Category Archives: Supercritical CO2

[NMR] PhD position in Nijmegen – Solid State NMR #DNPNMR

From the Ampere Magnetic Resonance List

The Solid State NMR group in Nijmegen (Kentgens) is searching for a PhD: 

Supercritical chromatography hyphenated with hyperpolarized NMR

In our group we develop methods for high sensitivity on-chip NMR detection of mass-limited samples. This flow system allows flexible operation, including high pressures and supercritical solvents such as CO2. The main goal of the project is to develop and optimize a hyphenated setup combining supercritical chromatography with DNP-NMR to provide a fast analytical tool to study complex mixtures with superior information content. One of the advantages of supercritical solvents is the fact that fast mobility can lead to efficient liquid state (Overhauser) Dynamic Nuclear Polarization at relatively high magnetic fields. At present a Gyrotron mm-wave source operating at 395 GHz is available for this purpose, coupled to a 600 MHz NMR spectrometer and a 263 GHz EIO coupled to a 400 MHz NMR spectrometer to be developed further in this project.

The candidate has a MSc in Chemistry of Physics or a related discipline. 

We are looking for an enthusiastic candidate with a solid background in NMR and with an affinity for ‘out of the box’ methodology development.

The solid-state NMR group at Radboud University is part of the Institute for Materials and Molecules. The motto ‘From Molecules to Materials’ illustrates our focus on the design, synthesis and characterization of novel functional systems.

The general mission of the solid-state NMR group is to develop new methodology to optimize sensitivity and information content of NMR spectra and to apply these methods to target specific topics in functional molecular systems in terms of local structure and dynamics addressing structure/function relationships. We offer a stimulating and exciting international research environment with state of the art NMR spectrometers.

The advertised position is funded through NWO via the Top institute COAST (www.ti-coast.com). The COAST R&D program’s overall objective is to advance research, development and technical innovation in analytical science for the benefit of its application areas and science as a whole. In this project two academic groups and three industrial partners cooperate; the combination of academic groups specialising in NMR methodology developments (RU Nijmegen), separation methodology (UvA), and Bruker and Waters who are the dominating technology providers in the respective NMR and SFC fields, together with Shell as a potential end user of the technology makes a strong consortium to come up with a viable SFC-NMR approach.

For more information, visit the RU website for PhD’s or send an email to Prof.dr. A.P.M. Kentgens.

— 

Marian de With

Radboud University | Institute for Molecules and Materials

Secretary for depts. of Biophysical Chemistry and Solid State NMR

Tel. +31 24 3652678 

Web: www.ru.nl/science/solidstatenmr, www.ru.nl/biophyschem

Visiting address:

Heyendaalseweg 135 | 6525 AJ Nijmegen | HG03.344

Postal address:

Postbox 9010 | Internal postbus 84 | 6500 GL Nijmegen 

Working hours: Monday 9-13, Thursday 9-13, Tuesday, Wednesday and Friday 9-17

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Towards Overhauser DNP in supercritical CO2

van Meerten, S.G., et al., Towards Overhauser DNP in supercritical CO2. J Magn Reson, 2016. 267: p. 30-6.

http://www.ncbi.nlm.nih.gov/pubmed/27082277

Overhauser Dynamic Nuclear Polarization (ODNP) is a well known technique to improve NMR sensitivity in the liquid state, where the large polarization of an electron spin is transferred to a nucleus of interest by cross-relaxation. The efficiency of the Overhauser mechanism for dipolar interactions depends critically on fast local translational dynamics at the timescale of the inverse electron Larmor frequency. The maximum polarization enhancement that can be achieved for (1)H at high magnetic fields benefits from a low viscosity solvent. In this paper we investigate the option to use supercritical CO2 as a solvent for Overhauser DNP. We have investigated the diffusion constants and longitudinal nuclear relaxation rates of toluene in high pressure CO2. The change in (1)H T1 by addition of TEMPO radical was analyzed to determine the Overhauser cross-relaxation in such a mixture, and is compared with calculations based on the Force Free Hard Sphere (FFHS) model. By analyzing the relaxation data within this model we find translational correlation times in the range of 2-4ps, depending on temperature, pressure and toluene concentration. Such short correlation times may be instrumental for future Overhauser DNP applications at high magnetic fields, as are commonly used in NMR. Preliminary DNP experiments have been performed at 3.4T on high pressure superheated water and model systems such as toluene in high pressure CO2.

Perspectives on DNP-enhanced NMR spectroscopy in solutions

van Bentum, J., et al., Perspectives on DNP-enhanced NMR spectroscopy in solutions. J Magn Reson, 2016. 264: p. 59-67.

http://www.ncbi.nlm.nih.gov/pubmed/26920831

More than 60years after the seminal work of Albert Overhauser on dynamic nuclear polarization by dynamic cross relaxation of coupled electron-nuclear spin systems, the quest for sensitivity enhancement in NMR spectroscopy is as pressing as ever. In this contribution we will review the status and perspectives for dynamic nuclear polarization in the liquid state. An appealing approach seems to be the use of supercritical solvents that may allow an extension of the Overhauser mechanism towards common high magnetic fields. A complementary approach is the use of solid state DNP on frozen solutions, followed by a rapid dissolution or in-situ melting step and NMR detection with substantially enhanced polarization levels in the liquid state. We will review recent developments in the field and discuss perspectives for the near future.

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