Quantum Size Effects on Effective Mass and Band gap of Semiconductor Quantum Dots

In this research we calculate the band gap of ZnS nano particle and show that it increases with decreasing its size. The simplest way for discussing this phenomenon and finding the band gap for different sizes is effective mass approximation. We show, this method isn't accurate for particles smaller than 2.5 nm. This is due to the fact that the effective mass of particles at this size is dependent of size. To calculate the band gap of small size ZnS, the density functional theory was used. This theory has also used to determine the effective mass for various particle sizes. Our calculation indicates the appearance of blue shift by decreasing the size of particle.