Synthesis and photophysical behavior of axially substituted phthalocyanine, tetrabenzotriazaporphyrin, and triazatetrabenzcorrole phosphorous complexes
- Antunes, Edith M, Nyokong, Tebello
- Authors: Antunes, Edith M , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264518 , vital:53741 , xlink:href="https://doi.org/10.1142/S1088424609000048"
- Description: The synthesis of phosphorous phthalocyanines, triazatetrabenzcorroles, and tetrabenzotriazaporphyrins with a variety of axial ligands is reported. The new complexes are: phosphorous dihydroxy tetrabenzotriazaporphyrin (5, PV(OH)2TBTAP), diphenyl phosphorous phthalocyanine (6, [PV(Ph)2Pc](OH)), diphenyl phosphorous triazatetrabenzcorrole (7, PV(Ph)2TBC), and dioctyl phosphorous triazatetrabenzcorrole (8, PV(C8H17)2TBC). The complexes are not aggregated in dimethylsulfoxide (DMSO) and pyridine. Upon axial coordination of a phenyl or octyl group, the complexes are soluble (and not aggregated) in dichloromethane (DCM) and tetrahydrofuran (THF). The triplet lifetimes range from 395 to 546 μs (for complexes 5 to 8), with the P(Ph)2TBC (7) complex showing the longest triplet lifetime (546 μs), while the smallest triplet quantum yield (ΦT = 0.27) was obtained for the [P(Ph)2Pc](OH) (6) complex. [P(OH)2Pc](OH) (3) showed the shortest triplet lifetime (113 μs) and the largest triplet quantum yield (ΦT = 0.52).
- Full Text:
- Date Issued: 2009
- Authors: Antunes, Edith M , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264518 , vital:53741 , xlink:href="https://doi.org/10.1142/S1088424609000048"
- Description: The synthesis of phosphorous phthalocyanines, triazatetrabenzcorroles, and tetrabenzotriazaporphyrins with a variety of axial ligands is reported. The new complexes are: phosphorous dihydroxy tetrabenzotriazaporphyrin (5, PV(OH)2TBTAP), diphenyl phosphorous phthalocyanine (6, [PV(Ph)2Pc](OH)), diphenyl phosphorous triazatetrabenzcorrole (7, PV(Ph)2TBC), and dioctyl phosphorous triazatetrabenzcorrole (8, PV(C8H17)2TBC). The complexes are not aggregated in dimethylsulfoxide (DMSO) and pyridine. Upon axial coordination of a phenyl or octyl group, the complexes are soluble (and not aggregated) in dichloromethane (DCM) and tetrahydrofuran (THF). The triplet lifetimes range from 395 to 546 μs (for complexes 5 to 8), with the P(Ph)2TBC (7) complex showing the longest triplet lifetime (546 μs), while the smallest triplet quantum yield (ΦT = 0.27) was obtained for the [P(Ph)2Pc](OH) (6) complex. [P(OH)2Pc](OH) (3) showed the shortest triplet lifetime (113 μs) and the largest triplet quantum yield (ΦT = 0.52).
- Full Text:
- Date Issued: 2009
Synthesis, photophysical and nonlinear optical properties of microwave synthesized 4-tetra and octa-substituted lead phthalocyanines
- Modibane, Desmond K, Nyokong, Tebello
- Authors: Modibane, Desmond K , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263452 , vital:53629 , xlink:href="https://doi.org/10.1016/j.poly.2009.03.013"
- Description: This work presents the photophysical and nonlinear optical behaviour of newly synthesized complexes: 2,(3)-tetrakis(4-benzyloxyphenoxyphthalocyaninato) lead (5a) and 2,3-octakis(4-benzyloxyphenoxyphthalocyaninato) lead (6a). The nonlinear optical behaviour of complexes 5a and 6a are compared with those of 2,(3)-tetraphenoxyphthalocyaninato lead (5b), 2,(3)-tetrakis(4-t-butylphenoxyphthalocyaninato) lead (5c), 2,3-octaphenoxyphthalocyaninato lead (6b) and 2,3-octakis(4-t-butylphenoxyphthalocyaninato) lead (6c). The synthesis of 5a and 6a was performed using microwave irradiation. Photophysical properties were studied for these complexes in dimethylsulfoxide, dimethylformamide, toluene, tetrahydrofuran and chloroform. The fluorescence spectra were different from excitation spectra due to demetallation upon excitation. High triplet quantum yields ranging from 0.80 to 0.86 (in DMSO, DMF and toluene) and low triplet lifetimes (20–50 μs in DMSO, and more than 10 μs in the rest of the solvents) were observed due to the presence of heavy atom. Nonlinear optical properties were studied in dimethylsulfoxide. The optical limiting threshold intensity (Ilim) for the PbPc derivatives were calculated and ranged from 2.1 to 6.6 W/cm2.
