Stability theories of nanobubbles at solid-liquid interface: A review

As nanobubbles are of far-reaching application in interface science, mining science, medical treatment, sewage treatment and other fields, researchers have carried out considerable research on the properties and influencing factors of nanobubbles. However, the abnormal lifetime of nanobubbles super stability is still an open question. According to the classical thermodynamic theories, bubbles at the nanoscale in water should be dissolved quickly, but a great number of research results in recent years indicate that nanobubbles can exist at the solid-liquid interface stably. The thorough understanding and mastery of the underlying stability mechanism of nanobubbles is the premise of the research and applications of nanobubbles. In this paper, the interfacial nanobubbles stability theories and models in recent ten years are reviewed, including contamination (impurity) theory, dynamic equilibrium theory and its extension theory, contact line pinning effect and nanobubbles internal pressure theory, etc. Furthermore, some suggestions for the future research on stability theories are proposed and the research focuses and development directions of nanobubbles in the future are also prospected. (C) 2016 Elsevier B.V. All rights reserved.