Comparative study on the Ru ware, Ru-type ware of Qingliangsi kiln and celadon of Zhanggongxiang kiln.

Thirty-three porcelain shards (28 Ru ware and 5 Ru-type ware) unearthed from Qinglingsi kiln and 31 celadon fragments from Zhanggongxiang kiln were studied systematically for tracing their correlation and difference in glaze and body characteristics through a variety of characterisation methods. Samples without HF corrosion were applied to achieve the microstructure and composition details by SEM and TEM. Results exhibited that there were certain similarities between Ru ware, Ru-type ware and Zhanggongxiang kiln celadon in glaze colour and thickness, body features, fracture structure; however, they showed obvious differences in body thickness, chemical composition of glaze and body, phase constituents and microstructure of glaze. Plentiful needle-like diopside were widely distributed in Zhanggongxiang kiln celadon glazes, while this type of crystals was only existed in few Ru and Ru-type ware glazes with small content. Besides, a large amount of residual quartz was present over the Ru ware glazes, which could have relation to the incorporation of agate. The liquid-liquid phase separation structure (Ca-rich droplets and Si-rich matrix) was generated within the interspaces of anorthite clusters or around the brims of anorthite needles or columns. The occurrence of phase separation was generally accompanied by Al2 O3 consumption, but suppressed in the areas far from anorthite due to the rise of Al2 O3 content, indicating that Al2 O3 was the most sensitive constituent for this glaze behaviour. The distinguished size, shape and distribution of phase-separated droplets or interconnected structures were closely associated with the scale and crowding level of anorthite crystallisation.

Catechol-Isolated Atomically Dispersed Nanocatalysts for Self-Motivated Cocatalytic Tumor Therapy.

Nanocatalytic tumor therapy based on Fenton nanocatalysts has attracted considerable attention because of its therapeutic specificity, enhanced outcomes, and high biocompatibility. Nevertheless, the rate-determining step in Fenton chemistry, which involves the transition of a high-valence metallic center (FeIII ) to a Fenton-active low-valence metallic center (FeII ), has hindered advances in nanocatalyst-based therapeutics. In this study, we constructed mesoporous single iron atomic nanocatalysts (mSAFe NCs) by employing catechols from dopamine to coordinate and isolate single iron atoms. The catechols also serve as reductive ligands, generating a field-effect-based cocatalytic system that instantly reduces FeIII species to FeII species within the mSAFe NCs. This self-motivated cocatalytic strategy enabled by mSAFe NCs accelerates the kinetics of the Fenton catalytic reaction, resulting in remarkable performance for nanocatalytic tumor therapy both in vitro and in vivo.

In Situ Synthesis of Natural Antioxidase Mimics for Catalytic Anti-Inflammatory Treatments: Rheumatoid Arthritis as an Example.

Mimicking the coordination geometry of the active metal sites of natural enzymes is an efficient strategy in designing therapeutic chemicals with enzymelike in vivo reaction thermodynamics and kinetics. In this study, this chemical concept has been applied for the in situ synthesis of natural antioxidase mimics for catalytic anti-inflammatory treatment by using rheumatoid arthritis, a common and hardly curable immune-mediated diseases, as an example. Briefly, a composite nanomedicine has been first constructed by loading cationic porphyrin ligands into a manganese-engineered mesoporous silica nanocarrier, which can respond to a mildly acidic environment to concurrently release manganous ions and porphyrin ligands, enabling their subsequent coordination and synthesis of manganese porphyrin with a coordination environment of an active Mn site similar to those of the metal sites in natural superoxide dismutase (SOD) and catalase. Due to the strong metal-ligand exchange coupling enabled by the N-ethylpyridinium-2-yl groups tetrasubstituted in the meso positions of N4-macroheterocycles, such a manganese porphyrin presents the SOD-like activity of disproportionating superoxide anions via outer-sphere proton-coupled one-electron transfer (diaquamanganese(III)/monoaquamanganese(II) cycling), as well as the catalase-like activity of disproportionating hydrogen peroxide via inner-sphere proton-coupled two-electron transfer (diaquamanganese(III)/dioxomanganese(V) cycling). Cellular experiments demonstrated the high antioxidative efficacy of the composite nanomedicine in M1 macrophages by promoting their polarization shift to the anti-inflammatory M2 phenotype. Equally importantly, the silicon-containing oligomers released from the manganese silicate nanocarrier can act as heterogeneous nucleation centers of hydroxyapatite for facilitating biomineralization by bone mesenchymal stem cells. Finally, an in vivo adjuvant-induced arthritis animal model further reveals the high efficacy of the nanomedicine in treating rheumatoid arthritis.

