Selection and characterization of suitable lipid excipients for use in the manufacture of didanosine-loaded solid lipid nanoparticles and nanostructured lipid carriers
- Kasongo, Kasongo W, Pardeike, Jana, Muller, Rainer H, Walker, Roderick B
- 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.
- Full Text:
- Date Issued: 2011
- 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.
- Full Text:
- Date Issued: 2011
Selective adsorption of PVP on the surface of silver nanoparticles
- Mdluli, Phumlani S, Sosibo, Ndabenhle M, Mashazi, Philani N, Nyokong, Tebello, Tshikhudo, Robert T, Skepu, Amanda, van der Lingen, Elma
- 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.
- Full Text:
- Date Issued: 2011
- 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.
- Full Text:
- Date Issued: 2011
Simulating Collective agency: Joint purpose, presence and power as Constraints to learning in a social Context
- Authors: Kulundu, Injairu
- 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.
- Full Text:
- Date Issued: 2011
- Authors: Kulundu, Injairu
- 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.
- Full Text:
- Date Issued: 2011
SOA driven architectures for service creation through enablers in an IMS testbed
- Tsietsi, Mosiuoa, Terzoli, Alfredo, Wells,George C
- Authors: Tsietsi, Mosiuoa , Terzoli, Alfredo , Wells,George C
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430726 , vital:72711 , https://ieeexplore.ieee.org/abstract/document/6144230
- Description: Standards development organisations have long been in agreement that the most appropriate and cost effective way of developing services for the IP Multimedia Subsystem (IMS) is through the use - and re-use - of service capabilities, which are the building blocks for developing complex services. IMS specifications provide a theoretical framework for how service capabilities can be aggregated into large service appli-cations. However, there is little evidence that mainstream IMS service development is capability-based, and many services are still designed in a monolithic way, with no re-use of existing functionality. Telecom-munication networks are well positioned to stimulate the Internet ser-vices market by exposing these service enablers to third parties. In this paper, we marry the two issues by defining an extended IMS service layer (EISL) that provides a service broker that is the central agent in both service interaction management and the execution of external re-quests from third parties. A prototypical implementation of the service broker is described that was developed using a converged SIP servlet container, and a discussion is also provided that details how third party developers could use HTTP APIs to interact with a service broker in or-der to gain access to network capabilities.
- Full Text:
- Date Issued: 2011
- Authors: Tsietsi, Mosiuoa , Terzoli, Alfredo , Wells,George C
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430726 , vital:72711 , https://ieeexplore.ieee.org/abstract/document/6144230
- Description: Standards development organisations have long been in agreement that the most appropriate and cost effective way of developing services for the IP Multimedia Subsystem (IMS) is through the use - and re-use - of service capabilities, which are the building blocks for developing complex services. IMS specifications provide a theoretical framework for how service capabilities can be aggregated into large service appli-cations. However, there is little evidence that mainstream IMS service development is capability-based, and many services are still designed in a monolithic way, with no re-use of existing functionality. Telecom-munication networks are well positioned to stimulate the Internet ser-vices market by exposing these service enablers to third parties. In this paper, we marry the two issues by defining an extended IMS service layer (EISL) that provides a service broker that is the central agent in both service interaction management and the execution of external re-quests from third parties. A prototypical implementation of the service broker is described that was developed using a converged SIP servlet container, and a discussion is also provided that details how third party developers could use HTTP APIs to interact with a service broker in or-der to gain access to network capabilities.
- Full Text:
- Date Issued: 2011
Syntheses and electrochemical characterization of new water soluble octaarylthiosubstituted manganese phthalocyanines
- Booysen, Irvin N, Matemadombo, Fungisai, Durmus, Mahmut, Nyokong, Tebello
- 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.
- Full Text:
- Date Issued: 2011
- 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.
- Full Text:
- 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
- Canlıca, Mevlüde, Booysen, Irvin Noel, Nyokong, Tebello
- 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.
- Full Text:
- Date Issued: 2011
- 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.
- Full Text:
- Date Issued: 2011
Synthesis and electrocatalytic behavior of cobalt (II)-tris (benzyl-mercapto)-monoaminophthalocyanine–single walled carbon nanotube nanorods
- Mugadza, Tawanda, Nyokong, Tebello
- 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.
- Full Text:
- Date Issued: 2011
- 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.
- Full Text:
- Date Issued: 2011
Synthesis and electrochemical behavior of novel peripherally and non-peripherally substituted ball-type cobalt phthalocyanine complexes
- Canlıca, Mevlüde, Booysen, Irvin Noel, Nyokong, Tebello
- 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.
- Full Text:
- Date Issued: 2011
- 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.
- Full Text:
- 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
- Erdoğmuş, Ali, Booysen, Irvin Noel, Nyokong, Tebello
- 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.
