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Single-molecule imaging is challenging but highly beneficial for investigating intermolecular interactions at the molecular level1-6. Van der Waals interactions at the sub-nanometre scale strongly influence various molecular behaviours under confinement conditions7-11. Inspired by the traditional compass12, here we use a para-xylene molecule as a rotating pointer to detect the host-guest van der Waals interactions in the straight channel of the MFI-type zeolite framework. We use integrated differential phase contrast scanning transmission electron microscopy13-15 to achieve real-space imaging of a single para-xylene molecule in each channel. A good correlation between the orientation of the single-molecule pointer and the atomic structure of the channel is established by combining the results of calculations and imaging studies. The orientations of para-xylene help us to identify changes in the van der Waals interactions, which are related to the channel geometry in both spatial and temporal dimensions. This work not only provides a visible and sensitive means to investigate host-guest van der Waals interactions in porous materials at the molecular level, but also encourages the further study of other single-molecule behaviours using electron microscopy techniques.
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Dielectrics with high, nonvolatile, and multiple polarizations are required for fabricating memcapacitors that enable high parallelism and low energy consumption in artificial neuromorphic computing systems as artificial synapses. Conventional ferroelectric materials based on displacive and order-disorder types generally have difficulty meeting these requirements due to their low polarization values (â¼150 µC/cm2) and persistent electrical hysteresis loops. In this study, we report a novel organic-inorganic hybrid (CETM)2InCl5·H2O (CETM = (CH3)3(CH2CH2Cl)N) exhibiting an intriguing polarization vs electric field (charge vs voltage) "hysteresis loop" and a record-high nonvolatile polarization over 30â¯000 µC/cm2 at room temperature. The polarization is highly dependent on the period and amplitude of the ac voltage, showing multiple nonvolatile states. Electrochemical impedance spectroscopy, time-dependent current behavior, disparate resistor response in the dehydrated derivative (CETM)2InCl5, and the negative temperature dependence of ionic conductance support that the memcapacitor behavior of (CETM)2InCl5·H2O stems from irreversible long-range migration of protons. First-principles calculations further confirm this and clarify the microscale mechanism of anisotropic polarization response. Our findings may open up a new avenue for developing memcapacitors by harnessing the benefits of ion migration in organic-inorganic hybrids.
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The quest for high-performance piezoelectric materials has been synonymous with the pursuit of the morphotropic phase boundary (MPB), yet the full potential of MPBs remains largely untapped outside of the realm of ferroelectrics. In this study, we reveal a new class of MPB by creating continuous molecular-based solid solutions between centro- and noncentrosymmetric compounds, exemplified by (tert-butylammonium)1-x(tert-amylammonium)xFeCl4 (0 ≤ x ≤ 1), where the MPB is formed due to disorder of molecular cations. Near the MPB, we discovered an exceptionally sensitive nonlinear optical material in the centrosymmetric phase, capable of activation at pressures as low as 0.12-0.27 GPa, and producing tunable second-harmonic generation (SHG) signals from zero to 18.8 times that of KH2PO4 (KDP). Meanwhile, synchrotron diffraction experiments have unveiled a third competing phase (P212121) appearing at low pressure, forming a triple-phase point near the MPB, thereby providing insight into the mechanism underpinning the nonlinear optical (NLO) switch behavior. These findings highlight the opportunity to harness exceptional physical properties in symmetry-breaking solid solution systems by strategically designing novel MPBs.
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Developing non-platinum group metal catalysts for the sluggish hydrogen oxidation reaction (HOR) is critical for alkaline fuel cells. To date, Ni-based materials are the most promising candidates but still suffer from insufficient performance. Herein, we report an unconventional hcp/fcc Ni (u-hcp/fcc Ni) heteronanocrystal with multiple epitaxial hcp/fcc heterointerfaces and coherent twin boundaries, generating rugged surfaces with plenty of asymmetric convex sites. Systematic analyses discover that such convex sites enable the adsorption of *H in unusual bridge positions with weakened binding energy, circumventing the over-strong *H adsorption on traditional hollow positions, and simultaneously stabilizing interfacial *H2O. It thus synergistically optimizes the HOR thermodynamic process as well as reduces the kinetic barrier of the rate-determining Volmer step. Consequently, the developed u-hcp/fcc Ni exhibits the top-rank alkaline HOR activity with a mass activity of 40.6â mA mgNi -1 (6.3â times higher than fcc Ni control) together with superior stability and high CO-tolerance. These results provide a paradigm for designing high-performance catalysts by shifting the adsorption state of intermediates through configuring surface sites.
