title: In situ measurement of contact angles and surface tensions of interfacial nanobubbles in ethanol aqueous solutions.
abstract: The astonishing long lifetime and large contact angles of interfacial nanobubbles are still in hot debate despite numerous experimental and theoretical studies. One hypothesis to reconcile the two abnormalities of interfacial nanobubbles is that they have low surface tensions. However, few studies have been reported to measure the surface tensions of nanobubbles due to the lack of effective measurements. Herein, we investigate the in situ contact angles and surface tensions of individual interfacial nanobubbles immersed in different ethanol aqueous solutions using quantitative nanomechanical atomic force microscopy (AFM). The results showed that the contact angles of nanobubbles in the studied ethanol solutions were also much larger than the corresponding macroscopic counterparts on the same substrate, and they decreased with increasing ethanol concentrations. More significantly, the surface tensions calculated were much lower than those of the gas-liquid interfaces of the solutions at the macroscopic scale but have similar tendencies with increasing ethanol concentrations. Those results are expected to be helpful in further understanding the stability of interfacial nanobubbles in complex solutions.
authors.affiliation: Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China. zhanglijuan@sinap.ac.cn hujun@sinap.ac.cn.
authors.forename: Binyu
authors.initials: B
authors.lastname: Zhao
authors.forename: Xingya
authors.initials: X
authors.lastname: Wang
authors.forename: Shuo
authors.initials: S
authors.lastname: Wang
authors.forename: Renzhong
authors.initials: R
authors.lastname: Tai
authors.forename: Lijuan
authors.initials: L
authors.lastname: Zhang
authors.forename: Jun
authors.initials: J
authors.lastname: Hu