Additive induced morphology changes of nano‐crystalline SrWO4

Large‐scale high‐quality SrWO₄ nanocrystals have been synthesized in aqueous solutions under mild hydrothermal conditions with citrate as a simple additive. The crystals undergo an interesting 0‐D to 1‐D and to 0‐D morphology changes and have been characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. The results showed that the experimental parameters had great influences on the shape evolution of products. The adjustment of these parameters such as the addition of the citrate and hydrothermal reaction conditions, can lead to obvious morphology changes of products, and the growth mechanism has been proposed. Room‐temperature photoluminescence indicated that the as‐prepared SrWO₄ nanocrystals had strong emission peaks at about 434 and 506 nm, respectively. This facile route could be employed to synthesize more promising nanomaterials with interesting self‐assembly structures. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Capsule‐like α‐Fe2O3 nanoparticles: Synthesis,characterization, and growth mechanism

Uniform capsule‐like α‐Fe₂O₃ particles were synthesized via a simple hydrothermal method, employing FeCl₃ and CH₃COONa as the precursors and sodium dodecyl sulfate (SDS) as soft template. X‐ray powder diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), and high‐resolution transmission electron microscopy were used to characterize the structure of synthesized products. Some factors influencing the formation of capsule‐like α‐Fe₂O₃ particles were systematically investigated, including different kinds of surfactants, the concentration of SDS, and reaction times. The investigation on the evolution formation reveals that SDS was critical to control the morphology of final products, and a possible five‐step growth mechanism was presented by tracking the structures of the products at different reaction stages.     

Facile solvothermal synthesis,growth mechanism and thermoelectric property of flower‐like Bi2Te3

Hierarchical flower‐like Bi₂Te₃ was synthesized through a facile solvothermal method. The crystal structure and morphology of the as‐prepared samples were characterized by X‐ray diffraction (XRD), filed emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and high resolution TEM. The reaction parameters such as reaction time, the amount of glucose, concentration of NaOH and the reaction temperature were systematically investigated. Based on the FESEM observations, a possible mechanism defined as a self‐assembly process accompanied by anisotropic growth mechanism was proposed. Moreover, the thermoelectric properties were measured at the temperature range of 300–600 K. The hierarchical flower‐like Bi₂Te₃ presented good thermoelectrical properties. The maximum ZT value reached up to 0.6 at 600 K, which was higher than that of Bi₂Te₃ nanoparticles.     

Catanionic surfactants assisted synthesis of dilead pentaoxochromate nanorods

Single‐crystalline dilead pentaoxochromate (Pb₂CrO₅) with nanorod‐shape has been synthesized by adjusting the pH value of the catanionic reverse micelles formed by a cationic surfactant CTAB (hexadecyltrimethylammonium bromide) and an anionic surfactant SDS (sodium dodecyl sulfonate), followed by a hydrothermal process. The results show that reaction parameters play important roles in the formation of the single‐crystalline Pb₂CrO₅. The reaction parameters include the kinds of the surfactants, the molar ratio (r) between the mixed cationic and anionic surfactants, reaction time and temperature. The as‐synthesized products are characterized by transmission electron microscopy (TEM), high‐resolution transmission electron microscopy (HRTEM) and powder X‐ray diffraction (XRD). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A simple glucose reduction route for the synthesis of sheet‐like copper dendrites

In the current paper we designed a simple glucose reduction route for synthesis of sheet‐like Cu dendrites on a high yield, using CuSO₄ as the starting material. The reaction was carried out at 180 °C for 18 h in the absence of any structure‐directing agent. The product was characterized by X‐ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and electron diffraction (ED). Some factors influencing the shapes of Cu microcrystals, including the reaction temperature, time, and the concentration of the starting CuSO₄, were investigated. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structure and photoluminescence properties of SrWO4 3D microspheres synthesized by the surfactant‐assisted hydrothermal method

In this paper, we report large‐scale high‐quality SrWO₄ 3D microspheres synthesized in aqueous solutions under mild conditions with cetyl trimethyl ammonium bromide as a simple cationic surfactant. These crystals have been characterized by X‐ray diffraction, transmission electron microscopy and field emission scanning electron microscopy techniques. The crystal growth processes were employed to investigate the formation mechanism of SrWO₄ 3D microspheres. Room‐temperature photoluminescence indicated that the as‐prepared SrWO₄ 3D microcrystals had strong emission peaks at about 432 and 505 nm, respectively.     

