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International Year of Light - Alasdair Mackenzie

Alasdair Mackenzie

Tell us about your PhD project

The Alexander group is investigating a phenomena called non-photochemical laser-induced nucleation (NPLIN). This is when you take a very intense pulse of laser light and shine it through a solution it can create crystals even though it is not inducing chemical changes in the molecules dissolved in there.

We don't have a complete picture of how the phenomena works, because we don't have a complete description of how crystals initially form in any way! Crystals are really important because the way they form gives the material properties to solids such as the hardness of steel or the taste of chocolate. Pharmaceutical companies are especially interested because the crystals in a tablet determine how fast the medicine starts working and the dose needed.

I am looking at what happens when we use NPLIN in a continuously flowing stream of solution with the hope of understanding more about the phenomena of crystal nucleation and demonstrate the usefulness of making pharmaceuticals in a continuous manner to hopefully reduce their cost.

Why is light important to your research?

Light and colour is what got me curious about science in the first place so I wouldn't be doing research at all if it wasn't so interesting! NPLIN has two essential ingredients which are the intense laser light and supersaturated solution. Yet light is also useful for a lot of other things around the lab.

Good illumination is essential for taking all the beautiful pictures of crystals, and the fact that it can be polarized means we can see features in otherwise colourless crystals. We then can analyse the crystals using Raman or infra-red laser light as well as shining x-rays to determine the crystal structure. We can also use laser light to see particles under a microscope that are otherwise too small to image.

Crystals formed by NPLIN

Crystals formed by NPLIN

Describe your average day of PhD work here in the School of Chemistry

An average day would be spent working in the lab in the morning, flowing solution and firing the laser. The afternoon would be then trying to solve problems that inevitably come up. This involves reading the literature, buying new parts, asking advice and preparing fresh solution.

If something eventually does work then it is analysing the measurements, interpreting the images, making graphs and preparing a presentation on the work. There is also a lot more admin work and cleaning of glassware than I expected!

The lab with chemicals and lenses and a CW illumination laser

The lab with chemicals and lenses and a CW illumination laser

What do you enjoy doing when you are not at work?

Scientists are a social bunch so there is always parties or at least coffee and cake to go to. Otherwise I play volleyball, enjoy the gym and listening to music. Enjoying the Scottish sunshine is important, whatever day that is this year!

What's your favourite chemical reaction?

It would have to be the intramolecular conversion of hydroxymethylene to formaldehyde via hydrogen quantum tunnelling (Schreiner et al 2008 Nature Letters 453, 906-909)

This is a reaction I read about in my undergraduate but not actually performed. They make the incredibly reactive carbene molecule hydroxymethylene at high temperatures and then instantly cool it to -263C in non-reactive argon. This creates a solid which stops the carbene from reacting with anything else and as there is a large energy barrier associated with rotating in a solid at those low temperatures it won???t rotate.

However because molecules are quantum mechanical objects they can do things that wouldn't make sense if they were as large as we are. The molecule undergoes quantum tunnelling where the hydrogen seems to teleport through the oxygen and appear on the carbon forming formaldehyde, a much more stable compound. This shows how the world of molecules have their own rules and that quantum mechanics can contribute to some non-intuitive chemistry.