DO ALKANETHIOLS ADSORB ONTO THE SURFACES OF TL-BA-CA-CU-O-BASED HIGH-TEMPERATURE SUPERCONDUCTORS - THE CRITICAL ROLE OF H2O CONTENT ON THE ADSORPTION PROCESS

The reactivity of Tl1.4Ba2CaCu2O7.0, a high-temperature superconductor (HTSC), toward a redox-active adsorbate molecule with thiol functiona lity has been investigated as a function of solvent type and H2O conte nt. Previously it had been reported that alkanethiols do not stably ch emisorb onto the surface of Tl2Ba2CaCu2O8/Tl2Ba2Ca2Cu3O10 phases, brin ging into question the generality of alkanethiol adsorption onto cupra te-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 f ilms. The redox activity of 1 was used to estimate adsorbate surface c overage, and it is shown that the addition of H2O to the modifying sol utions of 1 adversely affects the monolayer adsorption process. No red ox 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 t o the formation of a BaCO3 corrosion layer that prohibited the adsorpt ion of 1 onto the HTSC surface. The importance of sample stoichiometry on the adsorption process also is discussed.