PRESTO polarization transfer to quadrupolar nuclei: implications for dynamic nuclear polarization

Area of Science:

• Nuclear Magnetic Resonance (NMR) Spectroscopy
• Solid-State Chemistry
• Physical Chemistry

Background:

• Magic-angle-spinning (MAS) NMR is essential for studying solid materials.
• Transferring magnetization from protons ((1)H) to quadrupolar nuclei is key for sensitivity enhancement.
• Traditional cross-polarization (CP) methods face challenges with quadrupolar nuclei under MAS.

Purpose of the Study:

• To compare the performance of the PRESTO technique against traditional CP for (1)H to quadrupolar nuclei magnetization transfer under MAS.
• To evaluate PRESTO's effectiveness in improving quantitative intensities, lineshapes, sensitivity, and optimization.
• To highlight PRESTO's utility in dynamic nuclear polarization (DNP) NMR for quadrupolar nuclei.

Main Methods:

• Experimental and numerical investigations on model systems.
• Application of the PRESTO (Preparation, Recycling, Enhancement, Solid-state, Transfer, Optimization) technique.
• Comparison with conventional cross-polarization (CP) under magic-angle-spinning (MAS) conditions.
• Utilizing a single central transition selective 90° pulse and symmetry-based recoupling sequences.

Main Results:

• PRESTO consistently outperforms CP in (1)H to quadrupolar nuclei magnetization transfer under MAS.
• PRESTO provides more quantitative intensities and improved spectral lineshapes.
• PRESTO offers better overall sensitivity and more straightforward optimization compared to CP.
• PRESTO avoids the complex spin dynamics issues encountered during CP transfer.

Conclusions:

• PRESTO is a superior technique for magnetization transfer to quadrupolar nuclei in MAS NMR.
• The method's advantages are particularly significant for dynamic nuclear polarization (DNP) NMR applications.
• PRESTO enables more efficient polarization transfer, leading to higher sensitivity in NMR experiments.