Dec 28, 2018

BDPA-Nitroxide Biradicals Tailored for Efficient Dynamic Nuclear Polarization Enhanced Solid-State NMR at Magnetic Fields up to 21.1 T #DNPNMR

Wisser, Dorothea, Ganesan Karthikeyan, Alicia Lund, Gilles Casano, Hakim Karoui, Maxim Yulikov, Georges Menzildjian, et al. “BDPA-Nitroxide Biradicals Tailored for Efficient Dynamic Nuclear Polarization Enhanced Solid-State NMR at Magnetic Fields up to 21.1 T.” Journal of the American Chemical Society 140, no. 41 (October 17, 2018): 13340–49.

Dynamic nuclear polarization (DNP) solid-state nuclear magnetic resonance (NMR) has developed into an invaluable tool for the investigation of a wide range of materials. However, the sensitivity gain achieved with many polarizing agents suffers from an unfavorable field and magic angle spinning (MAS) frequency dependence. We present a series of new hybrid biradicals, soluble in organic solvents, that consist of an isotropic narrow electron paramagnetic resonance line radical, α,γ-bisdiphenylene-β-phenylallyl (BDPA), tethered to a broad line nitroxide. By tuning the distance between the two electrons and the substituents at the nitroxide moiety, correlations between the electron–electron interactions and the electron spin relaxation times on one hand and the DNP enhancement factors on the other hand are established. The best radical in this series has a short methylene linker and bears bulky phenyl spirocyclohexyl ligands. In a 1.3 mm prototype DNP probe, it yields enhancements of up to 185 at 18.8 T (800 MHz 1H resonance frequency) and 40 kHz MAS. We show that this radical gives enhancement factors of over 60 in 3.2 mm sapphire rotors at both 18.8 and 21.1 T (900 MHz 1H resonance frequency), the highest magnetic field available today for DNP. The effect of the rotor size and of the microwave irradiation inside the MAS rotor is discussed. Finally, we demonstrate the potential of this new series of polarizing agents by recording high field 27Al and 29Si DNP surface enhanced NMR spectra of amorphous aluminosilicates and 17O NMR on silica nanoparticles.

Dec 21, 2018

Tuning nuclear depolarization under MAS by electron T1e #DNPNMR

Lund, Alicia, Asif Equbal, and Songi Han. “Tuning Nuclear Depolarization under MAS by Electron T1e.” Physical Chemistry Chemical Physics, 2018, 19. 

Cross-Effect (CE) Dynamic Nuclear Polarization (DNP) mechanism under Magic Angle Spinning (MAS) induces depletion or “depolarization” of the NMR signal, in the absence of microwave irradiation. In this study, the role of T1e on nuclear depolarization under MAS was tested experimentally by systematically varying the local and global electron spin concentration using mono-, bi- and tri-radicals. These spin systems show different depolarization effects that systematically tracked with their different T1e rates, consistent with theoretical predictions. In order to test whether the effect of T1e is directly or indirectly convoluted with other spin parameters, the tri-radical system was doped with different concentrations of GdCl3, only tuning the T1e rates, while keeping other parameters unchanged. Gratifyingly, the changes in the depolarization factor tracked the changes in the T1e rates. The experimental results are corroborated by quantum mechanics based numerical simulations which recapitulated the critical role of T1e. Simulations showed that the relative orientation of the two g-tensors and e-e dipolar interaction tensors of the CE fulfilling spin pair also plays a major role in determining the extent of depolarization, besides the enhancement. This is expected as orientations influence the efficiency of the various level anti-crossings or the “rotor events” under MAS. However, experimental evaluation of the empirical spectral diffusion parameter at static condition showed that the local vs. global e-e dipolar interaction network is not a significant variable in the commonly used nitroxide radical system studied here, leaving T1e rates as the major modulator of depolarization.

Dec 19, 2018

Sensitivity Considerations in Microwave Paramagnetic Resonance Absorption Techniques

I recently read again through Feher's article on EPR sensitivity. After 61 years this article is still very important when building instrumentation for EPR or DNP. It explains many EPR concepts and the relevant instrumentation using simple, easy to understand concepts.
I must read for everyone working in the field of magnetic resonance instrumentation.

Feher, G. “Sensitivity Considerations in Microwave Paramagnetic Resonance Absorption Techniques.” Bell System Technical Journal 36, no. 2 (March 1957): 449–84.

Within the past few years the field of paramagnetic resonance absorption has become an important tool in physical and chemical research. In many ways its usefulness is limited by the sensitivity of the experimental setup. A typical example is the study of semiconductors in which case one would like to investigate as small a number of impurities as possible. It is the purpose of this paper to analyze the sensitivity limits of several experimental set ups under different operating conditions. This was done in the hope that an understanding of these limitations would put one in a better position to design a high sensitivity resonance experiment. In the last section the performance of the different experimental arrangements is tested. The agreement obtained with the predicted performance proves the essential validity of the analysis. This paper is primarily for experimental physicists confronted withe the problem of setting up a high sensitivity spectrometer.

Dec 17, 2018

Electron-Spin Relaxation of Triarylmethyl Radicals in Glassy Trehalose #DNPNMR

Triarylmethyl radicals are commonly used dissolution-DNP experiments (dDNP). This article is a good reference source for the electronic relaxation times T1e and T2e in different solvents.

Kuzhelev, Andrey A., Olesya A. Krumkacheva, Ivan O. Timofeev, Victor M. Tormyshev, Matvey V. Fedin, and Elena G. Bagryanskaya. “Electron-Spin Relaxation of Triarylmethyl Radicals in Glassy Trehalose.” Applied Magnetic Resonance 49, no. 11 (November 2018): 1171–80.

Trehalose was recently proposed as a promising immobilizer of biomolecules for room-temperature electron paramagnetic resonance (EPR) structural studies. The most crucial parameter in these investigations is electron-spin relaxation (namely, phase memory time Tm). Recently, triarylmethyl (TAM) spin labels attached to DNA in trehalose were found to have the longest Tm at room temperature as compared to the existing spin labels and immobilizers. Therefore, in this work, we investigated TAM radicals in trehalose including Finland trityl (H36 form), perdeuterated Finland trityl (D36 form), and a deuterated version of OX063. The temperature dependence of electron-spin relaxation time of these radicals immobilized in trehalose was measured at X-band frequency, and possible mechanisms of relaxation were considered. OX063D in glassy trehalose has longer Tm up to 200 K as compared to Finland trityl, but at higher temperatures, OX063D is inferior in its relaxation properties, and the deuterated form of Finland trityl is preferable for pulse dipolar EPR spectroscopy experiments at 298 K. The influence of various deuterations (TAM or trehalose) on the observed relaxation times was studied, being controlled by the electron-spin-echo envelope modulation at room temperature.

Dec 14, 2018

Large-scale ab initio simulations of MAS DNP enhancements using a Monte Carlo optimization strategy #DNPNMR

Perras, Frédéric A., and Marek Pruski. “Large-Scale Ab Initio Simulations of MAS DNP Enhancements Using a Monte Carlo Optimization Strategy.” The Journal of Chemical Physics 149, no. 15 (October 21, 2018): 154202.

Magic-angle-spinning (MAS) dynamic nuclear polarization (DNP) has recently emerged as a powerful technology enabling otherwise unrealistic solid-state NMR experiments. The simulation of DNP processes which might, for example, aid in refining the experimental conditions or the design of better performing polarizing agents, is, however, plagued with significant challenges, often limiting the system size to only 3 spins. Here, we present the first approach to fully ab initio large-scale simulations of MAS DNP enhancements. The Landau-Zener equation is used to treat all interactions concerning electron spins, and the low-order correlations in the Liouville space method is used to accurately treat the spin diffusion, as well as its MAS speed dependence. As the propagator cannot be stored, a Monte Carlo optimization method is used to determine the steady-state enhancement factors. This new software is employed to investigate the MAS speed dependence of the enhancement factors in large spin systems where spin diffusion is of importance, as well as to investigate the impacts of solvent and polarizing agent deuteration on the performance of MAS DNP.

Dec 12, 2018

Conformation of Bis-nitroxide Polarizing Agents by Multi- frequency EPR Spectroscopy #DNPNMR

To optimize the DNP process it is crucial to understand the EPR properties of the polarizing agents. This article demonstrates the need of multi-frequency, high-field EPR spectroscopy to gain a deep understanding of all EPR parameters and how they influence the DNP process.

