Nuclear Magnetic Resonance Relaxation Times Research Articles

Interpretation of NMR relaxation as a tool for characterising the adsorption strength of liquids inside porous materials.

Nuclear magnetic resonance (NMR) relaxation times are shown to provide a unique probe of adsorbate–adsorbent interactions in liquid-saturated porous materials. A short theoretical analysis is presented, which shows that the ratio of the longitudinal to transverse relaxation times (T1/T2) is related to an adsorbate–adsorbent interaction energy, and we introduce a quantitative metric esurf (based on the relaxation time ratio) characterising the strength of this surface interaction. We then consider the interaction of water with a range of oxide surfaces (TiO2 anatase, TiO2 rutile, γ-Al2O3, SiO2, θ-Al2O3 and ZrO2) and show that esurf correlates with the strongest adsorption sites present, as determined by temperature programmed desorption (TPD). Thus we demonstrate that NMR relaxation measurements have a direct physical interpretation in terms of the characterisation of activation energy of desorption from the surface. Further, for a series of chemically similar solid materials, in this case a range of oxide materials, for which at least two calibration values are obtainable by TPD, the esurf parameter yields a direct estimate of the maximum activation energy of desorption from the surface. The results suggest that T1/T2 measurements may become a useful addition to the methods available to characterise liquid-phase adsorption in porous materials. The particular motivation for this work is to characterise adsorbate–surface interactions in liquid-phase catalysis.

Research on the Remaining Oil Starting Mechanism in Different Pores of Polymer Surfactants Using NMR Analysis

With its unique structure and properties, polymer surfactants have been used in chemical flooding. Compared with ordinary polymer, polymer surfactants have a higher recovery degree. However, remaining oil starting mechanism in different pores using different polymer surfactants after water flooding is still unclear. NMR (Nuclear Magnetic Resonance) has a good effect on determination of rock oil saturation and analysis of pore structure. In this paper, oil displacement experiment using kerosene which contains no hydrogen was conducted and the problem caused by the similarity between oil phase relaxation time and water relaxation time in large pores was overcome. Through the change of NMR relaxation time, oil distribution situation in different pores of ordinary polymer, refining III polymer surfactant, and Haibo III polymer surfactant after polymer flooding was measured accurately. This paper also quantitatively analyzed the contribution degree to oil recovery in pores of different sizes, and evaluated oil displacement effect of the above three kinds of oil displacement systems. The results show that when only the swept volume is considered, recovery degree of Haibo III polymer surfactant is higher, reaching 53.66%. In different systems, middle pores contribute most to recovery degree. At the same time, the remaining oil in middle pores and large pores accounts more, which is the main attack direction towards tapping the potential of remaining oil in the oilfield.

Dynamics of methanol in ionic liquids: validity of the Stokes-Einstein and Stokes-Einstein-Debye relations.

The validity of Stokes-Einstein (SE) and Stokes-Einstein-Debye (SED) relations for methanol in the physical environment of the ionic liquid (IL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide is studied by means of nuclear magnetic resonance (NMR) relaxation time experiments, viscosity measurements and molecular dynamics (MD) simulations. The reorientational correlation times of the hydroxyl groups of pure methanol and of methanol in the IL/methanol mixtures were determined. For that purpose an approach for estimating NMR deuteron quadrupole coupling constants, presented by Wendt and Farrar (Mol. Phys. 1998, 95, 1077-1081), was confirmed. The self-diffusion coefficients of methanol were taken from the MD simulations. The viscosities of all systems were then measured and the SE and SED relations validated. For pure methanol both relations are valid, whereas they become increasingly invalid with increasing IL concentration, as indicated by effective volumes and radii that are too low. The deviation from the SE and SED relations could be related to dynamical heterogeneities described by the non-Gaussian parameter α(t) obtained from MD simulations. For pure methanol, α(t) is close to zero in accord with the validity of both relations. With increasing IL concentration the dynamical heterogeneities of methanol increase strongly. The times t* at the maximum of α(t) increase linearly with the relative number of methanol monomers in the mixtures. Thus, the dynamical heterogeneities are largest for single methanol molecules fully embedded in the IL environment. In their own environment methanol molecules are highly mobile, whereas in the IL-rich region the mobility is strongly reduced leading to the non-validity of SE and SED relations.

