Diffraction Resonance Research Articles

Atomic locations and adsorbate interactions of Al single and pair sites in H-ZSM-5 zeolite.

The distribution of substitutional aluminum (Al) atoms in zeolites affects molecular adsorbate geometry, catalytic activity, and shape and size selectivity. Accurately determining Al positions has been challenging. We used synchrotron resonant soft x-ray diffraction (RSXRD) at multiple energies near the Al K-edge combined with molecular adsorption techniques to precisely locate "single Al" and "Al pairs" in a commercial H-ZSM-5 zeolite. This analysis depicts three distinct Al tetrahedral (T) sites: T8, T6, and T4. A combined suite of characterizations, including ammonia temperature-dependent desorption, neutron powder diffraction, solid-state nuclear magnetic resonance spectroscopy, and density functional theory calculations, reveal isolated ammonia adsorption on T8 as "single Al" in the straight channel and bridged ammonia adsorption on T6 and T4 as an "Al pair" (AlT6-O-SiT5-O-AlT4) in the straight-sinusoidal intersection.

Origins and conservation of topological polarization defects in resonant photonic-crystal diffraction.

We present a continuative definition of topological charge to depict the polarization defects on any resonant diffraction orders in photonic crystal slab regardless they are radiative or evanescent. By using such a generalized definition, we investigate the origins and conservation of polarization defects across the whole Brillouin zone. We found that the mode crossings due to Brillouin zone folding contribute to the emergence of polarization defects in the entire Brillouin zone. These polarization defects eventually originate from the spontaneous symmetry breaking of line degeneracies fixed at Brillouin zone center or edges, or inter-band coupling caused by accidental Bloch band crossings. Unlike Bloch states, the polarization defects live and evolve in an unbound momentum space, obeying a local conservation law as a direct consequence of Stokes' theorem, but the total charge number is countless.

Combined 7Li NMR, density functional theory and operando synchrotron X-ray powder diffraction to investigate a structural evolution of cathode material LiFeV2O7.

In our recent study, we demonstrated using 7Li solid-state Nuclear Magnetic Resonance (ssNMR) and single-crystal X-ray diffraction that the cathode LiFeV2O7 possesses a defect associated with the positioning of vanadium atoms. We proposed that this defect could be the source of extra signals detected in the 7Li spectra. In this context, we now apply density functional theory (DFT) calculations to assign the experimental signals observed in 7Li NMR spectra of the pristine sample. The calculation results are in strong agreement with the experimental observations. DFT calculations are a useful tool to interpret the observed paramagnetic shifts and understand how the presence of disorder affects the spectra behavior through the spin-density transfer processes. Furthermore, we conducted a detailed study of the lithiated phase combining operando synchrotron powder X-ray diffraction (SPXRD) and DFT calculations. A noticeable volume expansion is observed through the first discharge cycle which likely contributes to the enhanced lithium dynamics in the bulk material, as supported by previously published ssNMR data. DFT calculations are used to model the lithiated phase and demonstrate that both iron and vanadium participate in the redox process. The unusual electronic structure of the V4+ exhibits a single electron on the 3dxy orbital perpendicular to the V-O-Li bond being a source of a negative Fermi contact shift observed in the 7Li NMR of the lithiated phase.

STRUCTURAL RESEARCH OF LI DOPED ZNO POWDERS

In this article, a series of Li-doped ZnO powders was prepared by melt growth from salt mixtures and investigated by means of Mass-Spectrometry (MS), Scanning Electron Microscopy (SEM), Powder X-Ray Diffraction (PXRD), Raman, Photoluminescence (PL) and Nuclear Magnetic Resonance (NMR) spectroscopies. The MS found that the Li concentration fell into the range from 0.87 to 3.31 atomic % for the prepared Li-doped powders. The powders constituted of slightly elongated particles, covering broad range from hundred nanometres to couple micrometres, as shown by SEM. The PXRD showed that the particles of all powders crystallized in the wurtzite (ZnO) structure with no impurities. The Rietveld analysis found that Li occupied octahedral interstitial positions in the ZnO lattice, together with the contraction of the lattice parameters a and c by 0.09 % and 0.13 %, respectively, upon doping with 1 % of Li ions. The Raman spectra exhibited A1(LO) and E1(LO) peaks absent in the undoped sample, supporting the Li incorporation into the ZnO lattice. The PL spectra of Li-doped samples exhibited a visible (~2.15 eV) and near infrared (~1.63 eV) luminescent bands associated with intrinsic defects and Li-Li nanoclusters, respectively. The presence of octahedral Li site along with multiple scattered Li sites was proved with almost zero electric field gradient (EFG) originating from octahedral voids in the wurtzite and various non-zero EFG in course of NMR measurement. Finally, the conducted structural research confirmed incorporation of Li into octahedral interstitials of the ZnO lattice supporting possible formation of Li-Li nanoclusters luminescent in the near infrared range.

