Asymmetrical zinc(II) phthalocyanines conjugated to nanomaterials for degradation of organic pollutants and inactivation of Staphylococcus aureus bacteria
- Authors: Mgidlana, Sithi
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431859 , vital:72809 , DOI 10.21504/10962/431860
- Description: This thesis reports on the syntheses and characterization of asymmetrical phthalocyanines (Pcs) with different ring substituents (tert-butyl, ester, diimide, trimethoxy, acetophenone, heptanoylphenoxy, perfluorophenoxy, dimethoxy, propanoic acid, acetic acid, carboxylic acid, aminophenoxy, acrylic acid). Several nanoparticles including metal tungstate, capped with glutathione and 1-mercaptohexanol are prepared and characterized using analytical techniques. The synthesized Pcs are covalently linked to various nanoparticles (NPs) through ester and amide bonds to form Pc-NP conjugates, in order to improve their catalytic properties. The Pcs and their conjugates are characterized using different analytical techniques. The photophysics and photochemistry of the MPcs and conjugates are studied. The conjugates T). The complexes and the conjugates with nanomaterials are evaluated for singlet oxygen-generating ability. Conjugates generate higher singlet oxygen in comparison to Pc complexes alone. The photocatalytic activity of the conjugates of ZnPc complexes with NiWO4, Ag2WO4, Bi2WO6, CoWO4, and Ag-Fe3O4-based nanoparticles is evaluated based on photodegradation of methylene blue, tetracycline, and dibenzothiophene. The photocatalytic efficiencies of the synthesized phthalocyanine complexes increased in the presence of nanoparticles. This work also reports on the photodynamic antimicrobial chemotherapy activity of these materials against Staphylococcus aureus (S. aureus) bacteria in DMSO. The results indicated that silver-based nanoconjugates exhibit high antimicrobial activity with high log reductions compared to NiWO4, CoWO4, and Ag-Fe3O4-based materials. The z-scan technique is employed to experimentally test the nonlinear optical response of complexes and nanoconjugates in solution. The nonlinear absorption coefficient, third-order optical susceptibility and optical limiting threshold of the materials are obtained from the Z-scan aperture data. The nonlinear absorption parameters improved in the presence of semiconductor quantum dots, with 1-ethanoic-CdTe/ZnSeS/ZnO giving the best results due to the presence of electron-donating substituents. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Mgidlana, Sithi
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431859 , vital:72809 , DOI 10.21504/10962/431860
- Description: This thesis reports on the syntheses and characterization of asymmetrical phthalocyanines (Pcs) with different ring substituents (tert-butyl, ester, diimide, trimethoxy, acetophenone, heptanoylphenoxy, perfluorophenoxy, dimethoxy, propanoic acid, acetic acid, carboxylic acid, aminophenoxy, acrylic acid). Several nanoparticles including metal tungstate, capped with glutathione and 1-mercaptohexanol are prepared and characterized using analytical techniques. The synthesized Pcs are covalently linked to various nanoparticles (NPs) through ester and amide bonds to form Pc-NP conjugates, in order to improve their catalytic properties. The Pcs and their conjugates are characterized using different analytical techniques. The photophysics and photochemistry of the MPcs and conjugates are studied. The conjugates T). The complexes and the conjugates with nanomaterials are evaluated for singlet oxygen-generating ability. Conjugates generate higher singlet oxygen in comparison to Pc complexes alone. The photocatalytic activity of the conjugates of ZnPc complexes with NiWO4, Ag2WO4, Bi2WO6, CoWO4, and Ag-Fe3O4-based nanoparticles is evaluated based on photodegradation of methylene blue, tetracycline, and dibenzothiophene. The photocatalytic efficiencies of the synthesized phthalocyanine complexes increased in the presence of nanoparticles. This work also reports on the photodynamic antimicrobial chemotherapy activity of these materials against Staphylococcus aureus (S. aureus) bacteria in DMSO. The results indicated that silver-based nanoconjugates exhibit high antimicrobial activity with high log reductions compared to NiWO4, CoWO4, and Ag-Fe3O4-based materials. The z-scan technique is employed to experimentally test the nonlinear optical response of complexes and nanoconjugates in solution. The nonlinear absorption coefficient, third-order optical susceptibility and optical limiting threshold of the materials are obtained from the Z-scan aperture data. The nonlinear absorption parameters improved in the presence of semiconductor quantum dots, with 1-ethanoic-CdTe/ZnSeS/ZnO giving the best results due to the presence of electron-donating substituents. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
Enhancing the electrocatalytic activity of phthalocyanines through finding the ideal combination of substituents in push-pull phthalocyanine-based systems
- Nkhahle, Reitumetse Precious
- Authors: Nkhahle, Reitumetse Precious
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432578 , vital:72882 , DOI 10.21504/10962/432578
- Description: Phthalocyanines (Pcs) are a class of synthetic pigments with a similar structure to porphyrins. The work presented in this thesis is centred around these electron-rich macrocycles and their use in electrocatalysis. This body of work provides a more rigorous analysis on asymmetric Pcs, focusing on finding the “ideal” combination of substituents in the synthesis of A3B-type Pcs and how these asymmetric structures compare with their symmetric counterparts (A4) in the electrocatalysis of hydrazine and nitrite. The choice in substituents in the syntheses of the Pcs was such that there is both electron-donating and electron-withdrawing groups to induce a push-pull effect. In the studies involving the electrocatalysis of hydrazine, asymmetric cobalt Pcs (CoPcs) possessing alkyl groups as the primary substituents, with variations in the acid-containing group, along with their symmetric counterparts, probes with potential for further improvement were identified. Using voltammetric and amperometric techniques, the analyte-electrode kinetics, mechanism in which the electrochemical reaction proceeds along with the limits of detection (LoD) were determined. In the general sense, the pentadecylphenoxy-derived CoPcs performed better than those containing the tert-butyl substituent as the dominant substituent with the asymmetric CoPcs producing more favourable results than their symmetric analogues. With respect to the probes designed for nitrite, a multi-dimensional approach was undertaken in that acetaminophen was chosen as the primary substituent whilst multiple changes in the asymmetric component were made. In addition to varying the carboxylic acid-containing substituent, alkyne- and amine-based substituents were also explored in which the alkyne-containing Pc was anchored onto the electrode surface through click chemistry while the amine-bearing Pc was covalently linked (and π-stacked) to nitrogen-doped graphene quantum dots (NGQDs). Another component that was altered was the central metal where CoPcs were compared to manganese Pcs (MnPcs). The most desirable peak oxidation potential for nitrite was observed in the MnPcs as it was the lowest with adsorption sometimes being a better suited method of electrode modification relative to clicking. The inclusion of NGQDs was found to be beneficial when combined with the symmetric CoPc whilst in the presence of an asymmetric Pc complex, less desirable results were observed. Overall, there were variations in the results with the symmetric CoPc sometimes being better than some of the asymmetric CoPcs demonstrating that a blanket-approach in terms of synthesizing and applying asymmetric Pcs is not always viable. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Nkhahle, Reitumetse Precious
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432578 , vital:72882 , DOI 10.21504/10962/432578
- Description: Phthalocyanines (Pcs) are a class of synthetic pigments with a similar structure to porphyrins. The work presented in this thesis is centred around these electron-rich macrocycles and their use in electrocatalysis. This body of work provides a more rigorous analysis on asymmetric Pcs, focusing on finding the “ideal” combination of substituents in the synthesis of A3B-type Pcs and how these asymmetric structures compare with their symmetric counterparts (A4) in the electrocatalysis of hydrazine and nitrite. The choice in substituents in the syntheses of the Pcs was such that there is both electron-donating and electron-withdrawing groups to induce a push-pull effect. In the studies involving the electrocatalysis of hydrazine, asymmetric cobalt Pcs (CoPcs) possessing alkyl groups as the primary substituents, with variations in the acid-containing group, along with their symmetric counterparts, probes with potential for further improvement were identified. Using voltammetric and amperometric techniques, the analyte-electrode kinetics, mechanism in which the electrochemical reaction proceeds along with the limits of detection (LoD) were determined. In the general sense, the pentadecylphenoxy-derived CoPcs performed better than those containing the tert-butyl substituent as the dominant substituent with the asymmetric CoPcs producing more favourable results than their symmetric analogues. With respect to the probes designed for nitrite, a multi-dimensional approach was undertaken in that acetaminophen was chosen as the primary substituent whilst multiple changes in the asymmetric component were made. In addition to varying the carboxylic acid-containing substituent, alkyne- and amine-based substituents were also explored in which the alkyne-containing Pc was anchored onto the electrode surface through click chemistry while the amine-bearing Pc was covalently linked (and π-stacked) to nitrogen-doped graphene quantum dots (NGQDs). Another component that was altered was the central metal where CoPcs were compared to manganese Pcs (MnPcs). The most desirable peak oxidation potential for nitrite was observed in the MnPcs as it was the lowest with adsorption sometimes being a better suited method of electrode modification relative to clicking. The inclusion of NGQDs was found to be beneficial when combined with the symmetric CoPc whilst in the presence of an asymmetric Pc complex, less desirable results were observed. Overall, there were variations in the results with the symmetric CoPc sometimes being better than some of the asymmetric CoPcs demonstrating that a blanket-approach in terms of synthesizing and applying asymmetric Pcs is not always viable. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
From more sustainable isocyanide-based multicomponent reactions to spiro-heterocyclic compound syntheses
- Authors: Salami, Sodeeq Aderotimi
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432229 , vital:72853 , DOI 10.21504/10962/432229
- Description: The global pharmaceutical industry has undergone profound transformations in the past two decades in the search for new drugs. For this reason, most pharmaceutical companies made significant investments not only in the development of new drugs but new methodologies. Modern drug development is confronted with the challenge of developing chemical reactions that are highly capable of providing most of the elements of structural complexity and diversity with the fewest possible synthetic steps for the specific target with the most intriguing properties. The discovery of more sustainable, environmentally friendly reactions capable of forming multiple bonds in a single step has been a challenge in organic synthesis over the years. Many organic chemists have recently started focusing on creative ways of reducing environmental pollution. The use of hazardous solvents has been reduced or eliminated in research to limit harm to both people and the environment. The pursuit of this goal has drawn many organic chemists to the study of various sustainable synthetic techniques including catalysis, aqueous organic reactions and mechanochemistry. The scope of this thesis was to apply sustainable techniques to design multicomponent synthetic protocols for the Passerini reaction and further apply these new protocols to construct spiro-heterocyclic compounds, all based on green chemistry principles. There is a need to develop rapid, efficient, and versatile strategies for the synthesis of bioactive molecules via multicomponent reactions. This project tried to avoid some of the pitfalls of traditional approaches, such as toxicity, low yield, long reaction times, harsh conditions, experimental complexity, and limited functionalization scope. This was achieved by focussing on the use of isonitriles and isothiocyanates as key reactive intermediates, and making extensive use of aqueous reaction conditions, mechanochemistry and microwave activation. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Salami, Sodeeq Aderotimi
