Organic adsorbates have higher affinities to fluorographene than to graphene

Abstract

The large surfaces of two-dimensional carbon-based materials, such as graphene and fluorographene, are exposed to analytes, impurities and other guest molecules, so an understanding of the strength and nature of the molecule–surface interaction is essential for their practical applications. Using inverse gas chromatography, we determined the isosteric adsorption enthalpies and entropies of six volatile organic molecules (benzene, toluene, cyclohexane, n-hexane, 1,4-dioxane, and nitromethane) to graphene and graphite fluoride powders. The adsorption entropies of the molecules ranged from −17 to −34cal/molK and the maximum adsorption-induced entropy loss occurred for nitromethane at the high-energy sites. The enthalpies of bulkier adsorbates were almost coverage-independent on both surfaces and ranged from −11 to −14kcal/mol. Despite the fact that fluorographene has lower surface energy than graphene and graphene represents an ideal surface for the π–π stacking, the adsorbates had lower adsorption enthalpies to fluorographene than to graphene by ∼9%. These findings imply that bulkier airbone organic contaminants readily adsorb to the investigated surfaces and can modify the measured surface properties.