In situ phosphorus K-edge X-ray absorption spectroscopy studies of calcium–phosphate formation and transformation on the surface of bacterial cellulose nanofibers

In this work, for the first time, in situ formation and transformation process of embryo calcium phosphate (Ca–P) minerals on three-dimensional bacterial cellulose nanofibers was investigated. Combined with XRD, X-ray absorption near-edge structure results revealed that the embryo precursor was amorphous calcium phosphate which was subsequently converted to β-tricalcium phosphate, octacalcium phosphate, and finally to the more thermodynamically stable form of hydroxyapatite. The methodology reported herein may be extended to the studies of Ca–P and other minerals on various substrates.     

In Situ Electropolymerization Enables Ultrafast Long Cycle Life and High-Voltage Organic Cathodes for Lithium Batteries

Organic cathode materials have attracted extensive attention because of their diverse structures, facile synthesis, and environmental friendliness. However, they often suffer from insufficient cycling stability caused by the dissolution problem, poor rate performance, and low voltages. An in situ electropolymerization method was developed to stabilize and enhance organic cathodes for lithium batteries. 4,4′,4′′-Tris(carbazol-9-yl)-triphenylamine (TCTA) was employed because carbazole groups can be polymerized under an electric field and they may serve as high-voltage redox-active centers. The electropolymerized TCTA electrodes demonstrated excellent electrochemical performance with a high discharge voltage of 3.95 V, ultrafast rate capability of 20 A g⁻¹, and a long cycle life of 5000 cycles. Our findings provide a new strategy to address the dissolution issue and they explore the molecular design of organic electrode materials for use in rechargeable batteries.     

Focal Mechanism and Rupture Process of the 2012 Mw 7.0 Santa Isabel,Mexico Earthquake Inverted by Teleseismic Data

The point source parameters of the April 12, 2012 Mw 7.0 Santa Isabel, Mexico, earth-quake indicated by teleseismic P and SH waveforms obtained by a means of traditional cut and paste (CAP) method show...     

Chiral derivatization coupled with liquid chromatography/mass spectrometry for determining ketone metabolites of hydroxybutyrate enantiomers

With PMP chiral derivatization, the D/L-2HB and D/L-3HB enantiomers can be distinctly determined by reversed-phase chromatographic separation. In addition, the detection sensitivities were greatly enhanced by LC-ESI-MS analysis due to the introduction of easily ionizable tertiary amino group from PMP.     

Modified two-derivative Runge–Kutta methods for the Schrödinger equation

A family of modified two-derivative Runge–Kutta (MTDRK) methods for the integration of the Schrödinger equation are obtained. Two new three-stage and fifth order TDRK methods are derived. The numerical results in the integration of the radial Schrödinger equation with the Woods–Saxon potential are reported to show the high efficiency of our new methods. The results of the error analysis are illustrated by the resonance problem.     

三维有序大孔二氧化钛表面超细钯纳米颗粒的构筑及其增强柴油炭烟催化燃烧性能（英文）

柴油机排放颗粒物(主要成分是炭烟)是城市大气PM2.5中一次颗粒物的主要来源和二次颗粒物形成的重要组分,严重危害大气环境和人类健康.利用颗粒物捕集器与催化剂相结合的连续过滤再生技术是满足柴油车国VI炭烟颗粒物排放标准的最有效技术,目前该技术所面临的挑战是研发在排气温度的柴油炭烟颗粒物催化氧化催化剂.柴油炭烟催化燃烧反应的本质是典型的气(氧气)-固(炭烟颗粒)-固(催化剂)三相深度氧化反应,因此我们研究组提出了高活性柴油炭烟燃烧催化剂设计应该遵循优化固-固接触与强化活化分子氧能力二者相结合的研究思路.为满足此设计思路的要求,本课题组前期采用孔径大于200 nm的三维有序大孔(3DOM)结构氧化物作为载体,利用大孔效应来实现PM在催化剂内部的有效扩散,从而提高催化剂与PM的接触效率.采用具有强活化分子氧能力的负载型贵金属(Au,Pt)纳米颗粒或贵金属-氧化物复合纳米颗粒作为活性位来提高催化剂对分子氧的活化能力,进而设计了多个系列高活性催化剂,并形成了担载贵金属纳米颗粒的可控制备方法与装置.然而,Au和Pt昂贵的价格限制了其广泛应用.价格相对便宜的Pd具有与Pt相似的催化性能,是其良好替代品.但是,目前关于3DOM氧化物表面负载型Pd纳米颗粒结构和尺寸与柴油炭烟催化燃烧性能之间的相关研究仍然较少.基于此,本文采用气泡辅助膜还原法制备了3DOM二氧化钛(TiO_2)担载超细Pd纳米颗粒催化剂.利用XRD,Raman,BET,SEM,TEM,ICP,XPS和H2-TPR等技术手段对催化剂进行表征,并以模拟柴油炭烟为研究对象,利用程序升温氧化反应(TPO)对催化剂的活性进行评价,深入探讨了催化剂的制备、结构及物化性质与炭烟催化燃烧反应性能之间的关系.XRD和Raman结果表明,TiO_2载体由锐钛矿(主)和金红石(次)两种物相组成.SEM照片显示,所制催化剂为规整的有序大孔结构,球形孔互相贯通,孔径均一,大孔腔平均尺寸为280 nm,孔窗尺寸为109 nm,这种三维有序大孔TiO_2的结构能够增强炭烟颗粒与催化剂之间的接触效率.TEM表征显示,平均粒径为1.1 nm的超细半球型Pd纳米颗粒高度分散于TiO_2载体的内壁上,两者间的优化界面面积有利于增加活化O2的活性位密度,这些活性位源于Pd与TiO_2间强相互作用.H2-TPR和XPS表征印证了上述观点,具有1.1 nm超细Pd颗粒的Pd/3DOM-TiO_2催化剂表现出强的低温氧化还原特性和丰富的表面吸附氧物种.在TPO测试中,相对于担载5.0 nm Pd颗粒的催化剂,具有1.1 nm尺寸超细Pd颗粒的Pd/3DOM-TiO_2催化剂展示了高的催化炭烟燃烧活性,T10,T50和T90分别为295,370和415 oC,且在5次TPO测试过程中表现出良好的催化和结构稳定性.这种具有3DOM结构和超细Pd纳米颗粒的纳米催化剂能够有效降低Pd的使用量,在催化炭烟燃烧的实际应用中大有潜力.     

