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Graphene quantum dots and their metallophthalocyanines nanoconjugates as novel photoluminescent nanosensors

  • Authors: Achadu, Ojodomo John
  • Date: 2018
  • Subjects: Quantum dots , Graphene , Phthalocyanines , Nanoconjugates , Novel photoluminescent nanosensors , Metallophthalocyanines
  • Language: English
  • Type: text , Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10962/60719 , vital:27821
  • Description: The fabrication and application of graphene quantum dots (GQDs)-based photoluminescent probes for the detection of analytes is presented. GQDs were functionalized with complexes such as metallophthalocyanines (MPcs), metal nanoparticles (Au@Ag NPs), 2,2,6,6-tetramethyl(piperidin-1-yl)oxyl (TEMPO), maleimide and thymine for the sensing of target analytes such as ascorbic acid (AA), biothiols (cysteine, homocysteine and glutathione) and mercury ion (Hg²+). The design strategy and approach was based on the quenching of the fluorescence of the GQDs upon functionalization with the above-mentioned complexes, which could be restored in the presence of the target analytes (due to their specific interaction affinity with the complexes). For the detection of AA, GQDs were covalently and/or non-covalently conjugated to TEMPO-bearing complexes to form GQDs-4A-TEMPO and GQDs-TEMPO-MPc systems with nanomolar limits of detection. For the detection of biothiols, Au@Ag NPs and maleimide-bearing complexes (MPc), which have specific affinity to interact with biothiols, were deployed. Hg²+ detection involved the use of GQDs and/or MPcs with thiol and thymine groups, respectively. In addition, a smart sensing platform was designed for the dual detection of biothiols and Hg²+ using supramolecular hybrid of polyethyleneimine functionalized-GQDs and MPc-Au@Ag conjugate. The probe could detect, in a sequential manner, Hg²+ and biothiols with high sensitivity. Results obtained from the LODs of the probes showed that GQDs sensing performances could be enhanced in the presence of MPcs. The probes designed in this work were successfully deployed in the assays of the target analytes in real samples and the recoveries obtained confirmed the analytical applicability of the probes.
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  • Date Issued: 2018

Functionalized Ru(II) polypyridines and phthalocyanines: Potential dyes for dye-sensitized solar cells(DSSCs)

  • 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
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  • Date Issued: 2011-01

Functionalized Ru(II) polypyridines and phthalocyanines: Potential dyes for dye-sensitized solar cells(DSSCs)

  • 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
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  • Date Issued: 2011-01

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

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

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

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.
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  • Date Issued: 2010

Substituent effects on the electrocatalytic activity of cobalt phthalocyanine in the presence of graphene quantum dots

  • Authors: Centane, Sixolile Sibongiseni
  • Date: 2019
  • Subjects: Phthalocyanines , Quantum dots , Electrocatalysis , Electrochemistry
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/67614 , vital:29121
  • Description: The electrocatalytic activity of metallophthalocyanines derivatives is explored. Cobalt monocarboxyphenoxy phthalocyanine (1), cobalt tetracarboxyphenoxy phthalocyanine (2), cobalt tetraaminophenoxy phthalocyanine (3) and cobalt tris-(tert-butylphenoxy) monocarboxyphenoxy phthalocyanine (4) are the phthalocyanines employed in this work. The metallophthalocyanines were employed alone as well as in the presence of the carbon based graphene quantum dots. The electrocatalytic behaviour of functionalized GQDs is also explored herein. The catalytic processes studies were conducted on a glassy carbon electrode surface. Modification of the electrode was achieved by the adsorption method. The materials were adsorbed either alone, as premixed/covalently linked GQDs/Pc conjugates or sequentially. Sequentially adsorbed electrodes involved the phthalocyanines on top or beneath GQDs. Sequentially modified electrodes where the phthalocyanine had higher currents and low detection limits than when the phthalocyanine is underneath. Premixed conjugates showed better activity than the covalently formed conjugates. The nanomaterials synthesized and used in this work were characterized using transmission electron microscopy, UV-Vis spectroscopy, dynamic light scattering, Raman spectroscopy, X-ray diffraction, Atomic Force Microscopy and X-ray photoelectron spectroscopy. The modified electrodes were characterized using cyclic voltammetry and scanning electrochemical spectroscopy. The electrocatalytic activity of the modified electrodes towards the oxidation of hydrazine was evaluated using cyclic voltammetry and chronoamperometry. Superior catalytic activity was observed for the conjugates compared to that of the individual conjugates.
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  • Date Issued: 2019

Selective and sensitive electrochemical detection of the Human Epidermal Growth Receptor 2 breast cancer biomarker, using Co (II) phthalocyanine-nanoparticle based platforms

  • Authors: Centane, Sixolile Sibongiseni
  • Date: 2024-10-11
  • Subjects: Electrochemical sensors , HER-2 protein , Breast Cancer , Biochemical markers , Phthalocyanines , Nanoparticles
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/466569 , vital:76753 , DOI https://doi.org/10.21504/10962/466570
  • Description: Breast cancer is the world’s leading cause of cancer related deaths in women worldwide. The main reason lies in its late detection, mostly in the metastatic stage resulting in poor after-therapy prognosis, despite advances in methods of diagnosis and therapy. The reason for late-stage detection, is because breast cancer like any other cancers is asymptomatic in its early stages. Significant and characterizable features present in the later stages. Furthermore, conventional methods for breast cancer detection are more useful in the identification of the phenotypic features of cancer cells that arise at a later stage of the disease. Another issue with conventional methods where cancer diagnosis is concerned is that they tend to be specialist-dependent, time consuming and costly. Thus, easy, fast and inexpensive detection methods need to be developed urgently. Biomarker-based cancer diagnosis has emerged as one of the most promising strategies for early diagnosis, monitoring disease progression, and subsequent cancer treatment. This thesis focuses on the design and development of novel electrochemical biosensor platforms towards the low cost, efficient, sensitive and simple detection of early-stage breast cancer biomarker, human epidermal growth factor 2 (HER2). The electrochemical method is preferred because of its moderate cost, rapid response, ease of operation, readily quantifiable signal as well as high sensitivity and selectivity with lower detection limits. This thesis reports on two strategies towards signal amplification and sensitive detection of HER2, namely signal based amplification and target-based amplification. The former focuses on electrode or transducer modification techniques for improved signal to noise ratio. In which case; novel nanocomposites of phthalocyanines, graphene quantum dots, gold nanoparticles and cerium oxide nanoparticles are used for electrode modification for signal amplification and biorecognition element immobilization. The biorecognition elements of choice, are an aptamer and antibody known to be specific to the HER2 antigen for an enhanced sensor sensitivity and specificity. The second strategy focuses on increasing the number of detectable targets on the electrode surface towards enhanced sensitivity, precision and sensor accuracy. In which case; the performance of the aptamer and the antibody as recognition elements was explored. Furthermore, the effect of arrangement of these recognition elements on the electrode surface is investigated and reported upon. The strategies covered in this thesis are expected to result in novel biosensor platforms that can detect the HER2 biomarker with high precision, reproducibility, sensitivity and stability; towards low cost and effective early-stage breast cancer diagnostic tools. , Thesis (PhD) -- Faculty of Science, Chemistry, 2024
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  • Date Issued: 2024-10-11

Synthesis, photochemical and photophysical properties of gallium and indium phthalocyanine derivatives

  • Authors: Chauke, Vongani Portia
  • Date: 2008
  • Subjects: Phthalocyanines , Photochemotherapy , Electrochemistry , Gallium , Indium
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4375 , http://hdl.handle.net/10962/d1005040 , Phthalocyanines , Photochemotherapy , Electrochemistry , Gallium , Indium
  • Description: The syntheses of octasubstituted and unsusbstitituted Gallium(III) chloride and indium(III) chloride phthalocyanines (GaPc and InPc), their photophysical, photochemical and nonlinear optical parameters are hereby presented. The photocatalytic oxidation of 1-hexene using the synthesized GaPc and InPc complexes as well as electrochemical characterization is also presented in this thesis. Fluorescence quantum yields do not vary much among the four Ga complexes, except for complex 21c; therefore it was concluded that the effect of substituents is not significant among them. Solvents however, had an effect on the results. Lower Φ[subscript F] values were obtained in low viscosity solvents like toluene, relative to highly viscous solvents, such as DMSO. The triplet quantum yields were found to be lower in DMSO than in DMF and toluene. The rate constants for fluorescence, intersystem crossing and internal conversion as well as fluorescence and triplet lifetimes are reported. Photodegradation and singlet oxygen quantum yields have also been reported. There was no clear correlation between the latter parameters. It was however established that the four gallium MPcs were stable, within the allowed stability range for phthalocyanines. High quantum yields of triplet state (Φ[subscript T] ranging from 0.70 to 0.91 in dimethysulfoxide, DMSO) and singlet oxygen generation (Φ[subscript greek capital letter delta], ranging from 0.61 to 0.79 in DMSO) were obtained. Short triplet lifetimes 50 to 60 μs were obtained in DMSO). Calculated non-linear parameters of these complexes are compared with those of the corresponding GaPc derivatives and tetrasubstituted GaPc and InPc complexes. The optical limiting threshold intensity (I[subscript lim]) values for the InPc and GaPc derivatives were calculated and compared with those of corresponding tetrasubstituted InPc and GaPc complexes. The octasubstituted were found to be better optical limiters. Photocatalytic oxidation of 1-hexene by GaPc (21a-c) and InPc (22a-c) derivatives is also presented. The photocatalytic oxidation products for 1-hexene were 1,2- epoxyhexane and 1-hexen-3-ol. The % conversion values of 1-hexene and % selectivity of 1,2-epoxyhexane were generally higher for InPc derivatives. Even though InPc derivatives showed better photocatalytic results than GaPc derivatives, the former were less stable relative to the latter. Both type I and type II mechanism were implicated in the photocatalysis mechanism.
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  • Date Issued: 2008

Development of graphene materials and phthalocyanines for application in dye-sensitized solar cells

  • Authors: Chindeka, Francis
  • Date: 2020
  • Subjects: Dye-sensitized solar cells , Graphene , Phthalocyanines , Molecular orbitals , Impedance spectroscopy
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/166092 , vital:41328
  • Description: Two sets of dye-sensitized solar cells (DSSCs) were fabricated. In the first set, dye-sensitized solar cells (DSSC) were fabricated by incorporating graphene materials as catalysts at the counter electrode. Platinum was also used as a catalyst for comparative purposes. Different phthalocyanines: hydroxyl indium tetracarboxyphenoxy phthalocyanine (1), chloro indium octacarboxy phthalocyanine (2) and dibenzoic acid silicon phthalocyanine (3) were used as dyes. Complex 3 gave the highest power conversion efficiency (η) of 3.19% when using nitrogen doped reduced graphene oxide nanosheets (NrGONS) as a catalyst at the counter electrode, and TiO2 containing rGONS at the anode. The value obtained is close to 3.8% obtained when using Pt catalyst instead of NrGONS at the cathode, thus confirming that NrGONS is a promising candidate to replace the more expensive Pt. The study also shows that placing rGONS on both the anode and cathode improves efficiency. In the second set, DSSCs were fabricated by using 2(3,5-biscarboxyphenoxy), 9(10), 16(17), 23(24)-tri(tertbutyl) phthalocyaninato Cu (4) and Zn (5) complexes as dyes on the ITO-TiO2 photoanodes containing reduced graphene oxide nanosheets (rGONS) or nitrogen-doped rGONS (NrGONS). The evaluation of the assembled DSSCs revealed that using ITO-TiO2-NrGONS-CuPc (4) photoanode had the highest fill factor (FF) and power conversion efficiency (ɳ) of 69 % and 4.36 % respectively. These results show that the asymmetrical phthalocyanine complexes (4) and (5) showed significant improvement on the performance of the DSSC compared to previous work on symmetrical carboxylated phthalocyanines with ɳ = 3.19%.
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  • Date Issued: 2020

The photophysical properties of low symmetry phthalocyanines in conjunction with quantum dots

  • Authors: D'Souza, Sarah
  • Date: 2011
  • Subjects: Phthalocyanines , Photochemistry , Zinc , Quantum dots , Spectrum analysis , Nanoparticles
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4331 , http://hdl.handle.net/10962/d1004992 , Phthalocyanines , Photochemistry , Zinc , Quantum dots , Spectrum analysis , Nanoparticles
  • Description: he synthesis, extensive spectroscopic characterization and photophysical studies of low symmetry zinc phthalocyanine have been conducted. Comparisons have been made taking into consideration the influence of the solvent properties as well as substituent type and position. Photosensitizing properties of the zinc phthalocyanine derivatives in the presence of thiol capped CdTe quantum dots (QDs) were compared. The QDs were used as energy transfer donors and to facilitate with energy transfer through Förster resonance energy transfer (FRET) from the QDs to the MPcs. The linkage of unsymmetrically substituted 4-monoaminophenoxy zinc phthalocyanine (ZnAPPc) to CdTe quantum dots capped with mercaptopropionic acid (MPA), L-cysteine (L-cys) or thioglycolic acid (TGA) has been achieved using the coupling agents ethyl-N3 dimethylaminopropyl)carbodiimide (EDC) and N-hydroxy succinimide (NHS), which facilitate formation of an amide bond to form the QD-ZnAPPc-linked complex. The formation of the amide bond was confirmed using UV-Vis, Raman and IR spectroscopies, as well as AFM (atomic force microscopy). Förster resonance energy transfer (FRET) resulted in stimulated emission of ZnAPPc in both the linked (QDZnAPPc-linked) and mixed (QD:ZnAPPc-mixed) conjugates for MPA only. The linked L-cys and TGA complexes (QD-ZnAPPc-linked) gave the largest FRET efficiencies hence showing the advantages of covalent linking. Fluorescence quantum yields of QDs were decreased in QD:ZnAPPc-mixed and QD:ZnAPPc-linked. High triplet state quantum yields were obtained for the linked QD-phthalocyanine derivatives (ZnAPPc)and monoaminozinc phthalocyanine (ZnAPc) compared to when ZnAPPc and ZnAPc were mixed with MPA QDs without a chemical bond.
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  • Date Issued: 2011

Physicochemical properties and photodynamic therapy activities of indium and zinc phthalocyanine-nanoparticle conjugates

  • Authors: Dube, Edith
  • Date: 2019
  • Subjects: Indium , Zinc , Phthalocyanines , Breast -- Cancer -- Photochemotherapy , Nanoparticles
  • Language: English
  • Type: text , Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10962/76506 , vital:30589
  • Description: The syntheses and characterization of symmetric and asymmetric Pcs functionalized at the peripheral position are reported. The Pcs contain either zinc or indium as central metals and have carboxyphenoxy, phenoxy propanoic acid, benzothiazole phenoxy, thiophine ethoxy or di-O-isopropylidene-α-D-glucopyranose as ring substituents. The Pcs were linked to NPs via an amide bond or through self-assembly. The photophysics and photochemistry of the Pcs were assessed when alone and with conjugates. All the studied Pcs showed good photophysicochemical behaviour with relatively high triplet and singlet oxygen quantum yields corresponding to their low fluorescence quantum yield. The Pcs with indium in their central cavity exhibited higher triplet and singlet oxygen quantum yields in comparison to their zinc counterparts due to the heavy–atom effect obtained from the former. Asymmetrical Pcs displayed higher triplet and singlet oxygen quantum yields than their symmetrical counterparts. The triplet quantum yield, generally increased on linkage to nanoparticles (NPs) due to the heavy–atom effect of gold and silver in NPs. The conjugates to gold nanospheres yielded higher triplet and singlet quantum yields than their gold nanotriangles counterparts due to the higher loading by the former probably encouraged by their relatively small particle size. 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. All complexes displayed poor phototoxicity with >50Îll viability at concentrations≤ 160μg/mL, however the conjugates showed<50% cell viabilityatconcentrations≤ 160μg/mLprobably due to the enhanced singlet oxygen quantum yield. The findings from this work show the importance of linking photosensitises such as phthalocyanines to metal nanoparticles for the enhancement ofsinglet oxygen quantum yield and ultimately the photodynamic effect.
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  • Date Issued: 2019

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.
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  • Date Issued: 2015

Photophysicochemical studies of phenylthio phthalocyanines interaction with gold nanoparticles and applications in dye sensitised solar cells and optical limiting

  • Authors: Forteath, Shaun
  • Date: 2012
  • Subjects: Phthalocyanines , Nanoparticles , Photochemistry
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4334 , http://hdl.handle.net/10962/d1004995 , Phthalocyanines , Nanoparticles , Photochemistry
  • Description: The syntheses, spectroscopic characterisation, photophysical and photochemical studies have been conducted for a variety of phenylthio substituted phthalocyanines (Pcs). Comparisons have been made taking into consideration the influence of the central metal ion, solvent properties and substituent type. The optical limiting properties were also determined for all the Pcs synthesised. A low-symmetry metallophthalocyanine complex was similarly characterised and the photoelectrochemical parameters determined when used as a sensitiser of nanoporous ZnO. The symmetric analogue was conjugated to gold nanoparticles to determine the influence of interactions on its photophysical properties and distinct differences occurred in the absorption and fluorescence spectra suggesting successful formation of conjugates.
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  • Date Issued: 2012

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

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

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

Synthesis, photophysics and electrochemical study of tin macrocycles

  • Authors: Khene, Mielie Samson
  • Date: 2008
  • Subjects: Electrochemistry , Photochemistry , Phthalocyanines , Macrocyclic compounds , Spectrum analysis
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4376 , http://hdl.handle.net/10962/d1005041 , Electrochemistry , Photochemistry , Phthalocyanines , Macrocyclic compounds , Spectrum analysis
  • Description: Three non-peripherally substituted tin(IV) macrocylic compounds, octahexylphthalocyaninato dichlorotin(IV) (35a), octahexyltetrabenzo-5,10,15-triazaporphyrinato dichlorotin(IV) (35b) and octadecylphthalocyaninato dichlorotin(IV) (35c) were synthesized and their photophysical and electrochemical behaviour studied. Complex (35b), containing a CH group in place of one of the aza nitrogen atom of the phthalocyanine core, shows a split Q band due to its lower symmetry. The triplet state quantum yields were found to be lower than would be expected on the basis of the heavy atom effect of tin as the central metal for phthalocyanine derivatives (35a and 35c). In contrast, (35b) shows a triplet quantum yield ΦT = 0.78. The triplet state lifetimes were solvent dependent, and were higher in THF than in toluene. Cyclic voltammetry and spectroelectrochemistry of the complexes revealed only ring based redox processes. This thesis also reports on the microwave syntheses of tetrasulphonated tin phthalocyanine and tetrasulphonated tin α,β,γ-tetrabenzcorrole. The latter was only formed at low ratios (< 1:8) of 4-sulfophthalic acid to urea. Both complexes are aggregated in aqueous media, but can be partly or fully disaggregated by the addition of Triton X-100. The SnTSTBC complex has lower triplet life times and yields, while binding constant and quenching (of bovine serum albumin) constant are lower for SnTSTBC, compared to SnTSPc. Finally Non-peripherally (α) tetra- (40) and octa-(38a) substituted dodecyl-mercapto tin(IV) phthalocyanines where synthesized and the electrochemical behavior studied. Cyclic voltammetry and spectroelectrochemistry show ring-based reductions for (38a) and (40); the former shows two ring oxidations, while the latter shows only one ring based oxidation. The adsorption kinetics of (38a) and (40) on a gold electrode have been investigated by electrochemical impedance spectroscopy (EIS). The equilibrium constant (K) for the adsorption and the Gibbs free energy ΔG(ads) of the self-assembled monolayer (SAMs) were evaluated based on the Frumkin isotherm. The interaction factor between adsorbate –adsorbate molecules is also discussed.
  • Full Text:
  • Date Issued: 2008

