کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
603309 880204 2011 6 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Approaches to hydration, old and new: Insights through Hofmeister effects
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی شیمی کلوئیدی و سطحی
پیش نمایش صفحه اول مقاله
Approaches to hydration, old and new: Insights through Hofmeister effects
چکیده انگلیسی

Hydration effects in colloidal interactions or problems involving electrolytes are usually taken care of by effective electrostatic potentials that subsume notions like hydrated ion size, Gurney potentials, soft and hard, chaotropic and cosmotropic ions, and inner and outer Helmholtz planes. Quantum fluctuation (dispersion) forces between ions and between ions and surfaces are missing from classical theories, at least not explicit in standard approaches to hydration. This paper outlines an evolving back-to-basics approach that allows these ion specific forces to be included in theories quantitatively. In this approach ab initio quantum mechanics is used to calculate dynamic polarisabilities of ions and to quantify bare ion radii. The ionic dispersion potentials between ions, and between ions and surfaces in water can then be given explicit analytic form from an extension of Lifshitz theory. They are included in the theory along with electrostatic potentials. In a first stage the primitive (continuum solvent) model provides a skeletal theory on which to build in hydration. Extension of the ab initio calculations to include “dressed” ions, i.e. water hydration shells for cosmotropic ions, quadrupolar and octupolar polarisability contributions and; for colloids, allowance for a surface hydration layer, permits quantification of Hofmeister effects and Gurney potentials. With these extensions, primary hydration forces (short range repulsion) arise due to an interplay between surface hydration layers and specific ion interactions. Apparent longer range “secondary hydration forces” are shown to be a consequence of ion-surface dispersion interactions and are not true “hydration forces”.

Figure optionsDownload high-quality image (56 K)Download as PowerPoint slideResearch highlights
► Classical colloid science is missing ion-specific quantum forces (Hofmeister effects).
► Forces and ion size accessible quantitatively using ab initio quantum mechanics
► Hydration, missing from the primitive model, can be included through QM extensions.
► Nonlocal polarisability (higher multipole contributions) gives a predictive theory.
► Reinterpretation of measurement of pH, surface potentials, surface forces is necessary.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Current Opinion in Colloid & Interface Science - Volume 16, Issue 6, December 2011, Pages 612–617
نویسندگان
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