Photophysical properties and photodynamic therapy effect of zinc phthalocyanine-spermine-single walled carbon nanotube conjugate on MCF-7 breast cancer cell line
- Ogbodu, Rachael O, Limson, Janice L, Prinsloo, Earl, Nyokong, Tebello
- Authors: Ogbodu, Rachael O , Limson, Janice L , Prinsloo, Earl , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189493 , vital:44851 , xlink:href="https://doi.org/10.1016/j.synthmet.2015.03.011"
- Description: The present study shows improved photodynamic therapy (PDT) effect of zinc mono carboxy phenoxy phthalocyanine (ZnMCPPc (1)) upon conjugation to spermine (via amide bond) as a targeting molecule on MCF-7 breast cancer cells. The ZnMCPPc-spermine (2) conjugate was adsorbed onto single walled carbon nanotubes (represented as ZnMCPPc-spermine-SWCNT (3)). There was no change in the fluorescence quantum yield of complex 1 following formation of 2 or 3. Complexes 2 and 3 showed improved photophysical properties; with over 50% increases in triplet and singlet oxygen quantum yields compared to 1. Complexes 1, 2 and 3 were relatively not toxic to MCF-7 cancer cells when incubated with 5–40 μM of each complex for 24 h in the dark. The PDT results showed that at 40 μM complex 1 resulted in only 64% decrease in cell viability, while 2 and 3 improved the PDT effect of 1 to 97% and 95% decrease in cell viability at 40 μM respectively.
- Full Text:
- Date Issued: 2015
- Authors: Ogbodu, Rachael O , Limson, Janice L , Prinsloo, Earl , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189493 , vital:44851 , xlink:href="https://doi.org/10.1016/j.synthmet.2015.03.011"
- Description: The present study shows improved photodynamic therapy (PDT) effect of zinc mono carboxy phenoxy phthalocyanine (ZnMCPPc (1)) upon conjugation to spermine (via amide bond) as a targeting molecule on MCF-7 breast cancer cells. The ZnMCPPc-spermine (2) conjugate was adsorbed onto single walled carbon nanotubes (represented as ZnMCPPc-spermine-SWCNT (3)). There was no change in the fluorescence quantum yield of complex 1 following formation of 2 or 3. Complexes 2 and 3 showed improved photophysical properties; with over 50% increases in triplet and singlet oxygen quantum yields compared to 1. Complexes 1, 2 and 3 were relatively not toxic to MCF-7 cancer cells when incubated with 5–40 μM of each complex for 24 h in the dark. The PDT results showed that at 40 μM complex 1 resulted in only 64% decrease in cell viability, while 2 and 3 improved the PDT effect of 1 to 97% and 95% decrease in cell viability at 40 μM respectively.
- Full Text:
- Date Issued: 2015
Photophysical properties gallium octacarboxy phthalocyanines conjugated to CdSe@ ZnS quantum dots
- Tshangana, Charmaine, Nyokong, Tebello
- Authors: Tshangana, Charmaine , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189055 , vital:44812 , xlink:href="https://doi.org/10.1016/j.saa.2015.06.086"
- Description: L-Glutathione (GSH) capped core CdSe (2.3 nm) and core shell CdSe@ZnS quantum dots (QDs) (3.0 nm and 3.5 nm) were coordinated to gallium octacarboxy phthalocyanine (ClGaPc(COOH)8) to form ClGaPc(COOH)8–QDs conjugates. An efficient transfer of energy from the QDs to the Pcs was demonstrated through Förster resonance energy transfer (FRET), the FRET efficiencies in all cases was above 50%. The photophysical parameters (triplet state and fluorescence quantum yields and lifetimes) were also determined for the conjugates. There was a decrease in the fluorescence lifetimes of ClGaPc(COOH)8 in the presence of all the QDs, due to the heavy atom effect. The triplet quantum yields increased in the conjugates. The lifetimes also became longer for the conjugates compared to Pc alone.
- Full Text:
- Date Issued: 2015
- Authors: Tshangana, Charmaine , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189055 , vital:44812 , xlink:href="https://doi.org/10.1016/j.saa.2015.06.086"
- Description: L-Glutathione (GSH) capped core CdSe (2.3 nm) and core shell CdSe@ZnS quantum dots (QDs) (3.0 nm and 3.5 nm) were coordinated to gallium octacarboxy phthalocyanine (ClGaPc(COOH)8) to form ClGaPc(COOH)8–QDs conjugates. An efficient transfer of energy from the QDs to the Pcs was demonstrated through Förster resonance energy transfer (FRET), the FRET efficiencies in all cases was above 50%. The photophysical parameters (triplet state and fluorescence quantum yields and lifetimes) were also determined for the conjugates. There was a decrease in the fluorescence lifetimes of ClGaPc(COOH)8 in the presence of all the QDs, due to the heavy atom effect. The triplet quantum yields increased in the conjugates. The lifetimes also became longer for the conjugates compared to Pc alone.
- Full Text:
- Date Issued: 2015
Photophysical properties of zinc phthalocyanine–uridine single walled carbon nanotube–conjugates
- Ogbodu, Rachael O, Amuhaya, Edith K, Mashazi, Philani N, Nyokong, Tebello
- Authors: Ogbodu, Rachael O , Amuhaya, Edith K , Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193586 , vital:45350 , xlink:href="https://doi.org/10.1016/j.saa.2015.04.040"
- Description: The photophysical properties of the conjugate of uridine and zinc mono carboxy phenoxy phthalocyanine (ZnMCPPc–uridine, 4) are reported in this work. The conjugate was also adsorbed onto single walled carbon nanotubes (ZnMCPPc–uridine–SWCNT, 5). The X-ray photoelectron spectroscopy of 4 showed three N 1s peaks while that of 5 showed four N 1s peak, a new peak at 399.4 eV of 5 was assigned to pyrrolidonic nitrogen, due to the interaction of the pyrrolic nitrogen of 4 with the oxygen moiety of SWCNT–COOH in 5. The triplet lifetime, triplet and singlet oxygen quantum yields of the zinc mono carboxy phenoxy phthalocyanine increased by over 40% in the presence of uridine. SWCNTs resulted in only a small quenching of the triplet state parameters of 4.
