Fluorescence “turn-ON” nanosensor for cyanide ion using supramolecular hybrid of graphene quantum dots and cobalt pyrene-derivatized phthalocyanine
- Achadu, Ojodomo John, Nyokong, Tebello
- Authors: Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187594 , vital:44674 , xlink:href="https://doi.org/10.1016/j.dyepig.2018.08.038"
- Description: A functional hybrid of graphene quantum dots (GQDs) and cobalt pyrene-derivatized phthalocyanine (CoPc) used as a sensitive nanoprobe for the recognition of cyanide ion (CN−) is described in this work. The fluorescence of GQDs was quenched upon non-covalent (π-π stacking) hybrid formation with CoPc via a possible energy transfer pathway. However, in the presence of CN−, the interaction between GQDs and CoPc was perturbed, such that the fluorescence of GQDs initially quenched by CoPc was found to be efficiently recovered in the presence of CN−. Amongst the molecules and anions tested to ascertain their effects on the fluorescence behaviour of the hybrid, only CN− ion induced the tunable “off-on” restoration of the fluorescence of GQDs, which demonstrates the selectivity of the hybrid towards CN−. The restored fluorescence signals of the GQDs were linearly modulated by different concentrations of CN− and were used for the quantitative assay of CN− with high sensitivity coupled with rapid detection time. The detection was in the linear range of 1.0–50.0 nM with limits of detection (LOD) of 0.5 nM. The analysis of spiked samples for the recovery of CN− further demonstrated the applicability of the hybrid for the satisfactory detection of the target analyte.
- Full Text:
- Date Issued: 2019
- Authors: Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187594 , vital:44674 , xlink:href="https://doi.org/10.1016/j.dyepig.2018.08.038"
- Description: A functional hybrid of graphene quantum dots (GQDs) and cobalt pyrene-derivatized phthalocyanine (CoPc) used as a sensitive nanoprobe for the recognition of cyanide ion (CN−) is described in this work. The fluorescence of GQDs was quenched upon non-covalent (π-π stacking) hybrid formation with CoPc via a possible energy transfer pathway. However, in the presence of CN−, the interaction between GQDs and CoPc was perturbed, such that the fluorescence of GQDs initially quenched by CoPc was found to be efficiently recovered in the presence of CN−. Amongst the molecules and anions tested to ascertain their effects on the fluorescence behaviour of the hybrid, only CN− ion induced the tunable “off-on” restoration of the fluorescence of GQDs, which demonstrates the selectivity of the hybrid towards CN−. The restored fluorescence signals of the GQDs were linearly modulated by different concentrations of CN− and were used for the quantitative assay of CN− with high sensitivity coupled with rapid detection time. The detection was in the linear range of 1.0–50.0 nM with limits of detection (LOD) of 0.5 nM. The analysis of spiked samples for the recovery of CN− further demonstrated the applicability of the hybrid for the satisfactory detection of the target analyte.
- Full Text:
- Date Issued: 2019
Photophysical properties of a series of alloyed and non-alloyed water-soluble l-cysteine-capped core quantum dots
- Adegoke, Oluwasesan, Nyokong, Tebello, Forbes, Patricia B
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188486 , vital:44758 , xlink:href="https://doi.org/10.1016/j.jallcom.2016.10.276"
- Description: Photophysical properties of quantum dots (QDs) such as their photoluminescence (PL) quantum yield (QY), exciton lifetime and PL stability are important parameters used to unravel their chemical and physical characteristics. In this work, we have comparatively investigated the photophysical properties of a series of L-cysteine-capped non-alloyed (CdTe and CdSe) and alloyed (CdZnTe, CdSeS, CdSeTe and CdSeTeS) core QDs. Each of the QDs varied in their size and PL emission wavelength. We observe no physical relationship between the PL QY of the QDs and their PL stability. Based on the PL stability assessment, CdTe QDs with a high PL QY value of 88% exhibited poor PL stability while moderate PL stability was observed for CdZnTe (QY = 78%); CdSe (QY = 3%); and CdSeTe QDs (QY = ∼3%). Alloyed CdSeS (QY = ∼69%) and CdSeTeS (QY = 23%) QDs exhibited good PL stability and can serve as potential fluorophores for a wide range of chemical and biological applications. Generally, it is proposed that the structural nature of the QDs played a significant role in their overall photophysical properties. The information provided in this work will assist in the selection of core QDs suitable for different applications.
- Full Text:
- Date Issued: 2017
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188486 , vital:44758 , xlink:href="https://doi.org/10.1016/j.jallcom.2016.10.276"
- Description: Photophysical properties of quantum dots (QDs) such as their photoluminescence (PL) quantum yield (QY), exciton lifetime and PL stability are important parameters used to unravel their chemical and physical characteristics. In this work, we have comparatively investigated the photophysical properties of a series of L-cysteine-capped non-alloyed (CdTe and CdSe) and alloyed (CdZnTe, CdSeS, CdSeTe and CdSeTeS) core QDs. Each of the QDs varied in their size and PL emission wavelength. We observe no physical relationship between the PL QY of the QDs and their PL stability. Based on the PL stability assessment, CdTe QDs with a high PL QY value of 88% exhibited poor PL stability while moderate PL stability was observed for CdZnTe (QY = 78%); CdSe (QY = 3%); and CdSeTe QDs (QY = ∼3%). Alloyed CdSeS (QY = ∼69%) and CdSeTeS (QY = 23%) QDs exhibited good PL stability and can serve as potential fluorophores for a wide range of chemical and biological applications. Generally, it is proposed that the structural nature of the QDs played a significant role in their overall photophysical properties. The information provided in this work will assist in the selection of core QDs suitable for different applications.
- Full Text:
- Date Issued: 2017
Fluorescence behavior and singlet oxygen generating abilities of aluminum phthalocyanine in the presence of anisotropic gold nanoparticles
- Mthethwa, Thandekile, Nyokong, Tebello
- Authors: Mthethwa, Thandekile , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189865 , vital:44941 , xlink:href="https://doi.org/10.1016/j.jlumin.2014.09.005"
- Description: Gold nanoparticles (spheres, rods and bipyramids) were synthesized. The nanocrystals were characterized by UV–visible spectrometry, transmission electron microscopy (TEM) and X-ray diffractometry (XRD). The as prepared gold nanoparticles were then conjugated to a quaternized 2,(3)-tetra [2-(dimethylamino) ethanethio] substituted Al(OH) phthalocyanine (complex 1). The conjugation of phthalocyanines with gold nanoparticles resulted in a decrease in the fluorescence quantum yields and lifetimes. Conversely, an increase in the singlet oxygen quantum yields was observed for the conjugated complex 1 in the presence of AuNPs.
- Full Text:
- Date Issued: 2015
- Authors: Mthethwa, Thandekile , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189865 , vital:44941 , xlink:href="https://doi.org/10.1016/j.jlumin.2014.09.005"
- Description: Gold nanoparticles (spheres, rods and bipyramids) were synthesized. The nanocrystals were characterized by UV–visible spectrometry, transmission electron microscopy (TEM) and X-ray diffractometry (XRD). The as prepared gold nanoparticles were then conjugated to a quaternized 2,(3)-tetra [2-(dimethylamino) ethanethio] substituted Al(OH) phthalocyanine (complex 1). The conjugation of phthalocyanines with gold nanoparticles resulted in a decrease in the fluorescence quantum yields and lifetimes. Conversely, an increase in the singlet oxygen quantum yields was observed for the conjugated complex 1 in the presence of AuNPs.
- Full Text:
- Date Issued: 2015
Situated environmental learning in Southern Africa at the start of the UN decade of education for sustainable development
- O'Donoghue, Rob B, Lotz-Sisitka, Heila
- Authors: O'Donoghue, Rob B , Lotz-Sisitka, Heila
- Date: 2006
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183059 , vital:43908 , xlink:href="https://doi.org/10.1017/S0814062600001737"
- Description: Within the globalising trajectory of modernism, conservation, then environmental (EE) and now sustainability education (ESD) have each emerged as developing responses to risk produced by and in the modern state. Through adopting a long term process perspective, this paper narrates the emergence of situated learning perspectives and a developing re-orientation of EE at the start of the United Nations Decade of Education for Sustainable Development (UNDESD). We identified the need to examine ESD practice in responses to recent ESD consultations in 14 southern African countries, where a rhetorical marking was noted in discussions on ESD practices, particularly with regard to changing teaching and learning processes. The paper narrates how an interplay of review, research and practical engagement activities have all contributed to an extended critical review of learning interactions in environmental education in an attempt to provide useful perspective for educational activities within the UNDESD. We found that EE and ESD initiatives only acquired more substantive meaning and coherent orientation when examined within ongoing inquiries into situated learning, agency and risk reduction in contexts of poverty, vulnerability and risk, the key concern to us in this paper and the primary focus of the WEHAB (Water, Energy, Health, Agriculture and Biodiversity) sustainable development agenda in the region.
- Full Text:
- Date Issued: 2006
- Authors: O'Donoghue, Rob B , Lotz-Sisitka, Heila
- Date: 2006
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183059 , vital:43908 , xlink:href="https://doi.org/10.1017/S0814062600001737"
- Description: Within the globalising trajectory of modernism, conservation, then environmental (EE) and now sustainability education (ESD) have each emerged as developing responses to risk produced by and in the modern state. Through adopting a long term process perspective, this paper narrates the emergence of situated learning perspectives and a developing re-orientation of EE at the start of the United Nations Decade of Education for Sustainable Development (UNDESD). We identified the need to examine ESD practice in responses to recent ESD consultations in 14 southern African countries, where a rhetorical marking was noted in discussions on ESD practices, particularly with regard to changing teaching and learning processes. The paper narrates how an interplay of review, research and practical engagement activities have all contributed to an extended critical review of learning interactions in environmental education in an attempt to provide useful perspective for educational activities within the UNDESD. We found that EE and ESD initiatives only acquired more substantive meaning and coherent orientation when examined within ongoing inquiries into situated learning, agency and risk reduction in contexts of poverty, vulnerability and risk, the key concern to us in this paper and the primary focus of the WEHAB (Water, Energy, Health, Agriculture and Biodiversity) sustainable development agenda in the region.
- Full Text:
- Date Issued: 2006
Environmental entrepreneurship as an innovation catalyst for social change: A systematic review as a basis for future research
- Diale, Dineo, Kanakana-Katumba, Mukondeleli G, Maladzhi, Rendani W
- Authors: Diale, Dineo , Kanakana-Katumba, Mukondeleli G , Maladzhi, Rendani W
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/450641 , vital:74970 , xlink:href="https://www.astesj.com/publications/ASTESJ_060145.pdf"
- Description: There are pressures to adopt sustainable behaviour more so in generating profits and benefiting the society to accelerate green efforts through a green framework. The overarching goal of the paper is premised through various works of literature, building the ecosystem the elements highlighted by most researchers in the field of environmental entrepreneurship. The various models reviewed consists of generic incubators and entrepreneurship, and societal and environmental factors. Environmental entrepreneurship is often used interchangeably with concepts such as green entrepreneurship and ecopreneurship which under-researched globally, with non-existent efforts on the applicability and modelling of key environmental entrepreneurship within a specific context utilising the system dynamics approach. In order to assess the environmental entrepreneurship ecosystem, the authors adopted a system dynamic approach to determine key variables that enable the development of the system. A literature review was conducted, and of the 135 articles reviewed, n= 92 peer-reviewed articles met the criteria that the researchers set. Some of the results emanating from a systematic review are environmental policy, green skills, financial and non-financial support, societal and behavioural factors, environmental agility, ethics and governance, and access to markets. The theoretical results are simulated using system dynamics modelling. Due to limited research on the abovementioned topic, a possible impacting variable (Exogenous variables) was broadened to add value to, and have an impact on, the study. Upon reviewing the above-mentioned models, the framework emerged signalling elements to be simulated in the system dynamics model, which were then theoretically contextualised for the South African context. The theoretical virtual system dynamic model forming part of the framework will be tested and validated in the next study. The applicability of the theoretical ecosystem to South African context as well as future recommendations are provided in the study.
- Full Text:
- Date Issued: 2021
- Authors: Diale, Dineo , Kanakana-Katumba, Mukondeleli G , Maladzhi, Rendani W
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/450641 , vital:74970 , xlink:href="https://www.astesj.com/publications/ASTESJ_060145.pdf"
- Description: There are pressures to adopt sustainable behaviour more so in generating profits and benefiting the society to accelerate green efforts through a green framework. The overarching goal of the paper is premised through various works of literature, building the ecosystem the elements highlighted by most researchers in the field of environmental entrepreneurship. The various models reviewed consists of generic incubators and entrepreneurship, and societal and environmental factors. Environmental entrepreneurship is often used interchangeably with concepts such as green entrepreneurship and ecopreneurship which under-researched globally, with non-existent efforts on the applicability and modelling of key environmental entrepreneurship within a specific context utilising the system dynamics approach. In order to assess the environmental entrepreneurship ecosystem, the authors adopted a system dynamic approach to determine key variables that enable the development of the system. A literature review was conducted, and of the 135 articles reviewed, n= 92 peer-reviewed articles met the criteria that the researchers set. Some of the results emanating from a systematic review are environmental policy, green skills, financial and non-financial support, societal and behavioural factors, environmental agility, ethics and governance, and access to markets. The theoretical results are simulated using system dynamics modelling. Due to limited research on the abovementioned topic, a possible impacting variable (Exogenous variables) was broadened to add value to, and have an impact on, the study. Upon reviewing the above-mentioned models, the framework emerged signalling elements to be simulated in the system dynamics model, which were then theoretically contextualised for the South African context. The theoretical virtual system dynamic model forming part of the framework will be tested and validated in the next study. The applicability of the theoretical ecosystem to South African context as well as future recommendations are provided in the study.
