Anion\nIntercalation into Graphite Drives Surface Wetting

Abstract

The unique layered\nstructure of graphite with its tunable interlayer\ndistance establishes almost ideal conditions for the accommodation\nof ions into its structure. The smooth and chemically inert nature\nof the graphite surface also means that it is an ideal substrate for\nelectrowetting. Here, we combine these two unique properties of this\nmaterial by demonstrating the significant effect of anion intercalation\non the electrowetting response of graphitic surfaces in contact with\nconcentrated aqueous and organic electrolytes as well as ionic liquids.\nThe structural changes during intercalation/deintercalation were probed\nusing in situ Raman spectroscopy, and the results were used to provide\ninsights into the influence of intercalation staging on the rate and\nreversibility of electrowetting. We show, by tuning the size of the\nintercalant and the stage of intercalation, that a fully reversible\nelectrowetting response can be attained. The approach is extended\nto the development of biphasic (oil/water) systems that exhibit a\nfully reproducible electrowetting response with a near-zero voltage\nthreshold and unprecedented contact angle variations of more than\n120° within a potential window of less than 2 V.