Overhauser effects in insulating solids
We report magic angle spinning, dynamic nuclear polarization (DNP) experiments at magnetic fields of 9.4 T, 14.1 T, and 18.8 T using the narrow line polarizing agents 1,3-bisdiphenylene-2-phenylallyl (BDPA) dispersed in polystyrene, and sulfonated-BDPA (SA-BDPA) and trityl OX063 in glassy glycerol/w...
| Main Authors: | , , , , , , , , , , |
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| Other Authors: | |
| Format: | Article |
| Language: | en_US |
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American Institute of Physics (AIP)
2017
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| Online Access: | http://hdl.handle.net/1721.1/109520 https://orcid.org/0000-0001-9092-612X https://orcid.org/0000-0003-1589-832X |
| _version_ | 1826205575535394816 |
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| author | Caporini, M. A. Mentink-Vigier, F. Rosay, M. Maas, W. E. Baldus, M. Vega, S. Corzilius, Bjorn Walish, Joseph John Swager, Timothy M Griffin, Robert Guy Can, Thach V |
| author2 | Massachusetts Institute of Technology. Department of Chemistry |
| author_facet | Massachusetts Institute of Technology. Department of Chemistry Caporini, M. A. Mentink-Vigier, F. Rosay, M. Maas, W. E. Baldus, M. Vega, S. Corzilius, Bjorn Walish, Joseph John Swager, Timothy M Griffin, Robert Guy Can, Thach V |
| author_sort | Caporini, M. A. |
| collection | MIT |
| description | We report magic angle spinning, dynamic nuclear polarization (DNP) experiments at magnetic fields of 9.4 T, 14.1 T, and 18.8 T using the narrow line polarizing agents 1,3-bisdiphenylene-2-phenylallyl (BDPA) dispersed in polystyrene, and sulfonated-BDPA (SA-BDPA) and trityl OX063 in glassy glycerol/water matrices. The 1H DNP enhancement field profiles of the BDPA radicals exhibit a significant DNP Overhauser effect (OE) as well as a solid effect (SE) despite the fact that these samples are insulating solids. In contrast, trityl exhibits only a SE enhancement. Data suggest that the appearance of the OE is due to rather strong electron-nuclear hyperfine couplings present in BDPA and SA-BDPA, which are absent in trityl and perdeuterated BDPA (d21-BDPA). In addition, and in contrast to other DNP mechanisms such as the solid effect or cross effect, the experimental data suggest that the OE in non-conducting solids scales favorably with magnetic field, increasing in magnitude in going from 5 T, to 9.4 T, to 14.1 T, and to 18.8 T. Simulations using a model two spin system consisting of an electron hyperfine coupled to a 1H reproduce the essential features of the field profiles and indicate that the OE in these samples originates from the zero and double quantum cross relaxation induced by fluctuating hyperfine interactions between the intramolecular delocalized unpaired electrons and their neighboring nuclei, and that the size of these hyperfine couplings is crucial to the magnitude of the enhancements. Microwave power dependent studies show that the OE saturates at considerably lower power levels than the solid effect in the same samples. Our results provide new insights into the mechanism of the Overhauser effect, and also provide a new approach to perform DNP experiments in chemical, biophysical, and physical systems at high magnetic fields. |
| first_indexed | 2024-09-23T13:15:19Z |
| format | Article |
| id | mit-1721.1/109520 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T13:15:19Z |
| publishDate | 2017 |
| publisher | American Institute of Physics (AIP) |
| record_format | dspace |
| spelling | mit-1721.1/1095202022-10-01T14:03:36Z Overhauser effects in insulating solids Caporini, M. A. Mentink-Vigier, F. Rosay, M. Maas, W. E. Baldus, M. Vega, S. Corzilius, Bjorn Walish, Joseph John Swager, Timothy M Griffin, Robert Guy Can, Thach V Massachusetts Institute of Technology. Department of Chemistry Francis Bitter Magnet Laboratory (Massachusetts Institute of Technology) Can, Thach Van Corzilius, Bjorn Walish, Joseph John Swager, Timothy M Griffin, Robert Guy We report magic angle spinning, dynamic nuclear polarization (DNP) experiments at magnetic fields of 9.4 T, 14.1 T, and 18.8 T using the narrow line polarizing agents 1,3-bisdiphenylene-2-phenylallyl (BDPA) dispersed in polystyrene, and sulfonated-BDPA (SA-BDPA) and trityl OX063 in glassy glycerol/water matrices. The 1H DNP enhancement field profiles of the BDPA radicals exhibit a significant DNP Overhauser effect (OE) as well as a solid effect (SE) despite the fact that these samples are insulating solids. In contrast, trityl exhibits only a SE enhancement. Data suggest that the appearance of the OE is due to rather strong electron-nuclear hyperfine couplings present in BDPA and SA-BDPA, which are absent in trityl and perdeuterated BDPA (d21-BDPA). In addition, and in contrast to other DNP mechanisms such as the solid effect or cross effect, the experimental data suggest that the OE in non-conducting solids scales favorably with magnetic field, increasing in magnitude in going from 5 T, to 9.4 T, to 14.1 T, and to 18.8 T. Simulations using a model two spin system consisting of an electron hyperfine coupled to a 1H reproduce the essential features of the field profiles and indicate that the OE in these samples originates from the zero and double quantum cross relaxation induced by fluctuating hyperfine interactions between the intramolecular delocalized unpaired electrons and their neighboring nuclei, and that the size of these hyperfine couplings is crucial to the magnitude of the enhancements. Microwave power dependent studies show that the OE saturates at considerably lower power levels than the solid effect in the same samples. Our results provide new insights into the mechanism of the Overhauser effect, and also provide a new approach to perform DNP experiments in chemical, biophysical, and physical systems at high magnetic fields. National Institute of General Medical Sciences (U.S.) (Grant No. GM095843) National Institute for Biomedical Imaging and Bioengineering (U.S.) (NIBIB, Grant No. EB-002804)) National Institute for Biomedical Imaging and Bioengineering (U.S.) (NIBIB, Grant No. EB002026) 2017-06-01T20:37:55Z 2017-06-01T20:37:55Z 2014-08 2014-05 Article http://purl.org/eprint/type/JournalArticle 0021-9606 1089-7690 http://hdl.handle.net/1721.1/109520 Can, T. V., M. A. Caporini, F. Mentink-Vigier, B. Corzilius, J. J. Walish, M. Rosay, W. E. Maas, M. Baldus, S. Vega, T. M. Swager, and R. G. Griffin. "Overhauser effects in insulating solids." Journal of Chemical Physics 141, 064202 (2014). © 2014 AIP Publishing LLC. https://orcid.org/0000-0001-9092-612X https://orcid.org/0000-0003-1589-832X en_US http://dx.doi.org/10.1063/1.4891866 Journal of Chemical Physics Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf American Institute of Physics (AIP) PMC |
| spellingShingle | Caporini, M. A. Mentink-Vigier, F. Rosay, M. Maas, W. E. Baldus, M. Vega, S. Corzilius, Bjorn Walish, Joseph John Swager, Timothy M Griffin, Robert Guy Can, Thach V Overhauser effects in insulating solids |
| title | Overhauser effects in insulating solids |
| title_full | Overhauser effects in insulating solids |
| title_fullStr | Overhauser effects in insulating solids |
| title_full_unstemmed | Overhauser effects in insulating solids |
| title_short | Overhauser effects in insulating solids |
| title_sort | overhauser effects in insulating solids |
| url | http://hdl.handle.net/1721.1/109520 https://orcid.org/0000-0001-9092-612X https://orcid.org/0000-0003-1589-832X |
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