Selenium-Based Self-Assembled Monolayers: the Nature of Adsorbate-Surface Interactions

EZEQUIEL DE LA LLAVE; DAMIAN A SCHERLIS

LANGMUIR

AMER CHEMICAL SOC

Año: 2010 vol. 26 p. 173 - 178

0743-7463

In recent years, self-assembled monolayers (SAMs) of selenols have been characterized using electrochemistry,scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), thermal desorption spectroscopy, andother experimental approaches. Interest in the relative stability and conductance of the Se-Au interface as compared toS-Au prompted different investigations which have led to contradictory results. From the theoretical side, on the otherhand, the study of selenol-based SAMs has concentrated on the investigation of the electron transport across the Se-Aucontact, whereas the structural and the thermodynamic features of the monolayer were essentially neglected. In thisArticle, we examine the binding of selenols to the Au(111) surface using density functional theory with plane wave basissets and periodic boundary conditions. Our calculations provide insights on the geometry of the headgroup, the stabilityof the monolayer, and the electronic properties of the bond. In particular, we propose that the presence of a conjugatedbackbone might be a major factor determining the relative conductance at the monolayer, by differentially enhancingthe intramolecular electron transport in selenols with respect to thiols. This surmise, if confirmed, would explain theconflictive data coming from the available experiments.