Dual action of asymmetrical zinc (II) phthalocyanines conjugated to silver tungstate nanoparticles towards photodegradation of tetracycline and inactivation of Staphylococcus aureus bacteria
- Mgidlana, Sithi, Sen, Pinar, Nyokong, Tebello
- Authors: Mgidlana, Sithi , Sen, Pinar , Nyokong, Tebello
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/360400 , vital:65085 , xlink:href="https://doi.org/10.1016/j.jphotochem.2022.114444"
- Description: Asymmetric (A3B) Zn(II) phthalocyanines containing dimethoxy phenoxy as the dominant substituent and (phenoxy) propanoic acid (1), (phenoxy) acetic acid (2), and (phenoxy) acrylic acid (3) as the other substituents were synthesized and linked to silver tungstate nanoparticles (Ag2WO4 NPs). The photocatalytic activities of the prepared complexes 1–3 and nanoconjugates were evaluated for the photodegradation of tetracycline (TC) under visible-light irradiation and for photodynamic antimicrobial chemotherapy (PACT) activity against S. aureus. The results revealed that complex 3 had the best photocatalytic and PACT performance compared to 1 and 2, corresponding to the higher singlet oxygen quantum yield of the former in dimethyl sulfoxide. The photodegradation reaction was also examined using EPR and a mechanism for generation of singlet oxygen under visible light was confirmed. Photoinactivation of S. aureus improved in the presence of TC, when the two are applied together.
- Full Text:
- Date Issued: 2023
- Authors: Mgidlana, Sithi , Sen, Pinar , Nyokong, Tebello
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/360400 , vital:65085 , xlink:href="https://doi.org/10.1016/j.jphotochem.2022.114444"
- Description: Asymmetric (A3B) Zn(II) phthalocyanines containing dimethoxy phenoxy as the dominant substituent and (phenoxy) propanoic acid (1), (phenoxy) acetic acid (2), and (phenoxy) acrylic acid (3) as the other substituents were synthesized and linked to silver tungstate nanoparticles (Ag2WO4 NPs). The photocatalytic activities of the prepared complexes 1–3 and nanoconjugates were evaluated for the photodegradation of tetracycline (TC) under visible-light irradiation and for photodynamic antimicrobial chemotherapy (PACT) activity against S. aureus. The results revealed that complex 3 had the best photocatalytic and PACT performance compared to 1 and 2, corresponding to the higher singlet oxygen quantum yield of the former in dimethyl sulfoxide. The photodegradation reaction was also examined using EPR and a mechanism for generation of singlet oxygen under visible light was confirmed. Photoinactivation of S. aureus improved in the presence of TC, when the two are applied together.
- Full Text:
- Date Issued: 2023
Fabrication of asymmetrical morpholine phthalocyanines conjugated chitosan-polyacrylonitrile nanofibers for improved photodynamic antimicrobial chemotherapy activity
- Sindelo, Azole, Mafukidze, Donovan M, Nyokong, Tebello
- Authors: Sindelo, Azole , Mafukidze, Donovan M , Nyokong, Tebello
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229873 , vital:49719 , xlink:href="https://doi.org/10.1016/j.pdpdt.2022.102760"
- Description: The work is based on the synthesis and photodynamic antimicrobial chemotherapy (PACT) activities of neutral (1 and 2) and cationic (1Q and 2Q) morpholine substituted phthalocyanines. For applicability, these complexes were covalently linked to modified polyacrylonitrile (PAN) to form 1-PAN, 2-PAN, 1Q-PAN, and 2Q-PAN, respectively. Chitosan was conjugated to PAN (to form PAN-CS) which was then linked to the Pcs to form PAN-CS-1, PAN-CS-2, PAN-CS-1Q, and PAN-CS-2Q, respectively. Singlet oxygen quantum yields improved following the inclusion of chitosan. The PACT activities of the complexes alone and when anchored to both PAN and PAN-CS was evaluated against bacteria: S. aureus, E. coli and fungi C. albicans. Cationic phthalocyanine showed high efficacy values of >7 log reduction value for all microorganisms. These results translated into excellent bacterial colony reduction of >90% against both S. aureus and C. albicans after 1 h of photoirradiation on PAN-CS support.
- Full Text:
- Date Issued: 2022
- Authors: Sindelo, Azole , Mafukidze, Donovan M , Nyokong, Tebello
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229873 , vital:49719 , xlink:href="https://doi.org/10.1016/j.pdpdt.2022.102760"
- Description: The work is based on the synthesis and photodynamic antimicrobial chemotherapy (PACT) activities of neutral (1 and 2) and cationic (1Q and 2Q) morpholine substituted phthalocyanines. For applicability, these complexes were covalently linked to modified polyacrylonitrile (PAN) to form 1-PAN, 2-PAN, 1Q-PAN, and 2Q-PAN, respectively. Chitosan was conjugated to PAN (to form PAN-CS) which was then linked to the Pcs to form PAN-CS-1, PAN-CS-2, PAN-CS-1Q, and PAN-CS-2Q, respectively. Singlet oxygen quantum yields improved following the inclusion of chitosan. The PACT activities of the complexes alone and when anchored to both PAN and PAN-CS was evaluated against bacteria: S. aureus, E. coli and fungi C. albicans. Cationic phthalocyanine showed high efficacy values of >7 log reduction value for all microorganisms. These results translated into excellent bacterial colony reduction of >90% against both S. aureus and C. albicans after 1 h of photoirradiation on PAN-CS support.
- Full Text:
- Date Issued: 2022
Novel cationic-chalcone phthalocyanines for photodynamic therapy eradication of S. aureus and E. coli bacterial biofilms and MCF-7 breast cancer
- Openda, Yolande Ikala, Babu, Balaji, Nyokong, Tebello
- Authors: Openda, Yolande Ikala , Babu, Balaji , Nyokong, Tebello
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/300129 , vital:57895 , xlink:href="https://doi.org/10.1016/j.pdpdt.2022.102863"
- Description: New tetrasubstituted zinc (II) and indium (III) phthalocyanines bearing dimethylamino chalcone group (complexes 3 and 4) as well as their quaternized analogs (3a and 4a) have been assessed for their photodynamic therapy (PDT) of cancer as well as photodynamic antimicrobial chemotherapy activities against biofilms and planktonic cultures of pathogenic bacteria of Staphylococcus aureus and Escherichia coli. Compared to the non-quaternized phthalocyanines 3 and 4, the cationic phthalocyanines 3a and 4a exhibit a higher photodynamic inactivation against the planktonic cells with log reduction values above 9 at a concentration of 1.25 µM. This was attributed to the positive charge which enhances cellular uptake. More interestingly, 3a and 4a show a higher photodynamic inactivation (less than 3% of S. aureus survived) on their biofilm counterparts thanks to their stronger affinity to these cells. 3a and 4a Pcs also exhibited interesting PDT activity against MCF-7 cancer cells giving IC50 values of 17.9 and 7.4 μM, respectively following 15 min irradiation. The obtained results in this work show that the positively charged phthalocyanines 3a and 4a are potential antibacterial photosensitizers that show some selectivity toward the Gram-positive and Gram-negative bacteria as well as MCF-7 breasts cancer cells.
