Angular-dependent magnetoresistance modulated by interfacial magnetic state in Pt/LSMO heterostructures.

The interfaces between heavy metals and antiferromagnetic materials have garnered significant attention due to their interesting physical properties. La0.35Sr0.65MnO3 (LSMO), as a typical manganite, exhibits an antiferromagnetic ground state that can be controlled through epitaxial strain and interfacial spin-orbit coupling. In this work, we reported the diverse magnetoresistance, influenced by the interfacial magnetic state, in Pt (3 nm)/LSMO (6-20 nm) heterostructures. The strong spin-orbit coupling of Pt and Dzyaloshinskii-Moriya interaction alter the spin structure and enhance the electron scattering at the Pt/LSMO interface, resulting in positive magnetoresistance. The interfacial angular-dependent magnetoresistance modulated by the interfacial magnetic states was also observed in the Pt/LSMO (20 nm) heterostructures. Our findings contribute to a broader understanding of interfacial properties between heavy metals and antiferromagnetic manganites.

Realization of High Magnetization in Artificially Designed Ni/NiO Layers through Exchange Coupling.

High-magnetization materials play crucial roles in various applications. However, the past few decades have witnessed a stagnation in the discovery of new materials with high magnetization. In this work, Ni/NiO nanocomposites are fabricated by depositing Ni and NiO thin layers alternately, followed by annealing at specific temperatures. Both the as-deposited samples and those annealed at 373 K exhibit low magnetization. However, the samples annealed at 473 K exhibit a significantly enhanced saturation magnetization exceeding 607 emu cm-3 at room temperature, surpassing that of pure Ni (480 emu cm-3 ). Material characterizations indicate that the composite comprises NiO nanoclusters of size 1-2 nm embedded in the Ni matrix. This nanoclustered NiO is primarily responsible for the high magnetization, as confirmed by density functional theory calculations. The calculations also indicate that the NiO clusters are ferromagnetically coupled with Ni, resulting in enhanced magnetization. This work demonstrates a new route toward developing artificial high-magnetization materials using the high magnetic moments of nanoclustered antiferromagnetic materials.

Minimizing and Controlling Hydrogen for Highly Efficient Formamidinium Lead Triiodide Solar Cells.

Formamidinium lead triiodide (FAPbI3) currently holds the record conversion efficiency in the single-junction perovskite solar cell. Iodine management is known to be essential to suppress defect-induced nonradiative losses in FAPbI3 active layers. However, the origin of nonradiative losses and the underlying mechanism of suppressing such losses by iodine-concentration management remain unknown. Here, through first-principles simulation, we demonstrate that native point defects are not responsible for the nonradiative losses in FAPbI3. Instead, hydrogen ions, which can be abundant under both iodine-rich and iodine-poor conditions in FAPbI3, act as efficient nonradiative recombination centers and are proposed to be responsible for the suppressed power conversion efficiency. Moreover, iodine-moderate synthesis conditions can favor the formation of electrically inactive molecular hydrogen, which can dramatically suppress the detrimental hydrogen ions. This work identifies the dominant nonradiative recombination centers in the widely used FAPbI3 layers and rationalizes how the prevailing iodine management reduces the nonradiative losses. Minimizing the unintentional hydrogen incorporation in the perovskite is critical for achieving high device performance.

Boosting Oxygen Reduction Activity of Manganese Oxide Through Strain Effect Caused By Ion Insertion.

Transition-metal oxides with a strain effect have attracted immense interest as cathode materials for fuel cells. However, owing to the introduction of heterostructures, substrates, or a large number of defects during the synthesis of strain-bearing catalysts, not only is the structure-activity relationship complicated but also their performance is mediocre. In this study, a mode of strain introduction is reported. Transition-metal ions with different electronegativities are intercalated into the cryptomelane-type manganese oxide octahedral molecular sieves (OMS-2) structure with K ions as the template, resulting in the octahedral structural distortion of MnO6 and producing strains of different degrees. Experimental studies reveal that Ni-OMS-2 with a high compressive strain (4.12%) exhibits superior oxygen reduction performance with a half-wave potential (0.825 V vs RHE) greater than those of other reported manganese-based oxides. This result is related to the increase in the covalence of MnO6 octahedral configuration and shifting down of the eg band center caused by the higher compression strain. This research avoids the introduction of new chemical bonds in the main structure, weakens the effect of eg electron filling number, and emphasizes the pure strain effect. This concept can be extended to other transition-metal-oxide catalysts.

