Polyamide nanofiber membranes functionalized with zinc phthalocyanines
- Goethals, Annelies, Mugadza, Tawanda, Arslanoglu, Yasin, Zugle, Ruphino, Antunes, Edith M, Van Hulle, Stijn W, Nyokong, Tebello, De Clerck, Karen
- Authors: Goethals, Annelies , Mugadza, Tawanda , Arslanoglu, Yasin , Zugle, Ruphino , Antunes, Edith M , Van Hulle, Stijn W , Nyokong, Tebello , De Clerck, Karen
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241505 , vital:50945 , xlink:href="https://doi.org/10.1002/app.40486"
- Description: Electrospinning is an efficient method for the production of polyamide nanofiber membranes that are suitable for water filtration. Previous studies have shown that nanofiber membranes have high clean water permeability. The pathogen removal efficiency can be improved by functionalization with (organic) biocides. However, these membranes, like other membranes, are vulnerable to fouling which reduces the filtration efficiency. Therefore the present article investigates the potential of zinc phthalocyanines, which can produce singlet oxygen in the presence of visible light, as a functionalizing agent. The polyamide nanofiber membranes were functionalized with phthalocyanines using both a pre-functionalizing and post-functionalizing method. Only the post-functionalization method shows to result in nanofiber membranes capable of producing singlet oxygen. After 30 min 45% of 1,2-diphenylisobenzofuran (DPBF), used as an oxygen quencher, was removed by reaction with singlet oxygen. This resulted in a removal rate of 0.33 mol DBPF mol−1Zn min−1. During short term leaching tests, phthalocyanines could not be detected.
- Full Text:
- Date Issued: 2014
- Authors: Goethals, Annelies , Mugadza, Tawanda , Arslanoglu, Yasin , Zugle, Ruphino , Antunes, Edith M , Van Hulle, Stijn W , Nyokong, Tebello , De Clerck, Karen
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241505 , vital:50945 , xlink:href="https://doi.org/10.1002/app.40486"
- Description: Electrospinning is an efficient method for the production of polyamide nanofiber membranes that are suitable for water filtration. Previous studies have shown that nanofiber membranes have high clean water permeability. The pathogen removal efficiency can be improved by functionalization with (organic) biocides. However, these membranes, like other membranes, are vulnerable to fouling which reduces the filtration efficiency. Therefore the present article investigates the potential of zinc phthalocyanines, which can produce singlet oxygen in the presence of visible light, as a functionalizing agent. The polyamide nanofiber membranes were functionalized with phthalocyanines using both a pre-functionalizing and post-functionalizing method. Only the post-functionalization method shows to result in nanofiber membranes capable of producing singlet oxygen. After 30 min 45% of 1,2-diphenylisobenzofuran (DPBF), used as an oxygen quencher, was removed by reaction with singlet oxygen. This resulted in a removal rate of 0.33 mol DBPF mol−1Zn min−1. During short term leaching tests, phthalocyanines could not be detected.
- Full Text:
- Date Issued: 2014
Forced degradation studies of clobetasol 17‐propionate in methanol, propylene glycol, as bulk drug and cream formulations by RP‐HPLC
- Fauzee, Ayesha F B, Walker, Roderick B
- Authors: Fauzee, Ayesha F B , Walker, Roderick B
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184005 , vital:44154 , xlink:href="https://doi.org/10.1002/jssc.201200969"
- Description: A rapid, simple, stability-indicating forced degradation study of clobetasol 17-propionate was conducted using RP-HPLC. The method was used to analyze clobetasol 17-propionate in methanol, propylene glycol, and a cream formulation. Isocratic elution of clobetasol and its degradation products was achieved using a Nova-Pak® 4 μm C18 150 mm × 3.9 mm id cartridge column and a mobile phase of methanol: water (68:32 v/v) at a flow rate of 0.9 mL min−1. Quantitation was achieved with UV detection at 239 nm. Nondegraded clobetasol was eluted at a retention time of 6.0 min. Clobetasol 17-propionate was subjected to different stress conditions viz., acidic, basic, heat, oxidation, light, and neutral hydrolysis. The greatest degradation occurred under strong base and oxidative conditions. Strong base-degraded clobetasol produced additional peaks at retention times of 1.8, 4.0, 5.0, and 8.0 min and clobetasol oxidation degradation peaks eluted at 2.2 and 24 min. Complete validation was performed for linearity, accuracy, and precision over the concentration range 0.15–15 μg mL−1. All data were analyzed statistically and this RP-HPLC method proved to be accurate, precise, linear, and stability indicating for the quantitation of clobetasol 17-propionate in methanol, propylene glycol, and cream formulations.
- Full Text:
- Date Issued: 2013
- Authors: Fauzee, Ayesha F B , Walker, Roderick B
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184005 , vital:44154 , xlink:href="https://doi.org/10.1002/jssc.201200969"
- Description: A rapid, simple, stability-indicating forced degradation study of clobetasol 17-propionate was conducted using RP-HPLC. The method was used to analyze clobetasol 17-propionate in methanol, propylene glycol, and a cream formulation. Isocratic elution of clobetasol and its degradation products was achieved using a Nova-Pak® 4 μm C18 150 mm × 3.9 mm id cartridge column and a mobile phase of methanol: water (68:32 v/v) at a flow rate of 0.9 mL min−1. Quantitation was achieved with UV detection at 239 nm. Nondegraded clobetasol was eluted at a retention time of 6.0 min. Clobetasol 17-propionate was subjected to different stress conditions viz., acidic, basic, heat, oxidation, light, and neutral hydrolysis. The greatest degradation occurred under strong base and oxidative conditions. Strong base-degraded clobetasol produced additional peaks at retention times of 1.8, 4.0, 5.0, and 8.0 min and clobetasol oxidation degradation peaks eluted at 2.2 and 24 min. Complete validation was performed for linearity, accuracy, and precision over the concentration range 0.15–15 μg mL−1. All data were analyzed statistically and this RP-HPLC method proved to be accurate, precise, linear, and stability indicating for the quantitation of clobetasol 17-propionate in methanol, propylene glycol, and cream formulations.
