High-throughput phase elucidation of polycrystalline materials using serial rotation electron diffraction.

Rapid phase elucidation of polycrystalline materials is essential for developing new materials of chemical, pharmaceutical and industrial interest. Yet, the size and quantity of many crystalline phases are too small for routine X-ray diffraction analysis. This has become a workflow bottleneck in materials development, especially in high-throughput synthesis screening. Here we demonstrate the application of serial rotation electron diffraction (SerialRED) for high-throughput phase identification of complex polycrystalline zeolite products. The products were prepared from a combination of multiple framework T atoms ([Si,Ge,Al] or [Si,Ge,B]) and a simple organic structure-directing agent. We show that using SerialRED, five zeolite phases can be identified from a highly complex mixture. This includes phases with ultra-low contents undetectable using X-ray diffraction and phases with identical crystal morphology and similar unit cell parameters. By automatically and rapidly examining hundreds of crystals, SerialRED enables high-throughput phase analysis and allows the exploration of complex synthesis systems. It provides new opportunities for rapid development of polycrystalline materials.

InsteaDMatic: towards cross-platform automated continuous rotation electron diffraction.

A DigitalMicrograph script, InsteaDMatic, has been developed to facilitate rapid automated 3D electron diffraction/microcrystal electron diffraction data acquisition by continuous rotation of a crystal with a constant speed, denoted as continuous rotation electron diffraction. The script coordinates microscope functions, such as stage rotation, and camera functions relevant for data collection, and stores the experiment metadata. The script is compatible with any microscope that can be controlled by DigitalMicrograph and has been tested on both JEOL and Thermo Fisher Scientific microscopes. A proof of concept has been performed through employing InsteaDMatic for data collection and structure determination of a ZSM-5 zeolite. The influence of illumination settings and electron dose rate on the quality of diffraction data, unit-cell determination and structure solution has been investigated in order to optimize the data acquisition procedure.

Automated serial rotation electron diffraction combined with cluster analysis: an efficient multi-crystal workflow for structure determination.

Serial rotation electron diffraction (SerialRED) has been developed as a fully automated technique for three-dimensional electron diffraction data collection that can run autonomously without human intervention. It builds on the previously established serial electron diffraction technique, in which submicrometre-sized crystals are detected using image processing algorithms. Continuous rotation electron diffraction (cRED) data are collected on each crystal while dynamically tracking the movement of the crystal during rotation using defocused diffraction patterns and applying a set of deflector changes. A typical data collection screens up to 500 crystals per hour, and cRED data are collected from suitable crystals. A data processing pipeline is developed to process the SerialRED data sets. Hierarchical cluster analysis is implemented to group and identify the different phases present in the sample and to find the best matching data sets to be merged for subsequent structure analysis. This method has been successfully applied to a series of zeolites and a beam-sensitive metal-organic framework sample to study its capability for structure determination and refinement. Two multi-phase samples were tested to show that the individual crystal phases can be identified and their structures determined. The results show that refined structures obtained using automatically collected SerialRED data are indistinguishable from those collected manually using the cRED technique. At the same time, SerialRED has lower requirements of expertise in transmission electron microscopy and is less labor intensive, making it a promising high-throughput crystal screening and structure analysis tool.

SSZ-27: A Small-Pore Zeolite with Large Heart-Shaped Cavities Determined by Using Multi-crystal Electron Diffraction.

The high-silica zeolite SSZ-27 was synthesized using one of the isomers of the organic structure-directing agent that is known to produce the large-pore zeolite SSZ-26 (CON). The structure of the as-synthesized form was solved using multi-crystal electron diffraction data. Data were collected on eighteen crystals, and to obtain a high-quality and complete data set for structure refinement, hierarchical cluster analysis was employed to select the data sets most suitable for merging. The framework structure of SSZ-27 can be described as a combination of two types of cavities, one of which is shaped like a heart. The cavities are connected through shared 8-ring windows to create straight channels that are linked together in pairs to form a one-dimensional channel system. Once the framework structure was known, molecular modelling was used to find the best fitting isomer, and this, in turn, was isolated to improve the synthesis conditions for SSZ-27.

