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Physicochemical Aspects of Novel Surfactantless, Self-Templated Mesoporous SnO 2 Thin Films

2006; American Chemical Society; Volume: 110; Issue: 24 Linguagem: Inglês

10.1021/jp057141d

1520-6106

Celso Velásquez, Fernando Rojas, J.M. Esparza, A. Ortíz, Antonio Campero,

Mesoporous Materials and Catalysis

A novel method of synthesis consisting of the production of ordered arrangements of tubular pores distributed inside SnO2 annealed thin films, which are prepared from a rotating disk process carried out at 2000−3500 rpm, is herein described. The main novelty is that no surfactant molecules are required in order to create these ordered pore structures; the templating entities are supramolecular assemblies of oligomeric chains formed during the extra-long aging allowed to the sol−gel processing of tin(IV) tetra-tert-amiloxide, Sn(OAmt)4, chelated with acetylacetone molecules. Low angle X-ray diffraction peaks of SnO2 thin films calcined at 500 °C clearly certify the existence of ordered mesostructures when employing the right H2O/Sn(OAmt)4 molar ratio during the SnO2 sol−gel synthesis. The final SnO2 ordered mesostructures are reminiscent of those linked to MCM-41 and SBA-15 substrates. Pore-size distribution analyses proceeding from N2 sorption isotherms at 76 K on the SnO2 thin films calcined at 500 °C unequivocally confirm the presence of tubular mesopores (mode pore sizes ranging from 5 to 7 nm). The thicknesses of the SnO2 films range from 80 to 150 nm after performing a drying process at 100 °C and from 70 to 125 nm after calcining in air at 500 °C; these film thicknesses show, in general, decreasing trends when either the spinning rate or the H2O/(Sn(OAmt)4 ratio is increased.