Direct Observation of Supercritical Fluids in Nanospace by Means of High-Pressure NMR Spectroscopy

Abstract

High-pressure NMR spectroscopy enables us direct observation of fluids confined in nanospace. Since two distinct signals due to bulk and confined fluids are observed, the chemical shifts and the longitudinal relaxation times are obtained simultaneously. The temperature and pressure dependences of ¹²⁹Xe chemical shift of confined Xe strongly depend on the pore size and the surface properties of the matrices, while those of bulk Xe are approximately a linear function of density. The mean density in nanopore, which is estimated from the integrated signal intensities, accounts well for the ¹⁹F longitudinal relaxation times of confined SF₆ and CHF₃.