Proton Nuclear Magnetic Resonance Relaxation Research Articles

Elucidation of Liquid Structures and Transport Properties of Highly Concentrated LiN(SO2F)2/Ethylene Carbonate Electrolytes

The Li+ conduction mechanism in highly concentrated ethylene carbonate (EC) solution of lithium bis(fluorosulfonyl)amide (LiFSA) was studied based on the measurements of thermal properties, density, viscosity, ionic conductivity, self-diffusion coefficients, Raman spectra, and proton nuclear magnetic resonance relaxation time. The compositions of EC and LiFSA were varied from dilute to concentrated states ([EC]/[LiFSA] = 9.2–0.80). For compositions of [EC]/[LiFSA] ≤ 1.5, the free solvents decrease, and contact ion pairs and aggregates become dominant, causing a significant change in the transport properties. Faster diffusion of Li+ compared with solvent (Li+ hopping conduction) was observed when the molar composition of [EC]/[LiFSA] ≤ 1.0 as in the case of sulfolane.

Physicochemical characterization of green sodium oleate-based formulations. Part 3. Molecular and collective dynamics in rodlike and wormlike micelles by proton nuclear magnetic resonance relaxation

HypothesisSodium oleate (NaOL) self-aggregates in water forming rodlike micelles with different length depending on NaOL concentration; when KCl is added wormlike micelles form, which entangle giving rise to a viscoelastic dispersion. It is expected that aggregates with different size and shape exhibit different internal and overall molecular motions and collective dynamics. ExperimentsTwo low viscosity NaOL/water and two viscoelastic NaOL/KCl/water formulations with different NaOL concentration (0.23 and 0.43 M) were investigated by 1H fast field cycling NMR relaxometry over broad temperature and Larmor frequency ranges, after a first screening by 1H and 13C NMR spectroscopy at high frequency. FindingsThe analysis of the collected data indicated that fast conformational isomerization and rotation of NaOL about its long molecular axis and lateral diffusion of NaOL around the axis of the cylindrical aggregates are slightly affected by the aggregate shape and length. On the other hand, fluctuations of the local order director are quite different in the fluid and viscoelastic systems, reflecting the shape and size of the aggregates. Quantitative information was obtained on activation energy for fast internal and overall motions, correlation times and activation energy for lateral diffusion, and coherence length for collective order fluctuations.

Fast field cycling 1H-NMR relaxation properties during convective dehydration of mango fruits

The cultivation of mango fruits is increasing in the Mediterranean areas, including Italy, where a niche production has developed in the Tyrrhenian coast of Sicily. These fruits are rich in antioxidant substances, presenting a pleasant taste and aroma, fundamental qualities for the sensory acceptance of consumers. However, being climacteric fruits, mangoes are highly perishable, due to their rapid ripening after harvesting. As a result, large amounts of mangoes are lost annually in many areas of the world. In order to prevent this, the drying technique is widely used. It allows to lengthen the shelf-life of the fruits. In order to optimize this process, it is necessary to deepen the knowledge on the drying effects on the structure and mobility of the residual water in the fruit. The objective of this paper is to describe the effects of convective drying at different temperatures on the Fast Field Cycling Proton Nuclear Magnetic Resonance (FFC 1H-NMR) relaxation properties, water activity and shrinkage in Keitt mango fruits. The FFC 1H-NMR relaxometry investigations on mango fruits revealed that the convective drying lead not only to a reduction in the overall water content within the mango tissues, but also to a progressive immobilization of the same water, depending on the temperature. From a qualitative and microbiological point of view, the results may indicate that the measure of more immobilised water in the dried fruits can be useful to predict their shelf-life.

Analysis of Extra Virgin Olive Oils from Two Italian Regions by Means of Proton Nuclear Magnetic Resonance Relaxation and Relaxometry Measurements.

The interest in development of new non-destructive methods for characterization of extra virgin olive oils (EVOOs) has been increasing in the recent years. Among different experimental techniques, nuclear magnetic resonance (NMR) relaxation measurements are very promising in the field of food characterization and authentication. In this study, we focused on relaxation times T1 and T2 measured at different magnetic field strengths (namely, 2, 100, and 400 MHz) and 1H NMR T1 relaxometry dispersions directly on olive oil samples without any chemical/physical treatments. A large set of EVOO samples produced in two regions of Italy, Tuscany and Apulia, were investigated by means of 1H NMR relaxation techniques. The relaxation studies reported here show several common features between the two sets of EVOO samples, thus indicating that relaxation properties, namely, the ranges of values of T1 and T2 at 2 and 100 MHz, are characteristic of EVOOs, independently from the cultivars, climate, and geographic origin. This is a promising result in view of quality control and monitoring.

Simulation-Based Sensitivity Analysis of Regularization Parameters for Robust Reconstruction of Complex Material’s T1 − T21H LF-NMR Energy Relaxation Signals

We recently showed, in a simulation study using two artificial signals, that our PDCO (Primal Dual interior method for Convex Objectives) reconstruction algorithm can be efficiently used for the reconstruction of low-field proton nuclear magnetic resonance (1H LF-NMR) relaxation signals into T1 (spin–lattice) vs. T2 (spin–spin) time 2D graphs of a material’s composition. In the present study, for highly complex materials, we demonstrate the PDCO’s reconstruction efficacy for a much wider range of simulated signals with higher complexity and different signal-to-noise ratios (SNR) taken from actual reconstructed 1H LF-NMR spectroscopy signals of oleic acid and cattle manure. The optimal regularization parameters of the PDCO’s reconstructing algorithm were identified for this large range of simulated LF-NMR signals and noise values. These simulated compact graphical and numerical representations demonstrated 1H LF-NMR relaxation signals of complex materials can be accurately reconstructed into T1 − T2 time graphs of a material’s chemical and morphology. The present study further confirmed that an optimal single set of regulatory parameters for the data reconstruction algorithms could be used for different materials or different batches of the same material.

NMR and μ+SR detection of unconventional spin dynamics in Er(trensal) and Dy(trensal) molecular magnets

Measurements of proton Nuclear Magnetic Resonance (1H NMR) spectra and relaxation and of Muon Spin Relaxation ($\mu^{+}$SR) have been performed as a function of temperature and external magnetic field on two isostructural lanthanide complexes, Er(trensal) and Dy(trensal) featuring crystallographically imposed trigonal symmetry. Both the nuclear 1/T1 and muon $\lambda$ longitudinal relaxation rates, LRR, exhibit a peak for temperatures T lower than 30K, associated to the slowing down of the spin dynamics, and the width of the NMR absorption spectra starts to increase significantly at T ca. 50K, a temperature sizably higher than the one of the LRR peaks. The LRR peaks have a field and temperature dependence different from those previously reported for all Molecular Nanomagnets. They do not follow the Bloembergen-Purcell-Pound scaling of the amplitude and position in temperature and field and thus cannot be explained in terms of a single dominating correlation time $\tau$c determined by the spin slowing down at low temperature. Further, for T lower than 50K the spectral width does not follow the temperature behavior of the magnetic susceptibility chi. We suggest, using simple qualitative considerations, that the observed behavior is due to a combination of two different relaxation processes characterized by the correlation times $\tau$LT and $\tau$HT, dominating for T lower than 30K and T higher than 50K, respectively. Finally, the observed flattening of LRR for T lower than 5K is suggested to have a quantum origin.

Nuclear magnetic relaxation and diffusion study of the ionic liquids 1-ethyl- and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide confined in porous glass.

The molecular dynamics of the room-temperature ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (Bmim Tf2N) confined in porous glass is studied by nuclear magnetic resonance (NMR) relaxometry and diffusometry and is compared with the bulk dynamics over a wide temperature range. The molecular reorientation processes for anions and cations alike are found to be significantly affected by the presence of the glass interface at high temperatures. In this respect, the ionic liquid behaves similarly to polar liquids where proton NMR relaxation is governed by reorientations mediated by translational displacements (RMTDs). This process becomes less significant towards lower temperatures when the characteristic translational correlation times of the ions approach a timescale comparable with those of the RMTD process, and the relaxation dispersions in bulk and in confinement become similar below a temperature corresponding to about 1.2Tg , a value where the onset of dynamic heterogeneity has been observed before. The self-diffusion coefficient, on the other hand, is found to be strongly reduced than the bulk within the accessible temperature range of 248K and above and is significantly slower than expected from the tortuosity effect, suggesting that ion-surface interactions affect the macroscopic properties.