Molecular Dynamics of Proteins Investigated by NMR Relaxation Methods

The nuclear magnetic resonance relaxation times of solvent water nuclei are known to decrease upon addition of diamagnetic solute protein. For this reason NMR relaxation methods are able to provide information on molecular dynamics changes of water protons and their interaction with macromolecules' surfaces. We present results of measurements of relaxation rates R1 = 1/T1, R2 = 1/T2 and R1ρ = 1/T1ρ in the rotating frame for three proteins: chicken egg white lysozyme, egg white albumin, and bovine serum albumin, obtained at proton resonant frequency of 60 MHz. Besides the relaxation rates dependences on concentration in the 4 23% (g/100 g solution) range, the analysis of the Carr Purcell Meiboom Gill CPMG multi-echo T2 experiments with variable pulse rate τ was performed. The dependences of relaxation rates on protein concentration are linear at low concentration. When protein concentration increases the slope of the straight line rapidly changes at so-called critical concentration which depends on MW of the diluted protein. Investigated dispersion of T2, obtained using the CPMG method with a variable pulse rate, for concentrations higher and lower than the critical one, exhibits unequal behavior. At high concentration one-exponential curves and at low concentration two-exponential curves correspond closely with experimental data. The obtained parameters of exponents allow an estimation of the ratio of the amount of water with the determined motion freedom, that is free and bounded water, in solution. We showed that the CPMG dispersion method applied to aqueous protein solutions may widen the current understanding of the nature of molecular dynamics of hydrated water protons in non-perturbed environment.

Nuclear magnetic resonance characterization of shallow marine sediments from the Nankai Trough, Integrated Ocean Drilling Program Expedition 333

AbstractWe measured nuclear magnetic resonance (NMR) relaxation times on samples from Integrated Ocean Drilling Program Expedition 333 Sites C0011, C0012, and C0018. We compared our results to permeability, grain size, and specific surface measurements, pore size distributions from mercury injection capillary pressure, and mineralogy from X‐ray fluorescence. We found that permeability could be predicted from NMR measurements by including grain size and specific surface to quantify pore networks and that grain size is the most important factor in relating NMR response to permeability. Samples within zones of anomalously high porosity from Sites C0011 and C0012 were found to have different NMR‐permeability relationships than samples from outside these zones, suggesting that the porosity anomaly is related to a fundamental difference in pore structure. We additionally estimated the size of paramagnetic sites that cause proton relaxation and found that in most of our samples, paramagnetic material is present mainly as discrete, clay‐sized grains. This distribution of paramagnetic material may cause pronounced heterogeneity in NMR properties at the pore scale that is not accounted for in most NMR interpretation techniques. Our results provide important insight into the microstructure of marine sediments in the Nankai Trough.

Bootstrap Calibration and Uncertainty Estimation of Downhole NMR Hydraulic Conductivity Estimates in an Unconsolidated Aquifer

Characterization of hydraulic conductivity (K) in aquifers is critical for evaluation, management, and remediation of groundwater resources. While estimates of K have been traditionally obtained using hydraulic tests over discrete intervals in wells, geophysical measurements are emerging as an alternative way to estimate this parameter. Nuclear magnetic resonance (NMR) logging, a technology once largely applied to characterization of deep consolidated rock petroleum reservoirs, is beginning to see use in near-surface unconsolidated aquifers. Using a well-known rock physics relationship-the Schlumberger Doll Research (SDR) equation--K and porosity can be estimated from NMR water content and relaxation time. Calibration of SDR parameters is necessary for this transformation because NMR relaxation properties are, in part, a function of magnetic mineralization and pore space geometry, which are locally variable quantities. Here, we present a statistically based method for calibrating SDR parameters that establishes a range for the estimated parameters and simultaneously estimates the uncertainty of the resulting K values. We used co-located logging NMR and direct K measurements in an unconsolidated fluvial aquifer in Lawrence, Kansas, USA to demonstrate that K can be estimated using logging NMR to a similar level of uncertainty as with traditional direct hydraulic measurements in unconsolidated sediments under field conditions. Results of this study provide a benchmark for future calibrations of NMR to obtain K in unconsolidated sediments and suggest a method for evaluating uncertainty in both K and SDR parameter values.

