Ultrafine Particles

Abstract

Scientists have been dealing with particles with diameters in the range 1–100 nm, albeit in dispersed systems, since the founding of colloid chemistry in the 1860s. However, it is only in the last 25 years that we have been able to study individual particles of this size. The result has been the discovery that these “ultrafine” particles have properties not displayed by larger or smaller collections of atoms or molecules, properties that suggest many scientific and technological applications. Particles smaller than a tenth of a micron have properties different from those of larger particles of the same materials and are finding use as catalysts, filters, light absorbers, medical tools, magnetic media and new materials.