The length scales for stable gas nanobubbles at liquid/solid surfaces

We present results focusing on whether gas bubbles are stable at all length scales at liquid/solid surfaces. Tapping mode atomic force microscopy was used to observe nanoscale bubbles of air or hydrogen produced by two methods on hydrophilic and hydrophobic solid surfaces. The observed nanobubbles of air or hydrogen always have curvature radii of less than 2.0 mu m and heights of less than 100 nm, suggesting the possible instability of these nanobubbles beyond these length scales. This is further supported by the observation of blank circular areas on the electrode surface, which are interpreted as footprints of departed large bubbles with curvature radii equal to or above 2.0 mu m from the surface.