Chemical properties of hydrogen-bonded organic bilayers fabricated via self-assembly of COOH-functionalised oligophenylthiols on Au substrates

Here we present an investigation of chemical reactions induced by exposing organic, hydrogen-bonded films prepared from COOH-terminated oligophenylthiol molecules on Au to solutions of different reactants. Our study includes reactions with acids (trifluoroacetic acid, TFA) and metal ions (potassium (K+)- and copper (Cu2+)-ions). On the basis of XPS measurements the film thickness and the elemental ratios of the elements involved in the process have been quantified. Our results reveal that treatment of the bilayers with trifluoroacetic acid results in the removal of the second layer and the formation of highly oriented, COOH-terminated monolayers. While the immersion of the bilayers in solutions containing Cu2+-ions leads to the removal of the second layer and the formation of a Cu2+-terminated monolayer-surface, potassium ions are incorporated in the bilayers by immersion into an ethanolic solution of potassium hydroxide. The reasons of these differences are related to the different coordination spheres of the ions and their compatibility with the structure of the self-assembled film.