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
Cryo-electron microscopy achieves unprecedented resolution using new computational methods
24.03.2017 | DOE/Lawrence Berkeley National Laboratory
How cheetahs stay fit and healthy
24.03.2017 | Forschungsverbund Berlin e.V.
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.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
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...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy