(Ferrocenylpyrazolyl) zinc (II) benzoates as catalysts for the ring opening polymerization of ε-caprolactone
- Obuah, Collins, Lochee, Yemanlall, Jordaan, Johan H L, Otto, Daniel P, Nyokong, Tebello, Darkwa, James
- Authors: Obuah, Collins , Lochee, Yemanlall , Jordaan, Johan H L , Otto, Daniel P , Nyokong, Tebello , Darkwa, James
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189515 , vital:44853 , xlink:href="https://doi.org/10.1016/j.poly.2015.02.007"
- Description: The reaction of Zn(OAc)2 and C6H5COOH or 3,5-NO2-C6H3COOH with 3-ferrocenylpyrazolyl-methylenepyridine (L1), 3-ferrocenyl-5-methylpyrazolyl-methylenepyridine (L2), 3-ferrocenylpyrazolyl-ethylamine (L3) and 3-ferrocenyl-5-pyrazolyl-ethylamine (L4) afford the corresponding complexes [Zn(C6H5COO)2(L1)] (1), [Zn(C6H5COO)2(L2)] (2), [Zn(3,5-NO2-C6H3COO)2(L1)] (3), [Zn(3,5-NO2-C6H3 COO)2(L2)] (4), [Zn(C6H5COO)2(L3)] (5), [Zn(C6H5COO)2(L4)] (6), [Zn(3,5-NO2-C6H3COO)2(L3)] (7) and [Zn(3,5-NO2-C6H3COO)2(L4)] (8). These complexes behave as catalysts for the ring opening polymerization of e-caprolactone to produce polymers with molecular weight that range from 1480 to 7080 g mol1 and exhibited moderate to broad PDIs. Evidence of these complexes acting as catalysts was obtained from both the polymerization data and kinetic studies. The polymerization data show that variation of the [CL]/[C] from 100 to 800 produced PCL with relatively the same molecular weight indicative of a catalyst behavior. The appearance of induction period in kinetic plots strengthens the fact that these complexes are catalysts rather than initiators. MALDI-TOF MS and 1 H NMR data show di-hydroxy end groups, which support the coordination mechanism rather than insertion mechanism. To understand the broad PDIs obtained for some of the polymer, the electronic properties of the zinc complexes were investigated using cyclic voltammetry. The results show that the zinc complexes containing amine based ligands are highly electrophilic therefore making them unstable, hence the broad PDIs observed for zinc complexes containing amine based ligands. Among the eight complexes investigated, complex 7 is the most active catalyst with kp value of 1.18 107 h1 mol1 at 110 C.
- Full Text:
- Date Issued: 2015
- Authors: Obuah, Collins , Lochee, Yemanlall , Jordaan, Johan H L , Otto, Daniel P , Nyokong, Tebello , Darkwa, James
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189515 , vital:44853 , xlink:href="https://doi.org/10.1016/j.poly.2015.02.007"
- Description: The reaction of Zn(OAc)2 and C6H5COOH or 3,5-NO2-C6H3COOH with 3-ferrocenylpyrazolyl-methylenepyridine (L1), 3-ferrocenyl-5-methylpyrazolyl-methylenepyridine (L2), 3-ferrocenylpyrazolyl-ethylamine (L3) and 3-ferrocenyl-5-pyrazolyl-ethylamine (L4) afford the corresponding complexes [Zn(C6H5COO)2(L1)] (1), [Zn(C6H5COO)2(L2)] (2), [Zn(3,5-NO2-C6H3COO)2(L1)] (3), [Zn(3,5-NO2-C6H3 COO)2(L2)] (4), [Zn(C6H5COO)2(L3)] (5), [Zn(C6H5COO)2(L4)] (6), [Zn(3,5-NO2-C6H3COO)2(L3)] (7) and [Zn(3,5-NO2-C6H3COO)2(L4)] (8). These complexes behave as catalysts for the ring opening polymerization of e-caprolactone to produce polymers with molecular weight that range from 1480 to 7080 g mol1 and exhibited moderate to broad PDIs. Evidence of these complexes acting as catalysts was obtained from both the polymerization data and kinetic studies. The polymerization data show that variation of the [CL]/[C] from 100 to 800 produced PCL with relatively the same molecular weight indicative of a catalyst behavior. The appearance of induction period in kinetic plots strengthens the fact that these complexes are catalysts rather than initiators. MALDI-TOF MS and 1 H NMR data show di-hydroxy end groups, which support the coordination mechanism rather than insertion mechanism. To understand the broad PDIs obtained for some of the polymer, the electronic properties of the zinc complexes were investigated using cyclic voltammetry. The results show that the zinc complexes containing amine based ligands are highly electrophilic therefore making them unstable, hence the broad PDIs observed for zinc complexes containing amine based ligands. Among the eight complexes investigated, complex 7 is the most active catalyst with kp value of 1.18 107 h1 mol1 at 110 C.
- Full Text:
- Date Issued: 2015
A comparative study of the singlet oxygen generation capability of a zinc phthalocyanine linked to graphene quantum dots through π-π stacking and covalent conjugation when embedded in asymmetric polymer membranes
- Mafukidze, Donovan M, Nyokong, Tebello
- Authors: Mafukidze, Donovan M , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187461 , vital:44655 , xlink:href="https://doi.org/10.1016/j.molstruc.2018.11.096"
- Description: Following the establishment of graphene quantum dots as potential phthalocyanine supports in photoactive membrane preparation for phthalocyanines lacking linkage functional groups, the practical efficiency of p-p stacking versus covalent linkage was investigated. Synthesized materials were characterized using FT-IR, Raman, powder X-ray diffraction, and UVeVis spectroscopies and also by transmission electron and scanning electron microscopies. Phthalocyanine loadings onto graphene quantum dots of 0.40 mg/mg and 0.14 mg/mg (Pc mass/conjugate mass) for the p-p stacked and covalent linked conjugates respectively were observed. Covalent linkage to graphene quantum dots proved to be functionally superior to p-p linkage, where singlet oxygen quantum yield value of the phthalocyanine in the membrane for the covalent linked conjugate was approximately twice that of the p-p stacked membrane.
