10.4 Parameters of Nanomaterials Promising for Sensing
10.4.1 Processability
The fabrication of sensing layers by the nanomaterials to be used as analyte receptor is a
very tricky process as well as important process since the sensor sensitivity depends on
thickness, chemical composition, crystallinity, morphology, transducer properties, etc.
The present state-of-the-art fabrication of sensor layer by various nanomaterials has
been extensively studied, and numerous research articles are available in various sensorrelated journals and books. The most common names of such processes are electrochemical deposition, pellet preparation, dip coating, drop coating, spin coating, film casting,
printing, layer-by-layer deposition, Langmuir–Blodgett film casting, self-assembly techniques, etc. Here the procedure of individual process is not elaborated as those have been
briefly discussed elsewhere. There are two main ways in order to fabricate the sensing
layer through processing of the nanomaterials by the above techniques, viz., solution
processability and thermal processability.
The inorganic nanomaterials are generally thermally very much stable, but
melting those nanomaterials at achievable temperature is quite impossible. On the
other hand, the thermal melting of organic especially polymer nanomaterials is
possible, but they often start to decompose or degrade before melting. For hybrid
nanomaterials although the properties are improved as well as influence greatly on
the type of materials mixture used, however, the properties should be very close to
that of the parent inorganic or organic materials. In other words, the thermal
processing of nanomaterials is not used at all or sometimes used but in very rare
cases. The modified thermal processing might be used for some inorganic
nanomaterials during the synthesis.
The solution processability is quite promising for organic polymer nanomaterials and
polymer-based hybrid nanomaterials. This is because the vast organic polymers are
soluble in many solvents according to their structural skeleton. However, some structurally rigid polymers like conjugated polymers as well as their hybrid nanomaterials are
insoluble or poorly soluble in organic solvent. By following this route, the processing of
inorganic nanomaterials is not possible as almost all the inorganic nanomaterials are not
soluble in organic solvent. However, the insoluble inorganic nanomaterials are processed
from their suspension. For example, the gold–tin dioxide nanocomposite was brush coated
onto cylindrical alumina tube by making a paste of powder with water (Manjula et al.
2011). As illustrated in Fig. 10.14, a thick receptor film of most of the inorganic
nanomaterials was deposited by painting or coating an aqueous paste of powders on the
ceramic interdigitated substrate followed by drying under controlled temperature (Neri
et al. 2013). The Langmuir–Blodgett or layer-by-layer deposition method may be used for
the inorganic nanomaterials insoluble in the solvent. Even the Langmuir–Blodgett technique was used to deposit SWCNT sensing layer on the pre-deposited cadmium
arachidate buffer following the same method (Penza et al. 2005a). Pellet making is
found to be the last solution for the processing of infusible and insoluble nanomaterials.
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367
10.4.1 Processability
The fabrication of sensing layers by the nanomaterials to be used as analyte receptor is a
very tricky process as well as important process since the sensor sensitivity depends on
thickness, chemical composition, crystallinity, morphology, transducer properties, etc.
The present state-of-the-art fabrication of sensor layer by various nanomaterials has
been extensively studied, and numerous research articles are available in various sensorrelated journals and books. The most common names of such processes are electrochemical deposition, pellet preparation, dip coating, drop coating, spin coating, film casting,
printing, layer-by-layer deposition, Langmuir–Blodgett film casting, self-assembly techniques, etc. Here the procedure of individual process is not elaborated as those have been
briefly discussed elsewhere. There are two main ways in order to fabricate the sensing
layer through processing of the nanomaterials by the above techniques, viz., solution
processability and thermal processability.
The inorganic nanomaterials are generally thermally very much stable, but
melting those nanomaterials at achievable temperature is quite impossible. On the
other hand, the thermal melting of organic especially polymer nanomaterials is
possible, but they often start to decompose or degrade before melting. For hybrid
nanomaterials although the properties are improved as well as influence greatly on
the type of materials mixture used, however, the properties should be very close to
that of the parent inorganic or organic materials. In other words, the thermal
processing of nanomaterials is not used at all or sometimes used but in very rare
cases. The modified thermal processing might be used for some inorganic
nanomaterials during the synthesis.
The solution processability is quite promising for organic polymer nanomaterials and
polymer-based hybrid nanomaterials. This is because the vast organic polymers are
soluble in many solvents according to their structural skeleton. However, some structurally rigid polymers like conjugated polymers as well as their hybrid nanomaterials are
insoluble or poorly soluble in organic solvent. By following this route, the processing of
inorganic nanomaterials is not possible as almost all the inorganic nanomaterials are not
soluble in organic solvent. However, the insoluble inorganic nanomaterials are processed
from their suspension. For example, the gold–tin dioxide nanocomposite was brush coated
onto cylindrical alumina tube by making a paste of powder with water (Manjula et al.
2011). As illustrated in Fig. 10.14, a thick receptor film of most of the inorganic
nanomaterials was deposited by painting or coating an aqueous paste of powders on the
ceramic interdigitated substrate followed by drying under controlled temperature (Neri
et al. 2013). The Langmuir–Blodgett or layer-by-layer deposition method may be used for
the inorganic nanomaterials insoluble in the solvent. Even the Langmuir–Blodgett technique was used to deposit SWCNT sensing layer on the pre-deposited cadmium
arachidate buffer following the same method (Penza et al. 2005a). Pellet making is
found to be the last solution for the processing of infusible and insoluble nanomaterials.
10 Nanomaterials Based Sensors for Air Pollution Control
367