Controllable synthesis of hierarchical strontium molybdate by sonochemical method

Large‐scale chrysanthemum‐like strontium molybdate (SrMoO₄) with hierarchical structure has been successfully synthesized via a facile and fast ultrasound irradiation approach at room temperature. By varying the experimental conditions, SrMoO₄ with different morphologies, such as spindles, peanuts, spheres, and rods, can be obtained. The products are characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected‐area electron diffraction (SAED). The influent parameters including concentration, pH value, and surfactants have been investigated. A possible growth mechanism is proposed and the shape evolution of the products is characterized. The as‐prepared chrysanthemum‐like SrMoO₄ particles are used as the precursor for electrorheological fluid and their electrorheological property is investigated.     

Controlled synthesis of various morphologies of nanostructured zinc oxide: flower,nanoplate, and urchin

Nanoplates, flower‐like nanostructure of ZnO were successfully synthesized by employing ZnSO₄·7H₂O, NaOH as the starting materials at 120°C under hydrothermal condition. Keeping the same parameters, ZnO urchin shape was obtained by addition of vitamin C at 190°C. Characterizations were carried out by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) at room temperature. Selected area electron diffraction (SAED) pattern confirms that the product is single crystalline nature. The possible formation mechanisms for synthesized ZnO nanosturcture with various morphologies have also been proposed. PL spectrum from the ZnO flower‐like structures reveals weak UV emission and strong green emission. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Surfactant‐assisted synthesis of novel star‐like PbWO4 hierarchical architectures

Large‐scale star‐like PbWO₄ hierarchical architectures were controllably synthesized by a facile surfactant‐assisted technology under mild conditions in the presence of a mixed solvent of ethylene glycol and water. The morphology, structure, and phase composition of PbWO₄ architectures were characterized by X‐ray diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), field emission transmission electron microscopy (FE‐TEM), and nitrogen adsorption‐desorption isotherms. The possible formation mechanism of the star‐like PbWO₄ architectures (initial nucleating stage and a subsequent self‐assembly stage) was proposed based on the observations from a time‐dependent morphology evolution process, which may pave the way to shape‐controlled synthesis of inorganic nanocrystals with the complex structures. This route provides a facile strategy to fabricate complex hierarchical PbWO₄ structures. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A template‐free route for controlled synthesis of dumbbell‐like Sb2S3 microcrystals

Large amounts of dumbbell‐like Sb₂S₃ microcrystals were synthesized via a simple solvothermal treatment method. Various techniques such as x‐ray diffraction (XRD), field‐emission scanning electron microscope (FESEM), high‐resolution transmission electron microscope (HRTEM), selected area electron diffraction (SAED), and photoluminescence spectrometry (PL) have been used to characterize the obtained products. The results showed that the products belong to the orthorhombic Sb₂S₃ phase, and the dumbbell‐like Sb₂S₃ microcrystals were composed by uniform microrods. Besides, the morphologies of Sb₂S₃ microcrystals could be changed from microshperes to dumbbell‐like microcrystals by only adjusting the reaction solvent. The solvent effects are discussed in detail. Furthermore, the PL properties of the obtained Sb₂S₃ microcrystals clearly show shape effects. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Solvothermal growth of single‐crystal hexagonal prismatic SrCO3 microrods

Single‐crystal hexagonal prism SrCO₃ microrods have been prepared by a simple solvothermal route. The effects of the reaction time, the content of 1,2‐propanediol and the reactants mass on the products have been investigated, respectively. The as‐synthesized microrods were characterized by X‐ray powder diffraction (XRD), field‐emission scanning electron microscopy (FE‐SEM) and transmission electron microscopy (TEM). The results reveal that the products have uniform shape and excellent monodispersity. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Monodisperse CeO2 sub‐micro spherical aggregates with controllable building blocks

