This book contains new and original investigations in the area of semiconductor quantum dots, a special class of nanoparticle. Due to size quantization, some new phenomena occur in the specimen. These properties make them very attractive candidates for developing nano electronic, optoelectronic and optic devices. This work includes synthesis of semiconductor quantum dots and the study of their sizes, optical absorption, and luminescence phenomena. The modifications in the sample properties after Swift Heavy Ion (SHI) irradiation are also reported.Finally, the applications of quantum dots as electronic, photonic and optic switch are also recorded.