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Redox activity of CdTe quantum dots linked to nickel tetraaminophthalocyanine

  • Authors: Khene, Samson , Nyokong, Tebello
  • Date: 2011
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/246457 , vital:51478 , xlink:href="https://doi.org/10.1016/j.microc.2011.06.024"
  • Description: Cadmium tellurite quantum dots (CdTe-QDs) are linked to nickel tetraamino phthalocyanine (CdTe-QDs-NiTAPc) through an amide bond. Differential pulse voltammetry shows that that NiTAPc stabilizes the QDs against oxidative disintegration into metallic products on oxidation. Electrocatalytic oxidation of 2, 4-dichlorophenol (DCP) and pentachlorophenol (PCP) on CdTe-QDs and CdTe-QDs-NiTAPc adsorbed or electrodeposited onto a gold electrode were studied. Adsorbed CdTe-QDs-NiTAPc shows the lowest potential for DCP and PCP oxidation and it is also more stable to fouling by PCP and its oxidation products compared to adsorbed CdTe-QDs without NiTAPc. Electrodeposited CdTe-QDs or CdTe-QDs-NiTAPc show the best activity in terms of enhanced currents towards the oxidation of the chlorophenols.
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  • Date Issued: 2011

Selection and characterization of suitable lipid excipients for use in the manufacture of didanosine-loaded solid lipid nanoparticles and nanostructured lipid carriers

  • Authors: Kasongo, Kasongo W , Pardeike, Jana , Muller, Rainer H , Walker, Roderick B
  • Date: 2011
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/184016 , vital:44156 , xlink:href="https://doi.org/10.1002/jps.22711"
  • Description: This research aimed to evaluate the suitability of lipids for the manufacture of solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs) loaded with the hydrophilic drug, didanosine (DDI). The crystalline state and polymorphism of lipids with the best‐solubulizing potential for DDI was investigated using differential scanning calorimetry (DSC) and wide‐angle X‐ray scattering (WAXS). DSC and WAXS were also used to determine potential interactions between the bulk lipids and DDI. Precirol® ATO 5 and Transcutol® HP showed the best‐solubilizing potential for DDI. Precirol® ATO 5 exists in the β‐modification before heating; however, a mixture of both α‐ and β‐modifications were detected following heating. Addition of Transcutol® HP to Precirol® ATO 5 changes the polymorphism of the latter from the β‐modification to a form that exhibits coexistence of the α‐ and β‐modifications. DDI exists in a crystalline state when dispersed at 5% (w/w) in Precirol® ATO 5 or in a Precirol® ATO 5/Transcutol® HP mixture. DSC and WAXS profiles of DDI/bulk lipids mixture obtained before and after exposure to heat revealed no interactions between DDI and the lipids. Precirol® ATO 5 and a mixture of Precirol® ATO 5 and Transcutol® HP may be used to manufacture DDI‐loaded SLN and NLC, respectively.
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  • Date Issued: 2011

Selective adsorption of PVP on the surface of silver nanoparticles

  • Authors: Mdluli, Phumlani S , Sosibo, Ndabenhle M , Mashazi, Philani N , Nyokong, Tebello , Tshikhudo, Robert T , Skepu, Amanda , Van der Lingen, Elma
  • Date: 2011
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/247143 , vital:51550 , xlink:href="https://doi.org/10.1016/j.molstruc.2011.07.049"
  • Description: The use of surfactants to affect the shape evolution of silver nanoparticles is explored. This allows one to fine-tune the morphological evolution and the optical properties of the metal nanoparticles. Polyvinyl pyrrolidone (PVP) has been used as a surfactant to control the growth of silver nanoparticles at room temperature. In this paper, molecular dynamics simulations were performed to understand regio-selective adsorption of PVP that leads to the preferential growth of silver nanoparticles in dimethylformamide (DMF). The interaction energies between PVP and Ag(1 1 0), Ag(1 0 0) and Ag(1 1 1) crystal planes were calculated and in addition the length density profile of the surfactant on silver surfaces was also examined. Importantly, it has been demonstrated that the length distribution profiles analysis obtained from the molecular dynamics study fully explained the adsorption of PVP on the surface of silver nanoparticles through the carbonyl group of the PVP ring. The application of molecular dynamics simulation technique is important in understanding the evolution of silver nanoparticles and is vital in choosing the right surfactants.
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  • Date Issued: 2011

