Electrocatalytic Activity of Cobalt Phthalocyanines Revisited: Effect of the Number of Oxygen Atoms and Conjugation to Carbon Nanomaterials
- Ndebele, Nobuhle, Mgidlana, Sithi, Nyokong, Tebello
- Authors: Ndebele, Nobuhle , Mgidlana, Sithi , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185700 , vital:44416 , xlink:href="https://doi.org/10.1007/s12678-021-00670-x"
- Description: The synthesis and characterization of tetrakis[4(4-acetlyphenoxy)phthalocyanato] cobalt (II) (1) are presented. Complex 1 together with the reported tetrakis dimethyl 5-(phenoxy)-isophthalatephthalocyaninato] cobalt (II) (2) are conjugated to carbon-based nanomaterials: graphene quantum dots (GQDs) and single-walled carbon nanotubes (SWCNTs) via π-π stacking, taking advantage of the π electrons on the graphitic structure of the nanomaterial as well as on the aromatic rings of the Co phthalocyanines (CoPcs). The electrocatalytic behaviour of the CoPcs, GQDs, SWCNTs and their respective conjugates towards the electrochemical oxidation of catechol was studied. The electrocatalytic probes were drop-dried onto the electrode surface of the glassy carbon electrode (GCE). The electrochemical oxidation of catechol was studied using cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry. Complex 2 when linked to GQDs gave the lowest oxidation peak potentials of 0.33 V. Low catechol detection limits (LOD) of 0.057 µM was obtained for complex 2 with SWCNT. Thus, complex 2 containing more oxygen atoms outperformed complex 1 with less oxygen atoms. The CoPcs on their own showed moderate electrocatalytic behaviour, hence showing the importance of conjugating them to the carbon nanomaterials. SWCNT-based electrodes performed better than GQDs, and an improvement in the LoDs, sensitivity and the catalytic rate was observed upon conjugation.
- Full Text:
- Date Issued: 2021
- Authors: Ndebele, Nobuhle , Mgidlana, Sithi , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185700 , vital:44416 , xlink:href="https://doi.org/10.1007/s12678-021-00670-x"
- Description: The synthesis and characterization of tetrakis[4(4-acetlyphenoxy)phthalocyanato] cobalt (II) (1) are presented. Complex 1 together with the reported tetrakis dimethyl 5-(phenoxy)-isophthalatephthalocyaninato] cobalt (II) (2) are conjugated to carbon-based nanomaterials: graphene quantum dots (GQDs) and single-walled carbon nanotubes (SWCNTs) via π-π stacking, taking advantage of the π electrons on the graphitic structure of the nanomaterial as well as on the aromatic rings of the Co phthalocyanines (CoPcs). The electrocatalytic behaviour of the CoPcs, GQDs, SWCNTs and their respective conjugates towards the electrochemical oxidation of catechol was studied. The electrocatalytic probes were drop-dried onto the electrode surface of the glassy carbon electrode (GCE). The electrochemical oxidation of catechol was studied using cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry. Complex 2 when linked to GQDs gave the lowest oxidation peak potentials of 0.33 V. Low catechol detection limits (LOD) of 0.057 µM was obtained for complex 2 with SWCNT. Thus, complex 2 containing more oxygen atoms outperformed complex 1 with less oxygen atoms. The CoPcs on their own showed moderate electrocatalytic behaviour, hence showing the importance of conjugating them to the carbon nanomaterials. SWCNT-based electrodes performed better than GQDs, and an improvement in the LoDs, sensitivity and the catalytic rate was observed upon conjugation.
- Full Text:
- Date Issued: 2021
Electrocatalytic activity of manganese tetra 4-aminophenyl porphyrin in the presence of graphene quantum dots
- Jokzai, Mbulelo, Mpeta, Lekhetho S, Nyokong, Tebello
- Authors: Jokzai, Mbulelo , Mpeta, Lekhetho S , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231443 , vital:49888 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.02.040"
- Description: A manganese tetra 4-aminophenyl porphyrin (MnTAPP) was synthesized and attached to graphene quantum dots (GQDs) via covalent and π-π interaction to give MnTAPP@GQDs and MnTAPP--GQDs, respectively. There was an increase (using dynamic light scattering and transmission electron microscopy) in size of the GQDs in the presence of the porphyrin due to aggregation. The porphyrins in the absence and presence of GQDs were then adsorbed onto a glassy carbon electrode using drop and dry method. The electrochemical behavior was tested by cyclic voltammetry and chronoamperometry towards hydrazine. Both methods of combining MnTAPP with GQDs improved the activity of the electrocatalysis compared to individual components. MnTAPP@GQDs showed better catalytic rate constant of 4.36 × 102 Ms−1 and lowest LoD of 0.0023 mM followed by MnTAPP--GQDs. Furthermore, the sensor showed good selectivity in the presence of interfering analytes. All probes showed good stability.
- Full Text:
- Date Issued: 2021
- Authors: Jokzai, Mbulelo , Mpeta, Lekhetho S , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231443 , vital:49888 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.02.040"
- Description: A manganese tetra 4-aminophenyl porphyrin (MnTAPP) was synthesized and attached to graphene quantum dots (GQDs) via covalent and π-π interaction to give MnTAPP@GQDs and MnTAPP--GQDs, respectively. There was an increase (using dynamic light scattering and transmission electron microscopy) in size of the GQDs in the presence of the porphyrin due to aggregation. The porphyrins in the absence and presence of GQDs were then adsorbed onto a glassy carbon electrode using drop and dry method. The electrochemical behavior was tested by cyclic voltammetry and chronoamperometry towards hydrazine. Both methods of combining MnTAPP with GQDs improved the activity of the electrocatalysis compared to individual components. MnTAPP@GQDs showed better catalytic rate constant of 4.36 × 102 Ms−1 and lowest LoD of 0.0023 mM followed by MnTAPP--GQDs. Furthermore, the sensor showed good selectivity in the presence of interfering analytes. All probes showed good stability.
