Solid-state NMR Research Articles

Enhancing Moisture Tolerance of Sulfide Solid Electrolytes through Nano-Level Treatment Utilizing Lewis Acid Additives

Sulfide solid-state electrolytes (SSSEs), particularly the argyrodite Li6PS5Cl, are considered a promising solid electrolyte for all-solid-state batteries due to their excellent ductility and remarkable ionic conductivity. However, a significant challenge in the large-scale application of SSSEs is their lack of stability when exposed to humid air. To address these challenges, a prominent solution involves treating SSSE particles with Lewis acid additives at the nanoscale level method is employed. Some of the several Lewis acid additives considered in this study are aluminum acetylacetonate, tetrafluoro-1,4-benzoquinone, and tetracyano-ethylene. This treatment process is dispersing the SSSE particles in solution mixtures containing Lewis acid additives. Importantly, this method is designed to have minimal impact on the ionic conductivity of the SSSE. A series of investigations are conducted using various characterization techniques, including X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), in-situ Raman spectroscopy, solid-state nuclear magnetic resonance (NMR), and synchrotron-based X-ray Absorption Near-Edge Structure (XANES). These employed techniques are essential for analyzing the structural and chemical changes in SSSE particles treated with Lewis acid additives, leading to key findings. The key finding of the study is that the SSSE particles demonstrated outstanding atmospheric stability when treated with Lewis acid additives. This stability is attributed to the establishment of a Lewis acid-base interaction between the SSSE and the additives. This interaction effectively shields the SSSE from moisture in humid air, preventing structural deterioration in the bulk region. In other words, the Lewis acid additives create a protective layer that maintains the integrity of the SSSE, even in the presence of atmospheric moisture. Moreover, the Lewis acid additives treated SSSE samples demonstrated enhanced chemical stability in the ASSB system after being exposed to moisture as compared to the pristine SSSE. Highlighting the use of Lewis acid additives to enhance the moisture stability of SSSEs as a promising approach, this improvement in stability is crucial for the practical application of SSSEs in large-scale settings where exposure to humid conditions is inevitable. The study suggests that this method could pave the way for more reliable and durable all-solid-state batteries by addressing a critical limitation of SSSEs.

Solid Solution Behavior of High Performance BiOBrxI1-X Photoanodes Probed Using Solid-State NMR, XRD and Optical Spectroscopy

Bismuth oxyhalides (BIOX) are a family of solution-synthesizable 2D layered semiconductors constituted of earth-abundant elements namely bismuth, oxygen and the halogens. BIOX based thin films and heterojunctions are the subject of immense scientific interest due to their impressive performance in photocatalytic and photoelectrochemical devices. Solid solutions of Br/I bismuth oxyhalides exhibit continuously tunable absorption and emission spectra similar to that observed in mixed halide MAPbClxBryI3-x-y perovskites and mixed anion III-V GaAsxP1-x semiconductors. The excited state decay showed two components for all the mixed halide BiOX semiconductors with a dominant short-lived component in the nanosecond range and a weaker longer-lived component of ~100 ns. The average photoluminescence (PL) lifetime varied from 5.4 ns in bare BiOI to 1.49 ns in bare BiOBr with intermediate compositions exhibiting monotonically increasing average PL lifetimes with increasing iodine content. Using a combination of characterization techniques such as solid-state nuclear magnetic resonance (ssNMR), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and optical spectroscopy, we demonstrate the formation of atomic level solid solutions in Br/I bismuth oxyhalides. Through refinement of the lattice parameters using powder XRD and complementary atomic-level 209Bi SSNMR spectroscopy, we found that Vegard's law was obeyed by the BIOBrxI1-x solid solutions. By varying the Br:I ratio, it is also possible to tune the electronic band gap as well as the energy levels corresponding to the conduction band minimum (ECB, min) and the valence band maximum (EVB, max), thus allowing control over the thermodynamic driving force available to drive chemical reactions using photogenerated or electrically injected charge carriers. Suppression of the longitudinal optical phonon in solid solutions of Br/I bismuth oxyhalides is suggestive of lower phonon scattering of charge carriers and improved electronic transport. A synergistic enhancement of more than 1 order of magnitude in the photoelectrochemical water-splitting performance was obtained for the optimized solid solution (BiOBr0.67I0.33) under AM 1.5G 1 sun illumination. Our results pave the way for a one pot synthesis protocol to form BiOX thin films, powders and colloidal suspensions with deterministic control over the stoichiometry.

