Nanobubbles are very small gas cavities (for example, a nanoscope) that some physicists have observed in aqueous solutions, usually after certain substances have been dissolved in them. While some studies have reported observing these extremely small bubbles, some scientists have argued that they are just a solid or oily residue that formed during the experiments.
Researchers at the Center for Research and Studies at Avanzados Unidad Monterrey and Centro de Investigación en Matemáticas Unidad Monterrey in Mexico recently conducted an experiment aimed at further investigating the nature of these elusive and mysterious objects, specifically when xenon and krypton dissolve in water. Their studies, featured in physical review messagesdetermined the formation of what the team refers to as “nanoblocks,” yet found no evidence of nanobubbles.
“Our goal was to create xenon and krypton nanobubbles using a clean method,” Carlos Ruiz Suarez, one of the researchers who conducted the study, told Phys.org. “I must say that there are many scientists who claim that nanobubbles, although used in many applications, do not exist. Rather, they are thought to be petroleum/solid contaminants formed during experiments.”
To solve the “puzzle” of nanobubbles, Ruiz Suárez and colleagues devised a “clean” method that should theoretically allow them to produce “real” nanobubbles. This method entailed dissolving the noble gases xenon and krypton in water, by applying high pressure them, then remove the pressure and check the resulting fluid.
The team evaluated the results of this procedure in both Molecular dynamics simulation (MDS) and laboratory experiments. While they did in fact observe nanobubble-like particles, when they analyzed these particles, they were surprised that these particles were most likely amorphous structures of gas and water, not gas bubbles.
“To bring the noble atoms together to form bubbles, we need to increase their concentrations in the middle of the water,” Ruiz Suarez explained. “By doing MDS, we found that the correct ratios between water molecules The noble atoms were about 30 water molecules/atom. Thus, we needed to build a high-pressure cell to force the atoms to dissolve in water by pushing the gas inward. “
Xenon and Krypton are rabid gases. This means that they can only enter the water and aqueous solutions Under high pressure (more than 360 bar or atmospheres). However, once they enter the water, they can bond to each other through van der Waals’ forces.
“There is currently no way to see what’s inside the cell, but we assumed the bubbles were there because we believed we had MDS,” said Ruiz Suarez. “The next step for our work was to lower the pressure of the sample and see the bubbles. However, to our great surprise, there were not bubbles, but something else: nanostructures formed from gas and water, which we called nanoclusters. These are unique structures that give rise to The emergence of clathrate hydrates”.
The existence of nanobubbles is still a topic of debate in Particle physics And the latest work of these researchers could help solve this mystery. Just like xenon and krypton, many other gases used to create nanobubbles can also form clathrate hydrates (for example, water structures with molecules inside). Overall, the team’s findings suggest that what several previous studies identified as “nanobubbles” could be instead of these amorphous nanostructures formed from the clathrate hydrate.
“It is important to note that when an existing physical theory cannot explain experimental results, physicists prefer to call it a catastrophe,” said Ruiz Suarez. “Because nanobubbles have high pressure inside them (the smaller they are, the higher the pressure), the theory says that they have a very short life (in the order of microseconds). However, observations revealed that they existed for much longer, so this was called a ‘pressure bubble disaster’. in Laplace”.
If the results collected by this team of researchers are valid and reliable, they could contribute significantly to the current understanding of nanobubbles. Essentially, their findings suggest that the Laplace pressure bubble catastrophe does not exist, as the previously observed ‘nanobubbles’ are instead ‘nanobubbles’, or alternative structures resulting from clathrate hydrates in the experimentally used gases.
“We are now building an experimental device that allows us to see inside the cell and observe nanobubbles at high pressure,” said Ruiz Suarez. “We’d like to see its evolution when we lower the pressure and the moment it becomes a clathrate hydrate. At the same time, we’re also studying other important gases like oxygen and carbon dioxide.”
Angela M. Jaramillo-Granada et al., xenon and krypton dissolved in aqueous form. Nanoblocks: no evidence of nanobubbles, physical review messages (2022). DOI: 10.1103/ PhysRevLett.129.094501
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