20 research outputs found
Synthesis and characterization of silver nanoparticles for photovoltaic application
No full textMagister Scientiae - MScWith an increase in the amount of harmful carbon emissions in the atmosphere as well as a decrease in the availability of fossil fuels, there is a relatively high demand for alternate energy devices. Solar cells have become an alternative option in aid of leading the way for clean energy; however these devices are relatively expensive and have an efficiency that is relatively low in comparison to that of fossil fuelled energy. As a result the cost of the solar cell needs to be reduced by reducing the amount of silicon used in order to compete with fossil fuelled devices; however this decrease would lead to a decrease in efficiency. In recent years silver nanoparticles have been extensively researched as a result of its extraordinary optical, electrical, catalytic, magnetic and antibacterial properties. As a result of these properties, the nanoparticles may be applied to many research areas such as photovoltaics, catalysis and medical fields. The optical properties of silver nanoparticles may thus be exploited in order to increase absorption and in turn the efficiency of the solar cell devices. This study focuses on the optimization of the polyol synthesis to possibly obtain uniformly dispersed silver nanoparticles. The silver nanoparticles would then be incorporated onto amorphous silicon thin films, deposited by hot wire chemical vapour deposition, by spraying a suspension of the silver nanoparticles onto the thin films. The silver nanoparticles were viii characterized by Ultra Violet Visible Spectroscopy (UV-VIS), High Resolution Transmission Electron Microscopy, X-ray Diffraction, and Thermogravimetric Analysis. The thin films with the incorporated silver nanoparticles were characterized by UV-VIS, and High Resolution Scanning Electron Microscopy. It was shown that silver nanoparticles with various morphologies were produced by the polyol synthesis and may be used to enhance light trapping of thin film
photovoltaic devices
Synthesis and characterization of silver nanoparticles for photovoltaic application
No full textMagister Scientiae - MScWith an increase in the amount of harmful carbon emissions in the atmosphere as well as a decrease in the availability of fossil fuels, there is a relatively high demand for alternate energy devices. Solar cells have become an alternative option in aid of leading the way for clean energy; however these devices are relatively expensive and have an efficiency that is relatively low in comparison to that of fossil fuelled energy. As a result the cost of the solar cell needs to be reduced by reducing the amount of silicon used in order to compete with fossil fuelled devices; however this decrease would lead to a decrease in efficiency. In recent years silver nanoparticles have been extensively researched as a result of its extraordinary optical, electrical, catalytic, magnetic and antibacterial properties. As a result of these properties, the nanoparticles may be applied to many research areas such as photovoltaics, catalysis and medical fields. The optical properties of silver nanoparticles may thus be exploited in order to increase absorption and in turn the efficiency of the solar cell devices. This study focuses on the optimization of the polyol synthesis to possibly obtain uniformly dispersed silver nanoparticles. The silver nanoparticles would then be incorporated onto amorphous silicon thin films, deposited by hot wire chemical vapour deposition, by spraying a suspension of the silver nanoparticles onto the thin films. The silver nanoparticles were viii characterized by Ultra Violet Visible Spectroscopy (UV-VIS), High Resolution Transmission Electron Microscopy, X-ray Diffraction, and Thermogravimetric Analysis. The thin films with the incorporated silver nanoparticles were characterized by UV-VIS, and High Resolution Scanning Electron Microscopy. It was shown that silver nanoparticles with various morphologies were produced by the polyol synthesis and may be used to enhance light trapping of thin film
photovoltaic devices
Oligomerization of higher olefins
No full textIncludes abstract.Includes bibliographical references.A series of new substituted cyclopentadienyl ligands and their chromium complexes were successfully synthesised and characterised using a wide range of analytical and spectroscopic techniques such as NMR, mass spectrometry, elemental analysis and melting points.The ligands were then tested for the oligomerization of ethylene and 1-hexene. The chromium complexes were tested for the oligomerization of 1-hexene
Biosynthesis of silver nanoparticles using bitter leave (Veronica amygdalina) for antibacterial activities
No full textA green and facile biosynthesis of silver nanoparticles (SNPs) using dry Bitter leaves (DBL) (Vernonia amygdalina) aqueous extract as a capping and reducing agent was demonstrated in this work. The effect of the precursor's concentration on the size and shape of SNPs and its antibacterial activity is evaluated. The synthesized DBL_SNPs were characterized by using UV–visible spectroscopy, Fourier transforms infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and transmission electron microscopy (TEM)
Synthesis and characterization of nanofluids for cooling applications
No full textPhilosophiae Doctor - PhDLow thermal conductivity is a primary limitation in the development of energy-efficient heat transfer fluids that are required in numerous industrial sectors. Recently submicron and high aspect ratio particles (nanoparticles and nanotubes) were introduced into the heat transfer fluids to enhance the thermal conductivity of the resulting nanofluids. The aim of this project was to investigate the physico-chemical properties of nanofluids synthesized using submicron and high aspect ratio particles suspended in heat transfer fluids.South Afric
Synthesis and characterization of nanofluids for cooling applications
No full textPhilosophiae Doctor - PhDLow thermal conductivity is a primary limitation in the development of energy-efficient heat transfer fluids that are required in numerous industrial sectors. Recently submicron and high aspect ratio particles (nanoparticles and nanotubes) were introduced into the heat transfer fluids to enhance the thermal conductivity of the resulting nanofluids. The aim of this project was to investigate the physico-chemical properties of nanofluids synthesized using submicron and high aspect ratio particles suspended in heat transfer fluids.South Afric
Physicochemical Properties of Oil-Based Nanofluids Containing Hybrid Structures of Silver Nanoparticles Supported on Silica
No full textFunctional metal oxides synthesized using natural extracts from waste maize materials
No full textWe show in this article the possibilities of employing an environmentally friendly, uncomplicated, economical
and sustainable green synthesis technique effected by natural extracts from waste maize (zea mays lea) materials
to synthesize some functional transition single metal oxide nanoparticles (NPs). Copper oxides (Cu2O and CuO),
zinc oxide (ZnO), nickel oxide (NiO), chromium oxide (Cr2O3), iron oxide (Fe2O3) and cadmium oxide (CdO) were
successfully synthesized using this facile method. Structural characterizations by X-ray diffraction (XRD) for the
various oxides show the phases and space groups corresponding to their individual structures. Images from the
high resolution transmission electron microscope (HRTEM) revealed various shapes and sizes of the obtained
nanoparticles. Results from the attenuated total reflection-Fourier transform infrared (ATR-FTIR) revealed
different kinds of functional groups present in the synthesized metal oxide nanoparticles. We showed that the
phytochemicals in the natural extracts obtained from the waste materials from Zea mays lea plant is pivotal to the
bio-reduction, stabilization and chelation of the metal oxide nanoparticles
Opuntia spp. in Dye-Sensitized Solar Cells
No full textSolar energy is one of the most important renewable and sustainable forms of energy. Different technologies have been developed to harness this free energy and contribute to the world economy, especially in countries with no seasonal variations in solar radiation. Dye-sensitized solar cells (DSSCs) are simply used to collect solar energy and convert that visible light into electricity. This depends on the photosensitization of wide band-gap metal oxide semiconductors. The photoelectrode spectral sensitivity needs specific chemical dyes for the lower energy photons collection. Significant research efforts for identifying new organic dyes from natural sources have been carried out. Higher plants contain many natural pigments well-known to interact with solar radiation. The fruit of the Opuntia spe-cies contains a particular type and unique pigment called betalain. This type of compound has an interesting conjugation system with nitrogen atoms forming an unusual natural dye. Betalain has a potential interest in the photosensitization process when added to the DSSCs system. This chapter provides a review on the structural features and potential applications of the betalain pigments in the photosensitization solar cells
Antioxidant and antimicrobial activities of green-synthesized silver nanoparticles using a cocktaila aqueous extract of capparis sepiaria root and tabernaemontana elegans bark
No full textThe increasing incidence of antimicrobial resistance (AMR) poses a serious threat to public health, which necessitates the development of alternative countermeasures to combat it. Green nanotechnology, in particular the use of silver nanoparticles (AgNPs), shows promise in combating AMR. Although the synthesis of AgNPs using medicinal plant extracts has been explored, combining extracts from two medicinal plants to synthesize AgNPs with enhanced properties has received less attention. Therefore, this study addresses this gap by presenting the green synthesis of AgNPs using a cocktail of Capparis sepiaria–Tabernaemontana elegans (CsTe) aqueous extract as reducing, stabilizing, and capping agents. The focus is on assessing the antioxidant and antimicrobial activities of the synthesized CsTe-AgNPs. Various parameters, such as pH, temperature, extract and silver concentrations,
reaction ratio, and synthesis time, were optimized to enhance the efficiency of CsTe-AgNPs synthesis. The CsTe- AgNPs were monodispersed and spherical, with an average core
size of 14 ± 2.953 and 7 ± 3.849 nm, and hydrodynamic size of 23 ± 12.260 and 138 ± 2.086 nm for pH = 6 and pH = 11, respectively. The FTIR analysis revealed a shift in peaks of
biomolecules present in the CsTe extracts that could be responsible for the reduction of Ag salt to form CsTe-AgNPs. Notably, CsTe-AgNPs_pH11 had potent antimicrobial activity, with a minimum inhibitory concentration (MIC) of 12.5 ± 0 μg/mL against K. pneumoniae and P. aeruginosa, and a slightly higher MIC for C. albicans of 25 ± 5.449 μg/mL. This study demonstrated the effectiveness of using a mixture of two extracts to synthesize AgNPs with enhanced antioxidant and antimicrobial activities, and therefore, could serve as a promising reagent to combat AMR