- Full Text:
- Date Issued: 2019
- Authors: Mafukidze, Donovan M , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187461 , vital:44655 , xlink:href="https://doi.org/10.1016/j.molstruc.2018.11.096"
- Description: Following the establishment of graphene quantum dots as potential phthalocyanine supports in photoactive membrane preparation for phthalocyanines lacking linkage functional groups, the practical efficiency of p-p stacking versus covalent linkage was investigated. Synthesized materials were characterized using FT-IR, Raman, powder X-ray diffraction, and UVeVis spectroscopies and also by transmission electron and scanning electron microscopies. Phthalocyanine loadings onto graphene quantum dots of 0.40 mg/mg and 0.14 mg/mg (Pc mass/conjugate mass) for the p-p stacked and covalent linked conjugates respectively were observed. Covalent linkage to graphene quantum dots proved to be functionally superior to p-p linkage, where singlet oxygen quantum yield value of the phthalocyanine in the membrane for the covalent linked conjugate was approximately twice that of the p-p stacked membrane.
- Full Text:
- Date Issued: 2019
Acetophenone substituted phthalocyanines and their graphene quantum dots conjugates as photosensitizers for photodynamic antimicrobial chemotherapy against Staphylococcus aureus
- Openda, Yolande I, Sen, Pinar, Managa, Muthumuni, Nyokong, Tebello
- Authors: Openda, Yolande I , Sen, Pinar , Managa, Muthumuni , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186507 , vital:44506 , xlink:href="https://doi.org/10.1016/j.pdpdt.2019.101607"
- Description: This work reports on the synthesis and characterization of novel acetophenone substituted phthalocyanines along with the self-assembled nanoconjugates formed via π-π stacking interaction between the synthesized unmetalated (2), zinc (3) and indium (4) phthalocyanines and graphene quantum dots (GQDs) to form 2@GQDs, 3@GQDs and 4@GQDs. The complexes and conjugates exhibited high singlet oxygen ranging from 0.20 to 0.79 in DMSO for Pcs and nanoconjugates where in all cases, the indium complexes showed the highest singlet oxygen quantum yields. The photodynamic antimicrobial chemotherapy activity of both phthalocyanines and nanoconjugates were tested against Staphylococcus aureus. 4@GQDs was found to be highly effective causing a 9.68 log reduction of the bacteria at 10 μM (based on Pc) when compared to 3.77 log reduction of 3@GQDs.
- Full Text:
- Date Issued: 2020
- Authors: Openda, Yolande I , Sen, Pinar , Managa, Muthumuni , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186507 , vital:44506 , xlink:href="https://doi.org/10.1016/j.pdpdt.2019.101607"
- Description: This work reports on the synthesis and characterization of novel acetophenone substituted phthalocyanines along with the self-assembled nanoconjugates formed via π-π stacking interaction between the synthesized unmetalated (2), zinc (3) and indium (4) phthalocyanines and graphene quantum dots (GQDs) to form 2@GQDs, 3@GQDs and 4@GQDs. The complexes and conjugates exhibited high singlet oxygen ranging from 0.20 to 0.79 in DMSO for Pcs and nanoconjugates where in all cases, the indium complexes showed the highest singlet oxygen quantum yields. The photodynamic antimicrobial chemotherapy activity of both phthalocyanines and nanoconjugates were tested against Staphylococcus aureus. 4@GQDs was found to be highly effective causing a 9.68 log reduction of the bacteria at 10 μM (based on Pc) when compared to 3.77 log reduction of 3@GQDs.
- Full Text:
- Date Issued: 2020
Application of gold and palladium nanoparticles supported on polymelamine microspheres in the oxidation of 1-phenylethanol and some other phenyl substituted alcohols
- Storm, Ené, Maggott, Emile D, Mashazi, Philani N, Nyokong, Tebello, Malgas-Enus, Rehana, Mapolie, Selwyn F
- Authors: Storm, Ené , Maggott, Emile D , Mashazi, Philani N , Nyokong, Tebello , Malgas-Enus, Rehana , Mapolie, Selwyn F
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/299824 , vital:57858 , xlink:href="https://doi.org/10.1016/j.mcat.2022.112456"
- Description: Melamine formaldehyde and melamine resorcinol formaldehyde microspheres were decorated with Au and Pd nanoparticles and applied as heterogeneous catalysts in the oxidation of 1-phenylethanol. The catalysts showed similar activities irrespective of the support employed. Moderate conversion activities of 48–50% were achieved when using acetonitrile as solvent; however, when employing water as solvent, the supported catalysts formed a three-phase, emulsion system which facilitated the catalytic conversion of 1-phenylethanol to acetophenone at much higher conversions of around 83%. The oxidant, TBHP, decomposed rapidly in acetonitrile, whilst it remained stable in aqueous solution, leading to the enhanced activities observed when using water as solvent. These systems also proved to be recyclable for up to five cycles, with only slight loss of activity observed; this can be attributed to the physical loss of catalyst during the workup procedure conducted between each cycle.
- Full Text:
- Date Issued: 2022
- Authors: Storm, Ené , Maggott, Emile D , Mashazi, Philani N , Nyokong, Tebello , Malgas-Enus, Rehana , Mapolie, Selwyn F
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/299824 , vital:57858 , xlink:href="https://doi.org/10.1016/j.mcat.2022.112456"
- Description: Melamine formaldehyde and melamine resorcinol formaldehyde microspheres were decorated with Au and Pd nanoparticles and applied as heterogeneous catalysts in the oxidation of 1-phenylethanol. The catalysts showed similar activities irrespective of the support employed. Moderate conversion activities of 48–50% were achieved when using acetonitrile as solvent; however, when employing water as solvent, the supported catalysts formed a three-phase, emulsion system which facilitated the catalytic conversion of 1-phenylethanol to acetophenone at much higher conversions of around 83%. The oxidant, TBHP, decomposed rapidly in acetonitrile, whilst it remained stable in aqueous solution, leading to the enhanced activities observed when using water as solvent. These systems also proved to be recyclable for up to five cycles, with only slight loss of activity observed; this can be attributed to the physical loss of catalyst during the workup procedure conducted between each cycle.
- Full Text:
- Date Issued: 2022
Asymmetrical and symmetrical zinc phthalocyanine-cobalt ferrite conjugates embedded in electrospun fibers for dual photocatalytic degradation of azo dyes: Methyl Orange and Orange G
- Mapukata, Sivuyisiwe, Kobayashi, Nagao, Kimura, Mutsumi, Nyokong, Tebello
- Authors: Mapukata, Sivuyisiwe , Kobayashi, Nagao , Kimura, Mutsumi , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186960 , vital:44551 , xlink:href="https://doi.org/10.1016/j.jphotochem.2019.04.048"
- Description: The conjugation of a symmetrical and an asymmetrical zinc phthalocyanine with amine functionalised cobalt ferrite magnetic nanoparticles (CoFe MNPs) for enhanced photophysics and photocatalysis is reported. The MNPs, 2-[5-(phenoxy)-isophthalic acid] 9(10), 16(17), 23(24)-tris (tertbutyl) phthalocyaninato Zn (II) (2) and 2, 10, 16, 24 – tetra 5-(phenoxy)-isophthalic acid phthalocyaninato] Zn (II) (3) as well as their respective conjugates are embedded into electrospun polyamide-6 (PA-6) fibers for support and catalyst regeneration. The resulting photocatalyts (CoFe/PA-6, 2/PA-6, 3/PA-6, CoFe-2/PA-6, and CoFe-3/PA-6) were compared based on their photophysical properties and photocatalytic efficiencies in degrading azo dyes; Methyl Orange (MO) and Orange G (OG). CoFe-2/PA-6 and CoFe-3/PA-6 were found to be more effective photocatalysts than their respective electrospun Pcs and MNPs. The degradation of OG was found to follow pseudo first order kinetics and the Langmuir–Hinshelwood model while that of MO does not.