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432229 , vital:72853 , DOI 10.21504/10962/432229
- Description: The global pharmaceutical industry has undergone profound transformations in the past two decades in the search for new drugs. For this reason, most pharmaceutical companies made significant investments not only in the development of new drugs but new methodologies. Modern drug development is confronted with the challenge of developing chemical reactions that are highly capable of providing most of the elements of structural complexity and diversity with the fewest possible synthetic steps for the specific target with the most intriguing properties. The discovery of more sustainable, environmentally friendly reactions capable of forming multiple bonds in a single step has been a challenge in organic synthesis over the years. Many organic chemists have recently started focusing on creative ways of reducing environmental pollution. The use of hazardous solvents has been reduced or eliminated in research to limit harm to both people and the environment. The pursuit of this goal has drawn many organic chemists to the study of various sustainable synthetic techniques including catalysis, aqueous organic reactions and mechanochemistry. The scope of this thesis was to apply sustainable techniques to design multicomponent synthetic protocols for the Passerini reaction and further apply these new protocols to construct spiro-heterocyclic compounds, all based on green chemistry principles. There is a need to develop rapid, efficient, and versatile strategies for the synthesis of bioactive molecules via multicomponent reactions. This project tried to avoid some of the pitfalls of traditional approaches, such as toxicity, low yield, long reaction times, harsh conditions, experimental complexity, and limited functionalization scope. This was achieved by focussing on the use of isonitriles and isothiocyanates as key reactive intermediates, and making extensive use of aqueous reaction conditions, mechanochemistry and microwave activation. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
Liposomal formulations of metallophthalocyanines-nanoparticle conjugates for hypoxic photodynamic therapy and photoelectrocatalysis
- Authors: Nwahara, Nnamdi Ugochinyere
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432159 , vital:72847 , DOI 10.21504/10962/432159
- Description: This thesis investigates new strategies to enhance the efficacy of photodynamic therapy (PDT) under hypoxic conditions using in-vitro cancer cell models. Phthalocyanines are chosen as viable photosensitizer complexes owing to the favourable absorption properties. To this end, this thesis reports on the synthesis and photophysicochemical properties of various zinc and silicon phthalocyanines (Pcs). To afford better photophysicochemical properties, the reported Pcs were conjugated to different nanoparticles (NPs) through chemisorption as well as amide bond formation to yield Pc-NP conjugates. All the studied Pcs showed relatively high triplet and singlet oxygen quantum yields corresponding to their low fluorescence quantum yields. The various mechanisms for hypoxic response include (i) Type I PDT, (ii) PDT coupled with oxygen-independent therapy and (iii) in-situ oxygen generation using catalase-mimicking nanoparticles which serve to supplement in-vitro oxygen concentrations using MPcs or MPc-NPs conjugates. The mechanisms were assessed using electrochemical, computational techniques and catalase mimicking experiments. The as-synthesised Pcs or Pc-NPs were subjected to liposomal loading before PDT studies which led to enhanced biocompatibility and aqueous dispersity. The in-vitro dark cytotoxicity tests and photodynamic therapy activities of the fabricated Pc-liposomes and Pc-NPs-liposomes on either Henrietta Lacks (HeLa) or Michigan Cancer Foundation-7 (MCF-7) breast cancer cells are presented herein. This work further showed that folic acid (FA) functionalization of liposomes could be exploited for active drug delivery and herein led to an almost 3-fold increase in drug uptake vs non-FA functionalised liposomes in accordance with folate receptor (FR) expression levels between HeLa and MCF-7 cells. The in-vitro dark cytotoxicity and photodynamic therapy of selected Pc complexes and conjugates were accessed using MCF-7 and HeLa cell lines. The various mechanisms; (i) Type I PDT, (ii) PDT coupled with oxygen -independent therapy and (iii) in-situ oxygen generation using catalase-mimicking nanoparticles were shown to adequately compensate for the otherwise attenuation of PDT activity under hypoxia. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Nwahara, Nnamdi Ugochinyere
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432159 , vital:72847 , DOI 10.21504/10962/432159
- Description: This thesis investigates new strategies to enhance the efficacy of photodynamic therapy (PDT) under hypoxic conditions using in-vitro cancer cell models. Phthalocyanines are chosen as viable photosensitizer complexes owing to the favourable absorption properties. To this end, this thesis reports on the synthesis and photophysicochemical properties of various zinc and silicon phthalocyanines (Pcs). To afford better photophysicochemical properties, the reported Pcs were conjugated to different nanoparticles (NPs) through chemisorption as well as amide bond formation to yield Pc-NP conjugates. All the studied Pcs showed relatively high triplet and singlet oxygen quantum yields corresponding to their low fluorescence quantum yields. The various mechanisms for hypoxic response include (i) Type I PDT, (ii) PDT coupled with oxygen-independent therapy and (iii) in-situ oxygen generation using catalase-mimicking nanoparticles which serve to supplement in-vitro oxygen concentrations using MPcs or MPc-NPs conjugates. The mechanisms were assessed using electrochemical, computational techniques and catalase mimicking experiments. The as-synthesised Pcs or Pc-NPs were subjected to liposomal loading before PDT studies which led to enhanced biocompatibility and aqueous dispersity. The in-vitro dark cytotoxicity tests and photodynamic therapy activities of the fabricated Pc-liposomes and Pc-NPs-liposomes on either Henrietta Lacks (HeLa) or Michigan Cancer Foundation-7 (MCF-7) breast cancer cells are presented herein. This work further showed that folic acid (FA) functionalization of liposomes could be exploited for active drug delivery and herein led to an almost 3-fold increase in drug uptake vs non-FA functionalised liposomes in accordance with folate receptor (FR) expression levels between HeLa and MCF-7 cells. The in-vitro dark cytotoxicity and photodynamic therapy of selected Pc complexes and conjugates were accessed using MCF-7 and HeLa cell lines. The various mechanisms; (i) Type I PDT, (ii) PDT coupled with oxygen -independent therapy and (iii) in-situ oxygen generation using catalase-mimicking nanoparticles were shown to adequately compensate for the otherwise attenuation of PDT activity under hypoxia. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
Porphyrinoid dyes for photodynamic anticancer and antimicrobial therapy treatments
- Authors: Soy, Rodah Cheruto
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432252 , vital:72855 , DOI 10.21504/10962/432252
- Description: The search for alternative therapies and non-toxic photosensitizer drugs that can efficiently generate cytotoxic reactive oxygen species for biomedical applications, such as in alternative photodynamic therapy (PDT) for cancer treatment and photodynamic antimicrobial chemotherapy (PACT) for drug-resistant bacteria treatment is on the rise. Nevertheless, the lack of photosensitizer dyes that absorb light strongly within the therapeutic window (620−850 nm) that can locally target the tumor and bacterial cells and generate singlet oxygen efficiently are some of the main challenges in PDT and PACT treatment. This study sought to address the challenges that impede PDT and PACT from realizing their full potential by synthesizing a series of meso-aryltetrapyrrolic photosensitizer dyes that absorb light within the therapeutic window. These include meso-tetraarylporphyrin (Por), A3-type meso-triarylcorrole (Cor), meso-tetraarylchlorin (Chl), and N-confused meso-tetraarylporphyrin (NCP) dyes with 4-thiomethylphenyl (1), thien-3-yl (2), thien-2-yl (3), 5-bromo-thien-2-yl (4), 4-methoxyphenyl (5), 3-methoxyphenyl (6), 4-hydroxyphenyl (7) and 4-hydroxy-3-methoxyphenyl (8) meso-aryl rings. Por, Cor, Chl and NCP dyes and and their Ga(III), P(V), In(III) and/or Sn(IV) complexes with 1-8, 1-4, 5-8 and 5 meso-aryl rings were studied, along with two A2B-type Ga(III) meso-triarylcorroles with pentafluorophenyl rings at the A2 positions and 3,6-di-t-butyl-9H-carbazole (9) or N-butyl-4-carbazole (10) rings at the B position that were prepared in the laboratory of Prof. Xu Liang of Jiangsu University in the People’s Republic of China. The carbazole nitrogen of 10-GaCor was quaternized at Rhodes University with ethyl iodide to form a cationic species (10-GaCor-Q) for PDT and PACT activity studies. The structures of the synthesized dyes were confirmed using UV-visible absorption and 1H NMR spectroscopy, and MALDI-TOF-mass spectrometry. 1-4-InPor In(III) porphyrins, 1-4-PVCor, 1-4-GaCor A3 PV and GaIII corrole dyes were also conjugated to gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) via sulfur-gold and sulfur-silver affinities. The successful conjugation of the dyes onto the nanoparticles to form dye-AuNP or dye-AgNP nanoassemblies was confirmed using transmission electron microscopy (TEM), energy dispersive X-ray (EDX) spectroscopy, X-ray powered diffraction (XRD), and (X-ray photon spectroscopy) XPS. The photophysicochemical, photostability, and lipophilicity properties of the dyes and their PDT and PACT activities were investigated, and the structure-property relationships were analyzed. This was accomplished by analyzing the changes in the properties of the dyes due to the meso-aryl substituents, central ions, molecular symmetry, and heavy atom effects. Time-dependent-density functional theory (TD-DFT) calculations were also used to further probe the electronic and optical spectroscopic properties of the dyes. The analysis of the photophysicochemical, photostability, and lipophilicity data for the synthesized dyes demonstrated that there are inherent structure-property relationships for the dyes studied. The TD-DFT calculations also assisted in rationalizing the observed optical spectroscopic data for the dyes. The introduction of different meso-aryl substituents resulted in minor absorption spectral changes on the parent structures of the dyes due to their inductive and mesomeric effects, while the insertion of Ga(III), In(III), and Sn(IV) electropositive metal centers resulted in marked red shifts of the B bands due to favorable interactions with the porphyrin or porphyrinoid ligand core. The lower symmetries of the corrole, chlorin, and N-confused porphyrin dyes resulted in enhanced absorption properties within the therapeutic window relative to porphyrins. The heavy atom effect from the Ga(III), In(III), and Sn(IV) central ions, the meso-aryl groups, and the external heavy atom effect from the AuNPs and AgNPs significantly reduced the fluorescence quantum yield values of the dyes resulting in high singlet oxygen quantum yields. The dye complexes also exhibited properly balanced lipophilic properties and high photostabilities. The P(V) ion of the A3 PV corrole dyes reduced the aggregation effects, enhanced cellular uptake, and lowered the lipophilicity values relative to the A3 GaIII corrole dyes. The porphyrin and porphyrinoid complexes studied exhibited relatively low in vitro dark cytotoxicity toward MCF-7 cancer cells, which is enhanced for AuNP nanoconjugates of 1-InPor, 1-3-PVCor, and 1-3-GaCor. The dyes also have low in vitro dark cytotoxicity toward planktonic and biofilm cells of S. aureus and E. coli. The complexes also exhibited favorable PDT and PACT activities toward MCF-7 cancer cells, and planktonic and biofilm S. aureus and E. coli bacteria due to their high singlet oxygen quantum yields. AuNP and AgNP nanoconjugates of 1-4-InPor, 1-4-PVCor, and 1-4-GaCor exhibited enhanced PDT and PACT activities due to the favorable synergistic effects of nanoparticles. The PDT and PACT activities of A3 PV corrole dyes and the nanoconjugates of 1-4-PVCor are slightly higher than those of A3-type GaIII corroles and their nanoconjugates due to decreased aggregation effects and enhanced PS drug uptake. The cationic 10-GaCor-Q species also exhibit favorable PDT and PACT activities in contrast to the neutral 9-10-GaCor dyes due to enhanced PS drug penetration into the tumor or bacteria cells. The complexes also exhibited high Log10 reduction values for planktonic S. aureus suggesting that the dyes are highly efficient PS dyes. The activities of the complexes toward planktonic E. coli bacteria are moderate except for 10-GaCor-Q, 2-4-PVCor-AgNPs, and 5-8-SnChl chlorins exhibiting relatively favorable activity with > 3 Log10 CFU.mL−1 values. The dyes also exhibit moderate activities toward the S. aureus and E. coli biofilm cells, which are lower than for the planktonic cells, as shown by their lower Log10 reduction values. The data demonstrate that the low symmetry corrole, chlorin, and N-confused porphyrin complexes that absorb light strongly within the therapeutic window have significantly enhanced PDT and PACT activities relative to their porphyrin analogs. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Soy, Rodah Cheruto
