2013/07/20 by Faezeh Pousaneh, Pousaneh, Faezeh, A. Ciach +3 · 1 citation
Biochemistry, Genetics and Molecular Biology · Physics and Astronomy · #Advanced Thermodynamics and Statistical Mechanics #Chemical and Physical Studies #FOS: Physical sciences #Quantum Electrodynamics and Casimir Effect #Soft Condensed Matter (cond-mat.soft)
paper · pdf · doi:10.48550/arxiv.1307.5379
openalex publication_date 2013/07/20 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We show that hydrophilic ions present in a confined, near-critical aqueous\nmixture can lead to an attraction between like charge surfaces with opposing\npreferential adsorption of the two species of the mixture, even though the\ncorresponding Casimir potential in uncharged systems is repulsive. This\nprediction agrees with recent experiment [Nellen itet al., Soft\nMatter bf80, 061143 (2011)]. We also show that oppositely charged\nhydrophobic surfaces can repel each other, although the Casimir potential\nbetween uncharged surfaces with like preferential adsorption (selectivity) is\nattractive. This behavior is expected when the electrostatic screening length\nis larger than the correlation length, and one of the confining surfaces is\nstrongly selective and weakly charged, whereas the other confining surface is\nweakly selective and strongly charged. The Casimir potential can change sign\nbecause the hydrophilic ions near the weakly hydrophobic surface can\novercompensate the effect of hydrophobicity, and this surface can act as a\nhydrophilic one. We also predict a more attractive interaction between\nhydrophilic surfaces and a more repulsive interaction between hydrophobic\nsurfaces than given by the sum of the Casimir and Deby-H "uckel potentials. Our\ntheory is derived systematically from a microscopic approach, and combines the\nLandau-type and Debye-H "uckel theories with an additional contribution of an\nentropic origin.\n