Solvent relaxation NMR

Pulsed nuclear magnetic resonance (NMR) experiments are commonly used for sensitive and accurate structural identification of unknown compounds and for investigating the physical properties of mixtures. We have developed a miniaturised bench-top NMR as part of an on-going project of creating small, cheap, low-power NMR instrumentation for deployment in both laboratory settings and field-work.

The physical basis for the instrument is the measurement of the relaxation rates of the solvent molecules following excitation of the nuclei by a radiofrequency pulse. The NMR solvent relaxation times are sensitive to the available surface area in a dispersion of particles in a fluid. The basic idea is that a molecule adsorbed at an interface has a much shorter relaxation time than one in the bulk. Typically for a silica in water dispersion the bulk spin relaxation times will be of the order of 2 s, whereas the surface ones will be ~1 ms. In the fast exchange limit we measure a dynamic average of these times.

Recent results were discussed at the 24th European Colloids and Interface Society Meeting [1] some of which were published in Langmuir [2] Our commercial partner in this venture is XiGo Nanotools.

References

1. Molecules at the solid-liquid interface: a miniature NMR to characterise colloidal systems. CL Cooper, B Cattoz, SW Prescott and T Cosgrove. 24^th Conference of the European Colloids and Interfaces Society, Prague, Czech Republic, September 2010.
   [Project website]
2. Surfactant-mediated desorption of polymer from the nanoparticle interface. B Cattoz, T Cosgrove, M Crossman and SW Prescott. Langmuir, 28(5), 2485–2492, 2012.
   [DOI Lookup]