Synthesis and physicochemical behaviour of aluminium trikis and tetrakis (diaquaplatinum) octacarboxyphthalocynine
- Malinga, Nduduzo, Dolotova, Olga, Bulgakov, Roman, Antunes, Edith M, Nyokong, Tebello
- Authors: Malinga, Nduduzo , Dolotova, Olga , Bulgakov, Roman , Antunes, Edith M , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242687 , vital:51068 , xlink:href="https://doi.org/10.1016/j.dyepig.2012.05.011"
- Description: The combination of chemotherapy and photodynamic therapy was investigated by the synthesis and characterisation of phthalocyanine conjugates with Pt complexes. The complexes synthesized are: hydroxoaluminum trikis(diaquaplatinum) octacarboxyphthalocyanine (OHAlOCPc(Pt)3) and hydroxoaluminum tetrakis(diaquaplatinum) octacarboxyphthalocyanine (OHAlOCPc(Pt)4). The platinated phthalocyanine complexes gave long triplet lifetimes of 577 and 526 μs for OHAlOCPc(Pt)3 and OHAlOCPc(Pt)4, respectively. The triplet quantum yields were found to be 0.45 for OHAlOCPc(Pt)3 and 0.57 OHAlOCPc(Pt)4 while the singlet oxygen quantum yields were found to be 0.38 and 0.48, respectively.
- Full Text:
- Date Issued: 2012
- Authors: Malinga, Nduduzo , Dolotova, Olga , Bulgakov, Roman , Antunes, Edith M , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242687 , vital:51068 , xlink:href="https://doi.org/10.1016/j.dyepig.2012.05.011"
- Description: The combination of chemotherapy and photodynamic therapy was investigated by the synthesis and characterisation of phthalocyanine conjugates with Pt complexes. The complexes synthesized are: hydroxoaluminum trikis(diaquaplatinum) octacarboxyphthalocyanine (OHAlOCPc(Pt)3) and hydroxoaluminum tetrakis(diaquaplatinum) octacarboxyphthalocyanine (OHAlOCPc(Pt)4). The platinated phthalocyanine complexes gave long triplet lifetimes of 577 and 526 μs for OHAlOCPc(Pt)3 and OHAlOCPc(Pt)4, respectively. The triplet quantum yields were found to be 0.45 for OHAlOCPc(Pt)3 and 0.57 OHAlOCPc(Pt)4 while the singlet oxygen quantum yields were found to be 0.38 and 0.48, respectively.
- Full Text:
- Date Issued: 2012
Photophysical and photochemical properties of a novel thiol terminated low symmetry zinc phthalocyanine complex and its gold nanoparticles conjugate
- Mthethwa, Thandekile P, Durmus, Mahmut, Nyokong, Tebello
- Authors: Mthethwa, Thandekile P , Durmus, Mahmut , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231474 , vital:49891 , xlink:href="https://doi.org/10.1039/C3DT32698E"
- Description: A novel thiol functionalized zinc phthalocyanine complex (ZnPcSH) is reported in this work. This complex was conjugated to gold nanoparticles. The photophysical and photochemical properties of the complex and the conjugate were investigated. Upon conjugation a blue shift was observed from the UV-Vis spectra. The conjugate showed a decrease in the fluorescence quantum yield and lifetime. An increase in the triplet quantum yield and lifetime was observed for ZnPcSH following conjugation to gold nanoparticles. Both ZnPcSH and its conjugate with gold nanoparticles showed high singlet oxygen quantum yields with the conjugate being higher than the Pc alone.
- Full Text:
- Date Issued: 2013
- Authors: Mthethwa, Thandekile P , Durmus, Mahmut , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231474 , vital:49891 , xlink:href="https://doi.org/10.1039/C3DT32698E"
- Description: A novel thiol functionalized zinc phthalocyanine complex (ZnPcSH) is reported in this work. This complex was conjugated to gold nanoparticles. The photophysical and photochemical properties of the complex and the conjugate were investigated. Upon conjugation a blue shift was observed from the UV-Vis spectra. The conjugate showed a decrease in the fluorescence quantum yield and lifetime. An increase in the triplet quantum yield and lifetime was observed for ZnPcSH following conjugation to gold nanoparticles. Both ZnPcSH and its conjugate with gold nanoparticles showed high singlet oxygen quantum yields with the conjugate being higher than the Pc alone.
- Full Text:
- Date Issued: 2013
Voltammetric detection of vitamin B1 at carbon paste electrodes and its determination in tablets
- Oni, Joshua, Westbroek, Philippe, Nyokong, Tebello
- Authors: Oni, Joshua , Westbroek, Philippe , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289692 , vital:56663 , xlink:href="https://doi.org/10.1002/1521-4109(200209)14"
- Description: The voltammetric behavior of vitamin B1 in alkaline medium at carbon paste electrode (CPE) is discussed. A method based on cyclic voltammetry for the determination of vitamin B1 at carbon paste electrode modified with manganese phthalocyanine (MnPc-CPE) is presented. In pH 10 buffer, the modified electrode showed catalytic activity towards the oxidation of vitamin B1 by considerably increasing the oxidation current of one of the observed waves compared to the oxidation current obtained at an unmodified electrode. The modified electrode was stable towards the determination of vitamin B1 compared to the unmodified electrode that is completely poisoned after a few scans. A linear relationship between the oxidation current and the concentration of vitamin B1 in solution was observed. The detection limit for vitamin B1 at the modified electrode was of the order of 10−5 mol dm−3. Commercial vitamin B1 tablets were analyzed using the modified electrodes.