- Full Text:
- Date Issued: 2015
- Authors: Ogbodu, Rachael O , Amuhaya, Edith K , Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193586 , vital:45350 , xlink:href="https://doi.org/10.1016/j.saa.2015.04.040"
- Description: The photophysical properties of the conjugate of uridine and zinc mono carboxy phenoxy phthalocyanine (ZnMCPPc–uridine, 4) are reported in this work. The conjugate was also adsorbed onto single walled carbon nanotubes (ZnMCPPc–uridine–SWCNT, 5). The X-ray photoelectron spectroscopy of 4 showed three N 1s peaks while that of 5 showed four N 1s peak, a new peak at 399.4 eV of 5 was assigned to pyrrolidonic nitrogen, due to the interaction of the pyrrolic nitrogen of 4 with the oxygen moiety of SWCNT–COOH in 5. The triplet lifetime, triplet and singlet oxygen quantum yields of the zinc mono carboxy phenoxy phthalocyanine increased by over 40% in the presence of uridine. SWCNTs resulted in only a small quenching of the triplet state parameters of 4.
- Full Text:
- Date Issued: 2015
Photophysical studies of newly derivatized mono substituted phthalocyanines grafted onto silica nanoparticles via click chemistry
- Fashina, Adedayo, Amuhaya, Edith, Nyokong, Tebello
- Authors: Fashina, Adedayo , Amuhaya, Edith , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189537 , vital:44855 , xlink:href="https://doi.org/10.1016/j.saa.2014.12.070"
- Description: This work reports on the synthesis, characterization and photophysical studies of newly derived phthalocyanine complexes and the phthalocyanine–silica nanoparticles conjugates. The derived phthalocyanine complexes have one terminal alkyne group. The derived phthalocyanine complexes showed improved photophysical properties (ФF, ФT, ΦΔ and τT) compared to the respective phthalocyanine complexes from which they were derived. The derived phthalocyanine complexes were conjugated to the surface of an azide functionalized silica nanoparticles via copper (1) catalyzed cyclo-addition reaction. All the conjugates showed lower triplet quantum yields ranging from 0.37 to 0.44 compared to the free phthalocyanine complexes. The triplet lifetimes ranged from 352 to 484 μs for the conjugates and from 341 to 366 μs for the free phthalocyanine complexes.
- Full Text:
- Date Issued: 2015
- Authors: Fashina, Adedayo , Amuhaya, Edith , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189537 , vital:44855 , xlink:href="https://doi.org/10.1016/j.saa.2014.12.070"
- Description: This work reports on the synthesis, characterization and photophysical studies of newly derived phthalocyanine complexes and the phthalocyanine–silica nanoparticles conjugates. The derived phthalocyanine complexes have one terminal alkyne group. The derived phthalocyanine complexes showed improved photophysical properties (ФF, ФT, ΦΔ and τT) compared to the respective phthalocyanine complexes from which they were derived. The derived phthalocyanine complexes were conjugated to the surface of an azide functionalized silica nanoparticles via copper (1) catalyzed cyclo-addition reaction. All the conjugates showed lower triplet quantum yields ranging from 0.37 to 0.44 compared to the free phthalocyanine complexes. The triplet lifetimes ranged from 352 to 484 μs for the conjugates and from 341 to 366 μs for the free phthalocyanine complexes.
- Full Text:
- Date Issued: 2015
Photophysicochemical properties and in vitro cytotoxicity of zinc tetracarboxyphenoxy phthalocyanine–quantum dot nanocomposites
- Oluwole, David O, Tilbury, Chelsea M, Prinsloo, Earl, Limson, Janice L, Nyokong, Tebello
- Authors: Oluwole, David O , Tilbury, Chelsea M , Prinsloo, Earl , Limson, Janice L , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/240846 , vital:50878 , xlink:href="https://doi.org/10.1016/j.poly.2015.12.060"
- Description: Cadmium based quantum dots (QDs) capped with two different ligands (thioglycolic acid, TGA, and glutathione, GSH) were synthesized. The QDs are: CdTe, CdTe/ZnO, CdTeSe, CdTeSe/ZnO and CdSe/ZnS (the last one for TGA only). Cytotoxicity of the QDs against MCF-7 epithelial breast cancer was evaluated. The TGA capped core QDs were found to be highly cytotoxic to the cell lines when compared to GSH capped ones. The glutathione capped QDs were covalently linked to zinc tetracarboxyphenoxy phthalocyanine (ZnTCPPc). Cytotoxicity and photophysicochemical properties of the conjugates were investigated. The toxicity of the core QDs was reduced in the presence of ZnTCPPc. Enhanced triplet quantum yields and long triplet lifetimes were obtained for ZnTCPPc in the presence of all QDs.
- Full Text:
- Date Issued: 2015
- Authors: Oluwole, David O , Tilbury, Chelsea M , Prinsloo, Earl , Limson, Janice L , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/240846 , vital:50878 , xlink:href="https://doi.org/10.1016/j.poly.2015.12.060"
- Description: Cadmium based quantum dots (QDs) capped with two different ligands (thioglycolic acid, TGA, and glutathione, GSH) were synthesized. The QDs are: CdTe, CdTe/ZnO, CdTeSe, CdTeSe/ZnO and CdSe/ZnS (the last one for TGA only). Cytotoxicity of the QDs against MCF-7 epithelial breast cancer was evaluated. The TGA capped core QDs were found to be highly cytotoxic to the cell lines when compared to GSH capped ones. The glutathione capped QDs were covalently linked to zinc tetracarboxyphenoxy phthalocyanine (ZnTCPPc). Cytotoxicity and photophysicochemical properties of the conjugates were investigated. The toxicity of the core QDs was reduced in the presence of ZnTCPPc. Enhanced triplet quantum yields and long triplet lifetimes were obtained for ZnTCPPc in the presence of all QDs.
