Photochemically induced dynamic nuclear polarization of heteronuclear singlet order

TL;DR

This paper demonstrates a simple, cost-effective method to hyperpolarize nuclear spins using light in Earth's magnetic field and zero- to ultralow-field conditions, significantly enhancing NMR signals.

Contribution

It introduces a novel approach to perform photo-CIDNP hyperpolarization at low magnetic fields, producing strong signals and revealing different spin states with longer lifetimes.

Findings

Hyperpolarization enhances NMR signals by several hundred times.

Different hyperpolarized states are observed at Earth field and ZULF.

The method is applicable to various molecular systems like amino acids and nucleotides.

Abstract

Photochemically induced dynamic nuclear polarization (photo-CIDNP) is a method to hyperpolarize nuclear spins using light. In most cases, CIDNP experiments are performed at a high magnetic field and the sample is irradiated by the light inside a nuclear magnetic resonance (NMR) spectrometer. Here we demonstrate photo-CIDNP hyperpolarization generated in the Earth magnetic field and under zero- to ultralow field (ZULF) conditions. Irradiating a sample for several seconds with inexpensive light-emitting diodes produces a strong hyperpolarization of 1H and 13C nuclear spins enhancing the NMR signals several hundred times. The hyperpolarized spin states at the Earth field and in ZULF are different. In the latter case, the state corresponds to the singlet order between scalar-coupled 1H-13C nuclear spins. This state has a longer lifetime than the state hyperpolarized at Earth field. The method is simple and cost-efficient and should be applicable to many molecular systems known to exhibit photo-CIDNP, including amino acids and nucleotides.