A parallel line probe for spatially selective electrochemical NMR spectroscopy.

In situ NMR is a valuable tool for studying electrochemical devices, including redox flow batteries and electrocatalytic reactors, capable of detecting reaction intermediates, metastable states, time evolution of processes or monitoring stability as a function of electrochemical conditions. Here we report a parallel line detector for spatially selective in situ electrochemical NMR spectroscopy. The detector consists of 17 copper wires and is doubly tuned to 1H/19F and X nuclei ranging from 63Cu (106.1 MHz) to 7Li (155.5 MHz). The flat geometry of the parallel line detector allows its insertion into a high electrode surface-to-volume electrochemical flow reactor, enabling a detector-in-a-reactor design. This integrated device is named "eReactor NMR probe". Combined with B1-selective pulse sequences, selective detection of the nuclei at the electrode-electrolyte interface, that is within a distance of 800 µm from the electrode surface, has been achieved. The selective detection of 7Li and 19F nuclei is demonstrated using two electrolytes, LiCl and LiBF4 solutions, respectively. A good B1 homogeneity with an 810° to 90° pulse intensity ratio of 68-72 % was achieved. Using electrochemical plating of lithium metal as a model reaction, we further demonstrated the operando functionality of the probe. The new eReactor NMR probe offers a general method for studying flow electrochemistry, and we envision applications in a wide range of environmentally relevant energy systems, for example, Li metal batteries, electrochemical ammonia synthesis, carbon dioxide capture and reduction, redox flow batteries, fuel cells, water desalination, lignin oxidation etc.

Tunneling Interpenetrative Lithium Ion Conduction Channels in Polymer-in-Ceramic Composite Solid Electrolytes.

Polymer-in-ceramic composite solid electrolytes (PIC-CSEs) provide important advantages over individual organic or inorganic solid electrolytes. In conventional PIC-CSEs, the ion conduction pathway is primarily confined to the ceramics, while the faster routes associated with the ceramic-polymer interface remain blocked. This challenge is associated with two key factors: (i) the difficulty in establishing extensive and uninterrupted ceramic-polymer interfaces due to ceramic aggregation; (ii) the ceramic-polymer interfaces are unresponsive to conducting ions because of their inherent incompatibility. Here, we propose a strategy by introducing polymer-compatible ionic liquids (PCILs) to mediate between ceramics and the polymer matrix. This mediation involves the polar groups of PCILs interacting with Li+ ions on the ceramic surfaces as well as the interactions between the polar components of PCILs and the polymer chains. This strategy addresses the ceramic aggregation issue, resulting in uniform PIC-CSEs. Simultaneously, it activates the ceramic-polymer interfaces by establishing interpenetrating channels that promote the efficient transport of Li+ ions across the ceramic phase, the ceramic-polymer interfaces, and the intervening pathways. Consequently, the obtained PIC-CSEs exhibit high ionic conductivity, exceptional flexibility, and robust mechanical strength. A PIC-CSE comprising poly(vinylidene fluoride) (PVDF) and 60 wt % PCIL-coated Li3Zr2Si2PO12 (LZSP) fillers showcasing an ionic conductivity of 0.83 mS cm-1, a superior Li+ ion transference number of 0.81, and an elongation of ∼300% at 25 °C could be produced on meter-scale. Its lithium metal pouch cells show high energy densities of 424.9 Wh kg-1 (excluding packing films) and puncture safety. This work paves the way for designing PIC-CSEs with commercial viability.

Ligand-Aided Glycolysis of PET Using Functionalized Silica-Supported Fe2O3 Nanoparticles.

The development of efficient catalysts for the chemical recycling of poly(ethylene terephthalate) (PET) is essential to tackling the global issue of plastic waste. There has been intense interest in heterogeneous catalysts as a sustainable catalyst system for PET depolymerization, having the advantage of easy separation and reuse after the reaction. In this work, we explore heterogeneous catalyst design by comparing metal-ion (Fe3+) and metal-oxide nanoparticle (Fe2O3 NP) catalysts immobilized on mesoporous silica (SiO2) functionalized with different N-containing amine ligands. Quantitative solid-state nuclear magnetic resonance (NMR) spectroscopy confirms successful grafting and elucidates the bonding mode of the organic ligands on the SiO2 surface. The surface amine ligands act as organocatalysts, enhancing the catalytic activity of the active metal species. The Fe2O3 NP catalysts in the presence of organic ligands outperform bare Fe2O3 NPs, Fe3+-ion-immobilized catalysts and homogeneous FeCl3 salts, with equivalent Fe loading. X-ray photoelectron spectroscopy analysis indicates charge transfer between the amine ligands and Fe2O3 NPs and the electron-donating ability of the N groups and hydrogen bonding may also play a role in the higher performance of the amine-ligand-assisted Fe2O3 NP catalysts. Density functional theory (DFT) calculations also reveal that the reactivity of the ion-immobilized catalysts is strongly correlated to the ligand-metal binding energy and that the products in the glycolysis reaction catalyzed by the NP catalysts are stabilized, showing a significant exergonic character compared to single ion-immobilized Fe3+ ions.

