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Aptamer-based biosensor for prostate specific antigen detection using cobalt phthalocyanine-exfoliated graphite composites

  • Authors: Benise, Emihle
  • Date: 2024-04-04
  • Subjects: Aptamer , Exfoliated graphite nano-platelets , Phthalocyanines , Impedance spectroscopy , Prostate-specific antigen
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/434850 , vital:73110
  • Description: The work focuses on the development of biosensors and their use for the detection of prostate specific antigen (PSA). Four cobalt phthalocyanines (CoPcs) complexes: (1) cobalt tetra pyridyloxy phthalocyanine, (2) cobalt tetra acetamidophenoxy phthalocyanine, (3) cobalt tris(acetamidophenoxy) mono benzoic acid phthalocyanine, and (4) cobalt tris(acetamidophenoxy) mono propionic acid phthalocyanine, an exfoliated graphite (EG), and aptamer are used to make probes for PSA detection. Each complex is π-π stacked onto the EG to form EG-CoPc(π-π) hybrid which was used to modify a glassy carbon electrode (GCE). EG and CoPc were also used to modify the GCE sequential (seq) with CoPc on top to give GCE-EG-CoPc(seq). For the detection PSA, PSA specific aptamer was either sequential added or covalently linked to complexes 3 and 4 on the modified electrodes and was only sequentially added onto complexes 1 and 2 modified electrodes. Electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) were the techniques used for the detection of PSA. The electrodes were found to be selective in bovine serum albumin, glucose and cysteine and stable when 50 DPV scans were run. Electrodes gave good % recovery when human serum was spiked with different PSA concentrations. , Thesis (MSc) -- Faculty of Science, Chemistry, 2024
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  • Date Issued: 2024-04-04

Enhancement of the electrocatalytic activity of phthalocyanines through the reduction in symmetry and conjugation to detonation nanodiamonds

  • Authors: Ncwane, Lunathi
  • Date: 2023-10-13
  • Subjects: Phthalocyanines , Electrocatalysis , Nanodiamonds , Hydrazine
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/424541 , vital:72162
  • Description: This thesis reports on the synthesis of novel phthalocynines tetrakis[(benzo[d]thiazol-2ylthio)phthalocyaninato]cobalt(II)chloride (complex 1) and tris(2-(ethylthio)benzo[d]thiazole)2-(phthalocyanine-9-ylthio)propionate cobalt(II) chloride (complex 2). The complexes are combined with DNDs via different techniques such as π-π stacking, covalent linkage and sequential modification on glassy carbon electrode. The synthesized MPcs and conjugates were characterized using UV-visible, mass, Fourier transform infrared, and Raman spectroscopies as well as transmission electron microscopy and dynamic light scattering. Combining MPcs with DNDs sought to improve electrooxidation of hydrazine. The electrochemical studies were conducted using cyclic voltammetry, chronocoloumetry, electrochemical impedance spectroscopy and chronoamperometry. Hydrazine was utilized as an analyte of interest, due to its mutagenic and carcinogenic effects. Glassy carbon electrodes (GCE) were modified using drop and dry method. The conjugation via covalent linkage proved to be the best way of enhancing electrocatalytic properties. Since it performed better in terms of limit of detection (0.33 μM), even though catalytic rate and sensitivity are not the highest. , Thesis (MSc) -- Faculty of Science, Chemistry, 2023
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  • Date Issued: 2023-10-13

Enhancing the electrocatalytic activity of phthalocyanines through finding the ideal combination of substituents in push-pull phthalocyanine-based systems

  • Authors: Nkhahle, Reitumetse Precious
  • Date: 2023-10-13
  • Subjects: Phthalocyanines , Electrocatalysis , Hydrazine , Nitrites , Activating group , Deactivating group
  • 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
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  • Date Issued: 2023-10-13

Halogenated Aza-BODIPY dyes for photodynamic anticancer and antimicrobial activity studies

