ORCID Profile
0000-0002-8271-3906
Current Organisation
Stockholm University
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Inorganic materials (incl. nanomaterials) | Biochemistry and cell biology | Structural biology (incl. macromolecular modelling) |
Publisher: International Union of Crystallography (IUCr)
Date: 2020
DOI: 10.1107/S2052252519016105
Abstract: 3D electron diffraction (3DED) has been used to follow polymorph evolution in the crystallization of glycine from aqueous solution. The three polymorphs of glycine which exist under ambient conditions follow the stability order β α γ. The least stable β polymorph forms within the first 3 min, but this begins to yield the α-form after only 1 min more. Both structures could be determined from continuous rotation electron diffraction data collected in less than 20 s on crystals of thickness ∼100 nm. Even though the γ-form is thermodynamically the most stable polymorph, kinetics favour the α-form, which dominates after prolonged standing. In the same s le, some β and one crystallite of the γ polymorph were also observed.
Publisher: Cold Spring Harbor Laboratory
Date: 05-04-2019
DOI: 10.1101/600387
Abstract: Micro-crystal electron diffraction (MicroED) has recently shown potential for structural biology. It enables studying biomolecules from micron-sized 3D crystals that are too small to be studied by conventional X-ray crystallography. However, to the best of our knowledge, MicroED has only been applied to re-determine protein structures that had already been solved previously by X-ray diffraction. Here we present the first unknown protein structure – an R2lox enzyme – solved using MicroED. The structure was phased by molecular replacement using a search model of 35% sequence identity. The resulting electrostatic scattering potential map at 3.0 Å resolution was of sufficient quality to allow accurate model building and refinement. Our results demonstrate that MicroED has the potential to become a widely applicable tool for revealing novel insights into protein structure and function, opening up new opportunities for structural biologists.
Publisher: Springer Science and Business Media LLC
Date: 11-03-2013
DOI: 10.1038/SREP01415
Publisher: AIP Publishing
Date: 15-10-2009
DOI: 10.1063/1.3248372
Abstract: GaAs thin films grown on Si (100) and (111) substrates by metal-organic chemical vapor deposition were investigated by electron microscopy. It was found that the growth rate of the GaAs epitaxial layers on Si (100) was faster than that on Si (111) due to a lower Si (111) surface energy. The morphologies and internal crystal structure quality of GaAs films grown on Si (111) were better than those grown on Si (100). It was also found that postannealing at high temperature can improve the morphology of the epitaxial layer surface and reduce lattice defects in the thin films.
Publisher: Elsevier BV
Date: 04-2018
DOI: 10.1016/J.STR.2018.02.015
Abstract: Recent developments of novel electron diffraction techniques have shown to be powerful for determination of atomic resolution structures from micron- and nano-sized crystals, too small to be studied by single-crystal X-ray diffraction. In this work, the structure of a rare lysozyme polymorph is solved and refined using continuous rotation MicroED data and standard X-ray crystallographic software. Data collection was performed on a standard 200 kV transmission electron microscope (TEM) using a highly sensitive detector with a short readout time. The data collection is fast (∼3 min per crystal), allowing multiple datasets to be rapidly collected from a large number of crystals. We show that merging data from 33 crystals significantly improves not only the data completeness, overall I/σ and the data redundancy, but also the quality of the final atomic model. This is extremely useful for electron beam-sensitive crystals of low symmetry or with a preferred orientation on the TEM grid.
Publisher: Royal Society of Chemistry (RSC)
Date: 17-09-2014
DOI: 10.1039/C4TA04301D
Publisher: Wiley
Date: 21-01-2021
Publisher: Cold Spring Harbor Laboratory
Date: 29-04-2020
DOI: 10.1101/2020.04.27.064188
Abstract: Visualizing drug inhibitor binding interactions at the atomic level is important for both structure-based drug design and fragment-based screening methods. Rapid and uniform soaking with potentially less lattice defects make small macromolecular crystals attractive targets for studying ligand biding using 3D microcrystal electron diffraction (MicroED). However, so far no drug inhibitor binding interactions could unambiguously be resolved by electron diffraction. Here, we use MicroED to study the binding of a sulfonamide inhibitor to human carbonic anhydrase isoform II (HCA II). We show that MicroED data can efficiently be collected in-house on a conventional TEM from thin hydrated microcrystals after a brief soaking with the clinical drug inhibitor acetazolamide (AZM). The data are of high enough quality to unequivocally fit and resolve the inhibitor bound to the active site of the protein. We anticipate MicroED can play an important role in future drug discovery experiments, complementing existing methods in structural biology such as x-ray and neutron diffraction.
Publisher: AIP Publishing
Date: 11-02-2013
DOI: 10.1063/1.4792053
Abstract: GaAs growth behaviour under the presence of Au nanoparticles on GaAs {111}B substrate is investigated using electron microscopy. It has been found that, during annealing, enhanced Ga surface diffusion towards Au nanoparticles leads to the GaAs epitaxial growth into {113}B faceted triangular pyramids under Au nanoparticles, governed by the thermodynamic growth, while during conventional GaAs growth, growth kinetics dominates, resulting in the flatted triangular pyramids at high temperature and the epitaxial nanowires growth at relatively low temperature. This study provides an insight of Au nanoparticle impact on GaAs growth, which is critical for understanding the formation mechanisms of semiconductor nanowires.
Publisher: Wiley
Date: 15-08-2013
Abstract: Novel silica nanoparticles mimicking virus surface topography are prepared. It is demonstrated that increases in nanoscale surface roughness promote both binding of biomolecules and cellular uptake thus, the cellular delivery efficiency is significantly increased (scale bars 20 μm).