Preferential Siting of Aluminum Heteroatoms in the Zeolite Catalyst Al-SSZ-70.

The adsorption and reaction properties of heterogeneous zeolite catalysts (e.g. for catalytic cracking of petroleum, partial oxidation of natural gas) depend strongly on the types and distributions of Al heteroatoms in the aluminosilicate frameworks. The origins of these properties have been challenging to discern, owing in part to the structural complexity of aluminosilicate zeolites. Herein, combined solid-state NMR and synchrotron X-ray powder diffraction analyses show the Al atoms locate preferentially in certain framework sites in the zeolite catalyst Al-SSZ-70. Through-covalent-bond 2D 27 Al{29 Si} J-correlation NMR spectra allow distinct framework Al sites to be identified and their relative occupancies quantified. The analyses show that 94 % of the Al atoms are located at the surfaces of the large-pore interlayer channels of Al-SSZ-70, while only 6 % are in the sub-nm intralayer channels. The selective siting of Al atoms accounts for the reaction properties of catalysts derived from SSZ-70.

Synthesis and Structure Determination of SCM-15: A 3D Large Pore Zeolite with Interconnected Straight 12×12×10-Ring Channels.

A new germanosilicate zeolite named SCM-15 (Sinopec Composite Material No. 15), the first zeolite containing a 3-dimensional (3D) channel system with interconnected 12-, 12-, and 10-ring channels (pore sizes: 6.1×7.2, 6.1×7.4, and 5.2×5.9 Å), has been synthesized using neutral 4-pyrrolidinopyridine as organic structure-directing agents (OSDAs). Its structure has been determined by combining single-crystal electron diffraction (SCED) and synchrotron powder X-ray diffraction (SPXD) data. The unique open framework structure of SCM-15 is related to that of FOS-5 (BEC), ITQ-7 (ISV), PKU-16 (POS), ITQ-26 (IWS), ITQ-21, Beta polymorph B, and SU-78B, since all these framework structures can be constructed from similar chains which are connected through shared 4-ring or double 4-ring (d4r) units. Based on this relation, six topologically reasonable 3D large or extra-large pore hypothetical zeolites are predicted.

High-throughput continuous rotation electron diffraction data acquisition via software automation.

Single-crystal electron diffraction (SCED) is emerging as an effective technique to determine and refine the structures of unknown nano-sized crystals. In this work, the implementation of the continuous rotation electron diffraction (cRED) method for high-throughput data collection is described. This is achieved through dedicated software that controls the transmission electron microscope and the camera. Crystal tracking can be performed by defocusing every nth diffraction pattern while the crystal rotates, which addresses the problem of the crystal moving out of view of the selected area aperture during rotation. This has greatly increased the number of successful experiments with larger rotation ranges and turned cRED data collection into a high-throughput method. The experimental parameters are logged, and input files for data processing software are written automatically. This reduces the risk of human error, and makes data collection more reproducible and accessible for novice and irregular users. In addition, it is demonstrated how data from the recently developed serial electron diffraction technique can be used to supplement the cRED data collection by automatic screening for suitable crystals using a deep convolutional neural network that can identify promising crystals through the corresponding diffraction data. The screening routine and cRED data collection are demonstrated using a sample of the zeolite mordenite, and the quality of the cRED data is assessed on the basis of the refined crystal structure.

Serial electron crystallography for structure determination and phase analysis of nanocrystalline materials.