- Full Text:
- Date Issued: 2021
Electrocatalytic activity of Schiff base containing copper phthalocyanines towards the detection of catechol
- Ndebele, Nobuhle, Sen, Pinar, Nyokong, Tebello
- Authors: Ndebele, Nobuhle , Sen, Pinar , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231410 , vital:49885 , xlink:href="https://doi.org/10.1016/j.poly.2021.115518"
- Description: In this study, four new copper phthalocyanine complexes were synthesised and studied as electrocatalysts for the detection of catechol. Two of these complexes were derived from a symmetrical benzaldehyde phthalocyanine complex via the condensation of the benzaldehyde substituents with amine reagents. The electrocatalysts proved to be highly stable towards the detection of catechol. The oxidation peaks obtained using cyclic voltammetry range from 0.20 to 0.38 V. Detection limits were obtained via chronoamperometry and are as low as 0.16 µM with fairly high sensitives being obtained. Overall all four copper complexes exhibited excellent electrocatalytic activity towards the electrooxidation of catechol.
- Full Text:
- Date Issued: 2021
- Authors: Ndebele, Nobuhle , Sen, Pinar , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231410 , vital:49885 , xlink:href="https://doi.org/10.1016/j.poly.2021.115518"
- Description: In this study, four new copper phthalocyanine complexes were synthesised and studied as electrocatalysts for the detection of catechol. Two of these complexes were derived from a symmetrical benzaldehyde phthalocyanine complex via the condensation of the benzaldehyde substituents with amine reagents. The electrocatalysts proved to be highly stable towards the detection of catechol. The oxidation peaks obtained using cyclic voltammetry range from 0.20 to 0.38 V. Detection limits were obtained via chronoamperometry and are as low as 0.16 µM with fairly high sensitives being obtained. Overall all four copper complexes exhibited excellent electrocatalytic activity towards the electrooxidation of catechol.
- Full Text:
- Date Issued: 2021
Electrocatalytic detection of l-cysteine using molybdenum POM doped-HKUST-1 metal organic frameworks
- Murinzi, Tafadzwa W, Watkins, Gareth M, Shumba, Munyaradzi, Nyokong, Tebello
- Authors: Murinzi, Tafadzwa W , Watkins, Gareth M , Shumba, Munyaradzi , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185748 , vital:44420 , xlink:href="https://doi.org/10.1080/00958972.2021.1907573"
- Description: Glass carbon electrodes (GCE) were modified with metal organic frameworks (MOFs) containing molybdenum polyoxometallates (Mo POMs) in a copper benzene tricarboxylate framework (HKUST-1). The Mo POMs were introduced via one-pot synthesis (Mo2) and post-synthetic modification (Mo1) techniques. The electrode modifiers were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermal analysis. The modified electrodes’ oxidation capacity toward L-cysteine was studied. Mo POMs significantly improved electron transfer kinetics compared to the bare GCE. The best Mo POM doped electrode (Mo1-GCE) had a catalytic rate constant of 2.2 × 104 M−1 s−1 and a limit of detection of 3.07 × 10−7 M. Under the employed experimental conditions, the detection response for L-cysteine was very fast (within 0.1 s) for all the modified electrodes and selective toward L-cysteine in the presence of other amino acids.
- Full Text:
- Date Issued: 2021
Electrocatalytic detection of l-cysteine using molybdenum POM doped-HKUST-1 metal organic frameworks
- Authors: Murinzi, Tafadzwa W , Watkins, Gareth M , Shumba, Munyaradzi , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185748 , vital:44420 , xlink:href="https://doi.org/10.1080/00958972.2021.1907573"
- Description: Glass carbon electrodes (GCE) were modified with metal organic frameworks (MOFs) containing molybdenum polyoxometallates (Mo POMs) in a copper benzene tricarboxylate framework (HKUST-1). The Mo POMs were introduced via one-pot synthesis (Mo2) and post-synthetic modification (Mo1) techniques. The electrode modifiers were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermal analysis. The modified electrodes’ oxidation capacity toward L-cysteine was studied. Mo POMs significantly improved electron transfer kinetics compared to the bare GCE. The best Mo POM doped electrode (Mo1-GCE) had a catalytic rate constant of 2.2 × 104 M−1 s−1 and a limit of detection of 3.07 × 10−7 M. Under the employed experimental conditions, the detection response for L-cysteine was very fast (within 0.1 s) for all the modified electrodes and selective toward L-cysteine in the presence of other amino acids.
- Full Text:
- Date Issued: 2021
Electrochemical detection of dopamine using phthalocyanine-nitrogen-doped graphene quantum dot conjugates
- Ndebele Nobuhle, Sen, Pinar, Nyokong, Tebello
- Authors: Ndebele Nobuhle , Sen, Pinar , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185724 , vital:44418 , xlink:href="https://doi.org/10.1016/j.jelechem.2021.115111"
- Description: Two cobalt phthalocyanine molecules were synthesized, a symmetrically substituted CoPc (1) and an unsymmetrically substituted CoPc (2). These CoPcs were π-π stacked onto nitrogen-doped graphene quantum dots (NGQDs). The CoPcs, NGQDs and their respective conjugates were used as electro-catalytic probes in the electrochemical oxidation of dopamine. The molecules were adsorbed onto a glassy carbon electrode (GCE) using the drop dry method, the GCE was used to support those catalysts. The electrooxidation of dopamine was studied using cyclic voltammetry and chronoamperometry. An improvement in the sensitivity and limit of detection was observed upon conjugation.
- Full Text:
- Date Issued: 2021
- Authors: Ndebele Nobuhle , Sen, Pinar , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185724 , vital:44418 , xlink:href="https://doi.org/10.1016/j.jelechem.2021.115111"
- Description: Two cobalt phthalocyanine molecules were synthesized, a symmetrically substituted CoPc (1) and an unsymmetrically substituted CoPc (2). These CoPcs were π-π stacked onto nitrogen-doped graphene quantum dots (NGQDs). The CoPcs, NGQDs and their respective conjugates were used as electro-catalytic probes in the electrochemical oxidation of dopamine. The molecules were adsorbed onto a glassy carbon electrode (GCE) using the drop dry method, the GCE was used to support those catalysts. The electrooxidation of dopamine was studied using cyclic voltammetry and chronoamperometry. An improvement in the sensitivity and limit of detection was observed upon conjugation.