Publisher: AIP Publishing
Date: 25-11-2013
DOI: 10.1063/1.4834377
Abstract: Simultaneous growth of ⟨111⟩B free-standing and ±[110] lateral GaAsP epitaxial nanowires on GaAs (001) substrates were observed and investigated by electron microscopy and crystallographic analysis. It was found that the growth of both free-standing and lateral ternary nanowires via Au catalysts was driven by the fact that Au catalysts prefer to maintain low-energy {111}B interfaces with surrounding GaAs(P) materials: in the case of free-standing nanowires, Au catalysts maintain {111}B interfaces with their underlying GaAsP nanowires while in the case of lateral nanowires, each Au catalyst remain their side {111}B interfaces with the surrounding GaAs(P) material during the lateral nanowire growth.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 02-08-2019
Abstract: We used 3D microcrystal electron diffraction (MicroED) to solve a new protein structure.
Publisher: American Chemical Society (ACS)
Date: 20-07-2021
Publisher: AIP Publishing
Date: 20-05-2013
DOI: 10.1063/1.4807597
Abstract: In this study, Pd was used as catalyst to grow one-dimensional InAs nanostructures on GaAs (111)B substrates in order to explore the growth mechanism and the effect of non-gold catalysts in growing epitaxial III-V nanostructures. With detailed morphological, structural, and chemical characterizations using electron microscopy, coupled with analysis of the Pd-In binary phase diagram, it was found that size of Pd nanoparticles plays a key role in determining the growth mechanism of one-dimensional InAs nanostructures.
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7CE01967J
Abstract: Locations of Brønsted acids confined in the 10-ring channel of ferrierite have been unravelled by refining structural models of as-made and probe-molecule-adsorbed s les against powder X-ray diffraction data, respectively.
Publisher: American Chemical Society (ACS)
Date: 18-05-2021
Publisher: American Chemical Society (ACS)
Date: 10-08-2020
DOI: 10.1021/JACS.0C06329
Publisher: Springer Science and Business Media LLC
Date: 2013
DOI: 10.1557/OPL.2013.990
Abstract: In this study, Pd thin film is used as catalyst to grow epitaxial InAs nanowires on GaAs(111) B substrate in a metal-organic chemical vapor deposition reactor to explore the growth mechanism and the effects of non-gold catalysts in the growth of III-V epitaxial nanowires. Through detailed morphological, structural and chemical characterization using scanning and transmission electron microscopy, it is found that defect-free zinc-blende structured epitaxial InAs nanowires are grown along the directions with four {111} sidewall facets forming a diamond shaped cross-section. Furthermore, the interface between the nanowire/catalyst is found to be the uncommon {113} planes. It is anticipated that these zinc-blende structured InAs nanowires are grown via the vapor-liquid-solid mechanism. The defect-free nature of these nanowires arises from the non- growth direction and non-{111} nanowire/catalyst interface.
Publisher: Wiley
Date: 16-03-2016
Abstract: A novel structural coding approach combining structure solution, prediction, and the targeted synthesis of new zeolites with expanding complexity and embedded isoreticular structures was recently proposed. Using this approach, the structures of two new zeolites in the RHO family, PST-20 and PST-25, were predicted and synthesized. Herein, by extending this approach, the next two higher generation members of this family, PST-26 and PST-28, have been predicted and synthesized. These two zeolites have much larger unit cell volumes (422,655 Å(3) and 614,912 Å(3), respectively) than those of the lower generations. Their crystallization was confirmed by a combination of both powder X-ray and electron diffraction techniques. Aluminate and water concentrations in the synthetic mixture were found to be the two most critical factors influencing the structural expansion of embedded isoreticular zeolites under the synthetic conditions studied herein.
Publisher: Elsevier BV
Date: 12-2021
DOI: 10.1016/J.DDTEC.2020.12.002
Abstract: Microcrystal electron diffraction (MicroED) has recently shown to be a promising technique for structure determination in structural biology and pharmaceutical chemistry. Here, we discuss the unique properties of electrons and motivate its use for diffraction experiments. We review the latest developments in MicroED, and illustrate its applications in macromolecular crystallography, fragment screening and structure guided drug discovery. We discuss the perspectives of MicroED in synthetic chemistry and pharmaceutical development. We anticipate that the rapid advances MicroED showcased here will promote further development of electron crystallography and open up new opportunities for drug discovery.
Publisher: Elsevier BV
Date: 10-2010
Publisher: Springer Science and Business Media LLC
Date: 19-08-2021
DOI: 10.1038/S41467-021-25335-7
Abstract: Micro-crystal electron diffraction (MicroED) has shown great potential for structure determination of macromolecular crystals too small for X-ray diffraction. However, specimen preparation remains a major bottleneck. Here, we report a simple method for preparing MicroED specimens, named Preassis, in which excess liquid is removed through an EM grid with the assistance of pressure. We show the ice thicknesses can be controlled by tuning the pressure in combination with EM grids with appropriate carbon hole sizes. Importantly, Preassis can handle a wide range of protein crystals grown in various buffer conditions including those with high viscosity, as well as s les with low crystal concentrations. Preassis is a simple and universal method for MicroED specimen preparation, and will significantly broaden the applications of MicroED.
Publisher: IEEE
Date: 12-2012
Publisher: American Association for the Advancement of Science (AAAS)
Date: 17-05-2019
Abstract: The chirality of a tiny organic crystal is determined with electron diffraction
Publisher: IEEE
Date: 12-2010
Publisher: American Chemical Society (ACS)
Date: 03-10-2013
DOI: 10.1021/CG4009569
Publisher: American Chemical Society (ACS)
Date: 04-02-2016
DOI: 10.1021/JACS.5B12484
Abstract: A bismuth-based metal-organic framework (MOF), [Bi(BTC)(H2O)]·2H2O·MeOH denoted CAU-17, was synthesized and found to have an exceptionally complicated structure with helical Bi-O rods cross-linked by 1,3,5-benzenetricarboxylate (BTC(3-)) ligands. Five crystallographically independent 1D channels including two hexagonal channels, two rectangular channels, and one triangular channel have accessible diameters of 9.6, 9.6, 3.6, 3.6, and 3.4 Å, respectively. The structure is further complicated by twinning. Rod-incorporated MOF structures typically have underlying nets with only one unique node and three or four unique edges. In contrast, topological analysis of CAU-17 revealed unprecedented complexity for a MOF structure with 54 unique nodes and 135 edges. The complexity originates from the rod packing and the rods themselves, which are related to aperiodic helices.
