Faculty Bibliography

This paper describes the design, construction and operation of hybrid dye/superconductor optical sensors. Here a reflective mirror layer positioned between the dye and superconductor components is used as a means to reject light signals that are not absorbed strongly by the dye. On resonance signals are shown to couple effectively with the effectively superconductor where they evoke measurable responses. These structures form the basis for color selective optical sensors.

In order to produce more stable and processable forms of YBa2Cu3O7-delta superconductors, a series of cation substitution reactions have been completed. Compounds in the family of Y-1-yCayBa1-yLayCu3O7-delta display an increased corrosion resistance with increasing substitution level. The composition of Y0.6Ca0.4Ba1.6La0.4Cu3O6.96 (T-c = 80 K) is found to be at least 100 times more stable than the parent compound, YBa2Cu3O6.94. In this paper, compositions yielding transition temperature above 83-85 K have been identified in YBa2-xSrxCu3O7-delta and Gd1-xCaxBa2-yLayCu3O7-delta systems suggesting that the surface reactivity, processability and superconducting properties can be tailored with the use of the appropriate cation compositions. Rational approaches for the systematic tailoring of high-T-c superconductors based on lattice engineering approaches are thus developed.

Thin films of (BEDT-TTF)(2)I-3 have been deposited by vapor-phase deposition onto high-temperature superconductor substrates. Results from X-ray powder diffraction, atomic force microscopy and scanning electron microscopy studies of these hybrid organic/inorganic structures indicate that the organic material is deposited in a poorly crystalline, predominantly disordered fashion. Interestingly, the self-assembly of an alkylamine monolayer onto the cuprate superconductor surface before (BEDT-TTF)(2)I-3 thin-film deposition appears to eliminate the direct interaction between the organic and inorganic superconductor materials and fosters growth of ordered and crystalline organic films.

The reactivity of Tl1.4Ba2CaCu2O7.0, a high-temperature superconductor (HTSC), toward a redox-active adsorbate molecule with thiol functionality has been investigated as a function of solvent type and H2O content. Previously it had been reported that alkanethiols do not stably chemisorb onto the surface of Tl2Ba2CaCu2O8/Tl2Ba2Ca2Cu3O10 phases, bringing into question the generality of alkanethiol adsorption onto cuprate-based HTSCs. Herein, we show that under rigorously dry conditions, 11-mercaptoundecanoylferrocene (1) adsorbs cleanly onto the surface of Tl1.4Ba2CaCu2O7.0 to form moderately stable, redox-active monolayer films. The redox activity of 1 was used to estimate adsorbate surface coverage, and it is shown that the addition of H2O to the modifying solutions of 1 adversely affects the monolayer adsorption process. No redox activity associated with 1 could be detected for electrodes soaked in 0.1 M solutions of 1 with 5% H2O in ethanol, which was attributed to the formation of a BaCO3 corrosion layer that prohibited the adsorption of 1 onto the HTSC surface. The importance of sample stoichiometry on the adsorption process also is discussed.