The electrocatalytic response of metallophthalocyanines when clicked to electrodes and to nanomaterials
- Authors: Mpeta, Lekhetho Simon
- Date: 2021
- Subjects: Phthalocyanines , Nanostructured materials , Electrocatalysis , Nanoparticles , Environmental chemistry , Electrodes , Organic wastes -- Purification
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/172191 , vital:42174 , 10.21504/10962/172191
- Description: Conjugates of nanomaterials and metallophthalocyanines (MPcs) have been prepared and their electrocatalytic activity studied. The prepared nanomaterials are zinc oxide and silver nanoparticles, reduced graphene oxide nanosheets and semiconductor quantum dots. The MPcs used in this work are cobalt (II) (1a), manganese(III) (1b) and iron (II) (1c) 2,9(10),16(17),23(24)- tetrakis 4-((4-ethynylbenzyl) oxy) phthalocyaninato, 2,9(10),16(17),23(24)- tetrakis(5-pentyn-oxy) cobalt (II) phthalocyaninato (2), 9(10),16(17),23(24)- tris-[4-tert-butylphenoxy)-2- (4-ethylbezyl-oxy) cobalt (II) phthalocyaninato (3), 9(10),16(17),23(24)- tris-[4-tertbutylphenoxy)-2-(pent-4yn-yloxy)] cobalt (II) phthalocyaninato (4), cobalt (II) (5a) and manganese (III) (5b) 2,9(10),16(17),23(24)- tetrakis [4-(4-(5-chloro-1H-benzo [d]imidazol-2-yl)phenoxy] phthalocyaninato and 9(10),16(17),23(24)- tris tert butyl phenoxy- 2- [4-(4-(5-chloro-1H-benzo[d]imidazole-2-yl)phenoxy] cobalt (II) phthalocyaninato (6). Some of these MPcs (1a, 3 and 4) were directly clicked on azide grafted electrode, while some (1b, 1c, 2, 5a and 5b) were clicked to azide functionalised nanomaterials and then drop-dried on the electrodes. One phthalocyanine (5b) was drop-dried on the electrode then silver nanoparticles were electrodeposited on it taking advantage of metal-N bond. Scanning electrochemical microscopy, voltammetry, chronoamperometry, electrochemical impedance spectroscopy are among electrochemical methods used to characterise modified electrodes. Transmission electron microscopy, X-ray photoelectron spectroscopy, Xray diffractometry, Raman spectroscopy and infrared spectroscopy were employed to study surface functionalities, morphology and topography of the nanomaterials and complexes. Electrocatalytic activity of the developed materials were studied towards oxidation of 2-mercaptoethanol, hydrazine and hydrogen peroxide while the reduction study was based on oxygen and hydrogen peroxide. In general, the conjugates displayed superior catalytic activity when compared to individual materials. Complex 2 alone and when conjugated to zinc oxide nanoparticles were studied for their nonlinear optical behaviour. And the same materials were explored for their hydrazine detection capability. The aim of this study was to develop sensitive, selective and affordable sensors for selected organic waste pollutants. Conjugates were found to achieve the aim of the study compared to when individual materials were employed.
- Full Text:
- Date Issued: 2021
The elucidation of nickel and zinc based Metal Organic Frameworks (MOFs) using a polycarboxylate-benzene ligand: a synthetic, spectroscopic, and thermoanalytical study
- Authors: Hodgson, Ivan Mark
- Date: 2022-04-06
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/290877 , vital:56795
- Description: Thesis (MSc) -- Faculty of Science, Chemistry, 2022
- Full Text:
- Date Issued: 2022-04-06
The exploitation of methane from landfill
- Authors: Schütte, Renate
- Date: 1992
- Subjects: Methane , Waste products as fuel , Refuse as fuel , Sanitary landfills -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4530 , http://hdl.handle.net/10962/d1015949
- Description: A review of literature on the subject of methane exploitation from landfill is presented in conjunction with the results of experiments concerning landfill gas extraction at the Grahamstown Landfill Site. A description of the LFG extraction system and the utilisation of LFG at the Grahamstown Landfill Site is included. Data concerning LFG enhancement parameters, LFG compositions and flow rates, refuse composition, LFG modelling, LFG pumping trials and the economics of LFG extraction and utilisation are presented. The indication is that LFG can be economically extracted and utilised as a heating fuel in South Africa.
