الفهرس 
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Abstract
Compounds of the II-VI group are semiconductors of unique properties. Accordingly compounds of such group are launched in many technological applications. Cadmium sulfide, CdS , as one of such group has been widely used in many applications such as field effect transistor, light emitting diodes, photocatalysis in addition to biological sensors. Materials physical properties in macroscopic scale can be turned for a strongly significant measure by just dwindling particle size. Nanoparticles of CdS have been synthesized utilizing co-precipitation technique. Structure and microstructure inspection were carried out employing direct and indirect techniques . TEM and SEM as a direct techniques were employed to measure the particle size and the morphology of the microstructure .For the indirect techniques the X-ray data analysis were applied to evaluate the crystallite size.The lattice parameters and the crystallite size were estimated using Debye Scherrir and Williamson-Hall expression. For investigating the effect of heat treatment on crystallite size samples were heated at 100,200,300,400 and 500Co for two hours. Calorimetric study was carried out using the differential scanning calorimetry (DSC) measurements. In order to confirm the stoichiometry and the chemical formula on EDX measurements were performed. To find out the electric properties of CdS, nanocomposite of CdSembedded in PVA was prepared. The DC and AC conductivities were measured at room and elevated temperatures. Moreover the measurements were obtained over a wide range of frequency from 50 KHZ up to 5MHZ.For studying the optical properties of CdS nanocomposite the absorption and emission of CdS- PVA films were investigated in the wavelength range 200 nm to 800 nm. Similar measurements were carried out for CdS nanoparticles dispersed in DMF. In addition all the measurements were carried out for the as- prepared and annealed samples of CdS in different forms , as prepared in PVA , PVA capped in DMF. Many parameters and coefficients have been revealed throughout this study such as the conduction activation energy, the frequency exponent factor , the conduction mechanism, the optical band gap, Urbach energy ,the type of the optical transitions, absorption wavelength, fluorescence wavelength , stokes shift and photostability for the different types of the CdS nanoparticles.