Exploring Multi-Anion Chemistry in Yttrium Oxyhydrides: Solid-State NMR Studies and DFT Calculations.

Rare earth oxyhydrides REOxH(3-2x), with RE = Y, Sc, or Gd and a cationic FCC lattice, are reversibly photochromic in nature. It is known that structural details and anion (O2-:H-) composition dictate the efficiency of the photochromic behavior. The mechanism behind the photochromism is, however, not yet understood. In this study, we use 1H, 2H, 17O, and 89Y solid-state NMR spectroscopy and density functional theory (DFT) calculations to study the various yttrium, hydrogen, and oxygen local environments, anion oxidation states, and hydride ion dynamics. DFT models of YOxH(3-2x) with both anion-ordered and anion-disordered sublattices are constructed for a range of compositions and show a good correlation with the experimental NMR parameters. Two-dimensional 17O-1H and 89Y-1H NMR correlation experiments reveal heterogeneities in the samples, which appear to consist of hydride-rich (x ≈ 0.25) and hydride-poor domains (x ≈ 1) rather than a single composition with homogeneous anion mixing. The compositional variation (as indicated by the different x values in YOxH(3-2x)) is determined by comparing static 1H NMR line widths with calculated 1H-1H dipolar couplings of yttrium oxyhydride models. The 1D 17O MAS spectrum demonstrates the presence of a small percentage of hydroxide (OH-) ions. DFT modeling indicates a reaction between the protons of hydroxides and hydrides to form molecular hydrogen (H+ + H- → H2). 1H MAS NMR indicates the presence of a mobile component that, based on this finding, is attributed to trapped molecular H2 in the lattice.

Disorder to order: how halide mixing in MAPbI3-xBrx perovskites restricts MA dynamics.

Mixed-halide lead perovskites are of particular interest for the design of tandem solar cells currently reaching record efficiencies. While halide phase segregation upon illumination of mixed perovskites is extensively studied, the effect of halide disorder on A cation dynamics is not well understood, despite its importance for charge carrier diffusion and lifetime. Here, we study the methylammonium (MA) reorientational dynamics in mixed halide MAPbI3-xBrx perovskites by a combined approach of experimental solid-state NMR spectroscopy and molecular dynamics (MD) simulations based on machine-learning force-fields (MLFF). 207Pb NMR spectra indicate the halides are randomly distributed over their lattice positions, whereas PXRD measurements show that all mixed MAPbI3-xBrx samples are cubic. The experimental 14N spectra and 1H double-quantum (DQ) NMR data reveal anisotropic MA reorientations depending on the halide composition and thus associated disorder in the inorganic sublattice. MD calculations allow us to correlate these experimental results to restrictions of MA dynamics due to preferred MA orientations in their local Pb8I12-nBrn "cages". Based on the experimental and simulated results, we develop a phenomenological model that correlates the 1H dipolar coupling and thus the MA dynamics with the local composition and reproduces the experimental data over the whole composition range. We show that the dominant interaction between the MA cations and the Pb-X lattice that influences the cation dynamics is the local electrostatic potential being inhomogeneous in mixed halide systems. As such, we generate a fundamental understanding of the predominant interaction between the MA cations and the inorganic sublattice, as well as MA dynamics in asymmetric halide coordinations.

Formation of substituted dioxanes in the oxidation of gum arabic with periodate.

