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Autumn 2008 Seminar Series
Friday, November 14 at 3:30 p.m.
Room 264 MacQuigg Labs
Stephen E. Rankin
Associate Professor of Chemical Engineering and Gill Professor of Engineering
Department of Chemical & Materials Engineering
University of Kentucky, Lexington
Design Principles for Surfactant-Templated Nanoporous Metal Oxides
Abstract
The sol-gel method is a room-temperature, chemical route to metal oxide materials. The low temperature of the method enables the incorporation of organic components through weak interactions (ionic and hydrogen bonding) or by covalent attachment, thus allowing self-assembly and interfacial engineering concepts to be utilized to control pore architecture. In this talk, I will describe ongoing research in which we explore new ways to use interfacial concepts to control the synthesis of surfactant-templated mesoporous metal oxide materials. The goal will be to highlight design principles that emerge from a fundamental understanding of the nanoscale processes at play.
In these materials, co-assembly of surfactants and metal oxide precursors leads to the formation of organized structures similar to lyotropic liquid crystals. One method of creating such structures is liquid-phase precipitation. I will begin by discussing a TEM study showing how one type of pore architecture Š spherical particles with radially orientated pores - is induced by alignment of surfactant micelles normal to the particle surface after precipitation of silica/surfactant aggregates. Coarse-grained Monte Carlo simulations suggest that alignment of micelles normal to interfaces may be induced by weak interactions of both polar and nonpolar components with the interface. This concept will be demonstrated to work in a different context to induce orthogonal alignment of close-packed cylindrical arrays of micelles within dip-coated sol-gel films. These films have potential use as components of photovoltaic structures (with titania as the metal oxide) and as photocatalysts (e.g., titanosilicates).
Finally, I will discuss the relationship between lyotropic phase behavior and pore architecture in materials prepared with mixed cationic and saccharide-based surfactants. The latter class of surfactants has recently begun to be explored in our group for its potential to not only template pores, but also to simultaneously guide functional groups to the pore surface for saccharide separations required for lignocellulosic ethanol production and biomimetic catalysis.
Bio
Prof. Rankin is an Associate Professor in the Chemical and Materials Engineering Department at the University of Kentucky. He received his B.S. and Ph.D. degrees in Chemical Engineering in 1993 from Carnegie Mellon University and in 1998 from the University of Minnesota, respectively. After brief postdoctoral appointments with Dow Corning and at Sandia National Laboratories, he joined the faculty at UK in 2000. Dr. RankinÕs research interests focus on experimental and modeling studies of the synthesis of metal oxide materials, porous materials, and of the interfacial phenomena governing the formation and function of those materials. He received a DOE Early Career Scientist & Engineer Award in 2000 and an NSF CAREER Award in 2004.
Please join our speaker for light refreshments in 479 Watts Hall following the talk.