Multidimensional Proton Nuclear Magnetic Resonance Relaxation Morphological and Chemical Spectrum Graphics for Monitoring and Characterization of Polyunsaturated Fatty‐Acid Oxidation

AbstractPolyunsaturated fatty acids (PUFA) are components of many commercial products such as edible oils, foods, cosmetics, medication, and in biological systems such as phospholipids of cellular membranes. Although PUFA aggregates are important functional components, they are also related to system degradation, because PUFA are susceptible to oxidation via their multiple double bonds and allylic carbons. Current technologies are not effective in characterizing the morphological and chemical structural domains of saturated, monounsaturated fatty acids (MUFA) and PUFA materials, or how the morphological structures of fatty acids, at the mesomolecular, nanomolecular, and molecular levels, affect their oxidation mechanisms. In this article, the 1H low‐field (LF) NMR energy relaxation time technology is proposed as a tool to analyze PUFA oils undergoing thermal oxidation. This technology generates two‐dimensional (2D) chemical and morphological spectra using a primal‐dual interior method for the convex objectives (PDCO) optimization solver for computational processing of the energy relaxation time signals T1 (spin–lattice) and T2 (spin–spin). The 2D graphical maps of T1 vs. T2 generated for butter, rapeseed oil, soybean oil, and linseed oil show that the different degrees of unsaturation of fatty‐acid oils affect their chemical and morphological domains, which influences their oxidative propensity. The technology of the 1H LF‐NMR energy relaxation time proved to be an effective tool to characterize and monitor PUFA oxidation.

Non-Destructive Quantification of Lipid and Water in Fresh Tuna Meat by a Single-Sided Nuclear Magnetic Resonance Scanner

ABSTRACTA portable single-sided nuclear magnetic resonance (NMR) surface scanner was applied to the non-destructive quantification of lipid and water in meat block samples of farmed bluefin tuna (Thunnus thynnus). Proton NMR relaxation measurements of the fresh meat block samples were performed at room temperature in a laboratory. Totally, 34 tuna meat block samples were measured; the required measurement time was approximately 70 s for each sample. The results yielded estimation errors of 3.7 and 2.7 g/100 g for the lipid and water weight fractions, respectively. The investigation depth of the sensor was as deep as 3 cm, which enables the non-destructive quantification of the meat of the intact whole tuna beneath the thick scales, skin, and subcutaneous fat in markets and seafood factories.

The interactions between wheat starch and Mesona chinensis polysaccharide: A study using solid-state NMR

The interaction between wheat starch and Mesona chinensis polysaccharide (MCP) was found to change the molecular mobility of the water and carbohydrate populations in starch-MCP gels, when measured using proton and carbon nuclear magnetic resonance relaxation methods. The starch and MCP mobilities appeared similar at a micron scale. However, at a distance of less than 5 nm could they be detected as having separate mobility states, indicating close interaction between the starch and MCP. The carbon-6 of the starch glucan monomer was observed to have the largest mobility change in the presence of MCP. Two mobility populations of carbon-6 were observed, possibly corresponding to the carbon-6 in the linear chains of both amylose and amylopectin, and another to the carbon-6 involved in the branching of amylopectin. The change in the mobility of one of the carbon-6 populations indicates an increase in molecular freedom of movement in the presence of MCP.