- Full Text:
- Date Issued: 2022
- Authors: Openda, Yolande Ikala , Babu, Balaji , Nyokong, Tebello
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/300129 , vital:57895 , xlink:href="https://doi.org/10.1016/j.pdpdt.2022.102863"
- Description: New tetrasubstituted zinc (II) and indium (III) phthalocyanines bearing dimethylamino chalcone group (complexes 3 and 4) as well as their quaternized analogs (3a and 4a) have been assessed for their photodynamic therapy (PDT) of cancer as well as photodynamic antimicrobial chemotherapy activities against biofilms and planktonic cultures of pathogenic bacteria of Staphylococcus aureus and Escherichia coli. Compared to the non-quaternized phthalocyanines 3 and 4, the cationic phthalocyanines 3a and 4a exhibit a higher photodynamic inactivation against the planktonic cells with log reduction values above 9 at a concentration of 1.25 µM. This was attributed to the positive charge which enhances cellular uptake. More interestingly, 3a and 4a show a higher photodynamic inactivation (less than 3% of S. aureus survived) on their biofilm counterparts thanks to their stronger affinity to these cells. 3a and 4a Pcs also exhibited interesting PDT activity against MCF-7 cancer cells giving IC50 values of 17.9 and 7.4 μM, respectively following 15 min irradiation. The obtained results in this work show that the positively charged phthalocyanines 3a and 4a are potential antibacterial photosensitizers that show some selectivity toward the Gram-positive and Gram-negative bacteria as well as MCF-7 breasts cancer cells.
- Full Text:
- Date Issued: 2022
The in vitro photo-sonodynamic combinatorial therapy activity of cationic and zwitterionic phthalocyanines on MCF-7 and HeLa cancer cell lines
- Nene, Lindokuhle Cindy, Buthelezi, Khanyisile, Prinsloo, Earl, Nyokong, Tebello
- Authors: Nene, Lindokuhle Cindy , Buthelezi, Khanyisile , Prinsloo, Earl , Nyokong, Tebello
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295891 , vital:57387 , xlink:href="https://doi.org/10.1016/j.jphotochem.2022.114116"
- Description: The syntheses and characterization studies of zwitterionic 2,9,16,23-tetrakis-(N-propane sultone-morpholino) zinc(II) (4) and 2,9,16,23-tetrakis-(2,5-dimethyl-4-(N-propane sultone-morpholinomethyl))-phenoxy zinc(II) (6) phthalocyanines are reported in this work. The photophysical properties, reactive oxygen species (ROS) generation and in vitro anticancer photodynamic (PDT), sonodynamic (SDT), and photo-sonodynamic combination (PSDT) therapy activities of the Pcs were studied and compared to their cationic counterparts: (2,9,16,23-tetrakis-(N-methyl-morpholino) Zn(II)Pc, 3), (2,9,16,23-tetrakis-(2,5-dimethyl-4-(N-methylmorpholine)-phenoxy) Zn(II)Pc, 5). The cationic Pcs maintained higher anticancer activity for all treatment types and had higher ROS generation compared to the zwitterionic Pcs. Singlet oxygen and hydroxyl radicals were generated during ultrasound and combination irradiations of the Pcs. The zwitterionic Pcs also generated carbon radicals under ultrasound and combination irradiations. The ability of the Pcs to generate ROS is essential for PDT, SDT and PSDT, thus making these Pcs potential anticancer probes for these treatment types. Furthermore, the Pcs demonstrated the ability to bind to bovine serum albumin protein.
- Full Text:
- Date Issued: 2022
- Authors: Nene, Lindokuhle Cindy , Buthelezi, Khanyisile , Prinsloo, Earl , Nyokong, Tebello
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295891 , vital:57387 , xlink:href="https://doi.org/10.1016/j.jphotochem.2022.114116"
- Description: The syntheses and characterization studies of zwitterionic 2,9,16,23-tetrakis-(N-propane sultone-morpholino) zinc(II) (4) and 2,9,16,23-tetrakis-(2,5-dimethyl-4-(N-propane sultone-morpholinomethyl))-phenoxy zinc(II) (6) phthalocyanines are reported in this work. The photophysical properties, reactive oxygen species (ROS) generation and in vitro anticancer photodynamic (PDT), sonodynamic (SDT), and photo-sonodynamic combination (PSDT) therapy activities of the Pcs were studied and compared to their cationic counterparts: (2,9,16,23-tetrakis-(N-methyl-morpholino) Zn(II)Pc, 3), (2,9,16,23-tetrakis-(2,5-dimethyl-4-(N-methylmorpholine)-phenoxy) Zn(II)Pc, 5). The cationic Pcs maintained higher anticancer activity for all treatment types and had higher ROS generation compared to the zwitterionic Pcs. Singlet oxygen and hydroxyl radicals were generated during ultrasound and combination irradiations of the Pcs. The zwitterionic Pcs also generated carbon radicals under ultrasound and combination irradiations. The ability of the Pcs to generate ROS is essential for PDT, SDT and PSDT, thus making these Pcs potential anticancer probes for these treatment types. Furthermore, the Pcs demonstrated the ability to bind to bovine serum albumin protein.
- Full Text:
- Date Issued: 2022
Aluminum corrosion retardation properties of acetamidophenoxy phthalocyanines: Effect of central metal
- Nnaji, Nnaemeka, Sen, Pinar, Nyokong, Tebello
- Authors: Nnaji, Nnaemeka , Sen, Pinar , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185433 , vital:44386 , xlink:href="https://doi.org/10.1016/j.molstruc.2021.130806"
- Description: Corrosion inhibition performances and adsorption behaviour at the aluminum-HCl solution interface were investigated for metal free (2), ClGa (3) and Co (4) tetrakis (4-acetamidophenoxy) phthalocyanine. Electrochemical techniques were used in the study and complemented with Fourier transform infrared, scanning electron microscopy and X-ray diffraction measurements. Potentiodynamic polarization technique gave inhibition efficiency values as 93.3% (2), 69.7% (3) and 87.7% (4) at 28°C at highest inhibitor concentration (10 µM) in the following order 2 > 4 > 3. These compounds exhibited good corrosion inhibition performance as mixed-type corrosion inhibitors. All applied techniques gave results which corroborated.
