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Title:	Preparation and characterization of semiconducting nanocrystals with potential application in nanophotonics
Authors:	Morteza Sasani Ghamsari (P37939)
Supervisor:	Shahdan Bin Radiman, Prof. Dr.
Keywords:	Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia Semiconductor nanocrystals
Issue Date:	18-Jul-2014
Description:	Semiconducting nanomaterials have attracted great attention due to the huge potential applications in quantum confinement based devices such as light emitting diodes (LED), optical switching devises, solar cells, detectors, and so on. From technological point of view, the preparation of these nanostructured materials with designable physical and chemical properties is very important and therefore, the modified methods or facile routes must be developed for controlling the shape, size, and morphology of obtained materials. In this research a suitable procedure to prepare PbS, ZnO, and TiO2 nanocrystals with potential applications in nanophotonics were obtained. In the first stage, a novel colloidal method was developed to prepare PbS nanocrystals. On the basis of optimized colloidal technique a solution source of lead ions was prepared and then an appropriate amount of polyvinyl alcohol (PVA) was added to prepare a precursor solution. Finally, a solution of sulphur ion was mixed by precursor solution to obtain PbS colloidal nanocrystals. Low and high resolution TEM, UV-Vis absorption, photoluminescence spectroscopy, were used to evaluate the size, shape, and optical properties of prepared sample. It has been found that the PVA surface modified PbS nanocrystals showed strong optical absorption and several emission peaks in the visible and NIR regions. In the second stage, a modified sol-gel method was used to prepare ZnO nanocrystals. In order to prepare ZnO nanocrystals, triethanolamine (TEA) was used to control the sol-gel chemical reactions. Water was employed to manage the crystalline defect density of ZnO nanocrystals and their optical properties. The influence of concentration ratio of Zinc acetate to TEA on the optical properties of obtained material was investigated. High resolution TEM, UV-Vis absorption, photoluminescence spectroscopy and FTIR were used to evaluate the size, shape, optical properties and chemical composition of prepared samples. The photoluminescence spectrum showed that the prepared sample emits strong blue emission. In the third stage, TiO2 nanocrystals were synthesized by modified sol-gel route. Low and high resolution TEM, UV-Vis spectrophotometer, FTIR, were used to evaluate the size, shape, optical properties and chemical composition of prepared samples. In this study, highly crystalline TiO2 colloidal nanoparticles with strong Violet-Blue emission were successfully prepared by reflux method. The photodecomposition test of methylene blue proves that the prepared colloidal TiO2 nanoparticles by modified method have high crystallinity and good photocatalytic properties. The precipitated and dried powder from colloidal sample has anatase structure which is confirmed by XRD. In addition, aging process was used to control the crystallinity of obtained TiO2 nanocrystals,Certification of Master's Doctoral Thesis" is not available
Pages:	155
Call Number:	QC611.8.N33G484 2014 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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