  • Authors: Magwaza, Temlandvo Matshidiso
  • Date: 2023-10-13
  • Subjects: BODIPY , Dyes and dyeing Chemistry , Active oxygen , Photosensitizing compounds , Photochemotherapy , Time-dependent density functional theory , Anti-infective agents
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/424514 , vital:72160
  • Description: This thesis reports on the synthesis and characterisation of differently substituted aza-BODIPY dyes for use in photodynamic antimicrobial chemotherapy (PACT) and photodynamic therapy (PDT) activity studies. The aza-BODIPY dyes were synthesised by adding phenyl and naphthyl rings at the 3,5-positions of the aza-BODIPY core, with methylthiolphenyl (9a and 9b, respectively) or thien-2-yl rings (9c and 9d, respectively) at the 1,7-positions. 9a-c were iodinated at the 2-position to form 10a-c, respectively, while 9d was diiodinated at the 2,6-positions to form 10d. The methylthiolphenyl-substituted dyes (10a and 10b) were successfully conjugated to gold nanoparticles (AuNPs) to form nanoparticles conjugates (10a-AuNPs and 10b-AuNPs), while attempts to conjugate the thien-2-yl-substituted dyes were unsuccessful. The photophysicochemical properties of 9a-d, 10a-d and nanoconjugates 10a-AuNPs and 10b-AuNPs were investigated to determine their suitability for use in the applications. Adding heavy atoms such as iodine at the 2,6-positions of the aza-BODIPY led to enhanced singlet oxygen generation since these dyes displayed moderate to high singlet oxygen quantum yields. None of the dyes exhibited any fluorescence. The PACT activity studies for 9c-d, 10a-d, and the 10a-AuNPs and 10b-AuNPs were carried out against Staphylococcus aureus and Escherichia coli with a Thorlabs M660L3 light-emitting diode (LED) with an irradiance of 280 mW/cm2 for all dyes other than 10d. A Thorlabs M730L4 LED with an irradiance of 160 mW/cm2 was used for 10d. Time dependence studies were only carried out against Staphylococcus aureus, so very low log reductions were observed against Escherichia coli in initial concentration studies. The 10a-AuNP and 10b-AuNP nanoconjugates exhibited high antimicrobial activity with a log reduction of 9.41 and 0.00% viable colonies, while the iodinated aza-BODIPY had a log reduction of 8.94. The in vitro photodynamic therapy activities and dark cytotoxicity were investigated against human MCF-7 breast cancer cells for dyes 9c-d and 10c-d with a Thorlabs M660L3 LED (280 mW/cm2) for all dyes. The dark cytotoxicity was minimal in each case with IC50 > 50. Iodinated dyes 10c and 10d had IC50 values of 11.6 and 8.2 μM, respectively, and non-iodinated dyes 9c and 9d had IC50 values of 12.5 and 19.2 μM. The heavy atom effect associated with the iodine atoms increases the singlet oxygen quantum yield and enhances the suitability of the dyes for photodynamic therapy. , Thesis (MSc) -- Faculty of Science, Chemistry, 2023
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  • 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: Liposomes , Photochemotherapy , Phthalocyanines , Photoelectrochemistry , Cancer Treatment
  • 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
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  • 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: Phthalocyanines , Electrocatalysis , Nitrites , Dopamine , Catechol , Detection limit
  • 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
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  • Date Issued: 2023-10-13

The photodynamic therapeutic activities and optical limiting properties of metalated asymmetric porphyrins and corroles

  • Authors: Burgess, Kristen Paige
  • Date: 2023-10-13
  • Subjects: Porphyrins , Corrole , Photochemotherapy , Anti-infective agents , Nonlinear optics , Z-scan technique , Active oxygen , Time-dependent density functional theory , Chemical synthesis
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/424490 , vital:72158
  • Description: Cancer is a devastating disease that is a leading cause of death worldwide. Despite the available cancer treatments, there is a significant need to improve the therapeutic approach towards this disease. Photodynamic therapy (PDT) is an alternative approach for treating cancer, which requires a photosensitiser, molecular oxygen and light. Although some porphyrin-based derivatives have been approved by the United States Food and Drug Administration (FDA) and other similar agencies elsewhere for photodynamic therapy, their relatively poor photophysicochemical properties mean that there is an ongoing need for new photosensitiser dyes. Singlet oxygen photosensitiser dyes can also be used to treat bacteria that develop antimicrobial resistance in the context of photodynamic antimicrobial chemotherapy (PACT). The main aim of this study was to synthesise and characterise a series of porphyrin dyes with 4-quinolinyl, thien-2-yl and 4-bromo-thien-2-yl meso-aryl groups and their Sn(IV) and In(III) complexes, as well as their corrole analogues. Corroles are contracted macrocycles that have interesting optical properties. The corroles selected for study were found to be difficult to synthesise and purify and had unfavourable photophysicochemical properties and were thus omitted from the PDT and PACT biological applications within this thesis. High- and low-symmetry A4 and ABAB type meso-tetraarylporphyrins porphyrins were synthesised to improve the photophysicochemical properties of the photosensitisers; the utility of these dyes as photosensitisers was studied against the MCF-7 breast cancer cell line for PDT and against Staphylococcus aureus and Escherichia coli for PACT. The thienyl-2-yl rings were introduced to red shift the lowest energy Q band towards the phototherapeutic window, while quaternisation of the nitrogen and sulfur atoms of the 4-quinolinyl and thien-2-yl rings to introduce a cationic nature was explored to improve the bioavailability of the drugs and uptake into the target cell walls for improved efficacy. Heavy Sn(IV) and In(III) central metal ions were introduced to enhance the singlet oxygen quantum yields and limit aggregation through axial ligation. The bromine atoms of the 4-bromo-thien-2-yl meso-aryl rings were also introduced to enhance the singlet oxygen quantum yields of the dyes. Furthermore, the utility of the porphyrin and corrole molecules for optical limiting properties to limit laser radiation to protect optical devices, including eyes, was explored by the z-scan technique. One of the dyes studied, Sn(IV) tetrathien-2-ylporphyrin, that exhibited the most favourable reverse saturable absorbance (RSA) response was embedded into a poly(bisphenol carbonate A) polymer thin film to further explore its suitability for practical applications. , Thesis (MSc) -- Faculty of Science, Chemistry, 2023
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  • Date Issued: 2023-10-13

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: Phthalocyanines , Sonochemistry , Photochemotherapy , Cancer Treatment
  • 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
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  • Date Issued: 2023-03-31

Photodynamic therapy using morpholine substituted porphyrins in the presence of cancer specific molecules linked to graphene quantum dots

  • Authors: Magaela, Ngwanabjala Bridged
  • Date: 2023-03-29
  • Subjects: Photochemotherapy , Morpholine , Biotin , Folic acid , MCF-7 , Quantum dots
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/422486 , vital:71947
  • Description: This thesis reports on the synthesis, characterization, photophysiochemical properties of morpholine substituted symmetrical and asymmetrical porphyrins. The synthesized porphyrins are conjugated to cancer selective biomolecules (folic acid and biotin) which are linked to nitrogen doped graphene quantum dots, as potential photosensitizers for photodynamic therapy (PDT). The symmetrical morpholine porphyrin complexes 2 (Sn(IV) 5,10,15,20 tetra-4-morpholinyl porphyrin) and 3 (Zn 5,10,15,20 tetra-4-morpholinyl porphyrin) had the same substituent but different central metals, and they were both conjugated to biotin decorated nitrogen doped graphene quantum dots (B-NGQDs), however complex 2 (Sn(IV) 5,10,15,20 tetra-4-morpholinyl porphyrin) was conjugated to B-NGQDs through an ester bond and complex 3 (Zinc 5,10,15,20 tetra-4-morpholinyl porphyrin) through 𝜋-𝜋 stacking. The effect of asymmetry was studied by comparing complex 3 (Zn 5,10,15,20 tetra-4-morpholinyl porphyrin) and complex 5 (Zn 5- bromophenyl-10-15-20-(tris-4- morpholinyl) porphyrin). Complex 5 (Zn 5- bromophenyl-10-15-20-(tris-4- morpholinyl) porphyrin) was an asymmetric porphyrin with morpholine and bromine as substituents. It was observed that asymmetry enhances singlet oxygen quantum yield and PDT activity. It was also observed that folic acid is a better targeting biomolecule when compared to biotin, and this was studied by comparing complex 3 conjugated to B-NGQDs and complex 3 conjugated to folic acid decorated nitrogen doped graphene quantum dots (FA-NGQDs). 3-FA-NGQDs had a better cellular uptake and PDT activity. , Thesis (MSc) -- Faculty of Science, Chemistry, 2023
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  • Date Issued: 2023-03-29

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
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  • Date Issued: 2022-10-14

Electrocatalytic activity of symmetric and asymmetric Co(II) and Mn(III) porphyrins in the presence of graphene quantum dots towards the oxidation of hydrazine

  • Authors: Jokazi, Mbulelo
  • Date: 2022-10-14
  • Subjects: Electrocatalysis , Hydrazine , Quantum dots , Graphene , Porphyrins
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/362894 , vital:65372
  • Description: The influence of metal porphyrins in electro-oxidation of hydrazine is explored. A series of symmetric and asymmetric porphyrins alone and in the presence of graphene quantum dots (GQDs) are employed in this work. Tetra 4-aminophenyl porphyrin, manganese tetra 4-aminophenyl porphyrin, manganese tetra 4-aminophenyl porphyrin--GQDs, and manganese tetra 4-aminophenyl porphyrin@GQDs are the symmetric porphyrins. The asymmetric porphyrin and composites are 5, 10, 15-tris(aminophenyl)-20-(4-carboxyphenyl) porphyrins, manganese 5, 10, 15-tris(aminophenyl)-20-(4-carboxyphenyl) porphyrins, cobalt 5, 10, 15-tris(aminophenyl)-20-(4-carboxyphenyl) porphyrins, manganese 5, 10, 15-tris(aminophenyl)-20-(4-carboxyphenyl) porphyrins--GQDs, and cobalt 5, 10, 15-tris(aminophenyl)-20-(4-carboxyphenyl) porphyrins--GQDs. These complexes were synthesized and characterized accordingly and applied for electrocatalysis. The electrocatalytic experiments were carried out using glassy carbon electrode and the modification was through drop-dry method. The porphyrin and GQDs synthesized were characterized using UV-Vis spectroscopy, Mass spectrometry, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and energy dispersive x-ray spectroscopy. The modified electrodes were characterized using cyclic voltammetry and electrochemical Impedance spectroscopy. The introduction of metal ion in the center of the porphyrin improved electrocatalysis. The presence of push-pull substituents in the porphyrin lowered the oxidation potential and improved the catalysis. The presence of GQDs improved catalysis in both symmetric and asymmetric porphyrin compared to individual components. Cobalt porphyrins showed better activity than manganese porphyrin. , Thesis (MSc) -- Faculty of Science, Chemistry, 2022
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  • Date Issued: 2022-10-14

Photodynamic anticancer and antimicrobial activities of π-extended BODIPY dyes and cationic mitochondria-targeted porphyrins

  • Authors: Chiyumba, Choonzo Nachoobe
  • Date: 2022-10-14
  • Subjects: Dyes and dyeing Chemistry , Mitochondria , Cancer Chemotherapy , Porphyrins , Molecules Models , Photochemotherapy
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/362785 , vital:65362
  • Description: Cancer is among the most devastating diseases and is mainly caused by gene mutation. This could be hereditary, or the mutation could be stimulated due to a lifestyle one lives, such as smoking, which induces lung cancer. The high morbidity rates of cancer are attributed to it being metastatic. The relatively poor physicochemical properties of existing drugs have caused treatment to be ineffective. Photofrin®, Foscan®, and Photogem® are some of the porphyrin-based derivatives approved by the Food and Drug Administration (FDA) for use in photodynamic therapy (PDT). Despite having such drugs, the quest to find better cancer drugs is still ongoing and 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dyes are among the molecules that are being studied as potential photosensitisers (PS) in PDT. However, these molecules suffer from poor solubility and ineffective generation of singlet oxygen, the main ingredient in PDT treatment. Furthermore, photosensitisers used in PDT face a problem with hypoxic conditions associated with cancer cells, which causes the generation of singlet oxygen to be relatively low. The PS also suffer from the untargeted treatment, increasing their toxicity. Therefore, the main aim of this study was to improve the bioavailability of BODIPY dyes. Thus, a series of BODPIY dyes were synthesised with hydrogen bond accepting atoms and heavy atoms that enhance singlet oxygen generation. Additionally, to override hypoxia conditions, porphyrins with mitochondria targeting properties were synthesised since it has been well established that the mitochondria will always have a decent amount of oxygen in cancerous cells. When employed as PS in PDT studies, these molecules have better cytotoxic abilities than BODIPY dyes, and this potency was credited to their mitochondria targeting ability and efficient singlet oxygen generation. Finally, this study reports the synthesis of di- and mono-substituted BODIPY dyes with improved solubility and porphyrins substituted with triphenyl phosphine, a mitochondria targeting moiety. On the other hand, the work further illustrates the synthesis of β-substituted cationic porphyrin with mitochondria targeting properties. , Thesis (MSc) -- Faculty of Science, Chemistry, 2022
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  • 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
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  • 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
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  • Date Issued: 2022-04-08

The systematic assembly of prostate specific antigen electrochemical sensors based on asymmetric Co(II) phthalocyanines, graphitic quantum dots and an aptamer

  • Authors: Nxele, Siphesihle Robin
  • Date: 2022-04-08
  • Subjects: Prostate-specific antigen , Electrochemical sensors , Phthalocyanines , Quantum dots , ‎Co(II) phthalocyanines , Aptamer‎
  • Language: English
  • Type: Doctoral thesis , text
  • Identifier: http://hdl.handle.net/10962/232893 , vital:50035 , DOI 10.21504/10962/232893
  • Description: The need for low-cost, efficient and simple diagnostic tools has led to more research going into this subject, with the aim of making such medical devices more accessible where they are needed. This has led to more researchers developing point-of-care devices for this purpose worldwide, by sensor fabrication. This thesis focuses on electrochemical sensor development for the early diagnosis of prostate cancer. It is common knowledge that prostate cancer is one of the most prevalent carcinomas that have claimed lives due to late diagnosis where even the most invasive treatments have failed. For this reason, development of early detection devices that can even be used in the comfort of home is necessary and quite crucial. Electrochemical sensors have gained much attention due to their ease of fabrication, cost effectiveness, simplicity, ease of use and high efficiency. Using nanocomposites as modifiers has also become popular as they provide greater stability and improve detection limits when used together with biomolecules. With that said, the work reported herein has combined nanocomposites of graphenebased quantum dots, gold nanoparticles, phthalocyanines and an aptamer in order to fabricate aptasensors for the electrochemical detection of prostate cancer biomarker. The aptamer is specifically designed to bind to the biomarker, and the nanocomposites are expected to enhance current output thus lowering detection limits and increasing stability and efficiency. Reproducible results are also expected. Prior to the detection of the prostate cancer biomarker, the quantum dots-phthalocyanine nanohybrids were used to detect L-cysteine, which is an amino acid, in order to verify the synergistic effects as electrode modifiers that lead to the enhancement of current output. This increase in current output is then v exploited for the improvement of aptasensor functionality upon incorporation of the aptamer, for the detection of prostate specific antigen. The research in this thesis has been carried out with the intention of contributing to the world of medical research, more so because of the ever-increasing need for medical care to become accessible to all and not only to those who can afford expensive technologies and treatments. , Thesis (PhD) -- Faculty of Science, Chemistry, 2022
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  • Date Issued: 2022-04-08

Photodynamic antimicrobial chemotherapy against Staphylococcus aureus and Escherichia coli sensitized using indium (III) cationic porphyrins linked to core-shell magnetic nanoparticles

  • Authors: Makola, Lekgowa Collen
  • Date: 2021-04
  • Subjects: Photochemotherapy , Photosensitizing compounds , Staphylococcus aureus , Escherichia coli , Indium , Porphyrins , Magnetic nanoparticles , Quaternize
  • Language: English
  • Type: thesis , text , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/177225 , vital:42801
  • Description: Photodynamic antimicrobial chemotherapy (PACT) is a well-known antimicrobial therapy technique used against multi-drug resistant pathogens. In this study, the syntheses, characterization, photophysicochemical properties, and the applications of symmetrically and asymmetrically substituted cationic indium (III) porphyrins linked to silver/copper ferrite core-shell (Ag/CuFe2O4) magnetic nanoparticles (MNPs) as potential photosensitizers for PACT are reported. The synthesized complexes include axially modified porphyrins quaternized through an axial ligand. All the asymmetrically substituted porphyrins were linked to the NPs via an ester bond and the symmetrically substituted porphyrins were linked (peripherally and /or axially) via self-assembly (Ag-S and/or Ag-N). The impact of axial modification, peripheral substituents, conjugation to the NPs, the number of positive charges, and the chain length of the alkyl halides quaternizing agents on PACT efficacy and photophysicochemical properties of porphyrins were studied. High singlet oxygen quantum yields and antimicrobial log reductions were observed. Lipophilicity and hydrophilicity of the porphyrins were also studies, where the complexes quaternized with methyl iodide showed relatively high hydrophilicity character. Upon in vitro PACT studies, the quaternized complexes were observed to have 0% viable colony, signifying their effectiveness. Moreover, the highest log reductions of 9.27 were observed against S. aureus and 9.58 were observed against E. coli. The findings from this work delineate that singlet oxygen generation alone is not a distinct factor on the PACT efficacy of the porphyrin complexes, since some of the complexes have practically the same singlet oxygen quantum but different PACT activity. However, other contributing factors including water solubility play a significant role. , Thesis (MSc) -- Faculty of Science, Department of Chemistry, 2021
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  • Date Issued: 2021-04

Effect of the nature of nanoparticles on the photophysicochemical properties and photodynamic antimicrobial chemotherapy of phthalocyanines

  • Authors: Magadla, Aviwe
  • Date: 2020
  • Subjects: Nanoparticles , Phthalocyanines , Anti-infective agents -- Therapeutic use , Photochemotherapy , Photochemistry
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/123107 , vital:35406
  • Description: In this work, the syntheses and characterisation of Zn monocaffeic acid tri–tert–butyl phthalocyanine (1), Zn monocarboxyphenoxy tri– tert–butylphenoxyl phthalocyanine (2), tetrakis phenoxy N,N-dimethyl-4-(methylimino) phthalocyanine indium (III) chloride (3) and tetrakis N,N-dimethyl-4-(methylimino) phthalocyanine indium (III) chloride (5) are presented. Complexes 3 and 5 were further quartenised with 1,3- propanesultone to form corresponding complexes (4) and (6), respectively. Complexes 1 and 2 were covalently linked to amino functionalised nanoparticles (NPs). Complexes 3, 4, 5 and 6 where linked to oleic acid/oleylamine capped (OLA/OLM) silver-iron dimers (Ag-Fe3O4 OLA/OLM) and silver-iron core shell (Ag@Fe3O4 OLA/OLM) NPs via interaction between the nanoparticles and the imino group on the phthalocyanines. The phthalocyanine-NP conjugates afforded an increase in triplet quantum yields with a corresponding decrease in fluorescence quantum yield as compared to the phthalocyanine complexes alone. Complexes 3, 4 and their conjugates were then used for photodynamic antimicrobial chemotherapy on E. coli. The zwitterionic photosensitiser 4 and its conjugates showed better efficiency for photodynamic antimicrobial chemotherapy compared to their neutral counterparts.
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  • Date Issued: 2020

Metallophthalocyanines linked to metal nanoparticles and folic acid for use in photodynamic therapy of cancer and photoinactivation of bacterial microorganisms.

  • Authors: Matlou, Gauta Gold
  • Date: 2020
  • Subjects: Cancer -- Photochemotherapy , Nanoparticles , Phthalocyanines , Anti-infective agents -- Therapeutic use , Photochemotherapy , Photochemistry
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/166540 , vital:41377
  • Description: This thesis presents on the synthesis and characterization of novel asymmetric and symmetrical metallophthalocyanines (MPcs) substituted with carboxylic acid functional groups and centrally metallated with zinc and indium. The MPcs are further covalently linked to cysteine capped silver nanoparticles (cys-AgNPs), amino functionalized magnetic nanoparticles (AMNPs) and folic acid (FA) through an amide bond between the carboxylic group of MPcs and the amino group of FA, cys-AgNPs or AMNPs. The covalent linkage of MPcs to FA improved the water solubility of MPcs and allowed for singlet oxygen quantum yield determination in water. Asymmetric MPcs and their conjugates were found to have improved photochemical and photophysical properties compared to symmetrical MPcs and their conjugates. The heavy atom effect of AMNPs and AgNPs improved the triplet and singlet oxygen quantum yields of MPcs. MPcs and their conjugates (MPc-FA, MPc-AMNPs, MPc-AgNPs) were found to have lower in vitro dark cytotoxicity and higher photodynamic therapy (PDT) activity on MCF-7 breast cancer cells. The water soluble MPc-FA had better PDT activity when compared to MPc-AMNPs due to the active targeting of folic acid-folate binding on cancer cell surface. MPcs and MPc-AgNPs conjugates also showed excellent in vitro cytotoxicity on S. aureus under light irradiation compared to dark cytotoxicity. The photosensitizing properties of MPcs and their conjugates are demonstrated for the first time in this thesis, both on breast cancer cells (MCF-7) through photodynamic therapy and on microorganisms (S. aureus) through photodynamic antimicrobial chemotherapy.
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  • Date Issued: 2020

