Global NMR Discussion Meetings

Hyperpolarization

  • Role of Quantum Coherence in Chirped DNP

    Mayur Manoj Jhamnani (New York University Abu Dhabi, United Arab Emirates)

    LinkedIn: @Mayur Jhamnani; X: @mayur_jhamnani

    Abstract: DNP is transforming NMR and MRI by significantly enhancing sensitivity through the transfer of polarization from electron spins to nuclear spins via microwave irradiation. However, the use of monochromatic continuous-wave irradiation limits the efficiency of DNP for systems with heterogeneous broad EPR lines. Broad-band techniques such as chirp irradiation offer a potential solution, particularly for Solid Effect (SE) DNP in such cases. Despite its widespread use, the role of quantum coherence generated during chirp irradiation remains unclear, even though it is a key factor in determining the maximum achievable DNP efficiency. In this work, we use density matrix formalism to provide a comprehensive understanding of the quantum coherence generated during non-adiabatic passages through electron-nucleus double-quantum (DQ) and zero-quantum (ZQ) SE transitions and their impact on Integrated Solid Effect DNP under chirp irradiation. Our analysis employs fictitious product-operator bases to trace the evolution of electron-nucleus coherence leading to integrated or differentiated SE. We also explore the role of decoherence in maximizing chirped DNP in microwave power or nutation frequency limited scenario. These findings provide an understanding of the role of coherence generated during pulsed-DNP and MAS-DNP at different temperature ranges. Our results reveal that quantum coherences generated during non-adiabatic passages critically determine whether the chirped DNP process yields Integrated Solid Effect (ISE), or Differential Solid Effect (DSE). By analyzing the evolution of the density matrix in DQ and ZQ subspaces, we show how coherence generation and its decay through decoherence play a decisive role in shaping the net DNP enhancement.

    1. Cory Widdifield Avatar
      Cory Widdifield

      Hello,

      Could you clarify what you mean when you state that adiabatic pulses do not generate coherence, while non-adiabatic pulses generate coherence?
      What would you say was the most surprising finding of your study? Is there a plan to confirm any of your theoretical findings experimentally?

      Reply
      1. Mayur Jhamnani Avatar
        Mayur Jhamnani

        Hello,

        Thanks for your question.

        1. When the chirped MW irradiation is adiabatic (i.e., satisfies the Landau Zener condition for adiabaticity), an initial density matrix that is a polarization, Sz, undergoes complete inversion to -Sz. However, if the chirp is non-adiabatic, an initial density matrix that is a polarization, Sz, does not undergo complete inversion, rather, some coherence is generated.

        2. Most surprising/important finding: We found that when the initial density matrix is a pure coherence (mSx + nSy)- an adiabatic pulse would lead to a generation of only coherence however, a non-adiabatic pulse would give both coherence and +/-polarization (sometimes +ve polarization is generated while other times -ve polarization is generated). This helped us explain the caveat between ISE and DSE in the paper: https://arxiv.org/html/2410.19170v1.

        3. Regarding experiments – our findings are experimentally hard to validate as there are several effects, powder averaging and B1 field inhomogeneity.

        Reply
    2. Arianna Actis Avatar
      Arianna Actis

      Hello Mayur, thank you for the presentation. It is a very interesting study.
      Could you comment more about why a chirp pulse is never adiabatic between ZQ and DQ transitions? Does it depend on the available mw power (omega1) and how?
      Why the decoherence process favours the ISE over the DSE?
      Thank you.

      Reply
    3. Mayur Jhamnani Avatar
      Mayur Jhamnani

      Hello,

      Thanks for your question.

      1. The MW chirp pulse can result in an adiabatic or non-adiabatic transition depending on the Landau-Zener (LZ) condition. The condition is that (pi*p^2) / 2k >> 1 for the chirp pulse to be adiabatic across a transition. Here p is the perturbation and k is the sweep rate.

      For a single quantum transition, perturbation is just MW power (in the rotating frame). As a result, it is much easier to ensure adiabaticity. However, the perturbation for DQ and ZQ transition have the pseudo-secular hyperfine coupling term (B) in the denominator. This means, higher MW power (beyond the available MW power) is required to excite these resonances adiabatically.

      2. The role of quantum coherence was causing the caveat between ISE and DSE. If the coherence is decayed, we can easily look at it from just a polarization standpoint. Since the SQ transition inverts the electron spin polarization from Sz to -Sz, the enhancement from the following ZQ transition will add to that from the DQ transition (leading to ISE). A detailed explanation is provided in https://arxiv.org/html/2410.19170v1.

      Reply
    4. Raj Chaklashiya Avatar
      Raj Chaklashiya

      Hi Mayur, interesting talk! I am curious, what would you expect the results to look like if you assume relaxation and coupling parameters from various known radicals (e.g. Trityl, AMUPOL, P1 centers). Would the resulting DNP mechanism be strongly dependent on the couplings/relaxations expected within such radicals?

