282560 Layer-by-Layer Silica Reactive Assembly On Nanoscale Chemical Templates

Wednesday, October 31, 2012: 12:52 PM
311 (Convention Center )
Juan Pablo Hinestrosa, Center for Nanophase Material Sciences, Oak Ridge National Laboratory, Oak Ridge, TN and Scott Retterer, Cnms, Oak Ridge National Laboratory, Oak Ridge, TN

Layer-by-Layer Silica Reactive Assembly on Nanoscale Chemical Templates

Juan Pablo Hinestrosa* & Scott Retterer*,µ

*Center for Nanophase Material Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37834

µBiosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37834

Reactive assembly of silica onto nano- and micro-scale organic templates was achieved using a combination of chemical lift-off and solution chemistry performed under mild conditions of pH and temperature. Well-defined gratings, honeycomb-lattices, and dot arrays were created by electron beam lithography and used as templates for the generation of silica nanostructures. Initially, an amine-silane monolayer was vapor deposited onto the patterned substrates.  They were subsequently reacted with silicic acid solutions made in buffers of varying pH and salt content at room temperature. The process of vapor treatment followed by the reactive assembly of silica in solution could be repeated multiple times to perform layer-by-layer deposition while keeping the nanoscale organic templates intact, as seen in the Figure.  It was observed that the conditions for the silicic acid deposition, namely pH, salts and solution age, had a strong effect on thickness of each layer and the morphology of the amorphous silica formed.

Following silica reactive assembly, the templates can be easily removed by sonication in acetone leaving only the silica nanostructures on the substrates. ‘Defects' in the arrays of silica nanostructures were relatively minor (~ 10% after three depositions) and do not affect the overall organization of the layers.  These defects were attributed to difficulties associated with completely removing the PMMA mask from underneath the deposited silica.  The number of defects increased with the addition of each silica layer. The biomimetic method described here allows for the generation of well-defined, complex nanostructures starting from small molecules under mild conditions; thus, we believe it provides a robust platform for high-throughput reactive assembly process and growth of organic-inorganic hybrid nanostructures.

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Figure. SEM images of silica gratings, honeycomb lattices and dot arrays after reactive assembly from silicic acid solution.

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See more of this Session: Templated Assembly of Inorganic Nanomaterials I
See more of this Group/Topical: Nanoscale Science and Engineering Forum