Interrogation of 3d Transition Bimetallic Nanocrystal Nucleation and Growth Using In Situ Electron Microscope and Synchrotron X-ray Techniques.

Understanding the nucleation and growth mechanism of 3d transition bimetallic nanocrystals (NCs) is crucial to developing NCs with tailored nanostructures and properties. However, it remains a significant challenge due to the complexity of 3d bimetallic NCs formation and their sensitivity to oxygen. Here, by combining in situ electron microscopy and synchrotron X-ray techniques, we elucidate the nucleation and growth pathways of Fe-Ni NCs. Interestingly, the formation of Fe-Ni NCs emerges from the assimilation of Fe into Ni clusters together with the reduction of Fe-Ni oxides. Subsequently, these NCs undergo solid-state phase transitions, resulting in two distinct solid solutions, ultimately dominated by γ-Fe3Ni2. Furthermore, we deconvolve the interplays between local coordination and electronic state concerning the growth temperature. We directly visualize the oxidation-state distributions of Fe and Ni at the nanoscale and investigate their changes. This work may reshape and enhance the understanding of nucleation and growth in atomic crystallization.

Amorphous Oxyhalide Matters for Achieving Lithium Superionic Conduction.

The recently surged halide-based solid electrolytes (SEs) are great candidates for high-performance all-solid-state batteries (ASSBs), due to their decent ionic conductivity, wide electrochemical stability window, and good compatibility with high-voltage oxide cathodes. In contrast to the crystalline phases in halide SEs, amorphous components are rarely understood but play an important role in Li-ion conduction. Here, we reveal that the presence of amorphous component is common in halide-based SEs that are prepared via mechanochemical method. The fast Li-ion migration is found to be associated with the local chemistry of the amorphous proportion. Taking Zr-based halide SEs as an example, the amorphization process can be regulated by incorporating O, resulting in the formation of corner-sharing Zr-O/Cl polyhedrons. This structural configuration has been confirmed through X-ray absorption spectroscopy, pair distribution function analyses, and Reverse Monte Carlo modeling. The unique structure significantly reduces the energy barriers for Li-ion transport. As a result, an enhanced ionic conductivity of (1.35 ± 0.07) × 10-3 S cm-1 at 25 °C can be achieved for amorphous Li3ZrCl4O1.5. In addition to the improved ionic conductivity, amorphization of Zr-based halide SEs via incorporation of O leads to good mechanical deformability and promising electrochemical performance. These findings provide deep insights into the rational design of desirable halide SEs for high-performance ASSBs.

Dinitrosyl Iron Complex-Derived Nanosized Zerovalent Iron (NZVI) as a Template for the Fe-Co Cracked NZVI: An Electrocatalyst for the Oxygen Evolution Reaction.

Nanosized zerovalent iron (NZVI) Fe@Fe3O4 with a core-shell structure derived from photocatalytic MeOH aqueous solution of dinitrosyl iron complex (DNIC) [(N3MDA)Fe(NO)2] (N3MDA = N,N-dimethyl-2-(((1-methyl-1H-imidazole-2-yl)methylene)amino)ethane-1-amine) (1-N3MDA), eosin Y, and triethylamine (TEA) is demonstrated. The NZVI Fe@Fe3O4 core shows a high percentage of zerovalent iron (Fe0 %) and is stabilized by a hydrophobic organic support formed through the photodegradation of eosin Y hybridized with the N3MDA ligand. In addition to its well-known reductive properties in wastewater treatment and groundwater remediation, NZVI demonstrates the ability to form heterostructures when it interacts with metal ions. In this research, Co2+ is employed as a model contaminant and reacted with NZVI Fe@Fe3O4 to result in the formation of a distinct Fe-Co heterostructure, cracked NZVI (CNZVI). The slight difference in the standard redox potentials between Fe2+ and Co2+, the magnetic properties of Co2+, and the absence of surface hydroxides of Fe@Fe3O4 enable NZVI to mildly reduce Co2+ and facilitate Co2+ penetration into the iron core. Taking advantage of the well-dispersed nature of CNZVI on an organic support, the reduction in particle size due to Co2+ penetration, and Fe-Co synergism, CNZVI is employed as a catalyst in the alkaline oxygen evolution reaction (OER). Remarkably, CNZVI exhibits a highly efficient OER performance, surpassing the benchmark IrO2 catalyst. These findings show the potential of using NZVI as a template for synthesizing highly efficient OER catalysts. Moreover, the study demonstrates the possibility of repurposing waste materials from water treatment as valuable resources for catalytic energy conversion, particularly in water oxidation processes.