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All two-dimensional (2D) materials of group IV elements from Si to Pb are stabilized by carrier doping and interface bonding from substrates except graphene which can be free-standing. The involvement of strong hybrid of bonds, adsorption of exotic atomic species, and the high concentration of crystalline defects are often unavoidable, complicating the measurement of the intrinsic properties. In this work, we report the discovery of seven kinds of hitherto unreported bulk compounds (RO)nPb (R = rare earth metals, n = 1,2), which consist of quasi-2D Pb square nets that are spatially and electronically detached from the [RO]δ+ blocking layers. The band structures of these compounds near Fermi levels are relatively clean and dominantly contributed by Pb, resembling the electron-doped free-standing Pb monolayer. The R2O2Pb compounds are metallic at ambient pressure and become superconductors under high pressures with much enhanced critical fields. In particular, Gd2O2Pb (9.1 µB/Gd) exhibits an interesting bulk response of lattice distortion in conjunction with the emergence of superconductivity and magnetic anomalies at a critical pressure of 10 GPa. Our findings reveal the unexpected facets of 2D Pb sheets that are considerably different from their bulk counterparts and provide an alternative route for exploring 2D properties in bulk materials.
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Currently, most predictions of metabolic-associated fatty liver disease (MAFLD) in school-aged children utilize indicators that usually predict nonalcoholic fatty liver disease (NAFLD). The present study aimed to develop new predictive models and predictors for children with MAFLD, which could enhance the feasibility of MAFLD screening programs in the future. A total of 331 school-aged overweight/obese children were recruited from six primary schools in Ningbo city, China. Hepatic steatosis and fibrosis were detected with controlled attenuation parameter (CAP) and liver stiffness measurement (LSM), respectively. Machine learning methods were adapted to build a set of variables to predict MAFLD in children. Then, the area under the curve (AUC) of multiple models and indices was compared to predict pediatric MAFLD. Compared with non-MAFLD children, children with MAFLD had more obvious metabolic disturbances, as they had higher anthropometric indicators, alanine aminotransferase, fasting plasma glucose, and inflammation indicators (white blood cell count, hemoglobin, neutrophil count) (all P < 0.05). The optimal variables for all subjects selected by random forest (RF) were alanine aminotransferase, uric acid, insulin, and BMI. The logistic regression (LR) model performed best, with AUC values of 0.758 for males and 0.642 for females in predicting MAFLD. LnAI-BMI, LnAI, and LnAL-WHtR were approving indices for predicting pediatric MAFLD in all participants, boys and girls individually. CONCLUSIONS: This study developed LR models and sex-specific indices for predicting MAFLD in overweight/obese children that may be useful for widespread screening and identification of children at high risk of MAFLD for early treatment. WHAT IS KNOWN: ⢠Most of the indicators predicting pediatric MAFLD are derived from the predictive indicators for NAFLD, but the diagnostic criteria for MAFLD and NAFLD are not exactly the same. ⢠The accuracy of predictors based on routine physical examination and blood biochemical indicators to diagnose MAFLD is limited. WHAT IS NEW: ⢠This study developed indicators based on routine examination parameters that have approving performance for MAFLD, with AUC values exceeding 0.70.
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Hepatopatia Gordurosa não Alcoólica , Obesidade Infantil , Masculino , Feminino , Criança , Humanos , Sobrepeso/complicações , Sobrepeso/diagnóstico , Hepatopatia Gordurosa não Alcoólica/diagnóstico , Alanina Transaminase , Obesidade Infantil/complicações , Obesidade Infantil/diagnóstico , AntropometriaRESUMO
The nanostructuring of single-molecule magnets (SMMs) on substrates, in nanotubes and periodic frameworks is highly desired for the future magnetic recording devices. However, the ability to organize SMMs into long-range ordered arrays in these systems is still lacking. Here, we report the incorporation of magnetic (RECl2 (H2 O)6 )+ (RE=rare earths) molecular groups into the framework of an organic metal halide perovskite (OMHP)-(H2 dabco)CsCl3 . Intriguingly, we show the incorporated rare-earth groups self-organized into long-range ordered arrays that uniformly and periodically distributed in the A sites of OMHP. The ordered (RECl2 (H2 O)6 )+ groups serve as SMMs in the perovskite frameworks, exhibiting large effective magnetic moment, moderate magnetic anisotropy and two-step relaxation behavior. With the additional merit of great structural flexibility and multifunction of OMHPs, the preparation of the first SMMs@OMHP magnetic materials furthers the development of molecular spintronics.
