Remarkable sensitivity for detection of bisphenol A on a gold electrode modified with nickel tetraamino phthalocyanine containing Ni–O–Ni bridges
- Chauke, Vongani, Matemadombo, Fungisai, Nyokong, Tebello
- Authors: Chauke, Vongani , Matemadombo, Fungisai , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/261280 , vital:53380 , xlink:href="https://doi.org/10.1016/j.jhazmat.2010.01.061"
- Description: This work reports the electrocatalysis of bisphenol A on Ni(II) tetraamino metallophthalocyanine (NiTAPc) polymer modified gold electrode containing Ni–O–Ni bridges (represented as Ni(OH)TAPc). The Ni(II)TAPc films were electro-transformed in 0.1 mol L−1 NaOH aqueous solution to form ‘O–Ni–O oxo bridges’, forming poly-n-Ni(OH)TAPc (where n is the number of polymerising scans). poly-30-Ni(OH)TAPc, poly-50-Ni(OH)TAPc, poly-70-Ni(OH)TAPc and poly-90-Ni(OH)TAPc films were investigated. The polymeric films were characterised by electrochemical impedance spectroscopy and the charge transfer resistance (RCT) values increased with film thickness. The best catalytic activity for the detection of bisphenol A was on poly-70-Ni(OH)TAPc. Electrode resistance to passivation improved with polymer thickness. The electrocatalytic behaviour of bisphenol A was compared to that of p-nitrophenol in terms of electrode passivation and regeneration. The latter was found to passivate the electrode less than the former. The poly-70-Ni(OH)TAPc modified electrode could reliably detect bisphenol A in a concentration range of 7 × 10−4 to 3 × 10−2 mol L−1 with a limit of detection of 3.68 × 10−9 mol L−1. The sensitivity was 3.26 × 10−4 A mol−1 L cm−2.
- Full Text:
- Date Issued: 2010
- Authors: Chauke, Vongani , Matemadombo, Fungisai , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/261280 , vital:53380 , xlink:href="https://doi.org/10.1016/j.jhazmat.2010.01.061"
- Description: This work reports the electrocatalysis of bisphenol A on Ni(II) tetraamino metallophthalocyanine (NiTAPc) polymer modified gold electrode containing Ni–O–Ni bridges (represented as Ni(OH)TAPc). The Ni(II)TAPc films were electro-transformed in 0.1 mol L−1 NaOH aqueous solution to form ‘O–Ni–O oxo bridges’, forming poly-n-Ni(OH)TAPc (where n is the number of polymerising scans). poly-30-Ni(OH)TAPc, poly-50-Ni(OH)TAPc, poly-70-Ni(OH)TAPc and poly-90-Ni(OH)TAPc films were investigated. The polymeric films were characterised by electrochemical impedance spectroscopy and the charge transfer resistance (RCT) values increased with film thickness. The best catalytic activity for the detection of bisphenol A was on poly-70-Ni(OH)TAPc. Electrode resistance to passivation improved with polymer thickness. The electrocatalytic behaviour of bisphenol A was compared to that of p-nitrophenol in terms of electrode passivation and regeneration. The latter was found to passivate the electrode less than the former. The poly-70-Ni(OH)TAPc modified electrode could reliably detect bisphenol A in a concentration range of 7 × 10−4 to 3 × 10−2 mol L−1 with a limit of detection of 3.68 × 10−9 mol L−1. The sensitivity was 3.26 × 10−4 A mol−1 L cm−2.
- Full Text:
- Date Issued: 2010
Spectroscopic behavior of cationic metallophthalocyanines in the presence of anionic quantum dots
- Idowu, Mopelola, Nyokong, Tebello
- Authors: Idowu, Mopelola , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/262699 , vital:53545 , xlink:href="https://doi.org/10.1016/j.saa.2009.10.050"
- Description: The interactions and spectroscopic properties between cationic zinc phthalocyanine derivatives (peripherally and non-peripherally tetrasubstituted and peripherally octa substituted with 2-diethylmethylaminoethylsulfanyl (βTZnPc, αTZnPc and βOZnPc)) and CdTe core quantum dots (QDs) capped with mercaptopropionic acid or thioglycolic acid (represented as CdTe@MPA and CdTe@TGA, respectively) have been studied in methanol:water mixture. Strong coupling of MPcs was deduced from the interaction since the UV–vis spectroscopic studies of the ground state complex formed on mixing both components showed loss of the phthalocyanine monomeric band with the formation of a dimeric band (spectrum of aggregated species). The dimerization constants were of the order of 104 M−1.
- Full Text:
- Date Issued: 2010
- Authors: Idowu, Mopelola , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/262699 , vital:53545 , xlink:href="https://doi.org/10.1016/j.saa.2009.10.050"
- Description: The interactions and spectroscopic properties between cationic zinc phthalocyanine derivatives (peripherally and non-peripherally tetrasubstituted and peripherally octa substituted with 2-diethylmethylaminoethylsulfanyl (βTZnPc, αTZnPc and βOZnPc)) and CdTe core quantum dots (QDs) capped with mercaptopropionic acid or thioglycolic acid (represented as CdTe@MPA and CdTe@TGA, respectively) have been studied in methanol:water mixture. Strong coupling of MPcs was deduced from the interaction since the UV–vis spectroscopic studies of the ground state complex formed on mixing both components showed loss of the phthalocyanine monomeric band with the formation of a dimeric band (spectrum of aggregated species). The dimerization constants were of the order of 104 M−1.
- Full Text:
- Date Issued: 2010
Spectroscopic studies of nanostructures of negatively charged free base porphyrin and positively charged tin porphyrins
- George, Reama C, Egharevba, Gabriel O, Nyokong, Tebello
- Authors: George, Reama C , Egharevba, Gabriel O , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/261661 , vital:53432 , xlink:href="https://doi.org/10.1016/j.poly.2010.01.028"
- Description: Spectroscopic studies were carried out on the homoaggregates of negatively charged free base meso-tetraphenylsulfonated porphyrin ([H2TPPS4]4−) and heteroaggregates of a mixture of protonated ([H4TPPS4]2−) and tin meso-tetra (N-methyl-4-pyridyl) porphyrin ([SnTMPyP]4+). The spectroscopic studies were done to determine the optimal conditions required for the fabrication of porphyrin nanorods by ionic self assembly of two oppositely charged porphyrins. In addition, the various spectral changes of [H4TPPS4]2− with concurrent change in pH and concentration are also investigated. In acid media at pH more than 3, and at concentrations less than 1 × 10−5 M, [H4TPPS4]2− molecules form J aggregates. A mixture of [H4TPPS4]2− and [SnTMPyP]4+ forms heteroaggregates of the J type in acid media. At pH’s 2 to 3, the optimum ratio for the formation of J aggregates is 3:1 and for pH 1, the optimum ratio is 2:1. Transmission electron microscope images of the nanostructures formed show that they are of cylindrical shape.
