¹⁹F solid state NMR by using 2mmMAS probe

JEOL 2mm MAS probe enables MA Spinning at nearly twice MAS speed of the conventional 3.2mm and 4mm MAS probe with 20 times the sample volume of the 1mm MAS probe. An attractive application of the 2mm MAS probe is ¹⁹F NMR. Strong ¹⁹F homonuclear dipolar coupling and wide chemical shift range cause a series of spinning side band (SSB) which make it difficult to analyze ¹⁹F spectra obtained by using the conventional 3.2mm and 4mm probes. The 2mm probe can achieve 40kHz MAS speeds, the resulting ¹⁹F spectra will had small well managed SSB’s.
Here, we introduce ¹⁹F solid state NMR spectra of Nafion known as a solid polymer electrolyte for fuel cells. Fig.1 shows ¹⁹F MAS spectra of Nafion at various MAS speeds. 40kHz MAS gives a clear ¹⁹F spectrum without overlapping of SSBs whereas overlap occur between center bands and their SSBs at MAS speeds less than 40kHz. Moreover, the much greater sensitivity of the 2mm probe than the 1mm probe enables direct observation of low sensitive nuclei such as ¹³C. Thus, ¹³C{¹⁹F} CPMAS( Fig.2) and ¹³C-¹⁹F 2D-HETCOR (Fig.3) can easily be obtained.

Chemical structure of Nafion

JNM-ECZ600R, 2mmHXMAS probe

Fig.1 ¹⁹F single pulse at various MAS frequencies. Peaks marked by * represent SSBs.

Fig.2 ¹³C {¹⁹F} CPMAS

Fig.3 ¹³C-¹⁹F HETCOR with high (left) and low (right) level thresholds.

• Reference: Q. Chen and K. Schmidt-Rohr, Macromolecules 2004, 37, 5995-6003
• Nafion is a trademark of The Chemorus Company.