Fabrication of electrospun fibers from a porphyrin linked to polyacrylonitrile polymer for photocatalytic transformation of phenols
- Jones, Ben, Mafukidze, Donovan M, Nyokong, Tebello
- Authors: Jones, Ben , Mafukidze, Donovan M , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186196 , vital:44472 , xlink:href="https://doi.org/10.1016/j.molstruc.2020.128191"
- Description: A novel mono-porphyrin (2) was employed for the photodegradation of 4-chlorophenol and 4-n-nonylphenol at pH 10.60. A partially modified polyacrylonitrile (PAN) polymer was utilized only as a support system for the photosensitiser to allow the formation of a covalent linkage. Complex 2 showed singlet oxygen values of 0.70 in dimethyl formamide and when conjugated (2-PAN) showed 0.39 in water. When employed against 4-chlorophenol a degradation efficiency (η) of 29.1% was achieved at 0.20 mol L−1 over a period of 10 min. When employed against 4-n-nonylphenol we obtained a η of 26.7% at 0.17 mol L−1 over a period of 10 min.
- Full Text:
- Date Issued: 2020
- Authors: Jones, Ben , Mafukidze, Donovan M , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186196 , vital:44472 , xlink:href="https://doi.org/10.1016/j.molstruc.2020.128191"
- Description: A novel mono-porphyrin (2) was employed for the photodegradation of 4-chlorophenol and 4-n-nonylphenol at pH 10.60. A partially modified polyacrylonitrile (PAN) polymer was utilized only as a support system for the photosensitiser to allow the formation of a covalent linkage. Complex 2 showed singlet oxygen values of 0.70 in dimethyl formamide and when conjugated (2-PAN) showed 0.39 in water. When employed against 4-chlorophenol a degradation efficiency (η) of 29.1% was achieved at 0.20 mol L−1 over a period of 10 min. When employed against 4-n-nonylphenol we obtained a η of 26.7% at 0.17 mol L−1 over a period of 10 min.
- Full Text:
- Date Issued: 2020
Fucoidan from Ecklonia maxima is a powerful inhibitor of the diabetes-related enzyme, Éø-glucosidase
- Daub, Chantal D, Mabate, Blessing, Malgas, Samkelo, Pletschke, Brett I
- Authors: Daub, Chantal D , Mabate, Blessing , Malgas, Samkelo , Pletschke, Brett I
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/425982 , vital:72304 , xlink:href="https://doi.org/10.1016/j.ijbiomac.2020.02.161"
- Description: Ecklonia maxima, an endemic South African seaweed, is a potential source of beneficial bioactive compounds. Among these compounds, fucoidan, a sulphated polysaccharide has a wide range of bioactivities including anti-diabetic activity. In this study, fucoidan was extracted from E. maxima by the hot water extraction method and then characterised by colorimetric assays for sugar composition. The extraction from E. maxima yielded 6.89% fucoidan which was found to contain 4.45 ± 0.25% L-fucose and 6.01 ± 0.53% sulphate. The water extracted E. maxima fucoidan had a low molecular weight of approximately 10 kDa. Structural studies (FT-IR, NMR and XRD) confirmed the structure and integrity of the fucoidan to be similar to previously studied fucoidans in literature. Finally, the activities of starch digestive enzymes; α-amylase and α-glucosidase, were investigated in the presence of the E. maxima fucoidan extract. Fucoidan from E. maxima was observed to be a potent mixed-type inhibitor of α-glucosidase with an IC50 range of 0.27–0.31 mg.ml-1, which was significantly lower than the commercial anti-diabetic standard, acarbose. Our present study demonstrated that fucoidan from E. maxima is a more powerful inhibitor compared to some standard anti-diabetic compounds and thus shows great potential for managing type 2 diabetes.
- Full Text:
- Date Issued: 2020
Fucoidan from Ecklonia maxima is a powerful inhibitor of the diabetes-related enzyme, Éø-glucosidase
- Authors: Daub, Chantal D , Mabate, Blessing , Malgas, Samkelo , Pletschke, Brett I
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/425982 , vital:72304 , xlink:href="https://doi.org/10.1016/j.ijbiomac.2020.02.161"
- Description: Ecklonia maxima, an endemic South African seaweed, is a potential source of beneficial bioactive compounds. Among these compounds, fucoidan, a sulphated polysaccharide has a wide range of bioactivities including anti-diabetic activity. In this study, fucoidan was extracted from E. maxima by the hot water extraction method and then characterised by colorimetric assays for sugar composition. The extraction from E. maxima yielded 6.89% fucoidan which was found to contain 4.45 ± 0.25% L-fucose and 6.01 ± 0.53% sulphate. The water extracted E. maxima fucoidan had a low molecular weight of approximately 10 kDa. Structural studies (FT-IR, NMR and XRD) confirmed the structure and integrity of the fucoidan to be similar to previously studied fucoidans in literature. Finally, the activities of starch digestive enzymes; α-amylase and α-glucosidase, were investigated in the presence of the E. maxima fucoidan extract. Fucoidan from E. maxima was observed to be a potent mixed-type inhibitor of α-glucosidase with an IC50 range of 0.27–0.31 mg.ml-1, which was significantly lower than the commercial anti-diabetic standard, acarbose. Our present study demonstrated that fucoidan from E. maxima is a more powerful inhibitor compared to some standard anti-diabetic compounds and thus shows great potential for managing type 2 diabetes.
- Full Text:
- Date Issued: 2020
Genetic diversity and morphological variation in African boxthorn (Lycium ferocissimum)–characterising the target weed for biological control
- McCulloch, Graham A, Mauda, Evans V, Chari, L D, Martin, Grant D, Gurdasani, Komal, Morin, L, Walter, G H, Raghu, S
- Authors: McCulloch, Graham A , Mauda, Evans V , Chari, L D , Martin, Grant D , Gurdasani, Komal , Morin, L , Walter, G H , Raghu, S
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423474 , vital:72064 , xlink:href="https://doi.org/10.1016/j.biocontrol.2020.104206"
- Description: Lycium ferocissimum (African boxthorn) is a Weed of National Significance in Australia. Biological control may have potential to manage this weed, but taxonomic uncertainty needs to be addressed first to facilitate searches for potential agents. We sampled putative L. ferocissimum (i.e. tentatively identified morphologically in the field) across its native range in South Africa and introduced range in Australia. Morphometric and genetic analyses were conducted to confirm the species identity of these samples, and to assess morphological and genetic variation across both ranges. All samples collected in Australia were confirmed as L. ferocissimum, with no evidence of hybridisation with any other Lycium species. Nuclear and chloroplast genetic diversity within L. ferocissimum across both South Africa and Australia was low, with no evidence of genetic structure. One of the two common chloroplast haplotypes found across Australia was found at only two sites in South Africa, both near Cape Town, suggesting that the Australian lineage may have originated from this region. Ten samples from South Africa putatively identified in the field as L. ferocissimum were genetically characterised as different (unidentified) Lycium species. Our morphometric analyses across different Lycium species in South Africa did not identify any leaf or floral characteristics unique to L. ferocissimum, and thus morphological identification of the latter species in its native range may remain problematic. To ensure the correct Lycium species is surveyed for candidate biological control agents we suggest that individuals should be permanently tagged and putative morphological determinations supplemented with genetic analyses to confirm species identity.