Unveiling the promotion role of ZnO on Zn-Al spinel oxide for CO2 hydrogenation

The Zn-Al spinel oxide stands out as one of the most active catalysts for high-temperature methanol synthesis from CO2 hydrogenation. However, the structure-activity relationship of the reaction remains poorly understood due to challenges in atomic-level structural characterizations and analysis of reaction intermediates. In this study, we prepared two Zn-Al spinel oxide catalysts via coprecipitation (ZnAl-C) and hydrothermal (ZnAl-H) methods, and conducted a comparative investigation in the CO2 hydrogenation reaction. Surprisingly, under similar conditions, ZnAl-C exhibited significantly higher selectivity towards methanol and DME compared to ZnAl-H. Comprehensive characterizations using X-ray diffraction (XRD), Raman spectroscopy and electron paramagnetic resonance (EPR) unveiled that ZnAl-C catalyst had abundant ZnO species on its surface, and the interaction between the ZnO species and its ZnAl spinel oxide matrix led to the formation of oxygen vacancies, which are crucial for CO2 adsorption and activation. Additionally, state-of-the-art solid-state nuclear magnetic resonance (NMR) techniques, including ex-situ and in-situ NMR analyses, confirmed that the surface ZnO facilitates the formation of unique highly reactive interfacial formate species, which was readily hydrogenated to methanol and DME. These insights elucidate the promotion effects of ZnO on the ZnAl spinel oxide in regulating active sites and reactive intermediate for CO2-to-methanol hydrogenation reaction, which is further evidenced by the significant enhancement in methanol and DME selectivity observed upon loading ZnO onto the ZnAl-H catalyst. These molecular-level mechanism understandings reinforce the idea of optimizing the ZnO-ZnAl interface through tailored synthesis methods to achieve activity-selectivity balance.

Investigation of the conditions (nature) of pentacoordinated aluminum oxide formation

Aluminum oxide is widely used as a catalyst carrier, including in internal combustion engine systems, where operating temperatures exceed 1000 °C. As such, aluminum oxide must exhibit enhanced thermal stability. This property is linked to the presence of pentacoordinated centers on the surface of the γ-phase of Al2O3. This paper examines the effect of the pH during aluminum hydroxide precipitation on the formation of pentacoordinated centers on the surface of aluminum oxide. The samples of aluminum hydroxide were synthesized via controlled double-jet precipitation, followed by thermal decomposition into oxides. Precipitation was carried out at constant pH levels, and for comparison, parallel samples were synthesized at pH values of 5, 6, 7, 8, and 9. The precursors for precipitation were a 1 M aluminum nitrate solution (Al3+) and a 10 wt. % ammonia solution (NH4OH). The solutions were introduced into the reactor in a dropwise mode with continuous stirring. The resulting aluminum oxide samples were analyzed using X-ray diffraction and nuclear magnetic resonance techniques. The data show a direct correlation between the pH of aluminum hydroxide precipitation and the presence of pentacoordinated centers on the aluminum oxide surface: the higher the pH, the lower the content of pentacoordinated atoms. Additionally, a relationship was observed between the pH value and the size of the coherent scattering region, with an increase in coherent scattering observed at higher pH levels.

Electronic Desymmetrization of Cu3(μ3-E) Clusters (E = S, Se) Induced by Edge-to-Face π-Stacking Interactions in the Second Coordination Sphere.

