Forged in the heat: doing journalism
- Authors: Stewart, Gavin
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/454696 , vital:75367 , https://hdl.handle.net/10520/EJC135804
- Description: Cue's instant success in 1987 came from a coincidence of events and places around, as much as inside, the Department of Journalism and Media Studies at Rhodes University.
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Formation, surface characterization, and electrocatalytic application of self-assembled monolayer films of tetra-substituted manganese, iron, and cobalt benzylthio phthalocyanine complexes
- Authors: Akinbulu, Isaac Adebayo , Ozoemena, Kenneth Iyke , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247163 , vital:51552 , xlink:href="https://doi.org/10.1007/s10008-010-1243-1"
- Description: Molecular thin films of manganese (SAM-2), iron (SAM-3), and cobalt (SAM-4) phthalocyanine complexes, non-peripherally tetra-substituted with benzylmercapto, were formed on polycrystalline gold disc electrode by self-assembly technique. Surface characteristics of the films were interrogated by cyclic voltammetry. Significant passivation of voltammetry processes associated with bare gold surface (gold oxidation and underpotential deposition of copper) confirmed formation of the films. Electrocatalytic property of the films was evidenced from better voltammetry responses (less positive oxidation potential and better current signal) of the insecticide, carbofuran, on these films, relative to that on bare gold electrode. In terms of less positive oxidation potential, the FePc derivative (3) gave the best response, while the best current signal was observed on SAM-2-modified gold electrode. The average heterogeneous rate constant, k, for the oxidation of carbofuran was 3.6 × 10−2 cm s−1 on the SAM film with the best current signal (SAM-2).
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Formulation development and in vitro evaluation of didanosine-loaded nanostructured lipid carriers for the potential treatment of AIDS dementia complex
- Authors: Wa Kasongo, Kasongo , Shegokar, Ranjita , Müller, Rainer H , Walker, Roderick B
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184210 , vital:44190 , xlink:href="https://doi.org/10.3109/03639045.2010.516264"
- Description: The purpose of this article was to investigate the feasibility of incorporating didanosine (DDI) into nanostructured lipid carriers (NLC) for potential treatment of AIDS dementia complex. Aqueous DDI-free and DDI-loaded NLC were manufactured using hot high-pressure homogenization. The lipid matrix contained a mixture of Precirol ® ATO 5 and Transcutol ® HP. Photon correlation spectroscopy revealed that the mean particle size for all formulations was below 250 nm with narrow polydispersity indices. In addition, the d99% values for all formulations determined using laser diffractometry were below 400 nm with the span values ranging from 0.84 to 1.0. The zeta potential values ranged from −18.4 to −11.4 mV and the encapsulation efficiency of NLC for DDI ranged from 33.02% to 78.34%. These parameters remained relatively constant for all formulations tested following storage for 2 months at 25°C indicating that all the formulations were relatively stable. Differential scanning calorimetry revealed a decrease in the degree of crystallinity of NLC in all formulations developed relative to the bulk lipid material. In addition, wide-angle X-ray scattering showed that NLC in all formulations tested existed in a single β-modification form and that DDI that had been incorporated into the NLC appeared to be molecularly dispersed in the lipid matrices. Images of the NLC formulations obtained using transmission electron microscopy revealed that all formulations contained a mixture of spherical and nonspherical particles irrespective of the amount of DDI that was added during the manufacture of the formulations.
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Gender and Racial Stereotyping in Rape Coverage: An analysis of rape coverage in a South African newspaper, Grocott’s Mail
- Authors: Bonnes, Stephanie M
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/453321 , vital:75245 , https://doi.org/10.1080/14680777.2011.623170
- Description: This article uses critical discourse analysis to discuss and analyse articles about rape that appeared in a South African newspaper, Grocott's Mail, between 14 October, 2008 and 29 October, 2009. Drawing on existing literature on “rape myths” in media coverage of rape, this article argues that Grocott's Mail perpetuates racial and gender stereotypes through the way in which it reports on rape. While not all of the articles included in the analysis use rape myths, most use one or more when discussing rape incidents. Specifically, Grocott's Mail tends to use rape myths that blame the victim for the rape and de-emphasise the role of the perpetrator in the rape.
