Nanohorse Hampered By Its Gait | September 17, 2010 Issue - Vol. 88 Issue 38 | Chemical & Engineering News
Volume 88 Issue 38 | p. 24 | Concentrates
Issue Date: September 17, 2010

Nanohorse Hampered By Its Gait

A "bipedal" molecule does a better job than a "four-legged" molecule moving across a surface
Department: Science & Technology
News Channels: JACS In C&EN
Keywords: tunneling, molecular walker
In this video, the authors envision a four-legged molecule "trotting" across a surface, moving diagonal leg pairs in unison like a real horse, which would permit the molecule to move unimpeded across a copper surface. * Animated gif will open in a new window.
Credit: Courtesy of Ludwig Bartels
8836horse_trot
 
In this video, the authors envision a four-legged molecule "trotting" across a surface, moving diagonal leg pairs in unison like a real horse, which would permit the molecule to move unimpeded across a copper surface. * Animated gif will open in a new window.
Credit: Courtesy of Ludwig Bartels
This video shows a four-legged molecule actual gait: it "paces" across a surface, moving two legs on one side at the same time, hindering the molecule's movement.
Credit: Courtesy of Ludwig Bartels
8836horse_pace
 
This video shows a four-legged molecule actual gait: it "paces" across a surface, moving two legs on one side at the same time, hindering the molecule's movement.
Credit: Courtesy of Ludwig Bartels

Although a four-legged molecular horse would seem to be suited for carrying a lot of nanocargo, researchers have found that a “bipedal” molecule does a better job moving across a surface (J. Am. Chem. Soc., DOI: 10.1021/ja1027343). Ludwig Bartels and colleagues at the University of California, Riverside, have extended their work on two-legged molecular walkers to include pentacenetetrone and dimethylpentacenetetrone—molecules that have four carbonyl oxygen “legs.” The researchers show that these molecules move across a copper surface in a “pacing” style, with two legs on one side moving in unison. This gait is different from the “trotting” style of a macroscopic horse, in which diagonal leg pairs move at the same time. The team compared the speeds with which two-legged and four-legged molecules could diffuse, or “walk,” across a surface. Whereas the legs of bipedal molecules can quantum mechanically tunnel through rough areas on a surface quickly, the four-legged molecules, with their pacing gait, have to coordinate the simultaneous tunneling of two legs—an unlikely scenario, Bartels says—and thus move more slowly.

 
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