Nanobubbles at Hydrophobic Surfaces - Drops and Bubbles in Contact with Solid Surfaces - page 172

entities and why are they only observed on layered crystalline surfaces? One pos-
sibility is that nanobubbles delaminate the surface of HOPG to produce graphene
layers which then coat the air-water interface and stabilize a range of exotic struc-
ture. Nanobubbles have been implicated in the formation of carbon nanostructures
from HOPG [60]. Other questions arise such as how hydrophobic does a substrate
need to be to support nanobubbles, recalling that the macroscopic and nanoscopic
contact angles differ. This also has implications for super-hydrophobic surfaces
where small gas pockets are trapped at surfaces. If these gas pockets are made
very small what contact angle will they adopt and how will this influence the su-
perhydrophobicity? Finally, enormous external pressures are used to 'crush' Harvey
nuclei, how would nanobubbles survive such a high external pressure? What is clear
is that understanding nanobubbles is going to demand input from scientists with a
wide range of expertise. It is notable that to date very few nanobubble researchers
have a background in the physics and chemistry of bubbles and therefore we hope
that the presence of this report in this topic will engage some of you in the challenge
of nanobubble research.
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