- Full Text:
- Date Issued: 1992
The growth of flue-cured tobacco in acid soils
- Authors: Ryding, William Wallace
- Date: 1969
- Subjects: Flue-cured tobacco -- Zimbabwe , Acid soils -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4495 , http://hdl.handle.net/10962/d1013110
- Description: The main effects of lime, aluminium, iron and manganese were studied in field and greenhouse grown tobacco; relations between soil and plant measurements were examined. Ground limestone, ground mixed lime, ground dolomite and slaked lime at rates equivalent to 1,000 and 2,000 lb. CaC0₃/acre increased yield and quality of flue-cured tobacco both on Triassic and granite sands, whether applied early (February/March) or late (September); the highest rate and late application were often best. Yields increased with 4,000 and 6,000 lb. dolomite/acre applied late, but quality decreased when the pH was about 6.0. Lime did not affect leaf maturity as reflected by nitrogen and reducing sugars concentration . Where leaf discolouration (slate) occurred, the best quality and least discoloured leaf had the lowest manganese concentration and was grown on limed soil. On a very acid and probably nitrogen deficient soil, lime, borax and nitrogen (nitrate only tested) reduced the discolouration and improved the quality, but potassium sulphate increased discolouration and decreased quality. Calcium concentration in the leaf was increased by lime, particularly calcitic materials, and magnesium concentration was increased by dolomite. Lime also increased the filling value and petroleum ether extract, but decreased manganese, boron, chloride and sometimes potassium, and had no effect on phosphorus, nitrogen, aluminium, iron, crude fibre, nicotine, reducing sugars and equilibrium moisture. The inorganic composition of greenhouse plants was similar; generally gypsum increased calcium concentration more than calcium carbonate but it did not affect manganese concentration, which was decreased by calcium carbonate. In the stem and roots of field grown plants (dolomite only tested), the concentration of magnesium was increased but the concentrations of calcium, potassium, aluminium and iron were unaffected. Although the concentration of nitrogen was increased and that of phosphorus was decreased in the stem, these were unaffected in the roots. Aluminium and iron behaved differently to other nutrient ions, being more concentrated in the roots than aerial plant parts. Boron and magnesium deficiencies were observed in a dry and wet year, respectively, suggesting that variable mineral deficiencies can affect responses to lime. Initially soil pH was affected more by source of lime, but later mostly by rates. Slaked lime increased the soil pH more than did ground limestone, mixed lime or dolomite. In a glasshouse experiment, pH was more important than calcium supply and in the field, the largest yields were often associated with the highest pH. In pot experiments, aluminium drastically reduced yields in nutrient solution but not in soils, whereas iron was more severe in soils; manganese had little effect on yield. Manganese was readily taken up and translocated to the tops, but aluminium and iron were mainly concentrated in the roots, as was found in field grown plants. Iron decreased manganese concentration in all plant parts and aluminium decreased calcium and manganese in nutrient solution only. Although aluminium and iron generally increased the concentration of phosphorus in the roots, they did not interfere with phosphorus transport in the plant. Manganese caused the leaf to become chlorotic and when no iron was present the upper leaves became yellow, and developed brown and white lesions. However, in soil grown plants, sufficient iron was present in the soil solution to prevent break down of tissue. Yellowing of the upper leaves also occurred when plants were grown in nutrient solution with aluminium and no iron; when both were present, the plants were darker in colour. Although aluminium damaged roots in nutrient solution, high rates of iron severely damaged leaves of plants grown in soil. Since the concentrations of aluminium, iron and manganese were decreased in the soil solution by liming, they were compared with plant growth and composition in 17 different soils, with and without lime. As was expected, lime increased soil pH. It also increased exchangeable calcium, but decreased exchangeable aluminium, iron and manganese; exchangeable magnesium and potassium and resin extractable phosphorus were not affected. As the Ratio Law does not hold for all Rhodesian soils, anion adsorption will be avoided if the soils are equilibrated with O.OOOSM CaC1₂; the concentrations of the cations in solution were affected in the same way as exchangeable cations, but phosphorus was increased. There was no relationship between yield of tobacco and its chemical composition. The correlations between soil solution data and plant composition were poor, except for manganese and phosphorus; the relation between Mn ppm. in plant vsa (superscript)Mn/a (superscript)Ca + Mg (enclosed in square root sign √) in solution, and P% vs pH₂ P0₄ or pH₂ P0₄ +½ pCa, were both curvilinear. On the other hand, all measurements of exchangeable cations were poorly correlated with plant composition. Finally yield was poorly correlated with soil solution data, and pH was as satisfactory as any other measurement tested. Manganese toxicity was observed on three soils, and a probable manganese deficiency on one. It was not possible to define a limit above which manganese toxicity occurred, but manganese deficiency developed at about 63 ppm. manganese. Variations in pH and the availability of aluminium, iron and manganese occurred when soils were incubated at about field capacity, generally the main effects having developed within seven days. In all soils, there was an initial increase in soil pH and a maximum value was reached in one to four days, decreasing by variable amounts with longer periods of incubation. Although the concentration of aluminium was larger than that of iron, the relation between both ions and soil pH was curvilinear, their concentrations increasing with decreasing pH. Increased temperature of incubation increased pH with a resultant decrease in the concentration of aluminium, but in one soil it appreciably increased the availability of iron in the early periods of incubation. Autumn and spring ploughing did not affect subsequent pH or the concentration of aluminium and iron in the soil solution. Manganese concentration varied from soil to soil and was not related to soil pH. In most soils there was a decrease in manganese concentration with length of incubation and it decreased more rapidly the lower the initial concentration. Temperature effects were variable and moisture affected the behaviour of manganese more than temperature. These findings and the distribution of aluminium, iron and manganese in the plant helped to explain the poor correlations.
