Reaction of Perrhenate with Phthalocyanine Derivatives in the Presence of Reducing Agents and Rhenium Oxide Nanoparticles in Biomedical Applications
- Ntsimango, Songeziwe, Gandidzanwa, Sendibitiyosi, Joseph, Sinelizwi V, Hosten, Eric C, Randall, Marvin, Edkins, Adrienne L, Khene, Samson M, Mashazi, Philani N, Nyokong, Tebello, Abrahams, Abubak’r, Tshentu, Zenixole R
- Authors: Ntsimango, Songeziwe , Gandidzanwa, Sendibitiyosi , Joseph, Sinelizwi V , Hosten, Eric C , Randall, Marvin , Edkins, Adrienne L , Khene, Samson M , Mashazi, Philani N , Nyokong, Tebello , Abrahams, Abubak’r , Tshentu, Zenixole R
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/300257 , vital:57910 , xlink:href="https://doi.org/10.1002/open.202200037"
- Description: A novel alternative route to access rhenium(V)−phthalocyanine complexes through direct metalation of metal-free phthalocyanines (H2Pcs) with a rhenium(VII) salt in the presence of various two-electron reducing agents is presented. Direct ion metalation of tetraamino- or tetranitrophthalocyanine with perrhenate (ReO4−) in the presence of triphenylphosphine led to oxidative decomposition of the H2Pcs, giving their respective phthalonitriles. Conversely, treatment of H2Pcs with ReO4− employing sodium metabisulfite yielded the desired ReVO−Pc complex. Finally, reaction of H2Pcs with ReO4− and NaBH4 as reducing agent led to the formation of rhenium oxide (RexOy) nanoparticles (NPs). The NP synthesis was optimised, and the RexOy NPs were capped with folic acid (FA) conjugated with tetraaminophthalocyanine (TAPc) to enhance their cancer cell targeting ability. The cytotoxicity profile of the resultant RexOy−TAPc−FA NPs was assessed and found to be greater than 80 % viability in four cell lines, namely, MDA−MB-231, HCC7, HCC1806 and HEK293T. Non-cytotoxic concentrations were determined and employed in cancer cell localization studies. The particle size effect on localization of NPs was also investigated using confocal fluorescence and transmission electron microscopy. The smaller NPs (≈10 nm) were found to exhibit stronger fluorescence properties than the ≈50 nm NPs and exhibited better cell localization ability than the ≈50 nm NPs.
- Full Text:
- Date Issued: 2022
- Authors: Ntsimango, Songeziwe , Gandidzanwa, Sendibitiyosi , Joseph, Sinelizwi V , Hosten, Eric C , Randall, Marvin , Edkins, Adrienne L , Khene, Samson M , Mashazi, Philani N , Nyokong, Tebello , Abrahams, Abubak’r , Tshentu, Zenixole R
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/300257 , vital:57910 , xlink:href="https://doi.org/10.1002/open.202200037"
- Description: A novel alternative route to access rhenium(V)−phthalocyanine complexes through direct metalation of metal-free phthalocyanines (H2Pcs) with a rhenium(VII) salt in the presence of various two-electron reducing agents is presented. Direct ion metalation of tetraamino- or tetranitrophthalocyanine with perrhenate (ReO4−) in the presence of triphenylphosphine led to oxidative decomposition of the H2Pcs, giving their respective phthalonitriles. Conversely, treatment of H2Pcs with ReO4− employing sodium metabisulfite yielded the desired ReVO−Pc complex. Finally, reaction of H2Pcs with ReO4− and NaBH4 as reducing agent led to the formation of rhenium oxide (RexOy) nanoparticles (NPs). The NP synthesis was optimised, and the RexOy NPs were capped with folic acid (FA) conjugated with tetraaminophthalocyanine (TAPc) to enhance their cancer cell targeting ability. The cytotoxicity profile of the resultant RexOy−TAPc−FA NPs was assessed and found to be greater than 80 % viability in four cell lines, namely, MDA−MB-231, HCC7, HCC1806 and HEK293T. Non-cytotoxic concentrations were determined and employed in cancer cell localization studies. The particle size effect on localization of NPs was also investigated using confocal fluorescence and transmission electron microscopy. The smaller NPs (≈10 nm) were found to exhibit stronger fluorescence properties than the ≈50 nm NPs and exhibited better cell localization ability than the ≈50 nm NPs.
- Full Text:
- Date Issued: 2022
Synthesis, photophysics and photochemistry of phthalocyanine-ɛ-polylysine conjugates in the presence of metal nanoparticles against Staphylococcus aureus
- Nombona, Nolwazi, Antunes, Edith M, Chidawanyika, Wadzanai J U, Kleyi, Phumelele, Tshentu, Zenixole R, Nyokong, Tebello
- Authors: Nombona, Nolwazi , Antunes, Edith M , Chidawanyika, Wadzanai J U , Kleyi, Phumelele , Tshentu, Zenixole R , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244439 , vital:51257 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.02.040"
- Description: This work reports on the photodynamic activity of Zn phthalocyanine-ɛ-polylysine conjugates in the presence of gold and silver nanoparticles (NPs) towards the inactivation of Staphylococcus aureus (S. aureus). The conjugates showed high photoinactivation with ∼6% growth at a drug dose of 3 μM and fluence of 39.6 mW/cm2 for 10 min irradiation time in the presence of silver nanoparticles. The presence of silver nanoparticels from the minimal inhibition concentration (MIC50) studies showed remarkable growth inhibition for the tested conjugates even at low concentrations. The MIC50 was lowest for the conjugate of 3 with ɛ-polylysine at concentrations of less than 0.0058 μM in the presence of AgNPs. The lethal photosensitization of microorganisms has emerged as a promising treatment since bacteria have reduced possibilities of developing resistance to photodynamic therapy.
- Full Text:
- Date Issued: 2015
- Authors: Nombona, Nolwazi , Antunes, Edith M , Chidawanyika, Wadzanai J U , Kleyi, Phumelele , Tshentu, Zenixole R , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244439 , vital:51257 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.02.040"
- Description: This work reports on the photodynamic activity of Zn phthalocyanine-ɛ-polylysine conjugates in the presence of gold and silver nanoparticles (NPs) towards the inactivation of Staphylococcus aureus (S. aureus). The conjugates showed high photoinactivation with ∼6% growth at a drug dose of 3 μM and fluence of 39.6 mW/cm2 for 10 min irradiation time in the presence of silver nanoparticles. The presence of silver nanoparticels from the minimal inhibition concentration (MIC50) studies showed remarkable growth inhibition for the tested conjugates even at low concentrations. The MIC50 was lowest for the conjugate of 3 with ɛ-polylysine at concentrations of less than 0.0058 μM in the presence of AgNPs. The lethal photosensitization of microorganisms has emerged as a promising treatment since bacteria have reduced possibilities of developing resistance to photodynamic therapy.
- Full Text:
- Date Issued: 2015
The development of palladium (II)-specific amine-functionalized silica-based microparticles
- Fayemi, Omolola E, Ogunlaja, Adeniyi S, Antunes, Edith M, Nyokong, Tebello, Tshentu, Zenixole R
- Authors: Fayemi, Omolola E , Ogunlaja, Adeniyi S , Antunes, Edith M , Nyokong, Tebello , Tshentu, Zenixole R
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241083 , vital:50903 , xlink:href="https://doi.org/10.1080/01496395.2014.978017"
- Description: The adsorption and separation of platinum(IV) and palladium(II) chlorido species ([PtCl6]2− and [PdCl4]2−) on silica-based microparticles functionalized with ammonium centers based on ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetriamine (TETA) and tris-(2-aminoethyl)amine (TAEA) were investigated. The functionalized sorbent materials were characterized using SEM, XPS, BET, and FTIR. The sorbents were used in the batch and column study for adsorption and selective separation of [PtCl62− and PdCl4]2−. The adsorption model for both [PtCl6]2− and [PdCl4]2− on the different sorbent materials fitted the Freundlich isotherm with R2 values > 0.99. The S-TETA sorbent material was palladium(II) specific. Pd(II) loaded on the silica column was recovered using 3% m/v thiourea solution as the eluting agent. Separation of platinum and palladium was achieved by selective stripping of [PtCl6]2− with 0.5 M of NaClO4 in 1.0 M HCl while Pd(II) was eluted with 0.5 M thiourea in 1.0 M HCl. The separation of palladium (Pd) from a mixture containing platinum (Pt), iridium (Ir), and rhodium (Rh) was successful on silica functionalized with triethylenetriamine (TETA) showing specificity for palladium(II) and a loading capacity of 0.27 mg/g. S-TETA showed potential for use in the recovery of palladium from platinum group metals such as from solutions of worn out automobile emission control catalytic convertors and other secondary sources.
- Full Text:
- Date Issued: 2015
- Authors: Fayemi, Omolola E , Ogunlaja, Adeniyi S , Antunes, Edith M , Nyokong, Tebello , Tshentu, Zenixole R
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241083 , vital:50903 , xlink:href="https://doi.org/10.1080/01496395.2014.978017"
- Description: The adsorption and separation of platinum(IV) and palladium(II) chlorido species ([PtCl6]2− and [PdCl4]2−) on silica-based microparticles functionalized with ammonium centers based on ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetriamine (TETA) and tris-(2-aminoethyl)amine (TAEA) were investigated. The functionalized sorbent materials were characterized using SEM, XPS, BET, and FTIR. The sorbents were used in the batch and column study for adsorption and selective separation of [PtCl62− and PdCl4]2−. The adsorption model for both [PtCl6]2− and [PdCl4]2− on the different sorbent materials fitted the Freundlich isotherm with R2 values > 0.99. The S-TETA sorbent material was palladium(II) specific. Pd(II) loaded on the silica column was recovered using 3% m/v thiourea solution as the eluting agent. Separation of platinum and palladium was achieved by selective stripping of [PtCl6]2− with 0.5 M of NaClO4 in 1.0 M HCl while Pd(II) was eluted with 0.5 M thiourea in 1.0 M HCl. The separation of palladium (Pd) from a mixture containing platinum (Pt), iridium (Ir), and rhodium (Rh) was successful on silica functionalized with triethylenetriamine (TETA) showing specificity for palladium(II) and a loading capacity of 0.27 mg/g. S-TETA showed potential for use in the recovery of palladium from platinum group metals such as from solutions of worn out automobile emission control catalytic convertors and other secondary sources.
- Full Text:
- Date Issued: 2015
The development of Palladium(II)-specific amine-functionalized silica-based microparticles : adsorption and column separation studies
- Fayemi, Omolola E, Ogunlaja, Adeniyi S, Antunes, Edith M, Nyokong, Tebello, Tshentu, Zenixole R
- Authors: Fayemi, Omolola E , Ogunlaja, Adeniyi S , Antunes, Edith M , Nyokong, Tebello , Tshentu, Zenixole R
- Date: 2015
- Language: English
- Type: Article
- Identifier: vital:7270 , http://hdl.handle.net/10962/d1020285
- Description: The adsorption and separation of platinum(IV) and palladium(II) chlorido species ([PtCl6]2− and [PdCl4]2−) on silica-based microparticles functionalized with ammonium centers based on ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetriamine (TETA) and tris-(2-aminoethyl)amine (TAEA) were investigated. The functionalized sorbent materials were characterized using SEM, XPS, BET, and FTIR. The sorbents were used in the batch and column study for adsorption and selective separation of [PtCl62− and PdCl4]2−. The adsorption model for both [PtCl6]2− and [PdCl4]2− on the different sorbent materials fitted the Freundlich isotherm with R2 values > 0.99. The S-TETA sorbent material was palladium(II) specific. Pd(II) loaded on the silica column was recovered using 3% m/v thiourea solution as the eluting agent. Separation of platinum and palladium was achieved by selective stripping of [PtCl6]2− with 0.5 M of NaClO4 in 1.0 M HCl while Pd(II) was eluted with 0.5 M thiourea in 1.0 M HCl. The separation of palladium (Pd) from a mixture containing platinum (Pt), iridium (Ir), and rhodium (Rh) was successful on silica functionalized with triethylenetriamine (TETA) showing specificity for palladium(II) and a loading capacity of 0.27 mg/g. S-TETA showed potential for use in the recovery of palladium from platinum group metals such as from solutions of worn out automobile emission control catalytic convertors and other secondary sources. , Original publication is available at http://dx.doi.org/10.1080/01496395.2014.978017
- Full Text: false
- Date Issued: 2015
- Authors: Fayemi, Omolola E , Ogunlaja, Adeniyi S , Antunes, Edith M , Nyokong, Tebello , Tshentu, Zenixole R
- Date: 2015
- Language: English
- Type: Article
- Identifier: vital:7270 , http://hdl.handle.net/10962/d1020285
- Description: The adsorption and separation of platinum(IV) and palladium(II) chlorido species ([PtCl6]2− and [PdCl4]2−) on silica-based microparticles functionalized with ammonium centers based on ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetriamine (TETA) and tris-(2-aminoethyl)amine (TAEA) were investigated. The functionalized sorbent materials were characterized using SEM, XPS, BET, and FTIR. The sorbents were used in the batch and column study for adsorption and selective separation of [PtCl62− and PdCl4]2−. The adsorption model for both [PtCl6]2− and [PdCl4]2− on the different sorbent materials fitted the Freundlich isotherm with R2 values > 0.99. The S-TETA sorbent material was palladium(II) specific. Pd(II) loaded on the silica column was recovered using 3% m/v thiourea solution as the eluting agent. Separation of platinum and palladium was achieved by selective stripping of [PtCl6]2− with 0.5 M of NaClO4 in 1.0 M HCl while Pd(II) was eluted with 0.5 M thiourea in 1.0 M HCl. The separation of palladium (Pd) from a mixture containing platinum (Pt), iridium (Ir), and rhodium (Rh) was successful on silica functionalized with triethylenetriamine (TETA) showing specificity for palladium(II) and a loading capacity of 0.27 mg/g. S-TETA showed potential for use in the recovery of palladium from platinum group metals such as from solutions of worn out automobile emission control catalytic convertors and other secondary sources. , Original publication is available at http://dx.doi.org/10.1080/01496395.2014.978017
