Insights into the surface and redox properties of single-walled carbon nanotube—cobalt (II) tetra-aminophthalocyanine self-assembled on gold electrode
- Authors: Ozoemena, Kenneth I , Nyokong, Tebello , Nkosi, Duduzile , Chambrier, Isabelle , Cook, Michael J
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/281258 , vital:55707 , xlink:href="https://doi.org/10.1016/j.electacta.2006.11.039"
- Description: This paper describes for the first time the electrochemical properties of redox-active self-assembled films of single-walled carbon nanotubes (SWCNTs) coordinated to cobalt(II)tetra-aminophthalocyanine (CoTAPc) by sequential self-assembly onto a preformed aminoethanethiol (AET) self-assembled monolayer (SAM) on a gold electrode. Both redox-active SAMs (Au-AET-SWCNT and Au-AET-SWCNT-CoTAPc) exhibited reversible electrochemistry in aqueous (phosphate buffer) solution. X-ray photoelectron spectroscopy (XPS) confirmed the appearance on the gold surface of the various elements found on the SAMs. Atomic force microscopy (AFM) images prove, corroborating the estimated electrochemical surface concentrations, that these SAMs lie normal to the gold surface. Electrochemical impedance spectroscopy (EIS) analyses in the presence of [Fe(CN)6]3−/4− as a redox probe revealed that the Au-AET-SWCNT-CoTAPc showed much lower (∼10 times) electron-transfer resistance (Ret) and much higher (∼10 times) apparent electron-transfer rate constant (kapp) compared to the Au-AET-SWCNT SAM. Interestingly, a preliminary electrocatalytic investigation showed that both SAMs exhibit comparable electrocatalytic responses towards the detection of dopamine in pH 7.4 phosphate buffer solutions (PBS). The electrochemical studies (cyclic voltammetry (CV) and EIS) prove that SWCNT greatly improves the electronic communication between CoTAPc and the Au electrode surface.
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- Date Issued: 2007
'She travels alone and unattended’: the visit to the Eastern Cape of the botanical artist, Marianne North
- Authors: Beard, Margot
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147759 , vital:38668 , https://doi.org/10.1080/00043389.2007.11877077
- Description: The visit of the botanical artist, Marianne North, to South Africa during 1882 to 1883, although frequently referred to, has not received much close attention; nor has her account of the visit, in her ‘Recollections of a happy’ life, been set against the actual conditions she would have encountered. This paper attempts to flesh out at least part of that visit, specifically the weeks she spent in the Eastern Cape Colony and, more particularly, her visits to Port Elizabeth, Grahamstown and Port Alfred. What were these three centres like at the time? Who were the people she mentions? Where did she stay? How do her observations tally with other accounts of the period?.
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- Date Issued: 2017
Synthesis, photophysical and photochemical studies of new water-soluble indium (III) phthalocyanines
- Authors: Durmus, Mahmut , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/283976 , vital:56007 , xlink:href="https://doi.org/10.1039/b618478b"
- Description: The preparation of water-soluble indium(III)phthalocyanine complexes is described for the first time in this study. Peripherally and non-peripherally 3-hydroxypyridine tetrasubstituted indium(III) phthalocyanines (5a, 6a) and their quaternarized derivatives (5b, 6b) have been synthesized and characterized by elemental analysis, IR, 1H NMR spectroscopy, electronic spectroscopy and mass spectra. The quaternarized compounds (5b, 6b) show excellent solubility in water, which makes them potential photosensitizers for use in photodynamic therapy (PDT) applications. Photochemical and photophysical measurements were conducted on 3-pyridyloxy appended indium(III) phthalocyanines in dimethylsulfoxide (DMSO) for non-ionic (5b, 6b) derivatives. General trends are described for quantum yields of photodegradation, fluorescence lifetimes, fluorescence quantum yields, triplet lifetimes and triplet quantum yields as well as singlet oxygen quantum yields of these compounds. 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) are very high (ΦΔ > 0.55). Thus, these complexes may be useful as Type II photosensitizers.
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- Date Issued: 2007
Towards continental transformation: understanding sustainable peace agreements in Africa
- Authors: Bischoff, Paul, 1954-
- Date: 2007
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/161409 , vital:40624 , https://0-hdl.handle.net.wam.seals.ac.za/10520/EJC15983
- Description: There are social and political questions to be asked about the new continent-wide institutions in and around what is still a young African Union (AU). These include questions such as whether the AU and its institutions can be built in ways that will allow this body to transform Africa's international relations, and how this is to be done. What are the norms and values that will inform this change and the African renewal promoted by the AU? Is the multilateral architecture of the AU able to encourage democracy and people-centredness, for instance? Will it, in the end, be able to deliver on the hoped-for "pan-African transnational democratic revolution"?.
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- Date Issued: 2007
Transforming the media: a cultural approach
- Authors: Steenveld, Lynette N
- Date: 2007
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147891 , vital:38682 , DOI: 10.1080/02560240485310061
- Description: The change from an Apartheid state to a liberal democratic one has wrought many changes at all levels of South African society: the economic, social, political, cultural. This paper explores the impacts of these changes on the South African print media industry, with a view to assessing their contribution to the development of a democratic citizenship. While acknowledging the constraining effects of economic structures of ownership, the paper locates these within the broader social and political context of post-apartheid South Africa. It thus attempts to synthesise elements of both a political economy and cultural approach to the analysis of cultural production.
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- Date Issued: 2007
Negotiating the Good Life
- Authors: Tabensky, Pedro
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/305688 , vital:58604 , xlink:href="http://10.1007/s10677-006-9030-x"
- Description: Book Review: Mark A. Young asks: “Is there a problem with community in America?” (p. 1). Agreeing with Robert Putnam’s views, embodied in Bowling Alone: The Collapse and Revival of American Community (New York: Touchstone Press, 2000), regarding the breakdown of communal values in the US, but not with his nostalgic recommendations regarding the ‘good old days’ of univocal homogenous communities, Young proposes an alternative solution to Putnam’s, starting from Aristotle’s sophisticated account of the self/community relation and drawing important insights from Alasdair MacIntyre, Charles Taylor, Amitai Etzione, Paul Ricoeur, Michael Sandel and especially Hannah Arendt.
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- Date Issued: 2007
Photochemistry, photophysics and nonlinear optical parameters of phenoxy and tert-butylphenoxy substituted indium (III) phthalocyanines
- Authors: Chauke, Vongani , Durmus, Mahmut , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/268787 , vital:54232 , xlink:href="https://doi.org/10.1016/j.jphotochem.2007.05.022"
- Description: This work hereby presents the syntheses, photochemistry and photophysics of octaphenoxy ((Cl)InOPPc) and octakis(4-tert-butylphenoxy)chloroindium ((Cl)InOTBPPc) phthalocyanines. Calculated nonlinear parameters of these complexes are compared with those of the corresponding GaPc derivatives and tetrasubstituted GaPc and InPc complexes. Fluorescence quantum yields do not vary much between (Cl)InOPPc and (Cl)InOTBPPc complexes in different solvents. High quantum yields of triplet state (ΦT ranging from 0.70 to 0.91 in dimethysulphoxide, DMSO) and singlet oxygen generation (ΦΔ, ranging from 0.61 to 0.79 in DMSO) were obtained. Short triplet lifetimes 50–60 μs were obtained in DMSO). The optical limiting threshold intensity (Ilim) for the InPc derivatives were calculated and compared with those of corresponding tetrasubstituted InPc and GaPc complexes. The latter were found to be better optical limiters.
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- Date Issued: 2007
Language policy and planning: general constraints and pressures
- Authors: Wright, Laurence
- Date: 2007
- Language: English
- Type: text , article
- Identifier: vital:7043 , http://hdl.handle.net/10962/d1007385
- Description: preprint , The general idea of language policy and planning is easily expressed. Christopher Brumfit, for one, defines language planning as “The attempt to control the use, status, and structure of a language through a language policy developed by a government or other authority” (see the Oxford Companion to the English Language). The Random House Dictionary of the English Language concurs, but adds some detail: language planning is “the development of policies or programmes designed to direct or change language use, as through the establishment of an official language, the standardization or modernization of a language, or the development or alteration of a writing system”. Such definitions could easily be multiplied, and they differ only slightly in nuance and depth.Language Policy is the formal, often legally entrenched, expression of language planning.
