Effect of number of positive charges on the photophysical and photodynamic therapy activities of quarternary benzothiazole substituted zinc phthalocyanine
- Matshitse, Refilwe, Nwaji, Njemuwa, Mananga, Muthumuni, Prinsloo, Earl, Nyokong, Tebello
- Authors: Matshitse, Refilwe , Nwaji, Njemuwa , Mananga, Muthumuni , Prinsloo, Earl , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187819 , vital:44700 , xlink:href="https://doi.org/10.1016/j.jphotochem.2018.08.033"
- Description: The synthesis, photophysicochemical and photodynamic therapy (PDT) activity of quaternary benzothiazole substituted zinc phthalocyanine (2, containing two charges, and 3, containing four charges) are reported in this work. Furthermore, the activity of the synthesized complex was compared to non-quaternary derivative (1). Higher triplet and singlet oxygen quantum yields of 0.92 and 0.85, respectively, for quaternized complexes 2 and 3 compared to complex 1 alone. Complexes 1, 2 and 3 showed relatively no dark toxicity against the epithelial breast cancer cells with cell survival of above 90 ± 3%. The quaternary derivatives (2 and 3) showed superior PDT activity with 30% or less of viable cells at concentration of 50.0 μg/mL in comparison to complex 1 alone which further lay credence to the importance of quaternization in the enhancement of PDT activity.
- Full Text:
- Date Issued: 2018
- Authors: Matshitse, Refilwe , Nwaji, Njemuwa , Mananga, Muthumuni , Prinsloo, Earl , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187819 , vital:44700 , xlink:href="https://doi.org/10.1016/j.jphotochem.2018.08.033"
- Description: The synthesis, photophysicochemical and photodynamic therapy (PDT) activity of quaternary benzothiazole substituted zinc phthalocyanine (2, containing two charges, and 3, containing four charges) are reported in this work. Furthermore, the activity of the synthesized complex was compared to non-quaternary derivative (1). Higher triplet and singlet oxygen quantum yields of 0.92 and 0.85, respectively, for quaternized complexes 2 and 3 compared to complex 1 alone. Complexes 1, 2 and 3 showed relatively no dark toxicity against the epithelial breast cancer cells with cell survival of above 90 ± 3%. The quaternary derivatives (2 and 3) showed superior PDT activity with 30% or less of viable cells at concentration of 50.0 μg/mL in comparison to complex 1 alone which further lay credence to the importance of quaternization in the enhancement of PDT activity.
- Full Text:
- Date Issued: 2018
Effects of Pluronic F127 micelles as delivering agents on the vitro dark toxicity and photodynamic therapy activity of carboxy and pyrene substituted porphyrins
- Managa, Muthumuni, Britton, Jonathan, Prinsloo, Earl, Nyokong, Tebello
- Authors: Managa, Muthumuni , Britton, Jonathan , Prinsloo, Earl , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/234439 , vital:50196 , xlink:href="https://doi.org/10.1016/j.poly.2018.06.031"
- Description: Metal free, Zn and ClGa containing carboxyphenoxy and phenoxy groups (complexes 1) and pyrene groups (complexes 2) were synthesized and embedded into Pluronic F127 micelles (represented as F127). Dark toxicity and photodynamic therapy activities of the embedded porphyrins were successfully studied on MCF-7 breast cancer cells. Dark toxicity showed more than 80% cell viability for all complexes. It was found that 1-Zn + F127 showed better photodynamic therapy activity compared to 1-H2 + F127, and 1-ClGa + F127, corresponding to the high partition coefficient for the Zn porphyrin derivatives. The same applies to 2-Zn + F127 compared to 2-H2 + F127, 2-ClGa + F127. 1-ClGa and 1-Zn were also linked to Pluronic F127 silica nanoparticles. PDT activities for embedded 1-ClGa + F127 and 1-Zn + F127 were much higher than when linked to Pluronic silica nanoparticles (PluS NPs), showing the importance of loading of porphyrins into Pluronic F127 as a drug delivering agent rather than linking. PDT studies at the highest concentration of 60 µg/ml showed decrease in cell viability down to 15.9% for 2-Zn + F127. The Kp was determined in biphasic octanol and water system.
- Full Text:
- Date Issued: 2018
- Authors: Managa, Muthumuni , Britton, Jonathan , Prinsloo, Earl , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/234439 , vital:50196 , xlink:href="https://doi.org/10.1016/j.poly.2018.06.031"
- Description: Metal free, Zn and ClGa containing carboxyphenoxy and phenoxy groups (complexes 1) and pyrene groups (complexes 2) were synthesized and embedded into Pluronic F127 micelles (represented as F127). Dark toxicity and photodynamic therapy activities of the embedded porphyrins were successfully studied on MCF-7 breast cancer cells. Dark toxicity showed more than 80% cell viability for all complexes. It was found that 1-Zn + F127 showed better photodynamic therapy activity compared to 1-H2 + F127, and 1-ClGa + F127, corresponding to the high partition coefficient for the Zn porphyrin derivatives. The same applies to 2-Zn + F127 compared to 2-H2 + F127, 2-ClGa + F127. 1-ClGa and 1-Zn were also linked to Pluronic F127 silica nanoparticles. PDT activities for embedded 1-ClGa + F127 and 1-Zn + F127 were much higher than when linked to Pluronic silica nanoparticles (PluS NPs), showing the importance of loading of porphyrins into Pluronic F127 as a drug delivering agent rather than linking. PDT studies at the highest concentration of 60 µg/ml showed decrease in cell viability down to 15.9% for 2-Zn + F127. The Kp was determined in biphasic octanol and water system.
