Dynamic Nuclear Polarization of Metal-Doped Oxide Glasses: A Test of the Generality of Paramagnetic Metal Polarizing Agents
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Nuclear magnetic resonance (NMR) spectroscopy can provide unique, atomic-level insights into the structure and dynamics of materials, but its applications are impeded by the intrinsically low sensitivity. Dynamic nuclear polarization (DNP) is poised to overcome this limitation, and indeed has revolutionized the study of surfaces; however, the current approaches are ill-suited for bulk solids. One potential pathway toward the hyperpolarization of bulk solids by DNP is through the inclusion of paramagnetic metal ions that can serve as polarizing agents. In this work, we compared the relative performance of two such dopants, Mn2+ and Gd3+, in three series of oxide glasses having chemical environments representative of those found in other crystalline and amorphous solids. In our studies, Gd3+ outperformed Mn2+, consistently providing more than one order of magnitude greater time savings. We attributed this difference mainly to the lack of hyperfine interaction to 55Mn.