Publisher: International Union of Crystallography (IUCr)
Date: 17-02-2021
DOI: 10.1107/S2059798320016368
Abstract: Microcrystal electron diffraction (MicroED) has recently emerged as a promising method for macromolecular structure determination in structural biology. Since the first protein structure was determined in 2013, the method has been evolving rapidly. Several protein structures have been determined and various studies indicate that MicroED is capable of (i) revealing atomic structures with charges, (ii) solving new protein structures by molecular replacement, (iii) visualizing ligand-binding interactions and (iv) determining membrane-protein structures from microcrystals embedded in lipidic mesophases. However, further development and optimization is required to make MicroED experiments more accurate and more accessible to the structural biology community. Here, we provide an overview of the current status of the field, and highlight the ongoing development, to provide an indication of where the field may be going in the coming years. We anticipate that MicroED will become a robust method for macromolecular structure determination, complementing existing methods in structural biology.
Publisher: Springer Science and Business Media LLC
Date: 17-09-0100
DOI: 10.1038/S41467-021-25817-8
Abstract: Porous electrodes with extraordinary capacitances in liquid electrolytes are oftentimes incompetent when gel electrolyte is applied because of the escalating ion diffusion limitations brought by the difficulties of infilling the pores of electrode with gels. As a result, porous electrodes usually exhibit lower capacitance in gel electrolytes than that in liquid electrolytes. Benefiting from the swift ion transport in intrinsic hydrated nanochannels, the electrochemical capacitance of the nanofluidic voidless electrode (5.56% porosity) is nearly equal in gel and liquid electrolytes with a difference of ~1.8%. In gel electrolyte, the areal capacitance reaches 8.94 F cm −2 with a gravimetric capacitance of 178.8 F g −1 and a volumetric capacitance of 321.8 F cm −3 . The findings are valuable to solid-state electrochemical energy storage technologies that require high-efficiency charge transport.
Publisher: American Chemical Society (ACS)
Date: 27-05-2011
DOI: 10.1021/CG2003657
Publisher: Elsevier BV
Date: 07-2018
Publisher: IOP Publishing
Date: 22-11-2013
DOI: 10.1088/0957-4484/24/50/505705
Abstract: Single-crystal tungsten nanobelts with thicknesses from tens to hundreds of nanometers, widths of several micrometers and lengths of tens of micrometers were synthesized using chemical vapor deposition. Surface energy minimization was believed to have played a crucial role in the growth of the synthesized nanobelts enclosed by the low-energy {110} crystal planes of body-centered-cubic structure. The anisotropic growth of the crystallographically equivalent {110} crystal planes could be attributable to the asymmetric concentration distribution of the tungsten atom vapor around the nanobelts during the growth process. The elastic moduli of the synthesized tungsten nanobelts with thicknesses ranging from 65 to 306 nm were accurately measured using a newly developed thermal vibration method. The measured modulus values of the tungsten nanobelts were thickness-dependent. After eliminating the effect of surface oxidization using a core-shell model, the elastic modulus of tungsten nanobelts became constant, which is close to that of the bulk tungsten value of 410 GPa.
Publisher: Wiley
Date: 05-01-2022
Abstract: Indomethacin is a clinically classical non-steroidal anti-inflammatory drug that has been marketed since 1965. The third polymorph, Form δ, was discovered by both melt and solution crystallization in 1974. δ-indomethacin cannot be cultivated as large single crystals suitable for X-ray crystallography and, therefore, its crystal structure has not yet been determined. Here, we report the structure elucidation of δ-indomethacin by 3D electron diffraction and reveal the truth that melt-crystallized and solution-crystallized δ-indomethacin are in fact two polymorphs with different crystal structures. We propose to keep the solution-crystallized polymorph as Form δ and name the melt-crystallized polymorph as Form θ. Intriguingly, both structures display plastic flexibility based on a slippage mechanism, making indomethacin the first drug to have two plastic polymorphs. This discovery and correction of a 47-year-old misunderstanding signify that 3D electron diffraction has become a powerful tool for polymorphic structural studies.
Publisher: Cold Spring Harbor Laboratory
Date: 10-06-2019
DOI: 10.1101/665448
Abstract: Micro-crystal electron diffraction (MicroED) has shown great potential for structure determination of macromolecular crystals too small for X-ray diffraction. However, specimen preparation remains a major bottleneck. Here, we report a simple method for preparing MicroED specimens, named Preassis, in which excess liquid is removed through an EM grid with the assistance of pressure. We show the ice thicknesses can be controlled by tuning the pressure in combination with EM grids with appropriate hole sizes. Importantly, Preassis can handle a wide range of protein crystals grown in various buffer conditions including those with high viscosity, as well as s les with low crystal contents. Preassis is a simple and universal method for MicroED specimen preparation, and will significantly broaden the applications of MicroED.
