Dr Dominik J. Kubicki is a materials chemist who uses solid-state Nuclear Magnetic Resonance (NMR) spectroscopy to understand materials at the atomic scale. His research focuses on the discovery of new functional materials, such as metal halide perovskites for solar cells, and understanding how their atomic-level structure determines their properties and function..

Why do you use solid-state NMR to study materials?

Determining the structure of solids can be surprisingly challenging. Solid-state NMR is unique in that it lets us zoom in on individu-
al elements within a material to understand their local environment. Some of the best
solar cell materials today have more than 10 components, and it’s fair to say we don’t fully understand what makes them tick, but sol- id-state NMR is bringing us closer to solving their mystery. For example, perovskite solar cells rely on small amounts of caesium ions to make them more stable. We use caesium-133 NMR to understand where these ions sit within the structure, how they interact with other components and how they move. The resulting caesium-133 NMR spectrum is a series of peaks at specific frequencies, and its appearance enables us to link composition and structure toproperties such as power conversion efficiency and long-term stability.

What does a solid-state NMR experiment look like?

We use a strategy called Magic Angle Spinning (MAS), first developed in the mid-1950s, the early days of NMR. Researchers realised back then that magnetic interactions in solids broaden NMR spectra, making them of little use. MAS solves this by spinning the sample at 54.7° relative to the magnetic field, the magic angle, at extremely high speeds, typically up
to 60,000 revolutions per second. That’s over 3.5 million RPM! The rotation removes some of these interactions, giving us sharp, detailed spectra. Just imagine the precision needed to spin a sample at those incredible speeds - it’s a testament to the technological advancement of our society. And the speeds get faster by the year - the latest record is about 10 million RPM in a rotor that’s only 0.4 mm in diameter

How do you synthesise new materials?

We make them using mechanochemistry, or driving chemical reactions using mechanical force. We grind the reagents in a ball mill for half an hour and that gives us the product, with nearly 100% efficiency. It’s as simple as it sounds. The beauty of it is that we can make hundreds of completely new, complex mate- rials within a single day. This means that we are no longer limited by how long chemical synthesis takes. Instead, we can focus our energy on understanding their atomic-level structure, their properties, and how the two are linked, to help us rationally design better materials. Mechanochemistry has another perk. Chemical manufacturing worldwide uses more than 30 billion litres of solvents annually. Mechanosynthesis doesn’t require solvents - the potential benefits to the environment and economy are massive.