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Fundamental Breakthrough in Detection of Atmospheric Free Radicals

Periodic Reporting for period 2 - RADICAL (Fundamental Breakthrough in Detection of Atmospheric Free Radicals)

Reporting period: 2021-11-01 to 2023-04-30

Atmospheric radicals, particularly hydroxyl (•OH) and nitrate (•NO3) radicals, are the drivers of chemical processes that determine atmospheric composition and thus influence local and global air quality and climate. Current techniques for measuring radicals are based on spectroscopic methods, which are technically complex, cumbersome and expensive. As a result, the measurement of atmospheric radicals is far-from-routine and only a few research groups worldwide can perform them in a very limited number of geographic locations.

There is therefore a need to develop new radical detection techniques which are much easier to implement and deploy than existing methods. The central aim of RADICAL is to develop and deliver the science and technology to electrically detect and quantify, for the first time, short lived •OH and •NO3 radicals in the atmosphere. This will be achieved using low cost and reproducible nanowire-based sensors. The implementation of these devices will result in enhanced monitoring and ultimately better regulation of air quality.

Three breakthrough science and technology targets have been identified: 1) fabrication and functionalisation of arrays of nanowire transistors for the selective and highly sensitive electrical detection of •OH and •NO3 radicals, 2) electrical detection of atmospheric •OH and •NO3 radicals under a range of laboratory conditions and 3) evaluation and validation of radical sensors under realistic conditions in an atmospheric simulation chamber and via deployment in the ambient atmosphere.

The RADICAL project brings together interdisciplinary expertise in electronics, computer modelling, materials and surface science, nanofabrication, radical chemistry, and atmospheric science from across Europe. This integration of knowledge aims to successfully accomplish the overall objective of the project. The advancements made in RADICAL have the potential to create a significant breakthrough in air quality and climate monitoring. As a result, European citizens stand to benefit from improved health outcomes.
Workpackage 1: Fabrication of Silicon devices
- Density functional theory has been used to investigate and optimise the design, fabrication and operation of the nanowire-based radical detectors.
- A reproducible process has been developed for the top-down fabrication of silicon nanowire transistors.
- The electrical and structural properties of silicon nanowire transistors have been fully characterised.

Workpackage 2: Development of Si nanowire functionalisation approaches
- A library of organic sensor molecules and their application for sensor development, including radical detection, has been created.
- Silicon substrates and devices have been functionalised for nitrogen dioxide, ozone and hydroxyl radical sensing experiments.

Workpackage 3: Device Testing and Optimisation
- The electrical response of functionalised silicon substrates and devices have been investigated for nitrogen dioxide, ozone and radical species.

Workpackage 4: Sensor Evaluation and Validation in Air
- The Irish Atmospheric Simulation Chamber facility has been prepared for the first radical detection experiments.

Workpackage 5: Dissemination, Exploitation and Communication
- A RADICAL website, two social media channels, and related videos and graphics have been developed.
- RADICAL's Dissemination, Exploitation and Communication and Data Management Plans are updated every six months.

Workpackage 6: Project Management and Coordination
- A private site for file sharing and tracking deliverables has been established.
- On-going project meetings are organised on a regular basis.
- RADICAL's Risk Register is updated every six months.
The RADICAL team has demonstrated that silicon nanowire transistors can be used as environmental gas sensors for nitrogen dioxide. Initial experiments indicate that nanowire sensors can also detect atmospheric radicals, as well as other species such as ozone. The team have also developed devices based on two dimensional materials that may also have potential use as environmental gas sensors.

Intellectual property (IP) identified from the project so far includes (i) the functionalisation of semiconductor substrates and nanowires, (ii) the fabrication of ambipolar sensor devices and (iii) the overall sensing platform. The consortium has taken steps to exploit results from the project, which has included taking part in EU innovation training and other accelerator services, and proactively engaging with companies around future opportunities and collaborations. The team will continue to work on a roadmap for commercialisation.

The sensor technology developed within RADICAL has the potential to make significant strides in advancing our understanding of the intricate dynamics between chemistry and climate. This advancement could pave the way for enhanced monitoring and control of air quality and climate, resulting in substantial benefits for the health and well-being of citizens. Additionally, if Europe attains a technological edge in this domain, it could stimulate the creation of new manufacturing jobs, thereby benefiting the citizens of Europe.
How atmospheric radicals such as hydroxyl (OH) transform the day-time air.
A project schematic showing the key tasks for RADICAL, and the consortium responsibilities.
How atmospheric radicals such as nitrate (NO3) transform the night-time air.
A diagram showing the key components of the RADICAL sensor.
A diagram showing the key benefits and applications of the RADICAL sensor.