Mixed transition-metal oxides@carbon core-shell nanostructures derived from heterometallic clusters for enhanced lithium storage

Multicomponent binary metal oxide-involved hybrid structures with unique physicochemical properties have received extensive attention due to their fascinating electrochemical performance. Herein, a flexible strategy, which involves the preparation of dual-functional heterometallic Fe₂M clusters and their subsequent sintering treatment, is developed to engineer novel 3D hierarchical porous structures assembled with MFe₂O₄（M = Co, Mn, Ni and Zn） nanoparticles confi...     

Intelligent Surfaces Thermally Switchable between the Highly Rough and Entirely Smooth States

Reversible switching from a highly rough surface to another entirely smooth surface under external stimuli is crucial for intelligent materials applied in the fields of anti-fogging,self-cleaning,oil-water separation and biotechnology.In this work,a thermal-responsive liquid crystal elastomer (LCE) surface covered with oriented micropillars is prepared via a facile two-step crosslinking method coupled with an extrusion molding program.The reversible change of topological structures of the LCE surface along with temperature is investigated by metallographic microscope,atomic force microscopy and optical contact angle measuring system.At room temperature,the LCE sample is filled with plenty of micropillars with an average length of 8.76 μm,resulting in a super-hydrophobic surface with a water contact angle (WCA) of 135°.When the temperature is increased to above the clearing point,all the micropillars disappear,the LCE surface becomes entirely fiat and presents a hydrophilic state with a WCA of 64°.The roughness-related wetting property of this microstructured LCE surface possesses good recyclability in several heating/cooling cycles.This work realizes a truly reversible transformation from a highly rough surface to an entirely smooth surface,and might promote the potential applications of this dynamic-responsive LCE surface in smart sensors and biomimetic control devices.     

Water-induced micellar structure change in Pluronic P103/water/o-xylene ternary system

Both laser light scattering (LLS) and small-angle X-ray scattering (SAXS) were used to study the water-induced formation and structure of micelles and supramolecules of Pluronic P103 [(EO)₁₇(PO)₆₀(EO)₁₇] in o-xylene, a selective solvent for the long middle block. In pure o-xylene, P103 molecules exist as unimer coils with an equivalent hard-sphere radius of 1.6 nm even at fairly high concentrations. Micelles with a PEO/water core and a PPO dominated corona were formed in the presence of water when the P103 concentration ≥0.046 g/mL. The size and structure of micelles have been studied as a function of solubilized water content Z (the molar ratio of water to EO units) in micelles. The micelles change from a somewhat open structure with some EO units either dangling out of the micellar core or being incorporated into neighboring micellar cores at low Z values to a flower-like structure with relatively sharp interface at high Z values. At low Z values (< about 2.9), micelles tend to have a structure with part of the poorly solvated PEO blocks present in the corona. With more water added to the core, the PEO blocks in the corona gradually entered into the core, and the PPO blocks backfolded to form loops. With increasing Z, the micellar core radius, R_c, and the hard-sphere volume fraction, ϕ, of micelles increased; the aggregation number, N, kept nearly a constant; but the hydrodynamic radius, 〈R_h〉₀, and the corona thickness, R_s, decreased. At high Z values (> about 2.9), micelles have a flower-like structure with the two end PEO blocks belonging to the small micellar core. With increasing Z, the values of R_c, ϕ, and N increased, while R_s kept nearly a constant. In the concentrated regime (C > 0.30 g/mL), a stiff polymer network at a critical ϕ value of 0.49 was formed. The supramolecular structures with a face-center cubic packing, and a possible hexagonal packing at higher polymer concentrations (i.e. > 0.55 g/mL), were observed, respectively. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 889–900, 1998     

Preparation of poly(hydroxyethyl methacrylate) and poly(hydroxypropyl methacrylate) latices

Hydroxyethyl methacrylate and hydroxypropyl methacrylate (both having extremely high solubilities in water) were polymerized in aqueous medium to obtain the respective polymer latices with a solid content as high as 10 wt.-%. The initial state of the polymerization is in solution rather than in dispersion, and the polymer product is sparingly soluble in the aqueous phase. The polymerization was carefully controlled to avoid forming hydrogel by using an oil soluble initiator and a mixture of sodium dodecyl sulfate and poly(vinyl alcohol). Solubilities of both monomers and polymers in water were also investigated.     

