Fluorescence behaviour of supramolecular hybrids containing graphene quantum dots and pyrene-derivatized phthalocyanines and porphyrins
- Achadu, Ojodomo John, Managa, Muthumuni, Nyokong, Tebello
- Authors: Achadu, Ojodomo John , Managa, Muthumuni , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188953 , vital:44801 , xlink:href="https://doi.org/10.1016/j.jphotochem.2016.10.029"
- Description: Novel pyrene-derivatized zinc and cobalt phthalocyanines (Pcs) and porphyrins (Ps) were immobilized on graphene quantum dots (GQDs) to form GQDs-Pcs and GQDs-Ps supramolecular hybrids via the π–π stacking interaction method. Spectroscopic evidence shows that the resultant hybrids were stable owing to the strong π–π stacking interaction between the GQDs and the respective Pcs and Ps, thus leading to the fabrication of interesting and functional supramolecular hybrids by taking advantage of the delocalized π electron systems of GQDs and the macrocycles. The conjugates showed increased fluorescence quantum yields for the Pcs/Ps, but decreased values for the GQDs in the conjugates. These novel hybrid materials could potentially be deployed for studies in both fundamental and applied perspectives due to the synergistic contributions resulting from the combination of their excellent electronic and optical properties.
- Full Text:
- Date Issued: 2017
- Authors: Achadu, Ojodomo John , Managa, Muthumuni , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188953 , vital:44801 , xlink:href="https://doi.org/10.1016/j.jphotochem.2016.10.029"
- Description: Novel pyrene-derivatized zinc and cobalt phthalocyanines (Pcs) and porphyrins (Ps) were immobilized on graphene quantum dots (GQDs) to form GQDs-Pcs and GQDs-Ps supramolecular hybrids via the π–π stacking interaction method. Spectroscopic evidence shows that the resultant hybrids were stable owing to the strong π–π stacking interaction between the GQDs and the respective Pcs and Ps, thus leading to the fabrication of interesting and functional supramolecular hybrids by taking advantage of the delocalized π electron systems of GQDs and the macrocycles. The conjugates showed increased fluorescence quantum yields for the Pcs/Ps, but decreased values for the GQDs in the conjugates. These novel hybrid materials could potentially be deployed for studies in both fundamental and applied perspectives due to the synergistic contributions resulting from the combination of their excellent electronic and optical properties.
- Full Text:
- Date Issued: 2017
Application of graphene quantum dots functionalized with thymine and thymine-appended zinc phthalocyanine as novel photoluminescent nanoprobes
- Achadu, Ojodomo John, Nyokong, Tebello
- Authors: Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188508 , vital:44760 , xlink:href="https://doi.org/10.1039/C6NJ03285K"
- Description: Graphene quantum dots (GQDs) and zinc phthalocyanine (ZnPc) were separately modified with thymine to obtain thymine-functionalized GQDs (T-GQDs) and ZnPc (T-ZnPc). T-GQDs and nanoconjugates of T-ZnPc with pristine GQDs (represented as pristine GQDs–T-ZnPc) or T-GQDs (represented as T-GQDs–T-ZnPc) were employed as fluorescent probes for the detection of mercury(II) ions (Hg2+). The as-synthesized T-GQDs alone demonstrated a highly sensitive and selective fluorescence “turn-OFF” process for Hg2+ detection due to the specific interaction between the thymine functionality on the T-GQDs with Hg2+. On the other hand, the fluorescence of pristine GQDs and T-GQDs was quenched (“turn-OFF”) upon coordination with T-ZnPc. However, the fluorescence emission was selectively restored (“turn-ON” process) in the presence of Hg2+ resulting in the sensitive detection of Hg2+ in the nanomolar concentration range (limit of detection = 0.05 nM, for the pristine GQDs–T-ZnPc probe). The probe containing pristine GQDs and the T-ZnPc complex demonstrated a higher specific and sensitive recognition of Hg2+ as compared to the T-GQDs alone or T-GQDs–T-ZnPc probes which are ascribed to the fluorescence “turn-ON” process of the former. Screening of different metal ions and counter ions proved that the probes are specifically suited for Hg2+ detection.
- Full Text:
- Date Issued: 2017
- Authors: Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188508 , vital:44760 , xlink:href="https://doi.org/10.1039/C6NJ03285K"
- Description: Graphene quantum dots (GQDs) and zinc phthalocyanine (ZnPc) were separately modified with thymine to obtain thymine-functionalized GQDs (T-GQDs) and ZnPc (T-ZnPc). T-GQDs and nanoconjugates of T-ZnPc with pristine GQDs (represented as pristine GQDs–T-ZnPc) or T-GQDs (represented as T-GQDs–T-ZnPc) were employed as fluorescent probes for the detection of mercury(II) ions (Hg2+). The as-synthesized T-GQDs alone demonstrated a highly sensitive and selective fluorescence “turn-OFF” process for Hg2+ detection due to the specific interaction between the thymine functionality on the T-GQDs with Hg2+. On the other hand, the fluorescence of pristine GQDs and T-GQDs was quenched (“turn-OFF”) upon coordination with T-ZnPc. However, the fluorescence emission was selectively restored (“turn-ON” process) in the presence of Hg2+ resulting in the sensitive detection of Hg2+ in the nanomolar concentration range (limit of detection = 0.05 nM, for the pristine GQDs–T-ZnPc probe). The probe containing pristine GQDs and the T-ZnPc complex demonstrated a higher specific and sensitive recognition of Hg2+ as compared to the T-GQDs alone or T-GQDs–T-ZnPc probes which are ascribed to the fluorescence “turn-ON” process of the former. Screening of different metal ions and counter ions proved that the probes are specifically suited for Hg2+ detection.
- Full Text:
- Date Issued: 2017
Graphene quantum dots decorated with maleimide and zinc tetramaleimido-phthalocyanine: Application in the design of “OFF-ON” fluorescence sensors for biothiols
- Achadu, Ojodomo John, Nyokong, Tebello
- Authors: Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188282 , vital:44741 , xlink:href="https://doi.org/10.1016/j.talanta.2017.01.031"
- Description: The fabrication of maleimide-derivatized graphene quantum dots (M-GQDs) and zinc phthalocyanine (2) as novel sensor probes for the selective detection of biothiols (cysteine, homocysteine or glutathione) through the rapid and specific Michael addition reaction between biothiols and the maleimide-derivatized probes is presented in this study. GQDs directly functionalized with maleimide units (M-GQDs) were synthesized and deployed for biothiols recognition following the principle of Michael addition. M-GQDs probe was found to be highly sensitive and selective towards biothiols detection in the nanomolar range in aqueous solution and at physiological pH (7.0). On the other hand, non-covalent interaction between pristine GQDs and novel zinc tetramaleimido-derivatized phthalocyanine resulted in the quenching of the pristine GQDs fluorescence emission which was switched back to the “ON” mode by Michael addition mechanism in the presence of biothiols. Tested relevant biomolecules did not interfere in the quantitative recognition of the biothiols. The probes showed to be highly sensitive, specific and selective for biothiols sensing in simulated real samples.
- Full Text:
- Date Issued: 2017
- Authors: Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188282 , vital:44741 , xlink:href="https://doi.org/10.1016/j.talanta.2017.01.031"
- Description: The fabrication of maleimide-derivatized graphene quantum dots (M-GQDs) and zinc phthalocyanine (2) as novel sensor probes for the selective detection of biothiols (cysteine, homocysteine or glutathione) through the rapid and specific Michael addition reaction between biothiols and the maleimide-derivatized probes is presented in this study. GQDs directly functionalized with maleimide units (M-GQDs) were synthesized and deployed for biothiols recognition following the principle of Michael addition. M-GQDs probe was found to be highly sensitive and selective towards biothiols detection in the nanomolar range in aqueous solution and at physiological pH (7.0). On the other hand, non-covalent interaction between pristine GQDs and novel zinc tetramaleimido-derivatized phthalocyanine resulted in the quenching of the pristine GQDs fluorescence emission which was switched back to the “ON” mode by Michael addition mechanism in the presence of biothiols. Tested relevant biomolecules did not interfere in the quantitative recognition of the biothiols. The probes showed to be highly sensitive, specific and selective for biothiols sensing in simulated real samples.
- Full Text:
- Date Issued: 2017
Fluorescence “switch on” of conjugates of CdTe@ ZnS quantum dots with Al, Ni and Zn tetraamino-phthalocyanines by hydrogen peroxide
- Adegoke, Oluwasesan, Khene, Samson M, Nyokong, Tebello
- Authors: Adegoke, Oluwasesan , Khene, Samson M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241750 , vital:50966 , xlink:href="https://doi.org/10.1007/s10895-013-1222-x"
- Description: In this study, we have developed a novel nanoprobe for H2O2 based on the conjugation of CdTe@ZnS quantum dots (QDs) to different metal tetraamino-phthalocyanine (MTAPc): (M = (OAc)Al, {OAc = acetate}, Ni and Zn). Chemical coordination of the QDs to the MTAPc resulted in the fluorescence “switch off” of the linked QDs which was associated with Förster resonance energy transfer (FRET). In the presence of varying concentration of H2O2, the fluorescence of the linked QDs was progressively “switched on” and the FRET mechanism between the QDs and the MTAPc was disrupted. The sensitivity/limit of detection of the nanoprobe followed the order: QDs-ZnTAPc (2.2 μM) > QDs-NiTAPc (4.4 μM) > QDs-AlTAPc (9.8 μM) while the selectivity followed the order: QDs-NiTAPc > QDs-AlTAPc > QDs-ZnTAPc. The varying degree of sensitivity/selectivity and mechanism of detection is discussed in detail.
- Full Text:
- Date Issued: 2013
- Authors: Adegoke, Oluwasesan , Khene, Samson M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241750 , vital:50966 , xlink:href="https://doi.org/10.1007/s10895-013-1222-x"
- Description: In this study, we have developed a novel nanoprobe for H2O2 based on the conjugation of CdTe@ZnS quantum dots (QDs) to different metal tetraamino-phthalocyanine (MTAPc): (M = (OAc)Al, {OAc = acetate}, Ni and Zn). Chemical coordination of the QDs to the MTAPc resulted in the fluorescence “switch off” of the linked QDs which was associated with Förster resonance energy transfer (FRET). In the presence of varying concentration of H2O2, the fluorescence of the linked QDs was progressively “switched on” and the FRET mechanism between the QDs and the MTAPc was disrupted. The sensitivity/limit of detection of the nanoprobe followed the order: QDs-ZnTAPc (2.2 μM) > QDs-NiTAPc (4.4 μM) > QDs-AlTAPc (9.8 μM) while the selectivity followed the order: QDs-NiTAPc > QDs-AlTAPc > QDs-ZnTAPc. The varying degree of sensitivity/selectivity and mechanism of detection is discussed in detail.
- Full Text:
- Date Issued: 2013
With or without you: stem-galling of a tephritid fly reduces the vegetative and reproductive performance of the invasive plant Chromolaena odorata (Asteraceae) both alone and in combination with another agent
- Aigbedion-Atalor, Pascal O, Day, Michael D, Itohan Idemudia, Wilson, David D, Paterson, Iain D
- Authors: Aigbedion-Atalor, Pascal O , Day, Michael D , Itohan Idemudia , Wilson, David D , Paterson, Iain D
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/418093 , vital:71508 , xlink:href="https://doi.org/10.1007/s10526-018-09917-x"
- Description: With or without another biological control agent, the specialist folivore Pareuchaetes pseudoinsulata, the stem-galling fly Cecidochares connexa reduced the performance of the invasive alien plant, Chromolaena odorata in Ghana. There was a strong significant negative relationship between gall densities of the gall fly and stem height, and the number of stems and flower heads of C. odorata. Pareuchaetes pseudoinsulata had very little impact on any C. odorata parameters. However, at sites where both C. connexa and P. pseudoinsulata occurred simultaneously, the performance of C. odorata was significantly reduced when compared with control plants. Increasing densities of both agents had a strong significant negative correlative effect on C. odorata plant parameters. Cecidochares connexa was recorded in all five regions of the country sampled, while P. pseudoinsulata was recorded in four regions. Densities of both agents declined in the dry season, but galls were persistent throughout the study period. This is the first report of the impact of C. connexa on C. odorata in the West African sub-region since its introduction to Cote d’Ivoire in 2003 and it is clear that the agent has a significant impact on C. odorata in Ghana. Further surveys are required to determine the impact of both biological control agents in other parts of the sub-region where they have established.
- Full Text:
- Date Issued: 2019
- Authors: Aigbedion-Atalor, Pascal O , Day, Michael D , Itohan Idemudia , Wilson, David D , Paterson, Iain D
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/418093 , vital:71508 , xlink:href="https://doi.org/10.1007/s10526-018-09917-x"
- Description: With or without another biological control agent, the specialist folivore Pareuchaetes pseudoinsulata, the stem-galling fly Cecidochares connexa reduced the performance of the invasive alien plant, Chromolaena odorata in Ghana. There was a strong significant negative relationship between gall densities of the gall fly and stem height, and the number of stems and flower heads of C. odorata. Pareuchaetes pseudoinsulata had very little impact on any C. odorata parameters. However, at sites where both C. connexa and P. pseudoinsulata occurred simultaneously, the performance of C. odorata was significantly reduced when compared with control plants. Increasing densities of both agents had a strong significant negative correlative effect on C. odorata plant parameters. Cecidochares connexa was recorded in all five regions of the country sampled, while P. pseudoinsulata was recorded in four regions. Densities of both agents declined in the dry season, but galls were persistent throughout the study period. This is the first report of the impact of C. connexa on C. odorata in the West African sub-region since its introduction to Cote d’Ivoire in 2003 and it is clear that the agent has a significant impact on C. odorata in Ghana. Further surveys are required to determine the impact of both biological control agents in other parts of the sub-region where they have established.
- Full Text:
- Date Issued: 2019
Fabrication and characterization of single walled carbon nanotubes-iron phthalocyanine nano-composite
- Akinbulu, Isaac A, Nyokong, Tebello
- Authors: Akinbulu, Isaac A , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/262622 , vital:53537 , xlink:href="https://doi.org/10.1039/C0NJ00395F"
- Description: Nano-composite of single walled carbon nanotubes (SWCNTs) and iron phthalocyanine, peripherally tetra-substituted with diethylaminoethanethiol (complex 2), was fabricated and characterized by infra red (IR) spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). TEM technique gave a convincing image of the nano-composite. Self-assembled monolayer (SAM) film of the composite (SWCNT-2-SAM) was formed on gold electrode. Its surface properties were investigated, relative to that of 2-SAM film, by cyclic voltammetry and scanning electron microscopy (SEM). Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry, using [Fe(CN)6]3− as redox probe, were used to investigate the dynamics of electron transport in the SWCNT-2-SAM film. Lower charge transfer resistance, RCT, of the SWCNT-2-SAM modified Au electrode, relative to that of the 2-SAM modified Au electrode, was an indication of enhanced electron transport in the presence of SWCNT. The SAM film of the nano-composite showed better electrocatalytic behaviour, relative to that of 2-SAM film, towards the oxidation of the insecticide, carbofuran. The electrode (SWCNT-2-SAM) showed good selectivity for carbofuran, in the presence of diazinon (a non-electroactive interferent) and at lower concentration of the electroactive interferents (chlorpyrifos and dichlorfos).
- Full Text:
- Date Issued: 2010
- Authors: Akinbulu, Isaac A , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/262622 , vital:53537 , xlink:href="https://doi.org/10.1039/C0NJ00395F"
- Description: Nano-composite of single walled carbon nanotubes (SWCNTs) and iron phthalocyanine, peripherally tetra-substituted with diethylaminoethanethiol (complex 2), was fabricated and characterized by infra red (IR) spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). TEM technique gave a convincing image of the nano-composite. Self-assembled monolayer (SAM) film of the composite (SWCNT-2-SAM) was formed on gold electrode. Its surface properties were investigated, relative to that of 2-SAM film, by cyclic voltammetry and scanning electron microscopy (SEM). Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry, using [Fe(CN)6]3− as redox probe, were used to investigate the dynamics of electron transport in the SWCNT-2-SAM film. Lower charge transfer resistance, RCT, of the SWCNT-2-SAM modified Au electrode, relative to that of the 2-SAM modified Au electrode, was an indication of enhanced electron transport in the presence of SWCNT. The SAM film of the nano-composite showed better electrocatalytic behaviour, relative to that of 2-SAM film, towards the oxidation of the insecticide, carbofuran. The electrode (SWCNT-2-SAM) showed good selectivity for carbofuran, in the presence of diazinon (a non-electroactive interferent) and at lower concentration of the electroactive interferents (chlorpyrifos and dichlorfos).
- Full Text:
- Date Issued: 2010
Comparative studies on photophysical and optical limiting characterizations of low symmetry phthalocyanine linked to Fe 3 O 4–Ag core–shell or hybrid nanoparticles
- Bankole, Owolabi M, Nyokong, Tebello
- Authors: Bankole, Owolabi M , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188788 , vital:44785 , xlink:href="https://doi.org/10.1039/C6NJ01511E"
- Description: Photophysical and nonlinear optical (NLO) behaviours of low symmetry zinc phthalocyanine (1) linked to Fe3O4/Ag core–shell (represented as Fe/Ag) or Fe3O4–Ag hybrid (represented as FeAg) nanoparticles were investigated in DMSO. Triplet quantum yields and NLO parameters of phthalocyanine improved due to the combined effects of magnetic–metallic nanoparticles. A direct relationship between the increased triplet excited state absorptions by already excited molecules and reverse saturable absorption (RSA) was established as the predominant mechanism responsible for nonlinearity of the samples. Our findings show that, at the same approximate concentrations and conditions, 1-FeAg enhanced the OL potentials of 1 more than 1-Fe/Ag.
- Full Text:
- Date Issued: 2016
- Authors: Bankole, Owolabi M , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188788 , vital:44785 , xlink:href="https://doi.org/10.1039/C6NJ01511E"
- Description: Photophysical and nonlinear optical (NLO) behaviours of low symmetry zinc phthalocyanine (1) linked to Fe3O4/Ag core–shell (represented as Fe/Ag) or Fe3O4–Ag hybrid (represented as FeAg) nanoparticles were investigated in DMSO. Triplet quantum yields and NLO parameters of phthalocyanine improved due to the combined effects of magnetic–metallic nanoparticles. A direct relationship between the increased triplet excited state absorptions by already excited molecules and reverse saturable absorption (RSA) was established as the predominant mechanism responsible for nonlinearity of the samples. Our findings show that, at the same approximate concentrations and conditions, 1-FeAg enhanced the OL potentials of 1 more than 1-Fe/Ag.
