Silicon nanowires as biochemistry sensors

Seven years ago, in 2014, two materials chemistry researchers at University College Cork (UCC), Professor Justin D. Holmes and Professor Yordan Georgiev (now at HZDR in Germany), were finishing up their work on a new type of low-cost sensor for liquid solutions. The sensor was built on home-grown Cork technology, a silicon Junctionless Nanowire Transistor (JNT), with a finely-tuned layer of organic molecules on the surface.

This sensor was built for biochemistry applications, where proteins such as streptavidin would interact with the organic layer and change the electric current through the JNT, thus creating a means of electrically detecting these proteins in solution.

What next?

The JNT had proven to be an accessible, adaptable foundation for a low-cost sensor, at least for liquid species. The obvious next challenge was to adapt this sensor to detect gas molecules.

This would be a type of ‘electronic nose’ that could ‘sniff’ out a molecule of interest, similar to how our noses identify scent molecules by matching them with different receptor cells.

A gas-phase JNT sensor would be a harder challenge because of the lower densities involved – the chance of contact between the sensor and a gas molecule of interest would be much lower.

But what could be done that wasn’t already ubiquitous within gas-phase sensors?

Blue sky thinking

This is when Justin and Yordan sat down with atmospheric chemist, Professor John Wenger, who leads the Centre for Research into Atmospheric Chemistry at UCC. It was at the time of the ‘dieselgate’ emissions scandal in 2014-2015, and Justin, Yordan, and John briefly entertained the idea of developing a new type of nitrogen dioxide gas sensor. But these exist in many forms already, and Justin knew that it would need to be a truly ground-breaking idea in order to attract research funding.

It was then that John suggested a sensor to detect short-lived radicals in the atmosphere:

“If you really want a blue-sky ambitious research idea, then go for radicals. Radicals are highly-reactive and short-lived, but control most of the key chemistry in the atmosphere. They determine the levels of air pollution in our lower atmosphere, and help moderate the pollutants that make it up to the upper atmosphere and ozone layer. But we don’t have an effective way of measuring them in real-time yet.“

Team effort

Thus the idea for RADICAL was born. Between 2014 and 2020, the team evolved to include additional partners that could help turn the idea into reality. This included materials chemist Dr Subhajit Biswas and atmospheric data scientist, Dr Stig Hellebust, both at UCC.

The team also grew to include key external expertise in organic and radical chemistry from Dr Victor Chechik (University of York) and chemistry modelling and simulation expertise from the National Technical University of Athens (led by Dr Leonidas Tsetseris) and Bulgarian tech SME, Smartcom (led by Dr Peter Statev).

UCC Academy, an in-house consultancy of UCC, joined to guide the project management and communications for RADICAL.

Funding success

But finding research funding is never easy. Over the past six years, RADICAL was nearly funded twice by the European Commission under different funding schemes, with helpful feedback that continued to shape this blue-sky idea into something concrete.

Finally in March 2020, Justin and the RADICAL team heard the good news that their idea was successfully funded under the European Union’s Horizon 2020 Research and Innovation Programme, as a four year FET-Open project.

Given the timing, celebrations were jubilant yet virtual, and the team is counting the days until a reunion allows a proper celebration of the long journey of RADICAL.

In the meantime, the RADICAL project officially started on 1 November 2020 and the team are hard at work modelling and planning the development of these ground-breaking new gas-phase radical sensors.

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About the author: Dr Tamela Maciel (UCC Academy) is the project manager and communications manager for RADICAL.