Nanochannel Arrays for Molecular Sieving and Electrochemical Analysis by Nanosphere Lithography Templated Graphoepitaxy of Block Copolymers.

The ability to design, fabricate, and manipulate materials at the nanoscale is fundamental to the quest to develop technologies to assemble nanometer-scale pieces into larger-scale components and materials, thereby transferring unique nanometer-scale properties to macroscopic objects. In this work, we describe a new approach to the fabrication of highly ordered, ultrahigh density nanochannel arrays that employs nanosphere lithography to template the graphoepitaxy of polystyrene-polydimethylsiloxane, diblock copolymers. By optimizing the well-controlled solvent vapor annealing, overcoating conditions, and the subsequent reactive ion etching processes, silica nanochannel (SNC) arrays with areal densities, ρA, approaching 1000 elements μm-2, are obtained over macroscopic scales. The integrity and functionality of the SNC arrays was tested by using them as permselective ion barriers to nanopore-confined disk electrodes. The nanochannels allow cations to pass to the disk electrode but reject anions, as demonstrated by cyclic voltammetry. This ion gating behavior can be reversed from cation-permselective to anion-permselective by chemically inverting the surface charge from negative to positive. Furthermore, the conformal SNC array structures obtained could easily be lifted, detached, and transferred to another substrate, preserving the hierarchical organization while transferring the nanostructure-derived properties to a different substrate. These results demonstrate how nanoscale behavior can be replicated over macroscale distances, using electrochemical analysis as a model.