- Full Text:
- Date Issued: 2016
Azide-derivatized gold nanosphere “clicked” to indium and zinc phthalocyanines for improved nonlinear optical limiting
- Bankole, Owolabi M, Nyokong, Tebello
- Authors: Bankole, Owolabi M , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188249 , vital:44738 , xlink:href="https://doi.org/10.1016/j.molstruc.2017.01.088"
- Description: We report on the conjugation of azide-derivatized gold nanoparticles (AuNPs) to alkyne moieties of ZnPc and InPc via azide-alkyne Huisgen cycloaddition reaction to form phthalocyanines-AuNPs (MPc-AuNPs) conjugates. The detailed structural characterizations of the composites were in good agreement with the expected results. The nonlinear absorption coefficients and other nonlinear optical limiting parameters were almost two times larger for the conjugates compared to free phthalocyanines. We established direct relationship between improved photophysical characterizations and enhanced nonlinear effects of reverse saturable absorption mechanisms favoured by excited triplet absorption of the phthalocyanines in the presence of AuNPs. The combination of InPc with AuNPs resulted in the lowest limiting intensity value of 0.06 J/cm2, hence the best performance in terms of optical limiting.
- Full Text:
- Date Issued: 2017
- Authors: Bankole, Owolabi M , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188249 , vital:44738 , xlink:href="https://doi.org/10.1016/j.molstruc.2017.01.088"
- Description: We report on the conjugation of azide-derivatized gold nanoparticles (AuNPs) to alkyne moieties of ZnPc and InPc via azide-alkyne Huisgen cycloaddition reaction to form phthalocyanines-AuNPs (MPc-AuNPs) conjugates. The detailed structural characterizations of the composites were in good agreement with the expected results. The nonlinear absorption coefficients and other nonlinear optical limiting parameters were almost two times larger for the conjugates compared to free phthalocyanines. We established direct relationship between improved photophysical characterizations and enhanced nonlinear effects of reverse saturable absorption mechanisms favoured by excited triplet absorption of the phthalocyanines in the presence of AuNPs. The combination of InPc with AuNPs resulted in the lowest limiting intensity value of 0.06 J/cm2, hence the best performance in terms of optical limiting.
- Full Text:
- Date Issued: 2017
Enhanced nonlinear optical responses of zinc diaminopyrimidin-2-ylthio phthalocyanine conjugated to AgxAuy alloy nanoparticles
- Bankole, Owolabi M, Osifeko, Olawale, Nyokong, Tebello
- Authors: Bankole, Owolabi M , Osifeko, Olawale , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/240382 , vital:50829 , xlink:href="https://doi.org/10.1016/j.jphotochem.2016.06.025"
- Description: In this article, the photophysical and nonlinear optical (NLO) characterizations of diaminopyrimidin-2-ylthio phthalocyaninatozinc (II) (2) before and after conjugation to AgxAuy nano-alloys are discussed. Phthalocyanines-AgxAuy (2-AgxAuy) composites showed enhanced triplet state and nonlinear optical behaviour when compared to free phthalocyanine. Optical limiting (OL) responses of the samples were evaluated using Z-scan technique at 532 nm and 10 ns in dimethyl sulfoxide. Reverse saturable absorption (RSA), which is a direct consequence of triplet absorption of already excited molecules was observed as the dominant mechanism responsible for nonlinearity of the samples. By virtue of the magnitude of absorption coefficients and other NLO optical parameters estimated in this work, 2-AgxAuy composites were found to exhibit stronger optical limiting responses than unconjugated phthalocyanine. The large third-order susceptibilities of the composites make them suitable materials for attenuating modern laser radiations, and also found useful in various optical applications.
- Full Text:
- Date Issued: 2016
- Authors: Bankole, Owolabi M , Osifeko, Olawale , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/240382 , vital:50829 , xlink:href="https://doi.org/10.1016/j.jphotochem.2016.06.025"
- Description: In this article, the photophysical and nonlinear optical (NLO) characterizations of diaminopyrimidin-2-ylthio phthalocyaninatozinc (II) (2) before and after conjugation to AgxAuy nano-alloys are discussed. Phthalocyanines-AgxAuy (2-AgxAuy) composites showed enhanced triplet state and nonlinear optical behaviour when compared to free phthalocyanine. Optical limiting (OL) responses of the samples were evaluated using Z-scan technique at 532 nm and 10 ns in dimethyl sulfoxide. Reverse saturable absorption (RSA), which is a direct consequence of triplet absorption of already excited molecules was observed as the dominant mechanism responsible for nonlinearity of the samples. By virtue of the magnitude of absorption coefficients and other NLO optical parameters estimated in this work, 2-AgxAuy composites were found to exhibit stronger optical limiting responses than unconjugated phthalocyanine. The large third-order susceptibilities of the composites make them suitable materials for attenuating modern laser radiations, and also found useful in various optical applications.
- Full Text:
- Date Issued: 2016
Nonlinear interactions of zinc phthalocyanine-graphene quantum dots nanocomposites: Investigation of effects of surface functionalization with heteroatoms
- Bankole, Owolabi M, Achadu, Ojodomo J, Nyokong, Tebello
- Authors: Bankole, Owolabi M , Achadu, Ojodomo J , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188474 , vital:44757 , xlink:href="https://doi.org/10.1007/s10895-016-2008-8"
- Description: This study reports the development of functional optical limiting materials composed of pristine graphene (GQDs), nitrogen-doped (NGQDs) and sulfur-nitrogen co-doped (SNGQDs) graphene quantum dots covalently linked to mono-amino substituted zinc phthalocyanine (Pc). Open aperture Z-scan technique was employed to monitor the behaviour of the conjugates under tightly focussed Gaussian laser beam using a mode-locked Nd:YAG laser delivering 10 nanosecond (FWHM) pulses at 532 nm wavelength. Nonlinear effect due to reverse saturable absorption was the predominant mechanism; and was attributed to the moderately enhanced triplet population. The major factor(s) responsible for the enhanced nonlinearities in the Pc-NGQDs and Pc-SNGQDs was fully described and attributed to the surface defects caused by the presence of heteroatoms of N and S.
- Full Text:
- Date Issued: 2017
- Authors: Bankole, Owolabi M , Achadu, Ojodomo J , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188474 , vital:44757 , xlink:href="https://doi.org/10.1007/s10895-016-2008-8"
- Description: This study reports the development of functional optical limiting materials composed of pristine graphene (GQDs), nitrogen-doped (NGQDs) and sulfur-nitrogen co-doped (SNGQDs) graphene quantum dots covalently linked to mono-amino substituted zinc phthalocyanine (Pc). Open aperture Z-scan technique was employed to monitor the behaviour of the conjugates under tightly focussed Gaussian laser beam using a mode-locked Nd:YAG laser delivering 10 nanosecond (FWHM) pulses at 532 nm wavelength. Nonlinear effect due to reverse saturable absorption was the predominant mechanism; and was attributed to the moderately enhanced triplet population. The major factor(s) responsible for the enhanced nonlinearities in the Pc-NGQDs and Pc-SNGQDs was fully described and attributed to the surface defects caused by the presence of heteroatoms of N and S.