- Full Text:
- Date Issued: 2020
- Authors: McCulloch, Graham A , Mauda, Evans V , Chari, L D , Martin, Grant D , Gurdasani, Komal , Morin, L , Walter, G H , Raghu, S
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423474 , vital:72064 , xlink:href="https://doi.org/10.1016/j.biocontrol.2020.104206"
- Description: Lycium ferocissimum (African boxthorn) is a Weed of National Significance in Australia. Biological control may have potential to manage this weed, but taxonomic uncertainty needs to be addressed first to facilitate searches for potential agents. We sampled putative L. ferocissimum (i.e. tentatively identified morphologically in the field) across its native range in South Africa and introduced range in Australia. Morphometric and genetic analyses were conducted to confirm the species identity of these samples, and to assess morphological and genetic variation across both ranges. All samples collected in Australia were confirmed as L. ferocissimum, with no evidence of hybridisation with any other Lycium species. Nuclear and chloroplast genetic diversity within L. ferocissimum across both South Africa and Australia was low, with no evidence of genetic structure. One of the two common chloroplast haplotypes found across Australia was found at only two sites in South Africa, both near Cape Town, suggesting that the Australian lineage may have originated from this region. Ten samples from South Africa putatively identified in the field as L. ferocissimum were genetically characterised as different (unidentified) Lycium species. Our morphometric analyses across different Lycium species in South Africa did not identify any leaf or floral characteristics unique to L. ferocissimum, and thus morphological identification of the latter species in its native range may remain problematic. To ensure the correct Lycium species is surveyed for candidate biological control agents we suggest that individuals should be permanently tagged and putative morphological determinations supplemented with genetic analyses to confirm species identity.
- Full Text:
- Date Issued: 2020
Green synthesis of antimicrobial silver nanoparticles using aqueous leaf extracts from three Congolese plant species (Brillantaisia patula, Crossopteryx febrifuga and Senna siamea)
- Kambale, Espoir K, Nkanga, Christian I, Mutonkole, Blaise-Pascal I, Bapolisi, Alain M, Tassa, Daniel O, Liesse, Jean-Marie I, Krause, Rui W M, Memvanga, Patrick B
- Authors: Kambale, Espoir K , Nkanga, Christian I , Mutonkole, Blaise-Pascal I , Bapolisi, Alain M , Tassa, Daniel O , Liesse, Jean-Marie I , Krause, Rui W M , Memvanga, Patrick B
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193419 , vital:45330 , xlink:href="https://doi.org/10.1016/j.heliyon.2020.e04493"
- Description: In the present study, silver nanoparticles (AgNPs) were synthesized using aqueous leaf extracts of three Congolese plant species, namely Brillantaisia patula (BR-PA), Crossopteryx febrifuga (CR-FE) and Senna siamea (SE-SI). The obtained AgNPs were studied for their optical, structural, surface morphological and antibacterial properties. The prepared AgNPs were characterized by using UV-Visible spectra, Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray spectroscopy (EDX) and X-ray diffractometer (XRD). The synthesized nanoparticles were spherical shaped and well-dispersed with average sizes ranging from 45 to 110 nm. The AgNPs derived from BR-PA, CR-FE and SE-SI exhibited higher antibacterial activity against three bacterial pathogens of the human skin compared to their respective crude extracts and AgNO3. This indicated that the biomolecules covering the nanoparticles may enhance the biological activity of metal nanoparticles. Hence, our results support that biogenic synthesis of AgNPs from Congolese plants constitutes a potential area of interest for the therapeutic management of microbial diseases such as infectious skin diseases.
- Full Text:
- Date Issued: 2020
- Authors: Kambale, Espoir K , Nkanga, Christian I , Mutonkole, Blaise-Pascal I , Bapolisi, Alain M , Tassa, Daniel O , Liesse, Jean-Marie I , Krause, Rui W M , Memvanga, Patrick B
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193419 , vital:45330 , xlink:href="https://doi.org/10.1016/j.heliyon.2020.e04493"
- Description: In the present study, silver nanoparticles (AgNPs) were synthesized using aqueous leaf extracts of three Congolese plant species, namely Brillantaisia patula (BR-PA), Crossopteryx febrifuga (CR-FE) and Senna siamea (SE-SI). The obtained AgNPs were studied for their optical, structural, surface morphological and antibacterial properties. The prepared AgNPs were characterized by using UV-Visible spectra, Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray spectroscopy (EDX) and X-ray diffractometer (XRD). The synthesized nanoparticles were spherical shaped and well-dispersed with average sizes ranging from 45 to 110 nm. The AgNPs derived from BR-PA, CR-FE and SE-SI exhibited higher antibacterial activity against three bacterial pathogens of the human skin compared to their respective crude extracts and AgNO3. This indicated that the biomolecules covering the nanoparticles may enhance the biological activity of metal nanoparticles. Hence, our results support that biogenic synthesis of AgNPs from Congolese plants constitutes a potential area of interest for the therapeutic management of microbial diseases such as infectious skin diseases.
- Full Text:
- Date Issued: 2020
Ground-truthing climate-matching predictions in a post-release evaluation
- Muskett, Phillippa C, Paterson, Iain D, Coetzee, Julie A
- Authors: Muskett, Phillippa C , Paterson, Iain D , Coetzee, Julie A
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423504 , vital:72067 , xlink:href="https://doi.org/10.1016/j.biocontrol.2020.104217"
- Description: Pereskia aculeata Miller (Cactaceae) is an invasive alien cactus which has negative impacts on indigenous plant biodiversity in South Africa. Catorhintha schaffneri Barilovsky and Garcia (Coreidae), the pereskia stem-wilter, was collected at coastal sites in the subtropical region of Santa Catarina state in southern Brazil and released as a biological control agent to control P. aculeata, in South Africa, in 2014. The introduced distribution of P. aculeata covers a wide variety of climatic conditions which was expected to influence the establishment success of the new agent. The thermal tolerance of C. schaffneri was investigated by developing a degree-day model and calculating the thermal limits of the species. The influence of humidity on egg hatchability and adult survival was also investigated. These data were then used to determine where the agent was likely to establish in South Africa using both weather station and microclimate temperature data. To ground-truth these predictions, sixteen release sites were selected covering a wide range of climatic conditions in the introduced distribution. Three releases of 30 adult C. schaffneri were conducted at each site and population establishment was recorded. Field establishment was recorded at only two of the sixteen experimental release sites. Low winter temperatures were predicted to prevent establishment at seven of the sixteen sites, but nine sites were considered climatically suitable according to the agent’s thermal physiology. Low rainfall and humidity could explain why the agent did not survive at some sites with suitable thermal climates. Many of the thermally suitable sites were affected by a severe drought over the course of the experiment, so further releases during periods with average rainfall and humidity are warranted and could confirm whether the drought was a significant factor influencing the failure of the agent to establish. Although climatic-matching and thermal physiology studies are valuable for tentative predictions of establishment success, there are numerous variables involved that require ground-truthing. Releasing the agent over a wide range of climatic zones believed to be within the thermal limits of the agent, and following releases with detailed post-release evaluations may be the best method of determining where future releases should be focused.