      Reply
    5. Arianna Actis Avatar
      Arianna Actis

      Thank you for your reply Mayur.

      Reply

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  • DNP Semianalytical Calculations and Quantum Mechanical Simulations in MAS and Static Conditions

    Raj Chaklashiya (Northwestern University and University of California, Santa Barbara, United States)

    LinkedIn: @Raj Chaklashiya

    Abstract: Dynamic Nuclear Polarization (DNP) continues to transform NMR spectroscopy by enhancing its signal by several orders of magnitude via polarization transfer from unpaired electron spins to nuclear spins, enabling studies of objects consisting of very few spins such as cells. However, maximizing its potential towards subcellular components consisting of even fewer spins would significantly benefit from optimization of signal enhancement towards its theoretical maximum, which is nontrivial to achieve due to the many different factors that go into signal enhancement. DNP Semianalytical Calculations via simple numerical model assumptions and first principles Quantum Mechanical Simulations via time-evolved Hamiltonian propagators are two distinct methods that can be used to predict DNP performance and assess potential sources of missing enhancement via comparison with experimental DNP frequency profiles. This talk is a tutorial that applies these methods to the analysis of DNP from a highly efficient DNP biradical, TEMTriPol-1, which consists of one part Trityl and another part TEMPO. Inclusion of the effects of microwave saturation and electron spin relaxation in semianalytical calculations and use of the QUEST Northwestern computing cluster in Spinevolution quantum mechanical simulations both provide key improvements to these methods that enable closer matching between experiment and simulation. The results point towards the critical need to understand the J-coupling distribution of DNP radicals to fully understand the underlying DNP mechanism and optimize DNP performance.

    1. Arianna Actis Avatar
      Arianna Actis

      Dear Raj, very interesting study. Could you comment more on the role of the J coupling on the shape of the DNP profile? How would a reduction of J affect the profile? Have you studied other biradicals with different combinations of relaxation times/J couplings?

      Reply
      1. Raj Chaklashiya Avatar
        Raj Chaklashiya

        Dear Arianna, thank you, and thanks for the questions!
        So regarding J coupling and the profile shape, we found that reducing the J coupling narrows the Trityl part of the DNP profile significantly, removing the “bump” in the DNP profile that shows up on the left side of the profile during experiment. It seems that reducing J has the net effect of making the overall DNP profile narrower, leading to clear discrepancies with the broader experimental DNP profile.
        This is the first established biradical that I have done this kind of study on, but I have done simulation studies in the past of multiradicals and coupled monoradicals with varying dipolar, J, and/or relaxation times, and the results can get quite interesting. I’m happy to go more in-depth on this if you’d like! Here are a couple papers where we discuss those cases in detail:
        Multi Electron Spin Cluster Enabled Dynamic Nuclear Polarization with Sulfonated BDPA –in our simulation section we see the impact of J coupling and relaxation times on coupled BDPA and find that there is a combination that matches experimental trends. J coupling matching the nuclear larmor frequency combined with a strong differential in t1e’s can result in an absorptive central feature in the DNP profile lineshape: https://pubs.acs.org/doi/full/10.1021/acs.jpclett.3c02428
        Dynamic Nuclear Polarization Using Electron Spin Cluster – this paper has detailed simulations on Trityl-based multiradicals and the conditions in which dipolar couplings are strong enough to result in strong DNP enhancements, as well as the impact of relaxation time differentials on the DNP profile: https://pubs.acs.org/doi/full/10.1021/acs.jpclett.4c00182

        Reply
    2. Kuntal Mukherjee Avatar
      Kuntal Mukherjee

      Dear Raj, very nice talk! I would like to know that in second method, when you are observing for static case, the dipolar interaction is also present there (which is primarily averaged out in case of MAS), how the role of dipolar interaction and J-coupling can be separately understood?
      Thank you.

      Reply
      1. Raj Chaklashiya Avatar
        Raj Chaklashiya

        Hi Kuntal,

        Thank you! Good question–so first to clarify, the dipolar coupling definitely plays a role in both the MAS and Static simulations–even though there is averaging of dipolar orientations that would make seeing their effects in the NMR spectra harder, its effects can still be seen in the DNP profile itself, because in both cases the dipolar coupling strength directly determines how coupled the two electron spins are–if they are too weakly coupled, the Cross Effect DNP cannot occur, while if they have strong enough coupling it can occur. So in this sense, it needs to be understood for both static and MAS.

        As to your question–in these simulations I assume a dipolar coupling constant at 12.5 MHz because I don’t expect the distance between the Trityl electron and the TEMPO electron of TEMTriPol-1 to change. However, J-Coupling is a different story, as it is already known based on liquid state EPR experiments that there is a broad distribution of J couplings.

