Alkali-assisted mild aqueous exfoliation for single-layered and structure-preserved graphitic carbon nitride nanosheets

Single-layered g-C₃N₄ nanosheets have been fabricated by delaminating directly its bulk counterpart in an alkaline solution. According to the theoretical modeling, the interaction of OH⁻ with terminal [sbnd]NH₂ or bridged [sbnd]NH[sbnd] group of the triazine units within bulk g-C₃N₄ crystal structure could result in decreased bonding energy between layers and promote the total delamination. The resulting g-C₃N₄ nanosheets colloid has a relatively high concentration (12 g/L) compared with the traditional ultrasonic assistant exfoliation method. The delaminated nanosheets are revealed by atomic force microscopy to show a lateral size of a hundred nanometers and a thickness of about 0.4 nm, which provides a direct evidence for the total exfoliation of g-C₃N₄ crystals into their single sheets. More importantly, the X-ray diffraction measurement confirms that the g-C₃N₄ nanosheets could be re-assembled with well-preserved original crystal structure. The exfoliation mechanism was also confirmed by the DFT calculation.