Abstract
We report a novel physicochemical route to produce highly crystalline nitrogen-doped graphene nanoribbons. The technique consists of an abrupt N2 gas expansion within the hollow core of nitrogen-doped multiwalled carbon nanotubes (CNx-MWNTs) when exposed to a fast thermal shock. The
multiwalled nanotube unzipping mechanism is rationalized using molecular dynamics and
density functional theory simulations, which highlight the importance of open-ended
nanotubes in promoting the efficient introduction of N2 molecules by capillary action within
tubes and surface defects, thus triggering an efficient and atomically smooth unzipping. The
so-produced nanoribbons could be few-layered (from graphene bilayer onward) and could
exhibit both crystalline zigzag and armchair edges. In contrast to methods developed
previously, our technique presents various advantages: (1) the tubes are not heavily oxidized;
(2) the method yields sharp atomic edges within the resulting nanoribbons; (3) the technique
could be scaled up for the bulk production of crystalline nanoribbons from available MWNT
sources; and (4) this route could eventually be used to unzip other types of carbon nanotubes
or intercalated layered materials such as BN, MoS2, WS2, etc.
