Highly ordered photoluminescent self-assembled films based on polyoxotungstoeuropate complex Na-9[EuW10O36]

A novel highly ordered layered superlattice multibilayer film is prepared by casting the chloroform solutions of ionic complex between a polyoxotungstoeuropate anion EuW10O369- (EuW10) and a hexadecyltrimethylammonium cation (C(16)TA) on hydrophilic substrates. A variety of techniques, including FT-IR and UV-vis spectroscopies, differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) have been used to characterize the structure of the composite film. The lamellae consist of alternating layers of polyoxotungstoeuropate and bimolecular layers of surfactant, with the surfactant alkyl chains tilted 30.8degrees to the lamellar surface and noninterdigititated. The photoluminescent behavior of the film at room temperature has also been investigated by fluorescence spectroscopy to show the characteristic Eu3+ emission pattern of D-5(0) --> F-7(j). The fluorescence spectra and fluorescence lifetime of the composite film are quite different from those found for EuW10 solid powder and EuW10 dilute aqueous solution.