- Full Text:
- Date Issued: 2013
The challenges of alleviating poverty through ecological restoration: Insights from South Africa's “working for water” program
- McConnachie, Matthew M, Cowling, Richard M, Shackleton, Charlie M, Knight, Andrew T
- Authors: McConnachie, Matthew M , Cowling, Richard M , Shackleton, Charlie M , Knight, Andrew T
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181003 , vital:43680 , xlink:href="https://doi.org/10.1111/rec.12038"
- Description: Public works programs have been posited as win–win solutions for achieving societal goals for ecological restoration and poverty alleviation. However, little is documented regarding the challenges of implementing such projects. A commonly cited example is South Africa's invasive alien plant control program “Working for Water” (WfW), which aims to create employment via restoring landscapes invaded with alien plants. Recent studies have raised questions over the effectiveness of this program in achieving both its restoration and poverty alleviation goals. This is the first study that we are aware of that synthesizes the knowledge of managers on both the poverty alleviation and environmental outcomes of a public works project. Herein, we sought to understand the challenges and constraints faced by 23 WfW managers in fulfilling the program's environmental and poverty alleviation objectives. We found that the challenges most frequently cited by managers related to the capacity and competence of managers and teams, followed by challenges relating to planning and coordination, specifically the challenges of being flexible and adaptive when constrained by operating procedures. In addition, the current focus on maximizing short-term employment was perceived by some as limiting the efficiency and long-term effectiveness of the WfW program in achieving its environmental and social goals. We suggest that improving the conditions and duration of employment could improve the effectiveness of invasive alien plant control and ecological outcomes. We also suggest that WfW measure the impacts of their interventions through an adaptive management approach so that it can learn and adapt to the challenges it faces.
- Full Text:
- Date Issued: 2013
- Authors: McConnachie, Matthew M , Cowling, Richard M , Shackleton, Charlie M , Knight, Andrew T
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181003 , vital:43680 , xlink:href="https://doi.org/10.1111/rec.12038"
- Description: Public works programs have been posited as win–win solutions for achieving societal goals for ecological restoration and poverty alleviation. However, little is documented regarding the challenges of implementing such projects. A commonly cited example is South Africa's invasive alien plant control program “Working for Water” (WfW), which aims to create employment via restoring landscapes invaded with alien plants. Recent studies have raised questions over the effectiveness of this program in achieving both its restoration and poverty alleviation goals. This is the first study that we are aware of that synthesizes the knowledge of managers on both the poverty alleviation and environmental outcomes of a public works project. Herein, we sought to understand the challenges and constraints faced by 23 WfW managers in fulfilling the program's environmental and poverty alleviation objectives. We found that the challenges most frequently cited by managers related to the capacity and competence of managers and teams, followed by challenges relating to planning and coordination, specifically the challenges of being flexible and adaptive when constrained by operating procedures. In addition, the current focus on maximizing short-term employment was perceived by some as limiting the efficiency and long-term effectiveness of the WfW program in achieving its environmental and social goals. We suggest that improving the conditions and duration of employment could improve the effectiveness of invasive alien plant control and ecological outcomes. We also suggest that WfW measure the impacts of their interventions through an adaptive management approach so that it can learn and adapt to the challenges it faces.
- Full Text:
- Date Issued: 2013
Ultrafast Photodynamics of the Indoline Dye D149 Adsorbed to Porous ZnO in Dye‐Sensitized Solar Cells
- Rohwer, Egmont, Richter, Christoph, Heming, Nadine, Strauch, Kerstin, Litwinski, Christian, Nyokong, Tebello, Schlettwein, Derck, Schwoerer, Heinrich
- Authors: Rohwer, Egmont , Richter, Christoph , Heming, Nadine , Strauch, Kerstin , Litwinski, Christian , Nyokong, Tebello , Schlettwein, Derck , Schwoerer, Heinrich
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242153 , vital:51006 , xlink:href="https://doi.org/10.1002/cphc.201200715"
- Description: We investigate the ultrafast dynamics of the photoinduced electron transfer between surface-adsorbed indoline D149 dye and porous ZnO as used in the working electrodes of dye-sensitized solar cells. Transient absorption spectroscopy was conducted on the dye in solution, on solid state samples and for the latter in contact to a I−/I3− redox electrolyte typical for dye-sensitized solar cells to elucidate the effect of each component in the observed dynamics. D149 in a solution of 1:1 acetonitrile and tert-butyl alcohol shows excited-state lifetimes of 300±50 ps. This signature is severely quenched when D149 is adsorbed to ZnO, with the fastest component of the decay trace measured at 150±20 fs due to the charge-transfer mechanism. Absorption bands of the oxidized dye molecule were investigated to determine regeneration times which are in excess of 1 ns. The addition of the redox electrolyte to the system results in faster regeneration times, of the order of 1 ns.
- Full Text:
- Date Issued: 2013
- Authors: Rohwer, Egmont , Richter, Christoph , Heming, Nadine , Strauch, Kerstin , Litwinski, Christian , Nyokong, Tebello , Schlettwein, Derck , Schwoerer, Heinrich
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242153 , vital:51006 , xlink:href="https://doi.org/10.1002/cphc.201200715"
- Description: We investigate the ultrafast dynamics of the photoinduced electron transfer between surface-adsorbed indoline D149 dye and porous ZnO as used in the working electrodes of dye-sensitized solar cells. Transient absorption spectroscopy was conducted on the dye in solution, on solid state samples and for the latter in contact to a I−/I3− redox electrolyte typical for dye-sensitized solar cells to elucidate the effect of each component in the observed dynamics. D149 in a solution of 1:1 acetonitrile and tert-butyl alcohol shows excited-state lifetimes of 300±50 ps. This signature is severely quenched when D149 is adsorbed to ZnO, with the fastest component of the decay trace measured at 150±20 fs due to the charge-transfer mechanism. Absorption bands of the oxidized dye molecule were investigated to determine regeneration times which are in excess of 1 ns. The addition of the redox electrolyte to the system results in faster regeneration times, of the order of 1 ns.
- Full Text:
- Date Issued: 2013
Higher education, academic communities, and the intellectual virtues
- Authors: Jones, Ward E
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/275647 , vital:55066 , xlink:href="https://doi.org/10.1111/edth.12005"
- Description: Because higher education brings members of academic communities in direct contact with students, the reflective higher education student is in an excellent position for developing two important intellectual virtues: confidence and humility. However, academic communities differ as to whether their members reach consensus, and their teaching practices reflect this difference. In this essay, Ward Jones argues that both consensus-reaching and non-consensus-reaching communities can encourage the development of intellectual confidence and humility in their students, although each will do so in very different ways.
- Full Text:
- Date Issued: 2012
- Authors: Jones, Ward E
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/275647 , vital:55066 , xlink:href="https://doi.org/10.1111/edth.12005"
- Description: Because higher education brings members of academic communities in direct contact with students, the reflective higher education student is in an excellent position for developing two important intellectual virtues: confidence and humility. However, academic communities differ as to whether their members reach consensus, and their teaching practices reflect this difference. In this essay, Ward Jones argues that both consensus-reaching and non-consensus-reaching communities can encourage the development of intellectual confidence and humility in their students, although each will do so in very different ways.
