Ionic liquid ultrathin films at the surface of Cu(100) and Au(111).
Monolayer to multilayer ultrathin films of the ionic liquid (IL) 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)amide have been prepared on Au(111) and Cu(100) surfaces using physical vapor deposition. The ion-surface interactions are studied using a combination of scanning tunnel microscopy, as well as ultraviolet and x-ray photoemission spectroscopies. It is found that the IL does not decompose at the surface of the metals, and that the IL interaction with the Cu(100) surface is much stronger than with the Au(111) surface. As a consequence, STM imaging at room temperature results in more stable imaging at the monolayer coverage on Cu(100) than on Au(111), and work function measurements indicate a large interface dipole upon deposition of a monolayer of IL on Cu. Additional IL depositions on the two surfaces result in two distinct behaviors for the IL core levels: a gradual energy shift of the core levels on Au and a set of two well defined monolayer and multilayer core level components found at fixed energies on Cu, due to the formation of a tightly bound monolayer. Finally, it is proposed that the particularly strong cation-Cu interaction leads to stabilization of the anion and prevents its decomposition at the surface of Cu(100).
Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, New Jersey 08854, USA.
Aleksandra B
AB
Biedron
Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, New Jersey 08854, USA.
Eric L
EL
Garfunkel
Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, New Jersey 08854, USA.
Edward W
EW
Castner
Department of Physics and Astronomy and Laboratory for Surface Modification, Rutgers University, 136 Frelinghuysen Road, Piscataway, New Jersey 08854, USA.
Sylvie
S
Rangan