- Full Text:
- Date Issued: 2017
Third order nonlinear optical properties of phthalocyanines in the presence nanomaterials and in polymer thin films
- Britton, Jonathan, Durmus, Mahmut, Khene, Samson M, Chauke, Vongani, Nyokong, Tebello
- Authors: Britton, Jonathan , Durmus, Mahmut , Khene, Samson M , Chauke, Vongani , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241772 , vital:50968 , xlink:href="https://doi.org/10.1142/S108842461350003X"
- Description: Third order nonlinear optical properties were determined for phthalocyanine complexes 1–10 containing In, Ga and Zn central metals and tetra- or octa-substituted with benzyloxyphenoxy, phenoxy, tert-butylphenoxy and amino groups at peripheral or non-peripheral positions. The phthalocyanines were embedded in poly (methyl methacrylate) polymer in the presence of CdTe quantum dots. All complexes 1–10 were studied in the presence of CdTe quantum dots and embedded in poly (methyl methacrylate) to form thin films. Complex 3 tetrasubstituted with tert-butylphenoxy groups at non-peripheral positions was also studied in the presence of CdS, CdSe quantum dots, fullerenes, single walled carbon nanotubes. Third order nonlinear optical parameters generally increase for Pcs in the presence of CdTe quantum dots.
- Full Text:
- Date Issued: 2013
- Authors: Britton, Jonathan , Durmus, Mahmut , Khene, Samson M , Chauke, Vongani , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241772 , vital:50968 , xlink:href="https://doi.org/10.1142/S108842461350003X"
- Description: Third order nonlinear optical properties were determined for phthalocyanine complexes 1–10 containing In, Ga and Zn central metals and tetra- or octa-substituted with benzyloxyphenoxy, phenoxy, tert-butylphenoxy and amino groups at peripheral or non-peripheral positions. The phthalocyanines were embedded in poly (methyl methacrylate) polymer in the presence of CdTe quantum dots. All complexes 1–10 were studied in the presence of CdTe quantum dots and embedded in poly (methyl methacrylate) to form thin films. Complex 3 tetrasubstituted with tert-butylphenoxy groups at non-peripheral positions was also studied in the presence of CdS, CdSe quantum dots, fullerenes, single walled carbon nanotubes. Third order nonlinear optical parameters generally increase for Pcs in the presence of CdTe quantum dots.
- Full Text:
- Date Issued: 2013
Think Piece. Working for Living: Popular Education as/at Work for Social-ecological Justice
- Burt, Jane C, James, Anna, Walters, Shirley, Von Kotze, Astrid
- Authors: Burt, Jane C , James, Anna , Walters, Shirley , Von Kotze, Astrid
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/388150 , vital:68310 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/165826"
- Description: Drawing on the working lives of popular educators who are striving for socioeconomic and socio-ecological justice, we demonstrate how popular education is a form of care work which is feminised, often undervalued and unrecognised as highly skilled work. It is relational work that aims to forge solidarity with communities and the environment. Given the state of the planet, the radical transformations that are needed, and the future projection of ‘work’ as including the care economy in large measure, we argue that popular education is a generative site for further exploration of research into work and learning. However, to move popular education as work from the margins means to rethink the current economic system of value. Addressing the contradiction that undervalues work for life/living, popular education engages transformative action motivated by a deep sense of solidarity and a focus on imagining alternatives as an act of hope.
- Full Text:
- Date Issued: 2020
- Authors: Burt, Jane C , James, Anna , Walters, Shirley , Von Kotze, Astrid
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/388150 , vital:68310 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/165826"
- Description: Drawing on the working lives of popular educators who are striving for socioeconomic and socio-ecological justice, we demonstrate how popular education is a form of care work which is feminised, often undervalued and unrecognised as highly skilled work. It is relational work that aims to forge solidarity with communities and the environment. Given the state of the planet, the radical transformations that are needed, and the future projection of ‘work’ as including the care economy in large measure, we argue that popular education is a generative site for further exploration of research into work and learning. However, to move popular education as work from the margins means to rethink the current economic system of value. Addressing the contradiction that undervalues work for life/living, popular education engages transformative action motivated by a deep sense of solidarity and a focus on imagining alternatives as an act of hope.
- Full Text:
- Date Issued: 2020
The antibody assisted detection of HER2 on a cobalt porphyrin binuclear framework and gold functionalized graphene quantum dots modified electrode
- Centane, Sixole, Nyokong, Tebello
- Authors: Centane, Sixole , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185931 , vital:44449 , xlink:href="https://doi.org/10.1016/j.jelechem.2020.114908"
- Description: In this work a novel simple, inexpensive and highly sensitive approach for the antibody assisted detection of the human epidermal growth factor receptor 2 (HER2) is presented. Three sensors using carboxylic group containing gold functionalized graphene quantum dots (SNGQDs@AuNPs), CoP-BNF (cobalt porphyrin binuclear framework) and CoP-BNF/SNGQDs@AuNPs (the conjugate) nanocomposites on a GCE were designed. The sensors were fabricated by covalent immobilization of the antibody to the GCE via an amide bond. The modified GCE was characterized using cyclic voltammetry and impedance spectroscopy. The performance of the sensors was assessed using electrochemical impedance spectroscopy. The selective recognition of the antibody towards HER2 on the electrode led to an increase of the electron transfer resistance (Rct). The different modified electrodes had low detection limit values: 0.0327 ng/mL, 0.0454 ng/mL and 0.1072 ng/mL towards the detection of HER2. The sensors showed good stability and reproducibility. The sensors showed promising potential in clinical applicability, in the detection of HER2 protein in human serum.
- Full Text:
- Date Issued: 2021
- Authors: Centane, Sixole , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185931 , vital:44449 , xlink:href="https://doi.org/10.1016/j.jelechem.2020.114908"
- Description: In this work a novel simple, inexpensive and highly sensitive approach for the antibody assisted detection of the human epidermal growth factor receptor 2 (HER2) is presented. Three sensors using carboxylic group containing gold functionalized graphene quantum dots (SNGQDs@AuNPs), CoP-BNF (cobalt porphyrin binuclear framework) and CoP-BNF/SNGQDs@AuNPs (the conjugate) nanocomposites on a GCE were designed. The sensors were fabricated by covalent immobilization of the antibody to the GCE via an amide bond. The modified GCE was characterized using cyclic voltammetry and impedance spectroscopy. The performance of the sensors was assessed using electrochemical impedance spectroscopy. The selective recognition of the antibody towards HER2 on the electrode led to an increase of the electron transfer resistance (Rct). The different modified electrodes had low detection limit values: 0.0327 ng/mL, 0.0454 ng/mL and 0.1072 ng/mL towards the detection of HER2. The sensors showed good stability and reproducibility. The sensors showed promising potential in clinical applicability, in the detection of HER2 protein in human serum.