- Full Text:
- Date Issued: 2018
Effects of the carboxylic acid substituents on the photophysical and nonlinear optical properties of asymmetrical Zn (II) phthalocyanines–quantum dots conjugates
- Mgidlana, Sithi, Oluwole, David O, Nyokong, Tebello
- Authors: Mgidlana, Sithi , Oluwole, David O , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187662 , vital:44684 , xlink:href="https://doi.org/10.1080/24701556.2018.1503684"
- Description: This work reports on three asymmetrical Zn(II) phthalocyanines, namely: zinc(II) 3–(4-phenoxy)propanoic acid) phthalocyanine(1), zinc(II) 3–(4-phenoxy carboxylic acid) phthalocyanine (2) and zinc(II) 3–(4–oxy)phenoxy)acetic acid phthalocyanine (3) when covalently linked to glutathione(GSH) capped CdTe/ZnSe and CdTe/ZnSe/ZnO quantum dots (QDs). Of the Pc complexes alone, 1 afforded the highest triplet quantum yield (ΦT) value of 0.67 with corresponding largest nonlinear absorption coefficient (βeff) value of 14.0 cm/GW compared to 2 and 3. The conjugates afforded improved triplet quantum yield and nonlinear optical behavior in comparison to the Pc complexes alone.
- Full Text:
- Date Issued: 2018
- Authors: Mgidlana, Sithi , Oluwole, David O , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187662 , vital:44684 , xlink:href="https://doi.org/10.1080/24701556.2018.1503684"
- Description: This work reports on three asymmetrical Zn(II) phthalocyanines, namely: zinc(II) 3–(4-phenoxy)propanoic acid) phthalocyanine(1), zinc(II) 3–(4-phenoxy carboxylic acid) phthalocyanine (2) and zinc(II) 3–(4–oxy)phenoxy)acetic acid phthalocyanine (3) when covalently linked to glutathione(GSH) capped CdTe/ZnSe and CdTe/ZnSe/ZnO quantum dots (QDs). Of the Pc complexes alone, 1 afforded the highest triplet quantum yield (ΦT) value of 0.67 with corresponding largest nonlinear absorption coefficient (βeff) value of 14.0 cm/GW compared to 2 and 3. The conjugates afforded improved triplet quantum yield and nonlinear optical behavior in comparison to the Pc complexes alone.
- Full Text:
- Date Issued: 2018
Electrocatalytic activity of a push-pull phthalocyanine in the presence of reduced and amino functionalized graphene quantum dots towards the electrooxidation of hydrazine
- Centane, Sixolile, Sekhosana, Kutloana E, Matshitse, Refilwe, Nyokong, Tebello
- Authors: Centane, Sixolile , Sekhosana, Kutloana E , Matshitse, Refilwe , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233456 , vital:50092 , xlink:href="https://doi.org/10.1016/j.jelechem.2018.05.005"
- Description: We report on the electrochemical behaviour of reduced graphene quantum dots (rGQDs) compared to amino functionalized graphene quantum dots (NH2GQDs). Reduction of the GQDs entails the elimination of the excessive carboxyl and hydrogen groups on the GQDs surface, thereby reducing the energy band gap. The energy band gap of graphene is directly proportional to the available oxygen atoms. The two GQD types were conjugated to a novel cobalt phthalocyanine (cobalt tris-(tert-butyl phenoxy)-mono-carboxyphenoxy phthalocyanine, CoPc) via covalent and nom-covalent interactions. The resulting conjugates were tested towards the electrooxidation of hydrazine. The conjugates are represented as rGQDs(π)CoPc, NH2(π)CoPc, rGQDs@CoPc and NH2GQDs@CoPc. The resulting conjugates were adsorbed onto a glassy carbon electrode using the drop and dry method. The lowest limit of detection (LOD) was obtained for rGQDs(π)CoPc.
- Full Text:
- Date Issued: 2018
- Authors: Centane, Sixolile , Sekhosana, Kutloana E , Matshitse, Refilwe , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233456 , vital:50092 , xlink:href="https://doi.org/10.1016/j.jelechem.2018.05.005"
- Description: We report on the electrochemical behaviour of reduced graphene quantum dots (rGQDs) compared to amino functionalized graphene quantum dots (NH2GQDs). Reduction of the GQDs entails the elimination of the excessive carboxyl and hydrogen groups on the GQDs surface, thereby reducing the energy band gap. The energy band gap of graphene is directly proportional to the available oxygen atoms. The two GQD types were conjugated to a novel cobalt phthalocyanine (cobalt tris-(tert-butyl phenoxy)-mono-carboxyphenoxy phthalocyanine, CoPc) via covalent and nom-covalent interactions. The resulting conjugates were tested towards the electrooxidation of hydrazine. The conjugates are represented as rGQDs(π)CoPc, NH2(π)CoPc, rGQDs@CoPc and NH2GQDs@CoPc. The resulting conjugates were adsorbed onto a glassy carbon electrode using the drop and dry method. The lowest limit of detection (LOD) was obtained for rGQDs(π)CoPc.
- Full Text:
- Date Issued: 2018
Electrospun 3, 5-dithienylvinyleneBODIPY embedded polystyrene nanofibers for the photocatalytic degradation of azo dyes in industrial wastewaters
- Lebechi, Augustus K, Gai, Lizhi, Shen, Zhen, Nyokong, Tebello, Mack, John
- Authors: Lebechi, Augustus K , Gai, Lizhi , Shen, Zhen , Nyokong, Tebello , Mack, John
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187679 , vital:44686 , xlink:href="https://doi.org/10.1142/S1088424618500360"
- Description: The potential utility of electrospun polystyrene (PS) nanofibers embedded with 2,6-diiodo-8-phenyl-1,7-dimethyl-3,5-di-2-thienylvinyleneBODIPY for the photocatalytic degradation of azo dyes is investigated. A comparison of the singlet oxygen quantum yield of the ππ-extended BODIPY dye in solution and in the PS nanofibers demonstrates that its photosensitizer properties are retained when it is embedded in the solid phase. The photocatalytic degradation properties of the PS nanofibers for Methyl Orange and Orange G were determined by using a Thorlabs 625 nm light emitting diode. The rate of photodegradation increases with the Orange G and Methyl Orange concentration and follows pseudo-first order kinetics at pH 6.7.