Simulating Collective agency: Joint purpose, presence and power as Constraints to learning in a social Context

  • Authors: Kulundu, Injairu M
  • Date: 2011
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/386530 , vital:68149 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122249"
  • Description: This paper reflects on the practice of social learning by using my experiences as a social development practitioner in two projects. The first, the Arkwork Collective, is an art-junk process that engages marginalised youth in Grahamstown, South Africa in a process that uses creative sculpture and drama to explore personal and social issues that exist in their immediate context. The second, Jonga Phambili Sinethemba looks into the impact of climate change and HIV/AIDS (amongst other issues) in the rural and peri-urban communities of Willowvale and Lesseyton in the Eastern Cape, South Africa. It seeks to provide a platform where members of each community can define the vulnerabilities, capabilities, social networks in their areas with the aim of bolstering the adaptive capacity of these communities. Snippets of my experiences in these projects are shared with the intention of demonstrating constraints to learning in a social context. Key ideas that the paper explores include honouring the lived experiences of participants as part of the process, prioritising the participation of each individual present as part of the ongoing conversation, the challenge of surfacing the vital independent links of a collective, drawing on the reflective capacity of a diverse group, assessing the quality of participation, building capabilities for ‘response-ability’ and rethinking facilitation. Each section sets out challenges and questions for practitioners in this field to reflect on. The paper suggests that in order to achieve the laudable aims of social learning, we need to peel back the common rhetoric of its participatory aims and acknowledge the complexity, flexibility and dedication that it requires.
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  • Date Issued: 2011

Study South Africa

  • Authors: International Education Association of South Africa (IEASA) , Jooste, Nico
  • Date: 2011
  • Subjects: Education, Higher -- South Africa , Universities and colleges -- South Africa , Technical Institutes -- South Africa , Vocational guidance -- South Africa
  • Language: English
  • Type: text , book
  • Identifier: http://hdl.handle.net/10962/64952 , vital:28639 , ISBN 9780620512244
  • Description: [Extract from article by Ms Merle Hodges]: Over the past year there have been numerous conferences dealing with one general topic. How is it possible for higher education, globally, to produce the same quality in its graduates, research and community outreach when the financial resources entering into the system are radically declining? The conclusion is overwhelmingly despondent. ‘Universities have to do more with less, academics and academic research will increasingly be pressurised by lower salaries internally and career temptations from the corporate world – the impact of which is the greater commodification of universities, and the inevitable decline in academic freedom.’ This global negativity is predicated on inter–related factors. The first, the long tail of the economic recession, is continuing to bite all sectors and higher education is no exception. Secondly, higher education is a little like marketing – when the pressure is on government, sectors like higher education are de–prioritised. In light of this, the position of internationalisation in higher education might seem to fade into the background. Interestingly, the inverse is true. While the zeitgeist of higher education generally appears dismal, the prospects of internationalisation appear rosy in comparison. I believe this is true because of two overlapping issues. Firstly, students are not going to give up on university because of a lingering economic downturn. What they are doing, however, is deciding to travel and study at destinations that would have been perceived as implausible a few years ago. Venezuela, Chile, South Korea and South Africa are all drawing US students more than ever before. This is partly because, I sense, the quality of qualifications is achieving parity across the globe; and also, because students who are prepared to travel realise that cultural specificity – the ability to learn new and unique aspects of a different culture while gaining the same core ingredients of a degree – sets it apart from the degree gained locally. A one semester course in Russian anthropology might appear entirely redundant when applying for a job. However, the very interconnectedness of global business means not only that the course is never a waste of time, but that it might mean the difference between landing a contract and failing to do so. The international student has the benefit of developing in ways that traditional (home-grown) higher education may not yet fully understand. Secondly, development in South Africa at least, has an additional meaning. Our universities are not only focused on developing graduates for multicultural or global competitiveness. Over the past five or so years our universities have been focused on development of the country itself. As an emerging power, the impetus has been on creating universities that address the fundamental needs of the people. Poverty, HIV, sustainability and innovative solutions to global problems are the very sap of South African universities in the 21st Century. How to create a sustainable environment, how to preserve marine and wildlife, how to create jobs, reduce poverty, and maximise innovation – these are the concerns that are preoccupying the minds of the country’s best academics. , 11th Edition
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  • Date Issued: 2011

