Measurement of One-Dimensional Spatially Resolved Self-Diffusion Coefficients and Longitudinal Relaxation Times with a Single B1 Gradient

1995 ◽  
Vol 106 (1) ◽  
pp. 32-39 ◽  
Author(s):  
E. Mischler ◽  
F. Humbert ◽  
B. Diter ◽  
D. Canet
Keyword(s):  
Diffusion Coefficients ◽  
Relaxation Times ◽  
One Dimensional ◽  
Self Diffusion ◽  
Spatially Resolved ◽  
Longitudinal Relaxation

scholarly journals Revisiting Anisotropic Diffusion of Carbon Dioxide in the Metal-Organic Framework Zn2(dobpdc)

2018 ◽  
Author(s):  
Alexander C. Forse ◽  
Stephen A. Altobelli ◽  
Stefan Benders ◽  
Mark S. Conradi ◽  
Jeffrey A. Reimer
Keyword(s):  
Diffusion Coefficients ◽  
Metal Organic Framework ◽  
Chemical Shift Anisotropy ◽  
Structural Defects ◽  
Gradient Field ◽  
Line Broadening ◽  
One Dimensional ◽  
Self Diffusion ◽  
Metal Organic ◽  
D Values

The diffusion of gases confined in nanoporous materials underpins membrane and adsorption-based gas separations, yet relatively few measurements of diffusion coefficients in the promising class of materials, metal-organic frameworks (MOFs), have been reported to date. Recently we reported self-diffusion coefficients for <sup>13</sup>CO<sub>2</sub> in the MOF, Zn<sub>2</sub>(dobpdc), (dobpdc<sup>4–</sup> = 4,4′-dioxidobiphenyl-3,3′-dicarboxylate) that has one-dimensional channels with a diameter of approximately 2 nm. By analyzing the evolution of the residual <sup>13</sup>C chemical shift anisotropy lineshape at different gradient strengths, we obtained self-diffusion coefficients both along (D<sub>||</sub>) and between (D<sub>⊥</sub>) the one-dimensional MOF channels. The observation of non-zero D⊥ was unexpected based on the single crystal X-ray diffraction structure and flexible lattice molecular dynamics simulations, and we proposed that structural defects may be responsible for self-diffusion between the MOF channels. Here we revisit this analysis and show that homogeneous line broadening must be taken into account to obtain accurate values for D⊥. In the presence of homogeneous line broadening, intensity at a particular NMR frequency represents signal from crystals with a range of orientations relative to the applied magnetic field and magnetic gradient field. To quantify these effects, we perform spectral simulations that take into account homogeneous broadening and allow improved D⊥ values to be obtained. Our new analysis best supports non-zero D⊥ at all studied dosing pressures and shows that our previous analysis overestimated D⊥.

scholarly journals Revisiting Anisotropic Diffusion of Carbon Dioxide in the Metal-Organic Framework Zn2(dobpdc)

2018 ◽  
Author(s):  
Alexander C. Forse ◽  
Stephen A. Altobelli ◽  
Stefan Benders ◽  
Mark S. Conradi ◽  
Jeffrey A. Reimer
Keyword(s):  
Diffusion Coefficients ◽  
Metal Organic Framework ◽  
Chemical Shift Anisotropy ◽  
Structural Defects ◽  
Gradient Field ◽  
Line Broadening ◽  
One Dimensional ◽  
Self Diffusion ◽  
Metal Organic ◽  
D Values

The diffusion of gases confined in nanoporous materials underpins membrane and adsorption-based gas separations, yet relatively few measurements of diffusion coefficients in the promising class of materials, metal-organic frameworks (MOFs), have been reported to date. Recently we reported self-diffusion coefficients for <sup>13</sup>CO<sub>2</sub> in the MOF, Zn<sub>2</sub>(dobpdc), (dobpdc<sup>4–</sup> = 4,4′-dioxidobiphenyl-3,3′-dicarboxylate) that has one-dimensional channels with a diameter of approximately 2 nm. By analyzing the evolution of the residual <sup>13</sup>C chemical shift anisotropy lineshape at different gradient strengths, we obtained self-diffusion coefficients both along (D<sub>||</sub>) and between (D<sub>⊥</sub>) the one-dimensional MOF channels. The observation of non-zero D⊥ was unexpected based on the single crystal X-ray diffraction structure and flexible lattice molecular dynamics simulations, and we proposed that structural defects may be responsible for self-diffusion between the MOF channels. Here we revisit this analysis and show that homogeneous line broadening must be taken into account to obtain accurate values for D⊥. In the presence of homogeneous line broadening, intensity at a particular NMR frequency represents signal from crystals with a range of orientations relative to the applied magnetic field and magnetic gradient field. To quantify these effects, we perform spectral simulations that take into account homogeneous broadening and allow improved D⊥ values to be obtained. Our new analysis best supports non-zero D⊥ at all studied dosing pressures and shows that our previous analysis overestimated D⊥.

scholarly journals Non-Exponential 1H and 2H NMR Relaxation and Self-Diffusion in Asphaltene-Maltene Solutions

Molecules ◽  
2021 ◽  
Vol 26 (17) ◽  
pp. 5218
Author(s):  
Kevin Lindt ◽  
Bulat Gizatullin ◽  
Carlos Mattea ◽  
Siegfried Stapf
Keyword(s):  
Diffusion Coefficients ◽  
Relaxation Times ◽  
Chemical Species ◽  
Nmr Relaxation ◽  
Molecular Size ◽  
Relaxation Rates ◽  
Vast Number ◽  
Self Diffusion ◽  
Slowing Down ◽  
The Individual