- Full Text:
- Date Issued: 2021
Electrochemical Detection of Nitrite on Electrodes Modified by Click Chemistry Using Asymmetrical Co (II) and Mn (III) Phthalocyanines Containing Push-Pull Substituents
- Nkhahle, Reitumetse, Nyokong, Tebello
- Authors: Nkhahle, Reitumetse , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231425 , vital:49886 , xlink:href="https://doi.org/10.1149/1945-7111/ac377f"
- Description: The more conventional route to synthesizing asymmetric push-pull phthalocyanines (Pcs) involves pairing electron-donating substituents with electron-withdrawing groups in either an A3B or AB3 manner. In this work, a push-pull system fashioned from a substituent bearing different functional groups was created. Symmetric and asymmetric cobalt and manganese Pcs in which acetaminophen was the dominant substituent were synthesized where the asymmetric analogues bore an alkyne-terminated substituent. These complexes were applied as sensors towards the electro-oxidation of nitrite. In addition to comparing the asymmetric Pcs to the symmetric counterparts, an assessment on the different central metals as well as the method of electrode modification was made. From the studies performed, the results showed that the manganese complexes are generally better suited (more so when clicked on to the electrode) in the electrocatalysis of nitrite with a limit of detection and a catalytic rate values of 2.15 μM and 6.91 × 106 s−1 M−1 being recorded for the asymmetric MnPc.
- Full Text:
- Date Issued: 2021
- Authors: Nkhahle, Reitumetse , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231425 , vital:49886 , xlink:href="https://doi.org/10.1149/1945-7111/ac377f"
- Description: The more conventional route to synthesizing asymmetric push-pull phthalocyanines (Pcs) involves pairing electron-donating substituents with electron-withdrawing groups in either an A3B or AB3 manner. In this work, a push-pull system fashioned from a substituent bearing different functional groups was created. Symmetric and asymmetric cobalt and manganese Pcs in which acetaminophen was the dominant substituent were synthesized where the asymmetric analogues bore an alkyne-terminated substituent. These complexes were applied as sensors towards the electro-oxidation of nitrite. In addition to comparing the asymmetric Pcs to the symmetric counterparts, an assessment on the different central metals as well as the method of electrode modification was made. From the studies performed, the results showed that the manganese complexes are generally better suited (more so when clicked on to the electrode) in the electrocatalysis of nitrite with a limit of detection and a catalytic rate values of 2.15 μM and 6.91 × 106 s−1 M−1 being recorded for the asymmetric MnPc.
- Full Text:
- Date Issued: 2021
Electrografting of isophthalic acid monolayer and covalent attachment of antibody onto carbon surfaces
- Mwanza, Daniel, Phal, Sereilakhena, Nyokong, Tebello, Tesfalidet, Solomon, Mashazi, Philani N
- Authors: Mwanza, Daniel , Phal, Sereilakhena , Nyokong, Tebello , Tesfalidet, Solomon , Mashazi, Philani N
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231345 , vital:49879 , xlink:href="https://doi.org/10.1016/j.electacta.2021.139360"
- Description: In this study, a 5-diazonium isophthalic acid was synthesized and electrografted onto glassy carbon (GCE) and screen-printed carbon (SPCE) electrodes. SPCE was used to demonstrate fabrication of a miniature device and to compare with conventional glassy carbon electrodes. The isophthalic acid (IPA) electrografted thin film was used for the immobilization of anti-methotrexate antibody (Ab) using carbodiimide activation chemistry to form antibody modified surfaces, GCE-IPA-Ab and SPCE-IPA-Ab. The GCE -IPA-Ab and SPCE-IPA-Ab surfaces were used as capacitive biosensors for the detection of methotrexate (MTX) in phosphate buffer (pH 7.4) using capacitive electrochemical impedance spectroscopy (EIS). The EIS data was analyzed using singular value decomposition (SVD). Principal component regression analysis gave R2 values of 0.99 for both the GCE-IPA-Ab and SPCE-IPA-Ab surfaces. The detection limit from the calibration curve of the GCE-IPA-Ab and SPCE-IPA-Ab was calculated to be 7.0 pmol.L−1 and 5.5 pmol.L−1, respectively.
- Full Text:
- Date Issued: 2021
- Authors: Mwanza, Daniel , Phal, Sereilakhena , Nyokong, Tebello , Tesfalidet, Solomon , Mashazi, Philani N
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231345 , vital:49879 , xlink:href="https://doi.org/10.1016/j.electacta.2021.139360"
- Description: In this study, a 5-diazonium isophthalic acid was synthesized and electrografted onto glassy carbon (GCE) and screen-printed carbon (SPCE) electrodes. SPCE was used to demonstrate fabrication of a miniature device and to compare with conventional glassy carbon electrodes. The isophthalic acid (IPA) electrografted thin film was used for the immobilization of anti-methotrexate antibody (Ab) using carbodiimide activation chemistry to form antibody modified surfaces, GCE-IPA-Ab and SPCE-IPA-Ab. The GCE -IPA-Ab and SPCE-IPA-Ab surfaces were used as capacitive biosensors for the detection of methotrexate (MTX) in phosphate buffer (pH 7.4) using capacitive electrochemical impedance spectroscopy (EIS). The EIS data was analyzed using singular value decomposition (SVD). Principal component regression analysis gave R2 values of 0.99 for both the GCE-IPA-Ab and SPCE-IPA-Ab surfaces. The detection limit from the calibration curve of the GCE-IPA-Ab and SPCE-IPA-Ab was calculated to be 7.0 pmol.L−1 and 5.5 pmol.L−1, respectively.