- Full Text:
- Date Issued: 2012
Layer by Layer Electrode Surface Functionalisation Using Carbon Nanotubes, Electrochemical Grafting of Azide‐Alkyne Functions and Click Chemistry
- Coates, Megan, Griveau, Sophie, Bedioui, Fethi, Nyokong, Tebello
- Authors: Coates, Megan , Griveau, Sophie , Bedioui, Fethi , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243509 , vital:51159 , xlink:href="https://doi.org/10.1002/elan.201200240"
- Description: Ferrocene was covalently bonded to a layer of adsorbed single-walled carbon nanotubes on a glassy carbon electrode surface using electrochemical grafting and click chemistry. Grafting of the 4-azidobenzenediazonium salt onto the surface was accomplished by electrochemical reduction. The surface-bound azide groups, with the use of a copper(I) catalyst, were reacted with ethynylferrocene to form covalent 1,2,3-triazole bonds by click chemistry. This layer by layer construction of the electrode surface results in stable electrodes by combining good electrical conductivity and increased surface area of the nanotubes with the versatility of the Sharpless click reaction.
- Full Text:
- Date Issued: 2012
- Authors: Coates, Megan , Griveau, Sophie , Bedioui, Fethi , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243509 , vital:51159 , xlink:href="https://doi.org/10.1002/elan.201200240"
- Description: Ferrocene was covalently bonded to a layer of adsorbed single-walled carbon nanotubes on a glassy carbon electrode surface using electrochemical grafting and click chemistry. Grafting of the 4-azidobenzenediazonium salt onto the surface was accomplished by electrochemical reduction. The surface-bound azide groups, with the use of a copper(I) catalyst, were reacted with ethynylferrocene to form covalent 1,2,3-triazole bonds by click chemistry. This layer by layer construction of the electrode surface results in stable electrodes by combining good electrical conductivity and increased surface area of the nanotubes with the versatility of the Sharpless click reaction.
- Full Text:
- Date Issued: 2012
The economics of suicide in South Africa
- Authors: Botha, Ferdi
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/396168 , vital:69155 , xlink:href="https://doi.org/10.1111/j.1813-6982.2012.01336.x"
- Description: This study investigates the economics of suicide in South Africa using the Mortality and Causes of Death data from death notification as well as regional economic data for the 2006-2008 period. Using an inflation rate that varies by month and across province of residence as a proxy for economic performance, the results indicate a negative relationship between inflation and suicide, suggesting that suicides are countercyclical. When controlling for month and province fixed effects, however, the inflation coefficient, albeit remaining negative, is no longer significant, except in the female sample. Suicide is more prevalent among younger individuals, while the greatest proportion of suicide is seen among men. Suicides also exhibit a strong seasonal variation, with peaks in spring and summer, with December having the highest suicide prevalence. The overall results indicate a negative but insignificant relationship between economic performance and suicide in South Africa, with socio-economic differences and individual characteristics accounting for most of the variation in suicide.
- Full Text:
- Date Issued: 2012
- Authors: Botha, Ferdi
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/396168 , vital:69155 , xlink:href="https://doi.org/10.1111/j.1813-6982.2012.01336.x"
- Description: This study investigates the economics of suicide in South Africa using the Mortality and Causes of Death data from death notification as well as regional economic data for the 2006-2008 period. Using an inflation rate that varies by month and across province of residence as a proxy for economic performance, the results indicate a negative relationship between inflation and suicide, suggesting that suicides are countercyclical. When controlling for month and province fixed effects, however, the inflation coefficient, albeit remaining negative, is no longer significant, except in the female sample. Suicide is more prevalent among younger individuals, while the greatest proportion of suicide is seen among men. Suicides also exhibit a strong seasonal variation, with peaks in spring and summer, with December having the highest suicide prevalence. The overall results indicate a negative but insignificant relationship between economic performance and suicide in South Africa, with socio-economic differences and individual characteristics accounting for most of the variation in suicide.
- Full Text:
- Date Issued: 2012
Adoption, use and perception of Australian acacias around the world
- Kull, Christian A, Shackleton, Charlie M, Cunningham, Peter J, Ducatillon, Catherine, Dufour-Dror, Jean-Mark, Esler, Karen J, Friday, James B, Gouveia, António C, Griffin, A R, Marchante, Elizabete, Midgley, Steven J, Pauchard, Aníbal, Rangan, Haripriya, Richardson, David M, Rinaudo, Tony, Tassin, Jacques, Urgenson, Lauren S, van Maltitz, Graham P, Zenni, Rafael D, Zylstra, Matthew J
- Authors: Kull, Christian A , Shackleton, Charlie M , Cunningham, Peter J , Ducatillon, Catherine , Dufour-Dror, Jean-Mark , Esler, Karen J , Friday, James B , Gouveia, António C , Griffin, A R , Marchante, Elizabete , Midgley, Steven J , Pauchard, Aníbal , Rangan, Haripriya , Richardson, David M , Rinaudo, Tony , Tassin, Jacques , Urgenson, Lauren S , van Maltitz, Graham P , Zenni, Rafael D , Zylstra, Matthew J
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182149 , vital:43804 , xlink:href="https://doi.org/10.1111/j.1472-4642.2011.00783.x"
- Description: To examine the different uses and perceptions of introduced Australian acacias (wattles; Acacia subgenus Phyllodineae) by rural households and communities. Eighteen landscape-scale case studies around the world, in Vietnam, India, Réunion, Madagascar, South Africa, Congo, Niger, Ethiopia, Israel, France, Portugal, Brazil, Chile, Dominican Republic and Hawai‘i. Qualitative comparison of case studies, based on questionnaire sent to network of acacia researchers. Information based on individual knowledge of local experts, published and unpublished sources. We propose a conceptual model to explain current uses and perceptions of introduced acacias. It highlights historically and geographically contingent processes, including economic development, environmental discourses, political context, and local or regional needs. Four main groupings of case studies were united by similar patterns: (1) poor communities benefiting from targeted agroforestry projects; (2) places where residents, generally poor, take advantage of a valuable resource already present in their landscape via plantation and/or invasion; (3) regions of small and mid-scale tree farmers participating in the forestry industry; and (4) a number of high-income communities dealing with the legacies of former or niche use of introduced acacia in a context of increased concern over biodiversity and ecosystem services. Economic conditions play a key role shaping acacia use. Poorer communities rely strongly on acacias (often in, or escaped from, formal plantations) for household needs and, sometimes, for income. Middle-income regions more typically host private farm investments in acacia woodlots for commercialization. Efforts at control of invasive acacias must take care to not adversely impact poor dependent communities.
