In situ Activation of Molecular Oxygen at Intermetallic Spacing-Optimized Iron Network-Like Sites for Boosting Electrocatalytic Oxygen Reduction.

The oxygen reduction reaction (ORR) catalyzed by transition-metal single-atom catalysts (SACs) is promising for practical applications in energy-conversion devices, but great challenges still remain due to the sluggish kinetics of O═O cleavage. Herein, a kind of high-density iron network-like sites catalysts are constructed with optimized intermetallic distances on an amino-functionalized carbon matrix (Fe-HDNSs). Quasi-in situ soft X-ray absorption spectroscopy and in situ synchrotron infrared characterizations demonstrate that the optimized intermetallic distances in Fe-HDNSs can in situ activate the molecular oxygen by fast electron compensation through the hybridized Fe 3d‒O 2p, which efficiently facilitates the cleavage of the O═O bond to *O species and highly suppresses the side reactions for an accelerated kinetics of the 4e- ORR. As a result, the well-designed Fe-HDNSs catalysts exhibit superior performances with a half-wave potential of 0.89 V versus reversible hydrogen electrode (RHE) and a kinetic current density of 72 mA cm-2@0.80 V versus RHE, exceeding most of the noble-metal-free ORR catalysts. This work offers some new insights into the understanding of 4e- ORR kinetics and reaction pathways to boost electrochemical performances of SACs.

Interface Engineering a High Content of Co3+ Sites on Co3O4 Nanoparticles to Boost Acidic Oxygen Evolution.

Non-noble metal oxides have emerged as potential candidate electrocatalysts for acidic oxygen evolution reactions (OERs) due to their earth abundance; however, improving their catalytic activity and stability simultaneously in strong acidic electrolytes is still a major challenge. In this work, we report Co3O4@carbon core-shell nanoparticles on 2D graphite sheets (Co3O4@C-GS) as mixed-dimensional hybrid electrocatalysts for acidic OER. The obtained Co3O4@C-GS catalyst exhibits a low overpotential of 350 mV and maintains stability for 20 h at a current density of 10 mA cm-2 in H2SO4 (pH = 1) electrolyte. X-ray photoelectron and X-ray absorption spectroscopies illustrate that the higher content of Co3+ sites boosts acidic OER. Operando Raman spectroscopy reveals that the catalytic stability of Co3O4@C nanoparticles during the acidic OER is enhanced by the introduction of graphite sheets. This interface engineering of non-noble metal sites with high valence states provides an efficient approach to boost the catalytic activity and enhance the stability of noble-metal-free electrocatalysts for acidic OER.

Intrinsic room-temperature ferromagnetism in a two-dimensional semiconducting metal-organic framework.

The development of two-dimensional (2D) magnetic semiconductors with room-temperature ferromagnetism is a significant challenge in materials science and is important for the development of next-generation spintronic devices. Herein, we demonstrate that a 2D semiconducting antiferromagnetic Cu-MOF can be endowed with intrinsic room-temperature ferromagnetic coupling using a ligand cleavage strategy to regulate the inner magnetic interaction within the Cu dimers. Using the element-selective X-ray magnetic circular dichroism (XMCD) technique, we provide unambiguous evidence for intrinsic ferromagnetism. Exhaustive structural characterizations confirm that the change of magnetic coupling is caused by the increased distance between Cu atoms within a Cu dimer. Theoretical calculations reveal that the ferromagnetic coupling is enhanced with the increased Cu-Cu distance, which depresses the hybridization between 3d orbitals of nearest Cu atoms. Our work provides an effective avenue to design and fabricate MOF-based semiconducting room-temperature ferromagnetic materials and promotes their practical applications in next-generation spintronic devices.

Fast Modulation of d-Band Holes Quantity in the Early Reaction Stages for Boosting Acidic Oxygen Evolution.