- Full Text:
- Date Issued: 2020
- Authors: Muskett, Phillippa C , Paterson, Iain D , Coetzee, Julie A
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423504 , vital:72067 , xlink:href="https://doi.org/10.1016/j.biocontrol.2020.104217"
- Description: Pereskia aculeata Miller (Cactaceae) is an invasive alien cactus which has negative impacts on indigenous plant biodiversity in South Africa. Catorhintha schaffneri Barilovsky and Garcia (Coreidae), the pereskia stem-wilter, was collected at coastal sites in the subtropical region of Santa Catarina state in southern Brazil and released as a biological control agent to control P. aculeata, in South Africa, in 2014. The introduced distribution of P. aculeata covers a wide variety of climatic conditions which was expected to influence the establishment success of the new agent. The thermal tolerance of C. schaffneri was investigated by developing a degree-day model and calculating the thermal limits of the species. The influence of humidity on egg hatchability and adult survival was also investigated. These data were then used to determine where the agent was likely to establish in South Africa using both weather station and microclimate temperature data. To ground-truth these predictions, sixteen release sites were selected covering a wide range of climatic conditions in the introduced distribution. Three releases of 30 adult C. schaffneri were conducted at each site and population establishment was recorded. Field establishment was recorded at only two of the sixteen experimental release sites. Low winter temperatures were predicted to prevent establishment at seven of the sixteen sites, but nine sites were considered climatically suitable according to the agent’s thermal physiology. Low rainfall and humidity could explain why the agent did not survive at some sites with suitable thermal climates. Many of the thermally suitable sites were affected by a severe drought over the course of the experiment, so further releases during periods with average rainfall and humidity are warranted and could confirm whether the drought was a significant factor influencing the failure of the agent to establish. Although climatic-matching and thermal physiology studies are valuable for tentative predictions of establishment success, there are numerous variables involved that require ground-truthing. Releasing the agent over a wide range of climatic zones believed to be within the thermal limits of the agent, and following releases with detailed post-release evaluations may be the best method of determining where future releases should be focused.
- Full Text:
- Date Issued: 2020
Host stage preference and performance of Dolichogenidea gelechiidivoris (Hymenoptera: Braconidae), a candidate for classical biological control of Tuta absoluta in Africa
- Aigbedion-Atalor, Pascal O, Mohamed, Samira A, Hill, Martin P, Zalucki, Myron P, Azrag, Abdelmutalab G A, Srinivasan, Ramasamy, Ekesi, Sunday
- Authors: Aigbedion-Atalor, Pascal O , Mohamed, Samira A , Hill, Martin P , Zalucki, Myron P , Azrag, Abdelmutalab G A , Srinivasan, Ramasamy , Ekesi, Sunday
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423516 , vital:72068 , xlink:href="https://doi.org/10.1016/j.biocontrol.2020.104215"
- Description: Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is native to South America but has invaded the Afro-Eurasian supercontinent where it is currently the most devastating invasive arthropod pest of tomato. As a part of the first classical biological control programme against T. absoluta in Africa, a larval parasitoid, Dolichogenidea gelechiidivoris Marsh. (Syn.: Apanteles gelechiidivoris Marsh) (Hymenoptera: Braconidae), of T. absoluta was imported from Peru into the quarantine facility of the International Centre of Insect Physiology and Ecology, Kenya. We report on the host larval preference of D. gelechiidivoris and the host suitability, and the parasitoid’s reproductive strategy, including lifetime fecundity and egg maturation dynamics. Dolichogenidea gelechiidivoris females preferentially oviposited in early (1st and 2nd) larval instars of T. absoluta but parasitized and completed development in all four instars of the host. Host instar did not affect D. gelechiidivoris sex-ratio but females reared on the first instar had significantly fewer eggs than when reared in late larval instars (3rd and 4th). Females of the parasitoid emerged with a high mature egg load which peaked 2 d post eclosion. The females of D. gelechiidivoris survived 8.51 ± 0.65 d and produced 103 ± 8 offspring per female at 26 ± 4 °C (range: 24 to 29 °C) and 50–70% relative humidity (RH) with males present and fed honey-water (80% honey). Increasing maternal age decreased the proportion of female offspring. Under the aforementioned laboratory conditions, the Gross and Net reproductive rates were 72 and 39.5 respectively, while the mean generation time was 20 d. The potential intrinsic rate of natural increase was 0.18. This study shows that D. gelechiidivoris is a potential biological control agent of T. absoluta and should be considered for release in Kenya and across Africa following host specificity testing and risk assessments.
- Full Text:
- Date Issued: 2020
- Authors: Aigbedion-Atalor, Pascal O , Mohamed, Samira A , Hill, Martin P , Zalucki, Myron P , Azrag, Abdelmutalab G A , Srinivasan, Ramasamy , Ekesi, Sunday
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423516 , vital:72068 , xlink:href="https://doi.org/10.1016/j.biocontrol.2020.104215"
- Description: Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is native to South America but has invaded the Afro-Eurasian supercontinent where it is currently the most devastating invasive arthropod pest of tomato. As a part of the first classical biological control programme against T. absoluta in Africa, a larval parasitoid, Dolichogenidea gelechiidivoris Marsh. (Syn.: Apanteles gelechiidivoris Marsh) (Hymenoptera: Braconidae), of T. absoluta was imported from Peru into the quarantine facility of the International Centre of Insect Physiology and Ecology, Kenya. We report on the host larval preference of D. gelechiidivoris and the host suitability, and the parasitoid’s reproductive strategy, including lifetime fecundity and egg maturation dynamics. Dolichogenidea gelechiidivoris females preferentially oviposited in early (1st and 2nd) larval instars of T. absoluta but parasitized and completed development in all four instars of the host. Host instar did not affect D. gelechiidivoris sex-ratio but females reared on the first instar had significantly fewer eggs than when reared in late larval instars (3rd and 4th). Females of the parasitoid emerged with a high mature egg load which peaked 2 d post eclosion. The females of D. gelechiidivoris survived 8.51 ± 0.65 d and produced 103 ± 8 offspring per female at 26 ± 4 °C (range: 24 to 29 °C) and 50–70% relative humidity (RH) with males present and fed honey-water (80% honey). Increasing maternal age decreased the proportion of female offspring. Under the aforementioned laboratory conditions, the Gross and Net reproductive rates were 72 and 39.5 respectively, while the mean generation time was 20 d. The potential intrinsic rate of natural increase was 0.18. This study shows that D. gelechiidivoris is a potential biological control agent of T. absoluta and should be considered for release in Kenya and across Africa following host specificity testing and risk assessments.