- Full Text:
- Date Issued: 1969
The high pressure catalytic hydrogenation of the tannin of black wattle (Acacia mollissima Willd)
- Authors: Silk, M H
- Date: 1947
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:21132 , http://hdl.handle.net/10962/6528
- Description: From Introduction: The wattle industry in South Africa has, from its commencement in the middle of the last century, gradually assumed a position of increasing importance in the economic structure of the country. Apart from the provision of a valuable tanning extract for home use and for export, the tree itself has proved of considerable importance to the Union’s mining industries. In addition there would appear to be possibilities for the utilisation in the near future, of the raw ground bark and the wattle extract for the manufacture of a number of by-products, including certain types of plastics.
- Full Text:
- Date Issued: 1947
The implementation and evaluation of a service-learning component in a second year undergraduate organic chemistry course
- Authors: Abel, Sarah Ruth
- Date: 2011 , 2010-10-03
- Subjects: Chemistry, Organic -- Study and teaching (Higher) -- South Africa , Action research in education -- South Africa , Experiential learning -- South Africa , Service learning -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4393 , http://hdl.handle.net/10962/d1006008 , Chemistry, Organic -- Study and teaching (Higher) -- South Africa , Action research in education -- South Africa , Experiential learning -- South Africa , Service learning -- South Africa
- Description: The project describes the action research implementation, and evaluation of learning, of a service-learning component in a second year undergraduate organic chemistry course. The research aims to explore the learning that takes place in a service-learning context while utilizing an action research methodology within the critical theory paradigm. This occurs in response to the world-wide call for Higher Education to produce people with civic competencies and responsiveness to the society in which they live (Boyer 1996). Educating young Chemists to see the importance of their knowledge and their responsibilities in society is an important pedagogical step in the effort to cross boundaries and make connections between people communities (Eyler and Giles 1999). The goal of this project was to explore and categorize the learning that takes place in a service-learning context and discover how these areas of learning impact the awareness of the parties involved with regard to the discipline of chemistry as well as social issues. The project makes use of Kolb‘s (1984) Experiential Learning Theory, and Eyler and Giles‘ (1999) categories of learning in service-learning and results indicate that service-learning can be a powerful pedagogical tool to increase learning in chemistry as well as in the areas of critical thinking, personal and social development, reflection and citizenship. Students‘ perceptions of themselves, their discipline and their responsibility to society were transformed by their experience of service-learning in their undergraduate chemistry course.
- Full Text:
- Date Issued: 2011
The influence of the integration of local knowledge during chemistry hands-on practical activities on grade 8/9 learners’ attitude towards science
- Authors: Ngqinambi, Akhona
- Date: 2020
- Subjects: Science -- Study and teaching (Secondary) -- South Africa , Science teachers -- South Africa , High school students -- Attitudes , Communities of practice -- South Africa , Science clubs -- South Africa , Science projects -- South Africa , Constructivism (Education) -- South Africa , Educational counseling -- South Africa , Local knowledge
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/144724 , vital:38373
- Description: With every passing year, there is a decrease in the number of learners pursuing science degrees after completion of grade 12. One of the main reasons for this is the negative attitude that high school learners have towards science learning and science as an entity. The Natural Sciences curriculum suggests the use of local knowledge to introduce the usefulness and the relatability of science to learners. This study is an intervention that seeks to ascertain the influence that local knowledge has on the attitudes of grade 8/9 learners when integrated into their chemistry hands-on practical activities. The study was informed by Vygotsky’s social constructivist theory and Wenger’s community of practice theory. Grade 8/9 learners from four high school science clubs did three local knowledge integrated experiments based on acids and bases. The learners completed pre- and post- surveys and were interviewed about their experiences. Volunteers at the science clubs were also interviewed. Excel was used to deductively analyse quantitative data. On the other hand, an inductive-deductive thematic approach was used to analyse the qualitative data. The findings of the study showed a divergence of qualitative and quantitative methods. The quantitative data showed that there was a slight decrease (but not statistically significant) in the attitude of the learners after engaging in chemistry hands-on practical activities into which local knowledge had been integrated. On the other hand, the qualitative data showed that there was a positive shift in the learners’ attitudes after they had been engaged in the chemistry hands-on practical activities. Additionally, the findings of the study revealed that the integration of local knowledge promotes conceptual understanding and improves the performance of the learners. This study thus recommends that local knowledge should be integrated into the grade 8 and 9 learners’ curriculum to enrich and promote contextualized science for learners. Additionally, the integration of local knowledge would promote conceptual understanding and spark interest and motivation in learners to pursue science-related careers.
