Church et al. (2016) demonstrated in situ detection of PAHs in aqueous samples,
using a graphene-based nanosensor. Au/Ti film on wafer of Si was separately
prepared by photolithography and etching, and chemical vapour deposition (CVD)
was used for preparing single graphene layer. The Si wafer was then transferred on
the graphene layer for fabrication of the nanosensor. Cyclic voltammetry (CV) and
electrochemical impedance spectroscopy (EIS) was used for analyzing the sensor
performance on toluene as model aromatic molecule.
5.4
Limitations
Nanosensors are associated with numerous advantages and excellent potentials for
application in environmental monitoring, assessment and sensing. But there are also
some limitations in utility of nanosensors. In their work Kaur et al. (2019) have
summarized some of the major challenges related to the applications of nanosensors,
some of which have been discussed here:
1. Cost: For large scale industrial applications, cost-effectiveness in terms of material, production, implementation and handling cost associated with any technique
is very important. However, cost-effectiveness of nanotechnology-based
applications is lower as compared to other techniques, hence, limiting their
practical application. The synthesis and characterization techniques, and raw
materials cost for development of several NMs is still higher as compared to
other conventional materials used for environmental sensing. For e.g., for pointof-care devices for applications like sensing of heavy metal/anion and pathogens,
most companies and industries still use conventional carbon/cellulose/fibre-based
platforms. Despite excellent gas sensing performance displayed by nanosensors,
metal oxide platform is still used for gas sensors available in the market. NMs
used for nanosensor applications like SiNWs, CdTe QDs, graphene and CNTs are
still costly materials for large scale practical nanosensor applications. There is
need for cost minimization for practical applicability of NMs-based sensors.
2. Sample preparation: Preconcentration and preparation of samples, prior to their
analysis is an important step to obtain accurate response from nanosensors, by
minimizing false-positive signals or cross-interference. For e.g., proper purification and isolation of complex analytes such as heavy metals, bacteria, food toxins,
pathogens, etc., is required prior to their analysis. But such pre sample processing
steps make the analysis less convenient and costly for practical applications.
Nowadays, microfluidic channels are being introduced with the nanosensor
setup for achieving the preprocessing steps, but robust device packaging is
necessary for such devices.
3. Concerns of nanotoxicity: Unknown toxicity profiles of nanomaterials (NMs)
have always been a matter of concern. More data and studies are required for
behaviour of NMs in environment, assessment of exposure, precise analysis of
toxicity of NMs in biological samples, and measurements of amounts or
concentrations of NMs permissible for discharge or exposure without any
5 Development of Environmental Nanosensors for Detection Monitoring. . .
133
using a graphene-based nanosensor. Au/Ti film on wafer of Si was separately
prepared by photolithography and etching, and chemical vapour deposition (CVD)
was used for preparing single graphene layer. The Si wafer was then transferred on
the graphene layer for fabrication of the nanosensor. Cyclic voltammetry (CV) and
electrochemical impedance spectroscopy (EIS) was used for analyzing the sensor
performance on toluene as model aromatic molecule.
5.4
Limitations
Nanosensors are associated with numerous advantages and excellent potentials for
application in environmental monitoring, assessment and sensing. But there are also
some limitations in utility of nanosensors. In their work Kaur et al. (2019) have
summarized some of the major challenges related to the applications of nanosensors,
some of which have been discussed here:
1. Cost: For large scale industrial applications, cost-effectiveness in terms of material, production, implementation and handling cost associated with any technique
is very important. However, cost-effectiveness of nanotechnology-based
applications is lower as compared to other techniques, hence, limiting their
practical application. The synthesis and characterization techniques, and raw
materials cost for development of several NMs is still higher as compared to
other conventional materials used for environmental sensing. For e.g., for pointof-care devices for applications like sensing of heavy metal/anion and pathogens,
most companies and industries still use conventional carbon/cellulose/fibre-based
platforms. Despite excellent gas sensing performance displayed by nanosensors,
metal oxide platform is still used for gas sensors available in the market. NMs
used for nanosensor applications like SiNWs, CdTe QDs, graphene and CNTs are
still costly materials for large scale practical nanosensor applications. There is
need for cost minimization for practical applicability of NMs-based sensors.
2. Sample preparation: Preconcentration and preparation of samples, prior to their
analysis is an important step to obtain accurate response from nanosensors, by
minimizing false-positive signals or cross-interference. For e.g., proper purification and isolation of complex analytes such as heavy metals, bacteria, food toxins,
pathogens, etc., is required prior to their analysis. But such pre sample processing
steps make the analysis less convenient and costly for practical applications.
Nowadays, microfluidic channels are being introduced with the nanosensor
setup for achieving the preprocessing steps, but robust device packaging is
necessary for such devices.
3. Concerns of nanotoxicity: Unknown toxicity profiles of nanomaterials (NMs)
have always been a matter of concern. More data and studies are required for
behaviour of NMs in environment, assessment of exposure, precise analysis of
toxicity of NMs in biological samples, and measurements of amounts or
concentrations of NMs permissible for discharge or exposure without any
5 Development of Environmental Nanosensors for Detection Monitoring. . .
133