Abstracts séléctionnés 2016

DFT Modeling of Corrosion Inhibition by Organic Molecules: Carboxylates as Inhibitors of Aluminum Corrosion. Costa, D.; Ribeiro, T.; Cornette, P.; Marcus, P. Journal of Physical Chemistry C 2016, 120 (50), 28607–28616. https://doi.org/10.1021/acs.jpcc.6b09578.

In order to model the adsorption of organic corrosion inhibitors on ultrathin oxide layers on aluminum, the formation of a self-assembled layer of gallic acid, the smallest tannin molecule, at the surface of an Al2O3 ultrathin layer supported by Al(111) was studied using periodic density functional theory including dispersion forces (DFT-D). A dense self-assembled layer (SAM) was formed with a density of 3.6 molecules/nm2, adsorbed in a monodentate way by ligand exchange, with an adsorption energy of 2.27 eV/molecule. The electronic analysis shows that the oxide levels are significantly stabilized by the covalent bonding with the COOH moiety of the molecule. The permittivity of the surface layers falls from 109 for the ultrathin Al2O3 film to 4 for the joint oxide and organic film. The permittivity of the surface constrained gallic acid SAM is 1.4, a value slightly lower than that of the free hexagonal compact, SAM (2.4). The organic layer forms an efficient barrier against electron transfer to dioxygen, thus providing good cathodic inhibition. The potential drop at the edge of the oxide and organic layer is found to be around 2 V. Studies of benzoates derivatives (benzoic acid and nitrobenzoic acid) show that the potential drop and the electronic work function difference (with respect to the nonfunctionalized oxide film) induced by the organic SAM increase linearly with the charge of the adsorbed molecules. The reported results give indications for the rational design of corrosion inhibitors.

Adsorption of Amino Acids and Peptides on Metal and Oxide Surfaces in Water Environment: A Synthetic and Prospective Review. Costa, D.; Savio, L.; Pradiera, C.-M. Journal of Physical Chemistry B 2016, 120 (29), 7039–7052. https://doi.org/10.1021/acs.jpcb.6b05954.

Amino acids and peptides are often used as “model” segments of proteins for studying their behavior in various types of environments, and/or elaborating functional surfaces. Indeed, though the protein behavior is much more complex than that of their isolated segments, knowledge of the binding mode as well as of the chemical structure of peptides on metal or oxide surfaces is a significant step toward the control of materials in a biological environment. Such knowledge has considerably increased in the past few years, thanks to the combination of advanced characterization techniques and of modeling methods. Investigations of biomolecule–surface interactions in water/solvent environments are quite numerous, but only in a few cases is it possible to reach an understanding of the molecule–(water)–surface interaction with a level of detail comparable to that of the UHV studies. This contribution aims at reviewing the recent data describing the amino acid and peptide interaction with metal or oxide surfaces in the presence of water.