The Vanderbilt chemists Associate Professor David Cliffel, Assistant Professor John McLean, graduate student Kellen Harkness and Lecturer Andrzej Balinski took advantage of the capabilities of a state-of-the-art instrument called an ion mobilitymass spectrometer (IM-MS) that can simultaneously identify thousands of individual particles.
The team coated the surfaces of gold nanoparticles ranging in size from two to four nanometers with two different chemical compounds. Then they broke the nanoparticles down into clusters of four gold atoms and ran these fragments through the IM-MS.
Molecules from the two coatings were still attached to the clusters. So, by analyzing the resulting pattern, the chemists showed that they could distinguish between original nanoparticles where the two surface compounds were completely separated, those where they were randomly mixed and those that had an intermediate degree of separation.
"There is no other way to analyze structure at this scale except X-ray crystallography," said Cliffel, "and X-ray crystallography is extremely difficult and can take months to get a single structure."
"IM-MS isn't quite as precise as X-ray crystallography but it is extremely practical," added McLean, who has helped pioneer the new instrument's development. "It can provide structural information in a few seconds. Two years ago a commercial version became available so people who want to use it no longer have to build one for themselves."
|Contact: David Salisbury|