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432252 , vital:72855 , DOI 10.21504/10962/432252
- Description: The search for alternative therapies and non-toxic photosensitizer drugs that can efficiently generate cytotoxic reactive oxygen species for biomedical applications, such as in alternative photodynamic therapy (PDT) for cancer treatment and photodynamic antimicrobial chemotherapy (PACT) for drug-resistant bacteria treatment is on the rise. Nevertheless, the lack of photosensitizer dyes that absorb light strongly within the therapeutic window (620−850 nm) that can locally target the tumor and bacterial cells and generate singlet oxygen efficiently are some of the main challenges in PDT and PACT treatment. This study sought to address the challenges that impede PDT and PACT from realizing their full potential by synthesizing a series of meso-aryltetrapyrrolic photosensitizer dyes that absorb light within the therapeutic window. These include meso-tetraarylporphyrin (Por), A3-type meso-triarylcorrole (Cor), meso-tetraarylchlorin (Chl), and N-confused meso-tetraarylporphyrin (NCP) dyes with 4-thiomethylphenyl (1), thien-3-yl (2), thien-2-yl (3), 5-bromo-thien-2-yl (4), 4-methoxyphenyl (5), 3-methoxyphenyl (6), 4-hydroxyphenyl (7) and 4-hydroxy-3-methoxyphenyl (8) meso-aryl rings. Por, Cor, Chl and NCP dyes and and their Ga(III), P(V), In(III) and/or Sn(IV) complexes with 1-8, 1-4, 5-8 and 5 meso-aryl rings were studied, along with two A2B-type Ga(III) meso-triarylcorroles with pentafluorophenyl rings at the A2 positions and 3,6-di-t-butyl-9H-carbazole (9) or N-butyl-4-carbazole (10) rings at the B position that were prepared in the laboratory of Prof. Xu Liang of Jiangsu University in the People’s Republic of China. The carbazole nitrogen of 10-GaCor was quaternized at Rhodes University with ethyl iodide to form a cationic species (10-GaCor-Q) for PDT and PACT activity studies. The structures of the synthesized dyes were confirmed using UV-visible absorption and 1H NMR spectroscopy, and MALDI-TOF-mass spectrometry. 1-4-InPor In(III) porphyrins, 1-4-PVCor, 1-4-GaCor A3 PV and GaIII corrole dyes were also conjugated to gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) via sulfur-gold and sulfur-silver affinities. The successful conjugation of the dyes onto the nanoparticles to form dye-AuNP or dye-AgNP nanoassemblies was confirmed using transmission electron microscopy (TEM), energy dispersive X-ray (EDX) spectroscopy, X-ray powered diffraction (XRD), and (X-ray photon spectroscopy) XPS. The photophysicochemical, photostability, and lipophilicity properties of the dyes and their PDT and PACT activities were investigated, and the structure-property relationships were analyzed. This was accomplished by analyzing the changes in the properties of the dyes due to the meso-aryl substituents, central ions, molecular symmetry, and heavy atom effects. Time-dependent-density functional theory (TD-DFT) calculations were also used to further probe the electronic and optical spectroscopic properties of the dyes. The analysis of the photophysicochemical, photostability, and lipophilicity data for the synthesized dyes demonstrated that there are inherent structure-property relationships for the dyes studied. The TD-DFT calculations also assisted in rationalizing the observed optical spectroscopic data for the dyes. The introduction of different meso-aryl substituents resulted in minor absorption spectral changes on the parent structures of the dyes due to their inductive and mesomeric effects, while the insertion of Ga(III), In(III), and Sn(IV) electropositive metal centers resulted in marked red shifts of the B bands due to favorable interactions with the porphyrin or porphyrinoid ligand core. The lower symmetries of the corrole, chlorin, and N-confused porphyrin dyes resulted in enhanced absorption properties within the therapeutic window relative to porphyrins. The heavy atom effect from the Ga(III), In(III), and Sn(IV) central ions, the meso-aryl groups, and the external heavy atom effect from the AuNPs and AgNPs significantly reduced the fluorescence quantum yield values of the dyes resulting in high singlet oxygen quantum yields. The dye complexes also exhibited properly balanced lipophilic properties and high photostabilities. The P(V) ion of the A3 PV corrole dyes reduced the aggregation effects, enhanced cellular uptake, and lowered the lipophilicity values relative to the A3 GaIII corrole dyes. The porphyrin and porphyrinoid complexes studied exhibited relatively low in vitro dark cytotoxicity toward MCF-7 cancer cells, which is enhanced for AuNP nanoconjugates of 1-InPor, 1-3-PVCor, and 1-3-GaCor. The dyes also have low in vitro dark cytotoxicity toward planktonic and biofilm cells of S. aureus and E. coli. The complexes also exhibited favorable PDT and PACT activities toward MCF-7 cancer cells, and planktonic and biofilm S. aureus and E. coli bacteria due to their high singlet oxygen quantum yields. AuNP and AgNP nanoconjugates of 1-4-InPor, 1-4-PVCor, and 1-4-GaCor exhibited enhanced PDT and PACT activities due to the favorable synergistic effects of nanoparticles. The PDT and PACT activities of A3 PV corrole dyes and the nanoconjugates of 1-4-PVCor are slightly higher than those of A3-type GaIII corroles and their nanoconjugates due to decreased aggregation effects and enhanced PS drug uptake. The cationic 10-GaCor-Q species also exhibit favorable PDT and PACT activities in contrast to the neutral 9-10-GaCor dyes due to enhanced PS drug penetration into the tumor or bacteria cells. The complexes also exhibited high Log10 reduction values for planktonic S. aureus suggesting that the dyes are highly efficient PS dyes. The activities of the complexes toward planktonic E. coli bacteria are moderate except for 10-GaCor-Q, 2-4-PVCor-AgNPs, and 5-8-SnChl chlorins exhibiting relatively favorable activity with > 3 Log10 CFU.mL−1 values. The dyes also exhibit moderate activities toward the S. aureus and E. coli biofilm cells, which are lower than for the planktonic cells, as shown by their lower Log10 reduction values. The data demonstrate that the low symmetry corrole, chlorin, and N-confused porphyrin complexes that absorb light strongly within the therapeutic window have significantly enhanced PDT and PACT activities relative to their porphyrin analogs. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
Prediction of mass spectra using an ab initio approach
- Authors: Novokoza, Yolanda
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/${Handle} , vital:72818
- Description: Access restricted. Expected release date in 2025. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Novokoza, Yolanda
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/${Handle} , vital:72818
- Description: Access restricted. Expected release date in 2025. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
Silica supported sulfuric acid-catalysed one-pot processes for the synthesis of n-heterocycles
- Authors: Ndagano, Urbain Nshokano
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431921 , vital:72815
- Description: Access restricted. Expected release in 2025. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Ndagano, Urbain Nshokano
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431921 , vital:72815
- Description: Access restricted. Expected release in 2025. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
Synthesis of natural product-inspired imido and 3,5-disubstituted-1,2,4-oxadiazolo phosphonates as potential anti-malarial agents
- Authors: Chithambo, Bertha
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431637 , vital:72792
- Description: Access restricted. Expected release date in 2024. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Chithambo, Bertha
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431637 , vital:72792
- Description: Access restricted. Expected release date in 2024. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
The electrocatalytic activity of metallophthalocyanines and their conjugates with carbon nanomaterials and metal tungstate nanoparticles
- Authors: Ndebele, Nobuhle
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431934 , vital:72816 , DOI 10.21504/10962/431933
- Description: In this dissertation, seventeen phthalocyanine complexes were synthesised. Of these, only four are known and have been published. These complexes were synthesised using the conventional statistical condensation method that involves refluxing the phthalonitrile(s) (4-((1,3-bis(dimethylamino)propan-2-yl)oxy)phthalonitrile, 4-(4-carboxyphenoxy)phthalonitrile, 4-(4-acetylphenoxy)phthalonitrile, dimethyl 5-(3,4-dicyanophenoxy)-isophthalate, 4-(4-(tert-butyl)phenoxy)phthalonitrile, 5-phenoxylpicolinic acid phthalonitrile 4-(4-formylphenoxy) phthalonitrile, and 4-(4-(3-oxo-3-phenylprop-1-enyl) phenoxy) phthalonitrile) with the metal salt and 1,8-diazabicyclo[5.4.0]undecane as a catalyst in a high-temperature solvent. And thereafter (when necessary), isolation and purification of the target compounds were achieved through the use of silica column chromatography. These compounds were characterised using various analytical techniques such as; ultraviolet-visible absorption, mass spectroscopy, and Fourier transform infrared spectra and elemental analysis. These techniques proved that the complexes were successfully synthesised and isolated as pure compounds. Carbon-based (graphene quantum dots and nitrogen-doped graphene quantum dots) and metal oxide (bismuth tungsten oxide and nickel tungsten oxide) nanomaterials were synthesised. Together with the purchased single-walled carbon nanotubes, these nanomaterials were conjugated to some of the MPc complexes via non-covalent (carbon-based nanomaterials) and covalent (metal oxides) linkage forming hybrid materials. These nanomaterials and hybrids were characterised using various analytical methods (ultraviolet-visible absorption, X-ray diffraction, Raman spectroscopy, thermographic analysis, and dynamic light scattering). Nanomaterials were utilised herein to determine their effect on the properties of MPc complexes and provide a synergistic effect in the hope of enhancing these properties. All complexes synthesised in this work (MPcs, nanomaterials and hybrids) were employed as electrocatalysts in electrochemical sensing. These electrocatalysts were embedded onto the glassy carbon electrode via an adsorption method known as drop-casting. The modified electrode surfaces were characterised using cyclic voltammetry, electrochemical impedance spectroscopy and scanning electrochemical microscopy to determine various electrochemical parameters. These electrocatalysts were used in the detection of either nitrite, catechol and/or dopamine. The detection limits, sensitivities, kinetics and catalytic constants were among other parameters determined for each electrocatalyst. These electrocatalysts proved to be stable electrocatalysts that could potentially be used for practical applications. The determined parameters were comparable and sometimes better than those obtained in literature. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Ndebele, Nobuhle
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431934 , vital:72816 , DOI 10.21504/10962/431933
