Improving singlet oxygen generating abilities of phthalocyanines
- Nwahara, Nnamdi, Britton, Jonathan, Nyokong, Tebello
- Authors: Nwahara, Nnamdi , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188943 , vital:44800 , xlink:href="https://doi.org/10.1080/00958972.2017.1313975"
- Description: Glutathione-capped graphene quantum dots (GQDs@GSH) were covalently linked to folic acid (FA). Aluminum tetrasulfonated phthalocyanine (ClAlTSPc) was then adsorbed on the GQDs@GSH-FA conjugate to form GQDs@GSH-FA/ClAlTSPc or on GQDs@GSH and pristine GQDs alone to form GQDs@GSH/ClAlTSPc and GQDs/ClAlTSPc, respectively. We report for the first time on the photophysicochemical behavior of the resulting nanoconjugates. The fluorescence quantum yields of pristine GQDs, GQDS@GSH, or GQDs@GSH-FA conjugate were quenched upon non-covalent interaction (π–π) with ClAlTSPc. There was an increase in triplet quantum yields from 0.38 for ClAlTSPc alone to 0.60, 0.75, and 0.73 when ClAlTSPc was linked to pristine GQDs, GQDs@GSH, and GQDs@GSH-FA, respectively. The singlet oxygen quantum yields also increased from 0.37 for ClAlTSPc alone to 0.42 (for ClALTSPc with pristine GQDs), 0.52 (for ClAlTSPc with GQDs@GSH), and 0.54 (for ClAlTSPc with GQDs@GSH-FA). Thus, the present work may lead to a new generation of carbon-based nanomaterial photodynamic therapy agents with overall performance superior to conventional agents in terms of singlet oxygen generation, water dispersibility, and biocompatibility.
- Full Text:
- Date Issued: 2017
- Authors: Nwahara, Nnamdi , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188943 , vital:44800 , xlink:href="https://doi.org/10.1080/00958972.2017.1313975"
- Description: Glutathione-capped graphene quantum dots (GQDs@GSH) were covalently linked to folic acid (FA). Aluminum tetrasulfonated phthalocyanine (ClAlTSPc) was then adsorbed on the GQDs@GSH-FA conjugate to form GQDs@GSH-FA/ClAlTSPc or on GQDs@GSH and pristine GQDs alone to form GQDs@GSH/ClAlTSPc and GQDs/ClAlTSPc, respectively. We report for the first time on the photophysicochemical behavior of the resulting nanoconjugates. The fluorescence quantum yields of pristine GQDs, GQDS@GSH, or GQDs@GSH-FA conjugate were quenched upon non-covalent interaction (π–π) with ClAlTSPc. There was an increase in triplet quantum yields from 0.38 for ClAlTSPc alone to 0.60, 0.75, and 0.73 when ClAlTSPc was linked to pristine GQDs, GQDs@GSH, and GQDs@GSH-FA, respectively. The singlet oxygen quantum yields also increased from 0.37 for ClAlTSPc alone to 0.42 (for ClALTSPc with pristine GQDs), 0.52 (for ClAlTSPc with GQDs@GSH), and 0.54 (for ClAlTSPc with GQDs@GSH-FA). Thus, the present work may lead to a new generation of carbon-based nanomaterial photodynamic therapy agents with overall performance superior to conventional agents in terms of singlet oxygen generation, water dispersibility, and biocompatibility.
- Full Text:
- Date Issued: 2017
Tuning the redox properties of metalloporphyrin-and metallophthalocyanine-based molecular electrodes for the highest electrocatalytic activity in the oxidation of thiols
- Bedioui, Fethi, Griveau, Sophie, Nyokong, Tebello, Appleby, A John, Caro, Claudia A, Gulppi, Miguel, Ochoa, Gonzalo, Zagal, José H
- Authors: Bedioui, Fethi , Griveau, Sophie , Nyokong, Tebello , Appleby, A John , Caro, Claudia A , Gulppi, Miguel , Ochoa, Gonzalo , Zagal, José H
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/283988 , vital:56009 , xlink:href="https://doi.org/10.1039/B618767F"
- Description: In this work we discuss different approaches for achieving electrodes modified with N4 macrocyclic complexes for the catalysis of the electrochemical oxidation of thiols. These approaches involve adsorption, electropolymerization and molecular anchoring using self assembled monolayers. We also discuss the parameters that determine the reactivity of these complexes. Catalytic activity is associated with the nature of the central metal, redox potentials and Hammett parameters of substituents on the ligand. Correlations between catalytic activity (log i at constant E) and the redox potential of catalysts for complexes of Cr, Mn, Fe, Co, Ni and Cu are linear with an increase of activity for more positive redox potentials. For a great variety complexes bearing the same metal center (Co) correlations between log i and Eo′ of the Co(II)/Co(I) couple have the shape of an unsymmetric volcano. This indicates that the potential of the Co(II)/Co(I) couple can be tuned using the appropiate ligand to achieve maximum catalytic activity. Maximum activity probably corresponds to a ΔG of adsorption of the thiol on the Co center equal to zero, and to a coverage of active sites by the thiol equal to 0.5.
- Full Text:
- Date Issued: 2007
- Authors: Bedioui, Fethi , Griveau, Sophie , Nyokong, Tebello , Appleby, A John , Caro, Claudia A , Gulppi, Miguel , Ochoa, Gonzalo , Zagal, José H
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/283988 , vital:56009 , xlink:href="https://doi.org/10.1039/B618767F"
- Description: In this work we discuss different approaches for achieving electrodes modified with N4 macrocyclic complexes for the catalysis of the electrochemical oxidation of thiols. These approaches involve adsorption, electropolymerization and molecular anchoring using self assembled monolayers. We also discuss the parameters that determine the reactivity of these complexes. Catalytic activity is associated with the nature of the central metal, redox potentials and Hammett parameters of substituents on the ligand. Correlations between catalytic activity (log i at constant E) and the redox potential of catalysts for complexes of Cr, Mn, Fe, Co, Ni and Cu are linear with an increase of activity for more positive redox potentials. For a great variety complexes bearing the same metal center (Co) correlations between log i and Eo′ of the Co(II)/Co(I) couple have the shape of an unsymmetric volcano. This indicates that the potential of the Co(II)/Co(I) couple can be tuned using the appropiate ligand to achieve maximum catalytic activity. Maximum activity probably corresponds to a ΔG of adsorption of the thiol on the Co center equal to zero, and to a coverage of active sites by the thiol equal to 0.5.