Direct Relationship Between Interfacial Microstructure and Confined Crystallization in Poly(Ethylene Oxide)/Silica Composites: The Study of Polymer Molecular Weight Effects

ABSTRACTWith particular focus on the characterization of polymer–nanoparticle interaction, the effects of polymer molecular weight (Mn) on confined crystallization of the interfacial region in poly(ethylene oxide) (PEO)/silica (SiO2) composites were investigated, employing differential scanning calorimetry, dynamic light scattering, and proton nuclear magnetic resonance relaxation techniques. Dependence of crystallization on Mn in PEO/SiO2 composites is found to be closely related to the microstructure changes in adsorbed polymer. PEO adsorbs in a manner that produces a tightly bound layer (amorphous) with constant thickness, independent of Mn, and creates a loosely bound layer with flattened structure for short PEO chains but coiled conformation for long chains. The contribution of this Mn‐dependent layer to crystallization grows with Mn, showing a transition from non‐crystalline phase to the formation of a crystallization peak (−25 to −33 °C), and then to crystallization together with non‐adsorbed PEO. The comprehensive description of the interfacial region should be a helpful tool in the preparation and modification of polymer nanocomposites. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1608–1616

Peculiarities of tissue water fractional composition in case of experimental whole-body hyperthermia

The present study, using proton nuclear magnetic resonance relaxation (NMR) method, was undertaken to compare the water fractional composition in nature tissues (group 1) with those damaged by experimental whole-body hyperthermia (group 2). We measured longitudinal or “spin-lattice” (T1) and transverse or “spin-spin” (T2) relaxation times of protons of tissues (brain, the atria of the heart, the kidneys and the renal cortex) from adult Wistar rats. The differences in T1, T2 and percentage of the intra- and extracellular water between group 1 and 2 were studied to help understand how the water moves in tissues at hyperthermia. The results of this study and the literature data allow to make conclusions about tissue water fractional composition in case of experimental whole-body hyperthermia: (1) fractional composition of water and the distribution of intra- and extracellular fluid in the tissue of the atria of the heart did not change (T1 and T2 relaxation times remained unchanged); (2) the crystalline water fraction increased in brain (longer T1 relaxation rate and shorter T2 relaxation rate). This is obstructing the exchange of protons between free and bound water in brain. Thus, loss of water by brain cells is prevented. The distribution between intra- and extracellular fluid in brain remained unchanged; (3) fraction of free water increased in renal tissue (simultaneous longer T1 and T2 relaxation rates) by reducing the volume of extracellular fluid; (4) thick hydration layer of water (longer T1 relaxation rate, T2 remained unchanged) was formed in the extracellular fluid of renal cortex. This water layer is formed around the sodium ions which concentration is increased in renal cortex tissue of rats from group 2. Аs a result, the amount of fluid secreted by kidneys is reduced, i.e. there is a retention of water in the body. The relevance of our research for the understanding of high temperatures’ adaptation mechanisms is discussed in this paper.

Surface Relaxivity of Cement Hydrates

Numerous aspects of the physical chemistry of colloidal systems are conditioned by the solid–liquid interface, and this is also the case for hydrated cement systems. Estimating the surface area is thus essential for studying the kinetics of cement hydration and admixture adsorption. Proton nuclear magnetic resonance (NMR) relaxation techniques have already proven useful for this objective, but, for hydrating cements at early ages, it is necessary to know the surface relaxivities of all of the individual phases present to correctly interpret the relaxation data. This paper reports the results of a comparison of NMR relaxometry and Brunauer–Emmett–Teller gas adsorption measurements on various synthetic cement hydrates with the aim of evaluating their individual surface relaxivities. We observe that all of the tested phases (anhydrous and hydrated) except for ettringite have surface relaxivities typical of common natural rocks. We also find that the amount of paramagnetic species as measured by electron spin...