- Full Text:
- Date Issued: 2019
- Authors: Mapukata, Sivuyisiwe , Kobayashi, Nagao , Kimura, Mutsumi , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186960 , vital:44551 , xlink:href="https://doi.org/10.1016/j.jphotochem.2019.04.048"
- Description: The conjugation of a symmetrical and an asymmetrical zinc phthalocyanine with amine functionalised cobalt ferrite magnetic nanoparticles (CoFe MNPs) for enhanced photophysics and photocatalysis is reported. The MNPs, 2-[5-(phenoxy)-isophthalic acid] 9(10), 16(17), 23(24)-tris (tertbutyl) phthalocyaninato Zn (II) (2) and 2, 10, 16, 24 – tetra 5-(phenoxy)-isophthalic acid phthalocyaninato] Zn (II) (3) as well as their respective conjugates are embedded into electrospun polyamide-6 (PA-6) fibers for support and catalyst regeneration. The resulting photocatalyts (CoFe/PA-6, 2/PA-6, 3/PA-6, CoFe-2/PA-6, and CoFe-3/PA-6) were compared based on their photophysical properties and photocatalytic efficiencies in degrading azo dyes; Methyl Orange (MO) and Orange G (OG). CoFe-2/PA-6 and CoFe-3/PA-6 were found to be more effective photocatalysts than their respective electrospun Pcs and MNPs. The degradation of OG was found to follow pseudo first order kinetics and the Langmuir–Hinshelwood model while that of MO does not.
- Full Text:
- Date Issued: 2019
Characterization and Electrocatalytic Activity of Nanocomposites Consisting of Nanosized Cobalt Tetraaminophenoxy Phthalocyanine, Multi‐walled Carbon Nanotubes and Gold Nanoparticles
- Shumba, Munyaradzi, Nyokong, Tebello
- Authors: Shumba, Munyaradzi , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188659 , vital:44773 , xlink:href="https://doi.org/10.1002/elan.201501058"
- Description: Glassy carbon electrodes were modified with composites containing cobalt tetraaminophenoxy phthalocyanine nanoparticles (CoTAPhPcNP), multi-walled carbon nanotubes (MWCNT) and gold nanorods (AuNRs). The modified electrodes were studied for their electrocatalytic behavior towards the reduction of hydrogen peroxide. Phthalocyanine nanoparticles significantly improved electron transfer kinetics as compared to phthalocyanines which are not in the nanoparticle form when alone or in the presence of multiwalled carbon nanotubes (MWCNTs). CoTAPhPcNP-MWCNT-GCE proved to be suitable for hydrogen peroxide detection with a catalytic rate constant of 3.45×103 M−1 s−1 and a detection limit of 1.61×10−7 M. Adsorption Gibbs free energy ΔGo was found to be −19.22 kJ mol−1 for CoTAPhPcNP-MWCNT-GCE.
- Full Text:
- Date Issued: 2016
- Authors: Shumba, Munyaradzi , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188659 , vital:44773 , xlink:href="https://doi.org/10.1002/elan.201501058"
- Description: Glassy carbon electrodes were modified with composites containing cobalt tetraaminophenoxy phthalocyanine nanoparticles (CoTAPhPcNP), multi-walled carbon nanotubes (MWCNT) and gold nanorods (AuNRs). The modified electrodes were studied for their electrocatalytic behavior towards the reduction of hydrogen peroxide. Phthalocyanine nanoparticles significantly improved electron transfer kinetics as compared to phthalocyanines which are not in the nanoparticle form when alone or in the presence of multiwalled carbon nanotubes (MWCNTs). CoTAPhPcNP-MWCNT-GCE proved to be suitable for hydrogen peroxide detection with a catalytic rate constant of 3.45×103 M−1 s−1 and a detection limit of 1.61×10−7 M. Adsorption Gibbs free energy ΔGo was found to be −19.22 kJ mol−1 for CoTAPhPcNP-MWCNT-GCE.
- Full Text:
- Date Issued: 2016
Conjugation of mono-substituted phthalocyanine derivatives to CdSe@ ZnS quantum dots and their applications as fluorescent-based sensors
- Adegoke, Oluwasesan, Nyokong, Tebello
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189842 , vital:44936 , xlink:href="https://doi.org/10.1016/j.synthmet.2013.11.016"
- Description: Unsymmetrically substituted derivatives of aluminium amino phthalocyanines were synthesized for the first time, fully characterized and conjugated to CdSe@ZnS quantum dots (QDs). The conjugates were employed as fluorescence-based sensors for anion sensing. Among the anions that enhanced the fluorescence of the probe, fluoride ion was chosen as the test ion to test the efficacy of the probe. Förster resonance energy transfer from the QDs to the phthalocyanine was observed as an indication for the fluorescence quenching of the QDs upon binding to the phthalocyanine. The fluorescence of the linked QDs was progressively enhanced, and linearly proportional to increasing concentrations of fluoride ion. The type of substituent attached to the phthalocyanine ring influenced the efficiency of fluorescence enhancement. The proposed nanoprobe has been employed to detect fluoride ion in cell culture medium and tap water.
- Full Text:
- Date Issued: 2014
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189842 , vital:44936 , xlink:href="https://doi.org/10.1016/j.synthmet.2013.11.016"
- Description: Unsymmetrically substituted derivatives of aluminium amino phthalocyanines were synthesized for the first time, fully characterized and conjugated to CdSe@ZnS quantum dots (QDs). The conjugates were employed as fluorescence-based sensors for anion sensing. Among the anions that enhanced the fluorescence of the probe, fluoride ion was chosen as the test ion to test the efficacy of the probe. Förster resonance energy transfer from the QDs to the phthalocyanine was observed as an indication for the fluorescence quenching of the QDs upon binding to the phthalocyanine. The fluorescence of the linked QDs was progressively enhanced, and linearly proportional to increasing concentrations of fluoride ion. The type of substituent attached to the phthalocyanine ring influenced the efficiency of fluorescence enhancement. The proposed nanoprobe has been employed to detect fluoride ion in cell culture medium and tap water.
- Full Text:
- Date Issued: 2014
Design and fabrication of electrochemical sensor based on molecularly imprinted polymer loaded onto silver nanoparticles for the detection of 17-β-Estradiol
- Regasa, Melkamu Biyana, Nyokong, Tebello
- Authors: Regasa, Melkamu Biyana , Nyokong, Tebello
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/300287 , vital:57913 , xlink:href="https://doi.org/10.1002/jmr.2978"
- Description: In this research report, we prepared an electrochemical sensor based on the molecularly imprinted poly(p-aminophenol) supported by silver nanoparticles capped with 2-mercaptobenzoxazole for the selective and sensitive detection of endocrine disrupting 17-β-estradiol (E2). The electropolymerization of the functional monomer prepared the proposed molecularly imprinted polymer (MIP) composite-based sensor in the presence of E2 as a template. The recognition materials were characterized using Fourier transform infrared, cyclic voltammetry (CV), square wave voltammetry (SWV), scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray powder diffraction techniques. The electrochemical measurements were performed by employing both CV and SWV methods. We did the optimization of critical parameters affecting the sensor performances through the experimental design and verification. The developed sensor showed a linear range from 10 pM to 100 nM with the calculated quantification and detection limits of 1.86 and 6.19 pM, respectively. The incorporation of AgNP with high electrical conductivity into the MIP matrix enhanced the sensor's performance. Furthermore, the sensor was applied to determine E2 in real water samples without any sample preconcentration steps to achieve the percent recovery of 91.87% to 98.36% and acceptable reusability and storage stability performances.
- Full Text:
- Date Issued: 2022
- Authors: Regasa, Melkamu Biyana , Nyokong, Tebello
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/300287 , vital:57913 , xlink:href="https://doi.org/10.1002/jmr.2978"
- Description: In this research report, we prepared an electrochemical sensor based on the molecularly imprinted poly(p-aminophenol) supported by silver nanoparticles capped with 2-mercaptobenzoxazole for the selective and sensitive detection of endocrine disrupting 17-β-estradiol (E2). The electropolymerization of the functional monomer prepared the proposed molecularly imprinted polymer (MIP) composite-based sensor in the presence of E2 as a template. The recognition materials were characterized using Fourier transform infrared, cyclic voltammetry (CV), square wave voltammetry (SWV), scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray powder diffraction techniques. The electrochemical measurements were performed by employing both CV and SWV methods. We did the optimization of critical parameters affecting the sensor performances through the experimental design and verification. The developed sensor showed a linear range from 10 pM to 100 nM with the calculated quantification and detection limits of 1.86 and 6.19 pM, respectively. The incorporation of AgNP with high electrical conductivity into the MIP matrix enhanced the sensor's performance. Furthermore, the sensor was applied to determine E2 in real water samples without any sample preconcentration steps to achieve the percent recovery of 91.87% to 98.36% and acceptable reusability and storage stability performances.
- Full Text:
- Date Issued: 2022
Detonation nanodiamonds-phthalocyanine photosensitizers with enhanced photophysicochemical properties and effective photoantibacterial activity
- Openda, Yolande I, Nyokong, Tebello
- Authors: Openda, Yolande I , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186012 , vital:44455 , xlink:href="https://doi.org/10.1016/j.pdpdt.2020.102072"
- Description: The nanophotosensitizers based on acetophenoxy tetrasubstituted metallophthalocyanines (MPc) and detonation nanodiamonds (DNDs) were successfully formed and their photophysicochemical properties were determined. The zinc(II)Pc and indium(III)Pc complexes along with their nanoconjugates were found to have high singlet oxygen quantum yields (0.72 − 0.84) associated with the heavy central metal effect. The ability of the functional groups present on the DNDs to bind to the bacteria cell and the improved solubility of the nanoconjugates due to DNDs resulted in effective photodynamic antimicrobial therapy (PACT) activity against S. aureus planktonic cells, with the highest log reduction of 9.72 ± 0.02 for the conjugate of InPc conjugate with DNDs after 30 min irradiation. PACT studies were investigated at a dose of 10 μg/mL for each sample. The results suggest that the readily synthesized nanoconjugates can be used as appropriate PACT agents.
- Full Text:
- Date Issued: 2020
- Authors: Openda, Yolande I , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186012 , vital:44455 , xlink:href="https://doi.org/10.1016/j.pdpdt.2020.102072"
- Description: The nanophotosensitizers based on acetophenoxy tetrasubstituted metallophthalocyanines (MPc) and detonation nanodiamonds (DNDs) were successfully formed and their photophysicochemical properties were determined. The zinc(II)Pc and indium(III)Pc complexes along with their nanoconjugates were found to have high singlet oxygen quantum yields (0.72 − 0.84) associated with the heavy central metal effect. The ability of the functional groups present on the DNDs to bind to the bacteria cell and the improved solubility of the nanoconjugates due to DNDs resulted in effective photodynamic antimicrobial therapy (PACT) activity against S. aureus planktonic cells, with the highest log reduction of 9.72 ± 0.02 for the conjugate of InPc conjugate with DNDs after 30 min irradiation. PACT studies were investigated at a dose of 10 μg/mL for each sample. The results suggest that the readily synthesized nanoconjugates can be used as appropriate PACT agents.
- Full Text:
- Date Issued: 2020
Development of nanocomposites of phosphorus-nitrogen co-doped graphene oxide nanosheets and nanosized cobalt phthalocyanines for electrocatalysis
- Shumba, Munyaradzai, Nyokong, Tebello
- Authors: Shumba, Munyaradzai , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188574 , vital:44766 , xlink:href="https://doi.org/10.1016/j.electacta.2016.07.079"
- Description: Conjugates of reduced phosphorus-nitrogen co-doped graphene oxide nanosheets (rPNDGONS), reduced phosphorus doped graphene oxide nanosheets (rPDGONS), reduced nitrogen doped graphene oxide nanosheets (rNDGONS), reduced pyrolised graphene oxide nanosheets (rpyGONS) with nanosized cobalt (II) phthalocyanine (CoPcNP) or cobalt tetra amino phenoxy phthalocyanine (CoTAPhPcNP) were characterised and tested for their electrocatalytic behaviour towards the detection of hydrogen peroxide. Cyclic and linear scan voltammetries, and chronoamperometry were used to evaluate the electrocatalytic nature of the designed probes. For hydrogen peroxide detection, CoPcNP-rPNDGONS-GCE oxidation gave sensitivity of 12.00 mA/M, limit of detection of 4.48 nM, a rate constant of 2.66 × 105 M−1 s−1, adsorption equilibrium constant of 3.7 × 102 M−1 and Gibbs free energy −14.84 kJmol−1. The lowest detection limit was obtained for CoTAPhPcNP-rPNDGONS-GCE at 1.21 nM.