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Geographic variation in the trophic ecology of an avian rocky shore predator, the African black oystercatcher, along the southern African coastline
- Authors: Kohler, Sophie A , Connan, Maëlle , Hill, Jaclyn M , Mablouké, Cécile , Bonnevie, Bo T , Ludynia, Katrin , Kemper, Jessica , Huisamen, Johan , Underhill, Leslie G , Cherel, Yves , McQuaid, Christopher D , Jaquemet, Sébastien
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444576 , vital:74252 , https://doi.org/10.3354/meps09215
- Description: The reflection of baseline isotopic signals along marine food chains up to higher trophic levels has been widely used in the study of oceanic top predators but rarely for intertidal predators. We investigated variation in the δ 13 C and δ 15 N ratios of a sedentary, rocky shore predator, the African black oystercatcher Haematopus moquini, over~ 2000 km of the southern African coastline, which is characterized by strong biogeographic patterns in primary productivity and intertidal communities. Blood and feathers from breeding adults and chicks and muscle tissues from primary prey items (mussels and limpets) were sampled between southern Namibia and the southeast coast of South Africa. 15 N enrichment was observed between the southeast and west coasts in oystercatcher tissues and their prey, mirroring an isotope shift between the oligotrophic Agulhas Current on the east coast and the eutrophic Benguela upwelling system on the west coast.
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Heritage–A conceptually evolving and dissonant phenomenon: Implications for heritage management and education practices in post-colonial Southern Africa
- Authors: Zazu, Clayton
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/387208 , vital:68215 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122250"
- Description: This conceptual paper is based on experiences and insights which have emerged from my quest to develop a conceptual framework for working with the term ‘heritage’ within an education for sustainable development study that I am currently conducting. Of specific interest to me, and having potential to improve the relevance and quality of heritage education in southern Africa, given the region’s inherent cultural diversity and colonial history, is the need for ‘heritage construct inclusivity’ within the processes constituting heritage education practices. Working around this broad research goal, I therefore needed to be clear about what I mean or refer to as heritage. I realised, however, how elusive and conceptually problematic the term ‘heritage’ is. I therefore, drawing from literature and experiences gained during field observations and focus group interviews, came up with the idea of working with three viewpoints of heritage. Drawing on real life cases I argue that current heritage management and education practices’ failure to recognise and respect the evolving, interconnectedness and multi layered nature of heritage, partly explain the same practices’ lack of relevance and agency to enhance the sustainable management of local heritage resources. I also suggest a few ideas which heritage educators in the context of post-colonial southern Africa may need to consider in their everyday heritage education practices. I also introduce the notion of conceptualising heritage as ‘cultural landscapes’, within which the evolving, dissonant and interconnected nature of heritage, and associated heritage constructs, may be reconciled.
