Comparative electrooxidation of sulphite by self-assembled monolayers (SAMs) of Co (II), Fe (II), Ni (II) and Mn (III) tetrakis benzylmercapto and dodecylmercapto metallophthalocyanines complexes on gold electrodes
- Agboola, Bolade, Nyokong, Tebello
- Authors: Agboola, Bolade , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/281223 , vital:55703 , xlink:href="https://doi.org/10.1016/j.talanta.2006.11.042"
- Description: This work reports on the use of Co(II), Fe(II), Mn(III) and Ni(II) tetrakis benzylmercapto and dodecylmercapto phthalocyanine complexes for gold electrode modification for electrooxidation of sulphite ions. The complexes were successfully used to modify gold electrodes by self-assembled monolayer (SAM) technique. The self-assembled films are stable and showed blocking characteristics towards the following Faradaic processes; gold surface oxidation, underpotential deposition (UPD) of copper and solution redox chemistry of [Fe(H2O)63+]/[Fe(H2O)62+]. All the modified electrodes showed improved catalytic activities than the unmodified gold electrode towards sulphite ion electrooxidation with all the modified electrodes exhibiting high resistance to electrode surface passivation. Better catalytic performance were obtained for the CoPcs, FePcs and MnPcs which have metal based redox processes within the range of the sulphite electrooxidation peak, while the NiPcs which did not show metal based redox reaction performed less. The catalytic current was found to be linear with sulphite ion concentration in the concentration range employed in this work (0.1–1 mM) and sensitivities ranging from 1.68 to 2.96 μA/mM were observed for all the modified electrodes. Mechanisms of the catalytic oxidation of sulphite ions are proposed.
- Full Text:
- Date Issued: 2007
- Authors: Agboola, Bolade , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/281223 , vital:55703 , xlink:href="https://doi.org/10.1016/j.talanta.2006.11.042"
- Description: This work reports on the use of Co(II), Fe(II), Mn(III) and Ni(II) tetrakis benzylmercapto and dodecylmercapto phthalocyanine complexes for gold electrode modification for electrooxidation of sulphite ions. The complexes were successfully used to modify gold electrodes by self-assembled monolayer (SAM) technique. The self-assembled films are stable and showed blocking characteristics towards the following Faradaic processes; gold surface oxidation, underpotential deposition (UPD) of copper and solution redox chemistry of [Fe(H2O)63+]/[Fe(H2O)62+]. All the modified electrodes showed improved catalytic activities than the unmodified gold electrode towards sulphite ion electrooxidation with all the modified electrodes exhibiting high resistance to electrode surface passivation. Better catalytic performance were obtained for the CoPcs, FePcs and MnPcs which have metal based redox processes within the range of the sulphite electrooxidation peak, while the NiPcs which did not show metal based redox reaction performed less. The catalytic current was found to be linear with sulphite ion concentration in the concentration range employed in this work (0.1–1 mM) and sensitivities ranging from 1.68 to 2.96 μA/mM were observed for all the modified electrodes. Mechanisms of the catalytic oxidation of sulphite ions are proposed.
- Full Text:
- Date Issued: 2007
Local institutions, actors, and natural resource governance in Kgalagadi Transfrontier Park and surrounds, South Africa
- Thondhlana, Gladman, Shackleton, Sheona E, Blignaut, James
- Authors: Thondhlana, Gladman , Shackleton, Sheona E , Blignaut, James
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67689 , vital:29130 , https://doi.org/10.1016/j.landusepol.2015.03.013
- Description: Publisher version , Crafting local institutions to allow more effective decision-making in the management of and access to natural resources in and beyond parks has long been considered key to collaborative governance. South Africa, in particular, has vigorously pursued collaborative governance as a desired approach to managing natural resources as evident in the new arrangements for previously restricted parks. However, though the discourse of collaborative governance has occupied conservation thinking and practice globally, few studies have looked at the interplay between local institutions, actors and collaborative governance involving indigenous hunter–gatherer communities in Southern Africa. In response, we assess the local actors and institutions that were put in place to facilitate collaborative governance of natural resources in the Kgalagadi Transfrontier Park and its surrounds in South Africa. Our findings show that though collaborative governance has a practical appeal, it is hampered by lack of participation in decision-making, information dissemination, transparency, trust and accountability, power relations, divergent interests and unequal access to natural resources. The findings also draw our attention to issues of heterogeneity, even within indigenous communities assumed to be homogenous by local conservation authorities as reflected in land settlement agreements in co-managed parks. We argue that collaborative governance arrangements need to reflect and be understood within the broader background of complex local realities.
- Full Text: false
- Date Issued: 2015
- Authors: Thondhlana, Gladman , Shackleton, Sheona E , Blignaut, James
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67689 , vital:29130 , https://doi.org/10.1016/j.landusepol.2015.03.013
- Description: Publisher version , Crafting local institutions to allow more effective decision-making in the management of and access to natural resources in and beyond parks has long been considered key to collaborative governance. South Africa, in particular, has vigorously pursued collaborative governance as a desired approach to managing natural resources as evident in the new arrangements for previously restricted parks. However, though the discourse of collaborative governance has occupied conservation thinking and practice globally, few studies have looked at the interplay between local institutions, actors and collaborative governance involving indigenous hunter–gatherer communities in Southern Africa. In response, we assess the local actors and institutions that were put in place to facilitate collaborative governance of natural resources in the Kgalagadi Transfrontier Park and its surrounds in South Africa. Our findings show that though collaborative governance has a practical appeal, it is hampered by lack of participation in decision-making, information dissemination, transparency, trust and accountability, power relations, divergent interests and unequal access to natural resources. The findings also draw our attention to issues of heterogeneity, even within indigenous communities assumed to be homogenous by local conservation authorities as reflected in land settlement agreements in co-managed parks. We argue that collaborative governance arrangements need to reflect and be understood within the broader background of complex local realities.