Serial electron crystallography has been developed as a fully automated method to collect diffraction data on polycrystalline materials using a transmission electron microscope. This enables useful data to be collected on materials that are sensitive to the electron beam and thus difficult to measure using the conventional methods that require long exposure of the same crystal. The data collection strategy combines goniometer translation with electron beam shift, which allows the entire sample stage to be probed. At each position of the goniometer, the locations of the crystals are identified using image recognition techniques. Diffraction data are then collected on each crystal using a quasi-parallel focused beam with a predefined size (usually 300-500 nm). It is shown that with a fast and sensitive Timepix hybrid pixel area detector it is possible to collect diffraction data of up to 3500 crystals per hour. These data can be indexed using a brute-force forward-projection algorithm. Results from several test samples show that 100-200 frames are enough for structure determination using direct methods or dual-space methods. The large number of crystals examined enables quantitative phase analysis and automatic screening of materials for known and unknown phases.

The patellar pubic percussion test: a simple bedside tool for suspected occult hip fractures.

PURPOSE: Patellar finger tapping produces a typical sound that can be detected by a stethoscope positioned on the pubic bone (patellar pubic percussion test (PPPT)). Characteristics of this sound are determined by continuity of bone between patella and pelvis. We hypothesized that a PPPT was able to detect overt hip fractures and occult hip fractures that may not be determined by a standard radiological examination. METHODS: Two independent observers performed a PPPT in patients with a suspected hip or pelvic fracture, just before a conventional radiograph (X-ray) was performed. The PPPT test was scored as negative (similar to contralateral side) or positive (different). Patients with a positive PPPT but with a negative X-ray underwent an additional CT scan. RESULTS: One hundred and ninety-one patients with suspected hip or pelvic fracture were included. A total of 161 patients (84%) were diagnosed with a fracture (hip, n = 142; pelvic, n = 19). An 85% sensitivity, a 70% specificity, a 0.94 positive predictive value, and a 0.47 negative predictive value of the PTTT were calculated. The inter-observer reliability (kappa) was 0.7. Eleven CT scans as indicated by a mismatch between PPPT (positive) and X-ray (no fracture) identified eight fractures (73%). A multivariate analysis demonstrated that a painful passive movement and the PPPT predicted a hip fracture. CONCLUSION: The PPPT is a simple bedside diagnostic tool that is sensitive in detecting clinically straight forward hip fractures as well as occult hip fractures. The PPPT can support decision-making for additional radiological examinations in case of potential occult pelvis or hip fractures.

Well-Defined Silanols in the Structure of the Calcined High-Silica Zeolite SSZ-70: New Understanding of a Successful Catalytic Material.

The structure of the calcined form of the high-silica zeolite SSZ-70 has been elucidated by combining synchrotron X-ray powder diffraction (XRPD), high-resolution transmission electron microscopy (HRTEM), and two-dimensional (2D) dynamic nuclear polarization (DNP)-enhanced NMR techniques. The framework structure of SSZ-70 is a polytype of MWW and can be viewed as a disordered ABC-type stacking of MWW-layers. HRTEM and XRPD simulations show that the stacking sequence is almost random, with each layer being shifted by ±1/3 along the ⟨110⟩ direction with respect to the previous one. However, a small preponderance of ABAB stacking could be discerned. DNP-enhanced 2D 29Si{29Si} J-mediated NMR analyses of calcined Si-SSZ-70 at natural 29Si isotopic abundance (4.7%) establish the through-covalent-bond 29Si-O-29Si connectivities of distinct Si sites in the framework. The DNP-NMR results corroborate the presence of MWW layers and, more importantly, identify two distinct types of Q3 silanol species at the surfaces of the interlayer regions. In the first, an isolated silanol group protrudes into the interlayer space pointing toward the pocket in the adjacent layer. In the second, the surrounding topology is the same, but the isolated -SiOH group is missing, leaving a nest of three Si-O-H groups in place of the three Si-O-Si linkages. The analyses clarify the structure of this complicated material, including features that do not exhibit long-range order. With these insights, the novel catalytic behavior of SSZ-70 can be better understood and opportunities for enhancement recognized.

Synthesis and Structure Determination of Large-Pore Zeolite SCM-14.