CoW Bimetallic Carbide Nanocatalysts: Computational Exploration, Confined Disassembly-Assembly Synthesis and Alkaline/Seawater Hydrogen Evolution.

Earth-abundant tungsten carbide exhibits potential hydrogen evolution reaction (HER) catalytic activity owing to its Pt-like d-band electronic structure, which, unfortunately, suffers from the relatively strong tungsten-hydrogen binding, deteriorating its HER performance. Herein, a catalyst design concept of incorporating late transition metal into early transition metal carbide is proposed for regulating the metal-H bonding strength and largely enhancing the HER performance, which is employed to synthesize CoW bi-metallic carbide Co6 W6 C by a "disassembly-assembly" approach in a confined environment. Such synthesized Co6 W6 C nanocatalyst features the optimal Gibbs free energy of *H intermediate and dissociation barrier energy of H2 O molecules as well by taking advantage of the electron complementary effect between Co and W species, which endows the electrocatalyst with excellent HER performance in both alkaline and seawater/alkaline electrolytes featuring especially low overpotentials, elevated current densities, and much-enhanced operation durability in comparison to commercial Pt/C catalyst. Moreover, a proof-of-concept Mg/seawater battery equipped with Co6 W6 C-2-600 as cathode offers a peak power density of 9.1 mW cm-2 and an open-circuit voltage of ≈1.71 V, concurrently realizing hydrogen production and electricity output.

Enhancing Tumor Catalytic Therapy by Co-Catalysis.

Fenton reactions have been recently applied in tumor catalytic therapy, whose efficacy suffers from the unsatisfactory reaction kinetics of Fe3+ to Fe2+ conversion. Here we introduce a co-catalytic concept in tumor catalytic therapy by using a two-dimensional molybdenum disulfide (MoS2 ) nanosheet atomically dispersed with Fe species. The single-atom Fe species act as active sites for triggering Fenton reactions, while the abundant sulfur vacancies generated on the nanosheet favor electron capture by hydrogen peroxide for promoting hydroxyl radical production. Moreover, the 2D MoS2 support also acts as a co-catalyst to accelerate the conversion of Fe3+ to Fe2+ by the oxidation of active Mo4+ sites to Mo6+ , thereby promoting the whole catalytic process. The 2D nanocatalyst exhibits a desirable catalytic performance, as well as a significantly enhanced anticancer efficacy both in vitro and in vivo, which indicates the feasibility for applying such a co-catalytic concept in tumor therapy.

N-Doped Carbon Electrocatalyst: Marked ORR Activity in Acidic Media without the Contribution from Metal Sites?

Fe-N-C electrocatalysts have been demonstrated to be the most promising substitutes for benchmark Pt/C catalysts for the oxygen reduction reaction (ORR). Herein, we report that N-doped carbon materials with trace amounts of iron (0-0.08 wt. %) show excellent ORR activity and durability comparable and even superior to those of Pt/C in both alkaline and acidic media without significant contribution by the metal sites. Such an N-doped carbon (denoted as N-HPCs) features a hollow and hierarchically porous architecture, and more importantly, a noncovalently bonded N-deficient/N-rich heterostructure providing the active sites for oxygen adsorption and activation owing to the efficient electron transfer between the layers. The primary Zn-air battery using N-HPCs as the cathode delivers a much higher power density of 158 mW cm-2 , and the maximum power density in the H2 -O2 fuel cell reaches 486 mW cm-2 , which is comparable to and even better than those using conventional Fe-N-C catalysts at cathodes.

Photosynthetic Cyanobacteria-Hybridized Black Phosphorus Nanosheets for Enhanced Tumor Photodynamic Therapy.

