Hierarchically structured functional porous silica and composite produced by evaporation-induced self-assembly

Recently so-called soft lithography approaches [Angew. Chem. Int. Ed. 37 (1998) 550] have been combined with surfactant [Adv. Mater. 9 (1997) 811, Nature 390 (1997) 674] and particulate [Science 282 (1998) 2244] templating procedures to create oxides with multiple levels of structural order. But the materials thus formed have been limited primarily to oxides with no specific functionality, and the associated processing times have ranged from hours to days. Using self-assembling inks we have combined evaporation-induced (silica/surfactant) self-assembly [Adv. Mater. 11 (1999) 579] with rapid prototyping techniques like micro-pen lithography [Science 283 (1999) 661, Mat. Res. Sec. Symp. Proc. 542 (1999) 159], ink-jet printing [Adv. Mater. 11 (1999) 734, Mat. Sci. Eng. C5 (1998) 289], and dip coating on micro-contact printed substrates to form hierarchically organized structures in seconds. By co-condensation of tetrafunctional silanes (Si(OR)(4)) with tri-functional organosilanes ((RO)(3)SiR ') [Chem. Commun. (1999) 1367, Chem. Commun. (1997) 1769, J. Am. Chem. Sec. 119 (1997) 4090] or bridged silsesquioxanes (RO)(3)Si-R '-(Si(OR)(3)) or by inclusion of organic additives, we have selectively derivatized the silica framework with functional R ' ligands or molecules. The rapid-prototyping procedures we describe are simple, employ readily available equipment. and provide a link between computer-aided design and self-assembled functional nanostructures. We expect that the ability to form arbitrary functional designs on arbitrary surfaces will be of practical importance for directly writing sensor arrays and Acidic or photonic systems. (C) 2001 Elsevier Science B.V. All rights reserved.