Monodisperse CeO₂ spherical aggregates with diameters ranging from 200 to 300 nm have been successfully synthesized through a facile hydrothermal method. The structure and morphology of the samples were characterized by powder X‐ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and field‐emission scanning electron microscopy (FE‐SEM). The building blocks (primary nanocrystals) of the spherical aggregates could be effectively tuned by adding different amount of urea. Furthermore, N₂ adsorption/desorption experiment displays a gradual increase of BET surface areas of spherical aggregates with increasing the amount of urea. Finally, the formation mechanism of CeO₂ spherical aggregates was preliminarily discussed. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of superconducting sphere‐like Mo2C nanoparticles in an autoclave

Sphere‐like Mo₂C nanoparticles have been synthesized through the reaction of sodium molybdate, anhydrous ethanol and sodium azide at 450 °C for 10 h in a sealed stainless steel autoclave. X‐ray powder diffraction results indicated that the final product was Mo₂C. Transmission electron microscopy (TEM) and scanning elctron microscopy (SEM) were employed to characterize the as‐prepared sample. The sample was mostly composed of sphere‐like particles, which has a superconducting transition temperature of 9.5 K, and its calculated surface area is 30.859 m²/g. The experimental parameters such as reaction temperature and reactants were studied to investigate the reaction mechanism. It was found that sodium azide and reaction temperature played key roles in the formation of sphere‐like Mo₂C nanoparticles. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and growth mechanism of ZnO rod‐like nanostructures by a microwave‐assisted low‐temperature aqueous solution route

A zinc oxide (ZnO) nanoarray (rod‐like nanostructure) was successfully synthesized through a low‐temperature aqueous solution and microwave‐assisted synthesis using zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O) and hexamethylenetetramine (HMTA) as raw materials, and using FTO glass as substrate. The effects of parameters in the preparation process, such as solution concentration, reaction temperature and microwave power, on the morphology and microstructure of ZnO nanoarray were studied. Phase structure and morphology of the products were characterized by X‐ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results indicated that hexagonal wurtzite structure ZnO nanoarray with good crystallization could be prepared through a low‐temperature solution method. When the concentration of the mixed solution was 0.05 M, the reaction temperature was 95 °C, and the reaction time was 4 h, high‐density ZnO regular nanorods of 200 nm diameter were obtained. A possible mechanism with different synthesis methods and the influence of microwave processing are also proposed in this paper.     

Hydrothermal conversion of ZnO2 to ZnO flowers: A mechanistic investigation and characterization

In this article, we report a novel but simple method for the phase transformation of ZnO₂ to flower‐like ZnO microstructures hydrothermally at 90 °C with and without the assistance of hexadecylamine as surfactant. The generation of zincate ion ZnO$^{2-}_{2}$ as a growth unit from the reaction between ZnO₂ and peroxide ion O$^{2-}_{2}$ in situ plays a key role in the phase transformation of ZnO₂ to ZnO. The morphology, structure, and composition of the products have been investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Powder X‐ray diffraction (PXRD) and energy dispersive X‐ray analysis (EDX). It has been demonstrated that the as‐fabricated ZnO flowers are composed of self‐assembled brooms and rods in the presence and absence of hexadecylamine respectively. On the basis of experimental results, a possible reaction mechanism and the growth processes involved in the formation of flower‐like ZnO microstructures are discussed.     

Synthesis and characterization of strontium chloroborate whiskers

Single crystalline strontium chloroborate (Sr₂B₅O₉Cl) whiskers with uniform diameter have been synthesized by a facile route based on the calcination of precursor. The precursor was prepared by the sedimentation reaction between SrCl₂ and Na₂B₄O₇ aqueous solution. The products were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared spectrum (FT‐IR). An optimal synthesis temperature for preparing Sr₂B₅O₉Cl whiskers was obtained, and the possible formation process was also presented.     

