Characterization of Bulk Nanobubbles Formed by Using a Porous Alumina Film with Ordered Nanopores
mediaposted on 04.06.2020, 19:36 by Teng Ma, Yasuo Kimura, Hideaki Yamamoto, Xingyao Feng, Ayumi Hirano-Iwata, Michio Niwano
Nanobubbles (NBs), with their unique physicochemical properties and promising applications, have become an important research topic. Generation of monodispersed bulk NBs with specified gas content remains a challenge. We developed a simple method for generating bulk NBs, using porous alumina films with ordered straight nanoscaled holes. Different techniques, such as nanoparticle tracking analysis (NTA), atomic force microscopy (AFM), and infrared absorption spectroscopy (IRAS), are used to confirm NB formation. The NTA data demonstrate that the minimum size of the NBs formed is less than 100 nm, which is comparable to the diameter of nanoholes in the porous alumina film. By generating NBs with different gases, including CO2, O2, N2, Ar, and He, we discovered that the minimum size of NBs negatively correlated with the solubility of encapsulated gases in water. Due to the monodispersed size of NBs generated from the highly ordered porous alumina, we determined that NB size is distributed discretely with a uniform increment factor of 2. To explain the observed characteristic size distribution of NBs, we propose a simple model in which two NBs of the same size are assumed to preferentially coalesce. This characteristic bubble size distribution is useful for elucidating the basic characteristics of nanobubbles, such as the long-term stability of NBs. This distribution can also be used to develop new applications of NBs, for example, nanoscaled reaction fields through bubble coalescence.
Read the peer-reviewed publication
uniform increment factorNB formationalumina filmIRASNTA dataBulk Nanobubblesbubble coalescenceN 2Porous Alumina Filmsize distributionNB sizeAFMnanoscaled reaction fieldsgas contentCO 2monodispersed sizebubble size distributionabsorption spectroscopyO 2nanoscaled holesalumina filmsphysicochemical propertiesresearch topicDifferent techniquesbulk NBsNanopores Nanobubblesencapsulated gasesforce microscopy100 nmmonodispersed bulk NBs