- Full Text:
- Date Issued: 2020
In vitro anti-cancer efficacy and phyto-chemical screening of solvent extracts of Kigelia africana (Lam.) Benth
- Mukavi, Justus W, Mayeku, Philip W, Nyaga, Justine M, Kituyi, Sarah N
- Authors: Mukavi, Justus W , Mayeku, Philip W , Nyaga, Justine M , Kituyi, Sarah N
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429439 , vital:72610 , xlink:href="https://www.cell.com/heliyon/pdf/S2405-8440(20)31325-6.pdf"
- Description: Kigelia africana is a medicinal plant growing naturally in many parts of Africa. In Kenya, a water concoction of the plant is used to treat breast and prostate cancers. Laboratory data on its anti-cancer activity and active principles is limited, hence no scientific rationale for its medicinal use. This study reports on in-vitro toxic activities of dichloromethane and methanol extracts of the plant against human breast cancer cells and phytochemical screening of the two extracts.
- Full Text:
- Date Issued: 2020
- Authors: Mukavi, Justus W , Mayeku, Philip W , Nyaga, Justine M , Kituyi, Sarah N
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429439 , vital:72610 , xlink:href="https://www.cell.com/heliyon/pdf/S2405-8440(20)31325-6.pdf"
- Description: Kigelia africana is a medicinal plant growing naturally in many parts of Africa. In Kenya, a water concoction of the plant is used to treat breast and prostate cancers. Laboratory data on its anti-cancer activity and active principles is limited, hence no scientific rationale for its medicinal use. This study reports on in-vitro toxic activities of dichloromethane and methanol extracts of the plant against human breast cancer cells and phytochemical screening of the two extracts.
- Full Text:
- Date Issued: 2020
Investigation of electrocatalytic behaviour of low symmetry cobalt phthalocyanines when clicked to azide grafted carbon electrodes
- Mpeta, Lakethe S, Sen, Pinar, Nyokong, Tebello
- Authors: Mpeta, Lakethe S , Sen, Pinar , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186304 , vital:44483 , xlink:href="https://doi.org/10.1016/j.jelechem.2020.113896"
- Description: This work describes the electrochemical properties of low symmetry cobalt phthalocyanines namely, tris-[(4-tert-butylphenoxy)-4-(pent-4-yn-1-yloxy) phthalocyaniato] cobalt (II) (3) and tris-[(4-tert-butylphenoxy)-4-(4-ethybylbenzyl-oxy) phthalocyaniato] cobalt (II) (5). The complexes were characterized by a number of techniques including UV–Vis, mass, and infrared spectra, as well as elemental analysis. The glassy carbon electrodes were first azide functionalized then clicked to low symmetry phthalocyanines. The click reaction was confirmed using X-ray photoelectron spectra. The constructed electrodes showed excellent electrocatalytic activity towards hydrazine oxidation. Oxidation peaks with low potentials of 0.21 V and 0.26 V, for complexes 3 and 5, respectively were obtained. Complex-5 gave a better detection limit of 0.94 μM and electrocatalytic rate constant of 5.6 × 106 M−1 s−1.
- Full Text:
- Date Issued: 2020
- Authors: Mpeta, Lakethe S , Sen, Pinar , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186304 , vital:44483 , xlink:href="https://doi.org/10.1016/j.jelechem.2020.113896"
- Description: This work describes the electrochemical properties of low symmetry cobalt phthalocyanines namely, tris-[(4-tert-butylphenoxy)-4-(pent-4-yn-1-yloxy) phthalocyaniato] cobalt (II) (3) and tris-[(4-tert-butylphenoxy)-4-(4-ethybylbenzyl-oxy) phthalocyaniato] cobalt (II) (5). The complexes were characterized by a number of techniques including UV–Vis, mass, and infrared spectra, as well as elemental analysis. The glassy carbon electrodes were first azide functionalized then clicked to low symmetry phthalocyanines. The click reaction was confirmed using X-ray photoelectron spectra. The constructed electrodes showed excellent electrocatalytic activity towards hydrazine oxidation. Oxidation peaks with low potentials of 0.21 V and 0.26 V, for complexes 3 and 5, respectively were obtained. Complex-5 gave a better detection limit of 0.94 μM and electrocatalytic rate constant of 5.6 × 106 M−1 s−1.
- Full Text:
- Date Issued: 2020
Modern supratidal microbialites fed by groundwater: functional drivers, value and trajectories
- Rishworth, Gavin M, Dodd, Carla, Perissinotto, Renzo, Bornman, Thomas G, Adams, Janine B, Anderson, Callum R, Cawthra, Hayley C, Dorrington, Hayley C, du Toit, Hendrik, Edworthy, Carla, Gibb, Ross-Lynne A, Human, Lucienne R D, Isemonger, Eric W, Lemley, David A, Miranda, Nelson A, Peer, Nasreen, Raw, Jacqueline L, Smith, Alan M, Steyn, Paul-Pierre, Strydom, Nadine A, Teske, Peter R, Welman, Peter R
- Authors: Rishworth, Gavin M , Dodd, Carla , Perissinotto, Renzo , Bornman, Thomas G , Adams, Janine B , Anderson, Callum R , Cawthra, Hayley C , Dorrington, Hayley C , du Toit, Hendrik , Edworthy, Carla , Gibb, Ross-Lynne A , Human, Lucienne R D , Isemonger, Eric W , Lemley, David A , Miranda, Nelson A , Peer, Nasreen , Raw, Jacqueline L , Smith, Alan M , Steyn, Paul-Pierre , Strydom, Nadine A , Teske, Peter R , Welman, Peter R
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/426008 , vital:72306 , xlink:href="https://doi.org/10.1016/j.earscirev.2020.103364"
- Description: Microbial mats were the dominant habitat type in shallow marine environments between the Palaeoarchean and Phanerozoic. Many of these (termed ‘microbialites’) calcified as they grew but such lithified mats are rare along modern coasts for reasons such as unsuitable water chemistry, destructive metazoan influences and competition with other reef-builders such as corals or macroalgae. Nonetheless, extant microbialites occur in unique coastal ecosystems such as the Exuma Cays, Bahamas or Lake Clifton and Hamelin Pool, Australia, where limitations such as calcium carbonate availability or destructive bioturbation are diminished. Along the coast of South Africa, extensive distributions of living microbialites (including layered stromatolites) have been discovered and described since the early 2000s. Unlike the Bahamian and Australian ecosystems, the South African microbialites form exclusively in the supratidal coastal zone at the convergence of emergent groundwater seepage. Similar systems were documented subsequently in southwestern Australia, Northern Ireland and the Scottish Hebrides, as recently as 2018, revealing that supratidal microbialites have a global distribution. This review uses the best-studied formations to contextualise formative drivers and processes of these supratidal ecosystems and highlight their geological, ecological and societal relevance.