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Lower olefins-generally referring to ethylene, propylene and butylene-are basic carbon-based building blocks that are widely used in the chemical industry, and are traditionally produced through thermal or catalytic cracking of a range of hydrocarbon feedstocks, such as naphtha, gas oil, condensates and light alkanes. With the rapid depletion of the limited petroleum reserves that serve as the source of these hydrocarbons, there is an urgent need for processes that can produce lower olefins from alternative feedstocks. The 'Fischer-Tropsch to olefins' (FTO) process has long offered a way of producing lower olefins directly from syngas-a mixture of hydrogen and carbon monoxide that is readily derived from coal, biomass and natural gas. But the hydrocarbons obtained with the FTO process typically follow the so-called Anderson-Schulz-Flory distribution, which is characterized by a maximum C2-C4 hydrocarbon fraction of about 56.7 per cent and an undesired methane fraction of about 29.2 per cent (refs 1, 10, 11, 12). Here we show that, under mild reaction conditions, cobalt carbide quadrangular nanoprisms catalyse the FTO conversion of syngas with high selectivity for the production of lower olefins (constituting around 60.8 per cent of the carbon products), while generating little methane (about 5.0 per cent), with the ratio of desired unsaturated hydrocarbons to less valuable saturated hydrocarbons amongst the C2-C4 products being as high as 30. Detailed catalyst characterization during the initial reaction stage and theoretical calculations indicate that preferentially exposed {101} and {020} facets play a pivotal role during syngas conversion, in that they favour olefin production and inhibit methane formation, and thereby render cobalt carbide nanoprisms a promising new catalyst system for directly converting syngas into lower olefins.
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Alcenos/síntese química , Monóxido de Carbono/química , Carbono/química , Carvão Mineral , Cobalto/química , Hidrogênio/química , Nanoestruturas/química , Gás Natural , Biomassa , Catálise , Metano/síntese química , Microscopia Eletrônica de Transmissão , Nanoestruturas/ultraestrutura , PressãoRESUMO
Creating high-density durable bifunctional active sites in an air electrode is essential but still challenging for a long-life rechargeable zinc-air battery with appealing power density. Herein, we discover a general strategy mediated by metastable rock salt oxides for achieving high-density well-defined transition-metal nanocrystals encapsulated in N-doped carbon shells (M@NC) which are anchored on a substrate by a porous carbon network as highly active and durable bifunctional catalytic sites. Small-size (15 ± 5 nm) well-dispersed Co2Fe1@NC in a high density (metal loading up to 54.0 wt %) offers the zinc-air battery a record power density of 423.7 mW cm-2. The dual protection from the complete graphitic carbon shells and the anchoring of the outer carbon network make Co2Fe1@NC chemically and mechanically durable, giving the battery a long cycling life. Systematic in-situ temperature-dependent characterizations as well as DFT modeling rationalize the rock salt oxide-mediated process and its indispensable role in achieving high-density nanosized M@NC. These findings open up opportunities for designing efficient electrocatalysts for high-performance Zn-air batteries and diverse energy devices.
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Treatment of advanced BRAFV600-mutant melanoma using BRAF inhibitors (BRAFi) eventually leads to drug resistance and selects for highly metastatic tumor cells. We compared the most differentially dysregulated miRNA expression profiles of vemurafenib-resistant and highly-metastatic melanoma cell lines obtained from GEO DataSets. We discovered miR-152-5p was a potential regulator mediating melanoma drug resistance and metastasis. Functionally, knockdown of miR-152-5p significantly compromised the metastatic ability of BRAFi-resistant melanoma cells and overexpression of miR-152-5p promoted the formation of slow-cycling phenotype. Furthermore, we explored the cause of how and why miR-152-5p affected metastasis in depth. Mechanistically, miR-152-5p targeted TXNIP which affected metastasis and BRAFi altered the methylation status of MIR152 promoter. Our study highlights the crucial role of miR-152-5p on melanoma metastasis after BRAFi treatment and holds significant implying that discontinuous dosing strategy may improve the benefit of advanced BRAFV600-mutant melanoma patients.
