Hydrophobic Versus Hydrophilic Polyelectrolyte Multilayers for Emissive Europium Films

Films containing lanthanide ions, having exceptionally narrow emissive bandwidths, are often used for high-performance photonic materials. The lanthanide ion is commonly coordinated with organic ligands to enhance emission intensity. However, the light output is influenced by the environment, such as the presence of water, surrounding the ligated metal center. In this work, hydrophobic and hydrophilic ultrathin polyelectrolyte films made using the multilayering technique were compared as hosts for Eu-III tris(dipicolinate), [Eu(DPA)(3)](3-), complexes. The concentration of a complex within the film depended on the number of residual excess positive polyelectrolyte repeat units, which in turn was controlled by the method of multilayer assembly. Because the hydrophobic polyelectrolyte multilayer excluded water more efficiently, the [Eu(DPA)(3)](3-) emission intensity and lifetime decreased only slightly on exposure of the emissive film to ambient humidity and maintained a quantum yield of 48%.

Automated summary

The study compared hydrophobic and hydrophilic ultrathin polyelectrolyte films made using the multilayering technique as hosts for Eu-III tris(dipicolinate) complexes. It was found that the hydrophobic polyelectrolyte multilayer excluded water more efficiently, resulting in only slight decreases in emission intensity and lifetime when exposed to ambient humidity, while maintaining a high quantum yield of 48%.