Layer-by-Layer Self-Assembled Ultrathin Multilayer Films of Lanthanide Polyoxometalates and Poly(allylamine Hydrochloride) and Their Photoluminescent Properties

摘要

Ultrathin multilayer films of two lanthanide polyoxometalates (LPOMs), K_(17)[Eu(P_2W_(17)O_(61))_2] (EPW) and K_(13)[Eu (SiW_(11)O_(39)_2] (ESW), and layer-by-layer self-assembly from dilute aqueous solution. UV-vis spectroscopy and ellipsometry respectively show that the absorbance values at characteristic wavelengths and the thicknesses of the multilayer films increase linearly with the number of LPOM/PAH bilayers, suggesting that the deposition process is linear and highly reproducible from layer to layer. Average thicknesses of ca. 3.4 and 2.4 nm were determined for the EPW/PAH and ESW/PAH bilayers by ellipsometry, respectively. In addition, scanning electron microscopy (SEM) and atomic force microscopy (AFM) inages provide the surface morphology of the LPOM/PAH films, indicating that the film surface is relatively uniform and smooth. The photoluminescent properties of these films have also been investigated byfluorescence spectroscopy. The LPOM/PAH multilayer film has a good thermal stability as shown by UV-vis, X-ray photoelectron, and fluorescence spectra.