Anomalous Ion Effects on Rupture and Lifetime of Aqueous Foam Films Formed from Monovalent Salt Solutions up to Saturation Concentration
Anomalous Ion Effects on Rupture and Lifetime of Aqueous Foam Films Formed from Monovalent Salt Solutions up to Saturation Concentration
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DOI：
10.1021/la801456j
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发表时间：
2008-10-21
期刊：
影响因子：
3.9
通讯作者：
Nguyen, Anh V.
中科院分区：
文献类型：
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作者：
Karakashev, Stoyan I.;Nguyen, Phong T.;Nguyen, Anh V.
我们报告的影响，离子的破裂和寿命的水泡沫膜形成的氯化钠（NaCl），氯化锂（LiCl），乙酸钠（NaAc），氯酸钠（NaClO3）使用显微干涉。在NaCl和LiCl的情况下，从低于0.1 M的盐溶液制备的泡沫膜是不稳定的，它们变薄直到破裂。从第一干涉图（出现在膜厚度为500 nm的量级上）直到膜破裂为止测量的膜寿命仅为1秒左右。然而，观察到从高于0.1 M的盐溶液制备的相对持久且不排水的膜。膜寿命显著延长1至2个数量级，即，从10到100秒。重要的是，膜的寿命和（平均）厚度的nondrainage膜增加，增加盐浓度。用表面活性剂稳定的泡沫膜没有观察到这种效果。薄膜的厚度和寿命也随着薄膜半径的增加而增加。膜表现出显著的表面波纹。大半径的膜通常包含站立的凹坑。存在一个临界膜半径，低于此半径，膜层变薄直至破裂。在NaAc和NaClO3的情况下，薄膜在所有半径和盐浓度下都不稳定，它们变薄直到破裂，排除了溶液粘度对稳定薄膜的影响。
We report the effects of ions on rupture and lifetime of aqueous foam films formed from sodium chloride (NaCl), lithium chloride (LiCl), sodium acetate (NaAc), and sodium chlorate (NaClO3) using microinterferometry. In the case of NaCl and LiCl, the foam films prepared from the salt solutions below 0.1 M were unstable-they thinned until rupturing. The film lifetime measured from the first interferogram (appearing at a film thickness on the order of 500 nm) until the film rupture was only a second or so. However, relatively long lasting and nondraining films prepared from salt solutions above 0.1 M were observed. The film lifetime was significantly longer by 1 to 2 orders of magnitude, i.e., from 10 to 100 s. Importantly, both the film lifetime and the (average) thickness of the nondraining films increased with increasing salt concentration. This effect has not been observed with foam films stabilized by surfactants. The film lifetime and thickness also increased with increasing film radius. The films exhibited significant surface corrugations. The films with large radii often contained standing dimples. There was a critical film radius below which the films thinned until rupturing. In the cases of NaAc and NaClO3, the films were unstable at all radii and salt concentrations-they thinned until rupturing, ruling out the effect of solution viscosity on stabilizing the films.