- Full Text:
- Date Issued: 2021
Enhanced photo-ablation effect of positively charged phthalocyanines-detonation nanodiamonds nanoplatforms for the suppression of Staphylococcus aureus and Escherichia coli planktonic cells and biofilms
- Openda, Yolande I, Nyokong, Tebello
- Authors: Openda, Yolande I , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185712 , vital:44417 , xlink:href="https://doi.org/10.1016/j.jphotochem.2021.113200"
- Description: Photodynamic antimicrobial therapy (PACT) is a powerful technic recommended to eliminate life-threatening pathogens that cause localized and superficial infections as pathogens cannot develop resistance to it. For this reason, new positively charged chalcone substituted zinc (3a) and indium (4a) metalated phthalocyanines (Pcs) were synthesized and were π-π interacted with detonation nanodiamonds (DNDs) nanoparticles to form new water soluble nanoplatfoms 3a@DNDs and 4a@DNDs. The conjugates generated high singlet oxygen quantum yields (ΦΔ) in water (1% DMSO, used for PACT studies) with values of 0.46 and 0.47 for 3a@DNDs and 4a@DNDs, respectively. Hence, they were tested for PACT against biofilms of S. aureus and E. coli, as well as their planktonic cells. The quaternized Pcs alone 3a and 4a as well as their nanoconjugates 3a@DNDs and 4a@DNDs were effective PACT agents with log10 CFU > 9 for E. coli and S. aureus. The quaternized derivatives were found to have higher ability to completely suppress both planktonic and biofilms of S. aureus and E. coli in vitro. Therefore, they could be used as appropriate photosensitive agents.
- Full Text:
- Date Issued: 2021
- Authors: Openda, Yolande I , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185712 , vital:44417 , xlink:href="https://doi.org/10.1016/j.jphotochem.2021.113200"
- Description: Photodynamic antimicrobial therapy (PACT) is a powerful technic recommended to eliminate life-threatening pathogens that cause localized and superficial infections as pathogens cannot develop resistance to it. For this reason, new positively charged chalcone substituted zinc (3a) and indium (4a) metalated phthalocyanines (Pcs) were synthesized and were π-π interacted with detonation nanodiamonds (DNDs) nanoparticles to form new water soluble nanoplatfoms 3a@DNDs and 4a@DNDs. The conjugates generated high singlet oxygen quantum yields (ΦΔ) in water (1% DMSO, used for PACT studies) with values of 0.46 and 0.47 for 3a@DNDs and 4a@DNDs, respectively. Hence, they were tested for PACT against biofilms of S. aureus and E. coli, as well as their planktonic cells. The quaternized Pcs alone 3a and 4a as well as their nanoconjugates 3a@DNDs and 4a@DNDs were effective PACT agents with log10 CFU > 9 for E. coli and S. aureus. The quaternized derivatives were found to have higher ability to completely suppress both planktonic and biofilms of S. aureus and E. coli in vitro. Therefore, they could be used as appropriate photosensitive agents.
- Full Text:
- Date Issued: 2021
Enhanced upconversion emission of Er3+-Yb3+ co-doped Ba5 (PO4) 3OH powder phosphor for application in photodynamic therapy
- Mokoena, Puseletso P, Poluwole, David O, Nyokong, Tebello, Swart, Hendrik C, Ntwaeaborwa, Odireleng M
- Authors: Mokoena, Puseletso P , Poluwole, David O , Nyokong, Tebello , Swart, Hendrik C , Ntwaeaborwa, Odireleng M
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185035 , vital:44318 , xlink:href="https://doi.org/10.1016/j.sna.2021.113014"
- Description: Er3+-Yb3+ co-doped Ba5(PO4)3OH nanoparticle powder phosphors were successfully synthesized by urea combustion method. The resulting powder phosphors were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), high resolution scanning electron microscopy (HRSEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). XRD data confirmed crystallization of pure hexagonal phase of Ba5(PO4)3OH and HRSEM images showed formation of ellipsoidal particles. XPS data combined with EDS analysis confirmed the materials composition that corresponds with identification of all the chemical elements constituting the materials. The in vitro dark cytotoxicity of the particles confirmed lack of cytocidal behaviour in the absence of light, but considerable photodynamic therapy (PDT) activity was observed upon illumination. Upon excitation using a 980 nm laser, multiple emission peaks in the green and red regions corresponding to the optical transitions of Er3+ ion were observed. Upon co-doping with Yb3+, upconverted red emission was detected and this was attributable to non-radiative energy transfer from Yb3+ to Er3+. The proposed mechanism of upconversion photoluminescence is discussed.
- Full Text:
- Date Issued: 2021
- Authors: Mokoena, Puseletso P , Poluwole, David O , Nyokong, Tebello , Swart, Hendrik C , Ntwaeaborwa, Odireleng M
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185035 , vital:44318 , xlink:href="https://doi.org/10.1016/j.sna.2021.113014"
- Description: Er3+-Yb3+ co-doped Ba5(PO4)3OH nanoparticle powder phosphors were successfully synthesized by urea combustion method. The resulting powder phosphors were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), high resolution scanning electron microscopy (HRSEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). XRD data confirmed crystallization of pure hexagonal phase of Ba5(PO4)3OH and HRSEM images showed formation of ellipsoidal particles. XPS data combined with EDS analysis confirmed the materials composition that corresponds with identification of all the chemical elements constituting the materials. The in vitro dark cytotoxicity of the particles confirmed lack of cytocidal behaviour in the absence of light, but considerable photodynamic therapy (PDT) activity was observed upon illumination. Upon excitation using a 980 nm laser, multiple emission peaks in the green and red regions corresponding to the optical transitions of Er3+ ion were observed. Upon co-doping with Yb3+, upconverted red emission was detected and this was attributable to non-radiative energy transfer from Yb3+ to Er3+. The proposed mechanism of upconversion photoluminescence is discussed.
- Full Text:
- Date Issued: 2021
Folic acid-modified phthalocyanine-nanozyme loaded liposomes for targeted photodynamic therapy
- Nwahara, Nnamdi, Abrahams, Garth, Prinsloo, Earl, Nyokong, Tebello
- Authors: Nwahara, Nnamdi , Abrahams, Garth , Prinsloo, Earl , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231369 , vital:49881 , xlink:href="https://doi.org/10.1016/j.pdpdt.2021.102527"
- Description: The hypoxic tumour microenvironment and poor spatiotemporal localization of photosensitizers are two significant obstacles that limit practical applications of photodynamic therapy. In response, a biocompatible, light-activatable liposome integrated with both a zinc phthalocyanine photodynamic component and Pt nanoparticles-decorated with MnO2 catalase-mimicking component are engineered. This multifunctional system was rationally designed using unsaturated phospholipids to achieve on-demand drug release following light irradiation. Specificity was achieved by folic acid functionalization resulting in folate-modified liposomes (FTLiposomes). We demonstrated its specific uptake by fluorescence imaging using folate receptor (FR) overexpressing HeLa and MCF-7 cells as in vitro models. This multifunctional liposome exhibits superior hypoxic anti-tumour effects and holds the potential to reduce side effects associated with untargeted therapy. Fluorescence of the constituent ZnPc and folate-receptor targeting could enable tracking and permit spatiotemporal regulation for improved cancer treatment.