Publisher: Springer Science and Business Media LLC
Date: 20-04-2023
DOI: 10.1038/S41557-023-01186-1
Abstract: Continuous-rotation 3D electron diffraction methods are increasingly popular for the structure analysis of very small organic molecular crystals and crystalline inorganic materials. Dynamical diffraction effects cause non-linear deviations from kinematical intensities that present issues in structure analysis. Here, a method for structure analysis of continuous-rotation 3D electron diffraction data is presented that takes multiple scattering effects into account. Dynamical and kinematical refinements of 12 compounds—ranging from small organic compounds to metal–organic frameworks to inorganic materials—are compared, for which the new approach yields significantly improved models in terms of accuracy and reliability with up to fourfold reduction of the noise level in difference Fourier maps. The intrinsic sensitivity of dynamical diffraction to the absolute structure is also used to assign the handedness of 58 crystals of 9 different chiral compounds, showing that 3D electron diffraction is a reliable tool for the routine determination of absolute structures.
Publisher: Wiley
Date: 02-2022
Publisher: International Union of Crystallography (IUCr)
Date: 20-08-2020
DOI: 10.1107/S1600576720009590
Abstract: 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.
Publisher: Cold Spring Harbor Laboratory
Date: 08-04-2021
DOI: 10.1101/2021.04.07.438860
Abstract: Microcrystal electron diffraction (MicroED) has the potential to considerably impact the field of structural biology. Indeed, the method can solve atomic structures of a wide range of molecules, beyond the reach of single particle cryo-electron microscopy, exploiting crystals too small for X-ray diffraction (XRD) even using X-ray free-electron lasers. However, until the first unknown protein structure – a R2-like ligand-binding oxidase from Sulfolobus acidocaldarius ( Sa R2lox) – was recently solved at 3.0 Å resolution, MicroED had only been used to study known protein structures previously obtained by XRD. Here, after adapting s le preparation protocols, the structure of the Sa R2lox protein originally solved by MicroED was redetermined by XRD at 2.1 Å resolution. In light of the higher resolution XRD data and taking into account experimental differences of the methods, the quality of the MicroED structure is examined. The analysis demonstrates that MicroED provided an overall accurate model, revealing biologically relevant information specific to Sa R2lox, such as the absence of an ether cross-link, but did not allow to detect the presence of a ligand visible by XRD in the protein binding pocket. Furthermore, strengths and weaknesses of MicroED compared to XRD are discussed in the perspective of this real-life protein ex le. The study provides fundaments to help MicroED become a method of choice for solving novel protein structures. The first unknown protein structure solved by microcrystal electron diffraction (MicroED) was recently published. The redetermination by X-ray diffraction of this protein structure provides new insights into the strengths and weaknesses of the promising MicroED method.
Publisher: American Chemical Society (ACS)
Date: 05-10-2012
DOI: 10.1021/NL303028U
Abstract: We report the epitaxial growth of defect-free zinc-blende structured InAs nanowires on GaAs{111}(B) substrates using palladium catalysts in a metal-organic chemical vapor deposition reactor. Through detailed morphological, structural, and chemical characterizations using electron microscopy, it is found that these defect-free InAs nanowires grew along the directions with four low-energy {111} faceted side walls and {1[combining overline]1[combining overline]3[combining overline]} nanowire/catalyst interfaces. It is anticipated that these defect-free nanowires benefit from the fact that the nanowire/catalyst interfaces does not contain the {111} planes, and the nanowire growth direction is not along the directions. This study provides an effective approach to control the crystal structure and quality of epitaxial III-V nanowires.
Publisher: Research Square Platform LLC
Date: 12-02-2021
DOI: 10.21203/RS.3.RS-209068/V1
Abstract: Micro-crystal electron diffraction (MicroED) has shown great potential for structure determination of macromolecular crystals too small for X-ray diffraction. However, specimen preparation remains a major bottleneck. Here, we report a simple method for preparing MicroED specimens, named Preassis, in which excess liquid is removed through an EM grid with the assistance of pressure. We show the ice thicknesses can be controlled by tuning the pressure in combination with EM grids with appropriate hole sizes. Importantly, Preassis can handle a wide range of protein crystals grown in various buffer conditions including those with high viscosity, as well as s les with low crystal contents. Preassis is a simple and universal method for MicroED specimen preparation, and will significantly broaden the applications of MicroED.
Publisher: Elsevier BV
Date: 06-2015
Publisher: American Chemical Society (ACS)
Date: 11-08-2022
DOI: 10.1021/JACS.2C05122
Publisher: IEEE
Date: 08-2010
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CC43867H
Abstract: Delicate α-Fe2O3 multi-shelled hollow spheres have been prepared by a simple and scalable spray drying method followed by annealing in air. The resulting material shows high specific capacity, good cycling stability, and excellent rate performance in lithium ion battery applications.
Publisher: Springer Science and Business Media LLC
Date: 27-07-2022
DOI: 10.1038/S41596-022-00720-8
Abstract: Metal-organic frameworks (MOFs) have attracted considerable interest due to their well-defined pore architecture and structural tunability on molecular dimensions. While single-crystal X-ray diffraction (SCXRD) has been widely used to elucidate the structures of MOFs at the atomic scale, the formation of large and well-ordered crystals is still a crucial bottleneck for structure determination. To alleviate this challenge, three-dimensional electron diffraction (3D ED) has been developed for structure determination of nano- (submicron-)sized crystals. Such 3D ED data are collected from each single crystal using transmission electron microscopy. In this protocol, we introduce the entire workflow for structural analysis of MOFs by 3D ED, from s le preparation, data acquisition and data processing to structure determination. We describe methods for crystal screening and handling of crystal agglomerates, which are crucial steps in s le preparation for single-crystal 3D ED data collection. We further present how to set up a transmission electron microscope for 3D ED data acquisition and, more importantly, offer suggestions for the optimization of data acquisition conditions. For data processing, including unit cell and space group determination, and intensity integration, we provide guidelines on how to use electron and X-ray crystallography software to process 3D ED data. Finally, we present structure determination from 3D ED data and discuss the important features associated with 3D ED data that need to be considered. We believe that this protocol provides critical details for implementing and utilizing 3D ED as a structure determination platform for nano- (submicron-)sized MOFs as well as other crystalline materials.
