Raman spectroscopy as a tool for studying the graphene - ionic liquids interaction

Resumen del póster presentado al 4th Scientific Meeting of BNC-b Students (JPhD), celebrado en Bellatera (España) del 6 al 7 de junio de 2019.Understanding the interaction between graphene and ionic liquids is crucial, especially when working with electronic devices based on this bidimensional material, as they may have a wide range of applications. Regardless its importance, little is known about the graphene-liquid interface and its dependence with factors such as the graphene thickness, substrate or the pH of the solution in contact with the material. In this work, we fabricate CVD graphene electrodes supported on different substrates- of insulating and conductive nature -; which are submerged in ionic solutions of increasing KCl concentration. The monitoring of the influence of the [KCl] on single layer graphene was performed under acidic and basic conditions and with an applied potential or in open circuit configuration. Raman spectroscopy is a powerful tool for characterizing graphene, and in this work we show also its capability for addressing charge carriers in graphene; since the energy shift of the first order Raman mode of graphene, namely G band, can be related to changes in the graphene Fermi level. Our results reveal a distinctively behavior of graphene when supported on conductive and insulating substrates: while the G band shifts with increasing [KCl] when it is supported on an insulating substrate, no shift is observed when the graphene is placed on a conductive substrate. Results regarding the influence of the pH of the solution reveal opposite shifts of the G band under acidic and basic conditions. Finally, we observed that the amount of induced carriers is directly related to the number of graphene layers.Peer reviewe