Electron Diffraction Patterns Research Articles

Dystrophic calcinosis: structural and morphological composition, and evaluation of ethylenediaminetetraacetic acid (‘EDTA’) for potential local treatment

BackgroundTo perform a detailed morphological analysis of the inorganic portion of two different clinical presentations of calcium-based deposits retrieved from subjects with SSc and identify a chemical dissolution of these deposits suitable for clinical use.MethodsChemical analysis using Fourier Transform IR spectroscopy (‘FTIR’), Raman microscopy, Powder X-Ray Diffraction (‘PXRD’), and Transmission Electron Microscopy (‘TEM’) was undertaken of two distinct types of calcinosis deposits: paste and stone. Calcinosis sample titration with ethylenediaminetetraacetic acid (‘EDTA’) assessed the concentration at which the EDTA dissolved the calcinosis deposits in vitro.ResultsFTIR spectra of the samples displayed peaks characteristic of hydroxyapatite, where signals attributable to the phosphate and carbonate ions were all identified. Polymorph characterization using Raman spectra were identical to a hydroxyapatite reference while the PXRD and electron diffraction patterns conclusively identified the mineral present as hydroxyapatite. TEM analysis showed differences of morphology between the samples. Rounded particles from stone samples were up to a few micron in size, while needle-like crystals from paste samples reached up to 0.5 µm in length.Calcium phosphate deposits were effectively dissolved with 3% aqueous solutions of EDTA, in vitro. Complete dissolution of both types of deposit was achieved in approximately 30 min using a molar ratio of EDTA/HAp of ≈ 300.ConclusionsStone and paste calcium-based deposits both comprise hydroxyapatite, but the constituent crystals vary in size and morphology. Hydroxyapatite is the only crystalline polymorph present in the SSc-related calcinosis deposits. Hydroxyapatite can be dissolved in vitro using a dosage of EDTA considered safe for clinical application. Further research is required to establish the optimal medium to develop the medical product, determine the protocol for clinical application, and to assess the effectiveness of EDTA for local treatment of dystrophic calcinosis.

Fully automated analysis approach for in situ electron diffraction

Despite the rapid development of the state-of-the-art in-situ/operando transmission electron microscopy technologies capable of generating a substantial volume of diffraction pattern images in a compressed time frame, the associated image interpretation apparatus remains incompletely automated. Since the analysis of the acquired data is predominantly focused on a subset of this extensive data set, there is the potential for critical information to be inadvertently omitted. Using a set of computer vision algorithms, we have developed a fully automated computational tool specifically tailored for the systematic analysis of electron diffraction patterns. Our research results demonstrate that the proposed methodology represents a viable and effective approach for the automated analysis of the substantial corpus of data collected during in-situ experimental investigations.

Photocatalysis and antimicrobial activity of ZnO@TiO2 core-shell nanoparticles

Wet chemical synthesis was used in this instance to create ZnO@TiO2 core-shell nanoparticles. By examining X-ray diffraction and Selected Area Electron Diffraction patterns, it was determined that the phase formation of prepared nanoparticles was a hexagonal primitive structure of ZnO and Tetragonal bcc structure of anatase phase of TiO2 devoid of impurity peaks. It was discovered that crystallites were 25 nm in size on average. The results of a surface morphology analysis utilizing High-Resolution Scanning Electron Microscopy and High-Resolution Transmission Electron Microscopy show that all of the particles are spherical. The energy dispersive X-ray spectroscopy study provided proof for the existence of core-shell elemental compositions. Fourier-Transform Infrared spectrum revealed the presence of characteristics of metal bonding with oxygen of ZnO and TiO2. UV-visible absorption analysis exhibited absorption peak in the UV region and the band gap energy of ZnO@TiO2 core-shell nanoparticles. The thermal behavior of ZnO@TiO2 core-shell nanoparticles was analyzed by using Thermogravimetric Analysis, Differential scanning calorimetry, and Differential Thermal Analysis techniques. The X-ray photoelectron spectroscopy analysis exhibited the coating of TiO2 (shell) on the surface of ZnO (core) for the formation of a core-shell nanostructure. Due to its extremely small crystallite size, wide surface area, and reduced band gap, the ZnO@TiO2 core-shell sample demonstrated outstanding photocatalytic activity when rhodamine-B dye was photocatalytically degraded in the presence of UV light irradiation. Finally, the antibacterial and antifungal activities of ZnO@TiO2 core-shell nanoparticles were investigated, and it was shown that antifungal activity was superior to antibacterial activity. A suitable material for environmental and biological applications that produced core-shell nanoparticles displayed regulated grain size, outstanding photocatalytic performance, and high antifungal activity.

