Mesoporous Hybrid Thin Films: Building Blocks for Complex Materials with Spatial Organization

G.J.A.A. SOLER ILLIA; P.C. ANGELOMÉ; M.C. FUERTES; A. WOLOSIUK; S. ALDABE BILMES; F.J. LÓPEZ-ALCARAZ; H. MÍGUEZ

San Francisco, CA, USA

Congreso; MRS 2007 Spring Meeting; 2007

Materials Research Society

In the last few years, synthesis routes have been developed to create Mesoporous Hybrid Thin Films (MHTF) by combining sol-gel synthesis, template self-assembly and surface modification. Currently, the two main routes explored (one-pot and post-grafting) permit to reproducibly obtain a palette of oxide and hybrid networks with a variety of organic or biological functions located in the inorganic framework or pore surface. These MHTF are indeed a “nanofacility”, where the properties of tailored functional pores as well as the distance between them can be controlled. The multifunctional features of MHTF arise from the combination of the properties imparted by the pore geometry and the organic modifiers.   We have explored the production of accessible MHTF by the two routes cited above. A post-grafting strategy was adopted for titania and zirconia mesoporous films, using R-G molecules, where R is the organic desired function and G a grafting group such as phosphate, phosphonate, carboxylate, silane, etc. A one-pot path was developed, based on the combination of metal chlorides and functional silanes, followed by consolidation and template extraction. The presence of the functional group leads to new properties: thiol-functionalised MHTF can behave as traps for pollutants, such as heavy metals. Functional surface groups can control the access and transport of organic molecules, thus opening the way to nanofiltering membranes. Modified pores can be used as a series of nanorreactors, permitting the inclusion of nanoparticles (NP), which lead to optical properties derived from an ordered and regular nanoheterogeneous system.   Each highly controlled MHTF issued from a reproducible and modular synthesis can be considered itself a building block for more complex structures, presenting order at larger scales, and novel properties derived from this multiscale order. Bilayer or multilayer stacks of MHTF presenting specific and different functions and frameworks have been produced by combining sequential film deposition, selective functionalization and dissolution. The resulting multilayer systems can present a great varierty of new properties, from localized chemical reaction control to modulable photonic crystal behaviour. Selected examples of optical and chemical behaviour of these multiscale materials will be presented.