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Nanobubbles Do Not Sit Alone at the Solid-Liquid Interface

dynamoliu 添加于 2013-5-4 19:30 | 1656 次阅读 | 0 个评论

作者
Peng H, Hampton MA, Nguyen AV
摘要
<p xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" xmlns:ACS=\"http://namespace.acs.org/2008/acs\" xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" .=\"articleBody_abstractText\">The unexpected stability and anomalous contact angle of gaseous nanobubbles at the hydrophobic solid-liquid interface has been an issue of debate for almost two decades. In this work silicon-nitride tipped AFM cantilevers are used to probe the HOPG-water interface with and without solvent-exchange (a common nanobubble production method). Without solvent-exchange the force obtained by the single force and force mapping techniques is consistent over the HOPG atomic layers and described by DLVO theory (strong EDL repulsion). With solvent-exchange the force is non-DLVO (no EDL repulsion) and the range of the attractive jump-in (>10 nm) over the surface is grouped into circular areas of longer range, consistent with nanobubbles, and the area of shorter range. The non-DLVO nature of the area between nanobubbles suggests that the interaction is no longer between a silicon-nitride tip and HOPG. Interfacial gas enrichment (IGE) covering the entire area between nanobubbles is suggested to be responsible for the non-DLVO forces. The absence of EDL repulsion suggests that both IGE and nanobubbles are not charged. The co-existence of nanobubbles and IGE provides further evidence of nanobubble stability by dynamic equilibrium. The IGE cannot be removed by contact mode scanning of a cantilever tip in pure water, but in a surfactant (SDS) solution the mechanical action of the tip and the chemical action of the surfactant molecules can successfully remove the enrichment. Strong EDL repulsion between the tip and nanobubbles/IGE in surfactant solutions is due to the polar heads of the adsorbed surfactant molecules.
详细资料
- 文献种类:期刊
- 期刊名称: Langmuir
- 期刊缩写: Langmuir
- 期卷页: 2013年 130418152221002页
- ISBN: 0743-7463
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