Nanotechnology Now - News Story: Taking It One Particle at a Time: Two new characterization platforms reveal that there’s more than one way to size up a nanoparticle.

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September 23rd, 2010

Taking It One Particle at a Time: Two new characterization platforms reveal that there’s more than one way to size up a nanoparticle.

Abstract:
Once upon a time, when particles were measured in micrometers and an optical microscope could do the heavy lifting, the size and distribution of particles in a solution were discovered through the strength of a researcher's eyesight.

To see the truly small particles, however, we needed to invent less direct solutions. After the invention of the laser, researchers determined that Rayleigh scattering could accomplish this task. As long as a particle is relatively small when compared to a given wavelength of light, it will scatter light in all directions. If it's highly-collimated light—a laser—it can be measured accurately, and the particle characteristics can be determined by watching how the intensity of reflect light changes over time. It's guaranteed to change, too, because all such small molecules are constantly moving about in Brownian motion.

This method, dynamic light scattering (DLS), has become the gold standard for characterization of very small particles since its invention not long after the laser. It is not, of course, the only way to analyze particles. Attenuators, sieves, filters, and centrifuges are all employed for larger particle sizes. But for analyzing samples containing broad distributions of species of widely differing molecular masses (such as proteins and aggregates), DLS is reliably the cost-effective choice.

Source:
rdmag.com

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