With support from the Chemical Measurement and Imaging program in the Division of Chemistry, Prof. Song-I Han and her group at the University of California - Santa Barbara are developing new instrumentation and methodologies for high magnetic field nuclear magnetic resonance (NMR) to probe the detailed microstructure of complex and heterogeneous materials, e.g. of multiphase block copolymers or amorphous silicon. The sensitivity of conventional NMR spectroscopy is insufficient to probe the microstructural properties at the surface or interface at the necessary sub-nanometer length scale. Prof. Han addresses this challenge by developing novel dynamic nuclear polarization (DNP)-amplified NMR instrumentation and methods at 7 Tesla that enhance signals by up to five orders of magnitudes through cryogenic cooling and polarization transfer from polarized electron spins to nuclear spins. A unique and crucial aspect of the approach is utilization of strategic electron spin probes specifically located through chemical functionalization, or intrinsic paramagnetic defects that are critical to the function or malfunction of the materials. Prof. Han is adding concurrent continuous wave and pulsed electron paramagnetic resonance (EPR) detection capabilities to a home-built spectrometer to provide complete materials characterization through the nuclear and electron spin probes.
The high field DNP approach may have high impact on the study of a wide range of functional and heterogeneous materials, e.g. a variety of multiphase polymer systems or amorphous and crystalline Si based photovoltaic materials, whose interfacial properties or intrinsic paramagnetic centers lie at the core of their function or malfunction. Educational impact is enhanced by provision of research opportunities for undergraduate students and by supporting professional development for women scientists pursuing high level science careers.