- Full Text:
- Date Issued: 2020
The investigation, development and characterisation of novel zirconium-based tanning agents
- Authors: Guthrie-Strachan, Jeffry James
- Date: 2006
- Subjects: Zirconium Tanning Leather
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4319 , http://hdl.handle.net/10962/d1004977
- Description: Various oxygen- and nitrogen-donor ligands were investigated as potential zirconium masking agents in zirconium tanning. α-Hydroxycarboxylic acid ligands were identified as effective zirconium(IV) chelators in acidic aqueous solution. Glycolic acid, lactic acid, mandelic acid, 4-hydroxymandelic acid, 4-chloromandelic acid and 4-bromomandelic acid complexes were synthesised, isolated and characterised using a range of analytical techniques. Linear Free Energy Relationships were examined to optimise the stability of the zirconium complexes. Hammett [sigma] plots and Yukawa-Tsuno modified σ plots of the mandelate ligand and zirconium complex series indicated that inductive effects dominate within the benzene ring, however, mesomeric effects are significant outside the ring. Zirconium 4-hydroxymandelate complex solutions were identified as the most effective tanning agents and achieved shrinkage temperatures of 80 and 97ºC for hide powder and goatskin, respectively. The zirconium and 4-hydroxymandelic acid interact synergistically to yield leather equivalent to combination tanned leather in one step. Tanning was performed similarly to vegetable tanning processes with a pickle pH of approximately 5 and fixation was achieved upon acidification. Pilot-scale tanning of goatskin produced white tanned leathers and crust leathers which were physically and aesthetically comparable to matched chromium tanned material.
- Full Text:
- Date Issued: 2006
The kinetics and mechanism of the oxidation of chromium (III) chloride
- Authors: Sole, Kathryn Clare
- Date: 1989 , 2013-08-28
- Subjects: Chromium chloride--Oxidation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4301 , http://hdl.handle.net/10962/d1004921 , Chromium chloride--Oxidation
- Description: The kinetic behaviour of anhydrous CrCl₃ in gaseous oxidising atmospheres has been examined in the temperature range 350 to 630°C in order to identify optimum reaction conditions and to establish the mechanism by which the reaction is controlled. The reaction under consideration is CrCl₃ (s) + ¾ O₂ (g) → ½ Cr₂O₃ (s) + ³/₂ Cl₂ (g). The main experimental techniques used were isothermal and programmed-temperature thermogravimetry, supplemented by scanning electron-microscopy, surface-area determinations and porosity measurements. The effects of sample pelletisation, gas flowrate, temperature, oxygen partial pressure, pellet porosity and the addition of other oxide species on the rate and extent of reaction have been studied. The reaction is shown to occur in a single step, starting at -350°C under non-isothermal conditions, and exhibiting a deceleratory rate over most of the reaction. Isothermal thermogravimetric curves were fitted to a number of kinetic rate expressions, and a series of statistical analyses used to identify the rate equation which best describes the experimental data. Supporting evidence was provided by scanning electron-microscopic examination of partially-reacted samples. It is concluded that the reaction is under chemical control, and that reaction occurs by means of a linearly-advancing reactant-product interface. The reaction kinetics can be described by a contracting-geometry rate expression. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 1989
The oxalate complexes of thorium
- Authors: Phillpotts, Charles Adrian Richard
- Date: 1962
- Subjects: Oxalates , Thorium , Complex compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4488 , http://hdl.handle.net/10962/d1013029
- Description: (1) The ammonium, potassium and sodium salts of three complex thorium oxalates were prepared and studied. (2) Their solubilities and conditions of stability were studied. (3) The reaction between thorium and excess oxalate, and vice versa, was studied by means of conductivity and high frequency conductivity measurements. (4) The formation constant of Th(C₂O₄)₄⁴⁻ and Th(C₂O₄)₃²⁻, and the solubility product of (NH₄)₂Th₂(C₂O₄)₅, were determined by a solubility method.