A compact high-performance low-field NMR apparatus for measurements on fluids at very high pressures and temperatures

We discuss an innovative new high-performance apparatus for performing low-field Nuclear Magnetic Resonance (NMR) relaxation times and diffusion measurements on fluids at very high pressures and high temperatures. The apparatus sensor design and electronics specifications allow for dual deployment either in a fluid sampling well logging tool or in a laboratory. The sensor and electronics were designed to function in both environments. This paper discusses the use of the apparatus in a laboratory environment. The operating temperature and pressure limits, and the signal-to-noise ratio (SNR) of the new system exceed by a very wide margin what is currently possible. This major breakthrough was made possible by a revolutionary new sensor design that breaks many of the rules of conventional high pressure NMR sensor design. A metallic sample holder capable of operating at high pressures and temperatures is provided to contain the fluid under study. The sample holder has been successfully tested for operation up to 36 Kpsi. A solenoid coil wound on a slotted titanium frame sits inside the metallic sample holder and serves as an antenna to transmit RF pulses and receive NMR signals. The metal sample holder is sandwiched between a pair of gradient coils which provide a linear field gradient for pulsed field gradient diffusion measurements. The assembly sits in the bore of a low-gradient permanent magnet. The system can operate over a wide frequency range without the need for tuning the antenna to the Larmor frequency. The SNR measured on a water sample at room temperature is more than 15 times greater than that of the commercial low-field system in our laboratory. Thus, the new system provides for data acquisition more than 200 times faster than was previously possible. Laboratory NMR measurements of relaxations times and diffusion coefficients performed at pressures up to 25 Kpsi and at temperatures up to 175 °C with crude oils enlivened with dissolved hydrocarbon gases (referred to as "live oils") are shown. This is the first time low-field NMR measurements have been performed at such high temperatures and pressures on live crude oil samples. We discuss the details of the apparatus design, tuning, calibration, and operation. NMR data acquired at multiple temperatures and pressures on a live oil sample are discussed.

Rapid measurements of heterogeneity in sandstones using low-field nuclear magnetic resonance

Sandstone rocks can contain microscopic variations in composition that complicate interpretation of nuclear magnetic resonance (NMR) relaxation time measurements. In this work, methods for assessing the degree of sample heterogeneity are demonstrated in three sandstones. A two-dimensional T1–Δχapp correlation (where Δχapp is the apparent solid/liquid magnetic susceptibility contrast) reveals the microscopic heterogeneity in composition, whilst a spatially resolved T1 profile reveals the macroscopic structural heterogeneity. To perform these measurements efficiently, a rapid measure of longitudinal T1 relaxation time has been implemented on a low-field NMR spectrometer with a magnetic field strength B0=0.3T. The “double-shot” T1 pulse sequence is appropriate for analysis of porous materials in general. Example relaxation time distributions are presented for doped water phantoms to validate the method. The acquisition time of the double-shot T1 sequence is equivalent to the single-shot Carr–Purcell Meiboom–Gill (CPMG) sequence used routinely in petrophysics to measure transverse T2 relaxation. Rapid T1 measurements enable practical studies of core plugs at magnetic field strengths previously considered inappropriate, as T1 is independent of molecular diffusion through pore-scale (internal) magnetic field gradients.

Total water, phosphorus relaxation and inter-atomic organic to inorganic interface are new determinants of trabecular bone integrity.