- Full Text:
- Date Issued: 2010
- Authors: George, Reama C , Egharevba, Gabriel O , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/261661 , vital:53432 , xlink:href="https://doi.org/10.1016/j.poly.2010.01.028"
- Description: Spectroscopic studies were carried out on the homoaggregates of negatively charged free base meso-tetraphenylsulfonated porphyrin ([H2TPPS4]4−) and heteroaggregates of a mixture of protonated ([H4TPPS4]2−) and tin meso-tetra (N-methyl-4-pyridyl) porphyrin ([SnTMPyP]4+). The spectroscopic studies were done to determine the optimal conditions required for the fabrication of porphyrin nanorods by ionic self assembly of two oppositely charged porphyrins. In addition, the various spectral changes of [H4TPPS4]2− with concurrent change in pH and concentration are also investigated. In acid media at pH more than 3, and at concentrations less than 1 × 10−5 M, [H4TPPS4]2− molecules form J aggregates. A mixture of [H4TPPS4]2− and [SnTMPyP]4+ forms heteroaggregates of the J type in acid media. At pH’s 2 to 3, the optimum ratio for the formation of J aggregates is 3:1 and for pH 1, the optimum ratio is 2:1. Transmission electron microscope images of the nanostructures formed show that they are of cylindrical shape.
- Full Text:
- Date Issued: 2010
Syntheses and investigation of the effects of position and nature of substituent on the spectral, electrochemical and spectroelectrochemical properties of new cobalt phthalocyanine complexes
- 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/10962/261677 , vital:53434 , xlink:href="https://doi.org/10.1016/j.poly.2010.01.004"
- Description: The syntheses of new cobalt phthalocyanine (CoPc) complexes, tetra-substituted with diethylaminoethanethio at the peripheral (complex 3a) and non-peripheral (complex 3b) positions, and with benzylmercapto at the non-peripheral position (complex 5), are reported. The effects of the nature and position of substituent on the spectral, electrochemical and spectroelectrochemical properties of these complexes are investigated. Solution electrochemistry of complex 3a showed three distinctly resolved redox processes attributed to CoIIIPc−2/CoIIPc−2 (E½ = +0.64 V versus Ag|AgCl), CoIIPc−2/CoIPc−2 (E½ = −0.24 V versus Ag|AgCl) and CoIPc−2/CoIPc−3 (E½ = −1.26 V versus Ag|AgCl) species. No ring oxidation was observed in complex 3a. Complex 3b showed both ring-based oxidation, attributed to CoIIIPc−1/CoIIIPc−2 species (Ep = +0.86 V versus Ag|AgCl), and ring-based reduction associated with CoIPc−2/CoIPc−3 species (E½ = −1.46 V versus Ag|AgCl), with the normal metal-based redox processes in CoPc complexes: CoIIIPc−2/CoIIPc−2 (Ep = +0.41 V versus Ag|AgCl) and CoIIPc−2/CoIPc−2 (E½ = −0.38 V versus Ag|AgCl). Solution electrochemistry of complex 5 showed the same type and number of species observed in complex 3a: CoIIIPc−2/CoIIPc−2 (Ep = +0.59 V versus Ag|AgCl), CoIIPc−2/CoIPc−2 (E½ = −0.26 V versus Ag|AgCl) and CoIPc−2/CoIPc−3 (E½ = −1.39 V versus Ag|AgCl) species. These processes were confirmed using spectroelectrochemistry.
- 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/10962/261677 , vital:53434 , xlink:href="https://doi.org/10.1016/j.poly.2010.01.004"
- Description: The syntheses of new cobalt phthalocyanine (CoPc) complexes, tetra-substituted with diethylaminoethanethio at the peripheral (complex 3a) and non-peripheral (complex 3b) positions, and with benzylmercapto at the non-peripheral position (complex 5), are reported. The effects of the nature and position of substituent on the spectral, electrochemical and spectroelectrochemical properties of these complexes are investigated. Solution electrochemistry of complex 3a showed three distinctly resolved redox processes attributed to CoIIIPc−2/CoIIPc−2 (E½ = +0.64 V versus Ag|AgCl), CoIIPc−2/CoIPc−2 (E½ = −0.24 V versus Ag|AgCl) and CoIPc−2/CoIPc−3 (E½ = −1.26 V versus Ag|AgCl) species. No ring oxidation was observed in complex 3a. Complex 3b showed both ring-based oxidation, attributed to CoIIIPc−1/CoIIIPc−2 species (Ep = +0.86 V versus Ag|AgCl), and ring-based reduction associated with CoIPc−2/CoIPc−3 species (E½ = −1.46 V versus Ag|AgCl), with the normal metal-based redox processes in CoPc complexes: CoIIIPc−2/CoIIPc−2 (Ep = +0.41 V versus Ag|AgCl) and CoIIPc−2/CoIPc−2 (E½ = −0.38 V versus Ag|AgCl). Solution electrochemistry of complex 5 showed the same type and number of species observed in complex 3a: CoIIIPc−2/CoIIPc−2 (Ep = +0.59 V versus Ag|AgCl), CoIIPc−2/CoIPc−2 (E½ = −0.26 V versus Ag|AgCl) and CoIPc−2/CoIPc−3 (E½ = −1.39 V versus Ag|AgCl) species. These processes were confirmed using spectroelectrochemistry.
- Full Text:
- Date Issued: 2010
Synthesis and electrochemical characterisation of new tantalum (V) alkythio phthalocyanines
- Chauke, Vongani, Nyokong, Tebello
- Authors: Chauke, Vongani , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/249093 , vital:51777 , xlink:href="https://doi.org/10.1016/j.ica.2010.05.003"
- Description: The synthesis and electrochemical characterisation of octa-pentylthio (4a) and octa-octylthio (4b) – phthalocyaninato tantalum (III) hydroxide are hereby reported. These TaPc complexes absorb in the near infrared region (∼800 nm in dichloromethane). They show good solubility in most common solvents especially non-viscous solvents such as dichloromethane and chloroform. NMR, mass and infrared spectroscopy and elemental analysis confirmed the structures and purity of the synthesised complexes. The cyclic voltammograms (CVs) showed reversible reduction couples and irreversible oxidation peaks. The latter exhibited adsorption behavior. The reduction processes were observed at −0.74 and −1.13 V (versus Ag|AgCl) for 4a, and −0.67, −1.02 and −1.48 V (versus Ag|AgCl) for 4b. Spectroelectrochemistry confirmed one metal reduction, with the rest of the redox processes being centered on the phthalocyanine ring.