- Full Text:
- Date Issued: 2015
Physicochemical and photodynamic antimicrobial chemotherapy studies of mono-and tetra-pyridyloxy substituted indium (III) phthalocyanines
- Osifeko, Olawale, Durmus, Mahmut, Nyokong, Tebello
- Authors: Osifeko, Olawale , Durmus, Mahmut , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189547 , vital:44856 , xlink:href="https://doi.org/10.1016/j.jphotochem.2014.12.011"
- Description: The synthesis and photophysicochemical properties of mono- and tetra-pyridyloxy substituted indium(III) phthalocyanines (InPcs) are presented in this study. General trends are described for quantum yields of fluorescence, triplet, singlet oxygen and photodegradation as well as lifetimes of fluorescence and triplet state of these compounds. The complexes exhibited high singlet oxygen quantum yields (ФΔ) ranging from 0.44 to 0.66 in DMF, and from 0.44 to 0.69 in DMSO and ФΔ = 0.31 for the quartenized tetra substituted InPc which is soluble in water. The triplet quantum yields (ФT) ranged from 0.77 to 0.95 in DMF and from 0.77 to 0.94) in DMSO. The tetra substituted photosensitizers do not differ in their inactivation of bacteria with over 8 log reduction of viable bacteria when compared with the mono substituted photosensitizer which could only manage a 1 log reduction.
- Full Text:
- Date Issued: 2015
- Authors: Osifeko, Olawale , Durmus, Mahmut , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189547 , vital:44856 , xlink:href="https://doi.org/10.1016/j.jphotochem.2014.12.011"
- Description: The synthesis and photophysicochemical properties of mono- and tetra-pyridyloxy substituted indium(III) phthalocyanines (InPcs) are presented in this study. General trends are described for quantum yields of fluorescence, triplet, singlet oxygen and photodegradation as well as lifetimes of fluorescence and triplet state of these compounds. The complexes exhibited high singlet oxygen quantum yields (ФΔ) ranging from 0.44 to 0.66 in DMF, and from 0.44 to 0.69 in DMSO and ФΔ = 0.31 for the quartenized tetra substituted InPc which is soluble in water. The triplet quantum yields (ФT) ranged from 0.77 to 0.95 in DMF and from 0.77 to 0.94) in DMSO. The tetra substituted photosensitizers do not differ in their inactivation of bacteria with over 8 log reduction of viable bacteria when compared with the mono substituted photosensitizer which could only manage a 1 log reduction.
- Full Text:
- Date Issued: 2015
Physicochemical behavior of nanohybrids of mono and tetra substituted carboxyphenoxy phthalocyanine covalently linked to GSH–CdTe/CdS/ZnS quantum dots
- Oluwole, David O, Nyokong, Tebello
- Authors: Oluwole, David O , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189480 , vital:44850 , xlink:href="https://doi.org/10.1016/j.poly.2014.10.024"
- Description: Zinc monocarboxyphenoxy and tetracarboxyphenoxy phthalocyanines were covalently linked with three different sizes of glutathione capped core/shell/shell {CdTe/CdS/ZnS(4.2), CdTe/CdS/ZnS(5.1) and CdTe/CdS/ZnS(6.7)}; a core shell {CdTe/CdS(3.1)} and core {CdTe(2.4)} quantum dots. The physicochemical behavior and Förster resonance energy transfer (FRET) processes of the nanohybrids were investigated. The highest FRET efficiency was observed with CdTe/CdS/ZnS(6.7) nanohybrids with 98% and the least efficiency was observed with CdTe(2.4) nanohybrids with 85%. The CdTe/CdS/ZnS(6.7) also showed the best physicochemical behavior. These good physicochemical properties make the synthesized nanohybrids viable photosensitizers.
- Full Text:
- Date Issued: 2015
- Authors: Oluwole, David O , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189480 , vital:44850 , xlink:href="https://doi.org/10.1016/j.poly.2014.10.024"
- Description: Zinc monocarboxyphenoxy and tetracarboxyphenoxy phthalocyanines were covalently linked with three different sizes of glutathione capped core/shell/shell {CdTe/CdS/ZnS(4.2), CdTe/CdS/ZnS(5.1) and CdTe/CdS/ZnS(6.7)}; a core shell {CdTe/CdS(3.1)} and core {CdTe(2.4)} quantum dots. The physicochemical behavior and Förster resonance energy transfer (FRET) processes of the nanohybrids were investigated. The highest FRET efficiency was observed with CdTe/CdS/ZnS(6.7) nanohybrids with 98% and the least efficiency was observed with CdTe(2.4) nanohybrids with 85%. The CdTe/CdS/ZnS(6.7) also showed the best physicochemical behavior. These good physicochemical properties make the synthesized nanohybrids viable photosensitizers.
- Full Text:
- Date Issued: 2015
Plasmodium falciparum Hop (PfHop) interacts with the Hsp70 chaperone in a nucleotide-dependent fashion and exhibits ligand selectivity
- Zininga, Tawanda, Makumire, Stanley, Gitau, Grace W, Njunge, James M, Pooe, Ofentse J, Klimek, Hanna, Scheurr, Robina, Raifer, Hartmann, Prinsloo, Earl, Przyborski, Jude M, Hoppe, Heinrich, Shonhai, Addmore
- Authors: Zininga, Tawanda , Makumire, Stanley , Gitau, Grace W , Njunge, James M , Pooe, Ofentse J , Klimek, Hanna , Scheurr, Robina , Raifer, Hartmann , Prinsloo, Earl , Przyborski, Jude M , Hoppe, Heinrich , Shonhai, Addmore
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431752 , vital:72801 , xlink:href=" https://doi.org/10.1371/journal.pone.0135326"
- Description: Heat shock proteins (Hsps) play an important role in the development and pathogenicity of malaria parasites. One of the most prominent functions of Hsps is to facilitate the folding of other proteins. Hsps are thought to play a crucial role when malaria parasites invade their host cells and during their subsequent development in hepatocytes and red blood cells. It is thought that Hsps maintain proteostasis under the unfavourable conditions that malaria parasites encounter in the host environment. Although heat shock protein 70 (Hsp70) is capable of independent folding of some proteins, its functional cooperation with heat shock protein 90 (Hsp90) facilitates folding of some proteins such as kinases and steroid hormone receptors into their fully functional forms. The cooperation of Hsp70 and Hsp90 occurs through an adaptor protein called Hsp70-Hsp90 organising protein (Hop). We previously characterised the Hop protein from Plasmodium falciparum (PfHop). We observed that the protein co-localised with the cytosol-localised chaperones, PfHsp70-1 and PfHsp90 at the blood stages of the malaria parasite. In the current study, we demonstrated that PfHop is a stress-inducible protein. We further explored the direct interaction between PfHop and PfHsp70-1 using far Western and surface plasmon resonance (SPR) analyses.
