Nonlinear optical dynamics of benzothiazole derivatized phthalocyanines in solution, thin films and when conjugated to nanoparticles
- Nwaji, Njemuwa, Jones, Benjamin M, Mack, John, Oluwole, David O, Nyokong, Tebello
- Authors: Nwaji, Njemuwa , Jones, Benjamin M , Mack, John , Oluwole, David O , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190426 , vital:44993 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.05.042"
- Description: Benzothiazole phthalocynines complexes: tetrakis[(benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] indium(III) chloride (1) and tetrakis[(benzo[d]thiazol-2-ylthio)phthalocyaninato] indium(III) chloride (2) were synthesisized and their nanosecond nonlinear optical behaviours in solution, solid state and when conjugated to metallic nanoparticles were examined and compared to those of the corresponding ZnPc and GaPc which are designated as: tetrakis[(4-benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] zinc(II) (3), tetrakis[(4-benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] gallium(III) chloride (4), tetrakis[(4-benzo[d]thiazol-2-ylthio)phthalocyaninato] zinc(II) (5) and tetrakis[(4-benzo[d]thiazol-2-ylthio)phthalocyaninato] gallium(III) chloride (6). Trends in the electronic structures were identified through a comparison of the UV–vis absorption and magnetic circular dichroism (MCD) spectroscopy of the complexes and calculated spectra predicted by time dependent density functional theory (TD-DFT). Of all the complexes and nanoconjugates, complex 2 (containing sulphur linkages and In as a central metal) gave the best optical limiting behaviour.
- Full Text:
- Date Issued: 2017
- Authors: Nwaji, Njemuwa , Jones, Benjamin M , Mack, John , Oluwole, David O , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190426 , vital:44993 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.05.042"
- Description: Benzothiazole phthalocynines complexes: tetrakis[(benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] indium(III) chloride (1) and tetrakis[(benzo[d]thiazol-2-ylthio)phthalocyaninato] indium(III) chloride (2) were synthesisized and their nanosecond nonlinear optical behaviours in solution, solid state and when conjugated to metallic nanoparticles were examined and compared to those of the corresponding ZnPc and GaPc which are designated as: tetrakis[(4-benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] zinc(II) (3), tetrakis[(4-benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] gallium(III) chloride (4), tetrakis[(4-benzo[d]thiazol-2-ylthio)phthalocyaninato] zinc(II) (5) and tetrakis[(4-benzo[d]thiazol-2-ylthio)phthalocyaninato] gallium(III) chloride (6). Trends in the electronic structures were identified through a comparison of the UV–vis absorption and magnetic circular dichroism (MCD) spectroscopy of the complexes and calculated spectra predicted by time dependent density functional theory (TD-DFT). Of all the complexes and nanoconjugates, complex 2 (containing sulphur linkages and In as a central metal) gave the best optical limiting behaviour.
- Full Text:
- Date Issued: 2017
Optical limiters with improved performance based on nanoconjugates of thiol substituted phthalocyanine with CdSe quantum dots and Ag nanoparticles
- Oluwole, David O, Yagodin, Alexey V, Britton, Jonathan, Martynov, Alexander G, Gorbunova, Yulia G, Tsivadze, Aslan Yu, Nyokong, Tebello
- Authors: Oluwole, David O , Yagodin, Alexey V , Britton, Jonathan , Martynov, Alexander G , Gorbunova, Yulia G , Tsivadze, Aslan Yu , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/238286 , vital:50605 , xlink:href="https://doi.org/10.1039/C7DT03867D"
- Description: Two alternative synthetic approaches affording a low-symmetry A3B-type phthalocyanine 1 bearing two [2′-(2′′-mercaptoethoxy)ethoxy] anchoring substituents were developed. Due to the presence of thiol groups, this phthalocyanine could be conjugated with TOPO-capped (TOPO - trioctylphosphine)-capped CdSe quantum dots (CdSe-QDs) or oleylamine capped silver nanoparticles (Ag-NPs). The nonlinear optical behaviour of starting phthalocyanine, quantum dots, nanoparticles and their conjugates was studied by using an open aperture Z-scan technique, revealing that the grafting of 1 onto the nanomaterials resulted in a significant enhancement of the optical limiting of 1-Ag and 1-CdSe in comparison with the individual components. The conjugate 1-CdSe, being the first example of Pc-based thiol conjugated with quantum dots, revealed superior limiting characteristics with a limiting threshold below 0.18 J cm−2.
- Full Text:
- Date Issued: 2017
- Authors: Oluwole, David O , Yagodin, Alexey V , Britton, Jonathan , Martynov, Alexander G , Gorbunova, Yulia G , Tsivadze, Aslan Yu , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/238286 , vital:50605 , xlink:href="https://doi.org/10.1039/C7DT03867D"
- Description: Two alternative synthetic approaches affording a low-symmetry A3B-type phthalocyanine 1 bearing two [2′-(2′′-mercaptoethoxy)ethoxy] anchoring substituents were developed. Due to the presence of thiol groups, this phthalocyanine could be conjugated with TOPO-capped (TOPO - trioctylphosphine)-capped CdSe quantum dots (CdSe-QDs) or oleylamine capped silver nanoparticles (Ag-NPs). The nonlinear optical behaviour of starting phthalocyanine, quantum dots, nanoparticles and their conjugates was studied by using an open aperture Z-scan technique, revealing that the grafting of 1 onto the nanomaterials resulted in a significant enhancement of the optical limiting of 1-Ag and 1-CdSe in comparison with the individual components. The conjugate 1-CdSe, being the first example of Pc-based thiol conjugated with quantum dots, revealed superior limiting characteristics with a limiting threshold below 0.18 J cm−2.
- Full Text:
- Date Issued: 2017
Optical limiting properties of 2, 6-dibromo-3, 5-distyrylBODIPY dyes at 532 nm
- Kubheka, Gugu, Mack, John, Kobayashi, Nagao, Kimura, Mitsumi, Nyokong, Tebello
- Authors: Kubheka, Gugu , Mack, John , Kobayashi, Nagao , Kimura, Mitsumi , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190405 , vital:44991 , xlink:href="https://doi.org/10.1142/S1088424617500511"
- Description: Optical limiting properties of 2,6-dibromo-3,5-distyrylBODIPY dyes were investigated by using the z-scan technique at 532 nm in the nanosecond pulse range. A strong reverse saturable absorption response was observed even in solution, which suggests that compounds of this type are potentially suitable for use in optical limiting applications.
- Full Text:
- Date Issued: 2017
- Authors: Kubheka, Gugu , Mack, John , Kobayashi, Nagao , Kimura, Mitsumi , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190405 , vital:44991 , xlink:href="https://doi.org/10.1142/S1088424617500511"
- Description: Optical limiting properties of 2,6-dibromo-3,5-distyrylBODIPY dyes were investigated by using the z-scan technique at 532 nm in the nanosecond pulse range. A strong reverse saturable absorption response was observed even in solution, which suggests that compounds of this type are potentially suitable for use in optical limiting applications.
