Das Siddhartha
Physics of Fluids Group, Faculty of Science of Technology, University of Twente, P.O. Box 217, NL-7500 AE Enschede, The Netherlands.
Phys Rev E Stat Nonlin Soft Matter Phys. 2011 Sep;84(3 Pt 2):036303. doi: 10.1103/PhysRevE.84.036303. Epub 2011 Sep 7.
In this paper we propose a scaling argument to quantify the role of added electrolyte salt in affecting the stability and the morphology of preformed surface nanobubbles on hydrophobic substrates like the water-OTS-silicon or the water-HOPG interfaces. The added salt controls the electric double layer formation as well as affects the zeta (ζ) potential at the air-water and solid-water interfaces. The resulting electrostatic wetting tension acts in conjunction with the air-water surface tension (analogous to electrowetting scenarios), thereby affecting the nanobubble morphologies. Weak ζ potential of the water-HOPG interface or the water-OTS-silicon interface at acidic pH ensures that the added salt will have imperceptible effect on the corresponding preformed surface nanobubbles, validating the experimental observations. However, at alkaline buffer pH for the OTS-silicon substrate, under certain system conditions, salt-induced ζ potential can be substantially high so that the properties of preformed surface nanobubbles will be affected. This paper will thus readdress the long-held universal notion that added salt, no matter in what concentration, will not influence the properties of preformed surface nanobubbles.
在本文中，我们提出了一种标度论证方法，以量化添加电解质盐对诸如水 - 十八烷基三氯硅烷 - 硅或水 - 高定向热解石墨界面等疏水基底上预先形成的表面纳米气泡的稳定性和形态的影响。添加的盐控制双电层的形成，并影响气 - 水界面和固 - 水界面处的zeta（ζ）电位。由此产生的静电润湿张力与气 - 水表面张力共同作用（类似于电润湿情况），从而影响纳米气泡的形态。在酸性pH值下，水 - 高定向热解石墨界面或水 - 十八烷基三氯硅烷 - 硅界面的弱ζ电位确保添加的盐对相应的预先形成的表面纳米气泡影响不明显，这验证了实验观察结果。然而，对于十八烷基三氯硅烷 - 硅基底，在碱性缓冲pH值下，在某些系统条件下，盐诱导的ζ电位可能会相当高，以至于预先形成的表面纳米气泡的性质会受到影响。因此，本文将重新审视长期以来的普遍观念，即无论添加盐的浓度如何，都不会影响预先形成的表面纳米气泡的性质。