- Full Text:
- Date Issued: 2007
Optical properties of water-soluble L-cysteine-capped alloyed CdSeS quantum dot passivated with ZnSeTe and ZnSeTe/ZnS shells
- Adegoke, Oluwasesan, Nyokong, Tebello, Forbes, Patricia B C
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193609 , vital:45352 , xlink:href="https://doi.org/10.1016/j.optmat.2015.05.024"
- Description: Alloyed quantum dots (QDs) passivated with shell materials have valuable optical characteristics suitable for a wide array of applications. In this work, alloyed ternary CdSeS QDs passivated with ZnSeTe and ZnSeTe/ZnS shells have been synthesized via a hot-injection method and a ligand exchange reaction employing L-cysteine as a thiol ligand has been used to obtain these water-soluble nanocrystals for the first time. The photoluminescence (PL) quantum yield (QY) of alloyed L-cysteine-capped CdSeS was 71.2% but decreased significantly to 5.2% upon passivation with a ZnSeTe shell. The red shift in PL emission of the CdSeS/ZnSeTe QDs was attributed to be strain-induced whilst a lattice-induced process likely created defect states in the core/shell interface hence contributing to the decline in the PL QY. Nonetheless, the fluorescence stability of CdSeS/ZnSeTe QDs in aqueous solution was unperturbed. Further passivation with a ZnS shell (CdSeS/ZnSeTe/ZnS) improved the PL QY to a value of 58.7% and thus indicates that the defect state in the QDs core/shell/shell structure was reduced. PL lifetime exciton measurements indicated that the rates of decay of the QDs influenced their photophysical properties.
- Full Text:
- Date Issued: 2015
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193609 , vital:45352 , xlink:href="https://doi.org/10.1016/j.optmat.2015.05.024"
- Description: Alloyed quantum dots (QDs) passivated with shell materials have valuable optical characteristics suitable for a wide array of applications. In this work, alloyed ternary CdSeS QDs passivated with ZnSeTe and ZnSeTe/ZnS shells have been synthesized via a hot-injection method and a ligand exchange reaction employing L-cysteine as a thiol ligand has been used to obtain these water-soluble nanocrystals for the first time. The photoluminescence (PL) quantum yield (QY) of alloyed L-cysteine-capped CdSeS was 71.2% but decreased significantly to 5.2% upon passivation with a ZnSeTe shell. The red shift in PL emission of the CdSeS/ZnSeTe QDs was attributed to be strain-induced whilst a lattice-induced process likely created defect states in the core/shell interface hence contributing to the decline in the PL QY. Nonetheless, the fluorescence stability of CdSeS/ZnSeTe QDs in aqueous solution was unperturbed. Further passivation with a ZnS shell (CdSeS/ZnSeTe/ZnS) improved the PL QY to a value of 58.7% and thus indicates that the defect state in the QDs core/shell/shell structure was reduced. PL lifetime exciton measurements indicated that the rates of decay of the QDs influenced their photophysical properties.
- Full Text:
- Date Issued: 2015
The electrochemical detection of prostate specific antigen on glassy carbon electrode modified with combinations of graphene quantum dots, cobalt phthalocyanine and an aptamer
- Nxele, Siphesihle R, Nyokong, Tebello
- Authors: Nxele, Siphesihle R , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185013 , vital:44316 , xlink:href="https://doi.org/10.1016/j.jinorgbio.2021.111462"
- Description: Herein, a novel aptasensor is developed for the electrochemical detection of prostate specific antigen (PSA) on electrode surfaces modified using various combinations of a Cobalt phthalocyanine (CoPc), an aptamer and graphene quantum dots (GQDs). Electrochemical impedance spectroscopy (EIS) as well as differential pulse voltammetry (DPV) are employed for the detection of PSA. In both analytical techniques, linear calibration curves were observed at a concentration range of 1.2–2.0 pM. The glassy carbon electrode where CoPc and GQDs are placed on the electrode when non-covalently linked followed by addition of the aptamer (GQDs-CoPc(ππ)-aptamer (sequential)) showed the best performance with a limit of detection (LoD) as low as 0.66 pM when using DPV. The detection limits were much lower than the dangerous levels reported for PSA in males tested for prostate cancer. This electrode showed selectivity for PSA in the presence of bovine serum albumin, glucose and L-cysteine. The aptasensor showed good stability, reproducibility and repeatability, deeming it a promising early detection device for prostate cancer.
- Full Text:
- Date Issued: 2021
- Authors: Nxele, Siphesihle R , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185013 , vital:44316 , xlink:href="https://doi.org/10.1016/j.jinorgbio.2021.111462"
- Description: Herein, a novel aptasensor is developed for the electrochemical detection of prostate specific antigen (PSA) on electrode surfaces modified using various combinations of a Cobalt phthalocyanine (CoPc), an aptamer and graphene quantum dots (GQDs). Electrochemical impedance spectroscopy (EIS) as well as differential pulse voltammetry (DPV) are employed for the detection of PSA. In both analytical techniques, linear calibration curves were observed at a concentration range of 1.2–2.0 pM. The glassy carbon electrode where CoPc and GQDs are placed on the electrode when non-covalently linked followed by addition of the aptamer (GQDs-CoPc(ππ)-aptamer (sequential)) showed the best performance with a limit of detection (LoD) as low as 0.66 pM when using DPV. The detection limits were much lower than the dangerous levels reported for PSA in males tested for prostate cancer. This electrode showed selectivity for PSA in the presence of bovine serum albumin, glucose and L-cysteine. The aptasensor showed good stability, reproducibility and repeatability, deeming it a promising early detection device for prostate cancer.
