Extensive research into the surface forces between hydrophobic surfaces has produced experimentally measured interaction forces that vary widely in range and in magnitude. This variability is attributed to interference from surface nanobubbles and the nature of the hydrophobic surface. Whilst the effects of nanobubbles are now recognised and can be addressed, the precise nature of the surface remains a confounding factor in measurements between hydrophobic surfaces. Here we show that a monolayer coating with hydrophobic properties is formed by exposing metal oxide surfaces to palmitic acid vapour. Surface forces measured between these smooth hydrophobic surfaces exhibited an exponential attraction. Neither patchy surface charges, nor surface nanobubbles could explain the measured forces. However, the observed interaction may be explained by the interaction of a single patch of bilayered palmitic acid molecules interacting with an exposed patch of the hafnia surface. Such an interaction is consistent with the observed exponential nature of the attraction and the agreement between the measured decay of the exponential attraction with the Debye length of the solution.

中文翻译：

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测量棕榈酸气相吸附产生的疏水性表面之间的远距离吸引力

对疏水性表面之间的表面力的广泛研究已经产生了实验测量的相互作用力，其相互作用的范围和大小各不相同。该可变性归因于来自表面纳米气泡的干扰和疏水性表面的性质。尽管现在已经认识到并且可以解决纳米气泡的影响，但是表面的精确性质仍然是疏水表面之间测量中的一个混杂因素。在这里，我们显示出通过将金属氧化物表面暴露于棕榈酸蒸气而形成具有疏水性的单层涂层。在这些光滑疏水表面之间测得的表面力表现出指数吸引力。斑驳的表面电荷或表面纳米气泡都无法解释测得的力。然而，观察到的相互作用可以通过双层棕榈酸分子的单个补丁与氧化the表面的暴露补丁相互作用来解释。这种相互作用与所观察到的吸引力的指数性质以及所测得的指数吸引力的衰减与溶液的德拜长度之间的一致性相一致。