widely used and discharged into the environment directly or indirectly due to various
human activities. Nanosensors find an important application for detection and
monitoring of such harmful compounds from environmental samples. Here, in this
portion of the chapter, we are mainly discussing the nanosensors classified according
to their environmental applications. Table 5.3 displays some recently developed
nanosensors for some major chemical and biological environmental pollutants.
5.3.3.1 Monitoring of Air Quality: Gas Sensors
Various industrial activities, combustion of biomass and fossil fuels for energy
production, vehicular emissions, natural causes like volcanic eruptions etc., result
in the release of various organic and inorganic gases, which beyond a certain limit
are the major sources of air pollution. Sulphur oxides (SO X ), carbon monoxide (CO),
carbon dioxide (CO 2 ), nitrogen oxides (NO X ), chlorofluorocarbons (CFCs), ammonia (NH 3 ), volatile organic compounds (VOC) are included as major air pollutants.
These pollutants can be further categorized as organic, inorganic and carcinogenic
gases.
Extensive research work has been performed for the utilization of nanomaterials
for development of nanosensors for detection of different gaseous pollutants. Semiconducting nano-MOX like NiO, Fe 2 O 3 , WO 3 , TiO 2 , ZnO, SnO 2 have been used as
highly sensitive, rapid and cost-effective materials for fabrication of resistive gas
sensors. These nanosensors can detect multiple gases and have simple electronic
interface. Limitations with MOX-based gas sensors is their long-term instability, and
working ability between 200
C to 500
C (Maduraiveeran and Jin 2017; Wetchakun
et al. 2011). On the other hand polymer-based gas sensors can operate under room
temperatures (Bai and Shi 2007). Therefore, these challenges can be overcome by
combining both MOX nanomaterials and conductive polymers into nanocomposites
for the development of gas sensors with high performance. The operating principles
for most of these gas sensors is the variation in electrical properties (like resistance)
resulted from transfer of charge or gas adsorption on the sensor surface (Hatchett and
Josowicz 2008).
Major organic gas pollutants are the VOCs these are types of flammable and
greenhouse gases including ethanol, styrene, vinyl acetate, butadiene, acetonitrile,
acetone, ethylene oxide, etc. These chemicals are mostly released from chemical
industries and these have acute toxic effects (Lu et al. 2019). Detection of VOCs
using efficient gas sensors is very important for monitoring of air quality. In their
work, Zhou et al. (2018) reported the gas sensing applications of branched
nanostructure based on one dimensional (1 D) nanomaterials. The heterostructures
were prepared by combination of Zn 2 SnO 4 nanorods and Mn 3 O 4 nanowires,
synthesized by a two-step hydrothermal method. The nanosensors exhibited outstanding and selective detection of acetone. Recently, Pramanik et al. (2013)
reported nanohybrid designed with bentonite modified polyaniline (PANI)
nanofibers. These nanohybrids were tested for detection of ethanol, toluene, benzene
and acetone, and the 0.23 wt% PANI containing nanohybrid displayed higher
sensitivity for acetone as compared to other gases. Khoang et al. (2012) produced
ethanol sensors with high performance using hierarchical nanostructures synthesized
116
U. Chakraborty et al.
human activities. Nanosensors find an important application for detection and
monitoring of such harmful compounds from environmental samples. Here, in this
portion of the chapter, we are mainly discussing the nanosensors classified according
to their environmental applications. Table 5.3 displays some recently developed
nanosensors for some major chemical and biological environmental pollutants.
5.3.3.1 Monitoring of Air Quality: Gas Sensors
Various industrial activities, combustion of biomass and fossil fuels for energy
production, vehicular emissions, natural causes like volcanic eruptions etc., result
in the release of various organic and inorganic gases, which beyond a certain limit
are the major sources of air pollution. Sulphur oxides (SO X ), carbon monoxide (CO),
carbon dioxide (CO 2 ), nitrogen oxides (NO X ), chlorofluorocarbons (CFCs), ammonia (NH 3 ), volatile organic compounds (VOC) are included as major air pollutants.
These pollutants can be further categorized as organic, inorganic and carcinogenic
gases.
Extensive research work has been performed for the utilization of nanomaterials
for development of nanosensors for detection of different gaseous pollutants. Semiconducting nano-MOX like NiO, Fe 2 O 3 , WO 3 , TiO 2 , ZnO, SnO 2 have been used as
highly sensitive, rapid and cost-effective materials for fabrication of resistive gas
sensors. These nanosensors can detect multiple gases and have simple electronic
interface. Limitations with MOX-based gas sensors is their long-term instability, and
working ability between 200
C to 500
C (Maduraiveeran and Jin 2017; Wetchakun
et al. 2011). On the other hand polymer-based gas sensors can operate under room
temperatures (Bai and Shi 2007). Therefore, these challenges can be overcome by
combining both MOX nanomaterials and conductive polymers into nanocomposites
for the development of gas sensors with high performance. The operating principles
for most of these gas sensors is the variation in electrical properties (like resistance)
resulted from transfer of charge or gas adsorption on the sensor surface (Hatchett and
Josowicz 2008).
Major organic gas pollutants are the VOCs these are types of flammable and
greenhouse gases including ethanol, styrene, vinyl acetate, butadiene, acetonitrile,
acetone, ethylene oxide, etc. These chemicals are mostly released from chemical
industries and these have acute toxic effects (Lu et al. 2019). Detection of VOCs
using efficient gas sensors is very important for monitoring of air quality. In their
work, Zhou et al. (2018) reported the gas sensing applications of branched
nanostructure based on one dimensional (1 D) nanomaterials. The heterostructures
were prepared by combination of Zn 2 SnO 4 nanorods and Mn 3 O 4 nanowires,
synthesized by a two-step hydrothermal method. The nanosensors exhibited outstanding and selective detection of acetone. Recently, Pramanik et al. (2013)
reported nanohybrid designed with bentonite modified polyaniline (PANI)
nanofibers. These nanohybrids were tested for detection of ethanol, toluene, benzene
and acetone, and the 0.23 wt% PANI containing nanohybrid displayed higher
sensitivity for acetone as compared to other gases. Khoang et al. (2012) produced
ethanol sensors with high performance using hierarchical nanostructures synthesized
116
U. Chakraborty et al.