Air‐Stable,Lead‐Free Zero‐Dimensional Mixed Bismuth‐Antimony Perovskite Single Crystals with Ultra‐broadband Emission

Lead‐free zero‐dimensional (0D) organic‐inorganic metal halide perovskites have recently attracted increasing attention for their excellent photoluminescence properties and chemical stability. Here, we report the synthesis and characterization of an air‐stable 0D mixed metal halide perovskite (C₈NH₁₂)₄Bi_0.57Sb_0.43Br₇?H₂O, in which individual [BiBr₆]^3? and [SbBr₆]^3? octahedral units are completely isolated and surrounded by the large organic cation C₈H₁₂N⁺. Upon photoexcitation, the bulk crystals exhibit ultra‐broadband emission ranging from 400 to 850 nm, which originates from both free excitons and self‐trapped excitons. This is the first example of 0D perovskites with broadband emission spanning the entire visible spectrum. In addition, (C₈NH₁₂)₄Bi_0.57Sb_0.43Br₇?H₂O exhibits excellent humidity and light stability. These findings present a new direction towards the design of environmentally‐friendly, high‐performance 0D perovskite light emitters.     

Mn掺杂LiFePO4的第一性原理研究

采用基于密度泛函理论的第一性原理方法, 计算了不同Mn掺杂浓度LiFe_1-xMn_xPO₄ (x=0,0.25,0.50,0.75) 的电子结构. 同时采用流变相辅助高温固相碳热还原法制备了LiFe_1-xMn_xPO₄ (x= 0,0.25,0.50,0.75) 材料. 理论计算表明: LiFePO₄具有E_g = 0.725 eV的带隙宽度, 为半导体材料. 通过Fe位掺杂25%的Mn离子可最大程度地 减小材料带隙宽度、降低Fe---O键及Li---O键键能, 进而提高材料的电子电导率及锂离子扩散速率. 实验结果亦表明, 当Mn掺杂量x=0.25时, 材料具有最优的电化学性能, 其具有约为158 mAh· g^-1的放电比容量以及551 Wh· kg^-1的能量密度. 理论计算与实验结果非常符合.     

Oxalic acid-assisted preparation of LiFePO4/C cathode material for lithium-ion batteries

LiFePO₄/C composite is synthesized by oxalic acid-assisted rheological phase method. Fe₂O₃ and LiH₂PO₄ are chosen as the starting materials, sucrose as carbon sources, and oxalic acid as the additive. The crystalline structure and morphology of the products are characterized by X-ray diffraction and field emission scanning electron microscopy. The charge–discharge kinetics of LiFePO₄ electrode is investigated using cyclic voltammetry and electrochemical impedance spectroscopy. It is found that the introduction of appropriate amount of oxalic acid leads to smaller particle sizes, more homogeneous size distribution, and some Fe₂P produced in the final products, resulting in reduced polarization, impedance, and improved Li⁺ ion diffusion coefficient. The best cell performance is delivered by the sample with R = 1.5 (R of the molar ratio of oxalic acid to LiH₂PO₄). Its discharge capacity is 154 mAh g⁻¹ at 0.2 C rate and 120 mAh g⁻¹ at 5.0 C rate. At the same time, it exhibits an excellent cycling stability; no obvious decrease even after 1,000 cycles at 1.0 C rate.     

对油脂过氧化值测定中碘化钾饱和溶液变质和保存的分析

碘化钾饱和溶液是测定油脂过氧化值试验中的一个重要试剂,油脂氧化过程中产生过氧化物,与碘化钾作用生成游离碘,以硫代硫酸钠标准溶液滴定。该试剂放置易氧化变黄,一般现配现用,但所配溶液不能被完全使用,浪费较大。笔者经研究发现,新配制的碘化钾饱和溶液和被氧化变黄的碘化钾饱和溶液的pH值相差较大,通过调整碘化钾饱和溶液的pH值,可防止碘化钾饱和溶液被氧化从而析出游离碘,同时节约试剂成本。     

Fourier-transform Raman and infrared spectroscopic analysis of dipyrrinones and mesobilirubins

The Fourier-transform Raman (FT-Raman), infrared (FT-IR), and UV-visible absorption spectra of four dipyrrinones and two mesobilirubins have been investigated in the solid state and in CH2Cl2 solutions. A detailed spectral analysis, assignment and discussion of these spectra are presented. The bands at 1735-1738, 1691-1707 and 1359-1377 cm(-1) which were assigned to the stretching vibrations of the C-O-C and C-O-H and symmetric deformation of C-H bonds, respectively, can act as a marker to distinguish the compounds of this class. The striking differences between the spectra of the compounds suggest that mesobilirubin XIIIalpha is tending to adopt as ridge-tile conformation, rather than linear conformation.     

Chelation-assisted method for the preparation of cathode material LiFePO<Subscript>4</Subscript>

LiFePO₄/C composite cathode material is prepared by ball milling with the assistance of EDTA chelation with using water as the media of ball mill procedure. FePO₄ and LiOH are used as starting materials; a certain amount of glucose is used as carbon sources and reduction agent. The structure and morphology of the composite are characterized by X-ray diffraction and scanning electron microscopy. Cyclic voltammetry, AC impedance measurements, and galvanostatic charge–discharge and cycling performances are used to characterize its electrochemical properties. The results indicate that the performances of composites prepared by chelation-assisted method are much better than common ball milling method which using alcohol or acetone as the media of ball mill procedure. The stable discharge capacity of the prepared composite is 150 and 105 mAh g⁻¹ at 1 and 10 C rate, respectively.     

Cr掺杂镓铟酸锌长余辉纳米粒子的制备及生物传感应用

通过水热法合成了不同含量In离子掺杂的ZnGa_1.99-xIn_xO₄∶Cr_{0. 01}³⁺长余辉纳米粒子(PLNPs)。通过In掺杂和改变反应pH条件,PLNPs的余辉强度和时长明显改善,近红外余辉时间超过96h,平均粒径为15.36nm。实验结果表明,PLNPs的余辉强度被多巴胺猝灭,PLNPs的相对余辉强度(F₀-F)/F₀与多巴胺浓度在0.005～20μmol/L范围内呈良好的线性关系,线性回归线方程为y=0.1789x+0.4427,相关系数R²=0.9974,对多巴胺的检出限为0.0024μmol/L,其在生物传感领域有应用潜力。     

Cu(OAc)2/TEMPO Cooperative Promoted Hydroamination Cyclization and Oxidative Dehydrogenation Cascade Reaction of Homopropargylic Amines

A novel and efficient Cu(OAc)₂‐catalyzed hydroamination cyclization and 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO)‐mediated oxidative dehydrogenation cascade reaction of homopropargylic amines has been developed. A library of 1,2‐disubstituted pyrrole derivatives were obtained in good‐to‐high yields in one pot with no step‐by‐step feeding process. This reaction involved TEMPO playing dual roles as both an oxidative dehydrogenation reagent and a ligand. An insight into the reaction mechanism was obtained by using several analytical determination methods.     

Absorption saturation and self-action processes under resonant excitation of the basic exciton transition in CdSe/ZnS colloidal quantum dots

The revealed absorption saturation and Fresnel diffraction of ultrashort laser pulses under resonant excitation of the basic exciton transition in CdSe/ZnS quantum dots (a strongly absorbing colloidal solution) have been explained by the processes of filling of states of a two-level system with the excited-state lifetime dependent on the light intensity and self-diffraction of the laser beam due to the formation of the transparency channel and the induced diaphragm.     

Effect of lithium boron oxide glass coating on the electrochemical performance of LiNi<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>O<Subscript>2</Subscript>

The effect of the lithium boron oxide glass coating on the electrochemical performance of LiNi_1/3Co_1/3Mn_1/3O₂ has been investigated via solution method. The morphology, structure, and electrochemical properties of the bare and coated LiNi_1/3Co_1/3Mn_1/3O₂ are characterized by scanning electron microscopy, X-ray diffraction, electrochemical impedance spectroscopy, and charge–discharge tests. The results showed that the lattice structure of LiNi_1/3Co_1/3Mn_1/3O₂ is not changed after coating. The coating sample shows good high-rate discharge performance (148 mAh g⁻¹ at 5.0 C rate) and cycling stability even at high temperature (with the capacities retention about 99% and 87% at room and elevated temperature after 50 cycles). The Li⁺ diffusion coefficient is also largely improved, while the charge transfer resistance, side reactions within cell, and the erosion of Hydrofluoric Acid all reduced. Consequently, the good electrochemical performances are obtained.