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An-Wu Xu

Publications and source records attributed to An-Wu Xu.

14 recordsLinked to original sources
PubMed2006

Synthesis of copper-core/carbon-sheath nanocables by a surfactant-assisted hydrothermal reduction/carbonization process.

A simple hydrothermal method has been developed for the one-step synthesis of copper-core/carbon-sheath nanocables in solution. The obtained nanostructures were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM), Raman, and UV-vis spectrum analysis. These copper@carbon nanocables formed through the hydrothermal reduction/carbonization in the presence of surfactant cetyltrimethylammonium bromide (CTAB) acting as the structure-directing agent by hydrothermal treatment. HRTEM and selected-area electron diffraction (SAED) indicate that the resulted Cu nanowires had the preferred [110] growth direction. The influence of the reaction temperature, reaction time, and pH on the final products was investigated in detail. The possible formation mechanism for copper-core/carbon-sheath nanocables was also proposed. Amorphous carbon nanotubes can be obtained by etching the copper core in the nanocables.

Journal Article↗
PubMed2006

Block-copolymer-controlled growth of CaCO3 microrings.

A novel way for directed solution growth of hollow superstructures of CaCO3 has been successfully developed on the basis of controlled self-assembly and polymer concentration gradients using a double-hydrophilic block copolymer with a hydrophobic modification as a directing agent. A formation mechanism of such rings is proposed on the basis of the formation of CaCO3 nanoparticles in unstructured block copolymer assemblies with subsequent aggregation of these primary nanoparticles. This leads to the formation of a polymer concentration gradient from the inside to the outside of the particle. As the polymer contains multiple chelating units, this leads to a selective dissolution of the center of the particle.

Calcium Carbonate↗
PubMed2006

Polymer-controlled crystallization of zinc oxide hexagonal nanorings and disks.

In this study, we have developed a novel route to the synthesis of ZnO nanorings, disks, and diskoidlike crystals on a large scale by a facile solution-based method by using polymers as crystal growth modifiers. The crystals precipitated with polyacrylamide (PAM) as the additive show ringlike morphology. A possible growth mechanism of the ZnO nanostructures based on typical polymer-crystals interactions in a mild aqueous solution is given. The polymer contains in the side chain a large number of amide ligands that are able to coordinate with Zn(2+) ions, that is, the otherwise just weakly exposed (001) face, leading to a lowering of surface energy and inhibition of growth along this direction and the formation of ringlike morphologies. While in the presence of carboxyl-functionalized polyacrylamide (PAM-COOH), nearly monodispersed disklike crystals were observed and finally evolved into diskoidlike microstructures with the reaction time prolonged. Polymer-directed crystal growth and mediated self-assembly of nanocrystals may provide promising routes to rational synthesis of various ordered inorganic and inorganic-organic hybrid materials with complex form and structural specialization.

Journal Article↗
PubMed2005

Novel multilamellar mesostructured molybdenum oxide nanofibers and nanobelts: synthesis and characterization.

One-dimensional molybdenum oxide nanostructures with layered mesostructures were prepared directly from commercial bulk MoO3 crystals by a surfactant-templated hydrothermal process. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, infrared spectra, and thermal analyses have been used to characterize the obtained molybdenum oxide nanomaterials. By use of cetyltrimethylammonium bromide as the structure-directing template, novel molybdenum oxide nanofibers with triple interlayer distances of 2.84, 2.66, and 2.46 nm have been obtained. The nanofibers have diameters of 20-100 nm and length up to 20 microm. The growth of multilamellar molybdenum oxide nanofibers can be interpreted by the combination of surfactant/inorganic self-assembly process and host/guest intercalation chemistry. On the basis of the X-ray diffraction and infrared results, a possible arrangement of surfactant in the interlayer space of molybdenum oxide by bilayer micelles with different tilt angles has been proposed. In addition, the thermal stability of surfactant has been improved by intercalation. Moreover, molybdenum oxide nanobelts with two kinds of interlayered structures were also produced in the presence of n-alkylamines (n = 12, 14, 16, and 18) following a similar method, these nanobelts show length up to more than 10 microm, width ranging between 200 and 600 microm, and width-to-thickness ratios of about 3-12. A linear relationship is observed between the interlayer distance and the number of carbon atoms in n-alkyl chains.

Journal Article↗
PubMed2004

Synthesis, characterization and antiviral activity against influenza virus of a series of novel manganese-substituted rare earth borotungstates heteropolyoxometalates.

A series of novel manganese-substituted mixed-valence rare earth borotungsto-heteropoly blues, Ln2H3[BW9(VI)W2(V)Mn(H2O)O39] x 12H2O (Ln(2), Ln = La, Ce, Pr, Nd, Sm, Eu and Gd), as well as their corresponding heteropoly acids (Ln(0)), have been prepared and characterized by cyclic voltammetry (CV), infrared (IR), ultraviolet (UV), thermal gravimetric (TG) and differential thermal (DTA) analysis, X-ray photoelectron spectroscopy (XPS) and electrochemistry. It's shown that the heteropoly blues anion in Ln(2) still retains the alpha-Keggin structure but with a slight distortion as heteropoly acids do, and Mn and W atoms distribute statistically in the whole molecular. At the same time, the cell toxicity and antiviral activity of these rare earth borotungstateheteropoly blues against influenza virus type A and type B in MDCK cells have been investigated using plaque reduction assay. The results elucidated that these complexes exhibit a significantly inhibitory activity and almost no cytotoxicity comparable with those obtained from virazole, and the anti-virus activity depend on the structure of these complexes.