Solid-State Lithium Batteries with in-Situ Polymerized Acrylate-Based Electrolytes Capable of Electrochemically Stable Operation at 100 ℃

In-situ polymerized acrylate-based polymers are very appealing as solid polymer electrolytes (SPEs) in lithium (Li) batteries due to the drop-in compatibility of such in-situ polymerization with conventional battery production, the ease of acrylate polymerization and their inexpensive, facile SPE chemistry. We identified, however, that such SPEs suffer from either a low cationic transference number with dual ion conducting salts (0.12-0.2) or a low ionic conductivity with single Li-ion conducting (SLIC) salts (6·10-6 S cm-1). In this project we overcame these limitations and developed significantly improved SPE with ionic conductivity of up to 2·10-4 Scm-1 and a relatively high Li-ion transference number of 0.4. With a significantly reduced fraction of mobile anions in the hybrid SPE, in-situ polymerized SPE cells with an LiFePO4 (LFP) cathode achieve a stable performance for over 100 cycles at temperatures as high as 100 °C, which is unattainable with conventional Li salts or electrolytes. Furthermore, the motional narrowing observed in the line-shapes of solid-state nuclear magnetic resonance (SS-NMR) spectra provided additional insights of the differences in Li nucleus environments and revealed a reduced activation energy for the hybrid salt SPEs due to their more open structure. This study opens the path for the fabrication of high-performance solid polymer lithium batteries capable of operating at high temperatures using commercial battery fabrication equipment. We expect that further tuning of the acrylate based SPE composition may allow further increases in its conductivity without sacrifices in its electrochemical stability or mechanical properties.

(Invited) Structural and Dynamics Analysis of Organic Semiconducting Materials by Solid State NMR

Our group have successfully developed several highly efficient blue and green thermally activated delayed fluorescence (TADF) emitters, which show the reverse intersystem crossingfrom triplet to singlet excited states. However the conformation and dynamics of TADF emitters related to RISC process in amorphous states is still unclear, because the experimental approach toward these information is limited due to difficulty of application of diffraction technique . Thus we have carried out multiscale simulations and solid-state NMR (ssNMR) analysis of organic amorphous thin films. The ssNMR is one of the powerful technique to obtain the structural and dynamics information of amorphous aggregated materials. In this presentation, we demonstrate structural and dynamics analysis of amorphous organic semiconducting materials using ssNMR.

Influence of Pristine NMC811 Secondary and Primary Particle Surfaces on the Materials Reactivity

Vehicle electrification currently relies on lithium-ion batteries using nickel, manganese and cobalt (NMC)-based lamellar oxides as positive electrode materials. In order to achieve higher energy densities, the market is now moving towards NMC with high nickel content. Nevertheless, these materials have been widely demonstrated to suffer from serious off-gassing problems that reduce cycle life and pose safety concerns. Not only gases resulting from the formation of SEI at the negative electrode, but the production of O2, CO and CO2 have also been noted by different research groups.1–3 Despite the large number of studies analyzing the material during and after cycling, we noted a lack of in-depth characterization of the surface of Nickel-rich NMCs in their initial state. The need for such information is increasingly necessary with the recent development of new technologies for surface modification such as coating to limit the instability of high Nickel content NMCs.4,5 The surface reactivity of Ni-rich layered transition metal oxides is instrumental to the performance of batteries based on these positive electrode materials. Most often, strong surface modifications are detailed with respect to a supposed ideal initial state. The study the LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode material in its pristine state, hence before any contact with electrolyte or cycling, was performed thanks to advanced microscopy and spectroscopy techniques in order to fully characterize its surface down to the nanometer scale. Scanning transmission-electron microscopy-electron energy-loss spectroscopy (STEM-EELS), solid state nuclear-magnetic-resonance (SS-NMR) and X-rays photoelectron spectroscopy (XPS) are combined and correlated in an innovative manner.Specifically, using a high magnetic field NMR spectrometer, it was possible to evaluate the total amount of diamagnetic Li in the samples. Thanks to XPS it was then possible to identify the lithiated species present on the surface and to use such information to better deconvolve the NMR spectra. Li2O, Li2SO4 and LiOH were identified as the main contaminants on the surface of NMC in its initial state. On the other hand, the quantity of Li2CO3 initially estimated by XPS could be substantially re-evaluated using NMR (54% by XPS vs. only 1% by NMR). These two techniques, providing only partial and often imprecise information when used separately, have proven to be fundamental instruments in the analysis of surface species when used in a complementary manner.The results demonstrate that in usual storage conditions after synthesis, the extreme surface is already chemically different from nominal values. In particular, nickel is found in a reduced state compared to the bulk value and a Mn enrichment is determined in the first few nanometers of primary particles. Further exposition to humid air allows for quantifying the formed lithiated species per gram of active material, identifying their repartition and proposing a reaction path in relation with the instability of the surface. Modifying synthesis conditions impacts noticeably the previously identified surface particularities and, consequently, the materials reactivity.References :(1) Jung, R.; Metzger, M.; Maglia, F.; Stinner, C.; Gasteiger, H. A. Oxygen Release and Its Effect on the Cycling Stability of LiNixMnyCozO2 (NMC) Cathode Materials for Li-Ion Batteries. Journal of The Electrochemical Society 2017, 164 (7), A1361–A1377. https://doi.org/10.1149/2.0021707jes.(2) Renfrew, S. E.; McCloskey, B. D. Residual Lithium Carbonate Predominantly Accounts for First Cycle CO2 and CO Outgassing of Li-Stoichiometric and Li-Rich Layered Transition-Metal Oxides. J. Am. Chem. Soc. 2017, 139 (49), 17853–17860. https://doi.org/10.1021/jacs.7b08461.(3) Renfrew, S. E.; McCloskey, B. D. The Role of Electrolyte in the First-Cycle Transformations of LiNi 0.6 Mn 0.2 Co 0.2 O 2. J. Electrochem. Soc. 2019, 166 (13), A2762–A2768. https://doi.org/10.1149/2.1561912jes.(4) Zhang, H.; Liu, H.; Piper, L. F. J.; Whittingham, M. S.; Zhou, G. Oxygen Loss in Layered Oxide Cathodes for Li-Ion Batteries: Mechanisms, Effects, and Mitigation. Chem. Rev. 2022, acs.chemrev.1c00327. https://doi.org/10.1021/acs.chemrev.1c00327.(5) Manthiram, A.; Song, B.; Li, W. A Perspective on Nickel-Rich Layered Oxide Cathodes for Lithium-Ion Batteries. Energy Storage Materials 2017, 6, 125–139. https://doi.org/10.1016/j.ensm.2016.10.007. Figure 1

