Terahertz spectroscopy of water in nonionic reverse micelles

The dynamics of water within a nanopool of a reverse micelle is heavily affected by the amphiphilic interface. In this work, the terahertz (THz) spectra of cyclohexane/Igepal/water nonionic reverse micelle mixture are measured by THz time-domain spectroscopy and analyzed with two Debye models and complex permittivity of background with volume ratios. Based on the fitted parameters of bulk and fast water, the molar concentration of all kinds of water molecules and hydration water molecule number per Igepal molecule are calculated. We find that slow hydration water has the highest proportion in water when the radius parameter ω0<10, while bulk water becomes the main component when ω0≥10. The feature radius ratio of nonhydrated and hydrated water to total water nanopool is roughly obtained from 0.39 to 0.85 with increasing ω0.