Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Hydrogen ions caught in the act of wandering

06.10.2005


Erik T.J. Nibbering of the Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy (MBI) and colleagues report for the first time experimental evidence of the motions of hydrogen ions (protons, H+) from acids via water to bases. Until now this has only been estimated as a possible reaction mechanism with theoretical calculations. With this study, the international research team provides insight into fundamental processes in nature (acid-base neutralization, proton transmission through water and through biomembranes), that may well become relevant for technological applications, e.g. in fuel cells. The scientists report on these findings in Science (Vol. 310, pp. 83 – 86) Nibbering’s team consisted of his colleagues from the MBI, Omar F. Mohammed (a Ph. D. student from Egypt) and the theoretician Jens Dreyer, and the group of Ehud Pines at Ben Gurion University of the Negev (Israel).

For a long time, it was not clear how the transfer of protons in aqueous solutions occurs. This is because protons do not move freely in water, but form complexes with water molecules (H2O) through hydrogen bonds. Hydronium (H3O+) is formed, but this ion will not stay alone, because it forms complexes with nearby water molecules in continuously exchanging configurations, e.g. in the form of the so-called Zundel (H5O2+) and Eigen (H9O4+) cations. Erik Nibbering and colleagues succeeded to make snapshots of the proton motions with ultrashort laser flashes. It turned out that hydrogen ions are transmitted from acid to base by water molecules.

Hydrogen ions are transmitted very efficiently through water. First theoretical considerations on this were made exactly 200 years ago by the german-baltic scientist Theodor von Grotthuss, and since exactly 100 years scientists use the phrase “Grotthuss mechanism” to indicate the jump-like transmission of protons to neighbouring water molecules. “One can use the picture of the improving a dike with sandbags”, says Nibbering. A chain of people will transport the sandbags more efficiently and faster towards the dike than everybody on his own. “You could speak of proton hopping”, explains Nibbering. Only recently, numerous theoretical refinements have become available. Detailed calculations, for example, made clear that proton transmission becomes possible when the surrounding water rearranges at particular points in time to enable the Zundel-cation and at other times the Eigen-cation configuration.



Furthermore, theoreticians have derived that the exchange of protons between acids and bases in aqueous solution should occur in a similar fashion. Now, the recent report in Science confirms the hopping model.

The experimental study has become possible by a technique, that enables the determination of the reaction progress in time steps of 150 femtoseconds. This is extremely fast. For comparison: A laser beam will reach the moon in one second. In 100 femtoseconds on the other hand a laser beam will only have reached a distance equivalent to the diameter of a human hair. The scientists have used in their experiments an aqueous acid-base mixture, with which they already have been performing proton transfer studies since two years. “Two years ago, we were not able to observe the intermediate steps. We could only see the beginning and the end of the proton transfer reaction”, says Nibbering. By a change of the components of the acid-base mixture the reaction has been slowed down so that now the sequential proton hopping via water molecules can be recorded.

Josef Zens | alfa
Further information:
http://www.fv-berlin.de

More articles from Physics and Astronomy:

nachricht What happens when we heat the atomic lattice of a magnet all of a sudden?
17.07.2018 | Forschungsverbund Berlin

nachricht Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Microscopic trampoline may help create networks of quantum computers

17.07.2018 | Information Technology

In borophene, boundaries are no barrier

17.07.2018 | Materials Sciences

The role of Sodium for the Enhancement of Solar Cells

17.07.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>