- Full Text: false
- Date Issued: 2015
The Development of Palladium(II)-Specific Amine-Functionalized Silica-Based Microparticles: Adsorption and Column Separation Studies
- Fayemi, Omolola E, Ogunlaja, Adeniyi S, Antunes, Edith M, Nyokong, Tebello, Tshentu, Zenixole R
- Authors: Fayemi, Omolola E , Ogunlaja, Adeniyi S , Antunes, Edith M , Nyokong, Tebello , Tshentu, Zenixole R
- Date: 2015
- Language: English
- Type: Article
- Identifier: vital:7269 , http://hdl.handle.net/10962/d1020278
- Description: The adsorption and separation of platinum(IV) and palladium(II) chlorido species ([PtCl6]2− and [PdCl4]2−) on silica-based microparticles functionalized with ammonium centers based on ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetriamine (TETA) and tris-(2-aminoethyl)amine (TAEA) were investigated. The functionalized sorbent materials were characterized using SEM, XPS, BET, and FTIR. The sorbents were used in the batch and column study for adsorption and selective separation of [PtCl62− and PdCl4]2−. The adsorption model for both [PtCl6]2− and [PdCl4]2− on the different sorbent materials fitted the Freundlich isotherm with R2 values > 0.99. The S-TETA sorbent material was palladium(II) specific. Pd(II) loaded on the silica column was recovered using 3% m/v thiourea solution as the eluting agent. Separation of platinum and palladium was achieved by selective stripping of [PtCl6]2− with 0.5 M of NaClO4 in 1.0 M HCl while Pd(II) was eluted with 0.5 M thiourea in 1.0 M HCl. The separation of palladium (Pd) from a mixture containing platinum (Pt), iridium (Ir), and rhodium (Rh) was successful on silica functionalized with triethylenetriamine (TETA) showing specificity for palladium(II) and a loading capacity of 0.27 mg/g. S-TETA showed potential for use in the recovery of palladium from platinum group metals such as from solutions of worn out automobile emission control catalytic convertors and other secondary sources. , Original publication is available at http://dx.doi.org/10.1080/01496395.2014.978017
- Full Text: false
- Date Issued: 2015
- Authors: Fayemi, Omolola E , Ogunlaja, Adeniyi S , Antunes, Edith M , Nyokong, Tebello , Tshentu, Zenixole R
- Date: 2015
- Language: English
- Type: Article
- Identifier: vital:7269 , http://hdl.handle.net/10962/d1020278
- Description: The adsorption and separation of platinum(IV) and palladium(II) chlorido species ([PtCl6]2− and [PdCl4]2−) on silica-based microparticles functionalized with ammonium centers based on ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetriamine (TETA) and tris-(2-aminoethyl)amine (TAEA) were investigated. The functionalized sorbent materials were characterized using SEM, XPS, BET, and FTIR. The sorbents were used in the batch and column study for adsorption and selective separation of [PtCl62− and PdCl4]2−. The adsorption model for both [PtCl6]2− and [PdCl4]2− on the different sorbent materials fitted the Freundlich isotherm with R2 values > 0.99. The S-TETA sorbent material was palladium(II) specific. Pd(II) loaded on the silica column was recovered using 3% m/v thiourea solution as the eluting agent. Separation of platinum and palladium was achieved by selective stripping of [PtCl6]2− with 0.5 M of NaClO4 in 1.0 M HCl while Pd(II) was eluted with 0.5 M thiourea in 1.0 M HCl. The separation of palladium (Pd) from a mixture containing platinum (Pt), iridium (Ir), and rhodium (Rh) was successful on silica functionalized with triethylenetriamine (TETA) showing specificity for palladium(II) and a loading capacity of 0.27 mg/g. S-TETA showed potential for use in the recovery of palladium from platinum group metals such as from solutions of worn out automobile emission control catalytic convertors and other secondary sources. , Original publication is available at http://dx.doi.org/10.1080/01496395.2014.978017
- Full Text: false
- Date Issued: 2015
Adsorption and separation of platinum and palladium by polyamine functionalized polystyrene-based beads and nanofibers
- Fayemi, Omolola E, Ogunlaja, Adeniyi S, Kempgens, Pierre F M, Antunes, Edith M, Torto, Nelson, Nyokong, Tebello, Tshentu, Zenixole R
- Authors: Fayemi, Omolola E , Ogunlaja, Adeniyi S , Kempgens, Pierre F M , Antunes, Edith M , Torto, Nelson , Nyokong, Tebello , Tshentu, Zenixole R
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241694 , vital:50961 , xlink:href="https://doi.org/10.1016/j.mineng.2013.06.006"
- Description: Adsorption and separation of platinum and palladium chlorido species (PtCl62- and PdCl42-) on polystyrene beads as well as nanofibers functionalized with ammonium centres based on ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA) and tris-(2-aminoethyl)amine (TAEA) are described. The functionalized sorbent materials were characterized by microanalysis, SEM, XPS, BET and FTIR. The surface area of the functionalized fibers was in the range 69–241 m2/g while it was 73–107 m2/g for the beads. The adsorption and loading capacities of the sorption materials were investigated using both the batch and column studies at 1 M HCl concentration. The adsorption studies for both PtCl62- and PdCl42- on the different sorbent materials fit the Langmuir isotherm with R2 values >0.99. The highest loading capacity of Pt and Pd were 7.4 mg/g and 4.3 mg/g respectively for the nanofiber sorbent material based on ethylenediamine (EDA) while the beads with ethylenediamine (EDA) gave 1.0 mg/g and 0.2 mg/g for Pt and Pd respectively. Metals loaded on the sorbent materials were recovered by using 3% m/v thiourea solution as the eluting agent with quantitative desorption efficiency under the selected experimental conditions. Separation of platinum from palladium was partially achieved by selective stripping of PtCl62- with 0.5 M of NaClO4 in 1.0 M HCl while PdCl42- was eluted with 0.5 M thiourea in 1.0 M HCl. Separation of platinum from iridium and rhodium under 1 M HCl concentration was successful on triethylenetriamine (TETA)-functionalized Merrifield beads. This material (M-TETA) showed selectivity for platinum albeit the low loading capacity.