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Proteínas de Transporte/genética , Melanoma/patologia , MicroRNAs/genética , Proteínas Proto-Oncogênicas B-raf/antagonistas & inibidores , Neoplasias Cutâneas/patologia , Proteínas de Transporte/metabolismo , Ciclo Celular/genética , Linhagem Celular Tumoral , Movimento Celular/genética , Desmetilação , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Resistencia a Medicamentos Antineoplásicos/genética , Feminino , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Humanos , Masculino , Melanoma/tratamento farmacológico , Melanoma/genética , MicroRNAs/metabolismo , Pessoa de Meia-Idade , Mutação , Metástase Neoplásica/genética , Regiões Promotoras Genéticas , Inibidores de Proteínas Quinases/farmacologia , Inibidores de Proteínas Quinases/uso terapêutico , Proteínas Proto-Oncogênicas B-raf/genética , Neoplasias Cutâneas/tratamento farmacológico , Neoplasias Cutâneas/genética , Vemurafenib/farmacologia , Vemurafenib/uso terapêutico , Melanoma Maligno CutâneoRESUMO
Vacancy engineering plays vital role in the design of high-performance electrocatalysts. Here, we introduced coupled cation-vacancy pairs in Ni-doped CoSe to achieve boosted hydrogen evolution reaction (HER) activity through a facile topochemical intercalation approach. Adjacent Co vacancy pairs and heteroatom Ni doping contribute together for the upshift of the Se 4pz orbital, which induces larger overlap between the Seâ 4p and Hâ 1s orbitals. As a result, the free energy of H adsorption can be lowered significantly. With an advanced HER activity of 185.7â mV at 10â mA cm-2 , this work provides new direction and guidance for the design of novel electrocatalysts.
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The pairing of ions of opposite charge is a central principle of chemistry. Even though the ability to intercalate anions is desirable for many applications, it remains a key challenge for numerous host materials with their outmost layers beingn anions. In this work, we introduce a hydrothermal ion-exchange synthesis to intercalate oxidative S and Se anions between the Se layers of FeSe, which leads to single crystals of novel compounds (Se/S)x(NH3)yFe2Se2. In particular, the unusual anion-anion bonding between the intercalated S (or Se) and Se layers exhibits strong ionic characteristics. The charge transfer through the Se layer to S (or Se) intercalants is further confirmed by the elevated oxidation state of Fe ions and the dominant hole carriers in the intercalated compounds. By intercalating S, for the first time superconductivity emerged in hole-doped iron chalcogenides. The generality of this chemical approach was further demonstrated with layered FeS and NiSe. Our findings thus open an avenue to exploring diverse aspects of anionic intercalation in similar materials.
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Here, we report the crystal structures and properties of Rb xNbSe2, with 0 ≤ x ≤ 0.5. With Rb intercalation, Rb xNbSe2 evolves from 2H (Phase I) for 0 ≤ x ≤ 0.025, to 6R (Phase II) for x â¼ 0.2 with space group R3 m (no. 166), and finally to 2H (Phase IV) for 0.375 ≤ x ≤ 0.5 with space group P63/ mmc (no. 194). In addition, Phase II is found to transform to a rare 6H structure (Phase III) with space group P63/ mmc (no. 194) by annealing at a relatively low temperature. We show the first 6H phase in the intercalated transition-metal dichalcogenides (TMDs) family obtained through a solid-state reaction. Moreover, both 6R and 6H phases are new polymorphs in the NbSe2 system. For the range 0.2 ≤ x ≤ 0.5 in Rb xNbSe2, we show metallic electronic transport behavior and a paramagnetic feature. The lack of superconductivity (SC) down to 2 K is most probably due to the decrease of hole carrier density with increasing Rb content. Through careful analysis of the structural data, we were able to assemble a phase diagram covering the range of 0 ≤ x ≤ 0.5 in Rb xNbSe2.
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BACKGROUND: Facial features vary in size and proportions between different races. This study aimed to measure the anthropometric variables of the labial region in Han Chinese young adults. MATERIALS AND METHODS: A total of 900 college students (475 male and 425 female) of Chinese Han ethnicity from the northern China were included. Measurements of the labial region included 14 linear items and seven proportions. RESULTS: All the linear measurements of the males were significantly higher than those of the females (all P < 0.001). Significant gender differences were found in the philtrum morphology, philtrum width, upper vermilion-cutaneous lip, lower vermilion-cutaneous lip, and vermilion. There are significant differences in the anthropometric variables of the labial region between male and female Han Chinese young adults. CONCLUSIONS: These data may be used as a reference standard for labial reconstructive and aesthetic surgery.