- Full Text:
- Date Issued: 2021
Ecosystem of renewable energy enterprises for sustainable development: A systematic review
- Diale, Dineo, Kanakana-Katumba, Mukondeleli G, Maladzhi, Rendani W
- Authors: Diale, Dineo , Kanakana-Katumba, Mukondeleli G , Maladzhi, Rendani W
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/450613 , vital:74967 , xlink:href="https://www.astesj.com/publications/ASTESJ_060146.pdf"
- Description: In the Global sphere, the social, environmental, and economic pillars are the main contributors and accelerators to the sustainable development goals. As a result, the latter creates a platform for interdisciplinary researchers, society and decision-makers to collaborate in formulating ways to minimize factors contributing to environmental concerns. Energy is currently referred to as one of the scarce resources. The scarcity of electricity is mainly experienced in the rural areas of most countries in the world. The mandate of the green economy is to introduce innovative ways to redress the inequalities and lack of access, especially when it comes to Energy. Based on the sector's efforts, questions arise as to what comprises the ecosystem that can be accelerated to enhance entry to the sector. Hence, the researchers focus on Renewable Energy with specific reference to the entrepreneurial motives to meet sustainable goals. The applicable sustainable goals are goal 7 (affordable and clean Energy) and Goal 8 (decent work and economic growth). Furthermore, Energy contributes to modern access and poverty reduction to accelerate the transitioning to a Green economy. The current paper hopes to answer the following questions: Firstly, how Renewable Energy enterprise can contribute to sustainable development goals theoretically. Secondly, how can the theoretical energy enterprise ecosystem be contextualized in the South African context? A theoretical review was conducted through a literature review of which n=47 sources met the criteria that the researchers set for ecosystem variables. The overarching goal of the paper is premised on various works of literature building the ecosystem of the elements highlighted by most researchers in the field of renewable energy enterprises or business ventures. From the various models, the framework emerged singling out the critical success factors of the ecosystem of the Renewable Energy enterprise. The theoretical ecosystem consists of accelerators, social factors, sustainable development goals, as well as selected business models. The latter ecosystem was then contextualized in the South African context for a complete framework. Some of the critical drivers derived from the latter broad ecosystem are: Renewable Energy Feed-in Tarrif (REFIT), Utility Renewable Energy business model, Customer renewable energy business model, Energy Justice (distributive justice), Off-grid (Mini-grid), Saurian Lilting lamp, Renewable powered irrigation system.
- Full Text:
- Date Issued: 2021
- Authors: Diale, Dineo , Kanakana-Katumba, Mukondeleli G , Maladzhi, Rendani W
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/450613 , vital:74967 , xlink:href="https://www.astesj.com/publications/ASTESJ_060146.pdf"
- Description: In the Global sphere, the social, environmental, and economic pillars are the main contributors and accelerators to the sustainable development goals. As a result, the latter creates a platform for interdisciplinary researchers, society and decision-makers to collaborate in formulating ways to minimize factors contributing to environmental concerns. Energy is currently referred to as one of the scarce resources. The scarcity of electricity is mainly experienced in the rural areas of most countries in the world. The mandate of the green economy is to introduce innovative ways to redress the inequalities and lack of access, especially when it comes to Energy. Based on the sector's efforts, questions arise as to what comprises the ecosystem that can be accelerated to enhance entry to the sector. Hence, the researchers focus on Renewable Energy with specific reference to the entrepreneurial motives to meet sustainable goals. The applicable sustainable goals are goal 7 (affordable and clean Energy) and Goal 8 (decent work and economic growth). Furthermore, Energy contributes to modern access and poverty reduction to accelerate the transitioning to a Green economy. The current paper hopes to answer the following questions: Firstly, how Renewable Energy enterprise can contribute to sustainable development goals theoretically. Secondly, how can the theoretical energy enterprise ecosystem be contextualized in the South African context? A theoretical review was conducted through a literature review of which n=47 sources met the criteria that the researchers set for ecosystem variables. The overarching goal of the paper is premised on various works of literature building the ecosystem of the elements highlighted by most researchers in the field of renewable energy enterprises or business ventures. From the various models, the framework emerged singling out the critical success factors of the ecosystem of the Renewable Energy enterprise. The theoretical ecosystem consists of accelerators, social factors, sustainable development goals, as well as selected business models. The latter ecosystem was then contextualized in the South African context for a complete framework. Some of the critical drivers derived from the latter broad ecosystem are: Renewable Energy Feed-in Tarrif (REFIT), Utility Renewable Energy business model, Customer renewable energy business model, Energy Justice (distributive justice), Off-grid (Mini-grid), Saurian Lilting lamp, Renewable powered irrigation system.
- Full Text:
- Date Issued: 2021
Partial cold treatment of citrus fruit for export risk mitigation for Thaumatotibia leucotreta (Lepidoptera: Tortricidae) as part of a systems approach
- Moore, Sean D, Kirkman, Wayne, Albertyn, Sonnica, Love, C N, Coetzee, Julie A, Hattingh, Vaughan
- Authors: Moore, Sean D , Kirkman, Wayne , Albertyn, Sonnica , Love, C N , Coetzee, Julie A , Hattingh, Vaughan
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423796 , vital:72094 , xlink:href="https://doi.org/10.1093/jee/tow138"
- Description: Some of South Africa’s citrus export markets require mandatory postharvest cold treatment of citrus fruit as a phytosanitary risk mitigation treatment for Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae). An alternative to this may be partial cold treatment as one of the final steps in a systems approach to mitigate phytosanitary risk. Consequently, the efficacy of such partial cold treatments was evaluated. It was first determined that a 2C cold treatment was significantly more effective against fourth and fifth instars (the most cold-tolerant instars) than treatments at 3C and 4C for a duration of 18 d. Secondly, it was determined that 2C for 18 d and 1C for 16 d were similarly effective, but both treatments were significantly more effective than 1C for 14 d. Mean mortality of fourth and fifth instars treated with 2C for 18 d in seven replicates from four trials was 99.94%. Finally, it was determined that the inability of the majority of surviving larvae to develop to adulthood would further increase the efficacy of a 2C for 18 d treatment to 99.96%. Inclusion of reproductive nonviability of survivors increased mortality to 99.99%.
