40-W Light Alters Nanoparticles

Nanoparticles are finding applications in biological and chemical sensing, but it has been difficult to produce particles of different and nonspherical shapes. A team at Northwestern University in Evanston, Ill., however, has reported a light-induced process that turns silver nanospheres into triangular prisms.

The researchers, who reported the work in the Nov. 30 issue of Science, have discovered that irradiating a sample of 8-nm-diameter spheres with a 40-W fluorescent light turns them into prisms measuring 100 nm on a side and 15 nm thick. Moreover, the reaction causes the particles --which scatter in the blue as spheres -- to scatter in the red, enabling the development of colored probes based on shape as well as on composition and size.