Novel self-assembled films of zirconium phosphonate/1,4,5,8-naphthalenediimides

The construction and characterization of novel self-assembled thin films of zirconium phosphonate/1,4,5,8-naphthalenediimides is described. The films were grown on silica or quartz substrates by deposition of alternated layers of Zr+4 and N,N′-di(2-phosphonoethyl)-1,4,5,8-naphthalenediimide (DPN). Films containing up to 16 layers were obtained. Film growth, followed by either absorption spectroscopy or ellipsometry, was linear with the number of layers, showing that equal amounts of material were deposited in each cycle. Atomic force microscopy (AFM) images showed, however, that the films were microscopically not homogeneous, but rather constituted of crystallites of DPN. When irradiated, the initially colorless films turned to a persistent pinky color reminiscent of that of DPN anion radical.