- Full Text:
- Date Issued: 2011
- Authors: Kull, Christian A , Shackleton, Charlie M , Cunningham, Peter J , Ducatillon, Catherine , Dufour-Dror, Jean-Mark , Esler, Karen J , Friday, James B , Gouveia, António C , Griffin, A R , Marchante, Elizabete , Midgley, Steven J , Pauchard, Aníbal , Rangan, Haripriya , Richardson, David M , Rinaudo, Tony , Tassin, Jacques , Urgenson, Lauren S , van Maltitz, Graham P , Zenni, Rafael D , Zylstra, Matthew J
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182149 , vital:43804 , xlink:href="https://doi.org/10.1111/j.1472-4642.2011.00783.x"
- Description: To examine the different uses and perceptions of introduced Australian acacias (wattles; Acacia subgenus Phyllodineae) by rural households and communities. Eighteen landscape-scale case studies around the world, in Vietnam, India, Réunion, Madagascar, South Africa, Congo, Niger, Ethiopia, Israel, France, Portugal, Brazil, Chile, Dominican Republic and Hawai‘i. Qualitative comparison of case studies, based on questionnaire sent to network of acacia researchers. Information based on individual knowledge of local experts, published and unpublished sources. We propose a conceptual model to explain current uses and perceptions of introduced acacias. It highlights historically and geographically contingent processes, including economic development, environmental discourses, political context, and local or regional needs. Four main groupings of case studies were united by similar patterns: (1) poor communities benefiting from targeted agroforestry projects; (2) places where residents, generally poor, take advantage of a valuable resource already present in their landscape via plantation and/or invasion; (3) regions of small and mid-scale tree farmers participating in the forestry industry; and (4) a number of high-income communities dealing with the legacies of former or niche use of introduced acacia in a context of increased concern over biodiversity and ecosystem services. Economic conditions play a key role shaping acacia use. Poorer communities rely strongly on acacias (often in, or escaped from, formal plantations) for household needs and, sometimes, for income. Middle-income regions more typically host private farm investments in acacia woodlots for commercialization. Efforts at control of invasive acacias must take care to not adversely impact poor dependent communities.
- Full Text:
- Date Issued: 2011
Electrooxidation of Chlorophenols Catalyzed by Nickel Octadecylphthalocyanine Adsorbed on Single‐Walled Carbon Nanotubes
- Khene, Samson, Nyokong, Tebello
- Authors: Khene, Samson , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247198 , vital:51555 , xlink:href="https://doi.org/10.1002/elan.201100155"
- Description: We described the synthesis of nickel octadecylphthalocyanine (NiPc(C10H21)8), followed by its adsorption on single-walled carbon nanotubes (SWCNT) to form SWCNT-NiPc(C10H21)8 conjugates. SWCNT-NiPc(C10H21)8 was used to modify a glassy carbon electrode (GCE) and for the electrooxidation of 4-chlorophenol and 2,4-dichlorophenol. The SWCNT and NiPc(C10H21)8 have a synergistic effect on each other in terms of improving electrocatalysis for the detection of chlorophenols. The stability of the electrode improved in the presence of NiPc(C10H21)8 or NiPc compared to the bare GCE. The presence of SWCNT improves the electrocatalytic behaviour of NiPc(C10H21)8 but not of unsubstituted NiPc. All modified electrodes showed improved stability towards the detection of 2,4-dichlorophenol. The best stability for 4-CP detection was observed in the presence of SWCNT for NiPc(C10H21)8.
- Full Text:
- Date Issued: 2011
- Authors: Khene, Samson , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247198 , vital:51555 , xlink:href="https://doi.org/10.1002/elan.201100155"
- Description: We described the synthesis of nickel octadecylphthalocyanine (NiPc(C10H21)8), followed by its adsorption on single-walled carbon nanotubes (SWCNT) to form SWCNT-NiPc(C10H21)8 conjugates. SWCNT-NiPc(C10H21)8 was used to modify a glassy carbon electrode (GCE) and for the electrooxidation of 4-chlorophenol and 2,4-dichlorophenol. The SWCNT and NiPc(C10H21)8 have a synergistic effect on each other in terms of improving electrocatalysis for the detection of chlorophenols. The stability of the electrode improved in the presence of NiPc(C10H21)8 or NiPc compared to the bare GCE. The presence of SWCNT improves the electrocatalytic behaviour of NiPc(C10H21)8 but not of unsubstituted NiPc. All modified electrodes showed improved stability towards the detection of 2,4-dichlorophenol. The best stability for 4-CP detection was observed in the presence of SWCNT for NiPc(C10H21)8.
- Full Text:
- Date Issued: 2011
Optimizing the electrocatalytic activity of surface confined Co macrocyclics for the electrooxidation of thiocyanate at pH 4
- Tshangana, Charmaine, Pavez, Jorge, Gulppi, Miguel A, De Mattos, Ivanildo Luiz, Arratia-Perez, Ramiro, Linares-Flores, Cristian, Paez, Maritza, Nyokong, Tebello, Zagal, Jos H
- Authors: Tshangana, Charmaine , Pavez, Jorge , Gulppi, Miguel A , De Mattos, Ivanildo Luiz , Arratia-Perez, Ramiro , Linares-Flores, Cristian , Paez, Maritza , Nyokong, Tebello , Zagal, Jos H
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247726 , vital:51612 , xlink:href="https://doi.org/10.1002/elan.201000599"
- Description: We have studied the trends in catalytic activity of several Co macrocyclics confined on the surface graphite electrodes for the oxidation of thiocyanate. A plot of log i (at constant E) versus the formal potential of the catalyst gives a volcano correlation, indicating that the Co(II/I) redox potential needs to be tuned, in order to achieve maximum reactivity. Graphite electrodes modified with Co phthalocyanine at pH 4 exhibit linear amperometric response for thiocyanate concentration in the range 10−7 and 10−3 M. Theoretical calculations show that electrocatalytic activity (as log i at constant E) plotted versus the energy of the LUMO of the Co complex also gives a volcano correlation.