- Full Text:
- Date Issued: 2002
- Authors: Oni, Joshua , Westbroek, Philippe , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289692 , vital:56663 , xlink:href="https://doi.org/10.1002/1521-4109(200209)14"
- Description: The voltammetric behavior of vitamin B1 in alkaline medium at carbon paste electrode (CPE) is discussed. A method based on cyclic voltammetry for the determination of vitamin B1 at carbon paste electrode modified with manganese phthalocyanine (MnPc-CPE) is presented. In pH 10 buffer, the modified electrode showed catalytic activity towards the oxidation of vitamin B1 by considerably increasing the oxidation current of one of the observed waves compared to the oxidation current obtained at an unmodified electrode. The modified electrode was stable towards the determination of vitamin B1 compared to the unmodified electrode that is completely poisoned after a few scans. A linear relationship between the oxidation current and the concentration of vitamin B1 in solution was observed. The detection limit for vitamin B1 at the modified electrode was of the order of 10−5 mol dm−3. Commercial vitamin B1 tablets were analyzed using the modified electrodes.
- Full Text:
- Date Issued: 2002
Optimal template removal from molecularly imprinted polymers by pressurized hot water extraction
- Batlokwa, Bareki Shima, Mokgadi, Janes, Nyokong, Tebello, Torto, Nelson
- Authors: Batlokwa, Bareki Shima , Mokgadi, Janes , Nyokong, Tebello , Torto, Nelson
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247813 , vital:51620 , xlink:href="https://doi.org/10.1007/s10337-010-1884-3"
- Description: An optimal extraction method for the removal of templates from molecularly imprinted polymers (MIPs) is presented. The extraction method is based on pressurized hot water extraction (PHWE). PHWE was evaluated by application to three distinctly colored MIPs for chlorophyll (green), quercetin (yellow) and phthalocynine (dark blue) with subsequent monitoring of template removal and template bleeding by an ultraviolet spectrophotometer. The templates were washed-off and the extraction efficiency (EE) was compared to that of soxhlet and ultrasonic extraction methods. PHWE employed hot water at an optimal temperature of 220 °C, pressure of 50 bars and flow rate of 2 mL min−1 to thoroughly wash-off the respective templates from their MIPs. The EE evaluated for PHWE was over 99.6% for all the MIPs with no subsequent or minimal template bleeding (more than 0.01%). The washing procedure was simple and relatively fast as it was achieved in 70 min at the most. At 95% confidence level (n = 3), soxhlet and ultrasonic recorded EE that was not significantly different (more than 94.5% in all cases) from that of PHWE (less than 99.6% in all cases). Soxhlet and ultrasonic had washing procedures that were slower (over 18 h) and employed large quantities (400 mL) of organic solvents modified with acids. The percentage relative standard deviations (%RSD) for the EE and recovery results were less than 2.3% in all cases indicating the high reproducibility of the method. Overall, the three methods performed comparably in extracting templates. PHWE seems to be the method of choice as it employed water which poses no environmental threat.
- Full Text:
- Date Issued: 2011
- Authors: Batlokwa, Bareki Shima , Mokgadi, Janes , Nyokong, Tebello , Torto, Nelson
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247813 , vital:51620 , xlink:href="https://doi.org/10.1007/s10337-010-1884-3"
- Description: An optimal extraction method for the removal of templates from molecularly imprinted polymers (MIPs) is presented. The extraction method is based on pressurized hot water extraction (PHWE). PHWE was evaluated by application to three distinctly colored MIPs for chlorophyll (green), quercetin (yellow) and phthalocynine (dark blue) with subsequent monitoring of template removal and template bleeding by an ultraviolet spectrophotometer. The templates were washed-off and the extraction efficiency (EE) was compared to that of soxhlet and ultrasonic extraction methods. PHWE employed hot water at an optimal temperature of 220 °C, pressure of 50 bars and flow rate of 2 mL min−1 to thoroughly wash-off the respective templates from their MIPs. The EE evaluated for PHWE was over 99.6% for all the MIPs with no subsequent or minimal template bleeding (more than 0.01%). The washing procedure was simple and relatively fast as it was achieved in 70 min at the most. At 95% confidence level (n = 3), soxhlet and ultrasonic recorded EE that was not significantly different (more than 94.5% in all cases) from that of PHWE (less than 99.6% in all cases). Soxhlet and ultrasonic had washing procedures that were slower (over 18 h) and employed large quantities (400 mL) of organic solvents modified with acids. The percentage relative standard deviations (%RSD) for the EE and recovery results were less than 2.3% in all cases indicating the high reproducibility of the method. Overall, the three methods performed comparably in extracting templates. PHWE seems to be the method of choice as it employed water which poses no environmental threat.
- Full Text:
- Date Issued: 2011
Opposing responses elicited by positively charged phthalocyanines in the presence of CdTe quantum dots
- Moeno, Sharon, Nyokong, Tebello
- Authors: Moeno, Sharon , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264506 , vital:53740 , xlink:href="https://doi.org/10.1016/j.jphotochem.2008.10.027"
- Description: Tetrapositively charged phthalocyanines and CdTe quantum dots (QDs) capped with thioglycolic acid (TGA) and mercaptopropionic acid (MPA) were synthesized. The response of the tetrapositively charged zinc phthalocyanines in the presence of quantum dots was studied. Aggregation and charge transfer were observed for [tetramethyl-2,(3)-[tetra-(2-mercaptopyridinephthalocyaninato)]zinc(II)]4+ (TmTMPyZnPc), however aggregation proved to be the more prominent process of the two. Fluorescence resonance energy transfer (FRET) was observed with [tetramethyl-2,(3)-[tetra-(2- pyridyloxyphthalocyaninato)]zinc(II)]4+ (TmTPyZnPc). In the FRET study the efficiency of FRET with TmTPyZnPc was determined to be 21% for both MPA and TGA capped CdTe QDs. For the charge transfer study the fluorescence of the quantum dots was quenched by the TmTMPyZnPc used, and from these quenching studies the quenching constants, binding constants and number of binding sites on the quantum dots were determined.
