Synthesis and field-emission properties of In2O3 nanostructures

Large-scale indium oxide nano/microstructures have been successfully synthesized by chemical vapor deposition. Scanning electron microscopy shows that the synthesized two kinds of products display two-section awls (the shape of synthesized products is like the awl which consists of a short-thick section and a long-thin section) and microcube morphologies. The as-synthesized products, characterized by XRD and TEM, are pure, structurally uniform and single crystalline. Field-emission measurements of these nano/microstructures showed low turn-on field of 3.2 V μm^− 1 and 4.1 V μm^− 1. The results showed that the two-section awl-like structure which has nanometer tips has better field-emission properties than the cube, which makes indium oxide structures promising candidates for further applications in field-emission microelectronic devices.     

Self-generation of three-dimensional hierarchical Cu2S architectures at room temperature

A simple approach is proposed to realize the three dimensional (3D) hierarchical Cu₂S architectures at room temperature in this letter. The 3D Cu₂S architectures are characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectrum (XPS). The effects of synthetic conditions, such as reaction time and the amount of reagents, on the morphology of the product are investigated. The growth mechanism of the product is proposed, based on the evolution of the morphologies with the increasing of reaction time. Our work provides a facile and easy method on designing for the fabrication of 3D hierarchical architecture materials.     

Synthesis of Sb2O3 nanorods under hydrothermal conditions

Sb₂O₃ nanorods were successfully prepared via a mild hydrothermal route based on the reactions between SbCl₃ and NH₃·H₂O in aqueous solution at 120-180 °C for 12 h. The as-prepared Sb₂O₃ nanorods were characterized by X-ray diffraction (XRD), transmission electronic microscopy (TEM), and X-ray photoelctron spectroscopy (XPS). Results showed that NH₃·H₂O played a significant role in the formation of Sb₂O₃ nanorods. The presence of NH₃·H₂O could greatly favor the reaction progress toward the right-hand side and led to the orientation growth of Sb₂O₃ nanorods. A possible mechanism for the formation of Sb₂O₃ nanocrystallites was discussed.     

Synthesis of magnesium borate nanorods

Single-crystalline magnesium borate Mg₂B₂O₅ nanorods have been synthesized via a simple route based on the calcinations of mixed powders containing Mg(OH)₂ and H₃BO₃. The nanorods have the typical diameters in the range of 70-120 nm and the lengths up to a few micrometers. An optimal synthesis temperature for Mg₂B₂O₅ nanorods was obtained, and the possible growth mechanism was also presented.     

Selective H2S detection by CuO functionalized ZnO nanotetrapods at room temperature

ZnO nanotetrapods have been synthesized by carbothermal method. The structure, phase, morphology of the synthesized sample were investigated by X-ray diffraction and X-ray photoelectron spectroscopy, Scanning electron microscopy, Transmission electron microscopy and Selected area electron diffraction. The gas-sensing characteristics of thick films of pure and CuO-functionalized ZnO Nanotetrapods have been compared. Pure ZnO nanotetrapod films were found to be sensitive to both H₂S and NO with similar sensitivities, at a temperature of 250–300 °C. It is demonstrated that functionalization of ZnO nanotetrapods with CuO, results in selectivity towards H₂S at a lower temperature of 50 °C.     

Facile and large-scale synthesis of hollow TiO2 nanostructures from TiCl3 solution

Hollow TiO₂ nanostructures were successfully synthesized by a hydrothermal process using TiCl₃ solution as Ti sources. The as-obtained product consists of quasi-spherical hollow nanostructures in the diameter of about 500 nm with anatase phase. The control experiments indicated that the synergism of H₂O₂ and KBF₄ plays an important role in the formation of hollow TiO₂ nanostructures. Compared with solid TiO₂ nanostructures, the photocatalytic property of hollow TiO₂ nanostructures has been markedly improved in degradation of methyl orange under UV light. This synthesis procedure is facile and thus promotes large-scale production of hollow TiO₂ nanostructures.     

Preparation of Sb2S3 nanostructures by the [BMIM][BF4] ionic liquid assisted low power sonochemical method

Sb₂S₃ nanorods were successfully synthesized by the ionic liquid assisted sonochemical method (ILASM). The starting reagents were Sb₂Cl₃, Thioacetamide, absolute ethanol (ETA) and the selected ionic liquid (IL) was 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF₄]). The synthesized materials were subjected to 200 °C annealing treatment under controlled vacuum conditions. X-ray powder diffraction analysis showed that ultrasound irradiation played a key role on the crystallization degree of Sb₂S₃, whilst Scanning Electron Microscopy analysis showed that the addition of IL was fundamental for the formation of 1-D Sb₂S₃ nanostructures. XPS confirmed the formation of Sb₂S₃.The optical properties (band gap) were similar to previously reported for bulk Sb₂S₃.     

