NMRdiffusometry

NMR diffusometry is a technique that uses Nuclear Magnetic Resonance (NMR) to measure the diffusion of molecules. Diffusion refers to the net movement of molecules from a region of higher concentration to a region of lower concentration due to random thermal motion. In NMR diffusometry, this random motion is detected by observing how the magnetic resonance signal of atomic nuclei changes over time due to their displacement.

The core principle of NMR diffusometry relies on the magnetic field gradient. A pulsed magnetic field gradient is applied to the sample. If molecules diffuse during the application of these gradients, their Larmor frequency shifts. A second gradient pulse, identical to the first, is applied. The degree of signal attenuation or enhancement between the two gradient pulses is directly related to the distance the molecules have diffused. This relationship is described by the Stejskal- Tanner equation, which relates the signal attenuation to the diffusion coefficient, gradient strength, gradient duration, and diffusion time.

By varying the strength or duration of the magnetic field gradients, different diffusion times can be probed, allowing for the measurement of self-diffusion coefficients. These coefficients provide quantitative information about the mobility of molecules within a system. NMR diffusometry is non-invasive and can be applied to a wide range of samples, including liquids, solids, and biological tissues. It is a valuable tool in various fields, such as chemistry for studying molecular interactions and reaction kinetics, materials science for characterizing porous media, and biomedical science for imaging brain water diffusion, which is related to neurological conditions.

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