Periodic Reporting for period 4 - MIDNP (Metal Ions Dynamic Nuclear Polarization:Novel Route for Probing Functional Materials with Sensitivity and Selectivity)
Reporting period: 2023-07-01 to 2024-12-31
Materials with specific electrical, optical or chemical properties often derive their special functions from small perturbations in their composition or structure. Thus, rational design of new functional materials demands sensitive and versatile determination of structural and compositional properties, a very difficult goal not presently available. The overarching goal of the MIDNP project is to develop a novel route for Magic-Angle Spinning Dynamic Nuclear Polarization (MAS-DNP) as an enabling methodology in materials science, introducing new opportunities for investigating and designing functional materials.
Solid State Nuclear Magnetic Resonance (ssNMR) spectroscopy is an excellent probe for local order/disorder, but unfortunately its sensitivity is limited. DNP, a process whereby the large electron spin polarization is transferred to the nuclear spins, had greatly expanded the range of materials systems and questions that can be probed by ssNMR. However, it commonly relies on the use of exogenous nitroxide radicals, thereby limiting its utilization in materials science to nonreactive surfaces.
In MIDNP we develop an alternative approach, utilizing paramagnetic dopants as endogenous polarization agents in the bulk. To effectively harness the electron spin polarization of the dopants for higher sensitivity, we: (a) addressed challenges such as the effect of bonding, spin interactions and relaxation on DNP via a mechanistic study of carefully selected dopants in energy materials; (b) Developed new techniques for NMR spectral assignment and explored alternative DNP mechanisms for paramagnetic solids; (c) Expanded the approach for sensitizing the detection of surfaces and interfaces and elucidate the critical role of surface chemistry in the efficacy of energy storage materials. (d) Developed a new structural tool for interfaces by combining sourced of polarization in DNP: exogenous radical which selectively increase the sensitivity to outer surface layers and endogenous DNP from metal ions which provide sensitivity in a selective manner to the inner layer.
The methodology developed as part of the MIDNP project and its applications has already provided critical insight into the structure and composition of materials with relevance to energy storage and conversion systems. Based on these insights, and future studies that will implement the developed methodology, on other materials systems, we expect MIDNP will contribute to the development of new and improved energy storage and conversion materials. Such materials are essential for developing long lasting and efficient systems for utilization of sustainable energy resources.
Solid State Nuclear Magnetic Resonance (ssNMR) spectroscopy is an excellent probe for local order/disorder, but unfortunately its sensitivity is limited. DNP, a process whereby the large electron spin polarization is transferred to the nuclear spins, had greatly expanded the range of materials systems and questions that can be probed by ssNMR. However, it commonly relies on the use of exogenous nitroxide radicals, thereby limiting its utilization in materials science to nonreactive surfaces.
In MIDNP we develop an alternative approach, utilizing paramagnetic dopants as endogenous polarization agents in the bulk. To effectively harness the electron spin polarization of the dopants for higher sensitivity, we: (a) addressed challenges such as the effect of bonding, spin interactions and relaxation on DNP via a mechanistic study of carefully selected dopants in energy materials; (b) Developed new techniques for NMR spectral assignment and explored alternative DNP mechanisms for paramagnetic solids; (c) Expanded the approach for sensitizing the detection of surfaces and interfaces and elucidate the critical role of surface chemistry in the efficacy of energy storage materials. (d) Developed a new structural tool for interfaces by combining sourced of polarization in DNP: exogenous radical which selectively increase the sensitivity to outer surface layers and endogenous DNP from metal ions which provide sensitivity in a selective manner to the inner layer.
The methodology developed as part of the MIDNP project and its applications has already provided critical insight into the structure and composition of materials with relevance to energy storage and conversion systems. Based on these insights, and future studies that will implement the developed methodology, on other materials systems, we expect MIDNP will contribute to the development of new and improved energy storage and conversion materials. Such materials are essential for developing long lasting and efficient systems for utilization of sustainable energy resources.
(a) We developed a new paramagnetic metal ion, Fe(III) as polarization agent which provides very high sensitivity in DNP. Furthermore we addressed and overcome some of the challenges of sensitivity enhancement through MIDNP in electrode materials.
(b) We demonstrated the remarkable sensitivity gained in solid state NMR from Fe(III) dopants in the anode materials Li4Ti5O12. The increased sensitivity enabled detection of an extremely challenging nucleus, 17O, which is only 0.038% abundant. Furthermore we found that instead of the common conception, that high sensitivity by direct polarization transfer from electrons to nuclei is localized around the electrons.
(3) We utilized the metal ions DNP approach to get high sensitivity in 89Y and 17O NMR of the oxygen ion conductor Yttrium doped Cerium oxide. The remarkable sensitivity allowed us to perform 89Y-89Y correlation spectroscopy which provided unique insight into the oxygen vacancy ordering in the material as a function of Y content.
(4)We addressed the problem of developing practical high energy cathodes materials which are needed in order to increase the energy stored in rechargeable cells. We employed a combination of polarization sources, external to the sample(nitroxide radicals) and endogenous (Fe(III) dopants) to enable the detection of a 2-5nm thin novel surface chemistry deposited at the surface through molecular layer deposition.