- Full Text:
- Date Issued: 2021
Enhanced Optical Limiting Behavior of an Indium Phthalocyanine–Single-Walled Carbon Nanotube Composite
- Sanusi, Kayode, Amuhaya, Edith K, Nyokong, Tebello
- Authors: Sanusi, Kayode , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193871 , vital:45401 , xlink:href="https://doi.org/10.1021/jp501469e "
- Description: The nonlinear optical behavior of 2(3),9(10),16(17),23(24)-tetrakis-(4-aminophenoxy) phthalocyaninato indium (III) chloride (2) and its carbon nanotube composite in dimethylsulfoxide (DMSO) and dimethylformamide (DMF) solutions is described. The nonlinear third-order susceptibility and second-order hyperpolarizability values are also reported. A large nonlinear absorption that increased on covalent linking with single-walled carbon nanotubes (SWCNTs) was observed for the compound in DMSO. The nanosecond nonlinear absorption and the optical limiting behavior of this complex are shown to be dominated by a strong excited state absorption from a two-photon pumped state. The optical limiter using the new nanocomposite material (SWCNT-2) in the appropriate solvent showed a much lower threshold for optical limiting together with a much lower transmission at high fluences than previously reported nanocomposite limiters. The optical properties of the phthalocyanine and its conjugate were found to show high sensitivity toward the change of solvent matrix.
- Full Text:
- Date Issued: 2014
- Authors: Sanusi, Kayode , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193871 , vital:45401 , xlink:href="https://doi.org/10.1021/jp501469e "
- Description: The nonlinear optical behavior of 2(3),9(10),16(17),23(24)-tetrakis-(4-aminophenoxy) phthalocyaninato indium (III) chloride (2) and its carbon nanotube composite in dimethylsulfoxide (DMSO) and dimethylformamide (DMF) solutions is described. The nonlinear third-order susceptibility and second-order hyperpolarizability values are also reported. A large nonlinear absorption that increased on covalent linking with single-walled carbon nanotubes (SWCNTs) was observed for the compound in DMSO. The nanosecond nonlinear absorption and the optical limiting behavior of this complex are shown to be dominated by a strong excited state absorption from a two-photon pumped state. The optical limiter using the new nanocomposite material (SWCNT-2) in the appropriate solvent showed a much lower threshold for optical limiting together with a much lower transmission at high fluences than previously reported nanocomposite limiters. The optical properties of the phthalocyanine and its conjugate were found to show high sensitivity toward the change of solvent matrix.
- Full Text:
- Date Issued: 2014
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
Solvent effect on the third-order nonlinear optical properties of α-and β-tertbutyl phenoxy-substituted tin (IV) chloride phthalocyanines
- Louzada, Marcel, Britton, Jonathan, Nyokong, Tebello, Khene, Samson M
- Authors: Louzada, Marcel , Britton, Jonathan , Nyokong, Tebello , Khene, Samson M
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188910 , vital:44797 , xlink:href="https://doi.org/10.1021/acs.jpca.7b07349"
- Description: This paper investigates the third-order nonlinear optical properties of 4α-(4-tert-butylphenoxy) phthalocyaninato dichlorotin(IV) (α-SnOtBpPc) and 4β-(4-tert-butylphenoxy) phthalocyaninato dichlorotin(IV) (β-SnOtBpPc) in different organic solvents. The third-order susceptibilities of α-SnOtBpPc and βSnOtBpPc are reported in different solvents, using Z-scan techniques with 10 ns laser pulses at 532 nm. Their nonlinear absorption coefficient and absorption cross sections were also determined. The molecular imaginary components of the secondorder hyperpolarizability Im[γ] of α-SnOtBpPc and β-SnOtBpPc were found to be 2.60 × 10−31 and 2.94 × 10−31 esu (tetrahydrofuran), 2.12 × 10−31 and 2.54 × 10−31 esu (chloroform), 3.06 × 10−31 and 2.54 × 10−31 esu (dichloromethane), and 1.27 × 10−31 and 1.50 × 10−31 esu (toluene), respectively. This study found that substitution at the α position has an effect of lowering the two-photon (2PA) cross section value for α-SnOtBpPc compared to that for β-SnOtBpPc, with values of 64.30 and 456.65 GM, respectively. The large 2PA cross section observed in β-SnOtBpPc is attributed to the decreased energy difference between the virtual state and the LUMO.
- Full Text:
- Date Issued: 2017
- Authors: Louzada, Marcel , Britton, Jonathan , Nyokong, Tebello , Khene, Samson M
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188910 , vital:44797 , xlink:href="https://doi.org/10.1021/acs.jpca.7b07349"
- Description: This paper investigates the third-order nonlinear optical properties of 4α-(4-tert-butylphenoxy) phthalocyaninato dichlorotin(IV) (α-SnOtBpPc) and 4β-(4-tert-butylphenoxy) phthalocyaninato dichlorotin(IV) (β-SnOtBpPc) in different organic solvents. The third-order susceptibilities of α-SnOtBpPc and βSnOtBpPc are reported in different solvents, using Z-scan techniques with 10 ns laser pulses at 532 nm. Their nonlinear absorption coefficient and absorption cross sections were also determined. The molecular imaginary components of the secondorder hyperpolarizability Im[γ] of α-SnOtBpPc and β-SnOtBpPc were found to be 2.60 × 10−31 and 2.94 × 10−31 esu (tetrahydrofuran), 2.12 × 10−31 and 2.54 × 10−31 esu (chloroform), 3.06 × 10−31 and 2.54 × 10−31 esu (dichloromethane), and 1.27 × 10−31 and 1.50 × 10−31 esu (toluene), respectively. This study found that substitution at the α position has an effect of lowering the two-photon (2PA) cross section value for α-SnOtBpPc compared to that for β-SnOtBpPc, with values of 64.30 and 456.65 GM, respectively. The large 2PA cross section observed in β-SnOtBpPc is attributed to the decreased energy difference between the virtual state and the LUMO.
- Full Text:
- Date Issued: 2017
Effects of axial ligands on the photophysical properties of silicon octaphenoxyphthalocyanine
- Maree, M David, Nyokong, Tebello, Suhling, Klaus, Phillips, David
- Authors: Maree, M David , Nyokong, Tebello , Suhling, Klaus , Phillips, David
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289582 , vital:56651 , xlink:href="https://doi.org/10.1142/S1088424602000452"
- Description: The photochemistry and photophysics of six axially substituted silicon phthalocyanines are reported and show the importance of the axial groups in the photochemistry of these compounds. The fluorescence quantum yields are especially affected by the axial ligand. A very good correlation was found for the experimentally determined fluorescence lifetimes and the theoretically determined lifetimes using the Strickler-Berg equation for the unaggregated molecules.
- Full Text:
- Date Issued: 2002
- Authors: Maree, M David , Nyokong, Tebello , Suhling, Klaus , Phillips, David
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289582 , vital:56651 , xlink:href="https://doi.org/10.1142/S1088424602000452"
- Description: The photochemistry and photophysics of six axially substituted silicon phthalocyanines are reported and show the importance of the axial groups in the photochemistry of these compounds. The fluorescence quantum yields are especially affected by the axial ligand. A very good correlation was found for the experimentally determined fluorescence lifetimes and the theoretically determined lifetimes using the Strickler-Berg equation for the unaggregated molecules.
- Full Text:
- Date Issued: 2002
Photophysical and nonlinear optical characteristics of pyridyl substituted phthalocyanine-detonation nanodiamond conjugated systems in solution
- Matshitse, Refilwe, Khene, Samson M, Nyokong, Tebello
- Authors: Matshitse, Refilwe , Khene, Samson M , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187079 , vital:44563 , xlink:href="https://doi.org/10.1016/j.diamond.2019.03.013"
- Description: In this study photophysical, nonlinear absorption and optical limiting properties of detonation nanodiamonds (DNDs)-phthalocyanine nanoconjugate systems containing: 2,9(10),16(17),23(24)-tetrakis-(4-pyridyloxy) phthalocyaninato (H2TPPc), 2,9(10),16(17),23(24)-tetrakis-(4-pyridyloxy) phthalocyanato zinc(II) (ZnTPPc) and 2,9(10),16(17),23(24)-tetrakis-(4-pyridyloxy) phthalocyanato silicon(IV) hydroxide (Si(OH)2TPPc), were investigated in dimethylsulfoxide solution. Pcs were non-covalently linked to nanondiamonds (also covalently linked for Si(OH)2TPPc) and investigated using 532 nm laser excitation at 10 ns pulses for their optical limiting properties. Complexes that have higher triplet state absorption also possessed enhanced nonlinear optical behaviour following reverse saturable absorption mechanism. Superior optical performance is observed when the Pcs had a central metal with axial ligands conjugated to DNDs in solution. Nanoconjugate of DNDs-Si(OH)2TPPc and respective Pc in solution gave the highest imaginary third-order susceptibility (Im[X(3)]) and hyperpolarizability (γ) at 2.91 × 10−8 and 3.17 × 10−8 esu and 3.88 × 10−28 and 4.22 × 10−28 esu, respectively, with Ilim value of 0.47 and 0.39 J·cm−2.
- Full Text:
- Date Issued: 2019
- Authors: Matshitse, Refilwe , Khene, Samson M , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187079 , vital:44563 , xlink:href="https://doi.org/10.1016/j.diamond.2019.03.013"
- Description: In this study photophysical, nonlinear absorption and optical limiting properties of detonation nanodiamonds (DNDs)-phthalocyanine nanoconjugate systems containing: 2,9(10),16(17),23(24)-tetrakis-(4-pyridyloxy) phthalocyaninato (H2TPPc), 2,9(10),16(17),23(24)-tetrakis-(4-pyridyloxy) phthalocyanato zinc(II) (ZnTPPc) and 2,9(10),16(17),23(24)-tetrakis-(4-pyridyloxy) phthalocyanato silicon(IV) hydroxide (Si(OH)2TPPc), were investigated in dimethylsulfoxide solution. Pcs were non-covalently linked to nanondiamonds (also covalently linked for Si(OH)2TPPc) and investigated using 532 nm laser excitation at 10 ns pulses for their optical limiting properties. Complexes that have higher triplet state absorption also possessed enhanced nonlinear optical behaviour following reverse saturable absorption mechanism. Superior optical performance is observed when the Pcs had a central metal with axial ligands conjugated to DNDs in solution. Nanoconjugate of DNDs-Si(OH)2TPPc and respective Pc in solution gave the highest imaginary third-order susceptibility (Im[X(3)]) and hyperpolarizability (γ) at 2.91 × 10−8 and 3.17 × 10−8 esu and 3.88 × 10−28 and 4.22 × 10−28 esu, respectively, with Ilim value of 0.47 and 0.39 J·cm−2.
- Full Text:
- Date Issued: 2019
Determination of 2′, 3′-Dideoxyinosine Using Iron (II) Phthalocyanine Modified Carbon Paste Electrode
- Ozoemena, Kenneth I, Stefan, Raluca-Ioana, Nyokong, Tebello
- Authors: Ozoemena, Kenneth I , Stefan, Raluca-Ioana , Nyokong, Tebello
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/300298 , vital:57914 , xlink:href="https://doi.org/10.1081/AL-200031940"
- Description: An amperometric sensor, based on carbon paste impregnated with iron (II) phthalocyanine complex (FePc), has been constructed for the assay of anti‐HIV agent dideoxyinosine (didanosine, DDI). Using chronoamperometry (E = +1.04 V versus Ag/AgCl) technique, the amperometric sensor can be used reliably for dideoxyinosine assay at pH 7.4 phosphate buffer in the 1.5–9.5 nmol/L concentration range with a detection limit of 5.7 × 10−10 mol/L. The surface of the electrode can easily be regenerated by simple polishing, obtaining a fresh surface ready for use in a new assay. The new amperometric sensor proved to be highly reliable for the assay of dideoxyinosine purity in raw material as well as for the uniformity content test of Videx® tablets.
- Full Text:
- Date Issued: 2004
- Authors: Ozoemena, Kenneth I , Stefan, Raluca-Ioana , Nyokong, Tebello
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/300298 , vital:57914 , xlink:href="https://doi.org/10.1081/AL-200031940"
- Description: An amperometric sensor, based on carbon paste impregnated with iron (II) phthalocyanine complex (FePc), has been constructed for the assay of anti‐HIV agent dideoxyinosine (didanosine, DDI). Using chronoamperometry (E = +1.04 V versus Ag/AgCl) technique, the amperometric sensor can be used reliably for dideoxyinosine assay at pH 7.4 phosphate buffer in the 1.5–9.5 nmol/L concentration range with a detection limit of 5.7 × 10−10 mol/L. The surface of the electrode can easily be regenerated by simple polishing, obtaining a fresh surface ready for use in a new assay. The new amperometric sensor proved to be highly reliable for the assay of dideoxyinosine purity in raw material as well as for the uniformity content test of Videx® tablets.
