Picture of a black hole

Strathclyde Open Access research that creates ripples...

The Strathprints institutional repository is a digital archive of University of Strathclyde's Open Access research outputs. Strathprints provides access to thousands of research papers by University of Strathclyde researchers, including by Strathclyde physicists involved in observing gravitational waves and black hole mergers as part of the Laser Interferometer Gravitational-Wave Observatory (LIGO) - but also other internationally significant research from the Department of Physics. Discover why Strathclyde's physics research is making ripples...

Strathprints also exposes world leading research from the Faculties of Science, Engineering, Humanities & Social Sciences, and from the Strathclyde Business School.

Discover more...

Electrostatic depletion forces between planar surfaces

Hatlo, Marius M. and Curtis, R.A. and Lue, Leo (2008) Electrostatic depletion forces between planar surfaces. Journal of Chemical Physics, 128 (16). ISSN 0021-9606

[img]
Preview
PDF
http_scitation.aip.org_getpdf_servlet_GetPDFServlet_filetype_pdf_id_JCPSA6000128000016164717000001_idtype_cvips_doi_10.1063_1.pdf - Final Published Version

Download (752kB) | Preview

Abstract

The interaction between two dielectric plates immersed in an electrolyte solution is examined by using a variational perturbation approximation for the grand partition function. This approach differs from previous treatments in that the screening length between the plates is treated as a variational parameter. A key finding is that adjacent to each plate is a layer of ion depletion with thickness given by about one-half of a Bjerrum length. Consequently, for plate-plate separations less than the Bjerrum length, nearly all the electrolyte is excluded from between the plates, and the interaction is given by the sum of a van der Waals interaction and an attractive osmotic depletion force. In contrast to the predictions of previous theories, the interaction between the plates at short range increases with increasing electrolyte concentration and may provide an important contribution to the salt-induced attraction, commonly referred to as salting out. Because the range of the osmotic depletion force is roughly equal to the Bjerrum length, it increases with the square of the valency of the electrolyte. At larger plate-plate separations, the van der Waals interaction is screened as electrolyte enters the space between the plates, leading to an exponential decay of the interactions, as has been previously observed. However, this interaction is slightly stronger than that previously predicted, due to ion depletion from the surface of the interface, also this effect increases with increasing electrolyte concentration.