- Full Text:
- Date Issued: 2013
- Authors: Fayemi, Omolola E , Ogunlaja, Adeniyi S , Kempgens, Pierre F M , Antunes, Edith M , Torto, Nelson , Nyokong, Tebello , Tshentu, Zenixole R
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241694 , vital:50961 , xlink:href="https://doi.org/10.1016/j.mineng.2013.06.006"
- Description: Adsorption and separation of platinum and palladium chlorido species (PtCl62- and PdCl42-) on polystyrene beads as well as nanofibers functionalized with ammonium centres based on ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA) and tris-(2-aminoethyl)amine (TAEA) are described. The functionalized sorbent materials were characterized by microanalysis, SEM, XPS, BET and FTIR. The surface area of the functionalized fibers was in the range 69–241 m2/g while it was 73–107 m2/g for the beads. The adsorption and loading capacities of the sorption materials were investigated using both the batch and column studies at 1 M HCl concentration. The adsorption studies for both PtCl62- and PdCl42- on the different sorbent materials fit the Langmuir isotherm with R2 values >0.99. The highest loading capacity of Pt and Pd were 7.4 mg/g and 4.3 mg/g respectively for the nanofiber sorbent material based on ethylenediamine (EDA) while the beads with ethylenediamine (EDA) gave 1.0 mg/g and 0.2 mg/g for Pt and Pd respectively. Metals loaded on the sorbent materials were recovered by using 3% m/v thiourea solution as the eluting agent with quantitative desorption efficiency under the selected experimental conditions. Separation of platinum from palladium was partially achieved by selective stripping of PtCl62- with 0.5 M of NaClO4 in 1.0 M HCl while PdCl42- was eluted with 0.5 M thiourea in 1.0 M HCl. Separation of platinum from iridium and rhodium under 1 M HCl concentration was successful on triethylenetriamine (TETA)-functionalized Merrifield beads. This material (M-TETA) showed selectivity for platinum albeit the low loading capacity.
- Full Text:
- Date Issued: 2013
Catalytic oxidation of thioanisole using oxovanadium (IV)‐functionalized electrospun polybenzimidazole nanofibers
- Walmsley, Ryan S, Hlangothi, Percy, Litwinski, Christian, Nyokong, Tebello, Torto, Nelson, Tshentu, Zenixole R
- Authors: Walmsley, Ryan S , Hlangothi, Percy , Litwinski, Christian , Nyokong, Tebello , Torto, Nelson , Tshentu, Zenixole R
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242083 , vital:51000 , xlink:href="https://doi.org/10.1002/app.38067"
- Description: Polybenzimidazole fibers, with an average diameter of 262 nm, were produced by the process of electrospinning. These fibers were used as a solid support material for the immobilization of oxovanadium(IV) which was achieved via a reaction with vanadyl sulfate. The oxovanadium(IV)-functionalized nanofibers were used as heterogeneous catalysts for the oxidation of thioanisole under both batch and pseudo-continuous flow conditions with great success. Under batch conditions near quantitative oxidation of thioanisole was achieved in under 90 min, even after four successive catalytic reactions. Under continuous conditions, excellent conversion of thioanisole was maintained throughout the period studied at flow rates of up to 2 mLh−1. This study, therefore, proposes that electrospun polybenzimidazole nanofibers, with their small diameters, impressive chemical and thermal stability, as well as coordinating benzimidazole group, may be a desirable support material for immobilization of homogeneous catalysts.
- Full Text:
- Date Issued: 2013
- Authors: Walmsley, Ryan S , Hlangothi, Percy , Litwinski, Christian , Nyokong, Tebello , Torto, Nelson , Tshentu, Zenixole R
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242083 , vital:51000 , xlink:href="https://doi.org/10.1002/app.38067"
- Description: Polybenzimidazole fibers, with an average diameter of 262 nm, were produced by the process of electrospinning. These fibers were used as a solid support material for the immobilization of oxovanadium(IV) which was achieved via a reaction with vanadyl sulfate. The oxovanadium(IV)-functionalized nanofibers were used as heterogeneous catalysts for the oxidation of thioanisole under both batch and pseudo-continuous flow conditions with great success. Under batch conditions near quantitative oxidation of thioanisole was achieved in under 90 min, even after four successive catalytic reactions. Under continuous conditions, excellent conversion of thioanisole was maintained throughout the period studied at flow rates of up to 2 mLh−1. This study, therefore, proposes that electrospun polybenzimidazole nanofibers, with their small diameters, impressive chemical and thermal stability, as well as coordinating benzimidazole group, may be a desirable support material for immobilization of homogeneous catalysts.
- Full Text:
- Date Issued: 2013
Oxovanadium (IV)-containing poly (styrene-co-4′-ethenyl-2-hydroxyphenylimidazole) electrospun nanofibers for the catalytic oxidation of thioanisole
- Walmsley, Ryan S, Litwinski, Christian, Antunes, Edith M, Hlangothi, Percy, Hosten, Eric C, McCleland, Cedric, Nyokong, Tebello, Torto, Nelson, Tshentu, Zenixole R
- Authors: Walmsley, Ryan S , Litwinski, Christian , Antunes, Edith M , Hlangothi, Percy , Hosten, Eric C , McCleland, Cedric , Nyokong, Tebello , Torto, Nelson , Tshentu, Zenixole R
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241665 , vital:50959 , xlink:href="https://doi.org/10.1016/j.molcata.2013.07.018"
- Description: The catalytic fibers have been fabricated by the electrospinning of a copolymer of styrene and 2-(2′-hydroxy-4′-ethenylphenyl)imidazole {p(ST-co-VPIM)} followed by a reaction with a methanolic vanadyl solution to afford the oxovanadium(IV)-containing poly(styrene-co-4′-ethenyl-2-hydroxyphenylimidazole) fibers {p(ST-co-VPIM)-VO fibers}. The relationship between polymer concentration and fiber diameter was investigated, and at high concentration (20 wt%) the fibers were quite large (average diameter of 3.8 μm) but as the concentration was reduced fibers of much lower diameter were produced (0.6 μm using 8 wt%). The BET surface area for p(ST-co-VPIM) fibers (0.6 μm diameter) was 47.9 m2 g−1 and functionalization of p(ST-co-VPIM) with vanadyl resulted in an increase in surface area to 60.7 m2 g−1 for p(ST-co-VPIM)-VO. The presence of vanadyl was confirmed by XPS and EPR. The EPR spectral analyses depicted complex speciation of vanadium within these polymer supports. These catalytic fibers were applied under batch and continuous flow conditions for the catalytic oxidation of thioanisole using hydrogen peroxide. The continuous flow method gave excellent and constant conversion throughout the 10 h period studied. The leaching of vanadium from the fiber support was 4% over the 10 h period indicating a significant stability of the material.
- Full Text:
- Date Issued: 2013
- Authors: Walmsley, Ryan S , Litwinski, Christian , Antunes, Edith M , Hlangothi, Percy , Hosten, Eric C , McCleland, Cedric , Nyokong, Tebello , Torto, Nelson , Tshentu, Zenixole R
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241665 , vital:50959 , xlink:href="https://doi.org/10.1016/j.molcata.2013.07.018"
- Description: The catalytic fibers have been fabricated by the electrospinning of a copolymer of styrene and 2-(2′-hydroxy-4′-ethenylphenyl)imidazole {p(ST-co-VPIM)} followed by a reaction with a methanolic vanadyl solution to afford the oxovanadium(IV)-containing poly(styrene-co-4′-ethenyl-2-hydroxyphenylimidazole) fibers {p(ST-co-VPIM)-VO fibers}. The relationship between polymer concentration and fiber diameter was investigated, and at high concentration (20 wt%) the fibers were quite large (average diameter of 3.8 μm) but as the concentration was reduced fibers of much lower diameter were produced (0.6 μm using 8 wt%). The BET surface area for p(ST-co-VPIM) fibers (0.6 μm diameter) was 47.9 m2 g−1 and functionalization of p(ST-co-VPIM) with vanadyl resulted in an increase in surface area to 60.7 m2 g−1 for p(ST-co-VPIM)-VO. The presence of vanadyl was confirmed by XPS and EPR. The EPR spectral analyses depicted complex speciation of vanadium within these polymer supports. These catalytic fibers were applied under batch and continuous flow conditions for the catalytic oxidation of thioanisole using hydrogen peroxide. The continuous flow method gave excellent and constant conversion throughout the 10 h period studied. The leaching of vanadium from the fiber support was 4% over the 10 h period indicating a significant stability of the material.
- Full Text:
- Date Issued: 2013
The development of catalytic oxovanadium (IV)-containing microspheres for the oxidation of various organosulfur compounds
- Ogunlaja, Adeniyi S, Khene, Samson M, Antunes, Edith M, Nyokong, Tebello, Torto, Nelson, Tshentu, Zenixole R
- Authors: Ogunlaja, Adeniyi S , Khene, Samson M , Antunes, Edith M , Nyokong, Tebello , Torto, Nelson , Tshentu, Zenixole R
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241783 , vital:50969 , xlink:href="https://doi.org/10.1016/j.apcata.2013.05.004"
- Description: The development of poly[allylSB-co-EGDMA] beads containing a tetradentate ligand was achieved via suspension polymerization. The catalyst poly[allylSB-co-EGDMA]-VO was synthesized by reacting VIVOSO4 with poly[allylSB-co-EGDMA]. XPS and EPR were used to confirm the presence of vanadium (V4+) on the beads. The synthesized catalyst (poly[allylSB-co-EGDMA]-VO) was found to have a BET surface area of 22 m2 g−1 and porosity of 135 Å, with the atomic force microscopy (AFM) showing more insight on the porous nature of the beads. Oxidation of thiophene (TH), benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was carried out using tert-butyl hydroperoxide (t-BuOOH) as oxidant. An overall conversion of 60%, 82%, 98% and 87% was achieved for thiophene (TH), benzothiophene (BT), dibenzothiophene (DBT) and 4,6 dimethyldibenzothiophene (4,6-DMDBT) respectively at higher (t-BuOOH) to substrate ratio and at a temperature of 40 °C. The efficient oxidation of the various organosulfur compounds presents potential for the possible application of this catalyst in oxidative desulfurization (ODS) of crude oil.
- Full Text:
- Date Issued: 2013
- Authors: Ogunlaja, Adeniyi S , Khene, Samson M , Antunes, Edith M , Nyokong, Tebello , Torto, Nelson , Tshentu, Zenixole R
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241783 , vital:50969 , xlink:href="https://doi.org/10.1016/j.apcata.2013.05.004"
- Description: The development of poly[allylSB-co-EGDMA] beads containing a tetradentate ligand was achieved via suspension polymerization. The catalyst poly[allylSB-co-EGDMA]-VO was synthesized by reacting VIVOSO4 with poly[allylSB-co-EGDMA]. XPS and EPR were used to confirm the presence of vanadium (V4+) on the beads. The synthesized catalyst (poly[allylSB-co-EGDMA]-VO) was found to have a BET surface area of 22 m2 g−1 and porosity of 135 Å, with the atomic force microscopy (AFM) showing more insight on the porous nature of the beads. Oxidation of thiophene (TH), benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was carried out using tert-butyl hydroperoxide (t-BuOOH) as oxidant. An overall conversion of 60%, 82%, 98% and 87% was achieved for thiophene (TH), benzothiophene (BT), dibenzothiophene (DBT) and 4,6 dimethyldibenzothiophene (4,6-DMDBT) respectively at higher (t-BuOOH) to substrate ratio and at a temperature of 40 °C. The efficient oxidation of the various organosulfur compounds presents potential for the possible application of this catalyst in oxidative desulfurization (ODS) of crude oil.
- Full Text:
- Date Issued: 2013
The development of novel nickel selective amine extractants
- Okewole, Adeleye I, Antunes, Edith M, Nyokong, Tebello, Tshentu, Zenixole R
- Authors: Okewole, Adeleye I , Antunes, Edith M , Nyokong, Tebello , Tshentu, Zenixole R
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241641 , vital:50957 , xlink:href="https://doi.org/10.1016/j.mineng.2013.04.019"
- Description: A chelating ion exchanger, prepared by functionalising Merrifield resin with 2,2′-pyridylimidazole, was utilized to selectively adsorb and separate nickel from other base metal ions in synthetic sulfate solutions. The sorbent material was characterized by scanning electron microscopy (SEM), microanalysis, infrared (IR), X-ray photoelectron spectroscopy (XPS) and BET surface area. The distribution ratio (D) and the sorption capacity of the microspheres toward Ni(II), Cu(II), Co(II) and Fe(II) ions was studied by using the batch and column methods, respectively. Ni(II) followed by Cu(II) showed the highest distribution ratio (D) and the highest sorption efficiency of nickel(II) ions around pH 2. The binary separation of nickel(II) from copper(II), cobalt(II) and iron(II) respectively, undertaken in a column study, through loading the metal ions at pH ≈ 2 followed by selective decomplexation, demonstrated the selectivity of the sorbent material for nickel(II). Thus, 2,2′-pyridylimidazole can be regarded as a nickel-specific extractant.
- Full Text:
- Date Issued: 2013
- Authors: Okewole, Adeleye I , Antunes, Edith M , Nyokong, Tebello , Tshentu, Zenixole R
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241641 , vital:50957 , xlink:href="https://doi.org/10.1016/j.mineng.2013.04.019"
- Description: A chelating ion exchanger, prepared by functionalising Merrifield resin with 2,2′-pyridylimidazole, was utilized to selectively adsorb and separate nickel from other base metal ions in synthetic sulfate solutions. The sorbent material was characterized by scanning electron microscopy (SEM), microanalysis, infrared (IR), X-ray photoelectron spectroscopy (XPS) and BET surface area. The distribution ratio (D) and the sorption capacity of the microspheres toward Ni(II), Cu(II), Co(II) and Fe(II) ions was studied by using the batch and column methods, respectively. Ni(II) followed by Cu(II) showed the highest distribution ratio (D) and the highest sorption efficiency of nickel(II) ions around pH 2. The binary separation of nickel(II) from copper(II), cobalt(II) and iron(II) respectively, undertaken in a column study, through loading the metal ions at pH ≈ 2 followed by selective decomplexation, demonstrated the selectivity of the sorbent material for nickel(II). Thus, 2,2′-pyridylimidazole can be regarded as a nickel-specific extractant.
- Full Text:
- Date Issued: 2013
A highly selective and sensitive pyridylazo-2-naphthol-poly (acrylic acid) functionalized electrospun nanofiber fluorescence “turn-off” chemosensory system for Ni 2+
- Adewuyi, Sheriff, Ondigo, Dezzline A, Zugle, Ruphino, Tshentu, Zenixole R, Nyokong, Tebello, Torto, Nelson
- Authors: Adewuyi, Sheriff , Ondigo, Dezzline A , Zugle, Ruphino , Tshentu, Zenixole R , Nyokong, Tebello , Torto, Nelson
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/246012 , vital:51428 , xlink:href="https://doi.org/10.1039/C2AY25182E"
- Description: A fluorescent nanofiber probe for the determination of Ni2+ was developed via the electrospinning of a covalently functionalized pyridylazo-2-naphthol-poly(acrylic acid) polymer. Fluorescent nanofibers with diameters in the range 230–800 nm were produced with uniformly dispersed fluorophores. The excitation and emission fluorescence were at wavelengths 479 and 557 nm respectively, thereby exhibiting a good Stokes' shift. This Ni2+ probe that employs fluorescence quenching in a solid receptor–fluorophore system exhibited a good correlation between the fluorescence intensity and nickel concentration up to 1.0 μg mL−1 based on the Stern–Volmer mechanism. The probe achieved a detection limit (3δ/S) of 0.07 ng mL−1 and a precision, calculated as a relative standard deviation (RSD) of more than 4% (n = 8). The concentration of Ni2+ in a certified reference material (SEP-3) was found to be 0.8986 μg mL−1, which is significantly comparable with the certified value of 0.8980 μg mL−1. The accuracy of the determinations, expressed as a relative error between the certified and the observed values of certified reference groundwater was ≤0.1%. The versatility of the nanofiber probe was demonstrated by affording simple, rapid and selective detection of Ni2+ in the presence of other competing metal ions by direct analysis, without employing any further sample handling steps.
- Full Text:
- Date Issued: 2012
- Authors: Adewuyi, Sheriff , Ondigo, Dezzline A , Zugle, Ruphino , Tshentu, Zenixole R , Nyokong, Tebello , Torto, Nelson
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/246012 , vital:51428 , xlink:href="https://doi.org/10.1039/C2AY25182E"
- Description: A fluorescent nanofiber probe for the determination of Ni2+ was developed via the electrospinning of a covalently functionalized pyridylazo-2-naphthol-poly(acrylic acid) polymer. Fluorescent nanofibers with diameters in the range 230–800 nm were produced with uniformly dispersed fluorophores. The excitation and emission fluorescence were at wavelengths 479 and 557 nm respectively, thereby exhibiting a good Stokes' shift. This Ni2+ probe that employs fluorescence quenching in a solid receptor–fluorophore system exhibited a good correlation between the fluorescence intensity and nickel concentration up to 1.0 μg mL−1 based on the Stern–Volmer mechanism. The probe achieved a detection limit (3δ/S) of 0.07 ng mL−1 and a precision, calculated as a relative standard deviation (RSD) of more than 4% (n = 8). The concentration of Ni2+ in a certified reference material (SEP-3) was found to be 0.8986 μg mL−1, which is significantly comparable with the certified value of 0.8980 μg mL−1. The accuracy of the determinations, expressed as a relative error between the certified and the observed values of certified reference groundwater was ≤0.1%. The versatility of the nanofiber probe was demonstrated by affording simple, rapid and selective detection of Ni2+ in the presence of other competing metal ions by direct analysis, without employing any further sample handling steps.
- Full Text:
- Date Issued: 2012
Imidazole-functionalized polymer microspheres and fibers–useful materials for immobilization of oxovanadium (IV) catalysts
- Walmsley, Ryan S, Ogunlaja, Adeniyi S, Coombes, Matthew J, Chidawanyika, Wadzanai J U, Litwinski, Christian, Torto, Nelson, Nyokong, Tebello, Tshentu, Zenixole R
- Authors: Walmsley, Ryan S , Ogunlaja, Adeniyi S , Coombes, Matthew J , Chidawanyika, Wadzanai J U , Litwinski, Christian , Torto, Nelson , Nyokong, Tebello , Tshentu, Zenixole R
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/246041 , vital:51431 , xlink:href="https://doi.org/10.1039/C2JM15485D"
- Description: Both polymer microspheres and microfibers containing the imidazole functionality have been prepared and used to immobilize oxovanadium(IV). The average diameters and BET surface areas of the microspheres were 322 μm and 155 m2 g−1 while the fibers were 1.85 μm and 52 m2 g−1, respectively. XPS and microanalysis confirmed the incorporation of imidazole and vanadium in the polymeric materials. The catalytic activity of both materials was evaluated using the hydrogen peroxide facilitated oxidation of thioanisole. The microspheres were applied in a typical laboratory batch reactor set-up and quantitative conversions (>99%) were obtained in under 240 min with turn-over frequencies ranging from 21.89 to 265.53 h−1, depending on the quantity of catalyst and temperature. The microspherical catalysts also proved to be recyclable with no drop in activity being observed after three successive reactions. The vanadium functionalized fibers were applied in a pseudo continuous flow set-up. Factors influencing the overall conversion and product selectivity, including flow rate and catalyst quantity, were investigated. At flow rates of 1–4 mL h−1 near quantitative conversion was maintained over an extended period. Keeping the mass of catalyst constant (0.025 g) and varying the flow rate from 1–6 mL h−1 resulted in a shift in the formation of the oxidation product methyl phenyl sulfone from 60.1 to 18.6%.
- Full Text:
- Date Issued: 2012
- Authors: Walmsley, Ryan S , Ogunlaja, Adeniyi S , Coombes, Matthew J , Chidawanyika, Wadzanai J U , Litwinski, Christian , Torto, Nelson , Nyokong, Tebello , Tshentu, Zenixole R
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/246041 , vital:51431 , xlink:href="https://doi.org/10.1039/C2JM15485D"
- Description: Both polymer microspheres and microfibers containing the imidazole functionality have been prepared and used to immobilize oxovanadium(IV). The average diameters and BET surface areas of the microspheres were 322 μm and 155 m2 g−1 while the fibers were 1.85 μm and 52 m2 g−1, respectively. XPS and microanalysis confirmed the incorporation of imidazole and vanadium in the polymeric materials. The catalytic activity of both materials was evaluated using the hydrogen peroxide facilitated oxidation of thioanisole. The microspheres were applied in a typical laboratory batch reactor set-up and quantitative conversions (>99%) were obtained in under 240 min with turn-over frequencies ranging from 21.89 to 265.53 h−1, depending on the quantity of catalyst and temperature. The microspherical catalysts also proved to be recyclable with no drop in activity being observed after three successive reactions. The vanadium functionalized fibers were applied in a pseudo continuous flow set-up. Factors influencing the overall conversion and product selectivity, including flow rate and catalyst quantity, were investigated. At flow rates of 1–4 mL h−1 near quantitative conversion was maintained over an extended period. Keeping the mass of catalyst constant (0.025 g) and varying the flow rate from 1–6 mL h−1 resulted in a shift in the formation of the oxidation product methyl phenyl sulfone from 60.1 to 18.6%.
