Applications of Long-Lived Singlet states in Diffusion NMR

Dr Monique Tourell
Postdoctoral Research Fellow, MR (Barth Group), Centre for Advanced Imaging
The University of Queensland, presents:

Applications of Long-Lived Singlet states in Diffusion NMR

Talk abstract: 

Diffusion-NMR is a well-established means of characterizing the structure and fluid transport properties of porous media. Morphological parameters, such as the pore-size distribution, porosity and tortuosity of the pore space can all be determined from measuring the restricted diffusion coefficient at “long” measurement times; i.e. when the displacement of the diffusing particles exceeds the characteristic length scale of the sample. In traditional MR diffusion experiments, the longitudinal relaxation time, T₁, sets an upper limit on the diffusion measurement time (a few seconds) and, consequently the length scales that can be investigated (~ 50 - 100 µm).

Singlet-assisted diffusion NMR (SAD-NMR) exploits long-lived singlet states to supersede this limit, allowing diffusion to be measured over several minutes [1]. SAD-NMR has recently been used to determine compartment sizes of up to 2 mm in diffusion-diffraction experiments [2] and measure the tortuosity in random packings of mono-sized spheres > 500 μm in diameter, with subsequent pore spaces > 150 μm [3]. Preliminary results of diffusion in 3D-printed scaffolds for tissue engineering, demonstrate the ability of SAD-NMR to characterize dynamic, anisotropic porous systems.

[1] Pileio, G et al. J.  Magn. Reson. 252 (2015)

[2] Pileio, G., and Ostrowska, S. J. Magn. Reson. 285 (2017)

[3] Tourell, M. C. et al. Phys. Chem. Chem. Phys. 20(20) (2018)