Orientation and mutual location of ions at the surface of ionic liquids.
The structure of the liquid-vacuum interface in room temperature ionic liquids (ILs) is investigated using angle-resolved X-ray photoelectron spectroscopy (ARXPS) and synchrotron X-ray photoelectron spectroscopy (SXPS). By varying the polar angle and comparing the results for the chosen ionic liquids, we identify the presence of a surface layer that is chemically different to the bulk. In particular, this layer: (i) is enriched by aliphatic carbon atoms from the saturated carbon chains of the anions and cations, and (ii) contains an unequal distribution of cations and anions in a direction normal to the surface. This unequal distribution creates a potential gradient which extends from the surface into the liquid. We show unequivocally that this layer is not due to the presence of impurities.
Lockett
Vera
V
Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095, Australia. Vera.Lockett@gmail.com
Sedev
Rossen
R
Harmer
Sarah
S
Ralston
John
J
Horne
Mike
M
Rodopoulos
Theo
T