A pair of cyclophane-encapsulated [Cu3(μ3-E)]3+ complexes (E = S and Se) were characterized by resonant X-ray diffraction anomalous fine structure (DAFS), revealing unexpected polarization among the three Cu sites attributed to long-range effects of π-stacking interactions with cocrystallized benzene molecules. The resonant K-edge energies of individual Cu sites within the cluster molecules were found to vary as a function of distance from the cocrystallized benzene. This pattern was interpreted in the context of T-shaped, edge-to-face π-stacking with the assistance of theoretical charge density difference calculations.

Synthesis and Characterizations of Dibenzo-Fused Perioctacene.

Dibenzoperioctacene (DBPO) with extended zigzag edges was synthesized and unambiguously characterized by a combination of nuclear magnetic resonance (NMR), mass spectrometry, and single-crystal X-ray diffraction analysis. Variable-temperature (VT) NMR analysis indicated the closed-shell character of DBPO, yet an electron paramagnetic resonance (EPR) signal was observed at room temperature suggesting its potential open-shell diradicaloid nature. The bond lengths in the single-crystal structure of DBPO aligned more closely with those of open-shell teranthene than closed-shell bisanthene. Spin-unrestricted density functional theory (DFT) calculations using various methods supported that ground state of DBPO might be on the borderline between closed- and open-shell singlet states, with a large singlet-triplet energy gap (ΔEST), consistent with the VT-NMR and EPR results. UV-vis-near infrared (NIR) absorption spectrum showed the longest-wavelength peak at 905 nm, marking the NIR optical properties of DBPO. DBPO exhibited a tendency to react with atmospheric oxygen, which additionally hinted at its possible open-shell character. Furthermore, the oxidized species of non-fluorescent DBPO exhibited strong emission at 820 and 915 nm, which opens its potential for oxygen detection via a "turn-on" NIR fluorescence response.

Enhancing Permanence of Corrosion Inhibitors Within Acrylic Protective Coatings for Outdoor Bronze Using Green Nanocontainers.

Outdoor bronze statues are constantly exposed to weather conditions and reactive compounds in the atmosphere that can interact with their surfaces. To avoid these interactions, a commonly used method is the application of coatings with corrosion inhibitors. However, a significant limitation of these inhibitors is their gradual loss over time. In this study, we aimed to improve the durability of 5-ethyl-1,3,4-thiadiazol-2-amine (AEDTA), the inhibitor chosen to formulate new acrylic coatings for outdoor bronzes. Methyl-β-cyclodextrin (Me-β-CD) was selected to host the inhibitor due to the capability of cyclodextrins to form complexes incorporating small organic molecules. The complexes of Me-β-CD and AEDTA were prepared and the inclusion of AEDTA was proved by Fourier-transform infrared spectroscopy, X-ray diffraction and nuclear magnetic resonance spectroscopy. Then, acrylic coatings were prepared at different concentrations of the Me-β-CD/AEDTA system. They were thermally aged and monitored every 24 h. To evaluate the volatilization of the corrosion inhibitor, solid phase microextraction-gas chromatography/mass spectrometry (SPME-GC/MS) and thermal desorption-GC/MS (TD-GC/MS) analyses were performed during the first 72 h. The results were compared to those of pure AEDTA films and Incralac®. The outcomes showed that Me-β-CD/AEDTA complexes are promising candidates for developing coatings with improved stability and longer retention of AEDTA.

Investigation of Single Proton Dissociation

We consider the single proton diffraction dissociation at low missing masses focusing on the interplay between diffractive processes and resonance production. The model incorporates the concept of duality, where the observed cross sections are explained by both smooth background processes and discrete resonance contributions. At low missing masses MX, this approach leverages the Regge proton trajectory to account for the role of resonances in the cross section. Recent experimental data are used to refine model parameters, enhancing the accuracy of predictions for the differential cross section behavior in the resonance region.