Synthesis of highly active and durable oxygen evolution reaction (OER) catalysts applied in acidic water electrolysis remains a grand challenge. Here, we construct a type of high-loading iridium single atom catalysts with tunable d-band holes character (h-HL-Ir SACs, ∼17.2 wt % Ir) realized in the early OER operation stages. The in situ X-ray absorption spectroscopy reveals that the quantity of the d-band holes of Ir active sites can be fast increased by 0.56 unit from the open circuit to a low working potential of 1.35 V. More remarkably, in situ synchrotron infrared and Raman spectroscopies demonstrate the quick accumulation of *OOH and *OH intermediates over holes-modulated Ir sites in the early reaction voltages, achieving a rapid OER kinetics. As a result, this well-designed h-HL-Ir SACs exhibits superior performance for acidic OER with overpotentials of 216 mV @10 mA cm-2 and 259 mV @100 mA cm-2 , corresponding to a small Tafel slope of 43 mV dec-1 . The activity of catalyst shows no evident attenuation after 60 h operation in acidic environment. This work provides some useful hints for the design of superior acidic OER catalysts.

Engineering a local acid-like environment in alkaline medium for efficient hydrogen evolution reaction.

Tuning the local reaction environment is an important and challenging issue for determining electrochemical performances. Herein, we propose a strategy of intentionally engineering the local reaction environment to yield highly active catalysts. Taking Ptδ- nanoparticles supported on oxygen vacancy enriched MgO nanosheets as a prototypical example, we have successfully created a local acid-like environment in the alkaline medium and achieve excellent hydrogen evolution reaction performances. The local acid-like environment is evidenced by operando Raman, synchrotron radiation infrared and X-ray absorption spectroscopy that observes a key H3O+ intermediate emergence on the surface of MgO and accumulation around Ptδ- sites during electrocatalysis. Further analysis confirms that the critical factors of the forming the local acid-like environment include: the oxygen vacancy enriched MgO facilitates H2O dissociation to generate H3O+ species; the F centers of MgO transfers its unpaired electrons to Pt, leading to the formation of electron-enriched Ptδ- species; positively charged H3O+ migrates to negatively charged Ptδ- and accumulates around Ptδ- nanoparticles due to the electrostatic attraction, thus creating a local acidic environment in the alkaline medium.

Observation on the effect of periodontal treatment on patients with combined periodontal-pulpal lesions.

OBJECTIVE: To evaluate the effect of periodontal treatment on combined periodontal-pulpal lesions. METHODS: A total of 327 patients with periodontal-pulpal lesions (360 affected teeth) were selected, and all affected teeth were treated with a complete root canal, and assigned into group A (periodontal treatment group, 180 affected teeth) and group B (non-periodontal treatment group, 180 affected teeth). Group A received periodontal basic treatment for 2 weeks after the completion of root canal treatment; 6 weeks later, if there were still more than 5 mm periodontal pockets and bleeding after detection, flap treatment was performed. Group B received root canal treatment and supragingival scaling. Follow-up was conducted at 3, 6, 12 and 24 months after surgery by observing the periodontal depth (PD), alveolar bone resorption and tooth mobility (TM). RESULT: In group A, the PDs before operation and 2 years after operation were (5.966±1.877) mm and (5.133±1.935) mm, and the PD was significantly decreased. In group B, the PDs before operation and 2 years after operation were (5.533±1.856) mm and (6.167±1.927) mm, and the PD was increased. There was no statistical difference in preoperative TM between the two groups (P>0.05). Two years after operation, TM in group A was significantly lower than that in group B (P<0.05). In terms of X-ray performance, there was no significant change in alveolar bone resorption in group A two years after operation compared with that before operation (P>0.05); two years after operation, alveolar bone resorption in group B was significantly reduced compared with that before operation (P<0.05). CONCLUSION: Periodontal treatment is a promising technique for patients with combined periodontal-pulpal lesions.

In-situ spectroscopic observation of dynamic-coupling oxygen on atomically dispersed iridium electrocatalyst for acidic water oxidation.

Uncovering the dynamics of active sites in the working conditions is crucial to realizing increased activity, enhanced stability and reduced cost of oxygen evolution reaction (OER) electrocatalysts in proton exchange membrane electrolytes. Herein, we identify at the atomic level potential-driven dynamic-coupling oxygen on atomically dispersed hetero-nitrogen-configured Ir sites (AD-HN-Ir) in the OER working conditions to successfully provide the atomically dispersed Ir electrocatalyst with ultrahigh electrochemical acidic OER activity. Using in-situ synchrotron radiation infrared and X-ray absorption spectroscopies, we directly observe that one oxygen atom is formed at the Ir active site with an O-hetero-Ir-N4 structure as a more electrophilic active centre in the experiment, which effectively promotes the generation of key *OOH intermediates under working potentials; this process is favourable for the dissociation of H2O over Ir active sites and resistance to over-oxidation and dissolution of the active sites. The optimal AD-HN-Ir electrocatalyst delivers a large mass activity of 2860 A gmetal-1 and a large turnover frequency of 5110 h-1 at a low overpotential of 216 mV (10 mA cm-2), 480-510 times larger than those of the commercial IrO2. More importantly, the AD-HN-Ir electrocatalyst shows no evident deactivation after continuous 100 h OER operation in an acidic medium.

