Interaction of water-soluble CdTe quantum dots with octacarboxy metallophthalocyanines
- Idowu, Mopelola, Nyokong, Tebello
- Authors: Idowu, Mopelola , 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.
- Full Text:
- Authors: Idowu, Mopelola , 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, Nyokong, Tebello
- Authors: Masilela, Nkosiphile , Idowu, Mopelola , 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 , 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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Photophysicochemical and fluorescence quenching studies of tetra-and octa-carboxy substituted silicon and germanium phthalocyanines
- Idowu, Mopelola, Nyokong, Tebello
- Authors: Idowu, Mopelola , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263500 , vital:53633 , xlink:href="https://doi.org/10.1016/j.jphotochem.2009.02.002"
- Description: Spectral, photophysical and photochemical properties of tetra- and octa-carboxy substituted metallophthalocyanines containing silicon and germanium as central metals ((OH)2GeTCPc, (OH)2SiTCPc, (OH)2GeOCPc and (OH)2SiOCPc) have been studied in dimethylsulfoxide (DMSO) and the trends in triplet, fluorescence, singlet oxygen quantum yields and triplet lifetimes are described for these compounds. The GePc derivatives exhibited high triplet quantum yields (ΦT = 0.79 for (OH)2GeOCPc and 0.82 for (OH)2GeTCPc compared to ΦT = 0.66 for (OH)2SiTCPc and 0.48 for (OH)2SiOCPc) due to the spin–orbit coupling induced by Ge(IV). The triplet lifetimes were higher for MOCPc (τT = 760 μs for (OH)2SiOCPc and 480 μs for (OH)2GeOCPc compared to τT = 210 μs for (OH)2SiTCPc and 260 μs for (OH)2GeTCPc). The fluorescent states of the metallophthalocyanine (MPc) complexes were effectively quenched by benzoquinone (BQ) and the quenching course was found to follow a diffusion-controlled (dynamic) bimolecular mechanism. Theoretical values of bimolecular rate constant for the interaction of the complexes with BQ were determined using the Stokes–Einstein–Smoluchowski model, and values together with the Stern–Volmer quenching constants were used in calculating the fluorescence lifetimes of the complexes.
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- Authors: Idowu, Mopelola , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263500 , vital:53633 , xlink:href="https://doi.org/10.1016/j.jphotochem.2009.02.002"
- Description: Spectral, photophysical and photochemical properties of tetra- and octa-carboxy substituted metallophthalocyanines containing silicon and germanium as central metals ((OH)2GeTCPc, (OH)2SiTCPc, (OH)2GeOCPc and (OH)2SiOCPc) have been studied in dimethylsulfoxide (DMSO) and the trends in triplet, fluorescence, singlet oxygen quantum yields and triplet lifetimes are described for these compounds. The GePc derivatives exhibited high triplet quantum yields (ΦT = 0.79 for (OH)2GeOCPc and 0.82 for (OH)2GeTCPc compared to ΦT = 0.66 for (OH)2SiTCPc and 0.48 for (OH)2SiOCPc) due to the spin–orbit coupling induced by Ge(IV). The triplet lifetimes were higher for MOCPc (τT = 760 μs for (OH)2SiOCPc and 480 μs for (OH)2GeOCPc compared to τT = 210 μs for (OH)2SiTCPc and 260 μs for (OH)2GeTCPc). The fluorescent states of the metallophthalocyanine (MPc) complexes were effectively quenched by benzoquinone (BQ) and the quenching course was found to follow a diffusion-controlled (dynamic) bimolecular mechanism. Theoretical values of bimolecular rate constant for the interaction of the complexes with BQ were determined using the Stokes–Einstein–Smoluchowski model, and values together with the Stern–Volmer quenching constants were used in calculating the fluorescence lifetimes of the complexes.
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Study of the photophysical behavior of tetrasulfonated metallophthalocyanines in the presence of CdTe quantum dots
- Idowu, Mopelola, Nyokong, Tebello
- Authors: Idowu, Mopelola , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264138 , vital:53701 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.02.040"
- Description: Förster resonance energy transfer (FRET) studies were carried out with CdTe quantum dots (QDs) synthesized in aqueous phase and various tetrasulfonated metallophthalocyanines (MPcS4, M = aluminum ((OH)AlPcS4), zinc (ZnPcS4), silicon ((OH)2SiPcS4) and germanium ((OH)2GePcS4) in a H2O:MeOH (1:1) solvent mixture. The QDs studied were capped with thioglycolic acid (TGA) or mercaptopropionic acid (MPA) with sizes ranging from 2.3 to 3.7 nm. Non-radiative energy transfer from QDs emission to MPcS4 complexes was observed. Study of the photophysics of the MPcs in the presence of the QDs revealed high triplet state quantum yields (ΦT, ranging from 0.41 to 0.85 in the presence of QDs), with corresponding long triplet state lifetimes (τT, which ranged from 140 to 610 μs in the presence of QDs) to allow for photosensitized reactions to occur. The efficiency of energy transfer and the donor–acceptor distance between the MPcs and the QDs were also evaluated.
