PhD in Chemistry - Amorphous Aggregates and Non-Classical Crystal Nucleation

You are invited to apply for a fully funded 3.5 year PhD position in the School of Chemistry, available to start on 1 October 2024 in the Ultrafast/slow Chemical Physics group at the University of Glasgow (https://www.wijnne.com/), with the aim to understand the role of amorphous structures in crystal nucleation

Crystal nucleation and its opposite vitrification (glass formation) are crucial processes in materials science, chemistry, drug development, biomineralisation, geology, and manufacturing whose understanding and control would enable the production of materials and products with desired characteristics. However, discoveries over the past two decades have radically changed our understanding of nucleation.

The process of nucleation is traditionally understood through the so-called classical theory of nucleation (CNT), which assumes that crystal nucleation is governed by the formation of a primitive crystal nucleus through the attachment and detachment of individual solute molecules. When the primitive nucleus reaches a critical size, it will continue to grow into a full-blown crystal. More recent work strongly suggested that crystals nucleate through a non-classical process in which many precursors form, which join to form a crystal nucleus.

In recent work, we have shown that instead supersaturated solutions form amorphous aggregates, which are the sites of crystal nucleation. Surprisingly, the aggregates have a vast range of sizes from molecular to visible to the naked eye. We have also found that liquids that normally crystallise on cooling can be made to form a glass instead in mixtures, which is enormously important for the development of novel amorphous drugs.

We will investigate the nature and role of these amorphous aggregates and their role in promoting or inhibiting crystallisation in order to establish a new fundamental model for crystal nucleation. This will involve a wide range of experiments (spectroscopy, microscopy, optical tweezing, calorimetry, rheometry, x-ray scattering, NMR, mass spec, etc.) to characterise amorphous aggregates on a huge range of length scales as a function of temperature, time, and other physicochemical parameters.

These new insights will then allow a greater degree of control over nucleation and the polymorphs produced through physical or chemical means. Conversely, it will provide new understanding on the factors that (de)stabilise metastable amorphous states. The impact is therefore expected to be broad from fundamental research to the manufacture of crystalline and amorphous products in the chemical industry, healthcare, advanced materials, etc.

Requirements

The ideal candidate will have a background in physical chemistry, chemical physics, engineering, photonics, nanotechnology, or materials science. No prior experience on the specialised experimental techniques is required - you will be fully trained during the PhD. You must be self-motivated, have good interpersonal skills, and be interested in conducting interdisciplinary work.

If you interested in applying, please contact [Email Address Removed] with a CV and cover letter, for informal enquiries.

You can also find details of the application process at:

http://www.gla.ac.uk/research/opportunities/howtoapplyforaresearchdegree/.

References

1.      Z. Liao, K. Wynne, et al., ‘Amorphous aggregates with a very wide size distribution play a central role in crystal nucleation’. (https://doi.org/10.26434/chemrxiv-2023-18zk5-v3)

2.      M. González-Jiménez, K. Wynne, et al., ‘Lifting Hofmeister’s curse: Impact of cations on diffusion, hydrogen bonding and clustering of water’, J. Am. Chem. Soc. 146, 368–376 (2024).

3.      B.A. Russell, K. Wynne, et al., ‘A second glass transition observed in single-component homogeneous liquids due to intramolecular vitrification’, J. Am. Chem. Soc. 145, 26061-26067 (2023).

4.      M. González-Jiménez, K. Wynne, et al., ‘Understanding the emergence of the boson peak in molecular glasses’, Nat. Commun. 14, 215 (2023).

5.      Z. Liao, K. Wynne, ‘Mesoscopic amorphous particles rather than oligomeric molecular aggregates are the cause of laser-induced crystal nucleation’, Proc. Natl. Acad. Sci. USA 119, e2207173119 (2022).

6.      Z. Liao, K. Wynne, ‘A metastable amorphous intermediate is responsible for laser-induced nucleation of glycine’, J. Am. Chem. Soc. 144, 6727-6733 (2022).

7.      F. Walton, K. Wynne, et al., ‘Polyamorphism mirrors polymorphism in the liquid–liquid transition of a molecular liquid’, J. Am. Chem. Soc. 142, 7591-7597 (2020).

8.      F. Walton, K. Wynne, ‘Control over phase separation and nucleation using a laser-tweezing potential’, Nat. Chem. 10, 506-510 (2018)