Complexing reagent-assisted microwave synthesis of uniform and monodisperse disk-like CeF3 particles

Highly uniform and monodisperse disk-like CeF₃ particles with diameter about 230 nm and thickness about 76 nm were successfully synthesized via a mild and facile microwave irradiation assisted by a complexing reagent, ethylenediamine tetraacetic acid disodium salt (Na₂H₂EDTA). The morphologies and crystal structure of the products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and scanning electron microscopy (SEM). XRD patterns showed that the as-prepared CeF₃ products have hexagonal structure and high crystallinity. SEM images showed that these disk-like CeF₃ nanocrystals had rough surfaces which were covered with many sheet-like structures. It was found that the reaction time and the complexing reagent played crucial roles on formation of uniform disk-like CeF₃ particles. A possible formation mechanism of the disk-like CeF₃ particles was preliminarily presented.     

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.     

Room temperature synthesis and characterization of different morphological TbF3 nano/microcrystals

At room temperature, a simple solution-based procedure employing NaBF₄ as the fluoride source has been developed to selectively prepare different morphological TbF₃ nano/microcrystals (disks, peanuts and spindles) with an orthorhombic structure. The crystal structure, morphology and photoluminescence properties of the as-prepared TbF₃ crystals were investigated by x-ray powder diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectrophotometer. The results revealed that large-scale and uniform disks with a mean thickness of 20 nm can be easily synthesized, and the spindle-like and peanut-like TbF₃ crystals were assembled from nanodisks. The effects of synthesis parameters such as NaBF₄, reaction time and molar ratio of the reactants were systematically investigated. The room temperature PL properties of these different morphological TbF₃ microcrystals were measured.     

A very simple and low cost route to Bi2S3 nanorods bundles and dandelion-like nanostructures

Bi₂S₃ nanorods bundles as well as three-dimensional dandelion-like nanostructures were synthesized in high yield at lower temperature (room temperature or ambient temperature of 15 °C) in a very simple system composed only of Bi(NO₃)₃, thioacetamide (TAA), hydrochloride acid and distilled water. It is the first report to obtain such nanostructures at such a low temperature and by such a simple method, and the reaction does not demand any additional energy such as heating or agitation. A splitting crystal growth and self-assemble mechanism should be responsible for the formation of these structures. This kind of novel Bi₂S₃ nanostructures may find potential applications in hydrogen storage, high-energy batteries, as well as luminescence and catalysis fields.     

Microwave synthesis of SrCO3 one-dimensional nanostructures assembled from nanocrystals using ethylenediamine additive

One-dimensional SrCO₃ nanostructures assembled from nanocrystals have been successfully synthesized by a microwave-assisted aqueous solution method at 90 °C using Sr(NO₃)₂, (NH₄)₂CO₃ and ethylenediamine (C₂H₈N₂). Our experiments show that the microwave heating time plays an important role in the size and morphology of SrCO₃. A rational mechanism based on the oriented attachment self-assembly is proposed for the formation of SrCO₃ nanostructures. The products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected-area electron diffraction (SAED). This method is simple, fast, low-cost and suitable for large-scale production of SrCO₃ nanostructures with different morphologies. We expect that this method may be extended to the preparation of nanostructures of other kinds of carbonates.     

Synthesis and characterization of CeCO3OH one-dimensional quadrangular prisms by a simple method

Orthorhombic single-crystalline cerium carbonate hydroxide (CeCO₃OH) one-dimensional (1D) quadrangular prisms have been successfully synthesized by a facile sonochemical reaction between cerous nitrate and carbamide in the presence of surfactant polyvinyl alcohol (PVA). The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM). The as-synthesized CeCO₃OH have uniform lengths and good dispersion. These one-dimensional CeCO₃OH structures are quadrangular prisms with edge length of about 300 nm. The quadrangular prisms have well-resolved edges and their surfaces are very smooth. Interestingly, each end of the prism is cut along the diagonal of underside plane to form two chamfered planes. Furthermore, room-temperature photoluminescence of CeCO₃OH samples have also been investigated.     

