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891.
892.
Dr. Bing Wang Dr. De Yu Wang Dr. Zhenxiang Cheng Prof. Dr. Xiaolin Wang Prof. Dr. Yuan Xu Wang 《Chemphyschem》2013,14(6):1245-1255
Phase stability is important to the application of materials. By first‐principles calculations, we establish the phase stability of chromium borides with various stoichiometries. Moreover, the phases of CrB3 and CrB4 have been predicted by using a newly developed particle swarm optimization (PSO) algorithm. Formation enthalpy–pressure diagrams reveal that the MoB‐type structure is more energetically favorable than the TiI‐type structure for CrB. For CrB2, the WB2‐type structure is preferred at zero pressure. The predicted new phase of CrB3 belongs to the hexagonal P‐6m2 space group and it transforms into an orthorhombic phase as the pressure exceeds 93 GPa. The predicted CrB4 (space group: Pnnm) phase is more energetically favorable than the previously proposed Immm structure. The mechanical and thermodynamic stabilities of predicted CrB3 and CrB4 are verified by the calculated elastic constants and formation enthalpies. The full phonon dispersion calculations confirm the dynamic stability of WB2‐type CrB2 and predicted CrB3. The large shear moduli, large Young’s moduli, low Poisson ratios, and low bulk and shear modulus ratios of CrB4? PSC and CrB4? PSD indicate that they are potential hard materials. Analyses of Debye temperature, electronic localization function, and electronic structure provide further understanding of the chemical and physical properties of these borides. 相似文献
893.
Wanhua Lei Dr. Guoyu Jiang Dr. Qianxiong Zhou Dr. Yuanjun Hou Prof. Baowen Zhang Prof. Xuexin Cheng Prof. Xuesong Wang 《Chemphyschem》2013,14(5):1003-1008
Nanoscaled coordination polymers based on biologically prevalent ions have potential applications in drug delivery and biomedical imaging. Herein, coordination polymer nanoparticles of anionic porphyrins, including meso‐tetra(4‐carboxyphenyl)‐porphyrin (H2TCPP4?) and meso‐tetra(4‐sulfonatophenyl)‐porphyrin (H2TPPS4?), and alkaline or alkaline earth metal cations, such as K+ and Ca2+, were constructed in aqueous solution in the presence of cucurbit[7]uril (CB7) or cucurbit[8]uril (CB8). UV/Vis absorption and fluorescence spectroscopy, dynamic light scattering (DLS), scanning electron spectroscopy (SEM), and atomic force microscopy (AFM) were applied to explore the assembly and particle formation of porphyrin anions and metal cations mediated by CBn. The particle size depends on the kinds of CBn and metal cations and their concentrations. The uptake of H2TPPS4? particles by tumor cells (A549 cells) was found to be more efficient than H2TPPS4? at 37 °C, showing the application potential of such assembled particles in biology and medicine. 相似文献
894.
Yongqiang Zhang ShengzhengWang Zhenyuan Miao Jianzhong Yao Wannian Zhang Chunquan Sheng 《中国化学》2013,(9):1139-1143
Iodiconazole is a novel antifungal agent that was developed in its racemic form. In order to investigate the ef- fects of the chiral center on the antifungal activity, R- and S-isomers of iodiconazole were prepared on the basis of the asymmetric Sharpless epoxidation. (S)-Iodiconazole was proved to have better antifungal activity than the (R)- isomer. The binding modes of the two isomers with lanosterol 14~z-demethylase were clarified by molecular dock- ing. 相似文献
895.