Soetbeer, Janne, Peter Gast, Joseph J Walish, Yanchuan Zhao, Christy George, Chen Yang, Timothy M Swager, Robert G Griffin, and Guinevere Mathies. “Conformation of Bis-Nitroxide Polarizing Agents by Multi- Frequency EPR Spectroscopy,”

The chemical structure of polarizing agents critically determines the efficiency of dynamic nuclear polarization (DNP). For cross-effect DNP, biradicals are the polarizing agents of choice and the interaction and relative orientation of the two unpaired electrons should be optimal. Both parameters are affected by the molecular structure of the biradical in the frozen glassy matrix that is typically used for DNP/MAS NMR and likely differs from the structure observed with X-ray crystallography. We have determined the conformations of six bis-nitroxide polarizing agents, including the highly efficient AMUPol, in their DNP matrix with EPR spectroscopy at 9.7 GHz, 140 GHz, and 275 GHz. The multi-frequency approach in combination with an advanced fitting routine allows us to reliably extract the interaction and relative orientation of the nitroxide moieties. We compare the structures of six bis-nitroxides to their DNP performance at 500 MHz/330 GHz.

Dec 11, 2018

[NMR] Postdoctoral position in NMR of polymer electrolytes for energy storage at UCSB (Santa Barbara, USA) #DNPNMR

Postdoctoral position in NMR of polymer ionic liquid electrolytes for energy storage at UCSB (Santa Barbara, USA)

The postdoctoral research position is based at the Materials Department, University of California Santa Barbara (UCSB), in the group of Prof. Raphaële Clément. The position is available from January, 1st, 2019, and comes with an initial one-year contract. 

Project Description

The research program focuses on the study of polymer ionic liquids (PILs), used as electrolytes in Li-ion rechargeable batteries, with solid-state NMR techniques. The postdoc will be working in close collaboration with the group of Prof. Segalman at UCSB, in charge of the synthesis of the PILs. 

Li-ion batteries are the technology of choice for numerous applications, yet the energy density and safety of commercial devices is often limited by using organic liquid electrolytes with high flammability and poor stability of electrode/electrolyte interfaces during operation. Ionic liquids are a class of functional liquid salts that address both voltage and thermal stability concerns [1]. Incorporation of ionic liquid moieties onto a polymer to form PILs synergistically combines the functionality of ionic liquids with the mechanical robustness of the polymer backbone, an important criterion for lithium metal batteries. Unfortunately, polymer electrolytes generally exhibit low ionic conductivity due to a fundamental trade-off between improved mechanical properties and ion mobility [2]. Thus, an understanding of promising systems that would enable a decoupling of polymer mechanics from ion transport would be beneficial towards the targeted design of novel polymer electrolytes with good mechanical properties and high ionic conductivity.

The postdoc will investigate the Li+ transport properties of several PIL compositions using 7Li pulsed field gradient (PFG) NMR to determine the Li self-diffusion coefficient on the macroscopic (1-2 mm) lengthscale, as well as NMR relaxometry to characterize ionic conductivity at the microscopic scale. In addition, NMR will be used to investigate Li-Li site exchange [3] and Li-ligand binding kinetics [4]. NMR measurements will be correlated with conductivity measurements obtained via AC impedance techniques.

Relevant publications 

[1] B. Garcia, S. Lavalle, G. Perron, C. Michot, and M. Armand, Room temperature molten salts as lithium battery electrolyte, Electrochim. Acta 49 (2004) 4583–4588. DOI: 10.1016/j.electacta.2004.04.041

[2] J. R. Sangoro, C. Iacob, A. L. Agapov, Y. Wang, S. Berdzinski, H. Rexhausen, V. Strehmel, C. Friedrich, A. P. Sokolov, and F. Kremer, Decoupling of ionic conductivity from structural dynamics in polymerized ionic liquids, Soft Matter 10 (2014) 3536–3540.

DOI: 10.1039/C3SM53202J

[3] M. N. d’Eurydice, E. T. Montrazi, C. A. Fortulan and T. J. Bonagamba, T2-tiltered T2-T2 Exchange NMR. J. Chem. Phys. 144 (2016) 204201. DOI: 10.1063/1.4951712

[4] Tan-Vu Huynh. NMR study of lithium mobility in polymer electrolytes. Ph.D. thesis. Université d’Orléans, 2015. English.

Requirements and Preferred Experience

The requirements for the position are a Ph.D. in Chemistry, Materials Science, Physics or Engineering, and experience with PFG-NMR and standard 2D solid-state NMR techniques. In addition to performing research, the postdoc will be expected to provide assistance with the training of graduate and undergraduate students in the group.

The Magnetic Resonance Facilities at UCSB

The spectroscopy facility of the Materials Research Laboratory at UCSB (see comprises several solid-state NMR spectrometers, including a 300 MHz system equipped with a MRI/diffusion probe, a 400 MHz DNP-NMR spectrometer, and 500 MHz and 800 MHz systems.

Additional Information

Interested candidates should send a cover letter, a résumé (including a list of publications), and the names and email addresses of at least two references to
Raphaële Clément

Assistant Professor, Materials Department
Materials Research Laboratory, Room 3009
University of California, Santa Barbara, CA 93106-5121

Phone: 805-893-4294

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Dec 10, 2018

DNP NMR Studies of Crystalline Polymer Domains by Copolymerization with Nitroxide Radical Monomers #DNPNMR

Verde-Sesto, Ester, Nicolas Goujon, Haritz Sardon, Pauline Ruiz, Tan Vu Huynh, Fermin Elizalde, David Mecerreyes, Maria Forsyth, and Luke A. O’Dell. “DNP NMR Studies of Crystalline Polymer Domains by Copolymerization with Nitroxide Radical Monomers.” Macromolecules 51, no. 20 (October 23, 2018): 8046–53.

Dynamic nuclear polarization (DNP) nuclear magnetic resonance (NMR) spectroscopy is increasingly recognized as a powerful and versatile tool for the characterization of polymers and polymer-based materials. DNP requires the presence of unpaired electrons, usually mono- or biradicals, and the method of incorporation of these groups and their distribution within the structure is crucial. Methods for covalently binding the radicals to the polymer and controlling their location (e.g., exclusively within a specific phase or at an interface) can allow the selective enhancement of a particular region or the measurement of domain sizes. We have prepared a series of polyurethanes by copolymerization of a nitroxide radical monomer with poly(ethylene glycol) (PEO) and diisocyanate linkers. The PEO is shown to form crystalline domains with the radical monomers in a separate phase, providing DNP enhancements of around 10 and allowing the domain size and morphology to be probed with the aid of X-ray scattering data. Additionally, electron paramagnetic resonance is used to estimate the inter-radical distances and density functional theory calculations are used to refine the PEO crystal structure.

Dec 8, 2018

[NMR] Post-doctoral position available #DNPNMR

A postdoctoral position is available to join the Emsley group at EPFL, Lausanne

We are looking for highly motivated candidates to take up a Postdoctoral position developing new methods in NMR spectroscopy to address challenging problems in chemistry and materials science. In particular we will be working on dynamic nuclear polarization enhanced NMR methods for materials. Examples of our recent work and the application areas that we work on can be found on our website:

We are looking for highly motivated candidates with strong scientific background, independence, and who enjoy teamwork. You should hold a relevant qualification in chemistry, physics or related disciplines. Skills in developing experimental multi-dimensional nuclear magnetic resonance are a plus. 

Our laboratory at EPFL is part of one the world’s leading chemistry departments, and is located Lausanne on the north shore of Lake Geneva. The laboratory is equipped with unique state of the art NMR spectrometers (including gyrotron DNP accessories at 400 and 900 MHz, a dissolution-DNP machine, and 100 kHz magic angle spinning probes). 
Motivated candidates should contact Lyndon Emsley by email at

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Dec 7, 2018

Long-range heteronuclear J-coupling constants in esters: Implications for 13C metabolic MRI by side-arm parahydrogen-induced polarization

Stewart, Neil J., Hiroyuki Kumeta, Mitsushi Tomohiro, Takuya Hashimoto, Noriyuki Hatae, and Shingo Matsumoto. “Long-Range Heteronuclear J-Coupling Constants in Esters: Implications for 13C Metabolic MRI by Side-Arm Parahydrogen-Induced Polarization.” Journal of Magnetic Resonance 296 (November 2018): 85–92.

Side-arm parahydrogen induced polarization (PHIP-SAH) presents a cost-effective method for hyperpolarization of 13C metabolites (e.g. acetate, pyruvate) for metabolic MRI. The timing and efficiency of typical spin order transfer methods including magnetic field cycling and tailored RF pulse sequences crucially depends on the heteronuclear J coupling network between nascent parahydrogen protons and 13C, post-parahydrogenation of the target compound. In this work, heteronuclear nJHC (1<n≤5) couplings of acetate and pyruvate esters pertinent for PHIP-SAH were investigated experimentally using selective HSQMBC-based pulse sequences and numerically using DFT simulations. The CLIP-HSQMBC technique was used to quantify 2/3-bond JHC couplings, and 4/5-bond JHC ≲ 0.5 Hz were estimated by the sel-HSQMBC-TOCSY approach. Experimental and numerical (DFT-simulated) nJHC couplings were strongly correlated (P < 0.001). Implications for 13C hyperpolarization by magnetic field cycling, and PH-INEPT and ESOTHERIC type spin order transfer methods for PHIP-SAH were assessed, and the influence of direct nascent parahydrogen proton to 13C coupling when compared with indirect TOCSY-type transfer through intermediate (non-nascent parahydrogen) protons was studied by the density matrix approach.

