Spatial and temporal visualization of a pH-dependent complexation equilibrium by nuclear magnetic resonance imaging

1992 ◽  
Vol 70 (10) ◽  
pp. 2693-2697 ◽  
Author(s):  
B. J. Balcom ◽  
T. A. Carpenter ◽  
L. D. Hall
Keyword(s):  
Aqueous Solution ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Ethylenediaminetetraacetic Acid ◽  
Copper Ions ◽  
Copper Ion ◽  
Spin Lattice Relaxation ◽  
Complexing Agent ◽  
Complexation Equilibrium ◽  
Nuclear Magnetic

Alteration of a chemical equilibrium, ethylenediaminetetraacetic acid chelation of aqueous copper, in response to a pH gradient that protonates the complexing agent, has been observed spatially and temporally by 1H nuclear magnetic resonance. Protonation of the complexing agent shifted the complexation equilibrium towards free copper ion. Free and bound copper ions alter the spin lattice relaxation time (T1) of water in the host polyacrylamide gel to different extents. Based on this difference, a T1 weighted (fast repetition time, short echo time) two-dimensional spin-warp imaging sequence mapped out the distribution of the free and bound species. Addition of a pH 3 aqueous solution to the gel was insufficient to alter the equilibrium; a pH 1 aqueous solution liberated the complexed copper. Quantitative one-dimensional experiments gave a T1 weighted profile that showed the reaction front is displaced a distance proportional to the square root of time.

Nuclear Magnetic Resonance Studies of δ-Stabilized Plutonium

2003 ◽  
Vol 802 ◽  
Author(s):  
N. J. Curro ◽  
L. Morales
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Low Frequency ◽  
Lattice Relaxation ◽  
Spin Fluctuations ◽  
Spin Lattice Relaxation ◽  
Cubic Symmetry ◽  
Magnetic Resonance Studies ◽  
Local Distortions ◽  
Nuclear Magnetic

Nuclear Magnetic Resonance studies of Ga stabilized δ-Pu reveal detailed information about the local distortions surrounding the Ga impurities as well as provides information about the local spin fluctuations experienced by the Ga nuclei. The Ga NMR spectrum is inhomogeneously broadened by a distribution of local electric field gradients (EFGs), which indicates that the Ga experiences local distortions from cubic symmetry. The Knight shift and spin lattice relaxation rate indicate that the Ga is dominantly coupled to the Fermi surface via core polarization, and is inconsistent with magnetic order or low frequency spin correlations.

Nuclear magnetic resonance (NMR) studies of sintering effects on the lithium ion dynamics in Li1.5Al0.5Ti1.5(PO4)3

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Edda Winter ◽  
Philipp Seipel ◽  
Tatiana Zinkevich ◽  
Sylvio Indris ◽  
Bambar Davaasuren ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Lithium Ion ◽  
Magic Angle Spinning ◽  
Spin Lattice Relaxation ◽  
Magic Angle ◽  
Nmr Studies ◽  
Lithium Ions ◽  
Jump Dynamics ◽  
Nuclear Magnetic

Abstract Various nuclear magnetic resonance (NMR) methods are combined to study the structure and dynamics of Li1.5Al0.5Ti1.5(PO4)3 (LATP) samples, which were obtained from sintering at various temperatures between 650 and 900 °C. 6Li, 27Al, and 31P magic angle spinning (MAS) NMR spectra show that LATP crystallites are better defined for higher calcination temperatures. Analysis of 7Li spin-lattice relaxation and line-shape changes indicates the existence of two species of lithium ions with clearly distinguishable jump dynamics, which can be attributed to crystalline and amorphous sample regions, respectively. An increase of the sintering temperature leads to higher fractions of the fast lithium species with respect to the slow one, but hardly affects the jump dynamics in either of the phases. Specifically, the fast and slow lithium ions show jumps in the nanoseconds regime near 300 and 700 K, respectively. The activation energy of the hopping motion in the LATP crystallites amounts to ca. 0.26 eV. 7Li field-gradient diffusometry reveals that the long-range ion migration is limited by the sample regions featuring slow transport. The high spatial resolution available from the high static field gradients of our setup allows the observation of the lithium ion diffusion inside the small (<100 nm) LATP crystallites, yielding a high self-diffusion coefficient of D = 2 × 10−12 m2/s at room temperature.

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