3D Heisenberg universality in the van der Waals antiferromagnet NiPS3

Van der Waals (vdW) magnetic materials are comprised of layers of atomically thin sheets, making them ideal platforms for studying magnetism at the two-dimensional (2D) limit. These materials are at the center of a host of novel types of experiments, however, there are notably few pathways to directly probe their magnetic structure. We confirm the magnetic order within a single crystal of NiPS3 and show it can be accessed with resonant elastic X-ray diffraction along the edge of the vdW planes in a carefully grown crystal by detecting structurally forbidden resonant magnetic X-ray scattering. We find the magnetic order parameter has a critical exponent of β ~ 0.36, indicating that the magnetism of these vdW crystals is more adequately characterized by the three-dimensional (3D) Heisenberg universality class. We verify these findings with first-principles density functional theory, Monte-Carlo simulations, and density matrix renormalization group calculations.

Development of Benzimidazole‐Containing Thermosetting Imide Oligomers With Enhanced Thermal Stability and Adhesive Properties

ABSTRACTIn this work, phenylethynyl‐terminated imide oligomers incorporating benzimidazole structures were synthesized and their structures were characterized using Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), and proton nuclear magnetic resonance (1H NMR). The solubility, curing behavior, thermal stability, thermomechanical properties, and adhesive performance were systematically evaluated. Different dianhydride structures and isomer ratios were utilized to optimize the performance of the oligomers. Thermogravimetric analysis (TGA) revealed 5% weight loss temperatures (T5%) exceeding 520°C under both nitrogen and air atmospheres, demonstrating excellent thermal stability. Lap shear strength (LSS) testing showed that oligomers based on 4,4′‐oxydiphthalic anhydride (ODPA) exhibited superior adhesive performance, particularly at elevated temperatures. The glass transition temperature (Tg) was significantly influenced by the ratio of 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (s‐BPDA) to 2,3,3′,4′‐biphenyltetracarboxylic dianhydride (a‐BPDA), with a maximum Tg of 482°C. These results underscore the potential of these oligomers for high‐performance adhesive applications in industries such as aerospace and electronics.

Characterization of Co1-xZnxFe2O4 nanoparticles synthesized by the autocombustion method

Nanosized particles of Co1-xZnxFe2O4, with x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1,0, were synthesized by the autocombustion method and characterized by X-ray diffraction (XRD) and ferromagnetic resonance (FMR). The results showed that the method can be used to produce particles with a crystallite size of less than 20 nm and that the anisotropy field of the particles decreases with increasing zinc concentration, ranging from 316 mT for Co0.6Zn0.4Fe2O4 to 31 mT for ZnFe2O4 (the anisotropy field could not be measured for CoFe2O4 and Co0.8Zn0.2Fe2O4). The present results may be useful for applications such as microwave absorption, hyperthermy, drug delivery and catalysis.

Vacancy-Driven Sodium Diffusion in Sodium Closo-Borohydride As Solid-State Electrolyte

Solid electrolyte is the cornerstone of the next-generation all-solid-state batteries. To realize the all-solid-state battery, the solid electrolyte must possess a high ionic conductivity and an electrochemical window that matches the electrode redox reaction potential. Recently, sodium closo-borohydrides have attracted significant attention for their high ionic conductivity and excellent reduction stability1,2. In this presentation, we will share our recent finding on the metastable nature of one of the sodium closo-borohydride chemistry using synchrotron X-ray diffraction and solid-state nuclear magnetic resonance spectroscopy. Additionally, we investigated the ions diffusion mechanism in the crystal structure that leads to high room-temperature ionic conductivity. Leveraging the high ionic conductivity, we realize an all-solid-state battery with high areal capacity and efficiency. 1Deysher, G., Oh, J. A. S., Chen, Y. T., Sayahpour, B., Ham, S. Y., Cheng, D., ... & Meng, Y. S. (2023). An Anode-Free Sodium All-Solid-State Battery. 2Oh, J. A. S., Deysher, G., Ridley, P., Chen, Y. T., Cheng, D., Cronk, A., ... & Meng, Y. S. (2023). High‐Performing All‐Solid‐State Sodium‐Ion Batteries Enabled by the Presodiation of Hard Carbon. Advanced Energy Materials, 13(26), 2300776.

Cu(II) Stability and UV-Induced Electron Transfer in a Metal-Organic Hybrid: An EPR, DFT, and Crystallographic Characterization of Copper-Doped Zinc Creatininium Sulfate.

