排序方式: 共有66条查询结果,搜索用时 15 毫秒
51.
Yin-Qing Zhang Sheng-Jie Wang Jun-Wei Wang Lan-Lan Lou Cui Zhang Shuangxi Liu 《Solid State Sciences》2009,11(8):1412-1418
A series of materials WO3/Zr-SBA-15 were synthesized by modifying zirconium-incorporated SBA-15 mesoporous molecular sieve with various loadings of tungsten oxide, followed by calcining at different temperatures. The structures and the surface states of these materials were determined by XRD, TEM, N2 adsorption–desorption and Raman spectroscopy, while the surface acidities were characterized by FT-IR spectroscopy of pyridine adsorption, NH3-TPD, and the Hammett indicator method. To evaluate the catalytic activities of the prepared materials, the benzoylation of anisole was chosen as the model reaction. All the results reveal that the synthesized samples are strong solid acids, even solid superacids under some conditions, with uniform mesoporous structure and high surface area. The dispersion state of the supported WO3, which depends on the WO3 loading and the calcination temperature, has a direct influence on the acidity and catalytic activity of the materials. Moreover, the high acid strength is attributed to the WO bond nature of the complex formed by the interaction between WO3 and the surface of Zr-SBA-15. 相似文献
52.
Pan M Sun H Lim JW Bakaul SR Zeng Y Xing S Wu T Yan Q Chen H 《Chemical communications (Cambridge, England)》2012,48(10):1440-1442
We show that seeded growth can be applied to creating two-dimensional (2D) dendritic Au nanostructures on sample grids, which can be directly characterized by transmission electron microscopy (TEM). The 2D synthesis of highly consistent structures offers a novel mechanistic perspective on the aggregation of colloidal Au nanocrystals on a surface. 相似文献
53.
环境因子对二型态银耳节孢子形态转换的影响 总被引:1,自引:0,他引:1
研究了氮源、碳源、碳氮比、pH值、温度、培养时间和香灰菌胞外液7种环境因子对银耳节孢子酵母型细胞向菌丝型细胞形态转换的影响.结果表明:7种环境因子对银耳节孢子形态转换均有一定的影响,其中经过滤除菌的香灰菌胞外液在液体培养基中的影响最大,菌丝型细胞占节孢子总数的9.89%;碳氮比总体水平上对形态转换影响较小,不同碳氮比条件下的菌丝型比率均小于2.40%;固体培养时pH3条件对形态转换的影响最小,菌丝型比率为0.04%.此外,各环境因子对节孢子形态转换的影响因固体和液体培养环境的不同而呈现一定差别. 相似文献
54.
[Eu(pABA)3Phen·H2O](C2H5OH)(pABA=对氨基苯甲酸根,Phen=邻菲咯啉)配合物晶体属三斜晶系,P1空间群,a=12268(3)nm,b=14005(3)nm,c=10440(3)nm;α=10269(2)°,β=10893(2)°,γ=9285(2)°;Z=2,T=273K。最终的R因子为0039。配合物中心Eu3+离子与周围pABA的6个氧原子和Phen的一对氮原子以及一个水分子的氧原子配位,配位多面体属畸变的单帽四方反棱柱体,水分子的氧原子占据帽位。 相似文献
55.
Nanostructured polyaniline films could be easily in situ polymerized on microslides via rapidly mixing aniline with ammonium persulfate in acid solution. The influence of different conditions including aniline, acid concentration, reaction time and acid kinds on the morphology and thickness of the resulting films was studied. The gas-sensing behavior of the nanostructured films to 100 ppm of NH3 was investigated through monitoring the change of the resistance. 相似文献
56.
A new class of dendrons and dendrimers containing azobenzene units (bearing up to 29 azobenzene groups for four generations) were designed and synthesized with the convergent method, which uses azobenzene derivatives as monomers and benzyl ester groups as linkages leading to photoresponsive dendrons and dendrimers with azobenzene units throughout their architecture. Photochemical isomerization experiments revealed that all of the dendrons and dendrimers undergo trans-cis isomerization by irradiation and cis-trans isomerization by either irradiation or heating. 相似文献
57.
