Leipzig Spin Resonance Colloquium
LSR Colloquium
Current Program
Trying to image tissue microstructure with MRI
I will talk about contrasts available to neuro-MRI, particularly at high field (susceptibility, MT/CEST and relaxation times), some of the factors affecting them in the brain (myelination, microstructure) and the main pitfalls in measuring them.
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New Horizons with Parahydrogen-Induced Polarization: Live Tracking of Hyperpolarization Dynamics and Solid State Spin Diffusion
In this talk I will cover some important new advances in PHIP research. Firstly, the use of low-field NMR to track adiabatic transitions in real-time, which offers a 'live' view into polarization processes, in contrast to the typical pulse-acquire approach to NMR. Secondly, I will briefly discuss distant dipolar fields and how high sample magnetization limits polarization transfer efficiency. Finally, the use of solid-state spin diffusion as a new approach for polarizing molecules using PHIP.
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Elucidating the Structure and Function of Battery Interfaces through Dynamic Nuclear Polarization – Solid State NMR Spectroscopy
Interfaces play a central role in the performance of rechargeable batteries as they control charge transfer between the electrodes and the electrolyte. The need for high energy batteries calls for the development of electrode materials which are inherently more reactive. These often lead to chemical and structural changes at the electrode-electrolyte interface that can completely block charge transfer and in turn cause battery failure. As such there is great interest in understanding interfacial phenomenon in battery cells and identifying means to control it.
Solid state NMR spectroscopy is a powerful approach for probing battery interfaces. In principle, it can be used to determine the composition and structure of the electrode-electrolyte interface, as well as its ion transport properties. However, sensitivity is often a major limitation which prevents full characterization of battery interfaces with NMR. In this talk, I will present several routes for overcoming this sensitivity limitation by utilizing different electron spin polarization sources in dynamic nuclear polarization (DNP).
I will describe how by combining insights from DNP-NMR experiments with exogenous organic radicals and endogenous paramagnetic metal ions, we can determine the architecture of the electrode interface.[1-3] I will then discuss how conduction electrons can be utilized to increase the sensitivity and selectively for probing the inner layers formed on lithium metal electrodes.[4] Finally, I will discuss the different mechanisms of polarization transfer across interfaces and how these can be used to determine the interface functionality – namely its permeability to lithium ions.
[1] D. Jardon-Alvarez, G. Reuveni, A. Harchol, M. Leskes “Enabling Natural Abundance 17O Solid State NMR by Direct Polarization from Paramagnetic Metal Ions”, J. Phys. Chem. Lett., 11, 14, 5439-5445 (2020)
[2] S. Haber, Rosy, A. Saha, O. Brontvein, R. Carmieli, A. Zohar, M. Noked, M. Leskes “Structure and Functionality of an Alkylated LixSiyOz Interphase for High Energy Cathodes from DNP NMR Spectroscopy”, Journal of the American Chemical Society, 143, 4694-4704 (2021)
[3] Y. Steinberg, E. Sebti, I. B. Moroz, A. Zohar, D. Jardón-Álvarez, T. Bendikov, A. Maity, R. Carmieli, R. J. Clément, M. Leskes “Composition and Structure of the solid electrolyte interphase on Na-Ion Anodes Revealed by Exo-and Endogenous Dynamic Nuclear Polarization─ NMR Spectroscopy”, Journal of the American Chemical Society, 146, 35, 24476-24492 (2024)
[4] A. Maity, A. Svirinovsky-Arbeli, Y. Buganim, C. Oppenheim, M. Leskes “Tracking Dendrites and Solid Electrolyte Interphase Formation with Dynamic Nuclear Polarization-NMR Spectroscopy”, Nature Communications, accepted (2024)
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Non-equilibrium processes studied by pressure-jump NMR
The equilibrium between a protein’s folded and unfolded state is strongly impacted by hydrostatic pressure. Many proteins can be unfolded by applying a modest amount (≤2.5 kbar) of hydrostatic pressure, applicable to measurements by NMR.
Rapidly and repeatedly dropping the pressure from denaturing conditions (i.e. 2.5 kbar) to 1 bar, synchronized with detection of the NMR spectrum, allows study of the actual folding process under native conditions. A device that allows such rapid (ms) and repeated (>100,000 times) switching, enables direct monitoring of the folding process by two- and three-dimensional NMR. Hydrostatic pressure also can be used to resolubilize oligomerized or otherwise aggregated peptides and proteins. Such experiments hold promise for revealing structural information on the Alzheimer’s related Aβ peptide in the oligomerized state, which differs substantially from the monomeric and the fibrillar states.
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Atomic-Scale Quantum Science with Spins on Surfaces
The desire to probe and control individual quantum systems has driven significant scientific and engineering advances in quantum coherent nanoscience. Single atoms and molecules on surfaces, on the other hand, have been extensively studied in search of novel electronic and magnetic functionalities. These two paths came together in 2015 when it was clearly demonstrated that individual spins on surfaces can be coherently controlled and read out in an all-electrical fashion [1]. The enabling technique is scanning tunneling microscopy (STM) combined with electron spin resonance (ESR) [2], which provides unprecedented coherent controllability at the Angstrom length scale.