Properties of polycarbonate containing BaTiO3 nanoparticles

The real part of the relative permittivity, ε′, and dielectric loss, tan δ, have been determined at audio frequencies at temperatures from about 5 K to 350 K for nano-composites composed of BaTiO3 nanoparticles and polycarbonate. The room temperature breakdown strength was also measured and thermal analysis, nuclear magnetic resonance and scanning electron microscopy studies were carried out. For some films the nanoparticles were surface-treated (STNP) while for others they were not (UNP). For concentrations of UNP greater than about 3.4 vol. %, ε′ is much larger than expected on the basis of laws of mixing. On the other hand, ε′ for materials made using STNP is well-behaved. Correspondingly, increased loss (ε″ or tan δ) in the vicinity of room temperature is observed for the materials made from UNP. The anomalously large values of relative permittivity and increased loss are attributed to the presence of large aggregates in the materials made using the UNP. For both UNP-and STNP-based materials, the breakdown strength is found to decrease as nanoparticle concentration increases. The breakdown strength for the materials made using STNP is found to be larger for all concentrations than for those containing UNP despite the presence of large aggregates in some of the STNP-based materials. This shows that breakdown is strongly affected by the nanoparticle surfaces and/or the interface layer. It is also found that the breakdown strength for materials made using UNP increases as particle size increases. Finally, variable temperature and pressure proton nuclear magnetic resonance relaxation measurements were made to assess the effect of nanoparticle inclusion on polymer motion, and the effects were found to be very minor.

Low temperature spin dynamics in Cr7Ni-Cu-Cr7Ni coupled molecular rings

Proton Nuclear Magnetic Resonance (NMR) relaxation measurements have been performed down to very low temperature (50 mK) to determine the effect of coupling two Cr7Ni molecular rings via a Cu2+ ion. No difference in the spin dynamics was found from nuclear spin lattice relaxation down to 1.5 K. At lower temperature, the 1H-NMR line broadens dramatically indicating spin freezing. From the plot of the line width vs. magnetization, it is found that the freezing temperature is higher (260 mK) in the coupled ring with respect to the single Cr7Ni ring (140 mK).

Nanosized solvent superstructures in ultramolecular aqueous dilutions: twenty years' research using water proton NMR relaxation

proton nuclear magnetic resonance (NMR) relaxation times T1, T2, T1/T2 are sensitive to motion and organization of water molecules. Especially, increase in T1/T2 reflects a higher degree of structuring. My purpose was to look at physical changes in water in ultrahigh aqueous dilutions. Samples were prepared by iterative centesimal (c) dilution with vigorous agitation, ranging between 3c and 24c (Avogadro limit 12c). Solutes were silica-lactose, histamine, manganese-lactose. Solvents were water, NaCl 0.15 M or LiCl 0.15 M. Solvents underwent strictly similar, simultaneous dilution/agitation, for each level of dilution, as controls. NMR relaxation was studied within 0.02-20 MHz. No changes were observed in controls. Increasing T1 and T1/T2 were found in dilutions, which persisted beyond 9c (manganese-lactose), 10c (histamine) and 12c (silica-lactose). For silica-lactose in LiCl, continuous decrease in T2 with increase in T1/T2 within the 12c-24c range indicated growing structuring of water despite absence of the initial solute. All changes vanished after heating/cooling. These findings were interpreted in terms of nanosized (>4-nm) supramolecular structures involving water, nanobubbles and ions, if any. Additional study of low dilutions of silica-lactose revealed increased T2 and decreased T1/T2 compared to solvent, within the 10(-3)-10(-6) range, reflecting transient solvent destructuring. This could explain findings at high dilution. Proton NMR relaxation demonstrated modifications of the solvent throughout the low to ultramolecular range of dilution. The findings suggested the existence of superstructures that originate stereospecifically around the solute after an initial destructuring of the solvent, developing more upon dilution and persisting beyond 12c.

Effects of nanobubbles on the physicochemical properties of water: The basis for peculiar properties of water containing nanobubbles

The mechanism with which nanobubbles (NBs) promote physiological activity is investigated using germination tests and nuclear magnetic resonance (NMR) relaxation-time measurements. The germination rates of barley seeds dipped in water containing NBs (bubbles formed from gas mixtures of nitrogen and pure air) were 15–25 percentage points greater than those of the seed dipped in distilled water with the same concentration of dissolved oxygen (DO). In addition, the proton NMR relaxation time, T2, of water containing NBs (bubbles formed from nitrogen) was measured and compared with the T2 of control water (water without bubbles or DO). After T2 measurements, both water containing NBs and control water were degassed, and the T2 values were subsequently measured again to examine its changes before and after degassing. Water containing NBs exhibited T2 values that were statistically longer than those of control water. After degassing, the T2 values of water containing NBs decreased, which indicated that the decrease in the NB number density shortened T2. On the basis of these results, we concluded that the number of NBs was positively correlated with the T2 value of the water. The increase in T2 with the generation of NBs indicated that the mobility of the water molecules increased; consequently, a longer time was required to reach the equilibrium state through spin–spin relaxation. These observations indicated that the NBs in water could influence the physical properties of water and that it could also be used to verify the stability of NBs in the water.

