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:
- 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:
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:
- 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.
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Effects of the number of ring substituents of cobalt carboxyphthalocyanines on the electrocatalytic detection of nitrite, cysteine and melatonin
- Matemadombo, Fungisai, Sehlotho, Nthapo, Nyokong, Tebello
- Authors: Matemadombo, Fungisai , Sehlotho, Nthapo , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263408 , vital:53625 , xlink:href="https://doi.org/10.1142/S108842460900125X"
- Description: Cobalt phthalocyanine (CoPc), cobalt tetracarboxy phthalocyanine (CoTCPc) and cobalt octacarboxy phthalocyanine (CoOCPc), adsorbed onto glassy carbon electrodes, have been used for the electrocatalytic detection of nitrite, L-cysteine and melatonin. The modified electrodes electrocatalytically detected nitrite around 800 mV vs.Ag|AgCl, a value less positive compared to that of an unmodified glassy carbon electrode (at 950 mV vs.Ag|AgCl) and also gave detection limits in the 10-7 M range for nitrite detection. L-cysteine was detected by the modified electrodes at potentials between 0.50 to 0.65 V vs.Ag|AgCl, with L-cysteine detection limits also in the 10-7 M range. The detection limits for melatonin ranged from 10-7 to 10-6 M. CoPc-modified electrodes displayed good separation of interferents (tryptophan and ascorbic acid) in the presence of melatonin. Analyses of commercial melatonin tablets using modified electrodes gave excellent agreement with manufacturer's value for all modified electrodes of this work.
- Full Text:
- Authors: Matemadombo, Fungisai , Sehlotho, Nthapo , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263408 , vital:53625 , xlink:href="https://doi.org/10.1142/S108842460900125X"
- Description: Cobalt phthalocyanine (CoPc), cobalt tetracarboxy phthalocyanine (CoTCPc) and cobalt octacarboxy phthalocyanine (CoOCPc), adsorbed onto glassy carbon electrodes, have been used for the electrocatalytic detection of nitrite, L-cysteine and melatonin. The modified electrodes electrocatalytically detected nitrite around 800 mV vs.Ag|AgCl, a value less positive compared to that of an unmodified glassy carbon electrode (at 950 mV vs.Ag|AgCl) and also gave detection limits in the 10-7 M range for nitrite detection. L-cysteine was detected by the modified electrodes at potentials between 0.50 to 0.65 V vs.Ag|AgCl, with L-cysteine detection limits also in the 10-7 M range. The detection limits for melatonin ranged from 10-7 to 10-6 M. CoPc-modified electrodes displayed good separation of interferents (tryptophan and ascorbic acid) in the presence of melatonin. Analyses of commercial melatonin tablets using modified electrodes gave excellent agreement with manufacturer's value for all modified electrodes of this work.
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Characterization of polymeric film of a new manganese phthalocyanine complex octa-substituted with 2-diethylaminoethanethiol, and its use for the electrochemical detection of bentazon
- Akinbulu, Isaac A, Nyokong, Tebello
- Authors: Akinbulu, Isaac A , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/262568 , vital:53534 , xlink:href="https://doi.org/10.1016/j.electacta.2009.07.074"
- Description: Manganese acetate octakis-(2-diethyaminoethanethiol) phthalocyanine (AcMnODEAETPc) was newly synthesized and characterized by spectroscopic and electrochemical methods. Solution electrochemistry of the complex showed three redox processes assigned to MnIIIPc−1/MnIIIPc−2, MnIIIPc−2/MnIIPc−2 and MnIIPc−2/MnIIPc−3 species. The new molecule was polymerized onto a glassy carbon electrode (GCE) to form thin films of different thickness, giving poly-10-AcMnODEAETPc-GCE, poly-20-AcMnODEAETPc-GCE and poly-30-AcMnODEAETPc-GCE, where 10, 20 and 30 represent the number of voltammetry scans during polymerization. Three distinct redox processes were observed on the modified electrode in 0.1 M phosphate buffer solution, pH 5, which confirmed the formation of the polymer. The current signal due to the herbicide, bentazon, was dependent on film thickness; the best signal was obtained on poly-20-AcMnODEAETPc-GCE while poly-10-AcMnODEAETPc-GCE gave the least signal. However, the signals due to the herbicide were better on the different films compared to the bare electrode. Electrochemical impedance spectroscopy (EIS) technique revealed that differences in film thickness offered different charge transfer resistances, Rct, hence difference in current signals for bentazon oxidation were observed on these films. A Tafel slope of 77 mV/decade, obtained for the herbicide on poly-20-AcMnODEAETPc-GCE, denotes a fast one electron transfer followed by a slow chemical step in the electro-oxidation of bentazon. The voltammetry signals of the herbicide on the films indicated the likely involvement of ring-based redox processes in the detection of the herbicide. A plot of background corrected current response, on this film, versus the concentration of bentazon was linear within the range 50–750 μM with a detection limit of 2.48 × 10−7 M.
