Ordered Blue Luminescent Ultrathin Films by the Effective Coassembly of Tris(8-hydroxyquinolate-5-sulfonate)aluminum and Polyanions with Layered Double Hydroxides

This article reports a novel method to assemble a small anion with exfoliated Mg-Al-layered double hydroxide (LDH) nanosheets into ordered ultrathin films (UTFs) by employing the layer-by-layer assembly technique. The premixing solution of tris(8-hydroxyquinolate-5-sulfonate)aluminum(11) (AQS(3-)) with three kinds of polyanions-poly(acrylic acid), ((C3H4O2)(n), PAA), poly(styrene 4-sulfonate) ([CH2CH(C6H4)SO3](m), PSS), and poly[5-methoxy-2-(3-sulfopropoxy)-1,4-phenylene vinylene] (C12H13O5S)(n), PPV)-has been used as building blocks to assemble alternatively with LDH nanosheets. The UV-vis absorption and fluorescence spectroscopy of (AQS-polyanion/LDH)(n), UTFs presents stepwise growth upon increasing deposited cydes in comparison with the (AQS/LDH)(n) film under the same experimental process. (AQS-PPV/LDH)(n) UTF displays complex fluorescence originating from AQS and PPV. The (AQS/LDH)(n) and (AQS-polyanion/LDH)(n) UTFs exhibit higher blue-polarized photoemission Characternwith a luminescence anisotropy (r) of ca. 0.12-0.20 and a longer fluorescence lifetime than that of the Na(3)AQS film with r = 0.04. X-ray diffraction, scanning electron microscopy, and atomic force microscopy demonstrated that the UTFs were orderly periodically layered structures with a thickness of ca. 3.0 nm per bilayer. Therefore, this work gives a feasible method for immobilizing small anions into the gallery of LDHs.