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Symmetry effect of cobalt phthalocyanines on the aluminium corrosion inhibition in hydrochloric acid

- Nnaji, Nnaemeka, Sen, Pinar, Nyokong, Tebello

Authors: Nnaji, Nnaemeka , Sen, Pinar , Nyokong, Tebello
Date: 2022
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/231323 , vital:49877 , xlink:href="https://doi.org/10.1016/j.matlet.2021.130892"
Description: The aluminium corrosion retardation potentials of phthalocyanine-based dyes, cobalt (II) 2,9,16-tris(4-(tert-butyl)phenoxy)-23-(pyridin-4-yloxy)phthalocyanine (D1) and cobalt (II) 2,9,16,24-tetrakis(4-(tert-butyl)phenoxy)phthalocyanine (D2) in 1 M hydrochloric acid were evaluated. Results from potentiodynamic polarization measurements show that inhibition efficiency increased with inhibitor concentration at 28 °C with values of 91.9 % and 87.0 % values respectively for D1 and D2 at 10 μM.
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Date Issued: 2022

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Photodegradation of tetracycline by asymmetrical zinc (II) phthalocyanines conjugated to cobalt tungstate nanoparticles

- Mgidlana, Sithi, Sen, Pinar, Nyokong, Tebello

Authors: Mgidlana, Sithi , Sen, Pinar , Nyokong, Tebello
Date: 2022
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/300233 , vital:57908 , xlink:href="https://doi.org/10.1016/j.molstruc.2022.132938"
Description: This work focused on syntheses of novel asymmetrically tetra substituted Zn phthalocyanines (ZnPc) each containing a single carboxyl group, with the other substituents bearing alkynyl (complex 1) and fluorine containing groups (complexes 2 and 3). The complexes were conjugated to cobalt tungstate nanoparticles and employed as efficient photocatalysts for degradation of tetracycline in water. ZnPc complexes and their conjugates showed good photophysical and photochemical properties behaviour with complex 1 giving higher triplet and singlet oxygen quantum yields compared to 2 and 3. Complex 1 showed higher activity towards the photodegradation of tetracycline compared to complexes 2 and 3, with higher kobs and initial rates for the former. The photocatalysis obeyed the Langmuir-Hinshelwood kinetic model.
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Date Issued: 2022

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A Change Project story: learning and caring for South Africa’s rivers

- Chetty, Preven

Authors: Chetty, Preven
Date: 2022
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/391060 , vital:68613 , xlink:href="https://eeasa.org.za/wp-content/uploads/2023/02/Final-EEASA-Bulletin-20212022-Final.pdf"
Description: Water quality and scarcity is a major concern in Southern Africa and globally especially as the threat of climate change looms even closer. The current drought in South Africa and worsening rainfall has exposed the brittle nature of this country’s resilience to water shortages. Compounded to this is the fact that most rivers in South Africa are not adequately cared for and are under tremendous strain. Everyone who depends on these rivers whether directly or indirectly will soon be entering a new era where water will no longer be a ubiquitous commodity.
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Date Issued: 2022

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Phthalocyanine based fabricated exfoliated graphite photoanode for electrodegradation of 4-acetamidophenol under visible light irradiation

- Mpeta, Lekhetho S, Nyokong, Tebello

Authors: Mpeta, Lekhetho S , Nyokong, Tebello
Date: 2022
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/295809 , vital:57380 , xlink:href="https://doi.org/10.1016/j.jphotochem.2022.114115"
Description: In this study exfoliated graphite (EG) was prepared from natural graphite flakes and incorporated with zinc phthalocyanine for fabrication of photoanode. The electron transfer capabilities of fabricated photoanode were examined by using cyclic voltammetry, electrochemical impedance spectroscopy and scanning electrochemical microscopy. Electrophotocatalytic degradation of 4-acetamidophenol in 0.1 M Na2SO4 electrolyte was performed. The photoanode with zinc phthalocyanine (EG-ZnPc) displayed better degradation compared to when only exfoliated graphite was used (EG). Furthermore, electrophotocatalytic degradation gave better performance (removal efficiency of 47.76%) than when individual electrochemical degradation and photodegradation techniques were used.
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Date Issued: 2022

