A Novel Design Toward Understanding and Characterizing Transport Behavior of Composite Mesoporous Silica Thin Films
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0921-T05-29
A Novel Design Toward Understanding and Characterizing Transport Behavior of Composite Mesoporous Silica Thin Films Zhu Chen1, David P Adams2, Michael J Vasile2, Nanguo Liu1, Yingbing Jiang1, George Xomeritakes1, and C. Jeffrey Brinker1,2 1 University of New Mexico, Albuquerque, NM, 87106 2 Sandia National Laboratories, Albuquerque, NM, 87106
ABSTRACT In this paper, we for the first time apply a so-called “bottom-up” approach in fabricating synthetic ion-channel by exploiting evaporation-induced self-assembly (EISA) to form highly ordered porous thin film silica structures with precisely defined pore size, connectivity and surface chemistry as well as mechanical/thermal robustness. Here we demonstrate a novel design to integrate the above porous and composite nanostructures into an electrochemical device in which transmembrane ion fluxes can be measured to characterize the transport behaviors of ions/molecules through our mesoporous silica thin film. The demonstration of DNA translocation indicates a possible application of the mesoporous thin film structure in low cost DNA sequencing.
INTRODUCTION In nature, various natural transmembrane proteins such as ion channels and aquaporins have exhibited outstanding transport properties such as high flux and exquisite selectivity to specific ions/molecules. For example, aquaporins conduct thousands of millions of water molecules per second (per channel), without conducting ions, and thus enable kidneys to process enormous quantities (150 liters) of water daily, out-performing the current desalination solution, reverse osmosis membranes. With the development of material science, there is current need to emulate such proven natural designs in robust engineering materials with known geometry and chemical structure using efficient, manufacturable processing approaches. While various socalled “top-down” solid-state materials such as silicon nitride or silicon dioxide with single nanopores have been fabricated to offer several potential advantages over biological pores including chemical, mechanical, and thermal robustness, there still remain some problems such as the difficulty to introduce functional ligands in hierarchical architectures resulting in optimized properties. In this paper, we, for the first time, apply a “bottom-up” approach in fabricating synthetic ion channels by exploiting evaporation-induced self-assembly (EISA) to form highly ordered porous thin film silica nanostructures with precisely defined pore size, structure and surface chemistry. The pore size (1nm to over 10nm) covers that of biological ion channels, but with much wider range. This synthetic system with well-defined and adjustable structure and surface chemistry is important for establishing structure/property relationships. Meanwhile, the EISA process allows us to use simple coating and printing procedures to
integrate these porous and composite nanostructures into electronic, fluidic, photonic, and membrane platforms, thereby providing a means to characterize their transport behav
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