- Full Text:
- Date Issued: 2009
- Authors: Moeno, Sharon , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264506 , vital:53740 , xlink:href="https://doi.org/10.1016/j.jphotochem.2008.10.027"
- Description: Tetrapositively charged phthalocyanines and CdTe quantum dots (QDs) capped with thioglycolic acid (TGA) and mercaptopropionic acid (MPA) were synthesized. The response of the tetrapositively charged zinc phthalocyanines in the presence of quantum dots was studied. Aggregation and charge transfer were observed for [tetramethyl-2,(3)-[tetra-(2-mercaptopyridinephthalocyaninato)]zinc(II)]4+ (TmTMPyZnPc), however aggregation proved to be the more prominent process of the two. Fluorescence resonance energy transfer (FRET) was observed with [tetramethyl-2,(3)-[tetra-(2- pyridyloxyphthalocyaninato)]zinc(II)]4+ (TmTPyZnPc). In the FRET study the efficiency of FRET with TmTPyZnPc was determined to be 21% for both MPA and TGA capped CdTe QDs. For the charge transfer study the fluorescence of the quantum dots was quenched by the TmTMPyZnPc used, and from these quenching studies the quenching constants, binding constants and number of binding sites on the quantum dots were determined.
- Full Text:
- Date Issued: 2009
Efficient energy transfer in ethynyl bridged corrole–BODIPY dyads
- Yan, Yu, Wu, Fan, Qin, Jiawei, Xu, Haijun, Shi, Maohu, Zhou, Jingfeng, Mack, John, Fomo, Gertrude, Nyokong, Tebello, Shen, Zhen
- Authors: Yan, Yu , Wu, Fan , Qin, Jiawei , Xu, Haijun , Shi, Maohu , Zhou, Jingfeng , Mack, John , Fomo, Gertrude , Nyokong, Tebello , Shen, Zhen
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/240899 , vital:50883 , xlink:href="https://doi.org/10.1039/C6RA12271J"
- Description: A series of new corrole–BODIPY dyads bridged by ethynyl linker moieties have been synthesized in high yields and fully characterized. The direction of energy transfer upon electronic excitation has been explored, and was found to be dependent on the number of corrole rings and their connection position on the BODIPY core. Intense bands in the absorption spectrum cover most of the visible region, which is potentially advantageous for capturing solar energy. Studies on the excitation spectra and lifetimes suggest that the energy transfer efficiency between the BODIPY and corrole moieties reaches almost 85%, which appears to be efficient in the context of energy transfer within the singlet manifold.
- Full Text:
- Date Issued: 2016
- Authors: Yan, Yu , Wu, Fan , Qin, Jiawei , Xu, Haijun , Shi, Maohu , Zhou, Jingfeng , Mack, John , Fomo, Gertrude , Nyokong, Tebello , Shen, Zhen
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/240899 , vital:50883 , xlink:href="https://doi.org/10.1039/C6RA12271J"
- Description: A series of new corrole–BODIPY dyads bridged by ethynyl linker moieties have been synthesized in high yields and fully characterized. The direction of energy transfer upon electronic excitation has been explored, and was found to be dependent on the number of corrole rings and their connection position on the BODIPY core. Intense bands in the absorption spectrum cover most of the visible region, which is potentially advantageous for capturing solar energy. Studies on the excitation spectra and lifetimes suggest that the energy transfer efficiency between the BODIPY and corrole moieties reaches almost 85%, which appears to be efficient in the context of energy transfer within the singlet manifold.
- Full Text:
- Date Issued: 2016
Excited state dynamics of zinc and aluminum phthalocyanine carboxylates
- Idowu, Mopelola, Ogunsipe, Abimbola, Nyokong, Tebello
- Authors: Idowu, Mopelola , Ogunsipe, Abimbola , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/271228 , vital:54523 , xlink:href="https://doi.org/10.1016/j.saa.2007.01.025"
- Description: Photophysical parameters for zinc and aluminium tetracarboxylphthalocyanines (ZnTCPc and AlTCPc, respectively) and their octacarboxy substituted counterparts (ZnOCPc and AlOCPc) were studied. Data for the fluorescence quenching of the complexes by benzoquinone (BQ) were treated using the Stern–Volmer analysis, and the quenching was found to follow a diffusion-controlled (dynamic) bimolecular mechanism. Theoretical values of bimolecular rate constant for complex-BQ interactions were determined using the Stokes–Einstein–Smoluchowski model; and the values, together with the Stern–Volmer quenching constants were used in calculating the fluorescence lifetimes of the complexes. The thermodynamics of the MPc-BQ interaction, in terms of solvent reorientation energy is also discussed.
- Full Text:
- Date Issued: 2007
- Authors: Idowu, Mopelola , Ogunsipe, Abimbola , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/271228 , vital:54523 , xlink:href="https://doi.org/10.1016/j.saa.2007.01.025"
- Description: Photophysical parameters for zinc and aluminium tetracarboxylphthalocyanines (ZnTCPc and AlTCPc, respectively) and their octacarboxy substituted counterparts (ZnOCPc and AlOCPc) were studied. Data for the fluorescence quenching of the complexes by benzoquinone (BQ) were treated using the Stern–Volmer analysis, and the quenching was found to follow a diffusion-controlled (dynamic) bimolecular mechanism. Theoretical values of bimolecular rate constant for complex-BQ interactions were determined using the Stokes–Einstein–Smoluchowski model; and the values, together with the Stern–Volmer quenching constants were used in calculating the fluorescence lifetimes of the complexes. The thermodynamics of the MPc-BQ interaction, in terms of solvent reorientation energy is also discussed.
- Full Text:
- Date Issued: 2007
Synthesis and characterization of Na (Y, Gd) F4 upconversion nanoparticles and an investigation of their effects on the photophysical properties of an unsubstituted tetrathiophenoxy phthalocyanine
- Taylor, Jessica M, Litwinski, Christian, Nyokong, Tebello, Antunes, Edith M
- Authors: Taylor, Jessica M , Litwinski, Christian , Nyokong, Tebello , Antunes, Edith M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241437 , vital:50939 , xlink:href="https://doi.org/10.1007/s11051-015-2889-5"
- Description: Sphere- and star-shaped Na(Y,Gd)F4:Yb/Er(Tm)upconversion nanoparticles (UCNP) were successfully synthesized utilizing a methanol-assisted thermal decomposition approach and their spectroscopic (absorption, emission and luminescence lifetime) properties fully characterized. The factors affecting the size and shape of the UCNPs were studied and discussed in detail. The size of the nanoparticles was determined using TEM primarily and found to be approximately 19 and 30 nm for the Er and Tm spheres, respectively, while the Er and Tm “stars” were found to be much larger with sizes ranging from 110 to 240 nm, respectively (as determined along the width of the nanoparticle). In addition, their influence on the spectroscopic properties of an unsubstituted tetrathiophenoxy phthalocyanine (H2Pc) was investigated. The UCNP were found to produce characteristic upconversion luminescence emissions in the blue, green, red and NIR regions. Simple mixing with an H2Pc in toluene was found to exert no obvious changes in the spectroscopic properties of the Pc, although a considerable increase in the radiative lifetimes is observed for the Pc in the presence of the UCNPs. The singlet oxygen generation mediated by the red light excitation of the H2Pc mixed with UCNP was found to decrease in the presence of the NPs.