- Full Text:
- Date Issued: 2018
- Authors: Lebechi, Augustus K , Gai, Lizhi , Shen, Zhen , Nyokong, Tebello , Mack, John
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187679 , vital:44686 , xlink:href="https://doi.org/10.1142/S1088424618500360"
- Description: The potential utility of electrospun polystyrene (PS) nanofibers embedded with 2,6-diiodo-8-phenyl-1,7-dimethyl-3,5-di-2-thienylvinyleneBODIPY for the photocatalytic degradation of azo dyes is investigated. A comparison of the singlet oxygen quantum yield of the ππ-extended BODIPY dye in solution and in the PS nanofibers demonstrates that its photosensitizer properties are retained when it is embedded in the solid phase. The photocatalytic degradation properties of the PS nanofibers for Methyl Orange and Orange G were determined by using a Thorlabs 625 nm light emitting diode. The rate of photodegradation increases with the Orange G and Methyl Orange concentration and follows pseudo-first order kinetics at pH 6.7.
- Full Text:
- Date Issued: 2018
Enhanced nonlinear optical response of benzothiazole substituted ball-type phthalocyanines in the presence of metallic nanoparticles
- Nwaji, Njemuwa, Mack, John, Nyokong, Tebello
- Authors: Nwaji, Njemuwa , Mack, John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188149 , vital:44727 , xlink:href="https://doi.org/10.1016/j.optmat.2018.05.052"
- Description: The synthesis of zinc-zinc, gallium-gallium and indium-indium ball-type phthalocyanines (complexes 4, 5 and 6) and the surface assembly of the complexes onto metallic gold and silver nanoparticles are reported in this work. Furthermore, their photophysical and nonlinear optical dynamics were investigated. Decreases in the fluorescence quantum yields with a corresponding increase in the triplet quantum yields of the nanoconjugates in comparison to complexes 4, 5 and 6 alone were observed. The mechanism of strong reverse saturable absorption observed was found to be predominantly dependent on excited state absorption. The optical limiting thresholds range from 0.09 to 0.19 J/cm2. Enhanced triplet parameters and nonlinear optical responses were found when the complexes were conjugated to metallic nanoparticles.
- Full Text:
- Date Issued: 2018
- Authors: Nwaji, Njemuwa , Mack, John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188149 , vital:44727 , xlink:href="https://doi.org/10.1016/j.optmat.2018.05.052"
- Description: The synthesis of zinc-zinc, gallium-gallium and indium-indium ball-type phthalocyanines (complexes 4, 5 and 6) and the surface assembly of the complexes onto metallic gold and silver nanoparticles are reported in this work. Furthermore, their photophysical and nonlinear optical dynamics were investigated. Decreases in the fluorescence quantum yields with a corresponding increase in the triplet quantum yields of the nanoconjugates in comparison to complexes 4, 5 and 6 alone were observed. The mechanism of strong reverse saturable absorption observed was found to be predominantly dependent on excited state absorption. The optical limiting thresholds range from 0.09 to 0.19 J/cm2. Enhanced triplet parameters and nonlinear optical responses were found when the complexes were conjugated to metallic nanoparticles.
- Full Text:
- Date Issued: 2018
Evaluation of the photophysicochemical properties and photodynamic therapy activity of nanoconjugates of zinc phthalocyanine linked to glutathione capped Au and Au3Ag1 nanoparticles
- Oluwole, David O, Manoto, Sello L, Malabi, Rudzani, Maphanga, Charles, Ombinda-Lemboumba, Saturnin, Mthunzi-Kufa, Patience, Nyokong, Tebello
- Authors: Oluwole, David O , Manoto, Sello L , Malabi, Rudzani , Maphanga, Charles , Ombinda-Lemboumba, Saturnin , Mthunzi-Kufa, Patience , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/237886 , vital:50563 , xlink:href="https://doi.org/10.1016/j.dyepig.2017.11.019"
- Description: We report on the synthesis of glutathione capped gold (AuNPs–GSH) and gold–silver (Au3Ag1NPs–GSH) nanoparticles and their covalent attachment to Zn monocarboxyphenoxy phthalocyanine (1) via amide bond formation. The photophysicochemical properties and photodynamic therapy (PDT) activity of the complex and its nanoconjugates were assessed. The conjugates afforded improved triplet and singlet oxygen quantum yield as well as PDT activity (except for 1-Au3Ag1NPs which afforded decreased activity) in comparison to complex 1.
- Full Text:
- Date Issued: 2018
- Authors: Oluwole, David O , Manoto, Sello L , Malabi, Rudzani , Maphanga, Charles , Ombinda-Lemboumba, Saturnin , Mthunzi-Kufa, Patience , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/237886 , vital:50563 , xlink:href="https://doi.org/10.1016/j.dyepig.2017.11.019"
- Description: We report on the synthesis of glutathione capped gold (AuNPs–GSH) and gold–silver (Au3Ag1NPs–GSH) nanoparticles and their covalent attachment to Zn monocarboxyphenoxy phthalocyanine (1) via amide bond formation. The photophysicochemical properties and photodynamic therapy (PDT) activity of the complex and its nanoconjugates were assessed. The conjugates afforded improved triplet and singlet oxygen quantum yield as well as PDT activity (except for 1-Au3Ag1NPs which afforded decreased activity) in comparison to complex 1.
