Preparation, structural and optical properties of AWO4 (A = Ca, Ba, Sr) nanofilms

AWO4 (A = Ca, Ba, Sr) nanofilms on a glass substrate are prepared through the combination of the reverse micelle system with the dip-coating technology, in which collodion is used as a dispersant and film-forming agent. The nanofilms are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL) and IR spectra, respectively. The results indicate that the tungstate nanoparticles having a tetragonal scheelite structure are well distributed on the substrate. PL results indicate that a blue-shift emission band peak of the nanofilms appears when they are excited at 240 nm relative to those of the bulk materials, and a red-shift emission band peak of nanofilms appears compared with nanoparticles, which can be attributed to the quantum size effect. IR spectra reveal that a large absorption band, which is ascribed to the W–O stretching vibration in WO4 tetrahedron, is observed around 820 cm−1.