- Full Text:
- Date Issued: 2016
- Authors: Shumba, Munyaradzai , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188574 , vital:44766 , xlink:href="https://doi.org/10.1016/j.electacta.2016.07.079"
- Description: Conjugates of reduced phosphorus-nitrogen co-doped graphene oxide nanosheets (rPNDGONS), reduced phosphorus doped graphene oxide nanosheets (rPDGONS), reduced nitrogen doped graphene oxide nanosheets (rNDGONS), reduced pyrolised graphene oxide nanosheets (rpyGONS) with nanosized cobalt (II) phthalocyanine (CoPcNP) or cobalt tetra amino phenoxy phthalocyanine (CoTAPhPcNP) were characterised and tested for their electrocatalytic behaviour towards the detection of hydrogen peroxide. Cyclic and linear scan voltammetries, and chronoamperometry were used to evaluate the electrocatalytic nature of the designed probes. For hydrogen peroxide detection, CoPcNP-rPNDGONS-GCE oxidation gave sensitivity of 12.00 mA/M, limit of detection of 4.48 nM, a rate constant of 2.66 × 105 M−1 s−1, adsorption equilibrium constant of 3.7 × 102 M−1 and Gibbs free energy −14.84 kJmol−1. The lowest detection limit was obtained for CoTAPhPcNP-rPNDGONS-GCE at 1.21 nM.
- Full Text:
- Date Issued: 2016
Development of phthalocyanine functionalised TiO 2 and ZnO nanofibers for photodegradation of methyl orange
- Mapukata, Sivuyisiwe, Nyokong, Tebello
- Authors: Mapukata, Sivuyisiwe , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186323 , vital:44485 , xlink:href="https://doi.org/10.1039/D0NJ03326J"
- Description: The photocatalytic activity of TiO2 and ZnO based catalysts, which is based on their ability to generate electron–hole pairs upon photoillumination is limited due to their wide band gaps and lack of efficient retrievability post-application. This work reports on the fabrication, characterisation and comparison of electrospun TiO2 and ZnO nanofibers when bare vs when functionalised with a phthalocyanine. The generated photocatalysts are attractive because they absorb visible light and are easily retrievable and hence reusable. With the Pc anchored onto their surfaces, the anatase TiO2 nanofibers and the wurzite ZnO nanofibers possessed singlet oxygen quantum yields of 0.22 and 0.16 in water, respectively. Evaluation of the photocatalytic efficiencies of the nanofibers was conducted by studying the photodegradation of methyl orange. The Pc decorated nanofibers were found to be more effective photocatalysts than the bare ones with the phthalocyanine TiO2 nanofibers being the best. The degradation kinetics were found to follow pseudo first order kinetics and obeyed the Langmuir Hinshelwood model. The nanocatalysts reported herein are therefore feasible candidates for real-life water purification applications.
- Full Text:
- Date Issued: 2020
- Authors: Mapukata, Sivuyisiwe , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186323 , vital:44485 , xlink:href="https://doi.org/10.1039/D0NJ03326J"
- Description: The photocatalytic activity of TiO2 and ZnO based catalysts, which is based on their ability to generate electron–hole pairs upon photoillumination is limited due to their wide band gaps and lack of efficient retrievability post-application. This work reports on the fabrication, characterisation and comparison of electrospun TiO2 and ZnO nanofibers when bare vs when functionalised with a phthalocyanine. The generated photocatalysts are attractive because they absorb visible light and are easily retrievable and hence reusable. With the Pc anchored onto their surfaces, the anatase TiO2 nanofibers and the wurzite ZnO nanofibers possessed singlet oxygen quantum yields of 0.22 and 0.16 in water, respectively. Evaluation of the photocatalytic efficiencies of the nanofibers was conducted by studying the photodegradation of methyl orange. The Pc decorated nanofibers were found to be more effective photocatalysts than the bare ones with the phthalocyanine TiO2 nanofibers being the best. The degradation kinetics were found to follow pseudo first order kinetics and obeyed the Langmuir Hinshelwood model. The nanocatalysts reported herein are therefore feasible candidates for real-life water purification applications.
- Full Text:
- Date Issued: 2020
Effect of peripheral fused ring substitution on the optical spectroscopy and electronic structure of metal phthalocyanine complexes
- Chidawanyika, Wadzanai J U, Mack, John, Shimizu, Soji, Kobayashi, Nagao, Nyokong, Tebello
- Authors: Chidawanyika, Wadzanai J U , Mack, John , Shimizu, Soji , Kobayashi, Nagao , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263353 , vital:53620 , xlink:href="https://doi.org/10.1142/S1088424609001339"
- Description: In this paper the impact of peripheral substitution with a strongly withdrawing fused ring group on the optical spectroscopy of a metal phthalocyanine complex is analyzed. We report the synthesis of [9 (or 10), 16 (or 17), 23 (or 24)-tri-tert-butylimidophthalocyaninato]zinc(II) (ZnttbIPc), which should eventually prove to be a useful precursor for forming dimeric compounds. The electronic structure is analyzed through a detailed analysis of the UV-visible absorption and magnetic circular dichroism spectra and time-dependent density functional theory calculations. Other than a marked splitting of the Q band, the spectrum is broadly similar to that of ZnPc in terms of the main π → π* electronic bands. The vibrational bands differ markedly in the Q band region when an imido group is added to ligand periphery, relative to what is observed in the case of zinc mononaphthotribenzotetraazaporphyrin (Zn3B1N) with an additional fused benzene ring. The absorption and emission spectra lack mirror symmetry as is the case with ZnPc and thus provide possible evidence for a second set of electronic origins in the Q band region arising from n → π* rather then π → π* transitions.