- Full Text:
- Date Issued: 2021
Aptamer versus antibody as probes for the impedimetric biosensor for human epidermal growth factor receptor
- Centane, Sixolile, Nyokong, Tebello
- Authors: Centane, Sixolile , Nyokong, Tebello
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229884 , vital:49720 , xlink:href="https://doi.org/10.1016/j.jinorgbio.2022.111764"
- Description: In the present work, the performance of aptamer and antibody bioreceptors for the detection of the human epidermal growth factor receptor (HER2) cancer biomarker on a glassy carbon electrode is reported. The carboxylic acid group rich graphene quantum dots (GQDs) modified with gold nanoparticles and a porphyrin binuclear framework (CoP-BNF) were used to modify the glassy carbon electrode. The aptamer and antibody were both amine functionalized and attached to GQDs and CoP-BNF through an amide bond. The designed immunosensors and aptasensors in this work were characterized using electrochemical impedance spectroscopy. The aptasensors, compared to the immunosensors gave better limit of detection values. The aptasensor outperforms the immunosensor in terms of its reusability and storability, while the immunosensor could not be regenerated for subsequent experiments. The potential applicability of all sensors in this work was also investigated, by detection of HER2 in spiked human serum with acceptable results.
- Full Text:
- Date Issued: 2022
- Authors: Centane, Sixolile , Nyokong, Tebello
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229884 , vital:49720 , xlink:href="https://doi.org/10.1016/j.jinorgbio.2022.111764"
- Description: In the present work, the performance of aptamer and antibody bioreceptors for the detection of the human epidermal growth factor receptor (HER2) cancer biomarker on a glassy carbon electrode is reported. The carboxylic acid group rich graphene quantum dots (GQDs) modified with gold nanoparticles and a porphyrin binuclear framework (CoP-BNF) were used to modify the glassy carbon electrode. The aptamer and antibody were both amine functionalized and attached to GQDs and CoP-BNF through an amide bond. The designed immunosensors and aptasensors in this work were characterized using electrochemical impedance spectroscopy. The aptasensors, compared to the immunosensors gave better limit of detection values. The aptasensor outperforms the immunosensor in terms of its reusability and storability, while the immunosensor could not be regenerated for subsequent experiments. The potential applicability of all sensors in this work was also investigated, by detection of HER2 in spiked human serum with acceptable results.
- Full Text:
- Date Issued: 2022
Co phthalocyanine mediated electrochemical detection of the HER2 in the presence of Au and CeO2 nanoparticles and graphene quantum dots
- Centane, Sixolile, Nyokong, Tebello
- Authors: Centane, Sixolile , Nyokong, Tebello
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/360372 , vital:65083 , xlink:href="https://doi.org/10.1016/j.bioelechem.2022.108301"
- Description: In this work, cobalt tetra phenoxy acetic acid phthalocyanine (CoTAPc) is investigated as an electron mediator, immobilization platform for an HB5 aptamer and to enhance the electrochemical signal for the detection of human epidermal growth factor receptor 2 (HER2). Furthermore, the CoTAPc was combined individually with sulphur/nitrogen doped graphene quantum dots (SNGQDs), gold nanoparticles (AuNPs) and cerium oxide nanoparticles (CeO2NPs), on a glassy carbon electrode (GCE) via sequential adsorption. The CoTAPc and SNGQDs were also π-π stacked, used for electrode modification similarly to the rest of the other surfaces and applied towards the electrochemical detection of HER2. The designed sensors were characterized using electrochemical impedance spectroscopy (EIS). The designed aptasensors showed detection limits as low as 6.0 pg/mL. The real life applicability of the designed aptasensors was tested in human serum samples. The aptasensors showed great storage stability, sensitivity and specificity towards HER2, implying great potential for applications in early diagnosis of breast cancer.
- Full Text:
- Date Issued: 2023
- Authors: Centane, Sixolile , Nyokong, Tebello
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/360372 , vital:65083 , xlink:href="https://doi.org/10.1016/j.bioelechem.2022.108301"
- Description: In this work, cobalt tetra phenoxy acetic acid phthalocyanine (CoTAPc) is investigated as an electron mediator, immobilization platform for an HB5 aptamer and to enhance the electrochemical signal for the detection of human epidermal growth factor receptor 2 (HER2). Furthermore, the CoTAPc was combined individually with sulphur/nitrogen doped graphene quantum dots (SNGQDs), gold nanoparticles (AuNPs) and cerium oxide nanoparticles (CeO2NPs), on a glassy carbon electrode (GCE) via sequential adsorption. The CoTAPc and SNGQDs were also π-π stacked, used for electrode modification similarly to the rest of the other surfaces and applied towards the electrochemical detection of HER2. The designed sensors were characterized using electrochemical impedance spectroscopy (EIS). The designed aptasensors showed detection limits as low as 6.0 pg/mL. The real life applicability of the designed aptasensors was tested in human serum samples. The aptasensors showed great storage stability, sensitivity and specificity towards HER2, implying great potential for applications in early diagnosis of breast cancer.
- Full Text:
- Date Issued: 2023
Use and users of municipal commonage around three small towns in the Eastern Cape, South Africa
- Davenport, Nicholas A, Shackleton, Charlie M, Gambiza, James
- Authors: Davenport, Nicholas A , Shackleton, Charlie M , Gambiza, James
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181116 , vital:43700 , xlink:href="https://doi.org/10.1016/j.jenvman.2010.11.003"
- Description: Municipal commonages surround many small towns throughout South Africa, and are an integral component of the national land reform programme. But little is known about their extent, use or value, and most appear to have limited or no management or investment. This paper reports on a survey of randomly selected households in three small towns in the Eastern Cape to ascertain the extent and purpose of use of municipal commonages. Between 27% and 70% of urban households used commonage depending on site. Key resources used were fuelwood, medicinal plants, and grazing of livestock. Typically, commonage using households were poorer and less educated than other urban residents, although the profile of users is unique for each town. Given the extensive use of commonage resources, and their contribution to the livelihoods of the poor, local municipalities need to develop and implement sound management strategies that account for all users of commonages, rather than the oft encountered focus on livestock owners and production.