Unveiled the Structure-Selectivity Relationship for Carbon Dioxide Reduction Triggered by Bi-Doped Cu-Based Nanocatalysts.

To investigate synergistic effect between geometric and electronic structures on directing CO2 RR selectivity, water phase synthetic protocol and surface architecture engineering strategy are developed to construct monodispersed Bi-doped Cu-based nanocatalysts. The strongly correlated catalytic directionality and Bi3+ dopant can be rationalized by the regulation of [*COOH]/[*CO] adsorption capacities through the appropriate doping of Bi3+ electronic modulator, resulting in volcano relationship between FECO /TOFCO and surface EVBM values. Spectroscopic study reveals that the dual-site binding mode ([Cu─µâ”€C(═O)O─Bi3+ ]) enabled by Cu1 Bi3+ 2 motif in single-phase Cu150 Bi1 nanocatalyst drives CO2-to-CO conversion. In contrast, the study of dynamic Bi speciation and phase transformation in dual-phase Cu50 Bi1 nanocatalyst unveils that the Bi0 -Bi0 contribution emerges at the expense of BOC phase, suggesting metallic Bi0 phase acting as [H]˙ formation center switches CO2 RR selectivity toward CO2-to-HCOO- conversion via [*OCHO] and [*OCHOK] intermediates. This work provides significant insight into how geometric architecture cooperates with electronic effect and catalytic motif/phase to guide the selectivity of electrocatalytic CO2 reduction through the distinct surface-bound intermediates and presents molecular-level understanding of catalytic mechanism for CO/HCOO- formation.

Experimental Revelation of Surface and Bulk Lattices in Faceted Cu2 O Crystals.

Semiconductor crystals have generally shown facet-dependent electrical, photocatalytic, and optical properties. These phenomena have been proposed to result from the presence of a surface layer with bond-level deviations. To provide experimental evidence of this structural feature, synchrotron X-ray sources are used to obtain X-ray diffraction (XRD) patterns of polyhedral cuprous oxide crystals. Cu2 O rhombic dodecahedra display two distinct cell constants from peak splitting. Peak disappearance during slow Cu2 O reduction to Cu with ammonia borane differentiates bulk and surface layer lattices. Cubes and octahedra also show two peak components, while diffraction peaks of cuboctahedra are comprised of three components. Temperature-varying lattice changes in the bulk and surface regions also show shape dependence. From transmission electron microscopy (TEM) images, slight plane spacing deviations in surface and inner crystal regions are measured. Image processing provides visualization of the surface layer with depths of about 1.5-4 nm giving dashed lattice points instead of dots from atomic position deviations. Close TEM examination reveals considerable variation in lattice spot size and shape for different particle morphologies, explaining why facet-dependent properties are emerged. Raman spectrum reflects the large bulk and surface lattice difference in rhombic dodecahedra. Surface lattice difference can change the particle bandgap.

Detection of nitrofurazone with metal-organic frameworks and reduced graphene oxide composites: insights from molecular dynamics simulations.