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Synthesis and in vitro biological studies of ursolic acid-based hybrid compounds

- Khwaza, Vuyolwethu

Authors: Khwaza, Vuyolwethu
Date: 2022
Subjects: Herbal medicine , Herbs -- Therapeutic use , Antineoplastic antibiotics
Language: English
Type: Doctoral theses , text
Identifier: http://hdl.handle.net/10353/27797 , vital:69689
Description: Ursolic acid UA, a pentacyclic triterpenoid that is commonly found in many medicinal herbs and fruits, has been identified as a potential source of therapeutic agents because of its potent biological effects, which include its potential anticancer and antimicrobial activities. However, its limited solubility, rapid metabolism and poor bioavailability inhibit its clinical applications. Numerous UA derivatives have been prepared over the past years in an effort to mitigate the drawbacks associated with UA, as new chemical entities for the treatment of various infections. There is very little progress in the discovery of efficient UA derivatives. In this study, a class of ester and amide-linked ursolic acid-based hybrid compounds fused with selected pharmaceutical scaffolds were successfully synthesized using amidation and esterification reactions and tested for antibacterial and cytotoxicity activities. Hybridizing UA with other known pharmaceutical scaffolds has the potential of overcoming its drawbacks. FT-IR, Mass Spectroscopy, and 1H13C-NMR spectroscopy were used to confirm the structures of the synthesized hybrid compounds. Among the tested ester-linked hybrid compounds in Chapter three, compounds 3.14-3.19,3.21, 3.34, 3.31, and 3.30 demonstrated significant antibacterial activities against some tested bacteria, with MIC values of 15.625 μgml. Furthermore, the in vitro cytotoxicity of these hybrids was determined using the MTT assay against three human tumor cell lines MCF7, MDA-MB-231, and HeLa cells. Compounds 3.19 and 3.34 were found to have better cytotoxic activity when compared to ursolic acid, with IC50 values of 46.99 and 48.18 μg ml respectively. Both compounds revealed more promising docking results, presenting favourable binding interactions as well as better docking energy against the MCF 7 protein target compared to the parent compound ursolic acid. In Chapter Four, among the tested amide-linked hybrid compounds, Compounds 4.17 and 4.24 demonstrated significant antibacterial activity against the majority of bacterial strains with MIC values of 15.625 gml. Compound 4.24 exhibited a MIC value of 15.625gmL against BS, SA, PV, KO, PM, and EC. Compound 4.23 was more cytotoxic to HeLa cells than ursolic acid. Furthermore, molecular docking calculations revealed that compound 4.16 strongly binds to the protein epidermal growth factor receptor while e compounds 4.17 and 4.24 showed a strong binding affinity for the methionyl-tRNA synthetase. In both cases, the hybrid compounds showed better conformational fittings in the active site of the targeted proteins as compared to the parent ursolic acid. , Thesis (MSc) -- Faculty of Science and Agriculture, 2022
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Date Issued: 2022

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Coastal fishes of the western Indian Ocean

- Heemstra, Phillip C. 1941-, Heemstra, Elaine, Ebert, Dave, Holleman, Wouter, Randall, John E