Dec 5, 2018

Electron decoupling with cross polarization and dynamic nuclear polarization below 6 K #DNPNMR

Sesti, Erika L., Edward P. Saliba, Nicholas Alaniva, and Alexander B. Barnes. “Electron Decoupling with Cross Polarization and Dynamic Nuclear Polarization below 6 K.” Journal of Magnetic Resonance 295 (October 2018): 1–5.

Dynamic nuclear polarization (DNP) can improve nuclear magnetic resonance (NMR) sensitivity by orders of magnitude. Polarizing agents containing unpaired electrons required for DNP can broaden nuclear resonances in the presence of appreciable hyperfine couplings. Here we present the first cross polarization experiments implemented with electron decoupling, which attenuates detrimental hyperfine couplings. We also demonstrate magic angle spinning (MAS) DNP experiments below 6 K, producing unprecedented nuclear spin polarization in rotating solids. 13C correlation spectra were collected with MAS DNP below 6 K for the first time. Longitudinal magnetization recovery times with MAS DNP (T1DNP, 1H) of urea in a frozen glassy matrix below 6 K were measured for both the solid effect and the cross effect. Trityl radicals exhibit a T1DNP (1H) of 18.7 s and the T1DNP (1H) of samples doped with 20 mM AMUPol is only 1.3 s. MAS below 6 K with DNP and electron decoupling is an effective strategy to increase NMR signal-to-noise ratios per transient while retaining short recovery periods.

Dec 3, 2018

Multi-resonant photonic band-gap/saddle coil DNP probehead for static solid state NMR of microliter volume samples #DNPNMR

Nevzorov, Alexander A., Sergey Milikisiyants, Antonin N. Marek, and Alex I. Smirnov. “Multi-Resonant Photonic Band-Gap/Saddle Coil DNP Probehead for Static Solid State NMR of Microliter Volume Samples.” Journal of Magnetic Resonance 297 (December 2018): 113–23. 

The most critical condition for performing Dynamic Nuclear Polarization (DNP) is achieving sufficiently high electronic B1e fields over the sample at the matched EPR frequencies, which for modern high-resolution NMR instruments fall into the millimeter wave (mmW) range. Typically, mmWs are generated by powerful gyrotrons and/or extended interaction klystrons (EIKs) sources and then focused onto the sample by dielectric lenses. However, further development of DNP methods including new DNP pulse sequences may require B1e fields higher than one could achieve with the current mmW technology. In order to address the challenge of significantly enhancing the mmW field at the sample, we have constructed and tested one-dimensional photonic band-gap (PBG) mmW resonator that was incorporated inside a double-tuned radiofrequency (rf) NMR saddle coil. The photonic crystal is formed by stacking ceramic discs with alternating high and low dielectric constants. The thicknesses of the discs are chosen to be λ/4 or 3λ/4, where λ is the wavelength of the incident mmW field in the corresponding dielectric material. When the mmW frequency is within the band gap of the photonic crystal, a defect created in the middle of the crystal confines the mmW energy, thus forming a resonant structure. An aluminum mirror in the middle of the defect has been used to split the structure in order to reduce its size and simplify the resonator tuning. The latter is achieved by adjusting the width of the defect by moving the aluminum mirror with respect to the dielectric stack using a gear mechanism. The 1D PBG resonator was the key element for constructing a multi-resonant integrated DNP/NMR probehead operating at 198 GHz EPR / 300 MHz 1H / 75.5 MHz 13C NMR frequencies. Initial tests of the multi-resonant DNP/NMR probehead were carried out using a quasioptical 200 GHz bridge and a Bruker Biospin Avance II spectrometer equipped with a standard Bruker 7 T wide-bore 89 mm magnet parked at 300.13 MHz 1H NMR frequency. The mmW bridge built with all solid-state active components allows for the frequency tuning between ca. 190 to ca. 198 GHz with the output power up to 27 dBm (0.5 W) at 192 GHz and up to 23 dBm (0.2 W) at 197.5 GHz. Room temperature DNP experiments with a synthetic single crystal high-pressure high-temperature (HPHT) diamond (0.3Å~0.3Å~3.0 mm3) demonstrated dramatic 1,500–fold enhancement of 13C natural abundance NMR signal at full incident mmW power. Significant 13C DNP enhancement (of about 90) have been obtained at incident mmW powers of as low as <100 μW. Further tests of the resonator performance have been carried out with a thin (ca. 100 μm thickness) composite polystyrene-microdiamond film by controlling the average mmW power at the optimal DNP conditions via a gated mode of operation. From these experiments, the PBG resonator with loaded Q≃250 and finesse provides up to 12-fold/11 db gain in the average mmW power vs. the non-resonant probehead configuration employing only a reflective mirror.

Nov 30, 2018

Saliba, Edward P., Erika L. Sesti, Nicholas Alaniva, and Alexander B. Barnes. “Pulsed Electron Decoupling and Strategies for Time Domain Dynamic Nuclear Polarization with Magic Angle Spinning.” The Journal of Physical Chemistry Letters 9, no. 18 (September 20, 2018): 5539–47.

Magic angle spinning (MAS) dynamic nuclear polarization (DNP) is widely used to increase nuclear magnetic resonance (NMR) signal intensity. Frequency-chirped microwaves yield superior control of electron spins, and are expected to play a central role in the development of DNP MAS experiments. Time domain electron control with MAS has considerable promise to improve DNP performance at higher fields and temperatures. We have recently demonstrated that pulsed electron decoupling using frequency-chirped microwaves improves MAS DNP experiments by partially attenuating detrimental hyperfine interactions. The continued development of pulsed electron decoupling will enable a new suite of MAS DNP experiments which transfer polarization directly to observed spins. Time domain DNP transfers to nuclear spins in conjunction with pulsed electron decoupling is described as a viable avenue toward DNP-enhanced, high-resolution NMR spectroscopy over a range of temperatures from <6K to 320 K.

Nov 28, 2018

Development of Very-Low-Temperature Millimeter-Wave Electron-Spin-Resonance Measurement System #DNPNMR

Fujii, Y., Y. Ishikawa, K. Ohya, S. Miura, Y. Koizumi, A. Fukuda, T. Omija, et al. “Development of Very-Low-Temperature Millimeter-Wave Electron-Spin-Resonance Measurement System.” Applied Magnetic Resonance 49, no. 8 (August 2018): 783–801.

We report the development of a millimeter-wave electron-spin-resonance (ESR) measurement system at the University of Fukui using a 3He/4He dilution refrigerator to reach temperatures below 1 K. The system operates in the frequency range of 125–130 GHz, with a homodyne detection. A nuclear-magnetic-resonance (NMR) measurement system was also developed in this system as the extension for millimeter-wave ESR/NMR double magnetic-resonance (DoMR) experiments. Several types of Fabry–Pérot-type resonators (FPR) have been developed: A piezo actuator attached to an FPR enables an electric tuning of cavity frequency. A flat mirror of an FPR has been fabricated using a gold thin film aiming for DoMR. ESR signal was measured down to 0.09 K. Results of ESR measurements of an organic radical crystal and phosphorous-doped silicon are presented. The NMR signal from 1H contained in the resonator is also detected successfully as a test for DoMR.

Nov 26, 2018

Rossini, Aaron J. “Materials Characterization by Dynamic Nuclear Polarization-Enhanced Solid-State NMR Spectroscopy.” The Journal of Physical Chemistry Letters 9, no. 17 (September 6, 2018): 5150–59.

High-resolution solid-state NMR spectroscopy is a powerful tool for the study of organic and inorganic materials because it can directly probe the symmetry and structure at nuclear sites, the connectivity/bonding of atoms and precisely measure inter-atomic distances. However, NMR spectroscopy is hampered by intrinsically poor sensitivity, consequently, the application of NMR spectroscopy to many solid materials is often infeasible. High-field dynamic nuclear polarization (DNP) has emerged as a technique to routinely enhance the sensitivity of solid-state NMR experiments by one to three orders of magnitude. This perspective gives a general overview of how DNP-enhanced solid-state NMR spectroscopy can be applied to a variety of inorganic and organic materials. DNP-enhanced solid-state NMR experiments provide unique insights into the molecular structure, which makes it possible to form structure-activity relationships that ultimately assist in the rational design and improvement of materials.

Nov 25, 2018

Two Open Postdoc Position in ssNMR and DNP of materials

The Division of Chemical & Biological Sciences at Ames Laboratory, a Department of Energy National Laboratory affiliated with Iowa State University, has two open positions for a postdoctoral associate with a background in solid-state NMRspectroscopy.

Position 1:
The chosen candidate will join a large multidisciplinary team consisting of researchers from both the Ames Laboratory, as well as other national laboratories and universities. The successful candidate will be responsible for conducting investigations of heterogeneous catalysts, polymers, and other materials by conventional as well as dynamic nuclear polarization (DNP) enhanced solid-state NMR spectroscopy. Aside from the aforementioned applications, the new candidate would be expected to also work in fundamental methods development of solid-state NMR and DNP, with main emphasis placed towards the characterization of surfaces and interfaces.

Position 2
The chosen candidate will become a part of a multidisciplinary team, consisting of Ames Laboratory as well as other U.S. DOE labs and universities, working towards the development, and understanding, of next generation supercapacitors. The work will mainly focus on the measurement of charge carrier dynamics and the characterization of electrode materials by both conventional as well as dynamic nuclear polarization (DNP) enhanced solid-state NMR. Studies of electrolyte-ion transport will use pulsed field gradient (PFG) NMR. The candidate will also be encouraged to work in the fundamental development of NMR methods and instrumentation.

Ames Laboratory is equipped with 9.4 and 14.1 T solid-state NMR spectrometers with MAS probes for rotor diameters ranging from 5 to 1.6-mm. The Laboratory is awaiting the delivery of a 110 kHz ultrafast MAS probe. Aside from these instruments, the lab is also equipped with a 9.4 T Bruker MAS-DNP NMR spectrometer with both 3.2 and 1.3-mm MAS-DNP probes. The successful candidate will collaborate with other PIs in the Division of Chemical and Biological Sciences and the Division of Materials Sciences and Engineering for synthetic and additional characterization needs.

More details can be found here:

Nov 23, 2018

NMR Studies of Protic Ionic Liquids

Overbeck, Viviane, and Ralf Ludwig. “NMR Studies of Protic Ionic Liquids.” In Annual Reports on NMR Spectroscopy, 95:147–90. Elsevier, 2018.

This review presents recent developments in the application of nuclear magnetic resonance (NMR) spectroscopy for studying the structure and dynamics of ionic liquids. We in particular focus on protic ionic liquids which are characterized by strong hydrogen bonding and proton transfer. Thus, the most relevant NMR-active nucleus is the proton, which undergoes rapid exchange on the NMR time scale. Also, other nuclei are considered if they provide information beyond simple characterization of this unique liquid material. We addressed several NMR techniques which are traditionally or just recently used in the field of ionic liquids research: relaxation time experiments, pulsed-field gradient NMR, fast-field-cycling NMR, electrophoretic NMR, and solid state NMR. Also, novel experiments such as dynamic nuclear polarization NMR are discussed.

Nov 21, 2018

Post-doc position in MAS DNP, Marseille, France

Postdoctoral position on “DNP NMR crystallography of functional organic materials at natural isotopic abundance”. 

The solid-state NMR group of the Institut de Chimie Radicalaire (ICR) at Aix-Marseille University is seeking motivated candidates for a postdoctoral position to work on an exciting project for excellent research funded by the European Research Council (ERC) in solid-state NMR and DNP of organic materials.

Project: The project, lead by Giulia Mollica, will combine methodological developments in dynamic nuclear polarisation solid-state NMR (MAS DNP), X-ray diffraction and computational methods (first principle calculations of NMR observable, crystal structure prediction) to develop an innovative analytical approach to solve the structure of functional organic powders at natural isotopic abundance. The work will mainly concern the study of organic systems of interest for pharmaceutical applications, electronic devices and energy. Computational work complementing experiments will be supported through collaborations with theoretical chemists in France and abroad.

The candidate will:

  • conceive new DNP NMR experiments to access spin-spin interactions on natural abundance spin systems
  • optimise the methods through numerical and analytical simulations
  • implement the newly devised experiments on the DNP NMR spectrometer
  • realise DFT calculations to help interpret the experimental results

Host institution/group: The Institut de Chimie Radicalaire (ICR) of Aix-Marseille University (AMU) is internationally recognised as a leader in the field of MAS DNP both for the development of new DNP-based analytical methods for the characterisation of organic solids and for the ideation of the most efficient polarising agents for MAS DNP. ICR provides a unique environment bringing together complementary expertise in fields like radical chemistry, MAS DNP, and materials science. The Solid-state NMR group of the ICR lab is interested in the characterisation of organic materials (pharmaceutical compounds, synthetic and natural polymeric materials) by a combination of NMR methods and computation. Computational work complementing experiments will be supported through collaborations with theoretical chemists in France and abroad.

The successful candidate will have access to a large range of liquid and SSNMR spectrometers via the analytical facility of AMU Spectropole ( located on the St. Jérôme Campus in Marseille. Two SSNMR 9.4 T spectrometers equipped with the latest developed hardware and numerous MAS probes (for rotor diameters of 1.3, 2.5, 3.2, 4 and 7 mm) are available on site. Solid-state DNP NMR experiments will be initially performed at the Bruker application center located near Strasbourg. A MAS DNP spectrometer will be installed in our laboratory in Marseille in 2019.

Requirements: Applicants are expected to have a degree in physical chemistry or physics, and a doctoral experience in solid-state NMR/DNP and/or computational methods on materials. Knowledge in computational methods for NMR is a clear asset, as it is experience with diffraction methods and crystallography.

The successful candidate will be initially recruited for 12 months (renewable). The net monthly salary will be between 2000 and 3000 €, depending on experience.

Preferred starting date: February 2019.

To apply through the CNRS portal: 

For informal queries about the position and/or the lab, please send an email to Giulia Mollica:

Recent selected publications:
-P. Cerreia-Vioglio, G. Mollica, M. Juramy, C.E. Hughes, P.A. Williams, S. Viel, P. Thureau, K.D.M. Harris, Insights into the Crystallization and Structural Evolution of Glycine Dihydrate by In Situ Solid-State NMR Spectroscopy, Angew. Chem. Int. Ed. 57, 6619 (2018).
-M. Dekhil, G. Mollica, T. Texier-Bonniot, F. Ziarelli, P. Thureau, S. Viel, Determining carbon–carbon connectivities in natural abundance organic powders using dipolar couplings, Chem. Commun. 52, 8565 (2016)
-G. Mollica, M. Dekhil, F. Ziarelli, P. Thureau, S. Viel, Quantitative Structural Constraints for Organic Powders at Natural Isotopic Abundance Using Dynamic Nuclear Polarization Solid-State NMR Spectroscopy, Angew. Chem. Int. Ed. 54, 6028 (2015).

Giulia Mollica - Chargée de Recherche CNRS - ICR Institut de Chimie Radicalaire (UMR CNRS 7273)
Aix-Marseille Université - Service 511 - ST JEROME - Avenue Escadrille Normandie Niemen - 13013 Marseille
Afin de respecter l'environnement, merci de n'imprimer cet email que si nécessaire.

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Magic angle spinning spheres

This article is indirectly related to DNP. It describes an exciting new idea from the Barnes lab how to spin samples in a MAS-NMR experiments and the perspective of integrating DNP.

Chen, Pinhui, Brice J Albert, Chukun Gao, Nicholas Alaniva, Lauren E Price, Faith J Scott, Edward P Saliba, et al. “Magic Angle Spinning Spheres.” SCIENCE ADVANCES, 2018, 8.

Magic angle spinning (MAS) is commonly used in nuclear magnetic resonance of solids to improve spectral resolution. Rather than using cylindrical rotors for MAS, we demonstrate that spherical rotors can be spun stably at the magic angle. Spherical rotors conserve valuable space in the probe head and simplify sample exchange and microwave coupling for dynamic nuclear polarization. In this current implementation of spherical rotors, a single gas stream provides bearing gas to reduce friction, drive propulsion to generate and maintain angular momentum, and variable temperature control for thermostating. Grooves are machined directly into zirconia spheres, thereby converting the rotor body into a robust turbine with high torque. We demonstrate that 9.5–mm–outside diameter spherical rotors can be spun at frequencies up to 4.6 kHz with N2(g) and 10.6 kHz with He(g). Angular stability of the spinning axis is demonstrated by observation of 79Br rotational echoes out to 10 ms from KBr packed within spherical rotors. Spinning frequency stability of ±1 Hz is achieved with resistive heating feedback control. A sample size of 36 ul can be accommodated in 9.5-mm-diameter spheres with a cylindrical hole machined along the spinning axis. We further show that spheres can be more extensively hollowed out to accommodate 161 ul of the sample, which provides superior signal-to-noise ratio compared to traditional 3.2-mm-diameter cylindrical rotors.

Nov 19, 2018

Using hyperpolarised NMR and DFT to rationalise the unexpected hydrogenation of quinazoline to 3,4-dihydroquinazoline

Richards, Josh E., Alexander J. J. Hooper, Oliver W. Bayfield, Martin C. R. Cockett, Gordon J. Dear, A. Jonathon Holmes, Richard O. John, et al. “Using Hyperpolarised NMR and DFT to Rationalise the Unexpected Hydrogenation of Quinazoline to 3,4-Dihydroquinazoline.” Chemical Communications 54, no. 73 (2018): 10375–78.