Renewable polysaccharide feedstocks are of interest in bio-based food packaging, coatings and hydrogels. Their physical properties often need to be tuned by chemical modification, e.g. by oxidation using periodate, to introduce carboxylic acid, ketone or aldehyde functional groups. The reproducibility required for application on an industrial scale, however, is challenged by uncertainty about the composition of product mixtures obtained and of the precise structural changes that the reaction with periodate induces. Here, we show that despite the structural diversity of gum arabic, primarily rhamnose and arabinose subunits undergo oxidation, whereas (in-chain) galacturonic acids are unreactive towards periodate. Using model sugars, we show that periodate preferentially oxidises the anti 1,2-diols in the rhamnopyranoside monosaccharides present as terminal groups in the biopolymer. While formally oxidation of vicinal diols results in the formation of two aldehyde groups, only traces of aldehydes are observed in solution, with the main final products obtained being substituted dioxanes, both in solution and in the solid state. The substituted dioxanes form most likely by the intramolecular reaction of one aldehyde with a nearby hydroxyl group, followed by hydration of the remaining aldehyde to form a geminal diol. The absence of significant amounts of aldehyde functional groups in the modified polymer impacts crosslinking strategies currently attempted in the preparation of renewable polysaccharide-based materials.

Operando benchtop NMR reveals reaction intermediates and crossover in redox flow batteries.

Redox flow batteries (RFBs) provide a promising battery technology for grid-scale energy storage. High-field operando NMR analyses of RFBs have yielded useful insight into their working mechanisms and helped improve battery performance. Nevertheless, the high cost and large footprint of a high-field NMR system limit its implementation by a wider electrochemistry community. Here, we demonstrate an operando NMR study of an anthraquinone/ferrocyanide-based RFB on a low-cost and compact 43 MHz benchtop system. The chemical shifts induced by bulk magnetic susceptibility effects differ remarkably from those obtained in high-field NMR experiments, due to the different orientations of the sample relative to the external magnetic field. We apply Evans method to estimate the concentrations of paramagnetic anthraquinone radical and ferricyanide anions. The degradation of 2,6-dihydroxy-anthraquinone (DHAQ) to 2,6-dihydroxy-anthrone and 2,6-dihydroxy-anthranol has been quantified. We further identified the impurities commonly present in the DHAQ solution to be acetone, methanol and formamide. The crossover of DHAQ and impurity molecules through the sseparation Nafion® membrane was captured and quantified, and a negative correlation between the molecular size and crossover rate was established. We show that a benchtop NMR system has sufficient spectral and temporal resolution and sensitivity for the operando study of RFBs, and anticipate a broad application of operando benchtop NMR methods for studying flow electrochemistry targeted for different applications.

Self-organized hetero-nanodomains actuating super Li+ conduction in glass ceramics.

Easy-to-manufacture Li2S-P2S5 glass ceramics are the key to large-scale all-solid-state lithium batteries from an industrial point of view, while their commercialization is greatly hampered by the low room temperature Li+ conductivity, especially due to the lack of solutions. Herein, we propose a nanocrystallization strategy to fabricate super Li+-conductive glass ceramics. Through regulating the nucleation energy, the crystallites within glass ceramics can self-organize into hetero-nanodomains during the solid-state reaction. Cryogenic transmission electron microscope and electron holography directly demonstrate the numerous closely spaced grain boundaries with enriched charge carriers, which actuate superior Li+-conduction as confirmed by variable-temperature solid-state nuclear magnetic resonance. Glass ceramics with a record Li+ conductivity of 13.2 mS cm-1 are prepared. The high Li+ conductivity ensures stable operation of a 220 µm thick LiNi0.6Mn0.2Co0.2O2 composite cathode (8 mAh cm-2), with which the all-solid-state lithium battery reaches a high energy density of 420 Wh kg-1 by cell mass and 834 Wh L-1 by cell volume at room temperature. These findings bring about powerful new degrees of freedom for engineering super ionic conductors.

Aluminium ion doping mechanism of lithium thiophosphate based solid electrolytes revealed with solid-state NMR.

We investigate the impact of Al incorporation on the structure and dynamics of Al-doped lithium thiophosphates (Li3-3xAlxPS4) based on ß-Li3PS4. 27Al and 6Li magic-angle spinning NMR spectra confirm that Al3+ ions occupy octahedral sites in the structure. Quantitative analyses of 27Al NMR spectra show that the maximum Al incorporation is x = 0.06 in Li3-3xAlxPS4. The ionic conductivity of ß-Li3PS4 is enhanced by over a factor 3 due to Al incorporation. Further increase of the Al doping level leads to the formation of a more complicated material consisting of multiple crystalline and distorted phases as indicated by 31P NMR spectra and powder X-ray diffraction. Consequently, novel Li ion diffusion pathways develop leading to a very high ionic conductivity at room temperature. NMR relaxometry shows that the activation barrier for long-range Li ion diffusion in ß-Li3PS4 hardly changes upon Al incorporation, but the onset temperature for motional narrowing comes down significantly due to Al doping. The activation barrier in the subsequently formed multiphase material decreases significantly, however, indicating a different more efficient Li ion conduction pathway.