Authors: Heemstra, Phillip C. 1941- , Heemstra, Elaine , Ebert, Dave , Holleman, Wouter , Randall, John E
Date: 2022
Subjects: Marine fishes Indian Ocean , Marine fishes Indian Ocean Identification
Language: English
Type: text , book
Identifier: http://hdl.handle.net/10962/310495 , vital:59157 , ISBN 978-1-990951-23-7 , ISBN 978-1-998950-35-5 , ISBN 978-1-990951-28-2
Description: The primary purpose of this book is to provide a means of identifying the more than 3 200 species of coastal fishes known to occur in the Western Indian Ocean (WIO). Coastal fishes are those that inhabit waters generally less than ~200 m deep, the waters over continental and insular shelves, and upper continental slopes. The book also includes some oceanic species and species that live in deeper water, but are sometimes caught in trawls in less than 200 m, or that migrate into shallower waters at night to feed. The Western Indian Ocean (WIO), as treated in these volumes, is the area between Cape Point, South Africa, and 77°34' E, at Kanyakumari (formerly Cape Cormorin), the southernmost point of India, and to 40° S, just south of St Paul Island. Although considered as separate water bodies, the Red Sea and Persian/Arabian Gulf have been included. Some contributors have also chosen to include species from Sri Lanka. The region thus encompasses the entire east and southern coasts of Africa, Madagascar and the various island clusters of the Comoros, the Seychelles, the Maldive and Lakshadweep islands, the Chagos Archipelago and the islands and sea mounts of the Mascarene Plateau, to as far as 40° S, and thus some fishes from St Paul and Amsterdam Islands have been included. This large expanse, stretching from tropical waters of the northwestern Indian Ocean to the warm temperate waters of False Bay, South Africa, includes a number of poorly known biogeographic areas. A map of the entire Indian Ocean is placed on the inside front cover of each printed volume, with some areas in greater detail on the inside back cover. The book does not include distribution maps for species, but gives localities from which species are known, with emphasis on WIO localities; our understanding of distributions of many species is often incomplete. Fishes are the most abundant and diverse group of vertebrates and have colonised every aquatic habitat on Earth: the oceans, lakes, rivers and caves, from polar seas at –2 °C to hot, freshwater springs at 44 °C, and from tropical reefs and mangrove forests to the deepest ocean depths. Fishes are also the most poorly known group of vertebrates. In the 2006 edition of Joseph Nelson’s Fishes of the World the estimate of the number of species of extant fishes worldwide stood at about 23 000. This number is growing annually, and was thought to be about 33 460 species at the end of 2016 (www.fishwisepro.com). Between the years 2000 and 2015 an average of 150 new species of marine fishes were described each year – of which 10% of the total (156 species) were from the WIO. The WIO is home to about 15% of all the marine fish species in the world’s oceans. Another measure of the diversity of fishes of this area is its relatively high level of endemicity, particularly around southern Africa and in the Red Sea. About 13% of southern African marine fishes are endemic, most of these in only five families: Clinidae with about 44 endemic species, Gobiidae with 28, Sparidae with 28, Pentanchidae with 6, and Batrachoididae with 7 endemic species. In the Red Sea at least 170 of the more than 1100 species are endemic. The WIO region is also home to a large human population, representing a wide range of ethnic and cultural backgrounds. The area includes the countries of South Africa, Mozambique, Tanzania, Kenya, Somalia, Eritrea, Sudan, Egypt, Israel, Jordan, Saudi Arabia, Yemen, Oman, United Arab Emirates, Qatar, Bahrain, Kuwait, Iraq, Iran, Pakistan, India and Sri Lanka, as well as the many island nations and territories. Many of the people living in coastal areas are dependent on fish catches and other marine resources for both sustenance and often a livelihood, as highly diversified artisanal fisheries make up the bulk of the fishing effort in the region. And, as elsewhere in the world, many of the fish resources have been compromised by commercial interests (including those of other countries), often leaving fish stocks in a poor state. This book has a number of purposes, all of which coalesce around providing users with a better understanding of the area’s fishes and their environment. Accordingly, it includes a number of background chapters covering subjects as diverse as the oceanography of the region, and the history and evolution of the bony fishes. In recent years genetic analysis has proved to be a powerful tool for taxonomists. In many instances molecular results have caused taxonomists to rethink both the definitions of certain taxa and the interrelationships of taxa. In some instances, what were long considered cohesive (monophyletic) taxa were found to include groups of fishes that are in fact not closely related (paraphyletic), while in other instances taxa thought to be distinct were found not to be, meriting their merging with other existing taxa. At times, long-accepted family groups have been divided into two or more distinct families, or separate families have been combined into a single one. Where possible such changes in our understanding of the relationships of fishes are reflected in these volumes. Where some contributors have taken a more conservative approach by awaiting more research and not adopting these changes, alternative taxonomies are noted (see also the introductory chapter on Naming organisms and determining their relationships). For each species in the book, the literature pertinent to that species in the WIO is given: the original species description reference, synonyms for the region and other important taxonomic and biological references. For many commercially important species or fishes of interest to anglers there is additional information on life history, size and capture, and for some but not all species, their IUCN conservation status if Near Threatened, Vulnerable, Endangered or Critically Endangered (in the first instance, valid at the time of writing. See www.iucnredlist.org for current information. Note: we have not included the IUCN conservation status where species are of Least Concern or Data Deficient). Most species are illustrated with photographs, drawings or paintings. Colour photographs and paintings are provided on plates for each volume. , 1st Edition
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Date Issued: 2022