SCM-14 (Sinopec Composite Material No. 14), a new stable germanosilicate zeolite with a 12×8×8-ring channel system, was synthesized using commercially available 4-pyrrolidinopyridine as organic structure-directing agents (OSDAs) in fluoride medium. The framework structure of SCM-14 was determined using rotation electron diffraction (RED), and refined against synchrotron X-ray powder diffraction (SXPD) data for both as-made and calcined materials. The framework structure of SCM-14 is closely related to that of three known zeolites: mordenite (MOR), GUS-1 (GON), and IM-16 (UOS). SCM-14 has the same projection as that of mordenite and GUS-1 when viewed along the 12-ring channels, and possesses two more straight 8-ring channels running perpendicular to the 12-ring channels. The structure of SCM-14 can be constructed by either the same layers as that of GUS-1 or the same columns as that of IM-16. Based on their structural relationship, three topologically reasonable hypothetical zeolites were predicted.

Locating Organic Guests in Inorganic Host Materials from X-ray Powder Diffraction Data.

Can the location of the organic structure-directing agent (SDA) inside the channel system of a zeolite be determined experimentally in a systematic manner? In an attempt to answer this question, we investigated six borosilicate zeolites of known framework structure (SSZ-53, SSZ-55, SSZ-56, SSZ-58, SSZ-59, and SSZ-60), where the location of the SDA had only been simulated using molecular modeling techniques in previous studies. From synchrotron powder diffraction data, we were able to retrieve reliable experimental positions for the SDA by using a combination of simulated annealing (global optimization) and Rietveld refinement. In this way, problems arising from data quality and only partially compatible framework and SDA symmetries, which can lead to indecipherable electron density maps, can be overcome. Rietveld refinement using geometric restraints were then performed to optimize the positions and conformations of the SDAs. With these improved models, it was possible to go on to determine the location of the B atoms in the framework structure. That is, two pieces of information that are key to the understanding of zeolite synthesis-the location of the organic SDA in the channel system and of the positions adopted by heteroatoms in the silicate framework-can be extracted from experimental data using a systematic strategy. In most cases, the locations of the SDAs determined experimentally compare well with those simulated with molecular modeling, but there are also some clear differences, and the reason for these differences can be understood. The approach is generally applicable, and has also been used to locate organic guests, linkers, and ligands in metal-organic compounds.

Fasciotomy for Deep Posterior Compartment Syndrome in the Lower Leg: A Prospective Study.

BACKGROUND: Patients with exercise-induced lower leg pain may suffer from deep posterior chronic exertional compartment syndrome (dp-CECS). Current evidence for the efficacy of surgery is based on retrospective studies. Effects of fasciotomy on symptoms associated with dp-CECS have not been systematically studied, and reasons for unsuccessful surgery are unknown. PURPOSE: To report the short- and long-term effects of fasciotomy on pain, tightness, and cramps in a prospective cohort of patients with isolated dp-CECS. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Between September 2011 and January 2015, pain, tightness, cramps, muscle weakness, and diminished sensation were scored (5-item verbal rating scale ranging from very severe [5 points] to absent [1 point]) in patients with dp-CECS before and after fasciotomy. Outcomes were graded as excellent, good, moderate, fair, or poor. Fair and poor cases were again analyzed during a follow-up visit in the outpatient department. RESULTS: Forty-four patients underwent surgery for isolated dp-CECS. Short-term follow-up (median, 4 months; range, 3-7 months) was complete in 42 of the 44 patients (95%; median patient age, 23 years; 23 male; 64 operated legs). Long-term follow-up (median, 27 months; range, 12-42 months) was complete in 34 of 37 eligible patients (92%). Before surgery, exertional pain was very severe (27%) or severe (61%). Fasciotomy improved all symptoms, both in the short term (preoperative vs postoperative pain, 4.1 ± 0.6 vs 2.3 ± 1.1; P < .001) and the long term (pain, 4.2 ± 0.6 vs 2.7 ± 1.3; P < .001). Levels of tightness, cramps, muscle weakness, and diminished sensation demonstrated similar significant improvements. Short- and long-term symptom scores did not differ. The short-term outcome was excellent in 29%, good in 29%, moderate in 21%, fair in 12%, and poor in 10% of patients. In the long term, outcomes were similar (excellent, 12%; good, 35%; moderate, 24%; fair, 18%; and poor, 12%). An unsatisfactory outcome (fair or poor) was often caused by alternative types of CECS (eg, anterior or lateral CECS) or to medial tibial stress syndrome. Based on their outcome, 76% of patients would opt for surgery again. CONCLUSION: Fasciotomy was beneficial in 71% of patients with dp-CECS in the lower leg; 47% of study patients experienced a good to excellent outcome. Outcomes were stable in the long term. Persistent complaints were often caused by other untreated conditions.

