Low-cost sensors improve detection of atmospheric free radicals
All around the world, huge amounts of pollutants such as nitrogen dioxide, methane, ammonia and volatile organic compounds are constantly released into the atmosphere, affecting both climate change and human health. Radicals play a crucial role in cleaning the atmosphere of these pollutants, but the chemical processes are complex and poorly understood. The EU-funded RADICAL(opens in new window) project developed a small, inexpensive sensor to measure radicals, potentially transforming the field of atmospheric research and offering a range of options for better air quality monitoring.
Breaking down atmospheric chemistry
The atmosphere has a remarkable ability to cleanse itself. The key actor is the hydroxyl radical (OH), which dominates air chemistry and is known as the ‘detergent of the atmosphere’. Hydroxyl radicals react with pollutants, breaking them down into less harmful byproducts. While this process does generate cleaner air, not all the chemical products are benign. Secondary pollutants such as ozone and sulfuric acid – a key component in acid rain – can also be produced. Atmospheric hydroxyl radicals are sparsely present – less than one part per trillion – and extremely reactive, often lasting no more than a second before bonding with other molecules. These characteristics make radicals very difficult to study. Currently there are only a few labs in the world with appropriate research facilities, one of them the Irish Atmospheric Simulation Chamber facility(opens in new window) where project studies were carried out.
Silicon nanowires transmit electrical signals
The RADICAL solution is an electronic sensor tuned with different organic layers. Chemical reactions cause an electrical response on the silicon nanowire, which allows the sensor to determine the presence of OH radicals and other pollutants. So far, the device has been validated for nitrogen dioxide, ammonia, and ozone. “The RADICAL sensor operates on the principle of an ‘e-nose’, much like the human nose detects smells. Gases interact with the sensor’s electrical system, creating signals that can be decoded, similar to how our brain identifies odours,” project coordinator Justin Holmes explains.
Benefits of better radical detection
With few facilities to study the complex chemistry of the atmosphere, the role of radicals in transforming air quality is not well-understood. The promise of the RADICAL solution – low cost, mobile and tuneable – will transform both atmospheric research and air quality monitoring. “Our RADICAL sensor has the potential to be a real game-changer by facilitating a much wider range of laboratory and field studies for advancing our knowledge in this critically important area of atmospheric science”, says John Wenger, RADICAL WP leader. The sensor can be used in a range of specific, sensitive environments, such as hospitals, industrial sites and remote locations. Its small size means it can be deployed as a wearable device, improving the safety of people working in dangerous conditions. The RADICAL sensor will transform our understanding of the atmosphere, from the chemical events playing out 10 kilometres above our heads to the quality of the air we inhale with each breath. The project team, composed of partners from Bulgaria, Germany, Greece, Ireland and the UK, is focused on improving the durability of the sensor, completing further field tests and forming business partnerships to deliver this exciting technology to the market.