- Description: In this dissertation, seventeen phthalocyanine complexes were synthesised. Of these, only four are known and have been published. These complexes were synthesised using the conventional statistical condensation method that involves refluxing the phthalonitrile(s) (4-((1,3-bis(dimethylamino)propan-2-yl)oxy)phthalonitrile, 4-(4-carboxyphenoxy)phthalonitrile, 4-(4-acetylphenoxy)phthalonitrile, dimethyl 5-(3,4-dicyanophenoxy)-isophthalate, 4-(4-(tert-butyl)phenoxy)phthalonitrile, 5-phenoxylpicolinic acid phthalonitrile 4-(4-formylphenoxy) phthalonitrile, and 4-(4-(3-oxo-3-phenylprop-1-enyl) phenoxy) phthalonitrile) with the metal salt and 1,8-diazabicyclo[5.4.0]undecane as a catalyst in a high-temperature solvent. And thereafter (when necessary), isolation and purification of the target compounds were achieved through the use of silica column chromatography. These compounds were characterised using various analytical techniques such as; ultraviolet-visible absorption, mass spectroscopy, and Fourier transform infrared spectra and elemental analysis. These techniques proved that the complexes were successfully synthesised and isolated as pure compounds. Carbon-based (graphene quantum dots and nitrogen-doped graphene quantum dots) and metal oxide (bismuth tungsten oxide and nickel tungsten oxide) nanomaterials were synthesised. Together with the purchased single-walled carbon nanotubes, these nanomaterials were conjugated to some of the MPc complexes via non-covalent (carbon-based nanomaterials) and covalent (metal oxides) linkage forming hybrid materials. These nanomaterials and hybrids were characterised using various analytical methods (ultraviolet-visible absorption, X-ray diffraction, Raman spectroscopy, thermographic analysis, and dynamic light scattering). Nanomaterials were utilised herein to determine their effect on the properties of MPc complexes and provide a synergistic effect in the hope of enhancing these properties. All complexes synthesised in this work (MPcs, nanomaterials and hybrids) were employed as electrocatalysts in electrochemical sensing. These electrocatalysts were embedded onto the glassy carbon electrode via an adsorption method known as drop-casting. The modified electrode surfaces were characterised using cyclic voltammetry, electrochemical impedance spectroscopy and scanning electrochemical microscopy to determine various electrochemical parameters. These electrocatalysts were used in the detection of either nitrite, catechol and/or dopamine. The detection limits, sensitivities, kinetics and catalytic constants were among other parameters determined for each electrocatalyst. These electrocatalysts proved to be stable electrocatalysts that could potentially be used for practical applications. The determined parameters were comparable and sometimes better than those obtained in literature. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
Rapid Synthesis of Thiol-Co-Capped CdTe/CdSe/ZnSe Multi-Core-Shell QDs and Their Encapsulation in Liposomes and Chitosan Nanoparticles; Comparative Bio-compatibility Studies Using Hela and Vero Cells
- Authors: Daramola, Olamide Abiodun
- Date: 2023-03-31
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/422617 , vital:71962 , DOI 10.21504/10962/422617
- Description: The common method that has been used to reduce the toxicity posed to living cells by CdTe Quantum Dots (QDs) is through the synthesis of CdTe multi-core-shells nanoparticles. In this process, the surface of CdTe QDs is usually coated by less toxic ZnS or ZnSe shells. This heterostructure compound does not only reduce the toxicity of CdTe QDs but can also be used in applications such as deep tissue imaging. The heterostructures can be in numerous forms such as CdTe/CdSe/ZnSe or CdTe/CdSe/ZnS or CdTe/CdS/ZnS multi-core-shell QDs. However, the drawbacks attributed to the fabrication of these compounds is long synthesis times (6- 24 h) in achieving the highest wavelength emission maxima. Others are the use of toxic reagents and poor reproducibility of synthesized materials. An additional problem is that the ZnSe or ZnS coating is insufficient to completely protect the highly toxic Cd metal from escaping into immediate solution. This limits their use in biochemistry and with living systems. Liposomes and biopolymers such as chitosan are known to be environmentally friendly compounds that have been used in various studies as delivery systems for QDs and model drugs for drug delivery applications. They are generally non-toxic and highly bio-compatible. In this study, the rapid synthesis of thiol-co-capped CdTe/CdSe/ZnSe multi-core-shell QDs with a maximum reaction time of 35 mins, gave reliable QDs with emission maxima at 625 nm. The multi-core-shell QDs were encapsulated in two different bio-compatible environments, namely liposome and chitosan nanoparticles (CNP) at 14 different formulations (F) for liposome and 12 different formulations for CNP. Cytotoxicity and florescence imaging studies using HeLa and Vero cells, were used to investigate the improved bio-compatibility. Various characterization techniques were used to elucidate the optical properties, morphology and physico-chemical properties of the QDs and nanocomposites. Two of the best formulations, QD-liposome vesicles (LVs)-F12 and QD-CNP-F9 (with chitosan), demonstrated high loading efficiencies of 42 ± 6 % and 59 ± 5 %, respectively. While the plain CdTe QDs showed high toxicity, some of the encapsulated materials, QD-LVs-F1 and F12, depicted no-toxicity against the cells (IC50 > 0.5 mg/ml). The QDs also retained most of their fluorescence and properties and could easily be tracked in cells and visualized around the nucleus, indicating the successful internalization of the QDs in the cytosol. These results shows that encapsulation of CdTe multi-core-shell QDs in liposomes produce better bio-compatibility compared to multi-core-shell QDs and better than CNP coating. These particles therefore show good promise in cell-labelling, drug delivery studies. Their core-shell nanoparticles have also shown good behavior in enhancing the memory of a device which is based on some recent collaborated works. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-03-31
- Authors: Daramola, Olamide Abiodun
- Date: 2023-03-31
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/422617 , vital:71962 , DOI 10.21504/10962/422617
- Description: The common method that has been used to reduce the toxicity posed to living cells by CdTe Quantum Dots (QDs) is through the synthesis of CdTe multi-core-shells nanoparticles. In this process, the surface of CdTe QDs is usually coated by less toxic ZnS or ZnSe shells. This heterostructure compound does not only reduce the toxicity of CdTe QDs but can also be used in applications such as deep tissue imaging. The heterostructures can be in numerous forms such as CdTe/CdSe/ZnSe or CdTe/CdSe/ZnS or CdTe/CdS/ZnS multi-core-shell QDs. However, the drawbacks attributed to the fabrication of these compounds is long synthesis times (6- 24 h) in achieving the highest wavelength emission maxima. Others are the use of toxic reagents and poor reproducibility of synthesized materials. An additional problem is that the ZnSe or ZnS coating is insufficient to completely protect the highly toxic Cd metal from escaping into immediate solution. This limits their use in biochemistry and with living systems. Liposomes and biopolymers such as chitosan are known to be environmentally friendly compounds that have been used in various studies as delivery systems for QDs and model drugs for drug delivery applications. They are generally non-toxic and highly bio-compatible. In this study, the rapid synthesis of thiol-co-capped CdTe/CdSe/ZnSe multi-core-shell QDs with a maximum reaction time of 35 mins, gave reliable QDs with emission maxima at 625 nm. The multi-core-shell QDs were encapsulated in two different bio-compatible environments, namely liposome and chitosan nanoparticles (CNP) at 14 different formulations (F) for liposome and 12 different formulations for CNP. Cytotoxicity and florescence imaging studies using HeLa and Vero cells, were used to investigate the improved bio-compatibility. Various characterization techniques were used to elucidate the optical properties, morphology and physico-chemical properties of the QDs and nanocomposites. Two of the best formulations, QD-liposome vesicles (LVs)-F12 and QD-CNP-F9 (with chitosan), demonstrated high loading efficiencies of 42 ± 6 % and 59 ± 5 %, respectively. While the plain CdTe QDs showed high toxicity, some of the encapsulated materials, QD-LVs-F1 and F12, depicted no-toxicity against the cells (IC50 > 0.5 mg/ml). The QDs also retained most of their fluorescence and properties and could easily be tracked in cells and visualized around the nucleus, indicating the successful internalization of the QDs in the cytosol. These results shows that encapsulation of CdTe multi-core-shell QDs in liposomes produce better bio-compatibility compared to multi-core-shell QDs and better than CNP coating. These particles therefore show good promise in cell-labelling, drug delivery studies. Their core-shell nanoparticles have also shown good behavior in enhancing the memory of a device which is based on some recent collaborated works. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-03-31
The development of ionic zinc(II) phthalocyanines for sono-photodynamic combination therapy of cervical and breast cancer
- Authors: Nene, Lindokuhle Cindy
- Date: 2023-03-31
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/422565 , vital:71958 , DOI 10.21504/10962/422565
- Description: This study focuses on the development of the sono-photodynamic combination therapy (SPDT) activity of phthalocyanines (Pcs) on the cervical and breast cancer cell lines in vitro. The SPDT technique utilizes ultrasound in combination with light to elicit cytotoxic effects for cancer eradication. In this work, a selection of tetra-peripherally substituted Zn(II) cationic and zwitterionic Pcs were prepared. The photophysical parameters of the Pcs were determined including their fluorescence behaviours and efficiency of the triplet excited state population. The effects of the ultrasonic parameters (frequencies (MHz) and power (W.cm-2)) on the stability of the Pcs were evaluated. Four parameters were evaluated: Par I (1 MHz: 1 W.cm-2), Par II (1 MHz: 2 W.cm-2), Par III (3 MHz: 1 W.cm-2) and Par IV (3 MHz: 2 W.cm-2). The stability of the Pcs reduced with the increase in the ultrasonic power (for Par II and Par IV). The Par I showed the least degradation compared to the other parameters and was therefore used for the SPDT treatments. The sonodynamic (SDT), photodynamic (PDT) therapy activities of the Pcs were studied and compared to their SPDT efficacies. The Pcs showed reactive oxygen species generation during the SDT, PDT and SPDT treatments. For the SDT and SPDT, singlet oxygen (1O2) and hydroxyl radicals (•OH) were detected. For PDT, only the 1O2 were detected. The cell cytotoxicity studies for the Pcs showed relatively higher therapeutic efficacies for the SDT treatments compared to the PDT treatments, where the SPDT showed higher therapeutic efficacies compared to both the SDT and PDT monotreatments on both the cell lines in vitro. Overall, the combination treatments were better compared to the monotreatments. The activities of the Pcs were compared by their differences in structures, including the type of R-group, type of quaternizing agent and type of nanoparticle conjugates. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-03-31
- Authors: Nene, Lindokuhle Cindy
- Date: 2023-03-31
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/422565 , vital:71958 , DOI 10.21504/10962/422565
- Description: This study focuses on the development of the sono-photodynamic combination therapy (SPDT) activity of phthalocyanines (Pcs) on the cervical and breast cancer cell lines in vitro. The SPDT technique utilizes ultrasound in combination with light to elicit cytotoxic effects for cancer eradication. In this work, a selection of tetra-peripherally substituted Zn(II) cationic and zwitterionic Pcs were prepared. The photophysical parameters of the Pcs were determined including their fluorescence behaviours and efficiency of the triplet excited state population. The effects of the ultrasonic parameters (frequencies (MHz) and power (W.cm-2)) on the stability of the Pcs were evaluated. Four parameters were evaluated: Par I (1 MHz: 1 W.cm-2), Par II (1 MHz: 2 W.cm-2), Par III (3 MHz: 1 W.cm-2) and Par IV (3 MHz: 2 W.cm-2). The stability of the Pcs reduced with the increase in the ultrasonic power (for Par II and Par IV). The Par I showed the least degradation compared to the other parameters and was therefore used for the SPDT treatments. The sonodynamic (SDT), photodynamic (PDT) therapy activities of the Pcs were studied and compared to their SPDT efficacies. The Pcs showed reactive oxygen species generation during the SDT, PDT and SPDT treatments. For the SDT and SPDT, singlet oxygen (1O2) and hydroxyl radicals (•OH) were detected. For PDT, only the 1O2 were detected. The cell cytotoxicity studies for the Pcs showed relatively higher therapeutic efficacies for the SDT treatments compared to the PDT treatments, where the SPDT showed higher therapeutic efficacies compared to both the SDT and PDT monotreatments on both the cell lines in vitro. Overall, the combination treatments were better compared to the monotreatments. The activities of the Pcs were compared by their differences in structures, including the type of R-group, type of quaternizing agent and type of nanoparticle conjugates. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-03-31
