Linking poverty, HIV/AIDS and climate change to human and ecosystem vulnerability in southern Africa: Consequences for livelihoods and sustainable ecosystem management
- Shackleton, Sheona E, Shackleton, Charlie M
- Authors: Shackleton, Sheona E , Shackleton, Charlie M
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181081 , vital:43697 , xlink:href="https://doi.org/10.1080/13504509.2011.641039"
- Description: People in southern Africa are facing escalating levels of risk, uncertainty and consequently vulnerability as a result of multiple interacting stressors, including HIV/AIDS, poverty, food insecurity, weak governance, climate change and land degradation, to name but a few. Vulnerability or livelihood insecurity emerges when poor people as individuals or social units have to face harmful threats or shocks with inadequate capacity to respond effectively. In such situations, people often have no choice but to turn to their immediate environment for support. Evidence suggests that rising levels of human vulnerability are driving increased dependency on biodiversity and ecosystem services, which in turn, and along with other threats, is rendering ecosystems more vulnerable. This paper explores the dynamic and complex linkages and feedbacks between human vulnerability and ecosystem vulnerability, drawing on data from the southern African region. Human vulnerability is conceptualized as a threat to ecosystem health, as driven by the interplay between a number of current and emerging factors. We focus on poverty, HIV/AIDS and more intense climate extremes as examples of stressors on livelihoods and direct and indirect drivers of ecosystem change. We discuss how some of the responses to increased vulnerability may pose threats to biodiversity conservation, ecosystem management and sustainable development, whilst considering potential solutions that rely on a thorough understanding of coupled social–ecological systems and the interplay between multiple stressors and responses at different scales.
- Full Text:
- Date Issued: 2012
- Authors: Shackleton, Sheona E , Shackleton, Charlie M
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181081 , vital:43697 , xlink:href="https://doi.org/10.1080/13504509.2011.641039"
- Description: People in southern Africa are facing escalating levels of risk, uncertainty and consequently vulnerability as a result of multiple interacting stressors, including HIV/AIDS, poverty, food insecurity, weak governance, climate change and land degradation, to name but a few. Vulnerability or livelihood insecurity emerges when poor people as individuals or social units have to face harmful threats or shocks with inadequate capacity to respond effectively. In such situations, people often have no choice but to turn to their immediate environment for support. Evidence suggests that rising levels of human vulnerability are driving increased dependency on biodiversity and ecosystem services, which in turn, and along with other threats, is rendering ecosystems more vulnerable. This paper explores the dynamic and complex linkages and feedbacks between human vulnerability and ecosystem vulnerability, drawing on data from the southern African region. Human vulnerability is conceptualized as a threat to ecosystem health, as driven by the interplay between a number of current and emerging factors. We focus on poverty, HIV/AIDS and more intense climate extremes as examples of stressors on livelihoods and direct and indirect drivers of ecosystem change. We discuss how some of the responses to increased vulnerability may pose threats to biodiversity conservation, ecosystem management and sustainable development, whilst considering potential solutions that rely on a thorough understanding of coupled social–ecological systems and the interplay between multiple stressors and responses at different scales.
- Full Text:
- Date Issued: 2012
Lost in translation: Transformation in the first round of institutional audits
- Authors: McKenna, Sioux , Quinn, Lynn
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187384 , vital:44627 , xlink:href="https://hdl.handle.net/10520/EJC132752"
- Description: The South African higher education institutional audit process was introduced alongside similar endeavors internationally. However, despite many similarities, each country foregrounds different concerns within their higher education quality processes. In their seminal article, Harvey and Green suggest five possible notions of quality, one of which is quality as transformation, and in South Africa the message has been clearly stated: notions of quality are intricately related to transformation. Local research has however suggested that the notion of 'transformation' as quality takes on particular nuances within the country’s context. In the two institutional case studies presented here, the 'quality as transformation' discourse appears to have been largely lost in translation. In one university transformation was not called upon to construct notions of quality; quality was primarily constructed by a discourse of excellence. In the other institution, the transformation aspects of quality seem to have been interpreted in a particularly reductionist way as relating solely to racial demographics. In both cases, this article argues that the 'quality as transformation' discourse prevalent in the audit documentation in the South African context was lost somewhere between the intentions embodied in national documents and the processes embarked upon by institutions.
- Full Text:
- Date Issued: 2012
- Authors: McKenna, Sioux , Quinn, Lynn
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187384 , vital:44627 , xlink:href="https://hdl.handle.net/10520/EJC132752"
- Description: The South African higher education institutional audit process was introduced alongside similar endeavors internationally. However, despite many similarities, each country foregrounds different concerns within their higher education quality processes. In their seminal article, Harvey and Green suggest five possible notions of quality, one of which is quality as transformation, and in South Africa the message has been clearly stated: notions of quality are intricately related to transformation. Local research has however suggested that the notion of 'transformation' as quality takes on particular nuances within the country’s context. In the two institutional case studies presented here, the 'quality as transformation' discourse appears to have been largely lost in translation. In one university transformation was not called upon to construct notions of quality; quality was primarily constructed by a discourse of excellence. In the other institution, the transformation aspects of quality seem to have been interpreted in a particularly reductionist way as relating solely to racial demographics. In both cases, this article argues that the 'quality as transformation' discourse prevalent in the audit documentation in the South African context was lost somewhere between the intentions embodied in national documents and the processes embarked upon by institutions.
- Full Text:
- Date Issued: 2012
Molecular catalysis of the oxygen reduction reaction by iron porphyrin catalysts tethered into Nafion layers
- He, Qinggang, Mugadza, Tawanda, Kang, Xiongwu, Zhu, Xiaobing, Chen, Shaowei, Kerr, John, Nyokong, Tebello
- Authors: He, Qinggang , Mugadza, Tawanda , Kang, Xiongwu , Zhu, Xiaobing , Chen, Shaowei , Kerr, John , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243168 , vital:51123 , xlink:href="https://doi.org/10.1016/j.jpowsour.2012.05.043"
- Description: This study was motivated by the need for improved understanding of the kinetics and transport phenomena in a homogeneous catalyst system for the oxygen reduction reaction (ORR). Direct interaction between the sulfonic groups of Nafion and an Fe(III) meso-tetra(N-methyl-4-pyridyl) porphine chloride (Fe(III)TMPyP) compound was observed using FTIR and in situ UV–Vis spectroelectrochemical characterizations. A positive shift of the half wave potential value (E1/2) for ORR on the iron porphyrin catalyst (Fe(III)TMPyP) was observed upon addition of a specific quantity of Nafion ionomer on a glassy carbon working electrode, indicating not only a faster charge transfer rate but also the role of protonation in the oxygen reduction reaction (ORR) process. A membrane electrode assembly (MEA) was made as a sandwich of a Pt-coated anode, a Nafion® 212 membrane, and a Fe(III)TMPyP + Nafion ionomer-coated cathode. This three-dimensional catalysis system has been demonstrated to be working in a H2/O2 proton exchange membrane (PEM) fuel cell test.
