Formation, Characterization, and Stability of Methaneselenolate Monolayers on Au(111): An Electrochemical High-Resolution Photoemission Spectroscopy and DFT Study

F. COMETTO; A. CALDERÓN; M. MORÁN; G. RUANO; H. ASCOLANI; G. ZAMPIERI; P. PAREDES-OLIVERA; E.M. PATRITO

LANGMUIR

AMER CHEMICAL SOC

Lugar: Washington; Año: 2014 vol. 30 p. 3754 - 3763

0743-7463

We investigated the mechanism of formation and stability of self-assembled monolayers (SAMs) of methaneselenolate on Au(111)prepared by the immersion method in ethanolic solutions of dimethyldiselenide (DMDSe). The adsorbed species were characterized byelectrochemical measurements and high-resolution photoelectron spec-troscopy (HR-XPS). The importance of the headgroup on formationmechanism and the stability of the SAMs was addressed by comparativelystudying methaneselenolate (MSe) and methanethiolate (MT) mono-layers. Density Functional Theory (DFT) calculations were performed toidentify the elementary reaction steps in the mechanisms of formation anddecomposition of the monolayers. Reductive desorption and HR-XPSmeasurements indicated that a MSe monolayer is formed at shortimmersion times by the cleavage of the Se−Se bond of DMDSe. However,the monolayer decomposes at long immersion times at room temperature,as evidenced by the appearance of atomic Se on the surface. The decomposition is more pronounced for MSe than for MTmonolayers. The MSe monolayer stability can be greatly improved by two modifications in the preparation method: immersionat low temperatures (−20 °C) and the addition of a reducing agent to the forming solution.