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, redoxactive 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.
Careful studies of the corrosion, redox, galvanic, and oxygen evolution/uptake reactions associated with YBa 2 Cu 3 O 72d and related compounds have been completed. These studies have led to an understanding of the many factors that contribute to the poor material characteristics exhibited by these popular high-T c phases. With knowledge of the structure-reactivity relationships, a powerful crystal engineering approach has been developed that is capable of producing cation substituted versions of YBa 2 Cu 3 O 72d ; the resulting compounds therefrom produced exhibit markedly improved processability, oxygen stability, and durability characteristics. These materials have been combined in thin film structures so as to make prototype SNS junctions and SQUID sensors which exhibit promising device performance characteristics.
The spontaneous adsorption of
alkylamines and fluorinated alkylamines onto the surface of
cuprate-based compounds is reported. These monolayer films allow
for control of the wetting properties, corrosion resistance, and
adhesion characteristics of these superconductors. The molecules
form densely packed, highly oriented structures on the
high-T
c surfaces as evidenced by contact angle,
X-ray photoelectron spectroscopy, X-ray reflectivity, and corrosion
resistance measurements. Thus, molecular level control over
important surface and interfacial properties of cuprate superconductors
is demonstrated.
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