Liquid-phase
exfoliation is the most suitable platform for large-scale
production of two-dimensional materials. One of the main open challenges
is related to the quest of green and bioderived solvents to replace
state-of-the-art dispersion media, which suffer several toxicity issues.
Here, we demonstrate the suitability of methyl-5-(dimethylamino)-2-methyl-5-oxopentanoate
(Rhodiasolv Polarclean) for sonication-assisted liquid-phase exfoliation
of layered materials for the case-study examples of WS
2
, MoS
2
, and graphene. We performed a direct comparison,
in the same processing conditions, with liquid-phase exfoliation using
N
-methyl-2-pyrrolidone (NMP) solvent. The amount of few-layer
flakes (with thickness <5 nm) obtained with Polarclean is increased
by ∼350% with respect to the case of liquid-phase exfoliation
using NMP, maintaining comparable values of the average lateral size,
which even reaches ∼10 μm for the case of graphene produced
by exfoliation in Polarclean, and of the yield (∼40%). Correspondingly,
the density of defects is reduced by 1 order of magnitude by Polarclean-assisted
exfoliation, as evidenced by the
I
(D)/
I
(G) ratio in Raman spectra of graphene as low as 0.07 ± 0.01.
Considering the various advantages of Polarclean over state-of-the-art
solvents, including the absence of toxicity and its biodegradability,
the validation of superior performances of Polarclean in liquid-phase
exfoliation paves the way for sustainable large-scale production of
nanosheets of layered materials and for extending their use in application
fields to date inhibited by toxicity of solvents (e.g., agri-food
industry and desalination), with a subsequent superb impact on the
commercial potential of their technological applications.