- Full Text: false
- Date Issued: 2015
Epidemiology, risk factors and molecular analysis of carbapenem-resistant Enterobacteriaceae (CRE) in Mthatha, Eastern Cape, South Africa:
- S.D.Vasaikar, P.Hanise, D.T.Abaver
- Authors: S.D.Vasaikar , P.Hanise , D.T.Abaver
- Date: 2021
- Subjects: Epidemiology Carbapenem-resistant Enterobacteriaceae Mthatha
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/3129 , vital:43143 , xlink:href="https://doi.org/10.3390/f10060467"
- Description: Abstract text. Background: The emergence of carbapenem resistance in Enterobacteriaceae is an important threat to global health. Reported outcomes of infections with carbapenem-resistant Enterobacteriaceae (CRE) are poor. Commonly used antibiotics are generally inactive against CRE. Therefore, timely detection of CRE is of paramount importance. This study aimed to investigate the resistance genes responsible for CRE in Mthatha and to identify risk factors. Methods and materials: Study design – Prospective cohort study. Study period – 23 April to 27 September 2019. Setting – Eastern Cape province, SA. Study population – All adult and paediatric CRE patients. CRE case definition according to CDC 2018. ID and AST-bioMérieux Vitek 2 system. Detection of the blaOXA-48, blaKPC, blaNDM, and blaVIM by the RESIST-4 OKNV assay (Coris). Patients were interviewed to determine risk factors associated with CRE. Results: Forty-four non-duplicate CRE patients were identified during the study period from microbiology lab at NMAH. Enterobacteriaceae species: K. pneumoniae 22 (61.4%), E. cloacae 10 (22.7%), E. coli 2 (4.5%) and K. oxytoca, P. rettgeri and M. morganii 1 each (4.3%). Adult patient 29 (65.9%0 and paediatric 15 (34.1%). Race: all black patients except one white. CRE genes-blaOXA-48 22 (50%), blaNDM 8 (18.2%), two isolates (4.5%) with both blaOXA and blaNDM. We did not find any blaKPC and blaVIM in our setting and 12 (27.2%) isolates were negative for all OKNV. Outcomes: Demised 18 (40.9%), still admitted in the ward 1 (2.3%), discharged home on basis of clinical grounds 22 (50%) and 3 (6.8%) were transferred back to the district hospitals. HAI in 27 (61.4%) with VAP 8, HABSI 8, CAUTI 5, SSI 3 and CLABSI in 3. Risk factors for CRE acquisition were antibiotic exposure 25 (58.7%), ICU stay 7 (15.9%), received medical care in last 6 months 35 (79.6%) and none travelled outside RSA. HIV positive – 19 (43.2%). Conclusion: In out setting our CRE mortality rate is 40.9%, common CRE genotypes are blaOXA-48 and blaNDM. K. pneumoniae is the most common CRE-producing Enterobacteriaceae and antibiotic exposure is an important risk factor in Mthatha and surrounding areas.
- Full Text:
- Date Issued: 2021
- Authors: S.D.Vasaikar , P.Hanise , D.T.Abaver
- Date: 2021
- Subjects: Epidemiology Carbapenem-resistant Enterobacteriaceae Mthatha
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/3129 , vital:43143 , xlink:href="https://doi.org/10.3390/f10060467"
- Description: Abstract text. Background: The emergence of carbapenem resistance in Enterobacteriaceae is an important threat to global health. Reported outcomes of infections with carbapenem-resistant Enterobacteriaceae (CRE) are poor. Commonly used antibiotics are generally inactive against CRE. Therefore, timely detection of CRE is of paramount importance. This study aimed to investigate the resistance genes responsible for CRE in Mthatha and to identify risk factors. Methods and materials: Study design – Prospective cohort study. Study period – 23 April to 27 September 2019. Setting – Eastern Cape province, SA. Study population – All adult and paediatric CRE patients. CRE case definition according to CDC 2018. ID and AST-bioMérieux Vitek 2 system. Detection of the blaOXA-48, blaKPC, blaNDM, and blaVIM by the RESIST-4 OKNV assay (Coris). Patients were interviewed to determine risk factors associated with CRE. Results: Forty-four non-duplicate CRE patients were identified during the study period from microbiology lab at NMAH. Enterobacteriaceae species: K. pneumoniae 22 (61.4%), E. cloacae 10 (22.7%), E. coli 2 (4.5%) and K. oxytoca, P. rettgeri and M. morganii 1 each (4.3%). Adult patient 29 (65.9%0 and paediatric 15 (34.1%). Race: all black patients except one white. CRE genes-blaOXA-48 22 (50%), blaNDM 8 (18.2%), two isolates (4.5%) with both blaOXA and blaNDM. We did not find any blaKPC and blaVIM in our setting and 12 (27.2%) isolates were negative for all OKNV. Outcomes: Demised 18 (40.9%), still admitted in the ward 1 (2.3%), discharged home on basis of clinical grounds 22 (50%) and 3 (6.8%) were transferred back to the district hospitals. HAI in 27 (61.4%) with VAP 8, HABSI 8, CAUTI 5, SSI 3 and CLABSI in 3. Risk factors for CRE acquisition were antibiotic exposure 25 (58.7%), ICU stay 7 (15.9%), received medical care in last 6 months 35 (79.6%) and none travelled outside RSA. HIV positive – 19 (43.2%). Conclusion: In out setting our CRE mortality rate is 40.9%, common CRE genotypes are blaOXA-48 and blaNDM. K. pneumoniae is the most common CRE-producing Enterobacteriaceae and antibiotic exposure is an important risk factor in Mthatha and surrounding areas.
- Full Text:
- Date Issued: 2021
Microelectrochemical patterning of gold surfaces using 4-azidobenzenediazonium and scanning electrochemical microscopy
- Coates, Megan, Cabet, Eva, Griveau, Sophie, Nyokong, Tebello, Bedioui, Fethi
- Authors: Coates, Megan , Cabet, Eva , Griveau, Sophie , Nyokong, Tebello , Bedioui, Fethi
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247926 , vital:51630 , xlink:href="https://doi.org/10.1016/j.elecom.2010.11.037"
- Description: This work describes for the first time the possibility of performing local micro electrochemical grafting of a gold substrate by 4-azidobenzenediazonium by SECM in a single and simple one step without complications from adsorption. The electrografted spots of diazonium were performed by positioning a Pt tip at a given distance above the gold substrate and the SECM was used in a three-electrode configuration (the Pt tip serving as the microanode) in acetonitrile containing 5 mM 4-azidobenzenediazonium and 0.1 M Bu4NBF4 during 10 ms. The dimensions of the derivatized areas of the substrates were finely tuned by using different experimental conditions (tip distance above the substrate, tip diameter, presence or absence of supporting electrolyte). The use of the azido-derivated diazonium molecule and these preliminary results open the gate to important applications and developments devoted to the local micro functionalization of electrodes by thin layers that allow the implementation of the emerging and attractive interfacial click reaction.
- Full Text:
- Date Issued: 2011
- Authors: Coates, Megan , Cabet, Eva , Griveau, Sophie , Nyokong, Tebello , Bedioui, Fethi
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247926 , vital:51630 , xlink:href="https://doi.org/10.1016/j.elecom.2010.11.037"
- Description: This work describes for the first time the possibility of performing local micro electrochemical grafting of a gold substrate by 4-azidobenzenediazonium by SECM in a single and simple one step without complications from adsorption. The electrografted spots of diazonium were performed by positioning a Pt tip at a given distance above the gold substrate and the SECM was used in a three-electrode configuration (the Pt tip serving as the microanode) in acetonitrile containing 5 mM 4-azidobenzenediazonium and 0.1 M Bu4NBF4 during 10 ms. The dimensions of the derivatized areas of the substrates were finely tuned by using different experimental conditions (tip distance above the substrate, tip diameter, presence or absence of supporting electrolyte). The use of the azido-derivated diazonium molecule and these preliminary results open the gate to important applications and developments devoted to the local micro functionalization of electrodes by thin layers that allow the implementation of the emerging and attractive interfacial click reaction.
