Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Solving single molecule mobility

18.10.2010
A versatile formula describes the energetic conditions needed to transport molecules laterally on surfaces

Nanotechnologists assemble intricate nanodevices, such as computer chips, molecule by molecule using ‘bottom-up’ techniques that mirror nature. One approach shuttles molecules along surfaces into new and functional arrangements using electrons from a scanning tunneling microscope (STM) tip.

However, because energy transfer between the atomic-scale tip and the surface chemical involves many complex interactions, laborious efforts are currently needed to understand even the simplest reactions.

Results from a new theoretical and experimental study, however, may soon allow non-specialists to easily construct molecular devices. Kenta Motobayashi and Yousoo Kim from the RIKEN Advanced Science Institute in Wako and their colleagues from RIKEN and Japanese universities have developed a mathematical formula that describes how STM-induced molecular vibrations couple with dynamic movements on surfaces—enabling precise calculation of the energy and number of electrons needed to initiate single molecule motions1.

When scientists use an STM to perform a straightforward molecular movement—for example, making carbon monoxide (CO) compounds ‘hop’ on palladium surfaces—they see that the fraction of successful movements depends heavily on the applied voltage. For CO, this is because hopping from one surface site to another requires a tunneling electron to initiate a specific stretching vibration. In the voltage range corresponding to this vibrational energy, CO hopping can increase exponentially, giving rise to so-called ‘action spectra’: curves of movement yields versus voltage with shapes characteristic to particular surface reactions.

Motobayashi, Kim and colleagues sought to uncover the microscopic mechanisms behind STM-stimulated diffusion by proposing a formula that relates movement yields to the energy transfer efficiency needed to excite reaction-triggering vibrations, while also accounting for thermal interactions. Fitting the CO action spectra to this formula revealed the exact magnitudes of critical reaction properties, like vibrational energies and rate constants, because the spectral curves were highly sensitive to small modification of the fit parameters.

Furthermore, the team’s new equation proved versatile enough to analyze the more complex motions of butene (C4H8) molecules on palladium, a process that involves multiple excitations. Analyzing the butene action spectra with the formula showed the presence of three distinct vibrations and enabled calculation of the reaction order—a fundamental chemical property that identifies the number of tunneling electrons needed to initiate surface movement.

According to Motobayashi, the surprising abilities of this simple method should expand bottom-up nanotechnology practices. “STM-based action spectroscopy, which can precisely identify chemical species thanks to our spectral fittings, promises to contribute greatly to the technique of composing molecular devices,” he states.

The corresponding author for this highlight is based at the Surface and Interface Science laboratory, RIKEN Advanced Science Institute

Journal information

1. Motobayashi, K., Kim, Y., Ueba, H. & Kawai, M. Insight into action spectroscopy for single molecule motion and reactions through inelastic electron tunneling. Physical Review Letters 105, 076101 (2010).

gro-pr | Research asia research news
Further information:
http://www.riken.jp
http://www.researchsea.com

More articles from Life Sciences:

nachricht Making fuel out of thick air
08.12.2017 | DOE/Argonne National Laboratory

nachricht ‘Spying’ on the hidden geometry of complex networks through machine intelligence
08.12.2017 | Technische Universität Dresden

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

Im Focus: Virtual Reality for Bacteria

An interdisciplinary group of researchers interfaced individual bacteria with a computer to build a hybrid bio-digital circuit - Study published in Nature Communications

Scientists at the Institute of Science and Technology Austria (IST Austria) have managed to control the behavior of individual bacteria by connecting them to a...

Im Focus: A space-time sensor for light-matter interactions

Physicists in the Laboratory for Attosecond Physics (run jointly by LMU Munich and the Max Planck Institute for Quantum Optics) have developed an attosecond electron microscope that allows them to visualize the dispersion of light in time and space, and observe the motions of electrons in atoms.

The most basic of all physical interactions in nature is that between light and matter. This interaction takes place in attosecond times (i.e. billionths of a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Midwife and signpost for photons

11.12.2017 | Physics and Astronomy

How do megacities impact coastal seas? Searching for evidence in Chinese marginal seas

11.12.2017 | Earth Sciences

PhoxTroT: Optical Interconnect Technologies Revolutionized Data Centers and HPC Systems

11.12.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>