Phase State of Polar Liquids in the Interplane Space of Graphite Oxide as Revealed by the Spin Probe Method

Behavior of polar liquids in the interplane space of graphite oxide (GO) and its related materials is of great interest due to the promising opportunity for using graphene oxide membranes as filters for liquid separation and purification. The main purpose of the present study is to investigate the phase state of water, ethanol, methanol, and acetonitrile in the interplane space of GO with different synthetic prehistory, namely, Brodie and Hummers materials. Molecular mobility data of the intercalated substances were obtained by analyzing the continuous-wave X-band electron paramagnetic resonance spectra of spin probe TEMPO located in the interplane space of GO. It was shown that all liquids under study can exist inside GO in the form of three fractions with different molecular mobilities. The relative amount of the most mobile liquid-like fraction in Hummers’ GO (H-GO) is several times larger than in Brodie’s GO (B-GO), and it reversibly increases with increasing temperature. An intriguing fact is that the molecular mobility of the liquid-like intercalated acetonitrile was found to be significantly lower than that of intercalated water and alcohols, whereas the viscosity of bulk acetonitrile was much lower than that of bulk water, methanol, and ethanol.