Characterization and application of phthalocyanine-magnetic nanoparticle conjugates anchored to electrospun polyamide nanofibers

This work presents the syntheses, photophysical and photochemical characterization of zinc tetracarboxyphenoxy phthalocyanine (ZnTCPPc, 3) and its gadolinium oxide nanoparticle conjugate (4). By means of spectroscopic and microscopic characterization, the conjugation of the ZnTCPPc to the silica coated gadolinium oxide nanoparticles (Si-Gd2O3 NPs, 2) through an amide bond was confirmed. The thermal stability, morphology, nanoparticle sizes and their conjugates with the Pc were studied using ThermoGravimetric Analysis (TGA), Fourier Transform Infrared spectroscopy (FTIR), Transmission Electron Microscopy (TEM) and powder X-ray diffractometry (XRD). Conjugation of ZnTCPPc to the magnetic nanoparticles, proved to have a negligible effect on the photophysical parameters of the phthalocyanine, where a slight decrease in fluorescence and triplet quantum yields and lifetimes was observed. The singlet oxygen quantum yield, however, increased slightly upon conjugation, suggesting that the overall efficiency of the ZnTCPPc as a photosensitizer had improved. Physical mixing of the ZnTCPPc and the silica-coated gadolinium nanoparticles also showed an improvement in the singlet oxygen quantum yield and triplet lifetime, also showing an enhanced efficiency for the photosensitizer and therefore photocatalysis. ZnTCPPc (3) alone and the Pc-gadolinium oxide nanoparticle conjugate (4) were therefore electrospun into nanofibers to create a solid support. The fibers were characterized and their diameter sizes and composition was studied confirming the incorporation of the phthalocyanine and gadolinium oxide nanoparticle. Increased singlet oxygen generation resulted in increased Photodegradation of the environmental pollutant Orange G and the fibers were found to be more efficient as photocatalysts compared to the photosensitizer in solution. The nanomaterial may therefore be applied to the photodegradation of Orange G

Improved photocatalytic degradation of Orange G using hybrid nanofibers

Functionalised electrospun polyamide-6 (PA-6) nanofibres incorporating gadolinium oxide nanoparticles conjugated to zinc tetracarboxyphenoxy phthalocyanine (ZnTCPPc) as the sensitizer were prepared for the photocatalytic degradation of Orange G. Fibres incorporating the phthalocyanine alone or a mixture of the nanoparticles and phthalocyanine were also generated. The singlet oxygen-generating ability of the sensitizer was shown to be maintained within the fibre mat, with the singlet oxygen quantum yields increasing upon incorporation of the magnetic nanoparticles. Consequently, the rate of the photodegradation of Orange G was observed to increase with an increase in singlet oxygen quantum yield. A reduction in the half-lives for the functionalised nanofibres was recorded in the presence of the magnetic nanoparticles, indicating an improvement in the efficiency of the degradation process

Surface modification of silica-coated gadolinium oxide nanoparticles with zinc tetracarboxyphenoxy phthalocyanine for the photodegradation of Orange G

Zinc tetracarboxyphenoxy phthalocyanine was covalently linked to Gd2O3 nanoparticles for the photocatalytic degradation of Orange G. Characterization of the composite was carried out using XRD, TEM, XPS, UV–vis spectroscopy and FT-IR spectroscopy. The composite showed improved photophysical properties over the phthalocyanine alone and the catalyst was found to be reusable. Analyses of the photodegradation rates of the azo dye indicated pseudo first-order kinetics

The synthesis and characterisation of magnetic nanoparticles and their interaction with a zinc phthalocyanine

A variety of nanoparticles (NPs), including FePt nanoparticles with Fe as the shell (2) or Pt as the shell (3), Pt NPs (4), and FePd (5) were synthesised, characterised and their effect on a zinc phthalocyanine (1) tetra-substituted with a pyridyl-oxy substituent studied using UV/Vis and fluorescence spectroscopy (including time correlated single photon counting, TCSPC). The nanoparticles were characterised using a number of techniques including UV/Vis and inductively coupled plasma-optical emission (ICP-OES) spectroscopies, transmission electron microscopy (TEM), differential scanning calorimetry (DSC), X-ray powder diffraction (XRD) and electron paramagnetic resonance (EPR) spectroscopy. Nanocomposites (NCs, 6,7) where the ZnPc (1) was used as the stabiliser, instead of oleic acid and or oleylamine, were also synthesised and characterised

Defect engineering of UiO-66 metal-organic framework (MOF) for improved hydrogen storage applications

Thesis (PhD)--Stellebosch University, 2021.ENGLISH ABSTRACT: Metal–organic frameworks (MOFs) as a relatively new class of porous crystalline materia ls have attracted much interest in many applications due to their high porosity, diverse structures, and controllable chemical structures. However, the specific geometrical morphologies, limited functions and unsatisfactory performances of pure MOFs hinder their further applicatio ns . Several modifying strategies for engineering MOF crystals have been developed based on their desired features and applications. In nature there are no "ideal crystals" with an infinite periodic repetition or ordering of the same groups of atoms in space. The structure of "real crystals" often deviates from the ideal arrangement and includes a significant density of structural irregularities or deficiencies. Crystal irregularities may arise from compositio na l inhomogeneities, and this term is often used interchangeably. By using defective technology strategies during their synthesis, crystal imperfections may be introduced into the MOF framework, thereby enhancing their performance in the envisioned applications. Defect engineering is one of the most effective approaches that one can use to change their physical and chemical features such as thermal stability, textural properties, mechanical properties and gas adsorption abilities. In order to achieve the desired changes, it is essential to control the defects, otherwise these defects may have an adverse effect on the MOFs. Therefore, it is vitally important to apply synthetic control over defects; the exact nature and concentration of the defects may be controlled by modifying the synthetic conditions and post-synthet ic modifications. Structurally characterising inherent or engineered defects is very challenging and this challenge has not been addressed substantially. This thesis explores the experimental creation of structural defects via post-synthetic modification, the role of structural defects and their relationship to gas adsorption, with emphasis on hydrogen adsorption. Through a combination of techniques, including powder X- ray diffraction (PXRD), thermogravimetric analysis (TGA), acid-base titration and Brunauer– Emmett–Teller (BET) surface area and pore size measurements, missing linkers and missing cluster defects have been identified and analysed. In Chapter 4, we seek to understand the relationship between some of the major synthetic parameters and the physicochem ic a l characteristics of UiO-66 (Universitetet i Oslo) MOF and discover a "non-defective" sampling technique for this material. The technique produces non-defective UiO-66 MOFs at a specific temperature (493 K), with the linker ratio being greater than that of the salt previously reported by Shearer et al. As described in Chapter 5, by varying the concentrations of modulator and the linker, we demonstrate that the linker vacancies can be systematically tuned, leading to significantly increased surface areas. The defects are caused by partial terephthalic acid eplacement with smaller formate groups from the formic acid modulator. The BET surface areas of the obtained samples range from 1200 to 1600 m2.g-1, and the best sample has a surface area that is about 30% higher than the theoretical value of the surface area of defect-free UiO- 66. Additionally, linker vacancies are proven to have profound effects on the gas adsorption behaviour of UiO-66 by improving the hydrogen uptake from 1.51 wt. % to 2.0 wt. % at 77 K and 1 bar. Chapters 5 and 6 include detailed studies of two conventional methods for generating defects (i.e., de novo defect technology and post-synthetic modification (PSM)) discussed in each chapter respectively. Still in chapter 5, experimental investigations are discussed that show the impact of modulator and linker concentration on H2 adsorption and thermal stability. Chapter 6 provides insight into the impact on thermal stability and adsorption properties brought about by the post-synthetic modification methods. The resultant materials typically have high surface areas, large pore volumes and structures with hierarchical pores, which makes them more practical for hydrogen storage applications.AFRIKAANSE OPSOMMING: Raadpleeg teks vir opsommingDoctora

Surface modification of silica-coated gadolinium oxide nanoparticles with zinc tetracarboxyphenoxy phthalocyanine for the photodegradation of Orange G

Zinc tetracarboxyphenoxy phthalocyanine was covalently linked to Gd2O3 nanoparticles for the photocatalytic degradation of Orange G. Characterization of the composite was carried out using XRD, TEM, XPS, UV–vis spectroscopy and FT-IR spectroscopy. The composite showed improved photophysical properties over the phthalocyanine alone and the catalyst was found to be reusable. Analyses of the photodegradation rates of the azo dye indicated pseudo first-order kinetics.Original publication is available at http://dx.doi.org/10.1016/j.molcata.2015.03.02

Investigation of the Efficacy of Dithiothreitol and Glutathione on In Vitro Fertilization of Cryopreserved Large White Boar Semen

The objectives of this study were to evaluate the properties of sperm motility and morphology under induced oxidative stress, compare the antioxidant capacity of dithiothreitol (DTT) and glutathione (GSH) following the cryopreservation of Large White boar semen, investigate the ability of cryopreserved Large White boar semen to fertilize the matured gilts oocytes and compare the efficacy of DTT and GSH antioxidants in improving the oocyte fertilization by cryopreserved Large White boar semen. The semen was collected from three Large White boars (ten ejaculates per boar) and transported (37 °C) to the laboratory. Semen freezing extenders were supplemented with 5 mM DTT, 5 mM GSH and a combination of 2.5 mM DTT + 2.5 mM GSH. A liquid nitrogen vapor method was used to freeze boar semen. Gilts’ ovaries were collected from the local abattoir and transported (37 °C) to the laboratory. The slicing method was used to retrieve the oocytes from the ovaries. Fresh semen and frozen-thawed semen were used for in vitro fertilization (IVF). For frozen-thawed semen, four treatments (control, 5 mM DTT, 5 mM GSH, and a combination of 2.5 mM DTT + 2.5 mM GSH) were used during IVF in order to evaluate the fertilizing ability of the antioxidants. The supplementation of 5 µM DTT to H2O2-treated semen significantly improved progressive motility (PM) by 14.82%. A combination of 2.5 mM DTT + 2.5 mM GSH treatment reduced percentage of sperm total motility (TM) and rapid motility (RAP) following thawing (p < 0.05). Fresh semen and a combination of 2.5 mM DTT + 2.5 mM GSH treatment recorded a higher percentage of zygotes with polyspermy (p < 0.05). The control treatment numerically recorded a high percentage of zygotes with 1 PN, while the 5 mM DTT treatment recorded a high percentage of zygotes with 2 PN