DNP-NMR of surface hydrogen on silicon microparticles

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

doi:10.1016/j.ssnmr.2019.04.008

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 journal › Article › peer-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 language	American English
Pages (from-to)	68-75
Number of pages	8
Journal	Solid State Nuclear Magnetic Resonance
Volume	101
DOIs	https://doi.org/10.1016/j.ssnmr.2019.04.008
State	Published - Sep 2019
Externally published	Yes

Bibliographical note

Funding Information:
This research was funded in part by the US National Science Foundation under Grant Nos. CHE-1410504 (CR), DMR-1508661 (S.T.) and CHE-1611134 ) (S.T.), the Nottingham University Engineering and Physical Sciences Partnered Access Fund and a Dartmouth College Global Exploratory and Development Grant. The Nottingham DNP MAS NMR Facility is funded by Grants EP/R042853/1 and EP/L022524/1 . We would like to thank Dr. Maxime J. Guinel for his help with the SEM experiments.

Funding Information:
This research was funded in part by the US National Science Foundation under Grant Nos. CHE-1410504 (CR), DMR-1508661 (S.T.)and CHE-1611134)(S.T.), the Nottingham University Engineering and Physical Sciences Partnered Access Fund and a Dartmouth College Global Exploratory and Development Grant. The Nottingham DNP MAS NMR Facility is funded by Grants EP/R042853/1 and EP/L022524/1. We would like to thank Dr. Maxime J. Guinel for his help with the SEM experiments.

Publisher Copyright:
© 2019 Elsevier Inc.

Keywords

DNP
Dynamic nuclear polarization
NMR
Nuclear magnetic resonance
Silicon particles
Surface

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10.1016/j.ssnmr.2019.04.008

Cite this

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title = "DNP-NMR of surface hydrogen on silicon microparticles",

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.",

keywords = "DNP, Dynamic nuclear polarization, NMR, Nuclear magnetic resonance, Silicon particles, Surface",

author = "Daphna Shimon and {van Schooten}, {Kipp J.} and Subhradip Paul and Zaili Peng and Susumu Takahashi and Walter K{\"o}ckenberger and Chandrasekhar Ramanathan",

note = "Funding Information: This research was funded in part by the US National Science Foundation under Grant Nos. CHE-1410504 (CR), DMR-1508661 (S.T.) and CHE-1611134 ) (S.T.), the Nottingham University Engineering and Physical Sciences Partnered Access Fund and a Dartmouth College Global Exploratory and Development Grant. The Nottingham DNP MAS NMR Facility is funded by Grants EP/R042853/1 and EP/L022524/1 . We would like to thank Dr. Maxime J. Guinel for his help with the SEM experiments. Funding Information: This research was funded in part by the US National Science Foundation under Grant Nos. CHE-1410504 (CR), DMR-1508661 (S.T.)and CHE-1611134)(S.T.), the Nottingham University Engineering and Physical Sciences Partnered Access Fund and a Dartmouth College Global Exploratory and Development Grant. The Nottingham DNP MAS NMR Facility is funded by Grants EP/R042853/1 and EP/L022524/1. We would like to thank Dr. Maxime J. Guinel for his help with the SEM experiments. Publisher Copyright: {\textcopyright} 2019 Elsevier Inc.",

year = "2019",

month = sep,

doi = "10.1016/j.ssnmr.2019.04.008",

language = "American English",

volume = "101",

pages = "68--75",

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AU - Shimon, Daphna

AU - van Schooten, Kipp J.

AU - Paul, Subhradip

AU - Peng, Zaili

AU - Takahashi, Susumu

AU - Köckenberger, Walter

AU - Ramanathan, Chandrasekhar

N1 - Funding Information: This research was funded in part by the US National Science Foundation under Grant Nos. CHE-1410504 (CR), DMR-1508661 (S.T.) and CHE-1611134 ) (S.T.), the Nottingham University Engineering and Physical Sciences Partnered Access Fund and a Dartmouth College Global Exploratory and Development Grant. The Nottingham DNP MAS NMR Facility is funded by Grants EP/R042853/1 and EP/L022524/1 . We would like to thank Dr. Maxime J. Guinel for his help with the SEM experiments. Funding Information: This research was funded in part by the US National Science Foundation under Grant Nos. CHE-1410504 (CR), DMR-1508661 (S.T.)and CHE-1611134)(S.T.), the Nottingham University Engineering and Physical Sciences Partnered Access Fund and a Dartmouth College Global Exploratory and Development Grant. The Nottingham DNP MAS NMR Facility is funded by Grants EP/R042853/1 and EP/L022524/1. We would like to thank Dr. Maxime J. Guinel for his help with the SEM experiments. Publisher Copyright: © 2019 Elsevier Inc.

PY - 2019/9

Y1 - 2019/9

N2 - 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.

AB - 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.

KW - DNP

KW - Dynamic nuclear polarization

KW - NMR

KW - Nuclear magnetic resonance

KW - Silicon particles

KW - Surface

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SN - 0926-2040

VL - 101

SP - 68

EP - 75

JO - Solid State Nuclear Magnetic Resonance

JF - Solid State Nuclear Magnetic Resonance

ER -

DNP-NMR of surface hydrogen on silicon microparticles

Abstract

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Keywords

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