- Full Text:
- Date Issued: 2011
- Authors: Davenport, Nicholas A , Shackleton, Charlie M , Gambiza, James
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181116 , vital:43700 , xlink:href="https://doi.org/10.1016/j.jenvman.2010.11.003"
- Description: Municipal commonages surround many small towns throughout South Africa, and are an integral component of the national land reform programme. But little is known about their extent, use or value, and most appear to have limited or no management or investment. This paper reports on a survey of randomly selected households in three small towns in the Eastern Cape to ascertain the extent and purpose of use of municipal commonages. Between 27% and 70% of urban households used commonage depending on site. Key resources used were fuelwood, medicinal plants, and grazing of livestock. Typically, commonage using households were poorer and less educated than other urban residents, although the profile of users is unique for each town. Given the extensive use of commonage resources, and their contribution to the livelihoods of the poor, local municipalities need to develop and implement sound management strategies that account for all users of commonages, rather than the oft encountered focus on livestock owners and production.
- Full Text:
- Date Issued: 2011
Knowledge of plant resource use based on location, gender and generation
- Dovie, Delali B K, Witkowski, Ed T F, Shackleton, Charlie M
- Authors: Dovie, Delali B K , Witkowski, Ed T F , Shackleton, Charlie M
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181202 , vital:43707 , xlink:href="https://doi.org/10.1016/j.apgeog.2008.07.002"
- Description: The differences in knowledge of biological resource use between societal and demographic groups are often poorly understood; yet they are an important element of sustainability. Differences in gender and generational knowledge of locally useful woody plant species in South African savannas are examined. The results showed that young people and middle-aged females were highly knowledgeable. Over half of the total 267 woody plant species in nine use categories (i.e., medicinal, fruits–seeds, fuelwood, beverage, cultural, furniture, craft, fencing and housing poles) had multiple uses. Therefore, differences in knowledge of resource selection and use between social or demographic groups (for example based on gender and age) may appropriately inform conservation prioritisation, planning and monitoring.
- Full Text:
- Date Issued: 2008
- Authors: Dovie, Delali B K , Witkowski, Ed T F , Shackleton, Charlie M
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181202 , vital:43707 , xlink:href="https://doi.org/10.1016/j.apgeog.2008.07.002"
- Description: The differences in knowledge of biological resource use between societal and demographic groups are often poorly understood; yet they are an important element of sustainability. Differences in gender and generational knowledge of locally useful woody plant species in South African savannas are examined. The results showed that young people and middle-aged females were highly knowledgeable. Over half of the total 267 woody plant species in nine use categories (i.e., medicinal, fruits–seeds, fuelwood, beverage, cultural, furniture, craft, fencing and housing poles) had multiple uses. Therefore, differences in knowledge of resource selection and use between social or demographic groups (for example based on gender and age) may appropriately inform conservation prioritisation, planning and monitoring.
- Full Text:
- Date Issued: 2008
A gold–chitosan composite with low symmetry zinc phthalocyanine for enhanced singlet oxygen generation and improved photodynamic therapy activity
- Dube, Edith, Oluwole, David O, Prinsloo, Earl, Nyokong, Tebello
- Authors: Dube, Edith , Oluwole, David O , Prinsloo, Earl , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233397 , vital:50087 , xlink:href="https://doi.org/10.1039/C8NJ00801A"
- Description: Novel zinc(II) 3-(4-((3,17,23-tris(4-(benzo[d]thiazol-2-yl)phenoxy)phthalocyanine-9-yl)oxy)phenyl)propanoic acid (complex 3) was synthesised. Complex 3 was subsequently reacted with gold nanoparticles (AuNPs), chitosan (CT) and a gold–chitosan (AuCT) hybrid to form 3-AuNPs, 3-CT and 3-AuCT, respectively. The conjugates afforded a decrease in fluorescence quantum yield with a corresponding increase in the triplet and singlet quantum yields compared to complex 3. The in vitro dark cytotoxicity and photodynamic therapy activity (PDT) of complex 3 and 3-AuCT composites were investigated against epithelial breast cancer cells (MCF-7) with both the samples showing minimum dark cytotoxicity. They both accounted for a cell viability of ≥90% at a concentration of ≤59.2 μg mL−1. 3-AuCT showed better PDT activity (compared to 3 alone) with less than 50% viable cells at a concentration of ≥29.6 μg mL−1 making it potentially applicable for PDT. On the other hand, AuCT displayed some activity against cancer cells, probably due to photothermal activity since gold is a light absorber, however it had more than 50% viable cells at a concentration of ≤59.2 μg mL−1.
- Full Text:
- Date Issued: 2018
- Authors: Dube, Edith , Oluwole, David O , Prinsloo, Earl , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233397 , vital:50087 , xlink:href="https://doi.org/10.1039/C8NJ00801A"
- Description: Novel zinc(II) 3-(4-((3,17,23-tris(4-(benzo[d]thiazol-2-yl)phenoxy)phthalocyanine-9-yl)oxy)phenyl)propanoic acid (complex 3) was synthesised. Complex 3 was subsequently reacted with gold nanoparticles (AuNPs), chitosan (CT) and a gold–chitosan (AuCT) hybrid to form 3-AuNPs, 3-CT and 3-AuCT, respectively. The conjugates afforded a decrease in fluorescence quantum yield with a corresponding increase in the triplet and singlet quantum yields compared to complex 3. The in vitro dark cytotoxicity and photodynamic therapy activity (PDT) of complex 3 and 3-AuCT composites were investigated against epithelial breast cancer cells (MCF-7) with both the samples showing minimum dark cytotoxicity. They both accounted for a cell viability of ≥90% at a concentration of ≤59.2 μg mL−1. 3-AuCT showed better PDT activity (compared to 3 alone) with less than 50% viable cells at a concentration of ≥29.6 μg mL−1 making it potentially applicable for PDT. On the other hand, AuCT displayed some activity against cancer cells, probably due to photothermal activity since gold is a light absorber, however it had more than 50% viable cells at a concentration of ≤59.2 μg mL−1.