Syntheses and electrochemical characterization of new water soluble octaarylthiosubstituted manganese phthalocyanines

  • Authors: Booysen, Irvin N , Matemadombo, Fungisai , Durmus, Mahmut , Nyokong, Tebello
  • Date: 2011
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/247614 , vital:51600 , xlink:href="https://doi.org/10.1016/j.dyepig.2010.09.012"
  • Description: This paper reports on the synthesis and characterization of new manganese phthalocyanine (MnPc) complexes: 2,3-octakis-[(2-mercaptopyridine) phthalocyaninato] acetato manganese (III) (1) and its quaternized (hence water soluble) derivative: 2,3-octakis-{[(N-methyl-2-mercaptopyridine) phthalocyaninato] acetato manganese (III)} sulphate (2). The complexes were used to form self assembled monolayers (SAMs). Voltammetry proved that both of the SAMs are well packed, strongly passivating and act as selective and efficient barriers to ion permeability. Furthermore, surface coverage studies confirmed that the MPc macrocycles adsorb onto the gold electrode as monolayers. Both MPc SAMs were successfully used as electrochemical sensors of nitrite.
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  • Date Issued: 2011

Syntheses, electrochemical and spectroelectrochemical properties of novel ball-type and mononuclear Co (II) phthalocyanines substituted at the peripheral and non-peripheral positions with binaphthol groups

  • Authors: Canlıca, Mevlüde , Booysen, Irvin Noel , Nyokong, Tebello
  • Date: 2011
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/247837 , vital:51622 , xlink:href="https://doi.org/10.1016/j.poly.2010.11.017"
  • Description: Mononuclear cobalt phthalocyanine (CoPc) substituted at the non-peripheral 8 and peripheral positions 9 with 1,1′-binaphthyl-8,8′-diol and ball-type dinuclear Co2Pc2 substituted at the non-peripheral 10 and peripheral 11 positions with the same substituent are reported. The complexes with 1,1′-binaphthol-bridges were prepared from the corresponding phthalonitriles 4–7. The effects of the position of substituent on spectral, electrochemical and spectroelectrochemical properties of these complexes were also explored. The mononuclear complexes 8 and 9 exhibited one metal reduction, one ring reduction and one ring oxidation. The redox properties of the ball-type complexes 10 and 11 exhibited two reduction processes assigned to [(CoIPc−2)2]2−/[(CoIPc−3)2]4− (I), (CoIIPc−2)2/[(CoIPc−2)2]2− (II) and one oxidation process assigned to [(CoIIIPc−2)2]2+/CoIIPc−2)2 (III). The ball-type complexes are much easier to oxidize and more difficult to reduce than the corresponding monomers 8 and 9.
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  • Date Issued: 2011

Synthesis and electrocatalytic behavior of cobalt (II)-tris (benzyl-mercapto)-monoaminophthalocyanine–single walled carbon nanotube nanorods

  • Authors: Mugadza, Tawanda , Nyokong, Tebello
  • Date: 2011
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/247882 , vital:51626 , xlink:href="https://doi.org/10.1016/j.electacta.2010.11.016"
  • Description: In this paper we report on synthesis and electrocatalytic behavior of cobalt (II)-tris(benzyl-mercapto)-monoaminophthalocyanine–single walled carbon nanotube nanorods towards the oxidation of amitrole. SWCNTs that were terminally functionalized with carboxylic acid groups were chemically linked to cobalt (II)-tris(benzyl-mercapto) monoaminophthalocyanine (CoMAPc) via an amide bond to form nanorods. UV–vis, FTIR, TEM, Raman and XRD spectroscopies were used in characterization of the nanorods (CoMAPc–SWCNT-linked), while cyclic voltammetry and chronoamperometry were used during the characterization of amitrole on the modified glassy carbon electrode. The linear dynamic range for the amitrole was from 1.0 × 10−6 M to 1.2 × 10−4 M, with a sensitivity of 6.76 A mol−1 L cm−2. The estimated limit of detection for amitrole was 0.10 μM, using the 3δ criterion. The catalytic rate constant was found to be 1.09 × 105 M−1 s−1.
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  • Date Issued: 2011