Publisher: IEEE
Date: 12-2010
Publisher: American Chemical Society (ACS)
Date: 30-09-2020
Publisher: American Chemical Society (ACS)
Date: 07-05-2010
DOI: 10.1021/JP100689S
Publisher: Springer Science and Business Media LLC
Date: 09-07-2019
DOI: 10.1038/S41467-019-10960-0
Abstract: Efficient use of energy for cooling applications is a very important and challenging field in science. Ultra-low temperature actuated ( T driving 80 °C) adsorption-driven chillers (ADCs) with water as the cooling agent are one environmentally benign option. The nanoscale metal-organic framework [Al(OH)(C 6 H 2 O 4 S)] denoted CAU-23 was discovered that possess favorable properties, including water adsorption capacity of 0.37 g H2O / g sorbent around p / p 0 = 0.3 and cycling stability of at least 5000 cycles. Most importantly the material has a driving temperature down to 60 °C, which allows for the exploitation of yet mostly unused temperature sources and a more efficient use of energy. These exceptional properties are due to its unique crystal structure, which was unequivocally elucidated by single crystal electron diffraction. Monte Carlo simulations were performed to reveal the water adsorption mechanism at the atomic level. With its green synthesis, CAU-23 is an ideal material to realize ultra-low temperature driven ADC devices.
Publisher: IEEE
Date: 12-2012
Publisher: American Chemical Society (ACS)
Date: 29-06-2012
DOI: 10.1021/NN300962Z
Abstract: The doping-dependent photoconductive properties of in idual GaAs nanowires have been studied by conductive atomic force microscopy. Linear responsivity against the bias voltage is observed for moderate n-doped GaAs wires with a Schottky contact under illumination, while that of the undoped ones exhibits a saturated response. The carrier lifetime of a single nanowire can be obtained by simulating the characteristic photoelectric behavior. Consistent with the photoluminescence results, the significant drop of minority hole lifetime, from several hundred to subpicoseconds induced by n-type doping, leads to the distinct photoconductive features. Moreover, by comparing with the photoelectric behavior of AlGaAs shelled nanowires, the equivalent recombination rate of carriers at the surface is assessed to be >1 × 10(12) s(-1) for 2 × 10(17)cm(-3) n-doped bare nanowires, nearly 30 times higher than that of the doping-related bulk effects. This work suggests that intentional doping in nanowires could change the charge status of the surface states and impose significant impact on the electrical and photoelectrical performances of semiconductor nanostructures.
Publisher: Wiley
Date: 02-2022
Publisher: Springer Science and Business Media LLC
Date: 23-08-2014
Publisher: IEEE
Date: 12-2014
Publisher: IOP Publishing
Date: 27-09-2012
DOI: 10.1088/0957-4484/23/41/415702
Abstract: Vertically oriented GaAs nanowires (NWs) are grown on Si(111) substrates using metal-organic chemical vapor deposition. Controlled epitaxial growth along the direction is demonstrated following the deposition of thin GaAs buffer layers and the elimination of structural defects, such as twin defects and stacking faults, is found for high growth rates. By systematically manipulating the AsH(3) (group-V) and TMGa (group-III) precursor flow rates, it is found that the TMGa flow rate has the most significant effect on the nanowire quality. After capping the minimal tapering and twin-free GaAs NWs with an AlGaAs shell, long exciton lifetimes (over 700 ps) are obtained for high TMGa flow rate s les. It is observed that the Ga adatom concentration significantly affects the growth of GaAs NWs, with a high concentration and rapid growth leading to desirable characteristics for optoelectronic nanowire device applications including improved morphology, crystal structure and optical performance.
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7CC03180G
Abstract: Bismuth subgallate was revealed as a coordination polymer providing insight into its solubility and gas sorption properties.
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CP52153B
Abstract: The development of technologically and economically viable strategies for large-scale fabrication of photoelectrodes is crucial for solar H2 production from photoelectrochemical water splitting. Herein, a low-cost and facile colloidal electrophoretic deposition approach was developed for scalable fabrication of hematite (α-Fe2O3) films. Large-sized uniform films (e.g. 80 mm × 70 mm) with tailored thickness and nanostructures can be easily prepared on conductive substrates within 2 minutes. The resultant films showed a high photocurrent of ∼1.1 mA cm(-2) at 1.23 V(RHE) under standard AM 1.5G illumination, which is among the highest reported values achieved on hematite films prepared using other complex colloidal approaches. The present work will pave a new avenue for fabrication of efficient photoelectrodes toward practically viable solar H2 production.
Publisher: American Chemical Society (ACS)
Date: 18-01-2013
DOI: 10.1021/NL304237B
Abstract: We report a novel phase separation phenomenon observed in the growth of ternary In(x)Ga(1-x)As nanowires by metalorganic chemical vapor deposition. A spontaneous formation of core-shell nanowires is investigated by cross-sectional transmission electron microscopy, revealing the compositional complexity within the ternary nanowires. It has been found that for In(x)Ga(1-x)As nanowires high precursor flow rates generate ternary In(x)Ga(1-x)As cores with In-rich shells, while low precursor flow rates produce binary GaAs cores with ternary In(x)Ga(1-x)As shells. First-principle calculations combined with thermodynamic considerations suggest that this phenomenon is due to competitive alloying of different group-III elements with Au catalysts, and variations in elemental concentrations of group-III materials in the catalyst under different precursor flow rates. This study shows that precursor flow rates are critical factors for manipulating Au catalysts to produce nanowires of desired composition.
