Engineering the electronic structure and optical properties of g-C3N4 by non-metal ion doping

Abstract

Graphite-like carbon nitride (g-C₃N₄) modified with different non-metal ions (boron and sulfur) was synthesized by directly heating a mixture of melamine and dopant with a continuous doping concentration. The effect of the doping ion and its concentration on the structural and optical properties of the samples were investigated in detail. Surprisingly, with the doping concentration increasing, an unexpected relative blue shift was determined in the photoluminescence (PL) spectra of the doped g-C₃N₄, showing an enhancement in the bandgap which is not in agreement with the typical red shifts in the PL spectra of no-metal ion-doped g-C₃N₄. To investigate this interesting variation in PL, density functional theory (DFT) has been used and a possible mechanism for the non-metal ion-modified g-C₃N₄ system was proposed. It is supposed that the blue shift of the non-metal ion-doped g-C₃N₄ could be mainly attributed to the doping-induced electronic redistribution and structural reconstruction.