- Full Text:
- Date Issued: 2011
- Authors: Tshangana, Charmaine , Pavez, Jorge , Gulppi, Miguel A , De Mattos, Ivanildo Luiz , Arratia-Perez, Ramiro , Linares-Flores, Cristian , Paez, Maritza , Nyokong, Tebello , Zagal, Jos H
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247726 , vital:51612 , xlink:href="https://doi.org/10.1002/elan.201000599"
- Description: We have studied the trends in catalytic activity of several Co macrocyclics confined on the surface graphite electrodes for the oxidation of thiocyanate. A plot of log i (at constant E) versus the formal potential of the catalyst gives a volcano correlation, indicating that the Co(II/I) redox potential needs to be tuned, in order to achieve maximum reactivity. Graphite electrodes modified with Co phthalocyanine at pH 4 exhibit linear amperometric response for thiocyanate concentration in the range 10−7 and 10−3 M. Theoretical calculations show that electrocatalytic activity (as log i at constant E) plotted versus the energy of the LUMO of the Co complex also gives a volcano correlation.
- Full Text:
- Date Issued: 2011
Porphyrin nanorods modified glassy carbon electrode for the electrocatalysis of dioxygen, methanol and hydrazine
- George, Reama C, Mugadza, Tawanda, Khene, Samson, Egharevba, Gabriel O, Nyokong, Tebello
- Authors: George, Reama C , Mugadza, Tawanda , Khene, Samson , Egharevba, Gabriel O , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247388 , vital:51576 , xlink:href="https://doi.org/10.1002/elan.201100081"
- Description: Porphyrin nanorods (PNR) were prepared by ionic self-assembly of two oppositely charged porphyrin molecules consisting of free base meso-tetraphenylsulfonate porphyrin (H4TPPS42−) and meso-tetra(N-methyl-4-pyridyl) porphyrin (MTMePyP4+M=Sn, Mn, In, Co). These consist of H4TPPS42−SnTMePyP4+, H4TPPS42−CoTMePyP4+, H4TPPS42−InTMePyP4+ and H4TPPS42−MnTMePyP4+ porphyrin nanorods. The absorption spectra and transmission electron microscopic (TEM) images of these structures were obtained. These porphyrin nanostructures were used to modify a glassy carbon electrode for the electrocatalytic reduction of oxygen, and the oxidation of hydrazine and methanol at low pH. The cyclic voltammogram of PNR-modified GCE in pH 2 buffer solution has five irreversible processes, two distinct reduction processes and three oxidation processes. The porphyrin nanorods modified GCE produce good responses especially towards oxygen reduction at −0.50 V vs. Ag|AgCl (3 M KCl). The process of electrocatalytic oxidation of methanol using PNR-modified GCE begins at 0.71 V vs. Ag|AgCl (3 M KCl). The electrochemical oxidation of hydrazine began at around 0.36 V on H4TPPS42−SnTMePyP4+ modified GCE. The GCE modified with H4TPPS42−CoTMePyP4+ H4TPPS42−InTMePyP4+ and H4TPPS42−MnTMePyP4+ porphyrin nanorods began oxidizing hydrazine at 0.54 V, 0.59 V and 0.56 V, respectively.
- Full Text:
- Date Issued: 2011
- Authors: George, Reama C , Mugadza, Tawanda , Khene, Samson , Egharevba, Gabriel O , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247388 , vital:51576 , xlink:href="https://doi.org/10.1002/elan.201100081"
- Description: Porphyrin nanorods (PNR) were prepared by ionic self-assembly of two oppositely charged porphyrin molecules consisting of free base meso-tetraphenylsulfonate porphyrin (H4TPPS42−) and meso-tetra(N-methyl-4-pyridyl) porphyrin (MTMePyP4+M=Sn, Mn, In, Co). These consist of H4TPPS42−SnTMePyP4+, H4TPPS42−CoTMePyP4+, H4TPPS42−InTMePyP4+ and H4TPPS42−MnTMePyP4+ porphyrin nanorods. The absorption spectra and transmission electron microscopic (TEM) images of these structures were obtained. These porphyrin nanostructures were used to modify a glassy carbon electrode for the electrocatalytic reduction of oxygen, and the oxidation of hydrazine and methanol at low pH. The cyclic voltammogram of PNR-modified GCE in pH 2 buffer solution has five irreversible processes, two distinct reduction processes and three oxidation processes. The porphyrin nanorods modified GCE produce good responses especially towards oxygen reduction at −0.50 V vs. Ag|AgCl (3 M KCl). The process of electrocatalytic oxidation of methanol using PNR-modified GCE begins at 0.71 V vs. Ag|AgCl (3 M KCl). The electrochemical oxidation of hydrazine began at around 0.36 V on H4TPPS42−SnTMePyP4+ modified GCE. The GCE modified with H4TPPS42−CoTMePyP4+ H4TPPS42−InTMePyP4+ and H4TPPS42−MnTMePyP4+ porphyrin nanorods began oxidizing hydrazine at 0.54 V, 0.59 V and 0.56 V, respectively.
- Full Text:
- Date Issued: 2011
The Electrochemical Behavior of Gold Nanoparticle‐Tantalum (V) Phthalocyanine Composites
- Chauke, Vongani, Chidawanyika, Wadzanai J U, Nyokong, Tebello
- Authors: Chauke, Vongani , Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247915 , vital:51629 , xlink:href="https://doi.org/10.1002/elan.201000521"
- Description: The formation of gold nanoparticle (AuNP) composites with tantalum phthalocyanines (TaPc) complexes {1a and 1b (Figure 1)} is reported. The TaPc-AuNPs conjugates were characterised by atomic force microscopy (AFM) and transmission electron microscopy. The AFM analyses show that conjugates of TaPc with AuNPs are more aggregated when compared to AuNPs alone. The conjugates and TaPc complexes were immobilized on a gold electrode by drop and dry method and these were characterized by electrochemical impedance spectroscopy. The charge transfer behaviour of AuNPs was enhanced in the presence of TaPc complexes. All the modified electrodes showed electrocatalytic oxidation of bisphenol A. The limits of detection for complexes 1a and 1b were 4.78×10−10 and 2.76×10−10 mol L−1, respectively.
- Full Text:
- Date Issued: 2011
- Authors: Chauke, Vongani , Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247915 , vital:51629 , xlink:href="https://doi.org/10.1002/elan.201000521"
- Description: The formation of gold nanoparticle (AuNP) composites with tantalum phthalocyanines (TaPc) complexes {1a and 1b (Figure 1)} is reported. The TaPc-AuNPs conjugates were characterised by atomic force microscopy (AFM) and transmission electron microscopy. The AFM analyses show that conjugates of TaPc with AuNPs are more aggregated when compared to AuNPs alone. The conjugates and TaPc complexes were immobilized on a gold electrode by drop and dry method and these were characterized by electrochemical impedance spectroscopy. The charge transfer behaviour of AuNPs was enhanced in the presence of TaPc complexes. All the modified electrodes showed electrocatalytic oxidation of bisphenol A. The limits of detection for complexes 1a and 1b were 4.78×10−10 and 2.76×10−10 mol L−1, respectively.