- Full Text:
- Date Issued: 2016
- Authors: Moore, Sean D , Kirkman, Wayne , Albertyn, Sonnica , Love, C N , Coetzee, Julie A , Hattingh, Vaughan
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423796 , vital:72094 , xlink:href="https://doi.org/10.1093/jee/tow138"
- Description: Some of South Africa’s citrus export markets require mandatory postharvest cold treatment of citrus fruit as a phytosanitary risk mitigation treatment for Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae). An alternative to this may be partial cold treatment as one of the final steps in a systems approach to mitigate phytosanitary risk. Consequently, the efficacy of such partial cold treatments was evaluated. It was first determined that a 2C cold treatment was significantly more effective against fourth and fifth instars (the most cold-tolerant instars) than treatments at 3C and 4C for a duration of 18 d. Secondly, it was determined that 2C for 18 d and 1C for 16 d were similarly effective, but both treatments were significantly more effective than 1C for 14 d. Mean mortality of fourth and fifth instars treated with 2C for 18 d in seven replicates from four trials was 99.94%. Finally, it was determined that the inability of the majority of surviving larvae to develop to adulthood would further increase the efficacy of a 2C for 18 d treatment to 99.96%. Inclusion of reproductive nonviability of survivors increased mortality to 99.99%.
- Full Text:
- Date Issued: 2016
Genetic diversity and morphological variation in African boxthorn (Lycium ferocissimum)–characterising the target weed for biological control
- McCulloch, Graham A, Mauda, Evans V, Chari, Lenin D, Martin, Grant D, Gurdasani, Komal, Morin, L, Walter, Grenville H, Raghu, S
- Authors: McCulloch, Graham A , Mauda, Evans V , Chari, Lenin D , Martin, Grant D , Gurdasani, Komal , Morin, L , Walter, Grenville 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, Lenin D , Martin, Grant D , Gurdasani, Komal , Morin, L , Walter, Grenville 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
‘If you choose to abort, you have acted as an instrument of Satan’: Zimbabwean health service Providers’ negative constructions of women presenting for post abortion care
- Chiweshe, Malvern T, Macleod, Catriona I
- Authors: Chiweshe, Malvern T , Macleod, Catriona I
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444200 , vital:74205 , xlink:href="https://doi.org/10.1007/s12529-017-9694-8"
- Description: Health service providers play a crucial role in providing post abortion care in countries where abortion legislation is restrictive and abortion is stigmatised. Research in countries where these factors apply has shown that health service providers can be barriers to women accessing post abortion services. Much of this research draws from attitude theory. In this paper, we utilise positioning theory to show how the ways in which Zimbabwean health service providers’ position women and themselves are rooted in cultural and social power relations. In light of recent efforts by the Zimbabwean Ministry of Health and foreign organisations to improve post abortion care, we explore the implications that these positionings have for post abortion care.
- Full Text:
- Date Issued: 2017
- Authors: Chiweshe, Malvern T , Macleod, Catriona I
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444200 , vital:74205 , xlink:href="https://doi.org/10.1007/s12529-017-9694-8"
- Description: Health service providers play a crucial role in providing post abortion care in countries where abortion legislation is restrictive and abortion is stigmatised. Research in countries where these factors apply has shown that health service providers can be barriers to women accessing post abortion services. Much of this research draws from attitude theory. In this paper, we utilise positioning theory to show how the ways in which Zimbabwean health service providers’ position women and themselves are rooted in cultural and social power relations. In light of recent efforts by the Zimbabwean Ministry of Health and foreign organisations to improve post abortion care, we explore the implications that these positionings have for post abortion care.
- Full Text:
- Date Issued: 2017
The synthesis and photophysicochemical properties of low-symmetry zinc phthalocyanine analogues
- Chidawanyika, Wadzanai J U, Nyokong, Tebello
- Authors: Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263397 , vital:53624 , xlink:href="https://doi.org/10.1016/j.jphotochem.2009.06.005"
- Description: The synthesis of a low-symmetry derivative, zinc mono-carboxy substituted phthalocyanine, ZnPc-COOH (4) has been reported. The photochemical and photophysical properties of ZnPc-COOH (4), ZnTMPyPc (5), ZnttbPc (6) and a previously synthesized low-symmetry derivative, ZnttbIPc (7), in various organic solvents are reported. The red-shifting of the spectra of 4 and 5 (relative to that of unsubstituted zinc phthalocyanine, ZnPc) is a function of the electron-donating sulfur-containing substituents attached to the periphery of the molecule. High triplet quantum yields (ФT) generally occur in response to substitution on the zinc phthalocyanine ring periphery. The highest ФT values and triplet lifetimes (τT) occur in DMSO for all derivatives as a result of the solvent's high viscosity. The strongly electron-withdrawing imido fused ring of ZnttbIPc (7) stabilizes it against photo-oxidative degradation relative to the other derivatives.
- Full Text:
- Date Issued: 2009
- Authors: Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263397 , vital:53624 , xlink:href="https://doi.org/10.1016/j.jphotochem.2009.06.005"
- Description: The synthesis of a low-symmetry derivative, zinc mono-carboxy substituted phthalocyanine, ZnPc-COOH (4) has been reported. The photochemical and photophysical properties of ZnPc-COOH (4), ZnTMPyPc (5), ZnttbPc (6) and a previously synthesized low-symmetry derivative, ZnttbIPc (7), in various organic solvents are reported. The red-shifting of the spectra of 4 and 5 (relative to that of unsubstituted zinc phthalocyanine, ZnPc) is a function of the electron-donating sulfur-containing substituents attached to the periphery of the molecule. High triplet quantum yields (ФT) generally occur in response to substitution on the zinc phthalocyanine ring periphery. The highest ФT values and triplet lifetimes (τT) occur in DMSO for all derivatives as a result of the solvent's high viscosity. The strongly electron-withdrawing imido fused ring of ZnttbIPc (7) stabilizes it against photo-oxidative degradation relative to the other derivatives.
- Full Text:
- Date Issued: 2009
Syntheses and photophysics of new phthalocyanine derivatives of zinc, cadmium and mercury
- Chidawanyika, Wadzanai J U, Ogunsipe, Abimbola, Nyokong, Tebello
- Authors: Chidawanyika, Wadzanai J U , Ogunsipe, Abimbola , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/283940 , vital:56005 , xlink:href="https://doi.org/10.1039/B615663K"
- Description: The syntheses of novel tetra{2,(3)-pyridyloxyphthalocyaninato} complexes of zinc, cadmium and mercury (TPyZnPc, TPyCdPc and TPyHgPc) are presented. Their spectral and photophysical properties (as well as those of their unsubstituted counterparts: ZnPc, CdPc and HgPc) are investigated. TPyZnPc and TPyCdPc are aggregated in non-coordinating solvents such as chloroform, while TPyHgPc is demetallated, as evident from their respective absorption spectra. The trends in fluorescence (ΦF), triplet (ΦT) and singlet oxygen (ΦΔ) quantum yields are explained in terms of relative strengths of spin–orbit coupling induced by the respective central metal ions in the complexes. The effect of the pyridyloxy substituents is a decrease in ΦF and an increase in ΦT values. The complexes are less fluorescent in DMSO but possess higher ΦT, triplet lifetimes (τT) and ΦΔ therein.