- Full Text:
- Date Issued: 2012
- Authors: He, Qinggang , Mugadza, Tawanda , Kang, Xiongwu , Zhu, Xiaobing , Chen, Shaowei , Kerr, John , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243168 , vital:51123 , xlink:href="https://doi.org/10.1016/j.jpowsour.2012.05.043"
- Description: This study was motivated by the need for improved understanding of the kinetics and transport phenomena in a homogeneous catalyst system for the oxygen reduction reaction (ORR). Direct interaction between the sulfonic groups of Nafion and an Fe(III) meso-tetra(N-methyl-4-pyridyl) porphine chloride (Fe(III)TMPyP) compound was observed using FTIR and in situ UV–Vis spectroelectrochemical characterizations. A positive shift of the half wave potential value (E1/2) for ORR on the iron porphyrin catalyst (Fe(III)TMPyP) was observed upon addition of a specific quantity of Nafion ionomer on a glassy carbon working electrode, indicating not only a faster charge transfer rate but also the role of protonation in the oxygen reduction reaction (ORR) process. A membrane electrode assembly (MEA) was made as a sandwich of a Pt-coated anode, a Nafion® 212 membrane, and a Fe(III)TMPyP + Nafion ionomer-coated cathode. This three-dimensional catalysis system has been demonstrated to be working in a H2/O2 proton exchange membrane (PEM) fuel cell test.
- Full Text:
- Date Issued: 2012
Oxovanadium (IV)-catalysed oxidation of dibenzothiophene and 4, 6-dimethyldibenzothiophene
- Ogunlaja, Adeniyi S, Chidawanyika, Wadzanai J U, Antunes, Edith M, Fernandes, Manuel A, Nyokong, Tebello, Torto, Nelson, Tshentu, Zenixole R
- Authors: Ogunlaja, Adeniyi S , Chidawanyika, Wadzanai J U , Antunes, Edith M , Fernandes, Manuel A , Nyokong, Tebello , Torto, Nelson , Tshentu, Zenixole R
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/246025 , vital:51429 , xlink:href="https://doi.org/10.1039/C2DT31433A"
- Description: The reaction between [VIVOSO4] and the tetradentate N2O2-donor Schiff base ligand, N,N-bis(o-hydroxybenzaldehyde)phenylenediamine (sal-HBPD), obtained by the condensation of salicylaldehyde and o-phenylenediamine in a molar ratio of 2 : 1 respectively, resulted in the formation of [VIVO(sal-HBPD)]. The molecular structure of [VIVO(sal-HBPD)] was determined by single crystal X-ray diffraction, and confirmed the distorted square pyramidal geometry of the complex with the N2O2 binding mode of the tetradentate ligand. The formation of the polymer-supported p[VIVO(sal-AHBPD)] proceeded via the nitrosation of sal-HBPD, followed by the reduction with hydrogen to form an amine group that was then linked to Merrifield beads followed by the reaction with [VIVOSO4]. XPS and EPR were used to confirm the presence of oxovanadium(IV) within the beads. The BET surface area and porosity of the heterogeneous catalyst p[VIVO(sal-AHBPD)] were found to be 6.9 m2 g−1 and 180.8 Å respectively. Microanalysis, TG, UV-Vis and FT-IR were used for further characterization of both [VIVO(sal-HBPD)] and p[VIVO(sal-AHBPD)]. Oxidation of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was investigated using [VIVO(sal-HBPD)] and p[VIVO(sal-AHBPD)] as catalysts. Progress for oxidation of these model compounds was monitored with a gas chromatograph fitted with a flame ionization detector. The oxidation products were characterized using gas chromatography-mass spectrometry, microanalysis and NMR. Dibenzothiophene sulfone (DBTO2) and 4,6-dimethyldibenzothiophene sulfone (4,6-DMDBTO2) were found to be the main products of oxidation. Oxovanadium(IV) Schiff base microspherical beads, p[VIVO(sal-AHBPD)], were able to catalyse the oxidation of sulfur in dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) to a tune of 88.0% and 71.8% respectively after 3 h at 40 °C. These oxidation results show promise for potential application of this catalyst in the oxidative desulfurization of crude oils.
- Full Text:
- Date Issued: 2012
- Authors: Ogunlaja, Adeniyi S , Chidawanyika, Wadzanai J U , Antunes, Edith M , Fernandes, Manuel A , Nyokong, Tebello , Torto, Nelson , Tshentu, Zenixole R
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/246025 , vital:51429 , xlink:href="https://doi.org/10.1039/C2DT31433A"
- Description: The reaction between [VIVOSO4] and the tetradentate N2O2-donor Schiff base ligand, N,N-bis(o-hydroxybenzaldehyde)phenylenediamine (sal-HBPD), obtained by the condensation of salicylaldehyde and o-phenylenediamine in a molar ratio of 2 : 1 respectively, resulted in the formation of [VIVO(sal-HBPD)]. The molecular structure of [VIVO(sal-HBPD)] was determined by single crystal X-ray diffraction, and confirmed the distorted square pyramidal geometry of the complex with the N2O2 binding mode of the tetradentate ligand. The formation of the polymer-supported p[VIVO(sal-AHBPD)] proceeded via the nitrosation of sal-HBPD, followed by the reduction with hydrogen to form an amine group that was then linked to Merrifield beads followed by the reaction with [VIVOSO4]. XPS and EPR were used to confirm the presence of oxovanadium(IV) within the beads. The BET surface area and porosity of the heterogeneous catalyst p[VIVO(sal-AHBPD)] were found to be 6.9 m2 g−1 and 180.8 Å respectively. Microanalysis, TG, UV-Vis and FT-IR were used for further characterization of both [VIVO(sal-HBPD)] and p[VIVO(sal-AHBPD)]. Oxidation of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was investigated using [VIVO(sal-HBPD)] and p[VIVO(sal-AHBPD)] as catalysts. Progress for oxidation of these model compounds was monitored with a gas chromatograph fitted with a flame ionization detector. The oxidation products were characterized using gas chromatography-mass spectrometry, microanalysis and NMR. Dibenzothiophene sulfone (DBTO2) and 4,6-dimethyldibenzothiophene sulfone (4,6-DMDBTO2) were found to be the main products of oxidation. Oxovanadium(IV) Schiff base microspherical beads, p[VIVO(sal-AHBPD)], were able to catalyse the oxidation of sulfur in dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) to a tune of 88.0% and 71.8% respectively after 3 h at 40 °C. These oxidation results show promise for potential application of this catalyst in the oxidative desulfurization of crude oils.