Ionothermal Synthesis and Structure of a New Layered Zirconium Phosphate.

A new layered zirconium phosphate material has been synthesized ionothermally using N-ethylpyridinium (Epy) bromide as both the solvent and the template, and its structure has been solved from synchrotron X-ray powder diffraction data using the charge-flipping routine implemented in Superflip. Rietveld refinement coupled with difference electron density map analysis was used to locate the organic cations between the layers. In the final stages of refinement, it became clear that not only ethylpyridinium but also pyridinium ions were present between the zirconium phosphate layers. These findings were then corroborated using elemental analysis, TGA, and solid-state (13)C CP/MAS NMR data.

Serial snapshot crystallography for materials science with SwissFEL.

New opportunities for studying (sub)microcrystalline materials with small unit cells, both organic and inorganic, will open up when the X-ray free electron laser (XFEL) presently being constructed in Switzerland (SwissFEL) comes online in 2017. Our synchrotron-based experiments mimicking the 4%-energy-bandpass mode of the SwissFEL beam show that it will be possible to record a diffraction pattern of up to 10 randomly oriented crystals in a single snapshot, to index the resulting reflections, and to extract their intensities reliably. The crystals are destroyed with each XFEL pulse, but by combining snapshots from several sets of crystals, a complete set of data can be assembled, and crystal structures of materials that are difficult to analyze otherwise will become accessible. Even with a single shot, at least a partial analysis of the crystal structure will be possible, and with 10-50 femtosecond pulses, this offers tantalizing possibilities for time-resolved studies.

SSZ-87: a borosilicate zeolite with unusually flexible 10-ring pore openings.

The structure of the as-synthesized borosilicate zeolite SSZ-87 has been solved by combining high-resolution X-ray powder diffraction (XPD) and rotation electron diffraction (RED) techniques. The unit cell and space group symmetry were found from the XPD data, and were essential for the initial analysis of the RED data. Although the RED data were only 15% complete, this proved to be enough for structure solution with the program Focus. The framework topology is the same as that of ITQ-52 (IFW), but for SSZ-87 the locations of the structure directing agent (SDA) and the B atoms could also be determined. SSZ-87 has large cages interconnected by 8- and 10-rings. However, results of hydroisomerization and Al insertion experiments are much more in line with those found for 12-ring zeolites. This prompted the structure analyses of SSZ-87 after calcination, and Al insertion. During calcination, the material is also partially deboronated, and the location of the resulting vacancies is consistent with those of the B atoms in the as-synthesized material. After Al insertion, SSZ-87 was found to contain almost no B and to be defect free. In its calcined and deboronated form, the pore system of SSZ-87 is more flexible than those of other 10-ring zeolites. This can be explained by the fact that the large cages in SSZ-87 are connected via single rather than double 10-ring windows and that there are vacancies in some of these 10-rings.

High-silica zeolite SSZ-61 with dumbbell-shaped extra-large-pore channels.

