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951.
Ya‐Ping Du Ya‐Wen Zhang Prof. Dr. Zheng‐Guang Yan Dr. Ling‐Dong Sun Prof. Dr. Song Gao Prof. Dr. Chun‐Hua Yan Prof. Dr. 《化学:亚洲杂志》2007,2(8):965-974
We report the synthesis of single‐crystalline and near‐monodispersed NaMF3 (M=Mn, Co, Ni, Mg), LiMAlF6 (M=Ca, Sr), and NaMgF3:Yb,Er nanocrystals (quasisquare nanoplates, nanorods, and nanopolygons) by the cothermolysis of multiple trifluoroacetates in hot combined organic solvents (oleic acid, oleylamine, and 1‐octadecene). The nanocrystals were characterized by XRD, TEM, superconductive quantum interference device (SQUID), and upconversion luminescence spectroscopy. By regulating the polarity of the dispersant, the NaMF3 (M=Mn, Co, Ni) nanoplates were partially aligned to form nanoarrays on copper TEM grids. The sizes of the NaMF3 nanocrystals were easily tuned by the use of proper synthetic conditions such as reaction temperature and time and solvent composition. On the basis of a series of experiments in which the reaction conditions were varied, together with GC–MS and FTIR analysis, the reaction pathways for the formation of these nanocrystals from trifluoroacetate precursors were proposed. The magnetic measurements showed that the differently sized NaMnF3 square plates displayed interesting weak ferromagnetic behavior on the nanometer scale. The strong red upconversion luminescence emitted from the NaMgF3:Yb,Er nanorods under 980‐nm near‐IR laser excitation suggests that NaMgF3 may be a good candidate host material for red upconversion luminescence. 相似文献
952.
Jeong Hwan Kim Ji Hoon Ko Byeong-Soo Bae 《Journal of Sol-Gel Science and Technology》2007,41(3):249-255
Multi-scale hybrid nanocomposites containing both ∼15 nm silica colloids and ∼2 nm oligosiloxanes in a methacryl polymer matrix
were newly designed and fabricated. Colloidal silica sols were dispersed in methacryl oligosiloxanes nano-hybrid resins synthesized
by sol-gel reaction of methacryloxypropylmethoxysilane and diphenylsilanediol. On the basis of TEM and SANS analyses, it was
confirmed that the silica colloids were compatibly dispersed and different sizes of colloidal silica and oligosiloxanes co-exist
in the solutions. Multi-scale hybrid nanocomposites fabricated by UV and thermal curing with incorporation of silica colloids
in the nano-hybrid materials show enhanced mechanical and thermal characteristics. 相似文献
953.
The geometry of the 4′-cyano-(4′-CNPTB) and the 4′-methoxy-(4′-MePTB) phenylthiolbenzoates were obtained by ab initio calculations
employing 6–31G basis set at Hartee-Fock level of theory. The results predict an extended form of the molecules and torsional
angle between the phenyl rings at 90.85(6)0 and 90.87(3)0, respectively. On the basis of vibrational analysis the frequency assignment was carried out. The calculated frequencies
were compared with the experimental IR spectral data in carbon tetrachloride, carbon disulfide solutions and in solid state. 相似文献
954.
Peng Xu Wei Zhong Haitao Wang Rong Tong Qiangguo Du 《Colloid and polymer science》2004,282(12):1409-1414
Copolymerization of methyl methacrylate, methyl acrylate, butyl methacrylate, and butyl acrylate in turn was performed in the modified microemulsion polymerization process, i.e., continuous addition of monomer to a preemulsified system. It was found that the particle size of the copolymer microlatex did not change distinctly with the monomer composition. The estimation of emulsifier coverage on the microlatex particles indicated that the process switched from a traditional microemulsion to a normal seeded emulsion polymerization very soon after monomer dropping began. Therefore, a longer dropping time is needed to produce a microlatex with narrow dispersed particle size. Besides, in the modified microemulsion polymerization less emulsifier is needed to produce a stable microlatex. This behavior is related to the mechanism of normal seeded emulsion polymerization during monomer dropping. 相似文献
956.
Highly dispersed molybdena-titania catalyst can be prepared by an equilibrium adsorption method. In this method, molybdate
anions adsorb onto the positively charged titania surfaces via electrostatic attraction by controlling the pH of the impregnating
solution and they increase as an inverse function of the pH. 95Mo-NMR and UV spectroscopic studies of impregnating solution show that the polymeric species like Mo7O24
6-ions are adsorbed on titania in the acidic impregnating solution. XRD, Raman, and XPS data of the calcined samples show that
mono-layer coverage of molybdenum oxide over-layer possesses a highly distorted MoO6 group with a molecular geometry resembling the distorted square pyramid.
The catalytic oxidation of methanol over the surface molybdate species on titania possesses higher turnover numbers and higher
selectivities of partial oxidation products than the catalysts supported on alumina, silica, zirconia, or magnesia. Changes
of the surface properties either after reduction and sulfiding treatment over monolayer catalyst on titania have also been
investigated. The NO chemisorption and XPS studies show that two types of active sites appeared after reduction treatment:
one site is active for hydrogenation of 1,3-butadiene and the other site is active for metathesis of propene. A higher degree
coordinative unsaturations of MO is required for hydrogenation than metathesis. After sulfiding treatments of the catalyst,
hydrogenation of 1,3-butadiene also requires triply coordinative unsaturation, and hydrogenolysis of thiophene requires the
ensemble of doubly or triply coordinative unsaturations. 相似文献
957.
František Kvasnička Rudolf Ševčík Michal Voldřich Jana Krátká 《Central European Journal of Chemistry》2004,2(3):417-424
A simple and rapid capillary zone electrophoresis (CZE) method for the determination of aristolochic acid (AA) in dietary
supplements and selected herbs is described. A clear separation of AA from other sample constituents was achieved within 5
minutes without any sample clean up. A mixture of 20 mM-morpholinethanesulphonic acid+10 mM-BisTrisPropane+0.2% hydroxyethylcelullose
in 10% methanol serves as a background electrolyte. The linearity, accuracy, intra-assay and detection limit of the developed
method are 200–6000 ng/mL, 95–103%, 3.5%, and 50 ng/ml, respectively. Ease of use, sufficient sensitivity and low running
cost are the most important attributes of the CZE method. The proposed CZE method was compared with HPLC. 相似文献
958.
Robert Pietrzak Mieczysław Kozłowski Helena Wachowska Jan Yperman 《Central European Journal of Chemistry》2004,2(2):278-289
Soluble products obtained from the oxidation of four types of coal, each characterised by different degree of coalification
and different degree of sulphur content, are studied. The coals are oxidised with peracetic acid (PAA) and nitric acid. Analyses
are performed by Atmospheric Pressure-Temperature Programmed Reduction (AP-TPR) and Fourier Transform Infrared Spectroscopy
(FTIR). The soluble products contain much more sulphur than the insoluble products of oxidation. The products obtained from
the reaction with HNO3 contain higher amounts of inorganic sulphur compounds, while those obtained from the reaction with PAA are characterised
by an increased content of organic sulphur species. 相似文献
959.
Chun‐Xiang Wang Chen‐Xia Du Zhi‐Feng Li 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(10):m488-m490
In the title compound, [Zn(C17H10N5O)2(H2O)2]·4H2O, cyclic water hexamers forming one‐dimensional metal–water chains are observed. The water clusters are trapped by the co‐operative association of coordination interactions and hydrogen bonds. The ZnII ion resides on a centre of symmetry and is in an octahedral coordination environment comprising two O atoms and two N atoms from two 2′‐(4,5‐diazafluoren‐9‐ylidene)picolinohydrazidate ligands and two water molecules. 相似文献
960.
Melinda Fekete Pál Kolonits Ngo Thi Hien Lajos Novák 《Central European Journal of Chemistry》2005,3(4):792-802
New tryptamine 5, 7 and β-carboline derivatives 3 were preparated by palladium-catalyzed coupling reaction of 5-bromotryptamine 1 with aryl boronic acids.
Dedicated to Professor András Lipták on his 70th birthday. 相似文献