ABSTRACT
Carbon materials possess valuable properties for the design of
electrodes used in electroanalytical chemistry, because of their
relatively wide potential windows in aqueous media, low cost, and
relative chemical inertness in most electrolyte solutions. There
are several available microstructures of carbon materials, such as
diamond, amorphous powders, glassy carbon (GC), carbon fiber,
graphite, nanotubes, and graphene [1]. Among all these carbon
materials, carbon nanotubes (CNTs) have been attracting extensive
interest and becoming a popular component, owing to their large
surface area and low-dimensional nature for diverse applications in
the fields of sensors, electronics, biomedicine, and engineering [2,
3]. CNTs are divided into single-walled carbon nanotubes (SWCNTs)
and multiwalled carbon nanotubes (MWCNTs): SWCNTs can be
considered one rolled-up sheet of graphene, while MWCNTs are
concentrical tubes of rolled-up graphene [3]. It should be noted
that the electronic properties and detailed electrochemical activity
of pristine SWCNT and MWCNT are different [3]. In most case, the
functionalized/hybrid CNTs are often employed for the fabrication
of the electrochemical and electronics sensors. Compared with the
electronics sensors, the request of functionalized/hybrid CNTs in
electrochemical sensors are not rigorous as the electronics except
for the CNT-field effect transistor (FET). In a typical case, one-
dimensional CNTs are lain on the substrate and build a conducting
network, leading to increased electrode surface area and enhanced
electron transfer, while the huge impenetrate hollow network is
in favor of exchanges of electrochemical active materials. However,
it should be pointed out that electrochemical sensors based on
SWCNT-FETs request semiconducting SWCNTs; hence elimination of
metallic SWCNTs is a necessary procedure.