- Full Text:
- Date Issued: 2015
- Authors: Zininga, Tawanda , Makumire, Stanley , Gitau, Grace W , Njunge, James M , Pooe, Ofentse J , Klimek, Hanna , Scheurr, Robina , Raifer, Hartmann , Prinsloo, Earl , Przyborski, Jude M , Hoppe, Heinrich , Shonhai, Addmore
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431752 , vital:72801 , xlink:href=" https://doi.org/10.1371/journal.pone.0135326"
- Description: Heat shock proteins (Hsps) play an important role in the development and pathogenicity of malaria parasites. One of the most prominent functions of Hsps is to facilitate the folding of other proteins. Hsps are thought to play a crucial role when malaria parasites invade their host cells and during their subsequent development in hepatocytes and red blood cells. It is thought that Hsps maintain proteostasis under the unfavourable conditions that malaria parasites encounter in the host environment. Although heat shock protein 70 (Hsp70) is capable of independent folding of some proteins, its functional cooperation with heat shock protein 90 (Hsp90) facilitates folding of some proteins such as kinases and steroid hormone receptors into their fully functional forms. The cooperation of Hsp70 and Hsp90 occurs through an adaptor protein called Hsp70-Hsp90 organising protein (Hop). We previously characterised the Hop protein from Plasmodium falciparum (PfHop). We observed that the protein co-localised with the cytosol-localised chaperones, PfHsp70-1 and PfHsp90 at the blood stages of the malaria parasite. In the current study, we demonstrated that PfHop is a stress-inducible protein. We further explored the direct interaction between PfHop and PfHsp70-1 using far Western and surface plasmon resonance (SPR) analyses.
- Full Text:
- Date Issued: 2015
Rapid bioassessment of the effects of repeated rotenone treatments on invertebrate assemblages in the Rondegat River, South Africa
- Bellingan, Terence A, Woodford, Darragh J, Gouws, J, Villet, Martin H, Weyl, Olaf L F
- Authors: Bellingan, Terence A , Woodford, Darragh J , Gouws, J , Villet, Martin H , Weyl, Olaf L F
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442279 , vital:73972 , https://doi.org/10.2989/16085914.2014.984651
- Description: The potential collateral effects of eradicating invasive fishes in streams necessitate the monitoring of invertebrate communities during treatment. In an environmental rehabilitation programme, non-native smallmouth bass were removed from the lower reaches of the Rondegat River, Western Cape, South Africa, in 2012 and again in 2013 using the piscicide rotenone. A monitoring programme tracked the ecological response of organisms to these activities using quantitative sampling of macroinvertebrates on stones and the ISO-certified SASS5 rapid bioassessment method for assessing macroinvertebrate community integrity. We recorded a significant decrease in macroinvertebrate densities from the stones-in-current biotope following both rotenone treatments. The average score per taxon (ASPT) declined after the first treatment, indicating a loss of taxa sensitive to diminished water quality, then recovered prior to the second treatment, and subsequently no decline was detected after the lower dose used in the 2013 treatment. The SASS values were too variable to reveal trends. The ASPTs indicated that the community may have been resistant to low dose and resilient to high dose, due to inter-treatment recovery following the 2012 treatment, suggesting that the invertebrate assemblage is resilient to the conservative use of rotenone for localised river rehabilitation when upstream sources of recruitment exist.
- Full Text:
- Date Issued: 2015
- Authors: Bellingan, Terence A , Woodford, Darragh J , Gouws, J , Villet, Martin H , Weyl, Olaf L F
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442279 , vital:73972 , https://doi.org/10.2989/16085914.2014.984651
- Description: The potential collateral effects of eradicating invasive fishes in streams necessitate the monitoring of invertebrate communities during treatment. In an environmental rehabilitation programme, non-native smallmouth bass were removed from the lower reaches of the Rondegat River, Western Cape, South Africa, in 2012 and again in 2013 using the piscicide rotenone. A monitoring programme tracked the ecological response of organisms to these activities using quantitative sampling of macroinvertebrates on stones and the ISO-certified SASS5 rapid bioassessment method for assessing macroinvertebrate community integrity. We recorded a significant decrease in macroinvertebrate densities from the stones-in-current biotope following both rotenone treatments. The average score per taxon (ASPT) declined after the first treatment, indicating a loss of taxa sensitive to diminished water quality, then recovered prior to the second treatment, and subsequently no decline was detected after the lower dose used in the 2013 treatment. The SASS values were too variable to reveal trends. The ASPTs indicated that the community may have been resistant to low dose and resilient to high dose, due to inter-treatment recovery following the 2012 treatment, suggesting that the invertebrate assemblage is resilient to the conservative use of rotenone for localised river rehabilitation when upstream sources of recruitment exist.
- Full Text:
- Date Issued: 2015
Resemiotising concerns from constituencies in the South African parliament
- Siebörger, Ian, Adendorff, Ralph D
- Authors: Siebörger, Ian , Adendorff, Ralph D
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/385362 , vital:68011 , xlink:href="https://doi.org/10.2989/16073614.2015.1061892"
- Description: Members of Parliament (MPs) in South Africa represent different constituencies across the country. In this article, we report on how MPs resemiotise concerns from their constituencies in spoken discourse in a parliamentary committee, and on the effectiveness with which this informa- tion is in turn resemiotised into a written committee report. Both resemiotisations form part of a genre chain which we investigated while conducting a linguistic ethnography of the communica- tion difficulties which occur in parliament's committee process. We use a multi-stranded theoretical foundation, including tools from Systemic Functional Linguistics, Interactional Sociolinguistics and Legitimation Code Theory to analyse MPs’ ability to communicate concerns from their constituen- cies in parliamentary discourse. We conclude that the success of MPs’ resemiotisations of these concerns depends on their ability to rescale them as relevant on a national level, and on their ability to negotiate the power relations at play in parliament.
- Full Text:
- Date Issued: 2015
- Authors: Siebörger, Ian , Adendorff, Ralph D
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/385362 , vital:68011 , xlink:href="https://doi.org/10.2989/16073614.2015.1061892"
- Description: Members of Parliament (MPs) in South Africa represent different constituencies across the country. In this article, we report on how MPs resemiotise concerns from their constituencies in spoken discourse in a parliamentary committee, and on the effectiveness with which this informa- tion is in turn resemiotised into a written committee report. Both resemiotisations form part of a genre chain which we investigated while conducting a linguistic ethnography of the communica- tion difficulties which occur in parliament's committee process. We use a multi-stranded theoretical foundation, including tools from Systemic Functional Linguistics, Interactional Sociolinguistics and Legitimation Code Theory to analyse MPs’ ability to communicate concerns from their constituen- cies in parliamentary discourse. We conclude that the success of MPs’ resemiotisations of these concerns depends on their ability to rescale them as relevant on a national level, and on their ability to negotiate the power relations at play in parliament.