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In vitro toxicity testing of zinc tetrasulfophthalocyanines in fibroblast and keratinocyte cells for the treatment of melanoma cancer by photodynamic therapy
- Authors: Maduray, Kaminee , Karsten, Alta , Odhay, Bharti , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247588 , vital:51597 , xlink:href="https://doi.org/10.1016/j.jphotobiol.2011.01.020"
- Description: A series of water-soluble tetrasulfonated metallophthalocyanines (MPcs) dyes have been studied to be used as a drug or photosensitizer (PS) in photodynamic therapy (PDT) for the treatment of cancers. During PDT the PS is administrated intravenously or topically to the patient before laser light at an appropriate wavelength is applied to the cancerous area to activate the PS. The activated PS will react with oxygen typically present in the cancerous tissue to generate reactive oxygen species for the destruction of the cancerous tissue. This in vitro study aimed at investigating the cytotoxic effects of different concentrations of zinc tetrasulfophthalocyanines (ZnTSPc) activated with a diode laser (λ = 672 nm) on melanoma, keratinocyte and fibroblast cells. To perform this study 3 × 104 cells/ml were seeded in 24-well plates and allowed to attach overnight, after which cells were treated with different concentrations of ZnTSPc. After 2 h, cells were irradiated with a constant light dose of 4.5 J/cm2. Post-irradiated cells were incubated for 24 h before cell viability was measured using the CellTiter-Blue Viability Assay. Data indicated high concentrations of ZnTSPc (60–100 μg/ml) in its inactive state are cytotoxic to the melanoma cancer cells. Also, results showed that photoactivated ZnTSPc (50 μg/ml) was able to reduce the cell viability of melanoma, fibroblast and keratinocyte cells to 61%, 81% and 83% respectively. At this photosensitizing concentration the efficacy the treatment light dose of 4.5 J/cm2 against other light doses of 2.5 J/cm2, 7.5 J/cm2 and 10 J/cm2 on the different cell lines were analyzed. ZnTSPc at a concentration of 50 μg/ml activated with a light dose of 4.5 J/cm2 was the most efficient for the killing of melanoma cancer cells with reduced killing effects on healthy normal skin cells in comparison to the other treatment light doses. Melanoma cancer cells after PDT with a photosensitizing concentration of 50 μg/ml and a treatment light dose of 4.5 J/cm2 showed certain apoptosis characteristics such as chromatin condensation and fragmentation of the nucleus. This concludes that low concentrations of ZnTSPc activated with the appropriate light dose can be used to induce cell death in melanoma cells with the occurrence of minimal damage to surrounding healthy tissue.
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Incorporating uncertainty in water resources simulation and assessment tools in South Africa
- Authors: Hughes, Denis A , Kapangaziwiri, E , Mallory, S J , Wagener, T , Smithers, J
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/438239 , vital:73445 , ISBN 978-1-4312-0128-0 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/18381.pdf
- Description: The main objective of the project was to contribute to the incorporation of uncer-tainty assessments in water resource decision making in South Africa, thereby quan-tifying the risks associated with specific decisions about planned future water re-source developments. This objective was supported by several specific aims: 1. De-velop an understanding of uncertainty and associated risks in water resource man-agement on the basis of literature and known practices, nationally and internation-ally. 2. Identify and characterise the main sources of uncertainty (focusing on cur-rent South African practice and typical situations of data availability). 3. Develop techniques and guidelines for quantifying the uncertainty associated with different models. This will include uncertainty in all relevant areas (hydrological, climate, economic, social, etc.). 4. Determine the effects of uncertainty on water resource management and identify what level of uncertainty is acceptable. 5. Develop guide-lines for the communication of uncertainty and the impacts to various stakeholder groups involved within water resource planning and management. This aim will need to address the issue of the links between uncertainty and risk. 6. Develop guidelines for incorporating uncertainty and the associated risk into water resource decision making processes. 7. Identify those areas of uncertainty that can be realistically re-duced and which will have the greatest impact on reducing the risks involved with water resource decision making.
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Invasion of a headwater stream by non-native fishes in the Swartkops River system, South Africa
- Authors: Ellender, Bruce R , Weyl, Olaf L F , Swartz, Ernst R
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/446866 , vital:74566 , https://doi.org/10.1080/15627020.2011.11407477
- Description: In South Africa, fishes in headwater streams are increasingly being threatened by non-native fish invasions. These invasions originate primarily from source populations in mainstream rivers and impoundments. In the Blindekloof stream, a Swartkops River headwater tributary, the non-native Micropterus salmoides was eradicated from the stream by conservation authorities in 1989. As a result of this eradication subsequent occurrences of non-native fishes are most likely a result of upstream invasions from the mainstream Swartkops River. The Blindekloof stream therefore provided a unique opportunity to investigate whether M. salmoides would reinvade after its removal in 1989 and if the more recently introduced Clarias gariepinus and Tilapia sparrmanii would invade the Blindekloof stream. During snorkel and electrofishing surveys four non-native species were recorded (M. salmoides, M. dolomieu, T. sparrmanii, C. gariepinus ).
