الفهرس 
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Abstract
Structured nanoscale materials have attracted widespread interest due to the tunability of their physical and electronic properties by size variation. Smiconductor nanocrystals (NCs) represent a class of quasi-Zero-dimensional objects as called as quantum dots. Bulk Crystalline structure is preserved in NCs, but due to quantum confinement. NCs have molecular-like discrete energy spectra, which exhibit strong size dependence. This provides an opportunity for a wide-range tailoring of their electronic and optical properties. In the present work, we studied the optical properties of CdSe NCs which can be tuned from ~1.8 e V (red) to ~3 e V (UV) by changing NC diameter from 11.5 to 1.32 nm.Since semiconductor nanomaterial have potential application in light emitting diode (LED), Lasers, solar cells, data storage media, optoelectronic devices, their photostability, optical and electronic properties have to be tested under various condition of temperature and irradiation of different light (lasers) intensities. We test the optical properties of semiconductor CdSe nanosrystals and their dependence on shape, temperature and power of excitation power. We found that the absorption spectra of the semiconductor nanospheres and nanorods of similar width is almost identical because the band gap depends on the most confinement dimension which is the width of the rod and the diameters of the spheres, On other hand the rods have more stoke shift than dots which indicated that the emitting state in rods is different than that of the dots.Temperature dependence of the emission properties of rods and dots confirms the phonon contribution.Power dependence of photoluminescence shows the possibilities of formation of the multiexcitonic states which is even more pronounced on spheres than that of the rods. This could be attributed to loss of the pumping energy through nonradiative Auger process or presence of surface trap states.