On the morphology of BaMoO4 crystals: A theoretical and experimental approach

BaMoO₄ crystals were obtained by a co‐precipitation method, and their structures were characterized by X‐ray diffraction and Rietveld refinement techniques. Field emission scanning electron microscopy was utilized to investigate the morphology of the as‐synthesized aggregates.‐ Through systematic first principle calculations within the density functional theory method at the B3LYP level, we investigated the structure; the surface stability of the (001), (101), (110), (100), (111), and (112) surfaces; and the morphological transformations of BaMoO₄. The relative surfaces energies were further varied to predict a complete map of the available morphologies through a Wulff construction approach. This revealed that the obtained experimental and theoretical morphologies coincided when the surface energy values of the (001) surface decreased while those of the (100) and (101) facets increased simultaneously. Analysis of the surface structures showed that the electronic properties were associated with the presence of undercoordinated [BaO_x] (x = 4, 5, and 6) and [MoO_y] (y = 3) clusters. The presented results provide a comprehensive catalog of the morphologies most likely to be present under realistic conditions, and will serve as a starting point for future studies on the surface chemistry of BaMoO₄ crystals.     

Synthesis via an organic molten salt solvent route and characterization of PbS nanocrystals

In this paper, four petals flowers‐like and quasi sphere‐like PbS nanostructures were successfully synthesized by an environment friendly organic molten salt solvent (OMSS) route at 200 °C, with different sulfur sources, e.g. thiourea and sodium thiosulfate, respectively. The as‐synthesized products were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), UV–vis absorption spectrum and photoluminescence (PL) spectrum, respectively. It was shown that four petals flowers‐like and quasi sphere‐like PbS nanocrystals were formed. It was also demonstrated that the morphologies of PbS nanocrystals were significantly influenced by different sulfur sources. The ultraviolet‐visible absorption peaks of PbS nanocrystals exhibited a large blue‐shift and the luminescence spectra had strong and broad emission bands centered at 488 nm and 492 nm. The possible formation mechanisms of the PbS nanostructures were discussed. The organic molten salt solvent (OMSS) method is preferable for synthesizing high‐quality PbS nanocrystals. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Low temperature synthesis of spindle‐like ZnO nanostructures under microwave irradiation

A simple and general microwave route is developed to synthesize nanostructured ZnO using Zn(acac)₂·H₂O (acac = acetylacetonate) as a single source precursor. The reaction time has a great influence on the morphology of the ZnO nanostructures and an interesting spindle‐like nanostructure is obtained. The microstructure and morphology of the synthesized materials are investigated by X‐ray diffraction (XRD), scanning electron microscopy (SEM), field‐emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high‐resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). It is found that all of them with hexagonal wurtzite phase are of single crystalline structure in nature. Ultraviolet–visible (UV‐vis) absorption spectra of these ZnO nanostructures are investigated and a possible formation mechanism for the spindle‐like ZnO nanostructures is also proposed.     

Preparation of shuttle‐like Sb2S3 nanorod‐bundles via a solvothermal approach under alkaline condition

Uniform shuttle‐like Sb₂S₃ nanorod‐bundles were synthesized via a polyvinylpyrrolidone (PVP) assisted solvothermal approach under alkaline condition, using antimony chloride (SbCl₃) and thiourea (CH₄N₂S, Tu) as the starting materials in ethanol. The phase structure, composition and morphology of the product were characterized by means of X‐ray diffraction (XRD), energy dispersive X‐ray spectrometry (EDS), transmission electron microscopy (TEM), and high‐resolution transmission electron microscopy (HRTEM). XRD and EDS results confirm that the synthesized Sb₂S₃ nanorod‐bundles have an orthorhombic structure and an atomic ratio of 3:2 for S:Sb. TEM and HRTEM results show that the shuttle‐like Sb₂S₃ bundles are composed of nanorods with a size distribution of 20‐40 nm and growing along c‐axis. Furthermore, experiments under different reaction conditions were carried out and the mechanism for the growth of nanorod‐bundles was discussed (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)