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U.S., Japan Team Measures Single-Molecule Machines in Action

by Editor1 last modified July 22, 2010 - 11:09

A multidisciplinary team of researchers from the U.S. and Japan may have pierced the veil around interactions of functional molecules, paving the way for molecular devices, display technologies, and "artificial muscles" in nanoelectromechanical devices.

U.S., Japan Team Measures Single-Molecule Machines in Action

The U.S, Japan team studied movement of single-molecules of rotaxane. Images shows movement of ring to different stations along the rod.

Scientists from UCLA, Northwestern University, University of California-Merced, Pennsylvania State University and Japan report they have succeeded in observing single-molecule interactions of bistable rotaxanes functioning in their native environment.

Rotaxanes are tiny, mechanically interlocked structures that consist of a dumbell-shaped molecule whose rod section is encircled by a ring. These structures behave as molecular "machines," with the ring moving along the rod from one station to another when stimulated by a chemical reaction, light or acidity.

But before scientists and commercial firms can tap the potential of these molecular machines, they need to better understand and to measure their function at the nanoscale.

Previous methods for observing the workings of these molecules have used chemical measurements in solution or looked at studying collections of the molecules attached to a surface. But these approaches were not able to provide researchers a detailed picture of how these molecules function in environments that would be relevant to molecular-device operation.

Looking Into the Single-Molecule Machine
The team is led by Paul Weiss from UCLA and Fraser Stoddart from Northwestern University.

Paul Weiss, distinguished professor of chemistry and biochemistry, holds UCLA's Fred Kavli Chair in Nanosystems Sciences and is director of the California NanoSystems Institute (CNSI) at UCLA. Fraser Stoddart is the Board of Trustees Professor of Chemistry and director of the Center for the Chemistry of Integrated Systems (CCIS) at Northwestern University.

The team developed a molecular design that firmly attached rotaxanes to a surface. This approach enabled the team to examine individual rotaxanes in their native environment using a scanning tunneling microscope (STM). As a result, the team was able to record station changes by the rotaxanes' rings along their rods in response to electrochemical signals.

The work was funded by the National Science Foundation, the Semiconductor Research Corporation and the Kavli Foundation.  The team's findings are published in the journal ACS Nano.