Exploiting Deep Eutectic Solvents in LiFePO4 Battery Recycling: From Cathode Leaching to Resynthesis

Nowadays, the increasing demand for electronic devices and electric vehicles influences the request for Lithium-Ion Batteries (LIBs), which are worldwide the most exploited electrochemical energy storage systems for portable devices and are expected to completely dominate also the sector of transportation soon. In particular, the use of LIBs with ordered-olivine structure LiFePO4 (LFP) cathodes stands out ever since their invention in 1997, being a valid solution in terms of durability, reliability, and safety, essential characteristics in the electric mobility application combined with the benefit of low content of critical raw materials, CRMs. Considering that the average life of LFP cathodes is about 5-8 years, the management of these materials as waste becomes essential: the growing number and volumes of LIBs that are currently produced is inevitably intended to correspond to the number of LIBs that will reach the end of their life, becoming waste that are accumulating, posing a staggering danger. [1,2] An also important consideration concerns the conditions required to synthesize LFP for electrochemical purposes, as it is necessary to coat the surface with conductive species, controlling the morphology and reducing the particle size, thus complicating the synthesis and making it economically more impactful. [3]In such a context, recycling combines the necessity to produce new LIBs with the need to cope with the increase in batteries’ waste accumulation: this can limit the disposal of waste batteries into landfills, thus decreasing the inevitable hazardous environmental consequences, while reducing the demand for new mining, re-assigning value to raw materials, in an attempt to minimize the costs that would be required to synthesize pristine LFP-based cathodes. Today, recycling is already implemented at the industrial level, exploiting the pyrometallurgy approach, which involves thermal treatments at very high temperatures (>1000°C) allowing for the recovery of only a fraction of valuable metals; nevertheless, this approach has a strong environmental impact due to the high energy demand and high carbon footprint. The hydrometallurgical approach is also employed, exploiting the leaching process with strong inorganic acids; however, this brings problematic issues, because producing such acids is itself a polluting process, and acidic wastewater management is a demanding problem. Moreover, today these processes involve the recycling of the most diffused cathode, LiCoO2, Li(Ni/Mn/Co)O2, LiMn2O4, and the sustainability of recycling relies on the possibility to recover valuable CRMs such as Co and Ni.In the proposed work we are currently investigating the degradation properties of Deep Eutectic Solvents (DESs), cheap and greener mixtures of compounds forming a eutectic system, liquid at room temperature. [4] In particular, the focus is on the leaching of LFP with a DES obtained by mixing different molar ratios of hydrogen bond acceptor and various hydrogen bond donors, in order to assess the best combination to leach the elements out of LFP structure. The key point of such approach is the design of a degradation system that can enable the conditions for the direct re-synthesis of new LFP material. Indeed, here the sustainability of the process cannot be driven by the recovery of CRMs, thus must rely on the close-loop recycling scheme. For this reason, we specifically designed DES compositions that allow for this process.The proposed DESs, which have been easily prepared at mild heating conditions, have been investigated through different techniques; the results obtained on the chemical-physical characterization (via FTIR spectroscopy, Solid-State NMR, viscosity, thermal analysis) will be presented. Among the different DESs, those with the best combination of properties (e.g. low viscosity, high thermal stability) have been explored for the leaching of LFP cathode. The leaching process has been optimized with respect to the temperature, duration, and cathode-to-DES ratio for different DESs, and the leaching yields have been evaluated through ICP-OES analysis. The obtained leached solution has been considered as the starting point for a sol-gel-like synthesis of new LFP material, finally characterized through XRD, TGA, ICP-OES, and SEM-EDX analysis. Tuning the parameters of the synthesis (temperature and duration of the heat treatment, ratio between LFP mass and conductive species to realize the coating) enables to control the morphology and the dimension of the synthesized particles, to find the best condition for the electrochemical application. The electrochemical performances of the resynthesized materials will also be presented.[1] Sun et al., J. Alloys Compd., 818 (2020)[2] Lv et al. ACS Sustain. Chem. Eng., 6 (2018)[3] Yuan et al., Energy Environ. Sci, 4 (2010)[4] Zhu et al., Resour. Conserv. Recycl., 188 (2023)