- Full Text:
- Date Issued: 1962
The oxidation and degradation products of black wattle tannin (Acacia mollissima)
- Authors: Heugh, Richard Anthony
- Date: 1948
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:21169 , http://hdl.handle.net/10962/6706
- Full Text:
- Date Issued: 1948
The photophysical properties of low symmetry phthalocyanines in conjunction with quantum dots
- Authors: D'Souza, Sarah
- Date: 2011
- Subjects: Phthalocyanines , Photochemistry , Zinc , Quantum dots , Spectrum analysis , Nanoparticles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4331 , http://hdl.handle.net/10962/d1004992 , Phthalocyanines , Photochemistry , Zinc , Quantum dots , Spectrum analysis , Nanoparticles
- Description: he synthesis, extensive spectroscopic characterization and photophysical studies of low symmetry zinc phthalocyanine have been conducted. Comparisons have been made taking into consideration the influence of the solvent properties as well as substituent type and position. Photosensitizing properties of the zinc phthalocyanine derivatives in the presence of thiol capped CdTe quantum dots (QDs) were compared. The QDs were used as energy transfer donors and to facilitate with energy transfer through Förster resonance energy transfer (FRET) from the QDs to the MPcs. The linkage of unsymmetrically substituted 4-monoaminophenoxy zinc phthalocyanine (ZnAPPc) to CdTe quantum dots capped with mercaptopropionic acid (MPA), L-cysteine (L-cys) or thioglycolic acid (TGA) has been achieved using the coupling agents ethyl-N3 dimethylaminopropyl)carbodiimide (EDC) and N-hydroxy succinimide (NHS), which facilitate formation of an amide bond to form the QD-ZnAPPc-linked complex. The formation of the amide bond was confirmed using UV-Vis, Raman and IR spectroscopies, as well as AFM (atomic force microscopy). Förster resonance energy transfer (FRET) resulted in stimulated emission of ZnAPPc in both the linked (QDZnAPPc-linked) and mixed (QD:ZnAPPc-mixed) conjugates for MPA only. The linked L-cys and TGA complexes (QD-ZnAPPc-linked) gave the largest FRET efficiencies hence showing the advantages of covalent linking. Fluorescence quantum yields of QDs were decreased in QD:ZnAPPc-mixed and QD:ZnAPPc-linked. High triplet state quantum yields were obtained for the linked QD-phthalocyanine derivatives (ZnAPPc)and monoaminozinc phthalocyanine (ZnAPc) compared to when ZnAPPc and ZnAPc were mixed with MPA QDs without a chemical bond.
- Full Text:
- Date Issued: 2011
The polarographic determination of trace elements in blister and refined copper
- Authors: Eve, Adrian John
- Date: 1954
- Subjects: Copper , Polarographs , Polarography
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4467 , http://hdl.handle.net/10962/d1011769 , Copper , Polarographs , Polarography
- Description: In the complete analysis of copper the following impurities are generally determined: silver, gold, lead, arsenic, antimony, selenium, tellurium, iron, zinc, cobalt, nickel, oxygen, sulphur, and, less commonly, tin and phosphorus. The actual copper content varies around 99.0% in blister copper; in the refined metal the content is somewhat higher, usually over 99.9%. The concentrations of the individual impurities vary from tenths to thousandths of one per cent.
- Full Text:
- Date Issued: 1954
The polysaccharides of Opuntia ficus-indica (L.) Mill. and Opuntia aurantiaca Lindl.
- Authors: McGarvie, Donald
- Date: 1977
- Subjects: Polysaccharides
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4438 , http://hdl.handle.net/10962/d1007597
- Description: The partially acetylated acidic mucilage isolated from the cactus Opuntia ficus-indica consists of a highly branched molecule containing D-galactose, L-arabinose, D-xylose, D-galacturonic acid and L-rhamnose in the ratio 2.9:6.6:3.8:1.3 : 1.0. A partial hydrolysis study led to the isolation of fourteen oligosaccharides and a degraded polysaccharide. Periodate oxidation of the degraded polysaccharide and methylation analysis of the degraded and reduced degraded polysaccharides led to the proposal of a structure for the degraded polysaccharide consisting of a chain of alternating α-l,4-D-galactopyranosyluronic acid and β-1,2-Lrhamnopyranosyl units with branches consisting of short chains of β-1,6-D-galactopyranosyl units Iinked to C-3 of the rhamnose residues. An insight into the nature of the peripheral side-chains was obtained by methylation studies of the oligosaccharides and the native polysaccharide. The majority of the side-chains are terminated by D-xylopyranosyl and L-arabinofuranosyl units while there is a small proportion of D-galactopyranosyl end-groups. The remaining units of the peripheral chains consists of mainly 1,3- and 1,5-1 inked L-arabinofuranosyl units. The acidic polysaccharide isolated from the jointed cactus Opuntia aurantiaca contains D-galactose, L-arabinose, D-xylose, D-galacturonic acid and L-rhamnose in the ratio 5.9:5 .5:3.4: 1. 2:1.0 . A partial hydrolysis study revealed a similar series of galactose containing oligosaccharides as was identified from the mucilage of Opuntia ficus-indica. The degraded polysaccharide isolated from the partial hydrolysate was methylated and a possible structure proposed for the repeating unit. Methylation studies of the native polysaccharide indicated a polysaccharide with a more complex structure than that for the mucilage of Opuntia ficus-indica.