Dynamics of pistachio oils by proton nuclear magnetic resonance relaxation dispersion

A number of pistachio oils were selected in order to test the efficacy of nuclear magnetic resonance relaxation dispersion (NMRD) technique in the evaluation of differences among oils (1) obtained from seeds subjected to different thermal desiccation processes, (2) retrieved from seeds belonging to the same cultivar grown in different geographical areas and (3) produced by using seed cultivars sampled in the same geographical region. NMRD measures relaxation rate values which are related to the dynamics of the chemical components of complex food systems. Results not only allowed to relate kinematic viscosity to relaxometry parameters but also were successful in the differentiation among the aforementioned oils. In fact, from the one hand, the larger the kinematic viscosity, the faster the rotational motions appeared as compared to the translational ones. On the other hand, relaxation rate curves (NMRD) varied according to the oxidative stresses and chemical composition of each sample. The present study showed for the first time that NMRD is a very promising technique for quick evaluations of pistachio oil quality without the need for time-consuming chemical manipulations.

Soy addition improves the texture of microwavable par-baked pocket-type flat doughs

Microwavable baked goods are used frequently by the food industry to enrobe meat, vegetable, and sweet items for convenient meal delivery but suffer from poor texture upon microwave re-heating. Par-baking the dough prior to the reheating stage provides an opportunity to supply fresh baked goods with a simple baking stage at retail locations. Nonetheless, reheating conditions signifi- cantly affect texture of reheated par-baked products, resulting in shrinkage, porosity reduction, and crust soft- ening. Appropriate formula modifications have been shown to reduce microwave-induced toughness of reheated bread by virtue of water-binding agents and lipids. The objective of this study was, therefore, to assess the effect of soy addition on the water state of microwavable par-baked doughs. Four dough formulations were developed by substituting wheat flour with increasing amounts of a soy blend. Addition of soy at 20 and 26% levels improved textural properties of microwaved products, resulting in a softer and less chewy texture. Thermogravimetric analysis (TG) showed increased water binding in soy formulations 20 and 26% with a broadening of the main peak (attributed to water loss) that shifted from 40 to 80 C. Differential scanning calorimetry (DSC) depicted a transition in the - 25/-10 C range, attributed to soy lipids melting, which broadened at high soy addition. This change in water dynamics was confirmed by proton nuclear magnetic resonance ( 1 H NMR) relaxation tests, T1 and T2, having lower values in soy products, and therefore, depicting a more solid-like matrix. Soy addition above 20% signifi- cantly improved the texture of microwave reheated par- baked flat doughs.

Probing Asphaltene Aggregation in Native Crude Oils with Low-Field NMR

We show that low-field proton nuclear magnetic resonance (NMR) relaxation and diffusion experiments can be used to study asphaltene aggregation directly in crude oils. Relaxation was found to be multiexponential, reflecting the composition of a complex fluid. Remarkably, the relaxation data for samples with different asphaltene concentrations can be collapsed onto each other by a simple rescaling of the time dimension with a concentration-dependent factor xi, whereas the observed diffusion behavior is unaffected by asphaltene concentration. We interpret this finding in terms of a theoretical model that explains the enhanced relaxation by the transitory entanglement of solvent hydrocarbons within asphaltene clusters and their subsequent slowed motion and diffusion within the cluster. We relate the measured scaling parameters xi to cluster sizes, which we find to be on the order of 2.2-4.4 nm for an effective sphere diameter. These sizes are in agreement with the typical values reported in the literature as well as with the small-angle X-ray scattering (SAXS) experiments performed on our samples.