Hydrothermal synthesis of single-crystal VO2(B) nanobelts

Single crystalline VO₂(B) nanobelts with a metastable structure were obtained through a simple hydrothermal synthetic method. The VO₂(B) nanobelts were characterized by means of X-ray diffraction, transmission electron microscopy, selected area electronic diffraction, field-emission scanning electron microscopy and X-ray energy-dispersive spectroscopy techniques. The as-obtained VO₂(B) nanobelts are 400–600 nm long, typically 100–150 nm wide and 20–30 nm thick. The belt-like VO₂(B) with a high surface area may be beneficial to lithium insertion between the VO₆ layers for application in batteries.     

VO2(R) nanobelts resulting from the irreversible transformation of VO2(B) nanobelts

VO₂(R) nanobelts were prepared by the irreversible transformation of VO₂(B) nanobelts at the elevated temperature. The morphology and size of the VO₂(R) nanobelts were dependent on that of the precursor. VO₂(B) nanobelts were synthesized by a hydrothermal route, and the process of the VO₂(B) nanobelts' formation was also discussed. The product was characterized by a combination of techniques including XRD, TEM, FE-SEM, HRTEM, DTA and FT-IR. The as-obtained VO₂(R) nanobelts have a monoclinic structure with a length of 350-600 nm, a wideness of 100-150 nm and a thickness of 20-30 nm.     

Vanadium dioxide nanobelts: Hydrothermal synthesis and magnetic properties

VO₂ (B) nanobelts were prepared by a hydrothermal method at 180 °C using V₂O₅·nH₂O sol and H₂C₂O₄·2H₂O as starting agents. The obtained nanobelts have diameters ranging from 50 to 100 nm in width, 20-30 nm in thickness with lengths up to 1.5 μm. Measurements of the static magnetic susceptibility provide evidence for two phase transitions at T₁ = 225 K and T₂ = 290 K, respectively. Below T₁, the data suggest the presence quasi-free as well as of strongly antiferromagnetic correlated spins associated to V⁴⁺-ions.     

Oxidative dehydrogenation of cyclohexane with Mg3(VO4)2 synthesized by the citrate process

Citric acid complexation under mild condition was proposed to prepare monophasic and well crystallized Mg₃(VO₄)₂ particle to be used as an active catalyst for the oxidative dehydrogenation of cyclohexane to cyclohexene. The catalyst prepared above was characterized by N₂-physisorption, X-ray diffraction, scanning electron microscopy, and thermal gravimetric analysis. The characterization results displayed that the Mg₃(VO₄)₂ particle was typically 100-160 nm and the specific surface area was 12.0-26.7 m²/g. Moreover, it showed that the purity and the structure of the catalyst were principally subjected to the calcination temperature and the amount of citric acid used in the sol-gel procedure. The Mg₃(VO₄)₂ catalyst calcined at 823 K for 6 h with a molar ratio of (Mg + V):citric acid = 1:1.2 exhibited the best catalytic performance with an excellent thermal stability.     

Hydrothermal synthesis of W and Mo co-doped VO2(B) nanobelts

W and Mo co-doped VO₂(B) nanobelts which used formic acid as reduction acid, NH₄VO₃ as vanadium source, (NH₄)₆W₇O₂₄?·?6H₂O and (NH₄)₆Mo₇O₂₄?·?4H₂O as doped sources were synthesised by the hydrothermal method. The samples were characterised by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). TEM and HRTEM images showed the samples had a length of 1?µm and a width of 100?nm. XRD, FTIR and XPS spectra revealed that Mo⁶⁺ and W⁶⁺ incorporated into the VO₂(B) lattice and formed solid-solution phases with VO₂(B).     

