observed in the number of emerging pollutants such as pharmaceuticals and persistent
organic pollutants present in water and other ecosystems. Thus, it is highly urgent to
develop corresponding specific and sensitive analytical techniques [28].
Traditional analytical approaches, including high-performance liquid chromatography and liquid/gas chromatography-mass spectrometry, have gradually
been evolving to improve their detection capabilities [9]. Simultaneously, novel
techniques with ultra-high sensitivity, simple operations and portability have also
emerged for the determination of pollutants in environmental samples [3, 95, 97].
Among these technologies, surface-enhanced Raman scattering appears to be one of
the most suitable methods for detecting environmental pollutants.
Raman scattering spectroscopy was discovered in 1928 [69]. Due to containing
abundant structural information of analytes, Raman scattering spectroscopy has
been considered as a ubiquitous tool in analytical science. Surface-enhanced Raman
scattering, exhibiting a significant enhancement of Raman scattering from a rough
metal surface, has greatly promoted the development of Raman technology towards
the practical applications [8, 22]. Recently, this approach has become a powerful
analytical technique for the detection of environmental pollutants because of its
outstanding advantages, such as “fingerprint” information, ultrahigh sensitivity, and
rapidity [62, 80].
4 Advances in Biosensors for Environmental Monitoring
Biosensors are analytical devices that can identify and detect a signal within a cell
or tissue. These are composed of bio-recognition elements and different kinds of
physicochemical transducers [27, 57]. Biosensors deliver the required portable
analytical tools and early warning systems owing to their specificity, sensitivity,
reusability, speed along with their ability for permanent and unattended operation in
the field. Enzyme-based biosensor is most commonly used for the determination of
heavy metals in the aqueous system. For serving this purpose, a wide variety of
enzymes such as glucose oxidase, urease, tyrosinase, peroxidase, etc. have been
reported [30, 70] (Maleki et al. 2017). Also, electrochemical sensors have been
proved to be a promising approach in heavy metal monitoring, due to their stable
and strong interaction with ultra-low levels of metal ions present in the system [40,
96]. A highly sensitive microfluidic Pb
2+ biosensor was designed by immobilization
of a lead-specific catalytic DNA on the polymethylmethacrylate microchannel [25].
With the covalent attachment of metallothionein onto a quartz crystal, a piezoelectric biosensor was designed to monitor Zn
2+ and Cd
2+ in the aqueous system
[75]. Chen et al. developed a piezoelectric nano-biosensor for accurate determination of Hg
2+ , using quartz crystal microbalance with dissipation monitoring
technology [19].
Recently, ion sensors based on Aluminium gallium nitride/Gallium nitride high
electron mobility transistors have been developed to monitor various ions. These
devices are sensitive towards charge characteristics at the surface and have the
260
R. Khan et al.
organic pollutants present in water and other ecosystems. Thus, it is highly urgent to
develop corresponding specific and sensitive analytical techniques [28].
Traditional analytical approaches, including high-performance liquid chromatography and liquid/gas chromatography-mass spectrometry, have gradually
been evolving to improve their detection capabilities [9]. Simultaneously, novel
techniques with ultra-high sensitivity, simple operations and portability have also
emerged for the determination of pollutants in environmental samples [3, 95, 97].
Among these technologies, surface-enhanced Raman scattering appears to be one of
the most suitable methods for detecting environmental pollutants.
Raman scattering spectroscopy was discovered in 1928 [69]. Due to containing
abundant structural information of analytes, Raman scattering spectroscopy has
been considered as a ubiquitous tool in analytical science. Surface-enhanced Raman
scattering, exhibiting a significant enhancement of Raman scattering from a rough
metal surface, has greatly promoted the development of Raman technology towards
the practical applications [8, 22]. Recently, this approach has become a powerful
analytical technique for the detection of environmental pollutants because of its
outstanding advantages, such as “fingerprint” information, ultrahigh sensitivity, and
rapidity [62, 80].
4 Advances in Biosensors for Environmental Monitoring
Biosensors are analytical devices that can identify and detect a signal within a cell
or tissue. These are composed of bio-recognition elements and different kinds of
physicochemical transducers [27, 57]. Biosensors deliver the required portable
analytical tools and early warning systems owing to their specificity, sensitivity,
reusability, speed along with their ability for permanent and unattended operation in
the field. Enzyme-based biosensor is most commonly used for the determination of
heavy metals in the aqueous system. For serving this purpose, a wide variety of
enzymes such as glucose oxidase, urease, tyrosinase, peroxidase, etc. have been
reported [30, 70] (Maleki et al. 2017). Also, electrochemical sensors have been
proved to be a promising approach in heavy metal monitoring, due to their stable
and strong interaction with ultra-low levels of metal ions present in the system [40,
96]. A highly sensitive microfluidic Pb
2+ biosensor was designed by immobilization
of a lead-specific catalytic DNA on the polymethylmethacrylate microchannel [25].
With the covalent attachment of metallothionein onto a quartz crystal, a piezoelectric biosensor was designed to monitor Zn
2+ and Cd
2+ in the aqueous system
[75]. Chen et al. developed a piezoelectric nano-biosensor for accurate determination of Hg
2+ , using quartz crystal microbalance with dissipation monitoring
technology [19].
Recently, ion sensors based on Aluminium gallium nitride/Gallium nitride high
electron mobility transistors have been developed to monitor various ions. These
devices are sensitive towards charge characteristics at the surface and have the
260
R. Khan et al.