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Towards efficient pulsed dynamic nuclear polarisation (DNP) enhanced NMR experiments

Researchers from ETH Zürich, Aarhus University (AU) and École Normale Supérieure (ENS) Paris have demonstrated that combination of clever pulse sequence engineering and state-of-the-art instrumentation paves the way for pulsed dynamic nuclear polarisation (DNP) experiments improving sensitivity and broadband performance in DNP enhanced nuclear magnetic resonance (NMR).

DNP provides fantastic opportunities to boost the sensitivity of NMR experiments by orders of magnitude, as has been demonstrated with impressive results in numerous studies since the introduction of the DNP concept in the 1950s. Tremendous progress has been seen through dissolution and in-situ DNP experiments, most of which has been based on continuous wave microwave irradiation. The realisation of pulsed experiments – which is believed to boost performance in a similar manner as has been seen in the NMR area over the past decades – has been lacking behind due to the need of fast pulsed microwave instrumentation and pulse sequences capable of coping with large electron-induced spin interactions.

With ETH researchers Nino Wili and Gunnar Jeschke, ENS researcher Kong Ooi Tan, and AU researchers Anders Bodholt Nielsen and Niels Chr. Nielsen and their teams joining efforts, a recent study published in Science Advances demonstrates new potentials for realising pulsed DNP experiments. The team combines state-of-the-art fast waveform, high-power microwave instrumentation with new pulse sequence design strategies to cope with the challenges and potentials of the dominant electron spin interactions. This enabled the design of new experiments with 1H DNP enhancements factors exceeding 360, along with radically improved broadband performance – which represents an important step ahead in realisation of pulsed DNP.

AU researchers Anders Bodholt Nielsen and Niels Chr. Nielsen are excited about the study and the coming years: "This study – being a wonderful example of international collaboration at its best – brings us an important step forward as it clearly demonstrates that it is possible to harvest significant gains in DNP by realisation of advanced pulsed experiments. This supports our belief that DNP in the coming years will be transformed in similar ways as we have seen for NMR over the past decades. It is not straightforward – especially not at high frequencies where it is difficult to realise high-power microwave irradiation – but definitely a high-priority challenge for the NMR/DNP/EPR community to undertake in the coming years. In the international team, we will continue our efforts, with the noting that first-author of the paper, Dr Nino Wili, will join the AU team in August 2022."