- Full Text:
- Date Issued: 2010
- Authors: Chauke, Vongani , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/249093 , vital:51777 , xlink:href="https://doi.org/10.1016/j.ica.2010.05.003"
- Description: The synthesis and electrochemical characterisation of octa-pentylthio (4a) and octa-octylthio (4b) – phthalocyaninato tantalum (III) hydroxide are hereby reported. These TaPc complexes absorb in the near infrared region (∼800 nm in dichloromethane). They show good solubility in most common solvents especially non-viscous solvents such as dichloromethane and chloroform. NMR, mass and infrared spectroscopy and elemental analysis confirmed the structures and purity of the synthesised complexes. The cyclic voltammograms (CVs) showed reversible reduction couples and irreversible oxidation peaks. The latter exhibited adsorption behavior. The reduction processes were observed at −0.74 and −1.13 V (versus Ag|AgCl) for 4a, and −0.67, −1.02 and −1.48 V (versus Ag|AgCl) for 4b. Spectroelectrochemistry confirmed one metal reduction, with the rest of the redox processes being centered on the phthalocyanine ring.
- Full Text:
- Date Issued: 2010
Synthesis and photophysical properties of 1, 1′-binaphthol substituted phthalocyanines
- Canlica, Meylude, Nyokong, Tebello
- Authors: Canlica, Meylude , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/249148 , vital:51782 , xlink:href="https://doi.org/10.1016/j.ica.2010.06.034"
- Description: We report on the synthesis, characterization and photophysical properties of a new symmetrically tetra substituted {at non-peripheral positions with tetra(1,1′-bi-binaphtoxy)} phthalocyanines containing H2, Mg(II), Al(III)Cl, Si(IV)Cl2 in the central cavity. The synthesized compounds were characterized by the elemental analyses, UV–Vis, FT-IR and 1H NMR spectroscopies. The fluorescence quantum yields, triplet quantum yields and lifetimes of the newly synthesized H2, Mg, Al, and Si phthalocyanines were explored. Triplet quantum yields ranged from 0.24 to 0.54. The triplet lifetime for the silicon phthalocyanine derivative was the highest ever reported for a phthalocyanine (∼3.5 ms).
- Full Text:
- Date Issued: 2010
- Authors: Canlica, Meylude , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/249148 , vital:51782 , xlink:href="https://doi.org/10.1016/j.ica.2010.06.034"
- Description: We report on the synthesis, characterization and photophysical properties of a new symmetrically tetra substituted {at non-peripheral positions with tetra(1,1′-bi-binaphtoxy)} phthalocyanines containing H2, Mg(II), Al(III)Cl, Si(IV)Cl2 in the central cavity. The synthesized compounds were characterized by the elemental analyses, UV–Vis, FT-IR and 1H NMR spectroscopies. The fluorescence quantum yields, triplet quantum yields and lifetimes of the newly synthesized H2, Mg, Al, and Si phthalocyanines were explored. Triplet quantum yields ranged from 0.24 to 0.54. The triplet lifetime for the silicon phthalocyanine derivative was the highest ever reported for a phthalocyanine (∼3.5 ms).
- Full Text:
- Date Issued: 2010
Synthetic pathways to water-soluble phthalocyanines and close analogs
- Dumoulin, Fabienne, Durmus, Mahmut, Ahsen, Vefa, Nyokong, Tebello
- Authors: Dumoulin, Fabienne , Durmus, Mahmut , Ahsen, Vefa , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/249082 , vital:51776 , xlink:href="https://doi.org/10.1016/j.ccr.2010.05.002"
- Description: The different types of water-soluble phthalocyanines are presented and their synthesis is reviewed.
- Full Text:
- Date Issued: 2010
- Authors: Dumoulin, Fabienne , Durmus, Mahmut , Ahsen, Vefa , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/249082 , vital:51776 , xlink:href="https://doi.org/10.1016/j.ccr.2010.05.002"
- Description: The different types of water-soluble phthalocyanines are presented and their synthesis is reviewed.
- Full Text:
- Date Issued: 2010
The effects of point of substitution on the electrochemical behavior of new manganese phthalocyanines, tetra-substituted with diethylaminoethanethiol
- Akinbulu, Isaac Adebayo, Nyokong, Tebello
- Authors: Akinbulu, Isaac Adebayo , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/249137 , vital:51781 , xlink:href="https://doi.org/10.1016/j.ica.2010.06.003"
- Description: The syntheses and comparative studies of the spectral, voltammetry and spectroelectrochemical properties of new manganese phthalocyanine complexes, tetra-substituted with diethylaminoethanethio at the peripheral (complex 3a) and non-peripheral positions (complex 3b) are reported. Solution electrochemistry of complex 3a showed quasi-reversible metal-based (MnIIIPc−2/MnIIPc−2, E1/2 = −0.07 V vs. Ag|AgCl) and ring-based (MnIIPc−2/MnIIPc−3, E1/2 = −0.78 V vs. Ag|AgCl) reductions, but no ring-based oxidation. However, complex 3b showed weak irreversible ring-oxidation signal (Ep = +0.86 vs. Ag|AgCl). Reversible metal-based (MnIIIPc−2/MnIIPc−2, E1/2 = −0.04 V vs. Ag|AgCl) and ring-based (MnIIPc−2/MnIIPc−3, E1/2 = −0.68 V vs. Ag|AgCl) reductions were also observed for complex 3b. Spectroelectrochemistry was used to confirm these processes. Reduction process involving the metal (MnIIIPc−2/MnIIPc−2) was associated with the formation of manganese μ-oxo complex in complex 3a.
