Luminescent europium complexes encapsulated in cage-like cubic ordered mesoporous silica

FDU-1 is a highly ordered, large-pore silica with a cage-like mesoporous cubic structure. FDU-1 was synthesized from tetraethyl orthosilicate (TEOS) in the presence of poly(ethylene oxide)–poly(butylene oxide)–poly(ethylene oxide) triblock copolymer (PEO–PBO–PEO) template in strongly acid media, using a microwave oven as heating source. Rare earth complexes were encapsulated in ordered mesoporous silica in order to improve their thermal stability, necessary for applications. Eu(dbm)3 · TPPO (dbm = dibenzoylmethane and TPPO = triphenylphosphine oxide) and Eu(pic)3 · 2Leu · 5H2O (pic = picrate and Leu = l-leucine) were encapsulated into FDU-1 silica and modified FDU-1 silica by 3-aminopropyltriethoxysilane (APTES). Thermogravimetry/derivative thermogravimetry (TG/DTG) showed that the decomposition temperature increased after encapsulation of the complex. Small angle X-ray diffraction (SAXRD) results showed that the mesoporous silica remains ordered after the encapsulation of the europium complexes. Rutherford back-scattering spectrometry (RBS) revealed a much higher Eu encapsulation for the dibenzoylmethane complex compared to picrate and, with a weight percent similar to the nominal concentration of Eu set at the synthesis process. All infrared spectra are similar and present the profile of amorphous silica. The complexes in FDU-1 silica still present luminescence.