Rapid Prototyping of Patterned Multifunctional Nanostructures
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Mat. Res. Soc. Symp. Proc. Vol. 625 © 2000 Materials Research Society
of organic additives, we have selectively derivatized the silica framework with functional R' ligands or molecules. The resulting materials exhibit form and function on multiple length scales: on the molecular scale, functional organic moieties are positioned on pore surfaces, on the mesoscale, mono-sized pores are organized into 1-, 2-, or 3-dimensional networks, providing size-selective accessibility from the gas or liquid phase, and on the macroscale, 2-dimensional arrays and fluidic or photonic systems may be defined. EXPERIMENTAL Precursor solutions used as inks were prepared by addition of surfactants (cationic, CTAB; CH 3(CH2),5N÷(CH 3)3Br- or non-ionic, Brij-56; CH 3(CH 2)15 -(OCH 2CH2 )10-OH and Pluronic P123, HO(CH 2CH20) 20(CH(CH 3)CH 2)O) 70 -(CH 2CH 20) 20-H), organosilanes (R'Si(OR) 3, see Table 1), or organic molecules (see Table 1) to an acidic silica sol prepared from TEOS [Si(OCH 2CH 3 )4] (A2**). The acid concentration employed in the A2** synthesis procedure was chosen to minimize the siloxane condensation rate, thereby promoting facile self-assembly during printing[20]. In a typical preparation, TEOS, ethanol, water and dilute HCi (mole ratios: 1:3.8:1:5x10 5 ) were refluxed at 60 *C for 90 min. The sol was diluted with 2 volumes of ethanol followed by further addition of water and HCl. Organosilanes (R'-Si(OR) 3, where R' is a nonhydrolyzable organic functional ligand) were added followed by surfactants and (optionally) organic additives (see Table 1). Surfactants were added in requisite amounts to achieve initial surfactant concentrations co ranging from 0.004 to 0.23 M (c,
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