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Electric-Field-Induced Orientation of Surfactant-Templated Nanoscopic Silica

Summary: Electric-Field-Induced Orientation of Surfactant-Templated
Nanoscopic Silica
Anthony Y. Ku, Dudley A. Saville, and Ilhan A. Aksay*
Department of Chemical Engineering, Princeton UniVersity, Princeton, New Jersey 08544
ReceiVed December 14, 2006. In Final Form: April 9, 2007
While exhibiting a well-defined nanometer-level structure, surfactant-templated nanoscopic silicas produced via
self-assembly do not always possess long-range order. We demonstrate that long-range order can be controlled by
guiding the self-assembly of nanostructured silica-surfactant hybrids with low-strength electric fields (E 200 V/m)
to produce nanoscopic silica with both the micrometer- and nanometer-level structures oriented parallel to the applied
field. Under the influence of the electric field, nanoscopic silica particles migrate, elongate, and merge into fibers with
a rate of migration proportional to the applied field strength. The linear dependence with the field strength indicates
that the process is governed by electroosmotic flow but not by polarization effects. Realignment of the short-range
ordered surfactant nanochannels along the fiber axis accompanies the migration.
The well-packed, tunable, monodisperse channel structure in
nanoscopic silica produced through the self-assembly of sur-
factants holds great promise for applications ranging from
microelectronics to environmental and biological separations to
catalytic hosts.1-10 In the system discussed in this work, the
synthesis involves mixing a silicate precursor into an acidified


Source: Aksay, Ilhan A. - Department of Chemical Engineering, Princeton University


Collections: Materials Science