Dr. Fyfe's general area of interest is in the application of NMR spectroscopy to the investigation and characterization of solids of chemical interest and includes the synthesis of a wide variety of materials and construction of appropriate hardware and the use of complementary techniques such as X-ray diffraction and electron microscopy. Current efforts emphasize high resolution solid-state NMR techniques and NMR microimaging.
In contrast to NMR spectra of liquids and solutions where very narrow signals are observed which can be used for structure elucidations, the NMR spectra of solids generally exhibit broad, mainly featureless absorptions. It is now possible to obtain the same "isotropic average" spectra in the solid state by a combination of the techniques of magnetic dilution, dipolar decoupling and &quo t;Magic Angle" spinning and to increase the signal/noise by cross-polarization. These spectra may be used to determine the structures of solid materials, even if they are non-crystalline, and a large range of nuclei such as 13C, 29Si, 27Al, 11B, 31P can be easily observed. Using these techniques we are investigating a wide variety of solids including polymers, catalysts, gels, surfaces, zeolites and organic and organometallic solids.
In NMR imaging, the three-dimensional distribution of a liquid within a solid matrix may be determined in a non-invasive and nondestructive manner (It should be emphasized that only the mobile component is imaged). Current work is centered on multinuclear imaging of small samples with as high a resolution as possible and investigating the effect of temperature on tissue treated with cryoprotectants and the interaction of polymers and composites with liquids and gases.
Lattice structure of zeolite ZSM-5 (Mobil Corp.), the "wonder catalyst" which converts methanol to gasoline together with its high-resolution 29Si MAS NMR spectrum. Changes in the spectra as a function of temperature and when organic molecules are added indicate that the lattice structure changes to accommodate the guest organics.