Showing papers by "Jilin University published in 2001"

New materials in hydrothermal synthesis.

Abstract: In this Account we describe the hydrothermal synthesis of some new materials including microporous crystals, ionic conductors, complex oxides and fluorides, low-dimensional aluminophosphates, inorganic-organic hybrid materials, and particularly condensed materials such as diamond and inorganic helical chains. Hydrothermal synthesis in biology and environment sciences is also introduced. The increasing interest in hydrothemal synthesis derives from its advantages in terms of high reactivity of reactants, easy control of solution or interface reactions, formation of metastable and unique condensed phases, less air pollution, and low energy consumption.

Dilute solution routes to various controllable morphologies of MCM-41 silica with a basic medium

Abstract: MCM-41 silica particles with several morphologies have been controllably synthesized with a basic medium. Nanospherical MCM-41 silica with an average size of 110 nm was produced through reaction of extremely low surfactant concentrations of CTAB with TEOS in the sodium hydroxide medium at 353 K, while a submicrometer-sized silica rod, 0.3−0.6 μm in diameter and 1 μm in length, and micrometer-sized oblate silica with nominal diameter around 1 μm were synthesized in aqueous ammonia, where the size and the morphology were controlled by varing the content of the solvent. A morphogenetic mechanism that is based on the deposition of self-assembled silicate surfactant rodlike micelles is proposed and explains well the controllability of the morphology.

Strongly acidic and high-temperature hydrothermally stable mesoporous aluminosilicates with ordered hexagonal structure

Abstract: Publisher Summary This chapter discusses strong acidic and high-temperature hydrothermally stable mesoporous aluminosilicates with well-ordered hexagonal structure. These mesoporous aluminosilicates have been successfully synthesized from the assembly of preformed aluminosilicate precursors with cetyltrimethylammonium bromide (CTAB) surfactant. The MAS-5 shows extraordinary stability both in boiling water and in steam. Temperature-programmed desorption of ammonia (NH3) shows that the acidic strength of MAS-5 is much higher than that of MCM-41.

Mesoporous Aluminosilicates with Ordered Hexagonal Structure, Strong Acidity, and Extraordinary Hydrothermal Stability at High Temperatures

Abstract: Highly ordered hexagonal mesoporous aluminosilicates (MAS-5) with uniform pore sizes have been successfully synthesized from assembly of preformed aluminosilcate precursors with cetyltrimethylammonium bromide (CTAB) surfactant. The aluminosilicate precursors were obtained by heating, at 100−140 °C for 2−10 h, aluminasilica gels at the Al2O3/SiO2/TEAOH/H2O molar ratios of 1.0/7.0−350/10.0−33.0/500−2000. Mesoporous MAS-5 shows extraordinary stability both in boiling water (over 300 h) and in steam (800 °C for 2 h). Temperature-programmed desorption of ammonia shows that the acidic strength of MAS-5 is much higher than that of MCM-41 and is comparable to that of microporous Beta zeolite. In catalytic cracking of 1,3,5-triisopropylbenzene and alkylation of isobutane with butene, MAS-5 exhibits greater catalytic activity and selectivity, as compared with MCM-41 and HZSM-5. The MAS-5 samples were characterized with infrared, UV−Raman, and NMR spectroscopy and numerous other techniques. The results suggest that ...

Organic light-emitting materials based on bis(arylacetylide)platinum(II) complexes bearing substituted bipyridine and phenanthroline ligands: photo- and electroluminescence from 3MLCT excited states.

Abstract: We present the synthesis and photophysical and electroluminescent properties for a series of platinum(II) alpha-diimine bis(arylacetylide) complexes. The molecular structures of five derivatives have been elucidated by X-ray crystallography. Intermolecular pi-pi interactions (between aromatic diimine and phenylacetylide moieties) are apparent in the crystal lattices of two of these. All bis(phenylacetylide) derivatives exhibit intense triplet metal-to-ligand charge transfer (MLCT) photoluminescence in the solid state and in fluid solutions at room temperature. The impact of different solvents, substituents on the diimine ligands, and complex concentrations upon their emissive behavior have been examined and demonstrates that their emission energies can be systematically modified. Application of the 3MLCT excited state of the [Pt(alpha-diimine) (C(triple bond)CPh)2] materials in single- and double-layer organic light-emitting devices are described. The bis(butadiynyl) complex [Pt(4,4'-dtbpy)(C(triple bond)C-C(triple bond)CPh)2] (dtbpy = 4,4'-di-tert-butyl-2,2'-bipyridine) displays strong solid-state and solution phosphorescence at 77 and 298 K; the associated excited state is proposed to arise from both acetylenic 3pi pi*(C(triple bond)C-C(triple bond)CPh) and 3MLCT [Pt --> pi*(diimine)] transitions.

Polarized absorption spectra of single-walled 4 A carbon nanotubes aligned in channels of an AlPO(4)-5 single crystal.

