Exposing nanobubble-like objects to a degassed environment

TL;DR

This study investigates the stability of nanobubble-like objects under degassed conditions and finds that contamination from PDMS in disposable needles can produce features resembling nanobubbles, highlighting potential sources of experimental artifacts.

Contribution

The paper reveals that nanobubble-like objects can be induced by PDMS contamination from disposable needles, which may explain inconsistencies in nanobubble research.

Findings

Nanobubble-like objects remained stable after degassing procedures.

Contamination from PDMS in needles can create nanobubble-like features.

Some nanobubbles may be artifacts caused by experimental contamination.

Abstract

The primary attribute of interest of surface nanobubbles is their unusual stability and a number of theories trying to explain this have been put forward. Interestingly, the dissolution of nanobubbles is a topic that did not receive a lot of attention yet. In this work we applied two different experimental procedures which should cause gaseous nanobubbles to completely dissolve. In our experiments we nucleated nanobubble-like objects by putting a drop of water on HOPG using a plastic syringe and disposable needle. In method A, the nanobubble-like objects were exposed to a flow of degassed water (1.17 mg/l) for 96 hours. In method B, the ambient pressure was lowered in order to degas the liquid and the nanobubble-like objects. Interestingly, the nanobubble-like objects remained stable after exposure to both methods. After thorough investigation of the procedures and materials used during our experiments, we found that the nanobubble-like object were induced by the use of disposable needles in which PDMS contaminated the water. It is very important for the nanobubble community to be aware of the fact that, although features look and behave like nanobubbles, in some cases they might in fact be or induced by contamination. The presence of contamination could also resolve some inconsistencies found in the nanobubble literature.