Organized Silica Films Generated by Evaporation-Induced Self-Assembly as Hosts for Iron Oxide Nanoparticles

In this work, we prepared oriented mesoporous thin films of silica on various solid substrates using the pluronic block copolymer P123 as a template. We attempted to insert guest iron oxide (FexOy) nanoparticles into these films by two different methods: (a) by co-precipitation-where iron precursors are introduced in the synthesis sol before deposition of the silica film-and subsequent oxide production during the film calcination step; (b) by preparing and calcining the silica films first then impregnating them with the iron precursor, obtaining the iron oxide nanoparticles by a second calcination step. We have examined the structural effects of the guest nanoparticles on the silica film structures using grazing incidence X-ray scattering (GISAXS), high-resolution transmission electron spectroscopy (HRTEM), spectroscopic ellipsometry, X-ray photoelectron spectroscopy (XPS), and Raman microscopy. Formation of nanoparticles by co-precipitation may induce substantial changes in the film structure leading, in our adopted process, to the appearance of lamellar ordering in the calcination stage. On the contrary, impregnation-based approaches perturb the film structures much more weakly, but are also less efficient in filling the pores with nanoparticles.