Synthesis and shape control of functionalized cadmium telluride nanoparticles
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Date
2010
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Abstract
The synthesis of organically and water soluble cadmium telluride nanoparticles by a
facile hybrid solution high temperature method is presented. This method involves the
reaction by the addition of an aqueous suspension or solution of a cadmium salt
(chloride, acetate, nitrate or carbonate) to a freshly prepared NaHTe solution. The
nanoparticles were prepared by passivating with organic surfactants such as
hexadecylamine (HDA) and tri-n-octylphosphine oxide (TOPO) for their solubility
and stability in organic solvents. To stabilize and make the nanoparticles water
soluble, L-cysteine ethyl ester hydrochloride and triethanolamine were used as
capping agents. The absorption and photoluminescence spectroscopy, fourier
transform infrared spectroscopy, powder X-ray diffraction, transmission electron
microscopy and high resolution transmission electron microscopy techniques were
used to confirm the quality of the as-synthesized nanoparticles. All measurements
were performed without any post preparative size separation of the nanoparticles.
The dissertation comprises of four chapters. The first chapter is a brief description of
the properties of nanomaterials and a literature review on some of the principal routes
to synthesize nanomaterials. The mechanisms of particle growth and shape control are
also discussed. Finally some key applications of CdTe are described.
The second chapter deals with the synthesis of HDA and TOPO-capped CdTe
nanoparticles. The reaction parameters such as reaction time, reduction time of tellurium, Cd:Te ratio, reaction temperature and cadmium source were varied to
investigate their influence on the optical properties and morphology of the particles. Details of the absorption features such as excitonic peaks and band edges are
presented. The emission properties are also discussed. The morphology of the
particles was investigated by electron microscopy and powder X-ray diffraction
techniques. It was found that the cadmium source (chloride, carbonate, acetate and
nitrate) had a profound effect on the final morphology of the particles. A detailed
mechanism for the particle growth is presented.
The synthesis of cysteine and TEA-capped CdTe nanoparticles are described in
Chapter three. A systematic study of the effects of the capping group, pH, reaction
time and cadmium source was carried out for the water soluble CdTe nanoparticles.
The absorption and emission data for the particles are discussed in detail. The electron
microscopy images confirm the nanosize and crystalline nature of the particles. In
addition fourier transform infrared spectroscopy was used to confirm the capping of
the particles by cysteine and TEA. All the cadmium sources were found to be
successful in producing high quality water soluble CdTe particles. The final chapter
four is a summary of general conclusions of the study.
Description
Submitted to the Faculty of Science and Agriculture In fulfilment of the requirement for the award of the degree of Master of Science in the Department of Chemistry
University of Zululand, 2010.
Keywords
Cadmium telluride nanoparticles, Facile hybrid solution