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971.
Haoshuang Gu Yongming Hu Hao Wang Xiangrong Yang Zhenglong Hu Ying Yuan Jin You 《Journal of Sol-Gel Science and Technology》2007,42(3):293-297
Single crystalline nanowires of lead titanate (PbTiO3) were fabricated by hydrothermal method at 200°C using lead acetate and n-tetrabutyl titanate as starting materials, where sodium hydroxide was served as a mineralizer. Crystalline phases, microstructure
and optical properties of PbTiO3 nanowires were investigated. The PbTiO3 nanowires were uniform and continuous along the long axis, and were composed of single crystalline PbTiO3 with a tetragonal perovskite structure. The diameter of a single nanowire was around 12 nm and the length reached up to 3 μm.
The chemical composition of the samples and the valence states of elements were determined by X-ray photoelectron spectroscopy
(XPS). The ultraviolet/visible absorption spectroscopic investigation suggested that the absorption edge of optical transition
of the first excitonic state occurred at around 320 nm. A blue-green light emission peaking at about 471 nm (2.63 eV) is observed
at room temperature, and the intensity of this emission increased with increasing excitation wavelength. Oxygen vacancies
are responsible for the light emission of PbTiO3 nanowires. 相似文献
972.
Mátyás Milen László Hazai Pál Kolonits György Kalaus Lajos Szabó Ágnes Gömöry Csaba Szántay 《Central European Journal of Chemistry》2005,3(1):118-136
Transformation of β-carboline derivatives into optically active entities were studied and the de and ee values of the resulted compounds were detected.
Dedicated to Professor Károly Lempert on his 80th birthday. 相似文献
973.
Reactions of two preformed trinuclear W/Cu/S clusters, [A](2)[WS(4)(CuCN)(2)] (1: A = Et(4)N; 2: A = PPh(4)), with different concentrations of acetic acid in MeCN generate two interesting 2D polymeric clusters [Et(4)N](3)[(WS(4)Cu(2))(2)(mu-CN)(3)].2MeCN (3), and [PPh(4)][WS(4)Cu(3)(mu-CN)(2)].MeCN (4), respectively. Compound 4 can also be readily obtained in a high yield from the reaction of 2 with equimolar [Cu(MeCN)(4)]PF(6) in MeCN. These compounds have been characterized by elemental analysis, IR spectra, thermal analysis, and single-crystal X-ray diffraction. An X-ray analysis reveals that compound 3 retains the WS(4)Cu(2) cluster core, which serves as a 3-connecting node to link equivalent nodes via single cyanide bridges, forming an anionic 2D (6,3) net. Compound 4 consists of a T-shaped WS(4)Cu(3) core, which also acts as a 3-connecting node, with links to 3 equivalent clusters either through single or double cyanide bridges, affording a different anionic 2D (6,3) network. The acetic acid induced aggregation of 3 and 4 from the two cluster precursors 1 and 2 suggests that this simple synthetic strategy is likely to be applicable to many related systems. 相似文献
974.
975.
Thermodynamics and crystallization kinetics of the hydrothermal synthesis of Na4Ti4Si3O10 (NaTS) were systemically studied by both experiments and model simulation. Experimental results showed that the curve of
crystallinity with time was a characteristic signmoid in the shape that indicated the crystallization of Na4Ti4Si3O10 was a typical spontaneous nucleation process on the laboratory scale. Crystallization of NaTS belongs to the liquid-liquid
transformation mechanism and the reaction is endothermic (ΔH = 15.3 kJ/mol). A mathematic model of crystallization kinetics was developed to simulate the synthesis of NaTS. Runge-Kutta
and simplex methods were adopted to solve the partial differential equations. Model results fitted well with the experimental
data and showed that the synthesis process belongs to spontaneous nucleation and crystal growth. Moreover, the very small
crystal growth constant (5.6·10−7) and gel dissolution constant (7.0·10−7) indicate they are the rate-limiting steps of the whole synthesis process. 相似文献
976.
Complex systems of paramagnetic centres existing in demineralised flame coal (71.4 wt% C), medium-rank coal (85.6 wt% C) and
anthracite (94.9 wt% C) were analysed by electron paramagnetic resonance spectroscopy (EPR). Different groups of paramagnetic
centres were searched in macerals (exinite, vitrinite, inertinite) of coals with carbon contents of 73.8 wt% C and 85.6 wt%
C. Experimental EPR spectra were fitted by different superposition of theoretical lines. Total concentration of paramagnetic
centres both in coal and macerals increases with carbon content in the sample. Total concentration of paramagnetic centres
in macerals increases from exinite to inertinite. Four groups of paramagnetic centres were found in medium-rank coal, and
only two groups exist in flame coal and anthracite. The EPR spectrum of medium-rank coal is a superposition of two broad and
two narrow lines. Both broad and narrow, and two narrow lines were measured in EPR spectra of flame coal and anthracite, respectively.
