Oxygen-17 dynamic nuclear polarisation enhanced solid-state NMR spectroscopy at 18.8 T

Area of Science:

• Solid-state Nuclear Magnetic Resonance (NMR) Spectroscopy
• Dynamic Nuclear Polarization (DNP)
• Materials Science

Background:

• Solid-state NMR spectroscopy is crucial for characterizing materials at the atomic level.
• Low sensitivity of certain NMR isotopes, like ¹⁷O, often limits detailed structural analysis.
• Dynamic Nuclear Polarization (DNP) is a technique used to enhance NMR signal sensitivity.

Purpose of the Study:

• To investigate the efficacy of ¹⁷O dynamic nuclear polarization (DNP) enhanced solid-state NMR.
• To explore different formulations for optimizing DNP performance on magnesium hydroxide (Mg(OH)₂).
• To compare the Overhauser (OH) and cross-effect (CE) polarization transfer mechanisms for ¹⁷O DNP-NMR.

Main Methods:

• Conducted ¹⁷O dynamic nuclear polarization (DNP) enhanced solid-state NMR experiments at a high magnetic field (18.8 T).
• Investigated various formulations of the Mg(OH)₂ compound.
• Employed the Overhauser (OH) polarization transfer scheme using o-terphenyl matrix doped with BDPA and the cross-effect (CE) mechanism with TEKPol.

Main Results:

• Achieved a signal enhancement factor of 17 for ¹⁷O in Mg(OH)₂ using the Overhauser (OH) DNP scheme.
• The cross-effect (CE) mechanism with TEKPol provided a slightly lower enhancement but allowed for more time-efficient data acquisition.
• Demonstrated the successful application of DNP to enhance ¹⁷O signals in solid-state NMR.

Conclusions:

• ¹⁷O dynamic nuclear polarization (DNP) significantly enhances solid-state NMR sensitivity for materials like Mg(OH)₂.
• Both Overhauser (OH) and cross-effect (CE) mechanisms are viable for ¹⁷O DNP-NMR, offering different trade-offs between enhancement and speed.
• The reported DNP-enhanced NMR methods open new avenues for detailed structural and dynamic studies of oxygen-containing solids.