Humidity-controlled mesostructuration in CTAB-templated silica thin film processing. The existence of a modulable steady state

Abstract

A study is presented of the self-assembly process that takes place during CTAB-templated silica film formation through in situ SAXS, interferometry and water titration investigations during evaporation associated with dip coating under various conditions. This work shows that the quantity of water present in the film when the mesostructuration takes place depends on the relative humidity (RH) during deposition. Indeed, the system contains considerable quantities of water at high RH, while it loses water at low RH. The water content is demonstrated to be a critical parameter, as poorly ordered, 2D-hexagonal or 3D-cubic final structures are obtained, depending on the RH, in agreement with the general physico-chemical laws of CTAB mesophases. Furthermore, changing the RH or the solvent vapour pressure just after evaporation induces a film composition change and a potential mesostructure modification, evidencing a modulable steady state, during which the mesostructure can be modified by external influences. The present study pinpoints the role of processing conditions that are often considered secondary to chemical conditions. The conclusions of this study into the CTAB-TEOS system are also relevant to other surfactant-templated systems which undergo evaporation-controlled self-assembly.

Photocatalytic Activity of TiO2-containing Al-Mesoporous Silica Thin Films

“…1 (9,12). With an increase in the Al content, the peak (1 0 0) broadened due to a decrease in the crystallinity, just as reported by Ogawa et al (9), confirming previous reports on the solid solubilization of Al atoms into "Al-FSM-16" by Kitayama et al (13) and "Al-MCM-41" by Eimer et al (14).…”

Mesoporous Silver Films from Dilute Mixed‐Surfactant Solutions by Using Dip‐Coating

“…Water vapor can swell the surfactant phase, leading to liquid-crystalline phase changes in the initially deposited micelle-containing film. [8] Similarly in this case the dip-coated film in the presence of formaldehyde adsorbs water, and loses mesostructural ordering. The film produced by using photocatalysis however was in a sealed container at the same humidity as when it was initially dipped, so would undergo no further phase changes, and retained an ordered mesoscale structure.…”

Accessibility of cylindrical channels within patterned mesoporous silica films using nanoparticle diffusion

“…6 Many techniques are devoted to the preparation of patterned mesoporous silica films including micromolding in capillaries (MIMIC), [7][8][9][10] direct UV or X-ray lithography, [11][12][13][14][15] micropen lithography (MPL), 16,17 ink-jet printing, 18 dip-pen nanolithography (DPN), [19][20][21] site-selective deposition via the underlying chemical modified substrate 22,23 and conventional photolithography. 24,25 While mesoporous silica films can be patterned at the device scale, several disadvantages of current technologies associated with pattern fabrication still need to be circumvented.…”