Tuning the physico-electrochemical properties of novel cobalt (II) octa [(3, 5-biscarboxylate)-phenoxy] phthalocyanine complex using phenylamine-functionalised SWCNTs
- Authors: Agboola, Bolade O , Ozoemena, Kenneth I , Nyokong, Tebello , Fukuda, Takamitsu , Kobayashi, Nagao
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/261692 , vital:53435 , xlink:href="https://doi.org/10.1016/j.carbon.2009.10.023"
- Description: The integration of phenylamine-functionalised SWCNTs (SWCNT-phenylamine) with a novel cobalt (II) octa[(3,5-biscarboxylate)-phenoxy] phthalocyanine (CoOBPPc) complex has been described. The physical and electrochemical properties of the CoOBPPc-SWCNT-phenylamine hybrid were evaluated using spectroscopy (IR and UV–vis), field emission scanning electron microscopy and electrochemistry (cyclic voltammetry and electrochemical impedance spectroscopy). Integration of SWCNT-phenylamine resulted in the physical transformation of the CoOBCPPc from the usually bluish colour of cobalt phthalocyanine complexes to a beautiful bright green colour. In addition, the heterogeneous electron transfer kinetics and electrocatalytic properties of the CoOBCPPc were greatly enhanced following the attachment of the SWCNT-phenylamine. The potential electrocatalytic application of the hybrid was tested using β-nicotinamide adenine dinucleotide (NADH) as a model biological analyte. Interestingly, the onset oxidation potential of this analyte was significantly reduced (300 mV) by this hybrid compared to the bare electrode.
- Full Text:
- Date Issued: 2010
Using JAIN SLEE as an interaction and policy manager for enabler-based services in next generation networks
- Authors: Tsietsi, Mosiuoa , Terzoli, Alfredo , Wells, George C
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431382 , vital:72770 , https://journals.pan.pl/dlibra/publication/100205/edition/86373/content
- Description: The IP Multimedia Subsystem is a telecommunications framework with a standard architecture for the provision of services. While the services themselves have not been standardised, standards do exist for basic technologies that can be re-used and aggregated in order to construct more complex services. These elements are called service capabilities by the 3GPP and service enablers by the OMA, both of which are repu-table standards bodies in this area. In order to provide re-usability, there is a need to manage access to the service capabilities. Also, in order to build complex services, there is a further need to be able to manage and coordinate the interactions that occur between service capabilities. The 3GPP and the OMA have separately defined network entities that are responsible for handling aspects of these requirements, and are known as a service capability interaction manager (SCIM) and a policy enforcer respectively. However, the internal structure of the SCIM and the policy enforcer have not been standardised by the relevant bodies. In addition, as the SCIM and the policy enforcer have been defined through complementary yet separate processes, there is an opportunity to unify efforts from both bodies. This paper builds on work and stand-ards defined by the bodies, and proposes the design of an interaction manager with features borrowed from both the SCIM and the policy en-forcer. To help validate the design, we have identified a platform known as JAIN SLEE which we believe conforms to the model proposed, and we discuss how JAIN SLEE can be used to implement our ideas.
- Full Text:
- Date Issued: 2010
‘We do not cook, we only assist them’
- Authors: Ratele, Kopano , Shefer, Tamara , Strebel, Anna , Fouten, Elron
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/277945 , vital:55334 , xlink:href="https://doi.org/10.1080/14330237.2010.10820414"
- Description: This article discusses how the gendering of activity by boys coincides with, contests or recreates constructions of hegemonic masculinity in the context of South Africa. The study used a qualitative methodology including a series of three focus groups with 14–16 year-old boys across six different schools in the Western Cape, South Africa. A discursive analysis in which particular attention was paid to how participants construct their masculinity in relation to what they may or may not do as boys/men was conducted. The findings foreground how articulations of masculinity by boys are characterised by efforts to gender activity in the process of, amongst other things, counter blushing—meaning not to be regarded as girl-like or a moffie, or other derogatory notions that do not fit with hegemonic masculinity in a particular context. However, resistances and alternative views on what boys/men can and cannot do also emerged, highlighting the contested nature of current constructions of masculinity among young people in South Africa.
