Multilayer films consisted of azulene-based dye molecules and polyelectrolyte: Preparation, characterization and photoluminescent property

Ultrathin multilayer films of two azulene-based (Az-based) dye molecules (Az), 3-methylazulene-1-carboxylic acid hydrazide (Az-1) and 5-(4-phenylamine)-2-(3-methylazulene-1-yl)-1,3,4-oxadiazoles (Az-2), and poly(sodium 4-styrenesulfonate) (PSS) have been prepared by layer-by-layer self-assembly and characterized by UV-vis spectroscopy, fluorescence spectroscopy, small-angle X-ray reflectivity measurements and atomic force microscopy (AFM) imaging. UV-vis spectra show that the characteristic absorbance values of the multilayer films increase almost linearly with the number of PSS/Az bilayers, suggesting that the deposition process is regular and highly reproducible from layer to layer. Average thicknesses for the PSS/Az-1 and PSS/Az-2 bilayers of the multilayer films are ca. 0.9 and 1.4 nm, respectively. AFM images provide the surface morphology of the PSS/Az films, indicating that the film surface is relatively uniform and smooth. The occurrence of photoluminescent activity conforms the potential for creating luminescent multilayer films with Az-based dye molecules.