- Full Text:
- Date Issued: 2015
Rewarding tax compliance: taxpayers’ attitudes and beliefs
- Bornman, Marina, Stack, Elizabeth M
- Authors: Bornman, Marina , Stack, Elizabeth M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/61039 , vital:27931
- Description: In a society the tax climate is determined by the interaction between taxpayers and tax authorities. In a ‘service and client’ climate, taxpayers do not expect authorities to automatically suspect them of being tax evaders. Evidence suggests that recognising good tax behaviour with strategies of rewards has a positive effect on voluntary tax compliance. Principles derived from the cognitive evaluation theory predict that when feelings of competence are affirmed and this is accompanied by a sense of autonomy it can enhance the intrinsic motivation for an action. The present research surveyed the attitudes and beliefs of taxpayers involved in small business on being rewarded for tax compliance. Results were corroborated with the principles of the cognitive evaluation theory and it was found that that the principles of the theory are applicable to rewarding tax compliance behaviour.
- Full Text:
- Date Issued: 2015
- Authors: Bornman, Marina , Stack, Elizabeth M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/61039 , vital:27931
- Description: In a society the tax climate is determined by the interaction between taxpayers and tax authorities. In a ‘service and client’ climate, taxpayers do not expect authorities to automatically suspect them of being tax evaders. Evidence suggests that recognising good tax behaviour with strategies of rewards has a positive effect on voluntary tax compliance. Principles derived from the cognitive evaluation theory predict that when feelings of competence are affirmed and this is accompanied by a sense of autonomy it can enhance the intrinsic motivation for an action. The present research surveyed the attitudes and beliefs of taxpayers involved in small business on being rewarded for tax compliance. Results were corroborated with the principles of the cognitive evaluation theory and it was found that that the principles of the theory are applicable to rewarding tax compliance behaviour.
- Full Text:
- Date Issued: 2015
Socio-spatial dynamics in the use of wild natural resources: Evidence from six rapidly growing medium-sized cities in Africa
- Schlesinger, Johannes, Drescher, Axel W, Shackleton, Charlie M
- Authors: Schlesinger, Johannes , Drescher, Axel W , Shackleton, Charlie M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180897 , vital:43668 , xlink:href="https://doi.org/10.1016/j.apgeog.2014.11.013"
- Description: Increasing urbanisation in sub-Saharan Africa transforms spatial configurations in and around towns and cities. At the same time wild natural resources play an important role in African livelihoods. Yet, little is known about the impact of urbanisation on the socio-spatial dynamics of the use of wild natural resources. Here we examined the importance of these resources for livelihoods, differences in their use between different locations along the urban-rural continuum, and the respective temporal dynamics. A total of 1158 households were interviewed in six medium-sized cities distributed across five African countries using a standardised questionnaire supplemented by expert interviews and spatial analyses employing Geographic Information Systems. Overall, even though periurban and rural households were more likely to use wild natural resources than those in the urban areas, the use of these resources was generally high along the entire urban-rural continuum. Despite the increasing urban pressure on these resources, they remain an integral part for most households, not only for those lacking access to productive resources, but also for those with a higher standard of living. This trend was found across all study towns, despite the marked differences in their respective socio-spatial as well as environmental settings.
- Full Text:
- Date Issued: 2015
- Authors: Schlesinger, Johannes , Drescher, Axel W , Shackleton, Charlie M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180897 , vital:43668 , xlink:href="https://doi.org/10.1016/j.apgeog.2014.11.013"
- Description: Increasing urbanisation in sub-Saharan Africa transforms spatial configurations in and around towns and cities. At the same time wild natural resources play an important role in African livelihoods. Yet, little is known about the impact of urbanisation on the socio-spatial dynamics of the use of wild natural resources. Here we examined the importance of these resources for livelihoods, differences in their use between different locations along the urban-rural continuum, and the respective temporal dynamics. A total of 1158 households were interviewed in six medium-sized cities distributed across five African countries using a standardised questionnaire supplemented by expert interviews and spatial analyses employing Geographic Information Systems. Overall, even though periurban and rural households were more likely to use wild natural resources than those in the urban areas, the use of these resources was generally high along the entire urban-rural continuum. Despite the increasing urban pressure on these resources, they remain an integral part for most households, not only for those lacking access to productive resources, but also for those with a higher standard of living. This trend was found across all study towns, despite the marked differences in their respective socio-spatial as well as environmental settings.
- Full Text:
- Date Issued: 2015
Some implications of MetaReality for environmental educators
- Authors: Price, Leigh
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/437034 , vital:73325 , ISBN 9781315660899 , https://www.routledge.com/Critical-Realism-Environmental-Learning-and-Social-Ecological-Change/Price-Lotz-Sistka/p/book/9780367597689
- Description: This chapter seeks to illuminate the use of dialectical critical realism in a PhD study that was conducted to explore and expand learning processes in sustain able agriculture work-place contexts (Mukute, 2010). The study was conducted in three case study sites in Leso-tho, South Africa and Zimbabwe. About 80 people in three study sites participated in the multiple case study research. In Zimbabwe the study was located in Hwedza District, St Margaret Primary School and its community that learns, practises and facilitates the learn-ing of Permaculture within the Schools and Colleges Permaculture Programme (SCOPE). In South Africa the study took place in Durban urban and peri-urban areas where a communi-ty of organic farmers, facilitators and entrepreneurs co-ordinated the marketing of their produce through Isidore Farm and Earth Mother Organic and support each other to learn and practise organic farming. In Lesotho the study took place in the Mafeteng and Mohale’s Hoek districts where the focus was on farmers who learn and practise the Machobane Farming System (MFS) and were supported in this by the Rural Self Development As-sociation (RSDA) and the Machobane Agricultural Develop-ment Foundation (MADF ). The other research participants were agricultural extension workers who tend to promote high external input agriculture, sustain able agriculture researchers and organic produce marketers.
