NMR relaxometry measurements were performed on a 20MHz
(0.47 T) spectrometer (Minispec PC-120, Bruker, Karlsruhe, Germany)
equipped with a thermostatted probe. The T2 relaxation
time was measured using the Carr–Purcell–Meiboom–Gill (CPMG)
sequence: 10,000 following echoes were recorded with a 90–180◦
pulse spacing of 1ms. The lengths of the 90◦ and 180◦ were 18 and
36s, respectively. Data were averaged over eight acquisitions and
a recycle delay was adjusted for each sample to avoid saturation.
The T1 relaxation time was measured using a fast saturation recovery
sequence (SR). One hundred points were acquired from 30ms
to the recovery delay of 10 s.