- Full Text:
- Date Issued: 2010
A Comparison Of The Resource Requirements Of Snort And Bro In Production Networks
- Authors: Barnett, Richard J , Irwin, Barry V W
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430040 , vital:72661 , https://www.iadisportal.org/applied-computing-2009-proceedings
- Description: Intrusion Detection is essential in modern networking. However, with the increas-ing load on modern networks, the resource requirements of NIDS are significant. This paper explores and compares the requirements of Snort and Bro, and finds that Snort is more efficient at processing network traffic than Bro. It also finds that both systems are capable of analysing current network loads on commodity hardware, but may be unable to do so for higher bandwidth networks. This is ben-eficial in a South African context due to the increasing international bandwidth that will come online with the launch of the SEACOM Cable, and local projects such as SANREN.
- Full Text:
- Date Issued: 2009
A method for automatically creating 3d animated scenes from annotated fiction text
- Authors: Glass, Kevin R , Bangay, Shaun D
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432699 , vital:72893 , https://www.iadisportal.org/ijcsis/papers/2009110208.pdf
- Description: This paper describes a strategy for automatically converting fiction text into 3D animations. It assumes the existence of fiction text annotated with avatar, object, setting, transition and relation annotations, and presents a transformation process that converts annotated text into quantified constraint systems, the solutions to which are used in the population of 3D environments. Constraint solutions are valid over temporal intervals, ensuring that consistent dynamic behaviour is produced. A substantial level of automation is achieved, while providing opportunities for creative manual intervention in animation process. The process is demonstrated using annotated examples drawn from popular fiction text that are converted into animation sequences, confirming that the desired results can be achieved with only high-level human direction.
- Full Text:
- Date Issued: 2009
Beyond just research: Experiences from Southern Africa in developing social learning partnerships for resource conservation initiatives
- 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
Characterization of manganese tetraarylthiosubstituted phthalocyanines self assembled monolayers
- Authors: Matemadombo, Fungisai , Durmus, Mahmut , Togo, Chamunorwa , Limson, Janice L , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263364 , vital:53621 , xlink:href="https://doi.org/10.1016/j.electacta.2009.04.059"
- Description: Manganese tetraarylthiosubstituted phthalocyanines (complexes 1–5) have been deposited on Au electrode surfaces through the self assembled monolayer (SAM) technique. SAM characteristics reported in this work are: ion barrier factor (∼1); interfacial capacitance (303–539 μF cm−2) and surface coverage (1.06 × 10−10–2.80 × 10−10 mol cm−2). Atomic force microscopy was employed in characterizing a SAM. SAMs of complexes 1–5 were employed to detect L-cysteine (with limit of detection ranging from 2.83 × 10−7 to 3.14 × 10−7 M at potentials of 0.68–0.75 V vs. Ag|AgCl) and nitrite (limit of detection ranging from 1.78 × 10−7 to 3.02 × 10−7 M at potentials of 0.69–0.76 V vs. Ag|AgCl).
- Full Text:
- Date Issued: 2009
Characterization of nickel tetrahydroxy phthalocyanine complexes and the electrocatalytic oxidation of 4-chlorophenol
- Authors: Khene, Samson M , Lobb, Kevin A , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263308 , vital:53616 , xlink:href="https://doi.org/10.1016/j.ica.2009.08.019"
- Description: This work reports on the use of nickel(II) tetrahydroxy (NiPc(OH)4) and (poly-Ni(OH)Pc(OH)4) phthalocyanine complexes as films on ordinary poly graphite electrode (OPGE) for the electrochemical oxidation of 4-chlorophenol (4-CP). The NiPc(OH)4 film was electrotransformed to Ni(OH)Pc(OH)4 film in aqueous 0.1 M NaOH solution to the ‘O–Ni–O oxo’ bridge form. The result showed that the Ni(OH)Pc(OH)4 film on OPGE was more electroactive in terms of increase in current and less catalytic in terms of potential compared to the adsorbed NiPc(OH)4 on OPGE. The reactivity of the two molecules was explained by theoretical calculations. The energies of the frontier orbitals of NiPc(OH)4, Ni(OH)Pc(OH)4 and 4-chlorophenol were calculated using density functional theory (DFT) method. The inter molecular hardness (η) and donor–acceptor hardness (ηDA) of Ni(OH)Pc(OH)4, NiPc(OH)4, Ni(OH)Pc(OH)4/4-chlorophenol and NiPc(OH)4/4-chlorophenol were estimated. The Ni(OH)Pc(OH)4, showed stronger interaction with 4-chlorophenol than NiPc(OH)4. DFT method was also used to model IR and Raman spectrum of H2Pc(OH)4 and NiPc(OH)4.