- Full Text:
- Date Issued: 2021
- Authors: Nwahara, Nnamdi , Abrahams, Garth , Prinsloo, Earl , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231369 , vital:49881 , xlink:href="https://doi.org/10.1016/j.pdpdt.2021.102527"
- Description: The hypoxic tumour microenvironment and poor spatiotemporal localization of photosensitizers are two significant obstacles that limit practical applications of photodynamic therapy. In response, a biocompatible, light-activatable liposome integrated with both a zinc phthalocyanine photodynamic component and Pt nanoparticles-decorated with MnO2 catalase-mimicking component are engineered. This multifunctional system was rationally designed using unsaturated phospholipids to achieve on-demand drug release following light irradiation. Specificity was achieved by folic acid functionalization resulting in folate-modified liposomes (FTLiposomes). We demonstrated its specific uptake by fluorescence imaging using folate receptor (FR) overexpressing HeLa and MCF-7 cells as in vitro models. This multifunctional liposome exhibits superior hypoxic anti-tumour effects and holds the potential to reduce side effects associated with untargeted therapy. Fluorescence of the constituent ZnPc and folate-receptor targeting could enable tracking and permit spatiotemporal regulation for improved cancer treatment.
- Full Text:
- Date Issued: 2021
Impact of axial ligation on photophysical and photodynamic antimicrobial properties of indium (III) methylsulfanylphenyl porphyrin complexes linked to silver-capped copper ferrite magnetic nanoparticles
- Makola, Collen L, Nyokong, Tebello, Amuhaya, Edith K
- Authors: Makola, Collen L , Nyokong, Tebello , Amuhaya, Edith K
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185942 , vital:44450 , xlink:href="https://doi.org/10.1016/j.poly.2020.114882"
- Description: Photodynamic antimicrobial chemotherapy (PACT) is a well-known technique used against bacteria that have developed resistance towards antibiotics. We herein report the synthesis, photophysical properties, and PACT activity of 2-hydroxypyridine axial ligated indium 5,10,15,20-tetrakis-(4-phenylmethylthio) porphyrin (3) and quaternized 2-hydroxypyridine axial ligated indium 5,10,15,20-tetrakis-(4-phenylmethylthio) porphyrin (4). The porphyrin complexes (3 and 4) were further linked to oleyamine (OLM)/oleic acid (OLA) capped Ag/CuFe2O4 and also 6-mercapto-1-hexanol functionalized (MCH-Ag/CuFe2O4) nanoparticles through silver - sulphur (Ag-S) and silver-nitrogen (Ag-N); self-assembly. The PACT studies were carried out using Staphylococcus aureus. While all the synthesized porphyrins demonstrated PACT activity, the quaternized complex and its conjugate showed the highest PACT activity with 0% cell viability after irradiation for 25 min, resulting in a log reduction of 8.31.
- Full Text:
- Date Issued: 2021
- Authors: Makola, Collen L , Nyokong, Tebello , Amuhaya, Edith K
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185942 , vital:44450 , xlink:href="https://doi.org/10.1016/j.poly.2020.114882"
- Description: Photodynamic antimicrobial chemotherapy (PACT) is a well-known technique used against bacteria that have developed resistance towards antibiotics. We herein report the synthesis, photophysical properties, and PACT activity of 2-hydroxypyridine axial ligated indium 5,10,15,20-tetrakis-(4-phenylmethylthio) porphyrin (3) and quaternized 2-hydroxypyridine axial ligated indium 5,10,15,20-tetrakis-(4-phenylmethylthio) porphyrin (4). The porphyrin complexes (3 and 4) were further linked to oleyamine (OLM)/oleic acid (OLA) capped Ag/CuFe2O4 and also 6-mercapto-1-hexanol functionalized (MCH-Ag/CuFe2O4) nanoparticles through silver - sulphur (Ag-S) and silver-nitrogen (Ag-N); self-assembly. The PACT studies were carried out using Staphylococcus aureus. While all the synthesized porphyrins demonstrated PACT activity, the quaternized complex and its conjugate showed the highest PACT activity with 0% cell viability after irradiation for 25 min, resulting in a log reduction of 8.31.
- Full Text:
- Date Issued: 2021
Modulation of the optical properties of chiral porphyrin dimers by introducing bridged chiral amide-bonds
- Qin, Mingfeng, Zhang, Zhen, Zhu, Weihua, Mack, John, Soy, Rodah C, Nyokong, Tebello, Liang, Xu
- Authors: Qin, Mingfeng , Zhang, Zhen , Zhu, Weihua , Mack, John , Soy, Rodah C , Nyokong, Tebello , Liang, Xu
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190815 , vital:45031 , xlink:href="https://doi.org/10.1142/S1088424620500492"
- Description: The d/l-enantiomers of a series of three Zn(II)tetraarylporphyrin dimers were synthesized and isolated by incorporating a bridging amide-bonded xanthene moiety at the para-position of one of the meso-aryl rings. The electronic structures and optical properties were modulated by incorporating chiral amino acid moieties into the amide-bonding moieties of the xanthene bridge that contain methyl, tolyl and 2-methylindole substituents. A cofacial dimer was formed in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) resulting in a significant red shift of the B band, due to a relative destabilization of the HOMO, which has large MO coefficients on the pyrrole nitrogens. The sign sequences observed in the B band region of the CD spectra due to the presence of the chiral amino acid moieties were modified due to this change in geometry. Significant CD intensity is also observed in the B band region of the CD spectra of anion radical species during in situ spectroelectrochemical measurements.
