The effect of the cobalt and manganese central metal ions on the nonlinear optical properties of tetra (4-propargyloxyphenoxy) phthalocyanines
- Authors: Mwanza, Daniel , Louzada, Marcel , Britton, Jonathan , Sekhosana, Kutloano E , Khene, Samson M , Nyokong, Tebello , Mashazi, Philani N
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233357 , vital:50083 , xlink:href="https://doi.org/10.1039/C8NJ00748A"
- Description: The metal-free (H2TPrOPhOPc), cobalt (CoTPrOPhOPc) and manganese (Mn(OAc)TPrOPhOPc) tetra propargyloxyphenoxy phthalocyanines were evaluated for their potential as optical limiting materials. The effect of the substituents and the central metal ions on the nonlinear optical properties was evaluated. The metal-free phthalocyanine exhibited better nonlinear optical properties when compared to the cobalt and manganese complexes owing to the metal ions quenching the excited state due to their half-filled d-orbitals. The nonlinear absorption coefficient (βeff, ×10−5 m MW−1) followed the trend of H2TPrOPhOPc > CoTPrOPhOPc > Mn(OAc)TPrOPhOPc. The values βeff (×10−5 m MW−1) using 532 nm Nd:YAG (560 nm monochromatic Ekspla) laser sources were 23.5 > 14.3 > 9.20 (14.4). The second-order nonlinear coefficient obtained using density functional theory calculations, the theoretical hyper-Rayleigh scattering (βHRS, ×10−28 esu), showed the decreasing trend for H2TPrOPhOPc (2.28) > CoTPrOPhOPc (2.10) > Mn(OAc)TPrOPhOPc (1.86). The 4-(propargyloxy)phenoxy substituents enhanced the optical limiting properties of the synthesized phthalocyanines.
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- Date Issued: 2018
The improved antibacterial efficiency of a zinc phthalocyanine when embedded on silver nanoparticle modified silica nanofibers
- Authors: Mapukata, Sivuyisiwe , Britton, Jonathan , Osifeko, Olawale L , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185784 , vital:44423 , xlink:href="https://doi.org/10.1016/j.pdpdt.2020.102100"
- Description: This work reports on the fabrication and modification of electrospun polymer free silica nanofibers (SiO2 NFs) with the aim of creating heterogeneous antibacterial catalysts. The optical and photophysical properties of the obtained NFs i.e. bare SiO2, Ag-SiO2, Pc-SiO2 and Pc@Ag-SiO2 NFs (Pc = phthalocyanine) were compared and reported. The singlet oxygen quantum yields of the Pc-SiO2 and Pc@Ag-SiO2 NFs were also quantified and found to be 0.08 and 0.12, respectively, in water. All the modified SiO2 NFs were found to possess photoactivity against S. aureus with the most effective being the Pc@Ag-SiO2 NFs due to the synergy between the Pc and Ag nanoparticles. The bare SiO2 NFs do not exhibit any antibacterial activity while the Ag-SiO2 and Pc@Ag-SiO2 NFs were found to also exhibit dark toxicity. The generated photocatalysts are attractive because they are active against bacteria and they are easily retrievable post-application. The nanocatalysts reported herein are therefore feasible candidates for real-life antibacterial applications.
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- Date Issued: 2021
The photocatalytic properties of zinc phthalocyanines supported on hematite nanofibers for use against methyl orange and Staphylococcus aureus
- Authors: Mapukata, Sivuyisiwe , Britton, Jonathan , Nwahara, Nnamdi , Nyokong, Tebello
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/230184 , vital:49751 , xlink:href="https://doi.org/10.1016/j.jphotochem.2021.113637"
- Description: Heterogeneous photocatalysis is a promising approach for environmental remediation from contaminants including microorganisms and organic pollutants. In this work, hematite nanofibers are fabricated and modified with a novel monosubstituted Pc (4) as well as an asymmetrical tetrasubstituted Pc (5) with the aim of creating hybrid photocatalysts. The photocatalytic activities of the unmodified and phthalocyanine modified hematite nanofibers were compared based on their efficiencies in the photoinactivation of S. aureus and photooxidation of methyl orange. For both applications, the hybrid nanofibers were found to be more efficient photocatalysts than the unmodified hematite nanofibers. Comparison of the modified nanofibers (4-Fe2O3 and 5-Fe2O3) showed that they have comparable antibacterial activity while the 5-Fe2O3 nanofibers are the best for the photooxidation of methyl orange. The singlet oxygen generation efficiency, high activity, versatility, regenerability and thus reusability of the fabricated hybrid nanofibers makes them ideal candidates for real life water treatment studies.
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- Date Issued: 2022
Third order nonlinear optical properties of phthalocyanines in the presence nanomaterials and in polymer thin films
- Authors: Britton, Jonathan , Durmus, Mahmut , Khene, Samson M , Chauke, Vongani , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241772 , vital:50968 , xlink:href="https://doi.org/10.1142/S108842461350003X"
- Description: Third order nonlinear optical properties were determined for phthalocyanine complexes 1–10 containing In, Ga and Zn central metals and tetra- or octa-substituted with benzyloxyphenoxy, phenoxy, tert-butylphenoxy and amino groups at peripheral or non-peripheral positions. The phthalocyanines were embedded in poly (methyl methacrylate) polymer in the presence of CdTe quantum dots. All complexes 1–10 were studied in the presence of CdTe quantum dots and embedded in poly (methyl methacrylate) to form thin films. Complex 3 tetrasubstituted with tert-butylphenoxy groups at non-peripheral positions was also studied in the presence of CdS, CdSe quantum dots, fullerenes, single walled carbon nanotubes. Third order nonlinear optical parameters generally increase for Pcs in the presence of CdTe quantum dots.
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- Date Issued: 2013