Development of biosensor systems for the detection of anti-cancer drugs and prostate cancer
- Authors: Mwanza, Daniel
- Date: 2022-10-14
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/365929 , vital:65803
- Description: Thesis embargoed. Expected release date early 2025. , Thesis (PhD) -- Faculty of Science, Chemistry, 2022
- Full Text:
- Date Issued: 2022-10-14
- Authors: Mwanza, Daniel
- Date: 2022-10-14
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/365929 , vital:65803
- Description: Thesis embargoed. Expected release date early 2025. , Thesis (PhD) -- Faculty of Science, Chemistry, 2022
- Full Text:
- Date Issued: 2022-10-14
Dual and targeted photodynamic therapy ablation of bacterial and cancer cells using phthalocyanines and porphyrins in the presence of carbon-based nanomaterials
- Authors: Openda, Yolande Ikala
- Date: 2022-10-14
- Subjects: Phthalocyanines , Porphyrins , Active oxygen , Biofilms , Breast Cancer Treatment , Nanostructured materials , Combination therapy , Photochemotherapy
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/365945 , vital:65804 , DOI https://doi.org/10.21504/10962//365946
- Description: Phthalocyanines (Pcs) and porphyrins bearing substituents that possess antibacterial/anticancer properties are used as photosensitizers (PS) for the first time in the work. For targeting specificity and improved photoactivity, the PSs were afterward functionalized with carbon nanomaterials such as graphene quantum dots (GQDs) and detonation nanodiamonds (DNDs) via covalent conjugation (amide or ester bonds) or by non-covalent conjugation (π-π stacking and electrostatic interactions). Furthermore, the PSs-DNDs nanoconjugates were conjugated to either chitosan-capped silver nanoparticles (CSAg) via amide bonds or to the bare silver nanoparticles (Ag NPs) using the silver- nitrogen affinity. The as-synthesized nanoconjugates were also fully characterized by spectroscopic and microscopic methods together with thermal analysis. The potential photocytotoxicity of the complexes alone and their nanoconjugates against S. aureus and/or E. coli planktonic and biofilm cultures has been evaluated in vitro. Compared to the non- quaternized PSs, the cationic analogs exhibited a higher photodynamic inactivation against the planktonic cells with log10 reduction values above 9 in the viable count using a concentration of ca. 1.25 μM following 30 min exposure to light (Light dose: 943 J/cm2 for Pcs and 250 mW/cm2 for porphyrins). Whereas, at a concentration of ca. 100 μM the cationic PSs showed complete eradication of biofilms upon 30 min exposure to light. As a result of conjugation to carbon-based nanomaterials and silver nanoparticles, the compounds proved to be more effective as they exhibited stronger antibacterial and anti-biofilm activities on the multi-drug resistant bacteria strains due to synergetic effect, compared to PSs alone. This suggests that the newly prepared nanohybrids (PS concentration ca. 100 μM) could be used as potential antimicrobial agents in the treatment of biofilm-related infections. The target nanoconjugates showed all the advantages of two different groups existing on a single entity. In light of the potential advantages of combined chemotherapy and photodynamic antimicrobial chemotherapy (PACT), this work reports for the first time the use of PACT-ciprofloxacin (CIP) dual therapy using selected indium quaternized PSs which showed higher photoactivity with complete eradication of both Gram-positive and Gram-negative bacteria biofilms at concentrations of 8 μM of PS versus 2 μg/mL of the antibiotic following 15 min irradiation time (light dose: 471 J/cm2 for Pcs and fluence: 250 mW/cm2 for porphyrins) on S. aureus. Whereas the total killing of E. coli was obtained when combining 8 or 16 μM of PS combined with 4 μg/mL of CIP. The combined treatment resulted in the complete eradication of the matured biofilms with the highest log10 reduction values of 7.05 and 7.20 on S. aureus and E. coli, respectively. Used as a model, positively charged dimethylamino-chalcone Pcs also exhibited interesting photodynamic therapy (PDT) activity against MCF-7 cancer cells giving IC50 values of 17.9 and 7.4 μM, respectively following 15 min irradiation. Additionally, the TD-B3LYP/LanL2DZ calculations were run on the dimethylaminophenyl- porphyrins to compare the singlet excitation energies of quaternized and non-quaternized porphyrins in vacuo. the study shows excellent agreement between time-dependent density- functional theory (TD-DFT) exciting energies and the experimental S1>S0 excitation energies. The small deviation observed between the calculated and experimental spectra arises from the solvent effect. The excitation energies observed in these UV-Vis spectra mostly originated from electron promotion between the highest occupied molecular orbital (HOMO) for the less intense band and the HOMO-1 for the most intense band of the ground states to the lower unoccupied molecular orbital (LUMO) of the excited states. , Thesis (PhD) -- Faculty of Science, Chemistry, 2022
- Full Text:
- Date Issued: 2022-10-14
- Authors: Openda, Yolande Ikala
- Date: 2022-10-14
- Subjects: Phthalocyanines , Porphyrins , Active oxygen , Biofilms , Breast Cancer Treatment , Nanostructured materials , Combination therapy , Photochemotherapy
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/365945 , vital:65804 , DOI https://doi.org/10.21504/10962//365946
- Description: Phthalocyanines (Pcs) and porphyrins bearing substituents that possess antibacterial/anticancer properties are used as photosensitizers (PS) for the first time in the work. For targeting specificity and improved photoactivity, the PSs were afterward functionalized with carbon nanomaterials such as graphene quantum dots (GQDs) and detonation nanodiamonds (DNDs) via covalent conjugation (amide or ester bonds) or by non-covalent conjugation (π-π stacking and electrostatic interactions). Furthermore, the PSs-DNDs nanoconjugates were conjugated to either chitosan-capped silver nanoparticles (CSAg) via amide bonds or to the bare silver nanoparticles (Ag NPs) using the silver- nitrogen affinity. The as-synthesized nanoconjugates were also fully characterized by spectroscopic and microscopic methods together with thermal analysis. The potential photocytotoxicity of the complexes alone and their nanoconjugates against S. aureus and/or E. coli planktonic and biofilm cultures has been evaluated in vitro. Compared to the non- quaternized PSs, the cationic analogs exhibited a higher photodynamic inactivation against the planktonic cells with log10 reduction values above 9 in the viable count using a concentration of ca. 1.25 μM following 30 min exposure to light (Light dose: 943 J/cm2 for Pcs and 250 mW/cm2 for porphyrins). Whereas, at a concentration of ca. 100 μM the cationic PSs showed complete eradication of biofilms upon 30 min exposure to light. As a result of conjugation to carbon-based nanomaterials and silver nanoparticles, the compounds proved to be more effective as they exhibited stronger antibacterial and anti-biofilm activities on the multi-drug resistant bacteria strains due to synergetic effect, compared to PSs alone. This suggests that the newly prepared nanohybrids (PS concentration ca. 100 μM) could be used as potential antimicrobial agents in the treatment of biofilm-related infections. The target nanoconjugates showed all the advantages of two different groups existing on a single entity. In light of the potential advantages of combined chemotherapy and photodynamic antimicrobial chemotherapy (PACT), this work reports for the first time the use of PACT-ciprofloxacin (CIP) dual therapy using selected indium quaternized PSs which showed higher photoactivity with complete eradication of both Gram-positive and Gram-negative bacteria biofilms at concentrations of 8 μM of PS versus 2 μg/mL of the antibiotic following 15 min irradiation time (light dose: 471 J/cm2 for Pcs and fluence: 250 mW/cm2 for porphyrins) on S. aureus. Whereas the total killing of E. coli was obtained when combining 8 or 16 μM of PS combined with 4 μg/mL of CIP. The combined treatment resulted in the complete eradication of the matured biofilms with the highest log10 reduction values of 7.05 and 7.20 on S. aureus and E. coli, respectively. Used as a model, positively charged dimethylamino-chalcone Pcs also exhibited interesting photodynamic therapy (PDT) activity against MCF-7 cancer cells giving IC50 values of 17.9 and 7.4 μM, respectively following 15 min irradiation. Additionally, the TD-B3LYP/LanL2DZ calculations were run on the dimethylaminophenyl- porphyrins to compare the singlet excitation energies of quaternized and non-quaternized porphyrins in vacuo. the study shows excellent agreement between time-dependent density- functional theory (TD-DFT) exciting energies and the experimental S1>S0 excitation energies. The small deviation observed between the calculated and experimental spectra arises from the solvent effect. The excitation energies observed in these UV-Vis spectra mostly originated from electron promotion between the highest occupied molecular orbital (HOMO) for the less intense band and the HOMO-1 for the most intense band of the ground states to the lower unoccupied molecular orbital (LUMO) of the excited states. , Thesis (PhD) -- Faculty of Science, Chemistry, 2022
- Full Text:
- Date Issued: 2022-10-14
Synthesis, characterization and host-guest complexes of supramolecular assemblies based on calixarenes and cucurbiturils
- Authors: Baa, Ebenezer
- Date: 2022-10-14
- Subjects: Supramolecular chemistry , Calixarenes , Cucurbiturils , Metal-organic frameworks , Macrocyclic compounds , Drug delivery systems
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/365621 , vital:65765 , DOI https://doi.org/10.21504/10962/365621
- Description: The field of supramolecular chemistry has grown large and wide in both deepness of understanding, range of topics covered and scope and applications. Supramolecular self-assemblies are facilitated by a wide range of non-covalent intra and inter molecular interactions that range from hydrogen bonding to π-interaction and van der Waals. Macrocyclic compounds such as cucurbiturils and calixarenes have emerged as important classes of compounds with excellent potential of forming supramolecular assemblies. The porous nature of these compounds enables them to form host-guest supramolecular complexes stabilized by diverse range of non-covalent interactions. Furthermore, these compounds contain donor atoms capable of forming bonds with metal ions to yield metal complexes with interesting porous characteristics that deviate from their traditional hydrophobic cavity. The versatile nature of the resulting pores imply that they can accommodate diverse types of guests. This work explores the synthesis and characterization of a host of calixarenes and cucurbiturils. Self-assembly of these macrocycles with various metal ions results to the formation of porous metal organic framework (MOF) complexes. Four new calixarene typed compounds obtained from aromatic aldehydes and twenty-six cucurbituril metal complexes are reported. These macrocylces and their metal complexes also form supramolecular complexes with DMSO, methanol, isoniazid hydrochloride and ciprofloxacin hydrochlorides through either self-assembly, mechanochemistry and exposure to solvent vapors. The bulk materials have been characterized using nuclear magnetic resonance spectroscopy (NMR), Fourier transformed infrared spectroscopy (FTIR), powder and single crystal diffraction techniques and thermal studies thermogravimetric analysis (TGA) and differential thermal calorimetry (DSC). Data obtained from this study reveals that calixarenes can form supramolecular complexes with a frequently used laboratory solvents with BN22 showing appreciable selectivity for DMSO sorption from a solvent mixture. These compounds also form supramolecular complexes with drug molecules such as isoniazid and ciprofloxacin. Furthermore, the data reveals that choice of synthetic route of supramolecular ensembles dictates if the guest drug molecule will occupy the intrinsic or extrinsic pores of cucurbituril complexes. Biological studies on the obtained complexes reveal that the cucurbituril complexes are non-cytotoxic while the calixarenes show antibacterial activity against Escherichia coli and Staphylococcus aureus. Additionally, the study showed that ciprofloxacin can be successfully released from a calixarene host in a simulated body fluid although the host was also found to cross the dialysis membrane. The results of this study are important in that; - they can be exploited and developed in the selective sorption of certain guests and - that they can be used in the development of drug delivery systems that play a dual role of delivery and therapeutic activity. , Thesis (PhD) -- Faculty of Science, Chemistry, 2022
