One-step-laser process used to develop highly-sensitive NO2 sensor

A highly sensitive and accurate Nitrogen Dioxide (NO2) sensor has life-saving potential applications in domestic, public, and industrial settings, claim the team that developed it.

NO2
Image by Nikola Belopitov from Pixabay

Scientists at Sussex University have collaborated with Oxford-based M-SOLV and researchers in Europe to develop a gas sensor that can provide accurate readings of NO2 levels in an affordable and portable Internet-of-Things device, which could synchronise with smartphones and applications.

NO2 originates from combustion engines and industrial processes and long-term exposure to the pollutant can cause respiratory issues, which can be particularly severe and even life-threatening for babies and asthma sufferers.

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European Union regulations allow a threshold of 20 parts-per-billion (ppb) of NO2 in the air to be overcome no more than 18 times in a year. The monthly average is regularly above this in London but monitoring of air quality to prevent exposure at ppb levels is currently only possible with unwieldy and expensive equipment.

According to Sussex University, the team’s breakthrough came when they developed an NO2 sensing layer based on a laser deposited carbon aerogel (LDCA), which they found to have exceptional selectivity towards NO2 over other common air pollutants.

Using a scalable and economical one-step-laser process, the thin, porous and well-adhered film of LDCA is then deposited on to electrodes, which can then be housed in a range of device structures for continuous air monitoring. The sensor is said to be so sensitive that it can detect close to 10 parts-per-billion of NO2 in under 15 minutes and can operate at room temperature and in humid conditions.

Professor Alan Dalton, head of the Materials Physics group at Sussex University said: “Like condensation on a windowpane, nanomaterials such as the carbon that we have used in this development, nearly always have surface water. Normally this is a really bad thing as it interferes with the technology, but in this case, we’ve been able to use this layer of water to our advantage to selectively dissolve NO2 instead of other volatiles normally found in ambient conditions.

“As a physicist this is really exciting as this is what gives our sensor such a high rate of sensitivity to NO2 in real-world conditions, ensuring that we avoid false positive readings.”

Potential applications for the sensor could include: as a safety device to monitor the air quality in a baby’s bedroom; to help inform the best walking or cycling routes and times of day to avoid high pollution levels. The scientists hope that the technology will be utilised by councils to track pollution levels in urban environments and industry.

Adam Brunton, Director of Business Development at M-SOLV, who are manufacturing the NO2 sensing device, said: “One nice thing about this sensor is that it is made using familiar equipment and materials that we already have in our Large Area Electronics Manufacturing Clean room here in Oxford. This means that it is compatible with standard smartphone manufacturing techniques and can be easily integrated with processing electronics, wireless communications, mobile networks, etc. Getting remote access to data from an individual device or a huge network of these sensors is therefore quite a straightforward process.”

A paper detailing the team’s findings is published in Applied Materials & Interfaces.