In the field of heavy metal sensing platform author [63] had reported a sensing
mechanism based on Pb-ISHEMT (i.e. lead-ion selective HEMT). The gating
material was made by ion selective membrane (ISM) incorporated with electrical
double layer (EDL). Using this material Pb was sensed up to 10
−10 M and detection
time <10 min. K. H. Chen et al. had reported HEMT towards Hg(II) using
Thioglycolic acid functionalized Au-gated AlGaN/GaN HEMT [62]. The outcomes
propose that handy, fast response, and wireless technology based heavy metal ion
sensors.
In extended gate FETs, the gate terminal is extended and connected to ITO, this
won’t add too cost to the device but provides flexibility of easy functionalization of
the gate terminal. In the series of heavy metal sensing, OFET with an
L-cysteine-immobilized extended gate electrode was designed for Hg (II) ion
sensing [64]. To improve the stability of the membrane towards acidic nature,
chalcogenide type of glass is commonly used in pH sensitive meter/probe. Author
here used Ge 28 Se 60 Sb 12 chalcogenide glass and metal copper was deposited to
make Cu-Ge-Se-Sb pattern to form a Cu (II) ion sensitive membrane over the gate
terminal was deposited and the analysis resulted in 10
−6 mol/L limit of detection
[65].
Detection using enzymes/inorganic species entrapped polymeric membranes:
Electrode developed by single-crystal lanthanum fluoride (LaF3) for fluorine
detection, named as Fluoride ion-sensitive electrode (FISE) by Frat and Ross in
1966. It has various features like good selectivity, stability, and rapid response [66].
The only limiting factor was its high cost. Later, in 1970 when Bergverd introduced
the concept of ISFET, then fluoride will be sensed by the combination of single
crystal LaF3 and ISFET. Later, some of the papers were reported towards fluoride
sensitive ISFET using polycrystalline LaF 3 and the membrane formed was
deposited with structure (Si-SiO 2 -Si 3 N 4 ,-LaF 3 ). This gate membrane will detect the
behaviour of the electrolyte in contact with it [67]. Similarly, buffer b-alanine
(2-aminopropionic
acid)
and
HCl
with
and
without
CDTA
(1,2-cyclohexanediamine tetraacetic acid) [68] and Storensen’s buffer (a mixture of
glycine and hydrochloric acid, pH 2.8) [69] was testified to govern free and total
fluoride concentrations. Sensing of fluoride completes when we get the complete
information about concentration of free fluorine and total fluorine. Therefore,
concept of pF-ISFET and pH-ISFET were introduced in which pH-ISFET is taken
as reference electrode and pF-ISFET is used to calculate concentration of fluorine
even at very low level [70]. In order to replace LaF 3 electrode constantly various
other materials were being reported. Some authors used plasticized uranyl salophen
supramolecular complex [71]. Further, LAPS (Light Addressable Potentiometric
Sensor) heterostructure (Au/Si/LaF 3 ) were investigated for sensitive fluoride
detection [72]. Polydimethylsiloxane (PDMS) functionalized the gold surface with
self-assembled monolayers (SAMs) of fluoride-sensitive ligands were also used
towards sensing of fluoride and sodium [73]. EIS based electrode using poly LaF 3
were also reported with 1.9 ppb detection limit. The device is accomplished by
sensitivity, detection limit, lesser hysteresis voltage, and slight drift ratio [74].
Materials for Electrical Detection of Water Pollutants
119
mechanism based on Pb-ISHEMT (i.e. lead-ion selective HEMT). The gating
material was made by ion selective membrane (ISM) incorporated with electrical
double layer (EDL). Using this material Pb was sensed up to 10
−10 M and detection
time <10 min. K. H. Chen et al. had reported HEMT towards Hg(II) using
Thioglycolic acid functionalized Au-gated AlGaN/GaN HEMT [62]. The outcomes
propose that handy, fast response, and wireless technology based heavy metal ion
sensors.
In extended gate FETs, the gate terminal is extended and connected to ITO, this
won’t add too cost to the device but provides flexibility of easy functionalization of
the gate terminal. In the series of heavy metal sensing, OFET with an
L-cysteine-immobilized extended gate electrode was designed for Hg (II) ion
sensing [64]. To improve the stability of the membrane towards acidic nature,
chalcogenide type of glass is commonly used in pH sensitive meter/probe. Author
here used Ge 28 Se 60 Sb 12 chalcogenide glass and metal copper was deposited to
make Cu-Ge-Se-Sb pattern to form a Cu (II) ion sensitive membrane over the gate
terminal was deposited and the analysis resulted in 10
−6 mol/L limit of detection
[65].
Detection using enzymes/inorganic species entrapped polymeric membranes:
Electrode developed by single-crystal lanthanum fluoride (LaF3) for fluorine
detection, named as Fluoride ion-sensitive electrode (FISE) by Frat and Ross in
1966. It has various features like good selectivity, stability, and rapid response [66].
The only limiting factor was its high cost. Later, in 1970 when Bergverd introduced
the concept of ISFET, then fluoride will be sensed by the combination of single
crystal LaF3 and ISFET. Later, some of the papers were reported towards fluoride
sensitive ISFET using polycrystalline LaF 3 and the membrane formed was
deposited with structure (Si-SiO 2 -Si 3 N 4 ,-LaF 3 ). This gate membrane will detect the
behaviour of the electrolyte in contact with it [67]. Similarly, buffer b-alanine
(2-aminopropionic
acid)
and
HCl
with
and
without
CDTA
(1,2-cyclohexanediamine tetraacetic acid) [68] and Storensen’s buffer (a mixture of
glycine and hydrochloric acid, pH 2.8) [69] was testified to govern free and total
fluoride concentrations. Sensing of fluoride completes when we get the complete
information about concentration of free fluorine and total fluorine. Therefore,
concept of pF-ISFET and pH-ISFET were introduced in which pH-ISFET is taken
as reference electrode and pF-ISFET is used to calculate concentration of fluorine
even at very low level [70]. In order to replace LaF 3 electrode constantly various
other materials were being reported. Some authors used plasticized uranyl salophen
supramolecular complex [71]. Further, LAPS (Light Addressable Potentiometric
Sensor) heterostructure (Au/Si/LaF 3 ) were investigated for sensitive fluoride
detection [72]. Polydimethylsiloxane (PDMS) functionalized the gold surface with
self-assembled monolayers (SAMs) of fluoride-sensitive ligands were also used
towards sensing of fluoride and sodium [73]. EIS based electrode using poly LaF 3
were also reported with 1.9 ppb detection limit. The device is accomplished by
sensitivity, detection limit, lesser hysteresis voltage, and slight drift ratio [74].
Materials for Electrical Detection of Water Pollutants
119