- Full Text:
- Date Issued: 2011
- 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.
- Full Text:
- Date Issued: 2011
Synthesis and photophysical behaviour of tantalum and titanium phthalocyanines in the presence of gold nanoparticles
- Chauke, Vongani P, Arslanoglu, Yasin, Nyokong, Tebello
- 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.
- Full Text:
- Date Issued: 2011
- 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.
- Full Text:
- Date Issued: 2011
Synthesis and photophysical properties of a novel zinc photosensitizer and its gold nanoparticle conjugate
- Moeno, Sharon, Antunes, Edith M, Nyokong, Tebello
- 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.
- Full Text:
- Date Issued: 2011
- 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.
- Full Text:
- Date Issued: 2011
Synthesis and photophysical studies of CdTe quantum dot-monosubstituted zinc phthalocyanine conjugates
- D'Souza, Sarah, Antunes, Edith M, Nyokong, Tebello
- 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.
- Full Text:
- Date Issued: 2011
- 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.
- Full Text:
- Date Issued: 2011
Synthesis and photophysical studies of monocarboxy phthalocyanines containing quaternizable groups
- Arslanoğlu, Yasin, Nyokong, Tebello
- 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.
- Full Text:
- Date Issued: 2011
- 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.
- Full Text:
- Date Issued: 2011
Synthesis and photophysical studies of phthalocyanine–gold nanoparticle conjugates
- Nombona, Nolwazi, Antunes, Edith M, Litwinski, Christian, Nyokong, Tebello
- 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.
- Full Text:
- Date Issued: 2011
- 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.
- Full Text:
- Date Issued: 2011
Synthesis, characterization and application of monocarboxy-phthalocyanine-single walled carbon nanotube conjugates in electrocatalysis
- Mugadza, Tawanda, Nyokong, Tebello
- 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.
- Full Text:
- Date Issued: 2011
- 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.
- Full Text:
- 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
- Canlıca, Mevlude, Nyokong, Tebello
- 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.
- Full Text:
- Date Issued: 2011
- 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.
- Full Text:
- Date Issued: 2011
Temperature activated ionic conductivity in gallium and indium phthalocyanines
- San, Sait Eren, Okutan, Mustafa, Nyokong, Tebello, Durmus, Mahmut, Ozturk, Birol
- 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.
- Full Text:
- Date Issued: 2011
- 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.
- Full Text:
- Date Issued: 2011
The determinants of household savings in South Africa
- Simleit, C, Keeotn, Gavin, Botha, Ferdi
- Authors: Simleit, C , Keeotn, Gavin , 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.
- Full Text:
- Date Issued: 2011
- Authors: Simleit, C , Keeotn, Gavin , 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.
- Full Text:
- Date Issued: 2011
The determination of the photosensitizing properties of mercapto substituted phthalocyanine derivatives in the presence of quantum dots capped with mercaptopropionic acid
- Moeno, Sharon, Antunes, Edith M, Nyokong, Tebello
- Authors: Moeno, Sharon , Antunes, Edith M , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247870 , vital:51625 , xlink:href="https://doi.org/10.1016/j.jphotochem.2010.12.009"
- Description: This work reports on the synthesis of several novel water soluble metallophthalocyanines containing Zn2+, In3+, Ga3+ or Si4+ as central metal ions and tetra substituted with mercaptoacetic acid and mercaptopropionic acid. The complexes were characterized using infra red, nuclear magnetic resonance and mass spectroscopies as well as elemental analysis. All the complexes are water soluble but the majority are highly aggregated in water and organic solvents. The complex containing Zn as a central metal and mercaptopropionic acid as a substituent was not aggregated allowing for the determination of photophysical parameters. This complex had triplet state quantum yield of 0.61 in DMF and 0.88 in DMSO while the fluorescence quantum yield was 0.13 in DMSO. The determination of photophysical properties of the complex containing Zn as a central metal and mercaptopropionic acid were carried out in the presence of mercaptopropionic acid capped CdTe quantum dots. There is an increase in triplet state quantum yield from 0.88 (for the phthalocyanine alone) to 0.94 (in the presence of CdTe quantum dots) in DMSO.
- Full Text:
- Date Issued: 2011
- Authors: Moeno, Sharon , Antunes, Edith M , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247870 , vital:51625 , xlink:href="https://doi.org/10.1016/j.jphotochem.2010.12.009"
- Description: This work reports on the synthesis of several novel water soluble metallophthalocyanines containing Zn2+, In3+, Ga3+ or Si4+ as central metal ions and tetra substituted with mercaptoacetic acid and mercaptopropionic acid. The complexes were characterized using infra red, nuclear magnetic resonance and mass spectroscopies as well as elemental analysis. All the complexes are water soluble but the majority are highly aggregated in water and organic solvents. The complex containing Zn as a central metal and mercaptopropionic acid as a substituent was not aggregated allowing for the determination of photophysical parameters. This complex had triplet state quantum yield of 0.61 in DMF and 0.88 in DMSO while the fluorescence quantum yield was 0.13 in DMSO. The determination of photophysical properties of the complex containing Zn as a central metal and mercaptopropionic acid were carried out in the presence of mercaptopropionic acid capped CdTe quantum dots. There is an increase in triplet state quantum yield from 0.88 (for the phthalocyanine alone) to 0.94 (in the presence of CdTe quantum dots) in DMSO.
- Full Text:
- Date Issued: 2011
The effects of carbon nanotubes on the electrocatalysis of hydrogen peroxide by metallo-phthalocyanines
- Mashazi, Philani N, Mugadza, Tawanda, Sosibo, Ndabenhle, Mdluli, Phumlani, Vilakazi, Sibulelo, Nyokong, Tebello
- Authors: Mashazi, Philani N , Mugadza, Tawanda , Sosibo, Ndabenhle , Mdluli, Phumlani , Vilakazi, Sibulelo , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247174 , vital:51553 , xlink:href="https://doi.org/10.1016/j.talanta.2011.07.069"
- Description: The pre-grafted screen-printed gold electrode modified with phenyl-amino monolayer was investigated for covalent immobilization of phenyl-amine functionalized single-walled carbon nanotubes (PA-SWCNT) and metal tetra-amino phthalocyanine (MTAPc) using Schiff-base reactions with benzene-1,4-dicarbaldehyde (BDCA) as cross-linker. The PA-SWCNT and MTAPc modified electrodes were applied as hybrids for electrochemical sensing of H2O2. The step-by-step fabrication of the electrode was followed using electrochemistry, impedance spectroscopy, scanning electron microscopy and Raman spectroscopy and all these techniques confirmed the fabrication and the immobilization of PA-SWCNT, MnTAPc and CoTAPc onto gold surfaces. The apparent electron transfer constant (kapp) showed that the carbon nanotubes and metallo-phthalocyanines hybrids possess good electron transfer properties compared to the bare, pre-grafted and the MTAPc modified gold electrode surfaces without PA-SWCNT. The electrochemical sensing of hydrogen peroxide was successful with PA-SWCNT–MTAPc hybrid systems showing higher electrocatalytic currents compared to the other electrodes. The analytical parameters obtained using chronoamperometry gave good linearity at H2O2 concentrations ranging from 1.0 to 30.0 μmol L−1. The values for the limit of detection (LoD) were found to be of the orders of 10−7 M using the 3δ for all the electrodes. The PA-SWCNT–MTAPc modified SPAuEs were much more sensitive compared to PA–MTAPc modified SPAuEs.
- Full Text:
- Date Issued: 2011
- Authors: Mashazi, Philani N , Mugadza, Tawanda , Sosibo, Ndabenhle , Mdluli, Phumlani , Vilakazi, Sibulelo , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247174 , vital:51553 , xlink:href="https://doi.org/10.1016/j.talanta.2011.07.069"
- Description: The pre-grafted screen-printed gold electrode modified with phenyl-amino monolayer was investigated for covalent immobilization of phenyl-amine functionalized single-walled carbon nanotubes (PA-SWCNT) and metal tetra-amino phthalocyanine (MTAPc) using Schiff-base reactions with benzene-1,4-dicarbaldehyde (BDCA) as cross-linker. The PA-SWCNT and MTAPc modified electrodes were applied as hybrids for electrochemical sensing of H2O2. The step-by-step fabrication of the electrode was followed using electrochemistry, impedance spectroscopy, scanning electron microscopy and Raman spectroscopy and all these techniques confirmed the fabrication and the immobilization of PA-SWCNT, MnTAPc and CoTAPc onto gold surfaces. The apparent electron transfer constant (kapp) showed that the carbon nanotubes and metallo-phthalocyanines hybrids possess good electron transfer properties compared to the bare, pre-grafted and the MTAPc modified gold electrode surfaces without PA-SWCNT. The electrochemical sensing of hydrogen peroxide was successful with PA-SWCNT–MTAPc hybrid systems showing higher electrocatalytic currents compared to the other electrodes. The analytical parameters obtained using chronoamperometry gave good linearity at H2O2 concentrations ranging from 1.0 to 30.0 μmol L−1. The values for the limit of detection (LoD) were found to be of the orders of 10−7 M using the 3δ for all the electrodes. The PA-SWCNT–MTAPc modified SPAuEs were much more sensitive compared to PA–MTAPc modified SPAuEs.
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- Date Issued: 2011