- Full Text:
- Date Issued: 2011
Self-assembled monolayers (SAMs) of cobalt tetracarboxylic acidchloride phthalocyanine covalently attached onto a preformed mercaptoethanol SAM
- Mashazi, Philani N, Ozoemena, Kenneth I, Maree, David M, Nyokong, Tebello
- Authors: Mashazi, Philani N , Ozoemena, Kenneth I , Maree, David M , Nyokong, Tebello
- Date: 2006
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/283792 , vital:55989 , xlink:href="https://doi.org/10.1016/j.electacta.2005.10.004"
- Description: A feasible method of fabricating phthalocyanine sensor was developed by covalent attachment of cobalt tetracarboxylic acidchloride phthalocyanine (CoTCACIPc) onto a preformed 2-mercaptoethanol (2-ME) self-assembled monolayer (SAM) modified gold electrode (designated as CoTCACIPc-2-ME-SAM). The surface concentration of the CoTCACIPc was found to be 4.58 × 10−10 mol/cm2. The sensor gave a linear response to L-cysteine over the concentration range 0.28–20 μM with a detection limit of 5 × 10−7 M and best response time of 2 s.
- Full Text:
- Date Issued: 2006
- Authors: Mashazi, Philani N , Ozoemena, Kenneth I , Maree, David M , Nyokong, Tebello
- Date: 2006
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/283792 , vital:55989 , xlink:href="https://doi.org/10.1016/j.electacta.2005.10.004"
- Description: A feasible method of fabricating phthalocyanine sensor was developed by covalent attachment of cobalt tetracarboxylic acidchloride phthalocyanine (CoTCACIPc) onto a preformed 2-mercaptoethanol (2-ME) self-assembled monolayer (SAM) modified gold electrode (designated as CoTCACIPc-2-ME-SAM). The surface concentration of the CoTCACIPc was found to be 4.58 × 10−10 mol/cm2. The sensor gave a linear response to L-cysteine over the concentration range 0.28–20 μM with a detection limit of 5 × 10−7 M and best response time of 2 s.
- Full Text:
- Date Issued: 2006
Enhanced triplet state yields in aqueous media of asymmetric zinc phthalocyanines when conjugated to silver nanoflowers
- D’Souza, Sarah, George, Reama, Göksel, Meltem, Atilla, Devrim, Durmuş, Mahmut, Nyokong, Tebello
- Authors: D’Souza, Sarah , George, Reama , Göksel, Meltem , Atilla, Devrim , Durmuş, Mahmut , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7279 , http://hdl.handle.net/10962/d1020315
- Description: Novel low symmetry water-soluble zinc phthalocyanines (ZnPcs, complexes 1 and 2) were synthesized and then mixed with silver nanoflowers. Photophysical and photochemical studies were performed in order to determine the efficiency of complexes 1 and 2 as photosensitizers when alone and when combined with the silver nanoflowers. The Pcs show low fluorescence quantum yields and excellent triplet quantum yields of 0.78 (for 1) and 0.66 (for 2) in aqueous media. The triplet quantum yield values increased to 0.80 and 0.89, respectively, in the presence of silver nanoflowers. Long triplet lifetimes ranging from 180 to 200 μs in DMSO were obtained for complexes 1, 2 and their conjugates with silver nanoflowers. , Original publication is available at http://dx.doi.org/10.1016/j.poly.2015.08.017
- Full Text: false
- Authors: D’Souza, Sarah , George, Reama , Göksel, Meltem , Atilla, Devrim , Durmuş, Mahmut , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7279 , http://hdl.handle.net/10962/d1020315
- Description: Novel low symmetry water-soluble zinc phthalocyanines (ZnPcs, complexes 1 and 2) were synthesized and then mixed with silver nanoflowers. Photophysical and photochemical studies were performed in order to determine the efficiency of complexes 1 and 2 as photosensitizers when alone and when combined with the silver nanoflowers. The Pcs show low fluorescence quantum yields and excellent triplet quantum yields of 0.78 (for 1) and 0.66 (for 2) in aqueous media. The triplet quantum yield values increased to 0.80 and 0.89, respectively, in the presence of silver nanoflowers. Long triplet lifetimes ranging from 180 to 200 μs in DMSO were obtained for complexes 1, 2 and their conjugates with silver nanoflowers. , Original publication is available at http://dx.doi.org/10.1016/j.poly.2015.08.017
- Full Text: false
Photodynamic antimicrobial chemotherapy activity of (5, 10, 15, 20-tetrakis (4-(4-carboxyphenycarbonoimidoyl) phenyl) porphyrinato) chloro gallium (III)
- Managa, Muthumuni, Amuhaya, Edith K, Nyokong, Tebello
- Authors: Managa, Muthumuni , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189043 , vital:44811 , xlink:href="https://doi.org/10.1016/j.saa.2015.06.088"
- Description: (5,10,15,20-Tetrakis(4-(4-carboxyphenycarbonoimidoyl)phenyl)porphyrinato) chloro gallium(III) (complex 1) was conjugated to platinum nanoparticles (PtNPs) (represented as 1-PtNPs). The resulting conjugate showed 18 nm red shift in the Soret band when compared to 1 alone. Complex 1 and 1-PtNPs showed promising photodynamic antimicrobial chemotherapy (PACT) activity against Staphylococcus aureus, Escherichia coli and Candida albicans in solution where the log reductions obtained were 4.92, 3.76, and 3.95, respectively for 1-PtNPs. The singlet oxygen quantum yields obtained were higher at 0.56 for 1-PtNPs in DMF while that of 1 was 0.52 in the same solvent. This resulted in improved PACT activity for 1-PtNPs compared to 1 alone.
- Full Text:
- Date Issued: 2015
- Authors: Managa, Muthumuni , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189043 , vital:44811 , xlink:href="https://doi.org/10.1016/j.saa.2015.06.088"
- Description: (5,10,15,20-Tetrakis(4-(4-carboxyphenycarbonoimidoyl)phenyl)porphyrinato) chloro gallium(III) (complex 1) was conjugated to platinum nanoparticles (PtNPs) (represented as 1-PtNPs). The resulting conjugate showed 18 nm red shift in the Soret band when compared to 1 alone. Complex 1 and 1-PtNPs showed promising photodynamic antimicrobial chemotherapy (PACT) activity against Staphylococcus aureus, Escherichia coli and Candida albicans in solution where the log reductions obtained were 4.92, 3.76, and 3.95, respectively for 1-PtNPs. The singlet oxygen quantum yields obtained were higher at 0.56 for 1-PtNPs in DMF while that of 1 was 0.52 in the same solvent. This resulted in improved PACT activity for 1-PtNPs compared to 1 alone.