- Full Text:
- Date Issued: 2009
- Authors: Modibane, Desmond K , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263452 , vital:53629 , xlink:href="https://doi.org/10.1016/j.poly.2009.03.013"
- Description: This work presents the photophysical and nonlinear optical behaviour of newly synthesized complexes: 2,(3)-tetrakis(4-benzyloxyphenoxyphthalocyaninato) lead (5a) and 2,3-octakis(4-benzyloxyphenoxyphthalocyaninato) lead (6a). The nonlinear optical behaviour of complexes 5a and 6a are compared with those of 2,(3)-tetraphenoxyphthalocyaninato lead (5b), 2,(3)-tetrakis(4-t-butylphenoxyphthalocyaninato) lead (5c), 2,3-octaphenoxyphthalocyaninato lead (6b) and 2,3-octakis(4-t-butylphenoxyphthalocyaninato) lead (6c). The synthesis of 5a and 6a was performed using microwave irradiation. Photophysical properties were studied for these complexes in dimethylsulfoxide, dimethylformamide, toluene, tetrahydrofuran and chloroform. The fluorescence spectra were different from excitation spectra due to demetallation upon excitation. High triplet quantum yields ranging from 0.80 to 0.86 (in DMSO, DMF and toluene) and low triplet lifetimes (20–50 μs in DMSO, and more than 10 μs in the rest of the solvents) were observed due to the presence of heavy atom. Nonlinear optical properties were studied in dimethylsulfoxide. The optical limiting threshold intensity (Ilim) for the PbPc derivatives were calculated and ranged from 2.1 to 6.6 W/cm2.
- Full Text:
- Date Issued: 2009
Synthesis, photophysical and photochemical properties of novel soluble tetra [4-(thiophen-3yl)-phenoxy] phthalocyaninato zinc (II) and Ti (IV) O complexes
- Erdoğmuş, Ali, Nyokong, Tebello
- Authors: Erdoğmuş, Ali , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263318 , vital:53617 , xlink:href="https://doi.org/10.1016/j.ica.2009.07.015"
- Description: The synthesis, photophysical and photochemical properties of zinc and oxo-titanium phthalocyanine derivatives 4-(tetra[4-(thiophen-3yl)-phenoxy]phthalocyaninato)zinc(II), (2); and 4-(tetra[4-(thiophen-3yl)-phenoxy]phthalocyaninato)oxo-titanium(IV), (3), are described for the first time. These peripherally substituted complexes (2 and 3) have been synthesized and characterized by elemental analysis, IR, 1H NMR and electronic spectroscopy. The compounds (2 and 3) have good solubility in organic solvents such as CHCl3, DCM, DMSO, DMF, THF and toluene and are not aggregated within a wide concentration range. General trends are described for singlet oxygen, photodegradation, fluorescence quantum yields, triplet quantum yields and triplet life times of these complexes in DMSO, DMF and THF. Compound 2 has higher fluorescence quantum yields, triplet quantum yields and triplet life times than 3, however, the former has lower singlet oxygen quantum yields and photodegradation quantum yields than the latter.
- Full Text:
- Date Issued: 2009
- Authors: Erdoğmuş, Ali , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263318 , vital:53617 , xlink:href="https://doi.org/10.1016/j.ica.2009.07.015"
- Description: The synthesis, photophysical and photochemical properties of zinc and oxo-titanium phthalocyanine derivatives 4-(tetra[4-(thiophen-3yl)-phenoxy]phthalocyaninato)zinc(II), (2); and 4-(tetra[4-(thiophen-3yl)-phenoxy]phthalocyaninato)oxo-titanium(IV), (3), are described for the first time. These peripherally substituted complexes (2 and 3) have been synthesized and characterized by elemental analysis, IR, 1H NMR and electronic spectroscopy. The compounds (2 and 3) have good solubility in organic solvents such as CHCl3, DCM, DMSO, DMF, THF and toluene and are not aggregated within a wide concentration range. General trends are described for singlet oxygen, photodegradation, fluorescence quantum yields, triplet quantum yields and triplet life times of these complexes in DMSO, DMF and THF. Compound 2 has higher fluorescence quantum yields, triplet quantum yields and triplet life times than 3, however, the former has lower singlet oxygen quantum yields and photodegradation quantum yields than the latter.