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Antropometria/métodos , Povo Asiático/etnologia , Face/anatomia & histologia , Lábio/anatomia & histologia , Adolescente , China/etnologia , Estudos Transversais , Feminino , Humanos , Masculino , Valores de Referência , Fatores Sexuais , Adulto JovemRESUMO
BACKGROUND: Rhinophyma is a rare disease characterized by chronic inflammation and hypertrophy of sebaceous glands, blood vessels, and fibrous tissue, associated with end-stage severe acne rosacea. There are multiple approaches to treatment and repair, including dermal shaving, secondary intention healing, free skin graft, and skin flaps. However, these methods have various disadvantages, such as prolonged healing, obvious scarring, and skin texture mismatch. Therefore, the authors adopted surgical excision with bilateral pedicled nasolabial flaps, which have better color, texture, thickness, and symmetry. METHODS: The authors present a case of severe nasal tip rhinophyma successfully treated by excision and repair with bilateral pedicled nasolabial flaps. This procedure combines deep excision of the focal lesion and coverage with bilateral nasolabial flaps. RESULTS: The bilateral pedicled nasolabial flaps were used for severe rhinophyma in a patient. After the operation, the flaps survived uneventfully in this study. Both functional and aesthetic results were satisfactory at 3 months. CONCLUSION: The authors offer an effective method for surgical treatment of rhinophyma. Excision of hypertrophic nasal tissue is an acknowledged effective treatment for patients with severe rhinophyma. After excision, reconstruction with nasolabial flaps results in satisfactory outcomes both functionally and aesthetically. Therefore, this approach should be considered an appropriate alternative in cases of severe rhinophyma.
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Rinofima/cirurgia , Retalhos Cirúrgicos/cirurgia , Derme/patologia , Humanos , Masculino , Pessoa de Meia-Idade , Nariz/cirurgia , Deformidades Adquiridas Nasais/cirurgia , Transplante de Pele , Resultado do TratamentoRESUMO
We report a new type of MAX phase (M=transition metals, A=main group elements, and X=C/N), Nb3 As2 C, designated as 321â phase. It differs from all the previous Mn+1 AXn phases in that it consists of an alternate stacking of one MX layer and two MA layers in its unit cell, while only one MA layer is allowed in usual MAX phases. The new 321â phase exhibits a bulk modulus of Nb3 As2 C up to 225(3)â GPa as determined by high-pressure synchrotron X-ray diffraction, one of the highest values among MAX phases. Isostructural 321 phases V3 As2 C, Nb3 P2 C, and Ta3 P2 C are also found to exist. First-principles calculations reveal the outstanding elastic stiffness in 321â phases. Among all 321â phases, Nb3 P2 C is predicted to have the highest elastic properties. These 321â phases, represented by a chemical formula Mn+1 An X, were added as new members to the MAX family and their other properties deserve future investigations.
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All-inorganic lead halide perovskites demonstrate improved thermal stability over the organic-inorganic halide perovskites, but the cubic α-CsPbI3 with the most appropriate bandgap for light harvesting is not structurally stable at room temperature and spontaneously transforms into the undesired orthorhombic δ-CsPbI3. Here, we present a new member of black-phase thin films of all-inorganic perovskites for high-efficiency photovoltaics, the orthorhombic γ-CsPbI3 thin films with intrinsic thermodynamic stability and ideal electronic structure. Exempt from introducing organic ligands or incorporating mixed cations/anions into the crystal lattice, we stabilize the γ-CsPbI3 thin films by a simple solution process in which a small amount of H2O manipulates the size-dependent phase formation through a proton transfer reaction. Theoretical calculations coupled with experiments show that γ-CsPbI3 with a lower surface free energy becomes thermodynamically preferred over δ-CsPbI3 at surface areas greater than 8600 m2/mol and exhibits comparable optoelectronic properties to α-CsPbI3. Consequently, γ-CsPbI3-based solar cells display a highly reproducible efficiency of 11.3%, among the highest records for CsPbI3 thin-film solar cells, with robust stability in ambient atmosphere for months and continuous operating conditions for hours. Our study provides a novel and fundamental perspective to overcome the Achilles' heel of the inorganic lead iodide perovskite and opens it up for high-performance optoelectronic devices.