- Full Text:
- Date Issued: 2007
- Authors: Chidawanyika, Wadzanai J U , Ogunsipe, Abimbola , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/283940 , vital:56005 , xlink:href="https://doi.org/10.1039/B615663K"
- Description: The syntheses of novel tetra{2,(3)-pyridyloxyphthalocyaninato} complexes of zinc, cadmium and mercury (TPyZnPc, TPyCdPc and TPyHgPc) are presented. Their spectral and photophysical properties (as well as those of their unsubstituted counterparts: ZnPc, CdPc and HgPc) are investigated. TPyZnPc and TPyCdPc are aggregated in non-coordinating solvents such as chloroform, while TPyHgPc is demetallated, as evident from their respective absorption spectra. The trends in fluorescence (ΦF), triplet (ΦT) and singlet oxygen (ΦΔ) quantum yields are explained in terms of relative strengths of spin–orbit coupling induced by the respective central metal ions in the complexes. The effect of the pyridyloxy substituents is a decrease in ΦF and an increase in ΦT values. The complexes are less fluorescent in DMSO but possess higher ΦT, triplet lifetimes (τT) and ΦΔ therein.
- Full Text:
- Date Issued: 2007
Transformative, transgressive social learning: Rethinking higher education pedagogy in times of systemic global dysfunction
- Lotz-Sisitka, Heila, Wals, Arjen E J, Kronlid, David O, McGarry, Dylan K
- Authors: Lotz-Sisitka, Heila , Wals, Arjen E J , Kronlid, David O , McGarry, Dylan K
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/372794 , vital:66623 , xlink:href="https://doi.org/10.1016/j.cosust.2015.07.018"
- Description: The nature of the sustainability challenges currently at hand is such that dominant pedagogies and forms of learning that characterize higher education need to be reconsidered to enable students and staff to deal with accelerating change, increasing complexity, contested knowledge claims and inevitable uncertainty. In this contribution we identified four streams of emerging transformative, transgressive learning research and praxis in the sustainability sciences that appear generative of a higher education pedagogy that appears more responsive to the key challenges of our time: (1) reflexive social learning and capabilities theory, (2) critical phenomenology, (3) socio-cultural and cultural historical activity theory, and (4) new social movement, postcolonial and decolonisation theory. The paper critiques the current tendency in sustainability science and learning to rely on resilience and adaptive capacity building and argues that in order to break with maladaptive resilience of unsustainable systems it is essential to strengthen transgressive learning and disruptive capacity-building.
- Full Text:
- Date Issued: 2015
- Authors: Lotz-Sisitka, Heila , Wals, Arjen E J , Kronlid, David O , McGarry, Dylan K
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/372794 , vital:66623 , xlink:href="https://doi.org/10.1016/j.cosust.2015.07.018"
- Description: The nature of the sustainability challenges currently at hand is such that dominant pedagogies and forms of learning that characterize higher education need to be reconsidered to enable students and staff to deal with accelerating change, increasing complexity, contested knowledge claims and inevitable uncertainty. In this contribution we identified four streams of emerging transformative, transgressive learning research and praxis in the sustainability sciences that appear generative of a higher education pedagogy that appears more responsive to the key challenges of our time: (1) reflexive social learning and capabilities theory, (2) critical phenomenology, (3) socio-cultural and cultural historical activity theory, and (4) new social movement, postcolonial and decolonisation theory. The paper critiques the current tendency in sustainability science and learning to rely on resilience and adaptive capacity building and argues that in order to break with maladaptive resilience of unsustainable systems it is essential to strengthen transgressive learning and disruptive capacity-building.
- Full Text:
- Date Issued: 2015
Is green space associated with reduced crime? A national-scale study from the Global South
- Venter, Zander S, Shackleton, Charlie M, Faull, Andrew, Lancaster, Lizette, Breetzke, Gregory, Edelstein, Ian
- Authors: Venter, Zander S , Shackleton, Charlie M , Faull, Andrew , Lancaster, Lizette , Breetzke, Gregory , Edelstein, Ian
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/402340 , vital:69843 , xlink:href="https://doi.org/10.1016/j.scitotenv.2022.154005"
- Description: Assumptions about the link between green space and crime mitigation are informed by literature that overwhelmingly originates in the Global North. Little is known about the association between green spaces and crime in the Global South. We utilized 10 years of precinct-level crime statistics (n = 1152) over South Africa, a global crime hotspot, to test the hypothesis that green space is associated with reduced crime rates. We found that, after controlling for a number of socio-demographic confounders (unemployment, income, age, education, land use and population density), for every 1% increase in total green space there is a 1.2% (0.7 to 1.7%; 95% confidence interval) decrease in violent crime, and 1.3% (0.8 to 1.8%) decrease in property crime, with no effect on sexual crimes. However, the direction of the association changed for property crimes when exploring the effect of green space characteristics including tree cover and park accessibility. Property crimes increase by 0.4% (0.1 to 0.7%) with a percentage increase in tree cover, and by 0.9% (0.5 to 1.3%) with every kilometer increase in proximity to a public park. Further research, including experimental studies, is needed to better isolate causal mechanisms behind crime-green space associations, especially considering that green space may map to race and income inequality and that there may be more crime reporting in affluent areas. Nevertheless, our results provide a complementary contribution to the evidence from the Global North, highlighting the need for more nuanced definitions of green space and its characteristics when considering links to crime. When viewed in light of the broader suite of ecosystem services provided by green space, our results support urban greening as a major strategy towards achieving just and sustainable cities and towns.
- Full Text:
- Date Issued: 2022
- Authors: Venter, Zander S , Shackleton, Charlie M , Faull, Andrew , Lancaster, Lizette , Breetzke, Gregory , Edelstein, Ian
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/402340 , vital:69843 , xlink:href="https://doi.org/10.1016/j.scitotenv.2022.154005"
- Description: Assumptions about the link between green space and crime mitigation are informed by literature that overwhelmingly originates in the Global North. Little is known about the association between green spaces and crime in the Global South. We utilized 10 years of precinct-level crime statistics (n = 1152) over South Africa, a global crime hotspot, to test the hypothesis that green space is associated with reduced crime rates. We found that, after controlling for a number of socio-demographic confounders (unemployment, income, age, education, land use and population density), for every 1% increase in total green space there is a 1.2% (0.7 to 1.7%; 95% confidence interval) decrease in violent crime, and 1.3% (0.8 to 1.8%) decrease in property crime, with no effect on sexual crimes. However, the direction of the association changed for property crimes when exploring the effect of green space characteristics including tree cover and park accessibility. Property crimes increase by 0.4% (0.1 to 0.7%) with a percentage increase in tree cover, and by 0.9% (0.5 to 1.3%) with every kilometer increase in proximity to a public park. Further research, including experimental studies, is needed to better isolate causal mechanisms behind crime-green space associations, especially considering that green space may map to race and income inequality and that there may be more crime reporting in affluent areas. Nevertheless, our results provide a complementary contribution to the evidence from the Global North, highlighting the need for more nuanced definitions of green space and its characteristics when considering links to crime. When viewed in light of the broader suite of ecosystem services provided by green space, our results support urban greening as a major strategy towards achieving just and sustainable cities and towns.
