Controlling pore size and uniformity of mesoporous titania by early stage low temperature stabilization Sebastiaan Johan Frans Herregods a,b,⇑ , Myrjam Mertens a , Kristof Van Havenbergh c , Gustaaf Van Tendeloo c , Pegie Cool b , Anita Buekenhoudt a , Vera Meynen b a VITO NV, Flemish Institute for Technological Research NV, Boeretang 200, B-2400 Mol, Belgium b Laboratory of Adsorption and Catalysis (LADCA), Department of Chemistry, University of Antwerp, CDE, Universiteitsplein 1, B-2610 Wilrijk, Belgium c EMAT, Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium article info Article history: Received 2 July 2012 Accepted 23 July 2012 Available online 12 October 2012 Keywords: Mesoporous Titania Evaporation induced self-assembly Thermal treatment abstract The control of the formation process during and after self-assembly is of utmost importance to achieve well structured, controlled template-assisted mesoporous titania materials with the desired properties for various applications via the evaporation induced self-assembly method (EISA). The present paper reports on the large influence of the thermal stabilization and successive template removal on the pore structure of a mesostructured TiO 2 material using the diblock copolymer Brij 58 as surfactant. A con- trolled thermal stabilization (temperature and duration) allows one to tailor the final pore size and uni- formity much more precise by influencing the self-assembly of the template. Moreover, also the successive thermal template removal needs to be controlled in order to avoid a structural collapse. N 2 - sorption, TGA, TEM, FT-Raman spectroscopy, and small angle & wide angle XRD have been used to follow the crystal growth and mesostructure organization after thermal stabilization and after thermal template removal, revealing its effect on the final pore structure. Ó 2012 Elsevier Inc. All rights reserved. 1. Introduction Since the discovery of the template-assisted approach by Beck and coworkers [1,2] the research on directed mesostructured materials experienced a major breakthrough. Nowadays, a variety of ionic and neutral templates [3,4] are applied in order to obtain different porous structures. The majority of these structures are silica-based materials [5], although mesoporous titania-based and other metaloxide materials gain growing interest due to their semiconducting properties and high stability (hydrothermal and chemical). Mesoporous titania materials are widely reported for applications in photocatalysis, DSSC, smart coatings, separation, etc. [6,7]. To meet the demands of the various applications, insight and control of the formation process are needed to direct the structural properties of these porous materials (e.g., pore size, pore size dis- tribution, etc.). In the case of titania, an evaporation induced self- assembly method (EISA) [8–10] is often applied to control the high reactivity of the Ti-source. The method is specifically designed to harmonize the hydrolysis and condensation of the inorganic source with the self-assembly of the template in order to avoid the forma- tion of a nonporous solid. Therefore, the reactivity of the inorganic source is tempered by working in an acidic solvent environment with a controlled water content [11,12]. During aging, the solvent evaporates resulting in the formation of a modulable steady state (MSS) where the inorganic network is still flexible, but the chemi- cal composition is constant [10,13]. During the MSS, it is possible to direct the template self-assembly by adjusting, for example, the surrounding atmosphere [6,10,13–15]. In addition, the estab- lished structural organization needs to be maintained during the successive process steps, like thermal stabilization and template removal. Before the thermal stabilization, the inorganic network is only weakly condensed due to the tempered reactivity of the inorganic source. The thermal stabilization of the weakly con- densed inorganic structure is applied in order to form a strongly condensed and stable inorganic network before template removal in order to avoid a structural collapse during the template removal. The effect of the high temperature template removal (calcination) is well-known in literature [16–20]. Also, the evaporation and con- densation during low temperature thermal stabilization have been studied through in situ FTIR [21–23]. However, a detailed study on the effect of the thermal stabilization (temperature and duration) on the final pore structure, specifically of a small pore material, is missing in literature. Although a detailed study on the thermal stabilization during the EISA method has not been reported, differ- ent stabilizations methods that are commonly used in practice to 0021-9797/$ - see front matter Ó 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jcis.2012.07.098 ⇑ Corresponding author at: VITO NV, Flemish Institute for Technological Research NV, Boeretang 200, B-2400 Mol, Belgium. Fax: +32 14 321186. E-mail address: sebastiaan.herregods@vito.be (S.J.F. Herregods). Journal of Colloid and Interface Science 391 (2013) 36–44 Contents lists available at SciVerse ScienceDirect Journal of Colloid and Interface Science www.elsevier.com/locate/jcis