Synthesis and electrochemical behavior of novel peripherally and non-peripherally substituted ball-type cobalt phthalocyanine complexes

  • Authors: Canlıca, Mevlüde , Booysen, Irvin Noel , Nyokong, Tebello
  • Date: 2011
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/247848 , vital:51623 , xlink:href="https://doi.org/10.1016/j.poly.2010.11.028"
  • Description: The syntheses of new ball-type Co(II) phthalocyanines containing 4,4′-(9H-fluorene-9,9-diyl)diphenol substituents at non-peripheral (complex 6) and peripheral (complex 7) positions are presented. These complexes were characterized by UV–Vis, FT-IR, mass spectroscopy and electrochemical methods. Both complexes exhibit metal and ring based redox processes, typical of cobalt phthalocyanine complexes. For 6, the metal based reduction was observed at −0.46 V followed by a ring based reduction at −1.40 V. The metal oxidation for 6 was observed at +0.16 V and the ring based oxidation at +1.05 V. For 7, reductions are easier but the oxidations are more difficult. The metal based reduction for 7 was observed at −0.38 V followed by a ring based reduction at −1.03 V. The metal oxidation for 7 was observed at +0.20 V and the ring based oxidation at +1.35 V.
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  • Date Issued: 2011

Synthesis and electrochemical properties of new tetra substituted cobalt phthalocyanine complexes, and their application in electrode modification for the electrocatalysis of l-cysteine

  • Authors: Erdoğmuş, Ali , Booysen, Irvin Noel , Nyokong, Tebello
  • Date: 2011
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/247893 , vital:51627 , xlink:href="https://doi.org/10.1016/j.synthmet.2010.11.028"
  • Description: This study investigates the synthesis and characterization new peripherally (β) tetra-substituted 4-(2-mercaptoquinoline phthalocyaninato) Co(II) (CoPcSHQn, 3), and 4-(2-phenoxy-4-trifluoromethylpyridine phthalocyaninato) Co(II) (CoPcOHPy, 4). These complexes were characterized by elemental analysis, IR, mass and electronic spectroscopies and electrochemical methods. Both complexes show well resolved redox peaks attributed to both ring and metal based processes. Spectroelectrochemistry was used to confirm the assignments of the redox processes. For CoPcSHQn (3): CoIPc−2/CoIPc−3 (E1/2 = −1.25 V, I), CoIIPc−2/CoIPc−2 (E1/2 = −0.57 V, II), CoIIIPc−2/CoIIPc−2 (E1/2 = +0.45 V, IV) and an irreversible process at Ep = +1.05 V vs Ag|AgCl for CoIIIPc−1/CoIIIPc−2 (V). Redox couple III at E1/2 = −0.15 V was ascribed to aggregation. In the case of CoPcOHPy (4): CoIPc−2/CoIPc−3 (E1/2 = −1.13 V, I), CoIIPc−2/CoIPc−2 (E1/2 = −0.45 V, II), CoIIIPc−2/CoIIPc−2 at E1/2 = +0.21 V (IV), and CoIIIPc−1/CoIIIPc−2 (E1/2 = +1.01 V vs Ag|AgCl, V). Again III is associated with the aggregated species. Both complexes were electrodeposited on a glassy carbon electrode (GCE). For complex 3 self-assembled monolayers was also formed. The modified (CoPc-GCE) electrodes electrocatalytically detected L-cysteine at Ep = 0.62 V (3-GCE) and 0.59 V (4-GCE) vs Ag|AgCl.
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  • Date Issued: 2011

