August 14, 2022


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Record the resolution on the atomic scale.  Thanks to the new recordings, the theory could have been refuted years ago

Record the resolution on the atomic scale. Thanks to the new recordings, the theory could have been refuted years ago

Ostwald ripening is the concept of emulsion aging, and the theory has been for years that small molecules dissolve and re-deposition on the surface of larger molecules. The large particles, in turn, will continue to grow until all the small particles have dissolved.

Research on this was conducted by Wilhelm Ostwald, who in 1909 was awarded the Nobel Prize in Chemistry. Years later, scientists at Berkeley Lab made atomic-scale recordings of the molecules and concluded that their growth was not driven by size differences but by defects. Details of their research are presented on the pages Nature Communications.

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Haimei Zheng, one of the paper’s authors, explains that her team’s findings are very important and, in fact, lead to a re-establishment of certain theories. However, before the scientists came to such conclusions, they decided to suspend a solution of cadmium sulfide (CdS) nanoparticles with cadmium chloride (CdCl).2) and hydrogen chloride (HCl). Then they illuminated the solution with an electron beam to produce Cd-CdCl nanoparticles2 They look like flat hexagonal discs. Cadmium atoms form the core, while cadmium chloride is responsible for the coating.

To capture the processes taking place at such a small scale, team members used a technology called high-resolution transmission electron microscopy of liquid cells. Thanks to this, they were able to capture the changes that occur inside the solution in the presence of an electron beam in real time, on an atomic scale, and ultimately the formation of Cd-CdCl2.

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In the course of the experiments, it was possible, among other things, to capture small Cd-CdCl nanoparticles2 Merging with the Big, which led to the creation of Akbar. Most surprising, however, is the fact that the growth was not affected by size differences, but rather by a crack-shaped defect that occurred in the coating of the larger nanoparticles initially.

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According to the authors of the publication, their recording has a high standard accuracy. An important role in achieving this breakthrough was played by the specialized electron microscope ThemIS, which is able to record changes in the atomic scale in liquids at a speed of 40-400 frames per second. Then the microscope’s high vacuum environment keeps the sample fluid intact.