- Full Text:
- Date Issued: 1977
The preparation of BODIPY and porphyrin dyes and their cyclodextrin inclusion complexes and Pluronic® F-127 encapsulation micelles for use in PDT and PACT
- Authors: Molupe, Nthabeleng
- Date: 2019
- Subjects: Dyes and dyeing -- Chemistry , Drug delivery systems , Fluorescence spectroscopy , Cancer -- Photochemotherapy , Photosensitizing compounds -- Therapeutic use , Cyclodextrins -- Biotechnology , Nanoparticles
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/117574 , vital:34528
- Description: Several novel BODIPY dyes ((4,4′-difluoro-1,7-tetramethyl-3,5-(3-dithiophene)-2,6-diiodo-8-(4-dimethylamino)-4-bora-3a,4a-diaza-s-indacene (1c), 4,4′-difluoro-1,7-tetramethyl-3,5-(3 dithiophene)-2,6-diiodo-8-(4-methylthio)-4-bora-3a,4a-diaza-s-indacene (3c) and 4,4′-difluoro-1,7-tetramethyl-3,5-(4-dibenzyloxybenzene)-2,6-diiodo-8-(4-methylbenzoate)-4 bora-3a,4a-diaza-s-indacene (4c)) and porphyrins (tetraacenaphthylporphyrin (7a) and Sn(IV) tetraacenaphthylporphyrin (7b)) were synthesized and characterized. Previously reported BODIPY dyes (4,4′-difluoro-1,7-tetramethyl-3,5-(2-dihydroxy)-2,6-diiodo-8-(4-bromo)-4-bora-3a,4a-diaza-s-indacene (5) and 4,4′-difluoro-1,7-tetramethyl-3,5-(2-dithiophene)-2,6-diiodo-8-(phenyl)-4-bora-3a,4a-diaza-s-indacene (6)) were also used. Pluronic® F-127 and cyclodextrins were used as solubilizing drug delivery agents for the synthesized BODIPY dyes. The encapsulation of BODIPY dyes with Pluronic® F-127 micelles improved the water solubility of the BODIPY 5. Further modification of Pluronic® F-127 by coating with folate-functionalized chitosan for targeted delivery of BODIPY 1c and 6 was explored. The BODIPY dyes and their encapsulation complexes exhibited significant inhibition of human MCF-7 breast cancer cell growth. When cyclodextrins were used as nanocarriers, the inclusion complexes of BODIPY 4c with mβCD were found to enhance the water-solubility of the dye. Greater photoinactivation of Staphylococcus aureus was observed for the inclusion complexes when compared to the effect of solutions of non-complexed BODIPY 4c. The cyclodextrin inclusion complexes of porphyrin 7b with mβCD were also found to enhance the water-solubility of 7b. When the photodynamic effect was evaluated, solutions of the porphyrin alone and their inclusion complexes were found to have significant photodynamic effects against human MCF-7 breast cancer cells.