Rapid Quantification of Pharmaceuticals via 1H Solid-State NMR Spectroscopy.

The physicochemical properties of active pharmaceutical ingredients (APIs) can depend on their solid-state forms. Therefore, characterization of API forms is crucial for upholding the performance of pharmaceutical products. Solid-state nuclear magnetic resonance (SSNMR) spectroscopy is a powerful technique for API quantification due to its selectivity. However, quantitative SSNMR experiments can be time consuming, sometimes requiring days to perform. Sensitivity can be considerably improved using 1H SSNMR spectroscopy. Nonetheless, quantification via 1H can be a challenging task due to low spectral resolution. Here, we offer a novel 1H SSNMR method for rapid API quantification, termed CRAMPS-MAR. The technique is based on combined rotation and multiple-pulse spectroscopy (CRAMPS) and mixture analysis using references (MAR). CRAMPS-MAR can provide high 1H spectral resolution with standard equipment, and data analysis can be accomplished with ease, even for structurally complex APIs. Using several API species as model systems, we show that CRAMPS-MAR can provide a lower quantitation limit than standard approaches such as fast MAS with peak integration. Furthermore, CRAMPS-MAR was found to be robust for cases that are inapproachable by conventional ultra-fast (i.e., 100 kHz) MAS methods even when state-of-the-art SSNMR equipment was employed. Our results demonstrate CRAMPS-MAR as an alternative quantification technique that can generate new opportunities for analytical research.

The Nature of Interface Interactions Leading to High Ionic Conductivity in LiBH4/SiO2 Nanocomposites.

Complex metal hydride/oxide nanocomposites are a promising class of solid-state electrolytes. They exhibit high ionic conductivities due to an interaction of the metal hydride with the surface of the oxide. The exact nature of this interaction and composition of the hydride/oxide interface is not yet known. Using 1H, 7Li, 11B, and 29Si NMR spectroscopy and lithium borohydride confined in nanoporous silica as a model system, we now elucidate the chemistry and dynamics occurring at the interface between the scaffold and the complex metal hydride. We observed that the structure of the oxide scaffold has a significant effect on the ionic conductivity. A previously unknown silicon site was observed in the nanocomposites and correlated to the LiBH4 at the interface with silica. We provide a model for the origin of this silicon site which reveals that siloxane bonds are broken and highly dynamic silicon-hydride-borohydride and silicon-oxide-lithium bonds are formed at the interface between LiBH4 and silica. Additionally, we discovered a strong correlation between the thickness of the silica pore walls and the fraction of the LiBH4 that displays fast dynamics. Our findings provide insights on the role of the local scaffold structure and the chemistry of the interaction at the interface between complex metal hydrides and oxide hosts. These findings are relevant for other complex hydride/metal oxide systems where interface effects leads to a high ionic conductivity.

Residual quadrupolar couplings observed in 7 Tesla deuterium MR spectra of skeletal muscle.

PURPOSE: Deuterium metabolic imaging could potentially be used to investigate metabolism in skeletal muscle noninvasively. However, skeletal muscle is a tissue with a high degree of spatial organization. In this study, we investigated the effect of incomplete motional averaging on the naturally abundant deuterated water signal in 7 Tesla deuterium spectra of the lower leg muscles and the dependence on the angle between the muscle fibers and the main magnetic field B0 , as determined by DTI. METHODS: Natural abundance deuterium MRSI measurements of the right lower leg muscles were performed at 7 Tesla. Three subjects were scanned in a supine position, with the right leg parallel with the B0 field. One subject was scanned twice; during the second scan, the subject was laying on his right side and the right knee was bent such that the angle between the right lower leg and B0 was approximately 45°. DTI was performed in the same subjects in the same positions at 3 Tesla to determine muscle fiber angles. RESULTS: We observed splittings in the natural abundance deuterated water signal. The size of the splittings varied between different muscles in the lower leg but were mostly similar among subjects for each muscle. The splittings depended on the orientation of the muscle fibers with respect to the main magnetic field B0 . CONCLUSION: Partial molecular alignment in skeletal muscle leads to residual deuteron quadrupolar couplings in deuterated water, the size of which depends on the angle between the muscle fibers and B0 .

Microscopic (Dis)order and Dynamics of Cations in Mixed FA/MA Lead Halide Perovskites.

Recent developments in the field of high efficiency perovskite solar cells are based on stabilization of the perovskite crystal structure of FAPbI3 while preserving its excellent optoelectronic properties. Compositional engineering of, for example, MA or Br mixed into FAPbI3 results in the desired effects, but detailed knowledge of local structural features, such as local (dis)order or cation interactions of formamidinium (FA) and methylammonium (MA), is still limited. This knowledge is, however, crucial for their further development. Here, we shed light on the microscopic distribution of MA and FA in mixed perovskites MA1-x FA x PbI3 and MA0.15FA0.85PbI2.55Br0.45 by combining high-resolution double-quantum 1H solid-state nuclear magnetic resonance (NMR) spectroscopy with state-of-the-art near-first-principles accuracy molecular dynamics (MD) simulations using machine-learning force-fields (MLFFs). We show that on a small local scale, partial MA and FA clustering takes place over the whole MA/FA compositional range. A reasonable driving force for the clustering might be an increase of the dynamical freedom of FA cations in FA-rich regions. While MA0.15FA0.85PbI2.55Br0.45 displays similar MA and FA ordering as the MA1-x FA x PbI3 systems, the average cation-cation interaction strength increased significantly in this double mixed material, indicating a restriction of the space accessible to the cations or their partial immobilization upon Br- incorporation. Our results shed light on the heterogeneities in cation composition of mixed halide perovskites, helping to exploit their full optoelectronic potential.

Structural Investigations of MA1-xDMAxPbI3 Mixed-Cation Perovskites.

Recently, a number of variations to the hybrid perovskite structure have been suggested in order to improve on the properties of methylammonium lead iodide, the archetypical hybrid halide perovskite material. In particular, with respect to the chemical stability of the material, steps should be taken. We performed an in-depth analysis of the structure of MAPbI3 upon incorporation of dimethylammonium (DMA) in order to probe the integrity of the perovskite lattice in relation to changes in the organic cation. This material, with formula MA1-xDMAxPbI3, adopts a 3D perovskite structure for 0 < x < 0.2, while a nonperovskite yellow phase is formed for 0.72 < x < 1. In the perovskite phase, the methylammonium and dimethylammonium ions are distributed randomly throughout the lattice. For 0.05 < x < 0.2, the phase-transition temperature of the material is lowered when compared to that of pure MAPbI3 (x = 0). The material, although disordered, has apparent cubic symmetry at room temperature. This leads to a small increase in the band gap of the material of about 20 meV. Using 14N NMR relaxation experiments, the reorientation times of the MA and DMA cations in MA0.8DMA0.2PbI3 were established to be 1.6 and 2.6 ps, respectively, indicating that both ions are very mobile in this material, on par with the MA ions in MAPbI3. All of the produced MA1-xDMAxPbI3 materials were richer in DMA than the precursor solution from which they were crystallized, indicating that DMA incorporation is energetically favorable and suggesting a higher thermodynamic stability of these materials when compared to that of pure MAPbI3.

Monitoring Heterogeneously Catalyzed Hydrogenation Reactions at Elevated Pressures Using In-Line Flow NMR.

We present a novel setup that can be used for the in-line monitoring of solid-catalyzed gas-liquid reactions. The method combines the high sensitivity and resolution of a stripline NMR detector with a microfluidic network that can withstand elevated pressures. In our setup we dissolve hydrogen gas in the solvent, then flow it with the added substrate through a catalyst cartridge, and finally flow the reaction mixture directly through the stripline NMR detector. The method is quantitative and can be used to determine the solubility of hydrogen gas in liquids; it allows in-line monitoring of hydrogenation reactions and can be used to determine the reaction kinetics of these reactions. In this work, as proof of concept we demonstrate the optimization of the Pd-catalyzed hydrogenation reactions of styrene, phenylacetylene, cyclohexene, and hex-5-en-2-one in a microfluidic context.

Solid-state NMR of hybrid halide perovskites.

Recent advances in the development of perovskite based solar cells have increased the demand for in-depth characterisation of the perovskite structures and the dynamics of their various constituents in relation to the potential impact on the photovoltaic performance. NMR can play an important role in this respect; NMR has been used to study the incorporation of different ionic species, characterize their internal dynamics and diffusion, and monitor the chemical stability of these technologically relevant materials, including upcoming lower dimensional perovskite materials. Furthermore, the flexibility of NMR allows the study of the materials under relevant conditions e.g. under illumination. Here we present an overview of the recent literature on NMR of (hybrid) halide perovskites, focusing on the insights that NMR can provide.

