Multi-techniques investigation of mesoporous zinc and tungsten titanates materials Karine Assaker a , Cédric Carteret b , Marie-José Stébé a , Jean-Luc Blin a,⇑ a Université de Lorraine/CNRS, SRSMC, UMR7565, F-54506 Vandoeuvre-lès-Nancy cedex, France b Université de Lorraine/CNRS, LCPME, UMR7564, F-54600 Villers-lès-Nancy, France article info Article history: Received 4 February 2014 Received in revised form 14 March 2014 Accepted 30 March 2014 Available online 13 April 2014 Keywords: Mesoporous titania Sol–gel Soft templating Tungsten Zinc abstract We have investigated the preparation of zinc and tungsten mesoporous titanates materials from a sol–gel method using a block copolymer as amphiphile. The mesoporous network is created through a soft tem- plating method. Samples have been characterized by SAXS, XRD, nitrogen adsorption–desorption, XPS, TEM, EDX, Raman and UV–Vis spectroscopies. The presence of tungsten induces the formation of ortho- rhombic crystal phase WO 3 besides the titania network and inhibits the formation of anatase, which is the predominant structure in the Zn–TiO 2 materials. No trace of ZnO is detected by XRD and Raman. However XPS suggests the presence of zinc ions in the mesoporous network and their linkage with oxy- gen atoms. The zinc oxide could therefore either be randomly dispersed or amorphous on the material surface. XPS and EDX also reveal that the tungsten clusters are located at the surface of the tungsten mes- oporous titanates. Studies of the Kubelka–Munk function showed that at low Zn content, the band gap energy is in the range of the anatase one and the photocatalytic efficiency of the corresponding zinc titanates is similar to the one of the pure titania mesoporous material. Beyond the addition of 1 mol.% of tungsten, the titanates present a band gap energy in the range 2.7–2.8 eV, close to the value of the orthorhombic WO 3 . For both kinds of titanates, the decrease of the band gap reduces their capacity for the photodegradation of methyl orange. Ó 2014 Elsevier Inc. All rights reserved. 1. Introduction Since the discovery of MCM-41 in 1992 by Mobil scientists [1,2], numerous studies concerning the preparation conditions, synthesis mechanism, characterization and use of silica mesoporous materi- als have been reported [3–7]. However the pure silica mesoporous materials have only the silanol groups as active sites and it limits their field of applications. For example they can be used as matrix for the immobilization of enzyme [8,9]. One way to increase the number of active site consists in incorporating metal atoms within their framework [10]. The properties of the recovered materials will depend on the type of element introduced in the silica net- work and on its concentration. The metal oxides, which induce basic, acidic or redox catalysis properties, can either be added to the synthesis mixture in the form of a metal alkoxide in order to copolymerize with the silicon alkoxide or be grafted or exchanged after the precipitation of the pure silica. For example silica SBA-15 containing aluminum can be used for the Friedel–Crafts alkylation of 2,4-ditert-butyl-phenol with cinnamyl alcohol [11]. Another way to extend the application field of mesoporous materials deals with the preparation of non silica mesostructures [12–15]. Among the different oxides, titania is of particular interest [16–20]. As a matter of fact, titanium dioxide represents a good photocatalyst for wastewater treatment, air purification, and self-cleaning surfaces. The principles of the photocatalytic properties of TiO 2 are well known [21,22], when the energy of photons of incident light is larger than the ‘‘band gap’’ of the TiO 2 particles, electrons and holes are generated in the conduction and valence bands respectively and migrate to the TiO 2 surface. The implied processes require the formation of radicals OH, O 2 À ,H 2 O 2 , or O 2 , which play an important role in the photodecomposition of organic compounds [21]. The photocatalytic efficiency is favored by an increase of the surface area and from this point of view mesoporous TiO 2 are excellent candidates for this application [23,24]. Two mechanisms can lead to the formation of these ordered TiO 2 mesostructures [25–27]. The first one is the soft templating pathway which implies the co-assembly of the titania precursor and surfactant, similar to the preparation of ordered mesoporous silica. However, using the templated synthesis TiO 2 with amorphous walls are usually recov- ered. The crystalline structure is obtained after heating the mate- rial at higher temperature, but this process is often responsible http://dx.doi.org/10.1016/j.micromeso.2014.03.044 1387-1811/Ó 2014 Elsevier Inc. All rights reserved. ⇑ Corresponding author. Tel.: +33 3 83 68 43 70; fax: +33 3 83 68 43 44. E-mail address: Jean-Luc.Blin@univ-lorraine.fr (J.-L. Blin). Microporous and Mesoporous Materials 194 (2014) 208–218 Contents lists available at ScienceDirect Microporous and Mesoporous Materials journal homepage: www.elsevier.com/locate/micromeso