Synthesis, Characterization, and Biological Study of Carboxyl- and Amino-Rich g-C₃N₄ Nanosheets by Different Processing Routes

Graphitic-phase carbon nitride (g-C₃N₄) is a graphene analogue, which has attracted much attention for its unique physicochemical properties. The bulk g-C₃N₄ is often fragmented and ionized to nanosheets, obtaining improved performance or confer novel properties. It is reported that g-C₃N₄ nanosheets using different processing methods can be modified with different functional groups, resulting in different electrical characteristics. However, the surface charge of g-C₃N₄ nanosheets is seldom mentioned as a factor influencing their biological applications. In our present study, we prepared two kinds of uniformly dispersed g-C₃N₄ nanosheets of high quality, the carboxyl- and amino-rich g-C₃N₄ nanosheets. Although both the carboxyl- and amino-rich g-C₃N₄ nanosheets displayed good biocompatibility in vitro and in vivo, however, they are at very different levels of surface charge, which are relative to different cellular uptake, penetration mechanism and lysosome escape ability of the nanosheets.