Web Release Date: March 13,
Infrared and Computational Studies of Spontaneously Adsorbed Amine Reagents on YBa2Cu3O7: Structural Characterization of Monolayers atop Anisotropic Superconductor Surfaces
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Contribution from the Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712, and Department of Chemistry and Physics, Chicago State University, Chicago, Illinois 60628
Received March 4, 1997
Abstract:
Methods capable of forming highly organized monolayers on top of YBa2Cu3O7 (YBCO), a high-Tc superconductor, have been identified and are described for the first time. Here, grazing reflectance infrared fourier transform spectroscopy (GRIFTS) is employed to evaluate the degree of order for these monolayer structures. Through these investigations, it is found that while octadecylamine forms a well-ordered, crystalline-like monolayer on the surface of c-axis-oriented YBa2Cu3O7 thin films, the same reagent adsorbed onto polycrystalline YBa2Cu3O7 pellets affords disordered, liquid-like monolayers. Computational studies of alkylamine packing, using a molecular mechanics methodology, reveal two plausible structures for the crystalline-like monolayer. A GRIFTS comparison of primary, secondary, and tertiary alkylamine reagents also has been completed, and the substitution pattern dependence of the monolayer order has been assessed experimentally. Moreover, comparisons between amine monolayers on top of YBa2Cu3O7 and alkyl thiol reagents on gold surfaces are made using GRIFTS and thermal desorption experiments. This work documents the initial report of the assembly and characterization of organized monolayers supported on high-Tc superconductor surfaces, the most complex substrate yet reported capable of fostering ordered adsorbate layers.
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