Carbon-based nanomaterials find a useful application as the functional channel in
the chemiresistor/FET nanosensors systems. For instance, the respective planar and
tubular geometries of graphene and CNTs provide greater binding of electrode
surface with analyte molecules due to maximum exposure of the atoms on the
surface. CNTs possess many desired properties for nanosensing applications, some
of which are (Riu et al. 2006):
1. Unidirectional properties of CNTs-based materials can be greatly controlled due
to high ratio of length-to-radius for CNTs.
2. Based on their diameter, chirality and any other surface functionalization, CNTs
can behave as insulating, metallic or semiconducting materials.
3. CNTs can be encapsulated with gases and can be used to store separating gases or
hydrogen. Metals can also be encapsulated inside CNTs to make magnetic or
electrical nanocables.
4. CNTs are inert, robust and have high mechanical strength.
Carbon-based nanostructures can ensure highly sensitive, low limit and label-free
sensing of analyte due to the comparability of their dimensions to the Debye length
(λ D ), which is a measure of penetration of electric field into the bulk material and is
also responsible for modification of the electrode material’s properties upon analyte
exposure (Nehra et al. 2019). Additionally, these nanomaterials also have the
advantage for their ability of concurrent detection of multiple analytes. The use of
graphene-based 2-D nanomaterials has gained much interest as channel materials for
FET sensors due to their unique structure and excellent electronic properties.
Graphene is a zero-gap semiconductor material with high room temperature electron
mobility. Nanostructure based on graphene and RGO have high sensitivity to
electronic changes upon the adsorption of target analyte molecules, and also have
high specific surface area, thus making them important for sensor applications.
Further, functionalization of the surfaces of carbon-based nanomaterials by
incorporation of some inorganic nanomaterials or through covalent/non-covalent
interactions, enhance the surface properties of the electrode materials. The surfaces
of single-walled carbon nanotubes (SWCNTs) have been modified for their successful application as biosensors. The conductance of the nanotubes can be modified by
substitution of the solid-state gate by detecting molecules (Besteman et al. 2003).
Nanocarbon-modified electrodes can be applied for detection of various
biological and chemical analytes. They have been used as efficient gas sensors for
the detection of both indoor and outdoor harmful gas molecules. Highly sensitive gas
sensors for NO 2 , CO 2 , H 2 , etc., have been fabricated using carbon-based
nanomaterials. For e.g., NO 2 gas sensor was designed by using n-p-n heterojunction
of SnO 2 nanowires and CNTs (Nguyet et al. 2017). These nanomaterials have also
been used for hazardous organic molecules detection. For instance, highly sensitive
and rapid detection of 2,4,6-trinitrotoluene (TNT) was reported by Castro et al.,
using a novel biosensor fabricated with reduced graphene oxide/CNT
nanocomposites (Castro et al. 2018). Ren et al. reported colorimetric nanosensor
for the detection of 2,4,6 trinitrophenol (TNP) compounds using orange fluorescence
106
U. Chakraborty et al.
the chemiresistor/FET nanosensors systems. For instance, the respective planar and
tubular geometries of graphene and CNTs provide greater binding of electrode
surface with analyte molecules due to maximum exposure of the atoms on the
surface. CNTs possess many desired properties for nanosensing applications, some
of which are (Riu et al. 2006):
1. Unidirectional properties of CNTs-based materials can be greatly controlled due
to high ratio of length-to-radius for CNTs.
2. Based on their diameter, chirality and any other surface functionalization, CNTs
can behave as insulating, metallic or semiconducting materials.
3. CNTs can be encapsulated with gases and can be used to store separating gases or
hydrogen. Metals can also be encapsulated inside CNTs to make magnetic or
electrical nanocables.
4. CNTs are inert, robust and have high mechanical strength.
Carbon-based nanostructures can ensure highly sensitive, low limit and label-free
sensing of analyte due to the comparability of their dimensions to the Debye length
(λ D ), which is a measure of penetration of electric field into the bulk material and is
also responsible for modification of the electrode material’s properties upon analyte
exposure (Nehra et al. 2019). Additionally, these nanomaterials also have the
advantage for their ability of concurrent detection of multiple analytes. The use of
graphene-based 2-D nanomaterials has gained much interest as channel materials for
FET sensors due to their unique structure and excellent electronic properties.
Graphene is a zero-gap semiconductor material with high room temperature electron
mobility. Nanostructure based on graphene and RGO have high sensitivity to
electronic changes upon the adsorption of target analyte molecules, and also have
high specific surface area, thus making them important for sensor applications.
Further, functionalization of the surfaces of carbon-based nanomaterials by
incorporation of some inorganic nanomaterials or through covalent/non-covalent
interactions, enhance the surface properties of the electrode materials. The surfaces
of single-walled carbon nanotubes (SWCNTs) have been modified for their successful application as biosensors. The conductance of the nanotubes can be modified by
substitution of the solid-state gate by detecting molecules (Besteman et al. 2003).
Nanocarbon-modified electrodes can be applied for detection of various
biological and chemical analytes. They have been used as efficient gas sensors for
the detection of both indoor and outdoor harmful gas molecules. Highly sensitive gas
sensors for NO 2 , CO 2 , H 2 , etc., have been fabricated using carbon-based
nanomaterials. For e.g., NO 2 gas sensor was designed by using n-p-n heterojunction
of SnO 2 nanowires and CNTs (Nguyet et al. 2017). These nanomaterials have also
been used for hazardous organic molecules detection. For instance, highly sensitive
and rapid detection of 2,4,6-trinitrotoluene (TNT) was reported by Castro et al.,
using a novel biosensor fabricated with reduced graphene oxide/CNT
nanocomposites (Castro et al. 2018). Ren et al. reported colorimetric nanosensor
for the detection of 2,4,6 trinitrophenol (TNP) compounds using orange fluorescence
106
U. Chakraborty et al.