Synthesis of MoO3 nanobelts by medium energy nitrogen ion implantation

Ion implantation has been revealed as a potential technique to modify the surface of materials. In this work, MoO₃ nanobelts were synthesized on MoO₃ whisker surfaces by means of ion implantation with 60 keV nitrogen ions at a dose of 1 × 10¹⁶ atom/cm² and characterized by scanning electron microscopy, Raman spectroscopy, and transmission electron microscopy. The result showed that the nanostructures of MoO₃ occurred over the whisker surfaces and had belt-like shapes. The size of the synthesized MoO₃ nanobelts mostly ranged from 20 to 60 nm in width and 300 to 800 nm in length. The nanobelts were found to have an orthorhombic crystal structure with growth preferential in the [001] direction. The growth process of the nanobelts based on the common vapor-solid mechanism is discussed.     

Preparation of rod-like Sb2S3 dendrites processed in conventional hydrothermal

Large-scale rod-like antimony sulfide (Sb₂S₃) dendrites have been prepared by hydrothermal method using antimony chloride (SbCl₃), citric acid and thioacetamide as raw materials at 160 °C for 12 h. The powder X-ray diffraction pattern shows the Sb₂S₃ crystals belong to the orthorhombic phase with calculated lattice parameters a = 1.120 nm, b = 1.128 nm and c = 0.3830 nm. The quantification of energy dispersive X-ray spectrometry analysis peaks gives an atomic ratio of 2:3 for Sb:S. Transmission electron microscopy micrograph studies reveal the appearance of the as-prepared Sb₂S₃ is dendrites-like which is composed of nanorods with the typical width of 300-500 nm and length of 5-20 µm. Finally the influences of the reaction conditions are discussed and a possible mechanism for the formation of rod-like Sb₂S₃ dendrites is proposed.     

Facile one-pot synthesis and luminescence of hexagonal TbPO4·nH2O hollow spheres

Monodisperse hexagonal TbPO₄·nH₂O hollow spheres were successfully obtained by utilizing Tb(OH)CO₃ colloidal spheres as the precursor and NH₄H₂PO₄ as the phosphorus source through the hydrothermal process. The obtained hollow spheres were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), respectively. They have the average diameter of 200 nm. There are a number of tiny nanorods with the length of about 60 nm on the surface of the spheres. The obtained TbPO₄ hollow spheres exhibit green color emission from ⁵D₄ − ⁷F_J (J = 6, 5, 4, 3) transitions of the Tb³⁺ ions, which are expected to be applied in display applications and biological applications.     

Flame-made single phase Zn2TiO4 nanoparticles

Using zinc naphthenate and titanium tetra isopropoxide (1:1 mol.%) dissolved in ethanol as precursors, single phase Zn₂TiO₄ nanoparticles were synthesized by the flame spray pyrolysis technique. The Zn₂TiO₄ nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The BET surface area (SSA_BET) of the nanoparticles was measured by nitrogen adsorption. The average diameter of Zn₂TiO₄ spherical particles was in the range of 5 to 10 nm under 5/5 (precursor/oxygen) flame conditions. All peaks can be confirmed to correspond to the cubic structure of Zn₂TiO₄ (JCPDS No. 25-1164). The SEM result showed the presence of agglomerated nanospheres with an average diameter of 10-20 nm. The crystallite sizes of spherical particles were found to be in the range of 5-18 nm from the TEM image. An average BET equivalent particle diameter (d_BET) was calculated using the density of Zn₂TiO₄.     

Controlled synthesis and electrochemical properties of vanadium oxides with different nanostructures

Vanadium oxides (V₃O₇·H₂O and VO₂) with different morphologies have been selectively synthesized by a facile hydrothermal approach using glucose as the reducing and structure-directing reagent. The as-obtained V₃O₇·H₂O nanobelts have a length up to several tens of micrometers, width of about 60?C150?nm and thickness of about 5?C10?nm, while the as-prepared VO ₂ (B) nanobelts have a length of about 1·0?C2·7???m, width, 80?C140?nm and thickness, 2?C8?nm. It was found that the quantity of glucose, the reaction temperature and the reaction time had significant influence on the compositions and morphologies of final products. Vanadium oxides with different morphologies were easily synthesized by controlling the concentration of glucose. The formation mechanism was also briefly discussed, indicating that glucose played different roles in synthesizing various vanadium oxides. The phase transition from VO₂(B) to VO₂(M) were investigated and the phase transition temperature of the VO₂(M) appeared at around 68 °C. Furthermore, the electrochemical properties of V₃O₇·H₂O nanobelts, VO₂(B) nanobelts and VO₂(B) nanosheets were investigated and they exhibited a high initial discharge capacity of 296, 247 and 227 mAh/g, respectively.     

