DNP-NMR of surface hydrogen on silicon microparticles

Daphna Shimon*, Kipp J. van Schooten, Subhradip Paul, Zaili Peng, Susumu Takahashi, Walter Köckenberger, Chandrasekhar Ramanathan

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Dynamic nuclear polarization (DNP)enhanced nuclear magnetic resonance (NMR)offers a promising route to studying local atomic environments at the surface of both crystalline and amorphous materials. We take advantage of unpaired electrons due to defects close to the surface of the silicon microparticles to hyperpolarize adjacent 1H nuclei. At 3.3 T and 4.2 K, we observe the presence of two proton peaks, each with a linewidth on the order of 5 kHz. Echo experiments indicate a homogeneous linewidth of ∼150−300 Hz for both peaks, indicative of a sparse distribution of protons in both environments. The high frequency peak at 10 ppm lies within the typical chemical shift range for proton NMR, and was found to be relatively stable over repeated measurements. The low frequency peak was found to vary in position between −19 and −37 ppm, well outside the range of typical proton NMR shifts, and indicative of a high-degree of chemical shielding. The low frequency peak was also found to vary significantly in intensity across different experimental runs, suggesting a weakly-bound species. These results suggest that the hydrogen is located in two distinct microscopic environments on the surface of these Si particles.

Original languageAmerican English
Pages (from-to)68-75
Number of pages8
JournalSolid State Nuclear Magnetic Resonance
Volume101
DOIs
StatePublished - Sep 2019
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2019 Elsevier Inc.

Keywords

  • DNP
  • Dynamic nuclear polarization
  • NMR
  • Nuclear magnetic resonance
  • Silicon particles
  • Surface

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