PHIP and SABRE hyperpolarized NMR methods are used to follow the unexpected metal-catalysed hydrogenation of quinazoline (Qu) to 3,4-dihydroquinazoline as the sole product. A solution of [IrCl(IMes)(COD)] in dichloromethane reacts with H2 and Qu to form [IrCl(H)2(IMes)(Qu)2] (2). The addition of methanol then results in its conversion to [Ir(H)2(IMes)(Qu)3]Cl (3) which catalyses the hydrogenation reaction. Density functional theory calculations are used to rationalise a proposed outer sphere mechanism in which (3) converts to [IrCl(H)2(H2)(IMes)(Qu)2]Cl (4) and neutral [Ir(H)3(IMes)(Qu)2](6), both of which are involved in the formation of 3,4-dihydroquinazoline via the stepwise transfer of H+ and H, withH2 identified as the reductant. Successive ligand exchange in 3 results in the production of thermodynamically stable [Ir(H)2(IMes)(3,4-dihydroquinazoline)3]Cl (5).

Nov 16, 2018

Perspective on the Hyperpolarisation Technique Signal Amplification by Reversible Exchange (SABRE) in NMR Spectroscopy and MR Imaging

Robertson, Thomas B.R., and Ryan E. Mewis. “Perspective on the Hyperpolarisation Technique Signal Amplification by Reversible Exchange (SABRE) in NMR Spectroscopy and MR Imaging.” In Annual Reports on NMR Spectroscopy, 93:145–212. Elsevier, 2018.

Signal amplification by reversible exchange (SABRE) is a para-hydrogen-based technique that utilises a metal complex, normally centred on iridium, to propagate polarisation from para-hydrogen-derived hydride ligands to spin-½ nuclei located in a bound substrate. To date, substrates possessing 1H, 13C, 15N, 19F, 31P, 29Si, and 119Sn nuclei have been polarised by this technique. The exact positioning of these nuclei has a direct bearing on the enhancement observed and so substrates must be chosen or synthesised with care in order to maximise polarisation transfer, and hence the resulting enhancement. The chemical composition of the metal complex must be similarly appraised, as the exchange rate of substrates and para-hydrogen is implicated heavily in efficient polarisation transfer. The nature of the polarisation transfer, whether homogenous or heterogeneous, is another important facet to consider here, as is conducting SABRE in water-based systems. This review discusses the physical and theoretical aspects of the SABRE experiment, as well as the applications of the SABRE technique, namely, the detection of analytes at concentrations far below what would be possible with conventional NMR techniques and the collection of hyperpolarised magnetic resonance images. Advances relating to utilising singlet states for SABRE, pulse sequence design and the nature of the polarisation transfer mechanism are also discussed, and the implications for future SABRE-based discoveries highlighted.

Nov 14, 2018

Resolving the Core and the Surface of CdSe Quantum Dots and Nanoplatelets Using Dynamic Nuclear Polarization Enhanced PASS–PIETA NMR Spectroscopy #DNPNMR

Piveteau, Laura, Ta-Chung Ong, Brennan J. Walder, Dmitry N. Dirin, Daniele Moscheni, Barbara Schneider, Janine Bär, et al. “Resolving the Core and the Surface of CdSe Quantum Dots and Nanoplatelets Using Dynamic Nuclear Polarization Enhanced PASS–PIETA NMR Spectroscopy.” ACS Central Science 4, no. 9 (September 26, 2018): 1113–25.

Understanding the surface of semiconductor nanocrystals (NCs) prepared using colloidal methods is a longstanding goal of paramount importance for all their potential optoelectronic applications, which remains unsolved largely because of the lack of site-specific physical techniques. Here, we show that multidimensional 113Cd dynamic nuclear polarization (DNP) enhanced NMR spectroscopy allows the resolution of signals originating from different atomic and magnetic surroundings in the NC cores and at the surfaces. This enables the determination of the structural perfection, and differentiation between the surface and core atoms in all major forms of size- and shape-engineered CdSe NCs: irregularly faceted quantum dots (QDs) and atomically flat nanoplatelets, including both dominant polymorphs (zinc-blende and wurtzite) and their epitaxial nanoheterostructures (CdSe/CdS core/shell quantum dots and CdSe/CdS core/crown nanoplatelets), as well as magic-sized CdSe clusters. Assignments of the NMR signals to specific crystal facets of oleate-terminated ZB structured CdSe NCs are proposed. Significantly, we discover far greater atomistic complexity of the surface structure and the species distribution in wurtzite as compared to zinc-blende CdSe QDs, despite an apparently identical optical quality of both QD polymorphs.

Nov 12, 2018

NMR Spectroscopy Unchained: Attaining the Highest Signal Enhancements in Dissolution Dynamic Nuclear Polarization #DNPNMR

Niedbalski, Peter, Andhika Kiswandhi, Christopher Parish, Qing Wang, Fatemeh Khashami, and Lloyd Lumata. “NMR Spectroscopy Unchained: Attaining the Highest Signal Enhancements in Dissolution Dynamic Nuclear Polarization.” The Journal of Physical Chemistry Letters 9, no. 18 (September 20, 2018): 5481–89.

Dynamic nuclear polarization (DNP) via the dissolution method is one of the most successful methods for alleviating the inherently low Boltzmann-dictated sensitivity in nuclear magnetic resonance (NMR) spectroscopy. This emerging technology has already begun to positively impact chemical and metabolic research by providing the much-needed enhancement of the liquid-state NMR signals of insensitive nuclei such as 13C by several thousand-fold. In this Perspective, we present our viewpoints regarding the key elements needed to maximize the NMR signal enhancements in dissolution DNP, from the very core of the DNP process at cryogenic temperatures, DNP instrumental conditions, and chemical tuning in sample preparation to current developments in minimizing hyperpolarization losses during the dissolution transfer process. The optimization steps discussed herein could potentially provide important experimental and theoretical considerations in harnessing the best possible sensitivity gains in NMR spectroscopy as afforded by optimized dissolution DNP technology.

Nov 9, 2018

Computationally Assisted Design of Polarizing Agents for Dynamic Nuclear Polarization Enhanced NMR: The AsymPol Family #DNPNMR

Mentink-Vigier, Frédéric, Ildefonso Marin-Montesinos, Anil P. Jagtap, Thomas Halbritter, Johan van Tol, Sabine Hediger, Daniel Lee, Snorri Th. Sigurdsson, and Gaël De Paëpe. “Computationally Assisted Design of Polarizing Agents for Dynamic Nuclear Polarization Enhanced NMR: The AsymPol Family.” Journal of the American Chemical Society 140, no. 35 (September 5, 2018): 11013–19.

We introduce a new family of highly efficient polarizing agents for dynamic nuclear polarization (DNP)-enhanced nuclear magnetic resonance (NMR) applications, composed of asymmetric bis-nitroxides, in which a piperidine-based radical and a pyrrolinoxyl or a proxyl radical are linked together. The design of the AsymPol family was guided by the use of advanced simulations that allow computation of the impact of the radical structure on DNP efficiency. These simulations suggested the use of a relatively short linker with the intention to generate a sizable intramolecular electron dipolar coupling/J-exchange interaction, while avoiding parallel nitroxide orientations. The characteristics of AsymPol were further tuned, for instance with the addition of a conjugated carbon−carbon double bond in the 5-membered ring to improve the rigidity and provide a favorable relative orientation, the replacement of methyls by spirocyclohexanolyl groups to slow the electron spin relaxation, and the introduction of phosphate groups to yield highly water-soluble dopants. An in-depth experimental and theoretical study for two members of the family, AsymPol and AsymPolPOK, is presented here. We report substantial sensitivity gains at both 9.4 and 18.8 T. The robust efficiency of this new family is further demonstrated through high-resolution surface characterization of an important industrial catalyst using fast sample spinning at 18.8 T. This work highlights a new direction for polarizing agent design and the critical importance of computations in this process.

Nov 7, 2018

Photogenerated Radical in Phenylglyoxylic Acid for in Vivo Hyperpolarized 13C MR with Photosensitive Metabolic Substrates #DNPNMR

Marco-Rius, Irene, Tian Cheng, Adam P. Gaunt, Saket Patel, Felix Kreis, Andrea Capozzi, Alan J. Wright, Kevin M. Brindle, Olivier Ouari, and Arnaud Comment. “Photogenerated Radical in Phenylglyoxylic Acid for in Vivo Hyperpolarized 13 C MR with Photosensitive Metabolic Substrates.” Journal of the American Chemical Society 140, no. 43 (October 31, 2018): 14455–63.

