Rapid scan electron paramagnetic resonance at 1.0 GHz of defect centers in γ-irradiated organic solids

Shi, Yilin; Rinard, George A.; Quine, Richard W.

doi:10.1016/j.radmeas.2015.12.011

Cited by 9 publications

(10 citation statements)

References 34 publications

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“…Improved S/N has also been observed for irradiated teeth [36] and irradiated clipped fingernails [37], which have potential applications for radiation dosimetry. At L-band the S/N for radicals observed in γ-irradiated solids is improved by factors of 20 to 35 [30]. At 250 MHz rapid scan improves S/N relative to CW by about a factor of 10 for EPR imaging [38, 39].…”

Section: Improved Signal-to-noise For Rapid Scan Relative To Cwmentioning

confidence: 99%

Rapid-scan EPR imaging

Eaton

Shi

Woodcock

et al. 2017

Journal of Magnetic Resonance

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In rapid-scan EPR the magnetic field or frequency is repeatedly scanned through the spectrum at rates that are much faster than in conventional continuous wave EPR. The signal is directly-detected with a mixer at the source frequency. Rapid-scan EPR is particularly advantageous when the scan rate through resonance is fast relative to electron spin relaxation rates. In such scans, there may be oscillations on the trailing edge of the spectrum. These oscillations can be removed by mathematical deconvolution to recover the slow-scan absorption spectrum. In cases of inhomogeneous broadening, the oscillations may interfere destructively to the extent that they are not visible. The deconvolution can be used even when it is not required, so spectra can be obtained in which some portions of the spectrum are in the rapid-scan regime and some are not. The technology developed for rapid-scan EPR can be applied generally so long as spectra are obtained in the linear response region. The detection of the full spectrum in each scan, the ability to use higher microwave power without saturation, and the noise filtering inherent in coherent averaging results in substantial improvement in signal-to-noise relative to conventional continuous wave spectroscopy, which is particularly advantageous for low-frequency EPR imaging. This overview describes the principles of rapid-scan EPR and the hardware used to generate the spectra. Examples are provided of its application to imaging of nitroxide radicals, diradicals, and spin-trapped radicals at a Larmor frequency of ca. 250 MHz.

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Section: Improved Signal-to-noise For Rapid Scan Relative To Cwmentioning

confidence: 99%

Rapid-scan EPR imaging

Eaton

Shi

Woodcock

et al. 2017

Journal of Magnetic Resonance

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“…[23][24][25][26] Ionizing radiation, including grays, is known to create stable radicals in a variety of chemical systems. [27][28][29][30][31][32] More recently, Blank and coworkers demonstrated that radicals are created in glucose by exposure to ionizing plasma, 33 and were able to obtain εH ≈ 150 at 3.3 T and 50 K for stationary powders. 34 Here we utilize ionizing γ-radiation as a means of generating endogenous radicals and investigate their suitability for MAS DNP.…”

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confidence: 99%

“…For example, biradical polarizing agents have been added during precipitation and/or crystallization of organic solids from solution or directly incorporated into polymers by swelling them with a radical solution or precipitating them from a radical solution. − Metal centers added as dopants to organic solids , or intrinsic to inorganic materials , have also been used to hyperpolarize nuclei in the bulk. Alternatively, several early DNP studies used neutron beam irradiation to induce formation of radicals that are suitable for DNP. − Ionizing radiation, including γ-rays, is known to create stable radicals in a variety of chemical systems. − More recently, Blank and co-workers demonstrated that radicals are created in glucose by exposure to ionizing plasma and were able to obtain an ε H of ≈150 at 3.3 T and 50 K for stationary powders …”

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High-Field Magic Angle Spinning Dynamic Nuclear Polarization Using Radicals Created by γ-Irradiation

Carnahan

Venkatesh

Perras

et al. 2019

J. Phys. Chem. Lett.

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High-field magic angle spinning dynamic nuclear polarization (MAS DNP) is often used to enhance the sensitivity of solid-state nuclear magnetic resonance (ssNMR) experiments by transferring spin polarization from electron spins to nuclear spins. Here, we demonstrate that γirradiation induces the formation of stable radicals in inorganic solids, such as fused quartz and borosilicate glasses as well as organic solids such as glucose, cellulose, and a urea/polyethylene polymer. The radicals were then used to polarize 29 Si or 1 H spins in the core of some of these materials. Significant MAS DNP enhancements (e) greater than 400 and 30 were obtained for fused quartz and glucose, respectively. For other samples negligible e were obtained likely due to low concentrations of radicals or the presence of abundant quadrupolar spins. These results demonstrate that ionizing radiation is a promising alternative method for generating stable radicals suitable for high-field MAS DNP experiments.

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“…This magnet was designed to achieve wide magnetic field scans for L‐band (ca. 1.07 GHz) EPR spectroscopy, and in the same laboratory as the 250 MHz spectrometer, so this magnet was used for the UHF EPR spectroscopy. The parameters are given in the following list.…”

Section: Four‐coil Air‐core Magnetmentioning

confidence: 99%

UHF EPR spectrometer operating at frequencies between 400 MHz and 1 GHz

Quine

Rinard

Shi

et al. 2016

Concepts Magn Reson

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A spectrometer was designed and constructed to facilitate measurements of T1, T2, spin echo signal-to-noise, and resonator quality factor, Q, between about 400 and 1000 MHz. Pulse patterns are generated at 250 MHz and mixed with the output from a second source to perform excitation and detection. A cross-loop resonator was constructed in which the same sample could be measured in the same resonator over the full range of frequencies. An air-core, 4-coil, water-cooled electromagnet with a large experimental volume was built.

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Rapid scan electron paramagnetic resonance at 1.0 GHz of defect centers in γ-irradiated organic solids

Cited by 9 publications

References 34 publications

Rapid-scan EPR imaging

Rapid-scan EPR imaging

High-Field Magic Angle Spinning Dynamic Nuclear Polarization Using Radicals Created by γ-Irradiation

UHF EPR spectrometer operating at frequencies between 400 MHz and 1 GHz

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