The distribution of NMR relaxation times and diffusion coefficients in crude oils results from the vast number of different chemical species. In addition, the presence of asphaltenes provides different relaxation environments for the maltenes, generated by steric hindrance in the asphaltene aggregates and possibly by the spatial distribution of radicals. Since the dynamics of the maltenes is further modified by the interactions between maltenes and asphaltenes, these interactions—either through steric hindrances or promoted by aromatic-aromatic interactions—are of particular interest. Here, we aim at investigating the interaction between individual protonic and deuterated maltene species of different molecular size and aromaticity and the asphaltene macroaggregates by comparing the maltenes’ NMR relaxation (T1 and T2) and translational diffusion (D) properties in the absence and presence of the asphaltene in model solutions. The ratio of the average transverse and longitudinal relaxation rates, describing the non-exponential relaxation of the maltenes in the presence of the asphaltene, and its variation with respect to the asphaltene-free solutions are discussed. The relaxation experiments reveal an apparent slowing down of the maltenes’ dynamics in the presence of asphaltenes, which differs between the individual maltenes. While for single-chained alkylbenzenes, a plateau of the relaxation rate ratio was found for long aliphatic chains, no impact of the maltenes’ aromaticity on the maltene–asphaltene interaction was unambiguously found. In contrast, the reduced diffusion coefficients of the maltenes in presence of the asphaltenes differ little and are attributed to the overall increased viscosity.

scholarly journals Theoretical Modelling of Ion Exchange Processes in Glass: Advances and Challenges

2021 ◽  
Vol 11 (11) ◽  
pp. 5070
Author(s):  
Xesús Prieto-Blanco ◽  
Carlos Montero-Orille
Keyword(s):  
Ion Exchange ◽  
Diffusion Coefficients ◽  
Molten Salts ◽  
Theoretical Modelling ◽  
Copper Films ◽  
Theoretical Frameworks ◽  
Self Diffusion ◽  
Exchange Processes ◽  
The One ◽  
Made In

In the last few years, some advances have been made in the theoretical modelling of ion exchange processes in glass. On the one hand, the equations that describe the evolution of the cation concentration were rewritten in a more rigorous manner. This was made into two theoretical frameworks. In the first one, the self-diffusion coefficients were assumed to be constant, whereas, in the second one, a more realistic cation behaviour was considered by taking into account the so-called mixed ion effect. Along with these equations, the boundary conditions for the usual ion exchange processes from molten salts, silver and copper films and metallic cathodes were accordingly established. On the other hand, the modelling of some ion exchange processes that have attracted a great deal of attention in recent years, including glass poling, electro-diffusion of multivalent metals and the formation/dissolution of silver nanoparticles, has been addressed. In such processes, the usual approximations that are made in ion exchange modelling are not always valid. An overview of the progress made and the remaining challenges in the modelling of these unique processes is provided at the end of this review.

scholarly journals Self-Diffusion Coefficients, Aggregation Numbers and the Range of Existence of Spherical Micelles of Oxyethylated Alkylphenols

2021 ◽  
Author(s):  
Victor P. Arkhipov ◽  
Natalia A. Kuzina ◽  
Andrei Filippov
Keyword(s):  
Aqueous Solutions ◽  
Diffusion Coefficients ◽  
The Self ◽  
Self Diffusion ◽  
Aggregation Numbers ◽  
Temperature Ranges ◽  
Spherical Micelles ◽  
Limiting Values

AbstractAggregation numbers were calculated based on measurements of the self-diffusion coefficients, the effective hydrodynamic radii of micelles and aggregates of oxyethylated alkylphenols in aqueous solutions. On the assumption that the radii of spherical micelles are equal to the lengths of fully extended neonol molecules, the limiting values of aggregation numbers corresponding to spherically shaped neonol micelles were calculated. The concentration and temperature ranges under which spherical micelles of neonols are formed were determined.

scholarly journals Effect of Modification on the Fluid Diffusion Coefficient in Silica Nanochannels

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 4030
Author(s):  
Gengbiao Chen ◽  
Zhiwen Liu
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Surface Effect ◽  
Bulk Water ◽  
Self Diffusion ◽  
Average Diffusion Coefficient ◽  
Average Diffusion ◽  
Chain Lengths ◽  
Fluid Diffusion ◽  
Self Diffusion Coefficient

The diffusion behavior of fluid water in nanochannels with hydroxylation of silica gel and silanization of different modified chain lengths was simulated by the equilibrium molecular dynamics method. The diffusion coefficient of fluid water was calculated by the Einstein method and the Green–Kubo method, so as to analyze the change rule between the modification degree of nanochannels and the diffusion coefficient of fluid water. The results showed that the diffusion coefficient of fluid water increased with the length of the modified chain. The average diffusion coefficient of fluid water in the hydroxylated nanochannels was 8.01% of the bulk water diffusion coefficient, and the diffusion coefficients of fluid water in the –(CH2)3CH3, –(CH2)7CH3, and –(CH2)11CH3 nanochannels were 44.10%, 49.72%, and 53.80% of the diffusion coefficients of bulk water, respectively. In the above four wall characteristic models, the diffusion coefficients in the z direction were smaller than those in the other directions. However, with an increase in the silylation degree, the increased self-diffusion coefficient due to the surface effect could basically offset the decreased self-diffusion coefficient owing to the scale effect. In the four nanochannels, when the local diffusion coefficient of fluid water was in the range of 8 Å close to the wall, Dz was greater than Dxy, and beyond the range of 8 Å of the wall, the Dz was smaller than Dxy.

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