In its bulk state, magnesium oxide (MgO) is a chalky white, rather unreactive mineral that is best known as an ingredient in antacid medication. But when this compound is formed into nanoscale films, only a few atoms deep, things begin to change. While bulk MgO is an insulator, ultrathin MgO can transfer small amounts of charge to substances, such as metal catalysts, adsorbed on its surface—giving these films the ability to tune chemical reactivity and unlock new reaction routes.
Now, researchers led by Yousoo Kim and Maki Kawai at the RIKEN Advanced Science Institute in Wako have used MgO films to establish unprecedented control over bond-breaking pathways at the single molecule level. The team reports that water molecules adsorbed onto ultrathin MgO can be selectively split apart using the sharp tip of a scanning tunneling microscope (STM)1.
According to lead author Hyung-Joon Shin, understanding the activity of MgO films required a detailed study with a well-known compound. “The atomic-scale picture of a single water molecule on the MgO surface has been [in] demand for a long time,” says Shin. “And, we expected to see interesting dynamics from the water molecules.”
In their STM experiment, the researchers worked at temperatures close to absolute zero to produce stable images of water molecules adsorbed on ultrathin MgO. By injecting small amounts of tunneling current with the STM tip, they could make the water molecules ‘hop’ laterally around the surface—but only at applied voltages corresponding to the vibrational frequencies of hydrogen–oxygen bonds. Excitations beyond these vibrational thresholds caused a chemical reaction: the water molecules dissociated into a new species, which STM images and theoretical analysis revealed was a hydroxyl group.
Because the energy required to split water on the MgO film was much lower than the hydrogen–oxygen bond energy, the researchers theorized that ultrathin MgO traps tunneling electrons in the molecule—generating a resonance-enhanced vibration that shakes the molecule apart. “The vibrationally induced dissociation of single water molecules has never been observed before,” says Shin.
The team’s experiment yielded a third discovery about the MgO surface. By injecting tunneling electrons at voltages close to the hydrogen–oxygen bond energy, STM images showed that another chemical transformation occurred: this time, water molecules split into atomic oxygen. Having two selectable water dissociation pathways—one vibrational, one electronic—has potent implications for ‘green’ energy research, because water splitting is one of the simplest way to produce clean hydrogen fuel.
The corresponding author for this highlight is based at the Surface and Interface Science Laboratory, RIKEN Advanced Science Institute
Don't Give the Slightest Chance to Toxic Elements in Medicinal Products
23.03.2018 | Physikalisch-Technische Bundesanstalt (PTB)
North and South Cooperation to Combat Tuberculosis
22.03.2018 | Universität Zürich
Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.
The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...
An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.
The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
23.03.2018 | Event News
19.03.2018 | Event News
16.03.2018 | Event News
23.03.2018 | Life Sciences
23.03.2018 | Materials Sciences
23.03.2018 | Process Engineering