Dynamic Nuclear Polarization (DNP)

Main content

NMR is a powerful analytical technique for structural studies of organometallics. In addition to routine characterization of reaction products by solution-state NMR, we utilize magic angle spinning (MAS) solid-state NMR to examine single-site surface species, zeolites, and nanoparticles. Dynamic nuclear polarization (DNP) can increase NMR signal by up to 2 orders of magnitude via transferring paramagnetic electron polarization from a polarization agent (e.g., TEKPol), taking advantage of the much larger electron Zeeman interaction. We actively collaborate with research groups within ETH and also at ENS Lyon and EPFL to develop new DNP applications and methodologies. 

DNP Mechanism. 1. Microwave from the gyrotron saturates the EPR transition of polarization agents (TEKPOL is shown here). 2. The larger non-Boltzmann polarization is generated via the Cross Effect on solvent 1H. 3. Enhanced polarization is transferred from 1H to X via cross polarization.
DNP Instrumentation. Continuous-wave microwave is generated by the gyrotron, and then delivered to the sample inside the NMR magnet via waveguide. 
DNP enhanced 1H-13C CPMAS spectrum (600 MHz, ETH) of grafted phenol on silica (MatPhOH). Solid-state NMR signal was enhanced by a factor of 22 when DNP was active (red) compared to inactive (blue).

Selected Publications

Lesage, A., Lelli, M., Gajan, D., Caporini, M. A., Vitzthum, V., et al. (2010). Surface enhanced NMR spectroscopy by dynamic nuclear polarization. Journal of the American Chemical Society, 132, 15459-15461

Rossini, A. J., Zagdoun, A., Lelli, M., Lesage, A., Copéret, C. et al. (2013). Dynamic nuclear polarization surface enhanced NMR spectroscopy. Accounts in Chemical Research, 46, 1942-1951.

Wolf, P., Valla, M., Rossini, A. J., Comas-Vives, A., Núnez-Zarur, F. et al. (2014). NMR signatures of the active sites in Sn-β zeolite. Angewandte Chemie International Edition, 53, 10179-10183.

Valla, M., Rossini, A. J., Caillot, M., Chizallet, C., Raybaud, P. et al. (2015). Atomic description of the interface between silica and alumina in aluminosilicates through dynamic nuclear polarization surface-enhanced NMR spectroscopy and first-principled calculations. Journal of the American Chemical Society, 137, 10710-10719.

DNP study of aluminosilicates. A. DNP enhanced 1H-27Al CPMAS spectra (600 MHz, ETH) of aluminosilicates containing various concentrations of Al. B. DNP enhanced 1H-29Si CPMAS spectra (400 MHz, EPFL) of the same samples. C. DNP enhanced 29Si-27Al correlation spectra (400 MHz, EPFL) by scalar refocused INEPT (black) and dipolar refocused R3-INEPT (red). 

Piveteau, L., Ong, T. C., Rossini, A. J., Emsley, L., Copéret, C., and Kovalenko, M. (2015). Structure of colloidal quantum dots from dynamic nuclear polarization surface enhanced NMR spectroscopy. Journal of the American Chemical Society, 137, 13964-13971.

DNP enhanced 1H-77Se CP-CPMG spectra of phosphonate-capped WZ-CdSe quantum dots (black) and oleate-capped ZB-CdSe quantum dots (dark blue).  
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