New research has shown that graphene bubbles could yield1 multiwalled carbon nanotubes (MWCNTs) and fullerenes under controlled temperatures and pressures in arc discharge apparatus. This research is important for applications such as electronics and bioscience, which rely on the quality and yield of CNTs.
Until now, it has not been clear how MWCNTs and fullerenes form in arc discharge apparatus. Scientists believed that the nucleation and growth of arc discharge CNTs occur on the cathode. To pinpoint what exactly lies behind the formation of CNTs and fullerenes in arc discharge apparatus, the researchers imaged the process using electron microscopy.
The team found that fullerene and MWCNTs grew from bubbles of graphene films that formed on the anode surface under extreme temperature and pressure conditions. The tips of the MWCNTs indicate that the growth of the CNTs started with the formation of fullerene-like structures of 1 and 2 nm.
The pressure difference across the graphene surface results in the formation of bubbles. Fullerenes and CNTs form because the size and shape of a particular bubble is dependent on the pressure difference in that region.
"This work opens up new possibilities to devise methods using different types of graphenes to control the structure, quality and yield of fullerene and CNTs," says lead researcher Vinay Gupta. It reveals for the first time the role of graphene in the formation of fullerenes and CNTs, explaining the long-standing puzzle of their helium pressure dependence on formation, he adds.
