Semiconductor nanoparticles exhibit effects of quantum confinement of electrons and holes in dictating optical and electronic properties. One can thus tune the band gap by changing the particle size. As the Optical properties are strongly dependent on particle size, a particle size distribution is expected to cause inhomogeneous broadening of optical spectra. Nanocrystalline materials exhibit a variety of properties that are different and often considerably improved in comparison with bulk materials. These include increase strength, enhanced diffusivity, improved ductility/ toughness, reduced density, reduced elastic modulus, higher electrical resistivity and superior soft magnetic properties in comparison to bulk crystals. Luminescence which is an optical property is enhanced if the size of any particles is reduced up to nano -size. As the wavelength of light gets reduced. The present theoretical work is devoted to the Study of Broadening in the Photoluminescence peaks with variation in particle size of (ZnS, CdS) nanocrystals.

Synthesis and characterization of nano-sized particles has currently been a topic of intense investigation. In recent years, much effort has been devoted to the research of doped nanostructured materials. This kind of nanomaterials exhibits unusual physical and chemical properties in comparison with their bulk counterpart. As an important II-VI material, ZnS is chemically more stable and technologically better than other chalcogenides. In this thesis, we report an effective doping process by chemical route method to obtain nanosized ZnS: Cu particles. I have prepare five different samples with different concentration of copper. I have taken pure Zinc sulphide nanoparticle and after that I have put the copper in percentage of 0.005%, 0.01%, 0.015% and 0.02%. The influence of Cu doping concentration on electroluminescence has been studied.