Two-dimensional metal-organic framework (MOF) composites were produced by incorporating Fe-MOFs into reduced graphene oxide (rGO) nanosheets to form Fe-MOF/rGO composites by hydrothermal synthesis. SEM, TEM, XRD, XPS, and measurements of contact angles were used to characterize the composites. TEM studies revealed that the rod-like-shaped Fe-MOFs were extensively dispersed on the rGO sheets. Incorporating Fe-MOF into rGO significantly improves performance due to the large surface area, chemical stability, and high electrical conductivity. The response signals for the electrochemical sensing performance of Fe-MOF/rGO-modified electrodes to nitrofurazone (NFZ) were significantly enhanced. Differential pulse voltammetry was used to detect the NFZ, and the MOF/rGO sensor possesses a lower detection limit (0.77µM) with two dynamic ranges from 0.6-60 to 128-499.3 µM and high sensitivity (1.909 µA·mM-1·cm-2). Moreover, the anti-interference properties of the sensor were quite reproducible and stable. To understand the mechanism responsible for the enhanced sensing performance of the composite, grand canonical Monte Carlo calculations were performed for Fe-MOF/rGO composites with five unit cells of Fe-MOF and four layers of rGO. We attributed the improvement to the fact that the interface between the Fe-MOF and rGO absorbed increased NFZ molecules. The findings reported herein confirm that such Fe-MOF/rGO composites have significantly improved electrochemical performance and practical applicability of sensing nitrofurazone.

High-Pressure Synthesized Perovskite CdMnO3 with C-Type Antiferromagnetic Spin Configuration.

CdMnO3 had not been previously reported and was a missing piece in the A2+Mn4+O3 series. We succeeded in synthesizing this compound by a high-pressure method and confirmed that it is crystallized in a distorted perovskite structure with a Cd2+Mn4+O3 charge configuration. The obtained insulating CdMnO3 exhibits an antiferromagnetic transition at about 86 K. First-principles calculations revealed that the Mn4+ (t2g3) spins form a C-type antiferromagnetic structure, which is in sharp contrast to the G-type antiferromagnetism in the isostructural and isoelectronic CaMnO3. Significant overlap of the Mn-3d and O(2)-2p orbitals produces distorted octahedra with a large Mn-O(1)-Mn tilt and induces antiferromagnetic couplings in the ac plane and the ferromagnetic couplings along the b axis.

Early detection and intervention for acute perforated peptic ulcer after elective spine surgeries: a review of 13 cases from 24,026 patients.

BACKGROUND: To determine how perforated peptic ulcers be diagnosed earlier after patients undergoing an elective spine surgery. METHODS: Patients who underwent elective spine surgeries at our hospital between January 2000 and April 2018 and experienced an acute perforated peptic ulcer were included. An age-and gender-matched control group was comprised of 26 patients without a postoperative acute perforated peptic ulcer who received spine surgery during the same period. Medical records and imaging studies were thoroughly reviewed. RESULTS: Thirteen patients were enrolled in the study group, including eight females and five males. Three patients, two females and one male, died of uncontrolled peritonitis during the hospital stay. All patients in the study group experienced the sudden onset of abdominal pain, which was continuous and progressively worsening. Patients with elevated serum amylase, a peptic ulcer history and increased intraoperative blood loss had a tendency to develop a postoperative perforated peptic ulcer. CONCLUSION: Spine surgeons should be highly alert to these risk factors of postoperative perforated peptic ulcers inpatients who has history of peptic ulcer, large amount ofintraoperative blood loss and abnormal high serum amylase level after elective spine surgery. Early diagnosis and emergent surgical intervention promote better outcomes.

Cyclotetrabenzoin Acetate: A Macrocyclic Porous Molecular Crystal for CO2 Separations by Pressure Swing Adsorption*.

A porous molecular crystal (PMC) assembled by macrocyclic cyclotetrabenzoin acetate is an efficient adsorbent for CO2 separations. The 7.1×7.1 Šsquare pore of PMC and its ester C=O groups play important roles in improving its affinity for CO2 molecules. The benzene walls of macrocycle engage in an apparent [π⋅⋅⋅π] interaction with the molecule of CO2 at low pressure. In addition, the polar carbonyl groups pointing inward the square channels reduce the size of aperture to a 5.0×5.0 Šsquare, which offers kinetic selectivity for CO2 capture. The PMC features water tolerance and high structural stability under vacuum and various gas adsorption conditions, which are rare among intrinsically porous organic molecules. Most importantly, the moderate adsorbate-adsorbent interaction allows the PMC to be readily regenerated, and therefore applied to pressure swing adsorption processes. The eluted N2 and CH4 are obtained with over 99.9 % and 99.8 % purity, respectively, and the separation performance is stable for 30 cycles. Coupled with its easy synthesis, cyclotetrabenzoin acetate is a promising adsorbent for CO2 separations from flue and natural gases.

