Question

Why does band gap increase with decrease in size of nanoparticles?

Answer 1

Band gap

1. It is the distance between the conduction and valence bands of electrons.
2. It represents the minimum energy required to excite an electron to a state in the conduction band where it can conduct.
3. It happens when two adjacent bands are not wide enough to span the full range of electron energy levels.

Band gap increases with a decrease in particle size as the electron-hole pairs are now closer, and coulombic interaction between them cannot be neglected, causing higher kinetic energy.