Željka Petrović

Copper Protection by a Self-Assembled Monolayer of Alkanethiol Comparison with Benzotriazole

Self-assembled monolayers (SAMs) formed by the adsorption of alkanethiols onto copper is a simple method for producing coatings that can protect the metal against oxidation and corrosion. However, a contradiction regarding the influence of oxygen on the SAMs formation and barrier properties is still present. In this work the self-assembled monolayers of dodecanethiol were formed on the copper substrates from ethanolic solutions of dodecanethiol with and without the presence of dissolved oxygen. The protecting properties of monolayers, were studied in a sodium acetate solution with a pH of 6 using cyclic voltammetry and electrochemical impedance spectroscopy. The effect of exposing samples, prepared in the deoxygenated solutions, to air was also studied to examine the decrease in the protecting properties of the SAMs against copper corrosion. The protection efficiency of the dodecanethiol SAMs was compared with those of benzotriazole which is known as the best inhibitor for copper corrosion.

Modification of a Nitinol Surface by Phosphonate Self-Assembled Monolayers

Nitinol, as a shape memory alloy, is attractive material for medical implants and devices. Contrary to titanium, corrosion by releasing Ni2+ ions occurs during a long-term contact of Nitinol with (physiological) solutions containing Cl- ions. In order to develop chemically/electrochemically stable surfaces and interfaces, Nitinol was modified by self-assembled monolayers of dodecylphosphonate (-OH and –CH3 terminated) films, which were characterized by XPS, PM-IRRAS and contact angle measurements. Strongly bounded well-ordered films of high homogeneity and resistance were synthesized. An innovative method that allows in situ study of influence of thermal annealing, following SAM formation, on their protecting properties in simulated (physiological) solutions is presented. Changes of structural sensitive impedance parameters were correlated with the changes in the interfacial layer. Effective thermal annealing greatly enhances the quality of the self-assembled alkyl-phosphonate films, which behave as non-ideal dielectrics, i.e., the solid/liquid interfaces formed represent the blocking contact preventing charge-transfer reactions.