- Full Text:
- Authors: Akinbulu, Isaac A , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/262568 , vital:53534 , xlink:href="https://doi.org/10.1016/j.electacta.2009.07.074"
- Description: Manganese acetate octakis-(2-diethyaminoethanethiol) phthalocyanine (AcMnODEAETPc) was newly synthesized and characterized by spectroscopic and electrochemical methods. Solution electrochemistry of the complex showed three redox processes assigned to MnIIIPc−1/MnIIIPc−2, MnIIIPc−2/MnIIPc−2 and MnIIPc−2/MnIIPc−3 species. The new molecule was polymerized onto a glassy carbon electrode (GCE) to form thin films of different thickness, giving poly-10-AcMnODEAETPc-GCE, poly-20-AcMnODEAETPc-GCE and poly-30-AcMnODEAETPc-GCE, where 10, 20 and 30 represent the number of voltammetry scans during polymerization. Three distinct redox processes were observed on the modified electrode in 0.1 M phosphate buffer solution, pH 5, which confirmed the formation of the polymer. The current signal due to the herbicide, bentazon, was dependent on film thickness; the best signal was obtained on poly-20-AcMnODEAETPc-GCE while poly-10-AcMnODEAETPc-GCE gave the least signal. However, the signals due to the herbicide were better on the different films compared to the bare electrode. Electrochemical impedance spectroscopy (EIS) technique revealed that differences in film thickness offered different charge transfer resistances, Rct, hence difference in current signals for bentazon oxidation were observed on these films. A Tafel slope of 77 mV/decade, obtained for the herbicide on poly-20-AcMnODEAETPc-GCE, denotes a fast one electron transfer followed by a slow chemical step in the electro-oxidation of bentazon. The voltammetry signals of the herbicide on the films indicated the likely involvement of ring-based redox processes in the detection of the herbicide. A plot of background corrected current response, on this film, versus the concentration of bentazon was linear within the range 50–750 μM with a detection limit of 2.48 × 10−7 M.
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Exploring Learner Participation in Waste-Management Activities in a Rural Botswana Primary School
- Authors: Silo, Nthalivi
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386509 , vital:68148 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122820"
- Description: In Botswana, participation in environmental learning activities has been perceived as a central component of environmental education in formal education. Driven by the need to implement the objective of making the participatory approach part of the infusion of environmental education in the school curriculum as prescribed by the infusion policy, Botswana schools have come up with initiatives to involve learners in environmental education activities that seem to have ‘a direct, perceived benefit to the learners’ (NEESAP, 2007:9). Within this approach it is expected that learners should participate in these activities. However, Ketlhoilwe (2007) revealed that there has been a normalisation of environmental education into existing school culture through equating waste-management activities with environmental education. This generally entails cleaning activities by learners to maintain ‘clean schools’, which is directly associated with environmental education. Drawing from detailed case study data in one rural primary school with Standard 6 learners, I used Cultural Historical Activity Theory to investigate and explain how learners participate in these waste-management activities. Findings from this study revealed that attempts by teachers to meet the policy imperative through prescription of rules, and ascribing roles to learners in waste-management activities, create tensions. This gave rise to an elusive object of learner participation, as the purpose for their participation in these activities is not clear.
