instance, Mahmoudian et al. (2016) reported the synthesis of nanosensor using
nanospherical Pt coated with polypyrrole (Pt/PPy NSs) and used this for highly
sensitive detection of Hg
2+ in presence of other ions like Zn
2+ , Cu
2+ , Ag
+ , K
+ , Pd
2+ ,
Sn
2+ , Pb
2+ , Ni
2+ . Zhang et al. (2015a) prepared nanosensor for detection of trinitrotoluene (TNT) with low detection limit of 0.8 ppb and linear range of 0.01–3 ppm,
using hydrothermally synthesized PtPd nanocubes dispersed in graphene
nanoribbons (PtPd-rGO NRs). Rismetov et al., reported electrodeposition of Pt
NPs on boron doped diamond (BDD) surface for detection of hydrogen peroxide
(H 2 O 2 ) (Rismetov et al. 2014).
Silver (Ag) NPs possess excellent catalytic and SERS activities, and are extensively used for designing nanosensors and nanobiosensors (Wu et al. 2006). These
NPs have also been applied for detection of environmental pollutants. For e.g.,
Sebastian et al., reported microwave assisted synthesis of Ag NPs and applied
them for fabricating nanosensors for mercury Hg(II) ions with 2.1 μM limit of
detection (Sebastian et al. 2018). Ag NPs in conjugation with different matrices
like silicate network, polymers, metal oxides, graphene, have shown high stability
and outstanding sensing abilities. Kariuki et al. (2016) reported selective detection of
nitrobenzene using poly(amic) acid (PAA) embedded with Ag NPs (PAA-Ag NPs).
Ag NPs based immunosensors have also been used for highly selective, sensitive and
rapid detection of analytes like virus, microorganisms and other small inorganic and
organic molecules. Sepunaru et al. (2016) developed technique for sensing influenza
viruses which were tagged with Ag NPs. The sensing was based on linear enhancement in the magnitude and frequency of current with increase in virus concentration
and increment in the surface coverage of Ag NPs. Karthiga et al., reported colorimetric detection of toxic metal ions using Ag NPs synthesized by green method
(Karthiga and Anthony 2013). Various plant extracts (green tea, pepper seed,
sun-dried, neem bark, and fresh mango and neem leaf) were used to prepare green
Ag NPs. Pepper tea extract-based Ag NPs showed colorimetric sensing for Zn
2+ ,
Hg
2+ and Pb
2+ ions. Green tea and mango leaf extracts based Ag NPs showed
colorimetric detection for Hg
2+ and Pb
2+ ions. Selective colorimetric sensing for
Zn
2+ and Hg
2+ was exhibited by neem bark extract-based Ag NPs. Fresh neem and
sun-dried neem leaf based Ag NPs displayed selective detection of Hg
2+ and Hg
2+
and Pb
2+ ions, respectively. The detection was carried out at wide pH range of 2–11.
Copper (Cu) and palladium (Pd) NPs have gained recognition as suitable
materials for nanosensors due to their relatively low cost as compared to Au, Ag
and Pt and their excellent electrocatalytic behaviour and electrical conductivity. Cu
nanostructures exhibit unique features for electroanalytical measurements like better
signal-to-noise ratio, high surface area and high rate of mass transport (Abdel-Karim
et al. 2020). Li et al. (2015a) used single step electrodeposition for synthesis of Cu
nano-clusters, which showed high electrocatalytic performance, and were successfully applied for highly sensitive detection of nitrate. Pd NPs have been extensively
used for sensing applications for hazardous gases, toxic species and biomolecules.
Pd-based nanocomposites have exhibited better analyte mass diffusion, which also
enabled transfer of electrons between electrode and active site due to electron
tunnelling, resulting in excellent performance for electrochemical sensing (Xi et al.
5 Development of Environmental Nanosensors for Detection Monitoring. . .
113
nanospherical Pt coated with polypyrrole (Pt/PPy NSs) and used this for highly
sensitive detection of Hg
2+ in presence of other ions like Zn
2+ , Cu
2+ , Ag
+ , K
+ , Pd
2+ ,
Sn
2+ , Pb
2+ , Ni
2+ . Zhang et al. (2015a) prepared nanosensor for detection of trinitrotoluene (TNT) with low detection limit of 0.8 ppb and linear range of 0.01–3 ppm,
using hydrothermally synthesized PtPd nanocubes dispersed in graphene
nanoribbons (PtPd-rGO NRs). Rismetov et al., reported electrodeposition of Pt
NPs on boron doped diamond (BDD) surface for detection of hydrogen peroxide
(H 2 O 2 ) (Rismetov et al. 2014).
Silver (Ag) NPs possess excellent catalytic and SERS activities, and are extensively used for designing nanosensors and nanobiosensors (Wu et al. 2006). These
NPs have also been applied for detection of environmental pollutants. For e.g.,
Sebastian et al., reported microwave assisted synthesis of Ag NPs and applied
them for fabricating nanosensors for mercury Hg(II) ions with 2.1 μM limit of
detection (Sebastian et al. 2018). Ag NPs in conjugation with different matrices
like silicate network, polymers, metal oxides, graphene, have shown high stability
and outstanding sensing abilities. Kariuki et al. (2016) reported selective detection of
nitrobenzene using poly(amic) acid (PAA) embedded with Ag NPs (PAA-Ag NPs).
Ag NPs based immunosensors have also been used for highly selective, sensitive and
rapid detection of analytes like virus, microorganisms and other small inorganic and
organic molecules. Sepunaru et al. (2016) developed technique for sensing influenza
viruses which were tagged with Ag NPs. The sensing was based on linear enhancement in the magnitude and frequency of current with increase in virus concentration
and increment in the surface coverage of Ag NPs. Karthiga et al., reported colorimetric detection of toxic metal ions using Ag NPs synthesized by green method
(Karthiga and Anthony 2013). Various plant extracts (green tea, pepper seed,
sun-dried, neem bark, and fresh mango and neem leaf) were used to prepare green
Ag NPs. Pepper tea extract-based Ag NPs showed colorimetric sensing for Zn
2+ ,
Hg
2+ and Pb
2+ ions. Green tea and mango leaf extracts based Ag NPs showed
colorimetric detection for Hg
2+ and Pb
2+ ions. Selective colorimetric sensing for
Zn
2+ and Hg
2+ was exhibited by neem bark extract-based Ag NPs. Fresh neem and
sun-dried neem leaf based Ag NPs displayed selective detection of Hg
2+ and Hg
2+
and Pb
2+ ions, respectively. The detection was carried out at wide pH range of 2–11.
Copper (Cu) and palladium (Pd) NPs have gained recognition as suitable
materials for nanosensors due to their relatively low cost as compared to Au, Ag
and Pt and their excellent electrocatalytic behaviour and electrical conductivity. Cu
nanostructures exhibit unique features for electroanalytical measurements like better
signal-to-noise ratio, high surface area and high rate of mass transport (Abdel-Karim
et al. 2020). Li et al. (2015a) used single step electrodeposition for synthesis of Cu
nano-clusters, which showed high electrocatalytic performance, and were successfully applied for highly sensitive detection of nitrate. Pd NPs have been extensively
used for sensing applications for hazardous gases, toxic species and biomolecules.
Pd-based nanocomposites have exhibited better analyte mass diffusion, which also
enabled transfer of electrons between electrode and active site due to electron
tunnelling, resulting in excellent performance for electrochemical sensing (Xi et al.
5 Development of Environmental Nanosensors for Detection Monitoring. . .
113