Mixed Metal Amide-Hydride Solid Solutions for Energy Storage Applications

Metal amide-hydride materials have been extensively studied for usage in energy applications, especially as solid electrolytes for all-solid-state batteries and as hydrogen storage. In specific cases, the formation of mixed metal amide hydride solid solutions promotes fast hydrogen sorption kinetics and tune the thermodynamics, allowing hydrogen absorption/desorption below 150 °C in hydrogen storage systems. In addition, these intermediates, such as Li2(BH4)(NH2) or Li4(BH4)(NH2)3 are potentially ionic conductors that can be used as solid electrolytes for solid-state batteries’ applications. In this work, a series of M-N-H solid solution structures based on mixed MNH2-MH materials of Group 1 elements (M = K, Rb, Cs and their combinations), such as KNH2-KH, KNH2-RbH, RbNH2-KH, RbNH2-CsH, RbNH2-CsNH2, etc., are reported. The results obtained by experimental determination (e.g., ex-situ XRD / in-situ synchrotron powder X-ray diffraction, IR, 1H 2D solid-state MAS NMR, QENS) and theoretical calculations (e.g., molecular dynamics calculations) confirm the formation of mixed metal amide hydride solid solutions associated with an exchange between both anionic (NH2 - and H-) and cationic species (K, Rb and Cs). These structurally disordered solid solutions exhibit high ionic conductivity compared to the pure materials, e.g., mixed RbNH2-CsNH2 shows an ionic conductivity in the range of 4×10-5 S×cm-1 at 373 K compared to that of pure RbNH2 and CsNH2 (< 10-7 S×cm-1 at the same condition). Although this solid solution exhibits only moderate ionic conductivity, it offers the possibility of tuning the functional and physical properties of mixed metal amide-hydrides by structural modification.

Evidence for S331-G-S-L within the amyloid core of myocilin olfactomedin domain fibrils based on low-resolution 3D solid-state NMR spectra.

Myocilin-associated glaucoma is a protein-conformational disorder associated with formation of a toxic amyloid-like aggregate. Numerous destabilizing single point variants, distributed across the myocilin olfactomedin β-propeller (OLF, myocilin residues 245-504, 30 kDa) are associated with accelerated disease progression. In vitro, wild type (WT) OLF can be promoted to form thioflavin T (ThT)-positive fibrils under mildly destabilizing (37°C, pH 7.2) conditions. Consistent with the notion that only a small number of residues within a protein are responsible for amyloid formation, 3D 13C-13C solid-state NMR spectra show that OLF fibrils are likely to be composed of only about one third of the overall sequence. Here, we probe the residue composition of fibrils formed de novo from purified full-length OLF. We were able to make sequential assignments consistent with the sequence S331-G-S-L334. This sequence appears once within a previously identified amyloid-prone region (P1, G326AVVYSGSLYFQ) internal to OLF. Since nearly half of the pairs of adjacent residues (di-peptides) in OLF occur only once in the primary structure and almost all the 3-residue sequences (tri-peptides) are unique, remarkably few sequential assignments are necessary to uniquely identify specific regions of the amyloid core. This assignment approach could be applied to other systems to expand our molecular comprehension of how folded proteins undergo fibrillization.