Identification of the Active-Layer Structures for Acidic Oxygen Evolution from 9R-BaIrO3 Electrocatalyst with Enhanced Iridium Mass Activity.

Iridium-based perovskites show promising catalytic activity for oxygen evolution reaction (OER) in acid media, but the iridium mass activity remains low and the active-layer structures have not been identified. Here, we report highly active 1 nm IrOx particles anchored on 9R-BaIrO3 (IrOx/9R-BaIrO3) that are directly synthesized by solution calcination followed by strong acid treatment for the first time. The developed IrOx/9R-BaIrO3 catalyst delivers a high iridium mass activity (168 A gIr-1), about 16 times higher than that of the benchmark acidic OER electrocatalyst IrO2 (10 A gIr-1), and only requires a low overpotential of 230 mV to reach a catalytic current density of 10 mA cm-2geo. Careful scanning transmission electron microscopy, synchrotron radiation-based X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy analyses reveal that, during the electrocatalytic process, the initial 1 nm IrOx nanoparticles/9R-BaIrO3 evolve into amorphous Ir4+OxHy/IrO6 octahedrons and then to amorphous Ir5+Ox/IrO6 octahedrons on the surface. Such high relative content of amorphous Ir5+Ox species derived from trimers of face-sharing IrO6 octahedrons in 9R-BaIrO3 and the enhanced metallic conductivity of the Ir5+Ox/9R-BaIrO3 catalyst are responsible for the excellent acidic OER activity. Our results provide new insights into the surface active-layer structure evolution in perovskite electrocatalysts and demonstrate new approaches for engineering highly active acidic OER nanocatalysts.

Intrinsic Room-Temperature Ferromagnetism in V2C MXene Nanosheets.

Two-dimensional (2D) materials with intrinsic magnetic properties are intensively explored due to their potential applications in low-power-consumption electronics and spintronics. To date, only a handful of intrinsic magnetic 2D materials have been reported. Here, we report a realization of intrinsic ferromagnetic behavior in 2D V2C MXene nanosheets through layer mismatch engineering. The V2C MXene nanosheets with a small-angle twisting show a robust intrinsic ferromagnetic response with a saturation magnetic moment of 0.013 emu/g at room temperature. An in-depth study has been performed by X-ray absorption spectroscopy as well as electron paramagnetic resonance (EPR) and photoelectron spectroscopy analyses. It has been revealed that the symmetry-broken interlayer twisting reduced the degeneracy of V 3d states and the van Hove singularity. This led to a redistribution of the density of electronic states near the Fermi level and consequently activated the Stoner ferromagnetism with improved density of itinerant d electrons. This work highlights V2C MXene as a promising intrinsic room-temperature ferromagnetic material with potential applications in spintronics or spin-based electronics.

Embedding atomic cobalt into graphene lattices to activate room-temperature ferromagnetism.

Graphene is extremely promising for next-generation spintronics applications; however, realizing graphene-based room-temperature magnets remains a great challenge. Here, we demonstrate that robust room-temperature ferromagnetism with TC up to ∼400 K and saturation magnetization of 0.11 emu g-1 (300 K) can be achieved in graphene by embedding isolated Co atoms with the aid of coordinated N atoms. Extensive structural characterizations show that square-planar Co-N4 moieties were formed in the graphene lattices, where atomically dispersed Co atoms provide local magnetic moments. Detailed electronic structure calculations reveal that the hybridization between the d electrons of Co atoms and delocalized pz electrons of N/C atoms enhances the conduction-electron mediated long-range magnetic coupling. This work provides an effective means to induce room-temperature ferromagnetism in graphene and may open possibilities for developing graphene-based spintronics devices.

