Friday, June 30, 2017

Solvent suppression in DNP enhanced solid state NMR #DNPNMR


Yarava, J.R., et al., Solvent suppression in DNP enhanced solid state NMR. J Magn Reson, 2017. 277: p. 149-153.


We show how DNP enhanced solid-state NMR spectra can be dramatically simplified by suppression of solvent signals. This is achieved by (i) exploiting the paramagnetic relaxation enhancement of solvent signals relative to materials substrates, or (ii) by using short cross-polarization contact times to transfer hyperpolarization to only directly bonded carbon-13 nuclei in frozen solutions. The methods are evaluated for organic microcrystals, surfaces and frozen solutions. We show how this allows for the acquisition of high-resolution DNP enhanced proton-proton correlation experiments to measure inter-nuclear proximities in an organic solid.

[NMR] Postdoctoral Position in DNP-NMR at Dartmouth

Postdoctoral Position in DNP-NMR at Dartmouth 

A postdoctoral position is available in the group of Professor Chandrasekhar Ramanathan in the Department of Physics and Astronomy at Dartmouth College to investigate the spin physics of surfaces and low-dimensional spin systems using DNP-NMR. 

Our group works at the interface of quantum information processing and condensed matter and materials physics. We develop and use magnetic resonance methods (including NMR, DNP and EDMR) to control and characterize the spin dynamics of solid state spin systems. The lab currently houses a custom-built 94 GHz DNP system, a 7 T solid-state NMR system, a 9.4 T liquid state NMR system and zero- and low-field EDMR systems. Additional information, including recent publications, can be found at http://www.dartmouth.edu/~cramanathan

Application

The preferred applicant will have a PhD in Physics, Chemistry or a related field and strong experimental skills. Knowledge of RF, microwave and cryogenic techniques and magnetic resonance methods is strongly desired. Interested candidates are invited to submit an electronic application (CV, brief statement of research interests and list of references) to sekhar.ramanathan@dartmouth.edu

The anticipated start date is October 1, 2017 or soon after.

About Dartmouth

Founded in 1769, Dartmouth is a member of the Ivy League and has a deep commitment to combining outstanding undergraduate liberal arts and graduate education with distinguished research and scholarship. Dartmouth is located in the scenic Upper Valley region of New England, about a 2-hour drive from Boston and 3.5 hours from Montreal.

------------------------------
Chandrasekhar Ramanathan
Department of Physics and Astronomy
6127 Wilder Laboratory
Dartmouth College
Hanover, NH 03755

Tel: +1 (603) 646-9780



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Thursday, June 29, 2017

[NMR] [Help] Reply Reply All Forward Postdoc or PhD position at the MPI for Biophysical Chemistry in Göttingen, Germany



The “NMR Signal Enhancement Group” at the Max Planck Institute for
Biophysical Chemistry invites applications for a


Ph.D. or Postdoc Position
- Chemist for the synthesis of magnetic resonance contrast agents -
(Code Number 27-17)

We are looking for a highly motivated Ph.D. student or Postdoc who will work on the synthesis of contrast agents for magnetic resonance imaging experiments. The position is to be filled by January 2018.

He/she should have a strong background in synthetic chemistry, medicinal chemistry or related disciplines. Knowledge about magnetic resonance (MR) methods is advantageous.

We offer an international and highly productive and innovative working atmosphere and provide state-of-the-art MR equipment and collaboration possibilities.

For a Ph.D. student position, candidates should hold a Master’s (or equivalent) degree in life science. The Ph.D. position is limited to three years with a possible extension.

Postdoc candidates hold a Ph.D. degree in life science. The initial appointment for Postdocs is 2 years with possibilities for extension.

The payment and benefits are based on the TVöD guidelines.

The Max Planck Society is committed to increasing the number of individuals with disabilities in its workforce and therefore encourages applications from such qualified individuals. Furthermore, the Max Planck Society seeks to increase the number of women in those areas where they are underrepresented and therefore explicitly encourages women to apply.

Interested candidates should send their applications (application deadline: 30.09.2017) preferably via e-mail with reference to the code number 27-17, including a statement of research interests and two letters of recommendation send under separate cover, to



Max Planck Institute for Biophysical Chemistry
NMR Signal Enhancement Group
Dr. Stefan Glöggler
Am Fassberg 11, 37077 Göttingen
Germany

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Wednesday, June 28, 2017

Dynamic Nuclear Polarization of beta-Cyclodextrin Macromolecules #DNPNMR


Caracciolo, F., et al., Dynamic Nuclear Polarization of beta-Cyclodextrin Macromolecules. J Phys Chem B, 2017. 121(12): p. 2584-2593.