- Full Text:
- Date Issued: 2009
- Authors: Chidawanyika, Wadzanai J U , Mack, John , Shimizu, Soji , Kobayashi, Nagao , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263353 , vital:53620 , xlink:href="https://doi.org/10.1142/S1088424609001339"
- Description: In this paper the impact of peripheral substitution with a strongly withdrawing fused ring group on the optical spectroscopy of a metal phthalocyanine complex is analyzed. We report the synthesis of [9 (or 10), 16 (or 17), 23 (or 24)-tri-tert-butylimidophthalocyaninato]zinc(II) (ZnttbIPc), which should eventually prove to be a useful precursor for forming dimeric compounds. The electronic structure is analyzed through a detailed analysis of the UV-visible absorption and magnetic circular dichroism spectra and time-dependent density functional theory calculations. Other than a marked splitting of the Q band, the spectrum is broadly similar to that of ZnPc in terms of the main π → π* electronic bands. The vibrational bands differ markedly in the Q band region when an imido group is added to ligand periphery, relative to what is observed in the case of zinc mononaphthotribenzotetraazaporphyrin (Zn3B1N) with an additional fused benzene ring. The absorption and emission spectra lack mirror symmetry as is the case with ZnPc and thus provide possible evidence for a second set of electronic origins in the Q band region arising from n → π* rather then π → π* transitions.
- Full Text:
- Date Issued: 2009
Electrocatalytic activity of bimetallic Au–Pd nanoparticles in the presence of cobalt tetraaminophthalocyanine
- Maringa, Audacity, Mashazi, Philani N, Nyokong, Tebello
- Authors: Maringa, Audacity , Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189719 , vital:44925 , xlink:href="https://doi.org/10.1016/j.jcis.2014.10.056"
- Description: Au and Pd nanoparticles were individually or together electrodeposited on top of polymerized cobalt tetraaminophthalocyanine (poly-CoTAPc). When Pd and Au nanoparticles are co-deposited together, the electrode is denoted as Au–Pd (co-deposited)/poly-CoTAPc-GCE. X-ray photoelectron spectroscopy (XPS) was used to show the successful deposition of AuNPs, PdNPs and Au–Pd (co-deposited). The scanning electrochemical microscopy showed that Au–Pd (co-deposited)/poly-CoTAPc-GCE (with current range of 9.5–13.5 lA) was more conducting than Au–Pd (co-deposited)-GCE (with current range of 8–12 lA). Electrochemical impedance spectroscopy (EIS) showed that there was less resistance to charge transfer for Au–Pd (co-deposited)/poly-CoTAPc-GCE compared to the rest of the electrodes. Au–Pd (co-deposited)/poly-CoTAPc-GCE showed the best activity for the electrooxidation of hydrazine in terms of limit of detection (0.5 lM), hence shows promise as an electrocatalyst for electrooxidation of hydrazine.
- Full Text:
- Date Issued: 2015
- Authors: Maringa, Audacity , Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189719 , vital:44925 , xlink:href="https://doi.org/10.1016/j.jcis.2014.10.056"
- Description: Au and Pd nanoparticles were individually or together electrodeposited on top of polymerized cobalt tetraaminophthalocyanine (poly-CoTAPc). When Pd and Au nanoparticles are co-deposited together, the electrode is denoted as Au–Pd (co-deposited)/poly-CoTAPc-GCE. X-ray photoelectron spectroscopy (XPS) was used to show the successful deposition of AuNPs, PdNPs and Au–Pd (co-deposited). The scanning electrochemical microscopy showed that Au–Pd (co-deposited)/poly-CoTAPc-GCE (with current range of 9.5–13.5 lA) was more conducting than Au–Pd (co-deposited)-GCE (with current range of 8–12 lA). Electrochemical impedance spectroscopy (EIS) showed that there was less resistance to charge transfer for Au–Pd (co-deposited)/poly-CoTAPc-GCE compared to the rest of the electrodes. Au–Pd (co-deposited)/poly-CoTAPc-GCE showed the best activity for the electrooxidation of hydrazine in terms of limit of detection (0.5 lM), hence shows promise as an electrocatalyst for electrooxidation of hydrazine.
- Full Text:
- Date Issued: 2015
Electrocatalytic behaviour of surface confined pentanethio cobalt (II) binuclear phthalocyanines towards the oxidation of 4-chlorophenol
- Makinde, Zainab O, Louzada, Marcel, Mashazi, Philani N, Nyokong, Tebello, Khene, Samson M
- Authors: Makinde, Zainab O , Louzada, Marcel , Mashazi, Philani N , Nyokong, Tebello , Khene, Samson M
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188138 , vital:44726 , xlink:href="https://doi.org/10.1016/j.apsusc.2017.06.271"
- Description: Cobalt binuclear phthalocyanine (CoBiPc) bearing pentanethio substituents at the peripheral positions were synthesized. The immobilization of the synthesized cobalt phthalocyanines on gold electrode was achieved using self-assembled monolayer method (SAM). X-ray photoelectron spectroscopy (XPS) and Kelvin Probe (KP) techniques were used to characterise the formation of monomeric and binuclear phthalocyanine SAMs on the gold surface. The phthalocyanine SAMs on gold electrodes were investigated for electrocatalytic oxidation of 4-chlorophenol. The electrocatalytic properties of tetra- and octa- pentanethio substituted cobalt binuclear phthalocyanine (CoBiPc) are compared with their tetra- and octa-pentanethio substituted phthalocyanine (CoPc). The SAMs modified gold electrode surfaces showed a peak current enhancement and stability and reduction in electrocatalytic potentials compared to the bare or unmodified electrodes towards the detection of the 4-chlorophenol. The SAMs of cobalt binuclear phthalocyanines exhibited more enhanced electrocatalytic properties in terms of stability, detection peak current and reduction of the electrocatalytic over potential.
- Full Text:
- Date Issued: 2017
- Authors: Makinde, Zainab O , Louzada, Marcel , Mashazi, Philani N , Nyokong, Tebello , Khene, Samson M
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188138 , vital:44726 , xlink:href="https://doi.org/10.1016/j.apsusc.2017.06.271"
- Description: Cobalt binuclear phthalocyanine (CoBiPc) bearing pentanethio substituents at the peripheral positions were synthesized. The immobilization of the synthesized cobalt phthalocyanines on gold electrode was achieved using self-assembled monolayer method (SAM). X-ray photoelectron spectroscopy (XPS) and Kelvin Probe (KP) techniques were used to characterise the formation of monomeric and binuclear phthalocyanine SAMs on the gold surface. The phthalocyanine SAMs on gold electrodes were investigated for electrocatalytic oxidation of 4-chlorophenol. The electrocatalytic properties of tetra- and octa- pentanethio substituted cobalt binuclear phthalocyanine (CoBiPc) are compared with their tetra- and octa-pentanethio substituted phthalocyanine (CoPc). The SAMs modified gold electrode surfaces showed a peak current enhancement and stability and reduction in electrocatalytic potentials compared to the bare or unmodified electrodes towards the detection of the 4-chlorophenol. The SAMs of cobalt binuclear phthalocyanines exhibited more enhanced electrocatalytic properties in terms of stability, detection peak current and reduction of the electrocatalytic over potential.
- Full Text:
- Date Issued: 2017
Electrochemical and photophysical characterization of non-peripherally-octaalkyl substituted dichlorotin (IV) phthalocyanine and tetrabenzotriazaporphyrin compounds
- Khene, Samson M, Cammidge, Andrew N, Cook, Michael J, Nyokong, Tebello
- Authors: Khene, Samson M , Cammidge, Andrew N , Cook, Michael J , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/271216 , vital:54522 , xlink:href="https://doi.org/10.1142/S1088424607000886"
- Description: Three non-peripherally substituted tin(IV) macrocylic compounds, octahexylphthalocyaninato dichlorotin(IV) (3a), octahexyltetrabenzo-5,10,15- triazaporphyrinato dichlorotin(IV) (3b) and octadecylphthalocyaninato dichlorotin(IV) (3c) were synthesized and their photophysical and electrochemical behavior studied. Complex 3b, containing a CH group in place of one of the aza nitrogen atoms of the phthalocyanine core, shows a split Q-band due to its lower symmetry. The triplet state quantum yields were found to be lower than would be expected on the basis of the heavy atom effect of tin as the central metal for phthalocyanine derivatives (3a and 3c). In contrast, 3b shows a triplet quantum yield ΦT = 0.78. The triplet state lifetimes were solvent dependent, and were higher in tetrahydrofuran than in toluene. Cyclic voltammetry and spectroelectrochemistry of the complexes revealed only ring-based redox processes.
- Full Text:
- Date Issued: 2007
- Authors: Khene, Samson M , Cammidge, Andrew N , Cook, Michael J , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/271216 , vital:54522 , xlink:href="https://doi.org/10.1142/S1088424607000886"
- Description: Three non-peripherally substituted tin(IV) macrocylic compounds, octahexylphthalocyaninato dichlorotin(IV) (3a), octahexyltetrabenzo-5,10,15- triazaporphyrinato dichlorotin(IV) (3b) and octadecylphthalocyaninato dichlorotin(IV) (3c) were synthesized and their photophysical and electrochemical behavior studied. Complex 3b, containing a CH group in place of one of the aza nitrogen atoms of the phthalocyanine core, shows a split Q-band due to its lower symmetry. The triplet state quantum yields were found to be lower than would be expected on the basis of the heavy atom effect of tin as the central metal for phthalocyanine derivatives (3a and 3c). In contrast, 3b shows a triplet quantum yield ΦT = 0.78. The triplet state lifetimes were solvent dependent, and were higher in tetrahydrofuran than in toluene. Cyclic voltammetry and spectroelectrochemistry of the complexes revealed only ring-based redox processes.
- Full Text:
- Date Issued: 2007
Electrochemical detection of dopamine using phthalocyanine-nitrogen-doped graphene quantum dot conjugates
- Ndebele Nobuhle, Sen, Pinar, Nyokong, Tebello
- Authors: Ndebele Nobuhle , Sen, Pinar , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185724 , vital:44418 , xlink:href="https://doi.org/10.1016/j.jelechem.2021.115111"
- Description: Two cobalt phthalocyanine molecules were synthesized, a symmetrically substituted CoPc (1) and an unsymmetrically substituted CoPc (2). These CoPcs were π-π stacked onto nitrogen-doped graphene quantum dots (NGQDs). The CoPcs, NGQDs and their respective conjugates were used as electro-catalytic probes in the electrochemical oxidation of dopamine. The molecules were adsorbed onto a glassy carbon electrode (GCE) using the drop dry method, the GCE was used to support those catalysts. The electrooxidation of dopamine was studied using cyclic voltammetry and chronoamperometry. An improvement in the sensitivity and limit of detection was observed upon conjugation.
- Full Text:
- Date Issued: 2021
- Authors: Ndebele Nobuhle , Sen, Pinar , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185724 , vital:44418 , xlink:href="https://doi.org/10.1016/j.jelechem.2021.115111"
- Description: Two cobalt phthalocyanine molecules were synthesized, a symmetrically substituted CoPc (1) and an unsymmetrically substituted CoPc (2). These CoPcs were π-π stacked onto nitrogen-doped graphene quantum dots (NGQDs). The CoPcs, NGQDs and their respective conjugates were used as electro-catalytic probes in the electrochemical oxidation of dopamine. The molecules were adsorbed onto a glassy carbon electrode (GCE) using the drop dry method, the GCE was used to support those catalysts. The electrooxidation of dopamine was studied using cyclic voltammetry and chronoamperometry. An improvement in the sensitivity and limit of detection was observed upon conjugation.
- Full Text:
- Date Issued: 2021
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
Electrode modification using alkynyl substituted Fe (II) phthalocyanine via electrografting and click chemistry for electrocatalysis
- Nxele, Siphesihle R, Mashazi, Philani N, Nyokong, Tebello
- Authors: Nxele, Siphesihle R , Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189296 , vital:44835 , xlink:href="https://doi.org/10.1002/elan.201500212"
- Description: In this work, tetrakis(5-hexyn-oxy)Fe(II) phthalocyanine was synthesised in order to perform a click reaction between the terminal alkyne groups and an azide group on a glassy carbon electrode (GCE) surface. An azide group was formed on the electrode surface following electrografting using 4-azidobenzene diazonium tetrafluoroborate by electrochemical reduction. The Cu(I) catalyzed alkyne-azide Huisgen cycloaddition reaction was then employed in order to react the terminal alkyne groups on the phthalocyanine with the azide groups on the GCE surface. The modified electrode was employed to catalyse the oxidation of hydrazine. The electrode showed good electrocatalytic ability towards the detection of hydrazine with a sensitivity of 15.38 µA mM−1 and a limit of detection of 1.09 µM.
- Full Text:
- Date Issued: 2015
- Authors: Nxele, Siphesihle R , Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189296 , vital:44835 , xlink:href="https://doi.org/10.1002/elan.201500212"
- Description: In this work, tetrakis(5-hexyn-oxy)Fe(II) phthalocyanine was synthesised in order to perform a click reaction between the terminal alkyne groups and an azide group on a glassy carbon electrode (GCE) surface. An azide group was formed on the electrode surface following electrografting using 4-azidobenzene diazonium tetrafluoroborate by electrochemical reduction. The Cu(I) catalyzed alkyne-azide Huisgen cycloaddition reaction was then employed in order to react the terminal alkyne groups on the phthalocyanine with the azide groups on the GCE surface. The modified electrode was employed to catalyse the oxidation of hydrazine. The electrode showed good electrocatalytic ability towards the detection of hydrazine with a sensitivity of 15.38 µA mM−1 and a limit of detection of 1.09 µM.
