Nanobubble/Nanoparticle Clusters in Materials Science and Engineering

Nanobubbles typically have a diameter in the range of 20 to 1100 nm and can persist for weeks in aqueous environments. A first-principles theory has shown that the process that makes stable nanobubbles seem improbable, microbubble shrinkage, is responsible for not only their metastability but also their remarkable longevity. This theory has been experimentally confirmed with zeta potential measurements in deionized water as well as reported nanobubble size distributions published in the scientific literature from multiple laboratories. Nanoparticle tracking analysis (NTA) measurements of object size and relative scattering intensity were also performed with water containing fouling compounds in solution such as CaCO₃. Based on these measurements, we have demonstrated that nanobubbles can bind to embryonic nanoparticles making these embryos stable so that they do not dissolve back into solution. This effective reduction in dissolved solid below the solubility limit can then induce the dissolution of bulk solid that previously deposited in the water system. Reported observations of the dissolution of salts, such as calcium carbonate, typically found in fouling deposits have been attributed to this nanobubble/nanoparticle clustering phenomenon. The implications of our work for future exploitation of nanobubble/nanoparticle interactions will be discussed.