Nanoscale Phase and Orientation Mapping in Multiphase Polycrystalline Hafnium Zirconium Oxide Thin Films Using 4D-STEM and Automated Diffraction Indexing.

Ferroelectric hafnium zirconium oxide (HZO) holds promise for nextgeneration memory and transistors due to its superior scalability and seamless integration with complementary metal-oxide-semiconductor processing. A major challenge in developing this emerging ferroelectric material is the metastable nature of the non-centrosymmetric polar phase responsible for ferroelectricity, resulting in a coexistence of both polar and non-polar phases with uneven grain sizes and random orientations. Due to the structural similarity between the multiple phases and the nanoscale dimensions of the thin film devices, accurate measurement of phase-specific information remains challenging. Here, the application of 4D scanning transmission electron microscopy is demonstrated with automated electron diffraction pattern indexing to analyze multiphase polycrystalline HZO thin films, enabling the characterization of crystallographic phase and orientation across large working areas on the order of hundreds of nanometers. This approach offers a powerful characterization framework to produce a quantitative and statistically robust analysis of the intricate structure of HZO films by uncovering phase composition, polarization axis alignment, and unique phase distribution within the HZO film. This study introduces a novel approach for analyzing ferroelectric HZO, facilitating reliable characterization of process-structure-property relationships imperative to accelerating the growth optimization, performance, and successful implementation of ferroelectric HZO in devices.

Structural, optical and photoluminescence characteristics of apatite type lanthanide silicates

This article reports the solid state synthesis of apatite type rare earth-transition metal silicates Nd4MnSi3O13 and Sm4MnSi3O13. These oxyapatite type lanthanide silicates were characterized through structural, micro structural, optical and photoluminescence properties. The indexed X-ray diffraction patterns and Raman analysis confirm that both the samples crystallize in single phase hexagonal symmetry with space group P63/m. Transmission electron microscopy images along with electron diffraction pattern indicate the good crystalline nature of both the samples which further support the results obtained from X-ray diffraction study. The optical band gap energies are found to be 4.1 eV and 3.9 eV for Nd4MnSi3O13 and Sm4MnSi3O13 respectively. The wide optical band gap values of these semiconductor silicates make enable them for fundamental and technological applications. The luminescent properties and CIE coordinates showed the green-yellow emission of these synthesized silicates which further indicate that these compounds may have uses in solid state lighting because of the tunable luminescence.

Direct observation of the atomic density fluctuation originating from the first sharp diffraction peak in SiO2 glass

The intermediate-range order of covalently bonded glasses has been extensively studied in terms of their diffraction peaks observed at low scattering angles; these peaks are called the first sharp diffraction peaks (FSDPs). Although the atomic density fluctuations originating from the quasilattice planes are a critical scientific target, direct experimental observations of these fluctuations are still lacking. Here, we report the direct observation of the atomic density fluctuations in silica glass by energy-filtered angstrom-beam electron diffraction. The correspondence between the local electron diffraction patterns of FSDPs and the atomic configurations constructed based on the X-ray and neutron diffraction results revealed that the local atomic density fluctuations originated from the quasi-periodic alternating arrangements of the columnar chain-like atomic configurations and interstitial tubular voids, as in crystals. We also discovered longer-range fluctuations associated with the shoulder of the FSDP on the low-Q side. The hierarchical fluctuations inherent in materials could aid in the elucidation of their properties and performance.

High-speed 4-dimensional scanning transmission electron microscopy using compressive sensing techniques.