Single-crystal X-ray diffraction and electron paramagnetic resonance (EPR) spectroscopic experiments, complemented by quantum chemical DFT calculations, were carried out on the copper-doped metal-organic hybrid and Tutton salt analogue zinc creatininium sulfate to determine its crystal structure, to characterize the electronic structure of the doped Cu(II) binding site, and to propose a pathway for an excited-state, proton-coupled electron transfer (PCET) process in UV-exposed crystals. The crystal structure is isomorphous to that of cadmium creatininium sulfate, which has the transition ion, not in direct coordination with the creatinine, but forming a hexahydrate complex, which is bridged to a creatininium through an intervening sulfate ion. The EPR g (2.446, 2.112, 2.082) and copper hyperfine (ACu: -327, -59.6, 10.8 MHz) tensor parameters are consistent with doped copper replacing host zinc in the metal-hexahydrate complex. These parameters are similar to those observed for copper hexahydrate in doped Tutton salt systems at low temperature, where the unpaired electron occupies mainly the copper 3dx2-y2 orbital. At room temperature in the Tutton systems, vibration couplings stemming from a dynamic Jahn-Teller effect cause tensor averaging which results in a reduction in their maximum g-tensor and hyperfine tensor values. However, like for the doped isomorphous Cd creatinine crystal, the Cu(II) EPR exhibits little, or no room temperature averaging compared to its low temperature pattern. Samples exposed to 254 nm UV light generate a carbon-centered free radical species, characterized by an isotropic g-tensor (g = 2.0029) and an alpha-proton hyperfine coupling (-24 -14 +4 G). These parameters identify it as a creatinine radical cation formed by the oxidative release of one of its C2 methylene hydrogens. DFT calculations confirm the unpaired electronic structures of both the Cu(II) site and free radical. The growth in radical concentration with an increase in the UV exposure time coincides with a decrease in the copper EPR signal, indicating a coupled light-induced oxidation reduction process. A comparison of the crystal structure with the EPR parameters and DFT results provides evidence for a UV-induced PCET.

Characterizing X-Ray and Solution State Conformations for a Model Qubit System: {Cr7Ni} Ring Rotaxanes on a Mixed Metal Triangle.

The synthesis of a series of [4]rotaxanes, each consisting of three [2]rotaxanes joined via a central {CrNi2} triangular linker, is reported. The resultant four [4]rotaxanes were characterized by single crystal X-ray diffraction and electron paramagnetic resonance (EPR) spectroscopy. Orientation-selective 4-pulse double electron-electron resonance (DEER) measurements between the three {Cr7Ni} rings incorporated in each [4]rotaxane reveal that each system is conformationally fluxional in solution, with the most abundant conformations found to differ significantly from the crystal structure geometry for each compound. The degree of similarity between conformations is evaluated using a novel application of the earth mover's distance analysis.

Experimental study on the cyclic mineralization of CO2 enriched phase after absorption by a novel biphasic absorbent composed of DEEA and AEP.

The high energy consumption of Carbon Capture Utilization and Storage(CCUS) promotes the research of integrated absorption and mineralization technology. A novel DEEA/AEP biphasic absorbent is used to absorb [Formula: see text]. After phase separation, only one phase enriched with the absorption product is sent into the mineralization system, then reacts with [Formula: see text] to produce [Formula: see text] at normal temperature and pressure. The effects of temperature, Ca/C and dispersion of the system were investigated, and cyclic utilization experiment was also conducted. The process was characterized and analyzed by Thermal gravimetric analysis (TGA), X-ray diffraction (XRD), and nuclear magnetic resonance (13C NMR). The results showed that at 50 [Formula: see text]C, Ca/C = 1, the extent of mineralization of [Formula: see text]-enriched phase mineralization was 95.73% after ultrasonic treatment for 30 min. During 6 cycles, the volume percentage of [Formula: see text]-enriched phase could be maintained at 52-55%, and the [Formula: see text] load was 11.92mol/L. The results above indicate that the [Formula: see text]-enriched phase mineralization technology after absorption by biphasic absorbent can effectively capture [Formula: see text], realize recycling, and reduce CCUS energy consumption.