- Full Text:
- Date Issued: 2011
Beyond just research: Experiences from Southern Africa in developing social learning partnerships for resource conservation initiatives
- Shackleton, Charlie M, Cundill, Georgina, Knight, Andrew T
- Authors: Shackleton, Charlie M , Cundill, Georgina , Knight, Andrew T
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181157 , vital:43703 , xlink:href="https://doi.org/10.1111/j.1744-7429.2009.00559.x"
- Description: There is a well-acknowledged communication or knowledge gap between scientists and decision-makers. Many scientists who take on the challenge of narrowing this gap operate on the understanding that their role is to communicate their findings in a one-way flow of information: from science to decision-makers. However, to be effective scientists must engage in an ongoing social learning process with decision-makers, and regard themselves as facilitators, and also as one among many stakeholders who have valid and important ecological knowledge. The developing world poses some particular challenges in this regard, specifically in terms of the large number of local level subsistence resources users who are important de facto decision-makers. We examine four natural resource management case studies from South Africa that differ in spatial scale and complexity, ranging from a single village to a whole biome. We distil seven lessons to help guide development of social learning processes and organizations in similar situations relating to natural resource planning and management. The lessons pertain to: maintaining ‘key individuals’ within social learning processes; the role of researchers; the formulation of research questions that social learning processes require adaptive long-term funding and capacity support; that local resource users are key decision-makers in developing countries; some perspectives on knowledge; and the need to measure research success.
- Full Text:
- Date Issued: 2009
- Authors: Shackleton, Charlie M , Cundill, Georgina , Knight, Andrew T
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181157 , vital:43703 , xlink:href="https://doi.org/10.1111/j.1744-7429.2009.00559.x"
- Description: There is a well-acknowledged communication or knowledge gap between scientists and decision-makers. Many scientists who take on the challenge of narrowing this gap operate on the understanding that their role is to communicate their findings in a one-way flow of information: from science to decision-makers. However, to be effective scientists must engage in an ongoing social learning process with decision-makers, and regard themselves as facilitators, and also as one among many stakeholders who have valid and important ecological knowledge. The developing world poses some particular challenges in this regard, specifically in terms of the large number of local level subsistence resources users who are important de facto decision-makers. We examine four natural resource management case studies from South Africa that differ in spatial scale and complexity, ranging from a single village to a whole biome. We distil seven lessons to help guide development of social learning processes and organizations in similar situations relating to natural resource planning and management. The lessons pertain to: maintaining ‘key individuals’ within social learning processes; the role of researchers; the formulation of research questions that social learning processes require adaptive long-term funding and capacity support; that local resource users are key decision-makers in developing countries; some perspectives on knowledge; and the need to measure research success.
- Full Text:
- Date Issued: 2009
Metallophthalocyanine Based Carbon Paste Electrodes for the Determination of 2′, 3′‐Dideoxyinosine
- Ozoemena, Kenneth I, Stefan-van Staden, Raluca-Ioana, Nyokong, Tebello
- Authors: Ozoemena, Kenneth I , Stefan-van Staden, Raluca-Ioana , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263430 , vital:53627 , xlink:href="https://doi.org/10.1002/elan.200904581"
- Description: Novel electrochemical sensors based on carbon paste impregnated with metallopthalocyanine (MPc, M=Co, Fe) complexes, have been constructed for the assay of anti-HIV drug 2′,3′-dideoxyinosine (didanosine, DDI). Both modified electrodes showed electrocatalytic activity towards the oxidation of dideoxyinosine in phosphate buffer pH 7.4 with a working concentration range of 10−6–10−4 mol/L and a detection limit of 10−7 mol/L magnitude order. The sensor proved to be highly reliable for the assay of the purity of DDI - raw material as well as for the uniformity content test of Videx tablets.
- Full Text:
- Date Issued: 2009
- Authors: Ozoemena, Kenneth I , Stefan-van Staden, Raluca-Ioana , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263430 , vital:53627 , xlink:href="https://doi.org/10.1002/elan.200904581"
- Description: Novel electrochemical sensors based on carbon paste impregnated with metallopthalocyanine (MPc, M=Co, Fe) complexes, have been constructed for the assay of anti-HIV drug 2′,3′-dideoxyinosine (didanosine, DDI). Both modified electrodes showed electrocatalytic activity towards the oxidation of dideoxyinosine in phosphate buffer pH 7.4 with a working concentration range of 10−6–10−4 mol/L and a detection limit of 10−7 mol/L magnitude order. The sensor proved to be highly reliable for the assay of the purity of DDI - raw material as well as for the uniformity content test of Videx tablets.
- Full Text:
- Date Issued: 2009
Electrochemical Characterization of Self-Assembled Monolayer of a Novel Manganese Tetrabenzylthio-Substituted Phthalocyanine and Its Use in Nitrite Oxidation
- Matemadombo, Fungisai, Griveau, Sophie, Bedioui, Fethi, Nyokong, Tebello
- Authors: Matemadombo, Fungisai , Griveau, Sophie , Bedioui, Fethi , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/265950 , vital:53903 , xlink:href="https://doi.org/10.1002/elan.200804269"
- Description: Manganese phthalocyanine MnPc(SPh)4 has been synthesized and used to form self assembled monolayers on gold electrodes. The well packed SAM monolayer was characterized by analyzing the blocking of a number of Faradic processes by cyclic voltammetry, evaluating the electrical characteristics of the modified electrode by electrochemical impedance and imaging the modified surface by electrochemical scanning microscopy. Finally, MnPc(SPh)4-SAM modified electrode displayed an electrocatalytic behavior toward the oxidation of nitrite.
- Full Text:
- Date Issued: 2008
- Authors: Matemadombo, Fungisai , Griveau, Sophie , Bedioui, Fethi , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/265950 , vital:53903 , xlink:href="https://doi.org/10.1002/elan.200804269"
- Description: Manganese phthalocyanine MnPc(SPh)4 has been synthesized and used to form self assembled monolayers on gold electrodes. The well packed SAM monolayer was characterized by analyzing the blocking of a number of Faradic processes by cyclic voltammetry, evaluating the electrical characteristics of the modified electrode by electrochemical impedance and imaging the modified surface by electrochemical scanning microscopy. Finally, MnPc(SPh)4-SAM modified electrode displayed an electrocatalytic behavior toward the oxidation of nitrite.
