An infrared study of the few-layer graphene | ionic liquid interface: Reintroduction of in situ electroreflectance spectroscopy

• Fabrication of high quality few-layer graphene electrodes is described.
• Ideal polarizability of an ionic liquid | electrode interface is established.
• In situ electroreflectance spectroscopy is extended to the mid-infrared region.
• Potential dependent reflective properties of graphene are discussed.
• Plasmonic spectral enhancement is shown for a pure carbon electrode.

A simple method of producing high quality few-layer graphene (FLG) electrodes (< 5 nm thick) has been described and the in situ infrared measurements of the FLG/1-ethyl-3-methylimidazolium tetrafluoroborate system have been reported. Ideal polarizability of the system has been established and three different spectral modes have been discussed in order to provide a varied understanding of both the electronic and structural effects at the interface. The method of in situ electroreflectance spectroscopy has been extended to the study of FLG | ionic liquid interface, providing new information about the method and possibilities for future studies of specific adsorption and electronic structure of the interface. Plasmonic enhancement of the spectra has been demonstrated, providing excellent opportunities for the study of the electric double layer and infrared sensors.