  A simple one-stage solution-based method was developed to produce graphene
nanoribbons by sonicating graphite powder in organic solutions with polymer
surfactant. The graphene nanoribbons were deposited on silicon substrate, and
characterized by Raman spectroscopy and atomic force microscopy. Single-layer
and few-layer graphene nanoribbons with a width ranging from sub-10 nm to tens
of nm and length ranging from hundreds of nm to 1 {\mu}m were routinely
observed. Electrical transport properties of individual graphene nanoribbons
were measured in both the back-gate and polymer-electrolyte top-gate
configurations. The mobility of the graphene nanoribbons was found to be over
an order of magnitude higher when measured in the latter than in the former
configuration (without the polymer electrolyte), which can be attributed to the
screening of the charged impurities by the counter-ions in the polymer
electrolyte. This finding suggests that the charge transport in these
solution-produced graphene nanoribbons is largely limited by charged impurity
scattering.