Photocatalysis of 4-chloro and 4-nonylphenols using novel symmetric phthalocyanines and asymmetric porphyrin supported on polyacrylonitrite nanofibres

  • Authors: Jones, Benjamin Martin
  • Date: 2020
  • Subjects: Nanoparticles , Phthalocyanines , Electrospinning , Porphyrins , Nanofibers , Photocatalysis , Photocatalysis -- Environmental aspects
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/164770 , vital:41163
  • Description: This work explores the synthesis and characterisation of novel symmetrical phthalocyanines and novel asymmetric porphyrins that have been embedded or linked respectively,and electrospun into fibres for application in the photocatalysis of environmental pollutants. The phthalocyanines contain pyrrole moieties without hetero atom linkers to maintain a rigid structure. The porphyrin contains a carboxy moiety utilized to construct an amide bond between the complex and the polymer prior to the spinning process. The new compounds were characterized by elemental analyses, proton nuclear magnetic resonance (HNMR)Fourier-transform infrared spectroscopy (FTIR), MALDI-TOF and UV-vis spectroscopy. The general trends of fluorescence, triplet and singlet oxygen quantum yields are described as well as their appropriate lifetimes. The photocatalytic activity of phthalocyanine embedded fibres were compared against those that had been dyed. Unfortunately, during the degradation process, the dyed fibres leeched compound and the studies could not be continued. It was seen that the porphyrin fibres linked to the polymer showed the most efficient photocatalytic activity against 4-cholorphenol and 4-nonylphenol due to irradiation at lower wavelengths consequently having higher frequencies and transferring more energy.
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  • Date Issued: 2020

BODIPY and porphyrin dyes for direct glucose sensing and optical limiting applications

  • Authors: Ndebele, Nobuhle
  • Date: 2019
  • Subjects: Boron compounds , Boric acid , Porphyrins , Dyes and dying -- Chemistry
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/97221 , vital:31412
  • Description: A series of BODIPY dyes functionalised with boronic acid in the 3,5-positions were successfully synthesised and characterised by using various analytical techniques. The dyes were prepared through a slight modification of the conventional acid catalysed condensation method. Phenylboronic acid moieties were added as styryl groups at the 3,5-positions of the 1,3,5,7-tetrametylBODIPY cores using a modified Knoevengal condensation method. The addition of the styryls resulted in the main absorption band of the dyes red-shifting to the 630−650 nm region. The photophysical and electrochemical properties of these dyes were studied to determine whether the dyes are suitable for use in the fluorescent, colourimetric and electrochemical detection of glucose. Boronic acid moieties were added as bioreceptor recognition elements because they have an affinity for carbohydrates and therefore would be able to bind and “detect” glucose. The series of BODIPY dyes did not show a “turn-on” fluorescence effect upon addition with glucose at the physiological pH. This was attributed on the basis of molecular modelling to the absence of an MO localised on the boronic-acid-substituted styryl moieties that lie close in energy to the HOMO and LUMO that facilitates the formation of an intramolecular charge transfer state. However, colourimetric changes that are visible to the naked eye are observed at basic pH when glucose was added to the dye solutions. The dyes exhibited favourable electrochemical behaviour and were able to detect glucose directly in this context when glassy carbon electrodes are modified through the drop dry method. A series of Sn(IV) porphyrins with thienyl and phenyl groups at the meso-positions were successfully synthesised and characterised. Pyridine and tetrabutyl axial ligands were added to the porphyrins to limit aggregation. The optical limiting properties of these porphyrins and three styrylated BODIPY dyes were studied in benzene and dichloromethane. Dyes were also embedded in polystyrene and studied as thin films to further gauge their suitability for use in optical limiting applications. Second-order hyperpolarizability, third-order susceptibly, non-linear absorption with reversible saturable absorption and the optical limiting threshold, were the parameters studied. Three of the four porphyrins and the three styrylated BODIPY dyes showed favourable optical limiting behaviour, which was further enhanced when the dyes are embedded in polymer thin films.
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  • Date Issued: 2019
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