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

Nonlinear optical properties of Sn(IV) phthalocyanines: experimental and theoretical approach

  • Authors: Louzada, Marcel Severiano
  • Date: 2017
  • Subjects: Phthalocyanines , Nonlinear optics
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/57852 , vital:26996
  • Description: This work presents the nonlinear properties of six Sn(IV) Phthalocyanines. Three of the phthalocyanines are linked by an alkylthiol substituent and the rest are linked with a phenoxy substituent. For all six compounds non-linear optic analysis was carried out in four solvents: chloroform, toluene, dichloromethane, and tetrahydrofuran, and their differences were recorded. Calculation of the linear, singlet excited, triplet excited and two photon absorption cross-sections were also carried out and the results compared. To form a comparison the first order hyperpolarizabilities, DFT calculations were also performed and the results compared to see if the behaviour between the two properties can be predicted using DFT.
  • Full Text:
  • Date Issued: 2017

Evaluation of metallophthalocyanine functionalized photocatalytic asymmetric polymer membranes for pollution control and antimicrobial activity

  • Authors: Mafukidze, Donovan Musizvinoda Chidyamurimi
  • Date: 2021
  • Subjects: Photosensitizing compounds , Water -- Purification -- Photocatalysis , Phthalocyanines , Polymeric membranes , Porphyrins
  • Language: English
  • Type: text , Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10962/171357 , vital:42052 , 10.21504/10962/171357
  • Description: The conceptualisation of photosensitizing water treatment polymer membranes using phthalocyanine based photosensitizers is reported in this thesis. The key to successful preparation of stable photoactive polymer membranes was established as the covalent anchorage of the photosensitizer to a polymer, which was proven by singlet oxygen generation by the membranes without photosensitizer deterioration. Despite this limitation, the covalent linkage-incapable unsubstituted zinc (II) phthalocyanine (complex 2) was applied as a nanoconjugate of graphene quantum dots (2π(GQDs)). 2π(GQDs) was formed through π-π stacking, and was then covalently anchored, as a proof of concept. This concept was also applied to 2-(4-carboxyphenoxy) phthalocyaninato zinc (II) (complex 3) which is capable of covalent linkage but proved to deteriorate the efficiency of singlet oxygen formation with comparison to the covalent conjugates. Singlet oxygen generation by functionalized polymer membranes rendered them photocatalytic in the degradation of organic pollutants and microorganisms in water. Organic pollutant degradation capability was exemplified by 2π(GQDs) and a porphyrin-phthalocyanine heterodyad (complex 10) functionalized membranes (2π(GQDs)-memb and 10-memb respectively), where a MPc loading of approximately 0.139 μmol MPc/g of membrane was able to achieve a 4-chlorophenol degradation rate of 3.77 × 10−6 mol L−1 min−1 in a second order reaction with an initial 4-chlorophenol concentration of 3.24 × 10−4 mol L−1 for 2π(GQDs)-memb as an example. Antibacterial studies against S.aureus using a quaternized MPc and conjugates of silver triangular nanoprisms with zinc (II) and indium (III) MPcs showed note-worthy improvements in photodynamic antimicrobial chemotherapy (PACT) activity in comparison to the unquaternized MPc precursor, and the free zinc and indium MPcs respectively. Functionalization of polymer membranes with these higher activity photosensitizers translated to the formation of potentially superior biological fouling resistant membranes. The use of porphyrin-phthalocyanine polynuclei arrays (complex 10) in polymer membrane functionalization resulted in the use of a wider wavelength range (white light). The findings from this work as a whole, thus presents the potential applicability of phthalocyanine functionalized polymer membranes in water treatment technology.
  • Full Text:
  • Date Issued: 2021
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