- Full Text:
- Date Issued: 2015
Electrodeposited Benzothiazole Phthalocyanines for Corrosion Inhibition of Aluminium in Acidic Medium
- Nnaji, Nnaemeka, Nwaji, Njemuwa, Nyokong, Tebello
- Authors: Nnaji, Nnaemeka , Nwaji, Njemuwa , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186112 , vital:44464 , xlink:href="https://doi.org/10.1155/2020/8892559"
- Description: Tetrakis[(benzo[d]thiazol-2-yl-thio) phthalocyaninato] gallium(III)chloride (1) and tetrakis[(benzo[d]thiazol-2ylphenoxy) phthalocyaninato] gallium(III)chloride (2) were successfully electrodeposited onto aluminium for corrosion retardation in 1.0 M hydrochloric acid solution. The aim of this study was to compare the corrosion resistance of electrodeposited metallated phthalocyanines. Scanning electron microscopy, X-ray diffraction, electrochemical impedance spectroscopy (EIS), and polarization confirmed the aluminium corrosion inhibition potentials of complexes 1 and 2. EIS and polarization techniques showed that complex 2 performed better than complex 1, with values from EIS measurements of 82% for 1 and 86% for 2 in 1.0 M hydrochloric acid solution. The importance of electrodeposition in industries and a dearth of research on the use of electrodeposited metallated phthalocyanines necessitated this study, and results show that coatings formed by electrodeposition of 1 and 2 onto aluminium reduced its susceptibility to corrosion attack.
- Full Text:
- Date Issued: 2020
- Authors: Nnaji, Nnaemeka , Nwaji, Njemuwa , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186112 , vital:44464 , xlink:href="https://doi.org/10.1155/2020/8892559"
- Description: Tetrakis[(benzo[d]thiazol-2-yl-thio) phthalocyaninato] gallium(III)chloride (1) and tetrakis[(benzo[d]thiazol-2ylphenoxy) phthalocyaninato] gallium(III)chloride (2) were successfully electrodeposited onto aluminium for corrosion retardation in 1.0 M hydrochloric acid solution. The aim of this study was to compare the corrosion resistance of electrodeposited metallated phthalocyanines. Scanning electron microscopy, X-ray diffraction, electrochemical impedance spectroscopy (EIS), and polarization confirmed the aluminium corrosion inhibition potentials of complexes 1 and 2. EIS and polarization techniques showed that complex 2 performed better than complex 1, with values from EIS measurements of 82% for 1 and 86% for 2 in 1.0 M hydrochloric acid solution. The importance of electrodeposition in industries and a dearth of research on the use of electrodeposited metallated phthalocyanines necessitated this study, and results show that coatings formed by electrodeposition of 1 and 2 onto aluminium reduced its susceptibility to corrosion attack.
- Full Text:
- Date Issued: 2020
Electronic structure and NH-tautomerism of a novel metal-free phenanthroline-annelated phthalocyanine
- Martynov, Alexander G, Mack, John, Ngoy, Bokolombe P, Nyokong, Tebello, Gorbunova, Yulia G, Tsivadze, Aslan Yu
- Authors: Martynov, Alexander G , Mack, John , Ngoy, Bokolombe P , Nyokong, Tebello , Gorbunova, Yulia G , Tsivadze, Aslan Yu
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/239643 , vital:50751 , xlink:href="https://doi.org/10.1016/j.dyepig.2017.01.072"
- Description: A novel low-symmetry A3B-type phthalocyanine annelated with a pyrazino[2,3-f]phenanthroline ring system and substituted with six solubilizing diisopropylphenoxy-groups (1) was synthesized by metalfree DBU-promoted cross-condensation of diiminoisoindolines derived from 4,5- bis(diisopropylphenoxy)phthalonitrile and pyrazino[2,3-f][1,10]phenanthroline-2,3-dicarbonitrile. The use of these particular precursors affords A3B phthalocyanine in 15% yield, while cross-condensation of the corresponding dinitriles yields only trace amounts of the target compound. Comparative studies of the A3B-type phthalocyanine and its symmetrical octa(diisopropylphenoxy)-substituted counterpart 2 reveal striking differences in the Q band regions of their UVevisible absorption (UVeVis) spectra, which could be readily rationalized through a comparison with calculated TD-DFT spectra. Since 1 can have two NH-tautomers with equivalent and non-equivalent NH-groups, and DFT calculations predict that the former tautomer is only 2.3 kcal/mol more stable than the latter one, a comprehensive analysis of 13C NMR spectra was carried out through the application of 1 He13C HMBC and HSQC techniques. It demonstrated that only the tautomer with equivalent NH-groups is present in solution.
- Full Text:
- Date Issued: 2017
- Authors: Martynov, Alexander G , Mack, John , Ngoy, Bokolombe P , Nyokong, Tebello , Gorbunova, Yulia G , Tsivadze, Aslan Yu
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/239643 , vital:50751 , xlink:href="https://doi.org/10.1016/j.dyepig.2017.01.072"
- Description: A novel low-symmetry A3B-type phthalocyanine annelated with a pyrazino[2,3-f]phenanthroline ring system and substituted with six solubilizing diisopropylphenoxy-groups (1) was synthesized by metalfree DBU-promoted cross-condensation of diiminoisoindolines derived from 4,5- bis(diisopropylphenoxy)phthalonitrile and pyrazino[2,3-f][1,10]phenanthroline-2,3-dicarbonitrile. The use of these particular precursors affords A3B phthalocyanine in 15% yield, while cross-condensation of the corresponding dinitriles yields only trace amounts of the target compound. Comparative studies of the A3B-type phthalocyanine and its symmetrical octa(diisopropylphenoxy)-substituted counterpart 2 reveal striking differences in the Q band regions of their UVevisible absorption (UVeVis) spectra, which could be readily rationalized through a comparison with calculated TD-DFT spectra. Since 1 can have two NH-tautomers with equivalent and non-equivalent NH-groups, and DFT calculations predict that the former tautomer is only 2.3 kcal/mol more stable than the latter one, a comprehensive analysis of 13C NMR spectra was carried out through the application of 1 He13C HMBC and HSQC techniques. It demonstrated that only the tautomer with equivalent NH-groups is present in solution.
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- Date Issued: 2017