- Full Text:
- Date Issued: 2021
- Authors: Nnaji, Nnaemeka , Sen, Pinar , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185433 , vital:44386 , xlink:href="https://doi.org/10.1016/j.molstruc.2021.130806"
- Description: Corrosion inhibition performances and adsorption behaviour at the aluminum-HCl solution interface were investigated for metal free (2), ClGa (3) and Co (4) tetrakis (4-acetamidophenoxy) phthalocyanine. Electrochemical techniques were used in the study and complemented with Fourier transform infrared, scanning electron microscopy and X-ray diffraction measurements. Potentiodynamic polarization technique gave inhibition efficiency values as 93.3% (2), 69.7% (3) and 87.7% (4) at 28°C at highest inhibitor concentration (10 µM) in the following order 2 > 4 > 3. These compounds exhibited good corrosion inhibition performance as mixed-type corrosion inhibitors. All applied techniques gave results which corroborated.
- Full Text:
- Date Issued: 2021
Asymmetrical zinc (II) phthalocyanines cobalt tungstate nanomaterial conjugates for photodegradation of methylene blue
- Mgidlana, Sithi, Nyokong, Tebello
- Authors: Mgidlana, Sithi , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184991 , vital:44314 , xlink:href="https://doi.org/10.1016/j.jphotochem.2021.113421"
- Description: Herein, we present syntheses of three asymmetrical zinc(II) phthalocyanine (ZnPc) complexes and hydrothermal synthesis of cobalt tungstate nanoparticles. The ZnPc derivatives were covalently linked to cobalt tungstate nanoparticles. Photophysical and photochemical behaviour of Pcs and nanoconjugates were investigated. The nanoconjugates generated higher triplet quantum yield and singlet oxygen quantum yield than the ZnPcs alone. Furthermore, in this paper photocatalytic efficiencies of ZnPc complexes and nanoconjugates were investigated for the degradation of methylene blue and higher photocatalytic behaviour was observed for the conjugates. The kinetic model was used to study photocatalytic behaviour of all the prepared photocatalysts.
- Full Text:
- Date Issued: 2021
- Authors: Mgidlana, Sithi , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184991 , vital:44314 , xlink:href="https://doi.org/10.1016/j.jphotochem.2021.113421"
- Description: Herein, we present syntheses of three asymmetrical zinc(II) phthalocyanine (ZnPc) complexes and hydrothermal synthesis of cobalt tungstate nanoparticles. The ZnPc derivatives were covalently linked to cobalt tungstate nanoparticles. Photophysical and photochemical behaviour of Pcs and nanoconjugates were investigated. The nanoconjugates generated higher triplet quantum yield and singlet oxygen quantum yield than the ZnPcs alone. Furthermore, in this paper photocatalytic efficiencies of ZnPc complexes and nanoconjugates were investigated for the degradation of methylene blue and higher photocatalytic behaviour was observed for the conjugates. The kinetic model was used to study photocatalytic behaviour of all the prepared photocatalysts.
- Full Text:
- Date Issued: 2021
Photocatalytic and solar radiation harvesting potential of a free-base porphyrin-zinc (II) phthalocyanine heterodyad functionalized polystyrene polymer membrane for the degradation of 4-chlorophenol
- Mafukidze, Donovan M, Nyokong, Tebello
- Authors: Mafukidze, Donovan M , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185772 , vital:44422 , xlink:href="https://doi.org/10.1016/j.jphotochem.2021.113142"
- Description: In this work a novel porphyrin-phthalocyanine heterodyad (complex 4) was synthesized and embedded in polystyrene polymer membranes. The singlet oxygen generation of 4 improved in comparison to the parent porphyrin and phthalocyanine complexes giving singlet oxygen quantum yields of 0.67 and 0.51 (in dimethyl sulfoxide) where the porphyrin and phthalocyanine complementarily absorb respectively. Successful Buchwald-Hartwig coupling of complex 4 to amine functionalized polystyrene ((NH2)PS) gave a complex loading of 24.6 mg complex/g 4-PS. Embedding of 4-PS in polystyrene polymer membrane yielded the photoactive 4-memb which proved to be capable of degrading 4-chlorophenol at reaction rates of at least 1.12 × 10−7 molL-1 min-1 and half-life of 193 min in a pseudo first order reaction at an initial concentration of 3.10 × 10-5. Also, light harvesting experiments proved 4-memb to be active in the whole 300–700 nm wavelength range with the greatest activity being under white light.
- Full Text:
- Date Issued: 2021
- Authors: Mafukidze, Donovan M , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185772 , vital:44422 , xlink:href="https://doi.org/10.1016/j.jphotochem.2021.113142"
- Description: In this work a novel porphyrin-phthalocyanine heterodyad (complex 4) was synthesized and embedded in polystyrene polymer membranes. The singlet oxygen generation of 4 improved in comparison to the parent porphyrin and phthalocyanine complexes giving singlet oxygen quantum yields of 0.67 and 0.51 (in dimethyl sulfoxide) where the porphyrin and phthalocyanine complementarily absorb respectively. Successful Buchwald-Hartwig coupling of complex 4 to amine functionalized polystyrene ((NH2)PS) gave a complex loading of 24.6 mg complex/g 4-PS. Embedding of 4-PS in polystyrene polymer membrane yielded the photoactive 4-memb which proved to be capable of degrading 4-chlorophenol at reaction rates of at least 1.12 × 10−7 molL-1 min-1 and half-life of 193 min in a pseudo first order reaction at an initial concentration of 3.10 × 10-5. Also, light harvesting experiments proved 4-memb to be active in the whole 300–700 nm wavelength range with the greatest activity being under white light.
