• In the area defence and military for designing special equipments, detection of
toxic chemicals, forensics, etc.
• In agricultural sector for devising humidity sensors for automatic irrigation
systems, for detection of levels of harmful chemicals such as pesticides and
fungicides, monitoring of soil conditions and crop growth, etc.
• Significantly important utilization in environmental assessment, detection and
monitoring. They can be effectively used for the detection of toxic and harmful
gaseous pollutants released from industrial, domestic, vehicular, and natural
emissions, dangerous organic and inorganic chemicals contaminating the water
and soil, quality control of these natural resources, designing real time environment monitoring systems to check and regulate the levels of any
contaminants etc.
There are numerous other important applications of nanosensors, but this chapter
focuses on the applications of nanosensors in the field of detection, monitoring and
assessment of the environmental samples, with discussion of various types of
nanosensors based on different classifications applicable for this field. This chapter
also discusses the limitations and future scopes for the use of nanosensors in
environmental applications.
5.2
Working Principle of Nanosensors and Methods
for Nanosensors Development
The main components of a basic sensor are: (1) sensor material (2) transducer.
In principle, in the presence of the target analytes, the sensor materials are
responsive and sensitive to variation in environmental stimuli, which act as the
transduction principle, such as thermal (temperature, heat flow, entropy, specific
heat etc.), chemicals (concentration, pH, composition, oxidation/reduction potential,
rate of reaction etc.), magnetic (magnetic moment, flux density, permeability, field
intensity), optical (absorbance, transmittance, fluorescence etc.), mechanical (volume, area, length, pressure, mass flow, acoustic intensity and acoustic wavelength,
etc.), electrical (current, voltage, resistance, charge, etc.) variations (Middlehoek and
Noorlag 1982). These variations are converted to mostly electrical signals by the
transducer to give an output that can be analyzed.
In case of biosensors, another important component is the bio-recognition element such as enzymes, oligonucleotides and antibodies. These elements interact
with the target analyte to produce biological response which can be converted to
electrical response by the transducer.
The methods for production of nanosensors include three main approaches:
(1) top-down lithography, (2) bottom-up method and (3) self-assembly.
Most of the integrated circuits are developed by top-down lithography, which
involves carving out the required design from larger block of material. This method
is mostly used to prepare devices for micro electromechanical systems, but recently,
nanosized components have also been incorporated by this technique.
94
U. Chakraborty et al.
toxic chemicals, forensics, etc.
• In agricultural sector for devising humidity sensors for automatic irrigation
systems, for detection of levels of harmful chemicals such as pesticides and
fungicides, monitoring of soil conditions and crop growth, etc.
• Significantly important utilization in environmental assessment, detection and
monitoring. They can be effectively used for the detection of toxic and harmful
gaseous pollutants released from industrial, domestic, vehicular, and natural
emissions, dangerous organic and inorganic chemicals contaminating the water
and soil, quality control of these natural resources, designing real time environment monitoring systems to check and regulate the levels of any
contaminants etc.
There are numerous other important applications of nanosensors, but this chapter
focuses on the applications of nanosensors in the field of detection, monitoring and
assessment of the environmental samples, with discussion of various types of
nanosensors based on different classifications applicable for this field. This chapter
also discusses the limitations and future scopes for the use of nanosensors in
environmental applications.
5.2
Working Principle of Nanosensors and Methods
for Nanosensors Development
The main components of a basic sensor are: (1) sensor material (2) transducer.
In principle, in the presence of the target analytes, the sensor materials are
responsive and sensitive to variation in environmental stimuli, which act as the
transduction principle, such as thermal (temperature, heat flow, entropy, specific
heat etc.), chemicals (concentration, pH, composition, oxidation/reduction potential,
rate of reaction etc.), magnetic (magnetic moment, flux density, permeability, field
intensity), optical (absorbance, transmittance, fluorescence etc.), mechanical (volume, area, length, pressure, mass flow, acoustic intensity and acoustic wavelength,
etc.), electrical (current, voltage, resistance, charge, etc.) variations (Middlehoek and
Noorlag 1982). These variations are converted to mostly electrical signals by the
transducer to give an output that can be analyzed.
In case of biosensors, another important component is the bio-recognition element such as enzymes, oligonucleotides and antibodies. These elements interact
with the target analyte to produce biological response which can be converted to
electrical response by the transducer.
The methods for production of nanosensors include three main approaches:
(1) top-down lithography, (2) bottom-up method and (3) self-assembly.
Most of the integrated circuits are developed by top-down lithography, which
involves carving out the required design from larger block of material. This method
is mostly used to prepare devices for micro electromechanical systems, but recently,
nanosized components have also been incorporated by this technique.
94
U. Chakraborty et al.