- Full Text:
- Date Issued: 2015
- Authors: Taylor, Jessica M , Litwinski, Christian , Nyokong, Tebello , Antunes, Edith M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241437 , vital:50939 , xlink:href="https://doi.org/10.1007/s11051-015-2889-5"
- Description: Sphere- and star-shaped Na(Y,Gd)F4:Yb/Er(Tm)upconversion nanoparticles (UCNP) were successfully synthesized utilizing a methanol-assisted thermal decomposition approach and their spectroscopic (absorption, emission and luminescence lifetime) properties fully characterized. The factors affecting the size and shape of the UCNPs were studied and discussed in detail. The size of the nanoparticles was determined using TEM primarily and found to be approximately 19 and 30 nm for the Er and Tm spheres, respectively, while the Er and Tm “stars” were found to be much larger with sizes ranging from 110 to 240 nm, respectively (as determined along the width of the nanoparticle). In addition, their influence on the spectroscopic properties of an unsubstituted tetrathiophenoxy phthalocyanine (H2Pc) was investigated. The UCNP were found to produce characteristic upconversion luminescence emissions in the blue, green, red and NIR regions. Simple mixing with an H2Pc in toluene was found to exert no obvious changes in the spectroscopic properties of the Pc, although a considerable increase in the radiative lifetimes is observed for the Pc in the presence of the UCNPs. The singlet oxygen generation mediated by the red light excitation of the H2Pc mixed with UCNP was found to decrease in the presence of the NPs.
- Full Text:
- Date Issued: 2015
Interaction of water-soluble thiol capped CdTe quantum dots and bovine serum albumin
- Idowu, Mopelola, Lamprecht, Emmanuel, Nyokong, Tebello
- Authors: Idowu, Mopelola , Lamprecht, Emmanuel , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/265974 , vital:53906 , xlink:href="https://doi.org/10.1016/j.jphotochem.2008.02.008"
- Description: Luminescent water-soluble CdTe quantum dots (QDs) capped with different thiol carboxylic acids were synthesized in aqueous medium and then cross linked to bovine serum albumin (BSA) with 1-ethyl3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC). Enhancement of fluorescence emission intensity occurred for QDs in the presence of bovine serum albumin (BSA, mixed or linked) signifying inhibition of non-radiative recombination of the surface vacancies. Fluorescence studies reveal a positive deviation behaviour suggesting the occurrence of static and dynamic mechanisms of quenching together which was accounted for by the modified Stern–Volmer equation.
- Full Text:
- Date Issued: 2008
- Authors: Idowu, Mopelola , Lamprecht, Emmanuel , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/265974 , vital:53906 , xlink:href="https://doi.org/10.1016/j.jphotochem.2008.02.008"
- Description: Luminescent water-soluble CdTe quantum dots (QDs) capped with different thiol carboxylic acids were synthesized in aqueous medium and then cross linked to bovine serum albumin (BSA) with 1-ethyl3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC). Enhancement of fluorescence emission intensity occurred for QDs in the presence of bovine serum albumin (BSA, mixed or linked) signifying inhibition of non-radiative recombination of the surface vacancies. Fluorescence studies reveal a positive deviation behaviour suggesting the occurrence of static and dynamic mechanisms of quenching together which was accounted for by the modified Stern–Volmer equation.
- Full Text:
- Date Issued: 2008
Solvent-free axial ligand substitution in octaphenoxyphthalocyaninato silicon complexes using microwave irradiation
- Maree, M David, Nyokong, Tebello
- Authors: Maree, M David , Nyokong, Tebello
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/304830 , vital:58494 , xlink:href="https://journals.sagepub.com/doi/epdf/10.3184/030823401103168974"
- Description: Several axially substituted octaphenoxy silicon phthalocyanines were prepared by condensation of the complexes used as axial ligands with octaphenoxyphthalocyaninato (dichloro) silicon under microwave irradiation.
- Full Text:
- Date Issued: 2001
- Authors: Maree, M David , Nyokong, Tebello
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/304830 , vital:58494 , xlink:href="https://journals.sagepub.com/doi/epdf/10.3184/030823401103168974"
- Description: Several axially substituted octaphenoxy silicon phthalocyanines were prepared by condensation of the complexes used as axial ligands with octaphenoxyphthalocyaninato (dichloro) silicon under microwave irradiation.
