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, Nyokong, Tebello, Torto, Nelson
- Authors: Adewuyi, Sheriff , Ondigo, Dezzline A , Zugle, Ruphino , Tshentu, Zenixole , 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 , 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
A New Synthetic Method for Tetraazatricyclic Derivatives and Evaluation of Their Biological Properties
- Odame, Felix, Betz, Richard, Hosten, Eric C, Krause, Jason, Isaacs, Michelle, Hoppe, Heinrich C, Khanye, Setshaba D, Sayed, Yasien, Frost, P Carminita, Lobb, Kevin A, Tshentu, Zenixole
- Authors: Odame, Felix , Betz, Richard , Hosten, Eric C , Krause, Jason , Isaacs, Michelle , Hoppe, Heinrich C , Khanye, Setshaba D , Sayed, Yasien , Frost, P Carminita , Lobb, Kevin A , Tshentu, Zenixole
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123189 , vital:35413 , https://doi.org/10.1002/slct.201802930
- Description: Herein, we propose novel quinolones incorporating an INH moiety as potential drug templates against TB. The quinolone-based compounds bearing an INH moiety attached via a hydrazide–hydrazone bond were synthesised and evaluated against Mycobacterium tuberculosis H37Rv (MTB). The compounds were also evaluated for cytotoxicity against HeLa cell lines. These compounds showed significant activity (MIC90) against MTB in the range of 0.2–8 μM without any cytotoxic effects. Compounds 10 (MIC90; 0.9 μM), 11 (MIC90; 0.2 μM), 12 (MIC90; 0.8 μM) and compound 15 (MIC90; 0.8 μM), the most active compounds in this series, demonstrate activities on par with INH and superior to those reported for the fluoroquinolones. The SAR analysis suggests that the nature of substituents at positions −1 and −3 of the quinolone nucleus influences anti-MTB activity. Aqueous solubility evaluation and in vitro metabolic stability of compound 12 highlights favourable drug-like properties for this compound class.
- Full Text:
- Date Issued: 2018
- Authors: Odame, Felix , Betz, Richard , Hosten, Eric C , Krause, Jason , Isaacs, Michelle , Hoppe, Heinrich C , Khanye, Setshaba D , Sayed, Yasien , Frost, P Carminita , Lobb, Kevin A , Tshentu, Zenixole
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123189 , vital:35413 , https://doi.org/10.1002/slct.201802930
- Description: Herein, we propose novel quinolones incorporating an INH moiety as potential drug templates against TB. The quinolone-based compounds bearing an INH moiety attached via a hydrazide–hydrazone bond were synthesised and evaluated against Mycobacterium tuberculosis H37Rv (MTB). The compounds were also evaluated for cytotoxicity against HeLa cell lines. These compounds showed significant activity (MIC90) against MTB in the range of 0.2–8 μM without any cytotoxic effects. Compounds 10 (MIC90; 0.9 μM), 11 (MIC90; 0.2 μM), 12 (MIC90; 0.8 μM) and compound 15 (MIC90; 0.8 μM), the most active compounds in this series, demonstrate activities on par with INH and superior to those reported for the fluoroquinolones. The SAR analysis suggests that the nature of substituents at positions −1 and −3 of the quinolone nucleus influences anti-MTB activity. Aqueous solubility evaluation and in vitro metabolic stability of compound 12 highlights favourable drug-like properties for this compound class.
- Full Text:
- Date Issued: 2018
An ion-imprinted polymer for the selective extraction of mercury(II) ions in aqueous media
- Batlokwa, Bareki Shima, Chimuka, Luke, Tshentu, Zenixole, Cukrowska, Ewa, Torto, Nelson
- Authors: Batlokwa, Bareki Shima , Chimuka, Luke , Tshentu, Zenixole , Cukrowska, Ewa , Torto, Nelson
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6566 , http://hdl.handle.net/10962/d1004125
- Description: A double-imprinted polymer exhibiting high sensitivity for mercury(II) in aqueous solution is presented. Polymer particles imprinted with mercury(II) were synthesised by copolymerising the functional and cross-linking monomers, N’–[3– (Trimethoxysilyl)–propyl]diethylenetriamine (TPET) and tetraethylorthosilicate (TEOS). A double-imprinting procedure employing hexadecyltrimethylammonium bromide (CTAB), as a second template to improve the efficiency of the polymer, was adopted. The imprinted polymer was characterised by FTIR, scanning electron microscopy (SEM) and the average size determined by screen analysis using standard test sieves. Relative selective coefficients (k`) of the imprinted polymer evaluated from selective binding studies between Hg2+ and Cu2+ or Hg2+ and Cd2+ were 10 588 and 3 147, respectively. These values indicated highly-favoured Hg2+ extractions over the 2 competing ions. The results of spiked and real water samples showed high extraction efficiencies of Hg2+ ions, (over 84%) as evaluated from the detected unextracted Hg2+ ions by ICP-OES. The method exhibited a dynamic response concentration range for Hg2+ between 0.01 and 20 μg/mℓ, with a detection limit (LOD, 3σ) of 0.000036 μg/mℓ (36 ng/ℓ) that meets the monitoring requirements for the USA EPA of 2 000 ng/ℓ for Hg2+ in drinking water. Generally, the data (n=10) had percentage relative standard deviations (%RSD) of less than 4%. Satisfactory results were also obtained when the prepared sorbent was applied for the pre-concentration of Hg2+ from an aqueous certified reference material. These findings indicate that the double-imprinted polymer has potential to be used as an efficient extraction material for the selective pre–concentration of mercury(II) ions in aqueous environments.