- Full Text:
- Date Issued: 2020
- Authors: Rishworth, Gavin M , Dodd, Carla , Perissinotto, Renzo , Bornman, Thomas G , Adams, Janine B , Anderson, Callum R , Cawthra, Hayley C , Dorrington, Hayley C , du Toit, Hendrik , Edworthy, Carla , Gibb, Ross-Lynne A , Human, Lucienne R D , Isemonger, Eric W , Lemley, David A , Miranda, Nelson A , Peer, Nasreen , Raw, Jacqueline L , Smith, Alan M , Steyn, Paul-Pierre , Strydom, Nadine A , Teske, Peter R , Welman, Peter R
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/426008 , vital:72306 , xlink:href="https://doi.org/10.1016/j.earscirev.2020.103364"
- Description: Microbial mats were the dominant habitat type in shallow marine environments between the Palaeoarchean and Phanerozoic. Many of these (termed ‘microbialites’) calcified as they grew but such lithified mats are rare along modern coasts for reasons such as unsuitable water chemistry, destructive metazoan influences and competition with other reef-builders such as corals or macroalgae. Nonetheless, extant microbialites occur in unique coastal ecosystems such as the Exuma Cays, Bahamas or Lake Clifton and Hamelin Pool, Australia, where limitations such as calcium carbonate availability or destructive bioturbation are diminished. Along the coast of South Africa, extensive distributions of living microbialites (including layered stromatolites) have been discovered and described since the early 2000s. Unlike the Bahamian and Australian ecosystems, the South African microbialites form exclusively in the supratidal coastal zone at the convergence of emergent groundwater seepage. Similar systems were documented subsequently in southwestern Australia, Northern Ireland and the Scottish Hebrides, as recently as 2018, revealing that supratidal microbialites have a global distribution. This review uses the best-studied formations to contextualise formative drivers and processes of these supratidal ecosystems and highlight their geological, ecological and societal relevance.
- Full Text:
- Date Issued: 2020
New difluoroboron complexes based on N, O-chelated Schiff base ligands: Synthesis, characterization, DFT calculations and photophysical and electrochemical properties
- Sen, Pinar, Mpeta, Lekhetho S, Mack, John, Nyokong, Tebello
- Authors: Sen, Pinar , Mpeta, Lekhetho S , Mack, John , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186207 , vital:44473 , xlink:href="https://doi.org/10.1016/j.jlumin.2020.117262"
- Description: The synthesis of new Schiff bases and their dinuclear boron complexes is described, along with their characterization by 1H and 13C NMR, FT-IR, and UV–visible absorption spectroscopy, mass spectrometry, and EDX for elemental analysis. The optical and photophysical properties were examined in terms of their absorption and emission behavior, fluorescence quantum yields and fluorescence lifetimes. The flexible dinuclear boron complexes that are linked by a flexible carbon chain exhibited large Stokes shifts in the range from 92 nm to 115 nm in contrast to BODIPY dyes. Those properties make these complexes precious for applications in fluorescence materials. And also theoretical calculations were obtained by using Density Functional Theory (DFT) methods.
- Full Text:
- Date Issued: 2020
- Authors: Sen, Pinar , Mpeta, Lekhetho S , Mack, John , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186207 , vital:44473 , xlink:href="https://doi.org/10.1016/j.jlumin.2020.117262"
- Description: The synthesis of new Schiff bases and their dinuclear boron complexes is described, along with their characterization by 1H and 13C NMR, FT-IR, and UV–visible absorption spectroscopy, mass spectrometry, and EDX for elemental analysis. The optical and photophysical properties were examined in terms of their absorption and emission behavior, fluorescence quantum yields and fluorescence lifetimes. The flexible dinuclear boron complexes that are linked by a flexible carbon chain exhibited large Stokes shifts in the range from 92 nm to 115 nm in contrast to BODIPY dyes. Those properties make these complexes precious for applications in fluorescence materials. And also theoretical calculations were obtained by using Density Functional Theory (DFT) methods.
- Full Text:
- Date Issued: 2020
Nonlinear optical response and electrocatalytic activity of cobalt phthalocyanine clicked zinc oxide nanoparticles
- Mpeta, Lekhetho S, Sekhosana, Kutloano E, Nyokong, Tebello
- Authors: Mpeta, Lekhetho S , Sekhosana, Kutloano E , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186179 , vital:44471 , xlink:href="https://doi.org/10.1016/j.ica.2020.119661"
- Description: In this article, we report on the linking of cobalt tetrakis (4-pentyn-oxy) phthalocyanine (CoTPPc) to ZnO nanoparticles via click chemistry. Subsequently, electrocatalytic activity and nonlinear optical properties were investigated (the latter using an open Z-scan technique at 532 nm). The linking of CoTPPc with ZnO resulted in the lowest limiting intensity value of 0.27 J.Cm−2, the βeff (cmW−1) values were found to be 1.51 × 10-8 and 7.10 × 104 for ZnO and CoTPPc-ZnO respectively. The catalytic rate constants (M−1s−1) (and limits of detection) were 4.1 × 104 (12.87 µM), 5.7 × 104 (8.62 µM) and 7.36 × 104 (4.35 µM) for ZnO, CoTPPc and CoTPPc-ZnO. Hence linking ZnO nanoparticles to CoTPPc result in the enhancement of both nonlinear optical behaviour and catalytic activity.
- Full Text:
- Date Issued: 2020
- Authors: Mpeta, Lekhetho S , Sekhosana, Kutloano E , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186179 , vital:44471 , xlink:href="https://doi.org/10.1016/j.ica.2020.119661"
- Description: In this article, we report on the linking of cobalt tetrakis (4-pentyn-oxy) phthalocyanine (CoTPPc) to ZnO nanoparticles via click chemistry. Subsequently, electrocatalytic activity and nonlinear optical properties were investigated (the latter using an open Z-scan technique at 532 nm). The linking of CoTPPc with ZnO resulted in the lowest limiting intensity value of 0.27 J.Cm−2, the βeff (cmW−1) values were found to be 1.51 × 10-8 and 7.10 × 104 for ZnO and CoTPPc-ZnO respectively. The catalytic rate constants (M−1s−1) (and limits of detection) were 4.1 × 104 (12.87 µM), 5.7 × 104 (8.62 µM) and 7.36 × 104 (4.35 µM) for ZnO, CoTPPc and CoTPPc-ZnO. Hence linking ZnO nanoparticles to CoTPPc result in the enhancement of both nonlinear optical behaviour and catalytic activity.
- Full Text:
- Date Issued: 2020
On the move: New insights on the ecology and management of native and alien macrophytes
- Hofstra, Deborah, Schoelynck, Jonas, Ferrell, Jason, Coetzee, Julie A, de Winton, Mary, Bickel, Tobias O, Champion, Paul, Madsen, John, Bakker, Elisabeth S, Hilt, Sabine, Matheson, Fleur, Netherland, Mike, Gross, Elisabeth M
- Authors: Hofstra, Deborah , Schoelynck, Jonas , Ferrell, Jason , Coetzee, Julie A , de Winton, Mary , Bickel, Tobias O , Champion, Paul , Madsen, John , Bakker, Elisabeth S , Hilt, Sabine , Matheson, Fleur , Netherland, Mike , Gross, Elisabeth M
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/419346 , vital:71636 , xlink:href=" https://doi.org/10.1016/j.aquabot.2019.103190"
- Description: Globally, freshwater ecosystems are under threat. The main threats come from catchment land-use changes, altered water regimes, eutrophication, invasive species, climate change and combinations of these factors. We need scientific research to respond to these challenges by providing solutions to halt the deterioration and improve the condition of our valuable freshwaters. This requires a good understanding of aquatic ecosystems, and the nature and scale of changes occurring. Macrophytes play a fundamental role in aquatic systems. They are sensitive indicators of ecosystem health, as they are affected by run-off from agricultural, industrial or urban areas. On the other hand, alien macrophytes are increasingly invading aquatic systems all over the world. Improving our knowledge on the ecology and management of both native and alien plants is indispensable to address threats to freshwaters in order to protect and restore aquatic habitats. The International Aquatic Plants Group (IAPG) brings together scientists and practitioners based at universities, research and environmental organisations around the world. The main themes of the 15th symposium 2018 in New Zealand were biodiversity and conservation, management, invasive species, and ecosystem response and restoration. This Virtual Special Issue provides a comprehensive review from the symposium, addressing the ecology of native macrophytes, including those of conservation concern, and highly invasive alien macrophytes, and the implications of management interventions. In this editorial paper, we highlight insights and paradigms on the ecology and management of native and alien macrophytes gathered during the meeting.
- Full Text:
- Date Issued: 2020
- Authors: Hofstra, Deborah , Schoelynck, Jonas , Ferrell, Jason , Coetzee, Julie A , de Winton, Mary , Bickel, Tobias O , Champion, Paul , Madsen, John , Bakker, Elisabeth S , Hilt, Sabine , Matheson, Fleur , Netherland, Mike , Gross, Elisabeth M
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/419346 , vital:71636 , xlink:href=" https://doi.org/10.1016/j.aquabot.2019.103190"
- Description: Globally, freshwater ecosystems are under threat. The main threats come from catchment land-use changes, altered water regimes, eutrophication, invasive species, climate change and combinations of these factors. We need scientific research to respond to these challenges by providing solutions to halt the deterioration and improve the condition of our valuable freshwaters. This requires a good understanding of aquatic ecosystems, and the nature and scale of changes occurring. Macrophytes play a fundamental role in aquatic systems. They are sensitive indicators of ecosystem health, as they are affected by run-off from agricultural, industrial or urban areas. On the other hand, alien macrophytes are increasingly invading aquatic systems all over the world. Improving our knowledge on the ecology and management of both native and alien plants is indispensable to address threats to freshwaters in order to protect and restore aquatic habitats. The International Aquatic Plants Group (IAPG) brings together scientists and practitioners based at universities, research and environmental organisations around the world. The main themes of the 15th symposium 2018 in New Zealand were biodiversity and conservation, management, invasive species, and ecosystem response and restoration. This Virtual Special Issue provides a comprehensive review from the symposium, addressing the ecology of native macrophytes, including those of conservation concern, and highly invasive alien macrophytes, and the implications of management interventions. In this editorial paper, we highlight insights and paradigms on the ecology and management of native and alien macrophytes gathered during the meeting.
- Full Text:
- Date Issued: 2020
Optical limiting properties of indium 5, 10, 15, 20-tetrakis (4-aminophenyl) porphyrin covalently linked to semiconductor quantum dots
- Managa, Muthumuni, Mgidlana, Sithi, Khene, Samson M, Nyokong, Tebello
- Authors: Managa, Muthumuni , Mgidlana, Sithi , Khene, Samson M , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186101 , vital:44463 , xlink:href="https://doi.org/10.1016/j.ica.2020.119838"
- Description: 5,10,15,20-tetrakis(4-aminophenyl) porphyrin and it indium derivative were synthesised and characterized then covalently linked to CdTe/ZnSe/ZnO semiconductor quantum dots. The nonlinear absorption of the complexes was studied using the Z-scan technique at 532 nm and 10 ns pulse in dimethyl sulfoxide. Indium 5,10,15,20- tetrakis(4-aminophenyl) porphyrin (InTAPP) exhibited the strongest nonlinear optical behaviour in comparison with the metal free derivative. DFT calculations were carried out using SDD basis set at B3LYP level of theory. The nonlinear absorption coefficient (βeff) values were determined experimentally using Z-scan whereby the first static hyperpolarizability (βHRS) value were determined using DFT calcutions.
- Full Text:
- Date Issued: 2020
- Authors: Managa, Muthumuni , Mgidlana, Sithi , Khene, Samson M , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186101 , vital:44463 , xlink:href="https://doi.org/10.1016/j.ica.2020.119838"
- Description: 5,10,15,20-tetrakis(4-aminophenyl) porphyrin and it indium derivative were synthesised and characterized then covalently linked to CdTe/ZnSe/ZnO semiconductor quantum dots. The nonlinear absorption of the complexes was studied using the Z-scan technique at 532 nm and 10 ns pulse in dimethyl sulfoxide. Indium 5,10,15,20- tetrakis(4-aminophenyl) porphyrin (InTAPP) exhibited the strongest nonlinear optical behaviour in comparison with the metal free derivative. DFT calculations were carried out using SDD basis set at B3LYP level of theory. The nonlinear absorption coefficient (βeff) values were determined experimentally using Z-scan whereby the first static hyperpolarizability (βHRS) value were determined using DFT calcutions.
- Full Text:
- Date Issued: 2020
Photodynamic antimicrobial chemotherapy of a dimethylamino-functionalized asymmetric zinc (II) phthalocyanine and its quaternized derivative against Staphylococcus aureus when supported on asymmetric polystyrene polymer membranes
- Mafukidze, Donovan M, Nyokong, Tebello
- Authors: Mafukidze, Donovan M , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186168 , vital:44470 , xlink:href="https://doi.org/10.1016/j.reactfunctpolym.2020.104634"
- Description: Membrane applications are hindered by fouling. Photoactive membranes (containing photosensitizers) show photodynamic antimicrobial chemotherapy (PACT) activity which reduces biological fouling. In this work we use phthalocyanines (Pcs) as photosensitizers. The Pcs used are: 2-(4-carboxyphenoxy)-9(10), 16(17), 23(24)-tris(dimethylamino) phthalocyaninato zinc(II) (1) and the quaternized 2-(4-carboxyphenoxy)-9(10), 16(17), 23(24)-tris(trimethylamino) phthalocyanine zinc(II) methyl sulfate (2). Complex 2 showed an enhanced singlet oxygen quantum yield (ΦΔ) of 0.76 compared to 0.53 for 1. Complex 2 showed enhanced PACT activity against Staphylococcus aureus giving a log reduction value of 9.4, while its precursor (complex 1) gave 0.08. The complexes were then conjugated to amine-functionalized polystyrene and embedded into polystyrene to form membranes resulting in ΦΔ values of 0.24 and 0.27 for complexes 1 and 2 respectively in water. The latter membrane showed better PACT activity.
