Nonlinear optical properties of metal free thio alkyl and tert-butyl phenoxy phthalocyanine
- Authors: Joseph, Otto
- Date: 2021-10
- Subjects: Nonlinear optics , Phthalocyanines , Time-dependent density functional theory , Magnetic circular dichroism , Reverse saturable absorption (RSA) , Real Time Dependent Density Functional Theory (RT-TDDFT)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190712 , vital:45021
- Description: This work reports on the nonlinear optical properties of tetra - and octa substituted phthalocyanines (Pcs) utilising pentane thiol and 4-tertbutyl phenol as substituents. Their nonlinear absorption coefficient (𝛽) and absorption cross sections were determined using the Z-scan technique with a 10 ns pulse laser at 532 nm. The molecular second order hyperpolarizability Im[γ] was observed and the following Im[γ] trend was obtained for 𝛼-H2Pc(SC5H11)4 isomers, 5.93 ×10−31 (Cs) 2.24×10−32(D2h) > 1.21×10−32(C4h) > 1.05×10−32 (C2v) esu, respectively, in chloroform. Symmetry was seen to have an effect on the observed reverse saturable absorption (RSA) response. Based on the five level model rate equation nonlinear fit of the RSA response curves and Real Time Time Dependant Density Functional Theory (RT-TDDFT) results, the singlet excited state population dynamics was found to play a significant role in producing the observed Im[γ] trend. , Thesis (MSc) -- Faculty of Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10
- Authors: Joseph, Otto
- Date: 2021-10
- Subjects: Nonlinear optics , Phthalocyanines , Time-dependent density functional theory , Magnetic circular dichroism , Reverse saturable absorption (RSA) , Real Time Dependent Density Functional Theory (RT-TDDFT)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190712 , vital:45021
- Description: This work reports on the nonlinear optical properties of tetra - and octa substituted phthalocyanines (Pcs) utilising pentane thiol and 4-tertbutyl phenol as substituents. Their nonlinear absorption coefficient (𝛽) and absorption cross sections were determined using the Z-scan technique with a 10 ns pulse laser at 532 nm. The molecular second order hyperpolarizability Im[γ] was observed and the following Im[γ] trend was obtained for 𝛼-H2Pc(SC5H11)4 isomers, 5.93 ×10−31 (Cs) 2.24×10−32(D2h) > 1.21×10−32(C4h) > 1.05×10−32 (C2v) esu, respectively, in chloroform. Symmetry was seen to have an effect on the observed reverse saturable absorption (RSA) response. Based on the five level model rate equation nonlinear fit of the RSA response curves and Real Time Time Dependant Density Functional Theory (RT-TDDFT) results, the singlet excited state population dynamics was found to play a significant role in producing the observed Im[γ] trend. , Thesis (MSc) -- Faculty of Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10
Design of pH Sensitive Electrochemical Sensor for Catecholamine Neurotransmitters Detection and the Screening Off of Ascorbic Acid
- Tshenkeng, Keamogetse Tebogo Charlotte
- Authors: Tshenkeng, Keamogetse Tebogo Charlotte
- Date: 2021-10-29
- Subjects: Catecholamines , Electrochemical sensors , Neurotransmitters , Vitamin C , Cobalt , Phthalocyanines , Cobalt (II) tetra-(3-carboxyphenoxy) phthalocyanine (CoTCPhOPc)
- Language: English
- Type: thesis , text
- Identifier: http://hdl.handle.net/10962/176921 , vital:42772
- Description: This study presents the synthesis of cobalt (II) tetra-(3-carboxyphenoxy) phthalocyanine (CoTCPhOPc) through the cyclotetramerization of 4-(3-carboxyphe-noxy)phthalonitrile and its full characterization using Fourier transform infrared (FT-IR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, magnetic circular dichroism (MCD) spectroscopy, elemental analysis and mass spectrometry. The CoTCPhOPc was then immobilized onto phenylethylamino (PEA) pre-grafted gold electrode surface, Au-PEA using amide coupling reaction through a reaction with NHS and DCC to obtain Au-PEA-CoTCPhOPc. This yielded pH sensitive thin films due to the terminal carboxylic acid (–COOH) functional groups. Electrochemical and surface characterization was conducted to confirm the modification of the bare Au with PEA thin film (Au-PEA) and amide coupling of CoTCPhOPc (Au-PEA-CoTCPhOPc). The Au-PEA-CoTCPhOPc electrode was shown to possess pH selective properties towards negatively charged [Fe(CN)6]3-/4- and positively charged [Ru(NH3)6]2+/3+ redox probes. Au-PEA-CoTCPhOPc electrode surface enabled the detection of catecholamine neurotransmitters (dopamine, norepinephrine and epinephrine) and the screening off of ascorbic acid by means of pH sensitive functional groups. Bare Au and Au-PEA electrodes exhibited electro-oxidation and electroreduction of catecholamine neuro-transmitters and ascorbic acid at higher potentials compared to Au-PEA-CoTCPhOPc. There was no electro-oxidation or electroreduction of ascorbic acid at Au-PEA-CoTCPhOPc. For Au-PEA-CoTCPhOPc, excellent electrocatalytic oxidation with the limit of detection (LoD) determined using 3σ was found to be 1.32 (0.95), 2.11 (1.78) and 3.08 μM for electro-oxidation and electroreduction (in brackets) of dopamine, norepinephrine and epinephrine respectively. The limit of quantification (LoQ) was determined using 10σ and found to be 4.41 (3.17), 7.02 (5.93) and 10.3 μM electro-oxidation and electroreduction (in brackets) for dopamine, norepinephrine and epinephrine respectively. The Au-PEA-CoTCPhOPc thin film was shown to screen off ascorbic acid as no electrocatalytic oxidation was observed for up to 100.0 μM concentration. , Thesis (MSc) -- Faculty of Science, Department of Chemistry, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Tshenkeng, Keamogetse Tebogo Charlotte
- Date: 2021-10-29
- Subjects: Catecholamines , Electrochemical sensors , Neurotransmitters , Vitamin C , Cobalt , Phthalocyanines , Cobalt (II) tetra-(3-carboxyphenoxy) phthalocyanine (CoTCPhOPc)
- Language: English
- Type: thesis , text
- Identifier: http://hdl.handle.net/10962/176921 , vital:42772
- Description: This study presents the synthesis of cobalt (II) tetra-(3-carboxyphenoxy) phthalocyanine (CoTCPhOPc) through the cyclotetramerization of 4-(3-carboxyphe-noxy)phthalonitrile and its full characterization using Fourier transform infrared (FT-IR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, magnetic circular dichroism (MCD) spectroscopy, elemental analysis and mass spectrometry. The CoTCPhOPc was then immobilized onto phenylethylamino (PEA) pre-grafted gold electrode surface, Au-PEA using amide coupling reaction through a reaction with NHS and DCC to obtain Au-PEA-CoTCPhOPc. This yielded pH sensitive thin films due to the terminal carboxylic acid (–COOH) functional groups. Electrochemical and surface characterization was conducted to confirm the modification of the bare Au with PEA thin film (Au-PEA) and amide coupling of CoTCPhOPc (Au-PEA-CoTCPhOPc). The Au-PEA-CoTCPhOPc electrode was shown to possess pH selective properties towards negatively charged [Fe(CN)6]3-/4- and positively charged [Ru(NH3)6]2+/3+ redox probes. Au-PEA-CoTCPhOPc electrode surface enabled the detection of catecholamine neurotransmitters (dopamine, norepinephrine and epinephrine) and the screening off of ascorbic acid by means of pH sensitive functional groups. Bare Au and Au-PEA electrodes exhibited electro-oxidation and electroreduction of catecholamine neuro-transmitters and ascorbic acid at higher potentials compared to Au-PEA-CoTCPhOPc. There was no electro-oxidation or electroreduction of ascorbic acid at Au-PEA-CoTCPhOPc. For Au-PEA-CoTCPhOPc, excellent electrocatalytic oxidation with the limit of detection (LoD) determined using 3σ was found to be 1.32 (0.95), 2.11 (1.78) and 3.08 μM for electro-oxidation and electroreduction (in brackets) of dopamine, norepinephrine and epinephrine respectively. The limit of quantification (LoQ) was determined using 10σ and found to be 4.41 (3.17), 7.02 (5.93) and 10.3 μM electro-oxidation and electroreduction (in brackets) for dopamine, norepinephrine and epinephrine respectively. The Au-PEA-CoTCPhOPc thin film was shown to screen off ascorbic acid as no electrocatalytic oxidation was observed for up to 100.0 μM concentration. , Thesis (MSc) -- Faculty of Science, Department of Chemistry, 2021
- Full Text:
- Date Issued: 2021-10-29
Tetra 4-(propargyloxy)phenoxy phthalocyanines: synthesis, spectroscopic, nonlinear optical and electrocatalytic properties
- Authors: Mwanza, Daniel
- Date: 2017
- Subjects: Phthalocyanines , Nonlinear optics , Electrocatalysis , Spectrum analysis , Thermogravimetry , Phthalocyanines Spectra
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/65144 , vital:28695
- Description: This study presents the synthesis, spectroscopic, photophysical and theoretical characterisation of metal-free (H2TPrOPhOPc), cobalt (CoTPrOPhOPc) and manganese (MnTPrOPhOPc) tetra 4-(4-propargyloxy) phenoxy phthalocyanines. Thermal analysis using thermogravimetric analysis (TGA) confirmed the excellent thermal stability of synthesized tetra 4-(4- propargyloxy) phenoxy phthalocyanines. The metal complexes, CoTPrOPhOPc and MnTPrOPhOPc, exhibited better thermal stability when compared to H2TPrOPhOPc. The residual percentage weight remaining was approximately 70% for CoTPrOPhOPc and MnTPrOPhOPc and 45% for H2TPrOPhOPc after 600°C, clearly confirming the stability of the metal complexes. The MTPrOPhOPcs (where M = H2, Co and Mn) complexes exhibited excellent nonlinear optical properties with strong reverse saturable absorption (RSA), especially when 560 nm excitation laser was used. Their nonlinear optical properties followed this trend: H2TPrOPhOPc > CoTPrOPhOPc > MnTPrOPhOPc. According to the trend observed, the H2TPrOPhOPc was an excellent nonlinear optical limiter when compared to the CoTPrOPhOPc and MnTPrOPhOPc. All the investigated complexes exhibited optical limiting properties comparable to the phthalocyanine complexes reported in the literature. The MTPrOPhOPc complexes were further studied for their electrocatalytic and electroanalytical properties towards the detection of hydrogen peroxide. For the electrocatalytic studies, the synthesized complexes were immobilized onto gold electrode surfaces pre-functionalized with phenylazide (Au-PAz) monolayer. Copper (I) catalyzed alkynyl-azide cycloaddition reaction was used to covalently immobilize the MTPrOPhOPcs onto the gold electrode surfaces to form Au-PAz-MTPrOPhOPc. The MTPrOPhOPcs modified gold surfaces (Au-PAz-MTPrOPhOPc) exhibited good reproducibility and stability in various electrolyte conditions. Electrochemical and surface characterisation of the functionalised gold electrode surfaces confirmed the presence of the MTPrOPhOPcs and their electroanalysis was excellent towards electrocatalytic reduction of H2O2, with the limit of detection (LoD) and limit of quantification (LoQ) in the ^M range. The electrocatalytic reduction peaks for H2O2 were observed at -0.37 V for Au-PAz-MnTPrOPhOPc and -0.31 V for Au-PAz-CoTPrOPhOPc when Ag|AgCl pseudo-reference electrode was used. The Au-PAz-MnTPrOPhOPc and Au- PAz-CoTPrOPhOPc gold electrode surfaces showed good sensitivity and reproducibility towards the electrocatalytic reduction of hydrogen peroxide in pH 7.4 phosphate buffer solution. , Thesis (MSc) -- Faculty of Science, Chemistry, 2017
- Full Text:
- Date Issued: 2017
- Authors: Mwanza, Daniel
- Date: 2017
- Subjects: Phthalocyanines , Nonlinear optics , Electrocatalysis , Spectrum analysis , Thermogravimetry , Phthalocyanines Spectra
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/65144 , vital:28695
- Description: This study presents the synthesis, spectroscopic, photophysical and theoretical characterisation of metal-free (H2TPrOPhOPc), cobalt (CoTPrOPhOPc) and manganese (MnTPrOPhOPc) tetra 4-(4-propargyloxy) phenoxy phthalocyanines. Thermal analysis using thermogravimetric analysis (TGA) confirmed the excellent thermal stability of synthesized tetra 4-(4- propargyloxy) phenoxy phthalocyanines. The metal complexes, CoTPrOPhOPc and MnTPrOPhOPc, exhibited better thermal stability when compared to H2TPrOPhOPc. The residual percentage weight remaining was approximately 70% for CoTPrOPhOPc and MnTPrOPhOPc and 45% for H2TPrOPhOPc after 600°C, clearly confirming the stability of the metal complexes. The MTPrOPhOPcs (where M = H2, Co and Mn) complexes exhibited excellent nonlinear optical properties with strong reverse saturable absorption (RSA), especially when 560 nm excitation laser was used. Their nonlinear optical properties followed this trend: H2TPrOPhOPc > CoTPrOPhOPc > MnTPrOPhOPc. According to the trend observed, the H2TPrOPhOPc was an excellent nonlinear optical limiter when compared to the CoTPrOPhOPc and MnTPrOPhOPc. All the investigated complexes exhibited optical limiting properties comparable to the phthalocyanine complexes reported in the literature. The MTPrOPhOPc complexes were further studied for their electrocatalytic and electroanalytical properties towards the detection of hydrogen peroxide. For the electrocatalytic studies, the synthesized complexes were immobilized onto gold electrode surfaces pre-functionalized with phenylazide (Au-PAz) monolayer. Copper (I) catalyzed alkynyl-azide cycloaddition reaction was used to covalently immobilize the MTPrOPhOPcs onto the gold electrode surfaces to form Au-PAz-MTPrOPhOPc. The MTPrOPhOPcs modified gold surfaces (Au-PAz-MTPrOPhOPc) exhibited good reproducibility and stability in various electrolyte conditions. Electrochemical and surface characterisation of the functionalised gold electrode surfaces confirmed the presence of the MTPrOPhOPcs and their electroanalysis was excellent towards electrocatalytic reduction of H2O2, with the limit of detection (LoD) and limit of quantification (LoQ) in the ^M range. The electrocatalytic reduction peaks for H2O2 were observed at -0.37 V for Au-PAz-MnTPrOPhOPc and -0.31 V for Au-PAz-CoTPrOPhOPc when Ag|AgCl pseudo-reference electrode was used. The Au-PAz-MnTPrOPhOPc and Au- PAz-CoTPrOPhOPc gold electrode surfaces showed good sensitivity and reproducibility towards the electrocatalytic reduction of hydrogen peroxide in pH 7.4 phosphate buffer solution. , Thesis (MSc) -- Faculty of Science, Chemistry, 2017
- Full Text:
- Date Issued: 2017
The construction of phthalocyanine- carbon nanoparticle conjugates for applications in photodynamic therapy and non-linear optics
- Matshitse, Refilwe Manyama Stephina
- Authors: Matshitse, Refilwe Manyama Stephina
- Date: 2021-10-29
- Subjects: Phthalocyanines , Nanodiamonds , Photochemotherapy , Nonlinear optics , Quantum dots
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/188397 , vital:44750 , 10.21504/10962/188397
- Description: The syntheses and characterization of symmetric and asymmetric Pcs functionalized at the peripheral position and sometimes positively charged are reported. The Pcs had either H2, zinc or silicon as central metals and have pyridyloxy, benzothiozole phenoxy, and respective cationic analogues as ring substituents. The Pcs were linked to carbon based nanoparticles such as graphene quantum dots, carbon dots, and detonation nanodiamonds (DNDs) via an ester, amide bond and/or π - π stacking. The physicochemical characteristics of the Pcs were assessed when alone and when in a conjugated system. Both symmetrically and asymmetrically substituted benzothiozole Pcs when quaternised displayed higher triplet and singlet oxygen quantum yields than their unquaternised counterparts. Linkage to carbon nanoparticles (especially to detonation nanodiamonds) had an increasing effect on triplet and singlet oxygen quantum yield. However, a general decrease in singlet oxygen quantum yield on linkage to doped detonation nanodiamonds was associated with the screening effect of DNDs. Heteroatom doped DNDs-Pc nanohybrids have less singlet oxygen than Pcs alone due to molecular structural stability associated with strain that is relatively reduced upon linking Pcs. The In vitro dark cytotoxicity and photodynamic therapy of selected Pc complexes and conjugates against MCF-7 cells was tested. All studied Pc complexes and conjugates showed minimum dark toxicity making them applicable for PDT. When Pc complexes are alone, there is less phototoxicity with >22% cell viability at concentrations ≤ 50 μg/mL relative to conjugates with <22% cell viability at concentrations ≤ 50 μg/mL. There was no direct relationship between PDT and singlet oxygen quantum yields. Nonlinear optical characteristics of complexes was improved upon conjugation of DNDs. Absorbance, input energy, percentage loading, central metal, substituent of Pc and nature of interaction (covalent, noncovalent) are amongst some of the factors that influence nonlinear absorption properties of materials used in this study. All materials followed reverse saturable absorption through two photon absorption mechanism at the excitation wavelength of 532 nm. Aggregates reduce excited state lifetime and Beff under high concentrations/absorbance. A direct relationship between absorbance and Beff of DNDs nanoconjugated systems at low concentrations result in increased optical limiting characteristics of materials. The findings from this work show the importance of linking (nonlinear optics and photodynamic therapy) and doping (photodynamic therapy) photosensitisers such as phthalocyanines and sometimes boron dipyrromethenes onto carbon based nanoparticles for the enhanced characteristics in variable applications. , Thesis (PhD) -- Faculty of Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Matshitse, Refilwe Manyama Stephina
- Date: 2021-10-29
- Subjects: Phthalocyanines , Nanodiamonds , Photochemotherapy , Nonlinear optics , Quantum dots
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/188397 , vital:44750 , 10.21504/10962/188397
- Description: The syntheses and characterization of symmetric and asymmetric Pcs functionalized at the peripheral position and sometimes positively charged are reported. The Pcs had either H2, zinc or silicon as central metals and have pyridyloxy, benzothiozole phenoxy, and respective cationic analogues as ring substituents. The Pcs were linked to carbon based nanoparticles such as graphene quantum dots, carbon dots, and detonation nanodiamonds (DNDs) via an ester, amide bond and/or π - π stacking. The physicochemical characteristics of the Pcs were assessed when alone and when in a conjugated system. Both symmetrically and asymmetrically substituted benzothiozole Pcs when quaternised displayed higher triplet and singlet oxygen quantum yields than their unquaternised counterparts. Linkage to carbon nanoparticles (especially to detonation nanodiamonds) had an increasing effect on triplet and singlet oxygen quantum yield. However, a general decrease in singlet oxygen quantum yield on linkage to doped detonation nanodiamonds was associated with the screening effect of DNDs. Heteroatom doped DNDs-Pc nanohybrids have less singlet oxygen than Pcs alone due to molecular structural stability associated with strain that is relatively reduced upon linking Pcs. The In vitro dark cytotoxicity and photodynamic therapy of selected Pc complexes and conjugates against MCF-7 cells was tested. All studied Pc complexes and conjugates showed minimum dark toxicity making them applicable for PDT. When Pc complexes are alone, there is less phototoxicity with >22% cell viability at concentrations ≤ 50 μg/mL relative to conjugates with <22% cell viability at concentrations ≤ 50 μg/mL. There was no direct relationship between PDT and singlet oxygen quantum yields. Nonlinear optical characteristics of complexes was improved upon conjugation of DNDs. Absorbance, input energy, percentage loading, central metal, substituent of Pc and nature of interaction (covalent, noncovalent) are amongst some of the factors that influence nonlinear absorption properties of materials used in this study. All materials followed reverse saturable absorption through two photon absorption mechanism at the excitation wavelength of 532 nm. Aggregates reduce excited state lifetime and Beff under high concentrations/absorbance. A direct relationship between absorbance and Beff of DNDs nanoconjugated systems at low concentrations result in increased optical limiting characteristics of materials. The findings from this work show the importance of linking (nonlinear optics and photodynamic therapy) and doping (photodynamic therapy) photosensitisers such as phthalocyanines and sometimes boron dipyrromethenes onto carbon based nanoparticles for the enhanced characteristics in variable applications. , Thesis (PhD) -- Faculty of Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10-29
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
- Full Text:
- Date Issued: 2022-04-08
- 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
- Full Text:
- Date Issued: 2022-04-08
Functionalized Ru(II) polypyridines and phthalocyanines: Potential dyes for dye-sensitized solar cells(DSSCs)
- Adeloye, Adewale Olufunsho https://orcid.org/0000-0003-1736-5738
- Authors: Adeloye, Adewale Olufunsho https://orcid.org/0000-0003-1736-5738
- Date: 2011-01
- Subjects: Phthalocyanines , Dye-sensitized solar cells
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/24365 , vital:62645
- Description: This study describes the design, synthesis, characterization and preliminary investigation of the solar-to-electrical energy conversion efficiency of ruthenium(II) functionalized polypyridine and phthalocyanine complexes with extended π-conjugation. Polypyridinyl functionalized with anthracene, 2,3-dimethylacrylic acid and 1-methoxy-1-buten-3-yne were synthesized and characterized by infrared, UV-Vis, photoluminescence, 1H and 13C NMR and elemental analysis. The functionalized polypyridine molecules were used to synthesize various ruthenium(II) homoleptic/heteroleptic and/or heteronuclear complexes and their photophysical and electrochemical properties evaluated. The preliminary results of the solar-to-electrical conversion efficiencies of some synthesized Ru(II) polypyridyl complexes were presented in chapter 5. It was found out as expected that the ruthenium(II) polypyridine complexes containing either heteronuclear polypyridine ligands or their thiocyanate analogues of the types [Ru(L1)2L2(PF6)2], [RuL1(L2)2(PF6)2] and [RuL1L2(NCS)2], showed better photophysical properties (red-shifted metal-to-ligand charge-transfer (MLCT) transitions concomitant with enhanced molar extinction coefficients), luminescence and interesting electrochemical redox properties than those containing homonuclear ligand types [Ru(L1)3(PF6)2]. The ruthenium(II) anthracenyl functionalized phthalocyanine complexes which were obtained by electrophilic aromatic substitution reactions in the peripheral positions gave good solubility properties in various organic solvents and also showed interesting near infrared absorption and electroredox characteristics. Cyclic and square wave voltammetries of these complexes revealed major redox processes and the numbers of electron(s) transfer were determined by chronocoulometry. It was established that a mono- and/or multi-electronic transfer reactions can occur in the various ruthenium(II) complexes. The photophysical properties of some complexes showed them to be better and promising candidates in the design of chemosensors, organic light emitting diodes (OLEDs) and as photosensitizers, while their redox-active natures make them potential mediators in electron-transfer for various photochemical processes. However, due to low surface concentration and/or adsorption of some tested complexes on TiO2 semiconductor nanocrystalline particle, low currents were generated and the highest solar-to- electrical conversion efficiency recorded in this study was 0.10 percent. , Thesis (PhD) -- Faculty of Science and Agriculture, 2011
- Full Text:
- Date Issued: 2011-01
- Authors: Adeloye, Adewale Olufunsho https://orcid.org/0000-0003-1736-5738
- Date: 2011-01
- Subjects: Phthalocyanines , Dye-sensitized solar cells
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/24365 , vital:62645
- Description: This study describes the design, synthesis, characterization and preliminary investigation of the solar-to-electrical energy conversion efficiency of ruthenium(II) functionalized polypyridine and phthalocyanine complexes with extended π-conjugation. Polypyridinyl functionalized with anthracene, 2,3-dimethylacrylic acid and 1-methoxy-1-buten-3-yne were synthesized and characterized by infrared, UV-Vis, photoluminescence, 1H and 13C NMR and elemental analysis. The functionalized polypyridine molecules were used to synthesize various ruthenium(II) homoleptic/heteroleptic and/or heteronuclear complexes and their photophysical and electrochemical properties evaluated. The preliminary results of the solar-to-electrical conversion efficiencies of some synthesized Ru(II) polypyridyl complexes were presented in chapter 5. It was found out as expected that the ruthenium(II) polypyridine complexes containing either heteronuclear polypyridine ligands or their thiocyanate analogues of the types [Ru(L1)2L2(PF6)2], [RuL1(L2)2(PF6)2] and [RuL1L2(NCS)2], showed better photophysical properties (red-shifted metal-to-ligand charge-transfer (MLCT) transitions concomitant with enhanced molar extinction coefficients), luminescence and interesting electrochemical redox properties than those containing homonuclear ligand types [Ru(L1)3(PF6)2]. The ruthenium(II) anthracenyl functionalized phthalocyanine complexes which were obtained by electrophilic aromatic substitution reactions in the peripheral positions gave good solubility properties in various organic solvents and also showed interesting near infrared absorption and electroredox characteristics. Cyclic and square wave voltammetries of these complexes revealed major redox processes and the numbers of electron(s) transfer were determined by chronocoulometry. It was established that a mono- and/or multi-electronic transfer reactions can occur in the various ruthenium(II) complexes. The photophysical properties of some complexes showed them to be better and promising candidates in the design of chemosensors, organic light emitting diodes (OLEDs) and as photosensitizers, while their redox-active natures make them potential mediators in electron-transfer for various photochemical processes. However, due to low surface concentration and/or adsorption of some tested complexes on TiO2 semiconductor nanocrystalline particle, low currents were generated and the highest solar-to- electrical conversion efficiency recorded in this study was 0.10 percent. , Thesis (PhD) -- Faculty of Science and Agriculture, 2011
- Full Text:
- Date Issued: 2011-01
Functionalized Ru(II) polypyridines and phthalocyanines: Potential dyes for dye-sensitized solar cells(DSSCs)
- Adeloye, Adewale Olufunsho https://orcid.org/0000-0003-1736-5738
- Authors: Adeloye, Adewale Olufunsho https://orcid.org/0000-0003-1736-5738
- Date: 2011-01
- Subjects: Phthalocyanines , Dye-sensitized solar cells
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/24343 , vital:62638
- Description: This study describes the design, synthesis, characterization and preliminary investigation of the solar-to-electrical energy conversion efficiency of ruthenium(II) functionalized polypyridine and phthalocyanine complexes with extended π-conjugation. Polypyridinyl functionalized with anthracene, 2,3-dimethylacrylic acid and 1-methoxy-1-buten-3-yne were synthesized and characterized by infrared, UV-Vis, photoluminescence, 1H and 13C NMR and elemental analysis. The functionalized polypyridine molecules were used to synthesize various ruthenium(II) homoleptic/heteroleptic and/or heteronuclear complexes and their photophysical and electrochemical properties evaluated. The preliminary results of the solar-to-electrical conversion efficiencies of some synthesized Ru(II) polypyridyl complexes were presented in chapter 5. It was found out as expected that the ruthenium(II) polypyridine complexes containing either heteronuclear polypyridine ligands or their thiocyanate analogues of the types [Ru(L1)2L2(PF6)2], [RuL1(L2)2(PF6)2] and [RuL1L2(NCS)2], showed better photophysical properties (red-shifted metal-to-ligand charge-transfer (MLCT) transitions concomitant with enhanced molar extinction coefficients), luminescence and interesting electrochemical redox properties than those containing homonuclear ligand types [Ru(L1)3(PF6)2]. The ruthenium(II) anthracenyl functionalized phthalocyanine complexes which were obtained by electrophilic aromatic substitution reactions in the peripheral positions gave good solubility properties in various organic solvents and also showed interesting near infrared absorption and electroredox characteristics. Cyclic and square wave voltammetries of these complexes revealed major redox processes and the numbers of electron(s) transfer were determined by chronocoulometry. It was established that a mono- and/or multi-electronic transfer reactions can occur in the various ruthenium(II) complexes. The photophysical properties of some complexes showed them to be better and promising candidates in the design of chemosensors, organic light emitting diodes (OLEDs) and as photosensitizers, while their redox-active natures make them potential mediators in electron-transfer for various photochemical processes. However, due to low surface concentration and/or adsorption of some tested complexes on TiO2 semiconductor nanocrystalline particle, low currents were generated and the highest solar-to-electrical conversion efficiency recorded in this study was 0.10 percent. , Thesis (PhD) -- Faculty of Science and Agriculture, 2011
- Full Text:
- Date Issued: 2011-01
- Authors: Adeloye, Adewale Olufunsho https://orcid.org/0000-0003-1736-5738
- Date: 2011-01
- Subjects: Phthalocyanines , Dye-sensitized solar cells
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/24343 , vital:62638
- Description: This study describes the design, synthesis, characterization and preliminary investigation of the solar-to-electrical energy conversion efficiency of ruthenium(II) functionalized polypyridine and phthalocyanine complexes with extended π-conjugation. Polypyridinyl functionalized with anthracene, 2,3-dimethylacrylic acid and 1-methoxy-1-buten-3-yne were synthesized and characterized by infrared, UV-Vis, photoluminescence, 1H and 13C NMR and elemental analysis. The functionalized polypyridine molecules were used to synthesize various ruthenium(II) homoleptic/heteroleptic and/or heteronuclear complexes and their photophysical and electrochemical properties evaluated. The preliminary results of the solar-to-electrical conversion efficiencies of some synthesized Ru(II) polypyridyl complexes were presented in chapter 5. It was found out as expected that the ruthenium(II) polypyridine complexes containing either heteronuclear polypyridine ligands or their thiocyanate analogues of the types [Ru(L1)2L2(PF6)2], [RuL1(L2)2(PF6)2] and [RuL1L2(NCS)2], showed better photophysical properties (red-shifted metal-to-ligand charge-transfer (MLCT) transitions concomitant with enhanced molar extinction coefficients), luminescence and interesting electrochemical redox properties than those containing homonuclear ligand types [Ru(L1)3(PF6)2]. The ruthenium(II) anthracenyl functionalized phthalocyanine complexes which were obtained by electrophilic aromatic substitution reactions in the peripheral positions gave good solubility properties in various organic solvents and also showed interesting near infrared absorption and electroredox characteristics. Cyclic and square wave voltammetries of these complexes revealed major redox processes and the numbers of electron(s) transfer were determined by chronocoulometry. It was established that a mono- and/or multi-electronic transfer reactions can occur in the various ruthenium(II) complexes. The photophysical properties of some complexes showed them to be better and promising candidates in the design of chemosensors, organic light emitting diodes (OLEDs) and as photosensitizers, while their redox-active natures make them potential mediators in electron-transfer for various photochemical processes. However, due to low surface concentration and/or adsorption of some tested complexes on TiO2 semiconductor nanocrystalline particle, low currents were generated and the highest solar-to-electrical conversion efficiency recorded in this study was 0.10 percent. , Thesis (PhD) -- Faculty of Science and Agriculture, 2011