Here we show that compressive sensing allows 4-dimensional (4-D) STEM data to be obtained and accurately reconstructed with both high-speed and reduced electron fluence. The methodology needed to achieve these results compared to conventional 4-D approaches requires only that a random subset of probe locations is acquired from the typical regular scanning grid, which immediately generates both higher speed and the lower fluence experimentally. We also consider downsampling of the detector, showing that oversampling is inherent within convergent beam electron diffraction (CBED) patterns and that detector downsampling does not reduce precision but allows faster experimental data acquisition. Analysis of an experimental atomic resolution yttrium silicide dataset shows that it is possible to recover over 25 dB peak signal-to-noise ratio in the recovered phase using 0.3% of the totaldata. Lay abstract: Four-dimensional scanning transmission electron microscopy (4-D STEM) is a powerful technique for characterizing complex nanoscale structures. In this method, a convergent beam electron diffraction pattern (CBED) is acquired at each probe location during the scan of the sample. This means that a 2-dimensional signal is acquired at each 2-D probe location, equating to a 4-D dataset. Despite the recent development of fast direct electron detectors, some capable of 100kHz frame rates, the limiting factor for 4-D STEM is acquisition times in the majority of cases, where cameras will typically operate on the order of 2kHz. This means that a raster scan containing 256^2 probe locations can take on the order of 30s, approximately 100-1000 times longer than a conventional STEM imaging technique using monolithic radial detectors. As a result, 4-D STEM acquisitions can be subject to adverse effects such as drift, beam damage, and sample contamination. Recent advances in computational imaging techniques for STEM have allowed for faster acquisition speeds by way of acquiring only a random subset of probe locations from the field of view. By doing this, the acquisition time is significantly reduced, in some cases by a factor of 10-100 times. The acquired data is then processed to fill-in or inpaint the missing data, taking advantage of the inherently low-complex signals which can be linearly combined to recover the information. In this work, similar methods are demonstrated for the acquisition of 4-D STEM data, where only a random subset of CBED patterns are acquired over the raster scan. We simulate the compressive sensing acquisition method for 4-D STEM and present our findings for a variety of analysis techniques such as ptychography and differential phase contrast. Our results show that acquisition times can be significantly reduced on the order of 100-300 times, therefore improving existing frame rates, as well as further reducing the electron fluence beyond just using a faster camera.

Effects of CaCO3/MgO on Fe-Co-Mo catalyst in the reprocessing of recycled polypropylene to carbon nanotubes

In recent times, there has been a global discourse on the menace of plastic waste (PW) materials on the ecosystem and ways for effective management of PW. This has resulted in the utilization of PW in the research arena in the synthesis of smart nanomaterials of high value as a sustainable solution. In this study, the catalytic-pyrolysis procedure was used to develop carbon nanotubes (CNTs) from recycled polypropylene (PP) plastic in a one-step chemical vapour deposition (CVD) reactor. The impacts of CaCO3 and MgO as supports for Fe-Co-Mo catalysts in the production of CNTs were studied. Kinetic and thermodynamic parameters were determined from the thermal profile of the catalysts to establish the nature of the reaction in CNTs synthesis. Transmission electron microscopy (TEM), energy Dispersive X-ray (EDX), selected area electron diffraction pattern, particle size distribution (PSD), thermogravimetric analysis (TGA), Raman spectroscopy, Fourier transforms infrared (FTIR) and X-ray diffraction (XRD) were employed to characterize the catalysts and CNTs. The results obtained showed the impact of the supports on the yield, quality, and morphology of the synthesized CNTs. The CNTs yield from catalysts supported with CaCO3 and MgO were 35.12 % and 37.24% respectively. The average outer diameters of CNTs produced over the catalyst with CaCO3 and MgO supports were 36 and 29 nm respectively. The ID/IG ratio for CaCO3 and MgO supports were 0.6724 and 0.8401 respectively. The change in entropy for all phases were −274.41 and −1032.97 J/mol/K and −213.0, −318.48 and −1022.13 J/mol/K for CaCO3 and MgO supported catalyst respectively which confirmed non-spontaneous endothermic reaction. It was observed that MgO support showed better catalytic activity toward CNTs growth in terms of yield while those with CaCO3 support showed higher graphitization.

Structural refinement, dielectric and ferroelectric properties of Cr modified Ba0·90Sr0·10TiO3 ceramics

In this study, we investigated the impact of Chromium substitution on the structural, dielectric and ferroelectric characteristics of Ba0·90Sr0·10Ti1-3x/4CrxO3 (x = 0, 0.005, 0.010, 0.015 and 0.020) ceramics fabricated by solid state reaction method. Rietveld refinement of X-ray diffraction pattern confirmed tetragonal perovskite structure for all the samples. Based on the crystal structure and the lattice parameter obtained through XRD measurement, the Madelung energy of each sample was computed. SEM images revealed a reduction in grain size with rising Cr concentration. TEM, HRTEM, SAED and EDS analysis was carried out for BST-Cr3 sample. Diffused rings observed in Selective Area Electron Diffraction (SAED) patterns indicate the crystallinity of the sample. EDS analysis indicated the presence of Ba, Sr, Ti, O and Cr elements. In the temperature range of 30 °C–150 °C, dielectric measurements (dielectric constant ‘ε’ and tangent loss ‘tanδ’) have been made at different frequencies (1, 10, 50, 100 and 1000 kHz). The samples displayed a diffused phase transition, with noticeable reduction in Curie temperature ‘Tc’ and tangent loss ‘tanδ’ with the substitution of Cr. Polarization versus electric field loops were recorded at different electric fields (5, 10, 15, 20 and 25 kV/cm) and improved values of remnant polarization ‘Pr’ and coercive field ‘Ec’ were observed. A lower Ec value facilitates easier domain movement within the unit cell, leading to enhanced ferroelectric properties. Temperature dependent P-E loops indicated that as the temperature increased, the material became softer accompanied by simultaneous reduction in Pr and Ec values.

Characterization of Al2O3 coating of Nb fiber-reinforced TiAl composite

The Al2O3 coating was synthesized on surface of the Nb fiber via cathodic plasma electrolytic deposition (CPED) method. The microstructure and composition of the coating were elaborately analyzed. The results revealed that compact and uniform Al2O3 is fully contact with TiAl matrix and Nb fiber, which was composed of κ-Al2O3 and α-Al2O3 and successfully hold back the oxidation reactions at the juncture and refrain from formation of detrimental phases. Especially, three-dimensional characterization information can be obtained from two-dimensional converging beam electron diffraction (CBED) pattern, from which the crystal constants of Al2O3 can be obtained directly under only one applicable zone axis.

Phyco-synthesis of silver nanoparticles by environmentally safe approach and their applications

In recent years, there has been an increasing interest in the green synthesis of metallic nanoparticles, mostly because of the evident limitations associated with chemical and physical methods. Green synthesis, commonly referred to as "biogenic synthesis," is seen as an alternative approach to produce AgNPs (silver nanoparticles). The current work focuses on the use of Asterarcys sp. (microalga) for biological reduction of AgNO3 to produce AgNPs. The optimal parameters for the reduction of AgNPs were determined as molarity of 3 mM for AgNO3 and an incubation duration of 24 h at pH 9, using a 20:80 ratio of algal extract to AgNO3. The biosynthesized Ast-AgNPs were characterised using ultraviolet–visible spectroscopy (UV–Vis), zeta potential, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and high-resolution transmission electron microscopy (HR-TEM) with selected area electron diffraction (SAED) patterns. The nanoparticles exhibited their highest absorption in the UV–visible spectra at 425 nm. The X-ray diffraction (XRD) investigation indicated the presence of characteristic peaks at certain angles: 38.30° (1 1 1), 44.40° (2 0 0), 64.64° (2 2 0), and 77.59° (3 1 1) according to the JCPDS file No. 04-0783. Based on SEM and TEM, the Ast-AgNPs had an average size of 35 nm and 52 nm, respectively. The zeta potential was determined to be − 20.8 mV, indicating their stability. The highest antibacterial effectiveness is shown against Staphylococcus aureus, with a zone of inhibition of 25.66 ± 1.52 mm at 250 μL/mL conc. of Ast-AgNPs. Likewise, Ast-AgNPs significantly suppressed the growth of Fusarium sp. and Curvularia sp. by 78.22% and 85.05%, respectively, at 150 μL/mL conc. of Ast-AgNPs. In addition, the Ast-AgNPs exhibited significant photocatalytic activity in degrading methylene blue (MB), achieving an 88.59% degradation in 120 min, revealing multiple downstream applications of Ast-AgNPs.