Photodynamic therapy (PDT) has attracted tremendous attention due to its advantages such as high safety and effectiveness compared to traditional radiotherapy and chemotherapy. However, the intratumoral hypoxic microenvironment will inevitably compromise the PDT effect of the highly oxygen-dependent type II photosensitizers, implicating the urgent demand for continuous intratumoral oxygenation. Herein, biocompatible photosynthetic cyanobacteria have been modified with inorganic two-dimensional black phosphorus nanosheets (BPNSs) to be a novel bioreactor termed as Cyan@BPNSs. Upon 660 nm laser irradiation, the photosynthetic cyanobacteria generate oxygen continuously in situ through photosynthesis, followed by the photosensitization of BPNSs for activating oxygen into singlet oxygen (1 O2 ), resulting in a large amount of 1 O2 accumulation at the tumor site and the consequent strong tumor cell killing effect both in vitro and in vivo. This work provides an attractive strategy for efficient and biocompatible PDT, meanwhile extends the scope of microbiotic nanomedicine by hybridizing microorganisms with inorganic nanophotosensitizer.

Cryogenic Exfoliation of Non-layered Magnesium into Two-Dimensional Crystals.

Physical exfoliation of layered precursors is one of the most prevailing techniques to prepare two-dimensional (2D) crystals, which, however, is considered to be intrinsically inapplicable to non-layered bulks. Now, plane cleavage differentiation is identified in metallic magnesium at cryogenic temperature (CT), and a cryogenic exfoliation strategy of non-layered magnesium into 2D crystals is developed. The cleavage anisotropy of the Mg lattice in response to the external mechanical stress originates from the CT-induced specific inactivation of basal slip, which results in the basal cleavage perpendicular to c axis. The exfoliated novel 2D Mg crystals exhibit remarkable localized surface plasmon resonances, holding great promise for the applications in harvesting and converting solar energy. Beyond creating a new member for the burgeoning 2D family, this study may provide a useful tool for the physical exfoliations of various non-layered materials.

Long Straczekite δ-Ca0.24 V2 O5 ⋠H2 O Nanorods and Derived ß-Ca0.24 V2 O5 Nanorods as Novel Host Materials for Lithium Storage with Excellent Cycling Stability.

Nanorods of δ-Ca0.24 V2 O5 ⋅H2 O, a straczekite group mineral with an open double-layered structure, have been successfully fabricated by a facile hydrothermal method and can be transformed into the tunnel ß geometry (ß-Ca0.24 V2 O5 ) through a vacuum annealing treatment. The generated ß-Ca0.24 V2 O5 still preserves the nanorod construction of δ-Ca0.24 V2 O5 ⋅H2 O without substantial sintering and degradation of the nanostructure. As cathode materials, both calcium vanadium bronzes exhibit high reversible capacity, good rate capability, as well as superior cyclability. Compared with the hydrated vanadium bronze, the ß-Ca0.24 V2 O5 nanorods show better cycling performance (81.68 and 97.93 % capacity retention after 200 cycles at 100 and 400 mA g-1 , respectively) and excellent long-term cyclic stability with an average decay of 0.035 % per cycle over 500 cycles at 500 mA g-1 . Note that the double-layered δ-Ca0.24 V2 O5 ⋅H2 O electrode irreversibly converts into ß-Cax V2 O5 phase during the initial Li+ insertion/extraction process, while in contrast, the ß-phase calcium vanadium bronze electrode shows excellent structural stability during cycling. The excellent electrochemical performance demonstrates that the two calcium vanadium bronzes are potential cathode candidates for rechargeable lithium-ion batteries.

"Manganese Extraction" Strategy Enables Tumor-Sensitive Biodegradability and Theranostics of Nanoparticles.

Biodegradability of inorganic nanoparticles is one of the most critical issues in their further clinical translations. In this work, a novel "metal ion-doping" approach has been developed to endow inorganic mesoporous silica-based nanoparticles with tumor-sensitive biodegradation and theranostic functions, simply by topological transformation of mesoporous silica to metal-doped composite nanoformulations. "Manganese extraction" sensitive to tumor microenvironment was enabled in manganese-doped hollow mesoporous silica nanoparticles (designated as Mn-HMSNs) to fast promote the disintegration and biodegradation of Mn-HMSNs, further accelerating the breakage of Si-O-Si bonds within the framework. The fast biodegradation of Mn-HMSNs sensitive to mild acidic and reducing microenvironment of tumor resulted in much accelerated anticancer drug releasing and enhanced T1-weighted magnetic resonance imaging of tumor. A high tumor-inhibition effect was simultaneously achieved by anticancer drug delivery mediated by PEGylated Mn-HMSNs, and the high biocompatibility of composite nanosystems was systematically demonstrated in vivo. This is the first demonstration of biodegradable inorganic mesoporous nanosystems with specific biodegradation behavior sensitive to tumor microenvironment, which also provides a feasible approach to realize the on-demand biodegradation of inorganic nanomaterials simply by "metal ion-doping" strategy, paving the way to solve the critical low-biodegradation issue of inorganic drug carriers.

On the Mesoporogen-Free Synthesis of Single-Crystalline Hierarchically Structured ZSM-5 Zeolites in a Quasi-Solid-State System.

Hierarchically structured zeolites (HSZs) have gained much academic and industrial interest owing to their multiscale pore structures and consequent excellent performances in varied chemical processes. Although a number of synthetic strategies have been developed in recent years, the scalable production of HSZs single crystals with penetrating and three-dimensionally (3-D) interconnected mesopore systems but without using a mesoscale template is still a great challenge. Herein, based on a steam-assisted crystallization (SAC) method, we report a facile and scalable strategy for the synthesis of single-crystalline ZSM-5 HSZs by using only a small amount of micropore-structure-directing agents (i.e., tetrapropylammonium hydroxide). The synthesized materials exhibited high crystallinity, a large specific surface area of 468 m(2) g(-1) , and a pore volume of 0.43 cm(3) g(-1) without sacrificing the microporosity (≈0.11 cm(3) g(-1) ) in a product batch up to 11.7 g. Further, a kinetically controlled nucleation-growth mechanism is proposed for the successful synthesis of single-crystalline ZSM-5 HSZs with this novel process. As expected, compared with the conventional microporous ZSM-5 and amorphous mesoporous Al-MCM-41 counterparts, the synthesized HSZs exhibited significantly enhanced activity and stability and prolonged lifetime in model reactions, especially when bulky molecules were involved.

Synthesis of Iron Nanometallic Glasses and Their Application in Cancer Therapy by a Localized Fenton Reaction.

Metallic glasses and cancer theranostics are emerging fields that do not seem to be related to each other. Herein, we report the facile synthesis of amorphous iron nanoparticles (AFeNPs) and their superior physicochemical properties compared to their crystalline counterpart, iron nanocrystals (FeNCs). The AFeNPs can be used for cancer theranostics by inducing a Fenton reaction in the tumor by taking advantage of the mild acidity and the overproduced H2 O2 in a tumor microenvironment: Ionization of the AFeNPs enables on-demand ferrous ion release in the tumor, and subsequent H2 O2 disproportionation leads to efficient (.)OH generation. The endogenous stimuli-responsive (.)OH generation in the presence AFeNPs enables a highly specific cancer therapy without the need for external energy input.

Solvothermal-induced self-assembly of Fe2O3/GS aerogels for high Li-storage and excellent stability.

A novel solvothermal-induced self-assembly approach, using colloid sol as precursor, is developed to construct monolithic 3D metal oxide/GS (graphene sheets) aerogels. During the solvothermal process, graphene oxide (GO) is highly reduced to GS and self-assembles into 3D macroscopic hydrogels, accompanying with in situ transformation of colloid sol to metal oxides. As a proof of concept, Fe2 O3 /GS aerogels are synthesized based on Fe(OH)3 sol, in which GS self-assemble into an interconnected macroporous framework and Fe2 O3 nanocrystals (20-50 nm) uniformly deposit on GS. Benefitting from the integration of macroporous structures, large surface area, high electrical conductivity, and good electrode homogeneity, the hybrid electrode manifests a superior rate capability (930, 660 and 520 mAh g(-1) at 500, 2000 and 4000 mA g(-1), respectively) and excellent prolonged cycling stability at high rates (733 mAh g(-1) during 1000 charge/discharge cycles at 2000 mA g(-1)), demonstrating its great potential for application in high performance lithium ion batteries. The work described here provides a versatile pathway to construct various graphene-based hybrid aerogels.

Inert Filler Selection Strategies in Li-Ion Gel Polymer Electrolytes.

The main role of inert fillers in polymer electrolytes is to enhance ionic conductivity. However, lithium ions in gel polymer electrolytes (GPEs) conduct in liquid solvent rather than along the polymer chains. So far, the main role of inert fillers in improving the electrochemical performance of GPEs is still unclear. Here, various low-cost and common inert fillers (Al2O3, SiO2, TiO2, ZrO2) are introduced into GPEs to study their effects on Li-ion polymer batteries. It is found that the addition of inert fillers has different effects on ionic conductivity, mechanical strength, thermal stability, and, dominantly, interfacial properties. Compared with other gel electrolytes containing SiO2, TiO2, or ZrO2 fillers, those with Al2O3 fillers exhibit the most favorable performance. The high performance is ascribed to the interaction between the surface functional groups of Al2O3 and LiNi0.8Co0.1Mn0.1O2, which alleviates the decomposition of the organic solvent by the cathode, resulting in the formation of a high-quality Li+ conductor interfacial layer. This study provides an important reference for the selection of fillers in GPEs, surface modification of separators, and cathode surface coating.

Construction of a two-dimensional artificial antioxidase for nanocatalytic rheumatoid arthritis treatment.

Constructing nanomaterials mimicking the coordination environments of natural enzymes may achieve biomimetic catalysis. Here we construct a two-dimensional (2D) metal-organic framework (MOF) nanosheet catalyst as an artificial antioxidase for nanocatalytic rheumatoid arthritis treatment. The 2D MOF periodically assembles numbers of manganese porphyrin molecules, which has a metal coordination geometry analogous to those of two typical antioxidases, human mitochondrial manganese superoxide dismutase (Mn-SOD) and human erythrocyte catalase. The zinc atoms of the 2D MOF regulate the metal-centered redox potential of coordinated manganese porphyrin ligand, endowing the nanosheet with both SOD- and catalase-like activities. Cellular experiments show unique anti-inflammatory and pro-biomineralization performances of the 2D MOF, while in vivo animal model further demonstrates its desirable antiarthritic efficacy. It is expected that such a nanocatalytic antioxidation concept may provide feasible approaches to future anti-inflammatory treatments.

Bacterial Metabolism-Initiated Nanocatalytic Tumor Immunotherapy.

The low immunogenicity of tumors remains one of the major limitations of cancer immunotherapy. Herein, we report a bacterial metabolism-initiated and photothermal-enhanced nanocatalytic therapy strategy to completely eradicate primary tumor by triggering highly effective antitumor immune responses. Briefly, a microbiotic nanomedicine, designated as Cu2O@ΔSt, has been constructed by conjugating PEGylated Cu2O nanoparticles on the surface of an engineered Salmonella typhimurium strain (ΔSt). Owing to the natural hypoxia tropism of ΔSt, Cu2O@ΔSt could selectively colonize hypoxic solid tumors, thus minimizing the adverse effects of the bacteria on normal tissues. Upon bacterial metabolism within the tumor, Cu2O@ΔSt generates H2S gas and other acidic substances in the tumor microenvironment (TME), which will in situ trigger the sulfidation of Cu2O to form CuS facilitating tumor-specific photothermal therapy (PTT) under local NIR laser irradiation on the one hand. Meanwhile, the dissolved Cu+ ions from Cu2O into the acidified TME enables the nanocatalytic tumor therapy by catalyzing the Fenton-like reaction of decomposing endogenous H2O2 into cytotoxic hydroxyl radicals (·OH) on the other hand. Such a bacterial metabolism-triggered PTT-enhanced nanocatalytic treatment could effectively destroy tumor cells and induce a massive release of tumor antigens and damage-associated molecular patterns, thereby sensitizing tumors to checkpoint blockade (ICB) therapy. The combined nanocatalytic and ICB therapy results in the much-inhibited growth of distant and metastatic tumors, and more importantly, induces a powerful immunological memory effect after the primary tumor ablation.

Non-PCR Ultrasensitive Detection of Viral RNA by a Nanoprobe-Coupling Strategy: SARS-CoV-2 as an Example.

Developing efficient and highly sensitive diagnostic techniques for early detections of pathogenic viruses such as Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is vitally important for preventing its widespread. However, the conventional polymerase chain reaction (PCR)-based detection features high complexity, excessive time-consumption, and labor-intensiveness, while viral protein-based detections suffer from moderate sensitivity and specificity. Here, a non-PCR but ultrasensitive viral RNA detection strategy is reported based on a facile nanoprobe-coupling strategy without enzymatic amplification, wherein PCR-induced bias and other shortcomings are successfully circumvented. This approach endows the viral RNA detection with ultra-low background to maximum signal ratio in the linear signal amplification by using Au nanoparticles as reporters. The present strategy exhibits 100% specificity toward SARS-CoV-2 N gene, and ultrasensitive detection of as low as 52 cp mL-1 of SARS-CoV-2 N gene without pre-PCR amplification. This approach presents a novel ultrasensitive tool for viral RNA detections for fighting against COVID-19 and other types of pathogenic virus-caused diseases.