- Full Text:
- Authors: Silo, Nthalivi
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386509 , vital:68148 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122820"
- Description: In Botswana, participation in environmental learning activities has been perceived as a central component of environmental education in formal education. Driven by the need to implement the objective of making the participatory approach part of the infusion of environmental education in the school curriculum as prescribed by the infusion policy, Botswana schools have come up with initiatives to involve learners in environmental education activities that seem to have ‘a direct, perceived benefit to the learners’ (NEESAP, 2007:9). Within this approach it is expected that learners should participate in these activities. However, Ketlhoilwe (2007) revealed that there has been a normalisation of environmental education into existing school culture through equating waste-management activities with environmental education. This generally entails cleaning activities by learners to maintain ‘clean schools’, which is directly associated with environmental education. Drawing from detailed case study data in one rural primary school with Standard 6 learners, I used Cultural Historical Activity Theory to investigate and explain how learners participate in these waste-management activities. Findings from this study revealed that attempts by teachers to meet the policy imperative through prescription of rules, and ascribing roles to learners in waste-management activities, create tensions. This gave rise to an elusive object of learner participation, as the purpose for their participation in these activities is not clear.
- Full Text:
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:
- 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.
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Glumlazi
- Authors: Krueger, Anton
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229829 , vital:49715 , xlink:href="https://hdl.handle.net/10520/EJC47808"
- Full Text:
- Authors: Krueger, Anton
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229829 , vital:49715 , xlink:href="https://hdl.handle.net/10520/EJC47808"
- Full Text:
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:
- 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.
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Comparative electrocatalytic behavior of self-assembled monolayer of thiol derivatised Co (II) phthalocyanines on gold disk, ultramicro cylinder and fiber electrodes
- Nombona, Nolwazi, Geraldo, Daniela A, Hakuzimana, Jean, Schwarz, Anne, Westbroek, Philippe, Nyokong, Tebello
- Authors: Nombona, Nolwazi , Geraldo, Daniela A , Hakuzimana, Jean , Schwarz, Anne , Westbroek, Philippe , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263488 , vital:53632 , xlink:href="https://doi.org/10.1007/s10800-008-9716-y"
- Description: This paper reports on the use of thiol derivatised cobalt phthalocyanines as self assembled monolayers (SAMs) on gold disk electrode, gold ultramicro-cylinder electrode (UMCE) and on gold coated fiber for the detection of L-cysteine. The complexes are peripherally and non-peripherally substituted with phenylthio substituents. The SAM modified electrodes showed enhancement of catalytic currents and overpotential reduction occurred on the gold modified electrodes with different geometries. Electrocatalytic oxidation of L-cysteine on SAM modified gold coated fiber was reported for the first time. The gold coated fiber and ultramicro cylinder electrode were less stable towards the electrocatalytic oxidation of cysteine compared to its oxidation on the gold disk. The gold disk electrode gave better catalytic performance in terms of stability and reduction of overpotential.
- Full Text:
- Authors: Nombona, Nolwazi , Geraldo, Daniela A , Hakuzimana, Jean , Schwarz, Anne , Westbroek, Philippe , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263488 , vital:53632 , xlink:href="https://doi.org/10.1007/s10800-008-9716-y"
- Description: This paper reports on the use of thiol derivatised cobalt phthalocyanines as self assembled monolayers (SAMs) on gold disk electrode, gold ultramicro-cylinder electrode (UMCE) and on gold coated fiber for the detection of L-cysteine. The complexes are peripherally and non-peripherally substituted with phenylthio substituents. The SAM modified electrodes showed enhancement of catalytic currents and overpotential reduction occurred on the gold modified electrodes with different geometries. Electrocatalytic oxidation of L-cysteine on SAM modified gold coated fiber was reported for the first time. The gold coated fiber and ultramicro cylinder electrode were less stable towards the electrocatalytic oxidation of cysteine compared to its oxidation on the gold disk. The gold disk electrode gave better catalytic performance in terms of stability and reduction of overpotential.