- Full Text:
- Date Issued: 2015
The interaction between graphene quantum dots grafted with polyethyleneimine and Au@ Ag nanoparticles
- Achadu, Ojodomo John, Uddin, Imran, Nyokong, Tebello
- Authors: Achadu, Ojodomo John , Uddin, Imran , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188679 , vital:44775 , xlink:href="https://doi.org/10.1016/j.jphotochem.2016.03.016"
- Description: Graphene quantum dots grafted with polyethyleneimine (GQDs-PEI) and Au@Ag core-shell nanoparticles blend was demonstrated to be a novel biosensing nanoprobe for the rapid and highly sensitive detection of biothiols such as cysteine (Cys), homocysteine (Hcys) and glutathione (GSH). The fluorescence emission of GQDs-PEI was quenched efficiently upon interaction with Au@Ag core-shell nanoparticles. The quenched fluorescence emission of the GQDs-PEI was restored in the presence of the biothiols. The fluorimetric sensing is based on the strong affinity between the mercapto (SH) groups of the biothiols and the Au@Ag core-shell nanoparticles by which the interaction between GQDs-PEI and Au@Ag core-shell nanoparticles was disrupted with a consequent modulation (‘turn-on’) of the quenched GQDs-PEI emission. Thus, a new, simple, rapid and highly sensitive fluorescence nanoprobe for detecting biothiols has been developed in this work.
- Full Text:
- Date Issued: 2016
- Authors: Achadu, Ojodomo John , Uddin, Imran , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188679 , vital:44775 , xlink:href="https://doi.org/10.1016/j.jphotochem.2016.03.016"
- Description: Graphene quantum dots grafted with polyethyleneimine (GQDs-PEI) and Au@Ag core-shell nanoparticles blend was demonstrated to be a novel biosensing nanoprobe for the rapid and highly sensitive detection of biothiols such as cysteine (Cys), homocysteine (Hcys) and glutathione (GSH). The fluorescence emission of GQDs-PEI was quenched efficiently upon interaction with Au@Ag core-shell nanoparticles. The quenched fluorescence emission of the GQDs-PEI was restored in the presence of the biothiols. The fluorimetric sensing is based on the strong affinity between the mercapto (SH) groups of the biothiols and the Au@Ag core-shell nanoparticles by which the interaction between GQDs-PEI and Au@Ag core-shell nanoparticles was disrupted with a consequent modulation (‘turn-on’) of the quenched GQDs-PEI emission. Thus, a new, simple, rapid and highly sensitive fluorescence nanoprobe for detecting biothiols has been developed in this work.
- Full Text:
- Date Issued: 2016
An ethnobotanical survey of plants used traditionally to treat tuberculosis in the eastern region of O.R. Tambo district, South Africa
- Authors: B. Madikizela , L. Kambizi
- Date: 2017
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/11260/5526 , vital:44596
- Full Text:
- Authors: B. Madikizela , L. Kambizi
- Date: 2017
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/11260/5526 , vital:44596
- Full Text:
Photophysico-chemical properties and photoinactivation of Staphylococcus Aureus using zinc phthalocyanines linked silver nanoparticles conjugates
- Matlou, Gauta G, Nyokong, Tebello
- Authors: Matlou, Gauta G , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186278 , vital:44481 , xlink:href="https://doi.org/10.1016/j.dyepig.2020.108237"
- Description: The synthesis of zinc (II) tri (tert-butyl phenoxy) mono cinnamic acid Pc (complex 1) is reported for the first time in this work. Complex 1 and the reported zinc (II) tri (tert-butyl), mono cinnamic acid phthalocyanine (2), zinc (II) mono cinnamic acid substituted phthalocyanine (3) and zinc (II) tetra cinnamic acid substituted phthalocyanine (4) are conjugated to cysteine capped silver nanoparticles (cys-AgNPs) through an amide bond. The photophysicochemical properties and the photodynamic antimicrobial chemotherapy (PACT) activities of the Pc-cys-AgNPs conjugates and the Pcs alone on S. Aureus are reported. Improved triplet and singlet oxygen quantum yields were observed for the conjugated complexes compared to Pcs alone, due to the heavy atom effect of cys-AgNPs. Asymmetric complexes 1,2, 3 and their respective conjugates recorded higher photosensitizing properties and PACT activities compared to 4 and 4-cys-AgNPs, respectively. Higher log reductions and percentage reductions of S. Aureus were recorded for conjugated complexes compared to ZnPcs only, showing enhanced PACT activities due to their higher singlet oxygen quantum yields.
- Full Text:
- Date Issued: 2020
- Authors: Matlou, Gauta G , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186278 , vital:44481 , xlink:href="https://doi.org/10.1016/j.dyepig.2020.108237"
- Description: The synthesis of zinc (II) tri (tert-butyl phenoxy) mono cinnamic acid Pc (complex 1) is reported for the first time in this work. Complex 1 and the reported zinc (II) tri (tert-butyl), mono cinnamic acid phthalocyanine (2), zinc (II) mono cinnamic acid substituted phthalocyanine (3) and zinc (II) tetra cinnamic acid substituted phthalocyanine (4) are conjugated to cysteine capped silver nanoparticles (cys-AgNPs) through an amide bond. The photophysicochemical properties and the photodynamic antimicrobial chemotherapy (PACT) activities of the Pc-cys-AgNPs conjugates and the Pcs alone on S. Aureus are reported. Improved triplet and singlet oxygen quantum yields were observed for the conjugated complexes compared to Pcs alone, due to the heavy atom effect of cys-AgNPs. Asymmetric complexes 1,2, 3 and their respective conjugates recorded higher photosensitizing properties and PACT activities compared to 4 and 4-cys-AgNPs, respectively. Higher log reductions and percentage reductions of S. Aureus were recorded for conjugated complexes compared to ZnPcs only, showing enhanced PACT activities due to their higher singlet oxygen quantum yields.
- Full Text:
- Date Issued: 2020
The production and commercialization of palm wine from Hyphaene coriacea and Phoenix reclinata in Zitundo area, southern Mozambique
- Martins, Angelina R O, Shackleton, Charlie M
- Authors: Martins, Angelina R O , Shackleton, Charlie M
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/179802 , vital:43190 , xlink:href="https://doi.org/10.1016/j.sajb.2018.02.389"
- Description: In southern Mozambique a traditional wine is produced using the sap from two palm species, Hyphaene coriacea and Phoenix reclinata. Production of palm wine is one of the main livelihood activities in the Zitundo area. We examined the local production and trade of palm wine in the area. Using structured interviews we investigated the tapping activity, local management practices and the palm wine market, and assessed the incomes derived from palm wine sales and the tappers' perceptions on productivity, abundance and sales fluctuation. Tapping palms was practiced year round in five of the sixteen villages in the area and the mean number of palms tapped per day was 102 ± 52 per tapper. Tappers spent an average of 25 ± 18 h per week on tapping activities resulting in an average return to labour of R39 (± US$3) per hour. The mean, annual, net income from palm wine sales was R24,981 ± R12,094 (US$1878 ± 909) per tapper, which accounted for 85% ± 22% of the tappers' annual household income. Palm wine is a highly commercial commodity in Zitundo area, with an average commercialization index of 63% ± 23%, and is likely to help alleviate poverty in the area. Hyphaene coriacea was tapped more than Phoenix reclinata, although most tappers regard the wine from the latter to be of a better quality. The importance of palm tapping in local livelihoods and poverty alleviation needs greater acknowledgement by government and development agencies in the area, towards inclusion in sectoral development policies and conservation programmes.