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Scar treatments are considered a major issue in the plastic surgery field. Activation of the transforming growth factor-ß (TGF-ß)-mediated signaling pathway plays a key role in the scar pathogeneses, and high temperature requirement factor A1 (HTRA1) inhibits TGF-ß1 activation in tumor cells. Our study aims to investigate the role of HTRA1 in the pathogenesis of scars. The mRNA levels of HTRA1 was evaluated by real time PCR, HTRA1 protein expression was determined using western blot and immunohistochemistry, and a luciferase assay was applied to measure dynamic changes of TGF-ß1 activity. We found that the expression of HTRA1 was significantly elevated in keloid tissues, compared to normal skin, and TGF-ß1 mRNA levels slightly increase in the keloid tissue. Furthermore, active TGF-ß1 protein levels and Smad2 phosphorylation significantly increased in the keloid tissue. Treatment with the latent TGF-ß1 or recombinant human HTRA1 (rhHTRA1), alone or in combination, increased Smad2 phosphorylation levels in keloid fibroblasts and active TGF-ß1 contents of associated supernatants. Our results suggest that HTRA1 is involved in the pathogenesis of scars through regulating activation of latent TGF-ß1 in keloid fibroblasts, and our study reveals that HTRA1 is a novel target that regulates scar formation.
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Fibroblastos/metabolismo , Serina Peptidase 1 de Requerimento de Alta Temperatura A/fisiologia , Queloide/metabolismo , Fator de Crescimento Transformador beta1/metabolismo , Células Cultivadas , Fibroblastos/enzimologia , Serina Peptidase 1 de Requerimento de Alta Temperatura A/genética , Serina Peptidase 1 de Requerimento de Alta Temperatura A/metabolismo , Humanos , Queloide/enzimologia , Queloide/genética , RNA Mensageiro/metabolismo , Pele/enzimologia , Pele/metabolismo , Proteína Smad2/metabolismo , Fator de Crescimento Transformador beta1/genéticaRESUMO
Developing bifunctional efficient and durable non-noble electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is highly desirable and challenging for overall water splitting. Herein, Co-Mn carbonate hydroxide (CoMnCH) nanosheet arrays with controllable morphology and composition were developed on nickel foam (NF) as such a bifunctional electrocatalyst. It is discovered that Mn doping in CoCH can simultaneously modulate the nanosheet morphology to significantly increase the electrochemical active surface area for exposing more accessible active sites and tune the electronic structure of Co center to effectively boost its intrinsic activity. As a result, the optimized Co1Mn1CH/NF electrode exhibits unprecedented OER activity with an ultralow overpotential of 294 mV at 30 mA cm-2, compared with all reported metal carbonate hydroxides. Benefited from 3D open nanosheet array topographic structure with tight contact between nanosheets and NF, it is able to deliver a high and stable current density of 1000 mA cm-2 at only an overpotential of 462 mV with no interference from high-flux oxygen evolution. Despite no reports about effective HER on metal carbonate hydroxides yet, the small overpotential of 180 mV at 10 mA cm-2 for HER can be also achieved on Co1Mn1CH/NF by the dual modulation of Mn doping. This offers a two-electrode electrolyzer using bifunctional Co1Mn1CH/NF as both anode and cathode to perform stable overall water splitting with a cell voltage of only 1.68 V at 10 mA cm-2. These findings may open up opportunities to explore other multimetal carbonate hydroxides as practical bifunctional electrocatalysts for scale-up water electrolysis.
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Three new layered compounds, namely NaLiFeSe2, KLiFeSe2, and RbLiFeSe2, have been discovered. NaLiFeSe2 adopts a trigonal CaAl2Si2-type structure with space group P3Ì m1, while the other two possess a tetragonal ThCr2Si2-type structure with space group I4/mmm. Structural refinements reveal that Li and Fe atoms randomly occupy the same sites in all these compounds without ordering. It is found that the radius of the alkali metals plays a vital role in determining the symmetry of this series of compounds. The substitution of Li at the Fe site shortens the layer spacing and elongates the A-Se bond length in the ThCr2Si2-type structure. The elongated Na-Se bond length would destabilize the ThCr2Si2-type structure in NaLiFeSe2, suggesting that NaxFe2-ySe2 lies at the border of ThCr2Si2-type and CaAl2Si2-type structures. Magnetic and resistivity measurements demonstrate that these compounds exhibit anisotropic spin-glass and narrow-band-gap semiconducting characteristics. First-principles calculations indicate that the introduction of Li enhances strong localization and weakens the correlation of the 3d electrons of Fe, which are responsible for the observed spin-glass transition and semiconducting conductions.