The palladium-catalyzed cross-coupling reactions of trifluoroethyl iodide with aryl and heteroaryl boronic acid esters

The cross-coupling reactions of 1,1,1-trifluoro-2-iodoethane with aryl and heteroaryl boronic acid esters have been successfully achieved. The new protocol allows for a convenient introduction of trifluoroethyl groups into a variety of aryl and heteroaryl moieties under mild conditions.     

Systematic evaluation of structure-activity relationships of the riminophenazine class and discovery of a C2 pyridylamino series for the treatment of multidrug-resistant tuberculosis

Clofazimine, a member of the riminophenazine class of drugs, is the cornerstone agent for the treatment of leprosy. This agent is currently being studied in clinical trials for the treatment of multidrug-resistant tuberculosis to address the urgent need for new drugs that can overcome existing and emerging drug resistance. However, the use of clofazimine in tuberculosis treatment is hampered by its high lipophilicity and skin pigmentation side effects. To identify a new generation of riminophenazines that is less lipophilic and skin staining, while maintaining efficacy, we have performed a systematic structure-activity relationship (SAR) investigation by synthesizing a variety of analogs of clofazimine and evaluating their anti-tuberculosis activity. The study reveals that the central tricyclic phenazine system and the pendant aromatic rings are important for anti-tuberculosis activity. However, the phenyl groups attached to the C2 and N5 position of clofazimine can be replaced by a pyridyl group to provide analogs with improved physicochemical properties and pharmacokinetic characteristics. Replacement of the phenyl group attached to the C2 position by a pyridyl group has led to a promising new series of compounds with improved physicochemical properties, improved anti-tuberculosis potency, and reduced pigmentation potential.     

Fabrication of upended taper-shaped cuprous thiocyanate arrays on a copper surface at room temperature

A new strategy has been well designed to form upended taper-shaped cuprous thiocyanate (hereafter abbreviated as CuCNS) arrays on a copper substrate with use of a simple solution-phase method at room temperature. This method consists of a liquid-solid reaction between a solution of thiocyanate ammonium and the copper substrate itself in the assistance of formamide. Novel CuCNS arrays are approximately perpendicular to copper substrate surfaces. Every single crystal shows an upended taper-like morphology (i.e., the tip end points into the surface of copper substrate and the other big end of the taper exposes out, like a dart thrusting into the copper substrate). On the basis of structure and chemical bond analysis, CuCNS crystals tend to grow along the c-axis, which is essential for the formation of CuCNS arrays on a copper substrate. This approach also provides a facile strategy to produce different patterns on different copper substrates, which may be applicable to the synthesis of other inorganic materials with various potential applications.     

Photo-excited Oxygen Reduction and Oxygen Evolution Reactions Enable a High-Performance Zn–Air Battery

The storage of solar energy in battery systems is pivotal for a sustainable society, which faces many challenges. Herein, a Zn–air battery is constructed with two cathodes of poly(1,4-di(2-thienyl))benzene (PDTB) and TiO₂ grown on carbon papers to sandwich a Zn anode. The PDTB cathode is illuminated in a discharging process, in which photoelectrons are excited into the conduction band of PDTB to promote oxygen reduction reaction (ORR) and raise the output voltage. In a reverse process, holes in the valence band of the illuminated TiO₂ cathode are driven for the oxygen evolution reaction (OER) by an applied voltage. A record-high discharge voltage of 1.90 V and an unprecedented low charge voltage of 0.59 V are achieved in the photo-involved Zn–air battery, regardless of the equilibrium voltage. This work offers an innovative pathway for photo-energy utilization in rechargeable batteries.     