Colloidal synthesis of Cu2SnSe3 nanocrystals

While Cu₂SnSe₃ material has various potential applications including acousto-optics and photovoltaics, preparation methods of this material only in a bulk form or a thin film have been reported so far. In this work, for the first time, we demonstrate that highly crystalline Cu₂SnSe₃ nanoparticles can be prepared via colloidal synthesis. The Cu₂SnSe₃ nanocrystals have a cubic crystal structure with a lattice parameter of 5.68 Å, an average diameter of 18 nm, and an atomic ratio of approximately 2:1:3. The nanocrystals can be stably suspended in solution for several months. The suspended nanocrystalline form of Cu₂SnSe₃ could potentially be useful for printable acousto-optic and photovoltaic applications.     

A simple route to synthesize nanocrystalline TiO2 films at room temperature

At room temperature, TiO₂ films were deposited by direct current pulse magnetron sputtering. Varying the O₂/Ar flow ratio, TiO₂ films with different crystalline structures and surface morphologies were obtained. X-ray diffraction spectra and atomic force microscopy showed TiO₂ films mainly existed as amorphous and crystalline structures when the O₂/Ar flow ratio was less and more than 6/14, respectively. With these results, a critical point was found at O₂/Ar = 6/14. The film growth behavior was controlled by the shadowing effect and the mixture of crystallographic orientation and grain growth effects, when the O₂/Ar flow ratio was less and more than the critical point, respectively. The present work reveals a simple way to prepare the high quality anatase phase TiO₂ films at room temperature, as well as the growth mechanism behind it.     

Synthesis and photoluminescence of In2O3 nanocrystals and submicron crystals from InCl3•4H2O and thiourea

Two routes have been proposed for the synthesis of In₂O₃ powders from InCl₃•4H₂O and thiourea. One route involved a two-step procedure (that is, firstly, In₂S₃ clusters constructed with mainly nanoflakes were synthesized by heating the mixture of InCl₃•4H₂O and thiourea in air from room temperature to 200 °C, coupled with a subsequent washing treatment; secondly, In₂O₃ was obtained by calcining the In₂S₃ clusters in air at 600 °C for 6 h), and the other route was a one-step procedure (that is, In₂O₃ was synthesized directly by calcining the mixture of InCl₃•4H₂O and thiourea in air at 600 °C for 6 h). The resultant products were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electronic microscope and room temperature photoluminescence (RT-PL) spectra. It was observed that the In₂O₃ nanocrystals obtained via the two-step procedure exhibited PL peaks at about 453 and 471 nm, corresponding to the defeat-related emission; while the In₂O₃ submicron polyhedral crystals obtained via the one-step procedure and In₂O₃ pyramids obtained by calcining the only InCl₃•4H₂O in air at 600 °C for 6 h displayed a PL band centered at around 338 nm, corresponding to the band edge emission.     

Thermoelectric crystals Bi2Te2.88Se0.12 undoped and doped by CdCl2 or CdBr2 impurities, fabricated and characterized by XRD and Hall effect

Empirical studies on the fabrication of thermoelectric element Bi₂Te_2.88Se_0.12 undoped and doped by 0.08 wt.% CdCl₂ or CdBr₂ have been carried out. Zone melting method was employed to crystallize the solid solutions of the compounds. Structural characteristics of the grown crystals were examined by XRD technique. Measurements of thermoelectric parameters, such as electrical conductivity and Seebeck coefficient, showed a continuous deviation of the composition along the crystal growth direction. Effects of an impurity as a dopant on thermoelectric parameters were studied. Finally, Hall effect system was used to measure free carrier concentration and their mobility at 300 K. Results showed a significant increment on α²σ, due to dopant addition.     

Reduction of KMnO4 to Mn3O4 via hydrothermal process

A simple, inexpensive, low temperature and environmentally benign hydrothermal reduction route has been developed for the synthesis of octahedral Mn₃O₄ nanoparticles by using KMnO₄ and hexamethylenetetramine (HMT). It has been found that, Mn₃O₄ formation during hydrothermal process involves two steps. In the first step, an intermediate MnOOH is formed under the influence of self generated pressure in the autoclave. In the second step, formic acid produced via hydrolysis followed by oxidation of HMT, reduces MnOOH to Mn₃O₄. The powder X-ray diffraction (XRD) data confirms the formation of tetragonal γ-Mn₃O_4. Scanning electron micrograph images exhibit a good octahedral morphology of the product. The formation γ-Mn₃O₄ is further confirmed by Raman and FTIR spectroscopy.     

