Multiscale porous films as a versatile platform towards complex systems with spatially addressed physical and chemical properties

G. J. A. A. SOLER-ILLIA

Congreso; EUROMAT 2011; 2011

In the last years, there is an increasing interest in combining chemically designed nanobuilding blocks (NBB) into spatially complex functional structures that present properties at different length scales: nanoscopic, mesoscopic and micrometric. The properties of these systems are derived from the properties of the NBB that form them, but also in their synergy. Mesoporous Thin Films (MPTF) are an excellent example of this approach, presenting interesting sensing, catalytic, electrical and optical properties. Processing of MPTF is compatible with protocols used in the electronics and optics industry, opening the opportunity to fabricate novel responsive devices. MPTF, albeit complex systems with highly controlled features, are but the tip of the iceberg. New synthesis and processing protocols add new tools to the traditional strategies used to modify MPTF properties (pore architecture, inorganic skeleton or surface functions), permitting the access to microscale-derived properties. Adding colloidal templates or coupling co-assembly process with phase separation or dewetting processes leads to thin films with multiscale cavities. New stabilization methods permit to produce multilayer stacks. Selective adsorption, complexation, reduction or etching leads to complex architectures with localized chemical properties. These methods can be combined with lithographic patterning, leading to systems with novel electrical conductivity, selective transport or catalytic properties in only a few synthetic steps. In this work, selected examples of optical and chemical behaviour of these multiscale materials will be presented. Organic functional groups impart new sorption or controlled transport properties. Enzyme-containing MTF behave as efficient biocatalysts. Ordered mesopores used as an array of nanoreactors permit the inclusion of nanoparticles with tunable optical response. Multilayer MPTF present a great variety of new properties: localized chemical reaction control, modulable photonic crystal behaviour, or enhanced Raman effects. References: P. C. Angelomé et al Adv. Mater., 2006, 18, 2397. M. C. Fuertes et al. Adv. Funct. Mater, 2007, 17, 1247. A. Zelcer et al. J. Mater. Chem, 2009, 19, 4191. A. Calvo et al. J. Am. Chem. Soc, 2009, 131, 10866. M. C. Fuertes et al. Small, 2009, 5, 272-280 M. Bellino et al. Small, 2010, 6, 1221. E. D. Martínez, et al, Phys. Chem. Chem. Phys, 2010, 12, 14445. G. J. A. A. Soler-Illia, O. Azzaroni, Chem. Soc.Rev.2011, 40 1107