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A Novel Design Toward Understanding and Characterizing Transport Behavior of Composite Mesoporous Silica Thin Films

  • Zhu Chen (a1), David P Adams (a2), Michael J Vasile (a3), Nanguo Liu (a4), Yingbing Jiang (a5), George Xomeritakes (a6) and C. Jeffrey Brinker (a7)...

Abstract

Research in synthetic materials with controlled transport properties has been inspired by the exquisite selectivity exhibited by natural transmembrane proteins such as ion channels (for selectively transporting ions like sodium and potassium, etc) and aquaporins (for conducting high fluxes of water and excluding ions). In this poster we focus on the transport behavior of highly ordered mesoporous silica thin films synthesized by evaporation induced silica/surfactant self-assembly (EISA). This process allows us to integrate the nanostructures into electronic and fluidic systems by simple coating or spraying procedures, facilitating the characterization of their transport behaviors. Also, the nanocomposite architecture made by this process gives precisely defined pore size, orientation and surface chemistry, allowing tailoring of the motion of molecules and ions transported across the nanochannels. To approach our final goal of understanding and characterizing the transport behavior of our materials, we designed our experiments into three steps: first, we employed focused ion beam (FIB) lithography to drill a single sub-100-nm pore on a substrate support, providing a platform enabling the characterization of trans-membrane behavior of ions/molecules. Second, we developed two EISA approaches to form cubic thin film silica mesophases spanning the FIB-drilled pore. In one approach, we adapted our aerosol-assisted EISA where fusion of liquid crystalline aerosol droplets creates a thin membrane spanning the substrate pore. In the other approach, we modified our synthetic protocol to form ultra thin (20-nm) spanning films by spin-coating. Films with pore sizes ranging from 2nm to 7nm and surface chemistries including –OH, -COOH and –NH2 terminated pore surfaces were prepared in this fashion and integrated to the FIB-drilled single pore substrate support with uniformity to allow tailoring of the motion of ions and molecules. Third, we designed an electrochemical cell in which the FIB-drilled substrates are integrated to enable the measurements of ion fluxes using standard “patch-clamp” instruments. Experiments are conducted to demonstrate the transport characteristics of our materials by measuring transmembrane ion fluxes when specific molecules such as DNA are applied, a method relevant to low cost DNA sequencing. Also, by chemically or physically blocking all but one or several membrane pores, we are attempting to measure ion and water transport in individual synthetic nanopores and compare results with natural ion and water channels.

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References

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1. Liu, N. G., Assink, R. A., Brinker, C. J., Chem. Commun. 2003 370.
2. Liu, N. G., Assink, R. A., Brinker, C. J., Chem. Commun. 2003 1146.
3. Xomeritakis, G., et al. Microporous and Mesoporous Materials, 2003 66, 91.
4. Li, J., et al. Nature Materials, 2003 2, 611.
5. Brinker, C. J., Lu, Y., Sellinger, A.,Fan, H., Adv. Mater. 1999 11, 579.

Keywords

A Novel Design Toward Understanding and Characterizing Transport Behavior of Composite Mesoporous Silica Thin Films

  • Zhu Chen (a1), David P Adams (a2), Michael J Vasile (a3), Nanguo Liu (a4), Yingbing Jiang (a5), George Xomeritakes (a6) and C. Jeffrey Brinker (a7)...

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