1H dynamic nuclear polarization and nuclear spin-lattice relaxation rates have been studied in amorphous complexes of beta-cyclodextrins doped with different concentrations of the TEMPO radical. Nuclear polarization increased up to 10% in the optimal case, with a behavior of the buildup rate (1/TPOL) and of the nuclear spin-lattice relaxation rate (1/T1n) consistent with a thermal mixing regime. The temperature dependence of 1/T1n and its increase with the radical concentration indicate a relaxation process arising from the modulation of the electron-nucleus coupling by the glassy dynamics. The high-temperature relaxation is driven by molecular motions, and 1/T1n was studied at room temperature in liquid solutions for dilution levels close to the ones typically used for in vivo studies.

Friday, June 23, 2017

A DNP-supported solid-state NMR study of carbon species in fluid catalytic cracking catalysts #DNPNMR


Mance, D., et al., A DNP-supported solid-state NMR study of carbon species in fluid catalytic cracking catalysts. Chem Commun (Camb), 2017. 53(28): p. 3933-3936.


A combination of solid-state NMR techniques supported by EPR and SEM-EDX experiments was used to localize different carbon species (coke) in commercial fluid catalytic cracking catalysts. Aliphatic coke species formed during the catalytic process and aromatic coke species deposited directly from the feedstock respond differently to dynamic nuclear polarization signal enhancement in integral and crushed FCC particles, indicating that aromatic species are mostly concentrated on the outside of the catalyst particles, whereas aliphatic species are also located on the inside of the FCC particles. The comparison of solid-state NMR data with and without the DNP radical at low and ambient temperature suggests the proximity between aromatic carbon deposits and metals (mostly iron) on the catalyst surface. These findings potentially indicate that coke and iron deposit together, or that iron has a role in the formation of aromatic coke.

Wednesday, June 21, 2017

Facet dependent pairwise addition of hydrogen over Pd nanocrystal catalysts revealed via NMR using para-hydrogen-induced polarization


Wang, W., et al., Facet dependent pairwise addition of hydrogen over Pd nanocrystal catalysts revealed via NMR using para-hydrogen-induced polarization. Phys. Chem. Chem. Phys., 2017. 19(14): p. 9349-9353.


We demonstrated the facet dependence of pairwise addition of hydrogen in heterogeneous catalysis over Pd nanocrystal catalysts via NMR using para-hydrogen-induced polarization.

Monday, June 19, 2017

NMR signal enhancement of >50 000 times in fast dissolution dynamic nuclear polarization


Pinto, L.F., et al., NMR signal enhancement of >50 000 times in fast dissolution dynamic nuclear polarization. Chem Commun (Camb), 2017. 53(26): p. 3757-3760.


Herein, we report the synthesis and the study of a novel mixed biradical with BDPA and TEMPO radical units that are covalently bound by an ester group (BDPAesterTEMPO) as a polarizing agent for fast dissolution DNP. The biradical exhibits an extremely high DNP NMR enhancement of >50 000 times, which constitutes one of the largest signal enhancements observed so far, to the best of our knowledge.

Friday, June 16, 2017

Probing Surface Hydrogen Bonding and Dynamics by Natural Abundance, Multidimensional,17O DNP-NMR Spectroscopy #DNPNMR


Perras, F.A., et al., Probing Surface Hydrogen Bonding and Dynamics by Natural Abundance, Multidimensional,17O DNP-NMR Spectroscopy. The Journal of Physical Chemistry C, 2016. 120(21): p. 11535-11544.


Dynamic nuclear polarization (DNP)-enhanced solid-state nuclear magnetic resonance (SSNMR) spectroscopy is increasingly being used as a tool for the atomic-level characterization of surface sites. DNP surface-enhanced SSNMR spectroscopy of materials has, however, been limited to studying relatively receptive nuclei, and the particularly rare 17O nuclide, which is of great interest for materials science, has not been utilized. We demonstrate that advanced 17O SSNMR experiments can be performed on surface species at natural isotopic abundance using DNP. We use 17O DNP surface-enhanced 2D SSNMR to measure 17O{1H} HETCOR spectra as well as dipolar oscillations on a series of thermally treated mesoporous silica nanoparticle samples having different pore diameters. These experiments allow for a nonintrusive and unambiguous characterization of hydrogen bonding and dynamics at the surface of the material; no other single experiment can give such details about the interactions at the surface. Our data show that, upon drying, strongly hydrogen-bonded surface silanols, whose motions are greatly restricted by the interaction when compared to lone silanols, are selectively dehydroxylated.

Thursday, June 15, 2017

[NMR] Permanent Solid-State NMR Position in Reading, UK, with Johnson Matthey Plc

From the Ampere Magnetic Resonance List




Johnson Matthey PLC is a world leader in advanced materials and catalyst technology with over 13 000 employees worldwide. The Technology Centre, based at Sonning Common, undertakes research work for the group.

Key to the work of the research teams the Advanced Characterisation Group takes responsibility for development, operation and interpretation of analyses arising from bespoke methodologies across our suite of start of the art instrumentation. Due to the purchase of a new 600 MHz solid-state NMR system, we are expanding the spectroscopy team to someone with a specialism in Solid-State NMR.

Key responsibilities: 
Maintaining high EHS standards,
Defining and developing the instrument capabilities to maintain start-of-the-art analysis,
Continuously improving the workflow, sample preparation, and data analysis methods to improve service efficiency, repeatability and insight into materials,
Collaborating with other researchers inside and outside the company to leverage expertise,
Continued personal and professional development.

Are you the ideal candidate? You will have:
A PhD in Physics, materials science or Chemistry or equivalent experience,
Demonstrated expertise in Solid State NMR,
Experience performing DFT calculations,
Excellent analytical ability and attention to detail,
Software knowledge of Adobe Illustrator, LaTeX code, MS Office,
A strong fascination for technology and the application of materials in an industrial context,
The ability to develop new collaborations across academic and industrial sectors,
A demonstrable ability to innovate.

We offer a competitive package including, amongst other benefits, a company pension scheme, 25 days annual leave, medical benefits and after a qualifying period, a share incentive plan. All employees are encouraged to further their personal development through training and education by the Company.

Apply though Taleo at http://bit.ly/2tlitu7


If the reader of this email is not the intended recipient(s), please be advised that any dissemination, distribution or copying of this information is strictly prohibited. Johnson Matthey Plc has its main place of business at 5th Floor, 25 Farringdon Street, London (020 7269 8400).

Johnson Matthey Public Limited Company
Registered Office: 5th Floor, 25 Farringdon Street, London EC4A 4AB
Registered in England No 33774

Whilst Johnson Matthey aims to keep its network free from viruses you should note that we are unable to scan certain emails, particularly if any part is encrypted or password-protected, and accordingly you are strongly advised to check this email and any attachments for viruses. The company shall not accept any liability with regard to computer viruses transferred by way of email.

Please note that your communication may be monitored in accordance with Johnson Matthey internal policy documentation.


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Monday, June 12, 2017

Characterizing Substrate-Surface Interactions on Alumina-Supported Metal Catalysts by Dynamic Nuclear Polarization-Enhanced Double-Resonance NMR Spectroscopy #DNPNMR


Perras, F.A., et al., Characterizing Substrate-Surface Interactions on Alumina-Supported Metal Catalysts by Dynamic Nuclear Polarization-Enhanced Double-Resonance NMR Spectroscopy. J Am Chem Soc, 2017. 139(7): p. 2702-2709.


The characterization of nanometer-scale interactions between carbon-containing substrates and alumina surfaces is of paramount importance to industrial and academic catalysis applications, but it is also very challenging. Here, we demonstrate that dynamic nuclear polarization surface-enhanced NMR spectroscopy (DNP SENS) allows the unambiguous description of the coordination geometries and conformations of the substrates at the alumina surface through high-resolution measurements of 13C-27Al distances. We apply this new technique to elucidate the molecular-level geometry of 13C-enriched methionine and natural abundance poly(vinyl alcohol) adsorbed on gamma-Al2O3-supported Pd catalysts, and we support these results with element-specific X-ray absorption near-edge measurements. This work clearly demonstrates a surprising bimodal coordination of methionine at the Pd-Al2O3 interface.

SABRE Hyperpolarization of Bipyridine Stabilized Ir-Complex at High, Low and Ultralow Magnetic Fields


Pravdivtsev Andrey, N., SABRE Hyperpolarization of Bipyridine Stabilized Ir-Complex at High, Low and Ultralow Magnetic Fields, in Zeitschrift für Physikalische Chemie. 2017. p. 497.


