Dynamics of Water Intercalated in Graphite Oxide

Intercalated water in graphite oxide (GO) was investigated by using different techniques: broadband dielectric spectroscopy (BDS) (10(-2)-10(9) Hz; 140-300 K), differential scanning calorimetry, X-ray diffraction, and attenuated total reflection geometry in Fourier transform infrared spectroscopy (ATR-FTIR). We have studied the water concentration (c(w)) region from 0 wt % (anhydrous GO) up to 25 wt % since in this range the water crystallization is avoidable. The interlayer distance during hydration increases from 5.67 to 8 angstrom which corresponds to the uptake of a water monolayer in the interlayer space of GO. A clear relaxation due to water molecule reorientation is seen by BDS. The rotational water dynamics is dependent on the hydration level. At high water concentration (c(w) > 15 wt %), water-water interactions seem to dominate the dielectric response. This result is also compatible with those from FTIR and X-ray measurements. In this water concentration region, a slight dynamical crossover in the temperature dependence of the relaxation times is observed. We show that the crossover temperature on this system (T-cross) depends on the confinement size.