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Cultural historical activity theory, expansive learning and agency in permaculture workplaces
- Authors: Mukute, Mutizwa
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386474 , vital:68145 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122818"
- Description: This paper reports on how Cultural Historical Activity Theory was used to identify and analyse contradictions; model and implement solutions in the learning and practice of permaculture at one school and its community in Zimbabwe. This is one of three sustainable agriculture workplace learning sites being examined in a wider study on change-oriented learning and sustainability practices (Mukute, 2009). It gives a brief background to permaculture and the School and Colleges Permaculture Programme (SCOPE) in Zimbabwe. The paper focuses on how contradictions were used as sources of learning and development leading to ‘real life expansions’. This demonstrates and reflects on the value of an interventionist research theory and methodology employed in the study to enhance participants’ agency in sustainable agriculture workplaces.
- Full Text:
- Authors: Mukute, Mutizwa
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386474 , vital:68145 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122818"
- Description: This paper reports on how Cultural Historical Activity Theory was used to identify and analyse contradictions; model and implement solutions in the learning and practice of permaculture at one school and its community in Zimbabwe. This is one of three sustainable agriculture workplace learning sites being examined in a wider study on change-oriented learning and sustainability practices (Mukute, 2009). It gives a brief background to permaculture and the School and Colleges Permaculture Programme (SCOPE) in Zimbabwe. The paper focuses on how contradictions were used as sources of learning and development leading to ‘real life expansions’. This demonstrates and reflects on the value of an interventionist research theory and methodology employed in the study to enhance participants’ agency in sustainable agriculture workplaces.
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The synthesis, cyclic voltammetry and spectroelectrochemical studies of Co (II) phthalocyanines tetra-substituted at the α and β positions with phenylthio groups
- Nombona, Nolwazi, Nyokong, Tebello
- Authors: Nombona, Nolwazi , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264529 , vital:53742 , xlink:href="https://doi.org/10.1016/j.dyepig.2008.06.002"
- Description: Non-peripherally substituted cobalt 1,(4)-(tetraphenylthiophthalocyaninato) and peripherally substituted cobalt 2,(3)-(tetraphenylthiophthalocyaninato) complexes were synthesized. Redox processes were observed at E1/2 = −1.44 V (I), −0.39 V (II), +0.37 V (III), +0.78 V (IV) and 1.15 V (V) for the non-peripherally substituted and at E1/2 = −1.42 V (I), −0.57, −0.39 V (II), +0.27 V (III), +0.79 V (IV) and +1.10 V (V) for the peripherally substituted complexes, respectively. The couples were assigned to CoIPc−2/CoIPc−3 (I), CoIIPc−2/CoIPc−2 (II), CoIIIPc−2/CoIIPc−2 (III), and CoIIIPc−1/CoIIIPc−2 (IV) using spectroelectrochemistry. The last process (V) could not be ascertained by spectroelectrochemistry but is associated with ring oxidation. Upon reduction or oxidation, the Q band of the non-peripherally substituted complex became less red shifted compared to that of its peripherally substituted counterpart.