Manual and automatic assignment of two different Aβ40 amyloid fibril polymorphs using MAS solid-state NMR spectroscopy

Amyloid fibrils from Alzheimer’s amyloid-beta peptides (Aβ) are found to be polymorphic. So far, 14 Aβ40 fibril structures have been determined. The mechanism of why one particular protein sequence adopts so many different three-dimensional structures is yet not understood. In this work, we describe the assignment of the NMR chemical shifts of two Alzheimer’s disease fibril polymorphs, P1 and P2, which are formed by the amyloid-beta peptide Aβ40. The assignment is based on 13C-detected 3D NCACX and NCOCX experiments MAS solid-state NMR experiments. The fibril samples are prepared using an extensive seeding protocol in the absence and presence of the small heat shock protein αB-crystallin. In addition to manual assignments, we obtain chemical shift assignments using the automation software ARTINA. We present an analysis of the secondary chemical shifts and a discussion on the differences between the manual and automated assignment strategies.

Multi-Scale Modeling and Simulation of All-Solid-State Sodium-Ion Batteries with Polymer-Ceramic Hybrid Electrolytes

Lithium-ion batteries (LIBs) have been widely considered as the most promising power source for mobile devices. However, LIBs cannot meet the increasing global demand for electrochemical energy storage in the foreseeable future. Sodium ion-batteries (SIBs) are based on more ecofriendly and earth-abandoned materials. Commonly researched SIBs are based on liquid electrolytes. They pose leakage and thermal runaway risks. Solid polymer electrolytes solve these problems but need to operate at temperatures between 60-80°C to compensate insufficient ionic conductivity of polymer electrolytes at ambient temperatures.We present a polymer-ceramic hybrid electrolyte which overcomes the necessity to operate at high temperatures. It combines the advantages of high ion-conducting solid ceramic particles and flexible polymers. Sodium metal serves as the anode and PEO with inorganic fillers is used as cathode electrolyte. Due to their sustainability and high efficiency —comparable to LIBs— sodium-ion batteries are a promising candidate for small scale stationary energy storage applications or mobile energy storage applications with less constrains regarding energy density (e.g. trains, ships, submarines etc.). This contribution highlights a modeling approach for simulations of a single battery cell to develop an optimal cell design of the aforementioned battery system. A newly developed multiscale modeling method for hybrid polymer-ceramic sodium ion batteries reflects the different length scales of the active particle level and the electrode level. We precisely describe the spatially resolved mass and charge transport as well as electrochemical reactions in the active particle and the surrounding electrolyte employing a finite volume method [1]. Both domains are resolved in 3D and the model framework was validated against experimental data. The model output is incorporated in the connected pseudo-two-dimensional battery model for fast simulations of the overall battery cell considering mass and charge transport. The results support the importance of particle (active particle and ceramic filler particle) properties and configurations as well as electrolyte composition. Based on this, we exploit an evolutionary algorithm to suggest optimized battery designs for different use cases. In Addition, we present the evaluation of electrolyte properties with solid-state NMR spectroscopy and their model implementation [2]. μCT imaging experimentally investigates the cathode half-cell morphology. The derived virtual reconstructions enable realistic microstructure simulations of the battery cells. In this presentation, we will suggest two cell designs: The high-energy cell optimizes material efficiency and energy density. The high-power cell opts for high power densities (fast charging).In summary, we present a novel all-solid-state polymer-ceramic hybrid sodium-ion battery type for small stationary or large mobile energy storage units. Our contribution outlines a simulation approach that sheds light on macroscopic and microscopic processes inside the battery-cell using a multiscale modeling method. As a result, a high-energy and a high-power design is derived. Gerbig, M. Holzapfel and H. Nirschl, J. Electrochem. Soc., 170(4), 40517 (2023).Moradipour, A. Markert, T. Rudszuck, N. Röttgen, G. Dück, M. Finsterbusch, F. Gerbig, H. Nirschl and G. Guthausen, J Energ Power Technol, 05(04), 1–21 (2023).

Revealing and reconstructing the 3D Li-ion transportation network for superionic poly(ethylene) oxide conductor.