3D electron diffraction goes multipolar.

Over 30 years ago, it was shown that bonding between atoms has a noticeable effect on convergent beam electron diffraction patterns. The paper by Olech et al. [(2024). IUCrJ, 11, 309-324] demonstrates that its influence is also clearly present in 3D electron diffraction data, opening up new possibilities for quantum crystallography.

Fabrication of single-step novel synthesis of ZnCd(S0.5Se0.5)2 thin films for photoelectrochemical (PEC) cell application

In our study, we use a new method called the arrested precipitation technique (APT) to create CdZn(SSe)2 (CZSS) thin films. We obtain samples at different deposition times, ranging from 2.5 to 4 h, and analyze the effects of deposition time on the opto-structural, morphological, compositional, and photoelectrochemical (PEC) solar cell properties. As a result, we find that the band gap energy increases from 2.366 to 2.60 eV with prolonged growth time, as shown by UV–Vis spectra. X-ray diffraction (XRD) analysis confirms that the crystal structure is hexagonal, with the crystallite size increasing from 76 to 93 nm. The dislocation density and microstrain, determined by the Scherrer formula, decrease from 1.72 to 1.14 lines m−2 and from 4.75 × 10−3 to 3.87 × 10−3 (lines m−2), respectively. These results are validated using the Williamson-Hall (WH) plot and size-strain plot. The average grain size, evaluated using the standard scale bar method in scanning electron microscopy (SEM), ranges from 80 to 150 nm across CZ1 to CZ4 samples. Transmission electron microscopy (TEM) images of CZ4 and CZ2 reveal particle sizes of 101 nm and 87 nm, respectively, while selected area electron diffraction (SAED) patterns confirm the polycrystalline nature of the material. Energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) analyses confirm the presence of Cd, Zn, S, and Se elements in their intended stoichiometry. Notably, CZSS photoelectrodes deposited over 4 h show better performance in Photoelectrochemical cells (PEC), achieving the highest photoconversion efficiency (ɳ) at 2.33 %, as evidenced by J-V measurements.

Sustainable production of graphene quantum dots from rice husk for photo‐degradation of organochlorine pesticides

AbstractThe controlled synthesis of two‐dimensional nanocrystals of graphene particles instead of amorphous carbon quantum dots is highly challenging and requires tremendous efforts to optimize the reaction conditions. It has been observed that as a significant bio‐compatible zero‐dimensional material, graphene quantum dots are considered as a novel material for opto‐electronics, energy, biological and environmental applications. However, very few are known about their utilization in photocatalytic degradation of pesticides, especially organochlorine pesticides which are resistant to removal by conventional wastewater treatment methods. In this work, graphene quantum dots were produced from rice husk at relatively low temperatures, resulting in an average particle size of 3.3 nm. The high resolution transmission electron microscopy clearly showed the formation of spherical quantum dots having lattice fringes and the selected area electron diffraction pattern showed the crystallinity of the graphene quantum dots. A study of photodegradation of three highly toxic organochlorine pesticides namely, dichlorodiphenyl trichloro ethane, cypermethrin and fenvalerate were carried out using as‐synthesized graphene quantum dots from rice husk. Interestingly, all these pesticides were found to be degraded around 60 % to 70 % under visible light conditions. It confirmed that synthesized graphene quantum dots from rice husk can act as prominent photocatalyst for the degradation of pesticides and other pollutants.