- Full Text:
- Date Issued: 2010
- Authors: Akinbulu, Isaac Adebayo , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/249137 , vital:51781 , xlink:href="https://doi.org/10.1016/j.ica.2010.06.003"
- Description: The syntheses and comparative studies of the spectral, voltammetry and spectroelectrochemical properties of new manganese phthalocyanine complexes, tetra-substituted with diethylaminoethanethio at the peripheral (complex 3a) and non-peripheral positions (complex 3b) are reported. Solution electrochemistry of complex 3a showed quasi-reversible metal-based (MnIIIPc−2/MnIIPc−2, E1/2 = −0.07 V vs. Ag|AgCl) and ring-based (MnIIPc−2/MnIIPc−3, E1/2 = −0.78 V vs. Ag|AgCl) reductions, but no ring-based oxidation. However, complex 3b showed weak irreversible ring-oxidation signal (Ep = +0.86 vs. Ag|AgCl). Reversible metal-based (MnIIIPc−2/MnIIPc−2, E1/2 = −0.04 V vs. Ag|AgCl) and ring-based (MnIIPc−2/MnIIPc−3, E1/2 = −0.68 V vs. Ag|AgCl) reductions were also observed for complex 3b. Spectroelectrochemistry was used to confirm these processes. Reduction process involving the metal (MnIIIPc−2/MnIIPc−2) was associated with the formation of manganese μ-oxo complex in complex 3a.
- Full Text:
- Date Issued: 2010
The effects of point of substitution on the formation of manganese phthalocyanine-based molecular materials
- Akinbulu, Isaac Adebayo, Khene, Samson, Nyokong, Tebello
- Authors: Akinbulu, Isaac Adebayo , Khene, Samson , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/249103 , vital:51778 , xlink:href="https://doi.org/10.1016/j.tsf.2010.08.145"
- Description: Molecular films of manganese phthalocyanine (MnPc) complexes, tetra-substituted with 2-diethylaminoethanethio at the peripheral (Mn(OAc)-β-TDEAETPc, 1) and non-peripheral (Mn(OAc)-α-TDEAETPc, 2) positions were formed on glassy carbon electrode by electropolymerization and electrodeposition respectively. Atomic force microscopy images confirmed the presence of the films and revealed significant morphological differences. The films exhibited an electrocatalytic activity towards the oxidation of the insecticide, bendiocarb. Hydrodynamic technique, using rotating disc electrode voltammetry, was used to investigate the kinetics of electro-oxidation of the insecticide. Morphological differences of the films significantly influenced kinetic parameters. Values of Tafel slopes, obtained from Tafel plots, suggested that catalysis of bendiocarb occurred via outer sphere mechanism.
- Full Text:
- Date Issued: 2010
- Authors: Akinbulu, Isaac Adebayo , Khene, Samson , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/249103 , vital:51778 , xlink:href="https://doi.org/10.1016/j.tsf.2010.08.145"
- Description: Molecular films of manganese phthalocyanine (MnPc) complexes, tetra-substituted with 2-diethylaminoethanethio at the peripheral (Mn(OAc)-β-TDEAETPc, 1) and non-peripheral (Mn(OAc)-α-TDEAETPc, 2) positions were formed on glassy carbon electrode by electropolymerization and electrodeposition respectively. Atomic force microscopy images confirmed the presence of the films and revealed significant morphological differences. The films exhibited an electrocatalytic activity towards the oxidation of the insecticide, bendiocarb. Hydrodynamic technique, using rotating disc electrode voltammetry, was used to investigate the kinetics of electro-oxidation of the insecticide. Morphological differences of the films significantly influenced kinetic parameters. Values of Tafel slopes, obtained from Tafel plots, suggested that catalysis of bendiocarb occurred via outer sphere mechanism.
- Full Text:
- Date Issued: 2010
The synthesis and fluorescence behaviour of phthalocyanines unsymmetrically substituted with naphthol and carboxy groups
- Nombona, Nolwazi, Antunes, Edith M, Nyokong, Tebello
- Authors: Nombona, Nolwazi , Antunes, Edith M , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/261534 , vital:53418 , xlink:href="https://doi.org/10.1016/j.dyepig.2009.11.010"
- Description: Unsymmetrically substituted phthalocyanines 8,15,22-tris-(naphtho)-2-(carboxy)phthalocyanine, [8,15,22-tris-(naphtho)-2-(carboxy)phthalocyanato]zinc(II), 8,15,22-tris-(naphtho)-4,5-(3-carboxy-1,2-dioxyphenyl)phthalocyanine and [8,15,22-tris-(naphtho)-4,5-(3-carboxy-1,2-dioxyphenoxy)phthalocyanato]zinc(II) were prepared using the mixed phthalonitrile cyclotetramerization of 3-(1-naphthoxy) phthalonitrile with a carboxylic acid phthalonitrile. The phthalocyanines were separated using column chromatography employing a mixture of THF, ammonia and water. The novel compounds were characterized using UV–Vis, IR, 1H NMR and mass spectrometry as well as elemental analysis. Fluorescence quantum yields were found to range from 0.05 to 0.16.
- Full Text:
- Date Issued: 2010
- Authors: Nombona, Nolwazi , Antunes, Edith M , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/261534 , vital:53418 , xlink:href="https://doi.org/10.1016/j.dyepig.2009.11.010"
- Description: Unsymmetrically substituted phthalocyanines 8,15,22-tris-(naphtho)-2-(carboxy)phthalocyanine, [8,15,22-tris-(naphtho)-2-(carboxy)phthalocyanato]zinc(II), 8,15,22-tris-(naphtho)-4,5-(3-carboxy-1,2-dioxyphenyl)phthalocyanine and [8,15,22-tris-(naphtho)-4,5-(3-carboxy-1,2-dioxyphenoxy)phthalocyanato]zinc(II) were prepared using the mixed phthalonitrile cyclotetramerization of 3-(1-naphthoxy) phthalonitrile with a carboxylic acid phthalonitrile. The phthalocyanines were separated using column chromatography employing a mixture of THF, ammonia and water. The novel compounds were characterized using UV–Vis, IR, 1H NMR and mass spectrometry as well as elemental analysis. Fluorescence quantum yields were found to range from 0.05 to 0.16.