- Full Text:
- Date Issued: 2015
- Authors: Price, Leigh
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/437034 , vital:73325 , ISBN 9781315660899 , https://www.routledge.com/Critical-Realism-Environmental-Learning-and-Social-Ecological-Change/Price-Lotz-Sistka/p/book/9780367597689
- Description: This chapter seeks to illuminate the use of dialectical critical realism in a PhD study that was conducted to explore and expand learning processes in sustain able agriculture work-place contexts (Mukute, 2010). The study was conducted in three case study sites in Leso-tho, South Africa and Zimbabwe. About 80 people in three study sites participated in the multiple case study research. In Zimbabwe the study was located in Hwedza District, St Margaret Primary School and its community that learns, practises and facilitates the learn-ing of Permaculture within the Schools and Colleges Permaculture Programme (SCOPE). In South Africa the study took place in Durban urban and peri-urban areas where a communi-ty of organic farmers, facilitators and entrepreneurs co-ordinated the marketing of their produce through Isidore Farm and Earth Mother Organic and support each other to learn and practise organic farming. In Lesotho the study took place in the Mafeteng and Mohale’s Hoek districts where the focus was on farmers who learn and practise the Machobane Farming System (MFS) and were supported in this by the Rural Self Development As-sociation (RSDA) and the Machobane Agricultural Develop-ment Foundation (MADF ). The other research participants were agricultural extension workers who tend to promote high external input agriculture, sustain able agriculture researchers and organic produce marketers.
- Full Text:
- Date Issued: 2015
Specific rewards for tax compliance: responses of small business owners in Ekurhuleni, South Africa
- Bornman, Marina, Stack, Elizabeth M
- Authors: Bornman, Marina , Stack, Elizabeth M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/145325 , vital:38428 , https://heinonline.org/HOL/Page?handle=hein.journals/ejotaxrs13anddiv=35andg_sent=1andcasa_token=andcollection=journals
- Description: The literature reviewed documents the positive effects of rewards in encouraging desired behaviour, but rewards may have a crowding-in effect, strengthening intrinsic motivation, or a crowding-out effect, weakening it. External interventions may therefore be perceived as supportive, fostering self-esteem and self-determination, while those perceived as controlling may have the opposite effect. A number of countries have adopted a strategy of rewarding tax compliance. The rewards range from certificates awarded to compliant taxpayers, to privilege cards providing opportunities for discounts or special treatment, to lotteries in which compliant taxpayers can participate. The reward strategies are often accompanied by publicity programmes. Two such hypothetical strategies were presented to participants in a survey conducted amongst small business owners in Ekurhuleni, South Africa, to gauge their responses.
- Full Text:
- Date Issued: 2015
- Authors: Bornman, Marina , Stack, Elizabeth M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/145325 , vital:38428 , https://heinonline.org/HOL/Page?handle=hein.journals/ejotaxrs13anddiv=35andg_sent=1andcasa_token=andcollection=journals
- Description: The literature reviewed documents the positive effects of rewards in encouraging desired behaviour, but rewards may have a crowding-in effect, strengthening intrinsic motivation, or a crowding-out effect, weakening it. External interventions may therefore be perceived as supportive, fostering self-esteem and self-determination, while those perceived as controlling may have the opposite effect. A number of countries have adopted a strategy of rewarding tax compliance. The rewards range from certificates awarded to compliant taxpayers, to privilege cards providing opportunities for discounts or special treatment, to lotteries in which compliant taxpayers can participate. The reward strategies are often accompanied by publicity programmes. Two such hypothetical strategies were presented to participants in a survey conducted amongst small business owners in Ekurhuleni, South Africa, to gauge their responses.
- Full Text:
- Date Issued: 2015
Spectroscopic and nonlinear optical properties of the four positional isomers of 4α-(4-tert-butylphenoxy) phthalocyanine
- Ngubeni, Grace N, Britton, Jonathan, Mack, John, New, Edward, Hancox, Ian, Walker, Marc, Nyokong, Tebello, Jones, Tim S, Khene,Samson M
- Authors: Ngubeni, Grace N , Britton, Jonathan , Mack, John , New, Edward , Hancox, Ian , Walker, Marc , Nyokong, Tebello , Jones, Tim S , Khene,Samson M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241448 , vital:50940 , xlink:href="https://doi.org/10.1039/C5TC01601K"
- Description: The spectroscopic and nonlinear optical properties of the positional isomers of metal free 4α-(4-tert-butylphenoxy) phthalocyanine are presented. Second order nonlinear polarizability (β), imaginary hyperpolarizability (Im(γ)) and imaginary susceptibility (Im[χ(3)]) values were determined for the four positional isomers. The measured β values of the four isomers displayed the following trend, C4h (34.0 × 10−5 m MW−1) > D2h (28.8 × 10−5 m MW−1) > C2v (22.8 × 10−5 m MW−1) > Cs (13.7 × 10−5 m MW−1).
- Full Text:
- Date Issued: 2015
- Authors: Ngubeni, Grace N , Britton, Jonathan , Mack, John , New, Edward , Hancox, Ian , Walker, Marc , Nyokong, Tebello , Jones, Tim S , Khene,Samson M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241448 , vital:50940 , xlink:href="https://doi.org/10.1039/C5TC01601K"
- Description: The spectroscopic and nonlinear optical properties of the positional isomers of metal free 4α-(4-tert-butylphenoxy) phthalocyanine are presented. Second order nonlinear polarizability (β), imaginary hyperpolarizability (Im(γ)) and imaginary susceptibility (Im[χ(3)]) values were determined for the four positional isomers. The measured β values of the four isomers displayed the following trend, C4h (34.0 × 10−5 m MW−1) > D2h (28.8 × 10−5 m MW−1) > C2v (22.8 × 10−5 m MW−1) > Cs (13.7 × 10−5 m MW−1).
- Full Text:
- Date Issued: 2015
Steel Valley and the absence of environmental justice in the new South Africa: Critical realism's kinship with environmental justice
- Authors: Munnik, Victor
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/437067 , vital:73328 , ISBN 9781315660899 , https://www.routledge.com/Critical-Realism-Environmental-Learning-and-Social-Ecological-Change/Price-Lotz-Sistka/p/book/9780367597689
- Description: In this chapter I report work with critical realist perspective and tools to examine and review prevailing dispositions on indige-nous and institutional knowledge (Western science) in envi-ronmental learning. I open with a review of some of the macro social processes that have come to inscribe assumptions of incommensur able difference between the two kinds of knowledge. Whilst the previous hegemony of positivism would have resulted in the dismissal of much indigenous knowledge as mere superstition, contemporary intellectual perspectives (poststructural and hermeneutical) have shaped a proliferation of worldview modelling that has resulted in a macro-level ex-emplifying of indigenous knowledge as different from and op-posing Western science (Cobern and Aikenhead, 1998; Ai-kenhead, 2006). Here, the lack of adequate mediating tools has given rise to a problematic inscription of assumed differ-ence between the knowledge of indigenous peoples and that of scientific institutions. Furthermore, despite an overt emanci-patory intention in worldview discourses, the marginalization of indigenous peoples and knowledge remains. I then move into the micro arena with a case study of learning interactions in the South African science curriculum. Specifically, I explore some patterns of exclusion in relation to the manner in which stu-dents are able to gain access to the knowledge of scientific institutions. The experience and evidence reported is of a pre-liminary nature but the insights and emerging models of pro-cess provide a useful perspective on how assumed incom-mensurability of knowledge can be tenuous. The study suggests that a critical engagement with both indigenous knowledge and Western science can reveal integrative synergies.
- Full Text:
- Date Issued: 2015
- Authors: Munnik, Victor
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/437067 , vital:73328 , ISBN 9781315660899 , https://www.routledge.com/Critical-Realism-Environmental-Learning-and-Social-Ecological-Change/Price-Lotz-Sistka/p/book/9780367597689
- Description: In this chapter I report work with critical realist perspective and tools to examine and review prevailing dispositions on indige-nous and institutional knowledge (Western science) in envi-ronmental learning. I open with a review of some of the macro social processes that have come to inscribe assumptions of incommensur able difference between the two kinds of knowledge. Whilst the previous hegemony of positivism would have resulted in the dismissal of much indigenous knowledge as mere superstition, contemporary intellectual perspectives (poststructural and hermeneutical) have shaped a proliferation of worldview modelling that has resulted in a macro-level ex-emplifying of indigenous knowledge as different from and op-posing Western science (Cobern and Aikenhead, 1998; Ai-kenhead, 2006). Here, the lack of adequate mediating tools has given rise to a problematic inscription of assumed differ-ence between the knowledge of indigenous peoples and that of scientific institutions. Furthermore, despite an overt emanci-patory intention in worldview discourses, the marginalization of indigenous peoples and knowledge remains. I then move into the micro arena with a case study of learning interactions in the South African science curriculum. Specifically, I explore some patterns of exclusion in relation to the manner in which stu-dents are able to gain access to the knowledge of scientific institutions. The experience and evidence reported is of a pre-liminary nature but the insights and emerging models of pro-cess provide a useful perspective on how assumed incom-mensurability of knowledge can be tenuous. The study suggests that a critical engagement with both indigenous knowledge and Western science can reveal integrative synergies.
- Full Text:
- Date Issued: 2015
Structural and optical properties of alloyed quaternary CdSeTeS core and CdSeTeS/ZnS core–shell quantum dots
- Adegoke, Oluwasesan, Nyokong, Tebello, Forbes, Patricia B C
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193575 , vital:45349 , xlink:href="https://doi.org/10.1016/j.jallcom.2015.05.083"
- Description: Synthesis of fluorescent alloyed quantum dots (QDs) with unique optical properties suitable for a wide array of chemical, physical and biological applications is of research interest. In this work, highly luminescent and photostable alloyed quaternary CdSeTeS core QDs of two different sizes were fabricated via the organometallic hot-injection synthetic route. Characterization of the nanocrystals were performed using TEM, XRD, UV/vis and fluorescence spectrophotometric techniques. We have demonstrated in this work that the well fabricated alloyed quaternary CdSeTeS core QDs possess unique optical properties that are advantageous over conventional core/shell systems. Formation of the CdSeTeS/ZnS core/shell with the desired optical properties comes with a number of challenges, hence the advantages of the quaternary alloyed core over the core/shell QDs are (i) avoidance of the challenging process of determining the proper shell thickness which can provide the desired optical properties in the core/shell system and (ii) avoidance of the lattice-induced mismatch between the core and the shell material which can either lead to incomplete exciton confinement or dislocation at the core/shell interface.
- Full Text:
- Date Issued: 2015
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193575 , vital:45349 , xlink:href="https://doi.org/10.1016/j.jallcom.2015.05.083"
- Description: Synthesis of fluorescent alloyed quantum dots (QDs) with unique optical properties suitable for a wide array of chemical, physical and biological applications is of research interest. In this work, highly luminescent and photostable alloyed quaternary CdSeTeS core QDs of two different sizes were fabricated via the organometallic hot-injection synthetic route. Characterization of the nanocrystals were performed using TEM, XRD, UV/vis and fluorescence spectrophotometric techniques. We have demonstrated in this work that the well fabricated alloyed quaternary CdSeTeS core QDs possess unique optical properties that are advantageous over conventional core/shell systems. Formation of the CdSeTeS/ZnS core/shell with the desired optical properties comes with a number of challenges, hence the advantages of the quaternary alloyed core over the core/shell QDs are (i) avoidance of the challenging process of determining the proper shell thickness which can provide the desired optical properties in the core/shell system and (ii) avoidance of the lattice-induced mismatch between the core and the shell material which can either lead to incomplete exciton confinement or dislocation at the core/shell interface.
- Full Text:
- Date Issued: 2015
Surface modification of silica-coated gadolinium oxide nanoparticles with zinc tetracarboxyphenoxy phthalocyanine for the photodegradation of Orange G
- Ledwaba, Mpho, Masilela, Nkosiphile, Nyokong, Tebello, Antunes, Edith M
- Authors: Ledwaba, Mpho , Masilela, Nkosiphile , Nyokong, Tebello , Antunes, Edith M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193621 , vital:45353 , xlink:href="https://doi.org/10.1016/j.molcata.2015.03.023"
- Description: Zinc tetracarboxyphenoxy phthalocyanine was covalently linked to Gd2O3 nanoparticles for the photocatalytic degradation of Orange G. Characterization of the composite was carried out using XRD, TEM, XPS, UV–vis spectroscopy and FT-IR spectroscopy. The composite showed improved photophysical properties over the phthalocyanine alone and the catalyst was found to be reusable. Analyses of the photodegradation rates of the azo dye indicated pseudo first-order kinetics.