Engineering of hyperentangled complex quantum networks

Abstract We propose a novel scheme to engineer the atomic hyperentangled cluster and ring graph states invoking cavity-QED technique for applicative relevance to quantum biology and quantum communications utilizing the complex quantum networks. These states are engineered using both external quantized momenta states and energy levels of neutral atoms under off-resonant and resonant Atomic Bragg Diffraction (ABD) technique. The study of dynamical capacity and potential efficiency have certainly enhanced the range of usefulness of these states. In order to assess the operational behavior of such states when subjected to a realistic noise environment has also been simulated, demonstrating long enough sustainability of the proposed states. Moreover, experimental feasibility of the proposed scheme has also been elucidated under the prevailing cavity-QED research scenario.

Water-soluble chlorogenic acid-chitosan and polydatin-chitosan conjugates: antibacterial activity and inhibition of lipid and protein oxidation.

Chitosan (CS), an abundant alkaline polysaccharide, is valued for its biocompatibility, non-toxicity, and antibacterial properties. However, its limited solubility and modest antioxidant activity constrain its utility. Grafting polyphenols onto chitosan through the use of grafting reactions can enhance both the solubility and bioactivity of chitosan. Among the techniques employed, the free radical grafting method is favored for its simplicity, environmental sustainability, and its effectiveness in preserving biological activity. In this study, chlorogenic acid (CGA) and polydatin (PLD) were conjugated successfully to chitosan by a Vc/H2O2 redox system. Analytical techniques such as ultraviolet-visible (UV-visible) spectroscopy, fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and proton nuclear magnetic resonance (1H NMR) were employed to confirm the formation of covalent bonding between the polyphenol molecules and the chitosan backbone. The novel conjugates displayed superior antioxidant properties in comparison with pristine chitosan, as evidenced by their enhanced 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical, and hydroxyl radical scavenging capacities, and Fe2+ reducing power. Both CGA-CS and PLA-CS exhibited excellent lipid and protein oxidation inhibition capabilities. Furthermore, the conjugates were shown to have significant antibacterial effects against four common pathogenic bacteria: Pseudomonas fluorescens, Pseudomonas aeruginosa, Pseudomonas putida, and Staphylococcus aureus (P < 0.05). The newly synthesized water-soluble polyphenol-chitosan conjugates demonstrated remarkable biological activity, particularly CGA-CS. This study offers new insights and a strong theoretical foundation for developing natural food preservation materials with potential applications in the food industry. © 2024 Society of Chemical Industry.

Composition Determination of Heterometallic Trinuclear Clusters via Anomalous X-ray and Neutron Diffraction.

Anomalous X-ray diffraction (AXD) and neutron diffraction can be used to crystallographically distinguish between metals of similar electron density. Despite the use of AXD for structural characterization in mixed metal clusters, there are no benchmark studies evaluating the accuracy of AXD toward assessing elemental occupancy in molecules with comparisons with what is determined via neutron diffraction. We collected resonant diffraction data on several homo and heterometallic clusters and refined their anomalous scattering components to determine metal site occupancies. Theoretical resonant scattering terms for Fe0, Co0, and Zn0 were compared against experimental values, revealing theoretical values are ill-suited to serve as references for occupancy determination. The cluster featuring distinct cation and anion metal compositions [CoCp2*][(tbsL)Fe3(μ3-NAr)] was used to assess the accuracy of different f' references for occupancy determination (f'theoretical ± 15-17%; f'experimental ± 10%). This methodology was applied toward calculating the occupancy of three different clusters: (tbsL)Fe2Zn(py) (6), (tbsL)Fe2Zn(μ3-NAr)(py) (7), and [CoCp*2][(tbsL)Fe2Zn(μ3-NAr)] (8). The first two clusters maintain 100% Fe/Zn site isolation, whereas 8 showed metal mixing within the sites. The large crystal size of 8 enabled collection of neutron diffraction data which was compared against the results found with AXD. The ability of AXD to replicate the metal occupancies as determined by neutron diffraction supports the AXD occupancy methodology developed herein. Furthermore, the advantages innate to AXD (e.g., smaller crystal sizes, shorter collection times, and greater availability of synchrotron resources) versus neutron diffraction further support the need for its development as a standard technique.