US Patent 7625500 Security feature

A security feature having unique photoluminescent properties and a method for making the security feature. The security feature includes a silica carrier and a rare earth dopant dispersed throughout at least a portion of the silica carrier. The rare earth dopant includes a rare earth ion to which ligands and/or inorganic sensitizers are associated. The ligands and/or inorganic sensitizers are positioned to absorb energy and transfer the absorbed energy to the rare earth ion.