Mechanically attrited silicon for high refractive index nanocomposites

High-energy milling provides an effective and environmentally conscious method for nanosizing silicon. Colloidal suspensions of nanosized silicon are presently demonstrated and utilized for the fabrication of high refractive index nanocomposites. Si nanoparticles with average sizes of 20-40 nm and size distributions of about 25% have been separated from milled powder via sonication and centrifugation. These nanoparticles were analyzed using transmission electron microscopy, dynamic light scattering, X-ray diffraction and UV-vis/FTIR spectroscopy. Formation of stable colloids is in part attributed to a thin surface-oxide layer. The decrease in the average particle size causes a blue shift in their absorption spectrum, thus increasing transparency in the red part of the visible region. These Si nanoparticles were used to fabricate high refractive index nanocomposites, with refractive indexes up to 3.2, when dispersed in gelatin.