- Full Text:
- Date Issued: 2012
- Authors: Batlokwa, Bareki Shima , Chimuka, Luke , Tshentu, Zenixole , Cukrowska, Ewa , Torto, Nelson
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6566 , http://hdl.handle.net/10962/d1004125
- Description: A double-imprinted polymer exhibiting high sensitivity for mercury(II) in aqueous solution is presented. Polymer particles imprinted with mercury(II) were synthesised by copolymerising the functional and cross-linking monomers, N’–[3– (Trimethoxysilyl)–propyl]diethylenetriamine (TPET) and tetraethylorthosilicate (TEOS). A double-imprinting procedure employing hexadecyltrimethylammonium bromide (CTAB), as a second template to improve the efficiency of the polymer, was adopted. The imprinted polymer was characterised by FTIR, scanning electron microscopy (SEM) and the average size determined by screen analysis using standard test sieves. Relative selective coefficients (k`) of the imprinted polymer evaluated from selective binding studies between Hg2+ and Cu2+ or Hg2+ and Cd2+ were 10 588 and 3 147, respectively. These values indicated highly-favoured Hg2+ extractions over the 2 competing ions. The results of spiked and real water samples showed high extraction efficiencies of Hg2+ ions, (over 84%) as evaluated from the detected unextracted Hg2+ ions by ICP-OES. The method exhibited a dynamic response concentration range for Hg2+ between 0.01 and 20 μg/mℓ, with a detection limit (LOD, 3σ) of 0.000036 μg/mℓ (36 ng/ℓ) that meets the monitoring requirements for the USA EPA of 2 000 ng/ℓ for Hg2+ in drinking water. Generally, the data (n=10) had percentage relative standard deviations (%RSD) of less than 4%. Satisfactory results were also obtained when the prepared sorbent was applied for the pre-concentration of Hg2+ from an aqueous certified reference material. These findings indicate that the double-imprinted polymer has potential to be used as an efficient extraction material for the selective pre–concentration of mercury(II) ions in aqueous environments.
- Full Text:
- Date Issued: 2012
Photodynamic inactivation of Staphylococcus aureus using low symmetrically substituted phthalocyanines supported on a polystyrene polymer fiber
- Masilela, Nkosiphile, Kleyi, Phumelele, Tshentu, Zenixole, Priniotakis, Georgios, Westbroek, Philippe, Nyokong, Tebello
- Authors: Masilela, Nkosiphile , Kleyi, Phumelele , Tshentu, Zenixole , 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 , 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
Synthesis, characterization and biological activity of some Dithiourea Derivatives:
- Odame, Felix, Hosten, Eric, Krause, Jason, Isaacs, Michelle, Hoppe, Heinrich C, Khanye, Setshaba D, Sayed, Yasien, Frost, Carminita, Lobb, Kevin A, Tshentu, Zenixole
- Authors: Odame, Felix , Hosten, Eric , Krause, Jason , Isaacs, Michelle , Hoppe, Heinrich C , Khanye, Setshaba D , Sayed, Yasien , Frost, Carminita , Lobb, Kevin A , Tshentu, Zenixole
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/163046 , vital:41007 , DOI: 10.17344/acsi.2019.5689
- Description: Novel dithiourea derivatives have been designed as HIV-1 protease inhibitors using Autodock 4.2, synthesized and characterized by spectroscopic methods and microanalysis.
- Full Text:
- Date Issued: 2020
- Authors: Odame, Felix , Hosten, Eric , Krause, Jason , Isaacs, Michelle , Hoppe, Heinrich C , Khanye, Setshaba D , Sayed, Yasien , Frost, Carminita , Lobb, Kevin A , Tshentu, Zenixole
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/163046 , vital:41007 , DOI: 10.17344/acsi.2019.5689
- Description: Novel dithiourea derivatives have been designed as HIV-1 protease inhibitors using Autodock 4.2, synthesized and characterized by spectroscopic methods and microanalysis.