- Full Text:
- Date Issued: 2010
The synthesis and photophysical properties of novel cationic tetra pyridiloxy substituted aluminium, silicon and titanium phthalocyanines in water
- Masilela, Nkosiphile, Nyokong, Tebello
- Authors: Masilela, Nkosiphile , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/249159 , vital:51783 , xlink:href="https://doi.org/10.1016/j.jlumin.2010.04.011"
- Description: This work reports on the synthesis, characterisation and photophysical properties of new unquaternized β-2,(3)-tetra-(2 pyridiloxy) aluminium(III) (3a), silicon(IV) (3b), titanium(IV) (3c) phthalocyanines and their water-soluble quaternized counterparts, 4a, 4b and 4c, respectively. The water-soluble silicon(IV) (4b) and titanium(IV) (4c) phthalocyanine derivatives were found to be aggregated in aqueous media but were partially or fully disaggregated in the presence of a surfactant Cremophor® EL (CEL). The photophysical properties of aggregated complexes were investigated both in the presence of CEL and in pH 11 alone. Low triplet and fluorescence yield were obtained in pH 11 but an improvement was achieved upon addition of CEL for the aggregated complexes. The unquaternized silicon(IV) phthalocyanine complex (3b) gave the highest triplet quantum yield of 0.77 in DMF followed by its quaternized derivative (4b) with triplet yield of 0.73 in pH 11 plus CEL. The highest triplet lifetime of 220 μs was obtained for 4b in the presence of CEL. Higher fluorescence yields of 0.23 were obtained for quaternized water-soluble aluminium(III) phthalocyanine derivative (4a) in the presence of CEL.
- Full Text:
- Date Issued: 2010
- Authors: Masilela, Nkosiphile , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/249159 , vital:51783 , xlink:href="https://doi.org/10.1016/j.jlumin.2010.04.011"
- Description: This work reports on the synthesis, characterisation and photophysical properties of new unquaternized β-2,(3)-tetra-(2 pyridiloxy) aluminium(III) (3a), silicon(IV) (3b), titanium(IV) (3c) phthalocyanines and their water-soluble quaternized counterparts, 4a, 4b and 4c, respectively. The water-soluble silicon(IV) (4b) and titanium(IV) (4c) phthalocyanine derivatives were found to be aggregated in aqueous media but were partially or fully disaggregated in the presence of a surfactant Cremophor® EL (CEL). The photophysical properties of aggregated complexes were investigated both in the presence of CEL and in pH 11 alone. Low triplet and fluorescence yield were obtained in pH 11 but an improvement was achieved upon addition of CEL for the aggregated complexes. The unquaternized silicon(IV) phthalocyanine complex (3b) gave the highest triplet quantum yield of 0.77 in DMF followed by its quaternized derivative (4b) with triplet yield of 0.73 in pH 11 plus CEL. The highest triplet lifetime of 220 μs was obtained for 4b in the presence of CEL. Higher fluorescence yields of 0.23 were obtained for quaternized water-soluble aluminium(III) phthalocyanine derivative (4a) in the presence of CEL.
- Full Text:
- Date Issued: 2010
The use and appreciation of botanical gardens as urban green spaces in South Africa
- Ward, Catherine D, Parker, Caitlin M, Shackleton, Charlie M
- Authors: Ward, Catherine D , Parker, Caitlin M , Shackleton, Charlie M
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181146 , vital:43702 , xlink:href="https://doi.org/10.1016/j.ufug.2009.11.001"
- Description: There are few formal studies on the contribution of botanical gardens as urban green spaces, particularly within developing countries. Therefore, this paper reports on an assessment of the use and appreciation of botanical gardens as urban green spaces in South Africa. Users and staff were surveyed in six national botanical gardens. The gardens provided numerous benefits in terms of conservation, education and recreation. However, the people using the gardens were not demographically representative of the general population of the surrounding city or town. Generally, most of the visitors were middle- to old-aged, well-educated professionals with medium to high incomes. Most were white and English was their home language. There was an even gender representation. Most visited only a few times per year. The majority of users visited the gardens for recreation and psychological reasons rather than educational ones. However, the staff of each garden placed emphasis on education in the gardens and amongst surrounding schools. Most visitors appreciated the conservation dimensions of botanical gardens, and felt that there was insufficient public green space in their town or city. Understanding how people perceive and use the botanical gardens of South Africa is important to inform future research and strategies regarding the conservation of urban green space within a developing country.
- Full Text:
- Date Issued: 2010
- Authors: Ward, Catherine D , Parker, Caitlin M , Shackleton, Charlie M
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181146 , vital:43702 , xlink:href="https://doi.org/10.1016/j.ufug.2009.11.001"
- Description: There are few formal studies on the contribution of botanical gardens as urban green spaces, particularly within developing countries. Therefore, this paper reports on an assessment of the use and appreciation of botanical gardens as urban green spaces in South Africa. Users and staff were surveyed in six national botanical gardens. The gardens provided numerous benefits in terms of conservation, education and recreation. However, the people using the gardens were not demographically representative of the general population of the surrounding city or town. Generally, most of the visitors were middle- to old-aged, well-educated professionals with medium to high incomes. Most were white and English was their home language. There was an even gender representation. Most visited only a few times per year. The majority of users visited the gardens for recreation and psychological reasons rather than educational ones. However, the staff of each garden placed emphasis on education in the gardens and amongst surrounding schools. Most visitors appreciated the conservation dimensions of botanical gardens, and felt that there was insufficient public green space in their town or city. Understanding how people perceive and use the botanical gardens of South Africa is important to inform future research and strategies regarding the conservation of urban green space within a developing country.
- Full Text:
- Date Issued: 2010
The valuation of campus built heritage from the student perspective: comparative analysis of Rhodes University in South Africa and St. Mary’s College of Maryland in the United States
- Poor, Joan P, Snowball, Jeanette D
- Authors: Poor, Joan P , Snowball, Jeanette D
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67488 , vital:29102 , https://doi.org/10.1016/j.culher.2009.05.002
- Description: Pre-print , Many universities and colleges around the world have done extensive surveys of their campus built heritage resources. A detailed description and accounting of a campus's built heritage, landscape heritage and archaeology, are often used for historic preservation planning, and sustaining built culture is also an important aspect of campus master planning of future buildings. Such institutions of higher education have deep historical roots, in Europe it is not uncommon for buildings to be dated prior to the sixteenth century. In countries where European colonies were established, institutions of higher education often date to the eighteenth and early nineteenth centuries. Once students have arrived at their chosen campus, however, except for perhaps the first week orientation rituals, do the students actually develop ties to their campus built heritage? This research investigates the knowledge students possess of their respective campus built heritage and the importance of built heritage as a legacy to them. Two institutions are included in this study in an effort of draw comparative assessments. A student questionnaire was administered at Rhodes University in South Africa and St. Mary's College of Maryland in the United States during April 2008. Results indicate students on both campuses place positive intrinsic value on their respective campus built heritage. Just over half (52%) of Rhodes students and about 68% of St. Mary's students were willing to pay some positive amount to protect campus built heritage. Empirical probit model results combining the data from both institutions found that current student knowledge of their respective campus built heritage did not positively relate to the value they place on preservation, even though the visual identity was significant for students and influenced their decision to attend the particular institution. The lack of significance regarding a racial variable coefficient estimate suggests that the use of an institution's visual identity in terms of built heritage may have important marketing implications, particularly in cases where universities or colleges are trying to attract students from more diverse backgrounds. We found no significant relationships between willingness to pay to preserve an institution's built heritage and the demographic variables included in our empirical model. Fundraising data analysis includes positive willingness to pay for conserving built heritage, yet funding for new construction was not significant.