Synthesis and characterization of SnSe2 hexagonal nanoflakes

Single phase SnSe₂ was synthesized at 180 °C by hydrothermal co-reduction method from SnCl₂·2H₂O== and SeO₂, its morphology and growth direction were investigated. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and field emission scanning electron microscope (FESEM). Experimental results show that, the SnSe₂ powder almost consists of regular and homogenous hexagonal nanoflakes which grow along (0001) crystal plane, these nanoflakes are about 600-700 nm in side length and 30-40 nm in thickness.     

Synthesis of MoO3 nanoplates from a metallorganic molecular precursor

Orthorhombic phase MoO₃ nanoplates were synthesized directly by thermolysis of an air-stable metallorganic molecular precursor (molybdenum diethyldithiocarbamate oxide: Mo((C₂H₅)₂NCS₂)₂O₂, which was prepared simply through the precipitation reaction of ammonium peramolybdate and sodium diethyldithiocarbamate in distilled water under the ambient condition) in air at 350-400 °C for 5 h. The control experiments with ammonium peramolybdate as precursor could only obtain mostly irregular microcrystallites, indicating that the metallorganic molecular precursor, Mo((C₂H₅)₂NCS₂)₂O₂ played an important role in the successful synthesis of MoO₃ nanoplates.     

Preparation of SnO2 nanorods via oriented aggregation of nanoparticles

By annealing of precursors, SnO₂ nanorods or nanowires have been synthesized by the oriented aggregation of initial SnO₂ nanoparticles. Chlorine salts are very important for both preventing increase in size of the precursors and providing aqueous and kinetic circumstances that cause the oriented aggregation of the initial nanoparticles. The possible growth mechanism of SnO₂ nanorods is also discussed.     

Rare-earth (Nd, Sm, Eu, Gd and Y) enhanced CeO2 solid solution nanorods prepared by co-precipitation without surfactants

Rare-earth doped CeO₂ solid solution nanorods were successfully prepared via a simple co-precipitation method without surfactants at room temperature and pressure. The products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effects of the doping contents, pH values, aging times and the precipitation agents on the structure and morphology were investigated. We found that the yield and uniformity of the nanorods were significantly improved by doping with optimum contents of Nd, Sm, Eu, Gd or Y. The intrinsically anisotropic structure of the rare-earth hydroxides is the driving force for the growth of the nanorods. Raman spectra show a great increase in oxygen vacancy concentrations on the doped CeO₂ solid solutions compared with that of pure CeO₂.     

Green synthesis of ZnO2 nanoparticles from hydrozincite and hydrogen peroxide at room temperature

A green method based on the reaction between hydrozincite (Zn₅(CO₃)₂(OH)₆) powder and hydrogen peroxide (H₂O₂, 30 wt.%) in aqueous solution at room temperature was developed for the synthesis of ZnO₂ nanoparticles. Results from X-ray diffraction, transmission electron microscopy and Raman demonstrated that the resultant products were pure cubic phase ZnO₂ nanoparticles, whose sizes were in the range of 3.1-4.2 nm. Thermogravimetric analysis indicated that between 180 and 350 °C, the as-synthesized ZnO₂ nanoparticles had a weight loss of about 16.7%, consistent with the theoretical amount (16.4%) of the O₂ released from ZnO₂ decomposition (ZnO₂ = ZnO + 1/2O₂). The present method was green, simple and cost-effective, which should be suitable for large-scale production of multifunctional ZnO₂ nanoparticles.     

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.     

Controllable hydrothermal synthesis of Cu2S nanowires on the copper substrate

In this paper, a simple solution-based method has been applied to fabricate metal chalcogenide nanostructures. Abundant Cu₂S nanowires on Cu substrates are successfully prepared through the in-situ hydrothermal reaction between sulfur powder and Cu foil. It is observed that the addition of hydrazine and cetyltrimethylammonium bromide plays an important role in the growth of Cu₂S nanowires. A rolling-up mechanism of metal chalcogenide film is used to illustrate the growth of these nanostructures. UV-vis spectrum of Cu₂S nanowires reveals obvious absorption below the wavelength of 900 nm. The calculated band gap of Cu₂S nanowires (1.5 eV) shows obvious blue shift because of the quantum size effect.     

Synthesis and characterization of flower-like MoS2 microspheres by a facile hydrothermal route

Flower-like MoS₂ microspheres with high purity were successfully synthesized via a facile hydrothermal route by adding sodium silicate as an additive. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). XRD patterns showed that the MoS₂ microspheres had good crystallinity with well-stacked layered structure. TEM and SEM images showed that the MoS₂ microspheres had uniform sizes with mean diameter about 480 nm and were constructed with MoS₂ sheets with thickness of several nanometers. It was found that the possible precursor H₄SiMo₁₂O₄₀ obtained by sodium silicate reacting with sodium molybdate played a crucial role in the formation of the flower-like MoS₂ microspheres in our experiment. A possible formation mechanism of MoS₂ microspheres was preliminarily presented.