        However, if we assume both the dipolar and J couplings can change, what happens, and how do the effects differentiate from one another? I think in this case, the key difference lies in how they impact the EPR spin populations:
        – Dipolar coupling acts as a means to broaden electron spin populations. Stronger dipolar coupling results in broader EPR lines, while weaker dipolar coupling results in narrower EPR lines
        – J coupling acts as a means of splitting electron spin populations. Stronger +J coupling results in a wider split in the EPR line, while weaker +J coupling results in a narrower split in the EPR line. And crucially, negative J coupling when strong vs weak can flip this dependence (which results in the better fit with -J as opposed to +J)

        From this, one can see how dipolar coupling alone would result in different a different input EPR line, and therefore a different DNP profile–while it can broaden the already existing electron spin populations, it cannot necessarily create new populations further away. This means it would be harder for a small “bump” to suddenly appear due to dipolar broadening as opposed to J couplings–that bump however could easily be created if a population were shifted due to J couplings.

        The beauty of these simulations, however, is that it can be easy to test these hypotheses! We could input a range of dipolar coupling values and compare that with what happens if we input a range of J coupling values, and vice-versa, all while keeping the other coupling fixed.

        Let me know if you have any more questions!

        Reply
        1. Kuntal Mukherjee Avatar
          Kuntal Mukherjee

          Ok, that clears the query, thank you!

          Reply
          1. Raj Chaklashiya Avatar
            Raj Chaklashiya

            No problem!

            Reply

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  • 13C hyperpolarized NMR by Dissolution-DNP enables snapshot detection of degradation products in lithium-ion battery electrolytes

    Chloé Gioiosa (CRMN Lyon, France)

    LinkedIn: @Chloé Gioiosa

    Abstract: Dissolution Dynamic Nuclear Polarization (dDNP) is a powerful hyperpolarization technique enabling tremendous sensitivity gains in solution nuclear magnetic resonance (NMR). Over the last decades, researchers’ efforts have led to an extension of dDNP applications in numerous research fields. Lithium-ion batteries are among the most widespread rechargeable batteries, and a proper understanding of the physicochemical reactions at stake inside them is paramount to make them safer, more efficient, and sustainable. One of the key challenges lies in better understanding and limiting the degradation of the battery electrolyte, which can significantly impact the battery’s performance. While NMR has been used in attempts to understand these mechanisms, notably by investigating the degradation products, the intrinsic lack of sensitivity of this technique, combined with the limited accessible volume of such compounds, makes its application often challenging. This work combines several state-of-the-art dDNP methodologies, including using recently introduced hyperpolarizing polymers (HYPOP) to acquire hyperpolarized 13C NMR spectra of degraded battery electrolytes. We show that we can successfully detect 13C signals on formulated battery electrolyte solutions in different degradation stages, on a 600 MHz spectrometer, with sensitivity gains of up to 3 orders of magnitude. This work paves the way for studying lithium-ion battery electrolyte degradation under usage conditions (cycling, thermal aging, air exposure…) with a 13C detection limit below the micromolar range. This methodology has the potential to provide new insights into degradation mechanisms and the role and effectiveness of additives to mitigate electrolyte degradation.

    1. KSHAMA SHARMA Avatar
      KSHAMA SHARMA

      Dear Chloe, I have 2 questions:
      1. Considering the transient nature of hyperpolarized states, what is the practical time window available for spectral acquisition? To what extent does this limit your ability to resolve and differentiate between various chemical species?
      2. In achieving the observed sensitivity enhancements, did you encounter any trade-offs in spectral resolution, such as line broadening, arising either from polarization transfer mechanisms or sample handling procedures?

      Reply
      1. Chloé Gioiosa Avatar
        Chloé Gioiosa

        Dear Kshama,

        1. If we consider the shortest T1 measured on the methyl moieties of the carbonates, which is of approximately 5 seconds, you have around 10 seconds to dissolve and acquire your 90° pulse while ensuring that you see most of the carbon signals, although there is a possibility that some signals might be missing if the T1 is very short. It has already happened that some fast relaxing nuclei were missing from the spectrum. However, the fast injection system still allows us to see signals with T1 in the order of the second, but with diminished enhancements (hence why we report enhancements ranging from 100 to 1000). We also control the magnetic field during the transfer with solenoids to avoid any polarization losses due to a sudden change in the magnetic field strength.

        2. We did. We had to trade off some sensitivity enhancements to achieve a satisfying resolution by adding a “resting time” to the sequence, allowing the solution to stabilize inside the tube prior to the start of acquisition. Here, the fwhm was measured to be 3.5 Hz, and our best reported value was 1.3 Hz. We also had to deal with a lack of repeatability in the injected volume due to the significant pressure drop caused by the addition of the filter, resulting in additional losses of resolution. We are currently working on finding the best compromise to acquire a resolved spectrum with maximzed enhancement, in a repeatable manner.