- Full Text:
- Date Issued: 2018
- Authors: Martins, Angelina R O , Shackleton, Charlie M
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/179802 , vital:43190 , xlink:href="https://doi.org/10.1016/j.sajb.2018.02.389"
- Description: In southern Mozambique a traditional wine is produced using the sap from two palm species, Hyphaene coriacea and Phoenix reclinata. Production of palm wine is one of the main livelihood activities in the Zitundo area. We examined the local production and trade of palm wine in the area. Using structured interviews we investigated the tapping activity, local management practices and the palm wine market, and assessed the incomes derived from palm wine sales and the tappers' perceptions on productivity, abundance and sales fluctuation. Tapping palms was practiced year round in five of the sixteen villages in the area and the mean number of palms tapped per day was 102 ± 52 per tapper. Tappers spent an average of 25 ± 18 h per week on tapping activities resulting in an average return to labour of R39 (± US$3) per hour. The mean, annual, net income from palm wine sales was R24,981 ± R12,094 (US$1878 ± 909) per tapper, which accounted for 85% ± 22% of the tappers' annual household income. Palm wine is a highly commercial commodity in Zitundo area, with an average commercialization index of 63% ± 23%, and is likely to help alleviate poverty in the area. Hyphaene coriacea was tapped more than Phoenix reclinata, although most tappers regard the wine from the latter to be of a better quality. The importance of palm tapping in local livelihoods and poverty alleviation needs greater acknowledgement by government and development agencies in the area, towards inclusion in sectoral development policies and conservation programmes.
- Full Text:
- Date Issued: 2018
The effect of ascorbic acid on the photophysical properties and photodynamic therapy activities of zinc phthalocyanine-single walled carbon nanotube conjugate on MCF-7 cancer cells
- Ogbodu, Racheal O, Nyokong, Tebello
- Authors: Ogbodu, Racheal O , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189066 , vital:44813 , xlink:href="https://doi.org/10.1016/j.saa.2015.06.063"
- Description: Zinc mono carboxy phenoxy phthalocyanine (1) was chemical modified with ascorbic acid via an ester bond to give ZnMCPPc-AA (2). Complexes 2 and 1 were coordinated to single walled carbon nanotubes via π–π interaction to give ZnMCPPc-AA-SWCNT (3) and ZnMCPPc-SWCNT (4) respectively. Complexes 2, 3 and 4 showed better photophysical properties: with improved triplet lifetimes and quantum yields, and singlet oxygen quantum yields when compared to 1 alone. The photodynamic therapy activities of complexes 1, 2, 3 and 4 were tested in vitro on MCF-7 breast cancer cells. Ascorbic acid suppresses the photodynamic therapy effect of 1, due to its ability to reduce oxidative DNA damage as a result of its potent reducing properties. The highest phototoxicity was observed for 4 which resulted in 77% decrease in cell viability, followed by 3 which resulted in 67% decrease in cell viability. This shows the importance of combination therapy, where the phthalocyanines are the photodynamic therapy agents and single walled carbon nanotubes are the photothermal therapy agents.
- Full Text:
- Date Issued: 2015
- Authors: Ogbodu, Racheal O , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189066 , vital:44813 , xlink:href="https://doi.org/10.1016/j.saa.2015.06.063"
- Description: Zinc mono carboxy phenoxy phthalocyanine (1) was chemical modified with ascorbic acid via an ester bond to give ZnMCPPc-AA (2). Complexes 2 and 1 were coordinated to single walled carbon nanotubes via π–π interaction to give ZnMCPPc-AA-SWCNT (3) and ZnMCPPc-SWCNT (4) respectively. Complexes 2, 3 and 4 showed better photophysical properties: with improved triplet lifetimes and quantum yields, and singlet oxygen quantum yields when compared to 1 alone. The photodynamic therapy activities of complexes 1, 2, 3 and 4 were tested in vitro on MCF-7 breast cancer cells. Ascorbic acid suppresses the photodynamic therapy effect of 1, due to its ability to reduce oxidative DNA damage as a result of its potent reducing properties. The highest phototoxicity was observed for 4 which resulted in 77% decrease in cell viability, followed by 3 which resulted in 67% decrease in cell viability. This shows the importance of combination therapy, where the phthalocyanines are the photodynamic therapy agents and single walled carbon nanotubes are the photothermal therapy agents.
- Full Text:
- Date Issued: 2015
Electrocatalytic application for gold nanoparticles decorated sulfur-nitrogen co-doped graphene oxide nanosheets and nanosized cobalt tetra aminophenoxy phthalocyanine conjugates
- Shumba, Munyaradzi S, Nyokong, Tebello
- Authors: Shumba, Munyaradzi S , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188260 , vital:44739 , xlink:href="https://doi.org/10.1016/j.electacta.2017.03.154"
- Description: Sulfur and nitrogen affinity for gold is utilized to self-assemble gold nanorods (AuNRs) on S, N doped or S/N co-doped graphene oxide nanosheets (SGONS/AuNRs, NGONS/AuNRs or SNGONS/AuNRs) for enhancement of the electrocatalytic activity of nanosized cobalt tetra aminophenoxy phthalocyanine (complex 1) towards hydrogen peroxide detection. Of the electrodes containing AuNRs, 1-SNGONS/AuNRs-GCE gave the lowest limits of detection (LOD) of 0.012 μM followed by 1-SGONS/AuNRs-GCE and 1-AuNRs-SNGONS(seq)-GCE both with LOD of 0.016 μM. This work shows that in the absence of GONS (when AuNRs are alone and in the presence of 1 in 1/AuNRs-GCE), unfavorable detection limits are obtained and that doping of GONS is important in improving LOD. 1-SNGONS/AuNRs-GCE showed concentration dependent mechanisms resulting in two adsorption Gibbs energies (ΔGo) of −18.55 kJ mol−1 and −17.35 kJ mol−1 at high and low concentrations, respectively.