- Full Text:
- Date Issued: 2020
- Authors: Mafukidze, Donovan M , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186168 , vital:44470 , xlink:href="https://doi.org/10.1016/j.reactfunctpolym.2020.104634"
- Description: Membrane applications are hindered by fouling. Photoactive membranes (containing photosensitizers) show photodynamic antimicrobial chemotherapy (PACT) activity which reduces biological fouling. In this work we use phthalocyanines (Pcs) as photosensitizers. The Pcs used are: 2-(4-carboxyphenoxy)-9(10), 16(17), 23(24)-tris(dimethylamino) phthalocyaninato zinc(II) (1) and the quaternized 2-(4-carboxyphenoxy)-9(10), 16(17), 23(24)-tris(trimethylamino) phthalocyanine zinc(II) methyl sulfate (2). Complex 2 showed an enhanced singlet oxygen quantum yield (ΦΔ) of 0.76 compared to 0.53 for 1. Complex 2 showed enhanced PACT activity against Staphylococcus aureus giving a log reduction value of 9.4, while its precursor (complex 1) gave 0.08. The complexes were then conjugated to amine-functionalized polystyrene and embedded into polystyrene to form membranes resulting in ΦΔ values of 0.24 and 0.27 for complexes 1 and 2 respectively in water. The latter membrane showed better PACT activity.
- Full Text:
- Date Issued: 2020
Photophysical and nonlinear optical properties of the positional isomers of 4-(4-tertbutylphenoxy) substituted cobalt, nickel and copper phthalocyanines
- Neduvhuledza, Zelda, Nkaki, Thabo, Louzada, Marcel, Nyokong, Tebello, Khene, Samson M
- Authors: Neduvhuledza, Zelda , Nkaki, Thabo , Louzada, Marcel , Nyokong, Tebello , Khene, Samson M
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186067 , vital:44460 , xlink:href="https://doi.org/10.1016/j.optmat.2020.110195"
- Description: This paper reports on the third order nonlinear optical properties of cobalt, nickel and tetrakis(4- terbutylphenoxy)phthalocyaninatocopper(II) isomers, using the Z-scan technique. Metal-free isomers were found to have high nonlinear absorption coefficient (β) values compared to the metalated isomers. Metal-free C2v isomer was found to have the highest β value of 1.52 × 10− 10 mMW− 1 in THF. All the metal-free and metal phthalocyanine isomers nonlinear properties were found to be dependent on the singlet state absorption. Imaginary second order nonlinear hyperpolarizability (Im[γ]), ground state cross section (σg), excited states cross sections (σs and σt) and two photon absorption (TPA) cross section (σTPA) values are reported in this work. The five-energy level model rate equations were used to model the nonlinear response and absorption cross sections.
- Full Text:
- Date Issued: 2020
- Authors: Neduvhuledza, Zelda , Nkaki, Thabo , Louzada, Marcel , Nyokong, Tebello , Khene, Samson M
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186067 , vital:44460 , xlink:href="https://doi.org/10.1016/j.optmat.2020.110195"
- Description: This paper reports on the third order nonlinear optical properties of cobalt, nickel and tetrakis(4- terbutylphenoxy)phthalocyaninatocopper(II) isomers, using the Z-scan technique. Metal-free isomers were found to have high nonlinear absorption coefficient (β) values compared to the metalated isomers. Metal-free C2v isomer was found to have the highest β value of 1.52 × 10− 10 mMW− 1 in THF. All the metal-free and metal phthalocyanine isomers nonlinear properties were found to be dependent on the singlet state absorption. Imaginary second order nonlinear hyperpolarizability (Im[γ]), ground state cross section (σg), excited states cross sections (σs and σt) and two photon absorption (TPA) cross section (σTPA) values are reported in this work. The five-energy level model rate equations were used to model the nonlinear response and absorption cross sections.
- Full Text:
- Date Issued: 2020
Photophysico-chemical properties and photoinactivation of Staphylococcus Aureus using zinc phthalocyanines linked silver nanoparticles conjugates
- Matlou, Gauta G, Nyokong, Tebello
- Authors: Matlou, Gauta G , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186278 , vital:44481 , xlink:href="https://doi.org/10.1016/j.dyepig.2020.108237"
- Description: The synthesis of zinc (II) tri (tert-butyl phenoxy) mono cinnamic acid Pc (complex 1) is reported for the first time in this work. Complex 1 and the reported zinc (II) tri (tert-butyl), mono cinnamic acid phthalocyanine (2), zinc (II) mono cinnamic acid substituted phthalocyanine (3) and zinc (II) tetra cinnamic acid substituted phthalocyanine (4) are conjugated to cysteine capped silver nanoparticles (cys-AgNPs) through an amide bond. The photophysicochemical properties and the photodynamic antimicrobial chemotherapy (PACT) activities of the Pc-cys-AgNPs conjugates and the Pcs alone on S. Aureus are reported. Improved triplet and singlet oxygen quantum yields were observed for the conjugated complexes compared to Pcs alone, due to the heavy atom effect of cys-AgNPs. Asymmetric complexes 1,2, 3 and their respective conjugates recorded higher photosensitizing properties and PACT activities compared to 4 and 4-cys-AgNPs, respectively. Higher log reductions and percentage reductions of S. Aureus were recorded for conjugated complexes compared to ZnPcs only, showing enhanced PACT activities due to their higher singlet oxygen quantum yields.
- Full Text:
- Date Issued: 2020
- Authors: Matlou, Gauta G , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186278 , vital:44481 , xlink:href="https://doi.org/10.1016/j.dyepig.2020.108237"
- Description: The synthesis of zinc (II) tri (tert-butyl phenoxy) mono cinnamic acid Pc (complex 1) is reported for the first time in this work. Complex 1 and the reported zinc (II) tri (tert-butyl), mono cinnamic acid phthalocyanine (2), zinc (II) mono cinnamic acid substituted phthalocyanine (3) and zinc (II) tetra cinnamic acid substituted phthalocyanine (4) are conjugated to cysteine capped silver nanoparticles (cys-AgNPs) through an amide bond. The photophysicochemical properties and the photodynamic antimicrobial chemotherapy (PACT) activities of the Pc-cys-AgNPs conjugates and the Pcs alone on S. Aureus are reported. Improved triplet and singlet oxygen quantum yields were observed for the conjugated complexes compared to Pcs alone, due to the heavy atom effect of cys-AgNPs. Asymmetric complexes 1,2, 3 and their respective conjugates recorded higher photosensitizing properties and PACT activities compared to 4 and 4-cys-AgNPs, respectively. Higher log reductions and percentage reductions of S. Aureus were recorded for conjugated complexes compared to ZnPcs only, showing enhanced PACT activities due to their higher singlet oxygen quantum yields.