- Full Text:
- Date Issued: 2021
- Authors: Qin, Mingfeng , Zhang, Zhen , Zhu, Weihua , Mack, John , Soy, Rodah C , Nyokong, Tebello , Liang, Xu
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190815 , vital:45031 , xlink:href="https://doi.org/10.1142/S1088424620500492"
- Description: The d/l-enantiomers of a series of three Zn(II)tetraarylporphyrin dimers were synthesized and isolated by incorporating a bridging amide-bonded xanthene moiety at the para-position of one of the meso-aryl rings. The electronic structures and optical properties were modulated by incorporating chiral amino acid moieties into the amide-bonding moieties of the xanthene bridge that contain methyl, tolyl and 2-methylindole substituents. A cofacial dimer was formed in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) resulting in a significant red shift of the B band, due to a relative destabilization of the HOMO, which has large MO coefficients on the pyrrole nitrogens. The sign sequences observed in the B band region of the CD spectra due to the presence of the chiral amino acid moieties were modified due to this change in geometry. Significant CD intensity is also observed in the B band region of the CD spectra of anion radical species during in situ spectroelectrochemical measurements.
- Full Text:
- Date Issued: 2021
Naked Eye and Colorimetric Detection of Cyanide with a 1, 3‐Diethyl‐2‐thiobarbituric Acid Substituted Ferrocene Chemosensor
- Babu, Balaji, Mack, John, Nyokong, Tebello
- Authors: Babu, Balaji , Mack, John , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190567 , vital:45006 , xlink:href="https://doi.org/10.1002/slct.202100163"
- Description: A 1,3-diethyl-2-thiobarbituric-acid-substituted ferrocene (FET) has been evaluated for its cyanide sensing ability by UV-visible absorption spectroscopy and other characterization methods. FET provides a ratiometric colorimetric chemosensor for the CN− anion detection in 1 : 1 DMSO/H2O (v/v) solution. The addition of CN− results in an immediate color change from dark blue to pale orange that is visible to the naked eye. Mechanism studies and molecular modelling with TD-DFT calculations demonstrate that nucleophilic addition of CN− to an electrophilic sp2-hybridized carbon atom blocks charge transfer from the ferrocene ring complex to the thiobarbituric acid moiety. The FET sensor exhibits excellent selectivity for CN− and a limit of detection of 0.2 μM.
- Full Text:
- Date Issued: 2021
- Authors: Babu, Balaji , Mack, John , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190567 , vital:45006 , xlink:href="https://doi.org/10.1002/slct.202100163"
- Description: A 1,3-diethyl-2-thiobarbituric-acid-substituted ferrocene (FET) has been evaluated for its cyanide sensing ability by UV-visible absorption spectroscopy and other characterization methods. FET provides a ratiometric colorimetric chemosensor for the CN− anion detection in 1 : 1 DMSO/H2O (v/v) solution. The addition of CN− results in an immediate color change from dark blue to pale orange that is visible to the naked eye. Mechanism studies and molecular modelling with TD-DFT calculations demonstrate that nucleophilic addition of CN− to an electrophilic sp2-hybridized carbon atom blocks charge transfer from the ferrocene ring complex to the thiobarbituric acid moiety. The FET sensor exhibits excellent selectivity for CN− and a limit of detection of 0.2 μM.
- Full Text:
- Date Issued: 2021
Nanohybrid electrocatalyst based on cobalt phthalocyanine-carbon nanotube-reduced graphene oxide for ultrasensitive detection of glucose in human saliva
- Adeniyi, Omotayo, Nwahara, Nnamdi, Mwanza, Daniel, Nyokong, Tebello, Mashazi, Philani N
- Authors: Adeniyi, Omotayo , Nwahara, Nnamdi , Mwanza, Daniel , Nyokong, Tebello , Mashazi, Philani N
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231356 , vital:49880 , xlink:href="https://doi.org/10.1016/j.snb.2021.130723"
- Description: The current diabetes management systems require collecting blood samples via an invasive and painful finger pricking leading to the formation of callus, scarring and loss of sensibility to patients due to continuous monitoring. Therefore, a non-invasive and painless method of determining glucose levels would be desirable to diabetes patients who need constant monitoring. Saliva glucose measurement is a non-invasive alternative for diabetes management. A highly sensitive, stable, and selective non-enzymatic electrochemical sensor that can accurately quantify saliva glucose is required. A single-walled carbon nanotube/reduced graphene oxide/cobalt phthalocyanines nanohybrid modified glassy carbon electrode (GCE-SWCNT/rGO/CoPc) has been fabricated for the non-enzymatic determination of glucose in human saliva. The SWCNT/rGO/CoPc was characterized using various spectroscopic, microscopic, and electrochemical techniques. The synergistic effect between SWCNT, rGO, and CoPc facilitated excellent electron transfer process that improved the sensor sensitivity. The GCE-SWCNT/rGO/CoPc sensor exhibited two linear responses in the 0.30 μM to 0.50 mM and 0.50–5.0 mM glucose concentration ranges, and the detection limit was 0.12 μM. The sensor had an excellent saliva glucose detection sensitivity of 992.4 μA·mM−1·cm−2 and high specificity for glucose in the presence of other coexisting analytes. In addition, it showed good storage stability, reusability, and a fast response time of about 1.2 s. The GCE-SWCNT/rGO/CoPc nanohybrid electrode showed excellent potential for developing accurate, non-invasive, and painless glucose sensing.
- Full Text:
- Date Issued: 2021
- Authors: Adeniyi, Omotayo , Nwahara, Nnamdi , Mwanza, Daniel , Nyokong, Tebello , Mashazi, Philani N
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231356 , vital:49880 , xlink:href="https://doi.org/10.1016/j.snb.2021.130723"
- Description: The current diabetes management systems require collecting blood samples via an invasive and painful finger pricking leading to the formation of callus, scarring and loss of sensibility to patients due to continuous monitoring. Therefore, a non-invasive and painless method of determining glucose levels would be desirable to diabetes patients who need constant monitoring. Saliva glucose measurement is a non-invasive alternative for diabetes management. A highly sensitive, stable, and selective non-enzymatic electrochemical sensor that can accurately quantify saliva glucose is required. A single-walled carbon nanotube/reduced graphene oxide/cobalt phthalocyanines nanohybrid modified glassy carbon electrode (GCE-SWCNT/rGO/CoPc) has been fabricated for the non-enzymatic determination of glucose in human saliva. The SWCNT/rGO/CoPc was characterized using various spectroscopic, microscopic, and electrochemical techniques. The synergistic effect between SWCNT, rGO, and CoPc facilitated excellent electron transfer process that improved the sensor sensitivity. The GCE-SWCNT/rGO/CoPc sensor exhibited two linear responses in the 0.30 μM to 0.50 mM and 0.50–5.0 mM glucose concentration ranges, and the detection limit was 0.12 μM. The sensor had an excellent saliva glucose detection sensitivity of 992.4 μA·mM−1·cm−2 and high specificity for glucose in the presence of other coexisting analytes. In addition, it showed good storage stability, reusability, and a fast response time of about 1.2 s. The GCE-SWCNT/rGO/CoPc nanohybrid electrode showed excellent potential for developing accurate, non-invasive, and painless glucose sensing.
