Synthesis and characterisation of CdS and PbS nanoparticles in an imidazolium based ionic liquid
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Date
2018
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University of Zululand
Abstract
Semiconductor metal sulfides nanoparticles have been prepared using the imidazolium based ionic liquid surfactant as both the stabilizer and growth modifier. The structural and morphological properties of the as-prepared nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), ultraviolet visible and near infrared radiation (UV-Vis and NIR), photoluminescence and fourier transform infrared spectroscopy (FTIR). Various synthetic methods (thermolysis, microwave and room temperature syntheses) were used and reaction parameters such as temperature and injection protocols, precursor type were varied to study the optical and structural properties of the as-synthesized nanoparticles. The CdS nanoparticle synthesis was carried by altering the reaction temperature and the injection protocol using single and dual source precursors. Cadmium ethyl xanthate was used as single source precursor whereas cadmium acetate and dodecanethiol were used as dual source molecular precursors in the presence of 1-ethyl-3-methylimidazolium methanesulfonate ionic liquid. XRD studies confirmed the formation of cubic and hexagonal phases for low and high temperatures respectively. The SAED results revealed that the nanoparticles were crystalline and the morphological studies further showed formation of nano-sized particles in the range of 2 – 15 nm, with close to spherical shaped morphologies. Blue-shifted band gaps further confirmed formation of very small CdS nanoparticles, which were temperature dependent. In the synthesis of PbS nanoparticles, the effect of sulfur source (with the same lead source, lead acetate) was studied for dual source precursors with respect to temperature and lead ethyl xanthate complex was used as single source molecular precursor in the ionic liquid medium. Sodium sulfide and dodecanethiol were used as different sulfur sources. XRD studies confirmed formation of cubic phase of PbS. Electron microscopy analyses showed that the nanoparticle morphologies differed significantly depending on the synthetic factors such as temperature, nature of precursors and ranged from spherical to cubic shapes. TEM images together with SAED patterns revealed crystalline nanoparticles with sizes ranging from 29 to 53 nm. SEM images further confirmed formation of cubic shaped PbS nanoparticles. The study has successfully shown a facile method for the synthesis of CdS and PbS nanoparticles, this method can be used for other nanomaterials as well. Ionic liquids can indeed be used as both media solvents and as stabilizing/capping agents, replacing the traditionally known solvents. The use of various reaction parameters has led to different morphological and structural properties of the a-synthesized nanoparticles.
Description
A thesis submitted to the Faculty of Science and Agriculture in fulfillment of the requirements for the Degree of Master Of Science (Chemistry) in the Department of Chemistry at the University of Zululand, 2018
Keywords
nanoparticles --X-ray diffraction --ionic liquids --electron microscopy