Christophe Roussel

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Habilitation à Diriger les Recherches (HDR) in chemistry at the Ecole Normale Supérieure Paris-Saclay (Cachan, France)PhD Thesis in physical organic chemistry at the University of Bourgogne Franche-Comté (Besançon, France) / Ecole Normale Supérieure Paris-Saclay (Cachan, France)

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Method for the preparation of a sample comprising highly polarized nuclear spins and uses and devices for such a method

Jean-Philippe Ansermet, Jonas Milani, Christophe Roussel

Method for the preparation of a sample comprising highly polarized nuclear spins, comprising at least the following steps: a) bringing a polarization system, which using an electrochemical reaction can be converted into an EPR-active radical form thereof, in contact or close proximity with said sample; b) in situ electrochemically forming an EPR-active radical form of said polarization system; c) applying dynamic nuclear polarization techniques in the presence of a magnetic field by applying electromagnetic irradiation with a frequency adapted to transfer spin polarization from the electrons of the polarization system to the nuclear spins of the sample leading to a highly polarized state thereof. d) in situ electrochemically converting said polarization system, which is paramagnetic and comprises an EPR-active radical into a diamagnetic form without an EPR-active radical.

2021

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Electrochemical Overhauser dynamic nuclear polarization

Jean-Philippe Ansermet, Jonas Milani, Christophe Roussel, Mika Antero Tamski

Nuclear Magnetic Resonance (NMR) spectroscopy suffers from low sensitivity due to the low nuclear spin polarization obtained within practically achievable external magnetic fields. Dynamic Nuclear Polarization (DNP) refers to techniques that increase the NMR signal intensity by transferring spin polarization from electrons to the nuclei. Until now, a common method of introducing unpaired electrons to a sample has been to add to it a radical such as TEMPOL or trityl. The alternative we address here is to use electrochemical oxidation and/or reduction of a redox mediator to generate radical species that can be used for DNP. Surprisingly, the potential of electrochemically-generated radicals as a source of hyperpolarization for DNP has not been investigated so far. In this communication, we show the proof of principle of performing anin situDNP experiment at a low magnetic field in a solution phase, with electrochemically generated methyl viologen cation radicals. Electrochemistry as a source of radicals can offer exciting prospects for DNP. The electrode may be one that generates radicals with a high spin polarization. The concentration of radicals in the sample can be adjusted by changing the duration and magnitude of the applied electrode potential. Removal of the radical from the sample after spin polarization transfer is also possible, thereby increasing the lifetime of the nuclear hyperpolarization.

2020

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Condom evidence can be analysed using several analytical techniques, such as FTIR, MALDI-MS or DART-TOF-MS, but the only one that was used on real samples for transfer and persistence studies in the context of sexual assault or rape cases was Py-GC/MS. However, there has been no study to identify which specific pyrolysis parameters were the most suitable for the analysis of silicone-based lubricants, especially in terms of repeatability of the analyses. This study looked at the different reported pyrolysis parameter with the aim of optimizing these parameters for polydimethylsiloxane (PDMS) analysis and detection. Experimental parameters were refined while performing a full factorial experimental design (FFD) for the screening, extended to a face centered central composite design (FCCD) for the optimisation. Analyses were led on standard PDMS reference material for the optimisation. Two-way ANOVA statistics and surface responses were used to define the most adequate parameters for the analysis. The adequate parameters were then applied to five condom extracts that were analysed in replicates. Chemometrics was used to evaluate within and between sample variations. Separation of the samples was investigated and was not found to be applicable to the limited set of samples. Issues in reproducibility were highlighted and further investigation on different instruments are necessary to improve the reported study.

2020

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