amperometric methods were used for analysis. The AChE biosensor exhibited
outstanding activity, high stability and rapid detection for OPs. (Yang et al. 2014).
Yu et al. (2015) developed nanobiosensors for organophosphorus pesticide using
GCE modified with amino functionalised CNTs (CNT-NH 2 ). AChE incubation was
subsequently performed on the electrode, and differential pulse voltammetry (DPV)
was used for detection with LOD of 0.08 nM.
Atrazine is a herbicide widely used in the United States. Liu et al. (2014b)
developed anti-atrazine monoclonal antibodies functionalized Au NPs decorated
Au electrode. The electrode was used for highly sensitive determination of atrazine
using DPV technique. The variations produced on the electrode surface due to the
interaction of antigen and antibody were measured, and a LOD value as low as
74 pM was achieved.
Neonicotinoids are the largely used neuro-active insecticides. Apart from
destroying insects, these also have harmful effects on human health. Acetamiprid
is a neonicotinoid insecticide with chloropyridinyl group. Currently, aptamer-based
nanosensors for detection of acetamiprid are being explored for effective
neonicotinoids detection. In her review, Verdian have summarized such recently
developed aptamer-based nanosensors (Verdian 2018).
Heavy Metals
Chromium
Chromium pollution is a cause of concern due to carcinogenic effects of Cr(VI). This
chemical is released to the environment mainly by industrial activities. For e.g.,
chromium is used and released during dyes/pigments production, metal chrome
plating and leather tanning. For detection of Cr (VI), Leung et al. (2013) reported
colorimetric nanosensors using nanosized biomaterials amyloid-fibril.
El-Safty et al. (2008) reported visual detection of Cr (VI), Co(II), Pb(II) and Pd
(II) using optical nanosensor based on three dimensional (3D) nanostructures. The
nanosensor exhibited rapid detection of Cr (VI) and other analyte ions with
sub-picomolar recognition sensitivity.
Lead
Lead (Pb) is a poisonous heavy metal, and lead exposure can lead to serious diseases
like cancer, neurological and subtle cognitive defects. Several methods for detection
of Pb
2+ are based on label-free and label-based nanosensors. Recently, Memon et al.
(2019) reported the development of label-free colorimetric nanosensor for sensing
Pb
2+ in water. They designed the nanosensor with unmodified Au NPs adsorbed with
detached fragments of truncated 8–17 DNAzyme. The adsorbed AuNPs were
protected against aggregation induced by salt concentration. The presence of Pb
2+
was detected by change in the colour from blue to pink. High sensitivity and low
LOD of 0.2 nM was obtained along with selectivity for Pb
2+ .
Gao et al., developed a nanosensor for the detection of Pb
2+ and Cd
2+ using
AlOOH-graphene oxide (GO) nanocomposite. SWASV method was used for the
electrochemical detection of analytes. High adsorption capacity of AlOOH coupled
126
U. Chakraborty et al.
outstanding activity, high stability and rapid detection for OPs. (Yang et al. 2014).
Yu et al. (2015) developed nanobiosensors for organophosphorus pesticide using
GCE modified with amino functionalised CNTs (CNT-NH 2 ). AChE incubation was
subsequently performed on the electrode, and differential pulse voltammetry (DPV)
was used for detection with LOD of 0.08 nM.
Atrazine is a herbicide widely used in the United States. Liu et al. (2014b)
developed anti-atrazine monoclonal antibodies functionalized Au NPs decorated
Au electrode. The electrode was used for highly sensitive determination of atrazine
using DPV technique. The variations produced on the electrode surface due to the
interaction of antigen and antibody were measured, and a LOD value as low as
74 pM was achieved.
Neonicotinoids are the largely used neuro-active insecticides. Apart from
destroying insects, these also have harmful effects on human health. Acetamiprid
is a neonicotinoid insecticide with chloropyridinyl group. Currently, aptamer-based
nanosensors for detection of acetamiprid are being explored for effective
neonicotinoids detection. In her review, Verdian have summarized such recently
developed aptamer-based nanosensors (Verdian 2018).
Heavy Metals
Chromium
Chromium pollution is a cause of concern due to carcinogenic effects of Cr(VI). This
chemical is released to the environment mainly by industrial activities. For e.g.,
chromium is used and released during dyes/pigments production, metal chrome
plating and leather tanning. For detection of Cr (VI), Leung et al. (2013) reported
colorimetric nanosensors using nanosized biomaterials amyloid-fibril.
El-Safty et al. (2008) reported visual detection of Cr (VI), Co(II), Pb(II) and Pd
(II) using optical nanosensor based on three dimensional (3D) nanostructures. The
nanosensor exhibited rapid detection of Cr (VI) and other analyte ions with
sub-picomolar recognition sensitivity.
Lead
Lead (Pb) is a poisonous heavy metal, and lead exposure can lead to serious diseases
like cancer, neurological and subtle cognitive defects. Several methods for detection
of Pb
2+ are based on label-free and label-based nanosensors. Recently, Memon et al.
(2019) reported the development of label-free colorimetric nanosensor for sensing
Pb
2+ in water. They designed the nanosensor with unmodified Au NPs adsorbed with
detached fragments of truncated 8–17 DNAzyme. The adsorbed AuNPs were
protected against aggregation induced by salt concentration. The presence of Pb
2+
was detected by change in the colour from blue to pink. High sensitivity and low
LOD of 0.2 nM was obtained along with selectivity for Pb
2+ .
Gao et al., developed a nanosensor for the detection of Pb
2+ and Cd
2+ using
AlOOH-graphene oxide (GO) nanocomposite. SWASV method was used for the
electrochemical detection of analytes. High adsorption capacity of AlOOH coupled
126
U. Chakraborty et al.