- Full Text:
- Authors: Idowu, Mopelola , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264138 , vital:53701 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.02.040"
- Description: Förster resonance energy transfer (FRET) studies were carried out with CdTe quantum dots (QDs) synthesized in aqueous phase and various tetrasulfonated metallophthalocyanines (MPcS4, M = aluminum ((OH)AlPcS4), zinc (ZnPcS4), silicon ((OH)2SiPcS4) and germanium ((OH)2GePcS4) in a H2O:MeOH (1:1) solvent mixture. The QDs studied were capped with thioglycolic acid (TGA) or mercaptopropionic acid (MPA) with sizes ranging from 2.3 to 3.7 nm. Non-radiative energy transfer from QDs emission to MPcS4 complexes was observed. Study of the photophysics of the MPcs in the presence of the QDs revealed high triplet state quantum yields (ΦT, ranging from 0.41 to 0.85 in the presence of QDs), with corresponding long triplet state lifetimes (τT, which ranged from 140 to 610 μs in the presence of QDs) to allow for photosensitized reactions to occur. The efficiency of energy transfer and the donor–acceptor distance between the MPcs and the QDs were also evaluated.
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Synthesis, photophysical and photochemical studies of water soluble cationic zinc phthalocyanine derivatives
- Idowu, Mopelola, Nyokong, Tebello
- Authors: Idowu, Mopelola , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264245 , vital:53712 , xlink:href="https://doi.org/10.1016/j.poly.2008.11.021"
- Description: Peripherally and non-peripherally 2-diethylaminoethanethiol tetra-substituted zinc phthalocyanine (5a and 6a) and their quaternized derivatives (5b and 6b) have been synthesized and characterized. The quaternized derivatives (5b and 6b) show excellent solubility in aqueous medium. The photophysical and photochemical properties of the 2-diethylaminoethanethiol appended zinc phthalocyanine in dimethylsulfoxide (DMSO) for the non-ionic (5a and 6a) and in both DMSO and aqueous medium (phosphate buffered saline solution PBS, pH 7.4) (in the presence and absence of cremophore EL (CEL)) for the quaternized (5b and 6b) derivatives were studied and compared with that of the peripherally octa-substituted derivatives (7a and 7b). The complexes have intense absorption in the visible/near-IR region though the quaternized forms (5b, 6b and 7b) were slightly blue shifted and highly aggregate in aqueous solution. The triplet state quantum yields (ΦT) and the triplet lifetimes (τT) were found to be higher in DMSO (ΦT values ranged from 0.57 to 0.75 while τT values ranged from 190 to 220 μs in DMSO for all complexes) compared to aqueous medium (ΦT values ranged from 0.15 to 0.17 while τT values ranged from 20 to 70 μs in pH 7.4 buffer). Addition of cremophore EL in aqueous solution resulted in induced disaggregation leading to increased ΦT and τT.
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- Authors: Idowu, Mopelola , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264245 , vital:53712 , xlink:href="https://doi.org/10.1016/j.poly.2008.11.021"
- Description: Peripherally and non-peripherally 2-diethylaminoethanethiol tetra-substituted zinc phthalocyanine (5a and 6a) and their quaternized derivatives (5b and 6b) have been synthesized and characterized. The quaternized derivatives (5b and 6b) show excellent solubility in aqueous medium. The photophysical and photochemical properties of the 2-diethylaminoethanethiol appended zinc phthalocyanine in dimethylsulfoxide (DMSO) for the non-ionic (5a and 6a) and in both DMSO and aqueous medium (phosphate buffered saline solution PBS, pH 7.4) (in the presence and absence of cremophore EL (CEL)) for the quaternized (5b and 6b) derivatives were studied and compared with that of the peripherally octa-substituted derivatives (7a and 7b). The complexes have intense absorption in the visible/near-IR region though the quaternized forms (5b, 6b and 7b) were slightly blue shifted and highly aggregate in aqueous solution. The triplet state quantum yields (ΦT) and the triplet lifetimes (τT) were found to be higher in DMSO (ΦT values ranged from 0.57 to 0.75 while τT values ranged from 190 to 220 μs in DMSO for all complexes) compared to aqueous medium (ΦT values ranged from 0.15 to 0.17 while τT values ranged from 20 to 70 μs in pH 7.4 buffer). Addition of cremophore EL in aqueous solution resulted in induced disaggregation leading to increased ΦT and τT.
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