- Full Text:
- Date Issued: 2012
Part II Zef/poor white kitsch chique
- Authors: Krueger, Anton
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/225745 , vital:49255 , xlink:href="https://doi.org/10.1080/17533171.2012.715484"
- Description: Ninja, who fronts the freak hip-hop band Die Antwoord, might not be quite what Desmond Tutu had in mind when he described South Africans as the “Rainbow People of God,”24 a happy harmonious amalgamation of different races. In his introduction to their seminal comic track “Enter the Ninja,” Ninja presents himself, rather, as a mongrel gutter dog, both embracing and parodying a syncretic fusion of the many different cultures and races of South Africa, celebrating as well as subverting the rainbow nation discourse. As he said in an interview with News24: “South African culture is quite a fucking fruit salad … a fucking fucked rainbow nation. South Africa's totally fucked … but in a cool way.”25 The cool side of being “fucked” in this way is “Zef.” Zef denotes a particular style of vulgar humor (in the usual sense of the word “vulgar,” but also with a nod to its origin in the Latin vulgaris for “mob” or “commoners”), which has been emerging more and more in South Africa during the past decade. It involves a way of presenting a persona in a purposefully degrading way, exaggerating one's appearance and mannerisms as low class, ill bred, and boorish. I would like to consider the recent popularity of “Zef” and examine its connection specifically to popular Afrikaans folk rock culture, a lineage of white poverty, and the feeling of disgrace experienced by many white Afrikaners after the end of apartheid.
- Full Text:
- Date Issued: 2012
- Authors: Krueger, Anton
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/225745 , vital:49255 , xlink:href="https://doi.org/10.1080/17533171.2012.715484"
- Description: Ninja, who fronts the freak hip-hop band Die Antwoord, might not be quite what Desmond Tutu had in mind when he described South Africans as the “Rainbow People of God,”24 a happy harmonious amalgamation of different races. In his introduction to their seminal comic track “Enter the Ninja,” Ninja presents himself, rather, as a mongrel gutter dog, both embracing and parodying a syncretic fusion of the many different cultures and races of South Africa, celebrating as well as subverting the rainbow nation discourse. As he said in an interview with News24: “South African culture is quite a fucking fruit salad … a fucking fucked rainbow nation. South Africa's totally fucked … but in a cool way.”25 The cool side of being “fucked” in this way is “Zef.” Zef denotes a particular style of vulgar humor (in the usual sense of the word “vulgar,” but also with a nod to its origin in the Latin vulgaris for “mob” or “commoners”), which has been emerging more and more in South Africa during the past decade. It involves a way of presenting a persona in a purposefully degrading way, exaggerating one's appearance and mannerisms as low class, ill bred, and boorish. I would like to consider the recent popularity of “Zef” and examine its connection specifically to popular Afrikaans folk rock culture, a lineage of white poverty, and the feeling of disgrace experienced by many white Afrikaners after the end of apartheid.
- Full Text:
- Date Issued: 2012
PhDs by publications
- Niven, Penelope, Grant, Carolyn
- Authors: Niven, Penelope , Grant, Carolyn
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/281108 , vital:55693 , xlink:href="https://doi.org/10.1080/13562517.2012.640086"
- Description: PhDs by publications are a relatively new model for doctoral research, especially in the context of the Humanities or Education. This paper describes two writers’ experiences of conducting doctoral studies in this genre and in these faculties. Each discover alternative ways of employing a body of published research papers in development of an overarching thesis. The writers argue that whilst it can be a pragmatic choice for some, PhDs by publications are more likely to be highly complex meta-narratives and that an overview of past research is fraught with theoretical, conceptual and epistemological challenges in the quest for coherence. They claim that the nomenclature ‘PhDs by publications’ or ‘through publications’ is misleading: in the epistemological space of Humanities or Education studies, this mode of doctoral research is more accurately represented as a ‘PhD with or alongside publications’. They conclude that the particular affordance of the model is that it privileges accounts of the process of knowledge building and of descriptions of the gradual emergence of ‘doctoralness’ in the person of the researcher.
- Full Text:
- Date Issued: 2012
- Authors: Niven, Penelope , Grant, Carolyn
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/281108 , vital:55693 , xlink:href="https://doi.org/10.1080/13562517.2012.640086"
- Description: PhDs by publications are a relatively new model for doctoral research, especially in the context of the Humanities or Education. This paper describes two writers’ experiences of conducting doctoral studies in this genre and in these faculties. Each discover alternative ways of employing a body of published research papers in development of an overarching thesis. The writers argue that whilst it can be a pragmatic choice for some, PhDs by publications are more likely to be highly complex meta-narratives and that an overview of past research is fraught with theoretical, conceptual and epistemological challenges in the quest for coherence. They claim that the nomenclature ‘PhDs by publications’ or ‘through publications’ is misleading: in the epistemological space of Humanities or Education studies, this mode of doctoral research is more accurately represented as a ‘PhD with or alongside publications’. They conclude that the particular affordance of the model is that it privileges accounts of the process of knowledge building and of descriptions of the gradual emergence of ‘doctoralness’ in the person of the researcher.
- Full Text:
- Date Issued: 2012
Photooxidation of 4-chlorophenol sensitized by lutetium tetraphenoxy phthalocyanine anchored on electrospun polystyrene polymer fiber
- Zugle, Ruphino, Antunes, Edith M, Khene, Samson M, Nyokong, Tebello
- Authors: Zugle, Ruphino , Antunes, Edith M , Khene, Samson M , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245787 , vital:51405 , xlink:href="https://doi.org/10.1016/j.poly.2011.11.005"
- Description: An electrospun polystyrene (PS) fiber incorporating tetraphenoxy phthalocyanine complex of lutetium (LuTPPc/PS) as a photosensitizer was applied for the degradation of 4-chlorophenol in aqueous solution in the presence of visible light. The photocatalytic activity of the LuTPPc in the fiber was compared to that of zinc phthalocyanine (ZnPc) incorporated into the PS fiber, and the former showed higher activity. UV–Vis spectral changes of sample solutions indicated transformation of the analyte with first order kinetics and half-lives that are within one and half hours for LuTPPc/PS. Products identified from the spectral changes and gas chromatography were benzoquinone, hydroquinone and 4,4′-dihydroxydiphenol suggesting that the photodegradation of 4-chlorophenol was through both Types I and II mechanisms.
- Full Text:
- Date Issued: 2012
- Authors: Zugle, Ruphino , Antunes, Edith M , Khene, Samson M , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245787 , vital:51405 , xlink:href="https://doi.org/10.1016/j.poly.2011.11.005"
- Description: An electrospun polystyrene (PS) fiber incorporating tetraphenoxy phthalocyanine complex of lutetium (LuTPPc/PS) as a photosensitizer was applied for the degradation of 4-chlorophenol in aqueous solution in the presence of visible light. The photocatalytic activity of the LuTPPc in the fiber was compared to that of zinc phthalocyanine (ZnPc) incorporated into the PS fiber, and the former showed higher activity. UV–Vis spectral changes of sample solutions indicated transformation of the analyte with first order kinetics and half-lives that are within one and half hours for LuTPPc/PS. Products identified from the spectral changes and gas chromatography were benzoquinone, hydroquinone and 4,4′-dihydroxydiphenol suggesting that the photodegradation of 4-chlorophenol was through both Types I and II mechanisms.