- Full Text:
- Date Issued: 2022
Grand challenges in urban agriculture: ecological and social approaches to transformative sustainability
- Zimmerer, Karl S, Bell, Martha G, Chirisa, Innocent, Duvall, Chris S, Egerer, Monika, Hung, Po-Yi, Lerner, Amy M, Shackleton, Charlie M, Ward, James D, Ochoa, Carolina Y
- Authors: Zimmerer, Karl S , Bell, Martha G , Chirisa, Innocent , Duvall, Chris S , Egerer, Monika , Hung, Po-Yi , Lerner, Amy M , Shackleton, Charlie M , Ward, James D , Ochoa, Carolina Y
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/402287 , vital:69838 , xlink:href="https://doi.org/10.3389/fsufs.2021.668561"
- Description: This synopsis of the Grand Challenges of Urban Agriculture (UA) is framed by the urgent need to understand and strengthen the expanding yet highly diverse roles of UA amid rapid global urbanization, failures of predominant food systems, and crises in systems of physical and mental health. More than half of humanity lives in cities today and by 2030 this is projected to grow to 60.4 percent, ∼5 billion people (UN Habitat, 2020). More than 90 percent of urban demographic increase is anticipated to take place in the developing world. Ecological and social dimensions of UA are situated in these expanding spaces of cities, towns, and villages (along with their urban fringe or peri-urban areas), and among their diverse populations. UA is further situated in the powerful, far-reaching influences of urbanization processes that occur within and beyond these spaces. UA is thus integral to the prospect of Urban Sustainability as SDG 11 (“Make cities and human settlements inclusive, safe, resilient and sustainable”) of the U.N.’s 2030 Agenda for Sustainable Development.
- Full Text:
- Date Issued: 2021
- Authors: Zimmerer, Karl S , Bell, Martha G , Chirisa, Innocent , Duvall, Chris S , Egerer, Monika , Hung, Po-Yi , Lerner, Amy M , Shackleton, Charlie M , Ward, James D , Ochoa, Carolina Y
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/402287 , vital:69838 , xlink:href="https://doi.org/10.3389/fsufs.2021.668561"
- Description: This synopsis of the Grand Challenges of Urban Agriculture (UA) is framed by the urgent need to understand and strengthen the expanding yet highly diverse roles of UA amid rapid global urbanization, failures of predominant food systems, and crises in systems of physical and mental health. More than half of humanity lives in cities today and by 2030 this is projected to grow to 60.4 percent, ∼5 billion people (UN Habitat, 2020). More than 90 percent of urban demographic increase is anticipated to take place in the developing world. Ecological and social dimensions of UA are situated in these expanding spaces of cities, towns, and villages (along with their urban fringe or peri-urban areas), and among their diverse populations. UA is further situated in the powerful, far-reaching influences of urbanization processes that occur within and beyond these spaces. UA is thus integral to the prospect of Urban Sustainability as SDG 11 (“Make cities and human settlements inclusive, safe, resilient and sustainable”) of the U.N.’s 2030 Agenda for Sustainable Development.
- Full Text:
- Date Issued: 2021
Perceptions of affirmative action
- Scott, Judith, Amos, Trevor L, Richard Scott, W
- Authors: Scott, Judith , Amos, Trevor L , Richard Scott, W
- Date: 1996
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/270914 , vital:54491 , xlink:href="https://hdl.handle.net/10520/EJC-67e7bffd2"
- Description: Private and public South African employers have instituted affirmative action policies meant to provide employment opportunities to Black South Africans. A body of literature suggests that because of affirmative action policies Black hopes have been raised while Whites view such policies as having a negative impact on their opportunities. However, no extant literature details an empirical investigation of these suggestions. Therefore, this study focusses on the affirmative action perceptions held by 350 South African university commerce students.
- Full Text:
- Date Issued: 1996
- Authors: Scott, Judith , Amos, Trevor L , Richard Scott, W
- Date: 1996
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/270914 , vital:54491 , xlink:href="https://hdl.handle.net/10520/EJC-67e7bffd2"
- Description: Private and public South African employers have instituted affirmative action policies meant to provide employment opportunities to Black South Africans. A body of literature suggests that because of affirmative action policies Black hopes have been raised while Whites view such policies as having a negative impact on their opportunities. However, no extant literature details an empirical investigation of these suggestions. Therefore, this study focusses on the affirmative action perceptions held by 350 South African university commerce students.
- Full Text:
- Date Issued: 1996
Co-encapsulation of rifampicin and isoniazid in crude soybean lecithin liposomes
- Nkanga, Christian I, Noundou, Xavier S, Walker, Roderick B, Krause, Rui W M
- Authors: Nkanga, Christian I , Noundou, Xavier S , Walker, Roderick B , Krause, Rui W M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183536 , vital:44005 , xlink:href="https://doi.org/10.17159/0379-4350/2019/v72a11"
- Description: Despite the well-known anti-mycobacterial actions of isoniazid (INH) and rifampicin (RIF), the clinical success of tuberculosis (TB) therapy requires prolonged administration of multiple drugs in high doses, which often result in frequent adverse effects and low patient adherence. Although liposomes are promising candidates for controlled delivery of anti-TB drug, the high cost of synthetic and highly purified natural lipids currently used in liposomal technology might preclude the universal application of therapeutic liposomes. This work aimed at evaluating the potential of a cost-effective lipid material, crude soybean lecithin (CL), to co-encapsulate RIF and INH for liposomal dual delivery. RIF was encapsulated in CL-liposomes with/without cholesterol using film hydration method, after which INH was incorporated using a freeze–thawing technique. Dynamic light scattering, differential scanning calorimetry, X-ray diffraction and dialysis were used for liposome characterization. Liposomes containing CL alone (CLL) exhibited 90%encapsulation efficiency for RIF and 59%for INH. The mean size and surface charge of CLL were 1114nm and –63mV, respectively. In addition, CLL showed a controlled release profile for the co-encapsulated drugs. CLL would be promising vehicles for macrophage-targeting drug delivery. The present findings demonstrate the feasibility of using CL for preparation of combination products for liposomal delivery.