Understanding the Li-ions conduction network and transport dynamics in polymer electrolyte is crucial for developing reliable all-solid-state batteries. In this work, advanced nano- X-ray computed tomography combined with Raman spectroscopy and solid state nuclear magnetic resonance are used to multi-scale qualitatively and quantitatively reveal ion conduction network of poly(ethylene) oxide (PEO)-based electrolyte (from atomic, nano to macroscopic level). With the clear mapping of the microstructural heterogeneities of the polymer segments, aluminium-oxo molecular clusters (AlOC) are used to reconstruct a high-efficient conducting network with high available Li-ions (76.7%) and continuous amorphous domains via the strong supramolecular interactions. Such superionic PEO conductor (PEO-LiTFSI-AlOC) exhibites a molten-like Li-ion conduction behaviour among the whole temperature range and delivers an ionic conductivity of 1.87 × 10-4 S cm-1 at 35 °Ϲ. This further endows Li electrochemical plating/stripping stability under 50 μA cm-2 and 50 μAh cm-2 over 2000 h. The as-built Li|PEO-LiTFSI-AlOC|LiFePO4 full batteries show a high rate performance and a capacity retention more than 90% over 200 cycling at 250 μA cm-2, even enabling a high-loading LiFePO4 cathode of 16.8 mg cm-2 with a specific capacity of 150 mAh g-1 at 50 °Ϲ.

Correlating local structure and migration dynamics in Na/Li dual ion conductor Na5YSi4O12

Na5YSi4O12 (NYSO) is demonstrated as a promising electrolyte with high ionic conductivity and low activation energy for practical use in solid Na-ion batteries. Solid-state NMR was employed to identify the six types of coordination of Na+ ions and migration pathway, which is vital to master working mechanism and enhance performance. The assignment of each sodium site is clearly determined from high-quality 23Na NMR spectra by the aid of Density Functional Theory calculation. Well-resolved 23Na exchangespectroscopy and electrochemical tracer exchange spectra provide the first experimental evidence to show the existence of ionic exchange between sodium at Na5 and Na6 sites, revealing that Na transport route is possibly along three-dimensional chain of open channel-Na4-open channel. Variable-temperature NMR relaxometry is developed to evaluate Na jump rates and self-diffusion coefficient to probe the sodium-ion dynamics in NYSO. Furthermore, NYSO works well as a dual ion conductor in Na and Li metal batteries with Na3V2(PO4)3 and LiFePO4 as cathodes, respectively.

Surface Structure of Lecithin-Capped Cesium Lead Halide Perovskite Nanocrystals Using Solid-State and Dynamic Nuclear Polarization NMR Spectroscopy.

Inorganic colloidal cesium lead halide perovskite nanocrystals (NCs) encapsulated by surface capping ligands exhibit tremendous potential in optoelectronic applications, with their surface structure playing a pivotal role in enhancing their photophysical properties. Soy lecithin, a tightly binding zwitterionic surface-capping ligand, has recently facilitated the high-yield synthesis of stable ultraconcentrated and ultradilute colloids of CsPbX3 NCs, unlocking a myriad of potential device applications. However, the atomic-level understanding of the ligand-terminated surface structure remains uncertain. Herein, we use a versatile solid-state nuclear magnetic resonance (NMR) spectroscopic approach, in combination with dynamic nuclear polarization (DNP) and atomistic molecular dynamics (MD) simulations, to explore the effect of lecithin on the core-to-surface structures of CsPbX3 (X = Cl or Br) perovskites, sized from micron to nanoscale. Surface-selective (cross-polarization, CP) solid-state and DNP NMR (133Cs and 207Pb) methods were used to differentiate the unique surface and core chemical environments, while the head-groups {trimethylammonium [-N(CH3)3+] and phosphate (-PO4-)} of lecithin were assigned via 1H, 13C, and 31P NMR spectroscopy. A direct approach to determining the surface structure by capitalizing on the unique heteronuclear dipolar couplings between the lecithin ligand (1H and 31P) and the surface of the CsPbCl3 NCs (133Cs and 207Pb) is demonstrated. The 1H-133Cs heteronuclear correlation (HETCOR) DNP NMR indicates an abundance of Cs on the NC surface and an intimate proximity of the -N(CH3)3+ groups to the surface and subsurface 133Cs atoms, supported by 1H{133Cs} rotational-echo double-resonance (REDOR) NMR spectroscopy. Moreover, the 1H-31P{207Pb} CP REDOR dephasing curve provides average internuclear distance information that allows assessment of -PO4- groups binding to the subsurface Pb atoms. Atomistic MD simulations of ligand-capped CsPbCl3 surfaces aid in the interpretation of this information and suggest that ligand -N(CH3)3+ and -PO4- head-groups substitute Cs+ and Cl- ions, respectively, at the CsCl-terminated surface of the NCs. These detailed atomistic insights into surface structures can further guide the engineering of various relevant surface-capping zwitterionic ligands for diverse metal halide perovskite NCs.