- Full Text:
- Date Issued: 2017
Optical limiting properties of 3, 5-diphenyldibenzo-azaBODIPY at 532 nm
- Kubheka, Gugu, Achadu, Ojodomo J, Mack, John, Nyokong, Tebello
- Authors: Kubheka, Gugu , Achadu, Ojodomo J , Mack, John , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/232761 , vital:50022 , xlink:href="https://doi.org/10.1039/C7NJ01503H"
- Description: Optical limiting properties of 3,5-diphenyldibenzo-azaBODIPY were investigated by using the z-scan technique at 532 nm in the nanosecond pulse range and a strong reverse saturable absorption (RSA) response was observed, which can be readily attributed to a two-photon absorption (TPA) assisted excited state absorption (ESA) mechanism in the singlet manifold based on a consideration of the other photophysical properties. The effect of solvent and incorporation into polymer thin films has been investigated in depth. The results indicate that the selection of solvents that enhance the population of the S1 excited state on the nanosecond timescale or embedding the azaBODIPY dye into polymer thin films significantly improves the optical limiting properties.
- Full Text:
- Date Issued: 2017
- Authors: Kubheka, Gugu , Achadu, Ojodomo J , Mack, John , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/232761 , vital:50022 , xlink:href="https://doi.org/10.1039/C7NJ01503H"
- Description: Optical limiting properties of 3,5-diphenyldibenzo-azaBODIPY were investigated by using the z-scan technique at 532 nm in the nanosecond pulse range and a strong reverse saturable absorption (RSA) response was observed, which can be readily attributed to a two-photon absorption (TPA) assisted excited state absorption (ESA) mechanism in the singlet manifold based on a consideration of the other photophysical properties. The effect of solvent and incorporation into polymer thin films has been investigated in depth. The results indicate that the selection of solvents that enhance the population of the S1 excited state on the nanosecond timescale or embedding the azaBODIPY dye into polymer thin films significantly improves the optical limiting properties.
- Full Text:
- Date Issued: 2017
Optical Limiting Properties of 3, 5-Dithienylenevinylene BODIPY Dyes at 532 nm
- Harris, Jessica, Gai, Lizhi, Kubheka, Gugu, Mack, John, Nyokong, Tebello, Shen, Zhen
- Authors: Harris, Jessica , Gai, Lizhi , Kubheka, Gugu , Mack, John , Nyokong, Tebello , Shen, Zhen
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189274 , vital:44833 , xlink:href="https://doi.org/10.1002/chem.201702503"
- Description: The optical limiting properties of a series of near infrared absorbing 3,5-dithienylenevinylene BODIPY (borondipyrromethene) dyes (1–3) that contain donor and acceptor moieties in their p-conjugation systems were studied by using the z-scan technique at 532 nm in the nanosecond pulse range. A strong reverse saturable absorption response was observed when the compounds are embedded into poly(bisphenol carbonate A) polymer thin films, which demonstrates that BODIPY dyes with this type of structure are suitable for use in optical limiting applications.
- Full Text:
- Date Issued: 2017
- Authors: Harris, Jessica , Gai, Lizhi , Kubheka, Gugu , Mack, John , Nyokong, Tebello , Shen, Zhen
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189274 , vital:44833 , xlink:href="https://doi.org/10.1002/chem.201702503"
- Description: The optical limiting properties of a series of near infrared absorbing 3,5-dithienylenevinylene BODIPY (borondipyrromethene) dyes (1–3) that contain donor and acceptor moieties in their p-conjugation systems were studied by using the z-scan technique at 532 nm in the nanosecond pulse range. A strong reverse saturable absorption response was observed when the compounds are embedded into poly(bisphenol carbonate A) polymer thin films, which demonstrates that BODIPY dyes with this type of structure are suitable for use in optical limiting applications.
- Full Text:
- Date Issued: 2017
Performing mindful creativity
- Authors: Krueger, Anton
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/225574 , vital:49236 , xlink:href="https://doi.org/10.5920/pam.2017.05"
- Description: This essay is grounded in the practical experience of three South African theatre practitioners who have all had some experience of mindfulness. It's based on interviews conducted with a performer (Andrew Buckland), a director (Janni Young), and a designer (Illka Louw). The aim of my conversations with these three was to explore ways in which mindfulness continues to enhance artistic practises, seeing our dialogues as a springboard to exploring intersections between creative practise and theories about mindfulness. To assist me in this process, I also interviewed Rob Nairn - co-founder of both the Mindfulness Association (UK) and Mindfulness Africa (RSA) - about key issues highlighting convergences between creativity and mindfulness. Some of the issues which are addressed include: the artist's relationship with fear, differing definitions of the value of conceptualisation, as well as whether or not the monkey mind (that is, the wandering mind) might hamper or help creativity.
- Full Text:
- Date Issued: 2017
- Authors: Krueger, Anton
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/225574 , vital:49236 , xlink:href="https://doi.org/10.5920/pam.2017.05"
- Description: This essay is grounded in the practical experience of three South African theatre practitioners who have all had some experience of mindfulness. It's based on interviews conducted with a performer (Andrew Buckland), a director (Janni Young), and a designer (Illka Louw). The aim of my conversations with these three was to explore ways in which mindfulness continues to enhance artistic practises, seeing our dialogues as a springboard to exploring intersections between creative practise and theories about mindfulness. To assist me in this process, I also interviewed Rob Nairn - co-founder of both the Mindfulness Association (UK) and Mindfulness Africa (RSA) - about key issues highlighting convergences between creativity and mindfulness. Some of the issues which are addressed include: the artist's relationship with fear, differing definitions of the value of conceptualisation, as well as whether or not the monkey mind (that is, the wandering mind) might hamper or help creativity.