- Full Text:
- Date Issued: 2021
Synthesis of a near infrared-actuated phthalocyanine-lipid vesicle system for augmented photodynamic therapy
- Nwahara, Namdi, Managa, Muthumuni, Stoffels, Mihlali, Britton, Jonathan, Prinsloo, Earl, Nyokong, Tebello
- Authors: Nwahara, Namdi , Managa, Muthumuni , Stoffels, Mihlali , Britton, Jonathan , Prinsloo, Earl , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185395 , vital:44383 , xlink:href="https://doi.org/10.1016/j.synthmet.2021.116811"
- Description: The efficacy of photodynamic therapy (PDT) is often limited by the poor bio-distributive properties of conventional photosensitizers and the local hypoxic microenvironment that characterises most solid tumours. Herein, a novel in situ oxygenic lipid formulation for photodynamic therapy (PDT) is reported. Such a hybrid was synthesized by adsorbing bimetallic nanozyme, MnO2@PtNPs (NPs = nanoparticles) onto graphene quantum dots (GQDs) – zinc (II) phthalocyanine conjugates, followed by liposomal encapsulation, affording it enhanced water solubility. The MnO2@PtNPs, which are is shown to possess excellent catalase-like properties surpassing that of MnO2 or PtNPs alone, serves to catalyze H2O2 to O2, while the zinc (II) phthalocyanine (1) serves to transform the formed oxygen to generate cytotoxic singlet oxygen immediately. We show that by combining each function of the respective building blocks, the as-synthesized 1-GQDs-MnO2@PtNPs-liposomes not only maintains the properties of oxygen supplementation through H2O2 catalysis but also displays cooperative properties for enhanced singlet oxygen production. Consequently, a remarkably improved PDT efficacy was observed for 1-GQDs-MnO2@PtNPs-liposomes in both normoxia and hypoxia. These results demonstrate the potential applicability of such nanozyme constituted 1-GQDs-MnO2@PtNPs-liposomes for achieving tumour treatment in hypoxic conditions by PDT.
- Full Text:
- Date Issued: 2021
- Authors: Nwahara, Namdi , Managa, Muthumuni , Stoffels, Mihlali , Britton, Jonathan , Prinsloo, Earl , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185395 , vital:44383 , xlink:href="https://doi.org/10.1016/j.synthmet.2021.116811"
- Description: The efficacy of photodynamic therapy (PDT) is often limited by the poor bio-distributive properties of conventional photosensitizers and the local hypoxic microenvironment that characterises most solid tumours. Herein, a novel in situ oxygenic lipid formulation for photodynamic therapy (PDT) is reported. Such a hybrid was synthesized by adsorbing bimetallic nanozyme, MnO2@PtNPs (NPs = nanoparticles) onto graphene quantum dots (GQDs) – zinc (II) phthalocyanine conjugates, followed by liposomal encapsulation, affording it enhanced water solubility. The MnO2@PtNPs, which are is shown to possess excellent catalase-like properties surpassing that of MnO2 or PtNPs alone, serves to catalyze H2O2 to O2, while the zinc (II) phthalocyanine (1) serves to transform the formed oxygen to generate cytotoxic singlet oxygen immediately. We show that by combining each function of the respective building blocks, the as-synthesized 1-GQDs-MnO2@PtNPs-liposomes not only maintains the properties of oxygen supplementation through H2O2 catalysis but also displays cooperative properties for enhanced singlet oxygen production. Consequently, a remarkably improved PDT efficacy was observed for 1-GQDs-MnO2@PtNPs-liposomes in both normoxia and hypoxia. These results demonstrate the potential applicability of such nanozyme constituted 1-GQDs-MnO2@PtNPs-liposomes for achieving tumour treatment in hypoxic conditions by PDT.
- Full Text:
- Date Issued: 2021
The effects of the composition and structure of quantum dots combined with cobalt phthalocyanine and an aptamer on the electrochemical detection of prostate specific antigen
- Nxele, Siphesihle R, Nyokong, Tebello
- Authors: Nxele, Siphesihle R , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185002 , vital:44315 , xlink:href="https://doi.org/10.1016/j.dyepig.2021.109407"
- Description: The ability to functionalize and modify graphene-based quantum dots has also allowed for the tuning of their activity in different applications. A comparative study is carried out in this work where a prostate specific aptamer (PSA) and cobalt phthalocyanine molecule are combined with graphene quantum dots (GQDs), nitrogen doped graphene quantum dots (NGQDs) and graphitic carbon nitride quantum dots (gCNQDs) in order to determine the effects of quantum dots type (and therefore composition) on the electrocatalytic ability of the sensor to detect the analyte of interest. For the detection of prostate-specific antigen, electrochemical impedance spectroscopy (EIS) is employed to determine detection limits as well as sensitivity and selectivity of the aptasensors. Results showed a good performance of all sensors fabricated with the NGQDs based aptasensor showing the best performance with a detection limit of 1.54 pM in EIS as well as negligible interference in mixed samples. This electrode was further verified in spiked human serum samples and good recovery and low detection limits were determined, putting this aptasensor in good stead as a reliable, efficient PSA aptasensor.
- Full Text:
- Date Issued: 2021
- Authors: Nxele, Siphesihle R , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185002 , vital:44315 , xlink:href="https://doi.org/10.1016/j.dyepig.2021.109407"
- Description: The ability to functionalize and modify graphene-based quantum dots has also allowed for the tuning of their activity in different applications. A comparative study is carried out in this work where a prostate specific aptamer (PSA) and cobalt phthalocyanine molecule are combined with graphene quantum dots (GQDs), nitrogen doped graphene quantum dots (NGQDs) and graphitic carbon nitride quantum dots (gCNQDs) in order to determine the effects of quantum dots type (and therefore composition) on the electrocatalytic ability of the sensor to detect the analyte of interest. For the detection of prostate-specific antigen, electrochemical impedance spectroscopy (EIS) is employed to determine detection limits as well as sensitivity and selectivity of the aptasensors. Results showed a good performance of all sensors fabricated with the NGQDs based aptasensor showing the best performance with a detection limit of 1.54 pM in EIS as well as negligible interference in mixed samples. This electrode was further verified in spiked human serum samples and good recovery and low detection limits were determined, putting this aptasensor in good stead as a reliable, efficient PSA aptasensor.