为提高PtCo/C合金催化剂的电化学性能,采用微波法合成铂钴锰催化剂前驱体,经高温热处理形成合金,最后通过酸处理得到铂钴锰合金催化剂(PtCoMn/C)。电化学测试结果表明:适量锰的添加可提升PtCo/C催化剂的活性和耐久性。PtCoMn/C催化剂在 0.9 V(vs RHE)电压下的质量比活性(MA)达到 0.666 A·mgPt-1,是传统 Pt/C 的 2.66 倍,是 PtCo/C 催化剂的 1.30 倍。在30 000圈催化剂加速耐久性测试中,PtCoMn/C合金催化剂的电化学活性面积(ECSA)和质量比活性(MA)仅下降6.9%和27.1%,均远低于Pt/C催化剂。 相似文献
896.
A new copper and silver‐mediated cyanation of aryl iodides with DDQ as a cyanide source is achieved, providing nitriles with good yields. This new approach represents a safe method leading to aryl nitriles. 相似文献
897.
A series of novel axially chiral 2,2′‐bipyridine N,N′‐dioxides bearing C1 or C2‐symmetry have been synthesized by the use of enantiopure α‐amino acids as chiral sources. The absolute stereochemistry of the axial chirality of these organocatalysts has been clearly assigned by means of CD measurements together with literature protocols. The reactivities and enantioselectivities of these organocatalysts have been examined in the reactions of aromatic aldehydes with allyltrichlorosilane, thus providing the desired products with moderate yields and enantioselectivies. 相似文献
898.
Superparamagnetic iron oxide nanoparticles with narrow size distributions were successfully prepared in large scale by a facile one‐pot synthetic method in the presence of hydrophilic polymers, such as polyethylene glycol diacid (HOOC‐PEG‐COOH) and poly(acrylic acid) (PAA). The as‐prepared products were investigated in detail by powder X‐ray diffraction (XRD), thermogravimetric analyses (TGA), transmission electron microscopy (TEM), high‐resolution transmission electron microscopy (HRTEM), dynamic light scattering (DLS), and vibrating sample magnetometer (VSM). The interaction between polymers and iron oxide nanoparticles was investigated using Fourier transform infrared spectrometry (FT‐IR). The results show that polymers can be attached onto the surface of iron oxide nanoparticle by bridging coordination and monodentate fashion, respectively. The interaction affects iron oxide nanoparticle properties significantly, such as XRD diffraction intensity, hydrodynamic diameter, isoelectric point, and saturation magnetization. Furthermore, the results of in vitro experiments indicated that iron oxide‐PEG‐COOH nanoparticle is more cytotoxic than iron oxide‐PAA nanoparticle due to different coordinating modes. 相似文献
899.
对炭泡沫为支撑骨架的氧化硅气凝胶(SiO2/炭泡沫)和碳化硅(SiC/炭泡沫)复合材料分别采用XRD、SEM、激光导热仪、万能力学试验机进行物相、微观结构、热学及力学性能方面的表征.结果表明:所制备的SiO2/炭泡沫与原炭泡沫相比,具备更高的抗压强度(14.95 MPa)和更低的室温热导率(0.44 W·m-1·K-1).SiC/炭泡沫材料则保持了较高的抗压强度值(14.66 MPa),其在 1 200 ℃下具备极低的高温热导率(2.18W·m-1·K-1).热重分析表明,SiC/炭泡沫在氧化氛围中到610 ℃才发生质量的损失,而内部炭发生完全烧蚀的温度高达844 ℃,这表明该材料的抗氧化性能远好于纯的炭泡沫材料. 相似文献
900.
用基于第一性原理的密度泛函理论方法,对Cs3Bi2X9(X=Cl、Br、I)的光电特性进行理论计算,并系统阐述这3种晶体的表面效应对光电性能的影响。结果表明,3种材料的光学特性由铋原子和卤素原子最外层p轨道上的价电子主导。在可见光区中,材料的吸收峰会随卤素原子序数的增加呈现红移,其中一维结构的Cs3Bi2Cl9表面结构在光吸收能力上尤为特别且敏感;二维结构的Cs3Bi2Br9光吸收能力会受厚度影响;零维结构的Cs3Bi2I9非常稳定,且几乎不受表面特性和晶体厚度的影响。 相似文献