Lead‐Free,Air‐Stable All‐Inorganic Cesium Bismuth Halide Perovskite Nanocrystals

Lead‐based perovskite nanocrystals (NCs) have outstanding optical properties and cheap synthesis conferring them a tremendous potential in the field of optoelectronic devices. However, two critical problems are still unresolved and hindering their commercial applications: one is the fact of being lead‐based and the other is the poor stability. Lead‐free all‐inorganic perovskite Cs₃Bi₂X₉ (X=Cl, Br, I) NCs are synthesized with emission wavelength ranging from 400 to 560 nm synthesized by a facile room temperature reaction. The ligand‐free Cs₃Bi₂Br₉ NCs exhibit blue emission with photoluminescence quantum efficiency (PLQE) about 0.2 %. The PLQE can be increased to 4.5 % when extra surfactant (oleic acid) is added during the synthesis processes. This improvement stems from passivation of the fast trapping process (2–20 ps). Notably, the trap states can also be passivated under humid conditions, and the NCs exhibited high stability towards air exposure exceeding 30 days.     

A novel biological strategy for morphology control of PbWO4 crystals in tomato extract

PbWO(4) crystals were readily synthesized by reacting lead oxide (PbO(2)) with sodium tungstate (Na(2)WO(4)·2H(2)O) at room temperature in the presence of tomato extract. Biomolecules such as vitamins, proteins in the extract played both the roles of reductant and template. The size and morphology of the PbWO(4) crystals could be controlled by adjusting the concentration of the reactants. When the concentration ratio of PbO(2) and Na(2)WO(4) was increased, the morphologies of the products varied from spherical to fusiform. Room-temperature fluorescence spectra indicated the products had a slight blue shift compared to the solid structure, which may be due to the structure defects in the crystals. The possible mechanism of PbWO(4) crystal growth in tomato extract was discussed.     

粒径可控的纳米铁酸铋的制备及其光催化性能

采用改进的聚丙烯酰胺凝胶法制备了BiFeO3纳米颗粒,利用热重-差热、红外光谱及X射线衍射等手段研究了干凝胶的热分解及BiFeO3的成相过程.结果表明,在600℃煅烧可制备出高纯的BiFeO3纳米颗粒.同时发现,随着双丙烯酰胺含量的增加,所得样品晶粒尺寸逐渐减小,从而制备出平均粒径约52～110nm的系列BiFeO3颗...     

Domino Pd-catalyzed Heck cyclization and bismuth-catalyzed hydroamination: formal synthesis of elacomine and isoelacomine

The formal synthesis of hemiterpene spirooxindole alkaloids elacomine (1) and isoelacomine (2) is described. Heck reaction of protected iodoanilines with 5,6-dihydro-2H-pyran-2-one or six-membered unsaturated lactams was investigated. The coupling product was readily converted to a carbamoyl chloride with an incorporated diene unit. The spiro(pyrrolidine-3,3'-oxindole) skeleton, which corresponds to the carbon skeleton of 1 and 2, was efficiently constructed from this intermediate by using a domino palladium-catalyzed Heck reaction and bismuth-catalyzed hydroamination. An isolated byproduct of the reaction could also be converted to the spirooxindole skeleton.     

From {Bi22O26} to chiral ligand-protected {Bi38O45}-based bismuth oxido clusters

The reaction of [Bi(22)O(26)(OSiMe(2)tBu)(14)] (1) in THF with salicylic acid gave [Bi(22)O(24)(HSal)(14)] (2) first, which was converted into [Bi(38)O(45)(HSal)(22)(OH)(2)(DMSO)(16.5)]·DMSO·H(2)O (3·DMSO·H(2)O) after dissolution and crystallization from DMSO. Single-crystal X-ray diffraction analysis and ESI mass spectrometry associated with infrared multi-photon dissociation (IRMPD) tandem MS experiments confirm the formation of the large and quite stable bismuth oxido cluster 3. The reaction of compound 2 with the butoxycarbonyl(BOC)-protected amino acids phenylalanine and valine (BOC-PheOH and BOC-ValOH), respectively, resulted in the formation of chiral [Bi(38)O(45)(BOC-AA)(22)(OH)(2)] (AA=deprotonated amino acid), as shown by a combination of different analytical techniques such as elemental analysis, dynamic light scattering, circular dichroism spectroscopy, and ESI mass spectrometry.     

苯氨基甲酸甲酯分解催化剂Bi-Zn复合氧化物的制备及其催化性能

采用共沉淀法制备了一系列Bi-Zn复合氧化物催化剂并将其用于催化苯氨基甲酸甲酯(MPC)分解制备苯基异氰酸酯(PI).用热重、X射线衍射和傅里叶变换红外光谱考察了Bi/Zn摩尔比和焙烧温度对催化剂物相结构和表面性质的影响.结果表明,Zn的加入使Bi_2O_3由α晶相转变为活性更高的β晶相,500℃焙烧时Bi-Zn前驱体分解较为完全,析出Bi_2O_3粒子的同时伴生较多Bi_(7.65)Zn_(0.35)O_(11.83)晶相.在Bi/Zn摩尔比为2/1,焙烧温度为500℃条件下制得的催化剂活性最高,此时MPC转化率为86.O%,PI选择性为91.7%,优于单独使用Bi_2O_3时的催化性能.     

超高介电常数非铁电单晶

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Composition dependence of the photocatalytic activities of BiOCl(1-x)Br(x) solid solutions under visible light

We prepared BiOCl(1-x)Br(x) (x=0-1) solid solutions and characterized their structures, morphologies, and photocatalytic properties by X-ray diffraction, diffuse reflectance spectroscopy, scanning electron microscopy, Raman spectroscopy, photocurrent and photocatalytic activity measurements and also by density functional theory calculations for BiOCl, BiOBr, BiOCl(0.5)Br(0.5). Under visible-light irradiation BiOCl(1-x)Br(x) exhibits a stronger photocatalytic activity than do BiOCl and BiOBr, with the activity reaching the maximum at x=0.5 and decreasing gradually as x is increased toward 1 or decreased toward 0. This trend is closely mimicked by the photogenerated current of BiOCl(1-x)Br(x) , indicating that the enhanced photocatalytic activity of BiOCl(1-x)Br(x) with respect to those of BiOCl and BiOBr originates from the trapping of photogenerated carriers. Our electronic structure calculations for BiOCl(0.5)Br(0.5) with the anion (O(2-), Cl(-), Br(-)) and cation (Bi(3+)) vacancies suggest that the trapping of photogenerated carriers is caused most likely by Bi(3+) cation vacancies, which generate hole states above the conduction band maximum.