Unusual photoinduced crystal structure dynamics in TaTe2 with double zigzag chain superstructure

Transition metal dichalcogenides with superperiodic lattice distortions have been widely investigated as the platform of ultrafast structural phase manipulations. Here we performed ultrafast electron diffraction on RT TaTe2, which exhibits a peculiar double zigzag chain pattern of Ta atoms. From the time-dependent electron diffraction pattern, we revealed a photoinduced change in the crystal structure occurring within <0.5 ps, although there is no corresponding high-temperature equilibrium phase. We further clarified the slower response (∼1.5 ps) reflecting the lattice thermalization. Our result suggests the unusual ultrafast crystal structure dynamics specific to the non-equilibrium transient process in TaTe2.

Synthesis and characterization of monodispersed uniform-size aromatic thiolate-protected cobalt nanoclusters for antibacterial and dye degradation studies

In this work, we successfully synthesized monodispersed uniform-sized nanoclusters of less than 7 nm using a dual solvent interaction effect based on nanoclusters formation and growth of thiol-protected (TP) stabilized cobalt nanoclusters (CoNCs) mechanism. The spherical morphology synthesized nanoclusters was confirmed by high-resolution transmission electron microscopy (HRTEM) microscopy. The X-Ray diffraction analysis (XRD) and Selected area electron diffraction (SAED) pattern of the nanoclusters were confirmed the physical properties and crystallographic nature. The obtained small particles play a significant role in antibacterial studies using one gram-positive (Staphylococcus aureus) and one gram-negative (Escherichia coli) bacteria, and sensing of methyl orange in the detection range is 9.2615 × 10−6 to 2.1760 × 10−4 M for methyl orange (MO) rapid degradation.

Effect of oxidation temperature on physical properties of polycrystalline β-Ga2O3 grown by thermal oxidation of GaN in O2 ambient from 900 to 1400 °C

This study aimed to investigate the effect of oxidation temperature on the physical properties of β-Ga2O3 grown by thermal oxidation of GaN in the O2 ambient at high oxidation temperatures from 900 to 1400 °C. Notably, the analysis of the oxidation temperatures ranging from 1100 to 1400 °C remains unexplored in the other studies. The effects of the oxidation temperature on the physical properties were investigated via X-ray diffraction, X-ray photoelectron spectroscopy, and field-emission scanning electron microscopy (FESEM). At all oxidation temperatures, XPS results revealed oxygen deficiency. The top FESEM images indicated disordered nanocolumn structures on the surface of the oxide layer, which increased in abundance with oxidation temperatures exceeding 1100 °C. Energy-filtered high-resolution transmission electron microscopy images and the selected area electron diffraction patterns revealed that the top nanocolumns and the oxidized layer comprised polycrystalline β-Ga2O3. Additionally, the cross-sectional lamellae prepared through focused ion beam milling revealed an increase in the thickness of the β-Ga2O3 layer with oxidation temperature. To account for the variations in the oxide layer thickness, the oxidation temperatures were classified into two ranges of 900–1100 °C and 1100–1400 °C for calculating the activation energy. Moreover, this study assumed that the activation energy required for the oxidation process remained constant within each temperature interval. According to Arrhenius's model, the activation energy from 900 to 1100 °C was calculated to be 286.15 kJ/mol (2.97 eV). Furthermore, the activation energy from 1100 to 1400 °C was determined to be 111.33 kJ/mol (1.15 eV).

Magnetic suppression for a possible Fe-poor organic–inorganic hybrid superconductor Fe14Se16(tepa)0.8 (tepa = tetraethylenepentamine) with a superconducting transition at ∼42 K