Abstract: We report the polarized optical absorption spectra of single-walled $4\AA{}$ carbon nanotubes arrayed in the channels of an $\mathrm{AlPO}{}_{4}\ensuremath{-}5$ single crystal. When the light electric field $(E)$ is polarized parallel to the tube direction $(c)$, the spectra display a sharp peak at 1.37 eV, with two broadbands at 2.1 and 3.1 eV. In the $E\ensuremath{\perp}c$ configuration, the tube is nearly transparent in the measured energy region 0.5--4.1 eV. The optical dipole selection rules are discussed, and the absorption bands are assigned to the dipole transitions between the Van Hove singularities. The measured absorption spectra agreed well with the ab initio calculations of band structure based on the local density function approximation.

Lattice Contraction and Surface Stress of fcc Nanocrystals

Abstract: General equations for lattice contraction and surface stress of fcc nanocrystals are established based on the Laplace−Young equation and a consideration for the size-dependence of the solid−liquid interface energy. The predictions of our equations are in agreement with the experimental results on the measurement of lattice contraction and surface (interface) stress of nanoparticles and thin films and theoretical calculations.

Flexible meso-Bis(sulfinyl) Ligands as Building Blocks for Copper(II) Coordination Polymers: Cavity Control by Varying the Chain Length of Ligands.

Abstract: Fillings and cavities: Three novel pseudo-octahedral metal-organic frameworks, 1-3, consisting of macrometallacyclic noninterpenetrating meso networks and exhibiting weak antiferromagnetic interactions, have been constructed from CuII centers and structurally flexible R,S-bis(sulfinyl) ligands. Varying the chain length of ligands is found to control the cavity sizes of the networks.

New Polymer−Inorganic Nanocomposites: PEO−ZnO and PEO−ZnO−LiClO4 Films

Abstract: Polymer-inorganic nanocomposite films of PEO−ZnO and PEO−ZnO−LiClO4, where PEO stands for poly(ethylene oxide), have been prepared through a film-casting method. Interactions between PEO (MW = 600 000) and ZnO nanoparticles (average size 3.5 nm, with acetate groups on the surface) decrease the photoluminescence intensity of the PEO film to a great extent. These interactions, which are also manifested by the X-ray diffraction, depend on the concentration and the aggregation of the ZnO nanoparticles in the PEO−ZnO films. The cooperative effect of PEO and LiClO4 changes the unidentate coordination mode of the acetate groups with zinc into three coexisting modes: unidentate, bidentate, and bridging, suggesting that PEO segments, lithium ions, and the acetate groups on ZnO nanoparticle surface form cross-linking structures. Such cross-linking structures, on one hand, reduce Li+ClO4- ion pairs to release more free ions as charge carriers in the PEO−ZnO−LiClO4 film and, on the other, decrease the film crystalli...

The nature of basement beneath the Songliao Basin in NE China: geochemical and isotopic constraints

Abstract: The Songliao Basin, located in northeastern China with an area of about 260,000 km2 and having the Daqing Oil Field as the most important center of the petroleum industry in China, is much debated about the basement nature. According to the drill holes, its basement is mainly composed of granites and the Paleozoic strata, some of which have undergone weak metamorphism and somewhat deformation. Gneiss has also been identified, but the petrographical studies indicate that the gneiss is in fact deformed granitic intrusions. Therefore, the granites are the major rock types beneath the Songliao Basin. Geochemical research indicates that these granites are peraluminous, and generated mainly by partial melting of juvenile crust. Geochronological studies show that one undeformed granitic sample gives an U-Pb age of 305 ± 2 Ma, and the mylonitic granite yields an U-Pb age of 165 ± 3 Ma; neither sample contains inherited zircon, which suggests that the basement of the Songliao Basin is not Precambrian, but part of Phanerozoic orogenic belt. With respect to Sr-Nd isotopes, these basement granites are characterized by low ISr (≈0.705), high eNd(t) (−2.2–+2.4) and young Nd model ages (690 to 1160 Ma with most less than 1000 Ma) which is the same as that of the granites in the surrounding orogenic belts such as the Zhangguangcai, Great Xing'an and Lessor Xing'an Ranges, but distinctly different from granites emplaced in the adjacent Precambrian Jiamusi Massif. The simple mass balance calculation indicates that the mixing between the depleted mantle and ancient crust could not reasonably explain the Sr-Nd isotopic features, but the mixing modeling between the juvenile and pre-exited ancient crust suggests that the granites would have about 90% of the juvenile crustal component. Therefore, the Sr-Nd isotopic studies suggest that the basement of the Songliao Basin is juvenile crust, identical to the surrounding orogenic belts, and that there is no Precambrian basement to the Songliao Basin.

Self‐Assembly of Uniform Spherical Aggregates of Magnetic Nanoparticles through π–π Interactions

Abstract: Nanoparticles of Fe3 O4 coated with 2-carboxyterthiophene (TTP-COOH) self-assemble through π-π interactions to form uniform transparent microspheres. The interaction between individual particles is relatively weak and the spherical aggregates can be destroyed by sonication to leave the monodispersed nanoparticles.

