MECHANICALLY ATTRITED SILICON FOR HIGH REFRACTIVE-INDEX NANOCOMPOSITES

High-energy milling provides an effective and environmentally consciou s method for nanosizing silicon. Colloidal suspensions of nanosized si licon are presently demonstrated and utilized for the fabrication of h igh refractive index nanocomposites. Si nanoparticles with average siz es of 20-40 nm and size distributions of about 25% have been separated from milled powder via sonication and centrifugation. These nanoparti cles were analyzed using transmission electron microscopy, dynamic lig ht scattering, X-ray diffraction and UV-vis/FTIR spectroscopy. Formati on of stable colloids is in part attributed to a thin surface-oxide la yer. The decrease in the average particle size causes a blue shift in their absorption spectrum, thus increasing transparency in the red par t 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.