Preparation and luminescence properties of Ce3+ and/or Tb3+ doped LaPO4 nanofibers and microbelts by electrospinning

Ce3+ and/or Tb3+ doped LaPO4 nanofibers and microbelts have been prepared by a combination method of sol-gel process and electrospinning. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), low voltage cathodoluminescence (CL) and time-resolved emission spectra as well as kinetic decays were used to characterize the resulting samples. SEM and TEM results indicate the as-formed precursor fibers and belts are smooth. and the as-prepared nanofibers and microbelts consist of nanoparticles. The doped rare-earth ions show their characteristic emission under ultraviolet excitation, i.e. Ce3+ 5d-4f and Tb3+ D-5(4)-F-7(j) (J = 6-3) transitions, respectively. The energy transfer process from Ce3+ to Tb3+ in LaPO4:Ce3+, Tb3+ nanofibers was further studied by the time-resolved emission spectra.

Preparation and luminescence properties of Mn2+-doped ZnGa2O4 nanofibers via electrospinning process

One-dimensional Mn2+-doped ZnGa2O4 nanofibers were prepared by a simple and cost-effective electrospinning process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), energy-dispersive X-ray spectrum (EDS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) and cathodoluminescence (CL) spectra as well as kinetic decays were used to characterize the samples. SEM results indicated that the as-formed precursor fibers and those annealed at 700 degrees C are uniform with length of several tens to hundred micrometers, and the diameters of the fibers decrease greatly after being heated at 700 degrees C. Under ultraviolet excitation (246 nm) and low-voltage electron beams (1-3 kV) excitation, the ZnGa2O4:Mn2+ nanofibers presents the blue emission band of the ZnGa2O4 host lattice and the strong green emission with a peak at 505 nm corresponding to the T-4(1)-(6)A(1) transition of Mn2+ ion.

Facile Hydrothermal Synthesis and Luminescent Properties of Large-Scale GdVO4:Eu3+ Nanowires

Large-scale GdVO4:Eu3+ nanowires with diameters of about 15 nm and lengths of several micrometers were achieved by a facile hydrothermal method in the presence of disodium ethylenediamine tetraacetate (Na2H2L). The influences of several parameters, such as pH value, reaction temperature, and molar ratio of Na2H2L to Gd3+ on the final products were investigated. The formation mechanism of the as-obtained GdVO4:Eu3+ nanowires is proposed on the basis of time-dependent experiments. It is found that the organic additive Na2H2L, which acts as a shape modifier, has a dynamic effect by adjusting the growth rates of different facets, resulting in the formation of the GdVO4:Eu3+ nanowires. The luminescent spectrum of GdVO4:Eu3+ nanowires shows the strong characteristic dominant emission of the Eu3+ ions at 614 nm.

Facile chemical conversion synthesis and luminescence properties of uniform Ln3+ (Ln = Eu, Tb)-doped NaLuF4 nanowires and LuBO3 microdisks

Uniform NaLuF(4) nanowires and LuBO(3) microdisks have been successfully prepared by a designed chemical conversion method. The lutetium precursor nanowires were first prepared through a simple hydrothermal process. Subsequently, uniform NaLuF(4) nanowires and LuBO(3) microdisks were synthesized at the expense of the precursor by a hydrothermal conversion process. The whole process was carried out in aqueous condition without any organic solvents, surfactant, or catalyst. The conversion processes from precursor to the final products have been investigated in detail. The as-obtained Eu(3+) and Tb(3+)-doped LuBO(3) microdisks and NaLuF(4) nanowires show strong characteristic red and green emissions under ultraviolet excitation or low-voltage electron beam excitation. Moreover, the luminescence colors of the Eu(3+) and Tb(3+) codoped LuBO(3) samples can be tuned from red, orange, yellow, and green-yellow to green by simply adjusting the relative doping concentrations of the activator ions under a single wavelength excitation, which might find potential applications in the fields such as light display systems and optoelectronic devices.

Comparative study of Ga2O3 : Dy3+ phosphors prepared by three methods

Trivalent dysprosium (Dy3+)-activated beta-gallium oxide (beta-Ga2O3) phosphors were synthesized by solid-state (SS), coprecipitation (CP), and citrate gel (CG) methods, respectively. The resulting beta-Ga2O3:Dy3+ phosphors were well characterized by X-ray diffraction, field-emission scanning electron microscopy (FESEM), and by photoluminescence and cathodoluminescence spectra. The phosphors prepared by different methods show different luminescence properties under the excitation of UV and low-voltage cathode rays. There exists an energy transfer from the beta-Ga2O3 host lattices to Dy3+, and the energy transfer efficiency was higher in the CG-derived phosphors than those of the SS- and CP-derived phosphors. Factors influencing the intensity of luminescence and the energy transfer efficiency from beta-Ga2O3 host to Dy3+ in beta-Ga2O3:Dy3+ phosphors were investigated in detail. It is shown that the CG method is the most respected process for the preparation of beta-Ga2O3:Dy3+ phosphors.