Toward n-Alkane Hydroisomerization Reactions: High-Performance Pt-Al2O3/SAPO-11 Single-Atom Catalysts with Nanoscale Separated Metal-Acid Centers and Ultralow Platinum Content.

Long-chain n-alkane hydroisomerization reaction plays a vital role in petrochemical and coal chemical industries, which could produce high-quality hydrocarbon fuels and lubricant base oils for modern transportation and mechanical drive. However, minimizing precious metal usage while maintaining the catalyst performance remains a great challenge. Herein, a novel bifunctional catalyst toward n-alkane hydroisomerization reactions, Pt-Al2O3/SAPO-11 (Pt-A/S11) featuring nanoscale separated metal-acid active centers has been synthesized via a simple two-step procedure. In detail, Pt species was first loaded on the nanometer-sized alumina matrices through an incipient wetness impregnation method and then mixed with SAPO-11 molecular sieve to form the composite catalyst. Importantly, 0.015Pt-A/S11 catalyst with the ever-reported lowest Pt loading amount of 0.015 wt % exhibits an extraordinarily high isomer yield of 85.8% compared to previous published results and the traditional Pt-SAPO-11/Al2O3 (Pt-S11/A) catalyst accompanying with the direct contact between metal and acid sites (65.6%). It has been confirmed that the Pt species in 0.015Pt-A/S11 samples exist in single-atom form, leading to an excellent hydroisomerization performance. The possible reaction processes have been discussed to elucidate the exemplary catalytic performance of the synthesized Pt-A/S11 catalysts with nanoscale intimacy of metal-acid sites.

Discovery of electric devil's staircase in perovskite antiferroelectric.

The devil's staircase, describing step-like function for two competing frequencies, is well known over a wide range of dynamic systems including Huyghens' clocks, Josephson junction, and chemical reaction. In condensed matter physics, the devil's staircase has been observed in spatially modulated structures, such as magnetic ordering. It draws widespread attentions because it plays a crucial role in the fascinating phenomena including phase-locking behaviors, commensurate-incommensurate phase transition, and spin-valve effect. Here, we report the observation of polymorphic phase transitions consisting of several steps in PbZrO3-based system-namely, electric devil's staircase-originated from competing ferroelectric and antiferroelectric interactions. We fully characterize a specific electric dipole configuration by decomposing this competitive interaction in terms of basic structure and modulation function. Of particular interest is that the occurrence of many degenerate electric dipole configurations in devil's staircase enables superior energy storage performance. These observations are of great significance for exploring more substantive magnetic-electric correspondence and engineering practical high-power antiferroelectric capacitors.

Atomic reconfiguration among tri-state transition at ferroelectric/antiferroelectric phase boundaries in Pb(Zr,Ti)O3.

Phase boundary provides a fertile ground for exploring emergent phenomena and understanding order parameters couplings in condensed-matter physics. In Pb(Zr1-xTix)O3, there are two types of composition-dependent phase boundary with both technological and scientific importance, i.e. morphotropic phase boundary (MPB) separating polar regimes into different symmetry and ferroelectric/antiferroelectric (FE/AFE) phase boundary dividing polar and antipolar dipole configurations. In contrast with extensive studies on MPB, FE/AFE phase boundary is far less explored. Here, we apply atomic-scale imaging and Rietveld refinement to directly demonstrate the intermediate phase at FE/AFE phase boundary exhibits a rare multipolar Pb-cations ordering, i.e. coexistence of antipolar or polar displacement, which manifests itself in both periodically gradient lattice spacing and anomalous initial hysteresis loop. In-situ electron/neutron diffraction reveals that the same parent intermediate phase can transform into either FE or AFE state depending on suppression of antipolar or polar displacement, coupling with the evolution of long-/short-range oxygen octahedra tilts. First-principle calculations further show that the transition between AFE and FE phase can occur in a low-energy pathway via the intermediate phase. These findings enrich the structural understanding of FE/AFE phase boundary in perovskite oxides.