        Reply
        1. KSHAMA SHARMA Avatar
          KSHAMA SHARMA

          Thanks!

          Reply
    2. Raj Chaklashiya Avatar
      Raj Chaklashiya

      Nice Talk! One question I have is, how do polymers like HYPOP “preserve” the polarization within them for use in DNP? I find these materials to be very interesting and am wondering how they work and whether they are compatible with other radicals (e.g. metal-based radicals like Gd-DOTA).

      Reply
      1. Chloé Gioiosa Avatar
        Chloé Gioiosa

        Hello! Thank you for your question.

        In our case, the polymer is synthesized in a manner that allows the radicals (amino-TEMPO) to be grafted and incorporated within the polymer network. The polymer is therefore filled with radicals. Another important aspect is that it is a high-porosity polymer (up to 80%), which enables us to impregnate the polymer with the solution to hyperpolarize. Then, by shining microwaves on the impregnated powder, you can perform DNP in the same fashion as with a DNP juice.

        They can be synthesized with any radicals that :
        1. Contains a primary or secondary amine group
        2. Can survive at 100°C for 24h (curing process)

        If you want more details on the synthesis, you can go check this paper in which it is described : https://www.nature.com/articles/s41467-021-24279-2

        Reply
        1. Raj Chaklashiya Avatar
          Raj Chaklashiya

          Awesome, thanks!

          Reply

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  • Lighting Up the Hidden Nuclear Spins: Revisiting the Three-Spin Mixing Photo-CIDNP Mechanism in Solids under Static and MAS Conditions

    Sajith V Sadasivan (New York University Abu Dhabi, United Arab Emirates)

    LinkedIn: @Sajith V Sadasivan; X: @v_sadasivan

    Abstract: Nuclear Magnetic Resonance (NMR) spectroscopy, a key tool for probing molecular structure and dynamics, is fundamentally limited by the intrinsically low thermal polarization of nuclear spins, resulting in weak signal intensities. Dynamic Nuclear Polarization (DNP) enhances NMR sensitivity by transferring polarization from electron spins via microwave irradiation, yet it often demands cryogenic conditions and complex instrumentation. Photochemically induced DNP (photo-CIDNP) offers a promising, microwave-free alternative by exploiting optically generated spin polarization, with recent work using synthetic donor–chromophore–acceptor systems demonstrating significant 1H and 13C hyperpolarization in the solid state. Building on these advances, our present study expands the three-spin mixing (TSM) framework by establishing a generalized resonance condition valid across coupling regimes of radical pairs under both static and magic angle spinning (MAS) conditions. Through an operator-based effective Hamiltonian approach, it is shown that coherent singlet–triplet mixing, driven by hyperfine interactions, is central to the hyperpolarization mechanism through photo-CIDNP. Additionally, a Landau–Zener treatment captures the periodic level anti-crossings enabled by MAS, providing mechanistic insight into polarization transfer pathways. These findings offer critical guidance for optimizing photo-CIDNP transfer and rationally designing photoactive molecular systems for next-generation applications in biomedical imaging and materials characterization.

    1. KSHAMA SHARMA Avatar
      KSHAMA SHARMA

      Questions:
      1. How do the polarization levels and build-up times you are seeing with photo-CIDNP compare to what’s typically achieved using microwave-driven DNP? Are there any trade-offs or unexpected advantages in Photo-CIDNP?
      2. In developing the operator-based effective Hamiltonian model, what kinds of assumptions or simplifications did you have to make? And how do those choices affect the accuracy of your predictions?

      Reply
      1. Sajith V Sadasivan Avatar
        Sajith V Sadasivan

        Dear Kshama,

        Hope you are doing well. Thanks for your questions.

        Please find the responses to your questions below.

        1. How do the polarization levels and build-up times you are seeing with photo-CIDNP compare to what’s typically achieved using microwave-driven DNP? Are there any trade-offs or unexpected advantages in Photo-CIDNP?

        Response: Photo-CIDNP achieves moderate polarization enhancements but offers faster build-up and the possibility of operating towards room temperature with simpler hardware and high‐field compatibility.
        In De Biasi et al.’s experiments, the ¹H polarization builds up within seconds under continuous 450 nm laser irradiation. Please refer to https://doi.org/10.1021/jacs.4c06151 (Fig. 3). They obtained bulk NMR signal enhancements by factors of ∼100 at both 9.4 and 21.1 T for the 1H signal under MAS at 100 K. Since this is a non-thermal polarization, it’s not limited as in DNP (by a factor of ~660). It can be improved depending on radical chromophore efficiency and experimental conditions. Microwave DNP achieves larger enhancements but has slower build-up, higher complexity, and requires cryogenics.

        We have mentioned this in our article (Sec. III B): https://doi.org/10.1063/5.0265957. The perturbation strength, E1, responsible for three-spin mixing (TSM) at level crossings and net transition probabilities in photo-CIDNP can be compared to the three-spin flip process in the cross-effect DNP under MAS using Landau-Zener model. In photo-CIDNP, the corresponding perturbation term, which drives TSM, can be derived from the coefficients of the ZQ and DQ effective TSM Hamiltonian. For the cross-effect (CE), E1 is given by E1 = d*B/ωn. Please refer to https://doi.org/10.1063/1.4747449. E1 in CE DNP is weaker than in photo-CIDNP because, in CE, it is scaled down by the nuclear Larmor frequency, which increases significantly at high magnetic fields.

        2. In developing the operator-based effective Hamiltonian model, what kinds of assumptions or simplifications did you have to make? And how do those choices affect the accuracy of your predictions?

        Response: Our approach employs an operator-based theoretical framework to model the photo-CIDNP process in a three-spin system. This framework unifies Zeeman, hyperfine, and electron–electron (e–e) coupling interactions into a single effective Hamiltonian that governs the coherent dynamics driving three-spin mixing (TSM) and, ultimately, photo-CIDNP under zero- and double-quantum (ZQ/DQ) matching conditions.

        To facilitate analytical treatment, we analyze the Hamiltonian within the separate α and β manifolds of the nuclear spin using polarization (or polar) operators. A fictitious zero-quantum operator is introduced for the electron spins (radical pair) to simplify the spin dynamics. We also perform a transformation into a tilted frame, aligning the effective rotation axis with the quantization (z) axis. This allows us to extract effective precession frequencies for the nuclear spin in the α and β manifolds, which appear on the right-hand side of the ZQ/DQ matching conditions. To further analyze nuclear hyperpolarization, we transform the tilted-frame Hamiltonian into the interaction frame, following the strategy used in CP and DNP frameworks. This yields generalized resonance conditions for both ZQ and DQ transitions.

        Our model establishes these generalized matching conditions in a form that remains valid across all regimes of spin parameters, including variations in the g-tensor isotropic shift (Δ), electron–electron coupling strength (d), and hyperfine coupling constants (A and B). The resulting effective Hamiltonians introduce a dipolar scaling factor, which directly governs the rate of polarization transfer. An analytical solution for the time evolution of the density matrix under the effective Hamiltonian, along with the corresponding expression for the trace of the nuclear spin polarization ⟨Iz(t)⟩, reveals an intensity factor that defines the maximum achievable polarization. The total efficiency of nuclear hyperpolarization is determined by the interplay between this dipolar scaling and intensity factor, providing key insights into the rational design of photoactive sensitizer molecules and the optimization of experimental conditions for efficient photo-CIDNP. The excellent agreement between numerical simulations and analytical predictions under three distinct electron–electron coupling regimes—strong, intermediate, and weak—relative to Δ supports the reliability of our model and its ability to identify optimal conditions for three-spin mixing and photo-CIDNP. Overall, this study lays a robust theoretical foundation for optimizing nuclear polarization transfer in diverse photo-CIDNP applications.

        For more detailed information, please refer to https://doi.org/10.1063/5.0265957 or contact us.

        Thank you.

        Reply
        1. KSHAMA SHARMA Avatar
          KSHAMA SHARMA

          Dear Sajith,
          Yes, I’m doing well and hope you’re doing great too! Thank you for answering all the questions so thoroughly.

          Reply
          1. Sajith V Sadasivan Avatar
            Sajith V Sadasivan

            Good to know! I’m also doing good.

            You’re welcome.

            Reply
    2. Raj Chaklashiya Avatar
      Raj Chaklashiya

      Hi Sajith, nice talk! I am excited to see Photo-CIDNP is improved under MAS conditions. I was wondering, how high in magnetic field can you do this technique, whether that is modified by going from static to MAS conditions, and what fields it is optimal.

      Reply
    3. Sajith V Sadasivan Avatar
      Sajith V Sadasivan

      Hi Raj,

      Thank you for the nice comment and thoughtful question.

      Photo-CIDNP transfer under MAS relies on periodic anti-level crossings, which are governed by the matching conditions mentioned. MAS modulates the Hamiltonian terms periodically, which helps drive matching conditions repeatedly per rotor cycle, leading to better build-up and more uniform polarization (as compared to CE DNP as explained in Sec. IIIB, https://doi.org/10.1063/5.0265957). Under MAS, the effective fields can transiently match the conditions for efficient TSM, even if the static field would otherwise be unfavorable.

      At low fields, nuclear Larmor frequencies (ωₙ) are small, so matching conditions are relatively easy to satisfy. At higher fields, ωₙ becomes large, and achieving the matching becomes more stringent. The efficiency of polarization transfer can drop if the anti-level crossings shift away from optimal conditions. Having said this, it’s not just B₀, but also the relative g-shift (Δg), e-e coupling, and anisotropic hyperfine terms that matter (which are the important factors appearing in the matching condition). With proper molecular design (e.g., adjusting Δg and couplings), photo-CIDNP can still work efficiently even at 9.4 T, 21.1 T, or possibly higher fields.