Whether for 13C magnetic resonance studies in chemistry, biochemistry or biomedicine, hyperpolarization methods based on dynamic nuclear polarization (DNP) have become ubiquitous. DNP requires a source of unpaired electrons, which are commonly added to the sample to be hyperpolarized in the form of stable free radicals. Once polarized, the presence of these radicals is unwanted. These radicals can be replaced by nonpersistent radicals created by photo-irradiation of pyruvic acid (PA), which are annihilated upon dissolution or thermalization in the solid state. However, since PA is readily metabolized by most cells, its presence may be undesirable for some metabolic studies. In addition, some 13C substrates are photo-sensitive and, therefore, may degrade during photo-generation of PA radical, which requires ultraviolet (UV) light. We show here that photoirradiation of phenylglyoxylic acid (PhGA) using visible light produces a non-persistent radical that, in principle, can be used to hyperpolarize any molecule. We compare radical yields in samples containing PA and PhGA upon photo-irradiation with broadband and narrowband UV-visible light sources. To demonstrate the suitability of PhGA as a radical precursor for DNP, we polarized the gluconeogenic probe 13C-dihydroxyacetone, which is UV-sensitive, using a commercial 3.35 T DNP polarizer and then injected this into a mouse and followed its metabolism in vivo.

Nov 5, 2018

Adiabatic-NOVEL for Nano-Scale Magnetic Resonance Imaging #DNPNMR

Annabestani, Razieh, Maryam Mirkamali, and Raffi Budakian. “Adiabatic-NOVEL for Nano-Scale Magnetic Resonance Imaging.” ArXiv:1712.09128 [Quant-Ph], December 25, 2017.

We propose a highly efficient dynamic nuclear polarization technique that is robust against field in-homogeneity. This technique is designed to enhance the detection sensitivity in nano-MRI, where large Rabi field gradients are required. The proposed technique consists of an adiabatic half passage pulse followed by an adiabatic linear sweep of the electron Rabi frequency and can be considered as an adiabatic version of nuclear orientation via electron spin locking (adiabatic-NOVEL). We analyze the spin dynamics of an electron-nuclear system that is under microwave irradiation at high static magnetic field and at cryogenic temperature. The result shows that an amplitude modulation of the microwave field makes adiabatic-NOVEL highly efficient and robust against both the static and microwave field in-homogeneity.

Nov 2, 2018

Determination of binding affinities using hyperpolarized NMR with simultaneous 4-channel detection

Kim, Yaewon, Mengxiao Liu, and Christian Hilty. “Determination of Binding Affinities Using Hyperpolarized NMR with Simultaneous 4-Channel Detection.” Journal of Magnetic Resonance 295 (October 2018): 80–86.

Dissolution dynamic nuclear polarization (D-DNP) is a powerful technique to improve NMR sensitivity by a factor of thousands. Combining D-DNP with NMR-based screening enables to mitigate solubility or availability problems of ligands and target proteins in drug discovery as it can lower the concentration requirements into the sub-micromolar range. One of the challenges that D-DNP assisted NMR screening methods face for broad application, however, is a reduced throughput due to additional procedures and time required to create hyperpolarization. These requirements result in a delay of several tens of minutes in-between each NMR measurement. To solve this problem, we have developed a simultaneous 4-channel detection method for hyperpolarized 19F NMR, which can increase throughput four-fold utilizing a purpose-built multiplexed NMR spectrometer and probe. With this system, the concentration-dependent binding interactions were observed for benzamidine and benzylamine with the serine protease trypsin. A T2 relaxation measurement of a hyperpolarized reporter ligand (TFBC; CF3C6H4CNHNH2), which competes for the same binding site on the trypsin with the other ligands, was used. The hyperpolarized TFBC was mixed with trypsin and the ligand of interest, and injected into four flow cells inside the NMR probe. Across the set of four channels, a concentration gradient was created. From the simultaneously acquired relaxation datasets, it was possible to determine the dissociation constant (KD) of benzamidine or benzylamine without the requirement for individually optimizing experimental conditions for different affinities. A simulation showed that this 4-channel detection method applied to D-DNP NMR extends the screenable KD range to up to three orders of magnitude in a single experiment.

Oct 31, 2018

Monitoring of hydrogenation by benchtop NMR with parahydrogen-induced polarization

Jeong, Keunhong, Sein Min, Heelim Chae, and Sung Keon Namgoong. “Monitoring of Hydrogenation by Benchtop NMR with Parahydrogen-Induced Polarization.” Magnetic Resonance in Chemistry, August 29, 2018.

Reaction monitoring using nuclear magnetic resonance (NMR) spectroscopy is a powerful tool that provides detailed information on the characteristics and mechanism of the reaction. Although highfield NMR provides more accurate and abundant data, which can be explained in terms of Boltzmann factors, benchtop NMR is commonly used because of its low cost and simple maintenance. Therefore, hyperpolarization of the sample in benchtop NMR is a suitable protocol for real-time reaction monitoring. Herein, the principle-based experimental setup, integrating the reaction monitoring system in a 60-MHz benchtop NMR instrument with a parahydrogen-induced polarization (PHIP) system, is used. Enhanced signals by the ALTADENA mechanism were obtained after PHIP on styrene, and reasonable kinetic data were collected, supporting the known reactivity of Wilkinson’s catalyst. These results should provide a foundation for future applications of NMR-based reaction monitoring systems utilizing hyperpolarization.

Oct 29, 2018

A portable ventilator with integrated physiologic monitoring for hyperpolarized 129Xe MRI in rodents

Virgincar, Rohan S., Jerry Dahlke, Scott H. Robertson, Nathann Morand, Yi Qi, Simone Degan, Bastiaan Driehuys, and John C. Nouls. “A Portable Ventilator with Integrated Physiologic Monitoring for Hyperpolarized 129Xe MRI in Rodents.” Journal of Magnetic Resonance 295 (October 2018): 63–71.

Hyperpolarized (HP) 129Xe MRI is emerging as a powerful, non-invasive method to image lung function and is beginning to find clinical application across a range of conditions. As clinical implementation progresses, it becomes important to translate back to well-defined animal models, where novel disease signatures can be characterized longitudinally and validated against histology. To date, preclinical 129Xe MRI has been limited to only a few sites worldwide with 2D imaging that is not generally sufficient to fully capture the heterogeneity of lung disease. To address these limitations and facilitate broader dissemination, we report on a compact and portable HP gas ventilator that integrates all the gas-delivery and physiologic monitoring capabilities required for high-resolution 3D hyperpolarized 129Xe imaging. This ventilator is MR- and HP-gas compatible, driven by inexpensive microcontrollers and open source code, and allows for precise control of the tidal volume and breathing cycle in perorally intubated mice and rats. We use the system to demonstrate data acquisition over multiple breath-holds, during which lung motion is suspended to enable high-resolution 3D imaging of gas-phase and dissolved-phase 129Xe in the lungs. We demonstrate the portability and versatility of the ventilator by imaging a mouse model of lung cancer longitudinally at 2-Tesla, and a healthy rat at 7 T. We also report the detection of subtle spectroscopic fluctuations in phase with the heart rate, superimposed onto larger variations stemming from the respiratory cycle. This ventilator was developed to facilitate duplication and gain broad adoption to accelerate preclinical 129Xe MRI research.

Oct 26, 2018

Sensitivity-Enhanced 207 Pb Solid-State NMR Spectroscopy for the Rapid, Non-Destructive Characterization of Organolead Halide Perovskites #DNPNMR

Hanrahan, Michael P., Long Men, Bryan A. Rosales, Javier Vela, and Aaron J. Rossini. “Sensitivity-Enhanced 207 Pb Solid-State NMR Spectroscopy for the Rapid, Non-Destructive Characterization of Organolead Halide Perovskites.” Chemistry of Materials, October 4, 2018. 

Organolead halide and mixed halide perovskites (CH3NH3PbX3, CH3NH3PbX3–nYn, X and Y = Cl–, Br– or I–), are promising materials for photovoltaics and optoelectronic devices. 207Pb solid-state NMR spectroscopy has previously been applied to characterize phase segregation and halide ion speciation in mixed halide perovskites. However, NMR spectroscopy is an insensitive technique that often requires large sample volumes and long signal averaging periods. This is especially true for mixed halide perovskites, which give rise to extremely broad 207Pb solid-state NMR spectra. Here, we quantitatively compare the sensitivity of the various solid-state NMR techniques on pure and mixed halide organolead perovskites and demonstrate that both fast MAS and DNP can provide substantial gains in NMR sensitivity for these materials. With fast MAS and proton detection, high signal-to-noise ratio two-dimensional (2D) 207Pb-1H heteronuclear correlation (HETCOR) NMR spectra can be acquired in less than half an hour from only ca. 5 μL of perovskite material. Modest relayed DNP enhancements on the order of 1 to 20 were obtained for perovskites. The cryogenic temperatures (110 K) used for DNP experiments also provide a significant boost in sensitivity. Consequently, it was possible to obtain the 207Pb solid-state NMR spectrum of a 300 nm thick model thin film of CH3NH3PbI3 in 34 hours by performing solid-state NMR experiments with a sample temperature of 110 K. This result demonstrates the possibility of using NMR spectroscopy for characterization of perovskite thin films.