Hydrothermal Syntheses of Uranium Oxide Hydrate Materials with Sm(III) Ions: pH-Driven Diversities in Structures and Morphologies and Sm-Doped Porous Uranium Oxides Derived from Their Thermal Decompositions.

We report the hydrothermal syntheses of three uranyl oxide hydroxy-hydrate (UOH) materials containing Sm(III) ions (UOH-Sm) by controlling the solution pH and a new way to make Sm-doped porous uranium oxides with different U-to-Sm atomic ratios via their thermal decompositions. While layer-structured UOH-Sm phases with U-to-Sm atomic ratios of 1 (UOH-Sm1) and 4 (UOH-Sm2) were obtained from the reaction of schoepite and samarium nitrate with final solution pH values of over 4, similar reactions without pH adjustment with final solution pH values of less than 4 led to the formation of a uranyl oxide framework (UOF-Sm) with a U-to-Sm atomic ratio of 5.5. The crystal structure of compound UOF-Sm was revealed with synchrotron single-crystal X-ray diffraction and confirmed with transmission electron microscopy. The two-dimensional uranyl oxide hydroxide layers, similar to that for ß-U3O8, are linked by double pentagonal uranyl polyhedra to form a three-dimensional framework with Sm(III) ions in the channels. Scanning electron microscopy characterization revealed nanoplate crystal morphologies for the two UOH-Sm phases, in contrast to the needle morphology for UOF-Sm. Subsequent thermal treatments led to the formation of Sm-doped uranium oxides, maintaining the original crystal shapes and U-to-Sm ratios but with nanopores. This work demonstrated that the hydrothermal synthesis conditions, especially fine-tuning of the solution pH, have a significant impact on the uranium hydrolysis, thus leading to well-defined products. This will facilitate the targeted syntheses of UOH phases with lanthanide (Ln) ions and explore the subsequent applications of these materials and Ln-doped porous uranium oxides as potential nuclear or functional materials.

Electrocatalysts Based on Transition Metal Borides and Borates for the Oxygen Evolution Reaction.

Electrochemical water splitting is a clean and sustainable process for hydrogen production on a large scale as the electrical power required can be obtained from various renewable energy resources. The key challenge in electrochemical water splitting process is to develop low-cost electrocatalysts with high catalytic activity for the hydrogen evolution reaction (HER) on the cathode and the oxygen evolution reaction (OER) on the anode. OER is the most important half-reaction involved in water splitting, which has been extensively studied since the last century and a large amount of electrocatalysts including noble and non-noble metal-based materials have been developed. Among them, transition metal borides and borates (TMBs)-based compounds with various structures have attracted increasing attention owing to their excellent OER performance. In recent years, many efforts have been devoted to exploring the OER mechanism of TMBs and to improving the OER activity and stability of TMBs. In this review, recent research progress made in TMBs as efficient electrocatalysts for OER is summarized. The chemical properties, synthetic methodologies, catalytic performance evaluation, and improvement strategy of TMBs as OER electrocatalysts are discussed. The electrochemistry fundamentals of OER are first introduced in brief, followed by a summary of the preparation and performance of TMBs-based OER electrocatalysts. Finally, current challenges and future directions for TMBs-based OER electrocatalysts are discussed.

[U(H2O)2]{[(UO2)10O10(OH)2][(UO4)(H2O)2]}: A Mixed-Valence Uranium Oxide Hydrate Framework.

A uranium oxide hydrate framework, [U(H2O)2]{[(UO2)10O10(OH)2][(UO4)(H2O)2]} (UOF1), was synthesized hydrothermally using schoepite as a uranium precursor. The crystal strucutre of UOF1 was revealed with synchrotron single-crystal X-ray diffraction and confirmed with transmission electron miscroscopy. The typical uranyl oxide hydroxide layers similar to those in ß-U3O8 are further connected via double-pentagonal-bipyramidal uranium polyhedra to form a three-dimensional (3D) framework structure with tetravalent uranium species inside the channels. The presence of mixed-valence uranium was investigated with a combination of X-ray absorption near-edge structure and diffuse reflectance spectroscopy. Apart from the major hexavalent uranium, evidence for tetravalent uranium was also found, consistent with the bond valence sum calculations. The successful preparation of UOF1 as the first pure uranium oxide hydrate framework sheds light on the structural understanding of the alteration of UO2+x as either a mineral or spent nuclear fuel.