Publisher: American Chemical Society (ACS)
Date: 08-03-2012
DOI: 10.1021/CG201725G
Publisher: Wiley
Date: 31-05-2010
Publisher: CRC Press
Date: 22-11-2017
DOI: 10.1201/B15035-47
Publisher: Springer Science and Business Media LLC
Date: 10-05-2021
DOI: 10.1038/S41467-021-22590-6
Abstract: MyD88 and MAL are Toll-like receptor (TLR) adaptors that signal to induce pro-inflammatory cytokine production. We previously observed that the TIR domain of MAL (MAL TIR ) forms filaments in vitro and induces formation of crystalline higher-order assemblies of the MyD88 TIR domain (MyD88 TIR ). These crystals are too small for conventional X-ray crystallography, but are ideally suited to structure determination by microcrystal electron diffraction (MicroED) and serial femtosecond crystallography (SFX). Here, we present MicroED and SFX structures of the MyD88 TIR assembly, which reveal a two-stranded higher-order assembly arrangement of TIR domains analogous to that seen previously for MAL TIR . We demonstrate via mutagenesis that the MyD88 TIR assembly interfaces are critical for TLR4 signaling in vivo, and we show that MAL promotes unidirectional assembly of MyD88 TIR . Collectively, our studies provide structural and mechanistic insight into TLR signal transduction and allow a direct comparison of the MicroED and SFX techniques.
Publisher: International Union of Crystallography (IUCr)
Date: 05-07-2018
DOI: 10.1107/S1600576718007604
Abstract: The continuous rotation electron diffraction (cRED) method has the capability of providing fast three-dimensional electron diffraction data collection on existing and future transmission electron microscopes unknown structures could be potentially solved and refined using cRED data collected from nano- and submicrometre-sized crystals. However, structure refinements of cRED data using SHELXL often lead to relatively high R 1 values when compared with those refined against single-crystal X-ray diffraction data. It is therefore necessary to analyse the quality of the structural models refined against cRED data. In this work, multiple cRED data sets collected from different crystals of an oxofluoride (FeSeO 3 F) and a zeolite (ZSM-5) with known structures are used to assess the data consistency and quality and, more importantly, the accuracy of the structural models refined against these data sets. An evaluation of the precision and consistency of the cRED data by examination of the statistics obtained from the data processing software DIALS is presented. It is shown that, despite the high R 1 values caused by dynamical scattering and other factors, the refined atomic positions obtained from the cRED data collected for different crystals are consistent with those of the reference models refined against single-crystal X-ray diffraction data. The results serve as a reference for the quality of the cRED data and the achievable accuracy of the structural parameters.
Publisher: Springer Science and Business Media LLC
Date: 10-11-2022
DOI: 10.1038/S41557-022-01079-9
Abstract: The controllable packing of functional nanoparticles (NPs) into crystalline lattices is of interest in the development of NP-based materials. Here we demonstrate that the size, morphology and symmetry of such supercrystals can be tailored by adjusting the surface dynamics of their constituent NPs. In the presence of excess tetraethylammonium cations, atomically precise [Au
Publisher: American Chemical Society (ACS)
Date: 07-11-2012
DOI: 10.1021/JA308933K
Abstract: Bi(1.85)Mn(0.15)Te(3) hexagonal nanoplates with a width of ~200 nm and a thickness of ~20 nm were synthesized using a solvothermal method. According to the structural characterization and compositional analysis, the Mn(2+) and Mn(3+) ions were found to substitute Bi(3+) ions in the lattice. High-level Mn doping induces significant lattice distortion and decreases the crystal lattice by 1.07% in the a axis and 3.18% in the c axis. A high ferromagnetic state with a Curie temperature of ~45 K is observed in these nanoplates due to Mn(2+) and Mn(3+) ion doping, which is a significant progress in the field of electronics and spintronics.
Publisher: American Chemical Society (ACS)
Date: 29-11-2017
Publisher: American Chemical Society (ACS)
Date: 07-06-2013
DOI: 10.1021/JP4041666
Publisher: American Chemical Society (ACS)
Date: 03-12-2019
Publisher: American Chemical Society (ACS)
Date: 28-08-2018
Abstract: Aluminum-based metal-organic frameworks (MOFs), [Al(OH)(SDC)]
Publisher: American Chemical Society (ACS)
Date: 19-08-2011
DOI: 10.1021/CM201439D
Publisher: IEEE
Date: 12-2012
Publisher: International Union of Crystallography (IUCr)
Date: 22-04-2022
DOI: 10.1107/S1600576722002758
Abstract: Three-dimensional electron diffraction (3D ED)/microcrystal electron diffraction (MicroED) techniques are gaining in popularity. However, the data processing often does not fit existing graphical user interface software, instead requiring the use of the terminal or scripting. Scipion-ED , described in this article, provides a graphical user interface and extendable framework for processing of 3D ED/MicroED data. An illustrative project is described, in which multiple 3D ED/MicroED data sets collected on tetragonal lysozyme were processed with DIALS through the Scipion-ED interface. The ability to resolve unmodelled features in the electrostatic potential map was compared between three strategies for merging data sets.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0DT00235F
Abstract: Highly porous three-dimensional Al- and Ga-MOFs with radical catecholate linker molecules were synthesized and characterized by electron diffraction, molecular simulation, Rietveld refinement and N 2 sorption measurements.
Publisher: AIP Publishing
Date: 12-08-2013
DOI: 10.1063/1.4818682
Abstract: In this study, the structural quality of Au-catalyzed InAs nanowires grown by molecular beam epitaxy is investigated. Through detailed electron microscopy characterizations and analysis of binary Au-In phase diagram, it is found that defect-free InAs nanowires can be induced by smaller catalysts with a high In concentration, while comparatively larger catalysts containing less In induce defected InAs nanowires. This study indicates that the structural quality of InAs nanowires can be controlled by the size of Au catalysts when other growth conditions remain as constants.