- Full Text:
- Authors: Nombona, Nolwazi , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264529 , vital:53742 , xlink:href="https://doi.org/10.1016/j.dyepig.2008.06.002"
- Description: Non-peripherally substituted cobalt 1,(4)-(tetraphenylthiophthalocyaninato) and peripherally substituted cobalt 2,(3)-(tetraphenylthiophthalocyaninato) complexes were synthesized. Redox processes were observed at E1/2 = −1.44 V (I), −0.39 V (II), +0.37 V (III), +0.78 V (IV) and 1.15 V (V) for the non-peripherally substituted and at E1/2 = −1.42 V (I), −0.57, −0.39 V (II), +0.27 V (III), +0.79 V (IV) and +1.10 V (V) for the peripherally substituted complexes, respectively. The couples were assigned to CoIPc−2/CoIPc−3 (I), CoIIPc−2/CoIPc−2 (II), CoIIIPc−2/CoIIPc−2 (III), and CoIIIPc−1/CoIIIPc−2 (IV) using spectroelectrochemistry. The last process (V) could not be ascertained by spectroelectrochemistry but is associated with ring oxidation. Upon reduction or oxidation, the Q band of the non-peripherally substituted complex became less red shifted compared to that of its peripherally substituted counterpart.
- Full Text:
White Guys Can't Beg
- Authors: Krueger, Anton
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229796 , vital:49711 , xlink:href="https://hdl.handle.net/10520/EJC47812"
- Full Text:
- Authors: Krueger, Anton
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229796 , vital:49711 , xlink:href="https://hdl.handle.net/10520/EJC47812"
- Full Text:
What's wrong with Walden Two?
- Authors: Tabensky, Pedro
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/305791 , vital:58612 , xlink:href="https://hdl.handle.net/10520/EJC96066"
- Description: Despite being eminently forgettable from the literary point of view, B. F. Skinner's novel, Walden Two, provides us with an excellent opportunity, not so much to show what is wrong with mainstream accounts of free will, as Robert Kane thinks, but rather to explore another key and importantly neglected condition for genuine agency; namely, that properly lived human lives are those that are and must continue to be vulnerable to unforseable reversals, as Aldous Huxley speculates in his Brave New World. In short, I argue, perhaps scandalously, that one of the central conditions for genuine agency is that our lives are and must continue to be, to a large extent, out of our personal control. The promise of too much personal control, not too little (as Kane thinks), is what is wrong with Skinner's social utopia.
- Full Text:
- Authors: Tabensky, Pedro
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/305791 , vital:58612 , xlink:href="https://hdl.handle.net/10520/EJC96066"
- Description: Despite being eminently forgettable from the literary point of view, B. F. Skinner's novel, Walden Two, provides us with an excellent opportunity, not so much to show what is wrong with mainstream accounts of free will, as Robert Kane thinks, but rather to explore another key and importantly neglected condition for genuine agency; namely, that properly lived human lives are those that are and must continue to be vulnerable to unforseable reversals, as Aldous Huxley speculates in his Brave New World. In short, I argue, perhaps scandalously, that one of the central conditions for genuine agency is that our lives are and must continue to be, to a large extent, out of our personal control. The promise of too much personal control, not too little (as Kane thinks), is what is wrong with Skinner's social utopia.
- Full Text:
The synthesis and photophysicochemical behaviour of novel water-soluble cationic indium (III) phthalocyanine
- Durmus, Mahmut, Erdoğmuş, Ali, Ogunsipe, Abimbola, Nyokong, Tebello
- Authors: Durmus, Mahmut , Erdoğmuş, Ali , Ogunsipe, Abimbola , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263419 , vital:53626 , xlink:href="https://doi.org/10.1016/j.dyepig.2009.01.008"
- Description: The syntheses and characterization of 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III) and quaternized 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III) are described. The ground state electronic absorption spectra, photophysics and photochemistry of both dyes in DMSO as well as that of the quaternized compound in aqueous solution are also presented. A comparison of the photophysical and photochemical parameters of the two dyes revealed that quaternized 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III) was a better photosensitizer than its unquaternized counterpart. The quantum yield values of fluorescence (ΦF), triplet state formation (ΦT) and singlet oxygen formation (ΦΔ) for the cationic dye were found to be 0.03, 0.68 and 0.66 respectively in DMSO; these values were higher than those for 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III), which exhibited values of 0.02, 0.66 and 0.63, respectively in DMSO. The values for the cationic dye in aq. solution were 0.02, 0.59 and 0.56 respectively, suggesting that the water-soluble quaternized 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III) offers potential as a photosensitizer in photodynamic therapy treatment.