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- Date Issued: 2009
Characterization of polymeric film of a new manganese phthalocyanine complex octa-substituted with 2-diethylaminoethanethiol, and its use for the electrochemical detection of bentazon
- Authors: Akinbulu, Isaac A , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/262568 , vital:53534 , xlink:href="https://doi.org/10.1016/j.electacta.2009.07.074"
- Description: Manganese acetate octakis-(2-diethyaminoethanethiol) phthalocyanine (AcMnODEAETPc) was newly synthesized and characterized by spectroscopic and electrochemical methods. Solution electrochemistry of the complex showed three redox processes assigned to MnIIIPc−1/MnIIIPc−2, MnIIIPc−2/MnIIPc−2 and MnIIPc−2/MnIIPc−3 species. The new molecule was polymerized onto a glassy carbon electrode (GCE) to form thin films of different thickness, giving poly-10-AcMnODEAETPc-GCE, poly-20-AcMnODEAETPc-GCE and poly-30-AcMnODEAETPc-GCE, where 10, 20 and 30 represent the number of voltammetry scans during polymerization. Three distinct redox processes were observed on the modified electrode in 0.1 M phosphate buffer solution, pH 5, which confirmed the formation of the polymer. The current signal due to the herbicide, bentazon, was dependent on film thickness; the best signal was obtained on poly-20-AcMnODEAETPc-GCE while poly-10-AcMnODEAETPc-GCE gave the least signal. However, the signals due to the herbicide were better on the different films compared to the bare electrode. Electrochemical impedance spectroscopy (EIS) technique revealed that differences in film thickness offered different charge transfer resistances, Rct, hence difference in current signals for bentazon oxidation were observed on these films. A Tafel slope of 77 mV/decade, obtained for the herbicide on poly-20-AcMnODEAETPc-GCE, denotes a fast one electron transfer followed by a slow chemical step in the electro-oxidation of bentazon. The voltammetry signals of the herbicide on the films indicated the likely involvement of ring-based redox processes in the detection of the herbicide. A plot of background corrected current response, on this film, versus the concentration of bentazon was linear within the range 50–750 μM with a detection limit of 2.48 × 10−7 M.
- Full Text:
- Date Issued: 2009
Children navigating rural poverty: Rural children's use of wild resources to counteract food insecurity in the Eastern Cape, South Africa
- Authors: McGarry, Dylan K , Shackleton, Charlie M
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181191 , vital:43706 , xlink:href="https://doi.org/10.1080/10796120802677594"
- Description: This paper analyzes the role of natural resources in the lives of rural children experiencing heightened vulnerability to poverty and the impact of HIV/AIDS, a subject that previously has been unexplored. The authors highlight wild-food use by rural children as a regular activity that supplements their domestic diets. Over the course of 18 months in the Eastern Cape of South Africa, the authors used a broad quantitative and qualitative methodology to explore the food acquisition and consumption patterns for 850 children. They found that the quality of children's domestic diets was, on average, 60% lower than the Food and Agricultural Organization (FAO) guidelines. This occurred in a population where 62% of the children surveyed were supplementing their diets with wild foods; and 30% with over half their diet supplemented in this way. Significantly, dietary diversity increased by 13% when wild food supplementation occurred. Another result was the commercialization of wild foods (observed among 47% of the children), wherein significantly more vulnerable children sold these foods. Considering the heightened nutritional and energy needs of children, combined with the impact of poverty and HIV/AIDS on household food access, wild foods represent the last freely attainable food sources available to them.
- Full Text:
- Date Issued: 2009
Comparative electrocatalytic behavior of self-assembled monolayer of thiol derivatised Co (II) phthalocyanines on gold disk, ultramicro cylinder and fiber electrodes
- Authors: Nombona, Nolwazi , Geraldo, Daniela A , Hakuzimana, Jean , Schwarz, Anne , Westbroek, Philippe , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263488 , vital:53632 , xlink:href="https://doi.org/10.1007/s10800-008-9716-y"
- Description: This paper reports on the use of thiol derivatised cobalt phthalocyanines as self assembled monolayers (SAMs) on gold disk electrode, gold ultramicro-cylinder electrode (UMCE) and on gold coated fiber for the detection of L-cysteine. The complexes are peripherally and non-peripherally substituted with phenylthio substituents. The SAM modified electrodes showed enhancement of catalytic currents and overpotential reduction occurred on the gold modified electrodes with different geometries. Electrocatalytic oxidation of L-cysteine on SAM modified gold coated fiber was reported for the first time. The gold coated fiber and ultramicro cylinder electrode were less stable towards the electrocatalytic oxidation of cysteine compared to its oxidation on the gold disk. The gold disk electrode gave better catalytic performance in terms of stability and reduction of overpotential.
