Quantum Dots (QDs) are nanoscale semiconductor materials, usually composed of dozens to hundreds of atoms. They have attracted much attention because of their photoluminescence effect of emitting specific wavelength spectrum under external excitation. Quantum dots have many special properties, the most important of which is that their band structure can be tuned by controlling their size and shape. This makes them have a wide range of applications in materials science, semiconductor physics, electronics and optics. For example, quantum dots can be used to make efficient solar cells, single photon sources, biological imaging and fluorescent probes.