Testing predictions in electrochemical nanosystems

June 07, 2010

Physicists at the Technische Universitaet Muenchen (TUM) are gearing up for experimental tests of findings they arrived at through theoretical considerations: that electrochemical reactions take place more rapidly on isolated, nanometer-scale electrodes than on their familiar macroscopic counterparts, and that this surprising behavior is caused by thermal noise. Prof. Katharina Krischer and Dr. Vladimir Garcia-Morales published their results earlier this year in the Proceedings of the National Academy of Sciences (PNAS). The project is supported by the TUM Institute for Advanced Study, which emphasizes scientifically "risky" research that may have potential for creating new fields of technology.

Familiar processes take unfamiliar turns when they're observed on the nanoscale, where models that accurately describe macroscopic phenomena may not be reliable, or even applicable. Electrochemical reactions, for example, which normally appear to proceed smoothly, seem to halt and stumble in the nanoworld. When the electrodes involved are less than ten nanometers wide, chance plays a bigger role: Random movement of molecules makes the exact timing of reactions unpredictable.

Now, however, just such a process can be described by a theoretical model developed by the TUM physicists. They demonstrated their method in a study of nanoscale reactions, published in PNAS, which presented a new electrochemical "master equation" underlying the model. Their results show that thermal noise -- that is, the randomness of molecular movement and individual electron-transfer reactions -- actually plays a constructive role in a nanoscale electrochemical system, enhancing reaction rates.

"The effect predicted is robust," says Dr. Vladimir Garcia-Morales, recently named a Carl von Linde Junior Fellow of the TUM Institute for Advanced Study, "and it should show up in many experimental situations." To see for themselves, the researchers have turned their attention from the chalkboard and the computer to the lab bench. Their experiments present several technical challenges. One is not only to fabricate disk-shaped electrodes with a radius of just three to ten nanometers, but also to determine the electrode area accurately. Another tough requirement is setting up the electronics to minimize noise from external sources, to make sure the influence of internal, molecular noise can be observed.

"An important aspect," Dr. Garcia-Morales says, "is that the reported effect can change our view on the collective properties of many electrodes. Common intuition suggests that if one makes the electrode area ten times as large, the current would be ten times as high. But, as we show with our theory, the proportionality does not hold any more when the electrode dimension becomes as small as a few nanometers."

Experimental validation could also help to transpose the TUM researchers' theory to a variety of situations. They say their method accounts for effects that macroscopic models can't explain and could prove useful in addressing a variety of research questions. "The applicability of the electrochemical master equation is in fact beyond the specific problem addressed in the publication," Prof. Katharina Krischer stresses. "It establishes a general framework for stochastic processes involving electron-transfer reactions. For example, we now use it to predict the quality of electrochemical clocks at the nanoscale."
Support for this research has come from the European Union (Project DYNAMO), the Nanosystem Initiative Muenchen Cluster of Excellence, and the TUM Institute for Advanced Study.

Original publication:

Fluctuation enhanced electrochemical reaction rates at the nanoscale, Vladimir Garcia-Morales and Katharina Krischer, PNAS 107, 4528 (2010). Doi: 10.1073/pnas.0909240107

Prof. Katharina Krischer
Technische Universitaet Muenchen
Department of Physics (E19a)
James-Franck-Str. 1
85748 Garching, Germany
Tel: +49 89 289 12535, Fax: +49 89 289 12338

Technische Universitaet Muenchen (TUM) is one of Europe's leading universities. It has roughly 420 professors, 7,500 academic and non-academic staff (including those at the university hospital "Rechts der Isar"), and 24,000 students. It focuses on the engineering sciences, natural sciences, life sciences, medicine, and economic sciences. After winning numerous awards, it was selected as an "Elite University" in 2006 by the Science Council (Wissenschaftsrat) and the German Research Foundation (DFG). The university's global network includes an outpost in Singapore. TUM is dedicated to the ideal of a top-level research based entrepreneurial university. http://www.tum.de

Technical University of Munich (TUM)

Related Nanoscale Articles from Brightsurf:

Nanoscale machines convert light into work
Researchers have developed a tiny new machine that converts laser light into work.

Discovery will allow more sophisticated work at nanoscale
The movement of fluids through small capillaries and channels is crucial for processes ranging from blood flow through the brain to power generation and electronic cooling systems, but that movement often stops when the channel is smaller than 10 nanometers.

Valley-Hall nanoscale lasers
Topological photonics allows the creation of new states of light.

Dynamics of DNA replication revealed at the nanoscale
Using super-resolution technology a University of Technology Sydney led team has directly visualised the process of DNA replication in single human cells.

House cleaning on the nanoscale
A team of scientists at Friedrich-Alexander Universität Erlangen-Nürnberg (FAU) has developed a novel mechanical cleaning method for surfaces on the nanoscale.

As electronics shrink to nanoscale, will they still be good as gold?
As circuit interconnects shrink to nanoscale, will the pressure caused by thermal expansion when current flows through wires cause gold to behave more like a liquid than a solid -- making nanoelectronics unreliable?

A joint venture at the nanoscale
Scientists at Argonne National Laboratory report fabricating and testing a superconducting nanowire device applicable to high-speed photon counting.

Bending diamond at the nanoscale
A team of Australian scientists has discovered diamond can be bent and deformed, at the nanoscale at least.

Creating a nanoscale on-off switch for heat
Researchers create a polymer thermal regulator that can quickly transform from a conductor to an insulator, and back again.

Magnetic tuning at the nanoscale
Physicists from the German research center Helmholtz-Zentrum Dresden-Rossendorf (HZDR) are working to produce engineered magnetic nanostructures and to tailor material properties at the nanoscale.

Read More: Nanoscale News and Nanoscale Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.