- Full Text:
- Date Issued: 2001
Physicochemical properties of a zinc phthalocyanine – pyrene conjugate adsorbed onto single walled carbon nanotubes
- Ogbodu, Racheal O, Antunes, Edith M, Nyokong, Tebello
- Authors: Ogbodu, Racheal O , Antunes, Edith M , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7328 , http://hdl.handle.net/10962/d1020589
- Description: A conjugate between zinc monoamino phthalocyanine (ZnMAPc) and pyrene (Py) represented as ZnMAPc–Py (complex 3) was synthesized and characterized by various spectroscopic techniques and by elemental analysis. This manuscript also reports on the photochemical and photophysical properties of 3. This new compound exhibited higher triplet, fluorescence and singlet oxygen quantum yields in comparison to the phthalocyanine alone, hence showing the advantages of attaching pyrene to the Pc without breaking the conjugation. We also observed a decrease in photophysical parameters upon adsorbing the ZnMAPc–Py complex onto single walled carbon nanotubes (SWCNT). However, ZnMAPc–Py still generated some singlet oxygen when adsorbed onto SWCNT. , Original publication is available at http://dx.doi.org/10.1039/C3DT50335F
- Full Text:
- Authors: Ogbodu, Racheal O , Antunes, Edith M , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7328 , http://hdl.handle.net/10962/d1020589
- Description: A conjugate between zinc monoamino phthalocyanine (ZnMAPc) and pyrene (Py) represented as ZnMAPc–Py (complex 3) was synthesized and characterized by various spectroscopic techniques and by elemental analysis. This manuscript also reports on the photochemical and photophysical properties of 3. This new compound exhibited higher triplet, fluorescence and singlet oxygen quantum yields in comparison to the phthalocyanine alone, hence showing the advantages of attaching pyrene to the Pc without breaking the conjugation. We also observed a decrease in photophysical parameters upon adsorbing the ZnMAPc–Py complex onto single walled carbon nanotubes (SWCNT). However, ZnMAPc–Py still generated some singlet oxygen when adsorbed onto SWCNT. , Original publication is available at http://dx.doi.org/10.1039/C3DT50335F
- Full Text:
Photophysical and photochemical properties of zinc and aluminum phthalocyanines in the presence of magnetic fluid
- Idowu, Mopelola, Nyokong, Tebello
- Authors: Idowu, Mopelola , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/281298 , vital:55710 , xlink:href="https://doi.org/10.1016/j.jphotochem.2006.12.013"
- Description: The effect of magnetic fluid (MF) on the photophysical and photochemical parameters of zinc and aluminum phthalocyanines are reported. The complexes studied are zinc (II) phthalocyanine (ZnPc), chloroaluminum phthalocyanine ((Cl)AlPc) and tetrasulfonated aluminum phthalocyanine ((Cl)AlTSPc). The parameters are studied in dimethylsulfoxide (DMSO) for all complexes and also in aqueous media for (Cl)AlTSPc. The triplet lifetimes for (Cl)AlTSPc and ZnPc decreased while the triplet quantum yields increased in the presence of MF. For (Cl)AlPc, the triplet lifetimes were found to increase with decrease in laser energy while there was photoreduction to the Pc−3 species. Singlet oxygen and photodegradation quantum yields decreased in the presence of MF, suggesting quenching.
- Full Text:
- Date Issued: 2007
- Authors: Idowu, Mopelola , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/281298 , vital:55710 , xlink:href="https://doi.org/10.1016/j.jphotochem.2006.12.013"
- Description: The effect of magnetic fluid (MF) on the photophysical and photochemical parameters of zinc and aluminum phthalocyanines are reported. The complexes studied are zinc (II) phthalocyanine (ZnPc), chloroaluminum phthalocyanine ((Cl)AlPc) and tetrasulfonated aluminum phthalocyanine ((Cl)AlTSPc). The parameters are studied in dimethylsulfoxide (DMSO) for all complexes and also in aqueous media for (Cl)AlTSPc. The triplet lifetimes for (Cl)AlTSPc and ZnPc decreased while the triplet quantum yields increased in the presence of MF. For (Cl)AlPc, the triplet lifetimes were found to increase with decrease in laser energy while there was photoreduction to the Pc−3 species. Singlet oxygen and photodegradation quantum yields decreased in the presence of MF, suggesting quenching.
- Full Text:
- Date Issued: 2007
Photophysics and photochemistry of octaglucosylated zinc phthalocyanine derivatives
- Iqbal, Zafar, Ogunsipe, Abimbola, Nyokong, Tebello, Lyubimtsev, Alexey, Hanack, Michael, Ziegler, Thomas
- Authors: Iqbal, Zafar , Ogunsipe, Abimbola , Nyokong, Tebello , Lyubimtsev, Alexey , Hanack, Michael , Ziegler, Thomas
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244416 , vital:51255 , xlink:href="https://doi.org/10.1142/S1088424612500630"
- Description: The ground state electronic absorption spectra, photophysics and photochemistry of amphiphilic octaglucosylated zinc phthalocyanines containing oxygen or sulfur bridges are presented. Triplet quantum yield values for the two dyes (in DMF and DMSO) vary between 0.71 and 0.84, while singlet quantum yield values lie between 0.63 and 0.75. Fluorescence lifetimes were determined experimentally by time correlated single photon counting and semi-empirically by fluorescence quenching techniques; and values from both methods were within the same range. Kinetic data were obtained for the quenching of the triplet state of the phthalocyanines by ground state molecular oxygen; the bimolecular collisional quenching rate constant range between 2.35 × 108 and 1.13 × 109 M-1.s-1. These values suggest that triplet states of the dyes are effectively quenched by ground molecular oxygen.
- Full Text:
- Date Issued: 2012
- Authors: Iqbal, Zafar , Ogunsipe, Abimbola , Nyokong, Tebello , Lyubimtsev, Alexey , Hanack, Michael , Ziegler, Thomas
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244416 , vital:51255 , xlink:href="https://doi.org/10.1142/S1088424612500630"
- Description: The ground state electronic absorption spectra, photophysics and photochemistry of amphiphilic octaglucosylated zinc phthalocyanines containing oxygen or sulfur bridges are presented. Triplet quantum yield values for the two dyes (in DMF and DMSO) vary between 0.71 and 0.84, while singlet quantum yield values lie between 0.63 and 0.75. Fluorescence lifetimes were determined experimentally by time correlated single photon counting and semi-empirically by fluorescence quenching techniques; and values from both methods were within the same range. Kinetic data were obtained for the quenching of the triplet state of the phthalocyanines by ground state molecular oxygen; the bimolecular collisional quenching rate constant range between 2.35 × 108 and 1.13 × 109 M-1.s-1. These values suggest that triplet states of the dyes are effectively quenched by ground molecular oxygen.