- Full Text:
- Date Issued: 2021
Overcoming hurdles facing researchers in Africa
- Nyokong, Tebello, Ngoy, Bokolombe P, Amuhaya, Edith K
- Authors: Nyokong, Tebello , Ngoy, Bokolombe P , Amuhaya, Edith K
- Date: 2021
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/177511 , vital:42828 , https://doi.org/10.1038/s41563-021-00961-0
- Description: Several countries on the African continent recognize that a transition to a knowledge-based economic model would stimulate growth and enable scientific independence. Investing in new knowledge would drive the formation of highly qualified professionals and the use of advanced technologies, triggering in return positive economic trends. Importantly, a knowledge-based economy that values the impact of science on society would help reversing the migration of skilled workers and lead to brain gain.
- Full Text:
- Date Issued: 2021
- Authors: Nyokong, Tebello , Ngoy, Bokolombe P , Amuhaya, Edith K
- Date: 2021
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/177511 , vital:42828 , https://doi.org/10.1038/s41563-021-00961-0
- Description: Several countries on the African continent recognize that a transition to a knowledge-based economic model would stimulate growth and enable scientific independence. Investing in new knowledge would drive the formation of highly qualified professionals and the use of advanced technologies, triggering in return positive economic trends. Importantly, a knowledge-based economy that values the impact of science on society would help reversing the migration of skilled workers and lead to brain gain.
- Full Text:
- Date Issued: 2021
Photo-sonodynamic combination activity of cationic morpholino-phthalocyanines conjugated to nitrogen and nitrogen-sulfur doped graphene quantum dots against MCF-7 breast cancer cell line in vitro
- Nene, Lindokhule Cindy, Nyokong, Tebello
- Authors: Nene, Lindokhule Cindy , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231334 , vital:49878 , xlink:href="https://doi.org/10.1016/j.pdpdt.2021.102573"
- Description: In this work, we explore the reactive oxygen species (ROS) generation abilities of cationic morpholino-substituted-phthalocyanine (Pc) conjugated to nitrogen (NGQDs) and nitrogen-sulfur (NSGQDs) doped-graphene quantum dots upon irradiation with light for photodynamic therapy (PDT), ultrasound for sonodynamic therapy (SDT) and the combination of both in photo-sonodynamic therapy (PSDT). The in vitro cytotoxicity studies were conducted using the Michigan Cancer Foundation-7 breast cancer cell lines (MCF-7 cells). For PDT treatments, only the 1O2 was detected for all the sensitizers, whereas both the 1O2 and •OH radicals were evident after SDT and PSDT treatments. An increase in the 1O2 generation was observed for the conjugates compared to the GQDs and the Pc alone. However, the •OH radicals were reduced in the conjugates compared to the GQDs and the Pc alone. The NGQDs generally showed better ROS generation efficacy compared to the NSGQDs, alone and in the conjugates. The combination therapy also shows improved efficacy compared to the monotherapies for the Pcs and Pc-GQDs conjugates.
- Full Text:
- Date Issued: 2021
- Authors: Nene, Lindokhule Cindy , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231334 , vital:49878 , xlink:href="https://doi.org/10.1016/j.pdpdt.2021.102573"
- Description: In this work, we explore the reactive oxygen species (ROS) generation abilities of cationic morpholino-substituted-phthalocyanine (Pc) conjugated to nitrogen (NGQDs) and nitrogen-sulfur (NSGQDs) doped-graphene quantum dots upon irradiation with light for photodynamic therapy (PDT), ultrasound for sonodynamic therapy (SDT) and the combination of both in photo-sonodynamic therapy (PSDT). The in vitro cytotoxicity studies were conducted using the Michigan Cancer Foundation-7 breast cancer cell lines (MCF-7 cells). For PDT treatments, only the 1O2 was detected for all the sensitizers, whereas both the 1O2 and •OH radicals were evident after SDT and PSDT treatments. An increase in the 1O2 generation was observed for the conjugates compared to the GQDs and the Pc alone. However, the •OH radicals were reduced in the conjugates compared to the GQDs and the Pc alone. The NGQDs generally showed better ROS generation efficacy compared to the NSGQDs, alone and in the conjugates. The combination therapy also shows improved efficacy compared to the monotherapies for the Pcs and Pc-GQDs conjugates.
- 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
Photocatalytic desulfurization of dibenzothiophene using asymmetrical zinc (II) phthalocyanines conjugated to silver-magnetic nanoparticles
- 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/10962/185953 , vital:44451 , xlink:href="https://doi.org/10.1016/j.ica.2020.119970"
- Description: Asymmetrical Zn(II) phthalocyanines: mono (4-carboxy phenoxy) tris (phenylazo phenoxy) (1), mono (4-amino phenoxy) tris (phenylazo phenoxy) (2), mono (4-propanoic acid phenoxy) tris (phenylazo phenoxy) (3) zinc(II) phthalocyanines are synthesized and covalently linked to mercaptohexanol (mph) or mercaptopropionic acid (mpa) functionalized dimerized silver-magnetic nanoparticles (Ag-M). Complexes 1 and 3 are covalently linked to nanomaterials via ester bond whereas complex 2 is covalently linked to nanoparticles (NPs) via amide bond. The conjugates of complexes 1–3 with NPs gave higher singlet oxygen quantum than the Pcs alone. Electrospun fibers were fabricated from polystyrene (PS) solutions containing complexes 1 to 3 and their conjugates. The functionalized PS fibers were used for the phototransformation of dibenzothiophene. The increase in photocatalytic properties of phthalocyanines was observed in the presence of Ag-M with 3 alone and its conjugate with mph capped silver-magnetic nanoparticles showing the larger catalytic activity towards the transformation of dibenzothiophene.
