Same Charge, Different Response

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Broad Audience Highlights
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Ion-Specific Induced Charges at Aqueous Soft Interfaces
W. Wang, R. Park, A. Travesset and D. Vaknin
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Physical Review Letters
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Ions in water with the same charge, e.g. Fe3+ and La3+, behave dramatically differently at the air/water interface when interacting with a charged surface.  This difference violates classic electrostatic theory. The distributions of specific ion types were determined with unprecedented precision using newly developed surface sensitive synchrotron x-ray scattering and spectroscopic techniques. The research team was able to use these results to verify their recently-developed theoretical model that takes into account both classical and effective quantum behavior.  This model can be used to predict any distribution of trivalent and divalent ions. Determining the underlying interactions of ions with soft-matter templates in an aqueous solution is a crucial step towards the design of novel functional structures that mimic those of living organisms. This work has the potential to explain the many effects of aqueous environments and also to develop new methods for extracting metal ions from nuclear waste.