Formation and characterization of a SnO 2 –Al 2 O 3 system derived from a sol–gel process based on different tin precursors Piotr Kirszensztejn a, ⁎, Katarzyna Jurek b , Agnieszka Tolińska a , Adriana Kawałko a a Faculty of Chemistry, A. Mickiewicz University, Grunwaldzka 6, 60-780 Poznań, Poland b Faculty of Chemical Technology and Engineering, University of Technology and Life Science in Bydgoszcz, Seminaryjna 3,85-326 Bydgoszcz, Poland abstract article info Article history: Received 15 July 2010 Received in revised form 27 January 2011 Available online 23 February 2011 Keywords: Modified alumina; Sol–gel; β-diketonate complexes of tin; Texture A series of SnO 2 –Al 2 O 3 samples with SnO 2 to Al 2 O 3 molar ratio of 1:1, 0.5:1, 0.25:1 and 0.1:1, have been synthesized by the sol–gel technique using Al(C 3 H 7 O) 3 and tin (IV) dihydroxy 2,4-pentanedione acetate as precursors. Samples of the above series were characterized by thermal analysis, X-ray diffraction, Fourier transform infrared spectroscopy and nitrogen adsorption to establish their porous structure. The structures of the binary gel systems obtained were found to differ from those of the analogous series in which Sn(ac) 4 (acetic series) was used as precursor. The tin component introduced into the samples of both series was responsible for the narrowing of the range of diameters of the pores (contributing to the highest extent to the cumulative pore volume) relative to their range in pure aluminum gel. The range of the dominant pore diameters was at the same time shifted towards smaller values, but these changes were more pronounced for (ac) series. The use of β-diketonate complexes of tin instead of Sn(ac) 4 , leads also to changes in the character of OH group on the surface of the binary gel samples. For this series (acac) of binary gels in the whole range of concentrations of the tin component only one type of hydroxyl groups appears, not present in the monocomponent aluminum gel and in the binary gels of (ac) series. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The development of novel porous materials has been stimulated by a variety of their potential applications in photo-electronics, batteries and catalysis, which is related to their high surface area and narrow pore size distribution [1–3]. In this group of materials oxide semiconductors have attracted particular attention. However, their poor electric conductivity [4] and a lack of information regarding on how the method of preparation affects their structural properties, have hindered their use in practical applications. Of great interest among such oxide semiconductors is tin dioxide. The study of tin oxide is motivated by its applications as a solid state gas sensor material [5,6], oxidation catalyst [7–9], transparent conductive oxides (TCO) [10] and novel battery systems with three-dimensionally ordered macroporous (3DOM) electrode materials [11]. The key for understanding many aspects of the SnO 2 surface properties is the dual valency of Sn. The dual valency facilitates a reversible transformation of the surface composition depending on the oxygen chemical potential of the system. Reduction of the surface modifies the surface electronic structure by formation of the Sn5s derived surface states that lie deep within the band gap and also causes a lowering of the work function [12]. In most applications tin dioxide is modified by additives to either increase the charge carrier concentration by donor atoms, or to increase the gas sensitivity or the catalytic activity by metal additives. For these and other applications it is necessary to obtain SnO 2 containing materials possessing thermal, chemical and mechanical stability. One of the simplest and economic techniques of obtaining tin dioxide materials is the sol–gel method, however, the selection of precursor for a particular system is not always simple. Effective strategies to match the reactivities of the precursors are required to control homogeneity in the sample prepared, which is manifested in changes in the porous structure and the possibility of generation of strong acidic cites associated with the interface or linkage between the two components. On the other hand, in the selection process one has to consider also the possibility of controlling the impurity level as the content of impurities can result in reduced reproducibility of the material properties [13]. In our previous papers, we have described the effect of the method of preparation of a binary oxide gel system Al 2 O 3 –SnO 2 , on its porosity [14,15]. In these studies, aluminum isopropoxide and tin(IV) acetate were used as precursors in the sol–gel process. Tin (IV) acetate precipitates easily upon controlled addition of water. To avoid this precipitation one can stabilize the acetic precursor by substitution of acetic groups with less hydrolysable ones, for example with β-diketone. The aim of this study was to establish the changes in the final product, i.e. the binary oxide gel, in particular its textural parameters, upon replacement of some acetate groups with β-diketonate ligands in the tin precursor. The presence of β-diketonate ligands in the Journal of Non-Crystalline Solids 357 (2011) 1671–1676 ⁎ Corresponding author. Tel.: +48 61 829 1355; fax: +48 61 829 1505. E-mail address: kirszen@amu.edu.pl (P. Kirszensztejn). 0022-3093/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2011.01.027 Contents lists available at ScienceDirect Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/ locate/ jnoncrysol