- Full Text:
- Date Issued: 2018
Glycosylated zinc phthalocyanine-gold nanoparticle conjugates for photodynamic therapy
- Dube, Edith, Oluwole, David O, Nwaji, Njemuwa, Nyokong, Tebello
- Authors: Dube, Edith , Oluwole, David O , Nwaji, Njemuwa , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/234524 , vital:50205 , xlink:href="https://doi.org/10.1016/j.saa.2018.05.081"
- Description: In this work, we report on the synthesis of tris-[(2,2,7,7-tetramethyltetrahydro-3aH-bis([1,3]dioxolo)[4,5-b:4′,5′-d]pyran-5-yl)methoxy)-2-(4-benzo[d]thiazol-2-ylphenoxyphthalocyaninato] zinc(II) (complex 3) and its linkage to gold nanoparticles (AuNPs) of different shapes through S-Au/N-Au self-assembly. The conjugates of complex 3 (with both gold nanorods (AuNR) and nanospheres (AuNS)), displayed decreased fluorescence quantum yield with corresponding improved triplet and singlet quantum yields compared to complex 3 alone, however 3-AuNR showed improved properties than 3-AuNS. Complex 3 showed relatively low in vitro dark cytotoxicity against the epithelial breast cancer cells with cell survival ≥ 85% at concentration ≤ 160 μg/mL but afforded reduced photodynamic therapy activity which may be due to aggregation. 3-AuNR afforded superior PDT activity with more than 50% viable cells at concentration ≥ 40 μg/mL in comparison to 3-AuNS with more than 50% viable cells at concentration ≥ 80 μg/mL. The superior activity of 3-AuNR is attributed to the photothermal therapy effect since nanorods absorb more light at 680 nm than nanospheres.
- Full Text:
- Date Issued: 2018
- Authors: Dube, Edith , Oluwole, David O , Nwaji, Njemuwa , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/234524 , vital:50205 , xlink:href="https://doi.org/10.1016/j.saa.2018.05.081"
- Description: In this work, we report on the synthesis of tris-[(2,2,7,7-tetramethyltetrahydro-3aH-bis([1,3]dioxolo)[4,5-b:4′,5′-d]pyran-5-yl)methoxy)-2-(4-benzo[d]thiazol-2-ylphenoxyphthalocyaninato] zinc(II) (complex 3) and its linkage to gold nanoparticles (AuNPs) of different shapes through S-Au/N-Au self-assembly. The conjugates of complex 3 (with both gold nanorods (AuNR) and nanospheres (AuNS)), displayed decreased fluorescence quantum yield with corresponding improved triplet and singlet quantum yields compared to complex 3 alone, however 3-AuNR showed improved properties than 3-AuNS. Complex 3 showed relatively low in vitro dark cytotoxicity against the epithelial breast cancer cells with cell survival ≥ 85% at concentration ≤ 160 μg/mL but afforded reduced photodynamic therapy activity which may be due to aggregation. 3-AuNR afforded superior PDT activity with more than 50% viable cells at concentration ≥ 40 μg/mL in comparison to 3-AuNS with more than 50% viable cells at concentration ≥ 80 μg/mL. The superior activity of 3-AuNR is attributed to the photothermal therapy effect since nanorods absorb more light at 680 nm than nanospheres.
- Full Text:
- Date Issued: 2018
Improved Photophysical and Photochemical Properties of Thiopheneethoxy Substituted Metallophthalocyanines on Immobilization onto Gold‐speckled Silica Nanoparticles
- Dube, Edith, Oluwole, David O, Nyokong, Tebello
- Authors: Dube, Edith , Oluwole, David O , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187699 , vital:44688 , xlink:href="https://doi.org/10.1111/php.12879"
- Description: This work reports on the synthesis of tetrakis-[(thiophineethoxy) phthalocyaninato] indium(II) chloride (3). The photophysical behavior of complex 3 was compared to that of the Zn derivative (tetrakis-[(thiophineethoxy) phthalocyaninato] zinc(II) (complex 2)). The compounds were interacted with gold-speckled silica (GSS) nanoparticles via Au–S self assembly to afford the conjugates (2–GSS and 3–GSS). The photophysicochemical behavior of the compounds and their conjugates were assessed. The conjugates afforded a decrease in fluorescence quantum yields and lifetimes with improved triplet and singlet oxygen quantum yields in comparison with complexes 2 and 3 alone. The complexes and their conjugates could serve as good candidates for photodynamic therapy.
- Full Text:
- Date Issued: 2018
- Authors: Dube, Edith , Oluwole, David O , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187699 , vital:44688 , xlink:href="https://doi.org/10.1111/php.12879"
- Description: This work reports on the synthesis of tetrakis-[(thiophineethoxy) phthalocyaninato] indium(II) chloride (3). The photophysical behavior of complex 3 was compared to that of the Zn derivative (tetrakis-[(thiophineethoxy) phthalocyaninato] zinc(II) (complex 2)). The compounds were interacted with gold-speckled silica (GSS) nanoparticles via Au–S self assembly to afford the conjugates (2–GSS and 3–GSS). The photophysicochemical behavior of the compounds and their conjugates were assessed. The conjugates afforded a decrease in fluorescence quantum yields and lifetimes with improved triplet and singlet oxygen quantum yields in comparison with complexes 2 and 3 alone. The complexes and their conjugates could serve as good candidates for photodynamic therapy.
- Full Text:
- Date Issued: 2018
In-situ synthesis of gold nanoparticles on graphene quantum dots-phthalocyanine nanoplatforms: First description of the photophysical and surface enhanced Raman scattering behaviour
- Nwahara, Nnamdi, Achadu, Ojodomo John, Nyokong, Tebello
- Authors: Nwahara, Nnamdi , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187638 , vital:44682 , xlink:href="https://doi.org/10.1016/j.jphotochem.2018.04.011"
- Description: Owing to the need for new low-dimensional molecular assemblies with tailored electronic properties, the current study presents a facile approach for the synthesis and assembly of gold nanoparticles (AuNPs) onto functional graphene quantum dots (GQDs)-phthalocyanines (Pcs) arrays and the investigation of their photophysical and surface enhanced Raman scattering (SERS) properties. The GQDs were functionalized with L-glutathione (GSH) (to form GQDs@GSH) in order to assist coupling to the low symmetry Zn tris–(tert–butyl) mono carboxyphenoxy (propionic acid) phthalocyanine (complex 1) to form 1@GQDs. The affinity of gold (Au) to sulphur (S) was exploited for the assembly of the AuNPs onto 1@GQDs platform to form 1@GQDs-AuNPs. Transmission electron microscopic investigations confirmed the formation of monodispersed, spherical Pc/GQDs@GSH/AuNPs hybrids. The nanocomposite displayed high triplet quantum yields, which translated into high singlet oxygen quantum yield as high as 87%. Furthermore, the formed composites demonstrated strong surface enhanced Raman scattering (SERS) properties with an unprecedented intrinsic maximal enhancement factor of more than 30-fold. These nanostructures also retain more than 90% of their original SERS intensities after a week of storage, displaying superb stability under ambient conditions. These results highlight the remarkable potential of this composite as a unique Raman-based PDT dosimetric agent.
- Full Text:
- Date Issued: 2018
- Authors: Nwahara, Nnamdi , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187638 , vital:44682 , xlink:href="https://doi.org/10.1016/j.jphotochem.2018.04.011"
- Description: Owing to the need for new low-dimensional molecular assemblies with tailored electronic properties, the current study presents a facile approach for the synthesis and assembly of gold nanoparticles (AuNPs) onto functional graphene quantum dots (GQDs)-phthalocyanines (Pcs) arrays and the investigation of their photophysical and surface enhanced Raman scattering (SERS) properties. The GQDs were functionalized with L-glutathione (GSH) (to form GQDs@GSH) in order to assist coupling to the low symmetry Zn tris–(tert–butyl) mono carboxyphenoxy (propionic acid) phthalocyanine (complex 1) to form 1@GQDs. The affinity of gold (Au) to sulphur (S) was exploited for the assembly of the AuNPs onto 1@GQDs platform to form 1@GQDs-AuNPs. Transmission electron microscopic investigations confirmed the formation of monodispersed, spherical Pc/GQDs@GSH/AuNPs hybrids. The nanocomposite displayed high triplet quantum yields, which translated into high singlet oxygen quantum yield as high as 87%. Furthermore, the formed composites demonstrated strong surface enhanced Raman scattering (SERS) properties with an unprecedented intrinsic maximal enhancement factor of more than 30-fold. These nanostructures also retain more than 90% of their original SERS intensities after a week of storage, displaying superb stability under ambient conditions. These results highlight the remarkable potential of this composite as a unique Raman-based PDT dosimetric agent.
- Full Text:
- Date Issued: 2018
In-situ synthesis of gold nanoparticles on graphene quantum dots-phthalocyanine nanoplatforms: First description of the photophysical and surface enhanced Raman scattering behaviour
- Nwahara, Nnamdi, Achadu, Ojodomo John, Nyokong, Tebello
- Authors: Nwahara, Nnamdi , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188183 , vital:44730 , xlink:href="https://doi.org/10.1016/j.jphotochem.2018.04.011"
- Description: Owing to the need for new low-dimensional molecular assemblies with tailored electronic properties, the current study presents a facile approach for the synthesis and assembly of gold nanoparticles (AuNPs) onto functional graphene quantum dots (GQDs)-phthalocyanines (Pcs) arrays and the investigation of their photophysical and surface enhanced Raman scattering (SERS) properties. The GQDs were functionalized with L-glutathione (GSH) (to form GQDs@GSH) in order to assist coupling to the low symmetry Zn tris–(tert–butyl) mono carboxyphenoxy (propionic acid) phthalocyanine (complex 1) to form 1@GQDs. The affinity of gold (Au) to sulphur (S) was exploited for the assembly of the AuNPs onto 1@GQDs platform to form 1@GQDs-AuNPs. Transmission electron microscopic investigations confirmed the formation of monodispersed, spherical Pc/GQDs@GSH/AuNPs hybrids. The nanocomposite displayed high triplet quantum yields, which translated into high singlet oxygen quantum yield as high as 87%. Furthermore, the formed composites demonstrated strong surface enhanced Raman scattering (SERS) properties with an unprecedented intrinsic maximal enhancement factor of more than 30-fold. These nanostructures also retain more than 90% of their original SERS intensities after a week of storage, displaying superb stability under ambient conditions. These results highlight the remarkable potential of this composite as a unique Raman-based PDT dosimetric agent.
- Full Text:
- Date Issued: 2018
- Authors: Nwahara, Nnamdi , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188183 , vital:44730 , xlink:href="https://doi.org/10.1016/j.jphotochem.2018.04.011"
- Description: Owing to the need for new low-dimensional molecular assemblies with tailored electronic properties, the current study presents a facile approach for the synthesis and assembly of gold nanoparticles (AuNPs) onto functional graphene quantum dots (GQDs)-phthalocyanines (Pcs) arrays and the investigation of their photophysical and surface enhanced Raman scattering (SERS) properties. The GQDs were functionalized with L-glutathione (GSH) (to form GQDs@GSH) in order to assist coupling to the low symmetry Zn tris–(tert–butyl) mono carboxyphenoxy (propionic acid) phthalocyanine (complex 1) to form 1@GQDs. The affinity of gold (Au) to sulphur (S) was exploited for the assembly of the AuNPs onto 1@GQDs platform to form 1@GQDs-AuNPs. Transmission electron microscopic investigations confirmed the formation of monodispersed, spherical Pc/GQDs@GSH/AuNPs hybrids. The nanocomposite displayed high triplet quantum yields, which translated into high singlet oxygen quantum yield as high as 87%. Furthermore, the formed composites demonstrated strong surface enhanced Raman scattering (SERS) properties with an unprecedented intrinsic maximal enhancement factor of more than 30-fold. These nanostructures also retain more than 90% of their original SERS intensities after a week of storage, displaying superb stability under ambient conditions. These results highlight the remarkable potential of this composite as a unique Raman-based PDT dosimetric agent.
