Mesoporous oxides: what can we do with them?

EUGENIO OTAL; PAULA C. ANGELOMÉ; VALERIA DELLA SAVIA; M. CLAUDIA MARCHI; SARA A. BILMES; GALO J. A. A. SOLER-ILLIA

Buenos Aires

Otro; 7th J. J. Giambiagi Winter School; 2005

Since the development of the first mesoporous silica (Beck et al, 1992) a great variety of silica and transition metal mesoporous oxides have been synthesised by following different chemical routes. These oxides can be obtained as xerogels, powders, films or fibers with high surface areas (200-1000 m2/g), a variety of mesostructures (2D- or 3D- hexagonal, cubic, local order), pore diameters (3-12 nm) and amorphous or nanocrystalline walls. This versatility makes this kind of materials interesting for a lot of possible applications such as optical, electronics, catalysis, sensing, separation, etc. One step beyond, is to modify the oxide matrix with organic functions, in order to obtain a hybrid mesoporous composite, which combines the advantages and properties of mesoporous oxides and hybrid materials. The regular pore size and surface control also makes the pore systems ideal candidates for nanoparticle (NP) template, leading to NP@oxide composites, which can be tailored to combine the properties of two kinds of nanometric size elements, which are in intimate contact through an extended interface, all combined in a robust matrix. These two procedures leads to materials with different properties and potential applications than the pure mesoporous oxides. In this work, we present examples of multifunctional mesoporous films, created by adding organic functions to MP silica or transition metal oxides (TiO2, ZrO2 and Si/Ti, Si/Zr mixed oxides) either by co-condensation (“one pot”) or post synthesis grafting. We also present two alternative ways in order to obtain NP@oxide nanocomposites. CdS@SiO2 and CdS@TiO2 were obtained by chemical precipitation, and Au@TiO2 or Ag@TiO2 by photochemical or electrochemical reduction of the cations. All materials were supported as films, and were fully characterized by (HR)TEM, SEM, EDS, SAXS, XRD, FTIR, UV-Vis absorption, fluorescence and electrochemical methods.