- Full Text:
- Date Issued: 2010
- Authors: Poor, Joan P , Snowball, Jeanette D
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67488 , vital:29102 , https://doi.org/10.1016/j.culher.2009.05.002
- Description: Pre-print , Many universities and colleges around the world have done extensive surveys of their campus built heritage resources. A detailed description and accounting of a campus's built heritage, landscape heritage and archaeology, are often used for historic preservation planning, and sustaining built culture is also an important aspect of campus master planning of future buildings. Such institutions of higher education have deep historical roots, in Europe it is not uncommon for buildings to be dated prior to the sixteenth century. In countries where European colonies were established, institutions of higher education often date to the eighteenth and early nineteenth centuries. Once students have arrived at their chosen campus, however, except for perhaps the first week orientation rituals, do the students actually develop ties to their campus built heritage? This research investigates the knowledge students possess of their respective campus built heritage and the importance of built heritage as a legacy to them. Two institutions are included in this study in an effort of draw comparative assessments. A student questionnaire was administered at Rhodes University in South Africa and St. Mary's College of Maryland in the United States during April 2008. Results indicate students on both campuses place positive intrinsic value on their respective campus built heritage. Just over half (52%) of Rhodes students and about 68% of St. Mary's students were willing to pay some positive amount to protect campus built heritage. Empirical probit model results combining the data from both institutions found that current student knowledge of their respective campus built heritage did not positively relate to the value they place on preservation, even though the visual identity was significant for students and influenced their decision to attend the particular institution. The lack of significance regarding a racial variable coefficient estimate suggests that the use of an institution's visual identity in terms of built heritage may have important marketing implications, particularly in cases where universities or colleges are trying to attract students from more diverse backgrounds. We found no significant relationships between willingness to pay to preserve an institution's built heritage and the demographic variables included in our empirical model. Fundraising data analysis includes positive willingness to pay for conserving built heritage, yet funding for new construction was not significant.
- Full Text:
- Date Issued: 2010
Tuning the physico-electrochemical properties of novel cobalt (II) octa [(3, 5-biscarboxylate)-phenoxy] phthalocyanine complex using phenylamine-functionalised SWCNTs
- Agboola, Bolade O, Ozoemena, Kenneth I, Nyokong, Tebello, Fukuda, Takamitsu, Kobayashi, Nagao
- Authors: Agboola, Bolade O , Ozoemena, Kenneth I , Nyokong, Tebello , Fukuda, Takamitsu , Kobayashi, Nagao
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/261692 , vital:53435 , xlink:href="https://doi.org/10.1016/j.carbon.2009.10.023"
- Description: The integration of phenylamine-functionalised SWCNTs (SWCNT-phenylamine) with a novel cobalt (II) octa[(3,5-biscarboxylate)-phenoxy] phthalocyanine (CoOBPPc) complex has been described. The physical and electrochemical properties of the CoOBPPc-SWCNT-phenylamine hybrid were evaluated using spectroscopy (IR and UV–vis), field emission scanning electron microscopy and electrochemistry (cyclic voltammetry and electrochemical impedance spectroscopy). Integration of SWCNT-phenylamine resulted in the physical transformation of the CoOBCPPc from the usually bluish colour of cobalt phthalocyanine complexes to a beautiful bright green colour. In addition, the heterogeneous electron transfer kinetics and electrocatalytic properties of the CoOBCPPc were greatly enhanced following the attachment of the SWCNT-phenylamine. The potential electrocatalytic application of the hybrid was tested using β-nicotinamide adenine dinucleotide (NADH) as a model biological analyte. Interestingly, the onset oxidation potential of this analyte was significantly reduced (300 mV) by this hybrid compared to the bare electrode.
- Full Text:
- Date Issued: 2010
- Authors: Agboola, Bolade O , Ozoemena, Kenneth I , Nyokong, Tebello , Fukuda, Takamitsu , Kobayashi, Nagao
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/261692 , vital:53435 , xlink:href="https://doi.org/10.1016/j.carbon.2009.10.023"
- Description: The integration of phenylamine-functionalised SWCNTs (SWCNT-phenylamine) with a novel cobalt (II) octa[(3,5-biscarboxylate)-phenoxy] phthalocyanine (CoOBPPc) complex has been described. The physical and electrochemical properties of the CoOBPPc-SWCNT-phenylamine hybrid were evaluated using spectroscopy (IR and UV–vis), field emission scanning electron microscopy and electrochemistry (cyclic voltammetry and electrochemical impedance spectroscopy). Integration of SWCNT-phenylamine resulted in the physical transformation of the CoOBCPPc from the usually bluish colour of cobalt phthalocyanine complexes to a beautiful bright green colour. In addition, the heterogeneous electron transfer kinetics and electrocatalytic properties of the CoOBCPPc were greatly enhanced following the attachment of the SWCNT-phenylamine. The potential electrocatalytic application of the hybrid was tested using β-nicotinamide adenine dinucleotide (NADH) as a model biological analyte. Interestingly, the onset oxidation potential of this analyte was significantly reduced (300 mV) by this hybrid compared to the bare electrode.
- Full Text:
- Date Issued: 2010
Comparative behavior of conjugates of tantalum phthalocyanines with gold nanoparticles or single walled carbon nanotubes towards bisphenol A electrocatalysis
- Chauke, Vongani P, Antunes, Edith M, Nyokong, Tebello
- Authors: Chauke, Vongani P , Antunes, Edith M , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247152 , vital:51551 , xlink:href="https://doi.org/10.1016/j.jelechem.2011.06.019"
- Description: The characterization of tantalum phthalocyanine conjugates with gold nanoparticles and single wall carbon nanotubes as well as their electrocatalytic oxidation of bisphenol A is hereby presented. The formation of the conjugates was confirmed by X-ray diffraction and transmission electron microscope techniques. Single walled carbon nanotube conjugates of TaPc complexes showed the best catalysis as well as less passivation for bisphenol A detection and significant recovery of ∼98% compared to gold nanoparticle conjugates.