Interfacial sites in platinum-hydroxide-cobalt hybrid nanostructures for promoting CO oxidation activity.

Metal-oxide/hydroxide hybrid nanostructures provide an excellent platform to study the interfacial effects on tailoring the catalysis of metal catalysts. Herein, a hybrid nanostructure of Pt@Co(OH)2 supported on SiO2 was synthesized by incipient wetness impregnation of Co(OH)2 with the aid of H2O2 and successive urea-assisted deposition-precipitation of platinum nanoparticles. The Fenton-like reaction between Co2+ and H2O2 during the impregnation process facilitates the formation of active interfacial sites. This hybrid nanostructure exhibits much higher catalytic activity towards CO oxidation than Pt/SiO2 nanoparticles with a similar Pt loading and particle size. In situ diffuse reflectance infrared Fourier transform spectroscopy was used to track the CO adsorption processes and to identify the reaction intermediates during CO oxidation. It shows that the OH species at the Pt-OH-Co interfacial sites could readily react with CO adsorbed on neighboring Pt to yield CO2 by forming *COOH intermediates and oxygen vacancies. Under the CO + O2 oxidation conditions, O2 molecules are activated by the oxygen vacancy and react with the CO molecules adsorbed on Pt to generate CO2, via forming the highly active *OOH intermediates as observed by DRIFTS.

Single-Atom-Layer Catalysis in a MoS2 Monolayer Activated by Long-Range Ferromagnetism for the Hydrogen Evolution Reaction: Beyond Single-Atom Catalysis.

Single-atom-layer catalysts with fully activated basal-atoms will provide a solution to the low loading-density bottleneck of single-atom catalysts. Herein, we activate the majority of the basal sites of monolayer MoS2 , by doping Co ions to induce long-range ferromagnetic order. This strategy, as revealed by in situ synchrotron radiation microscopic infrared spectroscopy and electrochemical measurements, could activate more than 50 % of the originally inert basal-plane S atoms in the ferromagnetic monolayer for the hydrogen evolution reaction (HER). Consequently, on a single monolayer of ferromagnetic MoS2 measured by on-chip micro-cell, a current density of 10 mA cm-2 could be achieved at the overpotential of 137 mV, corresponding to a mass activity of 28, 571 Ag-1 , which is two orders of magnitude higher than the multilayer counterpart. Its exchange current density of 75 µA cm-2 also surpasses most other MoS2 -based catalysts. Experimental results and theoretical calculations show the activation of basal plane S atoms arises from an increase of electronic density around the Fermi level, promoting the H adsorption ability of basal-plane S atoms.

Synergetic Effect of Substitutional Dopants and Sulfur Vacancy in Modulating the Ferromagnetism of MoS2 Nanosheets.

The activation and modulation of the magnetism of MoS2 nanosheets are critical to the development of their application in next-generation spintronics. Here, we report a synergetic strategy to induce and modulate the ferromagnetism of the originally nonmagnetic MoS2 nanosheets. A two-step experimental method was used to simultaneously introduce substitutional V dopants and sulfur vacancy (Vs) in the MoS2 nanosheet host, showing an air-stable and adjustable ferromagnetic response at room temperature. The ferromagnetism could be modulated by varying the content of Vs through Ar plasma irradiation of different periods, with a maximum saturation magnetization of 0.011 emu g-1 reached at the irradiation time of 6 s (s). Experimental characterizations and first-principles calculations suggest that the adjustable magnetization is attributed to the synergetic effect of the substitutional V dopants and Vs in modulating the band structure of MoS2 nanosheets, resulting from the strong hybridization between the V 3d state and the Vs-induced impurity bands. This work suggests that the synergetic effect of substitutional V atoms and Vs is a promising route for tuning the magnetic interactions in two-dimensional nanostructures.

Potential-driven surface active structure rearrangement over FeP@NC towards efficient electrocatalytic hydrogen evolution.

