Nonlinear optical behavior of lanthanide phthalocyanines and their conjugates with a selection of nanomaterials
- Authors: Sekhosana, Kutloano Edward
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/4580 , vital:20695
- Description: This thesis presents novel asymmetrical and symmetrical lanthanide phthalocyanines (Pcs) characterized using a number techniques including proton nuclear magnetic resonance, electron spin resonance, time correlated single photon counting, FTIR spectrometry, MALDI-TOF mass spectrometry, UV-Vis spectrometry, Raman spectroscopy and CHNS elemental analysis. The design of theses lanthanide Pcs takes the form of mononuclear, binuclear, trinuclear, bis- and tris(phthalocyanines). Nanomaterials such as zinc oxide nanoparticles (ZnO NPs), multi-walled carbon nanotubes (MWCNTs) and graphene oxide nanosheets (GONS) (oxidized and reduced) were employed for covalent linkage to mono- and binuclear phthalocyanines as conjugates. Transmission electron microscopy was used to characterize ZnO NPs, MWCNTs and GONS alone and when linked to lanthanide Pcs. Lanthanide Pcs alone and when linked to ZnO NPs, MWCNTs and GONS where embedded in polymers such as poly (methyl methacrylate) (PMMA), poly (bisphenol A carbonate) (PBC) and poly (acrylic acid) (PAA) for thin film preparation. The thickness of the thin films was determined by utilization of the knife edge attachment of the A Bruker D8 Discover X-ray diffraction (XRD). Optical limiting properties of lanthanide Pcs alone and as conjugates in solution and when incorporated into polymers were determined by employing a Z-scan technique. It emerged that low symmetry lanthanide Pcs (19, 20 and 21), the blue forms of bis(phthalocyanines) (only in solution; 24 and 28) as well as tris(phthalocyanines) (30 and 31) exhibit low limiting threshold (Ilim) values in solution and thin films (particularly PBC and PAA). The low limiting threshold values make these lanthanide Pcs reliable optical limiters.
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- Date Issued: 2017
Nonlinear optical responses of phthalocyanines in the presence of nanomaterials or when embedded in polymeric materials
- Authors: Bankole, Owolabi Mutolib
- Date: 2017
- Subjects: Phthalocyanines , Phthalocyanines -- Optical properties , Alkynes , Triazoles , Nonlinear optics , Photochemistry , Complex compounds , Amines , Mercaptopyridine
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/45794 , vital:25548
- Description: This work describes the synthesis, photophysical and nonlinear optical characterizations of alkynyl Pcs (1, 2, 3, 8 and 9), 1,2,3-triazole ZnPc (4), mercaptopyridine Pcs (5, 6 and 7) and amino Pcs (10 and 11). Complexes 1, 2, 4, 7, 8, 9 and 11 were newly synthesized and characterized using techniques including 1H-NMR, MALDI-TOF, UV-visible spectrophotometry, FTIR and elemental analysis. The results of the characterizations were in good agreement with their molecular structures, and confirmed the purity of the new molecules. Complex 10 was covalently linked to pristine graphene (GQDs), nitrogen- doped (NGQDs), and sulfur-nitrogen co-doped (SNGQDs) graphene quantum dots; gold nanoparticles (AuNPs); poly(acrylic acid) (PAA); Fe3O4@Ag core-shell and Fe3O4- Ag hybrid nanoparticles via covalent bonding. Complex 11 was linked to Agx Auy alloy nanoparticles via NH2-Au and/or Au-S bonding, 2 and 3 were linked to gold nanoparticles (AuNPs) via clicked reactions. Evidence of successful conjugation of 2, 3, 10 and 11 to nanomaterials was revealed within the UV-vis, EDS, TEM, XRD and XPS spectra. Optical limiting (OL) responses of the samples were evaluated using open aperture Z-scan technique at 532 nm and 10 ns radiation in solution or when embedded in polymer mixtures. The analyses of the Z-scan data for the studied samples did fit to a two-photon absorption mechanism (2PA), but the Pcs and Pc-nanomaterial or polymer composites also possess the multi-photon absorption mechanisms aided by the triplet-triplet population to have reverse saturable absorption (RSA) occur. Phthalocyanines doped in polymer matrices showed larger nonlinear absorption coefficients (ßeff), third-order susceptibility (Im [x(3)]) and second-order hyperpolarizability (y), with an accompanying low intensity threshold (Ium) than in solution. Aggregation in DMSO negatively affected NLO behaviour of Pcs (8 as a case study) at low laser power, and improved at relatively higher laser power. Heavy atom-substituted Pcs (6) enhanced NLO and OL properties than lighter atoms such as 5 and 7. Direct relationship between enhanced photophysical properties and nonlinear effects favoured by excited triplet absorption of the 2, 3, 10 and 11 in presence of nanomaterials was established. Major factor responsible for the enhanced nonlinearities of 10 in the presence of NGQDs and SNGQDs were fully described and attributed to the surface defects caused by the presence of heteroatoms such as nitrogen and sulfur. The studies showed that phthalocyanines-nanomaterial composites were useful in applications such as optical switching, pulse compressor and laser pulse narrowing.
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- Date Issued: 2017
Synthesis of indium and lead phthalocyanine as photocatalysts for photodynamic antimicrobial chemotherapy and photo-oxidation of pollutants
- Authors: Oluwole, Oluyinka David
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/5293 , vital:20805
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- Date Issued: 2017
Synthesis of indium and lead phthalocyanine as photocatalysts for photodynamic antimicrobial chemotherapy and photo-oxidation of pollutants
- Authors: Osifeko, Olawale L
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/5221 , vital:20790
- Description: This thesis explores the synthesis of metallophthalocyanines as potential photosensitizers for application in photodynamic antimicrobial chemotherapy and phototransformation of environmental pollutants. The metallophthalocyanines containing amino substituent were conjugated with magnetic nanoparticle and semiconductor quantum dots via an amide bond and by chemisorption onto gold nanoparticles surface. Techniques such as time-resolved fluorescence measurements, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), elemental analysis, fourier transform infrared (FTIR), nuclear magnetic resonance (¹H, ¹³C, and cozy of symmetrical phthalocyanine), electronic spectroscopy, as well as mass spectroscopy were employed to characterize all metallophthalocyanines. Quarternized pyridyloxy substituted phthalocyanine and asymmetric (AB3) metallophthalocyanines were embedded in electrospun polystyrene fiber. General trends are described for quantum yields of fluorescence, triplet, singlet oxygen and photodegradation as well as lifetimes of fluorescence and triplet state of the compounds. There is an increase in triplet quantum yield for Pcs in the presence of gold nanoparticles (AuNPs) and semiconductor quantum dots (QDs), but not in the presence of magnetic nanoparticles (MNPs). Photodynamic inactivation of Escherichia coli with the quarternized photosensitizers at low concentrations totally inactivate the bacteria compared to non-charged photosensitiser. Also, a similar trend was observed for the magnetic nanoparticles conjugates. Photooxidations of bisphenol A and 4-chlorophenol were carried out in this study using two asymmetric Indium(III) phthalocyanines photosensitizers. The photooxidation reactions were compared with those of a symmetrical indium(III) phthalocyanines containing four quaternized 4-pyridyloxy substituents. The complexes were embedded in electrospun polystyrene fiber for heterogeneous photocatalysis. The immobilized photosensitizers possess good singlet oxygen generation potentials in aqueous media. The asymmetrical phthalocyanine containing 4-pyridylsulfanyl and one aminophenoxy showed the best photocatalytic behavior.
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- Date Issued: 2017
The effects of graphene and other nanomaterials on the electrocatalytic behaviour of phthalocyanines
- Authors: Shumba, Munyaradzi
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/37952 , vital:24712
- Description: Carbon based nanomaterials, gold nanorods and metallophthalocyanine nanoconjugates have been developed for electrocatalysis. Carbon based nanomaterials used are multiwalled carbon nanotubes, pristine graphene oxide nanosheets, nitrogen, boron, sulphur, phosphorus doped graphene oxide nanosheets. Cobalt phthalocyanine (CoPc), cobalt tetra aminophenoxy phthalocyanine (CoTAPc), cobalt tetra aminophenoxy phthalocyanine (CoTAPhPc), cobalt mono carboxyphenoxy phthalocyanine (CoMCPhPc) and cobalt tetra carboxyphenoxy phthalocyanine (CoTCPhPc) are the phthalocyanines employed in this work. Metallophthalocyanines were employed either in their bulk form or in their nanosized form. Electrode modification by these nanomaterials was either done sequentially, premixed or linked nanoconjugates. In all sequential modification, phthalocyanines were employed on top of other nanomaterials. Sequentially modified electrodes gave higher detection currents than both premixed and covalently bonded nanoconjugates. The nanomaterials reported here were characterised by transmission electron microscopy, Raman spectroscopy, time of flight secondary ion mass spectrometry, and X-ray diffraction among other techniques. The modified electrodes were further characterised by scanning electron microscopy, scanning electrochemical microscopy, X-ray photoelectron spectroscopy and cyclic voltammetry, while square wave, linear scan and cyclic voltammetry, rotating disc electrode and chronoamperometry have been used to evaluate the electrocatalytic behaviour of the previously mentioned towards either oxidation or reduction of L-cysteine and/or hydrogen peroxide respectively. Generally, the nanoconjugates resulted in superior catalytic performance compared to the performance of individual nanomaterials. Zinc octacarboxy phthalocyanine (ZnOCPc) conjugated to either GONS or rGONS were employed to compare electrocatalytic detection of hydrogen peroxide to its luminescence sensing.
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- Date Issued: 2017