Ionic liquid ultrathin films at the surface of Cu(100) and Au(111)

Abstract

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).

Surface Confinement Induces the Formation of Solid-Like Insulating Ionic Liquid Nanostructures

“…Bulk ILs are typically electro-sprayed at these field values. 38,69 Several images of the same structure were collected, alternatively keeping the tip at a fixed increasing electrostatic potential with respect to the substrate, or grounded. The effects of the application of the electric field were monitored by imaging the sample in the best imaging conditions, i.e.…”

Time-dependent changes in the growth of ultrathin ionic liquid films on Ag(111)

“… 7 – 10 Since 2008, 11 in vacuo physical vapour deposition (PVD) of ultrathin IL films combined with angle-resolved X-ray photoelectron spectroscopy (ARXPS) has proven to be a well-established method to investigate IL/solid interactions, wetting behaviour, and IL film growth in the coverage range from less than a monolayer to several multilayers. 11 – 17 Some studies have shown ways to control the liquid/solid interface, e.g. through modification of the IL 12 , 15 , 18 or the solid surface, 13 , 19 or simply by variation of the temperature of the support.…”

“… 14 , 20 On the herringbone-reconstructed Au(111) surface, the formation of the IL/solid interface in the sub-monolayer range, and the growth mode of subsequently deposited IL multilayers at RT were studied in great detail by ARXPS for two related ILs. 12 , 17 The first was 1,3-dimethyl imidazolium bis[(trifluoromethyl)sulfonyl]-imide ([C 1 C 1 Im][Tf 2 N]), that is, an IL with two methyl groups at the imidazolium cation, and the second was 1-methyl-3-octyl imidazolium bis[(trifluoromethyl)sulfonyl]-imide ([C 8 C 1 Im][Tf 2 N]), that is, the same IL with one octyl chain instead of one of the methyl groups; see Fig. 1 .…”

Structure formation and surface chemistry of ionic liquids on model electrode surfaces—Model studies for the electrode | electrolyte interface in Li-ion batteries

“…[TFSI] --based ILs with different cations with single crystalline surfaces has been investigated (ex situ) under UHV conditions [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] and in-situ in an electrochemical environment. [32][33][34][50][51][52][53][54][55] For example, employing angle-resolved X-ray photoelectron spectroscopy (ARXPS), Cremer ("checkerboard") arrangement on Au(111), with both anions and cations bound directly to the surface.…”