DOI: 10.1002/chem.200901423 Self-Assembling of Er 2 O 3 –TiO 2 Mixed Oxide Nanoplatelets by a Template- Free Solvothermal Route Beatriz Juliµn-López, [a] Mónica Martos, [a] Natalia Ulldemolins, [a] JosØ A. Odriozola, [b] Eloisa Cordoncillo, [a] and Purificación Escribano* [a] Introduction Classical areas of application, such as catalysts, passive elec- tronic components, or ceramic materials, are increasing in technical importance with the use of nanoscale oxide parti- cles with a high specific surface area and mean particle di- ameter between 30 and 300 nm. [1] Hence, one of the most important research areas of the last few decades has been the control of size distribution and shape in the synthesis of particles. Indeed, at the nanometer scale, many materials are known to display very different characteristics and reac- tivity from those of their bulk counterparts, because the final properties depend not only on the composition but also on the surface properties. [2–4] Furthermore, the combina- tion of attractive properties with a precise porosity is the re- quirement for new solid materials. Recently, porous materi- als with defined pore structure and size distribution have been widely applied in many industrial fields, such as sepa- ration, [5] adsorption, [6] catalysis, [7] and so on. In the last few years, a great number of reports have been published related to the synthesis of mesoporous metal oxides. The interest in this kind of material arises from the possibility of combining the intrinsic properties of the un- structured metal oxides with the additional features of a pe- riodic mesoporous solid. It is known that most of the poten- tial applications of the resulting materials (photocatalysis, solar cells, photochromism, sensing, and other applications in nanotechnology) are largely dependent on porosity, total surface area, structural uniformity, and particle size. [8] Mesoporous materials are usually synthesized with the help of a surfactant as soft template or mesoporous oxides (usually silica) as hard templates. [9] In fact, some authors have reported the synthesis of porous metal oxides without using any template, and obtained relatively low surface area and scattered pore size distribution. [10] Previous reports [11, 12] Abstract: An easy solvothermal route has been developed to synthesize the first mesoporous Er 2 O 3 –TiO 2 mixed oxide spherical particles composed of crystalline nanoplatelets, with high sur- face area and narrow pore size distri- bution. This synthetic strategy allows the preparation of materials at low temperature with interesting textural properties without the use of surfac- tants, as well as the control of particle size and shape. TEM and Raman anal- ysis confirm the formation of nanocrys- talline Er 2 O 3 –TiO 2 mixed oxide. Meso- scopic ordered porosity is reached through the thermal decomposition of organic moieties during the synthetic process, thus leading to a template-free methodology that can be extended to other nanostructured materials. High specific surface areas (up to 313 m 2 g À1 ) and narrow pore size distributions are achieved in comparison to the micro- metric material synthesized by the tra- ditional sol–gel route. This study opens new perspectives in the development, by solvothermal methodologies, of mul- tifunctional materials for advanced ap- plications by improving the classical pyrochlore properties (magnetization, heat capacity, catalysis, conductivity, etc.). In particular, since catalytic reac- tions take place on the surface of cata- lysts, the high surface area of these ma- terials makes them promising candi- dates for catalysts. Furthermore, their spherical morphology makes them ap- propriate for advanced technologies in, for instance, ceramic inkjet printers. Keywords: mesoporous materials · nanostructures · rare earths · solvo- thermal synthesis · titanates [a] Dr. B. Juliµn-López, Dr. M. Martos, N. Ulldemolins, Dr. E. Cordoncillo, Prof. P. Escribano Department of Inorganic and Organic Chemistry University Jaume I Avda. Sos Baynat, s/n, 12071 Castellon (Spain) Fax: (+ 34) 964728214 E-mail: escriban@qio.uji.es [b] Prof. J. A. Odriozola Department of Inorganic Chemistry, Institute of Materials Science University of Sevilla-CSIC Americo Vespucio 49, 41092 Isla de la Cartuja, Sevilla (Spain)  2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Chem. Eur. J. 2009, 15, 12426 – 12434 12426