- Full Text:
- Date Issued: 2012
Oxovanadium (IV)-catalysed oxidation of dibenzothiophene and 4, 6-dimethyldibenzothiophene
- Ogunlaja, Adeniyi S, Chidawanyika, Wadzanai J U, Antunes, Edith M, Fernandes, Manuel A, Nyokong, Tebello, Torto, Nelson, Tshentu, Zenixole R
- Authors: Ogunlaja, Adeniyi S , Chidawanyika, Wadzanai J U , Antunes, Edith M , Fernandes, Manuel A , Nyokong, Tebello , Torto, Nelson , Tshentu, Zenixole R
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/246025 , vital:51429 , xlink:href="https://doi.org/10.1039/C2DT31433A"
- Description: The reaction between [VIVOSO4] and the tetradentate N2O2-donor Schiff base ligand, N,N-bis(o-hydroxybenzaldehyde)phenylenediamine (sal-HBPD), obtained by the condensation of salicylaldehyde and o-phenylenediamine in a molar ratio of 2 : 1 respectively, resulted in the formation of [VIVO(sal-HBPD)]. The molecular structure of [VIVO(sal-HBPD)] was determined by single crystal X-ray diffraction, and confirmed the distorted square pyramidal geometry of the complex with the N2O2 binding mode of the tetradentate ligand. The formation of the polymer-supported p[VIVO(sal-AHBPD)] proceeded via the nitrosation of sal-HBPD, followed by the reduction with hydrogen to form an amine group that was then linked to Merrifield beads followed by the reaction with [VIVOSO4]. XPS and EPR were used to confirm the presence of oxovanadium(IV) within the beads. The BET surface area and porosity of the heterogeneous catalyst p[VIVO(sal-AHBPD)] were found to be 6.9 m2 g−1 and 180.8 Å respectively. Microanalysis, TG, UV-Vis and FT-IR were used for further characterization of both [VIVO(sal-HBPD)] and p[VIVO(sal-AHBPD)]. Oxidation of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was investigated using [VIVO(sal-HBPD)] and p[VIVO(sal-AHBPD)] as catalysts. Progress for oxidation of these model compounds was monitored with a gas chromatograph fitted with a flame ionization detector. The oxidation products were characterized using gas chromatography-mass spectrometry, microanalysis and NMR. Dibenzothiophene sulfone (DBTO2) and 4,6-dimethyldibenzothiophene sulfone (4,6-DMDBTO2) were found to be the main products of oxidation. Oxovanadium(IV) Schiff base microspherical beads, p[VIVO(sal-AHBPD)], were able to catalyse the oxidation of sulfur in dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) to a tune of 88.0% and 71.8% respectively after 3 h at 40 °C. These oxidation results show promise for potential application of this catalyst in the oxidative desulfurization of crude oils.
- Full Text:
- Date Issued: 2012
- Authors: Ogunlaja, Adeniyi S , Chidawanyika, Wadzanai J U , Antunes, Edith M , Fernandes, Manuel A , Nyokong, Tebello , Torto, Nelson , Tshentu, Zenixole R
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/246025 , vital:51429 , xlink:href="https://doi.org/10.1039/C2DT31433A"
- Description: The reaction between [VIVOSO4] and the tetradentate N2O2-donor Schiff base ligand, N,N-bis(o-hydroxybenzaldehyde)phenylenediamine (sal-HBPD), obtained by the condensation of salicylaldehyde and o-phenylenediamine in a molar ratio of 2 : 1 respectively, resulted in the formation of [VIVO(sal-HBPD)]. The molecular structure of [VIVO(sal-HBPD)] was determined by single crystal X-ray diffraction, and confirmed the distorted square pyramidal geometry of the complex with the N2O2 binding mode of the tetradentate ligand. The formation of the polymer-supported p[VIVO(sal-AHBPD)] proceeded via the nitrosation of sal-HBPD, followed by the reduction with hydrogen to form an amine group that was then linked to Merrifield beads followed by the reaction with [VIVOSO4]. XPS and EPR were used to confirm the presence of oxovanadium(IV) within the beads. The BET surface area and porosity of the heterogeneous catalyst p[VIVO(sal-AHBPD)] were found to be 6.9 m2 g−1 and 180.8 Å respectively. Microanalysis, TG, UV-Vis and FT-IR were used for further characterization of both [VIVO(sal-HBPD)] and p[VIVO(sal-AHBPD)]. Oxidation of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was investigated using [VIVO(sal-HBPD)] and p[VIVO(sal-AHBPD)] as catalysts. Progress for oxidation of these model compounds was monitored with a gas chromatograph fitted with a flame ionization detector. The oxidation products were characterized using gas chromatography-mass spectrometry, microanalysis and NMR. Dibenzothiophene sulfone (DBTO2) and 4,6-dimethyldibenzothiophene sulfone (4,6-DMDBTO2) were found to be the main products of oxidation. Oxovanadium(IV) Schiff base microspherical beads, p[VIVO(sal-AHBPD)], were able to catalyse the oxidation of sulfur in dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) to a tune of 88.0% and 71.8% respectively after 3 h at 40 °C. These oxidation results show promise for potential application of this catalyst in the oxidative desulfurization of crude oils.
- Full Text:
- Date Issued: 2012
Introducing chemistry students to the “real world” of chemistry
- Brown, Michael E, Cosser, Ronald C, Davies-Coleman, Michael T, Kaye, Perry T, Klein, Rosalyn, Lamprecht, Emmanuel, Lobb, Kevin A, Nyokong, Tebello, Sewry, Joyce D, Tshentu, Zenixole R, Van der Zeyde, Tino, Watkins, Gareth M
- Authors: Brown, Michael E , Cosser, Ronald C , Davies-Coleman, Michael T , Kaye, Perry T , Klein, Rosalyn , Lamprecht, Emmanuel , Lobb, Kevin A , Nyokong, Tebello , Sewry, Joyce D , Tshentu, Zenixole R , Van der Zeyde, Tino , Watkins, Gareth M
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/449360 , vital:74814 , xlink:href="https://doi.org/10.1021/ed8001539"
- Description: A majority of chemistry graduates seek employment in a rapidly changing chemical industry. Our attempts to provide the graduates with skills in entrepreneurship and the ability to understand and communicate with their chemical engineering colleagues, in addition to their fundamental knowledge of chemistry, are described. This is done at second-year level with practical projects in which student teams formulate and prepare relatively simple chemical products for marketing, followed a year later by a more advanced study of the feasibility of producing and marketing a fine chemical on a commercial scale.
