Spinning-Driven Dynamic Nuclear Polarization with Optical Pumping

Abstract

We propose a new, more efficient, and potentially cost effective, solid-state nuclear spin hyperpolarization method combining the cross-effect mechanism and electron spin optical hyperpolarization in rotating solids. We first demonstrate optical hyperpolarization in the solid state at low temperatures and low field and then investigate its field dependence to obtain the optimal condition for high-field electron spin hyperpolarization. The results are then incorporated into advanced magic-angle spinning dynamic nuclear polarization (MAS-DNP) numerical simulations that show that optically pumped MAS-DNP could yield breakthrough enhancements at very high magnetic fields. Based on these investigations, enhancements greater than the ratio of electron to nucleus magnetic moments (>658 for 1H) are possible without microwave irradiation. This could solve at once the MAS-DNP performance decrease with increasing field and the high cost of MAS-DNP instruments at very high fields.

A unified description for polarization-transfer mechanisms in magnetic resonance in static solids: Cross polarization and DNP

“…Following this idea, a Gedankenexperiment, where CE DNP can be mediated by generating polarization difference between two electrons with selective optical pumping (without microwave irradiation), was proposed recently. 43 This is technically possible because microwave irradiation is not required to facilitate CE DNP [see CE Hamiltonian in Eq. ( 27)].…”

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

“…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.…”

“…The simplest system for inducing DEP is a solution of “unlinked” dyes and radicals. − 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. An alternative approach to facilitate this encounter is the “hybridized” system, where dyes and radicals are connected by covalent or noncovalent bonds. − This is promising for photodriven DNP − , and EPR imaging . The derivatives of quinones, − polyaromatics, − fullerene, , BODIPY, porphyrins, − and phthalocyanine − have been used as the chromophores for these hybridized systems.…”

Optically Enhanced Solid-State 1H NMR Spectroscopy

“…In recent years, optically driven nuclear polarization in solids has attracted more and more attention, − primarily because of its potential to overcome the enhancement limits of standard microwave-induced DNP approaches imposed by the thermal electron polarization. Indeed, for 1 H nuclei, the theoretical maximum DNP enhancement ε max , which corresponds to the ratio of the electron and proton gyromagnetic ratios, ε max = |γ e /γ 1H |, is a factor of 658 .…”