- Full Text:
- Date Issued: 2017
Photolytic changes in the morphology of porphyrin-phthalocyanine nanostructures (P-PcNs) in the presence of platinum and gold salts
- George, Reama C, D'Souza, Sarah, Durmus, Mahmut, Nyokong, Tebello
- Authors: George, Reama C , D'Souza, Sarah , Durmus, Mahmut , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190416 , vital:44992 , xlink:href="https://doi.org/10.1080/24701556.2017.1284085"
- Description: Porphyrin-phthalocyanine nanostructures (P-PcNs) have been fabricated by electrostatic self-assembly of two oppositely charged molecules. The negatively charged molecule, meso-tetra-(4-phenylsulphonate)porphyrin (HT) and the positively charged species; {1,(4)-tetrakis-[(N-methyl(3-pyridyloxy) phthlocyaninato] chloro gallium(III)} sulphate, {2,(3)-tetrakis-[(N-methyl{(2-mercaptopyridine) phthalocyaninato} hydroxy manganese(III)} sulphate, {1,(4)-tetrakis-[(N-methyl-(3-pyridyloxy) phthalocyaninato] chloro indium(III)} sulphate, {2,3-octakis-{[(N-methyl-2-mercaptopyridine) phthalocyaninato] acetato manganese(III)} sulphate, {2,(3)-tetrakis-[(N-methyl(3-pyridyloxy) phthlocyaninato] choro gallium(III)} sulphate, {2,3-octakis-[(N-methy-3-pyridyloxy) phthalocyaninato] chloro indium(III)} sulphate, and {2,(3)-tetrakis-[(N-methyl (3-pyridyloxy) phthalocyaninato] chloro indium(III)} sulphate. Transmission electron microscopic (TEM) images showed that the formed nanostructures ranged from nanosheets to nanorods and nanotubes. The UV-Vis spectra confirmed that the molecules formed J-aggregates. The P-PcNs were exposed to incandescence light in the presence of platinum and gold salts. It was observed that the presence of platinum salts resulted in the destruction of the P-PcNs with possible formation of a Pt-Pc complex. While with the gold salt, the structures of P-PcNs were not only retained but were also enhanced to longer nanorods and nanofibers with the formation of gold nanoparticles.
- Full Text:
- Date Issued: 2017
- Authors: George, Reama C , D'Souza, Sarah , Durmus, Mahmut , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190416 , vital:44992 , xlink:href="https://doi.org/10.1080/24701556.2017.1284085"
- Description: Porphyrin-phthalocyanine nanostructures (P-PcNs) have been fabricated by electrostatic self-assembly of two oppositely charged molecules. The negatively charged molecule, meso-tetra-(4-phenylsulphonate)porphyrin (HT) and the positively charged species; {1,(4)-tetrakis-[(N-methyl(3-pyridyloxy) phthlocyaninato] chloro gallium(III)} sulphate, {2,(3)-tetrakis-[(N-methyl{(2-mercaptopyridine) phthalocyaninato} hydroxy manganese(III)} sulphate, {1,(4)-tetrakis-[(N-methyl-(3-pyridyloxy) phthalocyaninato] chloro indium(III)} sulphate, {2,3-octakis-{[(N-methyl-2-mercaptopyridine) phthalocyaninato] acetato manganese(III)} sulphate, {2,(3)-tetrakis-[(N-methyl(3-pyridyloxy) phthlocyaninato] choro gallium(III)} sulphate, {2,3-octakis-[(N-methy-3-pyridyloxy) phthalocyaninato] chloro indium(III)} sulphate, and {2,(3)-tetrakis-[(N-methyl (3-pyridyloxy) phthalocyaninato] chloro indium(III)} sulphate. Transmission electron microscopic (TEM) images showed that the formed nanostructures ranged from nanosheets to nanorods and nanotubes. The UV-Vis spectra confirmed that the molecules formed J-aggregates. The P-PcNs were exposed to incandescence light in the presence of platinum and gold salts. It was observed that the presence of platinum salts resulted in the destruction of the P-PcNs with possible formation of a Pt-Pc complex. While with the gold salt, the structures of P-PcNs were not only retained but were also enhanced to longer nanorods and nanofibers with the formation of gold nanoparticles.
- Full Text:
- Date Issued: 2017
Photophysical and nonlinear optical study of benzothiazole substituted phthalocyanines in solution and thin films
- Nwaji, Njemuwa, Bankole, Owolabi M, Britton, Jonathan, Nyokong, Tebello
- Authors: Nwaji, Njemuwa , Bankole, Owolabi M , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233088 , vital:50055 , xlink:href="https://doi.org/10.1142/S1088424617500079"
- Description: In this study, the photophysical, nonlinear absorption and nonlinear optical limiting properties of zinc and gallium phthalocyanine complexes: tetrakis[(benzo[d]thiazol-2-yl phenoxy)phthalocyaninato]zinc(II) (3), tetrakis[(benzo[d]thiazol-2-yl phenoxy)phthalocyaninato] gallium(III) chloride (4), tetrakis[(benzo[d]thiazol-2-ylthio)phthalocyaninato] zinc(II) (5), tetrakis[(benzo[d]thiazol-2-ylthio)phthalocyaninato] gallium(III) chloride (6), were investigated both in solution and when embedded in polystyrene thin films using 532 nm laser excitation at 10 ns pulses. It was also observed that complexes that have higher triplet state absorption also possessed enhanced nonlinear and optical limiting behavior. Superior optical performance was observed when the complexes were embedded in thin films compared to when they are in solution. Complex 6 in thin films gave the highest imaginary third-order susceptibility (Imm[X(3)(3)]) and hyperpolarizability (γ)γ) at 4.61 × 10-7-7 esu and 3.44 × 10-26-26 esu, respectively, with a low Ilimlim value of 0.06 J.cm-2.
- Full Text:
- Date Issued: 2017
- Authors: Nwaji, Njemuwa , Bankole, Owolabi M , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233088 , vital:50055 , xlink:href="https://doi.org/10.1142/S1088424617500079"
- Description: In this study, the photophysical, nonlinear absorption and nonlinear optical limiting properties of zinc and gallium phthalocyanine complexes: tetrakis[(benzo[d]thiazol-2-yl phenoxy)phthalocyaninato]zinc(II) (3), tetrakis[(benzo[d]thiazol-2-yl phenoxy)phthalocyaninato] gallium(III) chloride (4), tetrakis[(benzo[d]thiazol-2-ylthio)phthalocyaninato] zinc(II) (5), tetrakis[(benzo[d]thiazol-2-ylthio)phthalocyaninato] gallium(III) chloride (6), were investigated both in solution and when embedded in polystyrene thin films using 532 nm laser excitation at 10 ns pulses. It was also observed that complexes that have higher triplet state absorption also possessed enhanced nonlinear and optical limiting behavior. Superior optical performance was observed when the complexes were embedded in thin films compared to when they are in solution. Complex 6 in thin films gave the highest imaginary third-order susceptibility (Imm[X(3)(3)]) and hyperpolarizability (γ)γ) at 4.61 × 10-7-7 esu and 3.44 × 10-26-26 esu, respectively, with a low Ilimlim value of 0.06 J.cm-2.
- Full Text:
- Date Issued: 2017
Photophysical and optical limiting properties of a novel distyryl-BODIPY with fused crown ether moieties
- May, Aviwe K, Stone, Justin, Ngoy, Bokolombe P, Mack, John, Nyokong, Tebello, Kimura, Mutsumi, Kobayashi, Nagao
- Authors: May, Aviwe K , Stone, Justin , Ngoy, Bokolombe P , Mack, John , Nyokong, Tebello , Kimura, Mutsumi , Kobayashi, Nagao
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/239621 , vital:50749 , xlink:href="https://doi.org/10.1142/S1088424617500869"
- Description: The synthesis and characterization of a crown-ether-substituted 3,5-distyrylBODIPY dye with a 4-dimethylaminophenyl group at the meso-position is reported. The optical limiting properties were investigated at 532 nm, and the dye was found to have enhanced reverse saturable absorption responses during z-scan measurements. Theoretical calculations suggest that this may be due to the large dipole moment that is introduced by the benzo-fused crown ether and 4-dimethylaminophenyl substituents.