Composition/structure-dependent superconductivity for FeSe-based superconductors attracted great attention not only due to their high superconducting transition temperatures (TC), but also for understanding the origin of iron-based superconductivity. Here, we report a new Fe-poor organic-inorganic hybrid material Fe14Se16(tepa)0.8 with a paramagnetic-diamagnetic transition at ∼42 K grown by a high-temperature organic-solution-phase method with soluble iron/selenium sources in a tepa solution, alternative to previous intercalation strategies. The Fe14Se16(tepa)0.8 phase is in a tetragonal layered hybrid structure with a nanoplate shape. Composition analyses reveal a Fe-poor characteristic of the hybrid in contrast to previous FeSe-intercalated superconductor, and selected area electron diffraction pattern is featured by Fe3Se4 superstructures with a √2 × √2 of Fe vacancy order. Ab initio density functional calculations show that minus Fe3Se4 ions are stable in the hybrid and ∼0.25e−/Fe0.75Se is obviously larger than the reported values of approximately 0.2e−/FeSe in other FeSe-intercalated superconductors. Typical hysteresis loops and temperature dependence of dc/ac susceptibilities of the Fe14Se16(tepa)0.8 measured below ∼42 K suggest a presence of the Meissner effect in this material. Effects of synthesis conditions on structures and magnetic properties of the hybrids show a magnetic evolution from a long-range ferrimagnetic (FIM) order of Fe14Se16(tepa) to a coexistence of FIM and superconducting (SC) orders of Fe14Se16(tepa)0.9 and an SC order of Fe14Se16(tepa)0.8. X-ray absorption spectrum (XAS) confirms the presence of ferric/ferrous irons. Mössbauer studies reveal that the high-TC superconductivity originates from a suppression of the FIM order through tuning the spin states of irons from high-spin Fe3+ (S = 5/2) and Fe2+ (S = 2) in the Fe14Se16(tepa) to low-spin Fe3+ (S = 1/2) and Fe2+ (S = 0) in the Fe14Se16(tepa)0.8. Although no zero resistance is detected even at a temperature of 2 K, the resistivity at 2 K decreases by more than 1600 times compared to that in a normal state calculated by a variable range hopping (VRH) model, suggesting that the high-TC superconductivity of Fe14Se16(tepa)0.8 is possible.

A CASSCF/MRCI trajectory surface hopping simulation of the photochemical dynamics and the gas phase ultrafast electron diffraction patterns of cyclobutanone.

We present the simulation of the photochemical dynamics of cyclobutanone induced by the excitation of the 3s Rydberg state. For this purpose, we apply the complete active space self-consistent field method together with the spin-orbit multireference configuration interaction singles treatment, combined with the trajectory surface hopping for the inclusion of nonadiabatic effects. The simulations were performed in the spin-adiabatic representation, including nine electronic states derived from three singlet and two triplet spin-diabatic states. Our simulations reproduce the two previously observed primary dissociation channels: the C2 pathway yielding C2H4 + CH2CO and the C3 pathway producing c-C3H6 + CO. In addition, two secondary products, CH2 + CO from the C2 pathway and C3H6 from the C3 pathway, both of them previously reported, are also observed in our simulation. We determine the ratio of the C3:C2 products to be about 2.8. Our findings show that most of the trajectories reach their electronic ground state within 200fs, with dissociation events finished after 300fs. We also identify the minimum energy conical intersections that are responsible for the relaxation and provide an analysis of the photochemical reaction mechanism based on multidimensional scaling. Furthermore, we demonstrate a minimal impact of triplet states on the photodissociation mechanism within the observed timescale. In order to provide a direct link to experiments, we simulate the gas phase ultrafast electron diffraction patterns and connect their features to the underlying structural dynamics.

4D-STEM Mapping of Nanocrystal Reaction Dynamics and Heterogeneity in a Graphene Liquid Cell.

Chemical reaction kinetics at the nanoscale are intertwined with heterogeneity in structure and composition. However, mapping such heterogeneity in a liquid environment is extremely challenging. Here we integrate graphene liquid cell (GLC) transmission electron microscopy and four-dimensional scanning transmission electron microscopy to image the etching dynamics of gold nanorods in the reaction media. Critical to our experiment is the small liquid thickness in a GLC that allows the collection of high-quality electron diffraction patterns at low dose conditions. Machine learning-based data-mining of the diffraction patterns maps the three-dimensional nanocrystal orientation, groups spatial domains of various species in the GLC, and identifies newly generated nanocrystallites during reaction, offering a comprehensive understanding on the reaction mechanism inside a nanoenvironment. This work opens opportunities in probing the interplay of structural properties such as phase and strain with solution-phase reaction dynamics, which is important for applications in catalysis, energy storage, and self-assembly.