- Full Text:
- Date Issued: 2012
Photophysical and photochemical properties of novel phthalocyanines bearing non-peripherally substituted mercaptoquinoline moiety
- Yaşa, Göknur, Erdoğmuş, Ali, Uğur, Ahmet Lütf, Şener, M Kasım, Avcıata, Ulvi, Nyokong, Tebello
- Authors: Yaşa, Göknur , Erdoğmuş, Ali , Uğur, Ahmet Lütf , Şener, M Kasım , Avcıata, Ulvi , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244360 , vital:51250 , xlink:href="https://doi.org/10.1142/S1088424612500940"
- Description: The synthesis, photophysical and photochemical properties of nonperipherally (a) mercaptoquinoline substituted Zn(II), TiO(IV) and Mg(II) and quaternized Zn(II) phthalocyanines are described for the first time. These complexes (2 to 5) and their precursor are characterized by elemental analysis, FT-IR, 1 H NMR, electronic spectroscopy as well as mass spectroscopy. Complexes 2, 4 and 5 have good solubility in organic solvents such as CHCl3, DCM, DMSO, DMF, THF and toluene and are not aggregated in all solvents within a wide concentration range. Complex 3 showed very good solubility in water as well as DMSO and DMF. General trends are described for singlet oxygen, photodegradation and fluorescence quantum yields of these complexes in DMSO and DMF. While complex 2 has higher singlet oxygen and fluorescence quantum yields than 3, 4 and 5, complex 4 has higher fluorescence quantum yields in DMF and DMSO than 2, 3 and 5. The effect of the solvents and metal on the photophysical and photochemical parameters of the metallophthalocyanines are also reported.
- Full Text:
- Date Issued: 2012
- Authors: Yaşa, Göknur , Erdoğmuş, Ali , Uğur, Ahmet Lütf , Şener, M Kasım , Avcıata, Ulvi , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244360 , vital:51250 , xlink:href="https://doi.org/10.1142/S1088424612500940"
- Description: The synthesis, photophysical and photochemical properties of nonperipherally (a) mercaptoquinoline substituted Zn(II), TiO(IV) and Mg(II) and quaternized Zn(II) phthalocyanines are described for the first time. These complexes (2 to 5) and their precursor are characterized by elemental analysis, FT-IR, 1 H NMR, electronic spectroscopy as well as mass spectroscopy. Complexes 2, 4 and 5 have good solubility in organic solvents such as CHCl3, DCM, DMSO, DMF, THF and toluene and are not aggregated in all solvents within a wide concentration range. Complex 3 showed very good solubility in water as well as DMSO and DMF. General trends are described for singlet oxygen, photodegradation and fluorescence quantum yields of these complexes in DMSO and DMF. While complex 2 has higher singlet oxygen and fluorescence quantum yields than 3, 4 and 5, complex 4 has higher fluorescence quantum yields in DMF and DMSO than 2, 3 and 5. The effect of the solvents and metal on the photophysical and photochemical parameters of the metallophthalocyanines are also reported.
- Full Text:
- Date Issued: 2012
Photophysical and photochemical studies of sulfur containing phthalocyanine derivatives in the presence of folic acid
- Nombona, Nolwazi, Nyokong, Tebello
- Authors: Nombona, Nolwazi , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243180 , vital:51124 , xlink:href="https://doi.org/10.1016/j.ica.2012.03.051"
- Description: The syntheses of zinc and magnesium 9,16,23-tris-(5-trifluoromethyl-2-mercaptopyridine)-2-(carboxy)phthalocyaninato complexes are described for the first time. The photophysical and photochemical parameters of these molecules in the absence or presence of folic acid are compared to the corresponding oxygen bridged complexes and to 2,9,17,23-tetrakis-[(1,6-hexanedithiol)phthalocyaninato]zinc(II), [8,15,22-tris-(naptho)-2-(amidoethanethiol)phthalocyaninato]zinc(II) and zinc phthalocyanine tetrasulfonate. In the absence of folic acid, the complexes show relatively good triplet quantum yields (ranging from 0.52 to 0.88) in DMSO with reasonable triplet lifetime between 140 and 470 μs. The complexes showed high singlet oxygen quantum yield values ranging from 0.27 to 0.66 in the absence of folic acid. In the presence of folic acid, the triplet quantum yield values were between 0.37 and 0.75 and the lifetimes were significantly reduced (70–320 μs).
- Full Text:
- Date Issued: 2012
- Authors: Nombona, Nolwazi , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243180 , vital:51124 , xlink:href="https://doi.org/10.1016/j.ica.2012.03.051"
- Description: The syntheses of zinc and magnesium 9,16,23-tris-(5-trifluoromethyl-2-mercaptopyridine)-2-(carboxy)phthalocyaninato complexes are described for the first time. The photophysical and photochemical parameters of these molecules in the absence or presence of folic acid are compared to the corresponding oxygen bridged complexes and to 2,9,17,23-tetrakis-[(1,6-hexanedithiol)phthalocyaninato]zinc(II), [8,15,22-tris-(naptho)-2-(amidoethanethiol)phthalocyaninato]zinc(II) and zinc phthalocyanine tetrasulfonate. In the absence of folic acid, the complexes show relatively good triplet quantum yields (ranging from 0.52 to 0.88) in DMSO with reasonable triplet lifetime between 140 and 470 μs. The complexes showed high singlet oxygen quantum yield values ranging from 0.27 to 0.66 in the absence of folic acid. In the presence of folic acid, the triplet quantum yield values were between 0.37 and 0.75 and the lifetimes were significantly reduced (70–320 μs).
- Full Text:
- Date Issued: 2012
Photophysics and photochemistry of octaglucosylated zinc phthalocyanine derivatives
- Iqbal, Zafar, Ogunsipe, Abimbola, Nyokong, Tebello, Lyubimtsev, Alexey, Hanack, Michael, Ziegler, Thomas
- Authors: Iqbal, Zafar , Ogunsipe, Abimbola , Nyokong, Tebello , Lyubimtsev, Alexey , Hanack, Michael , Ziegler, Thomas
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244416 , vital:51255 , xlink:href="https://doi.org/10.1142/S1088424612500630"
- Description: The ground state electronic absorption spectra, photophysics and photochemistry of amphiphilic octaglucosylated zinc phthalocyanines containing oxygen or sulfur bridges are presented. Triplet quantum yield values for the two dyes (in DMF and DMSO) vary between 0.71 and 0.84, while singlet quantum yield values lie between 0.63 and 0.75. Fluorescence lifetimes were determined experimentally by time correlated single photon counting and semi-empirically by fluorescence quenching techniques; and values from both methods were within the same range. Kinetic data were obtained for the quenching of the triplet state of the phthalocyanines by ground state molecular oxygen; the bimolecular collisional quenching rate constant range between 2.35 × 108 and 1.13 × 109 M-1.s-1. These values suggest that triplet states of the dyes are effectively quenched by ground molecular oxygen.