The synthesis of the high-silica zeolite SSZ-61 using a particularly bulky polycyclic structure-directing agent and the subsequent elucidation of its unusual framework structure with extra-large dumbbell-shaped pore openings are described. By using information derived from a variety of X-ray powder diffraction and electron microscopy techniques, the complex framework structure, with 20 Si atoms in the asymmetric unit, could be determined and the full structure refined. The Si atoms at the waist of the dumbbell are only three-connected and are bonded to terminal O atoms pointing into the channel. Unlike the six previously reported extra-large-pore zeolites, SSZ-61 contains no heteroatoms in the framework and can be calcined easily. This, coupled with the possibility of inserting a catalytically active center in the channel between the terminal O atoms in place of H(+), afford SSZ-61 intriguing potential for catalytic applications.

Synthesis, structural elucidation, and catalytic properties in olefin epoxidation of the polymeric hybrid material [Mo3O9(2-[3(5)-pyrazolyl]pyridine)]n.

The reaction of [MoO2Cl2(pzpy)] (1) (pzpy = 2-[3(5)-pyrazolyl]pyridine) with water in an open reflux system (16 h), in a microwave synthesis system (120 °C, 2 h), or in a Teflon-lined stainless steel digestion bomb (100 °C, 19 h) gave the molybdenum oxide/pyrazolylpyridine polymeric hybrid material [Mo3O9(pzpy)]n (2) as a microcrystalline powder in yields of 72­79%. Compound 2 can also be obtained by the hydrothermal reaction of MoO3, pzpy, and H2O at 160 °C for 3 d. Secondary products isolated from the reaction solutions included the salt (pzpyH)2(MoCl4) (3) (pzpyH = 2-[3(5)-pyrazolyl]pyridinium), containing a very rare example of the tetrahedral MoCl4(2­) anion, and the tetranuclear compound [Mo4O12(pzpy)4] (4). Reaction of 2 with excess tert-butylhydroperoxide (TBHP) led to the isolation of the oxodiperoxo complex [MoO(O2)2(pzpy)] (5). Single-crystal X-ray structures of 3 and 5 are described. Fourier transform (FT)-IR and FT Raman spectra for 1, 4, and 5 were assigned based on density functional theory calculations. The structure of 2 was determined from synchrotron powder X-ray diffraction data in combination with other physicochemical information. In 2, a hybrid organic­inorganic one-dimensional (1D) polymer, ∞(1)[Mo3O9(pzpy)], is formed by the connection of two very distinct components: a double ladder-type inorganic core reminiscent of the crystal structure of MoO3 and 1D chains of corner-sharing distorted {MoO4N2} octahedra. Compound 2 exhibits moderate activity and high selectivity when used as a (pre)catalyst for the epoxidation of cis-cyclooctene with TBHP. Under the reaction conditions used, 2 is poorly soluble and is gradually converted into 5, which is at least partly responsible for the catalytic reaction.

A two-dimensional zeolitic imidazolate framework with a cushion-shaped cavity for CO2 adsorption.

A new two-dimensional zeolitic imidazolate framework (named as ZIF-L) was synthesized in zinc salt and 2-methylimidazole (Hmim) aqueous solution at room temperature. ZIF-L (Zn(mim)2·(Hmim)1/2·(H2O)3/2 or C10H16N5O3/2Zn) has unique cushion-shaped cavities and leaf-like crystal morphology, and exhibits excellent CO2 adsorption properties.

Hexakis(urea-κO)zinc(II) dinitrate at 110 and 250†K: uniaxial negative thermal expansion.

The crystal structure of the title compound, [Zn{CO(NH(2))(2)}(6)](NO(3))(2), has been determined at 110 and 250 K. The structure is stabilized by 12 individual hydrogen bonds, both intra- and intermolecular. Analysis of the thermal expansion tensor, based on unit cells determined over a temperature range of 180 K, shows uniaxial compression in the direction of the b axis during warming. The hydrogen bonds form layers perpendicular to this axis and these layers are connected by coordinative bonds parallel to the axis. As expected, the intermolecular hydrogen bonds expand during warming. Surprisingly, the coordinative bonds contract, accompanied by changes in the O-Zn-O angles. Overall, this behaviour can be described as an accordion-like effect.