Surface Coordination Chemistry of YBa2Cu3O7-

Langmuir, 14 (22), 6505 -6511, 1998. 10.1021/la980143n S0743-7463(98)00143-7
Web Release Date: October 2, 1998

Surface Coordination Chemistry of YBa₂Cu₃O_7-

Feng Xu, Kaimin Chen, Richard D. Piner, and Chad A. Mirkin*

Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208

Jason E. Ritchie and John T. McDevitt*

Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712

Michael O. Cannon and David Kanis*

Department of Chemistry, Chicago State University, Chicago, Illinois

Received February 5, 1998

In Final Form: August 13, 1998

Abstract:

The surface coordination chemistry of the cuprate superconductor, YBa₂Cu₃O₇_- has been extensively surveyed using cyclic voltammetry in conjunction with a series of redox-active ferrocenyl containing adsorbate molecules. Evidence supporting the adsorption of molecules with primary alkylamine, secondary alkylamine, tertiary alkylamine, arylamine, thiol, disulfide, and selenol functionalities is reported. Cyclic voltammetry, atomic force microscopy, scanning electron microscopy, X-ray powder diffraction and resistivity vs temperature measurements were utilized to evaluate the influence of the modification conditions on the bulk and surface properties of the high-T_c superconductor. The spontaneous adsorption of redox-active alkylamines, arylamines, and thiols onto the surfaces of cuprate materials has been shown to produce stable and robust monolayer films with no apparent damage to the bulk properties of the underlying superconductors. Of the molecules studied thus far, primary alkylamines have been determined to be the optimum adsorbates based upon surface coverage values and monolayer durability. Tertiary alkylamines form monolayers on YBa₂Cu₃O₇_- with an electrochemical persistence comparable to primary alkylamine monolayers, suggesting that hydrogen binding with the surface is not necessary for adsorption. We propose that amines act as Lewis bases and bind to Lewis acidic Cu surface site(s) in YBa₂Cu₃O₇_- to form stable coordination bond(s).

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