Photophysicochemical behavior and antimicrobial activity of dihydroxosilicon tris (diaquaplatinum) octacarboxyphthalocyanine
- Managa, Muthumuni, Idowu, Mopelola A I, Antunes, Edith M, Nyokong, Tebello
- Authors: Managa, Muthumuni , Idowu, Mopelola A I , 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.
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- Authors: Managa, Muthumuni , Idowu, Mopelola A I , 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.
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Interaction of water-soluble CdTe quantum dots with octacarboxy metallophthalocyanines
- Idowu, Mopelola A I, Nyokong, Tebello
- Authors: Idowu, Mopelola A I , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264197 , vital:53708 , xlink:href="https://doi.org/10.1016/j.jlumin.2008.11.005"
- Description: Water-soluble CdTe quantum dots capped with L-cysteine (QD-CYS) were found to improve the photophysical and photochemical properties of octacarboxy metallophthalocyanine (MOCPc, M=Zn(II), Al(III)(OH), Ge(IV)(OH)2 and Si(IV)(OH)2) complexes. Increased diffusional interactions between the molecules and the ground-state molecular oxygen were established resulting from the increase in the triplet-state quantum yield and lifetimes of the MOCPcs in the presence of QD-CYS. Energy transfer occurred from QD-CYS to the MOCPcs upon excitation of QD-CYS. It was found that an efficient energy transfer process, which is not directly related to the amount of spectral overlap between the donor (QD-CYS) and the acceptor (MOCPc) can occur. Singlet oxygen via fluorescence resonance energy transfer (FRET) mechanism was produced in the QD-MPc mixture.
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- Authors: Idowu, Mopelola A I , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264197 , vital:53708 , xlink:href="https://doi.org/10.1016/j.jlumin.2008.11.005"
- Description: Water-soluble CdTe quantum dots capped with L-cysteine (QD-CYS) were found to improve the photophysical and photochemical properties of octacarboxy metallophthalocyanine (MOCPc, M=Zn(II), Al(III)(OH), Ge(IV)(OH)2 and Si(IV)(OH)2) complexes. Increased diffusional interactions between the molecules and the ground-state molecular oxygen were established resulting from the increase in the triplet-state quantum yield and lifetimes of the MOCPcs in the presence of QD-CYS. Energy transfer occurred from QD-CYS to the MOCPcs upon excitation of QD-CYS. It was found that an efficient energy transfer process, which is not directly related to the amount of spectral overlap between the donor (QD-CYS) and the acceptor (MOCPc) can occur. Singlet oxygen via fluorescence resonance energy transfer (FRET) mechanism was produced in the QD-MPc mixture.
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Photophysical, photochemical and electrochemical properties of water soluble silicon, titanium and zinc phthalocyanines
- Masilela, Nkosiphile, Idowu, Mopelola A I, Nyokong, Tebello
- Authors: Masilela, Nkosiphile , Idowu, Mopelola A I , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264496 , vital:53739 , xlink:href="https://doi.org/10.1016/j.jphotochem.2008.10.009"
- Description: The photophysical, and photochemical properties of titanium, silicon and zinc octacarboxy phthalocyanine (OTiOCPc, (OH)2SiOCPc and ZnOCPc) and their tetrasulfonated counterparts (OTiTSPc, (OH)2SiTSPc and ZnTSPc) in phosphate-buffer solution (PBS), pH 10 were studied. The tetrasulfonated derivatives were also studied in the presence of a surfactant, cremophore EL (CEL) due to their high aggregation tendency in aqueous solutions. Triplet quantum yields ranged from 0.20 to 0.48 for MOCPcs and 0.32–0.65 for MTSPcs in the presence of CEL and in pH 10. High triplet lifetimes were observed for ZnTSPc (270 μs, in the presence of CEL) or ZnOCPc (130 μs) compared to values ranging from 50 to 70 μs for the rest of the complexes.
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- Authors: Masilela, Nkosiphile , Idowu, Mopelola A I , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264496 , vital:53739 , xlink:href="https://doi.org/10.1016/j.jphotochem.2008.10.009"
- Description: The photophysical, and photochemical properties of titanium, silicon and zinc octacarboxy phthalocyanine (OTiOCPc, (OH)2SiOCPc and ZnOCPc) and their tetrasulfonated counterparts (OTiTSPc, (OH)2SiTSPc and ZnTSPc) in phosphate-buffer solution (PBS), pH 10 were studied. The tetrasulfonated derivatives were also studied in the presence of a surfactant, cremophore EL (CEL) due to their high aggregation tendency in aqueous solutions. Triplet quantum yields ranged from 0.20 to 0.48 for MOCPcs and 0.32–0.65 for MTSPcs in the presence of CEL and in pH 10. High triplet lifetimes were observed for ZnTSPc (270 μs, in the presence of CEL) or ZnOCPc (130 μs) compared to values ranging from 50 to 70 μs for the rest of the complexes.
