Shape is turning out to be a particularly important feature of some commercially important nanoparticles—but in subtle ways. New studies* by scientists at the National Institute for Standards and Technology (NIST) show that changing the shape of cobalt nanoparticles from spherical to cubic can fundamentally change their behavior.
Building on a previous paper** that examined the properties of cobalt formed into spheres just a few nanometers in diameter, the new work explores what happens when the cobalt is synthesized instead as nanocubes. Nanoparticles of cobalt possess large magnetic moments—a measure of magnetic strength—and unique catalytic properties, and have potential applications in information storage, energy and medicine.
The team also showed that the cubes can be altered merely by observing with one of nanotechnology’s microscopes of choice. After a few minutes’ exposure to the illuminating beam of a transmission electron microscope, the nanocubes melt together, forming “nanowires” that are no longer separable as individual nanoparticles. The effect, not observed with the spheres, is surprising because the cubes average 50 nm across, much larger than the spheres’ 10 nm diameters. “You might expect the smaller objects to have a lower melting point,” Hight Walker says. “However, the sharp edges and corners in the nanocubes could be the locations to initiate melting.”
While Walker says that the melting effect could be a potential method for fabricating nanostructures, it also demands further attention. “This newfound effect demonstrates the need to characterize the physico-chemical properties of nanoparticles extremely well in order to pursue their applications in biology and medicine,” she says. ###
* G. Cheng, R.D. Shull and A.R. Hight Walker. Dipolar chains formed by chemically synthesized cobalt nanocubes. Journal of Magnetism and Magnetic Materials, May 11, 2009, Vol. 321, issue 10, pp. 1351—1355.
** G. Cheng, D. Romero, G.T. Fraser and A.R. Hight Walker. Magnetic-field-induced assemblies of cobalt nanoparticles. Langmuir, December 2005. See Oct. 20, 2007, Tech Beat article, “Magnetic Nanoparticles Assembled into Long Chains”.
Contact: Chad Boutin boutin@nist.gov 301-975-4261 National Institute of Standards and Technology (NIST)
1 comment:
Nice article. Thanks for sharing about cobalt nanoparticles.
Buy cobalt nanoparticles anywhere in globe.
Post a Comment