- Full Text:
- Date Issued: 2022-10-14
- Authors: Baa, Ebenezer
- Date: 2022-10-14
- Subjects: Supramolecular chemistry , Calixarenes , Cucurbiturils , Metal-organic frameworks , Macrocyclic compounds , Drug delivery systems
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/365621 , vital:65765 , DOI https://doi.org/10.21504/10962/365621
- Description: The field of supramolecular chemistry has grown large and wide in both deepness of understanding, range of topics covered and scope and applications. Supramolecular self-assemblies are facilitated by a wide range of non-covalent intra and inter molecular interactions that range from hydrogen bonding to π-interaction and van der Waals. Macrocyclic compounds such as cucurbiturils and calixarenes have emerged as important classes of compounds with excellent potential of forming supramolecular assemblies. The porous nature of these compounds enables them to form host-guest supramolecular complexes stabilized by diverse range of non-covalent interactions. Furthermore, these compounds contain donor atoms capable of forming bonds with metal ions to yield metal complexes with interesting porous characteristics that deviate from their traditional hydrophobic cavity. The versatile nature of the resulting pores imply that they can accommodate diverse types of guests. This work explores the synthesis and characterization of a host of calixarenes and cucurbiturils. Self-assembly of these macrocycles with various metal ions results to the formation of porous metal organic framework (MOF) complexes. Four new calixarene typed compounds obtained from aromatic aldehydes and twenty-six cucurbituril metal complexes are reported. These macrocylces and their metal complexes also form supramolecular complexes with DMSO, methanol, isoniazid hydrochloride and ciprofloxacin hydrochlorides through either self-assembly, mechanochemistry and exposure to solvent vapors. The bulk materials have been characterized using nuclear magnetic resonance spectroscopy (NMR), Fourier transformed infrared spectroscopy (FTIR), powder and single crystal diffraction techniques and thermal studies thermogravimetric analysis (TGA) and differential thermal calorimetry (DSC). Data obtained from this study reveals that calixarenes can form supramolecular complexes with a frequently used laboratory solvents with BN22 showing appreciable selectivity for DMSO sorption from a solvent mixture. These compounds also form supramolecular complexes with drug molecules such as isoniazid and ciprofloxacin. Furthermore, the data reveals that choice of synthetic route of supramolecular ensembles dictates if the guest drug molecule will occupy the intrinsic or extrinsic pores of cucurbituril complexes. Biological studies on the obtained complexes reveal that the cucurbituril complexes are non-cytotoxic while the calixarenes show antibacterial activity against Escherichia coli and Staphylococcus aureus. Additionally, the study showed that ciprofloxacin can be successfully released from a calixarene host in a simulated body fluid although the host was also found to cross the dialysis membrane. The results of this study are important in that; - they can be exploited and developed in the selective sorption of certain guests and - that they can be used in the development of drug delivery systems that play a dual role of delivery and therapeutic activity. , Thesis (PhD) -- Faculty of Science, Chemistry, 2022
- Full Text:
- Date Issued: 2022-10-14
Synthesis, In-Silico molecular modelling and biological studies of 1,4-Dihydroxyanthraquinone and its derivatives
- Authors: Kisula, Lydia Mboje
- Date: 2022-10-14
- Subjects: Computer simulation , Molecules Models , Dihydroxyanthraquinone , Trypanosomiasis , Leishmaniasis , Docking
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/365828 , vital:65793 , DOI https://doi.org/10.21504/10962/365828
- Description: This current study of investigation reports on the synthesis of 1,4-dihydroxyanthraquinone and its derivatives on explorations of their medicinal potential. The study initially aimed to synthesize an analogue of a natural anthraquinone, 1,3,6-trihydroxy-7-((S)-1- hydroxyethyl)anthracene-9,10-dione 5 using Friedel-Crafts acylation of phthalic anhydride and a benzene derivative. Synthetic transformation of anacardic acid 63, obtained as a by- product of the cashew industry successfully afforded 4-ethoxyisobenzofuran-1,3-dione 89. However, when attempted to couple 4-ethoxyisobenzofuran-1,3-dione 89 with 2- hydroxyacetophenone 91 in a Friedel-Crafts acylation manner to form 2-acetyl-1,8- dihydroxyanthracene-9,10-dione 87 the reaction did not work efficiently. A simple derivative of benzene which is; benzene-1,4-diol 102 was reacted instead with 3-ethoxyphthalic acid 71 and isobenzofuran-1,3-dione 96 to form 1,4,5-trihydroxy anthraquinone 72 and 1,4- dihydroxyanthraquinone 42, respectively. A modified Marschalk reaction was then used to introduce the hydroxyl alkyl group to 1,4-dihydroxy anthraquinone 42, which allowed further elaboration of the hydroxyl-substituent in moderate to good yields (22-80%). A molecular docking study was performed using Schrödinger software to predict the binding affinity of the test compounds to the target protein trypanothione reductase (PDB ID: 6BU7). An in-vitro screening of 1,4-dihydroxyanthraquinone derivatives and some selected precursors for antitrypanosomal, antiplasmodial, antibacterial, and cytotoxicity activities produced encouraging results. Derivatives of anacardic acid and cardanol from CNSL were found to have moderate activity against trypanosomes with no activity against Plasmodium falciparum. Almost 63% of synthesized 1,4-dihydroxyanthraquinone derivatives displayed activity against trypanosomes. The in-vitro evaluation and the in silico molecular docking studies revealed that 1,4-dihydroxyanthraquinone derivatives can be potential drug-like candidates active against T.brucei parasites (IC50 = 0.70-1.20 μM). Only four 1,4- iv dihydroxyanthraquinone derivatives with thiosemicarbazone, chloride, pyrrole, and diethanolamine functionality displayed activity against Plasmodium falciparum (IC50 = 3.17- 14.36 μM). In-vitro evaluated of test compounds against antibacterial screen and cytotoxicity effects significantly showed that 2-hydroxy-6-pentadecylbenzoic acid 63a and 2-((2- chlorophenyl)(piperazin-1-yl) methyl)-1,4-dihydroxyanthracene-9,10-dione 78 have potency against Staphylococcus aureus and reduced the viability of the cells below 20% at an initial concentration of 50 μg/mL. Only 1,4-dihydroxyanthraquinone derivatives with thiosemicarbazone 76, piperazine 78, and diethanolamine 80 motifs were active against HeLa cells and reduced the viability of cells below 20% at a concentration of 50 μg/mL. In conclusion, this current reported study has generated useful knowlege on the applicability of the agro-waste CNSL as an agent active against trypanosomiasis but also as a low-cost starting material to synthesize hydroxy anthraquinones. The study has further given an overview to the understanding of the medicinal value 1,4-dihydroxyanthraquinone derivatives as promising candidates towards developing drugs suitable for treating neglected tropical diseases particularly trypanosomiasis. , Thesis (PhD) -- Faculty of Science, Chemistry, 2022
- Full Text:
- Date Issued: 2022-10-14
- Authors: Kisula, Lydia Mboje
- Date: 2022-10-14
- Subjects: Computer simulation , Molecules Models , Dihydroxyanthraquinone , Trypanosomiasis , Leishmaniasis , Docking
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/365828 , vital:65793 , DOI https://doi.org/10.21504/10962/365828
- Description: This current study of investigation reports on the synthesis of 1,4-dihydroxyanthraquinone and its derivatives on explorations of their medicinal potential. The study initially aimed to synthesize an analogue of a natural anthraquinone, 1,3,6-trihydroxy-7-((S)-1- hydroxyethyl)anthracene-9,10-dione 5 using Friedel-Crafts acylation of phthalic anhydride and a benzene derivative. Synthetic transformation of anacardic acid 63, obtained as a by- product of the cashew industry successfully afforded 4-ethoxyisobenzofuran-1,3-dione 89. However, when attempted to couple 4-ethoxyisobenzofuran-1,3-dione 89 with 2- hydroxyacetophenone 91 in a Friedel-Crafts acylation manner to form 2-acetyl-1,8- dihydroxyanthracene-9,10-dione 87 the reaction did not work efficiently. A simple derivative of benzene which is; benzene-1,4-diol 102 was reacted instead with 3-ethoxyphthalic acid 71 and isobenzofuran-1,3-dione 96 to form 1,4,5-trihydroxy anthraquinone 72 and 1,4- dihydroxyanthraquinone 42, respectively. A modified Marschalk reaction was then used to introduce the hydroxyl alkyl group to 1,4-dihydroxy anthraquinone 42, which allowed further elaboration of the hydroxyl-substituent in moderate to good yields (22-80%). A molecular docking study was performed using Schrödinger software to predict the binding affinity of the test compounds to the target protein trypanothione reductase (PDB ID: 6BU7). An in-vitro screening of 1,4-dihydroxyanthraquinone derivatives and some selected precursors for antitrypanosomal, antiplasmodial, antibacterial, and cytotoxicity activities produced encouraging results. Derivatives of anacardic acid and cardanol from CNSL were found to have moderate activity against trypanosomes with no activity against Plasmodium falciparum. Almost 63% of synthesized 1,4-dihydroxyanthraquinone derivatives displayed activity against trypanosomes. The in-vitro evaluation and the in silico molecular docking studies revealed that 1,4-dihydroxyanthraquinone derivatives can be potential drug-like candidates active against T.brucei parasites (IC50 = 0.70-1.20 μM). Only four 1,4- iv dihydroxyanthraquinone derivatives with thiosemicarbazone, chloride, pyrrole, and diethanolamine functionality displayed activity against Plasmodium falciparum (IC50 = 3.17- 14.36 μM). In-vitro evaluated of test compounds against antibacterial screen and cytotoxicity effects significantly showed that 2-hydroxy-6-pentadecylbenzoic acid 63a and 2-((2- chlorophenyl)(piperazin-1-yl) methyl)-1,4-dihydroxyanthracene-9,10-dione 78 have potency against Staphylococcus aureus and reduced the viability of the cells below 20% at an initial concentration of 50 μg/mL. Only 1,4-dihydroxyanthraquinone derivatives with thiosemicarbazone 76, piperazine 78, and diethanolamine 80 motifs were active against HeLa cells and reduced the viability of cells below 20% at a concentration of 50 μg/mL. In conclusion, this current reported study has generated useful knowlege on the applicability of the agro-waste CNSL as an agent active against trypanosomiasis but also as a low-cost starting material to synthesize hydroxy anthraquinones. The study has further given an overview to the understanding of the medicinal value 1,4-dihydroxyanthraquinone derivatives as promising candidates towards developing drugs suitable for treating neglected tropical diseases particularly trypanosomiasis. , Thesis (PhD) -- Faculty of Science, Chemistry, 2022
- Full Text:
- Date Issued: 2022-10-14
Inhibition of aluminium corrosion using phthalocyanines: Experimental and computational studies
- Authors: Nnaji, Nnaemeka Joshua
- Date: 2022-04-08
- Subjects: Aluminum Corrosion , Electrochemistry , Phthalocyanines , Corrosion and anti-corrosives , Protective coatings , Density functionals
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/294643 , vital:57240 , DOI 10.21504/10962/294643
- Description: Metal deterioration over time is a process known as corrosion, an electrochemical process, which can occur by surface chemical actions on metals by its environment. Metal corrosion have great economic, security, and environmental consequences, and its control is a major research area in corrosion science. Amongst the different corrosion protecting approaches, the use of corrosion inhibitors and protective coatings have attracted enormous research interest in this area of scholasticism. This has necessitated the computational and electrochemical investigations of aluminium corrosion inhibitive potentials of some compounds in 1M HCl. Metal free (5_H2), ClGa(III) (5_Ga) and Co(II) (5_Co) tetrakis(4-acetamidophenoxy)phthalocyanines as well as Co(II) 2,9,16-tris(4-(tert-butyl)phenoxy)-23-(pyridin-4-yloxy)phthalocyanine (6) and Co(II) 2,9,16,24-tetrakis(4-(tert-butyl)phenoxy)phthalocyanine (7) were synthesized for the first time and studied for corrosion inhibition. The reported ClGa(III) tetrakis(benzo[d]thiazol-2-yl-thio)phthalocyaninine (1), ClGa(III) tetrakis(benzo[d]thiazol-2ylphenoxy)phthalocyanine (2), ClGa(III) tetrakis-4-(hexadecane-1,2-dioxyl)-bis(phthalocyanine) (3) and ClGa(III) tetrakis-4,4′-((4-(benzo[d]thiazol-2-yl)-1,2-bis(phenoxy)-bis(phthalocyanine) (4) were also employed for corrosion inhibition of Al in HCl. Corrosion inhibition measurements using electrochemical techniques showed that increased π conjugation caused (1) to (2) to outperform (1a) and (2a) respectively as aluminium corrosion inhibitors in 1.0 M hydrochloric acid. For similar reason, (4) outperformed 2. (1) and (2) were successfully electrodeposited onto aluminium for corrosion retardation in 1.0 M hydrochloric acid solution. Measurements obtained from electrochemical impedance spectroscopy gave corrosion inhibition efficiency values of 82% for 1 and 86% for 2 in 1.0 M hydrochloric acid solution and showed that electrodeposited phthalocyanines have enhanced aluminium corrosion retardation than when in solution. The use of reduced graphene oxide nanosheets (rGONS) alone as aluminium corrosion inhibitor is discouraged because of poor aluminium corrosion inhibition in 1M HCl. However, synergistic effects were observed when rGONS was mixed each with (4) and (3). (5_H2), (5_Ga) and (5_Co) decreased aluminium corrosion in 1M HCl and observation was that the heavier the atom the more decreased the protection and the free base performed best of the three. Studied tertbutylphenoxy-derived CoPcs (6 and 7) exhibited good aluminium corrosion inhibition properties in studied acidic solution and the unsymmetric CoPc (6) which has more heteroatoms, gave better performance. Quantum chemical calculations involved the use of density functional theoretical (DFT) approaches and gave results which corroborated with experimental findings. , Thesis (PhD) -- Faculty of Science, Chemistry, 2022
- Full Text:
- Date Issued: 2022-04-08
- Authors: Nnaji, Nnaemeka Joshua
- Date: 2022-04-08
- Subjects: Aluminum Corrosion , Electrochemistry , Phthalocyanines , Corrosion and anti-corrosives , Protective coatings , Density functionals
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/294643 , vital:57240 , DOI 10.21504/10962/294643
- Description: Metal deterioration over time is a process known as corrosion, an electrochemical process, which can occur by surface chemical actions on metals by its environment. Metal corrosion have great economic, security, and environmental consequences, and its control is a major research area in corrosion science. Amongst the different corrosion protecting approaches, the use of corrosion inhibitors and protective coatings have attracted enormous research interest in this area of scholasticism. This has necessitated the computational and electrochemical investigations of aluminium corrosion inhibitive potentials of some compounds in 1M HCl. Metal free (5_H2), ClGa(III) (5_Ga) and Co(II) (5_Co) tetrakis(4-acetamidophenoxy)phthalocyanines as well as Co(II) 2,9,16-tris(4-(tert-butyl)phenoxy)-23-(pyridin-4-yloxy)phthalocyanine (6) and Co(II) 2,9,16,24-tetrakis(4-(tert-butyl)phenoxy)phthalocyanine (7) were synthesized for the first time and studied for corrosion inhibition. The reported ClGa(III) tetrakis(benzo[d]thiazol-2-yl-thio)phthalocyaninine (1), ClGa(III) tetrakis(benzo[d]thiazol-2ylphenoxy)phthalocyanine (2), ClGa(III) tetrakis-4-(hexadecane-1,2-dioxyl)-bis(phthalocyanine) (3) and ClGa(III) tetrakis-4,4′-((4-(benzo[d]thiazol-2-yl)-1,2-bis(phenoxy)-bis(phthalocyanine) (4) were also employed for corrosion inhibition of Al in HCl. Corrosion inhibition measurements using electrochemical techniques showed that increased π conjugation caused (1) to (2) to outperform (1a) and (2a) respectively as aluminium corrosion inhibitors in 1.0 M hydrochloric acid. For similar reason, (4) outperformed 2. (1) and (2) were successfully electrodeposited onto aluminium for corrosion retardation in 1.0 M hydrochloric acid solution. Measurements obtained from electrochemical impedance spectroscopy gave corrosion inhibition efficiency values of 82% for 1 and 86% for 2 in 1.0 M hydrochloric acid solution and showed that electrodeposited phthalocyanines have enhanced aluminium corrosion retardation than when in solution. The use of reduced graphene oxide nanosheets (rGONS) alone as aluminium corrosion inhibitor is discouraged because of poor aluminium corrosion inhibition in 1M HCl. However, synergistic effects were observed when rGONS was mixed each with (4) and (3). (5_H2), (5_Ga) and (5_Co) decreased aluminium corrosion in 1M HCl and observation was that the heavier the atom the more decreased the protection and the free base performed best of the three. Studied tertbutylphenoxy-derived CoPcs (6 and 7) exhibited good aluminium corrosion inhibition properties in studied acidic solution and the unsymmetric CoPc (6) which has more heteroatoms, gave better performance. Quantum chemical calculations involved the use of density functional theoretical (DFT) approaches and gave results which corroborated with experimental findings. , Thesis (PhD) -- Faculty of Science, Chemistry, 2022
- Full Text:
- Date Issued: 2022-04-08
Singlet oxygen and optical limiting applications of BODIPYs and other molecular dyes
- Authors: May, Aviwe Khanya
- Date: 2022-04-08
- Subjects: Dyes and dyeing Chemistry , Phthalocyanines , Photochemotherapy , Active oxygen , Nonlinear optics , Time-dependent density functional theory , Photochemistry
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/294618 , vital:57238 , DOI 10.21504/10962/294620
- Description: A series of structurally diverse novel and previously synthesized BODIPY core dyes are synthesized and characterized in this thesis. These BODIPYs were synthesized using 2-methylpyrrole, 2-ethylpyrrole, 2,4-dimethylpyrrole and 3-ethyl-2,4-dimethylpyrrole as the starting pyrroles. The combination of different pyrroles with the same aldehyde results in BODIPY core dyes that are structural analogues. These core dyes were used as precursors to synthesise halogenated BODIPYs and novel styrylBODIPY dyes, which were successfully characterized using FT-IR and 1H NMR spectroscopy. The halogenated BODIPY core dyes and the styrylBODIPY dyes were also characterized using MALDI-TOF mass spectrometry. The introduction of heavy atoms on the BODIPY core leads to a red shift of the main spectral. In the presence of styryl groups, the main spectral band red shifts to the far red end of the visible region. As expected, the halogenated BODIPY core dyes also had moderate singlet oxygen quantum yields. These halogenated core dyes were found to be suitable as photosensitizers as all the dyes reduced bacterial viability to below 50% during photodynamic antimicrobial chemotherapy (PACT) studies against Staphylococcus aureus. The structure-property relationships studied demonstrate that the presence of protons rather than methyls at the 1,7-positions or iodines at the 2,6-positions results in more favorable PACT activity. This is likely to be related to the greater ability of the meso-aryl to rotate into the plane of the dipyrromethene ligand and suggests that there should be a stronger focus on dyes of this type in future studies in this field. During nonlinear optical (NLO) studies, all the styrylBODIPYs exhibited favorable reverse saturable absorption (RSA) responses. In the absence of methyl groups at the 1,7-positions, the meso-aryl ring lies closer to the π-system of the BODIPY core, enhancing donor (D)–π–acceptor (A) properties and resulting in slightly enhanced optical limiting (OL) parameters. Additionally, there is no evidence that the introduction of heavy atoms at the 2,6-positions significantly enhances OL properties. In a similar manner, alkyl substituents at these positions also do not significantly enhance OL properties; this was studied for the first time using 15 with ethyl groups at the 2,6-positions. The combination of z-scan data and transient spectroscopy for 16 demonstrated that the main mechanism responsible for the NLO properties of nonhalogenated BODIPY dyes is one-photon absorption from the ground state followed by ESA in the singlet manifold. From the NLO studies of 25, OL parameters of 1,3,5-tristyrylBODIPY dyes were found to be similar in magnitude to properties of distyrylBODIPY dyes, but to have less favorable optical properties for OL applications. The OL properties of scandium phthalocyanines were assessed for the first time, since the Sc(III) ion, unusually for a first row transition metal ion, is known to readily form sandwich complexes. The presence of a Sc(III) ion does not significantly enhance the OL properties of phthalocyanines relative to those of rare earth metal ions that also form complexes of this type. Because BODIPYs and phthalocyanines typically absorb significantly in the visible region, transparent PBC polymer thin films of disilane-bridged compounds with minimal absorption in this region were studied and exhibited an excellent RSA response. These compounds may be useful in the design of OL materials that can protect the human eye. The optimized geometries and spectroscopic properties of selected BODIPYs were studied. As expected, the presence of bromine, iodine, ethyl and styryl groups at different positions of the BODIPY core leads to a narrowing of the HOMO–LUMO band gap, which results in a red-shift of the main spectral band. Partial atomic charges have also been calculated for some of the styrylBODIPY dyes studied for application in OL, and electrostatic potential energy maps were also visualized to better assess how the dipole moment of BODIPY dyes can be modulated since this can affect the OL properties. For all the BODIPYs studied, the electronegativity of the atoms present influences charge distribution on the BODIPY structure. , Thesis (PhD) -- Faculty of Science, Chemistry, 2022
- Full Text:
- Date Issued: 2022-04-08
- Authors: May, Aviwe Khanya
- Date: 2022-04-08
- Subjects: Dyes and dyeing Chemistry , Phthalocyanines , Photochemotherapy , Active oxygen , Nonlinear optics , Time-dependent density functional theory , Photochemistry
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/294618 , vital:57238 , DOI 10.21504/10962/294620
- Description: A series of structurally diverse novel and previously synthesized BODIPY core dyes are synthesized and characterized in this thesis. These BODIPYs were synthesized using 2-methylpyrrole, 2-ethylpyrrole, 2,4-dimethylpyrrole and 3-ethyl-2,4-dimethylpyrrole as the starting pyrroles. The combination of different pyrroles with the same aldehyde results in BODIPY core dyes that are structural analogues. These core dyes were used as precursors to synthesise halogenated BODIPYs and novel styrylBODIPY dyes, which were successfully characterized using FT-IR and 1H NMR spectroscopy. The halogenated BODIPY core dyes and the styrylBODIPY dyes were also characterized using MALDI-TOF mass spectrometry. The introduction of heavy atoms on the BODIPY core leads to a red shift of the main spectral. In the presence of styryl groups, the main spectral band red shifts to the far red end of the visible region. As expected, the halogenated BODIPY core dyes also had moderate singlet oxygen quantum yields. These halogenated core dyes were found to be suitable as photosensitizers as all the dyes reduced bacterial viability to below 50% during photodynamic antimicrobial chemotherapy (PACT) studies against Staphylococcus aureus. The structure-property relationships studied demonstrate that the presence of protons rather than methyls at the 1,7-positions or iodines at the 2,6-positions results in more favorable PACT activity. This is likely to be related to the greater ability of the meso-aryl to rotate into the plane of the dipyrromethene ligand and suggests that there should be a stronger focus on dyes of this type in future studies in this field. During nonlinear optical (NLO) studies, all the styrylBODIPYs exhibited favorable reverse saturable absorption (RSA) responses. In the absence of methyl groups at the 1,7-positions, the meso-aryl ring lies closer to the π-system of the BODIPY core, enhancing donor (D)–π–acceptor (A) properties and resulting in slightly enhanced optical limiting (OL) parameters. Additionally, there is no evidence that the introduction of heavy atoms at the 2,6-positions significantly enhances OL properties. In a similar manner, alkyl substituents at these positions also do not significantly enhance OL properties; this was studied for the first time using 15 with ethyl groups at the 2,6-positions. The combination of z-scan data and transient spectroscopy for 16 demonstrated that the main mechanism responsible for the NLO properties of nonhalogenated BODIPY dyes is one-photon absorption from the ground state followed by ESA in the singlet manifold. From the NLO studies of 25, OL parameters of 1,3,5-tristyrylBODIPY dyes were found to be similar in magnitude to properties of distyrylBODIPY dyes, but to have less favorable optical properties for OL applications. The OL properties of scandium phthalocyanines were assessed for the first time, since the Sc(III) ion, unusually for a first row transition metal ion, is known to readily form sandwich complexes. The presence of a Sc(III) ion does not significantly enhance the OL properties of phthalocyanines relative to those of rare earth metal ions that also form complexes of this type. Because BODIPYs and phthalocyanines typically absorb significantly in the visible region, transparent PBC polymer thin films of disilane-bridged compounds with minimal absorption in this region were studied and exhibited an excellent RSA response. These compounds may be useful in the design of OL materials that can protect the human eye. The optimized geometries and spectroscopic properties of selected BODIPYs were studied. As expected, the presence of bromine, iodine, ethyl and styryl groups at different positions of the BODIPY core leads to a narrowing of the HOMO–LUMO band gap, which results in a red-shift of the main spectral band. Partial atomic charges have also been calculated for some of the styrylBODIPY dyes studied for application in OL, and electrostatic potential energy maps were also visualized to better assess how the dipole moment of BODIPY dyes can be modulated since this can affect the OL properties. For all the BODIPYs studied, the electronegativity of the atoms present influences charge distribution on the BODIPY structure. , Thesis (PhD) -- Faculty of Science, Chemistry, 2022