A strong limitation of nuclear magnetic resonance is its low inherent sensitivity that can be overcome by using an appropriate hyperpolarization technique. Presently, dynamic nuclear polarization and spin-exchange optical pumping are the only hyperpolarization techniques that are used in applied medicine. However, both are relatively complex in use and expensive. Here we present a modification of the signal amplification by reversible exchange (SABRE) hyperpolarization method – SABRE on stabilized Ir-complexes. A stabilized Ir-complex (here we used bipyridine for stabilization) can be hyperpolarized in a wide range of magnetic fields from a few μT upto 10 T with 15N polarization of about 1–3%. Moreover, the investigated complex can be incorporated into biomolecules or other bulky molecules; in this situation exchange with para-hydrogen will allow one to continuously generate hyperpolarization.

Friday, June 9, 2017

Oxygen-17 dynamic nuclear polarisation enhanced solid-state NMR spectroscopy at 18.8 T #DNPNMR


Brownbill, N.J., et al., Oxygen-17 dynamic nuclear polarisation enhanced solid-state NMR spectroscopy at 18.8 T. Chem Commun (Camb), 2017. 53(17): p. 2563-2566.


We report 17O dynamic nuclear polarisation (DNP) enhanced solid-state NMR experiments at 18.8 T. Several formulations were investigated on the Mg(OH)2 compound. A signal enhancement factor of 17 could be obtained when the solid particles were incorporated into a glassy o-terphenyl matrix doped with BDPA using the Overhauser polarisation transfer scheme whilst the cross effect mechanism enabled by TEKPol yielded a slightly lower enhancement but more time efficient data acquisition.

Monday, June 5, 2017

Surface-selective direct 17O DNP NMR of CeO2 nanoparticles #DNPNMR


Hope, M.A., et al., Surface-selective direct 17O DNP NMR of CeO2 nanoparticles. Chem Commun (Camb), 2017. 53(13): p. 2142-2145.


Surface-selective direct 17O DNP has been demonstrated for the first time on CeO2 nanoparticles, for which the first three layers can be distinguished with high selectivity. Polarisation build-up curves show that the polarisation of the (sub-)surface sites builds up faster than the bulk, accounting for the remarkable surface selectivity.

A tailored multi-frequency EPR approach to accurately determine the magnetic resonance parameters of dynamic nuclear polarization agents: application to AMUPol #DNPNMR


This is a very nice article illustrating the importance of understanding the EPR parameters of a polarizing agent used in DNP-NMR spectroscopy. Here the 9, 95 and 275 GHz EPR spectroscopy is used to characterize AMUPol and predict its performance in high-field DNP.



Gast, P., et al., A tailored multi-frequency EPR approach to accurately determine the magnetic resonance parameters of dynamic nuclear polarization agents: application to AMUPol. Phys. Chem. Chem. Phys., 2017. 19(5): p. 3777-3781.


To understand the dynamic nuclear polarization (DNP) enhancements of biradical polarizing agents, the magnetic resonance parameters need to be known. We describe a tailored EPR approach to accurately determine electron spin-spin coupling parameters using a combination of standard (9 GHz), high (95 GHz) and ultra-high (275 GHz) frequency EPR. Comparing liquid- and frozen-solution continuous-wave EPR spectra provides accurate anisotropic dipolar interaction D and isotropic exchange interaction J parameters of the DNP biradical AMUPol. We found that D was larger by as much as 30% compared to earlier estimates, and that J is 43 MHz, whereas before it was considered to be negligible. With the refined data, quantum mechanical calculations confirm that an increase in dipolar electron-electron couplings leads to higher cross-effect DNP efficiencies. Moreover, the DNP calculations qualitatively reproduce the difference of TOTAPOL and AMUPol DNP efficiencies found experimentally and suggest that AMUPol is particularly effective in improving the DNP efficiency at magnetic fields higher than 500 MHz. The multi-frequency EPR approach will aid in predicting the optimal structures for future DNP agents.

[NMR] PhD position in solid-state NMR of paramagnetic materials

A PhD position is available in the group of Andrew Pell at the Department of Materials Environmental and Environmental Chemistry (MMK), Stockholm University (Sweden), in solid-state NMR of paramagnetic materials.
Closing date: August 7, 2017.

