Synthesis of Lead Chalcogenide Nanoparticles and thin Films from Single-Source Precursors

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December, 2014
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Abstract
The work described herein deals with the synthesis and characterisation of lead chalcogenide thin films and nanocrystals from Single-source precursors. Single-source precursors of type imidodiisopropyl –dithio, -diseleno and -thioselenophosphinato complexes of lead have been synthesised and characterised. The as-synthesised compounds have been used for the fabrication of lead sulphide and lead selenide thin films by aerosol-assisted chemical vapour deposition and for the synthesis of nanocrystals by colloidal hot injection method. The as- grown thin films and nanoparticles of lead sulphide and lead selenide have been characterised by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray (EDAX) analyses. Optical band gaps of the nanoparticles produced have been evaluated using the absorption spectrum fitting procedure. The band gaps of the nanoparticles were wider than those of their respective bulk particles, indicating a significant tuning. PbSxSe1-x thin films have also been prepared by aerosol assisted chemical vapour deposition (AACVD) using novel Single-source precursors synthesised, characterised and their structures elucidated in this project. The complexes are [Pb((SePiPr2)(SPiPr2)N)2], [Pb((SePiPr2)2N)(S2CNEt2)] and [Pb((SePiPr2)2N)(S2CNHexMe)]. The thin films deposited from all three complexes showed the formation of PbSxSe1-x at temperatures ranging from 300 °C to 400 °C and PbSe at 450 °C. Distribution of sulphur and selenium within alloyed thin films is confirmed by scanning electron microscope studies and EDAX analysis.
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A thesis submitted to the Department of Chemistry, Kwame Nkrumah University of Science and Technology, Kumasi in partial fulfillment of the requirements for the award of PhD inorganic CHEMISTRY DEGREE.
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