- Full Text:
- Date Issued: 2017
- Authors: Shumba, Munyaradzi S , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188260 , vital:44739 , xlink:href="https://doi.org/10.1016/j.electacta.2017.03.154"
- Description: Sulfur and nitrogen affinity for gold is utilized to self-assemble gold nanorods (AuNRs) on S, N doped or S/N co-doped graphene oxide nanosheets (SGONS/AuNRs, NGONS/AuNRs or SNGONS/AuNRs) for enhancement of the electrocatalytic activity of nanosized cobalt tetra aminophenoxy phthalocyanine (complex 1) towards hydrogen peroxide detection. Of the electrodes containing AuNRs, 1-SNGONS/AuNRs-GCE gave the lowest limits of detection (LOD) of 0.012 μM followed by 1-SGONS/AuNRs-GCE and 1-AuNRs-SNGONS(seq)-GCE both with LOD of 0.016 μM. This work shows that in the absence of GONS (when AuNRs are alone and in the presence of 1 in 1/AuNRs-GCE), unfavorable detection limits are obtained and that doping of GONS is important in improving LOD. 1-SNGONS/AuNRs-GCE showed concentration dependent mechanisms resulting in two adsorption Gibbs energies (ΔGo) of −18.55 kJ mol−1 and −17.35 kJ mol−1 at high and low concentrations, respectively.
- Full Text:
- Date Issued: 2017
Nonlinear optical behavior of alkyne terminated phthalocyanines in solution and when embedded in polysulfone as thin films: effects of aggregation
- Bankole, Owolabi M, Yilmaz, Yusuf, Nyokong, Tebello
- Authors: Bankole, Owolabi M , Yilmaz, Yusuf , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189110 , vital:44817 , xlink:href="https://doi.org/10.1016/j.optmat.2015.11.041"
- Description: We report here for the first time, on the comparative studies of the photophysical and optical limiting behavior of our two novel phthalocyanines namely 2(3), 9(10), 16(17), 23(24)-tetrakis-(4-(5-methylhex-1-yn-3-yloxy)) phthalocyanines 2, and 2(3), 9(10), 16(17), 23(24)-tetrakis-(4-(5-methylhex-1-yn-3-yloxy)) phthalocyaninato zinc (II) (3) in solution and thin films. Nonlinear optical (NLO) properties of the samples in solution and contained in polysulfone (PSU) thin films were evaluated using Z-scan technique at 532 nm and 10 ns pulsed duration. Effects of aggregation and disaggregation on the NLO performance of metal-free phthalocyanine are reported in detail. Our findings showed that the prepared Pcs show larger nonlinear absorption coefficient and lower limiting thresholds when embedded in polysulfone films compared to in solutions. The values of nonlinear susceptibility and hyperpolarizability recorded for 3-PSU in this work are respectively, ∼2.09 × 10−8 esu and ∼1.02 × 10−26 esu. These values are among the largest values reported for phthalocyanines and other macrocycles doped on polymer matrices.
- Full Text:
- Date Issued: 2016
- Authors: Bankole, Owolabi M , Yilmaz, Yusuf , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189110 , vital:44817 , xlink:href="https://doi.org/10.1016/j.optmat.2015.11.041"
- Description: We report here for the first time, on the comparative studies of the photophysical and optical limiting behavior of our two novel phthalocyanines namely 2(3), 9(10), 16(17), 23(24)-tetrakis-(4-(5-methylhex-1-yn-3-yloxy)) phthalocyanines 2, and 2(3), 9(10), 16(17), 23(24)-tetrakis-(4-(5-methylhex-1-yn-3-yloxy)) phthalocyaninato zinc (II) (3) in solution and thin films. Nonlinear optical (NLO) properties of the samples in solution and contained in polysulfone (PSU) thin films were evaluated using Z-scan technique at 532 nm and 10 ns pulsed duration. Effects of aggregation and disaggregation on the NLO performance of metal-free phthalocyanine are reported in detail. Our findings showed that the prepared Pcs show larger nonlinear absorption coefficient and lower limiting thresholds when embedded in polysulfone films compared to in solutions. The values of nonlinear susceptibility and hyperpolarizability recorded for 3-PSU in this work are respectively, ∼2.09 × 10−8 esu and ∼1.02 × 10−26 esu. These values are among the largest values reported for phthalocyanines and other macrocycles doped on polymer matrices.
- Full Text:
- Date Issued: 2016
The interaction of silver nanoparticles with low symmetry cysteinyl metallophthalocyanines and their antimicrobial effect
- Masilela, Nkosiphile, Nyokong, Tebello
- Authors: Masilela, Nkosiphile , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193735 , vital:45391 , xlink:href="https://doi.org/10.1016/j.jphotochem.2013.01.009"
- Description: This work reports on the synthesis of silver nanoparticles and their antimicrobial activity alone and in the presence of low symmetry phthalocyanines. The photochemical behaviour of various low symmetry phthalocyanines in the presence of AgNPs is investigated in DMF. A slight improvement in the photochemical behaviour and antimicrobial activity was achieved in the presence of AgNPs for all the complexes. The spherically shaped AgNPs gave the highest antimicrobial activity compared to the triangular and cubic structures. The (OH)2GeMCsPc complex gave the highest antimicrobial activity towards Staphylococcus aureas, both alone and in the presence of AgNPs under illumination with light.
- Full Text:
- Date Issued: 2013
- Authors: Masilela, Nkosiphile , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193735 , vital:45391 , xlink:href="https://doi.org/10.1016/j.jphotochem.2013.01.009"
- Description: This work reports on the synthesis of silver nanoparticles and their antimicrobial activity alone and in the presence of low symmetry phthalocyanines. The photochemical behaviour of various low symmetry phthalocyanines in the presence of AgNPs is investigated in DMF. A slight improvement in the photochemical behaviour and antimicrobial activity was achieved in the presence of AgNPs for all the complexes. The spherically shaped AgNPs gave the highest antimicrobial activity compared to the triangular and cubic structures. The (OH)2GeMCsPc complex gave the highest antimicrobial activity towards Staphylococcus aureas, both alone and in the presence of AgNPs under illumination with light.
- Full Text:
- Date Issued: 2013
Comparison of carbon screen-printed and disk electrodes in the detection of antioxidants using CoPc derivatives
- Matemadombo, Fungisai, Apetrei, Constantin, Nyokong, Tebello, Rodríguez-Méndez, María Luz, de Saja, José Antonio
- Authors: Matemadombo, Fungisai , Apetrei, Constantin , Nyokong, Tebello , Rodríguez-Méndez, María Luz , de Saja, José Antonio
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244371 , vital:51251 , xlink:href="https://doi.org/10.1016/j.snb.2012.02.088"
- Description: Cobalt phthalocyanine (CoPc) and cobalt phthalocyanine carboxylic derivatives (CoTCPc and CoOCPc) have been used as electrocatalysts for the detection of the antioxidants vanillic acid, caffeic acid, pyrogallol, and ascorbic acid on screen-printed carbon and disk electrode surfaces. The cobalt phthalocyanines were used to detect vanillic acid (with limit of detection ranging from 1.15 μM to 2.42 μM at potentials of 0.55–0.88 V vs. Ag|AgCl), caffeic acid (with limit of detection ranging from 1.17 μM to 2.20 μM at potentials of 0.30–0.81 V vs. Ag|AgCl), pyrogallol (with limit of detection ranging from 1.16 μM to 3.63 μM at potentials of 0.52–0.63 V vs. Ag|AgCl), and ascorbic acid (with limit of detection ranging from 1.16 μM to 1.58 μM at potentials of 0.34–0.46 V vs. Ag|AgCl). The kinetic studies also demonstrate diffusion-controlled processes at the electrode surface. The SPCE electrodes have better detection properties towards vanillic acid, caffeic acid, pyrogallol while the disk electrodes had better ascorbic acid detection properties as proven by kinetic studies. Both types CoPc-influenced electrodes show 100% discrimination of the antioxidants.
- Full Text:
- Date Issued: 2012
- Authors: Matemadombo, Fungisai , Apetrei, Constantin , Nyokong, Tebello , Rodríguez-Méndez, María Luz , de Saja, José Antonio
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244371 , vital:51251 , xlink:href="https://doi.org/10.1016/j.snb.2012.02.088"
- Description: Cobalt phthalocyanine (CoPc) and cobalt phthalocyanine carboxylic derivatives (CoTCPc and CoOCPc) have been used as electrocatalysts for the detection of the antioxidants vanillic acid, caffeic acid, pyrogallol, and ascorbic acid on screen-printed carbon and disk electrode surfaces. The cobalt phthalocyanines were used to detect vanillic acid (with limit of detection ranging from 1.15 μM to 2.42 μM at potentials of 0.55–0.88 V vs. Ag|AgCl), caffeic acid (with limit of detection ranging from 1.17 μM to 2.20 μM at potentials of 0.30–0.81 V vs. Ag|AgCl), pyrogallol (with limit of detection ranging from 1.16 μM to 3.63 μM at potentials of 0.52–0.63 V vs. Ag|AgCl), and ascorbic acid (with limit of detection ranging from 1.16 μM to 1.58 μM at potentials of 0.34–0.46 V vs. Ag|AgCl). The kinetic studies also demonstrate diffusion-controlled processes at the electrode surface. The SPCE electrodes have better detection properties towards vanillic acid, caffeic acid, pyrogallol while the disk electrodes had better ascorbic acid detection properties as proven by kinetic studies. Both types CoPc-influenced electrodes show 100% discrimination of the antioxidants.
- Full Text:
- Date Issued: 2012
Photophysicochemical behaviour and antimicrobial properties of monocarboxy Mg (II) and Al (III) phthalocyanine-magnetite conjugates
- Idowu, Mopelola A I, Xego, Solami, Arslanoglu, Yasin, Mark, John, Antunes, Edith M, Nyokong, Tebello
- Authors: Idowu, Mopelola A I , Xego, Solami , Arslanoglu, Yasin , Mark, John , Antunes, Edith M , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188205 , vital:44734 , xlink:href="https://doi.org/10.1016/j.saa.2017.12.052"
- Description: Asymmetric Mg (II) or Al (III) phthalocyanine (containing a COOH group and 3-pyridylsulfanyl units) was conjugated via an amide bond to amino functionalized magnetic nanoparticle (AIMN) to form MgPc-AIMN or AlPc-AIMN conjugate, and characterized. The photophysicochemical behaviour of the phthalocyanine–AIMN conjugates was investigated and compared to the asymmetric Pcs and to the simple mixture of Pc with AIMNs without a chemical bond, (MPc-AIMN (mixed)). The directed covalent linkage of AIMNs to the asymmetrical metallopthalocyanines afforded improvements in the singlet oxygen (ФΔ) and triplet state quantum yield (ФT) as well as singlet oxygen lifetimes for the MPcs–AIMN-linked conjugates compared to MPc-AIMN (mixed) and MPcs alone. The asymmetric phthalocyanines and their conjugates showed effective antimicrobial activity against Escherichia coli bacteria under illumination.
- Full Text:
- Date Issued: 2018
- Authors: Idowu, Mopelola A I , Xego, Solami , Arslanoglu, Yasin , Mark, John , Antunes, Edith M , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188205 , vital:44734 , xlink:href="https://doi.org/10.1016/j.saa.2017.12.052"
- Description: Asymmetric Mg (II) or Al (III) phthalocyanine (containing a COOH group and 3-pyridylsulfanyl units) was conjugated via an amide bond to amino functionalized magnetic nanoparticle (AIMN) to form MgPc-AIMN or AlPc-AIMN conjugate, and characterized. The photophysicochemical behaviour of the phthalocyanine–AIMN conjugates was investigated and compared to the asymmetric Pcs and to the simple mixture of Pc with AIMNs without a chemical bond, (MPc-AIMN (mixed)). The directed covalent linkage of AIMNs to the asymmetrical metallopthalocyanines afforded improvements in the singlet oxygen (ФΔ) and triplet state quantum yield (ФT) as well as singlet oxygen lifetimes for the MPcs–AIMN-linked conjugates compared to MPc-AIMN (mixed) and MPcs alone. The asymmetric phthalocyanines and their conjugates showed effective antimicrobial activity against Escherichia coli bacteria under illumination.
- Full Text:
- Date Issued: 2018
Conjugates of low-symmetry Ge, Sn and Ti carboxy phthalocyanines with glutathione caped gold nanoparticles
- Masilela, Nkosiphile, Nyokong, Tebello
- Authors: Masilela, Nkosiphile , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247003 , vital:51536 , xlink:href="https://doi.org/10.1016/j.jphotochem.2011.08.009"
- Description: This work reports on conjugation of low symmetry Ge (GeMCPc), Ti (TiMCPc) and Sn (SnMCPc) carboxy phthalocyanines with glutathione capped gold nanoparticles (GSH-AuNPs). The photophysical behaviour of the novel phthalocyanines–GSH-AuNPs conjugate was investigated and compared to the monocarboxy Pcs and to the mixture of Pc with GSH-AuNPs without a chemical bond. Blue shifting of Q band of the phthalocyanines was observed on linking to GSH-AuNPs. An improvement in triplet lifetimes was obtained for all the MPcs–GSH-AuNPs-linked conjugates compared to the MPcs alone. The highest triplet quantum yield of 0.75 and the longest triplet lifetime of 130 μs were obtained for the GeMCPc–GSH-AuNPs-linked conjugate. Fluorescence quantum yields and lifetimes were low for the conjugates due to quenching by the nanoparticles.
- Full Text:
- Date Issued: 2011
- Authors: Masilela, Nkosiphile , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247003 , vital:51536 , xlink:href="https://doi.org/10.1016/j.jphotochem.2011.08.009"
- Description: This work reports on conjugation of low symmetry Ge (GeMCPc), Ti (TiMCPc) and Sn (SnMCPc) carboxy phthalocyanines with glutathione capped gold nanoparticles (GSH-AuNPs). The photophysical behaviour of the novel phthalocyanines–GSH-AuNPs conjugate was investigated and compared to the monocarboxy Pcs and to the mixture of Pc with GSH-AuNPs without a chemical bond. Blue shifting of Q band of the phthalocyanines was observed on linking to GSH-AuNPs. An improvement in triplet lifetimes was obtained for all the MPcs–GSH-AuNPs-linked conjugates compared to the MPcs alone. The highest triplet quantum yield of 0.75 and the longest triplet lifetime of 130 μs were obtained for the GeMCPc–GSH-AuNPs-linked conjugate. Fluorescence quantum yields and lifetimes were low for the conjugates due to quenching by the nanoparticles.
