Persistent luminescence of 'MG''AL IND. 2''O IND. 4':'EU''DY'nanoparticles prepared by the citrate sol-gel method - Maia, Alessandra de Souza; Stefani, Roberval; Kodaira, Cláudia Akemi; Felinto, Maria Claudia França da Cunha; Teotonio, Ercules Epaminondas Sousa; Brito, Hermi Felinto de (Brazilian Meeting on Inorganic Chemistry - BMIC, 2006)