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Fishes of Southern African estuaries: from species to systems

- Whitfield, Alan K

Authors: Whitfield, Alan K
Date: 2022
Subjects: Estuarine fishes -- South Africa , Estuarine fishes -- Africa, Southern , Fishes -- Africa, Southern -- Identification , Estuaries -- Africa, Southern
Language: English
Type: text , book
Identifier: http://hdl.handle.net/10962/97933 , vital:31512
Description: South Africa, despite its relatively small size, is often called “a world in one country”. This phrase arises mainly from the range of oceanographic and climatic features; geological and geomorphological attributes, the diversity of human cultures, languages, races and religions; the mix of developed and developing economies; the wide range in political opinion and parties; the vast array of mineral resources; and finally, what biologists find most interesting of all, the richness of the indigenous flora and fauna. Although southern African aquatic scientists cannot boast an equivalent of the Cape Floral Kingdom, the stretch of coast between northern Namibia and southern Mozambique has a particularly rich marine biota, accounting for almost 15% of all the coastal marine species known world-wide. The richness of the ichthyofauna is due to a number of factors, including the variety of habitats around the subcontinent, ranging from coral reefs, kelp beds, sheltered bays, sandy beaches, exposed rocky shores, coastal lakes to estuaries. In addition, southern Africa is the meeting place of three great oceans and is thus the recipient of species from each of these separate faunas. In comparison to land vertebrates, the world’s fish fauna is by no means well-known, either taxonomically or with regard to the biology of the component species. Apart from the very large number of fish species (estimated to be approximately 40 000), and the difficulties posed by the medium in which they live, there are other reasons for the above state of affairs. An obvious and universal reason is the shortage of funding available for taxonomic, biological and ecological studies, with increasing emphasis being placed on aquaculture, mariculture and fisheries related work. This situation is unlikely to improve and many research institutions around the world are operating on shrinking rather than expanding budgets. The onus of responsibility to disseminate information on the world’s fish faunas therefore rests squarely on the shoulders of those who are fortunate enough to be employed in the fascinating field of ichthyology. This book, which is a major revision and expansion of an earlier monograph (Whitfield 1998), is an attempt to synthesize the available information on fishes associated with southern African estuaries and to highlight the importance of conserving these systems for both fishes and people of the region. Limited reference is made to international estuarine fish research due to space constraints and readers are referred to global ichthyological reviews in this regard. The estuaries of southern Africa (defined as south of 26°S latitude for the purposes of this book) are highly diverse, both in terms of form and functioning. They range from the clear Kosi Estuary entering the coral rich subtropical Indian Ocean waters on the east coast, to the turbid Orange River flowing into the cool upwelled waters of the Atlantic Ocean on the west coast. The estuaries of the subcontinent are fed by catchments with a wide variety of climatic and geological characteristics. For example, the cool-temperate west coast is characterized by good winter rains and relatively dry summers, whereas on the subtropical east coast the opposite rainfall pattern prevails. While most south-western Cape estuaries are fed by rivers with low suspended sediment levels, those of KwaZulu-Natal normally carry high silt loads during the rainy season. Between Mossel Bay and St Francis Bay, rainfall patterns show no distinct seasonal peak and relatively acidic waters with low nutrient levels enter a variety of estuarine types along this section of the coast. The Eastern Cape is a region of transition between the subtropical and warm-temperate biogeographic provinces, and is prone to both droughts and floods occurring during any season of the year. The southern African estuarine environment is an unpredictable and often harsh habitat to occupy, yet each year millions of larval and juvenile fishes enter and thrive in these systems. The fish species that utilize estuaries as nursery areas exhibit great diversity in size, body form, salinity tolerance, diet, habitat preference and breeding behaviour. There is also a complete gradation in terms of the dependence that each species has on the estuarine environment. These and many other issues relating to the biology and ecology of estuary-associated fish species in southern Africa are explored in the chapters to follow. It is my sincere wish that our improved knowledge of these species and their environmental requirements will contribute to the wise management and conservation of these valuable ecosystems. , 2022 Edition
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Date Issued: 2022

