Tris(8-hydroxyquinoline-5-sulfonate)aluminum intercalated Mg-Al layered double hydroxide with blue luminescence by hydrothermal synthesis

Abstract

Blue luminescent hybrid materials (DDS-AQS(x %)/LDH) are successfully prepared by co-intercalating tris(8-hydroxyquinoline-5-sulfonate)aluminum anions (AQS3-) and dodecyl sulfonate (DDS-) with different molar ratios into Mg-Al layered double hydroxides (LDHs) by the hydrothermal and solution co-precipitation methods. A film of the material on a quartz substrate is obtained by the solvent evaporation method. The results show the blue luminescence is remarkably different from the pristine Na3AQS, which has cyan luminescence (ca. 450-470 nm vs. 495 nm). Furthermore, the hydrothermal product of DDS-AQS(66.67%)/LDH exhibits optimal luminous intensity and a significantly enhanced fluorescence lifetime. Nuclear magnetic resonance and Fourier-transform infrared spectroscopy indicate that the cyan-blue luminescence transition is due to the isomerization of meridianal to facial AQS via ligand flip caused by a host-guest electrostatic interaction, in combination with the dispersion and pre-intercalation effect of DDS. The hydrothermal conditions can promote a more ordered alignment of the intercalated fac-AQS compared with alignment in the solution state, and the rigid LDHs environment can confine the internal mobility of AQS to keep the facial configuration stable. This stability allows a facile preparation of large amounts of blue luminous powder/film, which is a new type of inorganic-organic hybrid photofunctional material. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.