Pb Stabilization by a New Chemically Durable Orthophosphate Phase: Insights into the Molecular Mechanism with X-ray Structural Analysis.

The rapid progression of piezoelectric technology and the upgradation of electronic devices have resulted in a global increase in Pb-based piezoelectric ceramic materials. In this study, the feasibility of incorporating Pb into a PbZr(PO4)2 double orthophosphate structure was evaluated by investigating the interaction mechanism of the perovskite with phosphate. The unique combination of X-ray absorption spectroscopy, selected area electronic diffraction, and Pawley refinement revealed that Pb was incorporated into a hexagonal structure and tetra-coordinated with oxygen in the phosphate-treated product. The chemical durability was enhanced through the structural alterations via Zr-O-P and Pb-O-P bond linkages. The stable phase encapsulating both Pb and phosphate showed effectiveness not only in stabilizing Pb but also in inhibiting P release as a secondary pollution risk within a wide pH range (1 ≤ pH ≤ 13). Despite the excellent chemical durability of the robust PbZr(PO4)2 crystalline phase, the increased Ti doping amounts at the Zr site resulted in a slight decrease in the lattice parameters and further enhanced the Pb stabilization effect through the formation of PbZrxTi(1-x)(PO4)2 solid solutions. This study demonstrates that the newly robust crystalline structure, developed through a well-designed thermal treatment scheme, provides an effective strategy for the treatment of Pb frequently encountered in electronic wastes.

Efficient Hydrogen Oxidation Catalyzed by Strain-Engineered Nickel Nanoparticles.

The hydroxide-exchange membrane fuel cell (HEMFC) is a promising energy conversion device. However, the development of HEMFC is hampered by the lack of platinum-group-metal-free (PGM-free) electrocatalysts for the hydrogen oxidation reaction (HOR). Now, a Ni catalyst is reported that exhibits the highest mass activity in HOR for a PGM-free catalyst as well as excellent activity in the hydrogen evolution reaction (HER). This catalyst, Ni-H2 -2 %, was optimized through pyrolysis of a Ni-containing metal-organic framework precursor under a mixed N2 /H2 atmosphere, which yielded carbon-supported Ni nanoparticles with different levels of strains. The Ni-H2 -2 % catalyst has an optimal level of strain, which leads to an optimal hydrogen binding energy and a high number of active sites.

New Templated Ostwald Ripening Process of Mesostructured FeOOH for Third-Harmonic Generation Bioimaging.

Emerging advances in iron oxide nanoparticles exploit their high magnetization for various applications, such as bioseparation, hyperthermia, and magnetic resonance imaging. In contrast to their excellent magnetic performance, the harmonic generation and luminescence properties of iron oxide nanoparticles have not been thoroughly explored, thus limiting their development as a tool in photomedicine. In this work, a seed/growth-inspired synthesis is developed combined with primary mineralization and a ligand-assisted secondary growth strategy to prepare mesostructured α-FeOOH nanorods (NRs). The sub-wavelength heterogeneity of the refractive index leads to enhanced third-harmonic generation (THG) signals under near-infrared excited wavelengths at 1230 nm. The as-prepared NRs exhibit an 11-fold stronger THG intensity compared to bare α-FeOOH NRs. Using these unique nonlinear optical properties, it is demonstrated that mesostructured α-FeOOH NRs can serve as biocompatible and nonbleaching contrast agents in THG microscopy for long-term labeling of cells as well as in angiography in vivo by modifying lectin to enhance the binding efficiency to the glycocalyx layers on the wall of blood vessels. These results provide a new insight into Fe-based nanoplatforms capable of emitting coherent light as molecular probes in optical microscopy, thus establishing a complementary microscopic imaging method for macroscopic magnetic imaging systems.

Site-Selective Occupancy of Eu2+ Toward Blue-Light-Excited Red Emission in a Rb3 YSi2 O7 :Eu Phosphor.

Establishing an effective design principle in solid-state materials for a blue-light-excited Eu2+ -doped red-emitting oxide-based phosphors remains one of the significant challenges for white light-emitting diodes (WLEDs). Selective occupation of Eu2+ in inorganic polyhedra with small coordination numbers results in broad-band red emission as a result of enhanced crystal-field splitting of 5d levels. Rb3 YSi2 O7 :Eu exhibits a broad emission band at λmax =622 nm under 450 nm excitation, and structural analysis and DFT calculations support the concept that Eu2+ ions preferably occupy RbO6 and YO6 polyhedra and show the characteristic red emission band of Eu2+ . The excellent thermal quenching resistance, high color-rendering index Ra (93), and low CCT (4013 K) of the WLEDs clearly demonstrate that site engineering of rare-earth phosphors is an effective strategy to target tailored optical performance.

Eu2+ Site Preferences in the Mixed Cation K2BaCa(PO4)2 and Thermally Stable Luminescence.

Site preferences of dopant Eu2+ on the locations of K+, Ba2+, and Ca2+ in the mixed cation phosphate K2BaCa(PO4)2 (KBCP) are quantitatively analyzed via a combined experimental and theoretical method to develop a blue-emitting phosphor with thermally stable luminescence. Eu2+ ions are located at K2 (M2) and K3 (M3) sites of KBCP, with the latter occupation relatively more stable than the former, corresponding to emissions at 438 and 465 nm, respectively. KBCP:Eu2+ phosphor exhibits highly thermal stable luminescence even up to 200 °C, which is interpreted as due to a balance between thermal ionization and recombination of Eu2+ 5d excited-state centers with the involvement of electrons trapped at crystal defect levels. Our results can initiate more exploration of activator site engineering in phosphors and therefore allow predictive control of photoluminescence tuning and thermally stable luminescence for emerging applications in white LEDs.

Interface-Controlled Synthesis of Au-BINOL Hybrid Nanostructures and Mechanism Study.

The combined functionality of components in organic-inorganic hybrid nanomaterials render them efficient nanoreactors. However, the development in this field is limited due to a lack of synthetic avenues and systematic control of the growth kinetics of hybrid structures. In this work, we take advantage of an ionic switch for regio-control of Au-BINOL(1,1'-Bi-2-naphthol) hybrid nanostructures. Aromatic BINOL molecules assemble into nanospheres, concomitant with the growth of the Au nanocrystals. The morphological evolution of Au nanocrystals is solely controlled by the presence of halides in the synthetic system. Here we show that quaternary ammonium surfactants (CTAB or CTAC), not only bridging Au and BINOL, but also contributing to the formation of concentric or eccentric structures when their concentrations are tuned to the range of 10-5 to 10-3 M. This facile strategy offers the potential advantage of scalable production, with diverse functional organic-inorganic hybrid nanocomposites being produced based on the specific archetype of Au-BINOL hybrid nanocomposites.

Hexagonal Perovskite Ba4Fe3NiO12 Containing Tetravalent Fe and Ni Ions.

BaFe xNi1- xO3 with end members of BaNiO3 ( x = 0) and BaFeO3 ( x = 1), which, respectively, adopt the 2H and 6H hexagonal perovskite structures, were synthesized, and their crystal structures were investigated. A new single phase, Ba4Fe3NiO12 ( x = 0.75), that adopts the 12R perovskite structure with the space group R3̅ m ( a = 5.66564(7) Å and c = 27.8416(3) Å), was found to be stabilized. Mössbauer spectroscopy results and structure analysis using synchrotron and neutron powder diffraction data revealed that nominal Fe3+ occupies the corner-sharing octahedral site while the unusually high valence Fe4+ and Ni4+ occupy the face-sharing octahedral sites in the trimers, giving a charge formula of Ba4Fe3+Fe4+2Ni4+O11.5. The magnetic properties of the compound are also discussed.