- Full Text:
- Date Issued: 2008
Social and ecological trade offs in combating land degradation: The case of invasion by a woody shrub (Euryops floribundus) at Macubeni, South Africa
- Shackleton, Charlie M, Gambiza, James
- Authors: Shackleton, Charlie M , Gambiza, James
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181235 , vital:43711 , xlink:href="https://doi.org/10.1002/ldr.849"
- Description: Woody plant invasions, either of alien or indigenous species, are deemed to result in loss of ecosystem goods and services in many areas throughout the world, resulting in significant degradation and economic costs. Invasion of Euryops floribundus, a species indigenous to South Africa, is perceived to have reduced the grazing available for domestic livestock. Consequently, a programme of manual eradication has been implemented to improve the grazing resource and provide jobs for poverty alleviation. However, there is potential for a conflict of interest as our study shows that almost all households rely on Euryops for fuel and at times fencing material, whereas only a minority of households own livestock. Moreover, comparison of invaded and non-invaded sites indicated that the invaded sites harbour greater plant species richness and higher grass culm density per unit area of grass cover, as well as higher forb and litter cover. While invaded sites had lower grass cover, overall plant cover was no different between invaded and non-invaded sites. Multivariate analysis indicated no obvious differentiation in community composition between invaded and non-invaded areas, suggesting stronger drivers of community composition other than Euryops invasion presumed to be facilitated by the effects of high livestock densities. Overall, our study suggests that the clearing operation may well benefit from a better understanding of the social needs, perceptions of degradation by the various stakeholders and ecological dynamics of the area, especially local reliance on the resources, and the dynamics of the invasion, particularly its extent, rate of spread and susceptibility for re-invasion in the cleared areas.
- Full Text:
- Date Issued: 2008
- Authors: Shackleton, Charlie M , Gambiza, James
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181235 , vital:43711 , xlink:href="https://doi.org/10.1002/ldr.849"
- Description: Woody plant invasions, either of alien or indigenous species, are deemed to result in loss of ecosystem goods and services in many areas throughout the world, resulting in significant degradation and economic costs. Invasion of Euryops floribundus, a species indigenous to South Africa, is perceived to have reduced the grazing available for domestic livestock. Consequently, a programme of manual eradication has been implemented to improve the grazing resource and provide jobs for poverty alleviation. However, there is potential for a conflict of interest as our study shows that almost all households rely on Euryops for fuel and at times fencing material, whereas only a minority of households own livestock. Moreover, comparison of invaded and non-invaded sites indicated that the invaded sites harbour greater plant species richness and higher grass culm density per unit area of grass cover, as well as higher forb and litter cover. While invaded sites had lower grass cover, overall plant cover was no different between invaded and non-invaded sites. Multivariate analysis indicated no obvious differentiation in community composition between invaded and non-invaded areas, suggesting stronger drivers of community composition other than Euryops invasion presumed to be facilitated by the effects of high livestock densities. Overall, our study suggests that the clearing operation may well benefit from a better understanding of the social needs, perceptions of degradation by the various stakeholders and ecological dynamics of the area, especially local reliance on the resources, and the dynamics of the invasion, particularly its extent, rate of spread and susceptibility for re-invasion in the cleared areas.
- Full Text:
- Date Issued: 2008
Cobalt Phthalocyanine Molecular Electrode for the Electrochemical Investigation of the Release of Glutathione upon Copper-Catalyzed Decomposition of S-Nitrosoglutathione
- Sehlotho, Nthapo, Griveau, Sophie, Nyokong, Tebello, Bedioui, Fethi
- Authors: Sehlotho, Nthapo , Griveau, Sophie , Nyokong, Tebello , Bedioui, Fethi
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/281201 , vital:55701 , xlink:href="https://doi.org/10.1002/elan.200603656"
- Description: Decomposition of S-nitrosoglutathione (GSNO) in phosphate buffer solution at physiological pH 7.4 in the presence of cuprous ion as a catalyst and sodium borohydride as a reducing agent is analyzed by observing the transient apparition of reduced glutathione GSH through its electrooxidation. Transient formation of GSH, upon decomposition of 1 mM GSNO in presence of 0.025 mM Cu(NO3)2 and 1 mM NaBH4 was detected by using an ordinary pyrolytic graphite electrode modified with an adsorbed monolayer of cobalt phthalocyanine at 0 V vs. SCE.
- Full Text:
- Date Issued: 2007
- Authors: Sehlotho, Nthapo , Griveau, Sophie , Nyokong, Tebello , Bedioui, Fethi
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/281201 , vital:55701 , xlink:href="https://doi.org/10.1002/elan.200603656"
- Description: Decomposition of S-nitrosoglutathione (GSNO) in phosphate buffer solution at physiological pH 7.4 in the presence of cuprous ion as a catalyst and sodium borohydride as a reducing agent is analyzed by observing the transient apparition of reduced glutathione GSH through its electrooxidation. Transient formation of GSH, upon decomposition of 1 mM GSNO in presence of 0.025 mM Cu(NO3)2 and 1 mM NaBH4 was detected by using an ordinary pyrolytic graphite electrode modified with an adsorbed monolayer of cobalt phthalocyanine at 0 V vs. SCE.
- Full Text:
- Date Issued: 2007
Synthesis, Photophysical and Photochemical Properties of Poly (oxyethylene)‐Substituted Phthalocyaninato Oxotitanium (IV) Complexes
- Atilla, Devrim, Durmus, Mahmut, Yılmaz, Özgür, Gürek, Ayşe Gül, Ahsen, Vefa, Nyokong, Tebello
- Authors: Atilla, Devrim , Durmus, Mahmut , Yılmaz, Özgür , Gürek, Ayşe Gül , Ahsen, Vefa , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/271263 , vital:54526 , xlink:href="https://doi.org/10.1002/ejic.200700057"
- Description: The synthesis, photophysical and photochemical properties of tetra- and chlorotetrapoly(oxyethylene)-substituted oxotitanium(IV) phthalocyanines are reported for the first time. The new compounds were characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy, electronic spectroscopy and mass spectra. These complexes showed monomeric behaviour in solution. General trends are described for photodegredation, singlet oxygen, triplet state and fluorescence quantum yields, and triplet and fluorescence lifetimes of these compounds in dimethyl sulfoxide (DMSO). Photophysical and photochemical properties of phthalocyanine complexes are very useful for PDT applications. The complexes showed high triplet quantum yields and triplet lifetimes in DMSO. The singlet oxygen quantum yields (ΦΔ), which give an indication of the potential of the complexes as photosensitizers in applications where singlet oxygen is required (Type II mechanism), were 0.72 and 0.78 for 3a and 5a, respectively. Thus, these complexes show potential as Type II photosensitizers. These complexes were also quenched by benzoquinone for fluorescence quenching studies.