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Invasion of a South African Anguilla mossambica (Anguillidae) population by the alien gill worm Pseudodactylogyrus anguillae (Monogenea)
- Authors: Parker, Denham , Weyl, Olaf L F , Taraschewski, Horst
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443367 , vital:74111 , https://hdl.handle.net/10520/EJC18196
- Description: The parasitic gill monogenean Pseudodactylogyrus anguillae is alien to Africa. In an investigation of 227 longfin eel, Anguilla mossambica, and 26 mottled eel, Anguilla marmorata, sampled from four river systems in the Eastern Cape, South Africa, this parasite was only present on the gills of A. mossambica sampled from the Great Fish River system. In the Great Fish River, it infected 73.2% of the sampled population at a mean intensity of 63.8 ± 34.3 parasites per fish. High prevalence and intensity are indicative of a well-established alien invasive parasitic species. Results showing the absence of P. anguillae from the co-occurring but less abundant A. marmorata indicate that this species may be less susceptible to P. anguillae infection.
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Invasive alien freshwater fishes in the Wilderness Lakes System, a wetland of international importance in the Western Cape Province, South Africa
- Authors: Olds, Alexis A , Smith, M K S , Weyl, Olaf L F , Russell, I A
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/446879 , vital:74567 , https://doi.org/10.1080/15627020.2011.11407491
- Description: The Wilderness Lakes System incorporates a RAMSAR listed wetland. Previous ichthyological surveys reported three invasive freshwater fishes; Oreochromis mossambicus (Mozambique tilapia), Gambusia affinis (mosquitofish) and Micropterus salmoides (largemouth bass) from this system. To assess the status of these alien fishes, the fish assemblages in the lakes system were sampled with seine nets and fyke nets in 2009 and 2010. A total of 87 893 fish comprising 16 species were caught. In addition to confirming the persistence of O. mossambicus and G. affinis in the system, the current study also reports the presence of a new invader, Cyprinus carpio (common carp). M. salmoides were absent from 2009 and 2010 samples.
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Investigation of homogeneous photosensitized oxidation activities of palladium and platinum octasubstituted phthalocyanines
- Authors: Ogunbayo, Taofeek B , Antunes, Edith M , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/248394 , vital:51682 , xlink:href="https://doi.org/10.1016/j.molcata.2010.11.008"
- Description: Photosensitized oxidation of 4-nitrophenol was studied in organic solutions with seven octasubstituted thio and aryloxy palladium and platinum phthalocyanines acting as photosensitizers. Kinetic studies conducted also showed that the complexes have different singlet oxygen quenching constants with direct implication on the quantum yield of photodegradation of 4-nitrophenol (Φ4-NP). Palladium analogues gave better results than the platinum analogues in terms of Φ4-NP with palladium-(dodecylthio)phthalocyanine giving the highest yield of 1.8 × 10−3. Gas chromatography (GC) and liquid chromatography connected to a mass spectrometer (LC–MS) were used to confirm the photodegradation products which were hydroquinone and 1,4-benzoquinone.
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Macrofaunal community structure in the littoral zone of a freshwater-deprived, permanently open Eastern Cape estuary
- Authors: Henninger, Tony O , Froneman, P William
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443954 , vital:74174 , https://doi.org/10.1080/15627020.2011.11407500
- Description: Spatial patterns in the macrofauna community structure within four distinct zones of the permanently open, freshwater-deprived Kariega Estuary on the southeastern coastline of southern Africa were investigated in March–May 2010. The zones within the littoral zone comprised a band of Zostera capensis (Setchell) exposed at spring low tide and comprising Zone I; a band of mud or sand, lacking vegetation, corresponded to Zone II; stands of Spartina maritima (Curtis) formed Zone III and a belt of Sarcocornia perennis (Miller) constituted Zone IV.