(5) We investigated the effect of transition metal ions concentration in the host framework and developed a new approach where the electron relaxation times can be determined based on straight forward NMR measurements.
(6) We examined how disorder in the material affects DNP efficiency - by comparing two host structures with identical chemical composition which differ only in their degree of ordering glass vs. crystalline material.
(7) We implemented MIDNP in porous materials and addressed the major challenges in this kind of materials and devised means to minimize these and obtained significant enhancement factors for the framework material itself as well as guest molecules introduced into it.
(8) We determined the chemical composition and the structure of the surface chemistry developing in a sodium ion anode in battery cells - utilizing DNP from both exogenous sources and endogenous sources we were able to distinguish the inner and outer composition of the solid electrolyte interphase (SEI) the most important component in battery cells that can be detrimental for the function and life time of the cell.
(9) We analyzed the contribution of spin diffusion to polarization transfer from metal ions in MIDNP.
During the MIDNP project we developed this new tool to investigate inorganic solids by rigorous experimental and theoretical studies. This understanding of the MIDNP process enabled implementing the approach in a wide range of materials systems with additional systems currently under investigation. MIDNP emerges as a powerful approach for studying both the bulk of inorganic solids and as a structural tool for interfaces. Except for regular research papers, MIDNP as been disseminated to the scientific community through multiple research presentations at conferences as well as several reviews and book chapter. We recently also published a practical guide to implementing the approach which we expect will increase the adoption of the methodology and its implementation across many classes of materials.
(b) We demonstrated the remarkable sensitivity gained in solid state NMR from Fe(III) dopants in the anode materials Li4Ti5O12. The increased sensitivity enabled detection of an extremely challenging nucleus, 17O, which is only 0.038% abundant. Furthermore we found that instead of the common conception, that high sensitivity by direct polarization transfer from electrons to nuclei is localized around the electrons.
(3) We utilized the metal ions DNP approach to get high sensitivity in 89Y and 17O NMR of the oxygen ion conductor Yttrium doped Cerium oxide. The remarkable sensitivity allowed us to perform 89Y-89Y correlation spectroscopy which provided unique insight into the oxygen vacancy ordering in the material as a function of Y content.
(4)We addressed the problem of developing practical high energy cathodes materials which are needed in order to increase the energy stored in rechargeable cells. We employed a combination of polarization sources, external to the sample(nitroxide radicals) and endogenous (Fe(III) dopants) to enable the detection of a 2-5nm thin novel surface chemistry deposited at the surface through molecular layer deposition.
(5) We investigated the effect of transition metal ions concentration in the host framework and developed a new approach where the electron relaxation times can be determined based on straight forward NMR measurements.
(6) We examined how disorder in the material affects DNP efficiency - by comparing two host structures with identical chemical composition which differ only in their degree of ordering glass vs. crystalline material.
(7) We implemented MIDNP in porous materials and addressed the major challenges in this kind of materials and devised means to minimize these and obtained significant enhancement factors for the framework material itself as well as guest molecules introduced into it.
(8) We determined the chemical composition and the structure of the surface chemistry developing in a sodium ion anode in battery cells - utilizing DNP from both exogenous sources and endogenous sources we were able to distinguish the inner and outer composition of the solid electrolyte interphase (SEI) the most important component in battery cells that can be detrimental for the function and life time of the cell.
(9) We analyzed the contribution of spin diffusion to polarization transfer from metal ions in MIDNP.
During the MIDNP project we developed this new tool to investigate inorganic solids by rigorous experimental and theoretical studies. This understanding of the MIDNP process enabled implementing the approach in a wide range of materials systems with additional systems currently under investigation. MIDNP emerges as a powerful approach for studying both the bulk of inorganic solids and as a structural tool for interfaces. Except for regular research papers, MIDNP as been disseminated to the scientific community through multiple research presentations at conferences as well as several reviews and book chapter. We recently also published a practical guide to implementing the approach which we expect will increase the adoption of the methodology and its implementation across many classes of materials.
The MIDNP approach pushes the boundaries of DNP and solid state NMR spectroscopy by expanding the methodology and the range of materials systems that can be investigated by this approach. In particular the ability to gain high sensitivity NMR spectra from the bulk of inorganic materials and the ability to detect reactive interfaces such as those formed on electrode materials provides a great advantage over the current methodology. During the project duration we were able to expand the range of metal ions that can be used for MIDNP in inorganic solids, developed thorough understanding of the underlying mechanisms that govern polarization transfer across the solids and across interfaces and utilized the apporach to study a broad range of materials systems (oxides, phosphates, porous solids and semiconductor nanoparticles) where such methodology was implemented for the first time, demonstrating the strength of this new apporach. Some of our results are currently being prepared for publication (application of MIDNP to nanoparticles, a new methodology to assign the spectra of paramagnetic solids, application of MIDNP to probe artificial SEI of Na ion anodes and a quantitative apporach of MIDNP to interfaces).
on with high sensitivity and selectivity.
on with high sensitivity and selectivity.