Density functional theory study on the stability, electronic structure and absorption spectrum of small size g-C3N4 quantum dots

Abstract The geometric stabilities, electronic properties as well as ultraviolet–visible (UV–Vis) absorption spectra of the g-C3N4 quantum dots were systematically investigated by density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations. Taking the tri-s-triazine as a basic building unit, three types of planar structures of the g-C3N4 quantum dots were designed. The chain-type g-C3N4 quantum dots are the lowest in energy. The growth pattern of the g-C3N4 quantum dots had been speculated. The absorption spectra of the triangular sheet structure are in good agreement with the experimental results, and the absorption spectra of the (g-C3N4)15 quantum dots with a 3.41 nm lateral size has covered most of the visible light area. These small size g-C3N4 quantum dots are promising to be used as graphitic carbon nitride-based composite materials for energy conversion.