Oct 25, 2018

[NMR] EPFL post-doc postion #DNPNMR

Dear colleagues, 

A post-doc position will be available at the LPMN group of EPFL, starting in the spring of 2019, to work on high field EPR and gyrotron-DNP. 

A job description can be found at
For enquires, please write to

Best regards,
Prof. Jean-Philippe Ansermet
LPMN-ICMP-FSB-station 3
Ecole Polytechnique Fédérale de Lausanne
1015 Lausanne-EPFL

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Oct 24, 2018

Efficiency of Water-Soluble Nitroxide Biradicals for Dynamic Nuclear Polarization in Rotating Solids at 9.4 T: bcTol-M and cyolyl-TOTAPOL as New Polarizing Agents #DNPNMR

Geiger, Michel-Andreas, Anil P. Jagtap, Monu Kaushik, Han Sun, Daniel Stöppler, Snorri T. Sigurdsson, Björn Corzilius, and Hartmut Oschkinat. “Efficiency of Water-Soluble Nitroxide Biradicals for Dynamic Nuclear Polarization in Rotating Solids at 9.4 T: BcTol-M and Cyolyl-TOTAPOL as New Polarizing Agents.” Chemistry - A European Journal 24, no. 51 (September 12, 2018): 13485–94.

Nitroxide biradicals are very efficient polarizing agents in magic angle spinning (MAS) cross effect (CE) dynamic nuclear polarization (DNP) nuclear magnetic resonance (NMR). Many recently synthesized, new radicals show superior DNP-efficiency in organic solvents but suffer from insufficient solubility in water or glycerol/water for biological applications. We report DNP efficiencies for two new radicals, the water-soluble bcTol-M and cyolyl-TOTAPOL, and include a comparison with three known biradicals, TOTAPOL, bcTol, and AMUPol. They differ by linker groups, featuring either a 3-aminopropane-1,2-diol or a urea tether, or by the structure of the alkyl substituents that flank the nitroxide groups. For evaluating their performances, we measured both signal enhancements e and DNP-enhanced sensitivity k, and compared the results to electron spin relaxation data recorded at the same magnetic field strength (9.4 T). In our study, differences in DNP efficiency correlate with changes in the nuclear polarization dynamics rather than electron relaxation.
The ratios of their individual e and k differ by up to 20%, which is explained by starkly different nuclear polarization build-up rates. For the radicals compared here empirically, using proline standard solutions, the new radical bcTol-M performs best while being most soluble in water/glycerol mixtures.

Oct 22, 2018

Heterogeneity of Network Structures and Water Dynamics in κ-Carrageenan Gels Probed by Nanoparticle Diffusometry #DNPNMR

Kort, Daan W. de, Erich Schuster, Freek J.M. Hoeben, Ryan Barnes, Meike Emondts, Henk M. Janssen, Niklas Lorén, Songi Han, Henk Van As, and John P.M. van Duynhoven. “Heterogeneity of Network Structures and Water Dynamics in κ-Carrageenan Gels Probed by Nanoparticle Diffusometry.” Langmuir 34, no. 37 (September 18, 2018): 11110–20. 

A set of functionalized nanoparticles (PEGylated dendrimers, d = 2.8 - 9 nm) was used to probe the structural heterogeneity in Na+/K+ induced κ-carrageenan gels. The self-diffusion behavior of these nanoparticles as observed by 1H PFG NMR, FRAP and RICS revealed a fast and a slow component, pointing towards microstructural heterogeneity in the gel network. The self-diffusion behavior of the faster nanoparticles could be modelled with obstruction by a coarse network (average mesh size <100 nm), while the slower-diffusing nanoparticles are trapped in a dense network (lower mesh size limit of 4.6 nm). Overhauser DNP-enhanced NMR relaxometry revealed a reduced local solvent water diffusivity near TEMPO-labelled nanoparticles trapped in the dense network, showing that heterogeneity in the physical network is also reflected in heterogeneous self-diffusivity of water. The observed heterogeneity in mesh sizes and in water self-diffusivity is of interest for understanding and modelling of transport through and release of solutes from heterogeneous biopolymer gels.

Oct 19, 2018

EPSRC Industrial CASE PhD Studentship “DNP-enhanced Solid-state NMR Studies of Pharmaceuticals” #DNPNMR

EPSRC Industrial CASE PhD Studentship “DNP-enhanced Solid-state NMR Studies of Pharmaceuticals”

Dr Jeremy Titman, School of Chemistry, University of Nottingham
Dr Tran N. Pham, GSK 

Solid-state nuclear magnetic resonance (NMR) is a powerful method for studying the molecular structure and dynamics of a broad range of systems from heterogeneous materials to biological molecules. In some situations solid-state NMR can suffer from low sensitivity, because of the small nuclear spin polarizations involved, so that long acquisition times or large sample volumes are required. However, weak NMR signals can be dramatically enhanced by dynamic nuclear polarization (DNP), which involves transfer of electron spin polarization from radicals implanted in the sample to nearby nuclei. The substantial enhancements (up to 300-fold) obtained with DNP make NMR studies of dilute species feasible for the first time and have already prompted exciting new NMR applications to interfaces, porous materials and microcrystalline substances.

The University of Nottingham has recently established a DNP-enhanced solid-state NMR Facility (unique in the UK) funded by a grant of £2.5 M from EPSRC. In this collaboration with GSK DNP-enhanced solid-state NMR will be used to study pharmaceutical formulations and drug delivery systems. These are challenging systems to study by solid-state NMR because of the often low concentration of the active pharmaceutical ingredient (API). However, the substantial signal enhancements obtained with DNP will allow natural abundance investigations of polymorphs or hydration states of APIs, of formulations involving amorphous APIs and of the interactions at the interfaces between APIs and excipients such as fillers, binders, lubricants and preservatives.

The PhD studentship is available immediately, and is fully funded for 4 years via a stipend covering PhD tuition fees (at the Home/EU rate) and a tax-free living allowance (£14,777 per annum). As part of the project the student will spend up to three months at the GSK Medicines Research Centre in Hertfordshire UK acquiring skills in formulation science and manufacturing samples.

The student will gain expertise in solid-state NMR spectroscopy, especially as applied to pharmaceutical formulations, as well as experience of DNP-enhanced methods. Transferable skills in computer programming, data analysis and scientific communication will also be acquired. In addition, the student will benefit from hands-on experience in industry, while pursuing a research project in an academic environment, and gain knowledge in the business of drug discovery and development.

Applications are invited from outstanding EU/UK students holding or expecting to gain a good undergraduate degree in Chemistry, Physics or a related subject. Prior experience in solid-state NMR is not essential. Note that the UK government has guaranteed EU eligibility for EPSRC funding for PhDs beginning before the end of the 2018-2019 academic year. Apply online at by 15th November 2018. For informal enquiries please contact:

The solid-state NMR group at Nottingham works on the design of new solid-state NMR experiments and their application to chemistry, energy research, nanotechnology and environmental science. The group has three solid-state NMR spectrometers, operating at 1H Larmor frequencies of 300, 600 and 800 MHz. A 600 MHz Dynamic Nuclear Polarization MAS NMR spectrometer was installed in Nottingham in November 2015. For more information about the solid-state NMR group see: The University of Nottingham is ranked in the top 100 universities in the world (QS World University Rankings).

Dr Jeremy J Titman
Associate Professor and Reader in Magnetic Resonance,
A43, School of Chemistry, University of Nottingham,
University Park, Nottingham, NG7 2RD, UK
Tel: +44 115 951 3560

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Yoder, J. L., P. E. Magnelind, M. A. Espy, and M. T. Janicke. “Exploring the Limits of Overhauser Dynamic Nuclear Polarization (O-DNP) for Portable Magnetic Resonance Detection of Low γ Nuclei.” Applied Magnetic Resonance 49, no. 7 (July 2018): 707–24.

Nuclear magnetic resonance (NMR) spectroscopy in portable, permanent magnet-based spectrometers is primarily limited to nuclei with higher gyromagnetic ratio, γ, such as 1H, 19F, and 31P due to the limited field strength achievable in these systems. Overhauser effect dynamic nuclear polarization (O-DNP), which transfers polarization from an unpaired electron to a nucleus by saturating an electron paramagnetic resonance transition with an oscillating radio frequency magnetic field, B1e, can increase the polarization of low γ nuclei by hundreds or even thousands, enabling detection in a portable system. We have investigated the potential for O-DNP to enhance signals using (4-amino-2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO hereafter) as a source of unpaired electrons in a homebuilt ultra-low field (ULF) O-DNP-NMR spectrometer. We have found, in general, that larger concentrations of TEMPO are required for effective O-DNP with low γ nuclei, which has a number of important effects. Spin exchange effects cause the EPR lines to overlap and ultimately merge at high concentrations of TEMPO, fundamentally increasing the maximum possible enhancement, while the electron–electron dipolar interaction reduces both longitudinal and transverse relaxation times for the electrons, dramatically increasing the required B1e strength. The relationship between TEMPO concentration, B1e magnitude and O-DNP enhancement is quantified, and strategies for achieving these fields are discussed.

