About
RADICAL BREAKTHROUGH
RADICAL (2020-2025) was an EU-funded research project to develop a brand-new way of detecting atmospheric radicals in real-time.
We have developed a small, low-cost electronic sensor that ‘sniffs’ out short-lived radicals such as hydroxyl which plays a key intermediary role in day-time air quality.
The sensor is an adaptable platform has also been successfully tuned with different organic layers to selectively detect nitrogen dioxide, ozone, ammonia and HOx gas.
This has never been done before. Our new RADICAL sensors are low cost, small and able to be rolled out on a global scale to help us better monitor and model the role of radicals in atmospheric chemistry. Versatile and portable, the RADICAL sensor can be deployed in diverse environments—from hospitals to industrial sites and even remote, dangerous locations—making it a powerful tool for both air quality monitoring and research.
What sets this sensor apart is its ability to detect gases at incredibly low concentrations—down to 1 part per billion—while delivering real-time, quantifiable data that was previously only possible with expensive lab equipment.
Read more on our blog: What is an electronic nose? by Professor Justin Holmes

RADICAL – An electronic sensor to detect atmospheric radicals
ROLE OF RADICALS IN AIR QUALITY
Air pollution is a growing problem that impacts our health, the climate and the ozone layer, but we do not fully understand the underlying chemistry cycles that control air quality.
Short-lived radicals are highly-reactive species possessing an unpaired electron. In the atmosphere, they are formed as by-products from polluting emissions such as nitrogen dioxide and ozone when exposed to sunlight, and it is thought that radicals play a key regulating role in air quality cycles.
For example, radicals play a beneficial role in cleaning the lower atmosphere of air pollutants.
During the day, the hydroxyl radical (•OH) is the main driver of photochemistry in air, while at night, the nitrate radical (•NO 3) is responsible for removing gas pollutants. Both radicals play a key role in determining the levels of two important air pollutants – ozone and nitrogen dioxide – through a series of complex chemical reactions in air.
In order to fully understand the impact of radicals on air quality and climate change, we need a way of tracking them on a global scale and in real-time.
Read more on our blog: How atmospheric radicals transform the air by Professor John Wenger
DETECTING RADICALS IN THE ATMOSPHERE
Currently, detecting and measuring these highly reactive and short-lived radicals remains technically complex, cumbersome and expensive (see review article Wang et al 2021).
As a result, only a few labs worldwide can perform such tests.
RADICAL has developed a new, low-cost way of measuring short-lived radicals in the atmosphere that can be easily implemented and deployed worldwide.
This has taken the form of a state-of-the-art electronic nose that will measure the presence of airborne hydroxyl radicals in both indoor and outdoor settings. This sensor platform has also been successfully tuned with different organic layers to selectively detect nitrogen dioxide, ozone, ammonia and HOx gas.
AIR QUALITY IMPACT
The World Health Organization (WHO) has described air pollution as the ‘ single biggest environmental health risk’, with an estimated 400,000 premature deaths in Europe attributable to poor air quality every year.
Short-lived atmospheric radicals are thought to play a key intermediary role in air quality cycles, and by directly monitoring the concentration of these radicals at local, regional and global scales, scientists will have a much greater ability to predict and control air quality to enable a better quality of life for citizens.
Currently, a wide variety of sensors measure air pollutants and particulate matter in cities across the globe, enabling scientists to closely monitor and predict the cycles of poor air quality.
Click here to view a map that shows real-time air quality readings from across Europe, as gathered by the European Environment Agency.
The state-of-the-art technology in our RADICAL sensors can be deployed at all of the world’s air quality and meteorological stations, leading to an unprecedented level of high-quality data on the concentration of radicals at a local, regional and global level. They can also be incorporated into sensor platforms on planes, ships, balloons and drones, or even adapted to wearable health sensors for the human body.
The knowledge developed in RADICAL has the potential to bring about a dramatic breakthrough in air quality and climate monitoring, leading to health benefits for European citizens.
EUROPEAN COLLABORATION
The RADICAL project was a collaboration between multidisciplinary partners across Europe including University College of Cork (Ireland), HZDR (Germany), University of York (United Kingdom), National Technical University of Athens (Greece), Smartcom (Bulgaria) and UCC Academy (Ireland).
Our extensive expertise spanned across the fields of material science, computer modelling, nanofabrication and nanoelectronics, as well as organic, radical and atmospheric chemistry.
RADICAL received funding from the European Union’s Horizon 2020 Research and Innovation Programme under grant agreement No 899282. It had a total budget of €3.2 million and ran for four years and 3 months from 1 November 2020 to 31 January 2025.