High mobility in α-phosphorene isostructures with low deformation potential.

The exceptionally low deformation potential is proposed as the key determinant for the high carrier mobility in α-phosphorene. This is related to its unique corrugated two-dimensional structure. Herein, we present a systematic first-principles density functional theory study on ten α-phosphorene isostructures by calculating the three key parameters of the carrier mobility. An electron mobility in the armchair direction with a value comparable to α-phosphorene is found in α-PAs, α-PCH, and α-AsCH, due to the structure-caused low deformation potential. The highest carrier mobility is predicted in α-graphane because of a two-orders-of-magnitude smaller deformation potential than the other isostructures. The low deformation potential can be correlated to the separation of charge carriers from neighbouring unit cells. This study highlights a feasible route to generating high mobility materials through deformation potential engineering.

Electric-field-mediated magnetic properties of all-oxide CoFe2O4/La0.67Sr0.33MnO3/Pb(Mg1/3Nb2/3)0.7Ti0.3O3 heterostructures.

Electric-field-mediated magnetic properties were investigated in CoFe2O4/La0.67Sr0.33MnO3/Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (CFO/LSMO/PMN-PT) heterostructures. The butterfly-like behavior of the magnetization under different electric fields indicates that the strain effect plays a critical role in the electric-field-mediated magnetic properties, leading to an increase in magnetization along the [100] direction but a decrease along the [01-1] direction in the CFO/LSMO/PMN-PT heterostructures. More interestingly, due to the large magnetostriction of the CFO layer, the coercivity of the CFO/LSMO/PMN-PT heterostructures decreases ∼50% along the [01-1] direction under the electric fields. The large modulation of the coercivity makes it possible to achieve electric-field-controlled magnetoresistance in the metal/CFO/LSMO/PMN-PT spin filter magnetic tunneling junctions.

Atomically Dispersed Single Co Sites in Zeolitic Imidazole Frameworks Promoting High-Efficiency Visible-Light-Driven Hydrogen Production.

As photocatalysis technology could transform renewable and clean solar energy into green hydrogen (H2 ) energy through solar water splitting, it is regarded as the "Holy Grail" in chemistry field in the 21st century. Unfortunately, the bottleneck of this technique still lies in the exploration of highly active, cost-effective, and robust photocatalysts. This work reports the design and synthesis of a novel zeolitic imidazole framework (ZIF) coupled Zn0.8 Cd0.2 S hetero-structured photocatalyst for high-performance visible-light-induced H2 production. State-of-the-art characterizations and theoretical computations disclose that the interfacial electronic interaction between ZIF and Zn0.8 Cd0.2 S, the high distribution of Zn0.8 Cd0.2 S on ZIF, and the atomically dispersed coordinately unsaturated Co sites in ZIF synergistically arouse the significantly improved visible-light photocatalytic H2 production performance.

Post-imprinting modification based on multilevel mesoporous silica for highly sensitive molecularly imprinted fluorescent sensors.

When molecularly imprinted fluorescent polymers (MIFPs) are prepared by the doping method (d-MIFPs), the fluorescent nanoparticles are quenched and passivated during the polymerization and elution process, and their detection sensitivity would be reduced. In this study, to overcome this drawback, MIFPs were synthesized by post-imprinting modification based on multilevel mesoporous structured silica. Briefly, multilevel mesoporous-structured BPA-imprinted polymers (MIPs) were prepared at first, and then, CdTe quantum dots were anchored onto the large pores of the MIPs to form p-MIFPs. Due to the well-maintained fluorescence intensity and low background, the sensitivity of the p-MIFPs was two orders of magnitude higher than that of the d-MIFPs. The F0/F- 1 of p-MIFPs was linear with BPA in the range of 0.005 to 4.0 µM with an LOD of 0.57 nM. Furthermore, post-imprinting modification was adopted to achieve ratiometric fluorescent MIPs (p-r-MIFPs) by simultaneously anchoring carbon dots and quantum dots onto the MIPs. The p-MIFPs and p-r-MIFPs were successfully applied to determine BPA in water samples with average recoveries ranging from 96.4% to 102.0% and an RSD below 4.1%. The results prove that post-imprinting modification is an effective method to construct MIFPs with conspicuous sensitivity, and multilevel mesoporous silica is an ideal matrix for the post-imprinting modification.