Synthesis of Cu11(OH)14(CrO4)4 nanobelts

Cu₁₁(OH)₁₄(CrO₄)₄ nanobelts have been synthesized by hydrothermal method in the absence of any surfactants. The as-synthesized products are characterized by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. The average thickness, widths and lengths of the nanobelts are about 15 nm, 40 nm, and several micrometers, respectively. It is interesting that Cu₁₁(OH)₁₄(CrO₄)₄ nanobelts are very sensitive to electron beam illumination. The influences of the reaction temperature on the morphologies of the resulting products have been investigated.     

Mechanochemical-molten salt synthesis of Na2Ti6O13 nanobelts

A novel route for the preparation of Na₂Ti₆O₁₃ nanobelts by mechanochemical treatment of the TiCl₄-Na₂SO₄·10H₂O-Na₂CO₃ mixture for 5 min followed by molten salt synthesis is described. The mixture of the amorphous TiO₂ and NaCl-Na₂SO₄·xH₂O-Na₂CO₃ salt matrix was generated during milling. The molten salt synthesis of the Na₂Ti₆O₁₃ nanobelts with lengths up to 0.5-2 μm and with a width in the range of 20-250 nm was carried out in the temperature range of 700-800 °C for 1 h. The partial formation of titanate nanotubes was observed after annealing at 600 °C and washing procedure. X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential thermal analysis (DTA) were used to characterize the formation and structure of Na₂Ti₆O₁₃ nanobelts.     

Conversion of V2O5·xH2O into orthorhombic V2O5 single-crystalline nanobelts

Orthorhombic V₂O₅ single-crystalline nanobelts have been synthesized by hydrothermal treating V₂O₅·xH₂O precipitate derived from aqueous solution of V₂O₅ and H₂O₂. The synthetic method is facile, fast, environmental friendly, and easy to scale up. The V₂O₅ single-crystalline nanobelts are 30-80 nm in width, 30-40 nm in thickness, and lengths up to several tens of micrometers. The V₂O₅·xH₂O precursor is crucial for the formation of orthorhombic V₂O₅ single-crystalline nanobelts. The influences of synthetic parameters, such as reaction time and reaction temperature, on the crystal structures and morphologies of the resulting products have been investigated. Time-dependent experiments show that V₂O₅·xH₂O are dehydrated gradually and converted into orthorhombic V₂O₅ single-crystalline nanobelts. High reaction temperature also favors the formation of orthorhombic V₂O₅ nanobelts.     

Structure of Pt3Co(1 1 0)c(2×4)-O surface studied by scanning tunneling microscopy

A Pt₃Co(1 1 0)c(2×4)-O surface has been investigated by scanning tunneling microscopy (STM), low-energy electron diffraction, and Auger electron spectroscopy. At a very initial oxidation stage exposed at 500°C, creation of missing and/or added row structures running to the [0 0 1] direction on clean Pt₃Co(1 1 0)2×1 surface was imaged from the steps. The surface is fully covered by a well-ordered c(2×4) structure at 2 L oxygen exposure. Atomic-resolution STM image shows the added row-type anti-phase Co-O zigzag chains along the [0 0 1] direction. Based on the images, the structure model for the c(2×4) surface was suggested as a first oxidized layer, which comes from the chemical reaction forming stoichiometric Co monoxide. Further oxygen exposure above 5 L, Co-O clusters imaged to large dots were formed on the surface with the size of about 5-7 Å.     

Preparation and characterization of single-crystalline gallium oxide nanobelts

Single-crystalline β-Ga₂O₃ nanobelts were synthesized by a simple physical evaporation method in argon atmosphere with the starting materials of Ga. The β-Ga₂O₃ nanobelts have a width of 50-100 nm and width-to-thickness ratios of 5-10, and length of up to a few millimeters, which may have potential applications in nanosize sensors or optoelectronic nanodevices.     

Hydrogen peroxide-assisted hydrothermal synthesis of hierarchical CuO flower-like nanostructures

Hierarchical CuO nanostructures were synthesized through a hydrogen peroxide-assisted hydrothermal route in which Cu(OH)₂ was the copper source. The CuO nanostructures were composed of numerous nanobelts that radiated from the center of the nanostructure and formed a flower-like shape with a diameter of 5-10 μm. The nanobelts had lengths of 2.5-5 μm and widths of 150-200 nm. The H₂O₂ concentration directly influenced the product morphology. As the concentration of H₂O₂ increased, the length and width of the nanobelts increased and the quantity of the nanobelts decreased. The possible formation mechanism of hierarchical CuO flower-like nanostructures was presented.     

Microwave-assisted preparation of Ca6Si6O17(OH)2 and β-CaSiO3 nanobelts

Xonotlite (Ca₆Si₆O₁₇(OH)₂) nanobelts were synthesized by a microwave-assisted hydrothermal method at 180 °C for 90 min independent of the feeding molar ratio of Ca(NO₃)₂·4H₂O to Na₂SiO₃·9H₂O in the range of 0.8-3.0. Crystalline wollastonite (β-CaSiO₃) nanobelts were obtained by microwave thermal transformation of Ca₆Si₆O₁₇(OH)₂ nanobelts at 800 °C for 2 h. Ca₆Si₆O₁₇(OH)₂ nanobelts were used as both the precursor and the template for the preparation of β-CaSiO₃ nanobelts. The morphology and size of Ca₆Si₆O₁₇(OH)₂ nanobelts could be well preserved during the microwave thermal transformation process. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED).     

Structure and magnetic properties of high coercive [PrFeBx/Cu]n films with out-of-plane orientation

Pr-Fe-B single layer and [PrFeB_x/Cu]_n films were prepared by magnetron sputtering on Si substrate heated at 650 °C. The influence of the composition and thickness of Cu spacer layer on the structure and magnetic properties of films with out-of-plane orientation are investigated. The [PrFeB_x/Cu]_n films present an enhanced coercivity and a lower remanence, in comparison with the results of Pr-Fe-B single layer. The coercivity H_c⊥ of about 19.7 kOe and the remanence ratio M_r/M_s of about 0.90 are achieved in the Mo(50 nm) / [PrFeB(300 nm) / Cu(2 nm)]₂ / Mo(50 nm) film.     

The production of flower-like NiFe2O4 superstructures consisting of nanosheets via the thermolysis of a heterometallic oxo-centered trinuclear complex

Flower-like NiFe₂O₄ superstructures consisting of nanosheets have been successfully synthesized by direct thermolysis of a heterometallic oxo-centered trinuclear complex [NiFe₂O(CH₃COO)₆(H₂O)₃·2H₂O] (NiFe-HOTC) at 400 °C for 6 h in a horizontal tube furnace. The composition and structure of the products were investigated by X-ray diffraction (XRD) and infrared spectra (IR). XRD analysis revealed a pure ferrite phase with high crystallinity. Morphological investigation by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed NiFe₂O₄ flowers with average diameter varying from 0.5 to 3 μm consist of nanosheets with average edge length in the range of 60-300 nm and thickness of about 30 nm. Furthermore, energy dispersive X-ray analysis (EDX) demonstrated that the atom ration of Ni, Fe and O is 1:2:4. In addition, magnetic measurements showed that the obtained flower-like NiFe₂O₄ are ferromagnetic at room temperature.