- Full Text:
- Authors: Durmus, Mahmut , Erdoğmuş, Ali , Ogunsipe, Abimbola , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263419 , vital:53626 , xlink:href="https://doi.org/10.1016/j.dyepig.2009.01.008"
- Description: The syntheses and characterization of 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III) and quaternized 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III) are described. The ground state electronic absorption spectra, photophysics and photochemistry of both dyes in DMSO as well as that of the quaternized compound in aqueous solution are also presented. A comparison of the photophysical and photochemical parameters of the two dyes revealed that quaternized 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III) was a better photosensitizer than its unquaternized counterpart. The quantum yield values of fluorescence (ΦF), triplet state formation (ΦT) and singlet oxygen formation (ΦΔ) for the cationic dye were found to be 0.03, 0.68 and 0.66 respectively in DMSO; these values were higher than those for 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III), which exhibited values of 0.02, 0.66 and 0.63, respectively in DMSO. The values for the cationic dye in aq. solution were 0.02, 0.59 and 0.56 respectively, suggesting that the water-soluble quaternized 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III) offers potential as a photosensitizer in photodynamic therapy treatment.
- Full Text:
The syntheses, characterization and fluorescence spectra of novel, octakis (alkylthiophthalocyanato) nickel (II) and palladium (II) complexes
- Ogunbayo, Taofeek Babatunde, Ogunsipe, Abimbola, Nyokong, Tebello
- Authors: Ogunbayo, Taofeek Babatunde , Ogunsipe, Abimbola , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263386 , vital:53623 , xlink:href="https://doi.org/10.1016/j.dyepig.2009.03.009"
- Description: The syntheses, characterization and fluorescence studies of several {octakis(alkylthio)phthalocyanato} palladium(II) and nickel(II) complexes are presented. The absorption spectra of some of the complexes showed extra peaks which are attributable to non-planar distortion, the extent of which, was found to dependent on alkyl chain length. The fluorescence excitation spectra of the nickel(II) derivatives were not in agreement with their absorption spectra, owing to structural changes upon excitation. Fluorescence quantum yields were very low (more than 1%) for all complexes as a consequence of the open-shell electronic structures of nickel(II) and palladium(II).
- Full Text:
- Authors: Ogunbayo, Taofeek Babatunde , Ogunsipe, Abimbola , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263386 , vital:53623 , xlink:href="https://doi.org/10.1016/j.dyepig.2009.03.009"
- Description: The syntheses, characterization and fluorescence studies of several {octakis(alkylthio)phthalocyanato} palladium(II) and nickel(II) complexes are presented. The absorption spectra of some of the complexes showed extra peaks which are attributable to non-planar distortion, the extent of which, was found to dependent on alkyl chain length. The fluorescence excitation spectra of the nickel(II) derivatives were not in agreement with their absorption spectra, owing to structural changes upon excitation. Fluorescence quantum yields were very low (more than 1%) for all complexes as a consequence of the open-shell electronic structures of nickel(II) and palladium(II).
- Full Text:
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:
- 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:
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:
- 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:
Nine Notes on Lisbon
- Authors: Krueger, Anton
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229807 , vital:49712 , xlink:href="https://hdl.handle.net/10520/EJC47812"
- Full Text:
- Authors: Krueger, Anton
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229807 , vital:49712 , xlink:href="https://hdl.handle.net/10520/EJC47812"
- Full Text:
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:
- 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:
Photophysicochemical and fluorescence quenching studies of tetra-and octa-carboxy substituted silicon and germanium phthalocyanines
- Idowu, Mopelola, Nyokong, Tebello
- Authors: Idowu, Mopelola , 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:
- Authors: Idowu, Mopelola , 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: