Studies on semiconductor nanoparticles and polymer nanocomposites
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Date
2002
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Abstract
Synthesis of nanometer-sized semiconductor materials using various synthetic methods has been an area of intense activity over the past decade. The emphasis has been mainly on the synthesis of semiconductor particles belonging to II-VI and III-V groups. These particles exhibit an increase in their electronic band gap with decreasing particle size, a property which is attributed to a strong quantum confinement effect. The ability to tune the physical properties of nanocrystallites makes them an important category of materials with potential use in a wide range of technological applications.
This project deals with the synthesis, characterisation and investigation of the properties of semiconductor nanoparticles and semiconductor-polymer nanocomposites. The strategy for the synthesis of nanoparticles involves the use of various single-source precursors, which are thermolysed in a coordinating solvent, tri-w-octylphosphine oxide (TOPO). In the present study the focus has been mainly to prepare CdS nanoparticles using various single source precursors. Attempts have been made to correlate the precursor characteristics and the size, size distribution and morphology of the nanoparticles synthesised using these precursors. The other nanocrystallites studied in the present project include ZnS, Mn doped ZnS and Mn doped CdS. The single-source precursors used for the synthesis of CdS nanoparticles are cadmium(II) complexes of:
Ethylxanthicacid; N,N' bis(thiocarbamoyl)hydrazine; N,N' -dioctyl thiourea; N,N'-diisopropyl thioureap; Thiocarbohydrazide; N,N' -dicyclohexyldithiooxamide; Thiosemicarbazide; 1 -(1 -carboxypropionyl)thiosemicarbazide; Glyoxalbis(thiosemicarbazone); 2,6-Diacetylpyridine bis(thiosemicarbazone);
Zinc(H) complexes of:
Ethylxanthicacid; N,N' -dioctyl thiourea; N.N; -bis(thiocarbamoyl)hydrazine
The second part of the project involves the synthesis, characterisation and investigation of the properties of CdS, HgS and PbS nanoparticles in polymer matrices. Various synthetic methods have been used for the preparation of the polymer nanocomposites. The polymeric media that have been used include polyacrylamide, polystyrene and polyaniline. The structural characterisation of the composite materials confirm their nanosized nature.
The thermal decomposition pattern of all precursors were studied by TGA. The optical properties of the nanoparticles and nanocomposites were investigated by UV-vis and photoluminescence (PL) spectroscopy. The structural properties were investigated by X-ray diffraction (XRD), energy dispersion analytical X-ray (EDAX), selected area electron diffraction (SAED), transmission electron microscopy (TEM) and electron paramagnetic resonance (EPR).
Description
submitted to the Faculty of science and agriculture in partial fulfilment of the requirements for the award of the degree of Doctor of Philosophy in the Department of Chemistry at University of Zululand, 2002.
Keywords
Nanotechnology, Semiconductors