Nanobubbles are nano-size domains of gas, which can either be surrounded by a liquid (bulk nanobubbles) or found at a liquid-solid interface (surface nanobubbles). The theory predicts that nanobubbles should dissolve in few milliseconds under typical conditions. Experimentally, surface nanobubbles have been observed to be stable for up to 5 days. Up to now, the discrepancy between the theoretical and experimental results remains a scientific mystery.

The first part of the talk will focus on surface nanobubbles. Here, the stability of surface nanobubbles was experimentally investigated in different media by Atomic Force Microscopy. We explain how the gathered experimental evidences enable to refute two mechanisms recently proposed to account for the long-term stability of surface nanobubbles.

The second part of the talk will be devoted to bulk nanobubbles. The existence of long-lived bulk nanobubbles is controversial among the scientific community, even so, several companies sell nanobubble generators and their use in industry is surprisingly widespread. In this work, we aim to investigate the production of long-lived bulk nanobubbles and their characterization. For this purpose, chemical and physical methods were tested to produce nanobubbles. The resulting particles were characterized and their stability further investigated.