Unveiling transient material synthesis in dilute solutions and their solid morphology combining dDNP and MAS-DNP.

Project Information

Oligo-DNP

Grant agreement ID: 796904

DOI

10.3030/796904

Project closed

EC signature date 27 March 2018

Start date 1 June 2018

End date 31 May 2020

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 187 419,60

EU contribution

€ 187 419,60

Coordinated by

ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE
Switzerland

Periodic Reporting for period 1 - Oligo-DNP (Unveiling transient material synthesis in dilute solutions and their solid morphology combining dDNP and MAS-DNP.)

Reporting period: 2018-06-01 to 2020-05-31

Summary of the context and overall objectives of the project

Introduction:
The problem addressed in this proposal can be summarised by the following questions: What are the early stage processes governing the silicate (compounds based on silicon and oxygen) formation in structural materials? How does the formation proceed under different conditions of concentration, temperature and pH? What is the influence of silicon-based material chemistry in dilute solutions?
These questions are all both academic and industrially relevant. Silicates and aluminosilicates (materials where aluminum replaces silicon atoms) comprise most of Earth's crust and mantle, as well as the other terrestrial planets, rocky moons, and asteroids. In the oceans, the simplest form of soluble silica (silicon dioxide), orthosilicic acid, is also present in dilute concentrations (parts per million). It is most likely in this form that silicon is taken up by living organisms.
The silicate formation process, which proceeds from monomers to oligomers to particles/gels determines the morphology and reactivity of the silica products and biological control of the silica morphology has generated an interest for novel mechanisms for biomimetic silica synthesis. In vitro orthosilicic acid at concentrations above 1mM and circumneutral pH, undergoes spontaneous condensation to larger silicate oligomers and eventually stable particles will form.
The atomic-level processes involved are very difficult to determine, and despite the introduction of a limited number of methods the questions above remain unanswered.

Objectives:
We've planned to use a combined approach involving nuclear magnetic resonance (NMR) and its parent technique dissolution dynamic nuclear polarisation (dDNP) to achieve both atomic level resolution and the necessary sensitivity to elucidate the early-stage of the nucleation process. NMR provides the atomic level resolution. dDNP is capable to overcome the low signal coming from the low sample volumes used and the fact the nuclear spin species observed have low natural abundance (~4% for 29Si and ~1% for 13C), thus providing the necessary sensitivity.

The overall objective was to establish a novel methodology capable to study the nucleation processes at a very initial stage (seconds from the initial reaction), at low concentration (mM) and at an atomic level.
The approach used is general and can allow for example the detection of the initial formation of calcium carbonate that is another material widely used in industry as the main component in numerous construction materials, such as cement and limestone aggregates, and can be used as a means of sequestering carbon dioxide (CO2) in reducing CO2 emissions.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The finalization of the dynamic nuclear polarization experiments requires the optimization of a number of steps: (1) set-up of the dissolution DNP (2) optimal radical design e formulation; (3) test of the set-up via preliminary experiments on calcium carbonate nucleation; (4) experiments on silicates.

Step (1):
The set-up work in (1) required to assemble a 1H-13C and a 1H-29Si probe according to the design already published in order to polarize at 1.4 K the samples of interest (polariser probes). We succeeded in assembling both two-channel probes. They were tested at room and low temperature (e.g. 77 K and 1.4 K) in order to address the functionality. Both probes were correctly assembled and was possible to tune and match them to 1H and 13C or to 1H and 29Si. A further test was conducted on the 1H-13C probe in order to perform CP experiments that would make the experiment faster and better. Currently the CP step of the experimental protocol is still under investigation.

Step (2):
In order to perform the work in (2) we first established internal and external collaborations for the synthetic part of the work. In order to investigate nitroxide radicals for high-field DNP, the collaboration with the group of Olivier Ouari at Marseille university (FR) has been strengthened. Olivier's group has synthesized a set of 12 new radicals that have been tested and characterised either using NMR and electron paramagnetic resonance (EPR). The EPR part of the characterization was partilally performed at EPFL concerning the room temperature measurements. Measures at low temperature using pulsed EPR equipment were performed using a long standing collaboration with the group of Gunnar Jeschke at ETH in Zurich.

The work performed in step (2) lead to the following publication: Gabriele Stevanato, Dominik Józef Kubicki, Georges Menzildjian, Anne-Sophie Chauvin, Katharina Keller, Maxim Yulikov, Gunnar Jeschke, Marinella Mazzanti, Lyndon Emsley, A factor two improvement in high-field dynamic nuclear polarization from Gd (iii) complexes by design, J. Am. Chem. Soc. 2019, 141, 22, 8746-8751. Further work on radical developments has also resulted in another full paper in JACS under press (Open and Closed Radicals: Local Geometry Around Unpaired Electrons Governs MAS DNP Performance, J. Am. Chem. Soc. 2020,142, XX, XXXX).

In addition, in terms of dissemination of the results achieved, the participant has took part to the following conferences:
1. 2018 Poster at ESR meeting 2018, London UK, April 2018.
2. 2018 Poster at Euromar 2018 International Conference, Nantes FR, 02-06 July 2018.
3. 2018 Oral presentation at GIDRM, Turin IT, 19-21 September 2018.
4. 2019 Poster at ENC, Asilomar USA, 7-13 April 2019.
5. 2019 Poster at EUROMAR, Berlin, 25-30 August 2019.
6. 2020 Poster at ENC, Baltimore USA, 7-14 March 2020.

The researcher also attended the Researchers meet innovators @TU Berlin from 11-12.07.2019.
During the lockdown period, several virtual conferences via Zoom have been organised and attended by the researcher in the broad area of NMR. All of the publications produced include a specific reference in the Acknowledgement section to the MSC grant. The scientific results have been further disseminated by using the open access repository Zenodo under the Creative Commons Attribution 4.0 International licence. A social media Twitter account has been opened recently to disseminate scientific results.
The researcher has also created a personal web-site to present his profile, research activities and publications: sites.google.com/view/gabristevanato

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The researcher has now acquired a valuable expertise in the broad field of dynamic nuclear polarization (DNP) that will be further enhanced in the next career step where he will be working in the field of hyperpolarisation through a set of different strategies (PHIP and SABRE). This will soon create a quite unique scientific profile with an expertise spanning across the major techniques and likely leading to a fully independent career path in the coming future.
During the course of the action, DNP investigation have significantly improved the state-of-the-art on radical design.
The large scientific network provided by the host institution and in particular by the supervisor has helped the researcher to expand his own network, developing new approaches and ideas to scientific thinking and planning experimental projects.
Most of the possible DNP applications like elucidation of the surface of structural materials via DNP, in-cell DNP are likely to make use of at least part of the results achieved in this action.

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