      In De Biasi et al.’s recent experiments, they obtained bulk 1H NMR signal enhancements by factors of ~100 at both 9.4 and 21.1 T under MAS at 100 K using PhotoPol-S (as compared to their experiments at 0.3 T, yielding enhancement ~ 16 fold under STATIC conditions using Photopol). Please refer to https://doi.org/10.1021/jacs.4c06151 (Fig.  2) and https://doi.org/10.1021/jacs.3c03937 (Fig. 3). In this case, the matching conditions at 21.1 T are achieved by significantly increasing the e-e coupling from 5.5 MHz in PhotoPol to 570 MHz in PhotoPol-S by eliminating the spacer segment. Since the 1H hyperfine couplings in PhotoPol and PhotoPol-S are expected to be less than 50 MHz, there is less flexibility to adjust this as compared to e-e couplings towards higher fields.

      Hope this answers your question.

      Reply
      1. Raj Chaklashiya Avatar
        Raj Chaklashiya

        Thank you for your detailed response! That is very interesting, and makes sense to me–so it is harder to make it work at higher fields, but better molecular design can improve it. It’s very interesting to know that already there are some designs that work at 9.4 and even at 21.1 T up to 100x enhancement. I am excited to see such optimized molecular designs in the future!

        Reply
    4. Sajith V Sadasivan Avatar
      Sajith V Sadasivan

      Same here!

      Reply

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  • Rapid Melting Strategies for benchtop DNP: A Step Toward Replenishable Hyperpolarization in Liquid-State NMR

    Yang Wang (Very High Field NMR Center of Lyon (CRMN Lyon), France)

    LinkedIn: @Yang Wang; X: @WangYan35529716; Bluesky: @yangwangcz.bsky.social‬

    Abstract: Hyperpolarization techniques can boost NMR sensitivity by over 10,000-fold [1]. Among these, dissolution dynamic nuclear polarization (dDNP) is well established but suffers major drawbacks: it is destructive, single-use, and results in dilution upon sample dissolution, leading to rapid signal decay and incompatibility with multi-scan NMR experiments [2].
    We are developing a benchtop DNP platform designed to enable replenishable hyperpolarization without dilution. This approach uses hyperpolarizing materials (HYPOPs) [3] within a compact benchtop polarizer [4], coupled directly to a benchtop NMR spectrometer for solution-state detection. Our long-term goal is a closed-loop system allowing repeated freeze-DNP-melt-flow cycles.
    A critical challenge is maintaining polarization during the melt. In our current system, the sample is transferred from a 77 K DNP cryostat inside a 1 T benchtop polarizer into a dedicated melting station. This first prototype uses a guided high-flux (500 L/min), high-temperature (630 °C) air stream to melt a 250 µL sample in 5 seconds.
    We are now working to reduce the melt time below 1 second by increasing airflow, temperature, and integrating high-power laser light. Ultimately, we aim to couple this rapid melt setup with DNP and solution-state hyperpolarized NMR for multi-scan acquisition capability.
    References:
    [1] Ardenkjær-Larsen, J. H., et al. PNAS 100.18 (2003): 10158-10163.
    [2] Golman, K., et al. Cancer Res. 66.22 (2006): 10855-10860.
    [3] El Daraï, T., Cousin, S.F., Stern, Q., et al. Nat. Commun. 12 (2021): 4695.
    [4] Bocquelet, C., et al. Sci. Adv. 10 (2024): eadq3780.

    1. KSHAMA SHARMA Avatar
      KSHAMA SHARMA

      Hi Yang! Thank you for the presentation.

      I was wondering if you observe any noticeable time lag associated with activating the heat gun during the melting process? If so, have you considered alternative heating methods, such as infrared or laser-based systems that might allow for a more rapid and controlled melt?

      Regarding the freeze-melt and then flow cycles, how reproducible are your polarization levels across repeated runs?

      Reply
      1. Yang Wang Avatar
        Yang Wang

        Hi Kshama,

        Thank you for your questions !

        Indeed, the heat gun does require a few seconds after activation to reach the target temperature. To address this, I preheat the gun to the desired temperature before exposing the sample, so that the hot air is already at the setpoint at the very start of the melting process.

        I have also considered three alternative heating strategies. Among them, infrared laser heating is particularly promising. We have recently acquired a 1 kW, 1 μm wavelength IR laser system, which is currently being installed. I hope to begin testing it in the coming months and are looking forward to sharing new results with you.

        In parallel, we are also simulating microwave heating approaches, although the heating speed appears to be limited in this case…

        Regarding your question on reproducibility, we unfortunately do not yet have experimental data. However, we are planning a series of repeated melt-DNP experiments in the coming months to verify the polarization reproducibility across cycles.