- Full Text:
- Date Issued: 2021
Enhanced Light-Driven Antimicrobial Activity of Cationic Poly (oxanorbornene) s by Phthalocyanine Incorporation into Polymer as Pendants
- Ahmetali, Erem, Sen, Pinar, Süer, N Ceren, Aksu, Burak, Nyokong, Tebello, Eren, Tarik, Sener, Kasim M
- Authors: Ahmetali, Erem , Sen, Pinar , Süer, N Ceren , Aksu, Burak , Nyokong, Tebello , Eren, Tarik , Sener, Kasim M
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185976 , vital:44453 , xlink:href=" https://doi.org/10.1002/macp.202000386"
- Description: Amphiphilic poly(oxanorbornene)s are promising synthetic polymers that mimic the structural properties and antimicrobial functions of naturally occurring antimicrobial peptides. Here, poly(oxanorbornene)s bearing pendant zinc(II) phthalocyanine and triphenyl(ethyl) phosphonium functionalities are synthesized by ring-opening metathesis polymerization (ROMP). Fluorescence, singlet oxygen and triplet quantum yields of polymers are measured in dimethyl sulfoxide and aqueous medium. The singlet oxygen quantum yields of copolymers with the highest triphenyl and triethyl phosphonium content are found to be 0.29 and 0.41, respectively. Then, antimicrobial activities of polymers against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) are investigated under both dark and light conditions. Synergistic effect of zinc(II) phthalocyanine and phosphonium-containing poly(oxanorbornene) is observed that the conjugate possessing the most triphenyl phosphonium side chains has the highest activity under light against both gram-positive and gram-negative bacterial strains after 80 min irradiation, reducing the survival of E. coli or S. aureus by 99.9999%. Hemolytic concentrations of the copolymers are found between 8 and 512 µg mL−1. Scanning electron microscopy (SEM) proves that the bacteria membrane deforms after contacting with the biocidal polymer.
- Full Text:
- Date Issued: 2020
- Authors: Ahmetali, Erem , Sen, Pinar , Süer, N Ceren , Aksu, Burak , Nyokong, Tebello , Eren, Tarik , Sener, Kasim M
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185976 , vital:44453 , xlink:href=" https://doi.org/10.1002/macp.202000386"
- Description: Amphiphilic poly(oxanorbornene)s are promising synthetic polymers that mimic the structural properties and antimicrobial functions of naturally occurring antimicrobial peptides. Here, poly(oxanorbornene)s bearing pendant zinc(II) phthalocyanine and triphenyl(ethyl) phosphonium functionalities are synthesized by ring-opening metathesis polymerization (ROMP). Fluorescence, singlet oxygen and triplet quantum yields of polymers are measured in dimethyl sulfoxide and aqueous medium. The singlet oxygen quantum yields of copolymers with the highest triphenyl and triethyl phosphonium content are found to be 0.29 and 0.41, respectively. Then, antimicrobial activities of polymers against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) are investigated under both dark and light conditions. Synergistic effect of zinc(II) phthalocyanine and phosphonium-containing poly(oxanorbornene) is observed that the conjugate possessing the most triphenyl phosphonium side chains has the highest activity under light against both gram-positive and gram-negative bacterial strains after 80 min irradiation, reducing the survival of E. coli or S. aureus by 99.9999%. Hemolytic concentrations of the copolymers are found between 8 and 512 µg mL−1. Scanning electron microscopy (SEM) proves that the bacteria membrane deforms after contacting with the biocidal polymer.
- Full Text:
- Date Issued: 2020
NIR Absorbing AzaBODIPY Dyes for pH Sensing
- Kubheka, Gugu, Mack, John, Nyokong, Tebello, Zhen, Shen
- Authors: Kubheka, Gugu , Mack, John , Nyokong, Tebello , Zhen, Shen
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186668 , vital:44523 , xlink:href="https://doi.org/10.3390/molecules25163689"
- Description: Two near-infrared (NIR) absorbing di(thien-2-nyl)-di(dimethylanilino)azaBODIPY dyes 2a and 2b were synthesized and characterized that differ depending on whether the dimethylaniline substituents are introduced at the 3,5- or 1,7-positions of the azaBODIPY core. The main spectral bands lie at 824 and 790 nm, respectively, in CH2Cl2. The effect of substituent position on the photophysical and pH sensing properties was analyzed through a comparison of the optical properties with the results of time-dependent density functional theory (TD-DFT) calculations. Protonation of the dimethylamino nitrogen atoms eliminates the intramolecular charge transfer properties of these compounds, and this results in a marked blue-shift of the main absorption bands to 696 and 730 nm, respectively, in CH2Cl2, and a fluorescence “turn-on” effect in the NIR region. The pH dependence studies reveal that the pKa values of the non-protonated 2a and 2b molecules are ca. 6.9 (±0.05) and 7.3 (±0.05), respectively, while that of the monoprotonated species for both dyes is ca. 1.4 (±0.05) making them potentially suitable for use as colorimetric pH indicators under highly acidic conditions.
- Full Text:
- Date Issued: 2020
- Authors: Kubheka, Gugu , Mack, John , Nyokong, Tebello , Zhen, Shen
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186668 , vital:44523 , xlink:href="https://doi.org/10.3390/molecules25163689"
- Description: Two near-infrared (NIR) absorbing di(thien-2-nyl)-di(dimethylanilino)azaBODIPY dyes 2a and 2b were synthesized and characterized that differ depending on whether the dimethylaniline substituents are introduced at the 3,5- or 1,7-positions of the azaBODIPY core. The main spectral bands lie at 824 and 790 nm, respectively, in CH2Cl2. The effect of substituent position on the photophysical and pH sensing properties was analyzed through a comparison of the optical properties with the results of time-dependent density functional theory (TD-DFT) calculations. Protonation of the dimethylamino nitrogen atoms eliminates the intramolecular charge transfer properties of these compounds, and this results in a marked blue-shift of the main absorption bands to 696 and 730 nm, respectively, in CH2Cl2, and a fluorescence “turn-on” effect in the NIR region. The pH dependence studies reveal that the pKa values of the non-protonated 2a and 2b molecules are ca. 6.9 (±0.05) and 7.3 (±0.05), respectively, while that of the monoprotonated species for both dyes is ca. 1.4 (±0.05) making them potentially suitable for use as colorimetric pH indicators under highly acidic conditions.