- Full Text:
- Date Issued: 2017
- Authors: May, Aviwe K , Stone, Justin , Ngoy, Bokolombe P , Mack, John , Nyokong, Tebello , Kimura, Mutsumi , Kobayashi, Nagao
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/239621 , vital:50749 , xlink:href="https://doi.org/10.1142/S1088424617500869"
- Description: The synthesis and characterization of a crown-ether-substituted 3,5-distyrylBODIPY dye with a 4-dimethylaminophenyl group at the meso-position is reported. The optical limiting properties were investigated at 532 nm, and the dye was found to have enhanced reverse saturable absorption responses during z-scan measurements. Theoretical calculations suggest that this may be due to the large dipole moment that is introduced by the benzo-fused crown ether and 4-dimethylaminophenyl substituents.
- Full Text:
- Date Issued: 2017
Photophysical behavior and photodynamic therapy activity of conjugates of zinc monocarboxyphenoxy phthalocyanine with human serum albumin and chitosan
- Oluwole, David O, Prinsloo, Earl, Nyokong, Tebello
- Authors: Oluwole, David O , Prinsloo, Earl , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188497 , vital:44759 , xlink:href="https://doi.org/10.1016/j.saa.2016.09.032"
- Description: Zincmonocarboxyphenoxy phthalocyanine (ZnMCPPc) was linked to human serum albumin (HSA) and chitosan via amide bond formation. The photophysical behavior and photodynamic therapy (PDT) activity (against human breast adenocarcinoma cell line (MCF-7 cells) of ZnMCPPc alone and its conjugates were investigated. The conjugates showed improved fluorescence, triplet and singlet oxygen quantum yields when compared to ZnMCPPc alone. The in vitro dark cytotoxicity and PDT studies were carried out at a dose of 3.6 μg/mL to 57.1 μg/mL. The in vitro dark cytotoxicity studies of ZnMCPPc showed cell viability more than 50% at 28.6 μg/mL and 57.1 μg/mL, while the conjugates showed > 50% in all their tested concentrations (3.6 to 57.1) μg/mL. Thus, conjugation of ZnMCPPc to HSA and chitosan improves its dark cytotoxicity, an important criteria for molecules meant for photodynamic therapy. Complex 1 showed the most efficacious PDT activity with cell viability more than 50% at concentration range of (14.3 to 57.1) μg/mL in comparison to the conjugates which only showed more than 50% cell viability at 28.6 μg/mL and 57.1 μg/mL for 1-HSA and 57.1 μg/mL for 1-Chitosan.
- Full Text:
- Date Issued: 2017
- Authors: Oluwole, David O , Prinsloo, Earl , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188497 , vital:44759 , xlink:href="https://doi.org/10.1016/j.saa.2016.09.032"
- Description: Zincmonocarboxyphenoxy phthalocyanine (ZnMCPPc) was linked to human serum albumin (HSA) and chitosan via amide bond formation. The photophysical behavior and photodynamic therapy (PDT) activity (against human breast adenocarcinoma cell line (MCF-7 cells) of ZnMCPPc alone and its conjugates were investigated. The conjugates showed improved fluorescence, triplet and singlet oxygen quantum yields when compared to ZnMCPPc alone. The in vitro dark cytotoxicity and PDT studies were carried out at a dose of 3.6 μg/mL to 57.1 μg/mL. The in vitro dark cytotoxicity studies of ZnMCPPc showed cell viability more than 50% at 28.6 μg/mL and 57.1 μg/mL, while the conjugates showed > 50% in all their tested concentrations (3.6 to 57.1) μg/mL. Thus, conjugation of ZnMCPPc to HSA and chitosan improves its dark cytotoxicity, an important criteria for molecules meant for photodynamic therapy. Complex 1 showed the most efficacious PDT activity with cell viability more than 50% at concentration range of (14.3 to 57.1) μg/mL in comparison to the conjugates which only showed more than 50% cell viability at 28.6 μg/mL and 57.1 μg/mL for 1-HSA and 57.1 μg/mL for 1-Chitosan.
- Full Text:
- Date Issued: 2017
Photophysical properties of a series of alloyed and non-alloyed water-soluble l-cysteine-capped core quantum dots
- Adegoke, Oluwasesan, Nyokong, Tebello, Forbes, Patricia B
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188486 , vital:44758 , xlink:href="https://doi.org/10.1016/j.jallcom.2016.10.276"
- Description: Photophysical properties of quantum dots (QDs) such as their photoluminescence (PL) quantum yield (QY), exciton lifetime and PL stability are important parameters used to unravel their chemical and physical characteristics. In this work, we have comparatively investigated the photophysical properties of a series of L-cysteine-capped non-alloyed (CdTe and CdSe) and alloyed (CdZnTe, CdSeS, CdSeTe and CdSeTeS) core QDs. Each of the QDs varied in their size and PL emission wavelength. We observe no physical relationship between the PL QY of the QDs and their PL stability. Based on the PL stability assessment, CdTe QDs with a high PL QY value of 88% exhibited poor PL stability while moderate PL stability was observed for CdZnTe (QY = 78%); CdSe (QY = 3%); and CdSeTe QDs (QY = ∼3%). Alloyed CdSeS (QY = ∼69%) and CdSeTeS (QY = 23%) QDs exhibited good PL stability and can serve as potential fluorophores for a wide range of chemical and biological applications. Generally, it is proposed that the structural nature of the QDs played a significant role in their overall photophysical properties. The information provided in this work will assist in the selection of core QDs suitable for different applications.
- Full Text:
- Date Issued: 2017
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188486 , vital:44758 , xlink:href="https://doi.org/10.1016/j.jallcom.2016.10.276"
- Description: Photophysical properties of quantum dots (QDs) such as their photoluminescence (PL) quantum yield (QY), exciton lifetime and PL stability are important parameters used to unravel their chemical and physical characteristics. In this work, we have comparatively investigated the photophysical properties of a series of L-cysteine-capped non-alloyed (CdTe and CdSe) and alloyed (CdZnTe, CdSeS, CdSeTe and CdSeTeS) core QDs. Each of the QDs varied in their size and PL emission wavelength. We observe no physical relationship between the PL QY of the QDs and their PL stability. Based on the PL stability assessment, CdTe QDs with a high PL QY value of 88% exhibited poor PL stability while moderate PL stability was observed for CdZnTe (QY = 78%); CdSe (QY = 3%); and CdSeTe QDs (QY = ∼3%). Alloyed CdSeS (QY = ∼69%) and CdSeTeS (QY = 23%) QDs exhibited good PL stability and can serve as potential fluorophores for a wide range of chemical and biological applications. Generally, it is proposed that the structural nature of the QDs played a significant role in their overall photophysical properties. The information provided in this work will assist in the selection of core QDs suitable for different applications.