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Photoinduced energy transfer between water-soluble CdTe quantum dots and aluminium tetrasulfonated phthalocyanine
- Idowu, Mopelola A I, Chen, Ji-Yao, Nyokong, Tebello
- Authors: Idowu, Mopelola A I , Chen, Ji-Yao , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/268564 , vital:54210 , xlink:href="https://doi.org/10.1039/B707808K"
- Description: Thiol stabilized CdTe quantum dots (QDs) synthesized in aqueous phase were used as energy donors to aluminium tetrasulfonated phthalocyanine (AlTSPc) through fluorescence resonance energy transfer (FRET). Energy transfer occurred from the QDs to AlTSPc upon photoexcitation of the QDs. An enhancement in efficiency of energy transfer with the nature of the carboxylic thiol stabilizers on the QDs was observed. The results showed that for enhanced FRET to occur, the donor–acceptor distance has to be lower than the critical distance. The quenching constant K as well as the binding constant kb values were calculated suggesting strong interaction of the QDs with the AlTSPc. Study of the photophysics of AlTSPc in the presence of the QDs revealed a high triplet state yield, hence the possibility of using QDs in combination with phthalocyanines as photosensitizers in photodynamic therapy. The triplet state lifetimes of AlTSPc in the presence of the QDs were calculated and the lifetime in the presence of CdTe capped with 3-mercaptopropionic acid (MPA) was found to be the longest. MPA capped QD in a mixture with AlTSPc resulted in long triplet lifetime and high triplet yield of the latter, and high energy transfer efficiency, hence was found to be most suitable as a potential candidate for photodynamic therapy of cancer studies.
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- Authors: Idowu, Mopelola A I , Chen, Ji-Yao , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/268564 , vital:54210 , xlink:href="https://doi.org/10.1039/B707808K"
- Description: Thiol stabilized CdTe quantum dots (QDs) synthesized in aqueous phase were used as energy donors to aluminium tetrasulfonated phthalocyanine (AlTSPc) through fluorescence resonance energy transfer (FRET). Energy transfer occurred from the QDs to AlTSPc upon photoexcitation of the QDs. An enhancement in efficiency of energy transfer with the nature of the carboxylic thiol stabilizers on the QDs was observed. The results showed that for enhanced FRET to occur, the donor–acceptor distance has to be lower than the critical distance. The quenching constant K as well as the binding constant kb values were calculated suggesting strong interaction of the QDs with the AlTSPc. Study of the photophysics of AlTSPc in the presence of the QDs revealed a high triplet state yield, hence the possibility of using QDs in combination with phthalocyanines as photosensitizers in photodynamic therapy. The triplet state lifetimes of AlTSPc in the presence of the QDs were calculated and the lifetime in the presence of CdTe capped with 3-mercaptopropionic acid (MPA) was found to be the longest. MPA capped QD in a mixture with AlTSPc resulted in long triplet lifetime and high triplet yield of the latter, and high energy transfer efficiency, hence was found to be most suitable as a potential candidate for photodynamic therapy of cancer studies.
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Spontaneous charge transfer between zinc tetramethyl-tetra-2, 3-pyridinoporphyrazine and CdTe and ZnS quantum dots
- Moeno, Sharon, Idowu, Mopelola A I, Nyokong, Tebello
- Authors: Moeno, Sharon , Idowu, Mopelola A I , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/265997 , vital:53908 , xlink:href="https://doi.org/10.1016/j.ica.2008.02.048"
- Description: Zinc tetramethyl-tetra-2,3-pyridinoporphyrazine (ZnTmtppa(-2)) gets reduced to the ZnTmtppa(-3) species on interaction with CdTe QDs capped with 2-mercaptoethanol (2-ME) or thioglycolic acid (TGA) and ZnS QDs capped with 2-ME. The interaction occurs without photolysis. The fluorescence of the QDs is quenched by ZnTmtppa resulting in large quenching constants. Binding of ZnTmtppa to QDs occurs with two molecules of the former binding to the latter.
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- Authors: Moeno, Sharon , Idowu, Mopelola A I , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/265997 , vital:53908 , xlink:href="https://doi.org/10.1016/j.ica.2008.02.048"
- Description: Zinc tetramethyl-tetra-2,3-pyridinoporphyrazine (ZnTmtppa(-2)) gets reduced to the ZnTmtppa(-3) species on interaction with CdTe QDs capped with 2-mercaptoethanol (2-ME) or thioglycolic acid (TGA) and ZnS QDs capped with 2-ME. The interaction occurs without photolysis. The fluorescence of the QDs is quenched by ZnTmtppa resulting in large quenching constants. Binding of ZnTmtppa to QDs occurs with two molecules of the former binding to the latter.
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Photophysical and photochemical properties of zinc and aluminum phthalocyanines in the presence of magnetic fluid
- Idowu, Mopelola A I, Nyokong, Tebello
- Authors: Idowu, Mopelola A I , 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.
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- Authors: Idowu, Mopelola A I , 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.
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