5.3.3.4 Nanosensors Used for Different Types of Analytes
Nanosensors can further be classified on the basis of their application for sensing
specific chemical and biological analytes. Current development in the field of
nanosensors for detection of some major environmental contaminants has been
discussed in this section:
Pesticides
Pesticides were developed and introduced for their applications to destroy pests.
Pesticides also include chemicals like insecticides, herbicides, fungicides, etc. But,
despite their applications, pesticides have emerged as one of the major environmental pollutants due to their toxicity, and potential for bioaccumulation. Major pesticide
classes include triazines, carbamates, organophosphorus (OPs) and neonicotinoids.
Detection of these pesticides from environmental samples is of utmost importance.
Nanosensors and nanobiosensors have been efficiently employed for highly sensitive and selective detection of pesticides. These sensors can be used for direct
sensing of pesticides from sample. Pesticides often affect a particular enzyme.
Hence, another method for pesticide detection involves direct or indirect monitoring
of such enzymes. Carbamates and organophosphates inhibit the formation of acetylcholinesterase (AChE) enzyme. Thus, AchE has been immobilized on solid electrode surface for sensitive and fast electrochemical detection, and indirectly sensing
of the associated pesticides (Willner and Vikesland 2018). For detection of AchE
inhibition, hydrolysis of acetylthiocholine is used as an analogous reaction. Yang
et al. (2014) used PPy-rGO (polyoyrrole-reduced graphene oxide) and Au NPs (~
20 nm) for fabrication of Au-PPy-rGO-based AChE nanobiosensors for detection of
OPs (Fig. 5.7). They used organophosphate paraxon-ethyl as a model pesticide.
Electrodeposition of Au NPs was done on PPy-rGO to improve the conductivity and
surface area of the electrode. Sulphonated rGO was electrochemically co-deposited
with pyrrole. rGO aggregation was avoided by incorporation into PPy. AChE was
co-deposited with a biocompatible silica matrix. The cyclic voltammetric (CV) and
Fig. 5.7 Illustration of organophosphorus pesticide detection using AChE biosensor fabricated
using Au-Ppy-rGO nanocomposite
5 Development of Environmental Nanosensors for Detection Monitoring. . .
125
Nanosensors can further be classified on the basis of their application for sensing
specific chemical and biological analytes. Current development in the field of
nanosensors for detection of some major environmental contaminants has been
discussed in this section:
Pesticides
Pesticides were developed and introduced for their applications to destroy pests.
Pesticides also include chemicals like insecticides, herbicides, fungicides, etc. But,
despite their applications, pesticides have emerged as one of the major environmental pollutants due to their toxicity, and potential for bioaccumulation. Major pesticide
classes include triazines, carbamates, organophosphorus (OPs) and neonicotinoids.
Detection of these pesticides from environmental samples is of utmost importance.
Nanosensors and nanobiosensors have been efficiently employed for highly sensitive and selective detection of pesticides. These sensors can be used for direct
sensing of pesticides from sample. Pesticides often affect a particular enzyme.
Hence, another method for pesticide detection involves direct or indirect monitoring
of such enzymes. Carbamates and organophosphates inhibit the formation of acetylcholinesterase (AChE) enzyme. Thus, AchE has been immobilized on solid electrode surface for sensitive and fast electrochemical detection, and indirectly sensing
of the associated pesticides (Willner and Vikesland 2018). For detection of AchE
inhibition, hydrolysis of acetylthiocholine is used as an analogous reaction. Yang
et al. (2014) used PPy-rGO (polyoyrrole-reduced graphene oxide) and Au NPs (~
20 nm) for fabrication of Au-PPy-rGO-based AChE nanobiosensors for detection of
OPs (Fig. 5.7). They used organophosphate paraxon-ethyl as a model pesticide.
Electrodeposition of Au NPs was done on PPy-rGO to improve the conductivity and
surface area of the electrode. Sulphonated rGO was electrochemically co-deposited
with pyrrole. rGO aggregation was avoided by incorporation into PPy. AChE was
co-deposited with a biocompatible silica matrix. The cyclic voltammetric (CV) and
Fig. 5.7 Illustration of organophosphorus pesticide detection using AChE biosensor fabricated
using Au-Ppy-rGO nanocomposite
5 Development of Environmental Nanosensors for Detection Monitoring. . .
125