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Our modern lives rely on sensors to allow society to run smoothly. Sensors in the road detect cars at traffic lights and adjust the flow through intersections accordingly. Sensors at shopping malls detect your presence and open doors to allow you to enter. Sensors measure the water level in your washing machine and ensure it doesn’t overflow.
Nanosensors are platforms with a characteristic dimension - nanometer in scale, and work in much the same way as a sensor; they detect either minute particles or miniscule quantities of something.
“Nanosensors are chemical or mechanical sensors that can be used to detect the presence of chemical species and nanoparticles, or monitor physical parameters such as temperature, on the nanoscale.” They find use in medical diagnostic applications, food and water quality sensing, and other chemicals.” (Nature)
Sensors will help us better understand the world we live in.
Aleksandra Lobnik, Founder of Centre for Sensor Technology at University of Maribor and Co-founder of Institute of Sensors and Environmental Protection
Nanosensors can be chemical sensors or mechanical sensors. They are used:
- To detect various chemicals in gases for pollution monitoring
- For medical diagnostic purposes 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 brain for understanding neurophysiology
Nanosensors aid in the progression of fields such as medical technology; precision agriculture; urban farming; plant nanobionics; prognostics and diagnostics; SERS-based sensors; and many industrial applications.
- Carbon Nanotube–Based Fluorescent Nanosensors
- Quantum Dot–Based Fluorescent Nanosensors
- DNA-Based Fluorescent Nanosensors
- Peptide-Based Fluorescent Nanosensors
- Plasmon Coupling–Based Nanosensors
- Plasmonic Enhancing–/Quenching–Based Nanosensors
- Magnetic Resonance Imaging-Based Nanosensors
- Photoacoustic-Based Nanosensors
- Multimodal Nanosensors (synergistic nanosensors with multiple modalities to overcome individual challenges)
How 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 goals in designing a sensor.
Nanosensors typically work by monitoring electrical changes in the sensor materials.
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.
Like chemical nanosensors, mechanical nanosensors also tend to measure electrical changes. The nanosensors used in the MEMS systems that car airbags depend upon are monitoring changes in capacitance. These systems have a miniscule weighted shaft attached to a capacitor. The shaft bends with changes in acceleration and this is measured as changes in capacitance.
Nanosensors have been developed to the point of measurement at the single-molecule level.
References and Further Reading
This article was updated on 3rd July, 2019.