Nature Chem. 6, 468–476 (2014)

Credit: NPG

Many synthetic methods used to make two-dimensional carbon nanosheets do not permit the introduction or retention of functional groups on their surface. The need for functionalization, however, is often paramount for the processability of the materials or for a particular application. Now, Holger Frauenrath and colleagues report the synthesis of extended, functional carbon nanosheets by the carbonization of self-assembled monolayers of amphiphilic molecules at the air/water interface. The amphiphiles contain hexayne segments with an ester head group and an alkyl chain tail, and the close-packing arrangement of the hexayne and alkyl chains within the monolayer is such that crosslinking under ultraviolet irradiation and at room temperature produces a greater than 80% sp2-hybridized carbon nanosheet. This extent of conjugation is similar to that achieved with high-temperature annealing conditions, however, by using this self-assembled monolayer route, the functionalized hydrophilic surface can be retained. The carbon nanosheets, which have a thickness of 1.9 nm, are also demonstrated to be effective substrates, with low background contrast, for transmission electron microscopy imaging of hydrophilic gold nanoparticles.