In-situ synthesis of Ni-Co-S nanoparticles embedded in novel carbon bowknots and flowers with pseudocapacitance-boosted lithium ion storage.

We design a facile approach to prepare a bimetallic transition-metal-sulphide-based 3D hierarchically-ordered porous electrode based on bimetallic metal-organic frameworks (Ni-Co-MOFs) by using confinement growth and in-situ sulphurisation techniques. In the novel resulting architectures, Ni-Co-S nanoparticles are confined in bowknot-like and flower-like carbon networks and are mechanically isolated but electronically well-connected, where the carbon networks with a honeycomb-like feature facilitate electron transfer with uninterrupted conductive channels from all sides. Moreover, these hierarchically-ordered porous structures together with internal voids can accommodate the volume expansion of the embedded Ni-Co-S nanoparticles. The pseudocapacitive behaviours displayed in the NCS@CBs and NCS@CFs occupied a significant portion in the redox processes. Because of these merits, both the as-built bowknot and flower networks show excellent electrochemical properties for lithium storage with superior rate capability and robust cycling stability (994 mAh g-1 for NCS@CBs and 888 mAh g-1 for NCS@CFs after 200 cycles). This unique 3D hierarchically-ordered structural design is believed to hold great potential applications in propagable preparation of carbon networks teamed up with sulphide nanocrystals for high energy storage.

Quantitative Determination of How Growth Conditions Affect the 3D Composition of InGaAs Nanowires.

Covering a broad optical spectrum, ternary InxGa1-xAs nanowires, grown by bottom-up methods, have been receiving increasing attention due to the tunability of the bandgap via In composition modulation. However, inadequate knowledge about the correlation between growth and properties restricts our ability to take advantage of this phenomenon for optoelectronic applications. Here, three different InGaAs nanowires were grown under different experimental conditions and atom probe tomography was used to quantify their composition, allowing the direct observation of the nanowire composition associated with the different growth conditions.

Uranium Oxide Hydrate Frameworks with Dy(III) or Lu(III) Ions: Insights Into the Framework Structures With Lanthanide Ions.

Two uranium oxide hydrate frameworks (UOHFs) with either Dy3+ or Lu3+ ions, Dy1.36(H2O)6[(UO2)10UO13(OH)4] (UOHF-Dy) or Lu2(H2O)8[(UO2)10UO14(OH)3] (UOHF-Lu), were synthesized hydrothermally and characterized with a range of structural and spectroscopic techniques. Although SEM-EDS analysis confirmed the same atomic ratio of ~5.5 for U : Dy and U : Lu, they displayed different crystal morphologies, needles for UOHF-Dy in the orthorhombic C2221 space group and plates for UOHF-Lu in the triclinic P-1 space group. Both frameworks are composed of ß-U3O8 type layers linked by pentagonal bipyramidal uranium polyhedra, with the Dy3+/Lu3+ ions inside the channels. However, the arrangements of Dy3+/Lu3+ ions are different, with disordered Dy3+ ions well aligned at the centers of the channels and single Lu3+ ions well-separated in a zigzag pattern in the channels. While the characteristic vibrational modes were revealed by Raman spectroscopy, the presence of a pentavalent uranium center in UOHF-Lu was confirmed with diffuse reflectance spectroscopy. The formation of two types of UOHFs with lanthanide ions, high or low symmetry, and the structure trend were discussed regards to synthesis conditions and lanthanide ionic radius. This work highlights the complex chemistry driving the formation of UOHFs with lanthanide ions and has implications to the spent nuclear fuel under geological disposal.

Serratia marcescens induces apoptosis in Diaphorina citri gut cells via reactive oxygen species-mediated oxidative stress.