Molecular Mechanism of P53 Peptide Permeation through Lipid Membranes from Solid-State NMR Spectroscopy and Molecular Dynamics Simulations.

Macrocyclic peptides show promise in targeting high-value therapeutically relevant binding sites due to their high affinity and specificity. However, their clinical application is often hindered by low membrane permeability, which limits their effectiveness against intracellular targets. Previous studies focused on peptide conformations in various solvents, leaving a gap in understanding their interactions with and translocation through lipid bilayers. Addressing this, our study explores the membrane interactions of stapled peptides, a subclass of macrocyclic peptides, using solid-state nuclear magnetic resonance (ssNMR) spectroscopy and molecular dynamics (MD) simulations. We conducted ssNMR measurements on ATSP-7041M, a prototypical stapled peptide, to understand its interaction with lipid membranes, leading to an MD-informed model for peptide membrane permeation. Our findings reveal that ATSP-7041M adopts a stable α-helical structure upon membrane binding, facilitated by a cation-π interaction between its phenylalanine side chain and the lipid headgroup. This interaction makes the membrane-bound state energetically favorable, facilitating membrane affinity and insertion. The bound peptide displayed asymmetric insertion depths, with the C-terminus penetrating deeper (approximately 9 Å) than the N-terminus (approximately 4.3 Å) relative to the lipid headgroups. Contrary to expectations, peptide dynamics was not hindered by membrane binding and exhibited rapid motions similar to cell-penetrating peptides. These dynamic interactions and peptide-lipid affinity appear to be crucial for membrane permeation. MD simulations indicated a thermodynamically stable transmembrane conformation of ATSP-7041M, reducing the energy barrier for translocation. Our study offers an in silico view of ATSP-7041M's translocation from the extracellular to the intracellular region, highlighting the significance of peptide-lipid interactions and dynamics in enabling peptide transit through membranes.

A Pillar[5]arene-Containing Metal-Organic Framework for Rapid and Highly Capable Adsorption of a Mustard Gas Simulant.

Mustard gas causes irreversible damage upon inhalation or contact with the human body. Consequently, the development of adsorbents for effective interception of mustard gas at low concentrations and high flow rates is an urgent necessity. Here we report a stable porous pillar[5]arene-containing metal-organic framework (MOF) based on zirconium (EtP5-Zr-scu), demonstrating that embedding pillar[5]arene units in MOFs can provide specific binding sites for efficient adsorption of a mustard gas simulant, 2-chloroethyl ethyl sulfide (CEES). EtP5-Zr-scu achieves a higher capacity and more rapid adsorption compared to its counterpart without embedded pillar[5]arene units (H4tcpt-Zr-scu) and perethylated pillar[5]arene (EtP5) alone. Single crystal X-ray diffraction and solid-state nuclear magnetic resonance reveal that the enhanced performance of EtP5-Zr-scu is derived from the host-guest complexation between CEES and pillar[5]arene moieties. Moreover, breakthrough experiments confirmed that the interception performance of EtP5-Zr-scu against CEES (800 ppm, 120 mL/min) was significantly improved (566 min/g) compared with H4tcpt-Zr-scu (353 min/g) and EtP5 (0.873 min/g), attributed to the integration of open channels with specific recognition sites. This work marks a significant advancement in the development of macrocycle-incorporated crystalline framework materials with recognition sites for the efficient capture of guest molecules.

Rhamnolipids and fengycins interact differently with biomimetic lipid membrane models of Botrytis cinerea and Sclerotinia sclerotiorum: Lipidomics profiles and biophysical studies

Rhamnolipids (RLs) and Fengycins (FGs) are biosurfactants with very promising antifungal properties proposed to reduce the use of synthetic pesticides in crops. They are amphiphilic molecules, both known to target the plasma membrane. They act differently on Botrytis cinerea and Sclerotinia sclerotiorum, two close Sclerotiniaceae phytopathogenic fungi. RLs are more efficient at permeabilizing S. sclerotiorum, and FGs are more efficient at permeabilizing B. cinerea mycelial cells. To study the link between the lipid membrane composition and the activity of RLs and FGs, we analyzed the lipid profiles of B. cinerea and S. sclerotiorum. We determined that unsaturated or saturated C18 and saturated C16 fatty acids are predominant in both fungi. We also showed that phosphatidylethanolamine (PE), phosphatidic acid (PA), and phosphatidylcholine (PC) are the main phospholipids (in this order) in both fungi, with more PA and less PC in S. sclerotiorum. The results were used to build biomimetic lipid membrane models of B. cinerea and S. sclerotiorum for all-atom molecular dynamic simulations and solid-state NMR experiments to more deeply study the interactions between RLs or FGs with different compositions of lipid bilayers. Distinctive effects are exerted by both compounds. RLs completely insert in all the studied model membranes with a fluidification effect. FGs tend to form aggregates out of the bilayer and insert individually more easily into the models representative of B. cinerea than those of S. sclerotiorum, with a higher fluidification effect. These results provide new insights into the lipid composition of closely related fungi and its impact on the mode of action of very promising membranotropic antifungal molecules for agricultural applications.