Bone is the living composite biomaterial having unique structural property. Presently, there is a considerable gap in our understanding of bone structure and composition in the native state, particularly with respect to the trabecular bone, which is metabolically more active than cortical bones, and is readily lost in post-menopausal osteoporosis. We used solid-state nuclear magnetic resonance (NMR) to compare trabecular bone structure and composition in the native state between normal, bone loss and bone restoration conditions in rat. Trabecular osteopenia was induced by lactation as well as prolonged estrogen deficiency (bilateral ovariectomy, Ovx). Ovx rats with established osteopenia were administered with PTH (parathyroid hormone, trabecular restoration group), and restoration was allowed to become comparable to sham Ovx (control) group using bone mineral density (BMD) and µCT determinants. We used a technique combining 1H NMR spectroscopy with 31P and 13C to measure various NMR parameters described below. Our results revealed that trabecular bones had diminished total water content, inorganic phosphorus NMR relaxation time (T1) and space between the collagen and inorganic phosphorus in the osteopenic groups compared to control, and these changes were significantly reversed in the bone restoration group. Remarkably, bound water was decreased in both osteopenic and bone restoration groups compared to control. Total water and T1 correlated strongly with trabecular bone density, volume, thickness, connectivity, spacing and resistance to compression. Bound water did not correlate with any of the microarchitectural and compression parameters. We conclude that total water, T1 and atomic space between the crystal and organic surface are altered in the trabecular bones of osteopenic rats, and PTH reverses these parameters. Furthermore, from these data, it appears that total water and T1 could serve as trabecular surrogates of micro-architecture and compression strength.

Relating nuclear magnetic resonance relaxation time distributions to void-size distributions for unconsolidated sand packs

Nuclear magnetic resonance (NMR) is used in near-surface geophysics to understand the pore-scale properties of geologic material. The interpretation of NMR data in geologic material assumes that the NMR relaxation time distribution ([Formula: see text]-distribution) is a linear transformation of the void-size distribution (VSD). This interpretation assumes fast diffusion and can be violated for materials with high surface relaxivity and/or large pores. We compared [Formula: see text]-distributions to VSDs using grain-size distributions (GSDs) as a proxy for VSDs. Measurements were collected on water-saturated sand packs with a range of grain sizes and surface relaxivities, such that some samples were expected to violate the fast diffusion assumption. Samples were prepared from silica sand with three different average grain sizes and were coated with the iron-oxide mineral hematite to vary the surface relaxivity. We found analytically that outside the fast diffusion regime, the [Formula: see text]-distributions are broader than in the fast diffusion regime, which could lead to misinterpretation of NMR data. The experimental results showed that the [Formula: see text]-distributions were not linear transformations of the GSDs. The GSDs were a single peak independent of the hematite coating. The [Formula: see text]-distributions were broader than the measured GSDs, and the center of the distribution depended on the coating. Using an equation that does not assume fast diffusion to transform the [Formula: see text]-distributions to NMR-estimated VSDs resulted in distributions that were centered on a single radius. However, our attempts to recover the VSDs, as estimated from laser particle size analysis, were unsuccessful; the NMR-estimated VSDs were broader and yielded average pore radii that were much smaller than expected. We found that our approach was useful for determining relative VSDs from [Formula: see text]-distributions; however, future research is needed to develop a method for calibrating the NMR-estimated VSDs for unconsolidated sands.

Molecular Motions of Adsorbed CO2 on a Tetrazole-Functionalized PIM Polymer Studied with 13C NMR

The CO2 adsorption in a polymer of intrinsic microporosity (PIM) functionalized by tetrazole (TZPIM) has been studied with in situ 13C nuclear magnetic resonance (NMR) spectroscopy at variable temperature and loading conditions. The CO2 molecules are seen to interact with tetrazole sites through physisorption. The adsorbed system was studied from 8 to 385 K at two loadings of CO2. The 13C NMR resonance lineshapes and relaxation times have been analyzed to give insights into the adsorption process. The CO2 molecules undergo site to site hopping with accompanying CO2 reorientations while adsorbed on TZPIM, resulting in line narrowing starting near 100 K. Correspondingly, the spin echo T2 passes through a minimum at 100 K. The analysis indicates that two kinds of adsorption sites are available.

