Individual Pd atoms in an inert copper surface are active sites for hydrogen dissociation.
Single-Molecule Surface Chemistry
E. Charles H. Sykes
Tufts University, Chemistry Department
Sykes Group Youtube Video "World's Smallest Electric Motor: Sykes Group Tufts"
"BBC Radio 4's interview with Charlie Sykes on the Today Programme"
The Sykes group utilizes state of the art scanning probes and surface science instrumentation to study technologically important systems. For example, scanning tunneling microscopy enables visualization of geometric and electronic properties of catalytically relevant metal alloy surfaces at the nanoscale. Using temperature programmed reaction studies of well defined model catalyst surfaces structure-property-activity relationships are drawn. Of particular interest is the addition of individual atoms of a reactive metal to a relatively inert host. In this way reactivity can be tuned, and provided the energetic landscapes are understood, novel bifunctional catalytic systems can be designed with unique properties that include low temperature activation and highly selective chemistry. Newly developed curved single crystal surface are also being used to open up previously inaccessible areas of structure sensitive surface chemistry and chiral surface geometries.
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Individual Pd atoms in an inert copper surface are active sites for hydrogen dissociation. |
In a different thrust, the group has developed a thioether molecular rotor system that is enabling us to study many important fundamental aspects of molecular rotation with unprecedented resolution. Molecular motors are ubiquitous in nature; they exhibit functions as varied as organizing the cellular cytoplasm by vesicle transport to powering the motion of cells and even driving whole body locomotion via muscle contraction. In stark contrast, current manmade devices, with the exception of liquid crystals, make no use of nanoscale molecular motion. This is partly due to a gap in the understanding of how individual molecular components behave in the face of opposing forces such as electronic friction, thermal fluctuations and coupling to neighboring molecules.
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STM image of three molecular rotors, 1 nm in size, spinning at over 1,000,000 times per second when heated to a temperature of 78 Kelvin. |
By using low-temperature scanning tunneling microscopy (LT-STM), we are able to record the dynamics of individual molecular rotors at the atomic-scale. At very low temperatures (20 K), the molecules transition between a locked or “frozen” state to one in which they spin at over 1 million times per second. There is a significant opportunity for single-molecule measurements to answer many of the current questions in the field of molecular rotors/motors and have a major impact on efforts to control all types of molecular motion. We have already investigated how these small, simple molecules as molecular rotors and we are beginning to devise methods for turning them into molecular motors.
Molecular Machines video detailing the Rotors Project
Educational Video detailing some of our work and its impact
We thank our sponsors:
U.S. Department of Energy (Grant # DE-FG02-10ER16170
American Chemical Society - Petroleum Research Fund (Grant #45256-G5),
National Science Foundation (Grant #0717978)
Arnold and Mabel Beckman Foundation (Young Investigator Award 2008)
Research Corporation (Cottrell Scholar Award 2008)
The Usen Family (Usen Family Career Development Professor)
The Camille & Henry Dreyfus Foundation, Inc.
Ashleigh Baber, Erin Iski, Heather Tierney and Tim Lawton thank the US Department of Education for GAANN fellowships