- Full Text:
- Date Issued: 2017
Photophysical properties of GaCl 5, 10, 15, 20-tetra (1-pyrenyl) porphyrinato incorporated into Pluronic F127 micelle
- Managa, Muthumuni, Britton, Jonathan, Amuhaya, Edith K, Nyokong, Tebello
- Authors: Managa, Muthumuni , Britton, Jonathan , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233101 , vital:50056 , xlink:href="https://doi.org/10.1016/j.jlumin.2016.12.043"
- Description: GaCl 5,10,15,20-Tetra(1-pyrenyl)porphyrin (GaClTPyP) was successfully synthesised and encapsulated into Pluronic F127. The unmetallated 5,10,15,20-tetra(1-pyrenyl)porphyrin (H2TPyP) precursor was also encapsulated into Pluronic F127. The fluorescence quantum yield for GaClTPyP at 0.045 was lower than that of H2TPyP at 0.13 due to the heavy atom effect of Ga in the former which encourages intersystem crossing to the triplet state, lowering the fluorescence. Fluorescence quantum yield values increased when GaClTPyP or H2TPyP were encapsulated in Pluronic F127. GaClTPyP/Pluronic F127 showed higher values of the binding constant (Kb) as well as Stern-Volmer constant (Ksv) when compared to H2ClTPyP/Pluronic F127. It was determined from fluorescence quenching studies for GaClTPyP was located more in the inner core (hydrophobic) of Pluronic F127 and H2TPyP more on the outer region. Single oxygen quantum yields (Ф△) were determined to be 0.32 and 0.53 for GaClTPyP and GaClTPyP/Pluronic F127 respectively, an increase for the latter compared to the former.
- Full Text:
- Date Issued: 2017
- Authors: Managa, Muthumuni , Britton, Jonathan , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233101 , vital:50056 , xlink:href="https://doi.org/10.1016/j.jlumin.2016.12.043"
- Description: GaCl 5,10,15,20-Tetra(1-pyrenyl)porphyrin (GaClTPyP) was successfully synthesised and encapsulated into Pluronic F127. The unmetallated 5,10,15,20-tetra(1-pyrenyl)porphyrin (H2TPyP) precursor was also encapsulated into Pluronic F127. The fluorescence quantum yield for GaClTPyP at 0.045 was lower than that of H2TPyP at 0.13 due to the heavy atom effect of Ga in the former which encourages intersystem crossing to the triplet state, lowering the fluorescence. Fluorescence quantum yield values increased when GaClTPyP or H2TPyP were encapsulated in Pluronic F127. GaClTPyP/Pluronic F127 showed higher values of the binding constant (Kb) as well as Stern-Volmer constant (Ksv) when compared to H2ClTPyP/Pluronic F127. It was determined from fluorescence quenching studies for GaClTPyP was located more in the inner core (hydrophobic) of Pluronic F127 and H2TPyP more on the outer region. Single oxygen quantum yields (Ф△) were determined to be 0.32 and 0.53 for GaClTPyP and GaClTPyP/Pluronic F127 respectively, an increase for the latter compared to the former.
- Full Text:
- Date Issued: 2017
Photophysical studies of 2, 6-dibrominated BODIPY dyes substituted with 4-benzyloxystyryl substituents
- Ngoy, Bokolombe Pitchou, Molupe, Nthabeleng, Harris, Jessica, Fomo, Gertrude, Mack, John, Nyokong, Tebello
- Authors: Ngoy, Bokolombe Pitchou , Molupe, Nthabeleng , Harris, Jessica , Fomo, Gertrude , Mack, John , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233068 , vital:50053 , xlink:href="https://doi.org/10.1142/S1088424617500420"
- Description: A series of novel 2,6-dibrominated BODIPY dyes with styryl groups at the 3,5-positions has been prepared, and their photophysical properties have been analyzed to assess their potential utility for use as photosensitizers in photodynamic therapy and in bioimaging.
- Full Text:
- Date Issued: 2017
- Authors: Ngoy, Bokolombe Pitchou , Molupe, Nthabeleng , Harris, Jessica , Fomo, Gertrude , Mack, John , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233068 , vital:50053 , xlink:href="https://doi.org/10.1142/S1088424617500420"
- Description: A series of novel 2,6-dibrominated BODIPY dyes with styryl groups at the 3,5-positions has been prepared, and their photophysical properties have been analyzed to assess their potential utility for use as photosensitizers in photodynamic therapy and in bioimaging.
- Full Text:
- Date Issued: 2017
Photophysical studies of meso-tetrakis (4-nitrophenyl) and meso-tetrakis (4-sulfophenyl) gallium porphyrins loaded into Pluronic F127 polymeric micelles
- Managa, Muthumuni, Ngoy, Bokolombe P, Mafukidze, Donovan M, Britton, Jonathan, Nyokong, Tebello
- Authors: Managa, Muthumuni , Ngoy, Bokolombe P , Mafukidze, Donovan M , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233132 , vital:50060 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.08.033"
- Description: 5,10,15,20-Tetra(4-nitrophenyl) porphyrinato gallium chloride (ClGaTNPP) and 5,10,15,20-tetra(4-sulfophenyl) porphyrinato gallium chloride (ClGaTSPP) and their metal free derivatives were successfully synthesised and were added to Pluronic F127 polymeric micelles to form ClGaTNPP-F127 (or H2TNPP-F127) and ClGaTSPP-F127 (or H2TSPP-F127), respectively. The fluorescence and singlet oxygen generating behaviour of the porphyrins were investigated following incorporation. The fluorescence lifetimes were short-lived upon incorporation into the polymer, compared to the porphyrin alone; suggesting the quenching of the lifetimes of the porphyrin by the polymers. Singlet oxygen quantum yields were determined to be 0.55 and 0.59 for ClGaTSPP and ClGaTSPP-F127, respectively. Thus there is an increase in singlet oxygen quantum yields in the presence of Pluronic F127 compared to the porphyrin alone. ClGaTSPP-F127 (or H2TSPP-F127) showed higher values of the binding constant (Kb) as well as high values of the Stern-Volmer constant (Ksv) compared to ClGaTNPP-F127 (or H2TNPP-F127).