Anion-Conductive Multiblock Aromatic Copolymer Membranes: Structure–Property Relationships

Anion-conductive multiblock copoly(arylene ether sulfone)s (mPES) were synthesized with different block lengths and ion-exchange capacities (IEC) to maximize ion conductivity and explore the relationship between chemical structure and morphology in anion-exchange membranes (AEM). Nuclear magnetic resonance (NMR) relaxometry was used to probe water mobility and domain size. The multiblock copolymers were synthesized by polycondensation of separately prepared hydroxy-terminated oligomers with fluoro-terminated oligomers. The polymers were made ion-conductive through selective chloromethylation of one of the two block types, followed by quaternization and hydroxide ion exchange. The resulting block structure, in which one type is hydrophilic and one type is hydrophobic, was designed to ensure a nanophase-separated morphology. The multiblock copolymers exhibited higher anion conductivity than their random copolymer counterparts at the same IEC. The multiblock copolymer that exhibited the highest anion conductivity was not the one with the highest IEC, but it was the one with the shortest NMR relaxation times for water, indicating a greater fraction of water interacts with the ionic polymer segments. Higher IEC values led to increased water absorption, an effective dilution of the ionic groups, and increased NMR relaxation times for water.

Estimation of water retention parameters from nuclear magnetic resonance relaxation time distributions

[1] For characterizing water flow in the vadose zone, the water retention curve (WRC) of the soil must be known. Because conventional WRC measurements demand much time and effort in the laboratory, alternative methods with shortened measurement duration are desired. The WRC can be estimated, for instance, from the cumulative pore size distribution (PSD) of the investigated material. Geophysical applications of nuclear magnetic resonance (NMR) relaxometry have successfully been applied to recover PSDs of sandstones and limestones. It is therefore expected that the multiexponential analysis of the NMR signal from water-saturated loose sediments leads to a reliable estimation of the WRC. We propose an approach to estimate the WRC using the cumulative NMR relaxation time distribution and approximate it with the well-known van-Genuchten (VG) model. Thereby, the VG parameter n, which controls the curvature of the WRC, is of particular interest, because it is the essential parameter to predict the relative hydraulic conductivity. The NMR curves are calibrated with only two conventional WRC measurements, first, to determine the residual water content and, second, to define a fixed point that relates the relaxation time to a corresponding capillary pressure. We test our approach with natural and artificial soil samples and compare the NMR-based results to WRC measurements using a pressure plate apparatus and to WRC predictions from the software ROSETTA. We found that for sandy soils n can reliably be estimated with NMR, whereas for samples with clay and silt contents higher than 10% the estimation fails. This is the case when the hydraulic properties of the soil are mainly controlled by the pore constrictions. For such samples, the sensitivity of the NMR method for the pore bodies hampers a plausible WRC estimation.Citation: Costabel, S., and U. Yaramanci (2013), Estimation of water retention parameters from nuclear magnetic resonance relaxation time distributions, Water Resour. Res., 49, 2068-2079, doi:10.1002/wrcr.20207.

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.

Phase transition temperature and paramagnetic effect in Al1−xCrxK(SO4)2·12H2O (x = 0, 0.07, and 0.2) crystals studied by 27Al nuclear magnetic resonance relaxation time

The physical properties of Al1−xCrxK(SO4)2·12H2O (x = 0, 0.07, and 0.2) single crystals as a function of temperature were studied by observing their 27Al nuclear magnetic resonance spectra and relaxation times. The effects of partial replacement of Al3+ ions with paramagnetic Cr3+ ions were examined on the basis of the physical properties of pure AlK(SO4)2·12H2O crystals. The phase transition temperatures TC varied depending on the concentration of paramagnetic ions. In addition, the spin–lattice relaxation time T1 of crystals containing Cr3+ ions was shorter than that of crystals without paramagnetic ions. The paramagnetic effects on T1 and TC were strongest for 27Al in Al0.8Cr0.2 K(SO4)2·12H2O crystals with 0.2 mol. % of Cr3+ ions.