BACKGROUND: Asian citrus psyllid, Diaphorina citri, is a notorious pest in the citrus industry because it transmits Candidatus Liberibacter asiaticus, which causes an uncurable, devastating disease in citrus worldwide. Serratia marcescens is widely distributed in various environments that exhibits toxic effects to many insects. To develop strategies for enhancing the efficiency of pathogen-induced host mortality, a better understanding of the toxicity mechanism of Serratia marcescens on Diaphorina citri is critical. RESULTS: Serratia marcescens KH-001 successfully colonized Diaphorina citri gut by feeding artificial diets, resulting in the damage of cells including nucleus, mitochondria, vesicles, and microvilli. Oral ingestion of Serratia marcescens KH-001 strongly induced apoptosis in gut cells by enhancing levels of Cyt c, p53 and caspase-1 and decreasing levels of inhibitors of apoptosis (IAP) and Bax inhibitor-1 (BI-1). The expression of dual oxidase (Duox) and nitric oxide synthase (Nos) was up-regulated by Serratia marcescens KH-001, which increased hydrogen peroxide (H2 O2 ) levels in the gut. Injection of abdomen of Diaphorina citri with H2 O2 accelerated the death of the adults and induced apoptosis in the gut cells by activating Cyt c, p53 and caspase-1 and suppressing IAP and BI-1. Pretreatment of infected Diaphorina citri with vitamin c (Vc) increased the adult survival and diminished the apoptosis-inducing effect. CONCLUSIONS: The colonization of Serratia marcescens KH-001 in the guts of Diaphorina citri increased H2 O2 accumulation, leading to severe changes and apoptosis in intestinal cells, which enhanced a higher mortality level of D. citr. This study identifies the underlying virulence mechanism of Serratia marcescens KH-001 on Diaphorina citri that contributes to a widespread application in the integrated management of citrus psyllid. © 2023 Society of Chemical Industry.

Kinetic Process with Anti-Frenkel Disorder in a CsPbI3 Perovskite.

Halide perovskites are rich in ionic diffusion phenomena due to their low activation energy. The soft lead iodide lattice can, in theory, endow the system with more complex defect collaborative motions. In this work, we systematically investigated the hopping mechanics of iodide interstitials with respect to various defect behaviors, such as anti-Frenkel disorder creation and annihilation. We found that the existence of iodide vacancies and interstitials can effectively lower the creation barrier of additional anti-Frenkel disorder in the halide perovskite. The free energy barriers for generating additional Frenkel defect pairs vary from 0.25 to 0.43 eV, in the proximity of those of the original iodide defects at 300 K. This finding suggests that the spontaneous creation of a specific level of anti-Frenkel disorder facilitates long-range annihilation and defect hopping processes.

Toward stabilization of formamidinium lead iodide perovskites by defect control and composition engineering.

Phase instability poses a serious challenge to the commercialization of formamidinium lead iodide (FAPbI3)-based solar cells and optoelectronic devices. Here, we combine density functional theory and machine learning molecular dynamics simulations, to investigate the mechanism driving the undesired α-δ phase transition of FAPbI3. Prevalent iodine vacancies and interstitials can significantly expedite the structural transition kinetics by inducing robust covalency during transition states. Extrinsically, the detrimental roles of atmospheric moisture and oxygen in degrading the FAPbI3 perovskite phase are also rationalized. Significantly, we discover the compositional design principles by categorizing that A-site engineering primarily governs thermodynamics, whereas B-site doping can effectively manipulate the kinetics of the phase transition in FAPbI3, highlighting lanthanide ions as promising B-site substitutes. A-B mixed doping emerges as an efficient strategy to synergistically stabilize α-FAPbI3, as experimentally demonstrated by substantially higher initial optoelectronic characteristics and significantly enhanced phase stability in Cs-Eu doped FAPbI3 as compared to its Cs-doped counterpart. This study provides scientific guidance for the design and optimization of long-term stable FAPbI3-based solar cells and other optoelectronic devices through defect control and synergetic composition engineering.

A trinity strategy enabled by iodine-loaded nitrogen-boron-doped carbon protective layer for dendrite-free zinc-ion batteries.