Understanding the variation of active structure during the hydrogen evolution reaction (HER) process is of great importance for aiding in the design of optimized electrocatalysts. Herein, we present a composite material of FeP nanoparticles coated by N-doped carbon (FeP@NC) as an efficient HER electrocatalyst, synthesized by a pyrolysis and equivalent-volume impregnation method. The as-prepared FeP@NC catalyst can accelerate the HER at a small overpotential of 135 mV with a current density of 10 mA cm-2 in acidic medium and also shows a robust long-term stability with a minor decay of about 10% of the initial current density after 15 h. Using in situ X-ray absorption spectroscopy (XAS), a potential-dependent surface rearrangement of a surface pentahedral Fe structure into an octahedral Fe moiety via surface hydroxylation is clearly observed during the HER process, resulting in a much higher electrocatalytic activity. The theoretical calculations further unveil that the rearrangement of the surface FeP5(OH) octahedral structure could effectively trigger the adjacent P atoms to act as favorable proton acceptor sites towards improving the reaction kinetics of the Volmer step for efficient electrochemical hydrogen evolution.

Reversible Tuning of the Ferromagnetic Behavior in Mn-Doped MoS2 Nanosheets via Interface Charge Transfer.

Reversible manipulation of the magnetic behavior of two-dimensional van der Waals crystals is crucial for expanding their applications in spin-based information-processing technologies. However, to date, most experimental approaches to tune the magnetic properties are single way and have very limited practical applications. Here, we report an interface charge-transfer method for obtaining a reversible and air-stable magnetic response at room temperature in Mn-doped MoS2 nanosheets. By adsorption of benzyl viologen (BV) molecules as the charge donor, the saturation magnetization of Mn-doped MoS2 nanosheets is enhanced by a magnitude of 60%, and the magnetization can be restored to the original value when the adsorbed BV molecules are removed. This cycle can be repeated many times on the same sample without detectable degradation. Experimental characterizations and first-principles calculations suggest that the enhanced magnetization can be attributed to the increase of Mn magnetic moment because of the enriched electrons transferred from BV molecules. This work shows that interface charge transfer may open up a new pathway for reversibly tuning the exchange interactions in two-dimensional nanostructures.

Sox2 promotes tumor aggressiveness and epithelial­mesenchymal transition in tongue squamous cell carcinoma.

Tongue squamous cell carcinoma (TSCC) is highly malignant and poorly differentiated, resulting in a high frequency of local recurrence and distant metastases. Sox2 (Sry­box2), an important factor in embryonic development and cell differentiation, has been shown to associate with malignant phenotypes and epithelial­mesenchymal transition (EMT) progression in numerous types of human tumors. However, the clinical relevance and molecular mechanisms of Sox2 in TSCC remain unclear. In the present study, the expression levels of Sox2 were assessed in 61 pairs of TSCC samples and corresponding adjacent non-cancerous tissues using immunohistochemical methods. Associations between Sox2 expression and clinicopathological features were evaluated. Furthermore, Sox2 was overexpressed and inhibited using full-length Sox2 cDNA and short hairpin RNA (shRNA) transfection in UM2 and Cal27 cell lines, respectively. The malignant phenotypes were assessed by plate clone formation assays, wound-healing assays and Transwell assays. EMT markers (E­cadherin, vimentin, Twist, Slug and Snail) and ß­catenin were detected by reverse transcription­polymerase chain reaction and western blot analysis following the alterations of Sox2 expression. The results indicated that Sox2 expression was markedly upregulated in TSCC samples and was significantly associated with tumor growth (pT stage), cell differentiation, lymphatic metastasis (pN stage) and clinical stage (pTNM stage). Cal27­shRNA­Sox2 cells not only exhibited a decreased capacity for cell proliferation, but also suppressed cell migration and invasion, and an attenuated colony formation capacity. By contrast, UM2­Sox2 cells exhibited accelerated cell malignant phenotypes and EMT progression. Moreover, when the expression of Sox2 was decreased by shRNA transduction, ß­catenin expression was attenuated. An opposing phenomenon was observed in UM2­Sox2 cells. In conclusion, this study suggests that Sox2 expression serves a role in TSCC malignant phenotypes and EMT progression, and that ß­catenin may act as a modulated factor in this progression.

Insight into the biological effects of acupuncture points by X-ray absorption fine structure.

