Carbon nanodots (CDs) continue to gamer research attention due to their low cost and unique properties similar with traditional semiconductor quantum dots.More and more researchers have believed that their energy bandgaps are created by structural defects and size effects.Since small nanoparticles have the large fraction of surface atoms, the other elements or groups at the surface (dubbed surface states) can affect structural defects and emissive electronic transitions, resulting in the changes of photoluminescent behaviors and redox properties.