Balance of the interfacial interactions of 4,4′-bipyridine at Bi(111) surface

The data from impedance spectroscopy, electrochemical in situ scanning tunnelling microscopy (STM), surface-enhanced infrared adsorption spectroscopy (SEIRAS) and density functional theory (DFT) were measured, combined and analysed to describe the 4,4′-bipyridine (4,4′-BP) adsorption at Bi(111) single crystal electrode from weakly acidified 0.5 M and 0.05 M Na2SO4 aqueous solutions (pH ≈ 5.5÷6.0). The influence of electrode potential (E) on the adsorption kinetics of 4,4′-bipyridine on Bi(111) has been demonstrated. The capacitance pits in the differential capacitance versus E curve have been observed. The in situ STM data reveal two molecular patterns at different concentration of the supporting electrolyte. The stable adsorbate adlayer detectable by using the infrared spectroscopy method has been observed within E from -0.75 to -0.5 V (vs. Ag|AgCl sat. KCl). The results of DFT calculations and SEIRAS data have been used to establish the various possible orientations of the 4,4′-BP molecules at Bi(111) surface. The DFT investigation has been focused on the factors governing the self-assembly of 4,4′-BP, such as the intermolecular van der Walls attractions and interplay between the surface and the nanostructure lattices, both essential for the interfacial self-assembly.