Fabrication of Ag@Si[O.sub.2]@[Y.sub.2][O.sub.3]:Er nanostructures for bioimaging: tuning of the upconversion fluorescence with silver nanoparticles

The nanostructures comprising silver cores and dense layers of [Y.sub.2][O.sub.3]:Er separated by a silica shell are used for studying the interaction between upconversion materials and metals in nanoscale. The architecture has allowed for versatile control of the [Y.sub.2][O.sub.3]:Er-metal interaction through control of the silica dielectric spacer thickness and the metal-core size and the nanoparticles are interesting as fluorescent labels in imaging experiments.