Project description
The aim of our research is to develop solid-state nuclear magnetic resonance (NMR) methods in order to allow a more accurate characterization, at the atomic scale, of the structure and dynamics of increasingly complex materials that are relevant in modern material science and chemistry. Specifically we focus on systems that contain paramagnetic metal ions, and how these ions dictate the properties of technologically important materials such as batteries, catalysts, and solid-state lighting phosphors.

Solid-state NMR is the method of choice for studying local structure and dynamics. However many interesting paramagnetic materials are, for technical reasons, beyond the ability of the current state of the art in solid-state NMR to study. This PhD project is therefore focussed on developing and specifically tailoring the techniques and capabilities of solid-state NMR for the analysis of samples containing these metal ions; for characterizing their presence, activity, role, and function in a range of different materials. Specifically the PhD student will develop new pulse schemes for exciting and detecting the NMR signals from quadrupolar nuclei (such as 2H, 14N, 23Na, 25Al, …) in paramagnetic materials, and incorporate these new schemes into more sophisticated experiments in order to separate the information from different spin interactions, which can then be interpreted in terms of both the structure and dynamics of the system. These new methods will then be applied to a range of paramagnetic materials, such as battery electrodes, ion conductors, or inorganic phosphors, with the specific choice depending on the interests of the student.

The student will acquire expertise in both the theoretical and experimental aspects of solid-state NMR on 400 and 600 MHz Bruker spectrometers. There will also be opportunities to travel to high-field NMR centres both within Sweden and Europe. Following the development of the new NMR methods the student will have the opportunity to apply them on a range of different materials that have been developed both at MMK and in collaboration with other laboratories around the world.

The project is interdisciplinary and contains elements from chemistry and physics. Therefore, strongly motivated students with a background in these areas, and particularly those with an interest in quantum mechanics, are encouraged to apply.

The Department of Materials and Environmental Chemistry, Stockholm University
The Department of Materials- and Environmental Chemistry (MMK) is one of the largest departments at the Faculty of Natural sciences with about 140 employees. The research activities of MMK are in the areas of Materials and Solid-state Chemistry focusing on different classes of materials; e.g. ceramics and glasses, self-assembled and porous materials, and soft matter. The work often encompasses synthesis, characterisation by X-ray diffraction and electron microscopy, NMR studies, modelling with computer simulations of materials with a potential for various applications. Environmental aspects are an important part of the research activities.

Application
For informal enquiries, email Andrew Pell at andrew.pell@mmk.su.se.
To obtain more information about the position, how to apply, and to submit your application visit http://www.su.se/english/about/vacancies/vacancies-new-list?rmpage=job&rmjob=3062&rmlang=UK

---------------------------------------------------
Andrew J. Pell
Assistant Professor

Department of Materials and Environmental Chemistry,
Arrhenius Laboratory,
Stockholm University,
Svante Arrhenius väg 16C,
SE-106 91 Stockholm,
Sweden


Tel: +46 (0)8-16 23 76

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Friday, June 2, 2017

Effect of electron spectral diffusion on static dynamic nuclear polarization at 7 Tesla #DNPNMR


Leavesley, A., et al., Effect of electron spectral diffusion on static dynamic nuclear polarization at 7 Tesla. Phys. Chem. Chem. Phys., 2017. 19(5): p. 3596-3605.


Here, we present an integrated experimental and theoretical study of 1H dynamic nuclear polarization (DNP) of a frozen aqueous glass containing free radicals at 7 T, under static conditions and at temperatures ranging between 4 and 20 K. The DNP studies were performed with a home-built 200 GHz quasi-optics microwave bridge, powered by a tunable solid-state diode source. DNP using monochromatic and continuous wave (cw) irradiation applied to the electron paramagnetic resonance (EPR) spectrum of the radicals induces the transfer of polarization from the electron spins to the surrounding nuclei of the solvent and solutes in the frozen aqueous glass. In our systematic experimental study, the DNP enhanced 1H signals are monitored as a function of microwave frequency, microwave power, radical concentration, and temperature, and are interpreted with the help of electron spin-lattice relaxation times, experimental MW irradiation parameters, and the electron spectral diffusion (eSD) model introduced previously. This comprehensive experimental DNP study with mono-nitroxide radical spin probes was accompanied with theoretical calculations. Our results consistently demonstrate that eSD effects can be significant at 7 T under static DNP conditions, and can be systematically modulated by experimental conditions.