Chemical and plasma-etched method uses in unzipping a
carbon nanotube (CNT). Graphene nano ribbon (GNR)
defines a thin elongated strip of graphene which
demonstrates straight edges. Transformation of electronic
state from semimetal to semiconductor depends on the
width of nanaotube [178]. Multi-layer graphene or singlelayer
graphene produces if the starting nanotube is multiwalled
or single walled. The width of the nanoribbons
thus produced depends on the diameter of the precursor
nanotubes. Multi-walled carbon nanotubes (MWNTs)
established by lithium (Li) and ammonia (NH3). Conversion
of graphene nanoribbon from (MWNTs) are
shown in Fig. 9.
Liquid NH3 (99.95 %) and dry tetrahydrofuran (THF)
used in growth of (MWNTs) retaining the dry ice bath
temperature of -77 C [179]. It was found that *60 %
fully exfoliated and (0–5 %) unexfoliated or partially
exfoliated nanotubes of (MWNTs). For Oxidation of
CNT’s side wall used H2SO4, KMnO4, and H2O2 in step by
step process [32]. At the beginning they reported that the
MWNT diameter was 40–80 nm and increased up to
100 nm. The step-by-step fabrication process from nanotube
to nanoribbon is shown in Fig. 10.
In controlled unzipping technique a pristine MWNT
(dia. *4–18 nm) suspension was put on to a Si substrate
pretreated with 3-aminopropyltriethoxysilane. A polymethylmethacrylate
(PMMA) solution [34]. They established
high quality of MWNTs which diameter were
*6–12 nm and step height GNRs were 0.8–2.0 nm. Again
single- to few-layer GNRs also depends on the plasma
etching time.
Another method for unzipping MWCNTs to GNRs
used electric field. An electric field was applied to a
single MWNT using a tungsten electrode and perceived
that the noncontact end of the MWCNT started unwrapping
and forming graphene nanoribbon. The fabrication
process of GNRs achieve a high-purity, defect-free controlled
synthesis process for scalable device in modern
electronics.