- Full Text:
- Date Issued: 2012
- Authors: Iqbal, Zafar , Ogunsipe, Abimbola , Nyokong, Tebello , Lyubimtsev, Alexey , Hanack, Michael , Ziegler, Thomas
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244416 , vital:51255 , xlink:href="https://doi.org/10.1142/S1088424612500630"
- Description: The ground state electronic absorption spectra, photophysics and photochemistry of amphiphilic octaglucosylated zinc phthalocyanines containing oxygen or sulfur bridges are presented. Triplet quantum yield values for the two dyes (in DMF and DMSO) vary between 0.71 and 0.84, while singlet quantum yield values lie between 0.63 and 0.75. Fluorescence lifetimes were determined experimentally by time correlated single photon counting and semi-empirically by fluorescence quenching techniques; and values from both methods were within the same range. Kinetic data were obtained for the quenching of the triplet state of the phthalocyanines by ground state molecular oxygen; the bimolecular collisional quenching rate constant range between 2.35 × 108 and 1.13 × 109 M-1.s-1. These values suggest that triplet states of the dyes are effectively quenched by ground molecular oxygen.
- Full Text:
- Date Issued: 2012
Physico-chemical properties of lutetium phthalocyanine complexes in solution and in solid polystyrene polymer fibers and their application in photoconversion of 4-nitrophenol
- Zugle, Ruphino, Nyokong, Tebello
- Authors: Zugle, Ruphino , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243520 , vital:51160 , xlink:href="https://doi.org/10.1016/j.molcata.2012.02.010"
- Description: The photophysical and photochemical behavior of two phthalocyanine complexes of lutetium peripherally substituted with tetraphenoxy and tetra-2-pyridiloxy groups were studied in solution and when dispersed in polystyrene polymer fiber. The phthalocyanines were found not to fluoresce significantly in solution and not at all within the fiber matrix as compared with standard unsubstituted zinc phthalocyanine. They showed very promising photoactivity in solution with high singlet oxygen quantum yields. Their photoactivity within the polymer fiber matrix was also demonstrated with the photoconversion of 4-nitrophenol, a water pollutant. The photodegradation process with both phthalocyanines follows first order kinetics similar to that observed for the zinc phthalocyanine and the photo-products were found to be hydroquinone, benzoquinone and 4-nitrocatechol.
- Full Text:
- Date Issued: 2012
- Authors: Zugle, Ruphino , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243520 , vital:51160 , xlink:href="https://doi.org/10.1016/j.molcata.2012.02.010"
- Description: The photophysical and photochemical behavior of two phthalocyanine complexes of lutetium peripherally substituted with tetraphenoxy and tetra-2-pyridiloxy groups were studied in solution and when dispersed in polystyrene polymer fiber. The phthalocyanines were found not to fluoresce significantly in solution and not at all within the fiber matrix as compared with standard unsubstituted zinc phthalocyanine. They showed very promising photoactivity in solution with high singlet oxygen quantum yields. Their photoactivity within the polymer fiber matrix was also demonstrated with the photoconversion of 4-nitrophenol, a water pollutant. The photodegradation process with both phthalocyanines follows first order kinetics similar to that observed for the zinc phthalocyanine and the photo-products were found to be hydroquinone, benzoquinone and 4-nitrocatechol.
- Full Text:
- Date Issued: 2012
Reverse saturation absorption spectra and optical limiting properties of chlorinated tetrasubstituted phthalocyanines containing different metals
- Tuhl, Ahmad, Manaa, Hacene, Makhseed, Saad, Al-Awadi, Nouria, Matthew, Jacob, Ibrahim, Hamada Mohamed, Nyokong, Tebello, Behbehani, Haider
- Authors: Tuhl, Ahmad , Manaa, Hacene , Makhseed, Saad , Al-Awadi, Nouria , Matthew, Jacob , Ibrahim, Hamada Mohamed , Nyokong, Tebello , Behbehani, Haider
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243498 , vital:51158 , xlink:href="https://doi.org/10.1016/j.optmat.2012.05.018"
- Description: A highly non-aggregated series of peripherally tetra(2,6-diisopropylphenoxy) substituted phthalocyanines (Pcs) containing different metals (Al, Ga, In and Zn) were prepared and their nonlinear optical properties (NLO), including the optical limiting behavior were investigated. This study explores the effect of the implanted metals along with the peripheral chlorine atoms on the NLO of the prepared complexes, thereby improving their optical limiting performance. The best wavelength at which the Pc complex exhibits the strongest nonlinear effect was determined over the low absorption window region (420–590 nm) comprised between the Q and B bands using a nanosecond pulsed laser with the aid of a Z-scan technique. The excited state absorption cross sections (σeff) have been found to be wavelength dependent with common double peaks at 505 nm and around 485 nm and the highest value was calculated for Pc1–In (1.1 × 10−16 cm2). The figure of merit spectra show different spectral structure when compared to the excited state absorption spectra and the largest figure of merit value was found to be around 107 for Pc1–In derivative. In full agreement with reverse saturation results, the optical limiting measurements, carried out at 485 nm and 532 nm for each derivative, show very low optical limiting thresholds at the former wavelength. In the continuous wave excitation regime, the Z-scan measurements, which were carried out at 632.8 and 532 nm, showed strong refractive and absorptive nonlinear effects.
- Full Text:
- Date Issued: 2012
- Authors: Tuhl, Ahmad , Manaa, Hacene , Makhseed, Saad , Al-Awadi, Nouria , Matthew, Jacob , Ibrahim, Hamada Mohamed , Nyokong, Tebello , Behbehani, Haider
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243498 , vital:51158 , xlink:href="https://doi.org/10.1016/j.optmat.2012.05.018"
- Description: A highly non-aggregated series of peripherally tetra(2,6-diisopropylphenoxy) substituted phthalocyanines (Pcs) containing different metals (Al, Ga, In and Zn) were prepared and their nonlinear optical properties (NLO), including the optical limiting behavior were investigated. This study explores the effect of the implanted metals along with the peripheral chlorine atoms on the NLO of the prepared complexes, thereby improving their optical limiting performance. The best wavelength at which the Pc complex exhibits the strongest nonlinear effect was determined over the low absorption window region (420–590 nm) comprised between the Q and B bands using a nanosecond pulsed laser with the aid of a Z-scan technique. The excited state absorption cross sections (σeff) have been found to be wavelength dependent with common double peaks at 505 nm and around 485 nm and the highest value was calculated for Pc1–In (1.1 × 10−16 cm2). The figure of merit spectra show different spectral structure when compared to the excited state absorption spectra and the largest figure of merit value was found to be around 107 for Pc1–In derivative. In full agreement with reverse saturation results, the optical limiting measurements, carried out at 485 nm and 532 nm for each derivative, show very low optical limiting thresholds at the former wavelength. In the continuous wave excitation regime, the Z-scan measurements, which were carried out at 632.8 and 532 nm, showed strong refractive and absorptive nonlinear effects.