- Full Text:
- Date Issued: 2019
- Authors: Nkanga, Christian I , Noundou, Xavier S , Walker, Roderick B , Krause, Rui W M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183536 , vital:44005 , xlink:href="https://doi.org/10.17159/0379-4350/2019/v72a11"
- Description: Despite the well-known anti-mycobacterial actions of isoniazid (INH) and rifampicin (RIF), the clinical success of tuberculosis (TB) therapy requires prolonged administration of multiple drugs in high doses, which often result in frequent adverse effects and low patient adherence. Although liposomes are promising candidates for controlled delivery of anti-TB drug, the high cost of synthetic and highly purified natural lipids currently used in liposomal technology might preclude the universal application of therapeutic liposomes. This work aimed at evaluating the potential of a cost-effective lipid material, crude soybean lecithin (CL), to co-encapsulate RIF and INH for liposomal dual delivery. RIF was encapsulated in CL-liposomes with/without cholesterol using film hydration method, after which INH was incorporated using a freeze–thawing technique. Dynamic light scattering, differential scanning calorimetry, X-ray diffraction and dialysis were used for liposome characterization. Liposomes containing CL alone (CLL) exhibited 90%encapsulation efficiency for RIF and 59%for INH. The mean size and surface charge of CLL were 1114nm and –63mV, respectively. In addition, CLL showed a controlled release profile for the co-encapsulated drugs. CLL would be promising vehicles for macrophage-targeting drug delivery. The present findings demonstrate the feasibility of using CL for preparation of combination products for liposomal delivery.
- Full Text:
- Date Issued: 2019
Encapsulation and physicochemical evaluation of efavirenz in liposomes
- Okafor, Nnamdi Ikemefuna, Nkanga, Christian I, Walker, Roderick B, Noundou, Xavier S, Krause, Rui W M
- Authors: Okafor, Nnamdi Ikemefuna , Nkanga, Christian I , Walker, Roderick B , Noundou, Xavier S , Krause, Rui W M
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183414 , vital:43988 , xlink:href="https://doi.org/10.1007/s40005-019-00458-8"
- Description: Antiretroviral therapy remains the most efective means of managing the human immune defciency virus/acquired immune defciency syndrome (HIV/AIDS). Application of therapeutics has been hampered by factors including poor bioavailability of most anti-retroviral compounds (ARV), side efects and an alarming emergence of drug resistant strains of the virus. Recent developments and use of drug delivery systems (DDS) has shown potential for improving the pharmacological profle of ARV. Amongst these complex DDS, liposomes have been explored for delivery of ARV. In this study, we have aimed at exploring efcient encapsulation of efavirenz (EFV), a potent ARV using diferent mass ratios of crude soybean lecithin and cholesterol. The EFV-loaded liposomes (EFL) were prepared using thin flm hydration and evaluated for particle size, zeta potential (ZP), encapsulation efciency (EE%), morphology and drug release studies. Diferential scanning calorimetry (DSC), X-ray difraction (XRD), energy dispersity spectroscopy (EDS) and Fourier transform infrared (FTIR) spectroscopy were used for comprehensive physicochemical characterization of EFL. EFL exhibited high encapsulation (99%) in 1:1 crude lecithin to cholesterol mass ratio. The average particle size and Zeta Potential of EFL were found to be 411.10±7.40 nm and −53.5.3±0.06 mV, respectively. EFL showed a relatively controlled EFV release behaviour that was similar to the dissolution profle of un-encapsulated EFV. This suggests that EFL represents a promising vehicle for efective EFV delivery while providing the advantages of a nano-scaled delivery system
- Full Text:
- Date Issued: 2020
- Authors: Okafor, Nnamdi Ikemefuna , Nkanga, Christian I , Walker, Roderick B , Noundou, Xavier S , Krause, Rui W M
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183414 , vital:43988 , xlink:href="https://doi.org/10.1007/s40005-019-00458-8"
- Description: Antiretroviral therapy remains the most efective means of managing the human immune defciency virus/acquired immune defciency syndrome (HIV/AIDS). Application of therapeutics has been hampered by factors including poor bioavailability of most anti-retroviral compounds (ARV), side efects and an alarming emergence of drug resistant strains of the virus. Recent developments and use of drug delivery systems (DDS) has shown potential for improving the pharmacological profle of ARV. Amongst these complex DDS, liposomes have been explored for delivery of ARV. In this study, we have aimed at exploring efcient encapsulation of efavirenz (EFV), a potent ARV using diferent mass ratios of crude soybean lecithin and cholesterol. The EFV-loaded liposomes (EFL) were prepared using thin flm hydration and evaluated for particle size, zeta potential (ZP), encapsulation efciency (EE%), morphology and drug release studies. Diferential scanning calorimetry (DSC), X-ray difraction (XRD), energy dispersity spectroscopy (EDS) and Fourier transform infrared (FTIR) spectroscopy were used for comprehensive physicochemical characterization of EFL. EFL exhibited high encapsulation (99%) in 1:1 crude lecithin to cholesterol mass ratio. The average particle size and Zeta Potential of EFL were found to be 411.10±7.40 nm and −53.5.3±0.06 mV, respectively. EFL showed a relatively controlled EFV release behaviour that was similar to the dissolution profle of un-encapsulated EFV. This suggests that EFL represents a promising vehicle for efective EFV delivery while providing the advantages of a nano-scaled delivery system
- Full Text:
- Date Issued: 2020
Electronic and nonlinear optical properties of 3-(((2-substituted-4-nitrophenyl) imino) methyl) phenol
- Ojo, Nathanael D, Krause, Rui W M, Obi-Egbedi, Nelson O
- Authors: Ojo, Nathanael D , Krause, Rui W M , Obi-Egbedi, Nelson O
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193408 , vital:45329 , xlink:href="https://doi.org/10.1016/j.comptc.2020.113050"
- Description: This work entails the study of electronic and nonlinear optical (NLO) properties of two synthesized Schiff bases namely 3-(((2-methyl-4-nitrophenyl)imino)methyl)phenol (MMP) and 3-(((2,4-dinitrophenyl)imino)methyl)phenol (DMP). Electronic absorption properties studied using UV–Visible spectrophotometry in ethanol reveal low-energy absorption indicating a low band gap. Time-dependent density functional calculations on their excited state properties with ωB97X-D/6-311++G(d,p) method show comparable transition energies and intensities with the experimental results. Energy gaps (ΔE) and NLO properties were evaluated from the frontier orbitals and hyperpolarizabilities (βtot and γ) in gas, cyclohexane and ethanol. Low ΔE obtained shows the potentials of the systems as organic semiconductor with remarkable band gap stabilization in ethanol. Higher βtot and γ than urea imply that the Schiff bases possess potentials for NLO applications. The solvatochromic shift in transition energies and perturbation of electronic properties reveal the solvent dependence of the electronic and optical properties of MMP and DMP due to solute-solvent interactions.
- Full Text:
- Date Issued: 2020
- Authors: Ojo, Nathanael D , Krause, Rui W M , Obi-Egbedi, Nelson O
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193408 , vital:45329 , xlink:href="https://doi.org/10.1016/j.comptc.2020.113050"
- Description: This work entails the study of electronic and nonlinear optical (NLO) properties of two synthesized Schiff bases namely 3-(((2-methyl-4-nitrophenyl)imino)methyl)phenol (MMP) and 3-(((2,4-dinitrophenyl)imino)methyl)phenol (DMP). Electronic absorption properties studied using UV–Visible spectrophotometry in ethanol reveal low-energy absorption indicating a low band gap. Time-dependent density functional calculations on their excited state properties with ωB97X-D/6-311++G(d,p) method show comparable transition energies and intensities with the experimental results. Energy gaps (ΔE) and NLO properties were evaluated from the frontier orbitals and hyperpolarizabilities (βtot and γ) in gas, cyclohexane and ethanol. Low ΔE obtained shows the potentials of the systems as organic semiconductor with remarkable band gap stabilization in ethanol. Higher βtot and γ than urea imply that the Schiff bases possess potentials for NLO applications. The solvatochromic shift in transition energies and perturbation of electronic properties reveal the solvent dependence of the electronic and optical properties of MMP and DMP due to solute-solvent interactions.
