Synthesis of Cadmium, Lead and Iron Sulfide Thin Films and Nanoparticles
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Date
2016
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University of Zululand
Abstract
The usefulness and application of semiconductor nanomaterials continue to expand the frontier of research in bringing their benefits via technological applications. Several synthetic methods for the preparation of semiconductor nanoparticles have been established. The design and development of a simple technique that is able to fabricate very pure, high quality and tunable morphology thin films and nanoparticles is therefore important and pressing. In this research project, Cadmium Sulfide, Lead Sulfide and Iron Sulfide nanoparticles and thin films were selected and synthesized because of their unique properties and applications. The use of single source precursors for the fabrication of these nanomaterials has been used by several routes such as hot injection, chemical vapour deposition and pyrolysis methods. Therefore, in this study, the synthesis of nine (9) heterocyclic dithiocarbamate metal complexes namely; bis(piperidinedithiocarbamato)cadmium(II) (1), bis(tetrahydroquinolinedithiocarbamato)cadmium(II) (2) and the pyridine adduct of bis(piperidinedithiocarbamato)cadmium(II) (3), bis-(piperidinedithiocarbamato)lead(II) (4) and bis-(tetrahydroquinolinedithiocarbamato)lead(II) (5), tris-(piperidinedithiocarbamato)iron(III) (6) and tris-(tetrahydroquinolinedithiocarbamato)iron(III) (7), bis-(piperidinedithiocarbamato)iron(II) (8) and bis-(tetrahydroquinolinedithiocarbamato)iron(II) (9) are presented. Single crystal structures of four single source precursors (1), (3), (6) and (7) have been elucidated in this study. These complexes have been used as single-source precursors (SSPs) for the fabrication of cadmium sulfide (CdS), lead sulfide (PbS) and iron sulfide (FeS) thin films by aerosol-assisted chemical vapour deposition (AACVD) and spin coating methods for PbS. Also, nanoparticles of similar metal sulfide were made by the hot injection and pyrolysis routes. Various parameters such as temperature, solvent and time were used to ascertain their properties.
The morphological, structural, optical properties and composition of the as-synthesized materials were found to depend on the reaction conditions used during the synthesis. The synthesized CdS thin films and nanoparticles were found to exhibit blue shifted optical properties, which were size and morphological dependent. Their morphologies and structural properties were investigated using different electron microscopy and diffraction techniques. Similarly, PbS thin films deposited were studied and their optical and structural properties show formation of high quality nanomaterials which are also temperature dependent. Optical properties of the deposited PbS thin films show blue shift compared to the bulk PbS. Best morphologies of PbS films deposited by spin coating method highlighted the usefulness of this route. Iron sulfide thin films deposited by AACVD method show that variation of parameters could result in the formation of high quality nanostructures. Furthermore, optically active greigite and pyrrhotite-iron sulfide nanoparticles were prepared by simply varying the temperature of the hot solvent. Pyrrhotite-Fe1-XS sensor device showed interesting performance when tested for humidity and different nitrogenous gases such NO2 and NH3. The gas sensors further revealed that stoichiometric structure of iron sulfide nanostructures have significant effect on the end-user device performance.
Description
A dissertation submitted to the Faculty of Science and Agriculture in fulfilment of the requirements for the Degree of Doctor of Philosophy (Phd) in the Department of Chemistry at the University Of Zululand, South Africa, 2016
Keywords
synthesis --cadmium --nanoparticles --sulfide