- Full Text:
- Date Issued: 2020
Synthesis and pharmacological evaluation of chlorin derivatives for photodynamic therapy of cholangiocarcinoma
- Gao, Ying-Hua, Li, Man-Yi, Saijad, Faiza, Wang, Jin-Hai, Meharban, Faiza, Gadoora, Malaz A, Yan, Yi-Jia, Nyokong, Tebello, Chen, Zhi-Long
- Authors: Gao, Ying-Hua , Li, Man-Yi , Saijad, Faiza , Wang, Jin-Hai , Meharban, Faiza , Gadoora, Malaz A , Yan, Yi-Jia , Nyokong, Tebello , Chen, Zhi-Long
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190873 , vital:45036 , xlink:href="https://doi.org/10.1016/j.ejmech.2020.112049"
- Description: Photodynamic therapy (PDT) has been developed as a promising therapeutic method in cancer treatment. The discovery of effective photosensitizer, which is the key factor of PDT, is highly desired. This paper reports the synthesis of novel chlorin derivatives, 5,10,15,20-tetraphenyl-[2:3]-[(methoxycarbonyl, carboxy)methano] chlorin I and 5,10,15,20-tetraphenyl-[2:3]- {[methoxycarbonyl, (2-hydroxyethyl)amide]methano}chlorin II. Their structures were characterized with UV–vis, 1HNMR, 13CNMR and HRMS spectroscopies. Photophysical and photochemical experiments results showed that compound I and II had an absorption maximum around 650 nm, with molar extinction coefficients of 1 × 104 M−1 cm−1. They had strong fluorescence emission in 650–660 nm upon excitation with 419–422 nm light. ESR showed that singlet oxygen was produced upon irradiation of compounds with 650 nm light in the presence of molecular oxygen. The photo-bleaching test indicated that the structure of compounds was stable. These new compounds exhibit excellent anti-tumor effects and lower toxicity compared to m-THPC in vitro and in vivo. Compound I and II had high tumor selectivity, which could induced tumor cells shrinkage and necrosis under 650 nm laser irradiation. Flow cytometry revealed that the compounds might mediate PDT effect at late apoptotic phase. These results make these compound I and II promising candidates for future study in photo-diagnosis and photodynamic therapy of cholangiocarcinoma.
- Full Text:
- Date Issued: 2020
- Authors: Gao, Ying-Hua , Li, Man-Yi , Saijad, Faiza , Wang, Jin-Hai , Meharban, Faiza , Gadoora, Malaz A , Yan, Yi-Jia , Nyokong, Tebello , Chen, Zhi-Long
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190873 , vital:45036 , xlink:href="https://doi.org/10.1016/j.ejmech.2020.112049"
- Description: Photodynamic therapy (PDT) has been developed as a promising therapeutic method in cancer treatment. The discovery of effective photosensitizer, which is the key factor of PDT, is highly desired. This paper reports the synthesis of novel chlorin derivatives, 5,10,15,20-tetraphenyl-[2:3]-[(methoxycarbonyl, carboxy)methano] chlorin I and 5,10,15,20-tetraphenyl-[2:3]- {[methoxycarbonyl, (2-hydroxyethyl)amide]methano}chlorin II. Their structures were characterized with UV–vis, 1HNMR, 13CNMR and HRMS spectroscopies. Photophysical and photochemical experiments results showed that compound I and II had an absorption maximum around 650 nm, with molar extinction coefficients of 1 × 104 M−1 cm−1. They had strong fluorescence emission in 650–660 nm upon excitation with 419–422 nm light. ESR showed that singlet oxygen was produced upon irradiation of compounds with 650 nm light in the presence of molecular oxygen. The photo-bleaching test indicated that the structure of compounds was stable. These new compounds exhibit excellent anti-tumor effects and lower toxicity compared to m-THPC in vitro and in vivo. Compound I and II had high tumor selectivity, which could induced tumor cells shrinkage and necrosis under 650 nm laser irradiation. Flow cytometry revealed that the compounds might mediate PDT effect at late apoptotic phase. These results make these compound I and II promising candidates for future study in photo-diagnosis and photodynamic therapy of cholangiocarcinoma.
- Full Text:
- Date Issued: 2020
Electrocatalytic Activity of Asymmetrical Cobalt Phthalocyanines in the Presence of N Doped Graphene Quantum Dots: The Push-pull Effects of Substituents
- Nkhahle, Reitumetse, Sekhosana, Kutloano E, Centane, Sixolile, Nyokong, Tebello
- Authors: Nkhahle, Reitumetse , Sekhosana, Kutloano E , Centane, Sixolile , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186904 , vital:44546 , xlink:href="https://doi.org/10.1002/elan.201800837"
- Description: A series of Co phthalocyanine (CoPc) derivatives and their respective nitrogen doped graphene quantum dot conjugates were used as catalysts towards the electrooxidation of hydrazine. Using a glassy carbon electrode as a support for the electrocatalysts, through cyclic voltammetry and chronoamperometry, the effects of combining the CoPcs with the nitrogen doped graphene quantum dots (NGQDs) were studied. The general observations made were that the NGQDs improve the catalytic activity of the CoPcs in both the p-p stacked and covalently linked conjugates by increasing the sensitivities and lowering the limits of detection with values as low as 0.43 mM being recorded.
- Full Text:
- Date Issued: 2019
- Authors: Nkhahle, Reitumetse , Sekhosana, Kutloano E , Centane, Sixolile , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186904 , vital:44546 , xlink:href="https://doi.org/10.1002/elan.201800837"
- Description: A series of Co phthalocyanine (CoPc) derivatives and their respective nitrogen doped graphene quantum dot conjugates were used as catalysts towards the electrooxidation of hydrazine. Using a glassy carbon electrode as a support for the electrocatalysts, through cyclic voltammetry and chronoamperometry, the effects of combining the CoPcs with the nitrogen doped graphene quantum dots (NGQDs) were studied. The general observations made were that the NGQDs improve the catalytic activity of the CoPcs in both the p-p stacked and covalently linked conjugates by increasing the sensitivities and lowering the limits of detection with values as low as 0.43 mM being recorded.
- Full Text:
- Date Issued: 2019
Fabrication of efficient nonlinear optical absorber using Zn phthalocyanine-semiconductor quantum dots conjugates
- Mgidlana, Sithi, Oluwole, David O, Nyokong, Tebello
- Authors: Mgidlana, Sithi , Oluwole, David O , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187496 , vital:44663 , xlink:href="https://doi.org/10.1016/j.poly.2018.11.024"
- Description: In this paper, we report on the synthesis of Zn(II) phthalocyanine derivatives and their conjugates with core/shell and core/shell/shell semiconductor quantum dots (SQDs). Zn(II) mono amino-carboxyethylphenoxy phthalocyanine (1), Zn(II) mono 3-carboxyphenoxy-tris(pyridin-2-yloxy) phthalocyanine (2) and Zn(II) mono aminophenoxy-tris(benzothiazole) phthalocyanine (3) were synthesized. The photophysical and optical limiting properties of the phthalocyanine (Pc) complexes and their conjugates with SQDs were investigated in dimethyl sulfoxide. The optical limiting behaviour of the Pc complexes and their conjugates were measured by the open aperture Z-scan technique at laser excitation wavelength of 532 nm with 10 ns pulse. The conjugates outperformed the Pc complexes alone with the conjugates of 2-SQDs affording highest nonlinear absorption coefficient (βeff) value of ∼80 cm/GW and lowest limiting threshold (Ilim) value of ∼0.27 J·cm−2 as compared to other samples while complex 1 gave low βeff and high Ilim values of 42.2 cm/GW and 1.39 J·cm−2, respectively.
