Viscosity effects on optically generated electron and nuclear spin hyperpolarization

Dale, Matthew; Cheney, Daniel J.; Vallotto, Claudio; Wedge, Christopher J.

doi:10.1039/d0cp04012f

Cited by 4 publications

(15 citation statements)

References 52 publications

(81 reference statements)

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“…This suggests that controlling the dynamics as well as the distance between the dye and the radical is important for both efficient DEP and long-lasting DEP. Based on the findings obtained in this study, we expect that the optimization of various dyes and radicals linked by flexible linkers will lead to the application of large and sustained DEP to ESR imaging and light-driven DNP. − …”

Section: Discussionmentioning

confidence: 82%

“…In addition, the ESR signal in the unlinked systems decayed within a few microseconds, whereas the ESR signal in the hybridized systems was observed for more than 10 μs. It has been reported that the integrated ESR signal over time is a good indicator of optically generated DNP, and hybridized systems are expected to show much better DNP performance than unlinked systems.…”

Section: Resultsmentioning

confidence: 99%

“…As a promising mechanism to achieve high electron spin polarization, dynamic electron polarization (DEP) via quenching of photoexcited states by stable radicals has been developed. − In particular, its application to DNP has the potential to break the intrinsic limit of the enhancement factor with radical electron spins in thermal equilibrium because it can generate large electron spin polarization even in low magnetic fields and at room temperature. This promise is becoming reality with the observation of Overhauser DNP driven by light irradiation without the microwave irradiation. − It was found that not only DEP efficiency but also long-lasting DEP are key factors toward efficient DNP …”

Section: Introductionmentioning

confidence: 99%

“…30−35 It was found that not only DEP efficiency but also long-lasting DEP are key factors toward efficient DNP. 32 The simplest system for inducing DEP is a solution of "unlinked" dyes and radicals. 8−29 However, since the encounter between the photoexcited species and the radicals is the rate-limiting step, intense laser irradiation and high concentration of dyes and radicals are necessary to obtain large DEP.…”

Section: Introductionmentioning

confidence: 99%

“…An alternative approach to facilitate this encounter is the "hybridized" system, where dyes and radicals are connected by covalent or noncovalent bonds. 34−56 This is promising for photodriven DNP [30][31][32][33][34][35]57 and EPR imaging. 58 The derivatives of quinones, 35−37 polyaromatics, 38−41 fullerene, 34,42 BODI-PY, 43 porphyrins, 44−52 and phthalocyanine 53−56 have been used as the chromophores for these hybridized systems.…”

Section: Introductionmentioning

confidence: 99%

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Dynamic Electron Polarization Lasting More Than 10 μs by Hybridizing Porphyrin and TEMPO with Flexible Linkers

et al. 2023

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Dynamic electron polarization (DEP), induced by quenching of photoexcited species by stable radicals, can hyperpolarize electron spins in solution at room temperature. Recently, development of technologies based on electron spin polarization such as dynamic nuclear polarization (DNP) has been progressing, where it is important to design molecules that achieve long-lasting DEP in addition to high DEP. Hybridization by linking dyes and radicals is a promising approach for efficient DEP, but strong interactions between neighboring dyes and radicals often result in the rapid decay of DEP. In this study, we introduce a flexible linker into the hybrid system of porphyrin and TEMPO to achieve both efficient DEP and long-lasting DEP. The structural flexibility of the linker switches the interaction between the radical and the triplet, which promotes the DEP process by bringing the radical and the triplet into close proximity, while avoiding abrupt relaxation due to strong interactions. As a result, the new hybridized system exhibits a larger DEP than the unlinked system, while at the same time achieving a DEP lasting more than 10 μs.

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Section: Discussionmentioning

confidence: 82%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dynamic Electron Polarization Lasting More Than 10 μs by Hybridizing Porphyrin and TEMPO with Flexible Linkers

et al. 2023

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Sample volume effects in optical overhauser dynamic nuclear polarization

Cheney

Wedge

2022

Journal of Magnetic Resonance

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Spin Hyperpolarization in Modern Magnetic Resonance

et al. 2023

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Magnetic resonance techniques are successfully utilized in a broad range of scientific disciplines and in various practical applications, with medical magnetic resonance imaging being the most widely known example. Currently, both fundamental and applied magnetic resonance are enjoying a major boost owing to the rapidly developing field of spin hyperpolarization. Hyperpolarization techniques are able to enhance signal intensities in magnetic resonance by several orders of magnitude, and thus to largely overcome its major disadvantage of relatively low sensitivity. This provides new impetus for existing applications of magnetic resonance and opens the gates to exciting new possibilities. In this review, we provide a unified picture of the many methods and techniques that fall under the umbrella term "hyperpolarization" but are currently seldom perceived as integral parts of the same field. Specifically, before delving into the individual techniques, we provide a detailed analysis of the underlying principles of spin hyperpolarization. We attempt to uncover and classify the origins of hyperpolarization, to establish its sources and the specific mechanisms that enable the flow of polarization from a source to the target spins. We then give a more detailed analysis of individual hyperpolarization techniques: the mechanisms by which they work, fundamental and technical requirements, characteristic applications, unresolved issues, and possible future directions. We are seeing a continuous growth of activity in the field of spin hyperpolarization, and we expect the field to flourish as new and improved hyperpolarization techniques are implemented. Some key areas for development are in prolonging polarization lifetimes, making hyperpolarization techniques more generally applicable to chemical/biological systems, reducing the technical and equipment requirements, and creating more efficient excitation and detection schemes. We hope this review will facilitate the sharing of knowledge between subfields within the broad topic of hyperpolarization, to help overcome existing challenges in magnetic resonance and enable novel applications.

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Viscosity effects on optically generated electron and nuclear spin hyperpolarization

Abstract: Optically-generated dynamic nuclear polarization is increased in viscous mixtures due to longer lived electron spin polarization.

Cited by 4 publications

References 52 publications

Dynamic Electron Polarization Lasting More Than 10 μs by Hybridizing Porphyrin and TEMPO with Flexible Linkers

Dynamic Electron Polarization Lasting More Than 10 μs by Hybridizing Porphyrin and TEMPO with Flexible Linkers

Sample volume effects in optical overhauser dynamic nuclear polarization

Spin Hyperpolarization in Modern Magnetic Resonance

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