- Full Text:
- Date Issued: 2017
- Authors: Managa, Muthumuni , Ngoy, Bokolombe P , Mafukidze, Donovan M , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233132 , vital:50060 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.08.033"
- Description: 5,10,15,20-Tetra(4-nitrophenyl) porphyrinato gallium chloride (ClGaTNPP) and 5,10,15,20-tetra(4-sulfophenyl) porphyrinato gallium chloride (ClGaTSPP) and their metal free derivatives were successfully synthesised and were added to Pluronic F127 polymeric micelles to form ClGaTNPP-F127 (or H2TNPP-F127) and ClGaTSPP-F127 (or H2TSPP-F127), respectively. The fluorescence and singlet oxygen generating behaviour of the porphyrins were investigated following incorporation. The fluorescence lifetimes were short-lived upon incorporation into the polymer, compared to the porphyrin alone; suggesting the quenching of the lifetimes of the porphyrin by the polymers. Singlet oxygen quantum yields were determined to be 0.55 and 0.59 for ClGaTSPP and ClGaTSPP-F127, respectively. Thus there is an increase in singlet oxygen quantum yields in the presence of Pluronic F127 compared to the porphyrin alone. ClGaTSPP-F127 (or H2TSPP-F127) showed higher values of the binding constant (Kb) as well as high values of the Stern-Volmer constant (Ksv) compared to ClGaTNPP-F127 (or H2TNPP-F127).
- Full Text:
- Date Issued: 2017
Photophysicochemical behaviour of anionic indium phthalocyanine when grafted onto AgxAuy and porous silica nanoparticles
- Dube, Edith, Oluwole, David O, Nyokong, Tebello
- Authors: Dube, Edith , Oluwole, David O , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188899 , vital:44796 , xlink:href="https://doi.org/10.1016/j.jlumin.2017.05.071"
- Description: This work reports on the synthesis of glutathione functionalised Ag3Au1 (Ag rich alloy, denoted as AgAu) and Ag1Au3 (Au rich alloy – denoted as AuAg) nano alloys as well as aminopropyl triethoxylsilane capped Ag1Au3 doped silica nanoparticles (NPs). The NPs were covalently linked to indium(III) chloride 2,9(10),16(17),23(24)–tetra–(3–carboxyphenoxy)phthalocyanine (1) via amide bond to form 1–AgAuNPs–GSH and 1–AuAgNPs–GSH. The AgAuNPs were also doped into aminopropyl triethoxylsilane (APTES) silica NPs (SiNPs-APTES) followed by linkage to complex 1 to form 1–AgAu-SiNPs–APTES. The photophysicochemical behaviour of complex 1 and its nanoconjugates were investigated. Decrease in the fluorescence quantum yields and lifetimes was observed in the conjugates in comparison to 1 alone. The singlet oxygen quantum yield for 1–AgAuNPs–GSH and 1–AuAgNPs–GSH decreased probably due to the screening effect caused by the NPs, while that of 1–AgAu-SiNPs–APTES increased in dimethylsulfoxide probably due to the permeability of the porous silica matrix to molecular oxygen.
- Full Text:
- Date Issued: 2017
- Authors: Dube, Edith , Oluwole, David O , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188899 , vital:44796 , xlink:href="https://doi.org/10.1016/j.jlumin.2017.05.071"
- Description: This work reports on the synthesis of glutathione functionalised Ag3Au1 (Ag rich alloy, denoted as AgAu) and Ag1Au3 (Au rich alloy – denoted as AuAg) nano alloys as well as aminopropyl triethoxylsilane capped Ag1Au3 doped silica nanoparticles (NPs). The NPs were covalently linked to indium(III) chloride 2,9(10),16(17),23(24)–tetra–(3–carboxyphenoxy)phthalocyanine (1) via amide bond to form 1–AgAuNPs–GSH and 1–AuAgNPs–GSH. The AgAuNPs were also doped into aminopropyl triethoxylsilane (APTES) silica NPs (SiNPs-APTES) followed by linkage to complex 1 to form 1–AgAu-SiNPs–APTES. The photophysicochemical behaviour of complex 1 and its nanoconjugates were investigated. Decrease in the fluorescence quantum yields and lifetimes was observed in the conjugates in comparison to 1 alone. The singlet oxygen quantum yield for 1–AgAuNPs–GSH and 1–AuAgNPs–GSH decreased probably due to the screening effect caused by the NPs, while that of 1–AgAu-SiNPs–APTES increased in dimethylsulfoxide probably due to the permeability of the porous silica matrix to molecular oxygen.
- Full Text:
- Date Issued: 2017
Photophysicochemical behaviour of metallophthalocyanines when doped onto silica nanoparticles
- Oluwole, David O, Nyokong, Tebello
- Authors: Oluwole, David O , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188518 , vital:44761 , xlink:href="https://doi.org/10.1016/j.dyepig.2016.08.053"
- Description: Aluminum(III) chloride 2,9(10),16(17),23(24)–tetra–(4–tert–butylphenoxy)phthalocyanine (1), zinc(II) 2,9(10),16(17),23(24)–tetra–(4–tert–butylphenoxy)phthalocyanine (2), zinc(II) 1,8(11),15(18),22(25)–tetra–(4–tert–butylphenoxy) phthalocyanine (3) and zinc(II) 2,9(10),16(17),23(24)–tetra–(4–carboxylphenoxy) phthalocyanine (4) were doped onto silica nanoparticles (SiNPs). There were no significant changes in fluorescence quantum yields and lifetimes of the metallophthalocyanines ( MPcs) when doped onto SiNPs. The triplet quantum yields of the MPcs alone range from 0.22 to 0.85 and in the presence of SiNPs the values range from 0.17 to 0.89. We observed a general decrease of triplet quantum yields of phthalocyanines in the conjugates except for 2 where there was an increase. The values were highly affected by aggregation. Complexes 1 and 3 were highly aggregated when doped onto SiNPs, while 2 and 4 did not show much aggregation.
- Full Text:
- Date Issued: 2017
- Authors: Oluwole, David O , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188518 , vital:44761 , xlink:href="https://doi.org/10.1016/j.dyepig.2016.08.053"
- Description: Aluminum(III) chloride 2,9(10),16(17),23(24)–tetra–(4–tert–butylphenoxy)phthalocyanine (1), zinc(II) 2,9(10),16(17),23(24)–tetra–(4–tert–butylphenoxy)phthalocyanine (2), zinc(II) 1,8(11),15(18),22(25)–tetra–(4–tert–butylphenoxy) phthalocyanine (3) and zinc(II) 2,9(10),16(17),23(24)–tetra–(4–carboxylphenoxy) phthalocyanine (4) were doped onto silica nanoparticles (SiNPs). There were no significant changes in fluorescence quantum yields and lifetimes of the metallophthalocyanines ( MPcs) when doped onto SiNPs. The triplet quantum yields of the MPcs alone range from 0.22 to 0.85 and in the presence of SiNPs the values range from 0.17 to 0.89. We observed a general decrease of triplet quantum yields of phthalocyanines in the conjugates except for 2 where there was an increase. The values were highly affected by aggregation. Complexes 1 and 3 were highly aggregated when doped onto SiNPs, while 2 and 4 did not show much aggregation.