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- Date Issued: 2009
Conservation, commercialisation and confusion: Harvesting of Ischyrolepis in a coastal forest, South Africa
- Authors: Shackleton, Charlie M , Parkin, Fiona , Chauke, Maphambe I , Downsborough, Linda , Olsen, Ashleigh , Brill, Greg , Weideman, Craig I
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181169 , vital:43704 , xlink:href="https://doi.org/10.1007/s10668-007-9106-3"
- Description: Harvesting of non-timber forest products is an integral component of rural livelihoods throughout the developing world. At times this is at odds with conservation objectives. Reconciliation of the two requires examination of local level contexts and needs. This paper reports on the harvesting needs for Ischyrolepis by a rural community in South Africa, against the setting that they had recently been prohibited from harvesting by the local conservation officials. Interviews were conducted with conservation officials to understand the reasoning for the prohibition. Local demand for Ischyrolepis was assessed by household surveys, as well as in-depth interviews with traders. The density and size class distribution of Ischyrolepis was determined using transects. The total annual demand for Ischyrolepis was determined to be approximately only 2.7% of the standing crop. The bulk of the annual demand was for small-scale trade, the income from which was a primary source of income for the few harvesters. Very little evidence could be found indicating that harvesting was damaging the resource or its habitat, and local knowledge suggested that the abundance of the species was stimulated by harvesting. Even if market demand were to increase, the size of the shoots required means that less than 20% of the standing crop could be harvested annually. Current regulations around harvesting are in a state of revision, and hence confusion prevails regarding if harvesting is permissible, and if so, under what conditions, which is detrimental to both conservation and livelihoods.
- Full Text:
- Date Issued: 2009
Creating a virtual classroom: evaluating the use of online discussion forums to increase teaching and learning activities
- Authors: Bezuidenhout, L Peta
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: Conference paper
- Identifier: vital:6070 , http://hdl.handle.net/10962/d1004635
- Description: In teaching large classes, the educationally beneficial informal interaction between students and between lecturer and students is generally reduced, while effective use of both students’ and lecturer’s time is often a challenge. During student consultations, especially over the already stressful test and examination periods, many of the questions asked by the students are the same or similar. The lecturer needs to respond to each query by providing the same detailed explanation for the problem, resulting in ineffective use of time for the lecturer, while students waste time waiting for an appointment, or more often, simply don’t bother to follow up on any queries they may have. Having a social presence is important for students’ cognitive development, but in a large class posing questions or interrogating issues during a lecture appears to be challenging for many students. It is often not easy for students to initiate discussions or establish relationships with peers or the lecturer due to feelings of vulnerability and due to the size and impersonal atmosphere of the lecture theatre. This paper deals with the introduction of online discussion forums in an introductory accounting course and the benefits and problems experienced by the students, tutors and lecturer as a result thereof. Feedback received from these participants is discussed. The introduction and use of these forums resulted in a virtual classroom being created, where significantly more teaching and learning activities took place, to the benefit of all participants. Participation could have been peripheral -in the form of simply reading discussions; or active – through posting questions, or responding to questions.
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- Date Issued: 2009
Cultural historical activity theory, expansive learning and agency in permaculture workplaces
- Authors: Mukute, Mutizwa
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386474 , vital:68145 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122818"
- Description: This paper reports on how Cultural Historical Activity Theory was used to identify and analyse contradictions; model and implement solutions in the learning and practice of permaculture at one school and its community in Zimbabwe. This is one of three sustainable agriculture workplace learning sites being examined in a wider study on change-oriented learning and sustainability practices (Mukute, 2009). It gives a brief background to permaculture and the School and Colleges Permaculture Programme (SCOPE) in Zimbabwe. The paper focuses on how contradictions were used as sources of learning and development leading to ‘real life expansions’. This demonstrates and reflects on the value of an interventionist research theory and methodology employed in the study to enhance participants’ agency in sustainable agriculture workplaces.
