Click chemistry electrode modification using 4-ethynylbenzyl substituted cobalt phthalocyanine for applications in electrocatalysis
- Mpeta, Lekhetho S, Fomo, Gertrude, Nyokong, Tebello
- Authors: Mpeta, Lekhetho S , Fomo, Gertrude , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187626 , vital:44681 , xlink:href="• https://doi.org/10.1080/00958972.2018.1466118"
- Description: In this work, we report on the synthesis and applications of a new cobalt tetrakis 4-((4-ethynylbenzyl) oxy) phthalocyanine (3) for the detection of hydrazine. The glassy carbon electrode (GCE) was first grafted through diazotization, providing the GCE surface layer with azide groups. Thereafter, the 1,3-dipolar cycloaddition reaction, catalyzed by a copper(I) catalyst was used to “click” complex 3 to the grafted surface of GCE. The new platform was then characterized using cyclic voltammetry (CV), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). This work shows that 3 is an effective sensor with sensitivity of 91.5 μA mM−1 and limit of detection of 3.28 μM which is a great improvement compared to other reported sensors for this analyte.
- Full Text:
- Authors: Mpeta, Lekhetho S , Fomo, Gertrude , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187626 , vital:44681 , xlink:href="• https://doi.org/10.1080/00958972.2018.1466118"
- Description: In this work, we report on the synthesis and applications of a new cobalt tetrakis 4-((4-ethynylbenzyl) oxy) phthalocyanine (3) for the detection of hydrazine. The glassy carbon electrode (GCE) was first grafted through diazotization, providing the GCE surface layer with azide groups. Thereafter, the 1,3-dipolar cycloaddition reaction, catalyzed by a copper(I) catalyst was used to “click” complex 3 to the grafted surface of GCE. The new platform was then characterized using cyclic voltammetry (CV), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). This work shows that 3 is an effective sensor with sensitivity of 91.5 μA mM−1 and limit of detection of 3.28 μM which is a great improvement compared to other reported sensors for this analyte.
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Low symmetric metallophthalocyanine modified electrode via click chemistry for simultaneous detection of heavy metals
- Fomo, Gertrude, Nwaji, Njemuwa, Nyokong, Tebello
- Authors: Fomo, Gertrude , Nwaji, Njemuwa , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187914 , vital:44709 , xlink:href="https://doi.org/10.1016/j.jelechem.2018.02.016"
- Description: Beside different methods and materials used to develop electrochemical sensors, the modification of the electrode using click reaction based on metallophthalocyanine (MPc) compounds are shown to improve the stability and sensitivity of the sensor. This work reported the development of electrochemical sensor for mercury (II), Lead (II), copper (II) and cadmium (II) ions detection based on the synthesized novel low symmetry alkyne terminated cobalt Phthalocyanine (CoPc) derivative. Differential pulse stripping voltammetry (DPSV) technique was employed for the first time in simultaneous determination of trace levels of the above metal ions using modified glassy carbon electrode (GCE) via click chemistry. Under the optimum experimental conditions, the anodic peak current is proportional to the concentrations of metal ions over a wide range of 0 to 0.1 mM with nanolevel detection limit of 81.94, 327.71, 55.87 and 347.06 nM and the sensitivity of 866.23 ± 5.48, 215.82 ± 2.16, 1979.48 ± 11.47 and 204.50 ± 1.10 μA/mM for Hg(II), Cu(II), Pb(II) and Cd(II), respectively. The selectivity of the clicked-CoPc modified GCE toward Hg(II), Cu(II), Pb(II), Cd(II) present no interference from these metals ions. The fabricated electrochemical sensor exhibited very good electrochemical properties such as good reproducibility, stability, reusability and is suitable for the detection of heavy metal ions in tap water in our laboratory.
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- Authors: Fomo, Gertrude , Nwaji, Njemuwa , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187914 , vital:44709 , xlink:href="https://doi.org/10.1016/j.jelechem.2018.02.016"
- Description: Beside different methods and materials used to develop electrochemical sensors, the modification of the electrode using click reaction based on metallophthalocyanine (MPc) compounds are shown to improve the stability and sensitivity of the sensor. This work reported the development of electrochemical sensor for mercury (II), Lead (II), copper (II) and cadmium (II) ions detection based on the synthesized novel low symmetry alkyne terminated cobalt Phthalocyanine (CoPc) derivative. Differential pulse stripping voltammetry (DPSV) technique was employed for the first time in simultaneous determination of trace levels of the above metal ions using modified glassy carbon electrode (GCE) via click chemistry. Under the optimum experimental conditions, the anodic peak current is proportional to the concentrations of metal ions over a wide range of 0 to 0.1 mM with nanolevel detection limit of 81.94, 327.71, 55.87 and 347.06 nM and the sensitivity of 866.23 ± 5.48, 215.82 ± 2.16, 1979.48 ± 11.47 and 204.50 ± 1.10 μA/mM for Hg(II), Cu(II), Pb(II) and Cd(II), respectively. The selectivity of the clicked-CoPc modified GCE toward Hg(II), Cu(II), Pb(II), Cd(II) present no interference from these metals ions. The fabricated electrochemical sensor exhibited very good electrochemical properties such as good reproducibility, stability, reusability and is suitable for the detection of heavy metal ions in tap water in our laboratory.
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One-pot synthesis of graphene quantum dots–phthalocyanines supramolecular hybrid and the investigation of their photophysical properties
- Fomo, Gertrude, Achadu, Ojodomo John, Nyokong, Tebello
- Authors: Fomo, Gertrude , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188126 , vital:44725 , xlink:href="https://doi.org/10.1007/s10853-017-1539-y"
- Description: The synthesis of graphene quantum dots (GQDs) using organic compounds as carbon sources via bottom-up approaches has been widely developed, whereas their hybrids with other materials have been previously achieved post-synthetically via multi-step procedures. A novel approach for the preparation of supramolecular hybrid conjugates of GQDs and phthalocyanines (Pcs) via an in situ one-step bottom-up route was employed in this study. The as-synthesized GQDs and their Pc conjugates were characterized using different spectroscopic techniques and their photophysicochemical properties evaluated. Notably, the singlet oxygen quantum yields of the Pcs in the presence of GQDs were found to be 0.51 and 0.74 for 1-GQDs and 2-GQDs, respectively, as compared to the Pcs alone (0.18 and 0.70 for complex 1 and 2, respectively). The increase in triplet quantum yield (ΦT) values is complemented by a decrease in fluorescence quantum yield (ΦF). ΦT value of 0.96 obtained for the complex 2 after conjugation with GQDs is better or higher than the value of 0.74 as reported in the literature when complex 2 was conjugated to semiconductor QDs. Hence, this novel approach resulted in the derivation of hybrid materials with potentials for various photophysicochemical applications such as photodynamic therapy and photocatalysis.
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- Authors: Fomo, Gertrude , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188126 , vital:44725 , xlink:href="https://doi.org/10.1007/s10853-017-1539-y"
- Description: The synthesis of graphene quantum dots (GQDs) using organic compounds as carbon sources via bottom-up approaches has been widely developed, whereas their hybrids with other materials have been previously achieved post-synthetically via multi-step procedures. A novel approach for the preparation of supramolecular hybrid conjugates of GQDs and phthalocyanines (Pcs) via an in situ one-step bottom-up route was employed in this study. The as-synthesized GQDs and their Pc conjugates were characterized using different spectroscopic techniques and their photophysicochemical properties evaluated. Notably, the singlet oxygen quantum yields of the Pcs in the presence of GQDs were found to be 0.51 and 0.74 for 1-GQDs and 2-GQDs, respectively, as compared to the Pcs alone (0.18 and 0.70 for complex 1 and 2, respectively). The increase in triplet quantum yield (ΦT) values is complemented by a decrease in fluorescence quantum yield (ΦF). ΦT value of 0.96 obtained for the complex 2 after conjugation with GQDs is better or higher than the value of 0.74 as reported in the literature when complex 2 was conjugated to semiconductor QDs. Hence, this novel approach resulted in the derivation of hybrid materials with potentials for various photophysicochemical applications such as photodynamic therapy and photocatalysis.
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Optimizing phthalocyanine based dye-sensitized solar cells: The role of reduced graphene oxide
- Chindeka, Francis, Mashazi, Philani N, Britton, Jonathan, Fomo, Gertrude, Oluwole, David O, Sindelo, Azole, Nyokong, Tebello
- Authors: Chindeka, Francis , Mashazi, Philani N , Britton, Jonathan , Fomo, Gertrude , Oluwole, David O , Sindelo, Azole , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187770 , vital:44695 , xlink:href="https://doi.org/10.1016/j.synthmet.2018.10.021"
- Description: Dye-sensitized solar cells (DSSC) were fabricated by incorporating graphene materials as catalysts at the counter electrode. Platinum was also used as a catalyst for comparison purposes. Different phthalocyanines: hydroxyl indium tetracarboxyphenoxy phthalocyanine (1), chloro indium octacarboxy phthalocyanine (2) and dibenzoic acid silicon phthalocyanine (3) were used as dyes. Complex 3 gave the highest power conversion efficiency (η) of 3.19% when using nitrogen doped reduced graphene oxide nanosheets (NrGONS) as a catalyst at the counter electrode, and TiO2 containing rGONS at the anode. The value is close to 3.8% obtained when using Pt catalyst instead of NrGONS at the cathode, thus confirming that NrGONS is a promising candidate to replace the more expensive Pt. The study also shows that placing rGONS on both the anode and cathode improves efficiency.
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- Authors: Chindeka, Francis , Mashazi, Philani N , Britton, Jonathan , Fomo, Gertrude , Oluwole, David O , Sindelo, Azole , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187770 , vital:44695 , xlink:href="https://doi.org/10.1016/j.synthmet.2018.10.021"
- Description: Dye-sensitized solar cells (DSSC) were fabricated by incorporating graphene materials as catalysts at the counter electrode. Platinum was also used as a catalyst for comparison purposes. Different phthalocyanines: hydroxyl indium tetracarboxyphenoxy phthalocyanine (1), chloro indium octacarboxy phthalocyanine (2) and dibenzoic acid silicon phthalocyanine (3) were used as dyes. Complex 3 gave the highest power conversion efficiency (η) of 3.19% when using nitrogen doped reduced graphene oxide nanosheets (NrGONS) as a catalyst at the counter electrode, and TiO2 containing rGONS at the anode. The value is close to 3.8% obtained when using Pt catalyst instead of NrGONS at the cathode, thus confirming that NrGONS is a promising candidate to replace the more expensive Pt. The study also shows that placing rGONS on both the anode and cathode improves efficiency.
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