- Full Text:
- Date Issued: 2017
Physiology and Spatio-temporal Relations of Nutrient Acquisition by Roots and Root Symbionts
- Valentine, Alex J, Kleinert, Aleysia, Thuynsma, Rochelle, Chimphango, Samson, Dames, Joanna F, Benedito, V A
- Authors: Valentine, Alex J , Kleinert, Aleysia , Thuynsma, Rochelle , Chimphango, Samson , Dames, Joanna F , Benedito, V A
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/448652 , vital:74749 , https://doi.org/10.1007/124_2016_11
- Description: Among the various functions of roots, nutrient acquisition (via soil uptake or through symbiotic relationships) is one of the most essential for land plants. Soil from natural and agricultural ecosystems may impede plant nutrient acquisition, by many factors such as mineral availabilities either in excess or deficient supply, depletion of organic matter, extreme variations in water supply, and many other physical and chemical features. In order to survive, plants need to undergo developmental and physiological mechanisms to cope with these extreme soil situations. Here we review how plants control nutrient acquisition by dynamically changing root architecture for improved soil space exploration, as well as altering cellular-level function for enhanced nutrient uptake, via apoplastic acidification, exudation of enzymes and metabolites (organic acids, secondary metabolites) and constantly changing the composition of transporters at the plasma membrane. These changes start with environmental cues which induce cell signaling and involve hormones and coordinated regulatory genes networks that drive the root’s developmental plasticity as well as the cell’s biochemical dynamics. Mutualistic root symbioses, such as mycorrhizae and rhizobial-induced nodulation, are also important to provide essential nutrients to the plant, which are tightly regulated in order to only occur at plant’s benefit. We also explore molecular mechanisms which roots have evolved to cope with nutritional, as well as other soil stresses, such as aluminium toxicity and heavy metals. Overall, understanding root dynamics under several environmental variables at different perspectives, from root architecture to biochemistry to genetic levels will allow us to better explore the spatial and temporal relations of roots with their mineral nutrient environment.
- Full Text:
- Date Issued: 2017
- Authors: Valentine, Alex J , Kleinert, Aleysia , Thuynsma, Rochelle , Chimphango, Samson , Dames, Joanna F , Benedito, V A
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/448652 , vital:74749 , https://doi.org/10.1007/124_2016_11
- Description: Among the various functions of roots, nutrient acquisition (via soil uptake or through symbiotic relationships) is one of the most essential for land plants. Soil from natural and agricultural ecosystems may impede plant nutrient acquisition, by many factors such as mineral availabilities either in excess or deficient supply, depletion of organic matter, extreme variations in water supply, and many other physical and chemical features. In order to survive, plants need to undergo developmental and physiological mechanisms to cope with these extreme soil situations. Here we review how plants control nutrient acquisition by dynamically changing root architecture for improved soil space exploration, as well as altering cellular-level function for enhanced nutrient uptake, via apoplastic acidification, exudation of enzymes and metabolites (organic acids, secondary metabolites) and constantly changing the composition of transporters at the plasma membrane. These changes start with environmental cues which induce cell signaling and involve hormones and coordinated regulatory genes networks that drive the root’s developmental plasticity as well as the cell’s biochemical dynamics. Mutualistic root symbioses, such as mycorrhizae and rhizobial-induced nodulation, are also important to provide essential nutrients to the plant, which are tightly regulated in order to only occur at plant’s benefit. We also explore molecular mechanisms which roots have evolved to cope with nutritional, as well as other soil stresses, such as aluminium toxicity and heavy metals. Overall, understanding root dynamics under several environmental variables at different perspectives, from root architecture to biochemistry to genetic levels will allow us to better explore the spatial and temporal relations of roots with their mineral nutrient environment.
- Full Text:
- Date Issued: 2017
Platinum nanoparticles supported on carbon nanodots as anode catalysts for direct alcohol fuel cells
- Gwebu, Sandile Surprise, Nomngongo, Philiswa Nosizo, Mashazi, Philani Nkosinathi, Maxakato, Nobanathi Wendy, Nyokong, Tebello
- Authors: Gwebu, Sandile Surprise , Nomngongo, Philiswa Nosizo , Mashazi, Philani Nkosinathi , Maxakato, Nobanathi Wendy , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233118 , vital:50058 , xlink:href="https://doi.org/10.20964/2017.07.09"
- Description: Carbon nanodots (CNDs) were successfully synthesized employing a cheap and green method using oats as a starting material. The Pt/CNDs electrocatalyst was synthesized using carbon nanodots as a reductant and support material without adjusting the pH of the solution. The synthesized materials were characterized using Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller Nitrogen adsorption (BET), X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM), X-ray diffractometry (XRD) and Inductively coupled plasma optical emission spectroscopy (ICP-OES). The FTIR results proved that the synthesized carbon nanodots contain carboxylic acid functional groups which facilitate the attachment of Pt nanoparticles. The BET surface area for carbon nanodots was found to be 312.5 m2 g -1 two times higher than that of commercial carbon. XPS results revealed the composition of the materials and the oxidation states of Pt in Pt/CNDs electrocatalyst. TEM images proved that the materials were of the nanoscale. XRD peaks proved that the carbon nanodots were amorphous and Pt (111) was present in the Pt/CNDs electrocatalyst. ICPOES determined the platinum concentration in Pt/CNDs electrocatalyst to be 8.12%. The electrochemical oxidation of methanol and ethanol were studied by cyclic voltammetry (CV) and chronoamperometry (CA). Cyclic voltammetry results showed that the Pt/CNDs electrocatalyst prepared by this method exhibit superior performance for methanol and ethanol electro-oxidation at room temperature.
- Full Text:
- Date Issued: 2017
Platinum nanoparticles supported on carbon nanodots as anode catalysts for direct alcohol fuel cells
- Authors: Gwebu, Sandile Surprise , Nomngongo, Philiswa Nosizo , Mashazi, Philani Nkosinathi , Maxakato, Nobanathi Wendy , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233118 , vital:50058 , xlink:href="https://doi.org/10.20964/2017.07.09"
- Description: Carbon nanodots (CNDs) were successfully synthesized employing a cheap and green method using oats as a starting material. The Pt/CNDs electrocatalyst was synthesized using carbon nanodots as a reductant and support material without adjusting the pH of the solution. The synthesized materials were characterized using Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller Nitrogen adsorption (BET), X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM), X-ray diffractometry (XRD) and Inductively coupled plasma optical emission spectroscopy (ICP-OES). The FTIR results proved that the synthesized carbon nanodots contain carboxylic acid functional groups which facilitate the attachment of Pt nanoparticles. The BET surface area for carbon nanodots was found to be 312.5 m2 g -1 two times higher than that of commercial carbon. XPS results revealed the composition of the materials and the oxidation states of Pt in Pt/CNDs electrocatalyst. TEM images proved that the materials were of the nanoscale. XRD peaks proved that the carbon nanodots were amorphous and Pt (111) was present in the Pt/CNDs electrocatalyst. ICPOES determined the platinum concentration in Pt/CNDs electrocatalyst to be 8.12%. The electrochemical oxidation of methanol and ethanol were studied by cyclic voltammetry (CV) and chronoamperometry (CA). Cyclic voltammetry results showed that the Pt/CNDs electrocatalyst prepared by this method exhibit superior performance for methanol and ethanol electro-oxidation at room temperature.