In this talk, a new approach to coherently control multiple electron spins in artificially built spin structures on surfaces will be presented [3]. We found remote spins, which are outside the tunnel junction, can be controlled by the local oscillating magnetic fields created by a single-atom magnet placed next to them in oscillating electric fields. The read-out of multiple spins is achieved by a sensor atom weakly coupled to them. While traditional STM studies have focused on spins located at the STM junction, our new approach paves the way for extending STM's capability to harness multiple spins in coherent manner. Furthermore, we recently succeeded in functionalizing the STM tip with spin-polarized magnetic atoms and an ESR-active spin center, which allows us to use this STM tip as a mobile ESR sensor and facilitate the precise detection of the electric and magnetic fields at the atomic level [4]. Our work widens the approaches for tailoring spin structures on surfaces with atomic precision in the realm of the quantum information science and the quantum sensing.
References
[1] S. Baumann et al., Science 350, 417 (2015) 417.
[2] Y. Chen et al., Adv. Mater. 35, 2107534 (2022).
[3] Y. Wang et al., Science 382, 87 (2023).
[4] T. Esat et al., Nat. Nano. 19, 1466 (2024).
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Metal-support Interactions in Heterogeneous Catalysis. Insights from Spin Density Studies of Open-shell Single Atom Catalysts
The quest to understand the structure of a catalyst is pivotal in chemistry and materials science. This understanding serves as a cornerstone for the rational development of catalysts and can significantly enhance the efficiency and specificity of catalytic processes. In this context, single-atom catalysts (SACs) have emerged as a frontier in catalysis research due to their unique set of properties. The isolated nature of the active metal atoms in these catalysts offers a series of practical advantages, including uniform active site. A critical step in the development of such systems is the structural determination of the isolated surface species with molecular-level precision. There exist a number of spectroscopic techniques able to inform on the geometric and electronic structure of potentially catalytic active sites. However, many of these methods either offer information averaged over the bulk sample or fail to capture the subtle details of chemical bonding. For paramagnetic (open-shell) metal atoms or ions, electron paramagnetic resonance (EPR) and related hyperfine techniques deliver unique insights into the structure of surface-stabilized atomic species and the interactions between the metal and its support. Specific examples will be discussed involving single metal atoms or ions on oxides and two-dimensional materials such as carbon nitride.
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Nanomagnets for Quantum Information
The transformation of quantum computing architectures from research laboratories to industrial prototypes necessitates platforms that cater to different quantum information processing tasks. The underexplored platform - nanomagnets - is rapidly demonstrating unique features that could further invigorate the advancement of quantum technologies [1-3]. I will discuss the nascent connection between quantum technology and nanomagnetism via a novel quantum hybrid platform for braiding-based topological quantum computation [4,5]. As well as our efforts to quantize helicity, joining the likes of electrical charge and light, and offering a new class of building blocks for realizing quantum logic elements [3,6,7].
[1] A. Soumyanarayanan, N. Reyren, A. Fert and C. Panagopoulos, Nature 539, 507 (2016).
[2] A. Bogdanov and C. Panagopoulos, Nature Reviews Physics 2, 492 (2020).
[3] C. Psaroudaki, E. Peraticos and C. Panagopoulos, Appl. Phys. Lett. 123, 260501 (2023).
[4] A. Soumyanarayanan, M. Raju, A. Oyarce, A. Tan, M. Im, A. Petrovic, P. Ho, M. Tran, C. Gan, F. Ernult and C. Panagopoulos, Nature Materials 16, 898 (2017).
[5] A. Petrovic, M. Raju, X. Tee, A. Louat, I. Aprile, R. Menezes, M. Wysznski, M. Reznikov, C. Renner, M. Milosevic and C. Panagopoulos, Phys. Rev. Lett. 126, 117205 (2021).
[6] C. Psaroudaki and C. Panagopoulos, Phys. Rev. B 106, 104422 (2022).
[7] C. Psaroudaki and C. Panagopoulos, Phys. Rev. Lett. 127, 067201 (2021).
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Towards macromolecular MRI - recent progress in mapping short-T2 material in-vivo
Toward high resolution myelin imaging
Magnetic susceptibility imaging has evolved significantly since the introduction of susceptibility-weighted imaging (SWI), which was initially developed for clinical applications such as detecting microhemorrhages. In the mid-2000s, advancements in high-resolution phase imaging led to the development of quantitative susceptibility mapping (QSM), a method that allows for the quantitative assessment of magnetic susceptibility in the brain. QSM has opened up new possibilities for neuroimaging, particularly in the quantification of iron in deep brain structures, a biomarker associated with various neurological conditions.
While QSM has provided valuable insights, it has primarily been limited to measuring a combined signal from different sources of magnetic susceptibility. In the brain, iron and myelin are the two dominant contributors, each with opposite magnetic properties—iron being paramagnetic and myelin being diamagnetic. This limitation has motivated the need for more refined techniques to disentangle these distinct sources of susceptibility.
In this presentation, I will introduce a technique developed in our lab called susceptibility source separation. This method provides a breakthrough by allowing the separate quantification of myelin and iron in the brain. Through susceptibility source separation, we can now obtain high-resolution maps that independently profile the distribution of myelin and iron. This is particularly valuable for studying the brain, where myelin and iron play crucial roles in both healthy brain function and the progression of neurological diseases. I will discuss the underlying physics that enables this separation, including the biophysical modeling and algorithm employed. The validation of the method has been demonstrated through various approaches including histology, showing its accuracy in separating the signals of myelin and iron. The clinical potential of this technique is significant, with early studies indicating its applicability to diseases such as multiple sclerosis, where both iron deposition and myelin degradation are key pathological features. In addition, the method holds promise for more accurate mapping of cortical myelination, which could improve our understanding of a variety of neurodegenerative diseases and brain aging.
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Program Archive
LSRC coordinator: Dr. Evgeniya Kirillina, contact email