CDS-MN NANOCRYSTALS IN TRANSPARENT XEROGEL MATRICES - SYNTHESIS AND LUMINESCENCE PROPERTIES

Mn2+-doped CdS nanocrystals (1-2 nm in size) dispersed in organic-inor ganic silica xerogels are prepared by combining a controlled precipita tion of nanocrystals in inverted micelles, a separation as a pure capp ed cluster powder, and a dispersion in hydrolyzed silicon alkoxide. ES R study identified two Mn2+ sites, one bulklike, and another one which is attributed to ions located near the surface and which represents t he main contribution. The average number of Mn2+ per particle is in th e 0.2-0.8 range. The luminescence is characteristic of a Mn2+ internal transition, with energy and lifetime as in bulk materials. This brigh t emission (quantum yield of 7%) corresponds to an energy transfer fro m surface trapped carriers to Mn2+ ions.