Light plays a fundamental role in a number of vital biological and industrial processes. It is the main driving force for photosynthesis, and essential for initiating charge separation in solar cells. In the Department of Chemistry’s new Lord Porter Ultrafast Laser Spectroscopy Laboratory, our researchers are studying these and other photochemical processes with unprecedented precision. Developing our understanding of these processes is crucial for the development of renewable energy and therapeutic technologies.
The laboratory is named after former University of Sheffield lecturer and Nobel Prize winner Sir George Porter. It boasts a range of advanced laser setups that can be used to study chemistry down to femtosecond timescales – close to the speed at which light is absorbed. Ultrafast laser spectroscopy allows us to examine, in many different ways, what happens to molecules and materials after they absorb light, both immediately after absorption and on a timescale of years.
The facility is the result of a multi-million pound EPSRC Capital Equipment Award, led by Professor Julia Weinstein from the Department of Chemistry, in collaboration with research groups from across science and engineering.
We can investigate chemical reactions along a huge range of timescales and energies – that’s an exciting combination that doesn’t exist in any other UK university.
Professor Julia Weinstein
Professor of Physical Chemistry
These new systems have much higher repetition rates than standard laser systems, allowing experiments to be performed faster and with improved signal-to-noise ratios. The high power of the lasers allows researchers to probe the same sample with electronic and vibrational spectroscopy at different timescales, using the same laser excitation and within the same facility.
One of the most unique parts of this lab is the fluorescence upconversion method, or FLUPS, which can probe very fast reactions of emissive species with great sensitivity. Only a small number of groups have access to this type of analysis.
Key results obtained using the facility are now beginning to be published in high impact journals. A recent paper by PhD student Jenny Train in the American Chemical Society journal Inorganic Chemistry describes how ultrafast transient absorption measurements show the formation of a charge-separated state in her osmium-based cage system. This state is formed within 13–21 ps, and decays on a timescale of around 200 ps, meaning it cannot be observed using standard analytical techniques. These results improve our understanding of how these materials can be used for photoredox reactions, which could help us develop more efficient and more selective catalysts.
Working in the laser lab is a really unique experience, not only am I using it for my own project on artificial photosynthesis, but I also get a lot of opportunities to collaborate with other groups on their research.
James Shipp
PhD student
The chemistry of light and how it interacts with matter is one of the most important and widespread topics in chemistry. As such, our undergraduates study this topic throughout their degree, from the basic principles of absorption and emission, to fourth year research projects based around the new laser lab.
Studying light-matter interactions involves a lot of analysis by bringing together different types of spectroscopy, which scientists in the laser lab can builds on and develop for use in cutting edge research. Students working in the lab get a wealth of experience with these fundamental techniques, as well as learning how to process and analyse the data they obtain.
A recent Sheffield chemistry graduate, Liam Smith, studied the fundamental chemistry behind artificial photosynthesis and solar energy conversion using the laser lab. This led to him securing a PhD position at the University of Manchester, where he is working with Rolls Royce.
I became competent working in a highly specialised laboratory environment, spending my days using state of the art, femtosecond pulsed Ti:Sapphire lasers.
Liam Smith
MSc(Res) Chemistry graduate
As new PhD researchers and masters students join the lab, our research into the fundamental role light plays in these vital processes will advance not only own, but also the wider scientific understanding of how to harness and enhance them.
Written by:
Josh Nicks, PhD student