- Full Text:
- Date Issued: 2017
Population size and development history determine street tree distribution and composition within and between Eastern Cape towns, South Africa
- Gwedla, Nanamhla, Shackleton, Charlie M
- Authors: Gwedla, Nanamhla , Shackleton, Charlie M
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180468 , vital:43392 , xlink:href="https://doi.org/10.1016/j.ufug.2017.04.014"
- Description: Street trees are a common feature of urban nature, providing ecological, economic and social benefits. These public functions are highly dependent on specific design principles, including the composition and diversity of tree species within the urban forest. Consequently, it is important to understand the patterns and correlates of street tree distribution and diversity to assess benefit flows. This requires sampling across and within towns. This paper reports on an assessment of the distribution, composition and diversity of street trees between and within multiple South African towns, and ascertains the correlations between tree density and composition with social contexts. Randomly selected streets were sampled in the affluent, township and low cost housing suburbs of ten Eastern Cape towns. Sixty-nine out of 300 sampled transects had street trees, with 888 trees enumerated, spanning 97 species. Alien tree species accounted for 71% of all the enumerated trees while indigenous trees species accounted for 12%. Tree density and composition were significantly lower in smaller towns and those marginalised during the previous racially-based political regime. Within towns, the poor areas had fewer street trees, with many streets having none. Collaboration and constant communication between the various government departments involved in suburb development is crucial to ensure a more rigorous incorporation of green infrastructure into the building and development plans of new housing developments.
- Full Text:
- Date Issued: 2017
- Authors: Gwedla, Nanamhla , Shackleton, Charlie M
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180468 , vital:43392 , xlink:href="https://doi.org/10.1016/j.ufug.2017.04.014"
- Description: Street trees are a common feature of urban nature, providing ecological, economic and social benefits. These public functions are highly dependent on specific design principles, including the composition and diversity of tree species within the urban forest. Consequently, it is important to understand the patterns and correlates of street tree distribution and diversity to assess benefit flows. This requires sampling across and within towns. This paper reports on an assessment of the distribution, composition and diversity of street trees between and within multiple South African towns, and ascertains the correlations between tree density and composition with social contexts. Randomly selected streets were sampled in the affluent, township and low cost housing suburbs of ten Eastern Cape towns. Sixty-nine out of 300 sampled transects had street trees, with 888 trees enumerated, spanning 97 species. Alien tree species accounted for 71% of all the enumerated trees while indigenous trees species accounted for 12%. Tree density and composition were significantly lower in smaller towns and those marginalised during the previous racially-based political regime. Within towns, the poor areas had fewer street trees, with many streets having none. Collaboration and constant communication between the various government departments involved in suburb development is crucial to ensure a more rigorous incorporation of green infrastructure into the building and development plans of new housing developments.
- Full Text:
- Date Issued: 2017
Predicting the risk of non-target damage to a close relative of a target weed using sequential no-choice tests, paired-choice tests and olfactory discrimination experiments
- Sutton, Guy F, Paterson, Iain D, Compton, Stephen G, Paynter, Quentin
- Authors: Sutton, Guy F , Paterson, Iain D , Compton, Stephen G , Paynter, Quentin
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417511 , vital:71459 , xlink:href="https://doi.org/10.1080/09583157.2015.1118615"
- Description: We investigated host-plant utilisation by the candidate biocontrol agent Paradibolia coerulea (Coleoptera: Chrysomelidae) on the target plant Spathodea campanulata Beauv. (Bignoniaceae) and a closely related non-target plant, Kigelia africana (Lam.) Benth. (Bignoniaceae). Paired-choice and sequential no-choice experiments were performed and coupled with olfactory discrimination experiments to test the insects’ responses to volatiles from both plant species as well as to cues from conspecific beetles. Although K. africana was utilised by P. coerulea, S. campanulata was preferred for both adult feeding and oviposition. Interestingly, whereas females were attracted to olfactory cues emitted by S. campanulata, males demonstrated no such olfactory discrimination. Females were also attracted to cues deposited by males, and males were deterred by cues from other males, but neither sex responded to female olfactory cues. Very few eggs were recorded on K. africana and none of the larvae that hatched on K. africana survived the first instar. Both S. campanulata and K. africana are suitable for adult feeding, but persistent utilisation of K. africana in the field is unlikely because larval development is only possible on S. campanulata and because the adult females are strongly attracted to volatiles emitted by the target plant. Nevertheless, if P. coerulea is released as a biocontrol agent, spill-over adult feeding could potentially occur on K. africana growing sympatrically with S. campanulata. Because P. coerulea cannot complete its development on K. africana, non-target damage will only occur where the target plant is present, with an intensity dependent on densities of adult beetles locally.
- Full Text:
- Date Issued: 2017
- Authors: Sutton, Guy F , Paterson, Iain D , Compton, Stephen G , Paynter, Quentin
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417511 , vital:71459 , xlink:href="https://doi.org/10.1080/09583157.2015.1118615"
- Description: We investigated host-plant utilisation by the candidate biocontrol agent Paradibolia coerulea (Coleoptera: Chrysomelidae) on the target plant Spathodea campanulata Beauv. (Bignoniaceae) and a closely related non-target plant, Kigelia africana (Lam.) Benth. (Bignoniaceae). Paired-choice and sequential no-choice experiments were performed and coupled with olfactory discrimination experiments to test the insects’ responses to volatiles from both plant species as well as to cues from conspecific beetles. Although K. africana was utilised by P. coerulea, S. campanulata was preferred for both adult feeding and oviposition. Interestingly, whereas females were attracted to olfactory cues emitted by S. campanulata, males demonstrated no such olfactory discrimination. Females were also attracted to cues deposited by males, and males were deterred by cues from other males, but neither sex responded to female olfactory cues. Very few eggs were recorded on K. africana and none of the larvae that hatched on K. africana survived the first instar. Both S. campanulata and K. africana are suitable for adult feeding, but persistent utilisation of K. africana in the field is unlikely because larval development is only possible on S. campanulata and because the adult females are strongly attracted to volatiles emitted by the target plant. Nevertheless, if P. coerulea is released as a biocontrol agent, spill-over adult feeding could potentially occur on K. africana growing sympatrically with S. campanulata. Because P. coerulea cannot complete its development on K. africana, non-target damage will only occur where the target plant is present, with an intensity dependent on densities of adult beetles locally.
- Full Text:
- Date Issued: 2017