Electrode surface modification using metallophthalocyanines and metal nanoparticles : electrocatalytic activity
- Authors: Maringa, Audacity
- Date: 2015
- Subjects: Phthalocyanines , Nanoparticles , Electrocatalysis , Scanning electron microscopy , X-ray photoelectron spectroscopy , Electrochemistry , Scanning electrochemical microscopy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4541 , http://hdl.handle.net/10962/d1017921
- Description: Metallophthalocyanines and metal nanoparticles were successfully synthesized and applied for the electrooxidation of amitrole, nitrite and hydrazine individually or when employed together. The synthesized materials were characterized using the following techniques: predominantly scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electrochemistry and scanning electrochemical microscopy (SECM). Different electrode modification methods were used to modify the glassy carbon substrates. The methods include adsorption, electrodeposition, electropolymerization and click chemistry. Modifying the glassy carbon substrate with MPc (electropolymerization) followed by metal nanoparticles (electrodeposition) or vice versa, made a hybrid modified surface that had efficient electron transfer. This was confirmed by electrochemical impedance studies with voltammetry measurements having lower detection potentials for the analytes. This work also describes for the first time the micropatterning of the glassy carbon substrate using the SECM tip. The substrate was electrografted with 4-azidobenzenediazonium salt and then the click reaction was performed using ethynylferrocene facilitated by Cu⁺ produced at the SECM tip. The SECM imaging was then used to show the clicked spot.
- Full Text:
- Date Issued: 2015
- Authors: Maringa, Audacity
- Date: 2015
- Subjects: Phthalocyanines , Nanoparticles , Electrocatalysis , Scanning electron microscopy , X-ray photoelectron spectroscopy , Electrochemistry , Scanning electrochemical microscopy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4541 , http://hdl.handle.net/10962/d1017921
- Description: Metallophthalocyanines and metal nanoparticles were successfully synthesized and applied for the electrooxidation of amitrole, nitrite and hydrazine individually or when employed together. The synthesized materials were characterized using the following techniques: predominantly scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electrochemistry and scanning electrochemical microscopy (SECM). Different electrode modification methods were used to modify the glassy carbon substrates. The methods include adsorption, electrodeposition, electropolymerization and click chemistry. Modifying the glassy carbon substrate with MPc (electropolymerization) followed by metal nanoparticles (electrodeposition) or vice versa, made a hybrid modified surface that had efficient electron transfer. This was confirmed by electrochemical impedance studies with voltammetry measurements having lower detection potentials for the analytes. This work also describes for the first time the micropatterning of the glassy carbon substrate using the SECM tip. The substrate was electrografted with 4-azidobenzenediazonium salt and then the click reaction was performed using ethynylferrocene facilitated by Cu⁺ produced at the SECM tip. The SECM imaging was then used to show the clicked spot.
- Full Text:
- Date Issued: 2015
Metallophthalocyanine-gold nanoparticle conjugates for photodynamic antimicrobial chemotherapy
- Mthethwa, Thandekile Phakamisiwe
- Authors: Mthethwa, Thandekile Phakamisiwe
- Date: 2015
- Subjects: Nanochemistry , Phthalocyanines , Photochemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4543 , http://hdl.handle.net/10962/d1017923
- Description: This thesis presents the synthesis of neutral and cationic metallophthalocyanines and their gold nanoparticles conjugates. The spectroscopic characterization of these compounds is presented herein. The studies presented in this work shows that the conjugation of gold nanoparticles influenced both photophysical and photochemical properties. Gold nanoparticles were found to enhance the singlet oxygen quantum yield while lowering the fluorescence quantum yields. This work also looks at the effect of anisotropic gold nanoparticles such as nanorods and bipyramids on the photophysical behaviour of the metallophthalocyanines. The effect of the size of the gold nanorods was investigated herein. The results show that photophysical and photochemical properties can be influenced by both size and shape of the nanoparticles. Physical characterization about the loading of nanoparticles was also looked into. Parameters such as the surface area, the number of surface atoms, the number of atoms as well as the number of nanoparticles loaded on the surface of the phthalocyanines were studied. The self-assembled monolayers formed by phthalocyanines on gold surfaces were studied using the X-ray photoelectron spectroscopy (XPS). The gold nanoparticles synthesized herein include both organic and water soluble, different capping agents (citrate, tetraammonium bromide (TAOBr) and cetrimethylammonium bromide (CTAB). The concentration of the gold nanoparticles was measured on the inductively coupled plasma (ICP) and their size and shape were obtained from the transmission electron microscopy (TEM) images. A cationic aluminium phthalocyanine and its conjugates were used for photoinactivation of bacteria and fungi. The results show significant reduction and higher activity in the presence of gold nanoparticles, especially nanorods. A small chapter in this work presents an attempted work on the binding of metallothionein protein with protophorphyrin (IX). The pH and concentration dependent binding studies were investigated
- Full Text:
- Date Issued: 2015
- Authors: Mthethwa, Thandekile Phakamisiwe
- Date: 2015
- Subjects: Nanochemistry , Phthalocyanines , Photochemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4543 , http://hdl.handle.net/10962/d1017923
- Description: This thesis presents the synthesis of neutral and cationic metallophthalocyanines and their gold nanoparticles conjugates. The spectroscopic characterization of these compounds is presented herein. The studies presented in this work shows that the conjugation of gold nanoparticles influenced both photophysical and photochemical properties. Gold nanoparticles were found to enhance the singlet oxygen quantum yield while lowering the fluorescence quantum yields. This work also looks at the effect of anisotropic gold nanoparticles such as nanorods and bipyramids on the photophysical behaviour of the metallophthalocyanines. The effect of the size of the gold nanorods was investigated herein. The results show that photophysical and photochemical properties can be influenced by both size and shape of the nanoparticles. Physical characterization about the loading of nanoparticles was also looked into. Parameters such as the surface area, the number of surface atoms, the number of atoms as well as the number of nanoparticles loaded on the surface of the phthalocyanines were studied. The self-assembled monolayers formed by phthalocyanines on gold surfaces were studied using the X-ray photoelectron spectroscopy (XPS). The gold nanoparticles synthesized herein include both organic and water soluble, different capping agents (citrate, tetraammonium bromide (TAOBr) and cetrimethylammonium bromide (CTAB). The concentration of the gold nanoparticles was measured on the inductively coupled plasma (ICP) and their size and shape were obtained from the transmission electron microscopy (TEM) images. A cationic aluminium phthalocyanine and its conjugates were used for photoinactivation of bacteria and fungi. The results show significant reduction and higher activity in the presence of gold nanoparticles, especially nanorods. A small chapter in this work presents an attempted work on the binding of metallothionein protein with protophorphyrin (IX). The pH and concentration dependent binding studies were investigated
- Full Text:
- Date Issued: 2015
Nonlinear optical studies of phthalocyanines and their conjugates with nanomaterials
- Authors: Sanusi, Sikiru Olukayode
- Date: 2015
- Subjects: Phthalocyanines , Nonlinear optics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4545 , http://hdl.handle.net/10962/d1017925
- Description: A number of metallophthalocyanines (MPcs) and metal-free phthalocyanines (H₂Pcs) have been synthesized and characterized using various characterization tools such as ¹H-NMR, TOF mass spectrometry, FT-IR, UV-visible spectrophotometry and CHNS elemental analysis. Some of the MPcs were covalently linked to nanomaterials such as silica nanoparticles (SiNPs), single-walled carbon nanotubes (SWCNTs), magnetite nanoparticles (MNPs) and quantum dots (QDs), or embedded in polymer thin-films using poly(methyl methacrylate) (PMMA) and poly(acrylic acid) (PAA) as the polymer sources. The phthalocyanine-nanomaterial composites (Pc-NMCs) were characterized with FT-IR, UV-visible spectrophotometry, transmission electron microscopy (TEM), thermogravimetry analysis and X-ray diffractometry. The nonlinear optical (NLO) properties (using the open-aperture Z-scan technique) of the MPcs and the Pc-NMCs were investigated. In general, most of the investigated MPcs showed good optical limiting behaviors, except for a few, like the non-peripherally-substituted 2-pyridyloxy phthalocyanines, which showed inhibited NLO response as a result of the ring-strain effects. The absence of a metal center was found to greatly reduce the inherent high nonlinearities expected of some of the phthalocyanine complexes. The octaphenoxy derivatives (61a – 61e) were found to exhibit reverse saturable absorption (RSA) that depends on the singlet-singlet transitions, hence making them less reliable optical limiters. The optical limiting properties of the MPcs were improved in the presence of nanomaterials such as the QDs, MNPs and SWCNTs, with MPc-QDs showing the best optical limiting behavior of the three. SiNPs have no significant effect on the optical limiting behavior of the MPcs. The optical limiting properties of the MPcs were greatly enhanced in the presence of PMMA or PAA polymers. The PAA polymer showed better optical limiting behavior compared to PMMA
- Full Text:
- Date Issued: 2015
- Authors: Sanusi, Sikiru Olukayode
- Date: 2015
- Subjects: Phthalocyanines , Nonlinear optics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4545 , http://hdl.handle.net/10962/d1017925
- Description: A number of metallophthalocyanines (MPcs) and metal-free phthalocyanines (H₂Pcs) have been synthesized and characterized using various characterization tools such as ¹H-NMR, TOF mass spectrometry, FT-IR, UV-visible spectrophotometry and CHNS elemental analysis. Some of the MPcs were covalently linked to nanomaterials such as silica nanoparticles (SiNPs), single-walled carbon nanotubes (SWCNTs), magnetite nanoparticles (MNPs) and quantum dots (QDs), or embedded in polymer thin-films using poly(methyl methacrylate) (PMMA) and poly(acrylic acid) (PAA) as the polymer sources. The phthalocyanine-nanomaterial composites (Pc-NMCs) were characterized with FT-IR, UV-visible spectrophotometry, transmission electron microscopy (TEM), thermogravimetry analysis and X-ray diffractometry. The nonlinear optical (NLO) properties (using the open-aperture Z-scan technique) of the MPcs and the Pc-NMCs were investigated. In general, most of the investigated MPcs showed good optical limiting behaviors, except for a few, like the non-peripherally-substituted 2-pyridyloxy phthalocyanines, which showed inhibited NLO response as a result of the ring-strain effects. The absence of a metal center was found to greatly reduce the inherent high nonlinearities expected of some of the phthalocyanine complexes. The octaphenoxy derivatives (61a – 61e) were found to exhibit reverse saturable absorption (RSA) that depends on the singlet-singlet transitions, hence making them less reliable optical limiters. The optical limiting properties of the MPcs were improved in the presence of nanomaterials such as the QDs, MNPs and SWCNTs, with MPc-QDs showing the best optical limiting behavior of the three. SiNPs have no significant effect on the optical limiting behavior of the MPcs. The optical limiting properties of the MPcs were greatly enhanced in the presence of PMMA or PAA polymers. The PAA polymer showed better optical limiting behavior compared to PMMA
- Full Text:
- Date Issued: 2015
Photophysical studies of Zinc phthalocyanine-silica nanoparticles conjugates
- Authors: Fashina, Adedayo
- Date: 2015
- Subjects: Nanoparticles , Phthalocyanines , Zinc , Silica , Photochemistry , Adsorption
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4537 , http://hdl.handle.net/10962/d1017917
- Description: This thesis reports on the synthesis and characterization of both symmetrical and asymmetrical Zinc phthalocyanine complexes. The complexes contained groups such as carboxylic, amino and alkyne for covalent grafting to the surface of silica nanoparticles. The use of symmetrical and asymmetrical complexes was geared towards comparing the non-specific binding of the symmetrical complexes to the specific binding observed in the asymmetrical complexes. The complexes were also doped within the silica matrix and compared to the surface grafted conjugates. The complexes and the conjugates were well characterized with a variety of techniques. The fluorescence lifetimes of the phthalocyanine complexes containing either terminal carboxylic groups or an alkyne group showed a mono-exponential decay while the amino containing phthalocyanine complexes gave a bi-exponential decay. A similar trend was observed for their respective conjugates. Some of the conjugates of the asymmetrical complexes showed a decrease in fluorescence lifetimes and a corresponding decrease in fluorescence quantum yields. The fluorescence quantum yields for all the symmetrical complexes studied showed either an improvement or retained the luminescence of the grafted phthalocyanine complex. Most of the conjugates showed a faster intersystem crossing time in comparison to the complexes alone. The grafted or doped conjugates containing symmetrical phthalocyanine complexes with carboxyl groups showed improvements both in fluorescence and triplet quantum yields. All the conjugates except two showed an increase in triplet lifetimes when compared to their respective phthalocyanine complexes. Optical nonlinearities of nine of the phthalocyanine complexes were studied and all the complexes showed characteristic reverse saturable absorption behavior. Complex 10 showed the most promising optical limiting behavior. The aggregation and dissolution studies of the conjugates were also carried out in a simulated biological medium and the silicon level detected was noticed to have increased with incubation time.
- Full Text:
- Date Issued: 2015
- Authors: Fashina, Adedayo
- Date: 2015
- Subjects: Nanoparticles , Phthalocyanines , Zinc , Silica , Photochemistry , Adsorption
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4537 , http://hdl.handle.net/10962/d1017917
- Description: This thesis reports on the synthesis and characterization of both symmetrical and asymmetrical Zinc phthalocyanine complexes. The complexes contained groups such as carboxylic, amino and alkyne for covalent grafting to the surface of silica nanoparticles. The use of symmetrical and asymmetrical complexes was geared towards comparing the non-specific binding of the symmetrical complexes to the specific binding observed in the asymmetrical complexes. The complexes were also doped within the silica matrix and compared to the surface grafted conjugates. The complexes and the conjugates were well characterized with a variety of techniques. The fluorescence lifetimes of the phthalocyanine complexes containing either terminal carboxylic groups or an alkyne group showed a mono-exponential decay while the amino containing phthalocyanine complexes gave a bi-exponential decay. A similar trend was observed for their respective conjugates. Some of the conjugates of the asymmetrical complexes showed a decrease in fluorescence lifetimes and a corresponding decrease in fluorescence quantum yields. The fluorescence quantum yields for all the symmetrical complexes studied showed either an improvement or retained the luminescence of the grafted phthalocyanine complex. Most of the conjugates showed a faster intersystem crossing time in comparison to the complexes alone. The grafted or doped conjugates containing symmetrical phthalocyanine complexes with carboxyl groups showed improvements both in fluorescence and triplet quantum yields. All the conjugates except two showed an increase in triplet lifetimes when compared to their respective phthalocyanine complexes. Optical nonlinearities of nine of the phthalocyanine complexes were studied and all the complexes showed characteristic reverse saturable absorption behavior. Complex 10 showed the most promising optical limiting behavior. The aggregation and dissolution studies of the conjugates were also carried out in a simulated biological medium and the silicon level detected was noticed to have increased with incubation time.
- Full Text:
- Date Issued: 2015
Photophysicochemical properties and in vitro photodynamic therapy activities of zinc phthalocyanine conjugates with biomolecules and single-walled carbon nanotubes
- Authors: Ogbodu, Racheal O
- Date: 2015
- Subjects: Photochemotherapy , Phthalocyanines , Biomolecules
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4544 , http://hdl.handle.net/10962/d1017924
- Description: The synthesis, photophysicochemcial properties, in vitro dark toxicity and photodynamic therapy (PDT) activities of different derivatives of zinc phthalocyanine (ZnPc) conjugates with biomolecules (folic acid, bovine serum albumin (BSA), ascorbic acid, uridine or spermine) and single-walled carbon nanotubes (SWCNTs) are presented in this work. The fluorescence quantum yields (ΦF) (Subscript F) of the ZnPc derivatives or ZnPc-biomolecule conjugates remained relatively the same as compared to the precursor Pcs. Slight increases were observed in the ΦF (Subscript F) values of conjugates containing substituents such as pyrene, folic acid or BSA with intrinsic fluorescence properties. The triplet quantum yield (ΦT ) (Subscript T) values for some ZnPc conjugates increases compared to the precursor ZnPcs due to extended π conjugation (for the conjugate with pyrene) and the presence of phenyl ring that support spin-orbit charge transfer intersystem crossing to triplet state. While some conjugates showed decreases in the ΦT (Subscript T) values compared to precursor ZnPcs due to the presence of substituents that could quench photo-excited state properties. The singlet oxygen quantum yield (ΦΔ ) values follow the trends of the triplet quantum yield values. The conjugates containing BSA also show increases in the ΦΔ values without corresponding increases in ΦT (Subscript T) values due to the ability of BSA to generate free radicals including singlet oxygen. The presence of SWCNTs decreases the photophysicochemcial properties of some ZnPc-SWCNT conjugates compared to the precursor ZnPcs due to photo-induced electron transfer from an excited Pc complex (electron donor) to SWCNTs (electron acceptor). However, increases were observed in some ZnPc-SWCNT conjugates as a result of fast charge recombination process due to highly short-lived radical ion pair produced. These phenomena affected the ΦF (Suscript F) values, ΦT (Suscript T) values, and the ΦΔ values. Increases or decreases in ΦT (Suscript T) values resulted in corresponding increases or decreases in ΦΔ values
- Full Text:
- Date Issued: 2015
- Authors: Ogbodu, Racheal O
- Date: 2015
- Subjects: Photochemotherapy , Phthalocyanines , Biomolecules
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4544 , http://hdl.handle.net/10962/d1017924
- Description: The synthesis, photophysicochemcial properties, in vitro dark toxicity and photodynamic therapy (PDT) activities of different derivatives of zinc phthalocyanine (ZnPc) conjugates with biomolecules (folic acid, bovine serum albumin (BSA), ascorbic acid, uridine or spermine) and single-walled carbon nanotubes (SWCNTs) are presented in this work. The fluorescence quantum yields (ΦF) (Subscript F) of the ZnPc derivatives or ZnPc-biomolecule conjugates remained relatively the same as compared to the precursor Pcs. Slight increases were observed in the ΦF (Subscript F) values of conjugates containing substituents such as pyrene, folic acid or BSA with intrinsic fluorescence properties. The triplet quantum yield (ΦT ) (Subscript T) values for some ZnPc conjugates increases compared to the precursor ZnPcs due to extended π conjugation (for the conjugate with pyrene) and the presence of phenyl ring that support spin-orbit charge transfer intersystem crossing to triplet state. While some conjugates showed decreases in the ΦT (Subscript T) values compared to precursor ZnPcs due to the presence of substituents that could quench photo-excited state properties. The singlet oxygen quantum yield (ΦΔ ) values follow the trends of the triplet quantum yield values. The conjugates containing BSA also show increases in the ΦΔ values without corresponding increases in ΦT (Subscript T) values due to the ability of BSA to generate free radicals including singlet oxygen. The presence of SWCNTs decreases the photophysicochemcial properties of some ZnPc-SWCNT conjugates compared to the precursor ZnPcs due to photo-induced electron transfer from an excited Pc complex (electron donor) to SWCNTs (electron acceptor). However, increases were observed in some ZnPc-SWCNT conjugates as a result of fast charge recombination process due to highly short-lived radical ion pair produced. These phenomena affected the ΦF (Suscript F) values, ΦT (Suscript T) values, and the ΦΔ values. Increases or decreases in ΦT (Suscript T) values resulted in corresponding increases or decreases in ΦΔ values