- Full Text:
- Date Issued: 2011
- Authors: Chauke, Vongani P , Antunes, Edith M , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247152 , vital:51551 , xlink:href="https://doi.org/10.1016/j.jelechem.2011.06.019"
- Description: The characterization of tantalum phthalocyanine conjugates with gold nanoparticles and single wall carbon nanotubes as well as their electrocatalytic oxidation of bisphenol A is hereby presented. The formation of the conjugates was confirmed by X-ray diffraction and transmission electron microscope techniques. Single walled carbon nanotube conjugates of TaPc complexes showed the best catalysis as well as less passivation for bisphenol A detection and significant recovery of ∼98% compared to gold nanoparticle conjugates.
- Full Text:
- Date Issued: 2011
Conjugates of low-symmetry Ge, Sn and Ti carboxy phthalocyanines with glutathione caped gold nanoparticles
- Masilela, Nkosiphile, Nyokong, Tebello
- Authors: Masilela, Nkosiphile , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247003 , vital:51536 , xlink:href="https://doi.org/10.1016/j.jphotochem.2011.08.009"
- Description: This work reports on conjugation of low symmetry Ge (GeMCPc), Ti (TiMCPc) and Sn (SnMCPc) carboxy phthalocyanines with glutathione capped gold nanoparticles (GSH-AuNPs). The photophysical behaviour of the novel phthalocyanines–GSH-AuNPs conjugate was investigated and compared to the monocarboxy Pcs and to the mixture of Pc with GSH-AuNPs without a chemical bond. Blue shifting of Q band of the phthalocyanines was observed on linking to GSH-AuNPs. An improvement in triplet lifetimes was obtained for all the MPcs–GSH-AuNPs-linked conjugates compared to the MPcs alone. The highest triplet quantum yield of 0.75 and the longest triplet lifetime of 130 μs were obtained for the GeMCPc–GSH-AuNPs-linked conjugate. Fluorescence quantum yields and lifetimes were low for the conjugates due to quenching by the nanoparticles.
- Full Text:
- Date Issued: 2011
- Authors: Masilela, Nkosiphile , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247003 , vital:51536 , xlink:href="https://doi.org/10.1016/j.jphotochem.2011.08.009"
- Description: This work reports on conjugation of low symmetry Ge (GeMCPc), Ti (TiMCPc) and Sn (SnMCPc) carboxy phthalocyanines with glutathione capped gold nanoparticles (GSH-AuNPs). The photophysical behaviour of the novel phthalocyanines–GSH-AuNPs conjugate was investigated and compared to the monocarboxy Pcs and to the mixture of Pc with GSH-AuNPs without a chemical bond. Blue shifting of Q band of the phthalocyanines was observed on linking to GSH-AuNPs. An improvement in triplet lifetimes was obtained for all the MPcs–GSH-AuNPs-linked conjugates compared to the MPcs alone. The highest triplet quantum yield of 0.75 and the longest triplet lifetime of 130 μs were obtained for the GeMCPc–GSH-AuNPs-linked conjugate. Fluorescence quantum yields and lifetimes were low for the conjugates due to quenching by the nanoparticles.
- Full Text:
- Date Issued: 2011
Cyclic voltammetry and spectroelectrochemistry of a novel manganese phthalocyanine substituted with hexynyl groups
- Quinton, Damien, Antunes, Edith M, Griveau, Sophie, Nyokong, Tebello, Bedioui, Fethi
- Authors: Quinton, Damien , Antunes, Edith M , Griveau, Sophie , Nyokong, Tebello , Bedioui, Fethi
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/248450 , vital:51687 , xlink:href="https://doi.org/10.1016/j.inoche.2010.11.029"
- Description: We report here on the synthesis of a new manganese phthalocyanine complex, namely Mn tetrakis(5-hexyn-oxy) phthalocyanine (3), specifically designed to possess an alkyne moiety for its potential use in controlled immobilization on electrodes via the so called “click” chemistry reaction. The electrochemical activity of complex 3 was investigated by cyclic voltammetry and the nature of the observed redox couples was elucidated by spectroelectrochemistry. This work has also shown that the reduction of Mn(III)Pc complex to Mn(II)Pc is accompanied by the formation of MnPc μ-oxo species. Further reduction results in the formation of Mn(II)Pc(− 3) rather than Mn(I)Pc(− 2).
- Full Text:
- Date Issued: 2011
- Authors: Quinton, Damien , Antunes, Edith M , Griveau, Sophie , Nyokong, Tebello , Bedioui, Fethi
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/248450 , vital:51687 , xlink:href="https://doi.org/10.1016/j.inoche.2010.11.029"
- Description: We report here on the synthesis of a new manganese phthalocyanine complex, namely Mn tetrakis(5-hexyn-oxy) phthalocyanine (3), specifically designed to possess an alkyne moiety for its potential use in controlled immobilization on electrodes via the so called “click” chemistry reaction. The electrochemical activity of complex 3 was investigated by cyclic voltammetry and the nature of the observed redox couples was elucidated by spectroelectrochemistry. This work has also shown that the reduction of Mn(III)Pc complex to Mn(II)Pc is accompanied by the formation of MnPc μ-oxo species. Further reduction results in the formation of Mn(II)Pc(− 3) rather than Mn(I)Pc(− 2).
- Full Text:
- Date Issued: 2011
Electrochemical behavior of phthalocyanines containing high oxidation state central metals
- Chauke, Vongani, Arslanoglu, Yasin, Nyokong, Tebello
- Authors: Chauke, Vongani , Arslanoglu, Yasin , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247111 , vital:51547 , xlink:href="https://doi.org/10.1016/j.poly.2011.05.028"
- Description: The syntheses of 2,(3)-(peripheral) and 1,(4)-(non-peripheral) (2-mercaptopyridine)phthalocyanine complexes of titanium(IV) oxide (5a and 6a, respectively), vanadium(IV) oxide (7a and 8a, respectively) and tantalum(V) hydroxide (9a, peripheral only) and their electrochemical characterization are presented in this report. Their electrochemistry is compared to that of thiophenyl and thiobenzyl substituted derivatives. The non-peripherally substituted complexes are more difficult to reduce than peripherally substituted derivatives. In addition, the mercaptopyridine substituted derivatives are more difficult to reduce compared to benzylmercapto and phenylmercapto derivatives, and aryl easier reduce than alkyl substitution. Spectroelectrochemistry of the complexes confirmed metal and ring redox processes for TaPc and TiPc derivatives and ring based processes only for VPc complexes.