- Full Text:
- Date Issued: 2018
Incorporation of metal free and Ga 5, 10, 15, 20-tetrakis (4-bromophenyl) porphyrin into Pluronic F127-folic acid micelles
- Managa, Muthumuni, Ngoy, Bucolome P, Mafukidze, Donovan M, Nyokong, Tebello
- Authors: Managa, Muthumuni , Ngoy, Bucolome P , Mafukidze, Donovan M , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233256 , vital:50073 , xlink:href="https://doi.org/10.1016/j.jlumin.2017.09.045"
- Description: ClGa 5,10,15,20-Tetrakis (4-bromophenyl) porphyrinato (ClGaTBrPP) and its metal free derivative were successfully synthesized and incorporated into Pluronic F127 polymeric micelles that has been conjugated to folic acid (FA) to form ClGaTBrPP-F127-FA (or H2TBrPP-F127-FA). For comparison, ClGaTBrPP-F127 and H2TBrPP-F127 (without FA) were also formed. The singlet oxygen quantum yield for ClGaTBrPP-F127-FA was higher (ΦΔ = 0.44) than that of H2TBrPP-F127-FA (ΦΔ = 0.37), due to the heavy atom effect of Ga in the former which encourages intersystem crossing to the triplet state. The same applies to ClGaTBrPP-F127 (ΦΔ = 0.47) and H2TBrPP-F127 (ΦΔ = 0.41). Thus, ΦΔ values decreased in the presence of FA, but still high enough for practical application of the nanodrug system. The binding constants Kb were determined to be 1.08 × 104 M−1, 2.51 × 105 M−1, 1.52 × 103 and 2.68 × 103 for H2TBrPP+F127-FA, ClGaTBrPP+F127-FA, ClGaTBrPP-F127 and H2TBrPP-F127, respectively. The Kp values were determined in biphasic octanol and water system.
- Full Text:
- Date Issued: 2018
- Authors: Managa, Muthumuni , Ngoy, Bucolome P , Mafukidze, Donovan M , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233256 , vital:50073 , xlink:href="https://doi.org/10.1016/j.jlumin.2017.09.045"
- Description: ClGa 5,10,15,20-Tetrakis (4-bromophenyl) porphyrinato (ClGaTBrPP) and its metal free derivative were successfully synthesized and incorporated into Pluronic F127 polymeric micelles that has been conjugated to folic acid (FA) to form ClGaTBrPP-F127-FA (or H2TBrPP-F127-FA). For comparison, ClGaTBrPP-F127 and H2TBrPP-F127 (without FA) were also formed. The singlet oxygen quantum yield for ClGaTBrPP-F127-FA was higher (ΦΔ = 0.44) than that of H2TBrPP-F127-FA (ΦΔ = 0.37), due to the heavy atom effect of Ga in the former which encourages intersystem crossing to the triplet state. The same applies to ClGaTBrPP-F127 (ΦΔ = 0.47) and H2TBrPP-F127 (ΦΔ = 0.41). Thus, ΦΔ values decreased in the presence of FA, but still high enough for practical application of the nanodrug system. The binding constants Kb were determined to be 1.08 × 104 M−1, 2.51 × 105 M−1, 1.52 × 103 and 2.68 × 103 for H2TBrPP+F127-FA, ClGaTBrPP+F127-FA, ClGaTBrPP-F127 and H2TBrPP-F127, respectively. The Kp values were determined in biphasic octanol and water system.
- Full Text:
- Date Issued: 2018
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.
- Full Text:
- Date Issued: 2018
- 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.
- Full Text:
- Date Issued: 2018
Novel nano-dyad of homoleptic sandwich-type phthalocyanines with nitrogen doped graphene quantum dots for nonlinear optics
- Oluwole, David O, Nwaji, Njemuwa, Nene, Lindokuhle C, Mokone, Lesedi, Dube, Edith, Nyokong, Tebello
- Authors: Oluwole, David O , Nwaji, Njemuwa , Nene, Lindokuhle C , Mokone, Lesedi , Dube, Edith , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233386 , vital:50086 , xlink:href="https://doi.org/10.1039/C8NJ01707G"
- Description: The syntheses of neodymium(III) 2,9,16,23-tetrakis-(2,6-di-tert-butyl-4-methylphenoxy)phthalocyanine (2), bis europium(III) 2,9,16,23-tetrakis-(2,6-di-tert-butyl-4-methylphenoxy)phthalocyanine (3), bis dysprosium(III) 2,9,16,23-tetrakis-(2,6-di-tert-butyl-4-methylphenoxy)phthalocyanine (4) and their conjugated analogues with nitrogen doped quantum dots (NGQDs) are reported herein. The optical nonlinearity of the sandwich-type phthalocyanine complexes and their conjugates with NGQDs were studied in dimethyl sulfoxide using the open aperture Z-scan technique at an excitation wavelength of 532 nm with a 10 ns pulse. The nonlinear absorption coefficient (βeff) value of the samples ranges from 15 cm GW−1 to 89.6 cm GW−1. Complex 4 and its conjugates afforded a strong optical limiting behaviour compared to the other samples. These fabricated complexes and their conjugates with NGQDs could serve as a plausible nonlinear optical (NLO) material due to their fascinating NLO properties.
- Full Text:
- Date Issued: 2018
- Authors: Oluwole, David O , Nwaji, Njemuwa , Nene, Lindokuhle C , Mokone, Lesedi , Dube, Edith , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233386 , vital:50086 , xlink:href="https://doi.org/10.1039/C8NJ01707G"
- Description: The syntheses of neodymium(III) 2,9,16,23-tetrakis-(2,6-di-tert-butyl-4-methylphenoxy)phthalocyanine (2), bis europium(III) 2,9,16,23-tetrakis-(2,6-di-tert-butyl-4-methylphenoxy)phthalocyanine (3), bis dysprosium(III) 2,9,16,23-tetrakis-(2,6-di-tert-butyl-4-methylphenoxy)phthalocyanine (4) and their conjugated analogues with nitrogen doped quantum dots (NGQDs) are reported herein. The optical nonlinearity of the sandwich-type phthalocyanine complexes and their conjugates with NGQDs were studied in dimethyl sulfoxide using the open aperture Z-scan technique at an excitation wavelength of 532 nm with a 10 ns pulse. The nonlinear absorption coefficient (βeff) value of the samples ranges from 15 cm GW−1 to 89.6 cm GW−1. Complex 4 and its conjugates afforded a strong optical limiting behaviour compared to the other samples. These fabricated complexes and their conjugates with NGQDs could serve as a plausible nonlinear optical (NLO) material due to their fascinating NLO properties.