Synthesis and evaluation of phosphonated N-heteroarylcarboxamides as DOXP-reductoisomerase (DXR) inhibitors

  • Authors: Bodill, Taryn , Conibear, Anne C , Blatch, Gregory L , Lobb, Kevin A , Kaye, Perry T
  • Date: 2011
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/448939 , vital:74772 , xlink:href="https://doi.org/10.1016/j.bmc.2010.11.062"
  • Description: The diethyl esters and disodium salts of a range of heteroarylcarbamoylphosphonic acids have been prepared and evaluated as analogues of the highly active DOXP-reductoisomerase (DXR) inhibitor, fosmidomycin. Computer-simulated docking studies, Saturation Transfer Difference (STD) NMR analysis and enzyme inhibition assays have been used to explore enzyme-binding and -inhibition potential, while in silico analysis of the DXR active site has highlighted the importance of including a well-parameterised metal co-factor in docking studies and has revealed the availability of an additional binding pocket to guide future drug design.
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  • Date Issued: 2011

Synthesis and photophysical behaviour of tantalum and titanium phthalocyanines in the presence of gold nanoparticles

  • Authors: Chauke, Vongani P , Arslanoglu, Yasin , Nyokong, Tebello
  • Date: 2011
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/247545 , vital:51593 , xlink:href="https://doi.org/10.1016/j.jphotochem.2011.04.020"
  • Description: We report on the synthesis of 2,(3)- (peripheral) and 1,(4)- (non-peripheral) (2-mercaptopyridine)phthalocyanine complexes of titanium (IV) oxide (5 and 6 respectively), and tantalum (III) hydroxide (7, peripheral only), their photochemical and photophysical parameters and the photocatalytic oxidation of cyclohexene in the presence of gold nanoparticles (AuNPs). The singlet oxygen quantum yield values increased in the presence of AuNPs, for complexes 5 and 6. The percentage conversion values for cyclohexene using 5, 6 and 7 were 27%, 20% and 14%, respectively. These values increased considerably in the presence of AuNPs, except complex for 7. The products obtained include cyclohexene oxide, 2-cyclohexen-1-ol, 2-cyclohexene-1-one and 1,2-cyclohexanediol. Low values of singlet oxygen quantum yields favour the formation of 1,2-cyclohexanediol.
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  • Date Issued: 2011

Synthesis and photophysical properties of a novel zinc photosensitizer and its gold nanoparticle conjugate

  • Authors: Moeno, Sharon , Antunes, Edith M , Nyokong, Tebello
  • Date: 2011
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/247100 , vital:51546 , xlink:href="https://doi.org/10.1016/j.jphotochem.2011.07.007"
  • Description: The peripherally tetra substituted zinc phthalocyanine with 1,6-hexanedithiol as substituent (THdTZnPc, 3) was synthesized and is reported for the first time in this work. The potential of this zinc complex as a suitable photosensitizer for use in photodynamic therapy was determined through the investigation of the photophysical and photochemical properties. In this work complex 3 is attached to gold nanoparticles through the terminal thiol groups of the phthalocyanine resulting in a 3-AuNP conjugate whose photophysicochemical properties are investigated. Fluorescence lifetimes were determined using time correlated single photon counting and they show an increase in the abundance of the monomeric species (τ2) for the Pc in the 3-AuNP conjugate: ∼1 and 0.71 (with respective lifetimes 2.69 ns and 2.86 ns) compared to the free complex 3 with abundances of 0.12 and 0.13 (with respective lifetimes 3.36 ns and 3.28 ns) in DMSO and DMF, respectively.
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  • Date Issued: 2011

Synthesis and photophysical studies of CdTe quantum dot-monosubstituted zinc phthalocyanine conjugates

