Fig. 5.

¹³C PFG NMR diffusion measurements for ¹³CO at 15 bar and 25 °C in the absence (bulk gas phase, left panel) and presence of npAu (right panel). In the latter case an NMR tube was filled with npAu discs (diameter: 3 mm, thickness: 200 microns). The signal attenuation Ψ was measured for 3 different diffusion times t in both cases: 6, 10 and 30 ms. In the presence of npAu, the curves show a biexponential behavior for 6 and 10 ms. By fitting both regimes, the diffusion coefficients D₁ and D₂ inside and outside npAu’s pore system could be determined (see Table 1)