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Microelectrochemical patterning of gold surfaces using 4-azidobenzenediazonium and scanning electrochemical microscopy
- Authors: Coates, Megan , Cabet, Eva , Griveau, Sophie , Nyokong, Tebello , Bedioui, Fethi
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247926 , vital:51630 , xlink:href="https://doi.org/10.1016/j.elecom.2010.11.037"
- Description: This work describes for the first time the possibility of performing local micro electrochemical grafting of a gold substrate by 4-azidobenzenediazonium by SECM in a single and simple one step without complications from adsorption. The electrografted spots of diazonium were performed by positioning a Pt tip at a given distance above the gold substrate and the SECM was used in a three-electrode configuration (the Pt tip serving as the microanode) in acetonitrile containing 5 mM 4-azidobenzenediazonium and 0.1 M Bu4NBF4 during 10 ms. The dimensions of the derivatized areas of the substrates were finely tuned by using different experimental conditions (tip distance above the substrate, tip diameter, presence or absence of supporting electrolyte). The use of the azido-derivated diazonium molecule and these preliminary results open the gate to important applications and developments devoted to the local micro functionalization of electrodes by thin layers that allow the implementation of the emerging and attractive interfacial click reaction.
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Morphology and identification of first instars of African blow flies (Diptera: Calliphoridae) commonly of forensic importance
- Authors: Szpila, Krzysztof , Villet, Martin H
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442225 , vital:73968 , https://doi.org/10.1603/ME10238
- Description: Scanning electron microscopy images of the first instars of Calliphora croceipalpis Jaennicke, 1876; Chrysomya chloropyga (Wiedemann, 1818); Chrysomya marginalis (Wiedemann, 1830); and Chrysomya putoria (Wiedemann, 1830) (Diptera: Calliphoridae) are presented for the first time, and the following morphological structures are documented: pseudocephalon, antenna, maxillary palpus, facial mask, labial lobe, thoracic and abdominal spinulation, spiracular field, posterior spiracles, and anal pads. Light microscopy photographs and line illustrations are provided for the cephaloskeleton in lateral and ventral views, and the “ectostomal sclerite” and “chitinized teeth” of the cephaloskeleton are recognized as integral parts of the mouthhooks. New diagnostic features of the cephaloskeleton and the spinulation of the abdominal segments are described. These results allow refinement, clarification, and correction of earlier descriptions, which are reviewed. The relative taxonomic importance of various morphological characters of the first instars of necrophagous blow flies is discussed, and details of the cephaloskeleton and the spinulation of the abdominal segments are highlighted as the characters most useful for species identification. Finally, a key for identifying first instars of common African carrion blow flies is provided.
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Ontogenetic dietary shift and morphological correlates for Diplodus capensis (Teleostei Sparidae) in southern Angola
- Authors: Richardson, Timothy J , Potts, Warren M , Santos, Carmen V D , Sauer, Warwick H H
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443984 , vital:74176 , https://doi.org/10.1080/15627020.2011.11407501
- Description: Allometric growth patterns of functional morphological variables that reflect resource use in fish were correlated with the diet of Diplodus capensis in southern Angola. A total of 114 individuals (76–336 mm FL) were collected for stomach content analysis and a further 35 individuals (80–320 mm FL) for morphometric analysis. The major dietary components belonged to the groups Chlorophyta, Cirripedia, Rhodophyta and Bivalvia, and made up 71.7% of the diet in terms of a computed ranking index. There was a clear ontogenetic dietary shift with small fish feeding predominantly on algae and large fish on barnacles and mussels. This increasingly durophagous diet corresponded with a positive allometric growth pattern in the gape dimensions (width, height and surface area), adductor mandibulae muscle process and incisor width. Conversely, the relative gut length followed an isometric growth pattern, suggesting a decreased absorptive capacity. This isometric growth pattern is attributed to the better digestibility of the durophagous prey items when compared with algae and further corroborates a link between the morphology and an ontogenetic dietary shift observed in this species.