Intramolecular cyclization in hyperbranched polyesters

The effect of monomer structure and catalyst on the synthesis of hyperbranched polyesters based on 4,4-(4′-hydroxyphenyl)pentanoic acid has been examined. The nature of the ester group and the catalyst have a significant effect on the molecular weight of the hyperbranched polyester but do not effect the degree of branching for these materials. The fate of the single ester group at the focal point of these hyperbranched macromolecules is probed by the synthesis and polymerization of ¹³C labeled methyl 4,4-(4′-hydroxyphenyl)pentanoate. Comparison of the molecular weights determined by ¹H- or ¹³C-NMR spectra with those determined by osmometry suggest that intramolecular cyclization does not occur to a significant extent in these systems. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1627–1633, 1997     

An efficient chiral phosphorus derivatizing agent for the determination of the enantiomeric excess of chiral alcohols and amines by 31P NMR spectroscopy

The chiral phosphorus derivatizing agent (CDA) 1 was prepared from optically pure (S)‐1,1‐bis‐2‐naphthol. It was first used in the determination of the enantiomeric excess of chiral alcohols and amines by means of ³¹P NMR spectroscopy. It showed that, for the chiral aromatic alcohols, no apparent kinetic resolution was noted and good base‐line separation was observed. Furthermore, the chemical shift difference (Δδ) of ³¹P NMR spectroscopy was much larger than those determined by the use of other chiral phosphorus derivatizing agents reported previously. However, for aliphatic alcohols, it showed not only obvious kinetic resolutions but incomplete base‐line separation. Moreover, we also found that the use of CDA 1 was suitable for the determination of enantiomeric excess of chiral primary amines. © 2002 John Wiley & Sons, Inc. Heteroatom Chem 13:93–95, 2002; DOI 10.1002/hc.10018     

静水压对立方钙钛矿CsSnX3(X=I, Br, Cl)光电性质的第一性原理探究

全无机无铅卤化物钙钛矿已经成为重要的新一代太阳能电池材料.采用密度泛函理论的第一性原理研究了不同静水压下CsSnX₃(X=I, Br, Cl)材料的晶体结构,电子结构和光学性能,并分析了其内在联系.结果表明施加静水压可使材料中Sn-X键长减小,使原子之间的耦合增强,带隙值减小,且随着卤族元素半径的增大,压力效应越明显;随着压力的增加,材料的吸收系数和复折射率增大,吸收光谱出现红移现象,在可见光区和近红外光区吸收增强.相比CsSnBr₃和CsSnCl₃,CsSnI₃在可见光区吸收最佳且受压力作用影响最小,更适用于钙钛矿太阳能电池材料.     

Rapid Experimental Screening of High-Entropy Diborides for Superior Oxidation Resistance

Due to the huge composition space, composition screening is of great importance to the optimization of high-entropy diborides (HEBs) with exceptional oxidation resistance. However, related studies are lacking. Here, a novel rapid, effective strategy to fully screen the compositions on the oxidation resistance of HEBs is proposed. Specifically, the synthesis of the equiatomic 1- to 9-cation multicomponent diborides of the IVB, VB, and VIB groups in seconds via an ultrafast ultrahigh-temperature synthesis technique is realized. Subsequently, combined with the thermogravimetric analysis and first-principles calculations, the roles of incorporated elements are systematically explored. The results show that Zr, Cr, Ta, Nb, and W elements are the key to the improved oxidation resistance of HEBs, while Ti, Mo, and V elements are destructive. In particular, the positive roles of metal elements are mainly attributed to the partial dissolution of the generated metal oxides into the generated B₂O₃ glass, which can improve the viscosity of B₂O₃ and thus enhance its high-temperature stability and reduce the oxygen diffusion rate, as confirmed by the first-principles calculations. This study paves a way to rapidly screen the elements in HEBs, which can be a guide for further anti-oxidation designs.     

Synthesis of submicron-sized composite particles with unique morphology by emulsifier-free seeded emulsion copolymerization

Polystyrene （PSt） microspheres with diameter of 375 nm to be used as the seeds for seeded emulsion polymerization were prepared via emulsion polymerization using potassium persulfate （KPS） as initiator in ethanol-water mixed solvents. Emulsifier-free seeded emulsion copolymerization of styrene （St） with acrylonitrile （AN） was carried out in the presence of poly（ethylene glycol） monomethoxymonomethacrylate （PEGm） macromonomer as reactive stabilizer and 2,2＇-azobisisobutyronitrile （AIBN） as initiator to obtain submicron-sized PEGm graft poly（styrene-coacrylonitrile） （PEGm-g-PSAN） composite particles with unique morphology. Scanning electron microscopy （SEM） indicated that St and AN together contributed to forming the unusual morphology. The concentration of St and AN, total monomer concentration, initiator type and the monomer adding method remarkably affected the morphology of the composite polymer particles.