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991.
A facile total synthesis of three members of the bisabolane sesquiterpene family, namely (±)-curcumene, (±)-xanthorrhizol and (±)-curcuhydroquinone had been achieved in high overall yield. The synthesis used bromobenzene derivatives as starting materials. The halogen-lithium exchange followed by addition of isoprenylacetone and reduction of the obtained carbinols are the key steps of the synthetic pathway. This synthetic approach provides a new route to the bisabolane sesquiterpenes. 相似文献
992.
采用硝酸铈、硝酸钕、尿素为原料,使用微波引诱燃烧法合成了多孔Ce1-xNdxO2-y固溶体。利用X射线衍射仪、Raman光谱仪、红外光谱仪、扫描电镜、N2吸附-脱附技术、紫外-可见吸收光谱仪等测试手段对产物进行了表征。XRD分析表明,Ce1-xNdxO2-y固溶体的粒径范围在40~60 nm之内,且所有产物为萤石结构。Raman测试表明,在Ce1-xNdxO2-y中,由于Nd3+的掺杂而产生氧空位,且空位浓度随Nd3+掺杂量的提高而增加。红外结果证明,Ce-O键的吸收峰在1400 cm-1左右处,由于Nd3+的掺杂而使得在2346 cm-1的吸收峰消失。从SEM和孔径分布结果可看出,产物为多孔结构。紫外-可见光吸收和可见光催化降解实验表明,随着Nd3+掺杂量的增加,Ce1-xNdxO2-y的紫外吸收增强;由于多孔结构和氧缺位的产生,产物在可见光范围内有较明显的吸收。 相似文献
993.
Dong-Yu Lv Zhu-Qing Gao Jin-Zhong Gu Jian-Zhao Liu Wei Dou 《Transition Metal Chemistry》2011,36(3):275-281
Two Mn(II) coordination polymers, namely [Mn(bpda)]
n
(1) and [Mn(bpda)(bpy)0.5]
n
(2) (H2bpda = 1,1′-biphenyl-3,3′-dicarboxylic acid and bpy = 4,4′-bipyridine), have been synthesized from H2bpdc, bpy, and MnSO4·2H2O under hydrothermal conditions. The complexes were characterized by physicochemical and spectroscopic methods, as well as
by X-ray crystallography. Compound 1 possesses a 3D structure consisting of carboxylate-bridged edge-sharing Mn–O–Mn double chains. Compound 2 features a 3D open structure with a dinuclear Mn(II) secondary building unit. Magnetic susceptibility measurements of compounds
1 and 2 exhibit antiferromagnetic interactions between the nearest Mn(II), with J = –11.3 cm−1 and g = 2.12 for 1, and J = –13.5 cm−1 and g = 2.12 for 2. 相似文献
994.
995.
Aiping Zhang Yi Zhang Puguang Wang Jun Li Ying Lv Shuang Gao 《Research on Chemical Intermediates》2011,37(8):975-984
Five catalysts containing PW or W active species that anchored onto aminosilylated mesoporous silica SBA-15 by a post-grafting
route were prepared and the resulting PW or W/APTES/SBA-15 hybrid materials were characterized by XRD, N2 adsorption/desorption, surface area analysis, TEM, FT-IR, and ICP (inductively coupled plasma atomic emission spectroscopy).
The names of these catalysts have been abbreviated as SBA-15m-a, SBA-15m-b, SBA-15m-c, SBA-15m-d, and SBA-15m-e according
to the different active species. The PW or W active species were highly dispersed in the channels of the modified mesoporous
materials. The interaction between PW or W species and amino groups grafted on the channel surface of SBA-15 led to the immobilization
of PW or W species. Their catalytic activity in the epoxidation of cyclooctene with H2O2 as oxidant was investigated. Among them, SBA-15m-a showed the best performance, with 98.9% conversion and 98.4% selectivity.
The catalyst could be reused for six times with a little decrease in activity. 相似文献
996.
Xinxiang Zhang Yulu Zhang Haiping Ye Bo Xiao Lianghong Yan Haibing Lv Bo Jiang 《Journal of Sol-Gel Science and Technology》2011,58(1):340-344
Antireflective (AR) coatings at 351 nm with different thickness were designed and prepared by sol–gel process using tetraethylorthosilicate
as precursor and ammonia as catalyst. The parameters of these coatings, including film thickness and refractive index, were
calculated by optical formula and the coatings were prepared accordingly. Sol dilution method was used to adjust the film
thickness. The wavelengths of maximum transmission measured by UV–Vis spectrophotometer, were used to monitor the film thickness.
It was found that AR coatings with higher thickness possess better abrasion-resistance. Hydroxyl terminated polydimethylsiloxane
(PDMS) was added into pure silica sol to improve both the abrasion-resistance and moisture-resistance of AR coating. 相似文献
997.
本文利用第一性原理PBE密度泛函理论计算的方法设计了一种由炔基链、吡啶环及少量氢原子组成的具有内凹六边形结构单元的新型理想二维碳纳米结构,并对其平面内负泊松比效应等力学性能和光学性能与电子结构进行了预测.计算表明,该2D材料具有较好的结构稳定性和特殊的力学性能.当将该2D结构在面内(bc面)沿c方向压缩时,其在b方向收缩;当沿c方向拉伸时,其在b方向伸长,即该2D结构同样具有期望的负泊松比效应.材料的泊松比为-3.26;将该2D结构沿b方向拉伸时,c方向将随之伸长;沿b方向压缩时,c方向将随之收缩.沿b方向拉伸或压缩时,泊松比约为-1.951.即该2D材料在面内具有非常显著的负泊松比效应.此外,该2D材料表现出半导体材料的电子结构特征和良好的光反射和折射性能.希望本工作能为具有本征负泊松比效应和优良电子与光学功能的理想二维碳纳米材料的开发提供一种理想的结构设计策略. 相似文献
998.
We theoretically study the band structures and the valley Chern numbers of the AB–AB and AB–BA stacked twisted double bilayer graphene under heterostrain effect. In the absence of heterostrain, due to the constrains by the spatial symmetries, the central two flat bands of the AB–AB are topological trivial bands, while in the AB–BA they have a finite Chern number. The heterostrain breaks all the point group symmetries and the constrains are lifted, hence the topological properties of the two arrangements can be tuned by different strain magnitudes ϵ and directions ϕ. The heterostrain has dissimilar impacts on the Chern numbers of the AB–AB and AB–BA, owing to their different band gaps, and these gaps can be modified by a vertical electric field. Our results show that the topological transitions for both arrangements occur in the ϵ range of 0.1%–0.4%, which can be realized in the graphene-based sample. 相似文献
999.
The hydrogen effect on the nucleation and motion of dislocations in single-crystal bcc Fe with(110)surface was investigated by both nanoindentation experiments ... 相似文献
1000.
Tianzhi Yu Shuxia Yang Yuling Zhao Peng Zhang Zhe Lv Duowang Fan Zhongrong Geng 《Research on Chemical Intermediates》2012,38(1):215-222
Three coumarin derivatives, 7-hydroxy-3-(2-pyridyl)coumarin (HPC), 7-(4-(5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl)benzyloxy)-3-(2-pyridyl)coumarin (Ox-PC), and 7-(4-(9H-carbazol-9-yl)butoxy)-3-(2-pyridyl)coumarin (Cz-PC), were synthesized and characterized by elemental analysis, 1H NMR, FT-IR, and UV?Cvis absorption spectra. The fluorescence behaviors of the compounds in methanol solutions and solid states were investigated. HPC exhibits weak green emission, whereas Cz-PC and Ox-PC show strong blue emissions in dilute solutions. 相似文献