- 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/10962/185953 , vital:44451 , xlink:href="https://doi.org/10.1016/j.ica.2020.119970"
- Description: Asymmetrical Zn(II) phthalocyanines: mono (4-carboxy phenoxy) tris (phenylazo phenoxy) (1), mono (4-amino phenoxy) tris (phenylazo phenoxy) (2), mono (4-propanoic acid phenoxy) tris (phenylazo phenoxy) (3) zinc(II) phthalocyanines are synthesized and covalently linked to mercaptohexanol (mph) or mercaptopropionic acid (mpa) functionalized dimerized silver-magnetic nanoparticles (Ag-M). Complexes 1 and 3 are covalently linked to nanomaterials via ester bond whereas complex 2 is covalently linked to nanoparticles (NPs) via amide bond. The conjugates of complexes 1–3 with NPs gave higher singlet oxygen quantum than the Pcs alone. Electrospun fibers were fabricated from polystyrene (PS) solutions containing complexes 1 to 3 and their conjugates. The functionalized PS fibers were used for the phototransformation of dibenzothiophene. The increase in photocatalytic properties of phthalocyanines was observed in the presence of Ag-M with 3 alone and its conjugate with mph capped silver-magnetic nanoparticles showing the larger catalytic activity towards the transformation of dibenzothiophene.
- Full Text:
- Date Issued: 2021
Photocatalytic desulfurization of dibenzothiophene using methoxy substituted asymmetrical zinc (II) phthalocyanines conjugated to metal tungstate nanomaterials
- Mgidlana, Sithi, Nwahara, Nnamdi, Nyokong, Tebello
- Authors: Mgidlana, Sithi , Nwahara, Nnamdi , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185760 , vital:44421 , xlink:href="https://doi.org/10.1016/j.poly.2021.115053"
- Description: We report on the syntheses of three asymmetrical zinc(II) phthalocyanine endowed with benzoic acid, phenylpropanoic acid, and phenylacetic acid units: (1), (2), and (3), respectively. Metal tungstate nanoparticles, capped with glutathione were prepared and characterized using analytical techniques. Complexes were covalently linked to nickel tungstate (NiWO4) and bismuth tungstate (Bi2WO6) through an amide bond. The complexes and the conjugates with nanomaterial were evaluated for singlet oxygen generating ability. Complexes 1–2 and their conjugates generate higher singlet oxygen compared to 3 and its corresponding conjugates. The conjugates show degradation of dibenzothiophene (DBT) in fuel with shorter half-lives and greater initial rate values compared to phthalocyanines alone.
- Full Text:
- Date Issued: 2021
- Authors: Mgidlana, Sithi , Nwahara, Nnamdi , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185760 , vital:44421 , xlink:href="https://doi.org/10.1016/j.poly.2021.115053"
- Description: We report on the syntheses of three asymmetrical zinc(II) phthalocyanine endowed with benzoic acid, phenylpropanoic acid, and phenylacetic acid units: (1), (2), and (3), respectively. Metal tungstate nanoparticles, capped with glutathione were prepared and characterized using analytical techniques. Complexes were covalently linked to nickel tungstate (NiWO4) and bismuth tungstate (Bi2WO6) through an amide bond. The complexes and the conjugates with nanomaterial were evaluated for singlet oxygen generating ability. Complexes 1–2 and their conjugates generate higher singlet oxygen compared to 3 and its corresponding conjugates. The conjugates show degradation of dibenzothiophene (DBT) in fuel with shorter half-lives and greater initial rate values compared to phthalocyanines alone.
- Full Text:
- Date Issued: 2021
Photocytotoxicity of heavy-atom-free thiobarbituric acid functionalized pyrene derivatives against MCF-7 cancer cells
- Babu, Balaji, Ali, Thaslima A, Ochappan, Thivagar, Mack, John, Nyokong, Tebello, Sethuraman, Mathur G
- Authors: Babu, Balaji , Ali, Thaslima A , Ochappan, Thivagar , Mack, John , Nyokong, Tebello , Sethuraman, Mathur G
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190556 , vital:45005 , xlink:href="https://doi.org/10.1016/j.pdpdt.2020.102102"
- Description: Two thiobarbituric acid-functionalized pyrene derivatives (P1, P2) have been synthesized to explore the photophysical properties and photodynamic activity of dyes of this type. Both compounds exhibit an intense intramolecular charge transfer (ICT) band at ca. 470 nm, which is absent in the spectra of the precursor. P1 and P2 exhibit singlet oxygen generation on irradiation with light with moderate singlet oxygen yields of 0.36 and 0.32, respectively, in DMSO. P1 showed better photodynamic activity against MCF-7 cells with an IC50 value of 18.3 μM under illumination at 455 nm for 60 min with a Thorlabs M455L3 LED (330 mW.cm−2).
- Full Text:
- Date Issued: 2021
- Authors: Babu, Balaji , Ali, Thaslima A , Ochappan, Thivagar , Mack, John , Nyokong, Tebello , Sethuraman, Mathur G
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190556 , vital:45005 , xlink:href="https://doi.org/10.1016/j.pdpdt.2020.102102"
- Description: Two thiobarbituric acid-functionalized pyrene derivatives (P1, P2) have been synthesized to explore the photophysical properties and photodynamic activity of dyes of this type. Both compounds exhibit an intense intramolecular charge transfer (ICT) band at ca. 470 nm, which is absent in the spectra of the precursor. P1 and P2 exhibit singlet oxygen generation on irradiation with light with moderate singlet oxygen yields of 0.36 and 0.32, respectively, in DMSO. P1 showed better photodynamic activity against MCF-7 cells with an IC50 value of 18.3 μM under illumination at 455 nm for 60 min with a Thorlabs M455L3 LED (330 mW.cm−2).
- Full Text:
- Date Issued: 2021