- Full Text:
- Date Issued: 2015
- Authors: Ledwaba, Mpho , Masilela, Nkosiphile , Nyokong, Tebello , Antunes, Edith M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193621 , vital:45353 , xlink:href="https://doi.org/10.1016/j.molcata.2015.03.023"
- Description: Zinc tetracarboxyphenoxy phthalocyanine was covalently linked to Gd2O3 nanoparticles for the photocatalytic degradation of Orange G. Characterization of the composite was carried out using XRD, TEM, XPS, UV–vis spectroscopy and FT-IR spectroscopy. The composite showed improved photophysical properties over the phthalocyanine alone and the catalyst was found to be reusable. Analyses of the photodegradation rates of the azo dye indicated pseudo first-order kinetics.
- Full Text:
- Date Issued: 2015
Synthesis and characterization of Na (Y, Gd) F4 upconversion nanoparticles and an investigation of their effects on the photophysical properties of an unsubstituted tetrathiophenoxy phthalocyanine
- Taylor, Jessica M, Litwinski, Christian, Nyokong, Tebello, Antunes, Edith M
- Authors: Taylor, Jessica M , Litwinski, Christian , Nyokong, Tebello , Antunes, Edith M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241437 , vital:50939 , xlink:href="https://doi.org/10.1007/s11051-015-2889-5"
- Description: Sphere- and star-shaped Na(Y,Gd)F4:Yb/Er(Tm)upconversion nanoparticles (UCNP) were successfully synthesized utilizing a methanol-assisted thermal decomposition approach and their spectroscopic (absorption, emission and luminescence lifetime) properties fully characterized. The factors affecting the size and shape of the UCNPs were studied and discussed in detail. The size of the nanoparticles was determined using TEM primarily and found to be approximately 19 and 30 nm for the Er and Tm spheres, respectively, while the Er and Tm “stars” were found to be much larger with sizes ranging from 110 to 240 nm, respectively (as determined along the width of the nanoparticle). In addition, their influence on the spectroscopic properties of an unsubstituted tetrathiophenoxy phthalocyanine (H2Pc) was investigated. The UCNP were found to produce characteristic upconversion luminescence emissions in the blue, green, red and NIR regions. Simple mixing with an H2Pc in toluene was found to exert no obvious changes in the spectroscopic properties of the Pc, although a considerable increase in the radiative lifetimes is observed for the Pc in the presence of the UCNPs. The singlet oxygen generation mediated by the red light excitation of the H2Pc mixed with UCNP was found to decrease in the presence of the NPs.
- Full Text:
- Date Issued: 2015
- Authors: Taylor, Jessica M , Litwinski, Christian , Nyokong, Tebello , Antunes, Edith M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241437 , vital:50939 , xlink:href="https://doi.org/10.1007/s11051-015-2889-5"
- Description: Sphere- and star-shaped Na(Y,Gd)F4:Yb/Er(Tm)upconversion nanoparticles (UCNP) were successfully synthesized utilizing a methanol-assisted thermal decomposition approach and their spectroscopic (absorption, emission and luminescence lifetime) properties fully characterized. The factors affecting the size and shape of the UCNPs were studied and discussed in detail. The size of the nanoparticles was determined using TEM primarily and found to be approximately 19 and 30 nm for the Er and Tm spheres, respectively, while the Er and Tm “stars” were found to be much larger with sizes ranging from 110 to 240 nm, respectively (as determined along the width of the nanoparticle). In addition, their influence on the spectroscopic properties of an unsubstituted tetrathiophenoxy phthalocyanine (H2Pc) was investigated. The UCNP were found to produce characteristic upconversion luminescence emissions in the blue, green, red and NIR regions. Simple mixing with an H2Pc in toluene was found to exert no obvious changes in the spectroscopic properties of the Pc, although a considerable increase in the radiative lifetimes is observed for the Pc in the presence of the UCNPs. The singlet oxygen generation mediated by the red light excitation of the H2Pc mixed with UCNP was found to decrease in the presence of the NPs.
- Full Text:
- Date Issued: 2015
Synthesis and characterization of ZnO nanoparticle synthesized by a microwave-assisted combustion method and catalytic activity for the removal of ortho-nitrophenol
- Assi, Navid, Mohammadi, Ali, Sadr Manuchehri, Q, Walker, Roderick B
- Authors: Assi, Navid , Mohammadi, Ali , Sadr Manuchehri, Q , Walker, Roderick B
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183850 , vital:44075 , xlink:href="https://doi.org/10.1080/19443994.2014.891083"
- Description: ZnO nanoparticles were manufactured using microwave-assisted combustion. The structural and morphological properties of the nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy, and Fourier transform infrared spectroscopy. Photocatalytic degradation of ortho-nitrophenol (O-NP) in aqueous solution using the synthesized nanoparticles was performed under UV–C irradiation and is reported for the first time. The effect of the initial O-NP concentration, amount of photocatalyst, pH, and salt was investigated during photodegradation. Analysis of the degraded samples using HPLC with UV detection revealed that photocatalysis in the presence of ZnO nanoparticles removed 98% of the O-NP in 5 h. In addition, the photocatalytic degradation kinetics of O-NP were studied, and the results suggest that the data are best fitted to pseudo-first-order kinetic and Langmuir–Hinshelwood models.
- Full Text:
- Date Issued: 2015
- Authors: Assi, Navid , Mohammadi, Ali , Sadr Manuchehri, Q , Walker, Roderick B
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183850 , vital:44075 , xlink:href="https://doi.org/10.1080/19443994.2014.891083"
- Description: ZnO nanoparticles were manufactured using microwave-assisted combustion. The structural and morphological properties of the nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy, and Fourier transform infrared spectroscopy. Photocatalytic degradation of ortho-nitrophenol (O-NP) in aqueous solution using the synthesized nanoparticles was performed under UV–C irradiation and is reported for the first time. The effect of the initial O-NP concentration, amount of photocatalyst, pH, and salt was investigated during photodegradation. Analysis of the degraded samples using HPLC with UV detection revealed that photocatalysis in the presence of ZnO nanoparticles removed 98% of the O-NP in 5 h. In addition, the photocatalytic degradation kinetics of O-NP were studied, and the results suggest that the data are best fitted to pseudo-first-order kinetic and Langmuir–Hinshelwood models.
- Full Text:
- Date Issued: 2015