- Full Text:
- Date Issued: 2015
Phthalocyanine-nanoparticle conjugates for photodynamic therapy of cancer and phototransformation of organic pollutants
- Authors: Khoza, Phindile Brenda
- Date: 2015
- Subjects: Phthalocyanines , Nanoparticles , Photochemotherapy , Cancer -- Chemotherapy , Zinc oxide , Photocatalysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4538 , http://hdl.handle.net/10962/d1017918
- Description: The synthesis and extensive spectroscopical characterization of novel phthalocyanines are reported. The new compounds were characterized by elemental analysis, FT-IR, ¹HNMR, mass spectrometry and UV–Vis spectroscopy. The new phthalocyanines showed remarkable photophysicochemical behaviour. The novel phthalocyanines were then conjugated to nanoparticles, silver and ZnO. The coupling of the novel Pcs to nanoparticles was through covalent bonding and ligand exchange. These conjugates were supported onto electrospun polystyrene fibers and chitosan microbeads for use as photocatalysts. The efficiency of the immobilized Pcs and Pc-nanoparticles was assessed by the phototrasfromation of organic pollutants, methyl orange and Rhodamine 6G as model dyes. Upon conjugating phthalocyanines to nanoparticles, there was a great increase in the rate of photodegradation of the model dyes. The photodynamic activity of the novel phthalocyanines upon conjugating to nanoparticles and selected targeting agents is also reported. The targeting agents employed in this study are folic acid and polylysine. Conjugating the phthalocyanines to folic acid or polylysine improved the solubility of the phthalocyanines in aqueous media. The potency of the conjugates was investigated on breast (MCF-7), prostate and melanoma cancer cell lines. The phthalocyanines showed no toxicity in the absence of light. However, upon illumination, a concentration dependent cellular decrease was observed.
- Full Text:
- Date Issued: 2015
- Authors: Khoza, Phindile Brenda
- Date: 2015
- Subjects: Phthalocyanines , Nanoparticles , Photochemotherapy , Cancer -- Chemotherapy , Zinc oxide , Photocatalysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4538 , http://hdl.handle.net/10962/d1017918
- Description: The synthesis and extensive spectroscopical characterization of novel phthalocyanines are reported. The new compounds were characterized by elemental analysis, FT-IR, ¹HNMR, mass spectrometry and UV–Vis spectroscopy. The new phthalocyanines showed remarkable photophysicochemical behaviour. The novel phthalocyanines were then conjugated to nanoparticles, silver and ZnO. The coupling of the novel Pcs to nanoparticles was through covalent bonding and ligand exchange. These conjugates were supported onto electrospun polystyrene fibers and chitosan microbeads for use as photocatalysts. The efficiency of the immobilized Pcs and Pc-nanoparticles was assessed by the phototrasfromation of organic pollutants, methyl orange and Rhodamine 6G as model dyes. Upon conjugating phthalocyanines to nanoparticles, there was a great increase in the rate of photodegradation of the model dyes. The photodynamic activity of the novel phthalocyanines upon conjugating to nanoparticles and selected targeting agents is also reported. The targeting agents employed in this study are folic acid and polylysine. Conjugating the phthalocyanines to folic acid or polylysine improved the solubility of the phthalocyanines in aqueous media. The potency of the conjugates was investigated on breast (MCF-7), prostate and melanoma cancer cell lines. The phthalocyanines showed no toxicity in the absence of light. However, upon illumination, a concentration dependent cellular decrease was observed.
- Full Text:
- Date Issued: 2015
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