- Full Text:
- Date Issued: 2019
The pyrrolizidine alkaloids of Senecio chrysocoma and Senecio paniculatus
- Authors: Logie, Catherine Gwynedd
- Date: 1996
- Subjects: Senecio -- Analysis Pyrrolizidines Botanical chemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4339 , http://hdl.handle.net/10962/d1005000
- Description: In order to compare the pyrrolizidine alkaloid content of two closely related species, Senecio chrysocoma and S. paniculatus, nine populations of plants distributed between the two species, were examined. Three novel pyrrolizidine alkaloids, 7ß-angelyl-l-methylene-8∝-pyrrolizidine, 7ß-angelyl-l-methylene-8∝-pyrrolizidine and 7ß-angelyl-l-methyleneSO!-pyrrolizidine-4-oxide, as well as eight known pyrrolizidine alkaloids, 7-angelylhastanecine, 9-angelylhastanecine, 7-angelylplatynecine, 9-angelylplatynecine, 9-angelylplatynecine-4-oxide, sarracine, neosarracine and retrorsine, were isolated and identified by NMR and GC-MS techniques. Traces of five tiglyl isomers, 9-tiglylplatynecine, 9-tigl ylplatynecine-4-oxide, 7ß-tiglyl-l-methylene-8∝-pyrrolizidine, sarranicine and neosarranicine, were also isolated and tentatively identified; however, these compounds could have been artefacts of the extraction and analytical procedures. While both species of plant investigated, S. chrysocoma and S. paniculatus, were found to be morphologically different, their pyrrolizidine alkaloid content was, in fact, very similar. The presence of retrorsine in S. paniculatus plant extracts, but not in those from S. chrysocoma plants, was the only major chemical difference observed. It is perhaps significant that retrorsine was the only macrocyclic pyrrolizidine to be identified. A comprehensive, computerised database of physical data for pyrrolizidine alkaloids has been compiled, which has facilitated the identification of new pyrrolizidines and the examination of trends in proton and carbon-13 NMR data for pyrrolizidine alkaloids. A stereospecific synthesis of 7ß-angelyl-l-methylene-8∝-pyrrolizidine was undertaken toconfirm the absolute stereochemistry of the product isolated from S. chrysocoma and S. paniculatus. An inseparable 5:2 mixture of 7ß-angelyl-l-methylene-8∝-pyrrolizidine and 7ß-angelyl-l,2-didehydro-l-methyl-8∝-pyrrolizidine, together with a small amount of tiglyl isomer, was finally synthesised. The application of various chiral differentiating chromatographic and spectroscopic techniques confirmed that both the natural and synthetic products had the same stereochemistry, permitting the natural alkaloid to be identified as 7ß-angelyl-methylene-8∝-pyrrol izidine
- Full Text:
- Date Issued: 1996
The removal of toxic anions from wastewater using electrospun nanofibers
- Authors: Moronkola, Bridget Adekemi
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4564 , http://hdl.handle.net/10962/d1020991
- Description: The presence of arsenic and phosphate in waters, especially wastewater, has become a worldwide problem even till the present time. The current regulation of drinking standard water has become more stringent and requires arsenic content to be reduced to a few parts per billion. Nevertheless, phosphorous pollution, known as the eutrophication, is regarded as one of the main causes of water quality deterioration. Hence, the decontamination of phosphorous from aqueous solutions is of importance for eutrophication control and phosphorous recovery. Efforts are being made to remove these contaminants, arsenic (v) and phosphate from wastewater using low cost adsorbents. In the present study, removal of arsenic(v) and phosphate from wastewater using two novel fabricated sorbent materials; polyvinylmethylketone functionalized 2-amino4,6-dihydroxylpyrimidine (APPMKNFs) prepared via a Schiff base condensation reaction and aminated polyvinylbenzylchloride (PVBC) prepared through a substitution reaction and then quaternized using three alkyl groups (R’ = CH₃, C₂H₅ and C₃H₇) were investigated. The experiments were carried out in batch and solid phase extraction mode. Preliminary experiments were done with series of four sorbent materials (APPMKNFs, R’ = CH₃, C₂H₅ and C₃H₇) in order to find out a suitable and low cost adsorbents for the effective removal of arsenic (v) and phosphate. The best sorbent materials were obtained after the optimization and preparation experiments. The APPMKNFs and R’ = CH₃ were effective for arsenic (v) and phosphate removal from wastewater. The effect of pH, initial sorbate concentration, amount of sorbent, effect of co-exisiting anions and the reusability in batch and solid phase extraction mode were also investigated. From the experiment conducted, the pH shows a decisive factor on arsenic and phosphate removal. Analysis of adsorbent dosage, Kinetic studies and co-existing anions were carried out in order to evaluate sorption parameters. The adsorption isotherms were well fitted by Langmuir than Freundlch isotherm for (APPMKNFs). And more...
