Microstructure, luminescence, and stability of a europium complex covalently bonded to an attapulgite clay

Attapulgite clay, natural silicate nanorods, can form nanocomposites with extreme chemical stability and remarkable exposure durability. Combining luminescent lanthanide complexes with attapulgite to improve their stability and even luminescent properties is fascinating, promising but challenging in the lanthanide composite field. A europium complex Eu(tta)(3)(H(2)O)(2) (Htta = 2-thenoyltrifluoroacetone) was covalently coupled on attapulgite (and MCM-41 or ZSM-5 for comparison) via ligand exchange reaction, generating the first example of attapulgite-based ternary europium complexes. The composites were characterized by (29)Si magic-angle spinning (MAS) NMR, CHN elemental analysis, inductively coupled plasma-atomic emission spectroscopy (ICP) for Eu(3+) contents, X-ray diffraction (XRD), and UV-vis absorption spectra. The results indicate that Eu(3+) complexes bond covalently to the outer surfaces of attapulgite, permeate the channels, and are stuck with the complexes bonded to the inner walls of the pores in MCM-41, or invade into the channels of ZSM-5 after decomposition. These structures were further evidenced by luminescence efficiency and coordinated waters of the complexes linked to matrixes. The composites display more efficient emission, enhanced thermal stability, and improved exposure durability in comparison with the isolated complexes, due to interactions of the complexes with the matrixes. The most efficient emission of attapulgite-based complexes among the composites results from the uniformly structured ternary europium complexes.