Reprinted with permission from Muidh Alheshibri, Jing Qian, Marie Jehannin, and Vincent S. J. Craig, A History of Nanobubbles, Langmuir 2016 32 (43), 11086-11100,. Copyright (2018) American Chemical Society.
Timeline of a brief selection of significant publications in the field of surface and bulk nanobubbles.
1950: Development of the Epstein−Plesset theory, which is used to predict the lifetime of a single bubble as a function of the bubble radius and saturation. According to this theory, a nanobubble in a saturated solution should dissolve within a few milliseconds.
1994: Surface nanobubbles were proposed to account for very long range attractive forces measured between hydrophobic surfaces. Illustration: Forces measured between two hydrophobic FSCl spheres as a function of the separation distance.
1997: The role of surface nanobubbles in the very long range attractive forces measured between hydrophobic surfaces claimed above was refuted by the short expected calculated lifetimes of surface nanobubbles.
2000: The first images of surface nanobubbles recorded using atomic force microscopy (AFM) were published. These studies demonstrated that surface nanobubbles were long-lived and exhibited anomalous contact angles. Illustration: surface nanobubbles on mica, in water, imaged in tapping mode by AFM,
2003: The use of bulk nanobubbles as ultrasound contrast agents was reported. Illustration: Fluorescence microscopy image of cells incubated with nanobubbles.
2006: The influence of salt and surfactants on the shape and size of surface nanobubbles was shown to be negligible, thus indicating that the stabilization of surface nanobubbles was unlikely because of contaminants. Illustration: AFM images of surface nanobubbles on a HOPG surface in water (left) and in 0.86 CMC SDS (middle) and 0.5 CMC CTAB (right) solutions;
2010: Replicas of bulk nanobubbles were imaged by cryo-scanning electron microscopy. 2014: The relative mass density of nanoparticles compared to the solvent was measured using a microresonator. The results indicate that the density of the particles believed to be bulk nanobubbles corresponds to the particles being gaseous. Illustration: Sketch of a microresonator sensor reprinted from the Archimedes user manual, Malvern Instuments. 2015: Seo et al. directly showed that surface nanobubbles are gaseous using a concurrent combination of fluorescence microscopy and other imaging techniques. This work built on a previous study, published in 2007, in which CO surface nanobubbles were indirectly shown to be gas-filled using infrared spectroscopy. Illustration: Right: Fluorescent image of surface nanobubbles. Left: Merged image at the identical location recorded with bright-field imaging, reflection interference contrast microscopy, and fluorescence microscopy.