Investigation of the State of Hydration of a Non-Stoichiometric Hydrate in a Low Dose Formulation Using 19F Solid-State NMR

A variable or non-stoichiometric hydrate of GDC-4379 was developed into a formulated capsule with a 1% drug loading. The water content of this hydrate varied from 0-0.7 moles over the relative humidity (RH) range of 0-98% (25°C). Since a variable state of hydration coupled with rapid equilibration of lattice water with the environmental RH can lead to challenges in formulation development, an analytical method to directly and accurately determine the state of hydration of the active in such a low dose formulation was deemed necessary. Owing to its high selectivity and fast acquisition times, 19F solid-state NMR was effectively utilized to directly determine the lattice water content of the active in the formulated capsule. By correlating Δδ, the chemical shift difference between the isotropic peaks, with the relative humidity and ultimately the lattice water content, the state of hydration of GDC-4379 in the formulated capsule was experimentally determined as 0.63 moles of water/mole of anhydrate.

A complete 3D-printed tool kit for Solid-State NMR sample and rotor handling

Solid state NMR (SSNMR) is a highly versatile and broadly applicable method for studying the structure and dynamics of biomolecules and materials. For scientists entering the field of SSNMR, the many quotidian activities required in the workflow to prepare samples for data collection can present a significant barrier to adoption. These steps include transfer of samples into rotors, marking the reflective surfaces for high sensitivity tachometer signal detection, inserting rotors into the magic-angle spinning (MAS) stator, achieving stable spinning, and removing and storing rotors to ensure reproducibility of data collection conditions. Even experienced spectroscopists experience occasional problems with these operations, and the cumulative probability of a delay to successful data collection is high enough to cause frequent disruptions to instrument schedules, particularly in the context of large facilities serving a diverse community of users. These problems are all amplified when utilizing rotors smaller than about 4 mm in diameter. Therefore, to improve the reliability and robustness of SSNMR sample preparation workflows, here we describe a set of tools for rotor packing, unpacking, tachometer marking, extraction and storage. Stereolithography 3D printing was employed as a cost-effective and convenient method for prototyping and manufacturing a full range of designs suitable for several types of probes and rotor geometries.

Solid-state NMR of active sites in TiO2 photocatalysis: a critical review

Titanium dioxide (TiO2) is one of the optimal semiconductor metal oxide photocatalysts with a wide range of application fields, such as heterogeneous catalysis, energy science, and environmental science. Solid-state nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for characterizing both structure and dynamics at an atomic-molecular level in heterogeneous catalysts. In this review, we first provide a brief discussion on the progress in investigating the structures of titanium and oxygen in bulk and on the surface of TiO2 by using various solid-state NMR techniques. Advances in the understanding of electronic structure and properties of TiO2 with distinct surface features, including various crystal facets and heteroatomic adsorption by chemical probe-assisted NMR techniques, are secondly presented. The solid-state NMR characterization of heteroatom active sites (such as 13C, 15N, 11B, 27Al) and their function in TiO2 photocatalysts is described in detail. Finally, a critical discourse assesses the current limitations and prospects of solid-state NMR in its application to the optimization and design of advanced TiO2 photocatalysts.

Can Subsurface Oxygen Species in Oxides Participate in Catalytic Reactions? An 17O Solid-State Nuclear Magnetic Resonance Study.

The impacts of subsurface species of catalysts on reaction processes are still under debate, largely due to a lack of characterization methods for distinguishing these species from the surface species and the bulk. By using 17O solid-state nuclear magnetic resonance (NMR) spectroscopy, which can distinguish subsurface oxygen ions in CeO2 (111) nanorods, we explore the effects of subsurface species of oxides in CO oxidation reactions. The intensities of the 17O NMR signals due to surface and subsurface oxygen ions decrease after the introduction of CO into CeO2 nanorods, with a more significant decrease observed for the latter, confirming the participation of subsurface oxygen species. Density functional theory calculations show that the reaction involves subsurface oxygen ions filling the surface oxygen vacancies created by the direct contact of surface oxygen with CO. This new approach can be extended to the study of the role of oxygen species in other catalytic reactions.