1,4-Phenylene Diisocyanide (PDI) Interaction with Low-Coordinated Gold Sites: Dissociation and Adsorbate-Induced Restructuring

摘要

The adsorption of 1,4-phenylene diisocyanide (PDI) on sputter-roughened Au(111) and FeO(111)/Pt(111)-supported Au nanoparticles of different size has been studied by vibrational sum frequency generation (SFG) spectroscopy, scanning tunneling microscopy (STM), and temperature-programmed desorption (TPD). The special step geometry of sputter-roughened Au(111) facilitates the dissociation of PDI and the adsorbed cyanide is identified by SFG and TPD. During longer exposure, mobile Au–PDI complexes lead to structural rearrangements on the sputter-roughened Au(111) surface. Initially, small Au adatoms and Au nanoclusters are detached from the step edges, which agglomerate to larger islands and finally form nanoparticles in the pits of the sputter-roughened Au(111) surface. PDI dissociation and PDI-induced restructuring is much less pronounced on the oxide-supported Au nanoparticles. The adsorption mode of PDI strongly depends on the size and number density of Au nanoparticles. For small and isolated nanoparticles, PDI adsorbs in vertical geometry with only one isocyanide group interacting with the surface, whereas a flat adsorption geometry with both isocyanide groups interacting with the surface is predominant for larger Au nanoparticles.