- Full Text:
- Date Issued: 2019
- Authors: Mgidlana, Sithi , Oluwole, David O , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187496 , vital:44663 , xlink:href="https://doi.org/10.1016/j.poly.2018.11.024"
- Description: In this paper, we report on the synthesis of Zn(II) phthalocyanine derivatives and their conjugates with core/shell and core/shell/shell semiconductor quantum dots (SQDs). Zn(II) mono amino-carboxyethylphenoxy phthalocyanine (1), Zn(II) mono 3-carboxyphenoxy-tris(pyridin-2-yloxy) phthalocyanine (2) and Zn(II) mono aminophenoxy-tris(benzothiazole) phthalocyanine (3) were synthesized. The photophysical and optical limiting properties of the phthalocyanine (Pc) complexes and their conjugates with SQDs were investigated in dimethyl sulfoxide. The optical limiting behaviour of the Pc complexes and their conjugates were measured by the open aperture Z-scan technique at laser excitation wavelength of 532 nm with 10 ns pulse. The conjugates outperformed the Pc complexes alone with the conjugates of 2-SQDs affording highest nonlinear absorption coefficient (βeff) value of ∼80 cm/GW and lowest limiting threshold (Ilim) value of ∼0.27 J·cm−2 as compared to other samples while complex 1 gave low βeff and high Ilim values of 42.2 cm/GW and 1.39 J·cm−2, respectively.
- Full Text:
- Date Issued: 2019
Inhibition of aluminium corrosion using benzothiazole and its phthalocyanine derivative
- Nnaji, Nnaemeka, Nwaji, Njemuwa, Fomo, Gertrude, Mack, John, Nyokong, Tebello
- Authors: Nnaji, Nnaemeka , Nwaji, Njemuwa , Fomo, Gertrude , Mack, John , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186949 , vital:44550 , xlink:href="https://doi.org/10.1007/s12678-019-00538-1"
- Description: Cyclic voltammetry and potentiodynamic polarization techniques were used to study the effects of 4-[4-(1,3-benzothiazol2yl)phenoxy] phthalonitrile (BT) and tetrakis[(benzo[d]thiazol-2ylphenoxy) phthalocyaninato] gallium(III)chloride (ClGaBTPc) as aluminium corrosion inhibitors in 1.0 M hydrochloric acid. The presence of the inhibitors in the concentration range of 2 to 10 μM was found to retard the aluminium corrosion process such that the inhibition efficiency was found to range from 28.2 to 76.1% for BT and from 71.5 to 82.7% for ClGaBTPc. The latter was a better inhibitor. Scanning electron microscopy and energy-dispersive X-ray measurements reveal effective metal surface protection by the inhibitors, most probably by shielding it from the corrosion attacks of Cl− from the acid. The calculated quantum chemical parameters agreed with experimental results.
- Full Text:
- Date Issued: 2019
- Authors: Nnaji, Nnaemeka , Nwaji, Njemuwa , Fomo, Gertrude , Mack, John , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186949 , vital:44550 , xlink:href="https://doi.org/10.1007/s12678-019-00538-1"
- Description: Cyclic voltammetry and potentiodynamic polarization techniques were used to study the effects of 4-[4-(1,3-benzothiazol2yl)phenoxy] phthalonitrile (BT) and tetrakis[(benzo[d]thiazol-2ylphenoxy) phthalocyaninato] gallium(III)chloride (ClGaBTPc) as aluminium corrosion inhibitors in 1.0 M hydrochloric acid. The presence of the inhibitors in the concentration range of 2 to 10 μM was found to retard the aluminium corrosion process such that the inhibition efficiency was found to range from 28.2 to 76.1% for BT and from 71.5 to 82.7% for ClGaBTPc. The latter was a better inhibitor. Scanning electron microscopy and energy-dispersive X-ray measurements reveal effective metal surface protection by the inhibitors, most probably by shielding it from the corrosion attacks of Cl− from the acid. The calculated quantum chemical parameters agreed with experimental results.
- Full Text:
- Date Issued: 2019
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
Improved nonlinear optical behaviour of ball type indium (III) phthalocyanine linked to glutathione capped nanoparticles
- Nwaji, Njemuwa, Oluwole, David O, Mack, John, Louzada, Marcel, Khene, Samson M, Britton, Jonathan, Nyokong, Tebello
- Authors: Nwaji, Njemuwa , Oluwole, David O , Mack, John , Louzada, Marcel , Khene, Samson M , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/239654 , vital:50752 , xlink:href="https://doi.org/10.1016/j.dyepig.2017.01.066"
- Description: The synthesis of ball–type indium phthalocyanine (complex 4) and its covalent attachment to glutathione (GSH–) capped (Ag, Au, CdTeSe, CdTeSe/ZnO) nanoparticles are reported in this work. Furthermore, their photophysical and nonlinear optical behaviour were investigated. We observed a decrease in the fluorescence quantum yield with corresponding increase in the triplet quantum yield of the nanoconjugates in comparison to complex 4 alone. The reverse saturable absorption was found to be dependent on excited state absorption. The optical limiting threshold ranges from 0.40–0.78 (J/cm2). The nanoconjugate of the complex 4 with GSH–CdTeSe/ZnO (QD1) accounted for the most improved triplet state parameters and nonlinear optical behaviour in comparison to complex 4 and the other nanoconjugates studied in this work.
- Full Text:
- Date Issued: 2017
- Authors: Nwaji, Njemuwa , Oluwole, David O , Mack, John , Louzada, Marcel , Khene, Samson M , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/239654 , vital:50752 , xlink:href="https://doi.org/10.1016/j.dyepig.2017.01.066"
- Description: The synthesis of ball–type indium phthalocyanine (complex 4) and its covalent attachment to glutathione (GSH–) capped (Ag, Au, CdTeSe, CdTeSe/ZnO) nanoparticles are reported in this work. Furthermore, their photophysical and nonlinear optical behaviour were investigated. We observed a decrease in the fluorescence quantum yield with corresponding increase in the triplet quantum yield of the nanoconjugates in comparison to complex 4 alone. The reverse saturable absorption was found to be dependent on excited state absorption. The optical limiting threshold ranges from 0.40–0.78 (J/cm2). The nanoconjugate of the complex 4 with GSH–CdTeSe/ZnO (QD1) accounted for the most improved triplet state parameters and nonlinear optical behaviour in comparison to complex 4 and the other nanoconjugates studied in this work.