- Full Text:
- Date Issued: 2004
A comparative physicochemical study of unsymmetrical indium phthalocyanines in the presence of magnetic nanoparticles or quantum dots
- Osifeko, Olawale L, Nyokong, Tebello
- Authors: Osifeko, Olawale L , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188743 , vital:44781 , xlink:href="https://doi.org/10.1080/00958972.2016.1152628"
- Description: Asymmetric indium phthalocyanine (3, containing an NH2 group) was conjugated (via an amide bond) to magnetic nanoparticle (MNP) functionalized with carboxylic acid or glutathione-capped CdTe/ZnSe/ZnO quantum dots to form 3-MNPs or 3-QDs. Techniques such as time-resolved fluorescence measurements, transmission electron microscopy, XPS, elemental analysis, FTIR, NMR (1H, 13C, and cozy), electronic spectroscopy, as well as mass spectroscopy were employed to characterize 3 and its nanoconjugates. The phthalocyanine conjugated to quantum dot (3-QDs) possesses the lowest Фpd higher Ф∆ and ФT as well as longer triplet lifetimes compares to 3-MNPs and free phthalocyanine.
- Full Text:
- Date Issued: 2016
- Authors: Osifeko, Olawale L , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188743 , vital:44781 , xlink:href="https://doi.org/10.1080/00958972.2016.1152628"
- Description: Asymmetric indium phthalocyanine (3, containing an NH2 group) was conjugated (via an amide bond) to magnetic nanoparticle (MNP) functionalized with carboxylic acid or glutathione-capped CdTe/ZnSe/ZnO quantum dots to form 3-MNPs or 3-QDs. Techniques such as time-resolved fluorescence measurements, transmission electron microscopy, XPS, elemental analysis, FTIR, NMR (1H, 13C, and cozy), electronic spectroscopy, as well as mass spectroscopy were employed to characterize 3 and its nanoconjugates. The phthalocyanine conjugated to quantum dot (3-QDs) possesses the lowest Фpd higher Ф∆ and ФT as well as longer triplet lifetimes compares to 3-MNPs and free phthalocyanine.
- Full Text:
- Date Issued: 2016
Photophysical and photochemical studies of sulfur containing phthalocyanine derivatives in the presence of folic acid
- Nombona, Nolwazi, Nyokong, Tebello
- Authors: Nombona, Nolwazi , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243180 , vital:51124 , xlink:href="https://doi.org/10.1016/j.ica.2012.03.051"
- Description: The syntheses of zinc and magnesium 9,16,23-tris-(5-trifluoromethyl-2-mercaptopyridine)-2-(carboxy)phthalocyaninato complexes are described for the first time. The photophysical and photochemical parameters of these molecules in the absence or presence of folic acid are compared to the corresponding oxygen bridged complexes and to 2,9,17,23-tetrakis-[(1,6-hexanedithiol)phthalocyaninato]zinc(II), [8,15,22-tris-(naptho)-2-(amidoethanethiol)phthalocyaninato]zinc(II) and zinc phthalocyanine tetrasulfonate. In the absence of folic acid, the complexes show relatively good triplet quantum yields (ranging from 0.52 to 0.88) in DMSO with reasonable triplet lifetime between 140 and 470 μs. The complexes showed high singlet oxygen quantum yield values ranging from 0.27 to 0.66 in the absence of folic acid. In the presence of folic acid, the triplet quantum yield values were between 0.37 and 0.75 and the lifetimes were significantly reduced (70–320 μs).
- Full Text:
- Date Issued: 2012
- Authors: Nombona, Nolwazi , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243180 , vital:51124 , xlink:href="https://doi.org/10.1016/j.ica.2012.03.051"
- Description: The syntheses of zinc and magnesium 9,16,23-tris-(5-trifluoromethyl-2-mercaptopyridine)-2-(carboxy)phthalocyaninato complexes are described for the first time. The photophysical and photochemical parameters of these molecules in the absence or presence of folic acid are compared to the corresponding oxygen bridged complexes and to 2,9,17,23-tetrakis-[(1,6-hexanedithiol)phthalocyaninato]zinc(II), [8,15,22-tris-(naptho)-2-(amidoethanethiol)phthalocyaninato]zinc(II) and zinc phthalocyanine tetrasulfonate. In the absence of folic acid, the complexes show relatively good triplet quantum yields (ranging from 0.52 to 0.88) in DMSO with reasonable triplet lifetime between 140 and 470 μs. The complexes showed high singlet oxygen quantum yield values ranging from 0.27 to 0.66 in the absence of folic acid. In the presence of folic acid, the triplet quantum yield values were between 0.37 and 0.75 and the lifetimes were significantly reduced (70–320 μs).
- Full Text:
- Date Issued: 2012
A novel axially palladium (II)-Schiff base complex substituted silicon (IV) phthalocyanine
- Sen, Pinar, Nyokong, Tebello
- Authors: Sen, Pinar , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186813 , vital:44536 , xlink:href="https://doi.org/10.1016/j.poly.2019.114135"
- Description: In this study, a novel silicon(IV) phthalocyanine is reported for the first time as a phthalocyanine derivative bearing axially a palladium(II)-Schiff base complex. The photophysical and photochemical properties of the new Si(IV)Pc, such as absorption, fluorescence, singlet oxygen quantum yields, triplet state quantum yields and exited state lifetimes were measured in DMSO. The new silicon phthalocyanine displayed very low fluorescence, showing efficient intersystem crossing resulting in high triplet and high singlet oxygen quantum yields in DMSO. When compared with the unsubstituted SiPcCl2, the singlet oxygen quantum yield value (UD = 0.47) in relation to the triplet quantum yield (UT = 0.82), which is an important determinant for PDT applications, increased. The photodynamic antimicrobial chemotherapy activity (PACT) of new Si(IV)Pc towards Staphylococcus aureus was determined in comparison to the unsubstituted SiPcCl2. The results of the photodynamic antimicrobial effect study demonstrated that the Pd(II) complex substituted SiPc (5) possesses excellent photodynamic activity with a reduction percentage value of 99.94% and a log red value of 3.26.
