PT Section Seminar: Professor Susan Perkin
Professor Susan Perkin
Professor Susan Perkin (University of Oxford)
Ionic Liquids: A Challenge to our Understanding of the Liquid State
Particle and surface interactions in electrolytes underpin the behavior of many systems in soft and biological matter, electrochemical devices, and materials science. Of particular recent interest are electrolytes at very high concentration, and the extreme case of ionic liquids: solvent-free salts in the liquid state under ambient conditions. Recent work has illuminated several important gaps in our understanding of interactions in concentrated electrolytes, together presenting fascinating puzzles for those interested in the nature of the (ionic) liquid state.
In my laboratory we perform high-resolution measurements of the force between uniform charged surfaces across liquids using a Surface Force Balance (SFB), and in this seminar I will present some examples of recent experiments with highly concentrated electrolytes and ionic liquids. Measurements of structure in the confined liquid show a switch in wavelength at a characteristic ion density indicating a transition from solvent- to ion-determined correlation length. Beyond the structural region an anomalously long electrostatic screening length is observed which increases with increasing volume fraction of ions in direct contrast to predictions of standard theories of dilute electrolyte[2,3].
To finish, I will outline new procedures under development in my laboratory to measure properties and interactions in liquids and soft matter confined to nanoscopic films between two atomically smooth graphene electrodes[4,5]. By polarizing the two graphene electrodes with opposite sign, an electric field can be applied across nano-films of liquid. This provides a new method for directly measuring the influence of electric fields on the optical and mechanical properties of nanoconfined liquids.
1. A. Smith, A. Lee, and S. Perkin. Phys. Rev. Lett. 118, 096002 (2017).
2. A. Smith, A. Lee, and S. Perkin, J. Phys. Chem. Lett. 7, 2157 (2016).
3. A. Lee, C. S. Perez-Martinez, A. Smith, S. Perkin. Phys. Rev. Lett. 119, 026002 (2017).
4. J. Britton et al., Langmuir 30, 11485-11492 (2014).
5. C. van Engers et al., Nano Letters 17, 3815-3821(2017).
Dr Tom Oliver
School of Chemistry
Tel: +44(0)117 928 7668