Although aqueous zinc ion batteries (AZIBs) have the merits of environmental friendliness, high safety and theoretical capacity, the slow kinetics associated with zinc deposition and unavoidable interfacial corrosion have seriously affected the commercialization of aqueous zinc ion batteries. In this work, an ingenious "trinity" design is proposed by applying a porous hydrophilic carbon-loaded iodine coating to the zinc metal surface (INBC@Zn), which simultaneously acts as an artificial protective layer, electrolyte additive and anode curvature regulator, so as to reduce the nucleation overpotential of Zn and promote the preferential deposition of (002) planes to some extent. With this synergistic effect, INBC@Zn exhibits high reversibility and strong side reaction inhibition. As a result, INBC@Zn shows high symmetric cycling stability up to 4500 h at 1 mA cm-2. An ultra-long cycle stability of 1500 cycles with high Coulombic efficiency (99.8 %) is achieved in the asymmetric cell. In addition, the INBC@Zn//NVO full cells exhibit impressive capacity retention (96 % after 1000 cycles at 3 A/g). Importantly, the designed pouch cell demonstrates stable performance and shows certain prospects for application. This work provides a facile and instructive approach toward the development of high-performance AZIBs.

Filling the gaps of uranium oxide hydrates with magnesium(II) ions: unique layered structures and the role of additional sodium(I) ions.

Alkaline earth metal ions play an important role in the formation of secondary uranium minerals due to their abundance in the Earth's crust. Although uranium oxide hydrate (UOH) minerals and synthetic phases with calcium, strontium and barium ions have been investigated, their counterparts with magnesium ions are much less studied. In this work, synthetic UOH materials with magnesium ions have been investigated with three new compounds being synthesised and characterised. Compound Mg2(H3O)2(H2O)6[(UO2)3O4(OH)]2 (U-Mg1 with a U : Mg ratio of 3 : 1) crystallises in the monoclinic P21/c space group having a layered crystal structure, constructed by ß-U3O8 layers with 6-fold coordinated Mg2+ ions as interlayer cations. Compound Na2Mg(H2O)4[(UO2)3O3(OH)2]2 (U-Mg2p with U : Mg : Na ratios of 6 : 1 : 2) crystallises in the triclinic P1̄ space group having a layered structure, constructed by a unique type of uranium oxide hydroxide layer containing both α-U3O8 and ß-U3O8 features, with alternating layers of 6-fold coordinated Mg2+ and 6-/8-fold coordinated Na+ interlayer cations. Compound Na2Mg(H2O)4[(UO2)4O3(OH)4]2 (U-Mg2n with U : Mg : Na ratios of 8 : 1 : 2) crystallises in the triclinic P1̄ space group having a corrugated layer structure, constructed by a unique type of uranium oxide hydroxide layer with mixed 6-fold coordinated Mg2+ and 7-fold coordinated Na+ interlayer cations. The structural diversity in the UOH-Mg system was achieved by adjusting the solution pH using NaOH, highlighting the importance of solution pH control and the additional Na+ ions in the formation of UOH phases. The extra structural flexibility offered by the Na+ ions emphasizes the opportunity for synthesising UOHs with dual-cations to further improve our understanding of the alteration products of spent nuclear fuel under geological disposal.

Origin of Enhanced Nonradiative Carrier Recombination Induced by Oxygen in Hybrid Sn Perovskite.

Oxygen ingression has been shown to substantially decrease the carrier lifetime of Sn-based perovskites, behind which the mechanism remains yet unknown. Our first-principles calculations reveal that in prototypical MASnI3 (MA = CH3NH3), oxygen by itself is not a recombination center. Instead, it tends to form substitutional OI through combining with native I vacancies (VI) and remarkably increases the original recombination rate of VI by 2-3 orders of magnitude. This rationalizes the experimentally observed sharp decline of carrier lifetime in perovskites exposed to air. The significantly enhanced carrier recombination is due to a smaller electron capture barrier of OI, resulting from lattice strengthening and the suppressed structural relaxation upon electron capture. These insights offer a route to further improve device performance via anion engineering in broad Sn-based perovskite optoelectronics operating in ambient air. Moreover, our results highlight the important role of lattice relaxation for nonradiative carrier capture in materials in general.