Oct 17, 2018

Structural Elucidation of Amorphous Photocatalytic Polymers from Dynamic Nuclear Polarization Enhanced Solid State NMR #DNPNMR

Brownbill, Nick J., Reiner Sebastian Sprick, Baltasar Bonillo, Shane Pawsey, Fabien Aussenac, Alistair J. Fielding, Andrew I. Cooper, and Frédéric Blanc. “Structural Elucidation of Amorphous Photocatalytic Polymers from Dynamic Nuclear Polarization Enhanced Solid State NMR.” Macromolecules 51, no. 8 (April 24, 2018): 3088–96. 

Dynamic nuclear polarization (DNP) solid-state nuclear magnetic resonance (NMR) offers a recent approach to dramatically enhance NMR signals and has enabled detailed structural information to be obtained in a series of amorphous photocatalytic copolymers of alternating pyrene and benzene monomer units, the structures of which cannot be reliably established by other spectroscopic or analytical techniques. Large 13C cross-polarization (CP) magic angle spinning (MAS) signal enhancements were obtained at high magnetic fields (9.4− 14.1 T) and low temperature (110−120 K), permitting the acquisition of a 13C INADEQUATE spectrum at natural abundance and facilitating complete spectral assignments, including when small amounts of specific monomers are present. The high 13C signal-to-noise ratios obtained are harnessed to record quantitative multiple contact CP NMR data, used to determine the polymers’ composition. This correlates well with the putative pyrene:benzene stoichiometry from the monomer feed ratio, enabling their structures to be understood.

Oct 15, 2018

Illuminating the dark metabolome to advance the molecular characterisation of biological systems #DNPNMR

This is a great review showcasing the capabilities of DNP-enhanced NMR spectroscopy for metabolomic studies.

Jones, Oliver A. H. “Illuminating the Dark Metabolome to Advance the Molecular Characterisation of Biological Systems.” Metabolomics 14, no. 8 (August 2018).

Background  The latest version of the Human Metabolome Database (v4.0) lists 114,100 individual entries. Typically, however, metabolomics studies identify only around 100 compounds and many features identified in mass spectra are listed only as ‘unknown compounds’. The lack of ability to detect all metabolites present, and fully identify all metabolites detected (the dark metabolome) means that, despite the great contribution of metabolomics to a range of areas in the last decade, a significant amount of useful information from publically funded studies is being lost or unused each year. This loss of data limits our potential gain in knowledge and understanding of important research areas such as cell biology, environmental pollution, plant science, food chemistry and health and biomedical research. Metabolomics therefore needs to develop new tools and methods for metabolite identification to advance as a field.

Oct 8, 2018

Resolving the Core and the Surface of CdSe Quantum Dots and Nanoplatelets Using Dynamic Nuclear Polarization Enhanced PASS–PIETA NMR Spectroscopy #DNPNMR

Piveteau, Laura, Ta-Chung Ong, Brennan J. Walder, Dmitry N. Dirin, Daniele Moscheni, Barbara Schneider, Janine Bär, et al. “Resolving the Core and the Surface of CdSe Quantum Dots and Nanoplatelets Using Dynamic Nuclear Polarization Enhanced PASS–PIETA NMR Spectroscopy.” ACS Central Science 4, no. 9 (September 26, 2018): 1113–25.

Understanding the surface of semiconductor nanocrystals (NCs) prepared using colloidal methods is a longstanding goal of paramount importance for all their potential optoelectronic applications, which remains unsolved largely because of the lack of site-specific physical techniques. Here, we show that multidimensional 113Cd dynamic nuclear polarization (DNP) enhanced NMR spectroscopy allows the resolution of signals originating from different atomic and magnetic surroundings in the NC cores and at the surfaces. This enables the determination of the structural perfection, and differentiation between the surface and core atoms in all major forms of size- and shape-engineered CdSe NCs: irregularly faceted quantum dots (QDs) and atomically flat nanoplatelets, including both dominant polymorphs (zinc-blende and wurtzite) and their epitaxial nanoheterostructures (CdSe/CdS core/shell quantum dots and CdSe/CdS core/crown nanoplatelets), as well as magic-sized CdSe clusters. Assignments of the NMR signals to specific crystal facets of oleate-terminated ZB structured CdSe NCs are proposed. Significantly, we discover far greater atomistic complexity of the surface structure and the species distribution in wurtzite as compared to zinc-blende CdSe QDs, despite an apparently identical optical quality of both QD polymorphs.

Oct 5, 2018

Probing the surface of γ-Al2O3 by oxygen-17 dynamic nuclear polarization enhanced solid-state NMR spectroscopy #DNPNMR

Li, Wenzheng, Qiang Wang, Jun Xu, Fabien Aussenac, Guodong Qi, Xingling Zhao, Pan Gao, Chao Wang, and Feng Deng. “Probing the Surface of γ-Al2O3 by Oxygen-17 Dynamic Nuclear Polarization Enhanced Solid-State NMR Spectroscopy.” Physical Chemistry Chemical Physics 20, no. 25 (June 27, 2018): 17218–25.

γ-Al2O3 is an important catalyst and catalyst support of industrial interest. Its acid/base characteristics are correlated to the surface structure, which has always been an issue of concern. In this work, the complex (sub-)surface oxygen species on surface-selectively labelled γ-Al2O3 were probed by 17O dynamic nuclear polarization surface-enhanced NMR spectroscopy (DNP-SENS). Direct 17O MAS and indirect 1H–17O cross-polarization (CP)/MAS DNP experiments enable observation of the (sub-)surface bare oxygen species and hydroxyl groups. In particular, a two-dimensional (2D) 17O 3QMAS DNP spectrum was for the first time achieved for γ-Al2O3, in which two O(Al)4 and one O(Al)3 bare oxygen species were identified. The 17O isotropic chemical shifts (δcs) vary from 56.7 to 81.0 ppm and the quadrupolar coupling constants (CQ) range from 0.6 to 2.5 MHz for the three oxygen species. The coordinatively unsaturated O(Al)3 species is characterized by a higher field chemical shift (56.7 ppm) and the largest CQ value (2.5 MHz) among these oxygen sites. 2D 1H → 17O HETCOR DNP experiments allow us to discriminate three bridging (Aln)-μ2-OH and two terminal (Aln)-μ1-OH hydroxyl groups. The structural features of the bare oxygen species and hydroxyl groups are similar for the γ-Al2O3 samples isotopically labelled by 17O2 gas or H217O. The results presented here show that the combination of surface-selective labelling and DNP-SENS is an effective approach for characterizing oxides with complex surface species.

Oct 3, 2018

Exploring Applications of Covalent Organic Frameworks: Homogeneous Reticulation of Radicals for Dynamic Nuclear Polarization #DNPNMR

Cao, Wei, Wei David Wang, Hai-Sen Xu, Ivan V. Sergeyev, Jochem Struppe, Xiaoling Wang, Frederic Mentink-Vigier, et al. “Exploring Applications of Covalent Organic Frameworks: Homogeneous Reticulation of Radicals for Dynamic Nuclear Polarization.” Journal of the American Chemical Society 140, no. 22 (June 6, 2018): 6969–77.

Rapid progress has been witnessed in the past decade in the fields of covalent organic frameworks (COFs) and dynamic nuclear polarization (DNP). In this contribution, we bridge these two fields by constructing radical-embedded COFs as promising DNP agents. Via polarization transfer from unpaired electrons to nuclei, DNP realizes significant enhancement of NMR signal intensities. One of the crucial issues in DNP is to screen for suitable radicals to act as efficient polarizing agents, the basic criteria for which are homogeneous distribution and fixed orientation of unpaired electrons. We therefore envisioned that the crystalline and porous structures of COFs, if evenly embedded with radicals, may work as a new “crystalline sponge” for DNP experiments. As a proof of concept, we constructed a series of proxyl-radical-embedded COFs (denoted as PR(x)-COFs) and successfully applied them to achieve substantial DNP enhancement. Benefiting from the bottom-up and multivariate synthetic strategies, proxyl radicals have been covalently reticulated, homogeneously distributed, and rigidly embedded into the crystalline and mesoporous frameworks with adjustable concentration (x%). Excellent performance of PR(x)-COFs has been observed for DNP 1H, 13C, and 15N solid-state NMR enhancements. This contribution not only realizes the direct construction of radical COFs from radical monomers, but also explores the new application of COFs as DNP polarizing agents. Given that many radical COFs can therefore be rationally designed and facilely constructed with well-defined composition, distribution, and pore size, we expect that our effort will pave the way for utilizing radical COFs as standard polarizing agents in DNP NMR experiments.