- Full Text:
- Date Issued: 2016
The solubility enhancement and the stability assessment of rifampicin, isoniazid and pyrazinamide in aqueous media
- Authors: Chen, Yu-Jen
- Date: 2000
- Subjects: Gel permeation chromatography , Rifampin , Isoniazid , Pyridazines
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4346 , http://hdl.handle.net/10962/d1005009 , Gel permeation chromatography , Rifampin , Isoniazid , Pyridazines
- Description: Tuberculosis (TB) is a highly contagious disease caused by the bacterium known as Mycobacterium tuberculosis which is widely spread in South Africa, especially in the rural areas of the Western Province. Rifampicin, isoniazid and pyrazinamide are the three most effective drugs against this organism. However, most of the current commercial anti-TB formulations are inconvenient to administrate. This results in patient non-compliance which has increased with incomplete tuberculosis treatment and further has intensified the mortality rate. The matter is especially severe amongst the paediatric and geriatric patients. Therefore, creating a "user-friendly" but non-alcoholic liquid formulation should improve the whole situation. The key to a successful formulation relies on sufficient concentrations of the drugs within the formulation together with acceptable stability of these drugs. Therefore, during the pre-formulation stage, the solubility and stability studies of rifampicin, isoniazid and pyrazinamide are to be conducted. Rifampicin, isoniazid and pyrazinamide were fully characterized and identified by means of spectroscopic and thermal techniques. A HPLC method for simultaneous analysis of the three drugs was developed and validated. This HPLC method was employed for all the solubility and stability assessments. Unbuffered HPLC water of pH value 7.01 was chosen as the aqueous solvent. This was decided after the stability of rifampicin, isoniazid and pyrazinamide was studied at a pH range of 2 to 10. The solubility and the stability studies of rifampicin, isoniazid, pyrazinamide, rifampicin with isoniazid, rifampicin with pyrazinamide, isoniazid with pyrazinamide and rifampicin combined with both isoniazid and pyrazinamide were performed in the presence of various agents. These agents can be categorized into three groups: the surfactants (poloxamer 188, poloxamer 407 and sorbitol) which could increase the intrinsic solubility or the drugs by altering the surface tensions of the aqueous solution medium, the suspending agents (carbopol 934 and carbopol 974P) which could enable the amount of dosage required to be homogeneously suspended in the formulation without considering the low intrinsic solubility factor of the drugs, and the complexing agents (ß-cyclodextrin, hydroxypropyl-ß-cyclodextrin and -cyclodextrin) which could initiated the inclusion complex between the host cyclodextrin and the drugs, thus further enhance the solubility of the drugs . The stability assessments were performed after 7-days stability trail with the HPLC method developed. Each drug/combination of drugs were stored in closed ampoules and subjected to 25, 40 and 60° C with or without nitrogen flushing while in the presence of the above mentioned agents. While assessing the solubility/stability of the drugs in the presence of the above mentioned surfactants, the phase-solubility curves indicate that both rifampicin and pyrazinamide fail to achieve the desired concentration. Moreover, the stability-time plots clearly indicate that these surfactants fail to enhance the general stabilities of the drugs. When the stabilizing effects of the above mentioned suspending agents were investigated, it was found that although the desired concentration could be easily accomplished by suspending the drug in the aqueous carbopol solutions, the stabilities of the different drug combinations were still below the regulatory level. Cyclodextrins are well known to form inclusion complexes with less polar drug molecules. The inclusion complexation could enhance both the solubility and the stability of the included drug molecules. The computer force field generated models of the cyclodextrin-drug were used to predict the complexation sites. The results indicated the all the inclusion complexation between the drugs and the cyclodextrins were favourable, but do not necessary protect the potential degradation sites of the drugs. The stability results confirmed the above findings as the cyclodextrins did not enhance the stability of the drugs. Various drug-drug interaction pathways were also predicted from the experimental observations which clearly indicated the stability reductions of these drugs in combination. This leads to the conclusion that a liquid formulation combining rifampicin, isoniazid and pyrazinamide should not initiate the use of aqueous solutions as the protic ions of the solution are able to initiate the degradation of these drugs.
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- Date Issued: 2000
The solubility of barium sulphate in water at 25°
- Authors: Rosseinsky, D R
- Date: 1957
- Subjects: Chemistry, Physical and theoretical , Solubility , Barium sulfate
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4491 , http://hdl.handle.net/10962/d1013097
- Description: Barium sulphate is a widely used analytical precipitate and for this reason its properties have been extensively studied. The variety of results encountered with barium sulphate samples prepared by different methods is an indication of the complex nature of this interesting substance. Intro., p. 8.
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- Date Issued: 1957
The solubility of mercurous chloride in water at 25°C
- Authors: Clur, Dennis Alwin
- Date: 1959
- Subjects: Mercury compounds -- Solubility , Mercuric chloride
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4522 , http://hdl.handle.net/10962/d1014705
- Description: [From Introduction]. In 1955, Dry and Gledhill, both formerly of this Department, published their paper on the Solubility of Mercurous Chloride in Water at 25°0, and it was originally intended that this thesis should be an extension of the study to cover the temperature range from 5 t o 55°0. A preliminary investigation at 25°0, however, failed to yield results which were consistent with their findings, even though their apparatus and experimental technique were used. In an effort to resolve these difficulties their method of saturating the calomel in the conductance cell was thoroughly investigated, and as this procedure was found to be responsible, it was necessary to evolve an entirely new approach. The technique finally adopted was to saturate the mercurous chloride solutions by mechanical stirring in siliconed vessels and to carry out the conductance, pH, and total mercury concentration measurements on the filter ed solution. This method gave good results, and was free from the many extrapolations prevalent in the original procedure.
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- Date Issued: 1959