- Full Text:
- Date Issued: 2009
Deconstructing language myths: which languages of learning and teaching in South Africa
- Authors: Dalvit, Lorenzo , Murray, Sarah , Terzoli, Alfredo
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431260 , vital:72759 , https://d1wqtxts1xzle7.cloudfront.net/91537059/Deconstructing_language_myths_which_languages_of_learning_and_teaching_in_South_Africa.sflb-libre.pdf?1664136385=response-content-disposi-tion=inline%3B+filename%3DDeconstructing_language_myths_which_lang.pdfExpires=1714984902Signature=dj35y~SObsQq0TnqD-oDUj3CX7lgNnKJcMAchC7rarU74xqfrMlVfOwi-MZrNZvWvpxyzquBsmr1veH-ggRVXQP7TX4eKQq3tXV-gJZg3xyo7QJoGwrGPTjC4btF2kNrVJc6TQulzuPFEz47GtjQ6Nint4SmE7A30EMUMd8j25KgCUdtzqwx9kjBs-niKu~z-pk-Xon5YOolMTepbOwNr9wKGj8JafblTdnFs-H8CZ-Et4BD2mYV3GxnR0QLfgawFgDYkOSZnYhkl6wFsXG~Euwlhcvtp0EgUOfP4id~Ov9hhA-rSQxl81X2Dh1BdMuT3GSsK6VNmO7TikSC7NeGlQ__Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA
- Description: In this article we argue for the use of African languages as Languages of Learning and Teaching (LoLT) for native speakers of such language in South Africa. We believe that both public and academic debate is in-fluenced by a set of ‘language myths’: 1) only one language should be used; 2) the earlier one starts using English as LoLT, the better; 3) us-ing English as LoLT improves English proficiency. These myths be seen as a direct manifestation of Western hegemony, and English-functional arguments are often the terms of reference. We will try a dif-ferent approach by highlighting the advantages of using an African lan-guage (ie isiXhosa) as LoLT and, whenever possible, we will try to put English on the ‘defence stand’. The purpose of this paper is not to ad-vocate the substitution of English with an African language. We believe that bilingual education is the appropriate choice for South Africa, but in order to achieve full equality between English and the African lan-guages in education, arguments in support of the latter must be put forward proactively. With our paper, we hope to contribute to this new perspective.
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- Date Issued: 2009
Development and validation of a stability-indicating method for the quantitation of paclitaxel in pharmaceutical dosage forms
- Authors: Mohammadi, Ali , Esimaeili, Farnaz , Dinarvand, Rasoul , Atyabi, Fatemeh , Walker, Roderick B
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184278 , vital:44196 , xlink:href="https://doi.org/10.1093/chromsci/47.7.599"
- Description: A simple, rapid stability-indicating isocratic assay has been developed and validated for the determination of Paclitaxel (PTX) in commercial injection formulations. The assay is performed using a Nucleosil RP-18 (5 µm, 250 × 4.0 mm i.d) column protected by a Nucleosil C18 precolumn (5 µm, 4.0 × 4.0 mm i.d.) with a mobile phase of methanol–water (80:20) and UV detection at 230 nm. The method was found to be specific for PTX in the presence of degradation products with an overall analytical run time of ~ 9 min. Accuracy reported as % bias was found to be 0.1–2.5% bias for all samples tested. Intra-assay precision (repeatability) was found to be 0.22–2.65% RSD, while inter-day precision (intermediate precision) was found to be 1.0–3.0% RSD for the samples studied. The calibration curve was found to be linear with the equation y = 29.78x + 7.65, and a linear regression coefficient of 0.9994 over the concentration range 0.05–20 µg/mL. The limits of quantitation and detection were 0.05 and 0.02 µg/mL, respectively. Taxol (30 mg/5 mL), a commercially available dosage form of PTX, was assayed and 100.6–103.6% of the label claim was recovered.
- Full Text:
- Date Issued: 2009
Diffraction efficiency and I–V characteristics of metal-free phthalocyanine doped nematic liquid crystals
- Authors: Köysal, Oguz , Okutan, Mustafa , San, S Eren , Nyokong, Tebello , Durmus, Mahmut
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263511 , vital:53634 , xlink:href="https://doi.org/10.1016/j.matchemphys.2008.10.056"
- Description: The synthesis and characterization of the tetra-4-benzyloxyphenoxy substituted metal-free phthalocyanine (H2Pc) is reported for the first time. Formation of the photoinduced gratings has been experienced in a metal-free phthalocyanine doped nematic liquid crystal (LC) system and its I–V properties are characterized by electrical measurements. Four samples are prepared at different doping percentages and in homogenously aligned sandwiched geometry. We report the results of two set of experiments on these samples. One of them is the grating diffraction experiment for the analysis of optically induced reorientation process which is a basis for possible holographic applications. Accessible diffraction efficiency is found to be linearly increasing as the amount of the phthalocyanine doping rises. In the scope of the other set of measurements I–V peculiarity of the system is also found to be enhanced and linearly dependent on doping.