Synthesis of KNbO3 nanostructures by a microwave assisted hydrothermal method

One-dimensional nanostructures of KNbO₃ have attracted a great interest in the scientific community, mainly because of their promising application as nanoelectromechanical systems (NEMS). However, the synthesis of KNbO₃ structures becomes complex due to the natural tendency to form non-stoichiometric potassium niobates. In this context, we report on the crystallization of one-dimensional KNbO₃ nanostructures through the reaction between Nb₂O₅ and KOH under microwave-assisted hydrothermal synthesis (M-H). The use of this synthesis method made possible a very fast synthesis of singlecrystalline powders. Based on SEM, TEM and XRD characterizations, the influence of the synthesis time and the reactants concentration in the structure and morphology of the resultant KNbO₃ was established. The conditions that favor the crystallization of nanofingers were determined to be small amounts of Nb₂O₅ and short reaction times.     

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 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.     

Synthesis of sphere-like Co3O4 nanocrystals via a simple polyol route

A simple polyol method was developed to synthesize uniform sphere-like Co₃O₄ nanocrystals in ethylene glycol. Powder X-ray diffraction (XRD) and electron diffraction (ED) showed that the as-prepared sample was indexed as the cubic spinel structure. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that the Co₃O₄ nanocrystals were spherical with the crystallite size in the range of 90-110 nm. Infrared spectra and Raman spectra confirmed the formation of the Co₃O₄ nanocrystals. The magnetic properties of the Co₃O₄ nanocrystals were measured by using a superconducting quantum interference device (SQUID) magnetometer, which showed that the as-prepared sample exhibited a tiny hysteresis loop with the magnetization value of 2.4 emu/g and the coercivity of 110 Oe.     

Synthesis and characterization of WO3 nanostructures prepared by an aged-hydrothermal method

Nanostructures of tungsten trioxide (WO₃) have been successfully synthesized by using an aged route at low temperature (60 °C) followed by a hydrothermal method at 200 °C for 48 h under well controlled conditions. The material was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Specific Surface Area (S_BET) were measured by using the BET method. The lengths of the WO₃ nanostructures obtained are between 30 and 200 nm and their diameters are from 20 to 70 nm. The growth direction of the tungsten oxide nanostructures was determined along [010] axis with an inter-planar distance of 0.38 nm.     

Synthesis of ultra-long single crystalline CuV2O6 nanobelts

Ultra-long single crystalline CuV₂O₆ nanobelts have been successfully synthesized via a facile homogeneous reaction between peroxovanadic acid and cupric acetate. The reaction parameters, such as reaction time, and with or without H₂O₂, have profound influences on the crystal structures and morphologies of the resulting products. The time-dependent experiments reveal that the formation of ultra-long CuV₂O₆ nanobelts is related to the disassembly of urchin-like Cu₃(OH)₂V₂O₇·2H₂O nanostructures composed of radially aligned nanobelts, and the growth of CuV₂O₆ along the direction of [010]. Without the addition of H₂O₂ aqueous solution, wide and short CuV₂O₆ nanobelts coexist with some irregular particles and microrods in the products.     

Synthesis of Co3O4 nanoparticles via the CTAB-assisted method

Cobalt oxide (Co₃O₄) nanoparticles were successfully synthesized by the cetyltrimethylammonium bromide (CTAB)-assisted method at normal pressure for the first time. The structure and morphology of the as-prepared Co₃O₄ nanoparticles were characterized by powder X-ray diffracton (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N₂-sorption analysis. XRD studies indicated that the as-prepared product was well-crystallized cubic phase of Co₃O₄ with a cell constant of α = 8.0722 Å. The EM images showed that the obtained Co₃O₄ sample consisted of dispersive quasi-spherical particles with the size ranged from 15 to 25 nm.     