- Full Text:
- Date Issued: 2012
Comparative photocatalytic efficiency of oxotitanium (IV) phthalocyanines for the oxidation of 1-hexene
- Tau, Prudence, Nyokong, Tebello
- Authors: Tau, Prudence , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/271193 , vital:54520 , xlink:href="https://doi.org/10.1016/j.molcata.2007.04.005"
- Description: The comparative photocatalytic activities of aryloxy and arylthio tetrasubstituted oxotitanium(IV) phthalocyanine complexes for the oxidation of 1-hexene in DCM are reported for the first time. The singlet oxygen quantum yield, photostability and photocatalytic properties are investigated. The catalysts effectively catalyse 1-hexene to 1,2-epoxyhexane and 1-hexen-3-ol as major and minor products respectively. The photooxidation products are formed via two reaction mechanisms, namely via singlet oxygen (Type II) and radical (Type I) reaction pathways. These are also dependent on the singlet oxygen quantum yields and photostabilities of the phthalocyanines. Complex 1a that is peripherally substituted with phenoxy groups exhibited the best activity in terms of overall performance.
- Full Text:
- Date Issued: 2007
- Authors: Tau, Prudence , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/271193 , vital:54520 , xlink:href="https://doi.org/10.1016/j.molcata.2007.04.005"
- Description: The comparative photocatalytic activities of aryloxy and arylthio tetrasubstituted oxotitanium(IV) phthalocyanine complexes for the oxidation of 1-hexene in DCM are reported for the first time. The singlet oxygen quantum yield, photostability and photocatalytic properties are investigated. The catalysts effectively catalyse 1-hexene to 1,2-epoxyhexane and 1-hexen-3-ol as major and minor products respectively. The photooxidation products are formed via two reaction mechanisms, namely via singlet oxygen (Type II) and radical (Type I) reaction pathways. These are also dependent on the singlet oxygen quantum yields and photostabilities of the phthalocyanines. Complex 1a that is peripherally substituted with phenoxy groups exhibited the best activity in terms of overall performance.
- Full Text:
- Date Issued: 2007
Photophysicochemical behavior and antimicrobial activity of dihydroxosilicon tris (diaquaplatinum) octacarboxyphthalocyanine
- Managa, Muthumuni, Idowu, Mopelola A, Antunes, Edith M, Nyokong, Tebello
- Authors: Managa, Muthumuni , Idowu, Mopelola A , Antunes, Edith M , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241527 , vital:50947 , xlink:href="https://doi.org/10.1016/j.saa.2014.01.087"
- Description: Platination of dihydroxosilicon octacarboxyphthalocyanine (OH)2SiOCPc was successfully carried out to give dihydroxosilicon tris(diaquaplatinum)octacarboxyphthalocyanine (OH)2SiOCPc(Pt)3 conjugate. Slight blue shifting of the absorption spectrum of (OH)2SiOCPc(Pt)3 was observed on conjugation with platinum. Comparative photophysicochemical behavior and antimicrobial photo-activities of (OH)2SiOCPc(Pt)3 conjugate with (OH)2SiOCPc or Pt nanoparticles revealed that the heavy atom, Pt on the periphery of the phthalocyanine significantly enhanced its singlet oxygen generation with a quantum yield of 0.56 obtained for the (OH)2SiOCPc(Pt)3 conjugate. The (OH)2SiOCPc(Pt)3 conjugate showed highest antimicrobial activity towards Candida albicans and Escherichia coli compared to (OH)2SiOCPc and Pt nanoparticles alone under illumination.
- Full Text:
- Date Issued: 2014
- Authors: Managa, Muthumuni , Idowu, Mopelola A , Antunes, Edith M , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241527 , vital:50947 , xlink:href="https://doi.org/10.1016/j.saa.2014.01.087"
- Description: Platination of dihydroxosilicon octacarboxyphthalocyanine (OH)2SiOCPc was successfully carried out to give dihydroxosilicon tris(diaquaplatinum)octacarboxyphthalocyanine (OH)2SiOCPc(Pt)3 conjugate. Slight blue shifting of the absorption spectrum of (OH)2SiOCPc(Pt)3 was observed on conjugation with platinum. Comparative photophysicochemical behavior and antimicrobial photo-activities of (OH)2SiOCPc(Pt)3 conjugate with (OH)2SiOCPc or Pt nanoparticles revealed that the heavy atom, Pt on the periphery of the phthalocyanine significantly enhanced its singlet oxygen generation with a quantum yield of 0.56 obtained for the (OH)2SiOCPc(Pt)3 conjugate. The (OH)2SiOCPc(Pt)3 conjugate showed highest antimicrobial activity towards Candida albicans and Escherichia coli compared to (OH)2SiOCPc and Pt nanoparticles alone under illumination.
- Full Text:
- Date Issued: 2014
Selective adsorption of PVP on the surface of silver nanoparticles
- Mdluli, Phumlani S, Sosibo, Ndabenhle M, Mashazi, Philani N, Nyokong, Tebello, Tshikhudo, Robert T, Skepu, Amanda, van der Lingen, Elma
- Authors: Mdluli, Phumlani S , Sosibo, Ndabenhle M , Mashazi, Philani N , Nyokong, Tebello , Tshikhudo, Robert T , Skepu, Amanda , van der Lingen, Elma
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247143 , vital:51550 , xlink:href="https://doi.org/10.1016/j.molstruc.2011.07.049"
- Description: The use of surfactants to affect the shape evolution of silver nanoparticles is explored. This allows one to fine-tune the morphological evolution and the optical properties of the metal nanoparticles. Polyvinyl pyrrolidone (PVP) has been used as a surfactant to control the growth of silver nanoparticles at room temperature. In this paper, molecular dynamics simulations were performed to understand regio-selective adsorption of PVP that leads to the preferential growth of silver nanoparticles in dimethylformamide (DMF). The interaction energies between PVP and Ag(1 1 0), Ag(1 0 0) and Ag(1 1 1) crystal planes were calculated and in addition the length density profile of the surfactant on silver surfaces was also examined. Importantly, it has been demonstrated that the length distribution profiles analysis obtained from the molecular dynamics study fully explained the adsorption of PVP on the surface of silver nanoparticles through the carbonyl group of the PVP ring. The application of molecular dynamics simulation technique is important in understanding the evolution of silver nanoparticles and is vital in choosing the right surfactants.
