title: Electrochemical self-assembly of alkanethiolate molecules on Ni(111) and polycrystalline Ni surfaces.
abstract: In this work, the electrochemical formation of alkanethiolate self-assembled monolayers (SAMs) on Ni(111) and polycrystalline Ni surfaces from alkanethiol-containing aqueous 1 M NaOH solutions was studied by combining Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), electrochemical techniques, and density functional theory (DFT) calculations. Results show that alkanethiolates adsorb on Ni concurrent with NiO electroreduction. The resulting surface coverage depends on the applied potential and hydrocarbon chain length. Electrochemical and XPS data reveal that alkanethiolate electroadsorption at room temperature takes place without S-C bond scission, in contrast to previous results from gas-phase adsorption. A complete and dense monolayer, which is stable even at very high cathodic potentials (-1.5 V vs SCE), is formed for dodecanethiol. DFT calculations show that the greater stability against electrodesorption found for alkanethiolate SAMs on Ni, with respect to SAMs on Au, is somewhat related to the larger alkanethiolate adsorption energy but is mainly due to the larger barrier to interfacial electron transfer present in alkanethiolate-covered Ni. A direct consequence of this work is the possibility of using electrochemical self-assembly as a straightforward route to build stable SAMs of long-chained alkanethiolates on Ni surfaces at room temperature.
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata, CONICET, Sucursal 4 Casilla de Correo 16, 1900 La Plata, Argentina.
authors.forename: Silvina
authors.initials: S
authors.lastname: Bengió
authors.forename: Mariano
authors.initials: M
authors.lastname: Fonticelli
authors.forename: Guillermo
authors.initials: G
authors.lastname: Benítez
authors.forename: Alberto Hernández
authors.initials: AH
authors.lastname: Creus
authors.forename: Pilar
authors.initials: P
authors.lastname: Carro
authors.forename: Hugo
authors.initials: H
authors.lastname: Ascolani
authors.forename: Guillermo
authors.initials: G
authors.lastname: Zampieri
authors.forename: Bárbara
authors.initials: B
authors.lastname: Blum
authors.forename: Roberto C
authors.initials: RC
authors.lastname: Salvarezza