- Full Text:
- Date Issued: 2019
- Authors: Sen, Pinar , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186813 , vital:44536 , xlink:href="https://doi.org/10.1016/j.poly.2019.114135"
- Description: In this study, a novel silicon(IV) phthalocyanine is reported for the first time as a phthalocyanine derivative bearing axially a palladium(II)-Schiff base complex. The photophysical and photochemical properties of the new Si(IV)Pc, such as absorption, fluorescence, singlet oxygen quantum yields, triplet state quantum yields and exited state lifetimes were measured in DMSO. The new silicon phthalocyanine displayed very low fluorescence, showing efficient intersystem crossing resulting in high triplet and high singlet oxygen quantum yields in DMSO. When compared with the unsubstituted SiPcCl2, the singlet oxygen quantum yield value (UD = 0.47) in relation to the triplet quantum yield (UT = 0.82), which is an important determinant for PDT applications, increased. The photodynamic antimicrobial chemotherapy activity (PACT) of new Si(IV)Pc towards Staphylococcus aureus was determined in comparison to the unsubstituted SiPcCl2. The results of the photodynamic antimicrobial effect study demonstrated that the Pd(II) complex substituted SiPc (5) possesses excellent photodynamic activity with a reduction percentage value of 99.94% and a log red value of 3.26.
- Full Text:
- Date Issued: 2019
Nonlinear optical response and electrocatalytic activity of cobalt phthalocyanine clicked zinc oxide nanoparticles
- Mpeta, Lekhetho S, Sekhosana, Kutloano E, Nyokong, Tebello
- Authors: Mpeta, Lekhetho S , Sekhosana, Kutloano E , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186179 , vital:44471 , xlink:href="https://doi.org/10.1016/j.ica.2020.119661"
- Description: In this article, we report on the linking of cobalt tetrakis (4-pentyn-oxy) phthalocyanine (CoTPPc) to ZnO nanoparticles via click chemistry. Subsequently, electrocatalytic activity and nonlinear optical properties were investigated (the latter using an open Z-scan technique at 532 nm). The linking of CoTPPc with ZnO resulted in the lowest limiting intensity value of 0.27 J.Cm−2, the βeff (cmW−1) values were found to be 1.51 × 10-8 and 7.10 × 104 for ZnO and CoTPPc-ZnO respectively. The catalytic rate constants (M−1s−1) (and limits of detection) were 4.1 × 104 (12.87 µM), 5.7 × 104 (8.62 µM) and 7.36 × 104 (4.35 µM) for ZnO, CoTPPc and CoTPPc-ZnO. Hence linking ZnO nanoparticles to CoTPPc result in the enhancement of both nonlinear optical behaviour and catalytic activity.
- Full Text:
- Date Issued: 2020
- Authors: Mpeta, Lekhetho S , Sekhosana, Kutloano E , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186179 , vital:44471 , xlink:href="https://doi.org/10.1016/j.ica.2020.119661"
- Description: In this article, we report on the linking of cobalt tetrakis (4-pentyn-oxy) phthalocyanine (CoTPPc) to ZnO nanoparticles via click chemistry. Subsequently, electrocatalytic activity and nonlinear optical properties were investigated (the latter using an open Z-scan technique at 532 nm). The linking of CoTPPc with ZnO resulted in the lowest limiting intensity value of 0.27 J.Cm−2, the βeff (cmW−1) values were found to be 1.51 × 10-8 and 7.10 × 104 for ZnO and CoTPPc-ZnO respectively. The catalytic rate constants (M−1s−1) (and limits of detection) were 4.1 × 104 (12.87 µM), 5.7 × 104 (8.62 µM) and 7.36 × 104 (4.35 µM) for ZnO, CoTPPc and CoTPPc-ZnO. Hence linking ZnO nanoparticles to CoTPPc result in the enhancement of both nonlinear optical behaviour and catalytic activity.
- Full Text:
- Date Issued: 2020
Phthalocyanine based fabricated exfoliated graphite photoanode for electrodegradation of 4-acetamidophenol under visible light irradiation
- Mpeta, Lekhetho S, Nyokong, Tebello
- Authors: Mpeta, Lekhetho S , Nyokong, Tebello
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295809 , vital:57380 , xlink:href="https://doi.org/10.1016/j.jphotochem.2022.114115"
- Description: In this study exfoliated graphite (EG) was prepared from natural graphite flakes and incorporated with zinc phthalocyanine for fabrication of photoanode. The electron transfer capabilities of fabricated photoanode were examined by using cyclic voltammetry, electrochemical impedance spectroscopy and scanning electrochemical microscopy. Electrophotocatalytic degradation of 4-acetamidophenol in 0.1 M Na2SO4 electrolyte was performed. The photoanode with zinc phthalocyanine (EG-ZnPc) displayed better degradation compared to when only exfoliated graphite was used (EG). Furthermore, electrophotocatalytic degradation gave better performance (removal efficiency of 47.76%) than when individual electrochemical degradation and photodegradation techniques were used.
- Full Text:
- Date Issued: 2022
- Authors: Mpeta, Lekhetho S , Nyokong, Tebello
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295809 , vital:57380 , xlink:href="https://doi.org/10.1016/j.jphotochem.2022.114115"
- Description: In this study exfoliated graphite (EG) was prepared from natural graphite flakes and incorporated with zinc phthalocyanine for fabrication of photoanode. The electron transfer capabilities of fabricated photoanode were examined by using cyclic voltammetry, electrochemical impedance spectroscopy and scanning electrochemical microscopy. Electrophotocatalytic degradation of 4-acetamidophenol in 0.1 M Na2SO4 electrolyte was performed. The photoanode with zinc phthalocyanine (EG-ZnPc) displayed better degradation compared to when only exfoliated graphite was used (EG). Furthermore, electrophotocatalytic degradation gave better performance (removal efficiency of 47.76%) than when individual electrochemical degradation and photodegradation techniques were used.
