Quantum dots are nanocrystals or nanostructures made of semiconductor materials those are small enough to exhibit quantum mechanical properties and that confines motion of conduction band electrons valance band holes, or excitations in all three Spatial directions exhibiting unique electrical and optical properties which are useful potentially in biomedical imaging and other energy applications. Quantum dots are tiny particles or nanocrystals of a semiconducting material with diameters in the range of 2-10 nanometers (10-50 atoms). Quantum dots display unique electronic properties, intermediate between those of bulk semiconductors and discrete molecules that are partly the result of the unusually high surface-to-volume ratios for these particles. The most apparent result of this is fluorescence, wherein the nanocrystals can produce distinctive colors determined by the size of the particles. The unique size and composition tunable electronic property of these very small, semiconducting quantum dots make them very appealing for a variety of applications and new technologies. Quantum dots are particularly significant for optical applications owing to their bright, pure colors along with their ability to emit rainbow of colors coupled with their high efficiencies, longer lifetimes and high extinction coefficient.