Interface controls spontaneous crystallization in thin films of the ionic liquid [C₂C₁Im][OTf] on atomically clean Pd(111).
A total of 5-30 monolayer thick films of the ionic liquid (IL) [C2C1Im][OTf] were vaporized in vacuo onto an atomically clean Pd(111) single crystal surface at 220 K. Time- and temperature-resolved infrared reflection-absorption spectroscopy reveals growth, interactions with the metallic support, and the macroscopic phase behavior of the layer. At 220 K, the IL layer first grows in the form of a glassy phase. Crystallization of the IL was witnessed above a critical thickness of about 10 monolayers. On the basis of the known bulk crystal structure of the IL, we suggest the formation of well-oriented checkerboard-like crystalline film structures on the surface. The preferential orientation manifested by the crystal phase with regard to the macroscopic metallic surface is attributed to strong interactions between anionic headgroups and the metal.
Lehrstuhl für Physikalische Chemie II, ‡Lehrstuhl für Chemische Reaktionstechnik, and §Erlangen Catalysis Resource Center, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) , Egerlandstraße 3, 91058 Erlangen, Germany.
Stefan
S
Schernich
Valentin
V
Wagner
Nicola
N
Taccardi
Peter
P
Wasserscheid
Mathias
M
Laurin
Jörg
J
Libuda