- Full Text:
- Date Issued: 2018
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.
- Full Text:
- Date Issued: 2018
- 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.
- Full Text:
- Date Issued: 2018
Optical limiting properties of 3, 5-dipyrenylvinyleneBODIPY dyes at 532 nm
- Kubheka, Gugu, Sanusi, Kayode, Mack, John, Nyokong, Tebello
- Authors: Kubheka, Gugu , Sanusi, Kayode , Mack, John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/237938 , vital:50567 , xlink:href="https://doi.org/10.1016/j.saa.2017.10.021"
- Description: The optical limiting (OL) properties of 3,5-dipyrenylvinyleneBODIPY dyes that contain both electron withdrawing and donating moieties have been investigated by using the z-scan technique at 532 nm in the nanosecond pulse range. The extension of the π-conjugation at the 3,5-positions with pyrenylvinylene groups results in a ca. 200 nm red shift of the main BODIPY spectral band to ca. 700 nm, so there is relatively weak absorbance at 532 nm under ambient light conditions. Reverse saturable absorbance (RSA) profiles are observed in response to incident pulsed laser light that is consistent with a two photon absorption-assisted excited state absorption (ESA) mechanism in CH2Cl2 solution and when the dyes are embedded in poly(bisphenol carbonate A) (PBC) polymer thin films. This demonstrates that 3,5-divinyleneBODIPY dyes are potentially suitable for use in OL applications, since limiting threshold fluence (Ilim) values of below 0.95 J cm−2 are observed when thin films are prepared.
- Full Text:
- Date Issued: 2018
- Authors: Kubheka, Gugu , Sanusi, Kayode , Mack, John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/237938 , vital:50567 , xlink:href="https://doi.org/10.1016/j.saa.2017.10.021"
- Description: The optical limiting (OL) properties of 3,5-dipyrenylvinyleneBODIPY dyes that contain both electron withdrawing and donating moieties have been investigated by using the z-scan technique at 532 nm in the nanosecond pulse range. The extension of the π-conjugation at the 3,5-positions with pyrenylvinylene groups results in a ca. 200 nm red shift of the main BODIPY spectral band to ca. 700 nm, so there is relatively weak absorbance at 532 nm under ambient light conditions. Reverse saturable absorbance (RSA) profiles are observed in response to incident pulsed laser light that is consistent with a two photon absorption-assisted excited state absorption (ESA) mechanism in CH2Cl2 solution and when the dyes are embedded in poly(bisphenol carbonate A) (PBC) polymer thin films. This demonstrates that 3,5-divinyleneBODIPY dyes are potentially suitable for use in OL applications, since limiting threshold fluence (Ilim) values of below 0.95 J cm−2 are observed when thin films are prepared.
- Full Text:
- Date Issued: 2018
Optical nonlinearity of pentadecylphenoxyl substituted sandwich–type metallophthalocyanines in the presence of Ag–CdSeTe/ZnTeSe nanocrystals: Effects of conjugation and central metals
- Oluwole, David O, Nyokong, Tebello
- Authors: Oluwole, David O , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187899 , vital:44708 , xlink:href="https://doi.org/10.1016/j.dyepig.2018.01.009"
- Description: Novel pentadecylphenoxyl substituted homoleptic sandwich–type metallophthalocyanines: bis (complexes 2 and 4 containing Eu and Dy, respectively) and tris (complexes 3 and 5 containing Eu and Dy, respectively) 2,9,16,23–tetrakis–(3–pentadecylphenoxyl) phthalocyanines and cadmium based (Ag–CdSeTe/ZnTeSe) nanocrystals (NCs) were synthesized. The nonlinear optical (NLO) behavior of the metallophthalocyanines and their composites with NCs were investigated using the open aperture Z–scan technique at excitation wavelength of 532 nm with 10 ns pulse. All of the samples exhibited interesting NLO attributes: among all the sandwich–type complexes, complex 5 afforded the most efficient NLO features accounting for large nonlinear absorption coefficient (βeff) value of 3500 cm/GW and limiting threshold (Ilim) value of 0.43 J cm−2. Overall, the composites of the triple decker sandwich–type complexes with Ag–CdSeTe/ZnTeSe yielded the best NLO characteristics with 3 and 5 accounting for the largest βeff value of 5500 cm/GW and Ilim value of 0.09 J cm−2. The synthesized complexes and their composites with NCs could be viable and efficient NLO absorber due to their interesting NLO activities.
- Full Text:
- Date Issued: 2018
- Authors: Oluwole, David O , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187899 , vital:44708 , xlink:href="https://doi.org/10.1016/j.dyepig.2018.01.009"
- Description: Novel pentadecylphenoxyl substituted homoleptic sandwich–type metallophthalocyanines: bis (complexes 2 and 4 containing Eu and Dy, respectively) and tris (complexes 3 and 5 containing Eu and Dy, respectively) 2,9,16,23–tetrakis–(3–pentadecylphenoxyl) phthalocyanines and cadmium based (Ag–CdSeTe/ZnTeSe) nanocrystals (NCs) were synthesized. The nonlinear optical (NLO) behavior of the metallophthalocyanines and their composites with NCs were investigated using the open aperture Z–scan technique at excitation wavelength of 532 nm with 10 ns pulse. All of the samples exhibited interesting NLO attributes: among all the sandwich–type complexes, complex 5 afforded the most efficient NLO features accounting for large nonlinear absorption coefficient (βeff) value of 3500 cm/GW and limiting threshold (Ilim) value of 0.43 J cm−2. Overall, the composites of the triple decker sandwich–type complexes with Ag–CdSeTe/ZnTeSe yielded the best NLO characteristics with 3 and 5 accounting for the largest βeff value of 5500 cm/GW and Ilim value of 0.09 J cm−2. The synthesized complexes and their composites with NCs could be viable and efficient NLO absorber due to their interesting NLO activities.
