Broadband "infinite-speed" magic-angle spinning NMR spectroscopy

Area of Science:

• Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy
• Materials Science
• Solid-state Chemistry

Background:

• High-Z spin-1/2 nuclei NMR, crucial for materials like tellurides, faces challenges from large chemical-shift anisotropies.
• These anisotropies generate strong spinning sidebands, obscuring essential centerband signals in fast magic-angle spinning (MAS) NMR.
• Existing methods struggle to resolve signals in broad spectra (up to 200 kHz), hindering analysis of thermoelectrics and phase-change materials.

Purpose of the Study:

• To develop a robust method for suppressing spinning sidebands in high-resolution NMR of high-Z nuclei.
• To adapt and optimize the two-dimensional magic-angle-turning (MAT) experiment for broad spectra and fast MAS conditions.
• To enable accurate peak identification and quantification in technologically relevant telluride materials.

Main Methods:

• Adaptation of Gan's two-dimensional magic-angle-turning (MAT) experiment using five 90-degree pulses.
• Implementation of corrections for long pulses and short rotation periods in fast MAS.
• Application of the modified MAT experiment to telluride samples with wide spectral ranges (up to 170 kHz) at 22 kHz MAS.

Main Results:

• The adapted MAT experiment effectively suppresses spinning sidebands over a wide spectral range.
• Minimal spectral distortions and negligible residual sidebands were observed.
• The method proved successful in analyzing technologically important tellurides, overcoming limitations of conventional MAS NMR.

Conclusions:

• The modified 2D MAT NMR technique provides a powerful solution for sideband suppression in high-Z nuclei.
• This advancement facilitates detailed analysis and characterization of materials like tellurides.
• The method enhances the utility of solid-state NMR for studying materials with broad spectral features.