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The effect of charge on Zn tetra morpholine porphyrin conjugated to folic acid-nitrogen doped graphene quantum dots for photodynamic therapy studies

- Magaela, N Bridged, Matshitse, Refilwe, Nyokong, Tebello

Authors: Magaela, N Bridged , Matshitse, Refilwe , Nyokong, Tebello
Date: 2022
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/295840 , vital:57383 , xlink:href="https://doi.org/10.1016/j.pdpdt.2022.102898"
Description: Zinc tetra morpholine porphyrin (complex 2), and its quaternized derivative (complex 3) were synthesized and conjugated to folic acid decorated nitrogen doped graphene quantum dots (FA-NGQDs) through π−π stacking to study their photodynamic therapy (PDT) efficacy. Photophysiochemical properties of complexes 2, 3, and their conjugates (2-FA-NGQDs, 3-FA-NGQDs) were studied. It was found that complex 3 had higher ϕΔ of 0.56 compared to complex 2 with ϕΔ of 0.24, and respective composites: 3-FA-NGQDs had higher ϕΔ compared to 2-FA-NGQDs. The PDT studies were conducted for nanoparticles (FA-NGQDs), complexes (2, 3), and respective composites (2-FA-NGQDs, and 3-FA-NGQDs) using MCF-7 breast cancer cell. Dark toxicity of all compounds was above 90% which is negligible. At a highest concentration of 40 µg/mL, 3-FA-NGQDs gave the lowest cell viability of 28% compared to all other conjugates and porphyrins alone.
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Date Issued: 2022

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Assessing the electrocatalytic activity of a localized push-pull system in cobalt phthalocyanine/graphene quantum dot hybrids

- Nkhahle, Reitumetse, Nyokong, Tebello

Authors: Nkhahle, Reitumetse , Nyokong, Tebello
Date: 2022
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/229909 , vital:49722 , xlink:href="https://doi.org/10.1016/j.matchemphys.2022.125842"
Description: In this study, two cobalt phthalocyanines (asymmetric complex 1) and symmetric (complex 2) were synthesized and conjugated to nitrogen-doped graphene quantum dots (NGQDs) through covalent and non-covalent means to create Co phthalocyanine (CoPc)-NGQDs hybrid systems. The CoPcs and conjugates were applied as electrode modifiers on a glassy carbon electrode in the electrochemical sensing of nitrite. Of the CoPcs alone, complex 1 performed better than complex 2 regarding the limits of detection (LoD) recorded (5.74 μM for 1 and 15.1 μM for 2). Regarding the conjugates/nanocomposites, the π-π stacked conjugate derived from complex 2 (2πNGQDs) demonstrated highly favourable electrochemical potential with an LoD value of 0.70 μM. The nanocomposites fashioned from complex 1 were marred by a reduced loading which rendered the conjugates poor electrochemical sensors. These observations however do not disqualify GQDs as complementary nanomaterials to phthalocyanines but rather shed light on seeking alternative routes to increasing the Pc loading in conjugates (more so in π-π stacked conjugates).
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Date Issued: 2022

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