Simultaneous in situ and Time-Resolved Study of Hierarchical Porous Films Templated by Salt Nanocrystals and Self-Assembled Micelles

摘要

Time-resolved simultaneous experiments using synchrotron radiation have been realized to study in situ the concurrent formation of different templates in hierarchical porous thin films. Silica hybrid organic—inorganic films have been dip-coated and processed to obtain two porous nanos-tructures: spherical ordered mesopores templated by surfactant micelle, and cubic pores formed by crystallization of sodium chloride salts. The experimental setup has allowed following in real time the chemical—physical processes behind the forma- tion of the two different templating agents. During deposition, the self-assembly and organization of the micelles have been studied by grazing incidence small-angle X-ray scattering while the crystallization of the salt template has been monitored by wide-angle X-ray scattering. After processing, the films have been further characterized by transmission electron microscopy, two-dimensional grazing incidence small-angle X-ray scattering and X-ray diffraction. The in situ analysis has revealed a short time delay between micelles and salt crystals formation; the micelles self-assemble and organize at the end of the first evaporation stage, when ethanol evaporates, while salt starts nucleating and growth only during the second stage, when water evaporation begins.