Forces between zinc sulphide surfaces; amplification of the hydrophobic attraction by surface charge

Teh, E-J, Ishida, N., Skinner, W.M., Parsons, D.F.ORCID: 0000-0002-3956-6031 and Craig, V.S.J. (2019) Forces between zinc sulphide surfaces; amplification of the hydrophobic attraction by surface charge. Physical Chemistry Chemical Physics, 21 (36). pp. 20055-20064.

Abstract

Smooth Zinc Sulphide (ZnS) surfaces were prepared by magnetron sputtering and the interaction forces were measured between them as a function of pH. At the isoelectric point (iep) of pH 7.1 the attractive force was well described by the van der Waals interaction calculated using Lifshitz theory for a layered system. Away from the iep, the forces were fitted using DLVO theory extended to account for surface roughness. At pH 9.8 the surfaces acquire a negative charge and an electrostatic repulsion is evident. Below the iep the surfaces acquire a positive charge leading to electrostatic repulsion. The forces in the range 3.8 < pH < 4.8 show an additional attraction on approach and much greater adhesion than at other pH values. This is attributed to the hydrophobic attraction being amplified by a small degree of charge on the surface as has previously been reported for adhesion measurements. The range of the measured forces is attributed to the long-range orientational order of water (>5 nm).

Item Type:	Journal Article
Murdoch Affiliation(s):	School of Engineering and Information Technology
Publisher:	Royal Society of Chemistry
Copyright:	© 2019 the Owner Societies
URI:	http://researchrepository.murdoch.edu.au/id/eprint/51532

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