Inline Reaction Monitoring of Amine-Catalyzed Acetylation of Benzyl Alcohol Using a Microfluidic Stripline Nuclear Magnetic Resonance Setup.

We present an in-depth study of the acetylation of benzyl alcohol in the presence of N, N-diisopropylethylamine (DIPEA) by nuclear magnetic resonance (NMR) monitoring of the reaction from 1.5 s to several minutes. We have adapted the NMR setup to be compatible to microreactor technology, scaling down the typical sample volume of commercial NMR probes (500 µL) to a microfluidic stripline setup with 150 nL detection volume. Inline spectra are obtained to monitor the kinetics and unravel the reaction mechanism of this industrially relevant reaction. The experiments are combined with conventional 2D NMR measurements to identify the reaction products. In addition, we replace DIPEA with triethylamine and pyridine to validate the reaction mechanism for different amine catalysts. In all three acetylation reactions, we find that the acetyl ammonium ion is a key intermediate. The formation of ketene is observed during the first minutes of the reaction when tertiary amines were present. The pyridine-catalyzed reaction proceeds via a different mechanism.

Hybrid particles derived from alendronate and bioactive glass for treatment of osteoporotic bone defects.

Osteoporosis is the most widespread metabolic bone disease which represents a major public health burden. Consequently, novel biomaterials with a strong capacity to regenerate osteoporotic bone defects are urgently required. In view of the anti-osteoporotic and osteopromotive efficacy of alendronate and 45S5 bioactive glass, respectively, we investigated the feasibility to synthesize novel hybrid particles by exploiting the strong interactions between these two compounds. Herein, we demonstrate the facile preparation of a novel class of hybrid particles of tunable morphology, chemical composition and structure. These hybrid particles (i) release alendronate and various inorganic elements (Ca, Na, Si, and P) in a controlled manner, (ii) exhibit a strong anti-osteoclastic effect in vitro, and (iii) stimulate regeneration of osteoporotic bone in vivo. Consequently, this novel class of hybrid biomaterials opens up new avenues of research on the design of bone substitutes with specific activity to facilitate regeneration of bone defects in osteoporotic patients.

Insight into the chromophore of rhodopsin and its Meta-II photointermediate by 19F solid-state NMR and chemical shift tensor calculations.

19F nuclei are useful labels in solid-state NMR studies, since their chemical shift and tensor elements are very sensitive to the electrostatic and space-filling properties of their local environment. In this study we have exploited a fluorine substituent, strategically placed at the C-12-position of 11-cis retinal, the chromophore of visual rhodopsins. This label was used to explore the local environment of the chromophore in the ground state of bovine rhodopsin and its active photo-intermediate Meta II. In addition, the chemical shift and tensor elements of the chromophore in the free state in a membrane environment and the bound state in the protein were determined. Upon binding of the chromophore into rhodopsin and Meta II, the isotropic chemical shift changes in the opposite direction by +9.7 and -8.4 ppm, respectively. An unusually large isotropic shift difference of 35.9 ppm was observed between rhodopsin and Meta II. This partly originates in the light-triggered 11-cis to all-trans isomerization of the chromophore. The other part reflects the local conformational rearrangements in the chromophore and the binding pocket. These NMR data were correlated with the available X-ray structures of rhodopsin and Meta II using bond polarization theory. For this purpose hydrogen atoms have to be inserted and hereto a family of structures were derived that best correlated with the well-established 13C chemical shifts. Based upon these structures, a 12-F derivative was obtained that best corresponded with the experimentally determined 19F chemical shifts and tensor elements. The combined data indicate strong changes in the local environment of the C-12 position and a substantially different interaction pattern with the protein in Meta II as compared to rhodopsin.

Dimethylammonium Incorporation in Lead Acetate Based MAPbI3 Perovskite Solar Cells.

Over the last years, several different pathways have been suggested for producing perovskite thin films for solar cell applications. While the merit of these methods with respect to the solar cell efficiency have been shown, the actual composition of the resulting thin films is often not investigated. Here, we show that methylammonium lead iodide films produced using lead acetate as a lead source can have up to 15 % dimethylammonium incorporated into their crystal structure, even though this ion is often consider to be too large for incorporation. The origin of this ion lies in the precursor solution, where it is formed in a reaction that is facilitated by the basic character of the acetate ions. We further show that these dimethylammonium ions are incorporated in a random fashion throughout the crystal structure, owing to the lack of observable ordered domains.