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- Date Issued: 2009
Effect of peripheral fused ring substitution on the optical spectroscopy and electronic structure of metal phthalocyanine complexes
- Authors: Chidawanyika, Wadzanai J U , Mack, John , Shimizu, Soji , Kobayashi, Nagao , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263353 , vital:53620 , xlink:href="https://doi.org/10.1142/S1088424609001339"
- Description: In this paper the impact of peripheral substitution with a strongly withdrawing fused ring group on the optical spectroscopy of a metal phthalocyanine complex is analyzed. We report the synthesis of [9 (or 10), 16 (or 17), 23 (or 24)-tri-tert-butylimidophthalocyaninato]zinc(II) (ZnttbIPc), which should eventually prove to be a useful precursor for forming dimeric compounds. The electronic structure is analyzed through a detailed analysis of the UV-visible absorption and magnetic circular dichroism spectra and time-dependent density functional theory calculations. Other than a marked splitting of the Q band, the spectrum is broadly similar to that of ZnPc in terms of the main π → π* electronic bands. The vibrational bands differ markedly in the Q band region when an imido group is added to ligand periphery, relative to what is observed in the case of zinc mononaphthotribenzotetraazaporphyrin (Zn3B1N) with an additional fused benzene ring. The absorption and emission spectra lack mirror symmetry as is the case with ZnPc and thus provide possible evidence for a second set of electronic origins in the Q band region arising from n → π* rather then π → π* transitions.
- Full Text:
- Date Issued: 2009
Effects of the number of ring substituents of cobalt carboxyphthalocyanines on the electrocatalytic detection of nitrite, cysteine and melatonin
- Authors: Matemadombo, Fungisai , Sehlotho, Nthapo , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263408 , vital:53625 , xlink:href="https://doi.org/10.1142/S108842460900125X"
- Description: Cobalt phthalocyanine (CoPc), cobalt tetracarboxy phthalocyanine (CoTCPc) and cobalt octacarboxy phthalocyanine (CoOCPc), adsorbed onto glassy carbon electrodes, have been used for the electrocatalytic detection of nitrite, L-cysteine and melatonin. The modified electrodes electrocatalytically detected nitrite around 800 mV vs.Ag|AgCl, a value less positive compared to that of an unmodified glassy carbon electrode (at 950 mV vs.Ag|AgCl) and also gave detection limits in the 10-7 M range for nitrite detection. L-cysteine was detected by the modified electrodes at potentials between 0.50 to 0.65 V vs.Ag|AgCl, with L-cysteine detection limits also in the 10-7 M range. The detection limits for melatonin ranged from 10-7 to 10-6 M. CoPc-modified electrodes displayed good separation of interferents (tryptophan and ascorbic acid) in the presence of melatonin. Analyses of commercial melatonin tablets using modified electrodes gave excellent agreement with manufacturer's value for all modified electrodes of this work.
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- Date Issued: 2009
Electrostatic self-assembly of quaternized 2,(3)-tetra (oxo-pyridine) phthalocyaninato chloroindium (III) with a series of tetrasulfonated phthalocyanines
- Authors: George, Reama C , Durmus, Mahmut , Egharevba, Gabriel O , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263330 , vital:53618 , xlink:href="https://doi.org/10.1016/j.poly.2009.07.035"
- Description: The self-assembly of oppositely charged phthalocyanines, fabricated using quaternized 2,(3)-tetra(oxo-pyridine) phthalocyaninato chloroindium (III) (QInPyPc) as the positively charge molecule and a series of tetrasulfonate phthalocyanine (MTSPc), M = 2H, Mn, Fe, Co and Ni as negatively charged molecules are reported. The self-assembly results in the formation of heteroaggregates. The metallated sulfonated phthalocyanines form nanorod and nanoleaf shaped structures as evidenced by transmission electron microscopy (TEM). The UV–Vis spectra showed blue shifted Q bands, suggesting that these structures were in a face-to-face arrangement. The Raman spectra of the heteroaggregates showed shifting compared to the spectra of the precursors.
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- Date Issued: 2009