The results provide information about the process of ice nucleation at a molecular level and take science a significant step closer to understanding the mysterious process through which ice forms around microscopic dust particles in the upper atmosphere. Because this is the basis of cloud formation, knowing how different particles promote ice formation is crucial for climate change models.
The authors began by cooling down a metallic surface to 5 degrees above absolute zero (around –268 Celsius) at which temperature it was possible to “trap” and obtain images of the smallest possible pieces (hexamers) of ice using a scanning tunnelling microscope (STM). The hexamer – the simplest and most basic “snow flake” – is composed of just six water molecules. Other ice nanoclusters containing seven, eight and nine molecules were also imaged.
On the difficulties of imaging these ice clusters, Prof Morgenstern said: “Scientists have long struggled to resolve single water molecules within ice clusters, because they are so vulnerable to damage induced by electrons – the very thing that creates the image. The high resolution could only be achieved by reducing the current to the smallest value technically possible.”
As well as performing experiments, the team used highly-accurate (‘first principles’) theoretical models to analyse how such a structure could form. Here the theory provided some surprising insights. In ice, water molecules usually bond to each other with equal strength but with the ice nanoclusters the team identified a pattern of alternating shorter and longer bonds between the water molecules. This pattern provided new information about the ability of water molecules to share their hydrogen bonds, revealing a hitherto unknown competition between the ability of water molecules to bind to a metal surface and simultaneously accept hydrogen bonds.
Dr Michaelides said, “We are all familiar with the freezing of water. It features prominently in our daily lives, from fridge freezers to winter snow. Despite all this, the question of how individual water molecules come together and give birth to ice crystals remains mysterious. Our research provides an insight into the most important and ubiquitous type of ice nucleation event, namely heterogeneous nucleation. State-of-the-art experimental and theoretical techniques allowed us to “watch” and accurately model what happens at very low temperatures.”
The research makes it possible to explain the ways in which water structures form on different substrates, such as transition metals and salt surfaces. It may also provide a new way of thinking about the structure of ice clusters that form on solid surfaces in general, opening the door for applications in a variety of fields as diverse as astronomy, electrochemistry, and energy research. It also takes us a step closer to understanding how water interacts with different aerosols and dust particles in the atmosphere, processes which drive cloud formation and have a large impact on the planet’s climate.
David Weston | alfa
Astronomers find unexpected, dust-obscured star formation in distant galaxy
24.03.2017 | University of Massachusetts at Amherst
Gravitational wave kicks monster black hole out of galactic core
24.03.2017 | NASA/Goddard Space Flight Center
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
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In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
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