Scientists weigh elusive gold atom with nanoscale

July 30th, 2008 - 6:15 pm ICT by IANS  

Washington, July 30 (IANS) Weighing a single golden atom is now possible, thanks to a nanoscale devised by Berkeley Lab and California University researchers. Alex Zettl, a physicist with Berkeley Lab, who led the team, said “for the past 15 years… the holy grail of nanoelectromechanical system (NEMS) has been to push them to a small enough size with high enough sensitivity so that they might resolve the mass of a single molecule or even single atom.”

“This has been a challenge even at cryogenic temperatures where reduced thermal noise improves the sensitivity. We have achieved sub-single-atom resolution at room temperature!”

There are about three million million million million gold atoms in a single kilogram. While there have been other NEMS that function as mass sensors before, most of these previous devices were fashioned from silicon, and none had achieved the magical single-atom resolution at room temperature.

The new NEMS mass sensor comprises a single carbon nanotube that is double-walled to provide uniform electrical properties and increased rigidity.

“Getting nanotubes to vibrate is fairly easy,” said Zettl’s colleague Kenneth Jensen. “The difficult part is detecting those small vibrations. We accomplished this by field-emitting, or spraying, electrons from the tip of the nanotube and detecting the resulting electrical current.”

Using their NEMS mass sensor, Zettl, his colleagues Jensen and Kim were able to weigh individual gold atoms and measure masses as small as two-fifths that of a gold atom at room temperature and in just a second.

The carbon nanotube mass sensor of Zettl’s group is a thousand times smaller by volume than typical NEMS resonators - measuring only about a billionth of a metre in diameter and 200 billionths of a metre in length.

These findings have been published in Nature Nanotechnology.

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