Animals↗
PubMed2003

Systematic synthesis and characterization of single-crystal lanthanide orthophosphate nanowires.

A simple hydrothermal method has been developed for the systematic synthesis of lanthanide orthophosphate crystals with different crystalline phases and morphologies. It has been shown that pure LnPO(4) compounds change structure with decreasing Ln ionic radius: i.e., the orthophosphates from Ho to Lu as well as Y exist only in the tetragonal zircon (xenotime) structure, while the orthophosphates from La to Dy exist in the hexagonal structure under hydrothermal treatment. The obtained hexagonal structured lanthanide orthophosphate LnPO(4) (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy) products have a wirelike morphology. In contrast, tetragonal LnPO(4) (Ln = Ho, Er, Tm, Yb, Lu, Y) samples prepared under the same experimental conditions consist of nanoparticles. The obtained hexagonal LnPO(4) (Ln = La --> Tb) can convert to the monoclinic monazite structured products, and their morphologies remained the same after calcination at 900 degrees C in air (Hexagonal DyPO(4) is an exceptional case, it transformed to tetragonal DyPO(4) by calcination), while the tetragonal structure for (Ho--> Lu, Y)PO(4) remains unchanged by calcination. The resulting LnPO(4) (Ln = La --> Dy) products consist almost entirely of nanowires/nanorods with diameters of 5-120 nm and lengths ranging from several hundreds of nanometers to several micrometers. Europium doped LaPO(4) nanowires were also prepared, and their photoluminescent properties were reported. The optical absorption spectrum of CePO(4) nanowires was measured and showed some differences from that of bulk CePO(4) materials. The possible growth mechanism of lanthanide phosphate nanowires was explored in detail. X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, electron diffraction, infrared absorption spectra, X-ray photoelectron spectroscopy, optical absorption spectra, and photoluminescence spectra have been employed to characterize these materials.

Journal Article↗
PubMed2003

A self-seeded, surfactant-directed hydrothermal growth of single crystalline lithium manganese oxide nanobelts from the commercial bulky particles.

Single crystalline lithium manganese oxide nanobelts were obtained through a self-seeded, surfactant-directed growth process from the commercial bulky particles under hydrothermal treatment. A possible mechanism was proposed to explain the growth of the nanobelts. This new process could be extended to prepare other one-dimensional nanomaterials such as Se nanorods, Te nanotubes, and MnO2 nanowires.

Journal Article↗
PubMed2003

Multidimensional frameworks assembled from silver(I) coordination polymers containing flexible bis(thioquinolyl) ligands: role of the intra- and intermolecular aromatic stacking interactions.

The two flexible multidentate ligands 1,3-bis(8-thioquinolyl)propane (C3TQ) and 1,4-bis(8-thioquinolyl)butane (C4TQ) were reacted with AgX (X = CF(3)SO(3)(-) or ClO(4)(-)) to give four new complexes: ([Ag(C3TQ)](ClO(4)))(n)() 1, ([Ag(C3TQ)](CF(3)SO(3)))(n)() 2, ([Ag(2)(C4TQ)(CF(3)SO(3))(CH(3)CN)](CF(3)SO(3)))(n)() 3, and ([Ag(C4TQ)](ClO(4)))(n)() 4. All complexes have been characterized by elemental analysis, IR, and (1)H NMR spectroscopy. Single-crystal X-ray analysis showed that chain structures form for all complexes in which the quinoline rings interact via various intra- (1) or intermolecular (2, 3, and 4) pi-pi aromatic stacking interactions, which in the latter cases results in multidimensional structures. Additional weak interactions, such as Ag.O and Ag.S contacts and C-H.O hydrogen bonding, are also present and help form stable, crystalline materials. It was found that the (CH(2))(n) spacers (n = 3 or 4) affect the orientation of the two terminal quinolyl rings, thereby significantly influencing the specific framework structure that forms. If the same ligand is used, on the other hand, then the different counteranions have the greatest effect on the final structure.

Journal Article↗
PubMed2003

A simple method to synthesize Dy(OH)(3) and Dy(2)O(3) nanotubes.

Here we report the first synthesis of Dy(OH)(3) nanotubes by facile hydrothermal treatment of bulky Dy(2)O(3) crystals. Dy(OH)(3) nanotubes were calcined to produce Dy(2)O(3) nanotubes. Ho(OH)(3) and Ho(2)O(3) nanotubes were also obtained by the same method. The growth of nanotubes occurred through a dissolution-recrystallization process.

Journal Article↗