الفهرس 
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Abstract
Now nanotechnology has become a key word in both public and scientific interest. Of particular interest is a class of nanoparticles known as quantum dots. they have unique optical and electronic properties, tunable band gap, sharp emission band with broad excitation and strong resistance to photobleaching. They display any chosen color in the spectrum from UV to IR, through a simple change in the size and composition. Their stable photoluminescent properties and photostability have made them promising candidates for use in bio-imaging applications and bioconjugation. Magnetic nanoparticles are another class of nanomaterials that have been studied for use in biomedical applications such as MRI contrast enhancement, magnetic immobilization and drug targeting because of their magnetic properties and small dimensions Engineering a hybrid core shell nanocomposites or nanoshell particles which posses properties that are deviated from those of the single component counterpart has gain a considerable attention in the last decades. The motivation is owing to the tunable physical and chemical properties arising from controlling the chemical composition and the relative sizes of the core and shell which leads to novel improved properties allowing for plethora of applications in different fields. These nanocomposite particles will have great potential to be used commercially in wide range of applications such as in biomedical applications; such as bioimaging, bioconjugation, biosensing, and biolabelling and magnetic applications; such as cell separation, MRI, magnetic fluid hyperthermia for cancer treatment and drug targeting In this thesis, the synthesis of CdSe nanocrystals and its core shell nanostructures has been verified, factors affecting growth and quantum yield were investigated and the fluorescence properties were enhanced with inorganic coatings and revealed with fluorescence laser scanning microscopy. A method for the synthesis of a single hybrid core shell nanocomposite combining the unique optical qualities of a semiconducting shell with magnetic properties of magnetic core was achieved. For this purpose, magnetite nanoparticles was prepared, stabilized and characterized with suitable instrumentations. Additonally, they have been utilized to prepare magnetic / luminescent nanostructure of Fe3O4@CdSe. The composition was confirmed with spectrophotometry and microscopy which revealed the growth of the semiconductor nanocrystals on the magnetic nanoparticles core. For the first time, the synthesis of Co nanoparticles was achieved in aqueous phase based on the reduction of the metal salt with simple and cheap chemistry. To achieve biocompatibility and stability, as well as to satisfy the needs for high moment NPs in biological applications, we are synthesizing core shell structures of both gold-coated cobalt (Co@ Au) and cobalt-coated gold (Au@ Co) NPs. The prepared nanocomposites have a large potential for the treatment of tumors through what is called magnetic fluid hyperthermia and for this sake the photostability as well as the chemical stability and the biocompatibility of the as-prepared nanostructures were investigated. To analyze the potential toxicity of the Co@Au nanocomposites, neutral red assay using the HepG2 cell line was performed and clearly indicated that Co@Au nanocomposites show no toxicity. With the same technique, we have investigated the photothermal effects of the nanocomposites by CW irradiation of the cells of interest with diode laser.