Investigation of Enantioselective Adsorption on Chiral Mineral Surfaces

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Proposal Title: Investigation of Enantioselective Adsorption on Chiral Mineral SurfacesProposal Number: CTS-0521719Principal Investigator: Paul SidesInstitution: Carnegie Mellon UniversityThe objective of this proposal is to demonstrate that chiral surfaces of minerals can function as enantioselective analysis and separations media. Many common inorganic materials have chiral bulk structures. Fundamental evidence for the enantiospecific adsorption of amino acids on single crystalline quartz and calcite will be produced. Ultra-high vacuum surface science tools will be used to quantify the differences in the adsorption energies of R- and S- amino acids onto chiral surfaces of quartz and calcite. The extent of the adsorption will be evaluated in vacuum by temperature programmed desorption and in aqueous solutions by detection of the zeta potential differences between surfaces of opposite handedness when amino acids are adsorbed. The zeta potential measurements will be made using a novel technique recently developed at Carnegie Mellon University. This technique will be adapted to make a differential measurement of enantioselective adsorption on R- and S- surfaces. Enantioselective adsorption on mineral surfaces has never before been studied under the controlled conditions possible in ultrahigh vacuum. The second novel feature is the use of a rotating disk method recently invented for measuring changes in zeta potential of inorganic surfaces associated with adsorption of charged molecules such as amino acids; this method makes possible a true differential measurement of enantioselectivity. The proposed investigation will contribute to the fundamental understanding of the enantiospecific adsorption of chiral compounds on inorganic chiral surfaces. In terms of the broader impacts, the proposed investigation will foster dissemination of knowledge about chirality, a subtle aspect of molecular structure that engineering disciplines such as materials science and chemical engineering have largely ignored. A new experiment based on enantiospecific adsorption will be incorporated in an existing laboratory course. This work could lead to better processes for performing separations of chiral molecules for use in pharmaceuticals, artificial flavors, and agrochemicals.