Assembly of one-dimensional organic luminescent nanowires based on quinacridone derivatives

The quinacridone derivatives N,N'-dialkyl-1,3,8,10-tetramethylquinacridone (CnTMQA, n = 6, 10, 14) were used as building blocks to assemble luminescent nano- and microscale wires. It was demonstrated that CnTMQA with different lengths of alkyl chains display obviously different wire formation properties. C10TMQA and C14TMQA showed a stronger tendency to form 1-D nano- and microstructures compared with C6TMQA. The C10TMQA molecules could be employed to fabricate the wires with different diameters, which exhibited a size-dependent luminescence property. The emission spectrum of the C10TMQA wires with diameters of 200-500 nm shows a broad emission band at 560 nm and a shoulder at around 535 nm, while the emission spectrum of the C10TMQA wires with diameters of 2-3 mu m reveals a narrower emission band at 563 nm. For the CnTMQA-based samples with different morphologies, the emission property change tendency agrees with that of the powder X-ray diffraction patterns of these samples.

Fabrication of conductive metallized nanostructures from self-assembled amphiphilic triblock copolymer templates: Nanospheres, nanowires, nanorings

Various metallized nanostructures (such as rings, wires with controllable lengths, spheres) have been successfully fabricated by coating metallic nanolayers onto soft nanotemplates through simple electroless methods. In particular, bimetallic nanostructures have been obtained by using simple methods. The multiple functional polymeric nanostructures, were obtained through the self-assembly of polystyrene/poly(4-vinyl pyridine) triblock copolymer (P4VP-b-PS-b-P4VP) in selective media by changing the common solvent properties. By combining field emission scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) characterization, it was confirmed that polymer/metal and bimetallic (Au@Ag) core-shell nanostructures could be achieved by chemical metal deposition method.

Single-crystalline nanowires of SiC synthesized by carbothermal reduction of electrospun PVP/TEOS composite fibres

Nanowires of SiC were synthesized by carbothermally reducing PVP/TEOS composite fibres obtained by electrospinning. High-resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED) indicated that the SiC nanowires are single crystalline in nature. Both Fourier-transformed infrared spectroscopy and HRTEM indicated that a thin layer of SiO2 was formed on the outer surface of the nanowire as a result of post-heat treatment for the removal of residual carbon. Such SiO2 layer protects the inner SiC fibre from further oxidation. The formation mechanism of single-crystalline SiC nanowires was proposed based on our understanding and characterizations. The growth of the nanowire is believed to be along the ( 111) of its cubic cell.

Fast and facile preparation of superhigh aspect-ratio Cu-thiourea nanowires in large quantity

Superhigh aspect-ratio Cu-thiourea (Cu(tu)) nanowires have been synthesized in large quantity via a fast and facile method. Nanowires of Cu (tu)Cl center dot 0.5H(2)O and Cu(tu)Br center dot 0.5H(2)O were found to be 60-100 nm and 100-200 nm, in diameter, and could extend to several millimeters in length. It is found to be the most convenient and facile approach to the fabrication of one-dimensional superhigh aspect-ratio nanomaterials in large scale so far.

Synthesis and photoluminescence of the Y2O3 : Eu3+ phosphor nanowires in AAO template

The monodisperse array and nanowires Of Y2O3:Eu3+ phosphor were synthesized using anodic aluminum oxide (AAO) template by sol-gel method. Scanning electron microscope (SEM) images indicated that Y2O3:Eu3+ nanowires are parallelly arranged, all of which are in uniform diameter of about 50 nm. The high-magnification SEM image showed that each nanowire is composed of a lot of agglutinating particles. The patterns of selected-area electron diffraction confirmed that Y2O3:EU3+ nanowires mainly consist of polycrystalline materials. Excitation and emission spectra Of Y2O3:E U3+/AAO composite films were measured. The characteristic red emission peak of EU3+ ion attributed to D-5(0)-->F-7(2) transition in Y2O3:EU3+/AAO nanowires broadened its halfwidth.

Synthesis of nanowires, nanorods and nanoparticles of ZnO through modulating the ratio of water to methanol by using a mild and simple solution method

ZnO nanowires, nanorods and nanoparticles through modulating the ratio of water to methanol have been synthesized by using a mild and simple solution method. The as-prepared ZnO nanostructures have been characterized by atomic force microscopy and X-ray photoelectron spectroscopy. With the increase of the ratio of water to methanol, the morphology of ZnO nanostructures varied form denser nanowires, to sparse nanowires, to nanorods, and then to nanoparticles. The ratio of water to methanol is supposed to play an important role in the formation of ZnO nanostructures. The mechanism of formation is related to the chemical potential, which is simply proportional to their surface ratio.

beta-cyclodextrin controlled assembling nanostructures from gold nanoparticles to gold nanowires

In this Letter, P-cyclodextrin (P-CD) was employed as stabilizer in the synthesis of gold nanoparticles. Gold nanoparticles were synthesized by the reduction of HAuCl4 by NaBH4 in the presence of P-CD. Varying the ratio of P-Cl) to HAuCl4, isolated gold nanoparticles could be assembled into nanowires. The nanoparticles and nanowires were characterized by transmission electron microscopy, UV/visible spectroscopy, infrared spectroscopy and X-ray photoelectron spectroscopy. The decreased relative intensity of skeletal and ring vibration in FT-IR spectra and the negative shift of the Au4f(7/2) binding energy in XPS spectra confirmed that beta-CD was chemisorped on An nanoparticles via hydroxyl group.

Morphology-controllable synthesis and characterization of single-crystal molybdenum trioxide

Molybdenum trioxide nanobelts and prism-like particles with good crystallinity and high surface areas have been prepared by a facile hydrothermal method, and the morphology could be controlled by using different inorganic salts, such as KNO3, Ca(NO3)(2), La(NO3)(3), etc. The possible growth mechanism of molybdenum trioxide prism-like particles is discussed on the basis of the presence of HI and the modification of metal cations. The as-prepared nanomaterials are characterized by means of powder X-ray diffraction (PXRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transformation infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and ultraviolet and visible spectroscopy (UV-vis). TEM and HRTEM micrographs show that the molybdenum trioxide nanobelts and prism-like particles have a relatively high degree of crystallinity and uniformity. BET specific surface areas of the as-prepared molybdenum trioxide nanocrystals are 67-79 m(2)g(-1). XPS analysis indicates that the hexavalent molybdenum is predominant in the nanocrystals. UV-vis spectra reveal that the direct band gap energy of the annealed molybdenum trioxide prism-like particles shows a pronounced blue shift compared to that of bulk MoO3 powder.

Preparation of cobalt hexacyanoferrate nanowires using carbon nanotubes as templates

A simple and convenient method for preparation of cobalt hexacyanoferrate (CoHCF) nanowires by electrodeposition was reported. Multiwall carbon nanotubes (MWNTs) were used as templates to fabricate CoHCF nanowires. MWNTs could affect the size of CoHCF nanoparticles and made them grow on the sidewalls of carbon nanotubes during the process of electrodeposition. Thus CoHCF nanowires could be obtained by this method. Field-emission scanning electron microscopy, UV-vis spectroscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to characterize these nanowires. These results showed the CoHCF nanowires could be easily and successfully obtained and it gave a novel approach to prepare inorganic nanowires.

Novel Mechanical Behavior Of Zno Nanorods

A novel stress-strain relation with two stages of linear elastic deformation is observed in [0 0 0 1]-oriented ZnO nanorods under uniaxial tensile loading. This phenomenon results from a phase transformation from wurtzite (WZ, P6(3)mc space group) to a body-centered tetragonal structure with four-atom rings (denoted as BCT-4) belonging to the P4(2)/mnm space group. The analysis here focuses on the effects of nanorod size and temperature on the phase transformation and the associated mechanical behavior. It is found that as size is increased from 19.5 to 45.5 angstrom, the critical stress for nucleation of the transformation decreases by 25% from 21.90 to 16.50 GPa and the elastic moduli of the WZ- and BCT-4-structured nanorods decrease by 24% (from 299.49 to 227.51 GPa) and 38% (from 269.29 to 166.86 GPa), respectively. A significant temperature effect is also observed, with the critical stress for transformation initiation decreasing 87.8% from 17.89 to 2.19 GPa as temperature increases from 300 to 1500 K. (c) 2007 Elsevier B.V. All rights reserved.