Multiscale nuclear magnetic relaxation dispersion of complex liquids in bulk and confinement

Abstract

The nuclear magnetic relaxation dispersion (NMRD) technique consists of measurement of the magnetic-field dependence of the longitudinal nuclear-spin-lattice relaxation rate 1/T. Usually, the acquisition of the NMRD profiles is made using a fast field cycling (FFC) NMR technique that varies the magnetic field and explores a very large range of Larmor frequencies (10 kHz < ω/(2π) <40 MHz). This allows extensive explorations of the fluctuations to which nuclear spin relaxation is sensitive. The FFC technique thus offers opportunities on multiple scales of both time and distance for characterizing the molecular dynamics and transport properties of complex liquids in bulk or embedded in confined environments. This review presents the principles, theories and applications of NMRD for characterizing fundamental properties such as surface correlation times, diffusion coefficients and dynamical surface affinity (NMR wettability) for various confined liquids. The basic longitudinal and transverse relaxation equations are outlined for bulk liquids. The nuclear relaxation of a liquid confined in pores is considered in detail in order to find the biphasic fast exchange relations for a liquid at proximity of a solid surface. The physical-chemistry of liquids at solid surfaces induces striking differences between NMRD profiles of aprotic and protic (water) liquids embedded in calibrated porous disordered materials. A particular emphasis of this review concerns the extension of FFC NMR relaxation to industrial applications. For instance, it is shown that the FFC technique is sufficiently rapid for following the progressive setting of cement-based materials (plasters, cement pastes, concretes). The technique also allows studies of the dynamics of hydrocarbons in proximity of asphaltene nano-aggregates and macro-aggregates in heavy crude oils as a function of the concentration of asphaltenes. It also gives new information on the wettability of petroleum fluids (brine and oil) embedded in shale oil rocks. It is useful for understanding the relations and correlations between NMR relaxation times T and T, diffusion coefficients D, and viscosity η of heavy crude oils. This is of particular importance for interpreting T, T, 2D T-T and D-T correlation spectra that could be obtained down-hole, thus giving a valuable tool for investigating in situ the molecular dynamics of petroleum fluids. Another domain of interest concerns biological applications. This is of particular importance for studying the complex dynamical spectrum of a folded polymeric structure that may span many decades in frequency or time. A direct NMRD characterization of water diffusional dynamics is presented at the protein interface. NMR experiments using a shuttle technique give results well above the frequency range accessible via the FFC technique; examples of this show protein dynamics over a range from fast and localized motions to slow and delocalized collective motions involving the whole protein. This review ends by an interpretation of the origin of the proto...

Nuclear Magnetic Resonance with Fast Field-Cycling Setup: A Valid Tool for Soil Quality Investigation

“…The former represents the "hopping" time of water among surficial binding sites, while the latter (τ s ) is the time of residence of water on the surface of the porous medium [18]. The τ s τ m ratio is referred to as NMR surface wettability [60,61].…”

“…The model obtained by Korb coworkers [59] (Equation (13)) can be applied only under the hypothesis that all the parameters reported in relation (14) are known. This model has been designed for the investigations of cement-based materials, plaster pastes and petroleum fluids [61]. However, recently it was also used in a paper by Bubici et al [60] where biochar water NMR wettability has been investigated.…”

A Multi-Scale Study of Water Dynamics under Confinement, Exploiting Numerical Simulations in Relation to NMR Relaxometry, PGSE and NMR Micro-Imaging Experiments: An Application to the Clay/Water Interface

“…This situation differs strongly from the modulation of the dipolar coupling, which includes also a contribution from the separation between the pair in interacting dipolar nuclei; see Equation ( A9 ). As a consequence, molecular diffusion of the confined dipolar probes becomes an important source of NMR relaxation, inducing a slow modulation of the NMR dipolar coupling in the case of confined fluids [ 33 , 35 , 36 , 39 , 67 , 70 ]. However, because of the specific orientation of the water molecules confined in the interlamellar space between two clay platelets, the orientation fluctuations of the director of these confined water molecules is strongly restricted until their desorption.…”

“…The short times of mobility for the confined water molecules (from pico-seconds up to 100 nanoseconds) were easily probed by classical neutron scattering experiments (INS, QENS and neutron spin echo). Field-cycling NMR relaxometry is also a powerful tool to investigate the mobility of a large class of confined fluids [ 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ] by probing the frequency variation of the relaxation rate. However, that method becomes useless when the NMR relaxation times of the confined fluids become smaller than the time required to switch the strength of the magnetic field.…”

Sn‐Based Alloys Synthesized in an Ionic Liquid at Room Temperature: Cu6Sn5 as a Case Study

“…Indeed, the standard approach is to record relaxation dispersion profiles in the liquid state and to model the fluctuations of the dipolar interactions -source of relaxation -experienced by the nuclei. [18,20] In other words, the goal in liquid is to model the dynamics of the molecule: rotation, diffusion in the bulk, diffusion at the surface of the particles, etc. [18,[21][22][23][24][25] In the present situation, it can be tricky to distinguish between the case of the cation (or anion) diffusing on the surface of the raw nanoparticles of diameter D and the case of nanoparticles covered by a layer of anion (or cation) leading to a diameter of D + d (d being approximately 20 times smaller than D).…”