- Full Text:
- Date Issued: 2012
Schottky barrier diode parameters of Ag/MgPc/p-Si structure
- Canlıca, Mevlüde, Coskun, Mustafa, Altındal, Ahmet, Nyokong, Tebello
- Authors: Canlıca, Mevlüde , Coskun, Mustafa , Altındal, Ahmet , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245820 , vital:51408 , xlink:href="https://doi.org/10.1142/S1088424612500824"
- Description: An Ag/Pc/p-Si Schottky barrier (SB) diode was fabricated. The current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G-V) measurements were carried out to determine the characteristic parameters such as barrier height, ideality factor and series resistance of the SB diode. The non-linear behavior of ln (I) vs. ln (V) and ln (I/V) vs. V1/2 plots indicated that the thermoionic emission theory can be applied to evaluate junction parameters for the investigated SB diode rather than space-charge limited conduction (SCLC) mechanism and bulk-limited Poole–Frenkel emission. The bulk doping concentration NB and fixed oxide charges Nf was determined from the measured high frequency C-V curve and was found to be 9.5 × 1014 cm-3 and 2.3 × 1013 cm-2, respectively. The values of barrier height obtained from Norde's function were compared with those from the forward bias current-voltage characteristic, and it was seen that there was a good agreement between barrier heights from both methods.
- Full Text:
- Date Issued: 2012
- Authors: Canlıca, Mevlüde , Coskun, Mustafa , Altındal, Ahmet , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245820 , vital:51408 , xlink:href="https://doi.org/10.1142/S1088424612500824"
- Description: An Ag/Pc/p-Si Schottky barrier (SB) diode was fabricated. The current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G-V) measurements were carried out to determine the characteristic parameters such as barrier height, ideality factor and series resistance of the SB diode. The non-linear behavior of ln (I) vs. ln (V) and ln (I/V) vs. V1/2 plots indicated that the thermoionic emission theory can be applied to evaluate junction parameters for the investigated SB diode rather than space-charge limited conduction (SCLC) mechanism and bulk-limited Poole–Frenkel emission. The bulk doping concentration NB and fixed oxide charges Nf was determined from the measured high frequency C-V curve and was found to be 9.5 × 1014 cm-3 and 2.3 × 1013 cm-2, respectively. The values of barrier height obtained from Norde's function were compared with those from the forward bias current-voltage characteristic, and it was seen that there was a good agreement between barrier heights from both methods.
- Full Text:
- Date Issued: 2012
Single walled carbon nanotubes functionalized with nickel phthalocyanines
- Khene, Samson, Nyokong, Tebello
- Authors: Khene, Samson , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245843 , vital:51410 , xlink:href="https://doi.org/10.1142/S1088424611004439"
- Description: In this work we report on electrochemical behavior of nickel phthalocyanine derivatives tetrasubstituted peripherally and non-peripherally with hydroxy and used to modify single walled carbon nanotubes. Nickel phthalocyanine complex octasubstituted at the peripheral positions with hydroxy groups was also used to modify single walled carbon nanotubes. Nickel phthalocyanine complex tetrasubstituted with amino groups at peripheral position was covalently and non-covalently linked to single walled carbon nanotubes. All the conjugates of nickel phthalocyanine derivatives with single walled carbon nanotubes were used for the electro oxidation of 4-chlorophenol. The nickel phthalocyanine octabsubstituted with hydroxy groups at the non-peripheral positions gave the best current response and the best resistance against electrode fouling for the oxidation of 4-chlorophenol.
- Full Text:
- Date Issued: 2012
- Authors: Khene, Samson , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245843 , vital:51410 , xlink:href="https://doi.org/10.1142/S1088424611004439"
- Description: In this work we report on electrochemical behavior of nickel phthalocyanine derivatives tetrasubstituted peripherally and non-peripherally with hydroxy and used to modify single walled carbon nanotubes. Nickel phthalocyanine complex octasubstituted at the peripheral positions with hydroxy groups was also used to modify single walled carbon nanotubes. Nickel phthalocyanine complex tetrasubstituted with amino groups at peripheral position was covalently and non-covalently linked to single walled carbon nanotubes. All the conjugates of nickel phthalocyanine derivatives with single walled carbon nanotubes were used for the electro oxidation of 4-chlorophenol. The nickel phthalocyanine octabsubstituted with hydroxy groups at the non-peripheral positions gave the best current response and the best resistance against electrode fouling for the oxidation of 4-chlorophenol.
- Full Text:
- Date Issued: 2012
Spectral, photophysical and photochemical properties of tetra-and octaglycosylated zinc phthalocyanines
- Iqbal, Zafar, Masilela, Nkosiphile, Nyokong, Tebello, Lyubimtsev, Alexey, Hanack, Michael, Ziegler, Thomas
- Authors: Iqbal, Zafar , Masilela, Nkosiphile , Nyokong, Tebello , Lyubimtsev, Alexey , Hanack, Michael , Ziegler, Thomas
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244428 , vital:51256 , xlink:href="https://doi.org/10.1039/c2pp05348a"
- Description: Photophysical and photochemical properties of a series of tetra- and octaglycosylated zinc phthalocyanines (ZnPcs) substituted with glucose and galactose moieties have been reported. Spectral properties of these phthalocyanines are compared in DMSO. Absorption spectra of the non-peripherally tetra-substituted ZnPcs 2 showed a significant red shift in their Q-band maxima as compared to the peripherally substituted analog 1. All the complexes gave high triplet quantum yields ranging from 0.68 to 0.88, whereas triplet lifetimes were in the range of 100–430 µs in argon-saturated solutions. The octagalactosylated ZnPc 3b showed the highest triplet quantum yield and singlet oxygen quantum yield of 0.88 and 0.69, respectively. The fluorescence quantum yields and lifetimes of all the compounds under investigation were within the range of zinc phthalocyanine complexes.
- Full Text:
- Date Issued: 2012
- Authors: Iqbal, Zafar , Masilela, Nkosiphile , Nyokong, Tebello , Lyubimtsev, Alexey , Hanack, Michael , Ziegler, Thomas
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244428 , vital:51256 , xlink:href="https://doi.org/10.1039/c2pp05348a"
- Description: Photophysical and photochemical properties of a series of tetra- and octaglycosylated zinc phthalocyanines (ZnPcs) substituted with glucose and galactose moieties have been reported. Spectral properties of these phthalocyanines are compared in DMSO. Absorption spectra of the non-peripherally tetra-substituted ZnPcs 2 showed a significant red shift in their Q-band maxima as compared to the peripherally substituted analog 1. All the complexes gave high triplet quantum yields ranging from 0.68 to 0.88, whereas triplet lifetimes were in the range of 100–430 µs in argon-saturated solutions. The octagalactosylated ZnPc 3b showed the highest triplet quantum yield and singlet oxygen quantum yield of 0.88 and 0.69, respectively. The fluorescence quantum yields and lifetimes of all the compounds under investigation were within the range of zinc phthalocyanine complexes.