- Full Text:
- Date Issued: 2011-01
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
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
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
Octa carboxy metal (II) phthalocyanine covalent films as pH sensitive electrochemical sensor for neurotransmitters
- Authors: Moyo, Iphithuli
- Date: 2023-10-13
- Subjects: Phthalocyanines , Thin films , Neurotransmitters , Carboxylic acids
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424525 , vital:72161
- Description: Octa acyl chloride metallophthalocyanines of cobalt (CoOAClPc) and iron (FeOAClPc) were synthesized and characterized using spectroscopic and electrochemical techniques. The metallophthalocyanines were fabricated as thin films onto phenylethylamine (PEA) pre-grafted Au electrode following a covalent amide reaction. The spectroscopic and electrochemical characterization confirmed the modification of the bare Au with PEA monolayer thin film (Au-PEA) and the covalent immobilization of MOAClPc to yield Au-PEA-MOAClPc (where M is Co and Fe). The acyl chloride functional groups were hydrolyzed forming pH sensitive thin films of terminal carboxylic acid (-COOH) functional groups (Au-PEA-MOCAPc). The Au-PEA-MOCAPc electrode exhibited pH selectivity and sensitivity properties towards the negatively charged [Fe(CN)6]3-/4- and positively charged [Ru(NH3)6]2+/3+ redox probes. The Au-PEA-MOCAPc electrodes were studied for their electrocatalytic and electroanalytical properties towards the detection of catecholamine neurotransmitters; dopamine (DA), epinephrine (EP) and norepinephrine (NOR). The electrodes were further investigated in the screening of ascorbic and uric acids by means of pH sensitive functional groups. The modification process exhibited good reproducibility. Excellent electrocatalytic and electroanalytical properties were observed. The limits of detection (LOD) determined using 3σ/m was found to be 64 nM, 0.22 μM and 0.17 μM for DA, EP and NOR respectively using Au-PEA-CoOCAPc. For Au-PEA-FeOCAPc, the LOD was found to 0.24 μM, 0.45 μM and 0.34 μM for DA, EP and NOR respectively. The Au-PEA-MOCAPc electrodes screened off the strong interferents, ascorbic and uric acid. The Au-PEA-FeOCAPc electrode was evaluated for its potential application in real sample analysis using new born calf serum, and it showed excellent percentage recoveries. , Thesis (MSc) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Moyo, Iphithuli
- Date: 2023-10-13
- Subjects: Phthalocyanines , Thin films , Neurotransmitters , Carboxylic acids
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424525 , vital:72161
- Description: Octa acyl chloride metallophthalocyanines of cobalt (CoOAClPc) and iron (FeOAClPc) were synthesized and characterized using spectroscopic and electrochemical techniques. The metallophthalocyanines were fabricated as thin films onto phenylethylamine (PEA) pre-grafted Au electrode following a covalent amide reaction. The spectroscopic and electrochemical characterization confirmed the modification of the bare Au with PEA monolayer thin film (Au-PEA) and the covalent immobilization of MOAClPc to yield Au-PEA-MOAClPc (where M is Co and Fe). The acyl chloride functional groups were hydrolyzed forming pH sensitive thin films of terminal carboxylic acid (-COOH) functional groups (Au-PEA-MOCAPc). The Au-PEA-MOCAPc electrode exhibited pH selectivity and sensitivity properties towards the negatively charged [Fe(CN)6]3-/4- and positively charged [Ru(NH3)6]2+/3+ redox probes. The Au-PEA-MOCAPc electrodes were studied for their electrocatalytic and electroanalytical properties towards the detection of catecholamine neurotransmitters; dopamine (DA), epinephrine (EP) and norepinephrine (NOR). The electrodes were further investigated in the screening of ascorbic and uric acids by means of pH sensitive functional groups. The modification process exhibited good reproducibility. Excellent electrocatalytic and electroanalytical properties were observed. The limits of detection (LOD) determined using 3σ/m was found to be 64 nM, 0.22 μM and 0.17 μM for DA, EP and NOR respectively using Au-PEA-CoOCAPc. For Au-PEA-FeOCAPc, the LOD was found to 0.24 μM, 0.45 μM and 0.34 μM for DA, EP and NOR respectively. The Au-PEA-MOCAPc electrodes screened off the strong interferents, ascorbic and uric acid. The Au-PEA-FeOCAPc electrode was evaluated for its potential application in real sample analysis using new born calf serum, and it showed excellent percentage recoveries. , Thesis (MSc) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
- «
- ‹
- 1
- ›
- »