  • Authors: D'Souza, Sarah , Antunes, Edith M , Nyokong, Tebello
  • Date: 2011
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/247825 , vital:51621 , xlink:href="https://doi.org/10.1016/j.ica.2010.12.027"
  • Description: The linkage of unsymmetrically monosubstituted 4-aminophenoxy zinc phthalocyanine (ZnAPPc, 5) to CdTe quantum dots capped with mercaptopropionic acid (MPA), L-cysteine (L-cys) or thioglycolic acid (TGA) has been achieved using the coupling agents ethyl-N(3-dimethylaminopropyl) carbodiimide and N-hydroxy succinimide, which facilitate formation of an amide bond to form the QD–ZnAPPc-linked conjugate. The formation of the amide bond was confirmed using Raman and IR spectroscopies. Atomic force microscopy (AFM) and UV–Vis spectroscopy were used further to characterise the conjugate. Förster resonance energy transfer (FRET) resulted in stimulated emission of ZnAPPc in both the linked (QD–ZnAPPc-linked) and mixed (QD:ZnAPPc-mixed) conjugates. The linked L-cys and TGA QDs conjugates (QD–ZnAPPc-linked) gave the largest FRET efficiencies hence showing the advantages of covalent linking. Fluorescence quantum yields of QDs were decreased in QD:ZnAPPc-mixed and QD:ZnAPPc-linked.
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  • Date Issued: 2011

Synthesis and photophysical studies of monocarboxy phthalocyanines containing quaternizable groups

  • Authors: Arslanoğlu, Yasin , Nyokong, Tebello
  • Date: 2011
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/246992 , vital:51535 , xlink:href="https://doi.org/10.1016/j.poly.2011.08.009"
  • Description: This work reports on the synthesis and photophysical properties of novel unsymmetrically substituted monocarboxy magnesium (MgPc, 3), aluminum (ClAlPc, 4) and unmetallated (H2Pc, 5) phthalocyanines. Magnesium phthalocyanine (3) was converted into water soluble quaternized derivative (QMgPc, 6) by reaction with methyl iodide. The synthesized phthalocyanines were characterized by IR, UV–Vis, NMR, mass spectrometry and elemental analyses. Photophysical and photochemical studies were carried out in order to determine the potential of the complexes as photosensitizers for use in photodynamic therapy. Triplet quantum yields ranged from 0.37 to 0.40 and triplet lifetimes from 110 to 140 μs in DMSO.
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  • Date Issued: 2011

Synthesis and photophysical studies of phthalocyanine–gold nanoparticle conjugates

  • Authors: Nombona, Nolwazi , Antunes, Edith M , Litwinski, Christian , Nyokong, Tebello
  • Date: 2011
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/248438 , vital:51686 , xlink:href="https://doi.org/10.1039/C1DT11151E"
  • Description: This work reports on the synthesis, characterization and photophysical studies of phthalocyanine–gold nanoparticle conjugates. The phthalocyanine complexes are: tris-(5-trifluoromethyl-2-mercaptopyridine)-2-(carboxy)phthalocyanine (3), 2,9,17,23-tetrakis-[(1, 6-hexanedithiol) phthalocyaninato]zinc(II) (8) and [8,15,22-tris-(naptho)-2(amidoethanethiol) phthalocyanato] zinc(II)(10). The gold nanoparticles were characterized using transmission electron microscopy, X-ray diffraction, atomic force microscopy and UV-vis spectroscopy where the size was confirmed to be ∼5 nm. The phthalocyanine Au nanoparticle conjugates showed lower fluorescence quantum yield values with similar fluorescence lifetimes compared to the free phthalocyanines. The Au nanoparticle conjugates of 3 and 10 also showed higher triplet quantum yields of 0.69 to 0.71, respectively. A lower triplet quantum yield was obtained for the conjugate compared to free phthalocyanine for complex 8. The triplet lifetimes ranged from 70 to 92 μs for the conjugates and from 110 to 304 μs for unbound Pc complexes.
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  • Date Issued: 2011

Synthesis, characterization and application of monocarboxy-phthalocyanine-single walled carbon nanotube conjugates in electrocatalysis

