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

Single-layered g-CN 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 NH or bridged NH group of the triazine units within bulk g-CN crystal structure could result in decreased bonding energy between layers and promote the total delamination. The resulting g-CN nanosheets colloid has a relatively high concentration (12g/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 0.4nm, which provides a direct evidence for the total exfoliation of g-CN crystals into their single sheets. More importantly, the X-ray diffraction measurement confirms that the g-CN nanosheets could be re-assembled with well-preserved original crystal structure. The exfoliation mechanism was also confirmed by the DFT calculation.