Exploration of the biological effects of transition metal ions in acupuncture points is essential to clarify the functional mechanism of acupuncture treatment. Here we show that in the SP6 acupuncture point (Sanyinjiao) the Fe ions are in a high-spin state of approximately t2g4.5eg1.5 in an Fe-N(O) octahedral crystal field. The Fe K-edge synchrotron radiation X-ray absorption fine structure results reveal that the Fe-N and Fe-O bond lengths in the SP6 acupuncture point are 2.05 and 2.13 Å, respectively, and are 0.05-0.10 Å longer than those in the surrounding tissue. The distorted atomic structure reduces the octahedral symmetry and weakens the crystal field around the Fe ions by approximately 0.3 eV, leading to the high-spin configuration of the Fe ions, which is favorable for strengthening the magnetotransport and oxygen transportation properties in the acupuncture point by the enhanced spin coherence. This finding might provide some insight into the microscopic effect of the atomic and electronic interactions of transition metal ions in the acupuncture point. Graphical Abstract ᅟ.

Upregulation of proline rich 11 is an independent unfavorable prognostic factor for survival of tongue squamous cell carcinoma patients.

Proline rich 11 (PRR11) serves an important role in the development and progression of a number of types of human cancer. However, the clinical role of PRR11 in tongue squamous cell carcinoma (TSCC) remains unknown. The present study aimed to investigate the expression and clinicopathological significance of PRR11 in TSCC. The Cancer Genome Atlas analysis demonstrated that the upregulation of PRR11 in TSCC correlated with poor prognosis. The data of the present study revealed that PRR11 mRNA and protein expression was markedly upregulated in human TSCC tissues. Immunohistochemistry on 72 archived paraffin-embedded TSCC specimens suggested that high levels of PRR11 expression were significantly associated with clinical stage (P<0.001), T classification (P=0.009), N classification (P=0.017) and vital status (P=0.010). In addition, patients with TSCC with higher PRR11 expression exhibited substantially shorter survival times compared with patients with lower PRR11 expression (P<0.001). Univariate and multivariate analyses indicated that PRR11 upregulation may be an independent prognostic factor for patients with TSCC (P=0.001). Taken together, and to the best of our knowledge, the results of the present study demonstrated for the first time that PRR11 is involved in the development and progression of TSCC, and may serve as a useful prognostic marker and an effective target for treating TSCC.

Direct self-focusing synthesis of monodisperse [Au8(PPh3)7]2+ nanoclusters.

Direct and scalable synthesis of monodisperse gold nanoclusters is highly desired but remains a great challenge due to the complexity of chemical reactions. In this regard, a suitable precursor is important as it can simplify the synthesis processes and offer controllability in tuning the product. In this study, we found that Au(PPh3)2Cl could be used as an effective precursor for the direct synthesis of atomically monodisperse [Au8(PPh3)7]2+ nanoclusters without the need of tedious post-synthetic purification steps. The Au(PPh3)2Cl precursor could be directly reduced by NaBH4 (0.25 molar equivalent) in a dichloromethane solution; this produced Au8 clusters with a 35% reaction yield. Time-dependent mass spectrometry and in situ UV-vis absorption spectroscopy reveal that the synthesis process is initiated by the rapid formation of the Au6-Au8 mixture, followed by a slow spontaneous self-focusing process that converges the mixture into atomically monodisperse Au8. The success of this direct synthesis has been hypothesized to arise from the relatively stronger Au(i)Au(i) aurophilic attraction between Au(i)-PPh3 complexes that facilitates the aggregation of Au(i)-PPh3 on Au(0) cores.

Strong Surface Hydrophilicity in Co-Based Electrocatalysts for Water Oxidation.

Developing efficient and durable oxygen evolution electrocatalyst is of paramount importance for the large-scale supply of renewable energy sources. Herein, we report the design of significant surface hydrophilicity based on cobalt oxyhydroxide (CoOOH) nanosheets to greatly improve the surface hydroxyl species adsorption and reaction kinetics at the Helmholtz double layer for high-efficiency water oxidation activity. The as-designed CoOOH-graphene nanosheets achieve a small surface water contact angle of ∼23° and a large double-layer capacitance (Cdl) of 8.44 mF/cm2 and thus could evidently strengthen surface species adsorption and trigger electrochemical oxygen evolution reaction (OER) under a quite low onset potential of 200 mV with an excellent Tafel slope of 32 mV/dec. X-ray absorption spectroscopy and first-principles calculations demonstrate that the strong interface electron coupling between CoOOH and graphene extracts partial electrons from the active sties and increases the electron state density around the Fermi level and effectively promotes the surface intermediates formation for efficient OER.