Surface Modification of C₃N₄ through Oxygen-Plasma Treatment: A Simple Way toward Excellent Hydrophilicity

We developed a universal method to prepare hydrophilic carbon nitrogen (C₃N₄) nanosheets. By treating C₃N₄ nanosheets with oxygen plasma, hydroxylamine groups (N-OH) with intense protonation could be introduced on the surface; moreover, the content of N-OH groups increased linearly with the oxygen-plasma treatment time. Thanks to the excellent hydrophilicity, uniformly dispersed C₃N₄ solution were prepared, which was further translated into C₃N₄ paper by simple vacuum filtration. Pure C₃N₄ paper with good stability, excellent hydrophilicity, and biocompatibility were proved to have excellent performance in tissue repair. Further research demonstrated that the oxygen-plasma treatment method can also introduce N-OH groups into other nitrogen-containing carbon materials (NCMs) such as N-doped graphene, N-doped carbon nanotube, and C₂N, which offers a new perspective on the surface modification and functionalization of these carbon nanomaterials.