La~(3+)掺杂NiCo层状双金属氢氧化物纳米片的合成及其电化学性能

稀土离子La~(3+)掺杂的NiCo层状双金属氢氧化物纳米片具有高的超级电容器性能,比容量达到1115 F/g(1A/g)、倍率性能为517 F/g(30 A/g)。研究表明,La~(3+)离子掺杂不改变NiCo层状双金属氢氧化物晶体结构,但会显著影响其电子和离子传导特性,从而改变其电化学性能。根据离子电负性标度,La~(3+)(1.327)和Co~(2+)(1.377)离子的电负性值最接近,掺杂La~(3+)会优先取代Co~(2+)离子位置。由于La~(3+)离子的尺寸作用(106 pm),使得最优掺杂比例较小仅为0.26%,电化学结果表明较少的La~(3+)掺杂比例依然会显著调节NiCo层状双金属氢氧化物的电子/离子输运性质。     

Sn掺杂MoO_3的制备、表征及气敏性能

以仲钼酸铵和四氯化锡为原料,采用水热法制备了不同Sn掺杂比例的MoO_3;利用X射线衍射(XRD),扫描电子显微镜(SEM)和Brunauer-Emmett Teller(BET)测试等手段对材料进行了物相、形貌结构和孔径表征;测试了其对乙醇、二氯甲烷、甲醇、甲醛、甲酸、四氯化碳、氨气和丙酮等气体的传感性能.结果表明,Sn掺杂未改变MoO_3的结构;290℃为气体传感测试的最佳测试温度;掺杂后的MoO_3对乙醇气体的灵敏度和响应时间均优于纯相MoO_3,Sn掺杂摩尔比为5%时效果最好,500 mg/m~3测试条件下对乙醇的灵敏度为19.64,响应时间为1.1 s.     

MgF自由基A2π-X2Σ+跃迁的高分辨激光诱导荧光光谱和Franck-Condon因子

MgF自由基被认为是适用于直接激光冷却的候选分子之一. 本文利用激光诱导荧光技术研究了MgF A²π-X²Σ⁺电子跃迁系统的转动分辨光谱. 在超声射流膨胀条件下利用两个镁针对SF₆/Ar气体混合放电产生MgF自由基. 在348∽370 nm范围内,实验记录了属于Δv=0,±1三个序的19个振动带. 通过对实验光谱的转动分析,确定了X²Σ⁺和A²π态的精确光谱常数. 利用实验结果结合和Rydberg-klein-rees方法计算了包括Franck-Condon因子(FCFs)在内的光谱常数. 实验结果和理论计算的FCFs之间存在显著差异,表明FCFs几乎不依赖于A²π态自旋-轨道耦合效应. 本文确定的势能曲线和FCFs为MgF分子激光冷却方案的理论模拟提供了必要的光谱数据.     

Morphology and structure studies of KDP and ADP crystallites in the water and ethanol solutions

On the basis of calculations of the bond strength (of constituent chemical bonds that form during crystal growth process) and expanded capacity of low Miller index planes in KH₂PO₄ (KDP) and NH₄H₂PO₄ (ADP) crystals, the ideal crystal morphologies and interactions between crystal surfaces and ethanol molecules are comprehensively studied. Our present results show that the crystallites morphology are mainly determined by the bond type, number, direction and strength, as well as the additive ingredient ethanol. Ethanol molecules may strongly affect ADP and KDP crystallites morphology by interacting with hydrogen bonds at crystal surfaces.     

Dependence of THz Time-Domain Spectroscopy on the Crystal Thickness and Optical Width in Electro-Optic Sampling

The processes of electro-optical (EO) sampling of terahertz (THz) pulse were studied theoretically by considering the finite optical probe width and the double-sampling within the same THz pulse. The dependence of THz time-domain waveforms on the crystal thickness and optical width in EO sampling was revealed. Furthermore, the optimal thickness was analyzed, which shows whether or not an antireflection film coated for the optical probe beam is needed.     

Bond energy prediction of Curie temperature of lithium niobate crystals

A general expression of the Curie temperature (Tc) and spontaneous polarization (Ps) of lithium niobate (LN) crystals is energetically proposed by employing the viewpoint of the bond energy of constituent chemical bonds within the LN crystallographic frame. The calculated Tc values of various pure and doped LN crystals are in a good agreement with those reported data. Ps values of these LN crystals can also be quantitatively estimated in this work. It is found that the Li site is a sensitive lattice position to dominate the ferroelectricity of LN crystals. This novel method provides us a good understanding of ferroelectric behaviors of LN crystals, which may be applicable to the estimation of ferroelectric behaviors of LN-type solids.