        Best regards,
        Yang

        Reply
        1. KSHAMA SHARMA Avatar
          KSHAMA SHARMA

          Sounds great Yang! All the best and thank you!

          Reply

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  • Dynamic Nuclear Polarization Mechanisms in Diamond Defect Systems: Analytical Models and Transfer Dynamics

    Shubham Kumar Debdatta (Indian Institute of Science, Bangalore, India)

    Abstract: Nitrogen-vacancy (NV) centers in diamond have become prominent platforms for dynamic nuclear polarization (DNP), offering a robust route to hyperpolarize surrounding ¹³C nuclear spins under ambient conditions. Experimental observations have revealed both microwave-assisted and microwave-independent DNP pathways, frequently rationalized in terms of level anti-crossings between coupled electronic and nuclear spin manifolds.
    In this work, we construct an analytical treatment of spin polarization transfer from NV centers to proximal ¹³C nuclei, employing the density matrix formalism in conjunction with average Hamiltonian theory. Under the condition of selective excitation of a single electronic transition, we invoke a reduced Hilbert space description to derive compact expressions for spin polarization resonance conditions, effective spin Hamiltonians, and transfer efficiency as a function of external magnetic field, hyperfine interaction strength, and applied microwave fields.
    The model is further generalized to incorporate NV–P1–¹³C configurations, where P1 centers—substitutional nitrogen defects with spin-½—mediate cross-relaxation pathways that enable microwave-free spin polarization transfer. This extension elucidates key dynamical features such as field-dependent polarization oscillations, resonance-enhanced transfer channels, and timescales associated with transient spin exchange processes.
    This theoretical framework offers a detailed understanding of DNP mechanisms across both isolated and interacting defect configurations. The results delineate optimal regimes for maximizing nuclear spin polarization in diamond-based systems, particularly under low magnetic fields and ambient conditions, with direct implications for enhancing the sensitivity of nuclear magnetic resonance (NMR) and other hyperpolarization-enabled techniques.

    1. Arianna Actis Avatar
      Arianna Actis

      Dear Shubham, thank you for the presentation, it is a very interesting study. If I understand correctly, the graph showing “Normalized Signal vs Time” shows the the polarization buildup on 13C. Could you comment on the factors that affect this polarization transfer? Thank you.

      Reply
    2. Shubham Kumar Debadatta Avatar
      Shubham Kumar Debadatta

      Thank you! I assume you’re referring to the NV–P1–13C cluster-based study. In this context, the transfer rate mostly depends on A_zz^Δ and A_zx^Δ, which represent the differences in secular and pseudo-secular hyperfine couplings. These differences are key factors governing the transfer rate.
      In the plot, the purple plot indicates no spin polarization transfer. This occurs when the 13C nuclear spin is positioned exactly midway between the NV center and the P1 center, resulting in zero difference in both secular and pseudo-secular hyperfine couplings—hence, no transfer takes place.
      Additionally, there is a dependence on θ (theta) and φ (phi), which are related to nuclear and electronic couplings. These angular dependencies reflect how spin polarization transfer is influenced by the relative positioning of the 13C nucleus—whether it’s closer to the NV or the P1 center—and by the physical distance between NV and P1.

      Reply
    3. Sajith V Sadasivan Avatar
      Sajith V Sadasivan

      Nice work, Shubham.

      Have you explored the simulations under MAS?

      Reply
    4. Shubham Kumar Debadatta Avatar
      Shubham Kumar Debadatta

      Thank you! I haven’t looked into the matching conditions under MAS yet.

      Reply
      1. Sajith V Sadasivan Avatar
        Sajith V Sadasivan

        Okay.

        Reply
    5. Arianna Actis Avatar
      Arianna Actis

      Hello Shubham, thank you for your answer. Did you try also to study clusters composed by multiple NV and P1 centres?

      Reply
    6. Shubham Kumar Debadatta Avatar
      Shubham Kumar Debadatta

      Yes, I am currently exploring cluster-based systems. At the moment, our primary focus is on the 14N nucleus (associated with the P1 center) within the NV–P1–13C spin system, examining its dynamics as a four-spin system.

      Reply
    7. Raj Chaklashiya Avatar
      Raj Chaklashiya

      Dear Shubham,
      Nice presentation! I was wondering, while your simulations show that the optimal matching conditions are at X Band, is there any way that you’ve seen to manipulate the spin system (e.g. via couplings) such that the optimal matching condition can occur at higher field? Like basically–what about the system would have to be changed for the optimal condition to be at high field?

