Teh, E-JenIshida, NaoyukiSkinner, William MenelaosParsons, DrewCraig, Vince2023-01-121463-9076http://hdl.handle.net/1885/282715Smooth 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 o pH o 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 (45 nm).V. S. J. Craig gratefully acknowledges support from the Australian Research Council through a Discovery Grant, DP140102371application/pdfen-AUThis journal is © the Owner Societies 2019201910.1039/c9cp02797a2021-11-28