- Full Text:
- Date Issued: 2020
Electronic and nonlinear optical properties of 2-(((5-aminonaphthalen-1-yl) imino) methyl) phenol
- Ojo, Nathanael D, Krause, Rui W M, Obi-Egbedi, Nelson O
- Authors: Ojo, Nathanael D , Krause, Rui W M , Obi-Egbedi, Nelson O
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193397 , vital:45328 , xlink:href="https://doi.org/10.1016/j.molliq.2020.114157"
- Description: In this study, solvent dependence of electronic and nonlinear optical properties of a new Schiff base, 2-(((5-aminonaphthalen-1-yl)imino)methyl) phenol (DANOHB), has been investigated. Electronic and optical properties of the Schiff base studied using Uv-visible absorption and fluorescence spectroscopic techniques in solution show that the Schiff base exhibits fluorescence with a quantum yield of 0.21 and a Stokes shift of 39 nm. Quantum chemical calculations were performed on the Schiff base at time-dependent density functional level of theory using Becke-3-Lee-Yang-Parr method with 6-311++G(d,p) basis set. Solvent dependence of the excited state energies (EE), energy gap (ΔE), first-order (β) and second-order (γ) hyperpolarizabilities were studied in gas, cyclohexane and ethanol. The medium perturbed the energy levels which implies that the reactivity, activity and stability of the system are solvent sensitive. The γ is more than thirty times higher than urea (standard NLO material) and this property is further enhanced in less polar medium. Small ΔE and large hyperpolarizabilities obtained for this system suggest its good potential in photonics and nonlinear optical devices.
- Full Text:
- Date Issued: 2020
- Authors: Ojo, Nathanael D , Krause, Rui W M , Obi-Egbedi, Nelson O
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193397 , vital:45328 , xlink:href="https://doi.org/10.1016/j.molliq.2020.114157"
- Description: In this study, solvent dependence of electronic and nonlinear optical properties of a new Schiff base, 2-(((5-aminonaphthalen-1-yl)imino)methyl) phenol (DANOHB), has been investigated. Electronic and optical properties of the Schiff base studied using Uv-visible absorption and fluorescence spectroscopic techniques in solution show that the Schiff base exhibits fluorescence with a quantum yield of 0.21 and a Stokes shift of 39 nm. Quantum chemical calculations were performed on the Schiff base at time-dependent density functional level of theory using Becke-3-Lee-Yang-Parr method with 6-311++G(d,p) basis set. Solvent dependence of the excited state energies (EE), energy gap (ΔE), first-order (β) and second-order (γ) hyperpolarizabilities were studied in gas, cyclohexane and ethanol. The medium perturbed the energy levels which implies that the reactivity, activity and stability of the system are solvent sensitive. The γ is more than thirty times higher than urea (standard NLO material) and this property is further enhanced in less polar medium. Small ΔE and large hyperpolarizabilities obtained for this system suggest its good potential in photonics and nonlinear optical devices.
- Full Text:
- Date Issued: 2020
Thien-2-yl substituted chlorins as photosensitizers for photodynamic therapy and photodynamic antimicrobial chemotherapy
- Babu, Balaji, Sindelo, Azole, Mack, John, Nyokong, Tebello
- Authors: Babu, Balaji , Sindelo, Azole , Mack, John , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190578 , vital:45007 , xlink:href="https://doi.org/10.1016/j.dyepig.2020.108886"
- Description: The synthesis and characterization of meso-tetra(thien-2-yl)chlorin (1) and meso-tetra(5-bromothien-2-yl)chlorin (2) is reported. These dyes have red-shifted absorption maxima compared to those of the analogous meso-tetraphenylchlorin (3). 1 and 2 have Q bands at 660 and 664 nm, respectively, singlet oxygen quantum yields of 0.60 and 0.64 and exhibit good photostability. The triplet states were found to have lifetimes of 8.6 μs in N2 purged DMF. Time-dependent cellular uptake of chlorins reached a maximum in MCF-7 cancer cells after 12 h. Upon irradiation with a Thorlabs M660L3 LED (280 mW cm−2), 2 exhibited better photocytotoxicity with an IC50 value of 2.7 μM against MCF-7 cells. The 2ʹ,7ʹ-dichlorodihydrofluorescein diacetate (DCFDA) assay provided evidence for intracellular generation of reactive oxygen species. Photodynamic inactivation of bacteria by the chlorins was also studied. 2 exhibits better activity with log reduction values of 7.42 and 8.34 towards Staphylococcus aureus and Escherichia coli, respectively, under illumination for 60 min at 660 nm with a Thorlabs M660L3 LED (280 mW cm−2). These results demonstrate that 2 is a promising candidate for future in vivo experiments and merits further in-depth investigation.
- Full Text:
- Date Issued: 2021
- Authors: Babu, Balaji , Sindelo, Azole , Mack, John , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190578 , vital:45007 , xlink:href="https://doi.org/10.1016/j.dyepig.2020.108886"
- Description: The synthesis and characterization of meso-tetra(thien-2-yl)chlorin (1) and meso-tetra(5-bromothien-2-yl)chlorin (2) is reported. These dyes have red-shifted absorption maxima compared to those of the analogous meso-tetraphenylchlorin (3). 1 and 2 have Q bands at 660 and 664 nm, respectively, singlet oxygen quantum yields of 0.60 and 0.64 and exhibit good photostability. The triplet states were found to have lifetimes of 8.6 μs in N2 purged DMF. Time-dependent cellular uptake of chlorins reached a maximum in MCF-7 cancer cells after 12 h. Upon irradiation with a Thorlabs M660L3 LED (280 mW cm−2), 2 exhibited better photocytotoxicity with an IC50 value of 2.7 μM against MCF-7 cells. The 2ʹ,7ʹ-dichlorodihydrofluorescein diacetate (DCFDA) assay provided evidence for intracellular generation of reactive oxygen species. Photodynamic inactivation of bacteria by the chlorins was also studied. 2 exhibits better activity with log reduction values of 7.42 and 8.34 towards Staphylococcus aureus and Escherichia coli, respectively, under illumination for 60 min at 660 nm with a Thorlabs M660L3 LED (280 mW cm−2). These results demonstrate that 2 is a promising candidate for future in vivo experiments and merits further in-depth investigation.
- Full Text:
- Date Issued: 2021