{Nb288O768(OH)48(CO3)12}: A Macromolecular Polyoxometalate with Close to 300 Niobium Atoms

A protein‐sized (ca. 4.2×4.2×3.6 nm³) non‐biologically derived molecule {Nb₂₈₈O₇₆₈(OH)₄₈(CO₃)₁₂} ( Nb₂₈₈ ) containing up to 288 niobium atoms has been obtained, which is by far the largest and the highest nuclearity polyoxoniobate (PONb). Particularly, in terms of metal nuclearity number, Nb₂₈₈ is the second largest cluster so far reported in classic polyoxometalate chemistry (V, Mo, W, Nb, and Ta). Nb₂₈₈ can be described as a giant windmill‐like cluster aggregate of six nanoscale high‐nuclearity PONb units {Nb₄₇O₁₂₈(OH)₆(CO₃)₂} ( Nb₄₇ ) joined together by six additional Nb ions. Interestingly, the 47‐nuclearity Nb₄₇ units generated in situ can be isolated and bridged by copper complexes to form an inorganic–organic hybrid three‐dimensional PONb framework, which exhibits effective catalytic activity for hydrolyzing nerve agent simulant of dimethyl methylphosphonate. The unique Nb₄₇ cluster also provides a new type of topology to very limited family of Nb‐O clusters.     

Experimental Evidence for a Triboluminescent Antiperovskite Ferroelectric: Tris(trimethylammonium) catena‐Tri‐μ‐chloro‐manganate(II) Tetrachloromanganate(II)

The perovskite structure is rich in ferroelectricity. In contrast, ferroelectric antiperovskites have been scarcely confirmed experimentally since the discovery of M₃AB‐type antiperovskites in the 1930s. Ferroelectricity is now revealed in an organic–inorganic hybrid X₃AB antiperovskite structure, which exhibits a clear ferroelectric phase transition 6/mmmF6mm with a high Curie point of 480 K. The physical properties across the phase transition are obviously changed along with the symmetry requirements, providing solid experimental evidence for the ferroelectric phase transition. More interestingly, the discovered antiperovskite shows intense photoluminescence and triboluminescence properties. The confirmation of the triboluminescent ferroelectric antiperovskite will open new avenues to explore excellent optoelectronic properties in the antiperovskite family.     

Introducing Fe2+ into Nickel–Iron Layered Double Hydroxide: Local Structure Modulated Water Oxidation Activity

Exploring materials with regulated local structures and understanding how the atomic motifs govern the reactivity and durability of catalysts are a critical challenge for designing advanced catalysts. Herein we report the tuning of the local atomic structure of nickel–iron layered double hydroxides (NiFe‐LDHs) by partially substituting Ni²⁺ with Fe²⁺ to introduce Fe‐O‐Fe moieties. These Fe²⁺‐containing NiFe‐LDHs exhibit enhanced oxygen evolution reaction (OER) activity with an ultralow overpotential of 195 mV at the current density of 10 mA cm^?2, which is among the best OER catalytic performance to date. In‐situ X‐ray absorption, Raman, and electrochemical analysis jointly reveal that the Fe‐O‐Fe motifs could stabilize high‐valent metal sites at low overpotentials, thereby enhancing the OER activity. These results reveal the importance of tuning the local atomic structure for designing high efficiency electrocatalysts.