- Full Text:
- Date Issued: 2022-04-08
Synthesis and evaluation of the medicinal potential of novel 4-hydroxycoumarin derivatives
- Authors: Manyeruke, Meloddy Hlatini
- Date: 2022-04-08
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/164458 , vital:41120 , doi:10.21504/10962/164458
- Description: This research has focused on the synthesis and biological evaluation of a broad range of compounds characterised by the presence of the pharmacologically significant 4-hydroxycoumalin scaffold. The compounds were designed to contain additional pharmachophoric centres to enhance bioactivity and generate lead compounds with dualaction potential. The use of 4-hydroxycoumarin as the primary synthon enabled access to various series of 4-hydroxycoumarin conjugates, the reactive 3-position on the 4-hydroxycoumarin moiety being exploited for regioselective construction of the targeted compounds in several steps. Some of the reactants required in the construction of these compounds were specially synthesised and included propargyloxy benzaldehydes, benzyloxy benzaldehydes and 2,3-dihydroxysuccino-dihydride. Overall, eight different families of novel compounds were accessed, comprising conjugates of 4-hydroxycoumarin with bisethylidenesuccinohyrazide, trifluoroacetamide, amino, benzyloxyphenyl-iminoethyl, benzylidenehyrazinyl-thiazoyl, benzylidenehydrazonoethyl, propargyloxybenzylidenehydrazonoethyl and phenylacryloyl moieties using protocols that required minimal work-up and purification. The eighty novel compounds synthesised in the study were fully characterised using HMRS and advanced NMR techniques. Cytotoxicity, HIV-1 IN and PR inhibitory, and antitrypanosomal, antimalarial and anti-Mtb assays were conducted on the synthesised coumarin derivatives. Several compounds exhibited activity against HIV-1 IN, the most potent being a bis-ethylidenesuccinohyrazide with an IC50 value of 3.5 μM. Various compounds exhibited anti-malarial activity (% pLDH viability in the range 62-77%), anti-trypanosomal activity (the most potent with an IC50 = 0.9 μM against T.b. brucei) and a measure of anti-Mtb activity. Apart from two chalconyl derivatives, none of the synthesised compounds exhibited significant cytotoxicity. Conflicting results were obtained from the in silico docking studies; in some cases supporting the observed in vitro assay data while, in others, exhibiting no correlation. , Thesis (PhD) -- Faculty of Science, Chemistry, 2020
- Full Text:
- Date Issued: 2022-04-08
- Authors: Manyeruke, Meloddy Hlatini
- Date: 2022-04-08
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/164458 , vital:41120 , doi:10.21504/10962/164458
- Description: This research has focused on the synthesis and biological evaluation of a broad range of compounds characterised by the presence of the pharmacologically significant 4-hydroxycoumalin scaffold. The compounds were designed to contain additional pharmachophoric centres to enhance bioactivity and generate lead compounds with dualaction potential. The use of 4-hydroxycoumarin as the primary synthon enabled access to various series of 4-hydroxycoumarin conjugates, the reactive 3-position on the 4-hydroxycoumarin moiety being exploited for regioselective construction of the targeted compounds in several steps. Some of the reactants required in the construction of these compounds were specially synthesised and included propargyloxy benzaldehydes, benzyloxy benzaldehydes and 2,3-dihydroxysuccino-dihydride. Overall, eight different families of novel compounds were accessed, comprising conjugates of 4-hydroxycoumarin with bisethylidenesuccinohyrazide, trifluoroacetamide, amino, benzyloxyphenyl-iminoethyl, benzylidenehyrazinyl-thiazoyl, benzylidenehydrazonoethyl, propargyloxybenzylidenehydrazonoethyl and phenylacryloyl moieties using protocols that required minimal work-up and purification. The eighty novel compounds synthesised in the study were fully characterised using HMRS and advanced NMR techniques. Cytotoxicity, HIV-1 IN and PR inhibitory, and antitrypanosomal, antimalarial and anti-Mtb assays were conducted on the synthesised coumarin derivatives. Several compounds exhibited activity against HIV-1 IN, the most potent being a bis-ethylidenesuccinohyrazide with an IC50 value of 3.5 μM. Various compounds exhibited anti-malarial activity (% pLDH viability in the range 62-77%), anti-trypanosomal activity (the most potent with an IC50 = 0.9 μM against T.b. brucei) and a measure of anti-Mtb activity. Apart from two chalconyl derivatives, none of the synthesised compounds exhibited significant cytotoxicity. Conflicting results were obtained from the in silico docking studies; in some cases supporting the observed in vitro assay data while, in others, exhibiting no correlation. , Thesis (PhD) -- Faculty of Science, Chemistry, 2020
- Full Text:
- Date Issued: 2022-04-08
A green approach for the synthesis of symmetrical and unsymmetrical 1,2,4,5-tetraoxanes as anti-protozoal agents
- Authors: Cossa, Teresa Manuel
- Date: 2021-10-29
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192786 , vital:45264
- Description: Thesis (PhD) -- Faculty of Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Cossa, Teresa Manuel
- Date: 2021-10-29
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192786 , vital:45264
- Description: Thesis (PhD) -- Faculty of Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10-29
Phthalocyanine-nanoparticle conjugates supported on inorganic nanofibers as photocatalysts for the treatment of biological and organic pollutants as well as for hydrogen generation
- Authors: Mapukata, Sivuyisiwe
- Date: 2021-10-29
- Subjects: Phthalocyanines , Nanofibers , Nanoparticles , Zinc , Hydrogen , Organic water pollutants , Water Purification , Electrospinning , Photocatalysis , Photodegradation , Anti-infective agents
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192831 , vital:45268 , 10.21504/10962/192831
- Description: This thesis reports on the synthesis, photophysicochemical and photocatalytic properties of various zinc phthalocyanines (Pcs). For enhanced properties and catalyst support, the reported Pcs were conjugated to different nanoparticles (NPs) through chemisorption as well as amide bond formation to yield Pc-NP conjugates. For increased catalyst surface area and catalyst reusability, the Pcs and some of their conjugates were also supported on electrospun inorganic nanofibers i.e. SiO2, hematite (abbreviated Hem and has formula α-Fe2O3), ZnO and TiO2 nanofibers. The effect that the number of charges on a Pc has on its antimicrobial activities was evaluated by comparing the photoactivities of neutral, octacationic and hexadecacationic Pcs against S. aureus, E. coli and C. albicans. The extent of enhancement of their antimicrobial activities upon conjugation (through chemisorption) to Ag NPs was also studied in solution and when supported on SiO2 nanofibers. The results showed that the hexadecacationic complex 3 possessed the best antimicrobial activity against all three microorganisms, in solution and when supported on the SiO2 nanofibers. Covalent conjugation of Pcs with carboxylic acid moieties (complexes 4-6) to amine functionalised NPs (Cys-Ag, NH2-Fe3O4 and Cys-Fe3O4@Ag) resulted in enhanced singlet oxygen generation and thus antibacterial efficiencies. Comparison of the photodegradation efficiencies of semiconductor nanofibers (hematite, ZnO and TiO2) when bare and when modified with a Pc (complex 6) were evaluated. Modification of the nanofibers with the Pc resulted in enhanced photoactivities for the nanofibers with the hematite nanofibers being the best. Modification of the hematite nanofibers with two different Pcs i.e. monosubstituted (complex 5) and an asymmetrical tetrasubstituted Pc (complex 6) showed that complex 6 better enhanced the activity of the nanofibers. Evaluation of the hydrogen generation efficiencies of the bare and modified TiO2 nanofibers calcined at different temperatures demonstrated that the anatase nanofibers calcined at 500 oC possessed the best catalytic efficiency. The efficiency of the TiO2 nanofibers was enhanced in the presence of the Co and Pd NPs as well as a Pc (complex 7), with the extent of enhancement being the greatest for the nanofibers modified with the Pd NPs. The reported findings therefore demonstrate the versatility of applications of Pcs for different water purification techniques when supported on different nanomaterials. , Thesis (PhD) -- Faculty of Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Mapukata, Sivuyisiwe
- Date: 2021-10-29
- Subjects: Phthalocyanines , Nanofibers , Nanoparticles , Zinc , Hydrogen , Organic water pollutants , Water Purification , Electrospinning , Photocatalysis , Photodegradation , Anti-infective agents
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192831 , vital:45268 , 10.21504/10962/192831
- Description: This thesis reports on the synthesis, photophysicochemical and photocatalytic properties of various zinc phthalocyanines (Pcs). For enhanced properties and catalyst support, the reported Pcs were conjugated to different nanoparticles (NPs) through chemisorption as well as amide bond formation to yield Pc-NP conjugates. For increased catalyst surface area and catalyst reusability, the Pcs and some of their conjugates were also supported on electrospun inorganic nanofibers i.e. SiO2, hematite (abbreviated Hem and has formula α-Fe2O3), ZnO and TiO2 nanofibers. The effect that the number of charges on a Pc has on its antimicrobial activities was evaluated by comparing the photoactivities of neutral, octacationic and hexadecacationic Pcs against S. aureus, E. coli and C. albicans. The extent of enhancement of their antimicrobial activities upon conjugation (through chemisorption) to Ag NPs was also studied in solution and when supported on SiO2 nanofibers. The results showed that the hexadecacationic complex 3 possessed the best antimicrobial activity against all three microorganisms, in solution and when supported on the SiO2 nanofibers. Covalent conjugation of Pcs with carboxylic acid moieties (complexes 4-6) to amine functionalised NPs (Cys-Ag, NH2-Fe3O4 and Cys-Fe3O4@Ag) resulted in enhanced singlet oxygen generation and thus antibacterial efficiencies. Comparison of the photodegradation efficiencies of semiconductor nanofibers (hematite, ZnO and TiO2) when bare and when modified with a Pc (complex 6) were evaluated. Modification of the nanofibers with the Pc resulted in enhanced photoactivities for the nanofibers with the hematite nanofibers being the best. Modification of the hematite nanofibers with two different Pcs i.e. monosubstituted (complex 5) and an asymmetrical tetrasubstituted Pc (complex 6) showed that complex 6 better enhanced the activity of the nanofibers. Evaluation of the hydrogen generation efficiencies of the bare and modified TiO2 nanofibers calcined at different temperatures demonstrated that the anatase nanofibers calcined at 500 oC possessed the best catalytic efficiency. The efficiency of the TiO2 nanofibers was enhanced in the presence of the Co and Pd NPs as well as a Pc (complex 7), with the extent of enhancement being the greatest for the nanofibers modified with the Pd NPs. The reported findings therefore demonstrate the versatility of applications of Pcs for different water purification techniques when supported on different nanomaterials. , Thesis (PhD) -- Faculty of Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10-29