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.

The use of 1H-NMR Relaxation Times of Water Adsorbed on Soils to Monitor Environment Pollution

Pursuing the goal to develop an express technique for the characterizing of forest ecology, this paper presents a description of the found dependence of nuclear magnetic resonance (NMR) relaxation times of water in soils on the pollution caused by vehicle exhausts. Test measurements were made in Mari El Republic of Russia where wildwood areas located close to human activity are showing degradation, which has drastically intensified in the resent several years. Samples were collected at distances between 100 m to 1.1 km from the highway towards the direction of virgin forest assuming that their contamination level was naturally varied. The measured spin-spin NMR relaxation time of wetted samples showed a growth of more than 20% with the increase of distance from the pollution source. Here we try to explain this effect. As the conclusion, we propose to use the transverse relaxation time of moisturized soil as an indicator for the environment pollution monitoring.

Probing pore characteristics of deformed chalk by NMR relaxation

1H Nuclear Magnetic Resonance (NMR) relaxation time was applied to investigate pores characteristic of chalk cores which were subjected to prior mechanical loading. The NMR relaxation responses of the cores loaded in elastic region (before yield) and in plastic region (after yield) were compared. T1,2 relaxation measurements performed on fully water saturated cores resolved a typical pore size corresponding to large pore body, which is affected by stress application particularly beyond the yield point. The 1/T1,2 relaxation rate also appeared to correlate with the volumetric strain. The NMR signal from the partially saturated cores (Sw<13%), however, showed no respectable change despite being loaded beyond the yield point. The T2 signal was dominated by two relaxation rates, which we argue corresponds to the surface water film (∼10nm) and micropores (∼0.1μm). The point that T1,2 NMR relaxation showed no significant change on partially saturated cores loaded beyond the yield point may indicate that the structure of water film remains unchanged despite progressive decay of pores structure during pore collapse failures.

Application of MRI to Monitor the Process of Navel Orange Ripening

Low field nuclear magnetic resonance (NMR) technique was used to evaluate the capacity of NMR spectrometry in characterizing the different behaviors of water protons in navel orange during growth. Carr-Purcell-Meiboom-Gill (CPMG) sequence and mult-exponential regress model were used to calculate the spin-spin relaxation time (T2) of orange samples. Meanwhile, chemical properties (etc. total sugar, acid and solid content) were tested. Statistics analysis shows a correlation between chemical properties of orange and NMR relaxation time during growth, which indicate that interactions between molecules and water protons in orange are involved. Evaluating the behavior of liquid water by NMR shows a new view for better understanding the mechanisms of the macromolecular formation. Changes in NMR relaxation time parameters would be helpful for understanding the mechanism of decay and damage. Therefore, it would be helpful for finding a better food preserving method for the long term storage in the future.

Synthesis of pseudopolyrotaxanes-coated Superparamagnetic Iron Oxide Nanoparticles as new MRI contrast agent

Superparamagnetic Iron Oxide Nanoparticles (SPIONs) were synthesized and coated with pseudopolyrotaxanes (PPRs) and proposed as a novel hybrid nanostructure for medical imaging and drug delivery. PPRs were prepared by addition of α-cyclodextrin rings to functionalized polyethylene glycol (PEG) chain with hydrophobic triazine end-groups. Non-covalent interactions between SPIONs and PPRs led to the assembly of SPIONs@PRs hybrid nanomaterials. Measurements of the 1H Nuclear Magnetic Resonance (NMR) relaxation times T1 and T2 allowed us to determine the NMR dispersion profiles. Comparison between our SPIONs@PRs hybrid nano-compound and the commercial SPION compound, Endorem®, showed a higher transverse relaxivity for SPIONs@PRs. In vitro MRI experiments showed that our SPIONs@PRs produces better negative contrast compared to Endorem® and can be considered as a novel MRI contrast agent.