Photoluminescent multilayer film based on polyoxometalate and tris(2,2-bipyridine)ruthenium

A photoluminescent multilayer film based on Keggin-type polyoxometalate PMo12O40 3 (PMo12) and transition metal complex tris(2,2-bipyridine) ruthenium [Ru(bpy)3] 2+ (Ru(bpy)) was prepared by using layer-by-layer assembly(LBL). The formation of multilayer film was monitored by ultraviolet absorption spectra. The absorption intensity of characteristic peaks increase with a four-layer cycle, indicating that the LBL assembly film grow linearly and reproducibly from layer to layer. The composition of the film was measured by X-ray photoelectron spectrum (XPS). The data of XPS confirmed the presence of the expected elements. The film exhibited photoluminescence arising from p t2g ligand-to-metal transition of Ru(bpy) and redox activity attributing to molybdenum-centered redox processes of PMo12. The surface morphology of multilayer film was characterized by atomic force microscopy (AFM). The result shows that the film had a smooth surface with root-mean-square (rms) roughness ca. 1.363 nm for {PEI/(PSS/PEI/PMo12/Ru(bpy))3}. The grains are homogeneously dispersed in the substrate and have a rather narrow diameter size distribution. r 2004 Published by Elsevier Inc.