Alkanethiols Adsorbed on Planar and Curved Palladium Surfaces: Composition and Stability Studies by Electrochemical Techniques and X-ray Photoelectron Spectroscopy

GASTÓN CORTHEY, ALDO A. RUBERT, GUILLERMO A. BENITEZ, FRANCISCO J. IBAÑEZ, MARIANO H. FONTICELLI*, ROBERTO C. SALVAREZZA

Manchester, United Kingdom

Congreso; Electrochem. 09; 2009

Stability and composition of alkanethiols adsorbed on planar and curved (monolayer-protected clusters, MPCs) Pd surfaces have been studied by electrochemical techniques and X-ray photoelectron spectroscopy (XPS). Similar XPS spectra for S and Pd have been obtained for both systems, indicating a similar composition. Alkanethiols adsorbed on Pd surfaces lead to a complex interface composed of thiolate and sulfide, with surface coverage qSulfide » 0.4 and qthiolate » 0.30 in the case of planar Pd. These complex adlayers exhibit organic chainlength dependence barrier properties similar to those formed on Au and Ag. In the other hand, these systems show an increased stability toward reductive desorption compared to similar adlayers on other metals. Nevertheless, it was possible to recover a clean planar Pd surface by reductive desorption.  Regarding the organic monolayer stability upon oxidants, ozone (O3) has been shown to remove sulfur species on both types of surfaces.  It is known that molecular oxygen (O2) leads to sulfur oxidation on planar Pd substrates. However, we observed that sulfur species on curved Pd surfaces do not change during nine months of exposure of powder MPCs to air. From the above mentioned results, it will be shown that: (1) the monolayers’ stability in aqueous solutions makes Pd a suitable platform for thiolate-based devices such as sensors and biosensors; and (2) electrochemical cleaning should be a simple way to prepare metallic nanoparticles from thiol-capped Pd nanoparticles adsorbed on conducting substrates.