  • Authors: Mugadza, Tawanda , Nyokong, Tebello
  • Date: 2011
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/247399 , vital:51577 , xlink:href="https://doi.org/10.1016/j.poly.2011.04.020"
  • Description: In this paper we report on the synthesis, characterization and use of monocarboxy-phthalocyanine-single walled carbon nanotube conjugates in the electrocatalysis of amitrole and diuron. UV–Vis, FTIR and XRD spectroscopies were used in the characterization of cobalt(II)-tris(benzyl-mercapto)-mono(carboxyphenoxy)-phthalocyanine conjugates (CoMCPc–PA-SWCNT(linked)), while AFM was used to show changes in surface morphologies of the modified electrodes. Cyclic voltammetry and chronoamperometry were used for the electrocatalytic oxidation of amitrole and diuron on the modified glassy carbon electrode. The catalytic rate constants for amitrole and diuron were found to be 1.83 × 106 and 1.99 × 106 M−1 s−1, respectively. The linear range for both was 1.0 × 10−5–2.0 × 10−4 M, with sensitivities of 5.10 and 3.70 A mol−1 L cm−2 for amitrole and diuron, respectively. The limits of detection were estimated to be 0.14 and 0.20 μM for amitrole and diuron, respectively, using the 3δ notation.
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  • Date Issued: 2011

Synthesis, characterization, and photophysical properties of novel ball-type dinuclear and mononuclear containing four 1, 1′-binaphthyl-8, 8′-diol bridged metallophthalocyanines with long triplet state lifetimes

  • Authors: Canlıca, Mevlude , Nyokong, Tebello
  • Date: 2011
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/248406 , vital:51683 , xlink:href="https://doi.org/10.1039/C0DT01749C"
  • Description: The syntheses of new ball-type dinuclear Si(IV)(CH3COO)2 and Ti(IV)O phthalocyanines and two different mononuclear Zn(II) and Ti(IV)O phthalocyanines containing four 1,1′-binaphthyl-8,8′-diol substituents on the peripheral positions are described. The structures of these compounds were characterized using the elemental analyzes, UV-Vis, FT-IR, 1H NMR and mass spectroscopies. The ΦF values are 0.14, 0.10, 0.04, 0.02, 0.07; ΦT values are 0.69, 0.71, 0.85, 0.33, 0.71 for 7–11, respectively. All complexes showed very long triplet lifetimes with τT 7510, 3190, 2880, 2370, 9470 μs for 7–11 in DMSO, respectively.
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  • Date Issued: 2011

Temperature activated ionic conductivity in gallium and indium phthalocyanines

  • Authors: San, Sait Eren , Okutan, Mustafa , Nyokong, Tebello , Durmus, Mahmut , Ozturk, Birol
  • Date: 2011
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/247686 , vital:51607 , xlink:href="https://doi.org/10.1016/j.poly.2010.12.047"
  • Description: The effects of introducing gallium and indium metals into phthalocyanine molecules were investigated via temperature and frequency dependent dielectric spectroscopy. The dielectric properties of Ga(III) and In(III) phthalocyanine pellets were measured at frequencies from 1 kHz to 1 MHz in the temperature range 300–530 K. The temperature dependence of the real part of the dielectric constant suggested that these compounds exhibit semiconductor behavior. The activation energy values were calculated from the Arrhenius plots at different frequencies. A distinct transition in these plots indicated the activation of ionic conductivity at higher temperatures.
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  • Date Issued: 2011

The determinants of household savings in South Africa

  • Authors: Simleit, C , Keeton, Gavin R , Botha, Ferdi
  • Date: 2011
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/396153 , vital:69154 , xlink:href="https://hdl.handle.net/10520/EJC21526"
  • Description: In South Africa, substantial government dissaving as well as poor household savings performance has caused a decline in aggregate savings. Whilst government dissaving has been successfully reversed, household savings continue to fall. Low domestic savings have required South Africa to attract large, volatile portfolio capital inflows to fund a structural current account deficit. Repeated reversals of such inflows have constrained domestic growth and hence an understanding of the factors that have caused this decline in savings is essential in order to formulate policies supportive of sustained higher rates of economic growth. Within the context of the existing literature, this article examines the various determinants of household savings using a vector error-correction model (VECM). The results suggest that interest rates, a wealth effect and upturns in the business cycle all contribute to explaining the decline in household savings. The presence of a partial offset between household savings and government savings also has important implications for the effectiveness of using the fiscal position of the South African government to boost savings.
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  • Date Issued: 2011
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