Publisher: Springer Science and Business Media LLC
Date: 12-12-2011
Abstract: GeMn/Ge epitaxial 'superlattices' grown by molecular beam epitaxy with different growth conditions have been systematically investigated by transmission electron microscopy. It is revealed that periodic arrays of GeMn nanodots can be formed on Ge and GaAs substrates at low temperature (approximately 70°C) due to the matched lattice constants of Ge (5.656 Å) and GaAs (5.653 Å), while a periodic Ge/GeMn superlattice grown on Si showed disordered GeMn nanodots with a large amount of stacking faults, which can be explained by the fact that Ge and Si have a large lattice mismatch. Moreover, by varying growth conditions, the GeMn/Ge superlattices can be manipulated from having disordered GeMn nanodots to ordered coherent nanodots and then to ordered nanocolumns. PACS : 75.50.Pp 61.72.-y 66.30.Pa 68.37.L.
Publisher: MDPI AG
Date: 09-11-2021
DOI: 10.3390/SYM13112131
Abstract: 3D electron diffraction (3D ED), also known as micro-crystal electron diffraction (MicroED), is a rapid, accurate, and robust method for structure determination of submicron-sized crystals. 3D ED has mainly been applied in material science until 2013, when MicroED was developed for studying macromolecular crystals. MicroED was considered as a cryo-electron microscopy method, as MicroED data collection is usually carried out in cryogenic conditions. As a result, some researchers may consider that 3D ED/MicroED data collection on crystals of small organic molecules can only be performed in cryogenic conditions. In this work, we determined the structure for sucrose and azobenzene tetracarboxylic acid (H4ABTC). The structure of H4ABTC is the first crystal structure ever reported for this molecule. We compared data quality and structure accuracy among datasets collected under cryogenic conditions and room temperature. With the improvement in data quality by data merging, it is possible to reveal hydrogen atom positions in small organic molecule structures under both temperature conditions. The experimental results showed that, if the s le is stable in the vacuum environment of a transmission electron microscope (TEM), the data quality of datasets collected under room temperature is at least as good as data collected under cryogenic conditions according to various indicators (resolution, I/σ(I), CC1/2 (%), R1, Rint, ADRA).
Publisher: Elsevier BV
Date: 11-2010
Publisher: IOP Publishing
Date: 07-12-2009
DOI: 10.1088/0957-4484/21/3/035604
Abstract: Straight, vertically aligned GaAs nanowires were grown on Si(111) substrates coated with thin GaAs buffer layers. We find that the V/III precursor ratio and growth temperature are crucial factors influencing the morphology and quality of buffer layers. A double layer structure, consisting of a thin initial layer grown at low V/III ratio and low temperature followed by a layer grown at high V/III ratio and high temperature, is crucial for achieving straight, vertically aligned GaAs nanowires on Si(111) substrates. An in situ annealing step at high temperature after buffer layer growth improves the surface and structural properties of the buffer layer, which further improves the morphology of the GaAs nanowire growth. Through such optimizations we show that vertically aligned GaAs nanowires can be fabricated on Si(111) substrates and achieve the same structural and optical properties as GaAs nanowires grown directly on GaAs(111)B substrates.
Publisher: Wiley
Date: 05-01-2022
Abstract: Indomethacin is a clinically classical non‐steroidal anti‐inflammatory drug that has been marketed since 1965. The third polymorph, Form δ, was discovered by both melt and solution crystallization in 1974. δ‐indomethacin cannot be cultivated as large single crystals suitable for X‐ray crystallography and, therefore, its crystal structure has not yet been determined. Here, we report the structure elucidation of δ‐indomethacin by 3D electron diffraction and reveal the truth that melt‐crystallized and solution‐crystallized δ‐indomethacin are in fact two polymorphs with different crystal structures. We propose to keep the solution‐crystallized polymorph as Form δ and name the melt‐crystallized polymorph as Form θ. Intriguingly, both structures display plastic flexibility based on a slippage mechanism, making indomethacin the first drug to have two plastic polymorphs. This discovery and correction of a 47‐year‐old misunderstanding signify that 3D electron diffraction has become a powerful tool for polymorphic structural studies.
Publisher: International Union of Crystallography (IUCr)
Date: 30-10-2021
DOI: 10.1107/S2052252521010101
Abstract: Time-resolved carbamazepine crystallization from wet ethanol has been monitored using a combination of cryoTEM and 3D electron diffraction. Carbamazepine is shown to crystallize exclusively as a dihydrate after 180 s. When the timescale was reduced to 30 s, three further polymorphs could be identified. At 20 s, the development of early stage carbamazepine dihydrate was observed through phase separation. This work reveals two possible crystallization pathways present in this active pharmaceutical ingredient.
Publisher: International Union of Crystallography (IUCr)
Date: 29-11-2022
DOI: 10.1107/S1600576722009633
Abstract: Three-dimensional electron diffraction (3D ED) has become an effective technique to determine the structures of submicrometre- (nanometre-)sized crystals. In this work, energy-filtered 3D ED was implemented using a post-column energy filter in both STEM mode and TEM mode [(S)TEM denoting (scanning) transmission electron microscope]. The setups for performing energy-filtered 3D ED on a Gatan imaging filter are described. The technique and protocol improve the accessibility of energy-filtered 3D ED post-column energy filters, which are available in many TEM laboratories. In addition, a crystal tracking method in STEM mode using high-angle annular dark-field imaging is proposed. This method enables the user to monitor the crystal position while collecting 3D ED data at the same time, allowing a larger tilt range without foregoing any diffraction frames or imposing extra electron dose. In order to compare the differences between energy-filtered and unfiltered 3D ED data sets, three well known crystallized inorganic s les have been studied in detail. For these s les, the final R 1 values improved by 10–30% for the energy-filtered data sets compared with the unfiltered data sets, and the structures became more chemically reasonable. Possible reasons for improvement are also discussed.
