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Chiral microporous rare-earth silico-germanates: Synthesis, structure and photoluminescence properties

2012; Elsevier BV; Volume: 166; Linguagem: Inglês

10.1016/j.micromeso.2012.04.032

1873-3093

Duarte Ananias, Filipe A. Almeida Paz, Luís D. Carlos, João Rocha,

Advanced NMR Techniques and Applications

Abstract The first examples of chiral microporous rare-earth silico-germanates were obtained by isomorphous substitution of Si 4+ by Ge 4+ in small-pore Na 3 [RESi 3 O 9 ]·3H 2 O (RE = Y 3+ , Eu 3+ ), using hydrothermal synthesis. Single-crystal X-ray diffraction and 29 Si solid-state NMR clearly demonstrate the framework insertion of Ge 4+ , with preference for two of the three crystallographic T 4+ sites. The isomorphous Ge 4+ for Si 4+ substitution originates a dispersion of the RE 3+ environments, resulting in multiple and broader Eu 3+ emission lines. Despite these, the main photoluminescence properties of pure Si- and Ge,Si-materials are very similar. A particularly intriguing feature is the detection, in both cases, of quasi-enantiomeric domains by selective excitation at 12 K.