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Optical limiting behavior of ring substituted zinc, indium and gallium phthalocyanines in the presence of quantum dots
- Authors: Britton, Jonathan , Litwinski, Christian , Durmus, Mahmut , Chauke, Vongani , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247122 , vital:51548 , xlink:href="https://doi.org/10.1142/S1088424611004142"
- Description: This paper presents the study of the effects of CdTe-TGA quantum dots (QDs) on optical limiting ability of different phthalocyanine (Pc) complexes (1–10) containing Zn, Ga, In central metals and substituted with benzyloxyphenoxy, phenoxy, tert-butylphenoxy and amino groups. The optical limiting parameters of Pcs were higher for tert-butylphenoxy when compared to benzyloxyphenoxy and phenoxy substituents, in DMSO. Non-peripheral substitution decreased the optical limiting parameters. Third-order susceptibility (Im[χ(3)]/α) values of Pcs in the absence and presence of CdTe QDs were in the 10-12 to 10-10 esu.cm range. Hyperpolarizabilities (γ) ranged from 10-31 to 10-29 esu L for Pc alone or in mixture with QDs. There is a general improvement in optical limiting ability of Pc complexes in the presence of CdTe TGA QDs. Due to these promising results, future work can be implemented for the creation of Pc:QD thin films, which would then be examined to ensure that their optical limiting ability is still acceptable.
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Optimal template removal from molecularly imprinted polymers by pressurized hot water extraction
- Authors: Batlokwa, Bareki Shima , Mokgadi, Janes , Nyokong, Tebello , Torto, Nelson
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247813 , vital:51620 , xlink:href="https://doi.org/10.1007/s10337-010-1884-3"
- Description: An optimal extraction method for the removal of templates from molecularly imprinted polymers (MIPs) is presented. The extraction method is based on pressurized hot water extraction (PHWE). PHWE was evaluated by application to three distinctly colored MIPs for chlorophyll (green), quercetin (yellow) and phthalocynine (dark blue) with subsequent monitoring of template removal and template bleeding by an ultraviolet spectrophotometer. The templates were washed-off and the extraction efficiency (EE) was compared to that of soxhlet and ultrasonic extraction methods. PHWE employed hot water at an optimal temperature of 220 °C, pressure of 50 bars and flow rate of 2 mL min−1 to thoroughly wash-off the respective templates from their MIPs. The EE evaluated for PHWE was over 99.6% for all the MIPs with no subsequent or minimal template bleeding (more than 0.01%). The washing procedure was simple and relatively fast as it was achieved in 70 min at the most. At 95% confidence level (n = 3), soxhlet and ultrasonic recorded EE that was not significantly different (more than 94.5% in all cases) from that of PHWE (less than 99.6% in all cases). Soxhlet and ultrasonic had washing procedures that were slower (over 18 h) and employed large quantities (400 mL) of organic solvents modified with acids. The percentage relative standard deviations (%RSD) for the EE and recovery results were less than 2.3% in all cases indicating the high reproducibility of the method. Overall, the three methods performed comparably in extracting templates. PHWE seems to be the method of choice as it employed water which poses no environmental threat.
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Optimizing the electrocatalytic activity of surface confined Co macrocyclics for the electrooxidation of thiocyanate at pH 4
- 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.
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Photocatalytic behaviour of tantalum (V) phthalocyanines in the presence of gold nanoparticles towards the oxidation of cyclohexene
- Authors: Chauke, Vongani P , Antunes, Edith M , Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247904 , vital:51628 , xlink:href="https://doi.org/10.1016/j.molcata.2010.11.023"
- Description: This paper presents the photocatalytic oxidation of cyclohexene using (OH)3TaPc derivatives in the absence or presence of gold nanoparticles (AuNPs). The photochemical parameters that include photodegradation (ΦP) and singlet oxygen (ΦΔ) quantum yields are also reported in this work. The ΦΔ values were 0.47 and 0.36 for complexes 1a and 1b, respectively. The ΦΔ values improved drastically in the presence of AuNPs to 0.75 and 0.88, respectively. The ΦP values ranged from 1.02 to 2.45 × 10−6, showing stability of TaPc derivatives in the absence and presence of AuNPs. The photocatalytic products identified using gas chromatograph (GC) are cyclohexene oxide, 2-cyclohexen-1-ol, 2-cyclohexene-1-one and 1,2-cyclohexanediol. The percentage conversion values were higher in the presence of AuNPs. Singlet oxygen was determined to be the main agent involved in the photocatalytic oxidation of cyclohexene. The product yield percentage values for both TaPc complexes (1a and 1b) and TaPc in the presence of AuNPs ranged from 6.3 to 21.2%.
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