Publisher: Wiley
Date: 30-10-2018
Abstract: Single-crystal electron diffraction has shown to be powerful for structure determination of nano- and submicron-sized crystals that are too small to be studied by single-crystal X-ray diffraction. However, it has been very challenging to obtain high quality electron diffraction data from beam sensitive crystals such as metal-organic frameworks (MOFs). It is even more difficult to locate guest species in the pores of MOF crystals. Here, we present synthesis of a novel porous cobalt MOF with 1D channels, [Co
Publisher: Springer Science and Business Media LLC
Date: 24-10-2012
Abstract: In this letter, we quantitatively investigated epitaxial GaAs nanowires catalyzed by thin Au films of different thicknesses on GaAs (111) B substrates in a metal-organic chemical vapor deposition reactor. Prior to nanowire growth, the de-wetting of Au thin films to form Au nanoparticles on GaAs (111) B in AsH 3 ambient at different temperatures is investigated. It is found that with increasing film thickness, the size of the Au nanoparticles increases while the density of the nanoparticles reduces. Furthermore, higher annealing temperature produces larger Au nanoparticles for a fixed film thickness. As expected, the diameters and densities of the as-grown GaAs nanowires catalyzed by these thin Au films reflect these trends.
Publisher: American Chemical Society (ACS)
Date: 21-08-2020
DOI: 10.1021/JACS.0C06978
Publisher: Springer Science and Business Media LLC
Date: 23-01-2023
DOI: 10.1038/S42004-022-00804-2
Abstract: The spherulitic morphology is considered to be the most common morphology of crystalline materials and is particularly apparent in melt-crystallized products. Yet, historically, the polycrystalline nature of spherulites has hindered successful crystal structure determination. Here, we report the direct structure determination of a clinical drug, vemurafenib (VMN), in compact spherulite form using 3D electron diffraction (3D ED). VMN has four known polymorphs. We first solved the crystal structures of α-, β-, and γ-VMN from compact spherulites using 3D ED, and the resulting structures were highly consistent with those obtained by single-crystal X-ray diffraction. We then determined the crystal structure of δ-VMN—the least stable polymorph which cannot be cultivated as a single crystal—directly from the compact spherulite s le. We unexpectedly discovered a new polymorph during our studies, denoted as ε-VMN. Single crystals of ε-VMN are extremely thin and not suitable for study by X-ray diffraction. Again, we determined the structure of ε-VMN in a compact spherulite form. This successful structure elucidation of all five VMN polymorphs demonstrates the possibility of directly determining structures from melt-grown compact spherulite s les. Thereby, this discovery will improve the efficiency and broaden the scope of polymorphism research, especially within the field of melt crystallization.
Publisher: American Chemical Society (ACS)
Date: 12-09-2019
DOI: 10.1021/ACS.INORGCHEM.9B01798
Abstract: A new aluminosilicate zeolite, denoted EMM-37, with a 3D small pore channel system, has been synthesized using a diquaternary ammonium molecule as the structure directing agent (SDA) and metakaolin as the aluminum source. The structures of both
Publisher: International Union of Crystallography (IUCr)
Date: 28-11-2014
DOI: 10.1107/S1600576714023875
Abstract: Phase identification and structure characterization are important in synthetic and materials science. It is difficult to characterize the in idual phases from multiphase crystalline powder s les, especially if some of the phases are unknown. This problem can be solved by combining rotation electron diffraction (RED) and powder X-ray diffraction (PXRD). Four phases were identified on the same transmission electron microscopy grid from a multiphase s le in the Ni–Se–O–Cl system, and their structures were solved from the RED data. Phase 1 (NiSeO 3 ) was found in the Inorganic Crystal Structure Database using the information from RED. Phase 2 (Ni 3 Se 4 O 10 Cl 2 ) is an unknown compound, but it is isostructural to Co 3 Se 4 O 10 Cl 2 , which was recently solved by single-crystal X-ray diffraction. Phase 3 (Ni 5 Se 6 O 16 Cl 4 H 2 ) and Phase 4 (Ni 5 Se 4 O 12 Cl 2 ) are new compounds. The fact that there are at least four different compounds in the as-synthesized material explains why the phase identification and structure determination could not be done by PXRD alone. The RED method makes phase identification from such multiphase powder s les much easier than would be the case using powder X-ray diffraction. The RED method also makes structure determination of submicrometre-sized crystals from multiphase s les possible.
Publisher: Springer Science and Business Media LLC
Date: 31-07-2020
DOI: 10.1038/S42003-020-01155-1
Abstract: Visualizing ligand binding interactions is important for structure-based drug design and fragment-based screening methods. Rapid and uniform soaking with potentially reduced lattice defects make small macromolecular crystals attractive targets for studying drug binding using microcrystal electron diffraction (MicroED). However, so far no drug binding interactions could unambiguously be resolved by electron diffraction alone. Here, we use MicroED to study the binding of a sulfonamide inhibitor to human carbonic anhydrase isoform II (HCA II). We show that MicroED data can efficiently be collected on a conventional transmission electron microscope from thin hydrated microcrystals soaked with the clinical drug acetazolamide (AZM). The data are of high enough quality to unequivocally fit and resolve the bound inhibitor. We anticipate MicroED can play an important role in facilitating in-house fragment screening for drug discovery, complementing existing methods in structural biology such as X-ray and neutron diffraction.
Publisher: American Chemical Society (ACS)
Date: 04-09-2013
DOI: 10.1021/JP406294T
Start Date: 05-2023
End Date: 04-2024
Amount: $1,129,423.00
Funder: Australian Research Council
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