- Full Text:
- Date Issued: 2012
Spectroscopic and physicochemical behavior of magnesium phthalocyanine derivatives mono-substituted with a carboxylic acid group
- Nombona, Nolwazi, Chidawanyika, Wadzanai J U, Nyokong, Tebello
- Authors: Nombona, Nolwazi , Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244450 , vital:51258 , xlink:href="https://doi.org/10.1016/j.molstruc.2011.12.051"
- Description: This work reports on the synthesis of novel unsymmetrically substituted magnesium phthalocyanine complexes containing one carboxyl group. The physicochemical behavior of these complexes were compared with those of their unmetallated and zinc counterparts. The MgPcs showed interesting absorption spectra with [8,15,22-Tris-(naphtho)-4,5-(3-carboxy-1,2-dioxyphenyl)phthalocyaninato]magnesium (II) showing a large split in the Q band whereas [8,15,22-Tris-(naphtho)-2-(carboxy) phthalocyaninato]magnesium(II) presented only a small splitting. The magnesium phthalocyanine derivatives displayed higher fluorescence quantum yields compared to unmetallated and zinc phthalocyanine counterparts. The latter gave admirable triplet and singlet oxygen quantum yields. These molecules can distinctly be employed in the field of photodynamic therapy in combination with fluorescence imaging.
- Full Text:
- Date Issued: 2012
- Authors: Nombona, Nolwazi , Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244450 , vital:51258 , xlink:href="https://doi.org/10.1016/j.molstruc.2011.12.051"
- Description: This work reports on the synthesis of novel unsymmetrically substituted magnesium phthalocyanine complexes containing one carboxyl group. The physicochemical behavior of these complexes were compared with those of their unmetallated and zinc counterparts. The MgPcs showed interesting absorption spectra with [8,15,22-Tris-(naphtho)-4,5-(3-carboxy-1,2-dioxyphenyl)phthalocyaninato]magnesium (II) showing a large split in the Q band whereas [8,15,22-Tris-(naphtho)-2-(carboxy) phthalocyaninato]magnesium(II) presented only a small splitting. The magnesium phthalocyanine derivatives displayed higher fluorescence quantum yields compared to unmetallated and zinc phthalocyanine counterparts. The latter gave admirable triplet and singlet oxygen quantum yields. These molecules can distinctly be employed in the field of photodynamic therapy in combination with fluorescence imaging.
- Full Text:
- Date Issued: 2012
Students’ navigation of the uncharted territories of academic writing
- Bharuthram, Sharita, McKenna, Sioux
- Authors: Bharuthram, Sharita , McKenna, Sioux
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187373 , vital:44626 , xlink:href="https://doi.org/10.1080/18146627.2012.742651"
- Description: Many students enter tertiary education unfamiliar with the ‘norms and conventions’ of their disciplines. Research into academic literacies has shown that in order to succeed in their studies, students are expected to conform to these norms and conventions, which are often unrecognized or seen as ‘common sense’ by lecturers. Students have to develop their own ‘map’ of their programme’s expectations in order to make sense of the seemingly mysterious practices they are expected to take on. This study, undertaken at a University of Technology in South Africa, details students’ perceptions of their writing difficulties and their attempts to navigate their way through various writing tasks. The findings reveal that students experience a range of difficulties and that the students often feel unsupported in their travails with academic writing.
- Full Text:
- Date Issued: 2012
- Authors: Bharuthram, Sharita , McKenna, Sioux
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187373 , vital:44626 , xlink:href="https://doi.org/10.1080/18146627.2012.742651"
- Description: Many students enter tertiary education unfamiliar with the ‘norms and conventions’ of their disciplines. Research into academic literacies has shown that in order to succeed in their studies, students are expected to conform to these norms and conventions, which are often unrecognized or seen as ‘common sense’ by lecturers. Students have to develop their own ‘map’ of their programme’s expectations in order to make sense of the seemingly mysterious practices they are expected to take on. This study, undertaken at a University of Technology in South Africa, details students’ perceptions of their writing difficulties and their attempts to navigate their way through various writing tasks. The findings reveal that students experience a range of difficulties and that the students often feel unsupported in their travails with academic writing.
- Full Text:
- Date Issued: 2012
Syntheses, protonation constants and antimicrobial activity of 2-substituted N-alkylimidazole derivatives
- Kleyi, Phumelele, Walmsley, Ryan S, Gundhla, Isaac Z, Walmsley, Tara A, Jauka, Tembisa I, Dames, Joanna F, Walker, Roderick B, Torto, Nelson, Tshentu, Zenixole R
- Authors: Kleyi, Phumelele , Walmsley, Ryan S , Gundhla, Isaac Z , Walmsley, Tara A , Jauka, Tembisa I , Dames, Joanna F , Walker, Roderick B , Torto, Nelson , Tshentu, Zenixole R
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184066 , vital:44165 , xlink:href="https://www.ajol.info/index.php/sajc/article/view/123858"
- Description: A series of N-alkylimidazole-2-carboxylic acid, N-alkylimidazole-2-carboxaldehyde and N-alkylimidazole-2-methanol derivatives [alkyl = benzyl, methyl, ethyl, propyl, butyl, heptyl, octyl and decyl] have been synthesized and the protonation constants determined. The antimicrobial properties of the compounds were tested against Gram-negative (Escherichi coli), Gram-positive (Staphylococcus aureus and Bacillus subtilis subsp. spizizenii) bacterial strains and yeast (C. albicans). Both the disk diffusion and broth microdilution methods for testing the antimicrobial activity showed that N-alkylation of imidazole with longer alkyl chains and the substitution with low pKa group at 2-position resulted in enhanced antimicrobial activity. Particularly, the N-alkylimidazole-2-carboxylic acids exhibited the best antimicrobial activity due to the low pKa of the carboxylic acid moiety. Generally, all the N-alkylimidazole derivatives were most active against the Gram-positive bacteria [S. aureus (MIC = 5–160 µg mL–1) and B. subtilis subsp. spizizenii (5–20 µg mL–1)], with the latter more susceptible. All the compounds showed poor antimicrobial activity against both Gram-negative (E. coli, MIC = 0.15 to >2500 µg mL–1) bacteria and all the compounds were inactive against the yeast (Candida albicans).
- Full Text:
- Date Issued: 2012
- Authors: Kleyi, Phumelele , Walmsley, Ryan S , Gundhla, Isaac Z , Walmsley, Tara A , Jauka, Tembisa I , Dames, Joanna F , Walker, Roderick B , Torto, Nelson , Tshentu, Zenixole R
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184066 , vital:44165 , xlink:href="https://www.ajol.info/index.php/sajc/article/view/123858"
- Description: A series of N-alkylimidazole-2-carboxylic acid, N-alkylimidazole-2-carboxaldehyde and N-alkylimidazole-2-methanol derivatives [alkyl = benzyl, methyl, ethyl, propyl, butyl, heptyl, octyl and decyl] have been synthesized and the protonation constants determined. The antimicrobial properties of the compounds were tested against Gram-negative (Escherichi coli), Gram-positive (Staphylococcus aureus and Bacillus subtilis subsp. spizizenii) bacterial strains and yeast (C. albicans). Both the disk diffusion and broth microdilution methods for testing the antimicrobial activity showed that N-alkylation of imidazole with longer alkyl chains and the substitution with low pKa group at 2-position resulted in enhanced antimicrobial activity. Particularly, the N-alkylimidazole-2-carboxylic acids exhibited the best antimicrobial activity due to the low pKa of the carboxylic acid moiety. Generally, all the N-alkylimidazole derivatives were most active against the Gram-positive bacteria [S. aureus (MIC = 5–160 µg mL–1) and B. subtilis subsp. spizizenii (5–20 µg mL–1)], with the latter more susceptible. All the compounds showed poor antimicrobial activity against both Gram-negative (E. coli, MIC = 0.15 to >2500 µg mL–1) bacteria and all the compounds were inactive against the yeast (Candida albicans).
- Full Text:
- Date Issued: 2012
Synthesis and photophysical behavior of a novel zinc phthalocyanine containing a single carboxylic acid and three phenylthio substituents
- Forteath, Shaun, Antunes, Edith M, Chidawanyika, Wadzanai J U, Nyokong, Tebello
- Authors: Forteath, Shaun , Antunes, Edith M , Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243207 , vital:51127 , xlink:href="https://doi.org/10.1016/j.jlumin.2012.03.050"
- Description: Zinc 2, (3)-tri-(phenylthio)-2, (3)-carboxy phthalocyanine (ZnPc(COOH)(SPh)3), zinc 2, (3)-tetra-(phenylthio) phthalocyanine (ZnPc(SPh)4) and 2, (3)-tetra-(phenylthio) phthalocyanine (H2Pc(SPh)4) were synthesized and their photophysical behavior were compared with those of a number of zinc phthalocyanine (ZnPc) derivatives. ZnPc(COOH)(SPh)3 and ZnPc(SPh)4 had similar fluorescence (ΦF=0.14) and triplet state (ΦT=0.65) quantum yields in dimethylsulfoxide, hence showing no effects of the replacement of one of the phenylthio groups with a carboxylic acid group. ZnPc(COOH)(SPh)3 displayed a slightly shorter triplet lifetime (τT=331 μs) than ZnPc (τT=350 μs) in DMSO, but within the range of ZnPc derivatives. The triplet lifetime for ZnPc(COOH)(SPh)3 is much longer than for the symmetrical derivative (ZnPc(SPh)4) with τT=149 μs in DMSO.
- Full Text:
- Date Issued: 2012
- Authors: Forteath, Shaun , Antunes, Edith M , Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243207 , vital:51127 , xlink:href="https://doi.org/10.1016/j.jlumin.2012.03.050"
- Description: Zinc 2, (3)-tri-(phenylthio)-2, (3)-carboxy phthalocyanine (ZnPc(COOH)(SPh)3), zinc 2, (3)-tetra-(phenylthio) phthalocyanine (ZnPc(SPh)4) and 2, (3)-tetra-(phenylthio) phthalocyanine (H2Pc(SPh)4) were synthesized and their photophysical behavior were compared with those of a number of zinc phthalocyanine (ZnPc) derivatives. ZnPc(COOH)(SPh)3 and ZnPc(SPh)4 had similar fluorescence (ΦF=0.14) and triplet state (ΦT=0.65) quantum yields in dimethylsulfoxide, hence showing no effects of the replacement of one of the phenylthio groups with a carboxylic acid group. ZnPc(COOH)(SPh)3 displayed a slightly shorter triplet lifetime (τT=331 μs) than ZnPc (τT=350 μs) in DMSO, but within the range of ZnPc derivatives. The triplet lifetime for ZnPc(COOH)(SPh)3 is much longer than for the symmetrical derivative (ZnPc(SPh)4) with τT=149 μs in DMSO.
- Full Text:
- Date Issued: 2012
Synthesis and photophysical properties of covalent conjugates of aqua platinum (II) and octacarboxy-substituted zinc phthalocyanine
- Bulgakov, Roman A, Kuznetsova, Nina A, Dolotova, Olga V, Solovieva, Ludmila I, Mack, John, Chidawanyika, Wadzanai J U, Kaliya, Oleg L, Nyokong, Tebello
- Authors: Bulgakov, Roman A , Kuznetsova, Nina A , Dolotova, Olga V , Solovieva, Ludmila I , Mack, John , Chidawanyika, Wadzanai J U , Kaliya, Oleg L , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242726 , vital:51073 , xlink:href="https://doi.org/10.1142/S1088424612501209"
- Description: New covalent conjugates of aqua platinum(II) and octacarboxy-substituted zinc phthalocyanine, bearing one, two, three and four aqua platinum moieties on the periphery of the Pc ligand have been synthesized and characterized. The effect of the stepwise introduction of the aqua platinums on the photophysical and photochemical properties of these compounds has been investigated in dimethylsulfoxide solution. It has been found that aqua platinum moieties have only a limited effect on the dynamics of the singlet and triplet excited states, on the ability to sensitize singlet oxygen formation and on the photostability. Each conjugate has a high singlet oxygen quantum yield (ΦΔ 0.51–0.62) and thus retains potential for use as a dual action anticancer drugs by acting as a sensitizer for PDT in addition to the likely chemotherapeutic effects of the Pt(II) complexes.
- Full Text:
- Date Issued: 2012
- Authors: Bulgakov, Roman A , Kuznetsova, Nina A , Dolotova, Olga V , Solovieva, Ludmila I , Mack, John , Chidawanyika, Wadzanai J U , Kaliya, Oleg L , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242726 , vital:51073 , xlink:href="https://doi.org/10.1142/S1088424612501209"
- Description: New covalent conjugates of aqua platinum(II) and octacarboxy-substituted zinc phthalocyanine, bearing one, two, three and four aqua platinum moieties on the periphery of the Pc ligand have been synthesized and characterized. The effect of the stepwise introduction of the aqua platinums on the photophysical and photochemical properties of these compounds has been investigated in dimethylsulfoxide solution. It has been found that aqua platinum moieties have only a limited effect on the dynamics of the singlet and triplet excited states, on the ability to sensitize singlet oxygen formation and on the photostability. Each conjugate has a high singlet oxygen quantum yield (ΦΔ 0.51–0.62) and thus retains potential for use as a dual action anticancer drugs by acting as a sensitizer for PDT in addition to the likely chemotherapeutic effects of the Pt(II) complexes.
- Full Text:
- Date Issued: 2012