- Full Text:
- Date Issued: 2018
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.
- Full Text:
- Date Issued: 2018
- 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.
- Full Text:
- Date Issued: 2018
Photo-induced resonance energy transfer and nonlinear optical response in ball-type phthalocyanine conjugated to semiconductor and graphene quantum dots
- Nwaji, Njemuwa, Achadu, Ojodomo John, Nyokong, Tebello
- Authors: Nwaji, Njemuwa , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187959 , vital:44713 , xlink:href="https://doi.org/10.1039/C7NJ05196D"
- Description: The synthesis of ball-type zinc and gallium phthalocyanines (complexes 2 and 3) and their covalent linkage to glutathione (GSH) and amine functionalized quantum dots QDs) are reported in this work. Furthermore, their photophysical, photo-induced resonance energy transfer and optical limiting responses were investigated. We observed a decrease in the fluorescence quantum yields with a corresponding increase in the triplet quantum yields of the nanoconjugates in comparison to the phthalocyanine complexes alone. The reverse saturable absorption was found to be dependent on the excited state absorption, and the observed limiting threshold ranged from 0.32 to 1.43 J cm−2. Enhanced triplet parameters and nonlinear optical performance were found when the complexes were covalently linked to semiconductor quantum dots compared to carbon based graphene quantum dots.
- Full Text:
- Date Issued: 2018
- Authors: Nwaji, Njemuwa , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187959 , vital:44713 , xlink:href="https://doi.org/10.1039/C7NJ05196D"
- Description: The synthesis of ball-type zinc and gallium phthalocyanines (complexes 2 and 3) and their covalent linkage to glutathione (GSH) and amine functionalized quantum dots QDs) are reported in this work. Furthermore, their photophysical, photo-induced resonance energy transfer and optical limiting responses were investigated. We observed a decrease in the fluorescence quantum yields with a corresponding increase in the triplet quantum yields of the nanoconjugates in comparison to the phthalocyanine complexes alone. The reverse saturable absorption was found to be dependent on the excited state absorption, and the observed limiting threshold ranged from 0.32 to 1.43 J cm−2. Enhanced triplet parameters and nonlinear optical performance were found when the complexes were covalently linked to semiconductor quantum dots compared to carbon based graphene quantum dots.
- Full Text:
- Date Issued: 2018
Photodynamic therapy activity of zinc phthalocyanine linked to folic acid and magnetic nanoparticles
- Matlou, Gauta G, Oluwole, David O, Prinsloo, Earl, Nyokong, Tebello
- Authors: Matlou, Gauta G , Oluwole, David O , Prinsloo, Earl , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/234429 , vital:50195 , xlink:href="https://doi.org/10.1016/j.jphotobiol.2018.07.025"
- Description: In this work, the photodynamic therapy (PDT) activities (using human carcinoma adherent MCF-7 cells) of zinc phthalocyanine derivatives: complexes 1 (Zn mono cinnamic acid phthalocyanine) and 2 (zinc mono carboxyphenoxy phthalocyanine) when covalently linked to folic acid (FA) and amine functionalized magnetic nanoparticles (AMNPs) are reported. The covalent linkage of asymmetric zinc cinnamic acid Pc (1) to FA (1-FA) through an amide bond is reported for the first time. Complex 1 is insoluble in water, but upon linkage to FA, (to form 1-FA) the molecule become water soluble, hence the UV–Vis spectrum and singlet oxygen quantum yield for 1-FA were also done in water since water solubility is essential for biological applications. The reported 2-FA is also water soluble. Linking complexes 1 and 2 to FA and AMNPs decreased the dark toxicity of 1 and 2 on MCF-7 cells. Pc-FA (1-FA and 2-FA) conjugates had better singlet oxygen quantum yields (Φ∆) in DMSO as compared to Pc-AMNPs (1-AMNPs and 2-AMNPs). The water- soluble 1-FA and 2-FA also achieved a better photodynamic therapy (PDT) activity as compared to 1-AMNPs and 2-AMNPs. Folic acid targeting on the tumor cells may have also facilitated better bioavailability of 1-FA and 2-FA and improved PDT activity on MCF-7 cells over AMNPs carriers.
- Full Text:
- Date Issued: 2018
Photodynamic therapy activity of zinc phthalocyanine linked to folic acid and magnetic nanoparticles
- Authors: Matlou, Gauta G , Oluwole, David O , Prinsloo, Earl , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/234429 , vital:50195 , xlink:href="https://doi.org/10.1016/j.jphotobiol.2018.07.025"
- Description: In this work, the photodynamic therapy (PDT) activities (using human carcinoma adherent MCF-7 cells) of zinc phthalocyanine derivatives: complexes 1 (Zn mono cinnamic acid phthalocyanine) and 2 (zinc mono carboxyphenoxy phthalocyanine) when covalently linked to folic acid (FA) and amine functionalized magnetic nanoparticles (AMNPs) are reported. The covalent linkage of asymmetric zinc cinnamic acid Pc (1) to FA (1-FA) through an amide bond is reported for the first time. Complex 1 is insoluble in water, but upon linkage to FA, (to form 1-FA) the molecule become water soluble, hence the UV–Vis spectrum and singlet oxygen quantum yield for 1-FA were also done in water since water solubility is essential for biological applications. The reported 2-FA is also water soluble. Linking complexes 1 and 2 to FA and AMNPs decreased the dark toxicity of 1 and 2 on MCF-7 cells. Pc-FA (1-FA and 2-FA) conjugates had better singlet oxygen quantum yields (Φ∆) in DMSO as compared to Pc-AMNPs (1-AMNPs and 2-AMNPs). The water- soluble 1-FA and 2-FA also achieved a better photodynamic therapy (PDT) activity as compared to 1-AMNPs and 2-AMNPs. Folic acid targeting on the tumor cells may have also facilitated better bioavailability of 1-FA and 2-FA and improved PDT activity on MCF-7 cells over AMNPs carriers.
- Full Text:
- Date Issued: 2018