Ultrafast Laplace NMR with hyperpolarized xenon gas

Abstract

Laplace NMR, consisting of diffusion and relaxation experiments, provides detailed information about dynamics of fluids in porous materials. Recently, we showed that two-dimensional Laplace NMR experiments can be carried out with a single scan based on spatial encoding. The method shortens the experiment time by one to three orders of magnitude, and therefore it is called ultrafast Laplace NMR. Furthermore, the singlescan approach facilitates significantly the use of nuclear spin hyperpolarization for boosting the sensitivity of the experiment, because a laborious hyperpolarization procedure does not need to be repeated. Here, we push the limits of the ultrafast Laplace NMR method by applying it, for the first time, in the investigation of a gas phase substance, namely hyperpolarized xenon gas. We show that, regardless of the fast diffusion of gas, layer-like spatial encoding is feasible, and an ultrafast diffusion T2 relaxation correlation experiment reveals significantly different signals of free gas and gas adsorbed in a mesoporous controlled pore glass (CPG). The observed diffusion coefficients are many orders of magnitude larger than those detected earlier from liquid phase substances, emphasizing the extended application range of the method. The challenges in the methodology, caused by the fast diffusion, are also discussed.

Hyperpolarized Laplace NMR

“…The spatial encoding has been also exploited in 1D LNMR experiments, as well as in correlating T 1 relaxation or diffusion parameters with spectroscopic data . Recently, it has been applied also in two‐dimensional LNMR . This so‐called ultrafast LNMR method shortens the experiment time by one to three orders of magnitude as compared with corresponding conventional LNMR experiments.…”

“…On the other hand, the spatial encoding slightly lowers the sensitivity of the ultrafast LNMR experiment as compared with the conventional experiment . However, similarly to ultrafast NMR spectroscopy, ultrafast LNMR allows the use of nuclear spin hyperpolarization to increase the sensitivity of experiment, leading to the overall sensitivity enhancement of several orders of magnitude …”

“…Ultrafast T 1 – T 2 and D – T 2 experiments have been used for the determination of T 2 relaxation times and diffusion coefficients of liquids and gases, distinguishing physical environments of liquids and gases in porous materials and resolving alkenes with different chain lengths . Several hyperpolarization methods, including dissolution DNP, parahydrogen‐induced polarization, and spin‐exchange optical pumping, have been combined with ultrafast LNMR to boost the experimental sensitivity. Ultrafast LNMR has been shown to be feasible also with low‐field, single‐sided NMR instruments with very inhomogeneous magnetic field .…”

Ultrafast Laplace NMR to study metal–ligand interactions in reversible polarisation transfer from parahydrogen

“…This has been used to develop ultrafast Laplace NMR experiments [17][18][19] which reduce the experiment time by one to four orders of magnitude compared to traditional approaches. 2 Consequently, ultrafast LNMR has been used to study molecular dynamics in a range of chemical systems including porous materials, 17,20 cellular metabolites, 21 and surfactant aggregates. 22 Nevertheless, these measurements can be limited by the low sensitivity of MR which is derived from perturbations of very small population differences across closely spaced nuclear spin energy levels.…”

Probing molecular dynamics with hyperpolarized ultrafast Laplace NMR using a low-field, single-sided magnet

“…Recently, it has been shown that multidimensional LNMR data can be measured in a single scan using a high-field spectrometer. 40 – 42 Similar to ultrafast NMR spectroscopy 3 and to 1D diffusion 43 – 46 and relaxation experiments, 47 , 48 this so-called ultrafast LNMR method is based on spatial encoding of multidimensional data. We have previously shown that ultrafast LNMR is compatible with single-sided NMR, by exploiting the field gradient intrinsic to single-sided magnets for spatial encoding.…”