Photophysical and photoelectrochemical properties of water soluble metallophthalocyanines
- Authors: Masilela, Nkosiphile
- Date: 2010
- Subjects: Phthalocyanines , Electrochemistry , Photoelectrochemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4330 , http://hdl.handle.net/10962/d1004991 , Phthalocyanines , Electrochemistry , Photoelectrochemistry
- Description: This work presents the synthesis, characterization, photophysicochemical and photoelectrochemical properties of anionic octa-caboxylated (MOCPcs), tetra-sulfonated (MTSPcs) and quaternized cationic (Q(T-2-Py)MPcs) water soluble aluminium, gallium, silicon, titanium and zinc phthalocynines. The peripherally tetra-substituted cationic (Q(T-2-Py)MPcs) and anionic (MTSPcs) were found to be aggregated in aqueous media, yet the octa-carboxylated (MOCPcs) counterparts were monomeric in solution. Cremophor EL (CEL) was used as a disaggregating agent, all the aggregated complexes disaggregated partially or completely in the presence of CEL. The photophysicochemical properties of aggregated complexes were investigated both in the presence of CEL and in aqueous media of pH 11 alone. Low triplet, singlet oxygen and fluorescence quantum yield were obtained in aqueous media (especially for the aggregated complexes) but a high improvement was achieved upon addition of CEL. The gallium complexes ((OH)GaOCPc and (OH)GaTSPc) showed good photophysicochemical properties with higher triplet and singlet oxygen quantum yields. For photoelectrochemistry the (MPcs) dyes were adsorbed to nanoporous ZnO, electrodeposited in the presence of eosin Y as structure directing agent (SDA) on FTO substrates by refluxing or soaking the films in a solution containing the dye of interest such that a full surface coverage was achieved. Quaternized cationic (Q(T-2-Py)MPc) and tetrasulfonated (MTSPcs) phthalocyanines formed strong aggregates when deposited on the surface of FTO/ZnO substrate leading. High external (IPCE) and internal (APCE) quantum efficiencies of up to 50.6% and 96.7% were achieved for the OTiOCPc complex. There was a lower overall cell efficiency for quaternized and tetrasulfonated metallophthalocyanines because of the strong aggregates when they were on the surface of the electrodes. Among the studied materials, OTiOCPc gave the highest overall cell efficiency of phthalocyanine electrodeposited on ZnO of so far = 0.48%.
- Full Text:
Photophysical studies of zinc and indium tetraaminophthalocyanines in the presence of CdTe quantum dots
- Authors: Britton, Jonathan
- Date: 2010
- Subjects: Indium , Zinc , Quantum dots , Phthalocyanines , Photochemotherapy , Nonlinear optics , Nanocrystals
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4332 , http://hdl.handle.net/10962/d1004993 , Indium , Zinc , Quantum dots , Phthalocyanines , Photochemotherapy , Nonlinear optics , Nanocrystals
- Description: CdTe QDs capped with mercaptopropionic acid (MPA) and thioglycolic acid (TGA) were covalently linked to zinc and indium tetraaminophthalocyanines (TAPcs) using N-ethyl-N(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) as the coupling agents. The results presented give evidence in favour of formation of an amide bond between the MTAPc and CdTe QDs. Both the linked ZnTAPc–QD complexes and the mixture of QDs and ZnTAPc (without chemical linking) showed Förster resonance energy transfer (FRET), though the linked showed less FRET, whereas the QD interactions with InTAPc yielded no evidence of FRET. Both MTAPcs quenched the QDs emission, with quenching constants of the order of 103–104M−1, binding constants of the order of 108-1010M-1 and the number of binding sites for the MTAPc upon the QD being 2. High energy transfer efficiencies were obtained (in some cases as high as 93%), due to the low donor to acceptor distances. Lastly, both MTAPc were shown to be poor optical limiters because their imaginary third-order susceptibility (Im[χ(3)]) was of the order of 10-17-10-16 (optimal range is 10-9-10-11), the hyperpolarizability (γ) of the order of 10-37-10-36 (optimal range is 10-29-10-34) and the k values were above one but below ten.
- Full Text:
Photophysiochemical studies of d¹⁰ metallophthalocyanines and their interaction with nanoparticles
- Authors: Chidawanyika, Wadzanai Janet Upenyu
- Date: 2010
- Subjects: Nanoparticles Phthalocyanines Photochemistry Electrochemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4335 , http://hdl.handle.net/10962/d1004996
- Description: The syntheses, extensive spectroscopic characterization, photophysical and photochemical studies have been conducted for a variation of d10 metallophthaloycanines (MPcs). Comparisons have been made taking into consideration the nfluence of the central metal ion, solvent properties, substituent type and position. Coordination to heavy central metals i.e. Hg gives enhanced triplet state properties. Low symmetry metallophthalocyanine complexes were similarly haracterized and the influence of nteractions with nanoparticles on their photophysical and photochemical properties determined. The MPcs have been linked and adsorbed or mixed with nanoparticles i.e. hemically functionalized single-walled carbon nanotubes SWCNT) and mercaptocarboxylic acid capped CdTe quantum dots (QDs) and changes in the spectra accounted for with respect to the proposed conjugate structures. Distinct differences ccur for linked and adsorbed or mixed conjugates in the bsorption, infrared (IR) and Raman spectra and for thermal ravimetric decay profiles, suggesting successful formation f covalent bonds (linked) and point to structurally ifferent materials. SWCNT quench MPc fluorescence by a photoinduced electron transfer mediated process to give low fluorescence quantum yields. The QDs were used as energy transfer donors and facilitate energy transfer, through Förster resonance energy transfer (FRET) from the QDs to the MPcs. Improved FRET efficiencies were found for linked MPc-QD conjugates relative to the mixed species. Photophysicochemical properties of MPcs were, in general, improved as a result of interactions with nanoparticles.
- Full Text: