Nonlocal correlation effects in water and aqueous electrolyte solutions at electrified interfaces
File(s)
Author(s)
Hedley, Jonathan
Type
Thesis
Abstract
Of water’s many anomalous properties and characteristics, its ability to influence electrostatic interactions between charged entities is perhaps one of its most profound, with consequences that stretch from the more efficient design of energy storage devices to insights on the origins of life. This ability goes far beyond the primitive solvent model, which considers water as an insulating dielectric, with dielectric constant ε ≈ 80. Being highly polar, and thus strongly correlated in space, water is better described by the language of nonlocal electrostatics. A direct result of its correlated structure, water exhibits strong signatures of overscreening, manifesting in oscillatory patterns in the electric field. This thesis explores these nonlocal correlation effects, and their impact on interactions between charged entities. Employing a field theoretical approach, a bimodal kernel of polarisation correlations was built to mimic the simulated nonlocal dielectric response of water, validated by the faithful reproduction of experimentally measured hydration force profiles. The consequences of this bimodal model are deep, suggesting that oscillations in the electric field are ubiquitous near all electrified interfaces in aqueous solution, and rationalising why these oscillations were sometimes not experimentally observed. Further, water-induced oscillations were found to control the double layer structure at low electrolyte concentrations, leading to ion physisorption in its potential wells. This picture was supported by comparison against atomic force microscopy experiments and capacitance measurements, revealing a marked departure from the classical Gouy-Chapman-Stern model. Applying models of the nonlocal dielectric response of water to DNA, a conceptually similar picture was obtained, supported by atomistic molecular dynamics simulations. Oscillations due to water structure had a strong influence on the surrounding electric field, demonstrating the generality of the results of this thesis. Structured water was also shown to enhance the DNA-DNA pair interaction, substantiating a physical electrostatic mechanism for sequence homology recognition.
Version
Open Access
Date Issued
2024-06
Date Awarded
2024-09
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Kornyshev, Alexei
Sponsor
Imperial College London
Great Britain. HM Government
Publisher Department
Chemistry
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)