Tuning Mesoporous Silica Films Accessibility Through Controlled Dissolution in NH 4 F: Investigation of Structural Change by Ellipsometry Porosimetry and X-ray Reflectivity

Jérôme Loizillon (1) , Magali Putero (1) , David Grosso (1)

1 IM2NP - Institut des Matériaux, de Microélectronique et des Nanosciences de Provence

In this work, we present a method to accurately increase the porosity of mesoporous silica films using a postsynthesis controlled partial dissolution in dilute NH4F aqueous solutions. This investigation was performed on around 100 nm thick films prepared by sol–gel chemistry and evaporation-induced self-assembly with various classical micellar templating agents. The evolution of the pore size, the pore interconnection size, the pore organization, and the film thickness were followed by ellipsometry porosimetry and X-ray reflectivity along the dissolution process. We show that the dissolution always proceeds in two well-distinct steps. First, the dissolution provokes the increase of the pore volume, with increasing pore and interconnection sizes, without modification of the structure and the thickness. Then, the collapse of the porous network leads to the reduction of the porosity and the thickness, confirming that a critical maximal porosity can be obtained with each of these systems. The dissolution kinetics, studied in different conditions of chemical attack, revealed that the dissolution follows a linear tendency in each case, facilitating the control over the porosity tuning. Finally, a mechanism for a sol–gel-based mesoporous silica dissolution mechanism is proposed. Overall, a convenient method to increase the pore size without damaging the pore structure is proposed

Domaines: Matériaux

Jérôme Loizillon, Magali Putero, David Grosso. Tuning Mesoporous Silica Films Accessibility Through Controlled Dissolution in NH 4 F: Investigation of Structural Change by Ellipsometry Porosimetry and X-ray Reflectivity. Journal of Physical Chemistry C, 2019, 123 (50), pp.30398-30406. ⟨10.1021/acs.jpcc.9b09109⟩. ⟨hal-02903109⟩