- Full Text:
- Date Issued: 2011
- Authors: Mdluli, Phumlani S , Sosibo, Ndabenhle M , Mashazi, Philani N , Nyokong, Tebello , Tshikhudo, Robert T , Skepu, Amanda , van der Lingen, Elma
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247143 , vital:51550 , xlink:href="https://doi.org/10.1016/j.molstruc.2011.07.049"
- Description: The use of surfactants to affect the shape evolution of silver nanoparticles is explored. This allows one to fine-tune the morphological evolution and the optical properties of the metal nanoparticles. Polyvinyl pyrrolidone (PVP) has been used as a surfactant to control the growth of silver nanoparticles at room temperature. In this paper, molecular dynamics simulations were performed to understand regio-selective adsorption of PVP that leads to the preferential growth of silver nanoparticles in dimethylformamide (DMF). The interaction energies between PVP and Ag(1 1 0), Ag(1 0 0) and Ag(1 1 1) crystal planes were calculated and in addition the length density profile of the surfactant on silver surfaces was also examined. Importantly, it has been demonstrated that the length distribution profiles analysis obtained from the molecular dynamics study fully explained the adsorption of PVP on the surface of silver nanoparticles through the carbonyl group of the PVP ring. The application of molecular dynamics simulation technique is important in understanding the evolution of silver nanoparticles and is vital in choosing the right surfactants.
- Full Text:
- Date Issued: 2011
Electrocatalytic activity of nanocomposites of sulphur doped graphene oxide and nanosized cobalt phthalocyanines
- 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/10962/188530 , vital:44762 , xlink:href="https://doi.org/10.1002/elan.201600226"
- Description: In this work we explore the electrocatalytic activity of nanocomposites of reduced sulphur doped graphene oxide nanosheets (rSDGONS) and cobalt phthalocyanine (CoPc) or cobalt tetra amino phthalocyanine (CoTAPc) towards hydrogen peroxide. Transmission electron microscopy, scanning electron microscopy, X-ray photon spectroscopy, X-ray diffraction, chronoamperometry, linear scan voltammetry and cyclic voltammetry were used to characterize the nanocomposites. Nanosized CoPc showed superior (in terms of currents) electrocatalytic oxidation and reduction of hydrogen peroxide compared to CoTAPc nanoparticles (CoTAPcNP). The lowest detection limit was obtained for hydrogen peroxide oxidation on electrodes modified with CoPcNP-rSDGONS at 1.49 µM. The same electrode gave a high adsorption equilibrium constant of 1.27×103 mol−1 and a Gibbs free energy of −17.71 kJ/mol, indicative of a spontaneous reaction on the electrode surface.
- 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/10962/188530 , vital:44762 , xlink:href="https://doi.org/10.1002/elan.201600226"
- Description: In this work we explore the electrocatalytic activity of nanocomposites of reduced sulphur doped graphene oxide nanosheets (rSDGONS) and cobalt phthalocyanine (CoPc) or cobalt tetra amino phthalocyanine (CoTAPc) towards hydrogen peroxide. Transmission electron microscopy, scanning electron microscopy, X-ray photon spectroscopy, X-ray diffraction, chronoamperometry, linear scan voltammetry and cyclic voltammetry were used to characterize the nanocomposites. Nanosized CoPc showed superior (in terms of currents) electrocatalytic oxidation and reduction of hydrogen peroxide compared to CoTAPc nanoparticles (CoTAPcNP). The lowest detection limit was obtained for hydrogen peroxide oxidation on electrodes modified with CoPcNP-rSDGONS at 1.49 µM. The same electrode gave a high adsorption equilibrium constant of 1.27×103 mol−1 and a Gibbs free energy of −17.71 kJ/mol, indicative of a spontaneous reaction on the electrode surface.
- Full Text:
- Date Issued: 2016
A comparative photophysicochemical study of phthalocyanines encapsulated in core–shell silica nanoparticles
- Fashina, Adedayo, Amuhaya, Edith, Nyokong, Tebello
- Authors: Fashina, Adedayo , Amuhaya, Edith , Nyokong, Tebello
- Language: English
- Type: text
- Identifier: vital:7271 , http://hdl.handle.net/10962/d1020286 , Original publication is available at http://dx.doi.org/10.1016/j.saa.2014.08.062
- Full Text: false
- Authors: Fashina, Adedayo , Amuhaya, Edith , Nyokong, Tebello
- Language: English
- Type: text
- Identifier: vital:7271 , http://hdl.handle.net/10962/d1020286 , Original publication is available at http://dx.doi.org/10.1016/j.saa.2014.08.062
- Full Text: false
Probing electrochemical and electrocatalytic properties of cobalt (II) and manganese (III) octakis (hexylthio) phthalocyanine as self-assembled monolayers
- Mashazi, Philani N, Antunes, Edith M, Nyokong, Tebello
- Authors: Mashazi, Philani N , Antunes, Edith M , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/249115 , vital:51779 , xlink:href="https://doi.org/10.1142/S108842461000277X"
- Description: New peripherally (β) and non-peripherally (α) substituted metal octakis(hexylthio)phthalocyanines (β- and α-MOcHexTPc) containing cobalt and manganese as metal centers were synthesized. Their characterization using electrochemical methods showed that these complexes exhibit several redox processes at E1/2 (mV vs. Ag∣AgCl) = 380 (212) (I), 1140 (864) (II), -450 (-460) (III) and -1170 (-1304) (IV) for β- (α-) CoOcHexTPc. These redox processes were assigned to CoIIIPc-2/CoIIPc-2 (I), CoIIIPc-1/CoIIIPc-2 (II), CoIIPc-2/CoIPc-2 (III) and CoIPc-2/CoIPc-3 (IV) using spectroelectrochemistry. For the β- (α-) MnOcHexTPc complex the redox processes were observed at E1/2 (mV vs. Ag∣AgCl) = -20 (5) (I), -530 (-640) (II) and -1270 (-1380) (III) and were assigned to MnIIIPc-2/MnIIPc-2 (I), MnIIPc-2/MnIIPc-3 (II) and MnIIPc-3/MnIIPc-4 (III). Electrochemical and microscopic characterization using AFM showed that the self-assembled monolayers (SAMs) are formed on the gold surface using these complexes. The electrochemical characterization showed the blocking of the Faradaic processes at SAMs modified electrodes and these reactions are well-known to easily occur at unmodified gold electrodes. The AFM characterization showed an increase in surface roughness upon modifying the gold surface with MOcHexTPc SAMs, further confirming the presence of the monolayers on the gold surface. The MOcHexTPc SAMs were investigated for their electrocatalytic application towards H2O2 detection. The MOcHexTPc SAMs modified gold electrodes gave excellent currents for H2O2 detection. The observed H2O2 electrocatalytic reduction peaks were close to where the metal redox processes from the MOcHexTPc occurred, showing the involvement of the metal redox processes in the electrocatalytic mediation reactions.
