Abstract
In this work we present a detailed surface science characterization of l-aspartic acid adsorption on a Cu(110) surface. Aspartic acid is one of the main components of the tripeptide RGD (arginine–glycine–aspartic acid). We replaced the traditional sublimation method to obtain molecular films by dosing aspartic acid directly from an aqueous solution through an electrospray ionization (ESI) device. X-ray photoelectron spectroscopy (XPS) and polarization modulation reflection absorption infrared spectroscopy (PM-RAIRS) evidenced different adsorption states ranging from a submonolayer regime up to multilayers. Molecule–substrate interactions guide the creation of the pattern observed in the submonolayer, but molecule–molecule interactions are prevailing from a certain coverage stage, promoting the overlayer growth while leaving exposed areas of bare copper. This is evidenced by scanning tunneling microscopy (STM) results, showing that single aspartic acid molecules self-organize in a two-dimensional (2D) chiral network at low coverage and start originating new molecular layers even before a saturated monolayer has been reached.
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