- Full Text:
- Date Issued: 2018
Characterization of porphyrin nanorods on fluorine doped tin oxide glass sheet
- George, Reama C, Falgenhauer, Jane, Geis, Clemens, Nyokong, Tebello, Schlettwein, Derck
- Authors: George, Reama C , Falgenhauer, Jane , Geis, Clemens , Nyokong, Tebello , Schlettwein, Derck
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193542 , vital:45344 , xlink:href="https://doi.org/10.1142/S1088424615500923"
- Description: Porphyrin nanorods (PNR) have been fabricated by electrostatic self-assembly of two oppositely charged porphyrin molecules. The free base meso-tetra-(4-phenylsulphonate) porphyrin (TPPS4)4) served as negatively charged counterpart for the positively charged metallo meso-tetra(4-NN-methylpyridyl) porphyrins (MTM’PyP) with either Sn, Co, Mn or In as central metal M. Films of PNR were prepared on fluorine doped tin oxide glass sheets (FTO) by using a drop-dry method. The electronic spectra revealed J-aggregation of the charged molecules for the colloid PNR as well as for the films. Transmission electron microscopy confirmed the formation of porphyrin nanorods. The laser microscope and scanning electron microscope (SEM) images of the PNR/FTO films showed the formation of three kinds of structures in the films which consist of differently branched or linear needles with their main axis grown in the direction of the solvent flow during preparation. During cyclic voltammetry either applying negative potentials from 0.0 V to -1.0 V or positive potentials from 0.0 V to ++2.2 V irreversible reduction or oxidation reactions were detected for the films. Consistently, SEM images taken following cyclic voltammetry showed the disintegration of the PNR on the films into smaller subunits. Spectroelectrochemical measurements showed the formation of porphyrin anionic radicals during oxidation by a decrease in the absorption intensities and broadening of spectra with an additional band appearing around 900 nm. A similar trend was observed when negative potentials were applied but in this case the cationic radical was produced. In both cases the decrease of the intensity of the J-aggregate confirms a loss of intermolecular coupling, again consistent with the smaller subunits observed in SEM analysis.
- Full Text:
- Date Issued: 2015
- Authors: George, Reama C , Falgenhauer, Jane , Geis, Clemens , Nyokong, Tebello , Schlettwein, Derck
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193542 , vital:45344 , xlink:href="https://doi.org/10.1142/S1088424615500923"
- Description: Porphyrin nanorods (PNR) have been fabricated by electrostatic self-assembly of two oppositely charged porphyrin molecules. The free base meso-tetra-(4-phenylsulphonate) porphyrin (TPPS4)4) served as negatively charged counterpart for the positively charged metallo meso-tetra(4-NN-methylpyridyl) porphyrins (MTM’PyP) with either Sn, Co, Mn or In as central metal M. Films of PNR were prepared on fluorine doped tin oxide glass sheets (FTO) by using a drop-dry method. The electronic spectra revealed J-aggregation of the charged molecules for the colloid PNR as well as for the films. Transmission electron microscopy confirmed the formation of porphyrin nanorods. The laser microscope and scanning electron microscope (SEM) images of the PNR/FTO films showed the formation of three kinds of structures in the films which consist of differently branched or linear needles with their main axis grown in the direction of the solvent flow during preparation. During cyclic voltammetry either applying negative potentials from 0.0 V to -1.0 V or positive potentials from 0.0 V to ++2.2 V irreversible reduction or oxidation reactions were detected for the films. Consistently, SEM images taken following cyclic voltammetry showed the disintegration of the PNR on the films into smaller subunits. Spectroelectrochemical measurements showed the formation of porphyrin anionic radicals during oxidation by a decrease in the absorption intensities and broadening of spectra with an additional band appearing around 900 nm. A similar trend was observed when negative potentials were applied but in this case the cationic radical was produced. In both cases the decrease of the intensity of the J-aggregate confirms a loss of intermolecular coupling, again consistent with the smaller subunits observed in SEM analysis.
- Full Text:
- Date Issued: 2015
Abundance and correlates of the Acacia dealbata invasion in the northern Eastern Cape, South Africa
- Gouws, Aidan J, Shackleton, Charlie M
- Authors: Gouws, Aidan J , Shackleton, Charlie M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/179735 , vital:43165 , xlink:href="https://doi.org/10.1016/j.foreco.2018.09.048"
- Description: An increase in the density and biomass of woody invasive plants contributes to the intensification of ecological impacts and can often be met with dissatisfaction by local communities. Despite their reliance on Acacia dealbata as a source of livelihood, villagers in the northern Eastern Cape have expressed concerns about the high densities of the species. This study sought to quantify the current abundance and growth of A. dealbata in selected landscapes in the northern Eastern Cape, around nine villages in rural Matatiele, Mount Fletcher and Maclear. Standard vegetation survey techniques were adopted to quantify the density, biomass and growth rate of A. dealbata. Overall, the average density, biomass and productivity of A. dealbata were estimated at approximately 7000 stems ha−1, 12 Mg ha−1 and 4 Mg ha−1 year−1, respectively. However, the abundance and productivity of A. dealbata were spatially variable between study areas. Acacia dealbata stems experienced significant growth over the period of a single year, contributing to substantial biomass production at the landscape level, despite continued harvest. Furthermore, relatively few biophysical variables were significantly influential correlates with the abundance of A. dealbata. Indeed, the degree of biological invasion can be highly variable across the landscape, shaped by the interaction of local-scale biophysical conditions.
- Full Text:
- Date Issued: 2019
- Authors: Gouws, Aidan J , Shackleton, Charlie M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/179735 , vital:43165 , xlink:href="https://doi.org/10.1016/j.foreco.2018.09.048"
- Description: An increase in the density and biomass of woody invasive plants contributes to the intensification of ecological impacts and can often be met with dissatisfaction by local communities. Despite their reliance on Acacia dealbata as a source of livelihood, villagers in the northern Eastern Cape have expressed concerns about the high densities of the species. This study sought to quantify the current abundance and growth of A. dealbata in selected landscapes in the northern Eastern Cape, around nine villages in rural Matatiele, Mount Fletcher and Maclear. Standard vegetation survey techniques were adopted to quantify the density, biomass and growth rate of A. dealbata. Overall, the average density, biomass and productivity of A. dealbata were estimated at approximately 7000 stems ha−1, 12 Mg ha−1 and 4 Mg ha−1 year−1, respectively. However, the abundance and productivity of A. dealbata were spatially variable between study areas. Acacia dealbata stems experienced significant growth over the period of a single year, contributing to substantial biomass production at the landscape level, despite continued harvest. Furthermore, relatively few biophysical variables were significantly influential correlates with the abundance of A. dealbata. Indeed, the degree of biological invasion can be highly variable across the landscape, shaped by the interaction of local-scale biophysical conditions.
- Full Text:
- Date Issued: 2019