Synthesis and characterization of Co3O4/RuO2 composite nanofibers fabricated by an electrospinning method

Co₃O₄-RuO₂ composite nanofibers (NFs) were synthesized by an electrospinning method and were calcinated at 400°C for 1 hr in air. Scanning electron microscopy and high-resolution transmission electron microscopy (HRTEM) examinations show that all the synthesized NFs have uniform surface morphology and their diameters are in the range of ~ 30-~70 nm. X-ray diffraction (XRD) results show that crystalline Co₃O₄ phase and RuO₂ phase coexist in the composite NF matrix which is confirmed by X-ray photoemission spectroscopy. In addition, the HRTEM energy-dispersive X-ray spectroscopy mapping results show that the Co₃O₄ and RuO₂ phases are uniformly distributed across the NF matrix.     

Synthesis of CaCu3Ti4O12 ceramic via a sol-gel method

The novel nano-ultrafine powders for the preparation of CaCu₃Ti₄O₁₂ ceramic were prepared by the sol-gel method and citrate auto-ignition method. The obtained precursor powders were pressed, sintered at 1000 °C to fabricate microcrystal CaCu₃Ti₄O₁₂ ceramic. The microcrystalline phase of CaCu₃Ti₄O₁₂ was confirmed by X-ray powder diffraction (XRD). The morphology and size of the grains of the powders and ceramics under different heat treatments were observed using scanning electron microscopy (SEM). The relative dielectric constant of the ceramic sintered at 1000 °C was measured with a magnitude of more than 10⁴ at room temperature, which was approaching to those of Pb-containing complex perovskite ceramics, and the loss tangent was less than 0.20 in a broad frequency region. The relative dielectric constant and loss tangent were also compared with that of CaCu₃Ti₄O₁₂ ceramic prepared by other reported methods.     

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.     

Synthesis of single crystal Bi2Te3 nanoplates via an inorganic-surfactant-assisted solvothermal route

Single crystal Bi₂Te₃ nanoplates have been successfully obtained by a solvothermal method adopting a lamellar structure as the precursor. Various techniques such as X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), high-resolution transmission electron microscope (HRTEM), and selected area electron diffraction (SAED) have been used to characterize the obtained products. The results show that the as-synthesized samples are rhombohedral-structured Bi₂Te₃ single-crystal nanoplates, whose growth direction is perpendicular to c-axis. In addition, some important experiment parameters such as the water/ethanol volume ratio and pH value have been discussed.     

Synthesis of CoSb3 by a modified polyol process

Thermoelectric (TE) materials are attracting renewed interest for clean energy conversion. Potentially high figure-of-merit (ZT) is achievable through the approach of preparing nanostructured TE materials. In this work, CoSb₃ nanoparticles were fabricated via a modified polyol process. X-ray diffractometer (XRD) and transmission electron microscope (TEM) were used to characterize the synthesized products. The results showed that high purity CoSb₃ nanoparticles could be prepared at a temperature as low as 180 °C. It was also found that the phase composition of the final products is highly dependent on reaction temperature and duration.     

One-pot synthesis of intestine-like SnO2/TiO2 hollow nanostructures

In the present study the intestine-like binary SnO₂/TiO₂ hollow nanostructures are one-pot synthesized in aqueous phase at room temperature via a colloid seeded deposition process in which the intestine-like hollow SnO₂ spheres and Ti(SO₄)₂ are used as colloid seeds and Ti-source, respectively. The novel core (SnO₂ hollow sphere)-shell (TiO₂) nanostructures possess a large surface area of 122 m²/g (calcined at 350 °C) and a high exposure of TiO₂ surface. The structural change of TiO₂ shell at different temperatures was investigated by means of X-ray diffraction and Raman spectroscopy. It was observed that the rutile TiO₂ could form even at room temperature due to the presence of SnO₂ core and the unique core-shell interaction.