Amperometric type transducer: This type of transducer involves the measurement
of the resulting current in an electrochemical setup from an electroactive specimen
as a result of oxidation or reduction. The measurement is usually carried out by
maintaining a constant potential difference at the working electrode with respect to
the reference electrode or the auxiliary electrode. The generated current is proportional to the bulk analyte concentration.
Conductometric type transducer: This type of transducer monitors enzyme reactions by utilizing ion conductometric or impedimetric devices. An alternative
measurement involving differential measurement is also suggested and performed
between the sensor with and without enzyme, respectively.
Ion charge or field effect type transducer: This type of transducer uses the
ion-sensitive field-effect transistor for determining the ion concentration.
Various materials have been explored as a candidate for fabrication of electrochemical biosensors. The potentialities of gold nanoparticle-based ensemble electrode as an electrochemical sensor was found useful for simultaneous detection of
arsenic, mercury and copper found in wastewater [41]. A hybrid of gold-platinum
nanocomposite has been discussed for the detection of mercury. The sensor was
evaluated by monitoring samples collected from the river and tap water [42].
Multiwall carbon nanotubes dispersed in Nafion solution in combination with
bismuth was used for detection of lead and cadmium by differential pulse anodic
stripping voltammetry. Carbon nanoparticles [43] and carbon nanotubes [44] are
also an effective sensing material for the detection of heavy metals. Recently,
Graphene has been proven a good sensing material for wastewater analysis [45]. In
an electrochemical sensor, the size of the working surface area of an electrode is
directly related to the efficiency of analytes. Materials at nanoscale effectively
utilize the increased surface of electrodes [45–47]. Screen printing fabrication
technique at nanoscale promises to employ a maximum of the contact surface area
of electrodes leading to higher efficiency in the measurement of analytes in samples
[48–50].
3.2.2 Thermal Biosensor
Biosensors are enzyme-driven. A specific enzyme suits the need for a specific
substrate. Any biochemical reaction in a biosensor is accompanied by the generation of heat. In totality, there is a change of enthalpy, which is used in principle for
the development of thermal biosensors. With proper calibration, a wide range of
biomolecules present in wastewater may be detected. The core of the thermal
biosensor lies in the development of the sensitive and efficient design of the
transducer element [51].
Based on the operating principle, thermal transducers may be classified as
thermomechanical, thermosensitive, thermocouple—based, etc. In practice, the
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R. Sinha et al.
of the resulting current in an electrochemical setup from an electroactive specimen
as a result of oxidation or reduction. The measurement is usually carried out by
maintaining a constant potential difference at the working electrode with respect to
the reference electrode or the auxiliary electrode. The generated current is proportional to the bulk analyte concentration.
Conductometric type transducer: This type of transducer monitors enzyme reactions by utilizing ion conductometric or impedimetric devices. An alternative
measurement involving differential measurement is also suggested and performed
between the sensor with and without enzyme, respectively.
Ion charge or field effect type transducer: This type of transducer uses the
ion-sensitive field-effect transistor for determining the ion concentration.
Various materials have been explored as a candidate for fabrication of electrochemical biosensors. The potentialities of gold nanoparticle-based ensemble electrode as an electrochemical sensor was found useful for simultaneous detection of
arsenic, mercury and copper found in wastewater [41]. A hybrid of gold-platinum
nanocomposite has been discussed for the detection of mercury. The sensor was
evaluated by monitoring samples collected from the river and tap water [42].
Multiwall carbon nanotubes dispersed in Nafion solution in combination with
bismuth was used for detection of lead and cadmium by differential pulse anodic
stripping voltammetry. Carbon nanoparticles [43] and carbon nanotubes [44] are
also an effective sensing material for the detection of heavy metals. Recently,
Graphene has been proven a good sensing material for wastewater analysis [45]. In
an electrochemical sensor, the size of the working surface area of an electrode is
directly related to the efficiency of analytes. Materials at nanoscale effectively
utilize the increased surface of electrodes [45–47]. Screen printing fabrication
technique at nanoscale promises to employ a maximum of the contact surface area
of electrodes leading to higher efficiency in the measurement of analytes in samples
[48–50].
3.2.2 Thermal Biosensor
Biosensors are enzyme-driven. A specific enzyme suits the need for a specific
substrate. Any biochemical reaction in a biosensor is accompanied by the generation of heat. In totality, there is a change of enthalpy, which is used in principle for
the development of thermal biosensors. With proper calibration, a wide range of
biomolecules present in wastewater may be detected. The core of the thermal
biosensor lies in the development of the sensitive and efficient design of the
transducer element [51].
Based on the operating principle, thermal transducers may be classified as
thermomechanical, thermosensitive, thermocouple—based, etc. In practice, the
196
R. Sinha et al.