Boosting dissolution-dynamic nuclear polarization by multiple-step dipolar order mediated 1H→13C cross-polarization

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• Multiple low-power 1 H→ 13 C polarization transfers were performed. • A 13 C polarization of ∼43.5% was accrued in the frozen solid-state. • 13 C polarization amassed with a build-up time constant ∼5.1 minutes. • A 13 C polarization of ∼27.5% was recorded in the liquid-state. • Low-power transfers are ∼69% as efficient as cross-polarization. Dissolution-dynamic nuclear polarization can be boosted by employing multiple-contact cross-polarization techniques to transfer polarization from 1 H to 13 C spins. The method is efficient and significantly reduces polarization build-up times, however, it involves high-power radiofrequency pulses in a superfluid helium environment which limit its implementation and applicability and prevent a significant scaling-up of the sample size. We propose to overcome this limitation by a stepwise transfer of polarization using a low-energy and low-peak power radiofrequency pulse sequence where the 1 H→ 13 C polarization transfer is mediated by a dipolar spin order reservoir. An experimental demonstration is presented for [1- 13 C]sodium acetate. A solid-state 13 C polarization of ∼43.5% was achieved using this method with a build-up time constant of ∼5.1 minutes, leading to a ∼27.5% 13 C polarization in the liquid-state after sample dissolution. The low-power multiple-step polarization transfer efficiency achieved with respect to the most advanced and highest-power multiple-contact cross-polarization approach was found to be ∼0.69.