Madhavi Krishnan
(University of Oxford)

 

The interaction between charged objects in solution is expected to recapitulate two central principles of electromagnetics: ⁽¹⁾ like-charged objects repel, and ⁽²⁾ they do so regardless of the sign of their electrical charge. We have recently demonstrated experimentally that the solvent plays a hitherto unforeseen but crucial role in interparticle interactions, and importantly, that interactions in the fluid phase can break charge-inversion symmetry. Thus, in water, negatively charged particles can attract at long range while positively charged particles repel. In solvents that exhibit an inversion of the net molecular dipole at an interface, e.g., alcohols, we find that the converse can be true: positively charged particles may attract whereas negatives repel ^[1,2]. A theory of interparticle interactions that invokes solvent structuring at an interface captures the observations ^{[3, 4]}. Our work establishes am interfacial mechanism by which the solvent gives rise to a strong and long-ranged force between objects in solution.
 

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Coffee and tea refreshments will be served at 10:30 on LB terrace (or at LB bar in case of bad weather)
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Link to Zoom registration:
https://zoom.us/meeting/register/HF4P98GRRm-qvK3eyCe9lA