- Full Text:
- Date Issued: 2022
Enhanced Light-Driven Antimicrobial Activity of Cationic Poly (oxanorbornene) s by Phthalocyanine Incorporation into Polymer as Pendants
- Ahmetali, Erem, Sen, Pinar, Süer, N Ceren, Aksu, Burak, Nyokong, Tebello, Eren, Tarik, Sener, Kasim M
- Authors: Ahmetali, Erem , Sen, Pinar , Süer, N Ceren , Aksu, Burak , Nyokong, Tebello , Eren, Tarik , Sener, Kasim M
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185976 , vital:44453 , xlink:href=" https://doi.org/10.1002/macp.202000386"
- Description: Amphiphilic poly(oxanorbornene)s are promising synthetic polymers that mimic the structural properties and antimicrobial functions of naturally occurring antimicrobial peptides. Here, poly(oxanorbornene)s bearing pendant zinc(II) phthalocyanine and triphenyl(ethyl) phosphonium functionalities are synthesized by ring-opening metathesis polymerization (ROMP). Fluorescence, singlet oxygen and triplet quantum yields of polymers are measured in dimethyl sulfoxide and aqueous medium. The singlet oxygen quantum yields of copolymers with the highest triphenyl and triethyl phosphonium content are found to be 0.29 and 0.41, respectively. Then, antimicrobial activities of polymers against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) are investigated under both dark and light conditions. Synergistic effect of zinc(II) phthalocyanine and phosphonium-containing poly(oxanorbornene) is observed that the conjugate possessing the most triphenyl phosphonium side chains has the highest activity under light against both gram-positive and gram-negative bacterial strains after 80 min irradiation, reducing the survival of E. coli or S. aureus by 99.9999%. Hemolytic concentrations of the copolymers are found between 8 and 512 µg mL−1. Scanning electron microscopy (SEM) proves that the bacteria membrane deforms after contacting with the biocidal polymer.
- Full Text:
- Date Issued: 2020
- Authors: Ahmetali, Erem , Sen, Pinar , Süer, N Ceren , Aksu, Burak , Nyokong, Tebello , Eren, Tarik , Sener, Kasim M
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185976 , vital:44453 , xlink:href=" https://doi.org/10.1002/macp.202000386"
- Description: Amphiphilic poly(oxanorbornene)s are promising synthetic polymers that mimic the structural properties and antimicrobial functions of naturally occurring antimicrobial peptides. Here, poly(oxanorbornene)s bearing pendant zinc(II) phthalocyanine and triphenyl(ethyl) phosphonium functionalities are synthesized by ring-opening metathesis polymerization (ROMP). Fluorescence, singlet oxygen and triplet quantum yields of polymers are measured in dimethyl sulfoxide and aqueous medium. The singlet oxygen quantum yields of copolymers with the highest triphenyl and triethyl phosphonium content are found to be 0.29 and 0.41, respectively. Then, antimicrobial activities of polymers against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) are investigated under both dark and light conditions. Synergistic effect of zinc(II) phthalocyanine and phosphonium-containing poly(oxanorbornene) is observed that the conjugate possessing the most triphenyl phosphonium side chains has the highest activity under light against both gram-positive and gram-negative bacterial strains after 80 min irradiation, reducing the survival of E. coli or S. aureus by 99.9999%. Hemolytic concentrations of the copolymers are found between 8 and 512 µg mL−1. Scanning electron microscopy (SEM) proves that the bacteria membrane deforms after contacting with the biocidal polymer.
- Full Text:
- Date Issued: 2020
Effects of pluronic silica nanoparticles on the photophysical and photodynamic therapy behavior of triphenyl-p-phenoxy benzoic acid metalloporphyrins
- Managa, Muthumuni, Britton, Jonathan, Prinsloo, Earl, Nyokong, Tebello
- Authors: Managa, Muthumuni , Britton, Jonathan , Prinsloo, Earl , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/239698 , vital:50756 , xlink:href="https://doi.org/10.1080/00958972.2016.1236372"
- Description: 5, 10, 15, Triphenyl-20-p-phenoxy benzoic acid porphyrins (P) containing Zn (ZnP), Ga (GaP), and Si (SiP) were synthesized and conjugated to pluronic-silica (PluS) nanoparticles (NPs) where the fluorescence and singlet oxygen generating behavior of the porphyrins were investigated. The highest singlet oxygen quantum yield (ΦΔ) was obtained for ZnP. When the porphyrins were conjugated to the PluS NPs, the ΦΔ was quenched and fluorescence was enhanced. The pore size of the NPs upon conjugation decreased from 18.9 nm for PluS NPs to 2.4 nm (for ZnP as an example) as determined by applying the Brunauer–Emmett–Teller method. The porphyrin complexes and their conjugates were tested for their photodynamic therapy (PDT) activity on MCF-7 breast cancer cells. It was found that ZnP and its conjugate showed the highest PDT activity. The p > 0.05 indicated that ZnP is significantly different than GaP and SiP.
- Full Text:
- Date Issued: 2016
- Authors: Managa, Muthumuni , Britton, Jonathan , Prinsloo, Earl , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/239698 , vital:50756 , xlink:href="https://doi.org/10.1080/00958972.2016.1236372"
- Description: 5, 10, 15, Triphenyl-20-p-phenoxy benzoic acid porphyrins (P) containing Zn (ZnP), Ga (GaP), and Si (SiP) were synthesized and conjugated to pluronic-silica (PluS) nanoparticles (NPs) where the fluorescence and singlet oxygen generating behavior of the porphyrins were investigated. The highest singlet oxygen quantum yield (ΦΔ) was obtained for ZnP. When the porphyrins were conjugated to the PluS NPs, the ΦΔ was quenched and fluorescence was enhanced. The pore size of the NPs upon conjugation decreased from 18.9 nm for PluS NPs to 2.4 nm (for ZnP as an example) as determined by applying the Brunauer–Emmett–Teller method. The porphyrin complexes and their conjugates were tested for their photodynamic therapy (PDT) activity on MCF-7 breast cancer cells. It was found that ZnP and its conjugate showed the highest PDT activity. The p > 0.05 indicated that ZnP is significantly different than GaP and SiP.
- Full Text:
- Date Issued: 2016
Asymmetrical zinc (II) phthalocyanines cobalt tungstate nanomaterial conjugates for photodegradation of methylene blue
- Mgidlana, Sithi, Nyokong, Tebello
- Authors: Mgidlana, Sithi , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184991 , vital:44314 , xlink:href="https://doi.org/10.1016/j.jphotochem.2021.113421"
- Description: Herein, we present syntheses of three asymmetrical zinc(II) phthalocyanine (ZnPc) complexes and hydrothermal synthesis of cobalt tungstate nanoparticles. The ZnPc derivatives were covalently linked to cobalt tungstate nanoparticles. Photophysical and photochemical behaviour of Pcs and nanoconjugates were investigated. The nanoconjugates generated higher triplet quantum yield and singlet oxygen quantum yield than the ZnPcs alone. Furthermore, in this paper photocatalytic efficiencies of ZnPc complexes and nanoconjugates were investigated for the degradation of methylene blue and higher photocatalytic behaviour was observed for the conjugates. The kinetic model was used to study photocatalytic behaviour of all the prepared photocatalysts.
