  Armchair graphene nanoribbons (AGNRs) with sub-nanometer width are potential
materials for fabrication of novel nanodevices thanks to their moderate direct
band gaps. AGNRs are usually synthesized by polymerizing precursor molecules on
substrate surface. However, it is time-consuming and not suitable for
large-scale production. AGNRs can also be grown by transforming precursor
molecules inside single-walled carbon nanotubes via furnace annealing, but the
obtained AGNRs are normally twisted. In this work, microwave heating is applied
for transforming precursor molecules into AGNRs. The fast heating process
allows synthesizing the AGNRs in seconds. Several different molecules were
successfully transformed into AGNRs, suggesting that it is a universal method.
More importantly, as demonstrated by Raman spectroscopy, aberration-corrected
high-resolution transmission electron microscopy and theoretical calculations,
less twisted AGNRs are synthesized by the microwave heating than the furnace
annealing. Our results reveal a route for rapid production of AGNRs in large
scale, which would benefit future applications in novel AGNRs-based
semiconductor devices.
