Dependence of electronic structure of g-C3N4 on the layer number of its nanosheets: A study by Raman spectroscopy coupled with first-principles calculations

Graphitic carbon nitride (g-C3N4) has attracted worldwide attention, because of its promising potential applications and theoretical prediction of its unique properties. Herein, 1-, 2- and 4-layer g-C3N4 nanosheets were synthesized in a well-crystallized form by controlling the intercalation time in a simple intercalation–exfoliation process. The electronic structures of the nanosheets were captured in their Raman spectra that clearly evolved with the layer number of the nanosheets for the first time. A clear correlation between the spectral properties and the layer number of the nanosheets was clarified by combining Raman spectra and the first-principles calculations. Raman vibrational modes of g-C3N4 were assigned. The layer–layer deformation vibrations and related in-plane twisting vibrations or symmetrical stretching vibrations reflected the change in the electronic structure of the nanosheets with different layers. The results may shed light on brand-new opportunities for significant improvements in the synthesis, structure, electronic and optical properties of single-layer and ultrathin g-C3N4 nanosheets toward desirable functional materials.