- Full Text:
- Date Issued: 2020
Substituent effect on the photophysical and nonlinear optical characteristics of Si phthalocyanine–Detonated nanodiamond conjugated systems in solution
- Matshitse, Refilwe, Nyokong, Tebello
- Authors: Matshitse, Refilwe , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186293 , vital:44482 , xlink:href="https://doi.org/10.1016/j.ica.2020.119447"
- Description: This work reports on the photophysical, nonlinear absorption and optical limiting properties of detonation nanodiamonds (DNDs)-silicon phthalocyanine nanoconjugate systems. Si(IV) hydroxide phthalocyanines employed are: 2,9(10),16(17),23(24)-tetrakis-(4-pyridyloxy) phthalocyaninato (Si(OH)2TPPc), 2,9(10),16(17),23(24)-tetrakis-(4-tert-butyl) phthalocyanato (Si(OH)2TBPc) and phthalocyanato(Si(OH)2Pc). Pcs were covalently linked to nanondiamonds and investigated using 532 nm laser excitation at 7 ns pulses for their optical limiting properties. Si(OH)2TBPc and Si(OH)2Pc gave larger triplet quantum yields when linked to DNDs, while the value decreased for Si(OH)2TPPc in the presence of DNDs due to aggregation. However all Pcs showed enhanced nonlinear optical properties in the presence of DNDs. DNDs-Si(OH)2TPPc and DNDs-Si (OH)2TBPc gave the highest imaginary third-order susceptibility (Im[X(3)]) and hyperpolarizability (γ) at 5.19 × 10−8 and 3.85 × 10−8 esu and 2.66 × 10−27 and 1.97 × 10−27 esu, respectively. DNDs-Si(OH)2TBPc nanoconjugates showed lowest limiting threshold (Ilim) value of 0.01 J.cm−2 relative to 0.09 for DNDs-Si (OH)2TPPc.
- Full Text:
- Date Issued: 2020
- Authors: Matshitse, Refilwe , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186293 , vital:44482 , xlink:href="https://doi.org/10.1016/j.ica.2020.119447"
- Description: This work reports on the photophysical, nonlinear absorption and optical limiting properties of detonation nanodiamonds (DNDs)-silicon phthalocyanine nanoconjugate systems. Si(IV) hydroxide phthalocyanines employed are: 2,9(10),16(17),23(24)-tetrakis-(4-pyridyloxy) phthalocyaninato (Si(OH)2TPPc), 2,9(10),16(17),23(24)-tetrakis-(4-tert-butyl) phthalocyanato (Si(OH)2TBPc) and phthalocyanato(Si(OH)2Pc). Pcs were covalently linked to nanondiamonds and investigated using 532 nm laser excitation at 7 ns pulses for their optical limiting properties. Si(OH)2TBPc and Si(OH)2Pc gave larger triplet quantum yields when linked to DNDs, while the value decreased for Si(OH)2TPPc in the presence of DNDs due to aggregation. However all Pcs showed enhanced nonlinear optical properties in the presence of DNDs. DNDs-Si(OH)2TPPc and DNDs-Si (OH)2TBPc gave the highest imaginary third-order susceptibility (Im[X(3)]) and hyperpolarizability (γ) at 5.19 × 10−8 and 3.85 × 10−8 esu and 2.66 × 10−27 and 1.97 × 10−27 esu, respectively. DNDs-Si(OH)2TBPc nanoconjugates showed lowest limiting threshold (Ilim) value of 0.01 J.cm−2 relative to 0.09 for DNDs-Si (OH)2TPPc.
- Full Text:
- Date Issued: 2020
Susceptibility of Staphylococcus aureus to porphyrin-silver nanoparticle mediated photodynamic antimicrobial chemotherapy
- Shabangu, Samuel M, Babu, Balaji, Soy, Rodah C, Ovim, James, Amuhaya, Edith, Nyokong, Tebello
- Authors: Shabangu, Samuel M , Babu, Balaji , Soy, Rodah C , Ovim, James , Amuhaya, Edith , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186262 , vital:44479 , xlink:href="https://doi.org/10.1016/j.jlumin.2020.117158"
- Description: Photodynamic antimicrobial chemotherapy (PACT) is employed against multi drug resistant Staphylococcus aureus using porphyrins combined with silver nanoparticles to bring about a combined photodynamic effect. We employ Zn-meso-5,10,15,20-tetra(4-pyridyl) (1), Zn-meso-5,10,15,20-tetrathienyl (2), and Zn-meso-5-(4- hydroxyphenyl)- 10,15,20-tris(2-thienyl)(3) porphyrins and their self-assembled conjugates with silver nanoparticles for PACT against Staphylococcus aureus. Complex 3 with nanoparticles was found to perform better resulting in 0% bacterial viability at 60 min.
- Full Text:
- Date Issued: 2020
- Authors: Shabangu, Samuel M , Babu, Balaji , Soy, Rodah C , Ovim, James , Amuhaya, Edith , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186262 , vital:44479 , xlink:href="https://doi.org/10.1016/j.jlumin.2020.117158"
- Description: Photodynamic antimicrobial chemotherapy (PACT) is employed against multi drug resistant Staphylococcus aureus using porphyrins combined with silver nanoparticles to bring about a combined photodynamic effect. We employ Zn-meso-5,10,15,20-tetra(4-pyridyl) (1), Zn-meso-5,10,15,20-tetrathienyl (2), and Zn-meso-5-(4- hydroxyphenyl)- 10,15,20-tris(2-thienyl)(3) porphyrins and their self-assembled conjugates with silver nanoparticles for PACT against Staphylococcus aureus. Complex 3 with nanoparticles was found to perform better resulting in 0% bacterial viability at 60 min.
- Full Text:
- Date Issued: 2020
Synthesis and biological evaluation of bis-N2, N2′-(4-hydroxycoumarin-3-yl) ethylidene]-2, 3-dihydroxysuccinodihydrazides
- Manyeruke, Meloddy H, Tshiwawa, Thendamudzimu, Hoppe, Heinrich, Isaacs, Michelle, Seldon, Ronnett, Warner, Digby F, Krause, Rui W M, Kaye, Perry T
- Authors: Manyeruke, Meloddy H , Tshiwawa, Thendamudzimu , Hoppe, Heinrich , Isaacs, Michelle , Seldon, Ronnett , Warner, Digby F , Krause, Rui W M , Kaye, Perry T
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193430 , vital:45331 , xlink:href="https://doi.org/10.1016/j.bmcl.2019.126911"
- Description: A series of N2,N2′-bis[4-hydroxycoumarin-3-yl)ethylidene]-2,3-dihydroxysuccino-hydrazides, containing 4-hydroxycoumarin, hydrazine and tartaric acid moieties, have been prepared and examined for possible biological activity. Several of these compounds exhibit promising HIV-1 integrase inhibition (IC50 = 3.5 μM), and anti-T. brucei (32% viability) and anti-mycobacterial (Visual MIC90 = 15.63 μM) activity.
- Full Text:
- Date Issued: 2020
- Authors: Manyeruke, Meloddy H , Tshiwawa, Thendamudzimu , Hoppe, Heinrich , Isaacs, Michelle , Seldon, Ronnett , Warner, Digby F , Krause, Rui W M , Kaye, Perry T
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193430 , vital:45331 , xlink:href="https://doi.org/10.1016/j.bmcl.2019.126911"
- Description: A series of N2,N2′-bis[4-hydroxycoumarin-3-yl)ethylidene]-2,3-dihydroxysuccino-hydrazides, containing 4-hydroxycoumarin, hydrazine and tartaric acid moieties, have been prepared and examined for possible biological activity. Several of these compounds exhibit promising HIV-1 integrase inhibition (IC50 = 3.5 μM), and anti-T. brucei (32% viability) and anti-mycobacterial (Visual MIC90 = 15.63 μM) activity.
- 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