- Full Text:
- Date Issued: 2011
- Authors: Chauke, Vongani , Arslanoglu, Yasin , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247111 , vital:51547 , xlink:href="https://doi.org/10.1016/j.poly.2011.05.028"
- Description: The syntheses of 2,(3)-(peripheral) and 1,(4)-(non-peripheral) (2-mercaptopyridine)phthalocyanine complexes of titanium(IV) oxide (5a and 6a, respectively), vanadium(IV) oxide (7a and 8a, respectively) and tantalum(V) hydroxide (9a, peripheral only) and their electrochemical characterization are presented in this report. Their electrochemistry is compared to that of thiophenyl and thiobenzyl substituted derivatives. The non-peripherally substituted complexes are more difficult to reduce than peripherally substituted derivatives. In addition, the mercaptopyridine substituted derivatives are more difficult to reduce compared to benzylmercapto and phenylmercapto derivatives, and aryl easier reduce than alkyl substitution. Spectroelectrochemistry of the complexes confirmed metal and ring redox processes for TaPc and TiPc derivatives and ring based processes only for VPc complexes.
- Full Text:
- Date Issued: 2011
Electrochemical, microscopic and spectroscopic characterization of benzene diamine functionalized single walled carbon nanotube-cobalt (II) tetracarboxy-phthalocyanine conjugates
- Mugadza, Tawanda, Nyokong, Tebello
- Authors: Mugadza, Tawanda , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247859 , vital:51624 , xlink:href="https://doi.org/10.1016/j.jcis.2010.10.057"
- Description: In this paper we report on the synthesis and characterization of 1,4-benzene diamine (BDA) functionalized single walled carbon nanotubes linked to cobalt (II) tetracarboxy-phthalocyanine. The characterization of the conjugate was through UV–vis, FTIR and X-ray diffraction (XRD) spectroscopies and by transmission electron microscope (TEM) and electrochemical methods. The conjugate is used for the electrochemical characterization of diuron. The catalytic rate constant for diuron was 4.4 × 103 M−1 s−1 and the apparent electron transfer rate constant was 18.5 × 10−6 cm s−1. The linear dynamic range was 1.0 × 10−5–2.0 × 10−4 M, with a sensitivity of ∼0.42 A mol−1L cm−2 and a limit of detection of 0.18 μM using the 3δ notation.
- Full Text:
- Date Issued: 2011
- Authors: Mugadza, Tawanda , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247859 , vital:51624 , xlink:href="https://doi.org/10.1016/j.jcis.2010.10.057"
- Description: In this paper we report on the synthesis and characterization of 1,4-benzene diamine (BDA) functionalized single walled carbon nanotubes linked to cobalt (II) tetracarboxy-phthalocyanine. The characterization of the conjugate was through UV–vis, FTIR and X-ray diffraction (XRD) spectroscopies and by transmission electron microscope (TEM) and electrochemical methods. The conjugate is used for the electrochemical characterization of diuron. The catalytic rate constant for diuron was 4.4 × 103 M−1 s−1 and the apparent electron transfer rate constant was 18.5 × 10−6 cm s−1. The linear dynamic range was 1.0 × 10−5–2.0 × 10−4 M, with a sensitivity of ∼0.42 A mol−1L cm−2 and a limit of detection of 0.18 μM using the 3δ notation.
- Full Text:
- Date Issued: 2011
Formation, surface characterization, and electrocatalytic application of self-assembled monolayer films of tetra-substituted manganese, iron, and cobalt benzylthio phthalocyanine complexes
- Akinbulu, Isaac Adebayo, Ozoemena, Kenneth Iyke, Nyokong, Tebello
- Authors: Akinbulu, Isaac Adebayo , Ozoemena, Kenneth Iyke , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247163 , vital:51552 , xlink:href="https://doi.org/10.1007/s10008-010-1243-1"
- Description: Molecular thin films of manganese (SAM-2), iron (SAM-3), and cobalt (SAM-4) phthalocyanine complexes, non-peripherally tetra-substituted with benzylmercapto, were formed on polycrystalline gold disc electrode by self-assembly technique. Surface characteristics of the films were interrogated by cyclic voltammetry. Significant passivation of voltammetry processes associated with bare gold surface (gold oxidation and underpotential deposition of copper) confirmed formation of the films. Electrocatalytic property of the films was evidenced from better voltammetry responses (less positive oxidation potential and better current signal) of the insecticide, carbofuran, on these films, relative to that on bare gold electrode. In terms of less positive oxidation potential, the FePc derivative (3) gave the best response, while the best current signal was observed on SAM-2-modified gold electrode. The average heterogeneous rate constant, k, for the oxidation of carbofuran was 3.6 × 10−2 cm s−1 on the SAM film with the best current signal (SAM-2).
- Full Text:
- Date Issued: 2011
- Authors: Akinbulu, Isaac Adebayo , Ozoemena, Kenneth Iyke , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247163 , vital:51552 , xlink:href="https://doi.org/10.1007/s10008-010-1243-1"
- Description: Molecular thin films of manganese (SAM-2), iron (SAM-3), and cobalt (SAM-4) phthalocyanine complexes, non-peripherally tetra-substituted with benzylmercapto, were formed on polycrystalline gold disc electrode by self-assembly technique. Surface characteristics of the films were interrogated by cyclic voltammetry. Significant passivation of voltammetry processes associated with bare gold surface (gold oxidation and underpotential deposition of copper) confirmed formation of the films. Electrocatalytic property of the films was evidenced from better voltammetry responses (less positive oxidation potential and better current signal) of the insecticide, carbofuran, on these films, relative to that on bare gold electrode. In terms of less positive oxidation potential, the FePc derivative (3) gave the best response, while the best current signal was observed on SAM-2-modified gold electrode. The average heterogeneous rate constant, k, for the oxidation of carbofuran was 3.6 × 10−2 cm s−1 on the SAM film with the best current signal (SAM-2).
- Full Text:
- Date Issued: 2011