      Reply
    8. Shubham Kumar Debadatta Avatar
      Shubham Kumar Debadatta

      Hi Raj, Thank you! I believe I may not be fully understanding your question. The matching conditions remain the same and are highly valid in the high-field regime. However, as the magnetic field strength increases, the range over which spin polarization transfer occurs becomes narrower. This is because, at higher fields, the matching condition primarily depends on the nuclear Larmor frequency, with much less influence from hyperfine couplings. This trend is also demonstrated in the presentation at 9.4 Tesla.

      Reply
      1. Raj Chaklashiya Avatar
        Raj Chaklashiya

        Thanks! That makes sense to me–so it would have to require tuning the nuclear larmor frequency for it to work well at high fields.

        Reply

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  • Seeing the unseen with Dynamic Nuclear Polarization

    Ribal Jabbour (New York University Abu Dhabi, UAE)

    Abstract: Dynamic Nuclear Polarization (DNP) is a technique that utilizes the sensing capability of electron spins to significantly enhance the sensitivity of NMR signals, particularly for low-sensitivity samples. Glassing agents are essential in the DNP process, as they facilitate the transfer of polarization from unpaired electron spins to nuclear spins while providing cryoprotection. Glycerol/D2O/H2O mixtures have been widely used as glassing agents for this purpose over the past two decades. However, glycerol exhibits two prominent peaks in NMR spectra, which can obscure signals in certain regions. Using alternative glassing agents can mitigate this issue, uncovering these regions for clearer analysis. Additionally, DNP without any glycerol can be employed to study off-the-shelf insulin, which can enable detailed structural of this critical biomolecule.

    1. Chloé Gioiosa Avatar
      Chloé Gioiosa

      Hi Ribal, Thank you for your presentation.

      Did you estimate the proton concentration in your final sample and how does it compare with a more traditional DNP juice formulation, and did you try different concentrations of radical to optimize the enhancement?

      Reply
    2. Ribal Jabbour Avatar
      Ribal Jabbour

      Hi Chloé,

      We did not estimate the proton concentration in the final sample yet.

      We did try different radical optimizations. 10 mM seems to be the optimal. For 20 mM the enhancement goes down to 30.

      Reply
    3. Arianna Actis Avatar
      Arianna Actis

      Hi Ribal, thank you for the presentation.
      Did you try radicals of different types, do you think they might give a better enhancement? And, following the previous question by Chloé, do you have an explanation why increasing the concentration of the radical you used decreases the enhancement?

      Reply
    4. Ribal Jabbour Avatar
      Ribal Jabbour

      Hi Arianna,

      We did not try different radicals. The radical we used (ASYMPol-POK) is, to my latest knowledge, the best-performing and commercially available one at this field. There is a plan to try AMUPol and see the difference between both. In general, when you increase your radical concentration, you are adding more paramagnetic species to your sample (sometimes high concentration may also overcouple your radicals and can terminate them), which leads to more paramagnetic relaxation and broadening, and this can affect your enhancement.

      Reply
    5. Raj Chaklashiya Avatar
      Raj Chaklashiya

      Hi Ribal, nice presentation! The different results depending on glassing agent used made me very curious, and I have a couple questions to this effect:
      1) What would you expect to occur if you tried DMSO solvent?
      2) There are some papers that use a special freezing method (https://www.jove.com/v/61733/cryogenic-sample-loading-into-magic-angle-spinning-nuclear-magnetic) that requires only 10-15% glycerol or DMSO for cryopreservation to run MAS DNP experiments without breaking cells:
      https://pubs.acs.org/doi/full/10.1021/jacs.1c06680 and https://www.frontiersin.org/journals/molecular-biosciences/articles/10.3389/fmolb.2021.789478/full — I am wondering if you would expect that decreasing glycerol content could potentially mimic the results you see in just insulin, while simultaneously providing some of the benefits of glycerol (which appear to be stronger signal based on the slide)

      Reply

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  • Exploring Adiabatic Inversion for Integrated Solid Effect

    Mayur Manoj Jhamnani – @mayur_jhamnani

    We explore the use of adiabatic inversion techniques to enhance the integrated solid effect (ISE). By carefully controlling the system parameters, we demonstrate how adiabatic inversion can be leveraged to improve the efficiency of polarization transfer via ISE. The findings have important implications for the development of triplet-DNP.

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  • Efficient Nuclear Polarization Using P1 Diamonds Under Magic Angle Spinning at 14.1 T from 30K to RT

    Celeste Tobar – @Celestial_023

    P1 center diamonds provide robust polarization for RT DNP, featuring unique spin properties and extended coherence and relaxation times. Our MAS-DNP experiments at 14.1 T (298K to 30K) reveal their efficiency and novel characteristics, showcasing their potential for NMR imaging and bio-NMR studies.

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  • A short tour of the MAS-DNP lab at the NHMFL (Maglab)

    Faith Scott – @faithscottdnp

    I will showcase some of the improvements we have made to the MAS-DNP user program instrumentation over the last few years. This includes upgrades to the cooling cabinet and the 3.2 mm custom MAS-DNP probe.

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