- Full Text:
- Date Issued: 2007
- Authors: Atilla, Devrim , Durmus, Mahmut , Yılmaz, Özgür , Gürek, Ayşe Gül , Ahsen, Vefa , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/271263 , vital:54526 , xlink:href="https://doi.org/10.1002/ejic.200700057"
- Description: The synthesis, photophysical and photochemical properties of tetra- and chlorotetrapoly(oxyethylene)-substituted oxotitanium(IV) phthalocyanines are reported for the first time. The new compounds were characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy, electronic spectroscopy and mass spectra. These complexes showed monomeric behaviour in solution. General trends are described for photodegredation, singlet oxygen, triplet state and fluorescence quantum yields, and triplet and fluorescence lifetimes of these compounds in dimethyl sulfoxide (DMSO). Photophysical and photochemical properties of phthalocyanine complexes are very useful for PDT applications. The complexes showed high triplet quantum yields and triplet lifetimes in DMSO. The singlet oxygen quantum yields (ΦΔ), which give an indication of the potential of the complexes as photosensitizers in applications where singlet oxygen is required (Type II mechanism), were 0.72 and 0.78 for 3a and 5a, respectively. Thus, these complexes show potential as Type II photosensitizers. These complexes were also quenched by benzoquinone for fluorescence quenching studies.
- Full Text:
- Date Issued: 2007
The effects of fire on post-fire seed germination of selected Savanna woody species
- Authors: Shackleton, Charlie M
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183104 , vital:43912 , xlink:href=" https://doi.org/10.1111/j.1365-2028.2007.00766.x"
- Description: Although fire is recognized as an integral component of savanna dynamics, there is a dearth of understanding of its impacts on woody plant seeds. This study examined the impacts of fire in stimulating or constraining post-fire germination of seven common savanna woody species. Seeds of two species (Combretum hereroense and Euclea natalensis) failed to germinate irrespective of fire treatment. For the remaining five species, fire effects were dependent on seed location as either on the soil surface or buried. For surface seeds, fire effects reduced germination in four of the species, and stimulated it for one species (Acacia swazica). For buried seeds, fire had no effect. A significant proportion of surface seeds were destroyed by fire, and overall germination was higher for buried seed for most species other than A. swazica.
- Full Text:
- Date Issued: 2007
- Authors: Shackleton, Charlie M
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183104 , vital:43912 , xlink:href=" https://doi.org/10.1111/j.1365-2028.2007.00766.x"
- Description: Although fire is recognized as an integral component of savanna dynamics, there is a dearth of understanding of its impacts on woody plant seeds. This study examined the impacts of fire in stimulating or constraining post-fire germination of seven common savanna woody species. Seeds of two species (Combretum hereroense and Euclea natalensis) failed to germinate irrespective of fire treatment. For the remaining five species, fire effects were dependent on seed location as either on the soil surface or buried. For surface seeds, fire effects reduced germination in four of the species, and stimulated it for one species (Acacia swazica). For buried seeds, fire had no effect. A significant proportion of surface seeds were destroyed by fire, and overall germination was higher for buried seed for most species other than A. swazica.
- Full Text:
- Date Issued: 2007
UV-Visible and Electrochemical Monitoring of Carbon Monoxide Release by Donor Complexes to Myoglobin Solutions and to Electrodes Modified with Films Containing Hemin
- Obirai, Joseph C, Hamadi, Sara, Ithurbide, Aurélie, Wartelle, Corinne, Nyokong, Tebello, Zagal, José, Top, Siden, Bedioui, Fethi
- Authors: Obirai, Joseph C , Hamadi, Sara , Ithurbide, Aurélie , Wartelle, Corinne , Nyokong, Tebello , Zagal, José , Top, Siden , Bedioui, Fethi
- Date: 2006
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/283906 , vital:56001 , xlink:href="https://doi.org/10.1002/elan.200603571"
- Description: This study reports on the evaluation of the CO donating behavior of tricarbonyl dichloro ruthenium(II) dimer ([Ru(CO)3Cl2]2) and 1,3-dimethoxyphenyl tricarbonyl chromium (C6H3(MeO)2Cr(CO)3) complex by UV-visible technique and electrochemical technique. The CO release was monitored by following the modifications of the UV-visible features of MbFe(II) in phosphate buffer solution and the redox features of reduced Hemin, HmFe(II), confined at the surface of a vitreous carbon electrode. In the latter case, the interaction between the hemin-modified electrode and the released CO was seen through the observation of an increase of the reduction current related to the FeIII/FeII redox process of the immobilized porphyrin. While the ruthenium-based complex, ([Ru(CO)3Cl2]2), depended on the presence of Fe(II) species to release CO, it was found that the chromium-based complex released spontaneously CO. This was facilitated by illuminating and/or simple stirring of the solution containing the complex.
- Full Text:
- Date Issued: 2006
- Authors: Obirai, Joseph C , Hamadi, Sara , Ithurbide, Aurélie , Wartelle, Corinne , Nyokong, Tebello , Zagal, José , Top, Siden , Bedioui, Fethi
- Date: 2006
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/283906 , vital:56001 , xlink:href="https://doi.org/10.1002/elan.200603571"
- Description: This study reports on the evaluation of the CO donating behavior of tricarbonyl dichloro ruthenium(II) dimer ([Ru(CO)3Cl2]2) and 1,3-dimethoxyphenyl tricarbonyl chromium (C6H3(MeO)2Cr(CO)3) complex by UV-visible technique and electrochemical technique. The CO release was monitored by following the modifications of the UV-visible features of MbFe(II) in phosphate buffer solution and the redox features of reduced Hemin, HmFe(II), confined at the surface of a vitreous carbon electrode. In the latter case, the interaction between the hemin-modified electrode and the released CO was seen through the observation of an increase of the reduction current related to the FeIII/FeII redox process of the immobilized porphyrin. While the ruthenium-based complex, ([Ru(CO)3Cl2]2), depended on the presence of Fe(II) species to release CO, it was found that the chromium-based complex released spontaneously CO. This was facilitated by illuminating and/or simple stirring of the solution containing the complex.
- Full Text:
- Date Issued: 2006