An electronic nose to detect harmful atmospheric free radicals

An international project involving researchers at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) is receiving 3.2 million euros from the European research and innovation program "Horizon 2020" to develop a cost-effective method for measuring certain air pollutants. The team, whose members hail from both industry and science, aims to develop electrical sensors to detect harmful particles in the atmosphere. Air pollution is considered a major cause of more than 400,000 premature deaths in the European Union each year. Accurately measuring it, however, still poses major challenges for researchers.

Although the negative health effects of certain air pollutants, so-called free radicals, have been known for a long time, detecting and measuring them is still technologically highly complex. "These free radicals are reactive compounds that drive chemical processes in the atmosphere, thereby impacting climate change and the formation of acid rain or photochemical smog - which are all harmful to human health and the environment," explains project leader Prof. Justin Holmes of University College Cork (UCC) in Ireland. Health is affected both indoors and outdoors.

The project team includes researchers from UCC, HZDR, the University of York (UK), the National Technical University of Athens (Greece), the Bulgarian company Smartcom and UCC Academy. Supported by an external consultant from UK-based air quality company Airlabs, Holmes and his team are working to develop cost-effective, high-tech instruments to measure harmful atmospheric radicals. The plan is to use this technology in aircraft, ships, and other platforms for air quality monitoring.

Sensitive, highly selective sensors

"To date, there are only a few research groups that are capable of performing such tests at only a few locations in the world. The process involves complex spectroscopic methods using large, expensive, and unwieldy equipment, which severely limits our knowledge of chemical processes in the atmosphere and thus our ability to control air quality and climate change," says Dr. Yordan Georgiev of the Institute of Ion Beam Physics and Materials Research at HZDR, outlining the motivation behind the project, which is called "RADICAL".

The international team now wants to eliminate this bottleneck by developing new methods to detect harmful radicals: "We want to create a technology that can be implemented relatively easily worldwide. To do this, we are working with partners from industry to advance the development of high-precision sensors that lend themselves to mass production, so we can ultimately provide real-time data on the distribution and transmission of free radicals in the atmosphere everywhere," Georgiev sums up the project goal. The HZDR researchers involved in the project are responsible for manufacturing the electrical sensors to detect free radicals in the atmosphere. They are based on silicon nanowires, which are, in a way, the receptors of an electronic "nose".

Detecting radicals worldwide in real time

The sensor mechanism essentially works like this: The electrically charged target molecules interact with the nanowire surface, changing the wire's electrical conductivity. These interactions are thus directly converted into easily detectable electrical signals. The scientists ensure the selectivity of the highly sensitive sensors by functionalizing the surface of the nanowire, affixing a layer of molecules to its surface that will only bind the target molecules.

Project partner Prof. John Wenger, who is Director of the Centre for Research into Atmospheric Chemistry at UCC, believes that this technology goes far beyond the current state of the art and could be implemented at any operational air quality and weather station in the world. This would greatly improve the ability to monitor and control air quality, enable more accurate climate predictions, and ultimately bring about a better quality of life for all of us.