Charge Disproportionation in Sr0.5Bi0.5FeO3 Containing Unusually High Valence Fe3.5.

A Sr analogue of Ca0.5Bi0.5FeO3, Sr0.5Bi0.5FeO3, containing unusually high valence Fe3.5+ ions was synthesized by using a high-pressure technique. It relieves the electronic instability due to the unusually high valence of Fe3.5+ by a single charge disproportionation (CD) transition (Fe3.5+ → 0.75Fe3+ + 0.25Fe5+) rather than the successive CD and intermetallic charge transfer (CT) transitions seen in Ca0.5Bi0.5FeO3. Conduction-band narrowing due to the significant bend in the Fe-O-Fe bond in the rhombohedral R3̅c crystal structure stabilized the charge-disproportionated state at low temperatures. Most importantly, Bi3+ ions in Sr0.5Bi0.5FeO3 do not act as countercations accepting oxygen holes as they do in Ca0.5Bi0.5FeO3, resulting in the absence of the intermetallic CT transition. The large cavity of the A-site Sr ions prevents the charge-transferred Bi5+ from being stabilized. In the charge-disproportionated state the nearest-neighbor Fe3+ spins align antiferromagnetically and one-fourth of the Fe3+ spins are randomly replaced by Fe5+ spins coupled ferromagnetically with the neighboring Fe3+ spins.

Turning the Halide Switch in the Synthesis of Au-Pd Alloy and Core-Shell Nanoicosahedra with Terraced Shells: Performance in Electrochemical and Plasmon-Enhanced Catalysis.

Au-Pd nanocrystals are an intriguing system to study the integrated functions of localized surface plasmon resonance (LSPR) and heterogeneous catalysis. Gold is both durable and can harness incident light energy to enhance the catalytic activity of another metal, such as Pd, via the SPR effect in bimetallic nanocrystals. Despite the superior catalytic performance of icosahedral (IH) nanocrystals compared to alternate morphologies, the controlled synthesis of alloy and core-shell IH is still greatly challenged by the disparate reduction rates of metal precursors and lack of continuous epigrowth on multiply twinned boundaries of such surfaces. Herein, we demonstrate a one-step strategy for the controlled growth of monodisperse Au-Pd alloy and core-shell IH with terraced shells by turning an ionic switch between [Br(-)]/[Cl(-)] in the coreduction process. The core-shell IH nanocrystals contain AuPd alloy cores and ultrathin Pd shells (<2 nm). They not only display more than double the activity of the commercial Pd catalysts in ethanol electrooxidation attributed to monatomic step terraces but also show SPR-enhanced conversion of 4-nitrophenol. This strategy holds promise toward the development of alternate bimetallic IH nanocrystals for electrochemical and plasmon-enhanced catalysis.

Mechanical performance of spider silk is robust to nutrient-mediated changes in protein composition.

Spider major ampullate (MA) silk is sought after as a biomimetic because of its high strength and extensibility. While the secondary structures of MA silk proteins (spidroins) influences silk mechanics, structural variations induced by spinning processes have additional effects. Silk properties may be induced by spiders feeding on diets that vary in certain nutrients, thus providing researchers an opportunity to assess the interplay between spidroin chemistry and spinning processes on the performance of MA silk. Here, we determined the relative influence of spidroin expression and spinning processes on MA silk mechanics when Nephila pilipes were fed solutions with or without protein. We found that spidroin expression differed across treatments but that its influence on mechanics was minimal. Mechanical tests of supercontracted fibers and X-ray diffraction analyses revealed that increased alignment in the amorphous region and to a lesser extent in the crystalline region led to increased fiber strength and extensibility in spiders on protein rich diets.