Measuring nanoparticles

When manufacturers claim to produce nanoparticles that are 30 nm in diameter, they are giving customers the average size of the nanoparticles being delivered. (From Nanowerk Spotlight’s Meaningful nanotechnology EHS research requires independent nanomaterial characterization)

“For example, it might be stated that a certain nanoparticle is being sold as 30 nm in diameter and, although ’30 nm’ might be close to the average diameter, there is usually a range of particle sizes that can extend from as much as small as 5 nm to as large as 300 nm.” (Vicki H. Grassian, a professor in the Department of Chemistry at the University of Iowa)

As I noted in my April 27, 2010 posting this size range could pose problems with Canada’s proposed plan/inventory/scheme. Happily, the US National Institute of Standards and Technology (NIST) has successfully measured and sorted nanoparticles with a device that operates like a coin sorter (separating pennies, dimes, nickels, and quarters). From the news item on physorg.com,

First introduced in March 2009 …, the device consists of a chamber with a cascading “staircase” of 30 nanofluidic channels ranging in depth from about 80 nanometers at the top to about 620 nanometers (slightly smaller than an average bacterium) at the bottom. Each of the many “steps” of the staircase provides another “tool” of a different size to manipulate nanoparticles in a method that is similar to how a coin sorter separates nickels, dimes and quarters.

In a new article in the journal Lab on a Chip, the NIST research team demonstrates that the device can successfully perform the first of a planned suite of nanoscale tasks—separating and measuring a mixture of spherical nanoparticles of different sizes (ranging from about 80 to 250 nanometers in diameter) dispersed in a solution.

Seems to me that is pretty exciting news. I wonder when this device will go into standard use. The usual answer to this question includes the number 5 as in 3-5 years, 5-7 years, or 5 years. In any case, the researchers are also hoping to use the technique to sort nanoparticles of different shapes as in tubes from spheres and that sort of thing.

For anyone interested in the researcher’s article the citation is,

S.M. Stavis, J. Geist and M. Gaitan. Separation and metrology of nanoparticles by nanofluidic size exclusion. Lab on a Chip, forthcoming, August 2010

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