- Full Text:
- Date Issued: 2020
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, Kleyi, Phumelele, Tshentu, Zenixole, Nyokong, Tebello
- Authors: Nombona, Nolwazi , Antunes, Edith M , Chidawanyika, Wadzanai , Kleyi, Phumelele , Tshentu, Zenixole , 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 , Kleyi, Phumelele , Tshentu, Zenixole , 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
Towards mineral beneficiation: from basic chemistry to applications
- Authors: Tshentu, Zenixole
- Subjects: Metallurgy , Ore-dressing , f-sa
- Language: English
- Type: text , Lectures
- Identifier: http://hdl.handle.net/10948/55783 , vital:53876
- Description: The role of mineral beneficiation in the survival, growth, development and sustainability of a developing economy cannot be overstated. Our development as a human species has always been involvedly linked with the use of mineral resources from the stone, bronze and iron ages through the early modern eras to the present. In the current modern era, characterized by highly technological equipment, fourth industrial revolution (4IR) and new energy technologies, the role of mineral beneficiation has been elevated. Precious metals find use in the fine chemicals and petrochemicals industry, fuel cells, electrical and electronic products, medical and dentistry applications, jewellery, autocatalysts, and glass and ceramics. The markets for precious metals keep growing and the supply does not meet demand. The development of methods for recovery of metal value from feeds of mineral ore solutions, solutions of spent secondary resources and from mining wastewaters remains of great importance. Further beneficiation strategies for utilization of mineral products in other “value-added” applications are also important for the growth of the mineral markets. The usage of platinum, palladium and rhodium in the autocatalyst industry has grown significantly and this has further elevated the importance of platinum group metals (PGMs), but other areas of application of the strategic metals need to be harnessed. The four stages of beneficiation, namely, primary, secondary, tertiary and final stage, provide an opportunity to beneficiate to greater value for domestic or export use. Our own research work is engaged in several of these stages, from hydrometallurgical recovery of base metals and platinum group metals from feeds of primary mining and solutions of waste secondary resources such as spent catalytic converters and e-waste to the use of metals in “value added” products such as metalbased catalysts for the fuel industry and in metallodrugs. Examples of “value added” products include rhodium as a promoter in molybdenum sulfide as a catalyst for hydrodesulfurization of fuel oil, vanadium as a catalyst in oxidative desulfurization of fuel oil, vanadium and palladium as therapeutic agents for diabetes and cancer, respectively. Current and future work involves (i) the development of metal-selective scavengers to recover lost metal value in mining wastewaters, and (ii) the design of metal-based catalytic materials for refinement of bio-based oils to biofuel as well as for production of green LPG through hydroprocessing. Our work centres around both basic and applied chemistry towards mineral beneficiation and with a bias towards greener production.
- Full Text:
- Authors: Tshentu, Zenixole
- Subjects: Metallurgy , Ore-dressing , f-sa
- Language: English
- Type: text , Lectures
- Identifier: http://hdl.handle.net/10948/55783 , vital:53876
- Description: The role of mineral beneficiation in the survival, growth, development and sustainability of a developing economy cannot be overstated. Our development as a human species has always been involvedly linked with the use of mineral resources from the stone, bronze and iron ages through the early modern eras to the present. In the current modern era, characterized by highly technological equipment, fourth industrial revolution (4IR) and new energy technologies, the role of mineral beneficiation has been elevated. Precious metals find use in the fine chemicals and petrochemicals industry, fuel cells, electrical and electronic products, medical and dentistry applications, jewellery, autocatalysts, and glass and ceramics. The markets for precious metals keep growing and the supply does not meet demand. The development of methods for recovery of metal value from feeds of mineral ore solutions, solutions of spent secondary resources and from mining wastewaters remains of great importance. Further beneficiation strategies for utilization of mineral products in other “value-added” applications are also important for the growth of the mineral markets. The usage of platinum, palladium and rhodium in the autocatalyst industry has grown significantly and this has further elevated the importance of platinum group metals (PGMs), but other areas of application of the strategic metals need to be harnessed. The four stages of beneficiation, namely, primary, secondary, tertiary and final stage, provide an opportunity to beneficiate to greater value for domestic or export use. Our own research work is engaged in several of these stages, from hydrometallurgical recovery of base metals and platinum group metals from feeds of primary mining and solutions of waste secondary resources such as spent catalytic converters and e-waste to the use of metals in “value added” products such as metalbased catalysts for the fuel industry and in metallodrugs. Examples of “value added” products include rhodium as a promoter in molybdenum sulfide as a catalyst for hydrodesulfurization of fuel oil, vanadium as a catalyst in oxidative desulfurization of fuel oil, vanadium and palladium as therapeutic agents for diabetes and cancer, respectively. Current and future work involves (i) the development of metal-selective scavengers to recover lost metal value in mining wastewaters, and (ii) the design of metal-based catalytic materials for refinement of bio-based oils to biofuel as well as for production of green LPG through hydroprocessing. Our work centres around both basic and applied chemistry towards mineral beneficiation and with a bias towards greener production.
- Full Text:
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