Controlling the Particle Size of Calcined SnO2 Nanocrystals

Abstract: Smaller SnO2 nanocrystals are prepared by a novel method. In this method, hydrous tin oxide nanoparticles are precipitated by dropping ammonium hydroxide into tin salt solution under sonication. Further calcination is conducted after the hydrous tin oxide nanoparticles are adsorbed onto the surface of SrCO3 nanoparticles. Calcination at 600 °C yields SnO2 particles with an average particle size of 3.5 nm. This compares with 5.9 nm for the sample prepared by the conventional method. The band gap of SnO2 nanocrystals increases from 3.65 eV with a particle size 5.9 nm to 3.97 eV with a particle size 3.5 nm.

A mechanical model for predicting critical thrust forces in drilling composite laminates

Abstract: Among the various forms of material damage, delamination due to drilling is one of the major concerns in machining a composite laminate. The thrust force has been cited as the primary cause of the delamination. The analysis for multidirectional composite laminates is based on linear elastic fracture mechanics (LEFM), classical bending plate theory and the mechanics of composites. This paper presents a general closed-form mechanical model for predicting the critical thrust force at which delamination is initiated at different ply locations. Good correlation is observed between the model and the experimental results.

Hydrothermal Synthesis of a Two-Dimensional Coordination Polymer [Fe(phen)(μ6-bta)1/2]n (bta = Benzene-1,2,4,5-tetracarboxylate, phen = 1,10-Phenanthroline)

Abstract: A metal-ligand complex [Fe(phen)(μ6-bta)1/2]n (phen = 1,10-phelanthroline; bta = benzene-1,2,4,5-tetracarboxylate ligand) has been hydrothermally synthesized and structurally characterized by single crystal X-ray crystallography, showing that it possesses a novel, two-dimensional polymeric structure.

Hydrothermal Synthesis and Characterization of Two New Zinc Phosphates Assembled about a Chiral Metal Complex: [CoII(en)3]2[Zn6P8O32H8] and [CoIII(en)3][Zn8P6O24Cl]·2H2O

Abstract: A racemic mixture of the chiral metal complex Co(en)3Cl3 has been used in the hydrothermal synthesis of the layered compound [CoII(en)3]2[Zn6P8O32H8] (1) and the three-dimensional connected framework compound [CoIII(en)3][Zn8P6O24Cl]·2H2O (2). Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by X-ray powder diffraction, ICP, elemental, and TG analyses. The structure of 1 consists of vertex-linking ZnO4 and PO3(OH) tetrahedral units forming macroanionic sheets with 4.6.8 nets. The framework structure of 2 built up of ZnO4, ZnO3Cl, and PO4 tetrahedra can be viewed as stacking of the zinc phosphate layers along the c axis linked by Cl atoms as pillars to generate intersecting tunnels with 12-membered-ring windows. Both structures 1 and 2 contain chiral structural motifs, the chiral characters of which are believed to be transferred from the chiral metal complex. The enantiomers of Co(en)3Cl3 are separated as Δ and Λ configurations in the structures of bo...

Emplacement age of the postorogenic A-type granites in Northwestern Lesser Xing'an Ranges, and its relationship to the eastward extension of Suolushan-Hegenshan-Zhalaite collisional suture zone

Abstract: A great amount of alkali-feldspar and alkaline granites have been found around Nenjiang, Northwest Lesser Xing’an Ranges, but their forming ages have been a controversial subject due to the lack of reliable geological and isotopic geochronological evidence. The zircon U-Pb isotopic dating results conducted in this note indicate that these granites emplaced at 260–290 Ma, coeval with the late stage of Late Paleozoic. Studies of mineralogy, petrology and geochemistry show that they are post-orogenic A-type granites, and consist of the northeastern extension of huge belt of Late Paleozoic A-type granite along North Xinjiang-Southeast Mongolia-Central Inner Mongolia. Therefore, we can determine that the Suolunshan-Hegenshan-Zhalaite collisional suture zone extends northeastward to Heihe with the collision age of Carboniferous.

Photocatalytic degradation of aqueous organocholorine pesticide on the layered double hydroxide pillared by Paratungstate A ion, Mg12Al6(OH)36(W7O24)·4H2O

Abstract: Layered double hydroxide pillared by Paratungstate A ion, Mg12Al6(OH)36(W7O24)·4H2O, was prepared via anion exchange reaction of the synthetic precursor, Mg4Al2(OH)12TA·xH2O (TA2−=terephthalate), and [W7O24]6− ion. Some physico-chemical properties were measured and the preparation conditions were studied. Trace aqueous organocholorine pesticide, hexachlorocyclohexane (HCH), was totally degraded and mineralized into CO2 and HCl by irradiating a Mg12Al6(OH)36(W7O24)·4H2O suspension in the near UV area. Disappearance of trace HCH follows Langmuir–Hinshelwood first-order kinetics. The model and mechanism for the photocatalytic degradation of HCH on the Mg12Al6(OH)36(W7O24)·4H2O were proposed, indicating that the interlayer space is the reaction field, and that photogeneration of OH radicals are responsible for the degradation pathway.