Focussing sunlight with tiny particles could improve the sustainability of the world’s most energy-hungry reactions. 

Making the chemicals that we need for industries like farming and pharmaceuticals uses nearly 5% of the world’s energy, and most of it comes from fossil fuels that emit CO2 when they’re used. Many of these processes already use catalysts, which create new pathways for the reactions, but they still need a lot of energy to get them started.

Energy from the sun is used in solar cells, but how else can we use the sun’s light? Although kick-starting the reactions normally uses heat, focussing the sun’s light onto the catalysts could give us another way to do that.

Catalysts are normally tiny molecules, so we need a way to focus the sun’s light on a very small and controlled space. My work focusses (pun not intended!) on creating nanoparticles that can do just that! They are made of plasmonic materials, which means they have lots of electrons that can slosh around inside the particle and create focussed light on their surfaces, especially at sharp corners. There are lots of these materials, like gold, silver and copper. I work with magnesium, which is more abundant on earth than these options and, therefore, is much more sustainable and cheaper.

For this strategy to work, we need to create tiny particles with precisely controlled sizes and shapes. You could fit around a billion (1,000,000,000) of these particles on the head of a pin, so this is not easy! We have to do it controlling the precise reaction conditions that we make the particles in, including not letting any oxygen or water into the reaction mixture. Then, we attach catalyst sites on the nanoparticle surface, ideally at the points where the light is focussed best. Capturing some of the sun’s energy in this way will help us lower our dependence on fossil fuels and on rare metals like gold, moving us closer towards a more sustainable future.

Elizabeth Hopper

NanoDTC Student, c2018