Layer-by-layer Multilayer Films Self-assembled from a Rare-earth-containing Poly-oxometalate Na9[Eu(W5O18)2] and Poly（allylamine hydrochloride） and Their Photoluminescent Properties

Ultrathin multilayer films of a rare-earth-containing polyoxo-metalate Na 9[Eu(W 5O 18) 2] (EW) and poly(allylamine hydrochloride) (PAH) have been prepared by layer-by-layer self-assembly from dilute aqueous solutions. The fabrication process of the EW/PAH multilayer films was followed by UV-vis spectroscopy and ellipsometry, which show that the deposition process is linear and highly reproducible from layer to layer. An average EW/PAH bilayer thickness of ca. 2.1 nm was determined by ellipsometry. In addition, the scanning electron microscopy (SEM) image of the EW/PAH film indicates that the film surface is relatively uniform and smooth. The photoluminescent properties of these films were also investigated by fluorescence spectroscopy.