Nanosensors use components like an analyte, sensor, transducer and detector to detect changes in electrical signals or other physical properties when molecules interact with sensor materials like carbon nanotubes or graphene. They can function as chemical or mechanical sensors and are used in applications such as pollution monitoring, medical diagnosis, MEMS devices, and more. Future applications of nanosensors include rapid COVID-19 detection and continued development in clinical diagnostics and other fields.

1. NANOSENSORS
Basics, applications, and construction

2. How Do Nanosensors Work?
An analyte, sensor, transducer and detector are the components of a
sensor system, with feedback from the detector to the sensor.
Sensitivity, specificity and ease of execution are the main
characteristics to consider when designing a sensor.
The materials used to build a nanosensor are related to its application. For
example, noble metal nanoparticles have size-dependent optical properties
and are often used in optical sensors. Popular materials for building
nanoscale sensors include carbon nanotubes and graphene.
Nanosensors typically work by monitoring electrical changes in the sensor
materials.

3. For example, carbon nanotube-based sensors work in this way.
When a molecule of nitrogen dioxide (NO2) is present, it will strip
an electron from the nanotube, which in turn causes the
nanotube to be less conductive.
If ammonia (NO3) is present, it reacts with water vapor and
donates an electron to the carbon nanotube, making it more
conductive. By treating the nanotubes with various coating
materials, they can be made sensitive to certain molecules and
immune to others.

4. Like chemical nanosensors, mechanical nanosensors also tend to
measure electrical changes. Those used in the MEMS systems that car
airbags depend upon are monitoring changes in capacitance. These
systems have a minuscule weighted shaft attached to a capacitor. The
shaft bends with changes in acceleration and this is measured as
changes in capacitance.
They have also been developed to the point of measurement at the
single-molecule level.

5. Types of nanosensors include:
•Carbon nanotubes, quantum dots, peptide or DNA-based
fluorescent nanosensors.
•Plasmon coupling–based nanosensors
•Plasmonic enhancing–/quenching–based nanosensors
•Magnetic resonance imaging-based nanosensors
•Photoacoustic-based nanosensors
•Multimodal nanosensors

6. Nanosensor Applications
Nanosensors can be chemical sensors or mechanical sensors. They are used in a
variety of applications across a range of industries, from biomedical to
environmental. Some common applications are highlighted below:
• Detecting various chemicals in gases for pollution monitoring.
• Medical diagnosis, either as bloodborne sensors or in lab-on-a-chip type
devices.
• To monitor physical parameters such as temperature, displacement and flow.
• As accelerometers in MEMS devices like airbag sensors.
• To monitor plant signaling and metabolism to understand plant biology.
• To study neurotransmitters in the brain to understand neurophysiology.
• To collect real-time measurements of soil conditions, such as pH, moisture,
nutrients, and residual pesticides for agricultural purposes.
• To detect pesticides on the surface of fruits and vegetables and to detect
carcinogens in food.
• To detect pathogens in food as part of food safety and quality control
measures.
• The real-time monitoring of the metabolic activity of cancer cells in response
to therapeutic intervention.
• The detection and monitoring of small-molecule metabolites.

7. Nanosensors: Looking to the Future
Nanosensors aid in the progression of fields such as medical technology; precision
agriculture; urban farming; chemicals, optics, plant nanobionics; prognostics and
diagnostics; biomedicine, SERS-based sensors; and many industrial applications.
As the cost of developing and producing nanosensors reduces, we will likely see
further applications emerge. The field of diagnostics, in particular, is set to
benefit from future advancements in nanosensor technology.
The SARS-CoV-2 (COVID-19) pandemic has recently thrown a spotlight on
nanosensor technology, thanks to recent research that has led to a new, super
quick method of detecting coronavirus using nano-based sensors.
In 2023, a team of researchers from the Norwegian University of Science and
Technology (NTNU), Oslomet and the University of Tabriz in East Azerbaijan
reported that they had developed a graphene-based nanosensor capable of
detecting coronavirus in blood samples. The platform was designed to overcome
the limitations of the currently available PCR and antibody tests.
It is likely that work will continue to develop nanosensors in rapid diagnostic
applications as well as in other areas of clinical diagnostics in the future.