Methylammonium lead chloride: A sensitive sample for an accurate NMR thermometer

Area of Science:

• Solid-state NMR spectroscopy
• Materials science
• Thermometry

Background:

• Accurate temperature calibration is crucial for reproducible solid-state NMR experiments.
• Existing NMR thermometry methods have limitations in temperature range or applicability.

Purpose of the Study:

• To introduce a new solid-state NMR thermometry standard.
• To validate its performance over a wide temperature range.
• To assess its utility for variable temperature NMR data acquisition.

Main Methods:

• Utilized methylammonium lead chloride (MAPbCl3) as a solid-state NMR thermometry sample.
• Measured the 207Pb NMR chemical shift's temperature dependence.
• Developed a frequency-ratio method for referencing chemical shifts using 1H and 13C signals.
• Investigated frictional heating in MAS rotors using the developed thermometer.

Main Results:

• The 207Pb NMR chemical shift of MAPbCl3 exhibits a linear temperature dependence (0.905±0.010ppmK-1) from 178K to >410K.
• The symmetric NMR lineshape is suitable for both spinning and non-spinning samples.
• The frequency-ratio method provides reliable chemical shift referencing.
• Frictional heating in MAS rotors was quantified and correlated with rotor diameter and spinning frequency.

Conclusions:

• Methylammonium lead chloride is a highly effective solid-state NMR thermometer for a broad temperature range.
• The proposed referencing method enhances accuracy for variable temperature NMR.
• This thermometer enables precise measurement of frictional heating in NMR rotors.