Xuemei Niu Shenghong Li Qinshi Zhao Shuangxi Mei Zhongwen Lin Handong Sun Yang Lu Cheng Wang Qitai Zheng 《Helvetica chimica acta》2003,86(2):299-306
Two novel ent‐abietane diterpenoids, 3α,20‐epoxy‐6β‐hydroxy‐1,7‐dioxo‐ent‐abiet‐15(17)‐en‐16‐oic acid ( 1 ) and ent‐abieta‐7,15(17)‐diene‐3β,16,18‐triol ( 2 ) were isolated from Isodon eriocalyx var. laxiflora. Their structures were determined by extensive spectroscopic analysis and confirmed by X‐ray crystallography. Compound 1 is an unprecedented example that establishes that a naturally occurring ent‐abietane diterpenoid can have an oxygenation pattern almost identical to those of 3α,20‐epoxy‐ent‐kaurane diterpenoids. 相似文献
58.
59.
Qintao Li Qinyi Shi Xianrui Zhao Shuangxi Xue Zhigang Li Zhigang Fang Jinlong Gong 《Applied Physics A: Materials Science & Processing》2011,102(3):601-604
Carbon nanotubes (CNTs) decorated by graphitic shells encapsulated Cu nanoparticles were fabricated by low-energy hydrocarbon
ion deposition with using Cu as hold substrate at 900°C. Scanning electron microscopy shows that the surface of CNTs becomes
very coarse by hydrocarbon ion treatment. The investigation of transmission electron microscope shows that the full surfaces
of CNTs are coated by dense graphitic shells encapsulated Cu nanoparticles. The graphitic shells consist of 7–10 layers and
the size of Cu core is 1–2 nm. 相似文献
60.
Jianqiang Wang Boyan Zhang Meiqing Shen Jun Wang Wulin Wang Jie Ma Shuangxi Liu Liwei Jia 《Journal of Sol-Gel Science and Technology》2011,58(1):259-268
The structural/textual characteristics and dynamic oxygen storage capacity (DOSC) of Fe0.1Ce0.9Ox and Fe0.1Ce0.6Zr0.3Ox samples prepared by sol–gel method are investigated by X-ray powder diffraction (XRD), Raman, Hydrogen temperature-programmed
reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS) and mass spectrometry with CO/O2 transient pulses. The dynamic oxygen storage capacity and rate are largely promoted by Fe doping, and their thermal stability
is enhanced by Fe and Zr co-doping. The DOSC (at 673 K) are ordered as: Fresh: Fe0.1Ce0.6Zr0.3Ox (566.6 μmol/g) > Fe0.1Ce0.9Ox (551.8 μmol/g) > Ce0.67Zr0.33O2 (287.5 μmol/g) > CeO2 (140.3 μmol/g); Annealed1,173K: Fe0.1Ce0.6Zr0.3Ox (101.6 μmol/g) > Ce0.67Zr0.33O2 (45.3 μmol/g) > Fe0.1Ce0.9Ox (44.9 μmol/g) > CeO2 (43.3 μmol/g). The H2-TPR results showed that Fe-incorporation improve the total oxygen storage capacity (TOSC) of mixed oxide and low temperature
activity. The TOSC are ordered as: Fe0.1Ce0.9Ox (1.53 mmol/g) > Fe0.1Ce0.6Zr0.3Ox (1.42 mmol/g) > Ce0.67Zr0.33O2 (1.16 mmol/g) > CeO2 (0.88 mmol/g). XRD and Raman results indicate that Fe0.1Ce0.9Ox and Fe0.1Ce0.6Zr0.3Ox are characterized with the fluorite-type cubic structure similar to CeO2. TPR and XPS analyses reveal that the introduction of Fe into ceria and ceria-zirconia mixed oxides strongly modified the
structural and textural properties, which influenced the kinetics of bulk oxygen diffusion. 相似文献