- Full Text:
- Date Issued: 2010
- Authors: Mashazi, Philani N , Antunes, Edith M , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/249115 , vital:51779 , xlink:href="https://doi.org/10.1142/S108842461000277X"
- Description: New peripherally (β) and non-peripherally (α) substituted metal octakis(hexylthio)phthalocyanines (β- and α-MOcHexTPc) containing cobalt and manganese as metal centers were synthesized. Their characterization using electrochemical methods showed that these complexes exhibit several redox processes at E1/2 (mV vs. Ag∣AgCl) = 380 (212) (I), 1140 (864) (II), -450 (-460) (III) and -1170 (-1304) (IV) for β- (α-) CoOcHexTPc. These redox processes were assigned to CoIIIPc-2/CoIIPc-2 (I), CoIIIPc-1/CoIIIPc-2 (II), CoIIPc-2/CoIPc-2 (III) and CoIPc-2/CoIPc-3 (IV) using spectroelectrochemistry. For the β- (α-) MnOcHexTPc complex the redox processes were observed at E1/2 (mV vs. Ag∣AgCl) = -20 (5) (I), -530 (-640) (II) and -1270 (-1380) (III) and were assigned to MnIIIPc-2/MnIIPc-2 (I), MnIIPc-2/MnIIPc-3 (II) and MnIIPc-3/MnIIPc-4 (III). Electrochemical and microscopic characterization using AFM showed that the self-assembled monolayers (SAMs) are formed on the gold surface using these complexes. The electrochemical characterization showed the blocking of the Faradaic processes at SAMs modified electrodes and these reactions are well-known to easily occur at unmodified gold electrodes. The AFM characterization showed an increase in surface roughness upon modifying the gold surface with MOcHexTPc SAMs, further confirming the presence of the monolayers on the gold surface. The MOcHexTPc SAMs were investigated for their electrocatalytic application towards H2O2 detection. The MOcHexTPc SAMs modified gold electrodes gave excellent currents for H2O2 detection. The observed H2O2 electrocatalytic reduction peaks were close to where the metal redox processes from the MOcHexTPc occurred, showing the involvement of the metal redox processes in the electrocatalytic mediation reactions.
- Full Text:
- Date Issued: 2010
Corrosion resistance of aluminum against acid activation: Impact of benzothiazole-substituted gallium phthalocyanine
- Nnaji, Nnaemeka, Nwaji, Njemuwa N, Mack, John, Nyokong, Tebello
- Authors: Nnaji, Nnaemeka , Nwaji, Njemuwa N , Mack, John , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187545 , vital:44670 , xlink:href="https://doi.org/10.3390/molecules24010207"
- Description: This study describes the adsorption behavior of organic inhibitors at the aluminum-HCl solution interface and their corrosion inhibition performance. The organic inhibitors employed are: 4-(benzo [d]thiazol-2ylthio)phthalonitrile (BTThio) and tetrakis[(benzo[d]thiazol-2-yl-thio)phthalocyaninato]gallium(III) chloride (ClGaBTThioPc). The corrosion behavior of these inhibitors is investigated using electrochemical and computational techniques. Open circuit potential results reveal predominant cathodic character for the mechanism of aluminum corrosion inhibition by the inhibitors. Inhibition efficiency values from potentiodynamic polarization measurements increase from 46.9 to 70.8% for BTThio and 59.7 to 81.0% for ClGaBTThioPc within the concentration range of 2 to 10 µM. Scanning electron microscopy (SEM) measurements reveal protection of the metal surface from acid attack, in the presence of the inhibitors and energy dispersive X-ray (EDX) measurements show that the most probable way by which the inhibitors protect the metal surface would be by shielding it from the corrosion attacks of Cl− from the acid. Quantum chemical parameters corroborate well with experimental findings.
- Full Text:
- Date Issued: 2019
- Authors: Nnaji, Nnaemeka , Nwaji, Njemuwa N , Mack, John , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187545 , vital:44670 , xlink:href="https://doi.org/10.3390/molecules24010207"
- Description: This study describes the adsorption behavior of organic inhibitors at the aluminum-HCl solution interface and their corrosion inhibition performance. The organic inhibitors employed are: 4-(benzo [d]thiazol-2ylthio)phthalonitrile (BTThio) and tetrakis[(benzo[d]thiazol-2-yl-thio)phthalocyaninato]gallium(III) chloride (ClGaBTThioPc). The corrosion behavior of these inhibitors is investigated using electrochemical and computational techniques. Open circuit potential results reveal predominant cathodic character for the mechanism of aluminum corrosion inhibition by the inhibitors. Inhibition efficiency values from potentiodynamic polarization measurements increase from 46.9 to 70.8% for BTThio and 59.7 to 81.0% for ClGaBTThioPc within the concentration range of 2 to 10 µM. Scanning electron microscopy (SEM) measurements reveal protection of the metal surface from acid attack, in the presence of the inhibitors and energy dispersive X-ray (EDX) measurements show that the most probable way by which the inhibitors protect the metal surface would be by shielding it from the corrosion attacks of Cl− from the acid. Quantum chemical parameters corroborate well with experimental findings.
- Full Text:
- Date Issued: 2019