Harshal Mungse1 Takashi Ichii1 Toru Utsunomiya1 Hiroyuki Sugimura1

1, Kyoto University, Kyoto, , Japan

Frequency modulation atomic force microscopy (FM-AFM) is found to be promising tool for atomic resolution imaging and solid/liquid interface study. Also it could be used in different environmental conditions such as vacuum, atmospheric air, and liquids. Hence this technique has great impact in the various research fields like surface science and nanotechnology. Ionic liquids (ILs), composed of organic cations and weakly coordinating organic/inorganic anions, exhibit remarkable and tunable physicochemical characteristics such as negligible vapor pressure, non flammability, wide electrochemical window, high thermal stability, broad liquid range, and excellent conductivity, which promises their potential for large range of applications like batteries, chemical reactions and processes, solar cells, catalysis, lubricants, etc. When IL is in contact with solid substrate, the properties of IL at the interface are different as compare to bulk IL hence to determine their interfacial behavior is so important for scientific and technological processes. Also to enhance the efficiency and selectivity of particular process the detailed knowledge of IL / solid interface is needed. Therefore, the investigation of IL/solid interfaces is very important study for not only in fundamental understanding point of view but also the industrial applications purpose.
Herein, we demonstrate the atomic resolution imaging of KBr (100) and KBr (111) crystal surface in 1-butyl-3-methylimidazolium hexafluorophosphate (BMI-PF6) IL by using FM-AFM with force sensor based on quartz tuning fork [1]. The (100) and (111) surfaces of alkali halides including KBr possess different surface properties because the (100) surface is electrically neutral while the (111) consists only of either cations or anions. Thus it is an interesting task to understand effect of surface nature on IL/KBr interface. The (100) sample was obtained just by cleavage and the (111) sample was fabricated by IL-assisted vacuum deposition [2]. Atomic resolution images of KBr (100) and (111) surfaces which were obtained in the IL reveals that, atomic arrangement of (111) surface was slightly distorted compared to the (100) surface, which would be because of its high surface energy and surface rearrangement. Furthermore, we demonstrate how IL molecules exist on two dimensional graphene nanosheets and at their interface. The detailed study will be discussed during presentation.

[1] T. Ichii, M. Negami, and H. Sugimura, J. Phys. Chem. C. 118, 26803 (2014).
[2] M. Yamauchi, S. Maruyama, N. Ohashi, K. Toyabe, and Y. Matsumoto, CrystEngComm, 18 3399 (2016).