- Full Text:
- Date Issued: 2017
Investigation of photophysicochemical properties of zinc phthalocyanines conjugated to metallic nanoparticles
- Dube, Edith, Nwaji, Njemuwa, Oluwole, David O, Mack, John, Nyokong, Tebello
- Authors: Dube, Edith , Nwaji, Njemuwa , Oluwole, David O , Mack, John , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233425 , vital:50089 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.09.020"
- Description: The syntheses of zinc(II) tetra–[3–(4–phenoxy) (propanoic acid) phthalocyanine] (2) and zinc(II) mono–[3–(4–phenoxy) (propanoic acid) phthalocyanine (3) are reported in this work. Compounds 2 and 3 were covalently linked to glutathione capped silver (AgNPs–GSH), gold (AuNPs–GSH) and silver-gold alloy (Ag3Au1NPs–GSH) nanoparticles (NPs) via an amide bond formation to afford the conjugates: 2–AgNPs–GSH, 3–AgNPs–GSH, 2–AuNPs–GSH, 3–AuNPs–GSH, 2-Ag3Au1NPs–GSH and 3-Ag3Au1NPs–GSH. The photophysicochemical behaviours of the compounds and their conjugates with NPs were assessed in solution. The conjugates afforded a decrease in fluorescence quantum yields and lifetimes with improved triplet quantum yields in comparison to the compounds. Accordingly, the AgNPs and AuNPs conjugates with the compounds afforded high singlet quantum yields. On the contrary, the conjugates of the alloy afforded decreased singlet quantum yields probably due to the screening effect. The compounds and their conjugates with NPs could serve as a viable and efficacious photosensitizer for photodynamic therapy.
- Full Text:
- Date Issued: 2017
- Authors: Dube, Edith , Nwaji, Njemuwa , Oluwole, David O , Mack, John , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233425 , vital:50089 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.09.020"
- Description: The syntheses of zinc(II) tetra–[3–(4–phenoxy) (propanoic acid) phthalocyanine] (2) and zinc(II) mono–[3–(4–phenoxy) (propanoic acid) phthalocyanine (3) are reported in this work. Compounds 2 and 3 were covalently linked to glutathione capped silver (AgNPs–GSH), gold (AuNPs–GSH) and silver-gold alloy (Ag3Au1NPs–GSH) nanoparticles (NPs) via an amide bond formation to afford the conjugates: 2–AgNPs–GSH, 3–AgNPs–GSH, 2–AuNPs–GSH, 3–AuNPs–GSH, 2-Ag3Au1NPs–GSH and 3-Ag3Au1NPs–GSH. The photophysicochemical behaviours of the compounds and their conjugates with NPs were assessed in solution. The conjugates afforded a decrease in fluorescence quantum yields and lifetimes with improved triplet quantum yields in comparison to the compounds. Accordingly, the AgNPs and AuNPs conjugates with the compounds afforded high singlet quantum yields. On the contrary, the conjugates of the alloy afforded decreased singlet quantum yields probably due to the screening effect. The compounds and their conjugates with NPs could serve as a viable and efficacious photosensitizer for photodynamic therapy.
- Full Text:
- Date Issued: 2017
Nonlinear optical dynamics of benzothiazole derivatized phthalocyanines in solution, thin films and when conjugated to nanoparticles
- Nwaji, Njemuwa, Jones, Benjamin, Mack, John, Oluwole, David O, Nyokong, Tebello
- Authors: Nwaji, Njemuwa , Jones, Benjamin , Mack, John , Oluwole, David O , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190426 , vital:44993 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.05.042"
- Description: Benzothiazole phthalocynines complexes: tetrakis[(benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] indium(III) chloride (1) and tetrakis[(benzo[d]thiazol-2-ylthio)phthalocyaninato] indium(III) chloride (2) were synthesisized and their nanosecond nonlinear optical behaviours in solution, solid state and when conjugated to metallic nanoparticles were examined and compared to those of the corresponding ZnPc and GaPc which are designated as: tetrakis[(4-benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] zinc(II) (3), tetrakis[(4-benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] gallium(III) chloride (4), tetrakis[(4-benzo[d]thiazol-2-ylthio)phthalocyaninato] zinc(II) (5) and tetrakis[(4-benzo[d]thiazol-2-ylthio)phthalocyaninato] gallium(III) chloride (6). Trends in the electronic structures were identified through a comparison of the UV–vis absorption and magnetic circular dichroism (MCD) spectroscopy of the complexes and calculated spectra predicted by time dependent density functional theory (TD-DFT). Of all the complexes and nanoconjugates, complex 2 (containing sulphur linkages and In as a central metal) gave the best optical limiting behaviour.
- Full Text:
- Date Issued: 2017
- Authors: Nwaji, Njemuwa , Jones, Benjamin , Mack, John , Oluwole, David O , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190426 , vital:44993 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.05.042"
- Description: Benzothiazole phthalocynines complexes: tetrakis[(benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] indium(III) chloride (1) and tetrakis[(benzo[d]thiazol-2-ylthio)phthalocyaninato] indium(III) chloride (2) were synthesisized and their nanosecond nonlinear optical behaviours in solution, solid state and when conjugated to metallic nanoparticles were examined and compared to those of the corresponding ZnPc and GaPc which are designated as: tetrakis[(4-benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] zinc(II) (3), tetrakis[(4-benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] gallium(III) chloride (4), tetrakis[(4-benzo[d]thiazol-2-ylthio)phthalocyaninato] zinc(II) (5) and tetrakis[(4-benzo[d]thiazol-2-ylthio)phthalocyaninato] gallium(III) chloride (6). Trends in the electronic structures were identified through a comparison of the UV–vis absorption and magnetic circular dichroism (MCD) spectroscopy of the complexes and calculated spectra predicted by time dependent density functional theory (TD-DFT). Of all the complexes and nanoconjugates, complex 2 (containing sulphur linkages and In as a central metal) gave the best optical limiting behaviour.
- Full Text:
- Date Issued: 2017