- Full Text:
- Date Issued: 2011
Livelihood benefits and costs from an invasive alien tree (Acacia dealbata) to rural communities in the Eastern Cape, South Africa
- Ngorima, A, Shackleton, Charlie M
- Authors: Ngorima, A , Shackleton, Charlie M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/179755 , vital:43168 , xlink:href="https://doi.org/10.1016/j.jenvman.2018.05.077"
- Description: The negative effects of invasive alien species (IAS) are increasingly invoked to justify widespread and usually top-down approaches for their management or eradication. However, very little of the research or discourse is based on investigating local perceptions, uses and struggles with IAS, and how their presence influences and changes local livelihoods. The objective of this study was to assess the perceptions and livelihood uses of Acacia dealbata by local communities at three localities in the montane grasslands of the Eastern Cape, South Africa, using a combination of random household interviews, focus group discussions and participatory tools. We calculated direct-use values for each product and household (based on quantity used and local prices) and disaggregated these by gender of the household head and wealth quartiles. The results revealed the dualistic role of A. dealbata in local livelihoods. On the one hand, A. dealbata was widely used for firewood (100% of households), tools (77%) and construction timber (73%), with limited use for traditional medicines and forage. The cumulative value of approximately ZAR 2870 (±US$224) per household per year (across all households) represents considerable cash saving to households, most of whom are quite poor by national and international measures. On the other hand, the increasing extent of A. dealbata (93% said it was increasing) exacerbates local household vulnerability though reported reductions in cultivated areas, crop yields and forage production, and allegedly higher risks of crime. This quandary is well encapsulated by the considerable majority of respondents (84%) not wanting higher extents and densities of A. dealbata, but an equally high majority not wanting its total removal from local landscapes. Most respondents disliked A. dealbata in fields, close to homesteads or along primary access routes, and were more tolerant of it away from such sites. Institutional and use dynamics have varied over several decades in response to the changing extent and densities of A. dealbata and the broader political and socio-economic contexts. These results indicate that greater efforts are required to understand perceptions and uses of IAS by the people who live with them, and to direct such understanding into more spatially and temporally contextualised response strategies where required.
- Full Text:
- Date Issued: 2019
- Authors: Ngorima, A , Shackleton, Charlie M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/179755 , vital:43168 , xlink:href="https://doi.org/10.1016/j.jenvman.2018.05.077"
- Description: The negative effects of invasive alien species (IAS) are increasingly invoked to justify widespread and usually top-down approaches for their management or eradication. However, very little of the research or discourse is based on investigating local perceptions, uses and struggles with IAS, and how their presence influences and changes local livelihoods. The objective of this study was to assess the perceptions and livelihood uses of Acacia dealbata by local communities at three localities in the montane grasslands of the Eastern Cape, South Africa, using a combination of random household interviews, focus group discussions and participatory tools. We calculated direct-use values for each product and household (based on quantity used and local prices) and disaggregated these by gender of the household head and wealth quartiles. The results revealed the dualistic role of A. dealbata in local livelihoods. On the one hand, A. dealbata was widely used for firewood (100% of households), tools (77%) and construction timber (73%), with limited use for traditional medicines and forage. The cumulative value of approximately ZAR 2870 (±US$224) per household per year (across all households) represents considerable cash saving to households, most of whom are quite poor by national and international measures. On the other hand, the increasing extent of A. dealbata (93% said it was increasing) exacerbates local household vulnerability though reported reductions in cultivated areas, crop yields and forage production, and allegedly higher risks of crime. This quandary is well encapsulated by the considerable majority of respondents (84%) not wanting higher extents and densities of A. dealbata, but an equally high majority not wanting its total removal from local landscapes. Most respondents disliked A. dealbata in fields, close to homesteads or along primary access routes, and were more tolerant of it away from such sites. Institutional and use dynamics have varied over several decades in response to the changing extent and densities of A. dealbata and the broader political and socio-economic contexts. These results indicate that greater efforts are required to understand perceptions and uses of IAS by the people who live with them, and to direct such understanding into more spatially and temporally contextualised response strategies where required.
- Full Text:
- Date Issued: 2019
Synthesis and photophysical properties of lead phthalocyanines
- Modibane, D.K., Nyokong, Tebello
- Authors: Modibane, D.K. , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/268636 , vital:54216 , xlink:href="https://doi.org/10.1016/j.poly.2007.12.004"
- Description: This work reports on the synthesis and photophysical parameters of tetra-and octa-substituted new lead phthalocyanines. The complexes synthesized are: 1,4-(tetraphenoxyphthalocyaninato)lead (7a), 1,4-(tetra-tert-butylphenoxyphthalocyaninato)lead (7b), 2,3-(tetraphenoxyphthalocyaninato)lead (8a), 2,3-(tetra-tert-butylphenoxyphthalocyaninato)lead (8b), 2,3-octaphenoxyphthalocyaninatolead (9a) 2,3-[octakis(4-t-butylphenoxyphthalocyaninato)]lead (9b). Photophysical properties were studied for these complexes in a dimethylsulfoxide, dimethylformamide, toluene, tetrahydrofuran and chloroform. The fluorescence spectra were different from excitation spectra due to demetallation upon excitation. High triplet quantum yields ranging from 0.70 to 0.88 (in DMSO, DMF and toluene) and low triplet lifetimes (20–50 μs in DMSO, and more than 10 μs in the rest of the solvents) were observed due to the presence of heavy atom.
- Full Text:
- Date Issued: 2008
- Authors: Modibane, D.K. , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/268636 , vital:54216 , xlink:href="https://doi.org/10.1016/j.poly.2007.12.004"
- Description: This work reports on the synthesis and photophysical parameters of tetra-and octa-substituted new lead phthalocyanines. The complexes synthesized are: 1,4-(tetraphenoxyphthalocyaninato)lead (7a), 1,4-(tetra-tert-butylphenoxyphthalocyaninato)lead (7b), 2,3-(tetraphenoxyphthalocyaninato)lead (8a), 2,3-(tetra-tert-butylphenoxyphthalocyaninato)lead (8b), 2,3-octaphenoxyphthalocyaninatolead (9a) 2,3-[octakis(4-t-butylphenoxyphthalocyaninato)]lead (9b). Photophysical properties were studied for these complexes in a dimethylsulfoxide, dimethylformamide, toluene, tetrahydrofuran and chloroform. The fluorescence spectra were different from excitation spectra due to demetallation upon excitation. High triplet quantum yields ranging from 0.70 to 0.88 (in DMSO, DMF and toluene) and low triplet lifetimes (20–50 μs in DMSO, and more than 10 μs in the rest of the solvents) were observed due to the presence of heavy atom.
- Full Text:
- Date Issued: 2008