- Full Text:
- Date Issued: 2010
- Authors: Brown, Michael E , Cosser, Ronald C , Davies-Coleman, Michael T , Kaye, Perry T , Klein, Rosalyn , Lamprecht, Emmanuel , Lobb, Kevin A , Nyokong, Tebello , Sewry, Joyce D , Tshentu, Zenixole R , Van der Zeyde, Tino , Watkins, Gareth M
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/449360 , vital:74814 , xlink:href="https://doi.org/10.1021/ed8001539"
- Description: A majority of chemistry graduates seek employment in a rapidly changing chemical industry. Our attempts to provide the graduates with skills in entrepreneurship and the ability to understand and communicate with their chemical engineering colleagues, in addition to their fundamental knowledge of chemistry, are described. This is done at second-year level with practical projects in which student teams formulate and prepare relatively simple chemical products for marketing, followed a year later by a more advanced study of the feasibility of producing and marketing a fine chemical on a commercial scale.
- Full Text:
- Date Issued: 2010
Photodynamic inactivation of Staphylococcus aureus using low symmetrically substituted phthalocyanines supported on a polystyrene polymer fiber
- Masilela, Nkosiphile, Kleyi, Phumelele, Tshentu, Zenixole R, Priniotakis, Georgios, Westbroek, Philippe, Nyokong, Tebello
- Authors: Masilela, Nkosiphile , Kleyi, Phumelele , Tshentu, Zenixole R , Priniotakis, Georgios , Westbroek, Philippe , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7330 , http://hdl.handle.net/10962/d1020591
- Description: This work reports on the antimicrobial photo-activities of a series of low symmetrically substituted phthalocyanine complexes in solution and in a fiber matrix. Phthalocyanine complexes were successfully electrospun into a polystyrene polymer. The fiber diameter ranged from 240 nm to 390 nm in average. The modified polymer fiber showed successful singlet oxygen production with the Ge monocarboxy phthalocyanine modified fiber giving the highest singlet oxygen quantum yield value of 0.46 due to lack of aggregation when in the polymer. All the unsymmetrically substituted complexes showed antimicrobial activity towards S. Aureus under illumination with visible light. The symmetrical ZnPc and ZnTPCPc showed no activity under illumination with light in the fiber matrix due to low singlet oxygen production. , Original publication is available at http://dx.doi.org/10.1016/j.dyepig.2012.10.001
- Full Text: false
- Authors: Masilela, Nkosiphile , Kleyi, Phumelele , Tshentu, Zenixole R , Priniotakis, Georgios , Westbroek, Philippe , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7330 , http://hdl.handle.net/10962/d1020591
- Description: This work reports on the antimicrobial photo-activities of a series of low symmetrically substituted phthalocyanine complexes in solution and in a fiber matrix. Phthalocyanine complexes were successfully electrospun into a polystyrene polymer. The fiber diameter ranged from 240 nm to 390 nm in average. The modified polymer fiber showed successful singlet oxygen production with the Ge monocarboxy phthalocyanine modified fiber giving the highest singlet oxygen quantum yield value of 0.46 due to lack of aggregation when in the polymer. All the unsymmetrically substituted complexes showed antimicrobial activity towards S. Aureus under illumination with visible light. The symmetrical ZnPc and ZnTPCPc showed no activity under illumination with light in the fiber matrix due to low singlet oxygen production. , Original publication is available at http://dx.doi.org/10.1016/j.dyepig.2012.10.001
- Full Text: false
The development of catalytic oxovanadium(IV)-containing microspheres for the oxidation of various organosulfur compounds
- Ogunlaja, Adeniyi S, Khene, M Samson, Antunes, Edith M, Nyokong, Tebello, Torto, Nelson, Tshentu, Zenixole R
- Authors: Ogunlaja, Adeniyi S , Khene, M Samson , Antunes, Edith M , Nyokong, Tebello , Torto, Nelson , Tshentu, Zenixole R
- Language: English
- Type: Article
- Identifier: vital:7324 , http://hdl.handle.net/10962/d1020574
- Description: The development of poly[allylSB-co-EGDMA] beads containing a tetradentate ligand was achieved via suspension polymerization. The catalyst poly[allylSB-co-EGDMA]-VO was synthesized by reacting VIVOSO4 with poly[allylSB-co-EGDMA]. XPS and EPR were used to confirm the presence of vanadium (V4+) on the beads. The synthesized catalyst (poly[allylSB-co-EGDMA]-VO) was found to have a BET surface area of 22 m2 g−1 and porosity of 135 Å, with the atomic force microscopy (AFM) showing more insight on the porous nature of the beads. Oxidation of thiophene (TH), benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was carried out using tert-butyl hydroperoxide (t-BuOOH) as oxidant. An overall conversion of 60%, 82%, 98% and 87% was achieved for thiophene (TH), benzothiophene (BT), dibenzothiophene (DBT) and 4,6 dimethyldibenzothiophene (4,6-DMDBT) respectively at higher (t-BuOOH) to substrate ratio and at a temperature of 40 °C. The efficient oxidation of the various organosulfur compounds presents potential for the possible application of this catalyst in oxidative desulfurization (ODS) of crude oil. , Original publication is available at http://dx.doi.org/10.1016/j.apcata.2013.05.004
- Full Text: false
- Authors: Ogunlaja, Adeniyi S , Khene, M Samson , Antunes, Edith M , Nyokong, Tebello , Torto, Nelson , Tshentu, Zenixole R
- Language: English
- Type: Article
- Identifier: vital:7324 , http://hdl.handle.net/10962/d1020574
- Description: The development of poly[allylSB-co-EGDMA] beads containing a tetradentate ligand was achieved via suspension polymerization. The catalyst poly[allylSB-co-EGDMA]-VO was synthesized by reacting VIVOSO4 with poly[allylSB-co-EGDMA]. XPS and EPR were used to confirm the presence of vanadium (V4+) on the beads. The synthesized catalyst (poly[allylSB-co-EGDMA]-VO) was found to have a BET surface area of 22 m2 g−1 and porosity of 135 Å, with the atomic force microscopy (AFM) showing more insight on the porous nature of the beads. Oxidation of thiophene (TH), benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was carried out using tert-butyl hydroperoxide (t-BuOOH) as oxidant. An overall conversion of 60%, 82%, 98% and 87% was achieved for thiophene (TH), benzothiophene (BT), dibenzothiophene (DBT) and 4,6 dimethyldibenzothiophene (4,6-DMDBT) respectively at higher (t-BuOOH) to substrate ratio and at a temperature of 40 °C. The efficient oxidation of the various organosulfur compounds presents potential for the possible application of this catalyst in oxidative desulfurization (ODS) of crude oil. , Original publication is available at http://dx.doi.org/10.1016/j.apcata.2013.05.004
- Full Text: false
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