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- Date Issued: 2007
Electrocatalytic oxidation of nitrite by tetra-substituted oxotitanium (IV) phthalocyanines adsorbed or polymerised on glassy carbon electrode
- Authors: Tau, Prudence , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/268762 , vital:54230 , xlink:href="https://doi.org/10.1016/j.jelechem.2007.07.019"
- Description: Comparative electrocatalytic oxidation of nitrite by tetra aryloxy-substituted oxotitanium(IV) and tetraamino phthalocyanine complexes is investigated in this work. The aryloxy complexes are substituted at the peripheral (4) and non-peripheral (5) positions with phenoxy (complexes a), 4-tert-butylphenoxy (complexes b), benzyloxy (complexes c) and 4-(benzyloxy)phenoxy (complexes d) groups. The glassy carbon electrode was employed and modified with the tetra aryloxy-substituted titanium phthalocyanine complexes (4 and 5) by adsorption, and with titanium tetraamino phthalocyanine (TiTAPc) by polymerisation. All complexes reduced the overpotential of the nitrite electrooxidation as well as enhanced the catalytic current by a 2 electron process.
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- Date Issued: 2007
Identity in the Siyagruva Series of novels: Toward an intercultural
- Authors: Kaschula, Russell H
- Date: 2007
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/175159 , vital:42548 , DOI: 10.4314/tvl.v44i2.29792
- Description: This article explores the notion of changing South African youth identity and how it is depicted in the Siyagruva [We are Grooving] Series of novels for young adults. The article highlights the need for a broadening of literary theory in order to include an appropriate theoretical approach for new South African youth literature. This theory explores intercultural literary discourse by making use of, for example, the work of intercultural theorists such as Ting-Toomey (1999), Gudykunst (2003) and others. It is argued that this form of literary discourse is now appropriate as a theoretical paradigm within multilingual South Africa where intercultural communication is becoming a reality. There is also reference to intracultural communication where differences are beginning to appear between young people who are perceived to come from the same cultural group, for example, the character Brunette in the Siyagruva Series who is perceived as a “coconut” by her friends, and thus finds herself having to justify her belonging within a particular in-group or culture. The article concentrates on selected novels, though reference is made to many of the twenty three published novels in the Siyagruva Series, twenty in English, and three translated into isiXhosa.
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- Date Issued: 2007
Spectroscopic characterisation and interactions of sulfonated titanium and tantalum phthalocyanines with methyl viologen
- Authors: Tau, Prudence , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/283129 , vital:55913 , xlink:href="https://doi.org/10.1016/j.ica.2006.12.035"
- Description: Sulfonated OTiPc(S)n and (Cl3)TaPc(S)n complexes are prepared and characterised by spectroscopic methods in DMSO, methanol and PBS 7.4. The dominant sulfonated species was the disulfophthalocyanine. OTiPc(S)n is highly aggregated in PBS 7.4 solution and tends to partially monomerise, on addition of Triton X-100, while (Cl3)TaPc(S)n showed broadened spectra in all solvents and was not affected by Triton X-100. The absorption and excitation spectra of OTiPc(S)n are similar and are mirror images of their emission spectra in DMSO, but differ in PBS and methanol. The fluorescence quantum yields (ϕF) and lifetimes (τF) were larger in DMSO than in methanol. In PBS 7.4, however, the ϕF and τF values were significantly smaller for OTiPc(S)n, which is typical of aggregated species. Gradual addition of the electron-acceptor MV2+ to solutions of MPc(S)n complexes resulted in the fluorescence quenching of complexes with higher quenching observed for OTiPc(S)n. The interaction of the MPc(S)n complexes with MV2+, and hence the stoichiometry and association constants are evaluated by means of Job method.
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- Date Issued: 2007
Synthesis, photophysical and photochemical properties of tetra-and octa-substituted gallium and indium phthalocyanines
- Authors: Durmus, Mahmut , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/271276 , vital:54529 , xlink:href="https://doi.org/10.1016/j.poly.2007.03.007"
- Description: The synthesis, photophysical and photochemical properties of the tetra- and octa-[4-(benzyloxyphenoxy)] substituted gallium(III) and indium(III) phthalocyanines are reported for the first time. The new compounds have been characterized by elemental analysis, IR, 1H NMR spectroscopy and electronic spectroscopy. General trends are described for quantum yields of photodegredation, fluorescence quantum yields and lifetimes, triplet lifetimes and triplet quantum yields as well as singlet oxygen quantum yields of these compounds in dimethylsulfoxide (DMSO). Substituted indium phthalocyanine complexes (7b–9b) showed much higher quantum yields of triplet state and shorter triplet lifetimes, compared to the substituted GaPc derivatives due to enhanced intersystem crossing (ISC) in the former. The gallium and indium phthalocyanine complexes showed phototransformation during laser irradiation due to ring reduction. 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) ranged from 0.51 to 0.94. Thus, these complexes show potential as photodynamic therapy of cancer.
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- Date Issued: 2007
Characterization of self-assembled monolayers of iron and cobalt octaalkylthiosubstituted phthalocyanines and their use in nitrite electrocatalytic oxidation
- Authors: Matemadombo, Fungisai , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/271182 , vital:54519 , xlink:href="https://doi.org/10.1016/j.electacta.2007.05.002"
- Description: Cobalt and iron phenylthiosubstituted phthalocyanines have been deposited on Au electrode surfaces through the self-assembled monolayer (SAM) technique. The so formed layers were studied using voltammetric and impedance techniques. These SAMs blocked a number of Faradic processes and electrocatalyzed the oxidation of nitrite. The electrocatalytic parameters of the cobalt and iron phenylthiosubstituted phthalocyanines deposited on Au electrodes in nitrite solution were studied. Nitrite overpotentials which are lower than ever reported were obtained in this work for the iron phenylthiosubstituted phthalocyanines with very high stability.
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- Date Issued: 2007
Syntheses and photophysics of new phthalocyanine derivatives of zinc, cadmium and mercury
- Authors: Chidawanyika, Wadzanai J U , Ogunsipe, Abimbola , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/283940 , vital:56005 , xlink:href="https://doi.org/10.1039/B615663K"
- Description: The syntheses of novel tetra{2,(3)-pyridyloxyphthalocyaninato} complexes of zinc, cadmium and mercury (TPyZnPc, TPyCdPc and TPyHgPc) are presented. Their spectral and photophysical properties (as well as those of their unsubstituted counterparts: ZnPc, CdPc and HgPc) are investigated. TPyZnPc and TPyCdPc are aggregated in non-coordinating solvents such as chloroform, while TPyHgPc is demetallated, as evident from their respective absorption spectra. The trends in fluorescence (ΦF), triplet (ΦT) and singlet oxygen (ΦΔ) quantum yields are explained in terms of relative strengths of spin–orbit coupling induced by the respective central metal ions in the complexes. The effect of the pyridyloxy substituents is a decrease in ΦF and an increase in ΦT values. The complexes are less fluorescent in DMSO but possess higher ΦT, triplet lifetimes (τT) and ΦΔ therein.
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- Date Issued: 2007
Rhodes University EE and Sustainability Unit
- Authors: Lotz-Sisitka, Heila , Schudel, Ingrid J
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/294423 , vital:57220 , xlink:href="https://doi.org/10.1177/097340820700100127"
- Description: In the early 1990s, in response to the emphasis laid on environment and development issues by the new South African Constitution, Rhodes University undertook several initiatives such as establishing the first Chair of Environmental Education (EE) in Africa. Another important initiative was the introduction of an open-entry participatory course for environmental educators. Owing to its flexible format and practice-based methodology, the course gained rapid popularity, necessitating the setting up of a Service Centre to help meet the increased demand. The Chair and the Service Centre have been providing a range of short courses in environment and sustainability education to professionals, and are today widely known as the Rhodes University Environmental Education and Sustainability Unit (RUEESU). The Unit offers PhD and Masters level programmes in EE, encourages meaningful research in key thematic areas, and is actively involved in publishing, and policy transformation. It also endeavours to define the role of Universities in enabling sustainability education.
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- Date Issued: 2007
Assessing the effects of invasive alien species on rural livelihoods: Case examples and a framework from South Africa
- Authors: Shackleton, Charlie M , McGarry, Dylan K , Fourie, Saskia , Gambiza, James , Shackleton, Sheona E , Fabricius, Christo
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181279 , vital:43715 , xlink:href="https://doi.org/10.1007/s10745-006-9095-0"
- Description: The detrimental impacts of invasive alien species (IAS) on ecosystem goods and services and local and regional economies are well documented. However, the use of IAS by rural communities is little understood, and rarely factored into IAS control programmes. Understanding the use of IAS by rural communities and factoring these into cost-benefit models is complex, depending upon a range of local-level attributes such as the time since invasion, abundance, and local-level costs and benefits. This paper reports on two case studies examining the role of IAS in rural livelihoods in the Eastern Cape, South Africa. In both cases, rural communities made widespread consumptive use of the IAS and generally would prefer higher densities, except in certain key localities. Several households traded in IAS products to generate supplementary income. We present a conceptual framework to guide interpretation of these and future case studies, considering attributes such as time since invasion, the competitiveness of the species, and the relative costs and benefits.
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- Date Issued: 2007
An analysis of the influence of question design on learners' approaches to number pattern generalisation tasks:
- Authors: Samson, Duncan , Schäfer, Marc
- Date: 2007
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141026 , vital:37938 , https://0-hdl.handle.net.wam.seals.ac.za/10520/EJC20890
- Description: This paper reports on a study of the extent to which question design affects the solution strategies adopted by children when solving linear number pattern generalisation tasks presented in pictorial and numeric contexts. The research tool comprised a series of 22 pencil-and-paper exercises based on linear generalisation tasks set in both numeric and two-dimensional pictorial contexts. The responses to these linear generalisation questions were classified by means of stage descriptors as well as stage modifiers. The method or strategy adopted was analysed and classified into one of seven categories. In addition, a meta-analysis focused on the formula derived for the nth term in conjunction with its justification. The results of this study strongly support the notion that question design can play a critical role in influencing learners' choice of strategy and level of attainment when solving pattern generalisation tasks. An understanding of the importance of appropriate question design has direct pedagogical application within the context of the mathematics classroom.
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- Date Issued: 2007
Does 'African mathematics' facilitate access to mathematics?: towards an ongoing critical analysis of ethnomathematics in a South African context
- Authors: Horsthemke, Kai , Schäfer, Marc
- Date: 2007
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141004 , vital:37936 , https://0-hdl.handle.net.wam.seals.ac.za/10520/EJC20885
- Description: Mosibudi Mangena, the Minister of Science and Technology, said in an address to the Annual Congress of the South African Mathematical Society at the University of the Potchefstroom, November 2, 2004: "There is one thing we need to address before anything else. We need to increase the number of young people, particularly blacks and women, who are able to successfully complete the first course in Mathematics at our universities." How is this to be achieved? A popular trend involves a call for the introduction and incorporation of so-called ethnomathematics, and more particularly 'African mathematics', into secondary and tertiary curricula. Although acknowledging the obvious benefits of so-called ethnomathematics, this paper critically analyses three aspects of ethnomathematics that have been neglected in past critiques. Our focus is not on the relationship as such between ethnomathematics and mathematics education. Our critique involves (1) epistemological and logical misgivings, (2) a new look at practices and skills, (3) concerns about embracing 'African mathematics' as valid and valuable - just because it is African.
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- Date Issued: 2007
Making visible constructions of dis/advantage through genealogical investigation: South African schooled literacies
- Authors: Prinsloo, Jeanne
- Date: 2007
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147869 , vital:38680 , DOI: 10.1080/02560040701398889
- Description: In this paper I assume the relevance of Foucauldian insights for conducting socio-cultural critique and I argue the significance of genealogical work in relation to understanding the present. Thus, I seek both to establish what could constitute a genealogical investigation and to illustrate this by describing and discussing a study, undertaken within a genealogical frame, into literacy practices within a specifically South African context. I investigated the differing schooled literacies in KwaZulu-Natal province in South Africa over three decades along the language lines of Afrikaans, English and Zulu. The findings propose that the differing sets of literacy practices validate different subjects – and that they are implicated in constructing dis/advantage.
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- Date Issued: 2007
Giving children a voice:
- Authors: Prinsloo, Jeanne
- Date: 2007
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/159277 , vital:40283 , https://hdl.handle.net/10520/EJC144676
- Description: It was in Johannesburg, South Africa, that the fifth World Summit on Media and Children took place from 24 to 27 March - a great jamboree where a thousand or so delegates from around 86 countries congregated together with 300 young people between the ages of 13 and 16.
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- Date Issued: 2007