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"Optically detected magnetic resonance for ultra-sensitive chemical analysis, imaging and process monitoring"

Final Report Summary - ODMR-CHEM (Optically detected magnetic resonance for ultra-sensitive chemical analysis, imaging and process monitoring)

Project objectives and main results: The goal of ODMR-CHEM was to develop new analytical tools that enable scientists to better understand chemical reactivity and selectivity in industrial processes. For example, many important industrial processes rely on understanding how solid-supported catalysts work at the pore length scale to produce a target chemical, or how improvements can be made in the way oil is extracted from rocks. The knowledge gained from these tools is aimed at (i) understanding the fundamental factors at play, then (ii) in future designing more efficient and more economic chemical processes.
Below we list the objectives of project ODMR-CHEM and summarize the achievements:
(1) Develop optical methods for low-field NMR spectroscopy that is specific to a given chemical group transformation or part of a molecule.
Results: At low magnetic field, NMR can provide chemical information in two ways. One is through the nuclear relaxation times, which gives information on the molecular dynamics and timescale of kinetic processes including molecular tumbling and surface adsorption. The second is the spin couplings, which report the structure of the chemical groups in the molecule and how atoms are connected. Both sources of information were investigated for feasibility of identifying chemical reactivity. The most successful method was NMR relaxation measurements in the microtesla to millitesla field region (work in manuscript). Our studies have allowed us to identify where optically detected NMR methodology is successful, where current limits are reached, and where existing NMR methods are outperformed.
A central part of this work was low-field optically detected NMR (ODMR). An instrument for ODMR measurements was built by the fellow within the financial regime of the research grant, at the return host laboratory. The ODMR instrument was used to measure nuclear relaxation times of common liquid solvents inside porous materials, which inform on the surface dynamics and chemical properties. The instrument remains set up for use on a permanent basis and has been fully operational since March 2017.
(2) Optimize acquisition methods using optical detection and understand the limits for low-field MRI in chemical systems, including spatial resolution, solutes dissolved at low concentration.
Results: At the outgoing host, low-field and zero-field NMR experimental protocols were developed to maximize information given on the chemistry of the studied system. At the return host, the fellow developed a license-free and market-ready instrumentation with a capability to run sophisticated low-field optically detected NMR experiments. Results showed that low-field MRI signals at mm-scale resolution can feasibly be obtained, but imaging experiments on a routine schedule remain a goal for future research beyond the present project.
(3) Apply in-line and zero-field NMR with efficient data acquisition to monitor interplay between chemical interconversion and rheology.
Results: The NMR apparatus described in (1) was used at the return host institute to acquire quantitative measurements on the surface dynamics of organic solvents in simple porous materials, including non-surface-treated silicas and alumina with uniform pore size distributions. These were used as a testbed to investigate whether information on reactivity and surface competition can be obtained.
The techniques developed during the project were integrated with the existing expertise and research interests of the return host institution / research group, in particular fast-field-cycling NMR measurements in the field range 1 mT to 1 T, where a commercial NMR instrument is used to interrogate liquids confined in rock and porous materials and provide measurements that are complementary to ODMR. The methods developed within the project are to be continued by the fellow and return host group working with an industrial company partner in the area of oil recovery and catalysis.
Listed below are further proposed outcomes of the project that have now been realized:
The research area on ultralow-field optically detected NMR has historically been led by groups in the USA. Project ODMR-CHEM has brought the research effort firmly into a world-renowned academic institution in the European Economic area.
Under the comprehensive training of both host institutes, the project has contributed to the track record and research maturity of the fellow as a leader and independent thinker in the low-field NMR research area. Beyond the project, he continues a career in spectroscopy working at the interface of theory, instrumentation and technological application of low-field NMR.
In the final year of the project, the fellow and principal scientist secured funding to continue the legacy of the work in the 2018-2022 pan-European initial training network funded by EC Horizon 2020 (Marie Curie ITN, project acronym “ZULF”).
Conclusions: ODMR-CHEM sought to develop new nuclear magnetic resonance (NMR) measurement techniques at low magnetic field. NMR is already a highly successful technique that is applied widely across analytical science to interrogate the structure and dynamics of molecules in solid, liquid and gas phases of matter. Objectives were focused on developing methodology that was more suitable for studies of chemistry in situ or an “on the plant” environment, or could provide data that was more reliable and informative that current state of the art techniques.
Generally, the work package (WP) objectives of the project were fulfilled. In WP1, new knowledge of atomic magnetometers and NMR detected at ultralow magnetic fields were acquired by the fellow. The fellow received training at the outgoing host that enabled him to build an ODMR instrument that can record the data to answer the scientific research questions. In WP2, results of which are detailed at greater length in the mid-term project report, the research showed that ODMR may be preferred over more conventional NMR techniques for the study of liquids in pores, most notably where the sample system contains large gradients and materials inhomogeneity. Both high-field NMR and low-field ODMR are complementary in their scope for chemical reactivity profiling. The expectation is that ODMR extends its applicability in the research area of porous materials as the experimental ODMR techniques continue to mature.
Socio-economic impacts: The intended, and successfully realized, main impact of the project is a measurement capability that enables new scientific knowledge to be obtained on how liquids, and in special cases how specific solutes in the liquids, behave dynamically when confined inside porous materials. The fellow has developed hardware and methodology to perform the experimental measurements and maximally exploited opportunities for portability, low-power consumption, “in the field” use and ease of transfer to market. The target groups are companies in the chemical engineering sector, one of whom the host institute and fellow already have agreements to work with beyond the project. The fellow also continues the work through long-term collaborations with the outgoing host (USA) and several university research laboratories in Europe (including ZULF training network). The scientific outcome of ODMR-CHEM will principally interest groups who are concerned with the effects of surface treatment on reactivity and adsorption dynamics. Further afield, the knowledge and competences gained in signal detection with atomic magnetometers has impacts in closely related scientific areas, particularly biomagnetic signal detection and brain/heart imaging.