Stable Mesostructured Silicate Films Containing Nanosized Zeolite

Evaporation-induced self-assembly via spin coating was employed for the formation of microporous/mesoporous composite films from preformed pure-silica MFI/ethanol and silica/CTABr/ethanol solutions. The thickness of MFI/mesoporous films is in the range of 100−400 nm depending on the different ratios between solutions containing microstructured nanoparticles and the preformed silica/surfactant assemblies forming the final coating suspensions. The structural evolution and crystal orientation of the polycrystalline films were investigated with grazing incidence diffraction (GID) at different penetration depths using synchrotron radiation. Highly ordered mesoporous films showing hexagonal arrangement of the pores and containing MFI nanocrystallites were obtained. Most of the MFI crystals are oriented with their a -axes (sinusoidal channels) perpendicular to the substrates and this orientation is preserved along the film thickness. The porous MFI/mesostructured film, as a function of the penetration depth (ranging from about 7.2 to 250 nm) shows less orientation of the mesostructure in the surface layer.