- Full Text:
- Date Issued: 2009
Synthesis, photophysical and photochemical properties of octa-substituted antimony phthalocyanines
- Modibane, Desmond Kwena, Nyokong, Tebello
- Authors: Modibane, Desmond Kwena , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264226 , vital:53711 , xlink:href="https://doi.org/10.1016/j.poly.2008.11.052"
- Description: This work reports on the synthesis and photophysicochemical parameters of unsubstituted [SbIIIPc]+I3- and octa-phenoxy ([SbIIIOPPc]+I3-) and -4-t-butylphenoxy ([SbIIIOTBPPc]+I3-) substituted antimony phthalocyanines. Photophysical and photochemical properties were studied for these complexes in dimethylsulfoxide, dimethylformamide and toluene. The excitation spectra of oxidized antimony (Sb(V)Pc) derivates were similar to absorption spectra. Low fluorescence quantum yields, high triplet quantum yields and low triplet lifetimes were observed as the result of heavy atom (antimony ion).
- Full Text:
- Date Issued: 2009
- Authors: Modibane, Desmond Kwena , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264226 , vital:53711 , xlink:href="https://doi.org/10.1016/j.poly.2008.11.052"
- Description: This work reports on the synthesis and photophysicochemical parameters of unsubstituted [SbIIIPc]+I3- and octa-phenoxy ([SbIIIOPPc]+I3-) and -4-t-butylphenoxy ([SbIIIOTBPPc]+I3-) substituted antimony phthalocyanines. Photophysical and photochemical properties were studied for these complexes in dimethylsulfoxide, dimethylformamide and toluene. The excitation spectra of oxidized antimony (Sb(V)Pc) derivates were similar to absorption spectra. Low fluorescence quantum yields, high triplet quantum yields and low triplet lifetimes were observed as the result of heavy atom (antimony ion).
- Full Text:
- Date Issued: 2009
Synthesis, photophysical and photochemical studies of water soluble cationic zinc phthalocyanine derivatives
- Idowu, Mopelola A I, Nyokong, Tebello
- Authors: Idowu, Mopelola A I , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264245 , vital:53712 , xlink:href="https://doi.org/10.1016/j.poly.2008.11.021"
- Description: Peripherally and non-peripherally 2-diethylaminoethanethiol tetra-substituted zinc phthalocyanine (5a and 6a) and their quaternized derivatives (5b and 6b) have been synthesized and characterized. The quaternized derivatives (5b and 6b) show excellent solubility in aqueous medium. The photophysical and photochemical properties of the 2-diethylaminoethanethiol appended zinc phthalocyanine in dimethylsulfoxide (DMSO) for the non-ionic (5a and 6a) and in both DMSO and aqueous medium (phosphate buffered saline solution PBS, pH 7.4) (in the presence and absence of cremophore EL (CEL)) for the quaternized (5b and 6b) derivatives were studied and compared with that of the peripherally octa-substituted derivatives (7a and 7b). The complexes have intense absorption in the visible/near-IR region though the quaternized forms (5b, 6b and 7b) were slightly blue shifted and highly aggregate in aqueous solution. The triplet state quantum yields (ΦT) and the triplet lifetimes (τT) were found to be higher in DMSO (ΦT values ranged from 0.57 to 0.75 while τT values ranged from 190 to 220 μs in DMSO for all complexes) compared to aqueous medium (ΦT values ranged from 0.15 to 0.17 while τT values ranged from 20 to 70 μs in pH 7.4 buffer). Addition of cremophore EL in aqueous solution resulted in induced disaggregation leading to increased ΦT and τT.
- Full Text:
- Date Issued: 2009
- Authors: Idowu, Mopelola A I , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264245 , vital:53712 , xlink:href="https://doi.org/10.1016/j.poly.2008.11.021"
- Description: Peripherally and non-peripherally 2-diethylaminoethanethiol tetra-substituted zinc phthalocyanine (5a and 6a) and their quaternized derivatives (5b and 6b) have been synthesized and characterized. The quaternized derivatives (5b and 6b) show excellent solubility in aqueous medium. The photophysical and photochemical properties of the 2-diethylaminoethanethiol appended zinc phthalocyanine in dimethylsulfoxide (DMSO) for the non-ionic (5a and 6a) and in both DMSO and aqueous medium (phosphate buffered saline solution PBS, pH 7.4) (in the presence and absence of cremophore EL (CEL)) for the quaternized (5b and 6b) derivatives were studied and compared with that of the peripherally octa-substituted derivatives (7a and 7b). The complexes have intense absorption in the visible/near-IR region though the quaternized forms (5b, 6b and 7b) were slightly blue shifted and highly aggregate in aqueous solution. The triplet state quantum yields (ΦT) and the triplet lifetimes (τT) were found to be higher in DMSO (ΦT values ranged from 0.57 to 0.75 while τT values ranged from 190 to 220 μs in DMSO for all complexes) compared to aqueous medium (ΦT values ranged from 0.15 to 0.17 while τT values ranged from 20 to 70 μs in pH 7.4 buffer). Addition of cremophore EL in aqueous solution resulted in induced disaggregation leading to increased ΦT and τT.
- Full Text:
- Date Issued: 2009
Synthesis, photophysics and photochemistry of novel tetra (quinoxalinyl) phthalocyaninato zinc (II) complexes
- Erdoğmuş, Ali, Ogunsipe, Abimbola, Nyokong, Tebello
- Authors: Erdoğmuş, Ali , Ogunsipe, Abimbola , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263441 , vital:53628 , xlink:href="https://doi.org/10.1016/j.jphotochem.2009.04.007"
- Description: The syntheses and spectral, photophysical and photochemical properties of some zinc phthalocyanine derivatives – {2, (3)-tetra(quinoxalinyl)phthalocyaninato zinc(II), (β-ZnPc) and 1, (4)-tetra(quinoxalinyl)phthalocyaninato zinc(II), (α-ZnPc)} – are presented. The β-substituted complex is more fluorescent and exhibits lower tendencies to undergo intersystem crossing than its α-substituted counterpart, as judged by the former's higher fluorescence quantum yield (ΦF) and lower triplet quantum yield (ΦT) than the latter's in three solvents (DMSO, DMF and toluene). Singlet oxygen quantum yield (ΦΔ) values show the same trends as ΦT values. The differences in the spectral and photophysical properties of α-ZnPc and β-ZnPc are partly attributed to greater molecular distortions in the former. Studies of the interaction of the triplet states of α-ZnPc and β-ZnPc with triplet oxygen showed that α-ZnPc is more vulnerable to oxygen quenching than β-ZnPc. Also, the smallest quenching rate constants were observed in DMSO, which is attributed to the higher viscosity of DMSO than DMF and toluene.
- Full Text:
- Date Issued: 2009
- Authors: Erdoğmuş, Ali , Ogunsipe, Abimbola , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263441 , vital:53628 , xlink:href="https://doi.org/10.1016/j.jphotochem.2009.04.007"
- Description: The syntheses and spectral, photophysical and photochemical properties of some zinc phthalocyanine derivatives – {2, (3)-tetra(quinoxalinyl)phthalocyaninato zinc(II), (β-ZnPc) and 1, (4)-tetra(quinoxalinyl)phthalocyaninato zinc(II), (α-ZnPc)} – are presented. The β-substituted complex is more fluorescent and exhibits lower tendencies to undergo intersystem crossing than its α-substituted counterpart, as judged by the former's higher fluorescence quantum yield (ΦF) and lower triplet quantum yield (ΦT) than the latter's in three solvents (DMSO, DMF and toluene). Singlet oxygen quantum yield (ΦΔ) values show the same trends as ΦT values. The differences in the spectral and photophysical properties of α-ZnPc and β-ZnPc are partly attributed to greater molecular distortions in the former. Studies of the interaction of the triplet states of α-ZnPc and β-ZnPc with triplet oxygen showed that α-ZnPc is more vulnerable to oxygen quenching than β-ZnPc. Also, the smallest quenching rate constants were observed in DMSO, which is attributed to the higher viscosity of DMSO than DMF and toluene.
- Full Text:
- Date Issued: 2009