Two types of paramagnetic centres with broad lines and one group with narrow lines exist in exinite and vitrinite from medium-rank
coal. Two narrow components were observed in EPR spectra of its inertinite. Two different broad electron paramagnetic resonance
signals were detected for macerals from low-coalificated coal. Paramagnetic centres systems of medium-rank coal samples reveal
the most complex character. Broad EPR lines were not observed for the higher coalificated samples, i.e., anthracite and inertinite
from medium-rank coal. Narrow lines do not occur in EPR spectra of low-coalificated macerals. Strong dipolar interactions
and fast spin-lattice relaxation processes are characteristic for paramagnetic centres with broad lines. Strong exchange interactions
and short spin-lattice relaxation time were measured for paramagnetic centres with the narrowest EPR signals. 相似文献
977.
The kinetics of the oxidation of five catecholamines viz., dopamine (A), L-dopa (B), methyldopa (C), epinephrine (D) and norepinephrine
(E) by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) in presence of HClO4 was studied at 30±0.1 °C. The five reactions followed identical kinetics with a first-order dependence on [CAT]
o
, fractional-order in [substrate]
o
, and inverse fractional-order in [H+]. Under comparable experimental conditions, the rate of oxidation of catecholamines increases in the order D>E>A>B>C. The
variation of ionic strength of the medium and the addition of p-toluenesulfonamide or halide ions had no significant effect
on the reaction rate. The rate increased with decreasing dielectric constant of the medium. The solvent isotope effect was
studied using D2O. A Michaelis-Menten type mechanism has been suggested to explain the results. Equilibrium and decomposition constants for
CAT-catecholamine complexes have been evaluated. CH3C6H4SO2NHCl of the oxidant has been postulated as the reactive oxidizing species and oxidation products were identified. An isokinetic
relationship is observed with β=361 K, indicating that enthalpy factors control the reaction rate. The mechanism proposed
and the derived rate law are consistent with the observed kinetics. 相似文献
978.
Qintong Huang Ningyue Chen Lichen Liu Karen S. Arias Sara Iborra Xianfeng Yi Chao Ma Weichi Liang Anmin Zheng Chuanqi Zhang Jibo Hu Zilin Cai Yi Liu Jiuxing Jiang Avelino Corma 《Chemical science》2020,11(44):12221
Aluminosilicate boggsite (Si/Al-BOG) has been hydrothermally synthesized without adding organic structure-directing agents (OSDAs) in the synthesis gel using the borosilicogermanium ITQ-47 (Si/B-ITQ-47) zeolite as seeds. The introduction of the costly and environmentally less benign phosphazene organic structure-directing agent is not required to grow the zeolite. Physicochemical characterization experiments show that Si/Al-BOG has good crystallinity, high surface area, tetrahedral Al3+ species, and acid sites. In order to test the catalytic performance of the zeolite, the synthesis of l,l-lactide from l-lactic acid was performed. Si/Al-BOG exhibits 88.2% conversion of l-lactic acid and 83.8% l,l-lactide selectivity, which are better than those of other zeolites studied up to now.Aluminosilicate boggsite (Si/Al-BOG) has been hydrothermally synthesized without adding organic structure-directing agents (OSDAs) in the synthesis gel using the borosilicogermanium ITQ-47 (Si/B-ITQ-47) zeolite as seeds. 相似文献
979.
Mao Jiang-Gao Huang Jin-Shun Ma Jian-Fang Ni Jia-Zuan 《Transition Metal Chemistry》1997,22(3):277-280
The reaction of diglycolic acid, O(CH2CO2H)2, with Cu(NO3)2·2H2O and lanthanoid nitrate hydrate produces a series of novel Ln–Cu mixed metal complexes, [Ln2Cu3{O(CH2CO2)2}6]·nH2O (Ln=La, Nd, n=9; Ln=Er, n=6), which have been characterized by elemental analysis, i.r. spectroscopy, magnetic measurements and X-ray crystallography. The Ln3+ and Cu2+ ions are connected by the carboxylate groups of the ligands, resulting in the formation of a complicated network. 相似文献
980.
Wen Ma Yu-Peng Tian Sheng-Yi Zhang Jie-Ying Wu Hoong-Kun Fun Suchada Chantrapromma 《Transition Metal Chemistry》2006,31(1):97-102
A new diferrocenyl-substituted macrocyclic ligand (H2L) and its complexes ML(M = CuII, NiII, ZnII, CdII) were prepared and characterized by IR, elemental analysis, absorption spectra and FAB mass spectra. The ferrocenyl-substituted
macrocyclic ligand was characterized by single crystal X-ray diffraction analysis. The superconjugative effect of the cyclopentadienyl
(CP) rings increase the activity of the hydrogen atoms in the tetra-azacyclotetradecane macrocyclic ligand. The imine nitrogen
atoms lose two protons and coordinate to the metal. The electrochemical properties of these compounds are discussed. 相似文献