- Full Text:
- Date Issued: 2021
- Authors: Mgidlana, Sithi , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184991 , vital:44314 , xlink:href="https://doi.org/10.1016/j.jphotochem.2021.113421"
- Description: Herein, we present syntheses of three asymmetrical zinc(II) phthalocyanine (ZnPc) complexes and hydrothermal synthesis of cobalt tungstate nanoparticles. The ZnPc derivatives were covalently linked to cobalt tungstate nanoparticles. Photophysical and photochemical behaviour of Pcs and nanoconjugates were investigated. The nanoconjugates generated higher triplet quantum yield and singlet oxygen quantum yield than the ZnPcs alone. Furthermore, in this paper photocatalytic efficiencies of ZnPc complexes and nanoconjugates were investigated for the degradation of methylene blue and higher photocatalytic behaviour was observed for the conjugates. The kinetic model was used to study photocatalytic behaviour of all the prepared photocatalysts.
- Full Text:
- Date Issued: 2021
Effect of ultrasonic frequency and power on the sonodynamic therapy activity of cationic Zn (II) phthalocyanines
- Nene, Lindokuhle C, Sindelo, Azole, Britton, Jonathan, Nyokong, Tebello
- Authors: Nene, Lindokuhle C , Sindelo, Azole , Britton, Jonathan , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185737 , vital:44419 , xlink:href="https://doi.org/10.1016/j.jinorgbio.2021.111397"
- Description: We report on the sonodynamic activity of cationic phthalocyanines (Pcs) and the effect of the variation of two parameters: ultrasound frequency and power (Par I (1 MHz, 1 W cm−2), Par II (1 MHz, 2 W cm−2), Par III (3 MHz, 1 W cm−2) and Par IV (3 MHz, 2 W cm−2)) on the efficiency of their reactive oxygen species generation and cancer eradication in vitro thereof. Where Par stands for the various combinations of these parameters. Four Pcs were investigated with substituents bearing diethylamine, ortho- and para-pyridine and morpholine groups. Overall, the para-pyridine and morpholine Pcs showed substantial sono-activity in the various ultrasound parameters with Par I and IV generally showing better singlet oxygen and hydroxyl radicals generation confirmed by electron paramagnetic resonance spectroscopy. In some cases, very high hydroxyl radicals' generation was observed at Par II. Furthermore, the fragmentation of the Pcs after Par II treatments was confirmed using UV–vis and magnetic circular dichroism spectroscopy. The reactive species generation efficacy decreased at Par III for all samples. Ultrasound assisted cytotoxicity of the Pcs was confirmed in vitro using the human (Michigan Cancer Foundation-7) breast cancer cell line.
- Full Text:
- Date Issued: 2021
- Authors: Nene, Lindokuhle C , Sindelo, Azole , Britton, Jonathan , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185737 , vital:44419 , xlink:href="https://doi.org/10.1016/j.jinorgbio.2021.111397"
- Description: We report on the sonodynamic activity of cationic phthalocyanines (Pcs) and the effect of the variation of two parameters: ultrasound frequency and power (Par I (1 MHz, 1 W cm−2), Par II (1 MHz, 2 W cm−2), Par III (3 MHz, 1 W cm−2) and Par IV (3 MHz, 2 W cm−2)) on the efficiency of their reactive oxygen species generation and cancer eradication in vitro thereof. Where Par stands for the various combinations of these parameters. Four Pcs were investigated with substituents bearing diethylamine, ortho- and para-pyridine and morpholine groups. Overall, the para-pyridine and morpholine Pcs showed substantial sono-activity in the various ultrasound parameters with Par I and IV generally showing better singlet oxygen and hydroxyl radicals generation confirmed by electron paramagnetic resonance spectroscopy. In some cases, very high hydroxyl radicals' generation was observed at Par II. Furthermore, the fragmentation of the Pcs after Par II treatments was confirmed using UV–vis and magnetic circular dichroism spectroscopy. The reactive species generation efficacy decreased at Par III for all samples. Ultrasound assisted cytotoxicity of the Pcs was confirmed in vitro using the human (Michigan Cancer Foundation-7) breast cancer cell line.
- Full Text:
- Date Issued: 2021
Synthesis and photophysical properties of nanocomposites of aluminum tetrasulfonated phthalocyanine covalently linked to glutathione capped CdTe/CdS/ZnS quantum dots
- Oluwole, David O, Britton, Jonathan, Mashazi, Philani N, Nyokong, Tebello
- Authors: Oluwole, David O , Britton, Jonathan , Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241379 , vital:50934 , xlink:href="https://doi.org/10.1016/j.synthmet.2015.04.015"
- Description: Aluminum tetrasulfonated phthalocyanine (ClAlTSPc) was covalently linked with different sizes of glutathione capped CdTe/CdS/ZnS quantum dots (QDs). The photophysical and Förster resonance energy transfer (FRET) properties of the nanoconjugates were investigated. The CdTe/CdS/ZnS(6.3) nanocomposite showed the highest enhancement in its photophysical properties while (CdTe/CdS/ZnS(3.2) nanocomposite showed the least. Highest FRET efficiency was observed in the linked CdTe/CdS/ZnS(6.3) nanocomposites at 93%. Hence, the combination of CdTe/CdS/ZnS with ClAlTSPc exhibited excellent photophysical properties.
- Full Text:
- Date Issued: 2015
- Authors: Oluwole, David O , Britton, Jonathan , Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241379 , vital:50934 , xlink:href="https://doi.org/10.1016/j.synthmet.2015.04.015"
- Description: Aluminum tetrasulfonated phthalocyanine (ClAlTSPc) was covalently linked with different sizes of glutathione capped CdTe/CdS/ZnS quantum dots (QDs). The photophysical and Förster resonance energy transfer (FRET) properties of the nanoconjugates were investigated. The CdTe/CdS/ZnS(6.3) nanocomposite showed the highest enhancement in its photophysical properties while (CdTe/CdS/ZnS(3.2) nanocomposite showed the least. Highest FRET efficiency was observed in the linked CdTe/CdS/ZnS(6.3) nanocomposites at 93%. Hence, the combination of CdTe/CdS/ZnS with ClAlTSPc exhibited excellent photophysical properties.
- Full Text:
- Date Issued: 2015