Hofmeister Effects

Specific ion effects have been extensively studied since 1888, when Hofmeister discovered ion specific effects on precipitation of purified egg white. Hofmeister showed that salts with the same cation but different anion precipitated the protein at different concentrations. This behaviour was also observed with some other colloidal suspensions. Accordingly, the effectiveness of different anions with the cation fixed, or of cations with fixed anion, can be ordered reproducibly in the so-called Hofmeister series. In colloid science and biochemistry, there is a plethora of experiments showing that ions with the same valence can induce very different behaviours. Such experiments include protein solubility, critical micelle concentration, surface tension, forces between charged surfaces and electrophoretic mobilities, to which we will pay special attention in this work. Regardless of the huge number of studies over the years, Hofmeister phenomena are still gaining popularity nowadays. This is due to, amongst other things, aqueous ion-containing interfaces are ubiquitous and play a key role in a plethora of physical, chemical, atmospheric, and biological processes. Hofmeister phenomena in bulk phases, in surfactant-based systems and at interfaces, in gels, in proteins and enzymes, and in real biological systems and medicine are some of the examples which have been extensively analysed in the last decades. Among these examples, ion specificity effects focused on biology are those that have mostly attracted the attention of the Hofmeister community nowadays. This is why there is a renewed interest in Hofmeister phenomena in colloids with biological applications.

[6] A. Martín-Molina, T. Del Castillo-Santaella, Y. Yang, J. Maldonado-Valderrama. Condensation of Model Lipid Films by Cholesterol: Specific Ion Effects.  Coatings 9 (2019) 474.

[5] L. Pérez-Mas, A. Martín-Molina, R. Kumar Jaind, M. Quesada-Pérez. Effect of dispersion forces on the behavior of thermosensitive nanogels: A coarse-grained simulation study. Journal of Molecular Liquids 288, 111101 (2019).

[4] T. Del Castillo-Santaella, J. Maldonado-Valderrama, J. Faraudo and A. Martín-Molina. Specific ion effects in Cholesterol monolayers. Materials 9 (2016) 340.

[3] F. Vereda, A. Martin-Molina, R. Hidalgo-Alvarez and  M. Quesada-Perez, Specific ion effects on the electrokinetic properties of iron oxide nanoparticles: experiments and simulations, Physical Chemistry Chemical Physics, 17 (2015) 17069-17078.

[2] M. Quesada-Pérez, R. Hidalgo-Álvarez and  A. Martín-Molina, Effect of ionic van der Waals forces on the diffuse potential of model colloids, Colloid and Polymer Science, 288 (2010) 151-158.

[1] A. Martín-Molina, J.G. Ibarra-Armenta and  M. Quesada-Pérez, Effect of ion dispersion forces on the electric double layer of colloids: a Monte Carlo simulation study, The Journal of Physical Chemistry B, 113 (2009) 2414-2421.

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