# Advanced Interpretation of Field Cycling NMR Relaxometry Dispersion Profiles From Hard and Soft Materials

## TL;DR

This paper reviews how fast field-cycling NMR can be used with the 3-Tau model to study the properties of both soft and hard materials through their relaxation profiles.

## Contribution

The paper introduces the 3-Tau model as a powerful tool for interpreting NMR dispersion profiles across diverse materials.

## Key findings

- The 3-Tau model can fit NMRD profiles from various materials and yield physically meaningful parameters.
- The model provides insights into surface chemistry, pore size, and biomarkers for diseases like sickle cell anemia.
- Changes in physical quantities from NMRD profiles can indicate curing rates and disease markers.

## Abstract

A fast field‐cycling NMR (FFC NMR) experiment measures the longitudinal (spin–lattice) relaxation rate as a function of applied magnetic field to yield a relaxation rate dispersion curve,
R1f, where
f is the proton Larmor frequency. The
R1f dispersions, or NMRD profiles, are exquisitely sensitive to the relative dynamics of proton spins across timescales in the range 10−9–10−4 s. These timescales span the translational and rotational dynamics of proton‐bearing fluids to dynamics at the surfaces of solids, soft material and macromolecules. FFC NMR is useful for studying fluid‐filled rocks and soils, porous silica and cementitious material, polymer systems, foodstuffs, protein systems, biological tissues and biofluids. The NMRD profiles are rich with information, but interpretation is challenging. A parametrized relaxometry model must generate an NMRD profile
R1f that can be fit to experimental data across three to four orders of magnitude of frequency. The 3‐Tau model has emerged as a model capable of fitting NMRD profiles from a broad range of material types yielding physically meaningful parameters. This review article demonstrates power of the FFC NMR experiment interpreted using the 3‐Tau model to reveal properties of hydrated hard and soft material.

This review demonstrates that NMR dispersion profiles from fast field cycling NMR relaxometry can be interpreted with the 3‐Tau model for a broad spectrum of soft and hard materials. Meaningful physical quantities provide insight into surface chemistry, bound water density, pore size, aqueous or solid iron (III) density and the free water diffusion coefficient. We show that changes in the physical quantities can reveal curing rates and biomarkers for tumours and sickle cell anaemia.