Low‐temperature urea‐assisted hydrothermal synthesis of Bi2S3 nanostructures with different morphologies

Different morphologies of single‐crystalline orthorhombic phase bismuth sulfide (Bi₂S₃) nanostructures, including sub‐microtubes, nanoflowers and nanorods were synthesized by a urea‐assisted hydrothermal method at a low temperature below 120 °C for 12 h. The as‐synthesized powders were characterized by X‐ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high‐resolution transmission electron microscopy (HRTEM) and UV‐vis spectrophotometry. The experimental results showed that the sulfur sources had a great effect on the morphology and size of the resulting powders. The formation mechanism of the Bi₂S₃ nanostructures with different morphologies was discussed. All Bi₂S₃ nanostructures showed an appearance of blue shift relative to the bulk orthorhombic Bi₂S₃, which might be ascribed to the quantum size effect of the final products. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystallization of silicon thin films by current‐induced joule heating using a tungsten overcoat

A modified crystallization process using current‐induced joule heating under vacuum is presented. A thin layer of high temperature resistant tungsten was sputtered on the amorphous silicon as the conducting and annealing medium. The thin film thickness was measured by α‐stepper. The high current density provided effective means in crystallizing the amorphous silicon layer. The crystalline morphology was studied by scanning electron microscopy (SEM) after Secco‐etch, transmission electron microscopy (TEM), and x‐ray diffraction (XRD), under different annealing conditions. The grain size was controlled in the range of 0.1‐0.5 μm and could be increased with annealing time. No tungsten silicide was found. Some defects were formed due to electron‐migration effect near the electrodes. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Facile hydrothermal synthesis of uniform 3D γ‐AlOOH architectures assembled by nanosheets

Uniform γ‐AlOOH architectures assembled by nanosheets were successfully synthesized in the mixture of deinonized water and dimethyl sulfoxide (DMSO) at 180 °C. The structure and morphology of products were characterized by X‐ray diffraction analysis (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The products displayed 3D microstructures with its length of 1 μm and diameter of 400‐500 nm. The obtained γ‐AlOOH structures exhibited large Brunauer‐Emmett‐Teller (BET) surface area of 216.5 m²/g and pore size of 3.7 nm. The formation mechanism of 3D γ‐AlOOH architectures was also discussed based on the experimental results. Furthermore, the γ‐AlOOH architectures exhibited preliminary photoluminescence (PL) phenomenon with a strong peak at 323 nm. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Different copper oxide nanostructures: Synthesis,characterization, and application for C‐N cross‐coupling catalysis

Cupric oxide and cuprous oxide micro‐/nanomaterials with well‐controlled sizes and morphologies have been synthesized via different crystal growth techniques. Structural and morphological characterizations of these copper oxide micro‐/nanomaterials were performed by X‐ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). After that, these copper oxide micro‐/nanomaterials were used as catalysts for a typical C‐N cross‐coupling reaction directly. The catalytic results showed that different copper oxide micro‐/nanomaterials had different catalytic activities in C‐N cross‐coupling reaction. The particle size of cupric oxide and the oxidation state of copper played vital roles in the catalytic process. Cupric oxide with small particle size has the best catalytic activity, while cupric oxide with different morphologies has almost the same yields and cuprous oxide has very poor yields. Further, the possible catalytic mechanism for copper oxide nanomaterials catalyzed cross‐coupling reaction was proposed. And the influence of particle size and oxidation state was carefully discussed. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Zr‐doped CeO2 Hollow slightly‐truncated nano‐octahedrons: One‐pot synthesis,characterization and their application in catalysis of CO oxidation

Zirconium‐doped ceria hollow slightly‐truncated nano‐octahedrons (HTNOs) (Ce_1‐xZr_xO₂) were synthesized by a one‐pot, facile hydrothermal method. The morphology and crystalline structure were characterized with powder X‐ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and the high resolution transmission electron microscopy (HRTEM). The composition and chemical valence on the surface of the as‐prepared Ce_1‐xZr_xO₂ powders were detected by X‐ray photoelectron spectroscopy (XPS) and energy dispersive spectrometry (EDS). The surface area and pore size distribution of as‐obtained Zr‐doped ceria HTNOs were measured by N₂ adsorption‐desorption measurement. Mechanisms for the growth of Zr‐doped ceria HTNOs are proposed as both oriented attachment and Ostwald ripening process and the formation of the hollow structure is strongly dependent on the addition of Zr⁴⁺ ions. Furthermore, the as‐obtained Zr‐doped ceria HTNOs revealed superior catalytic activity and thermal stability toward CO oxidation compared to pure ceria. It may provide a new path for the fabrication of inorganic hollow structures on introducing alien metal ions.     

Facile synthesis and characterization of hierarchical CuO nanoarchitectures by a simple solution route

The controlled synthesis of hierarchical CuO nanomaterials in a solution phase has been realized with high yield at low temperature using copper acetate hydrate and NaOH as starting materials with the assistance of surfactant under hydrothermal conditions. X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ultraviolet‐visible spectroscopy (UV‐Vis) were used to characterize the products. It was shown that the hierarchical CuO nanoarchitectures were formed through aggregation of tiny single‐crystal CuO nanorods. Experiments demonstrated that the morphology of CuO products was significantly influenced by hydrothermal temperature and reaction time. A rational growth mechanism based on oriented attachment was proposed for the selective formation of the hierarchical CuO nanoarchitectures. Our work demonstrated the growth of hierarchical CuO nanoarchitectures built from one‐dimentional nanorods through a one‐step solution‐phase chemical route under controlled conditions. In addition, The UV‐Vis spectrum of the hierarchical CuO nanoarchitectures showed large blue shift because of the quantum size effect. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Facile morphology‐controlled hydrothermal synthesis of flower‐like self‐organized ZnO architectures

Flower‐like self‐organized crystalline ZnO architectures were obtained through a facile and controlled hydrothermal process. As‐synthesized products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high‐resolution transmission electron microscopy (HRTEM), X‐ray diffraction (XRD), electron diffraction and UV‐Vis spectroscopy. XRD and electron diffraction results confirmed the obtained materials are pure wurtzite ZnO. The effects of different ratios of starting materials and solvent on the morphologies of ZnO hydrothermal products were also evaluated by SEM observations. It is suggested that the use of water, rather than ethanol as the solvent, as well as employing a precursor of Zn(Ac)₂ and 2NaOH (v/v) in hydrothermal reactions are responsible for the generation of specific flower‐like self‐assembled ZnO structures. (© 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.     

PMA‐b‐PAA‐controlled synthesis of one‐dimensional CaCO3 superstructures

Crystallization of calcium carbonate (CaCO₃) crystals by a gas‐liquid diffusion method has been carried out in aqueous solution using a double‐hydrophilic block copolymer (DHBC) poly(maleic anhydride)‐b‐poly(acrylic acid) (PMA‐b‐PAA). The as‐prepared products were characterized with X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), selected area electron diffraction (SAED), high‐resolution transmission electron microscopy (HRTEM) and infrared spectroscopic analysis (FT‐IR). Uniform one‐dimensional calcite micro/nanostructures with different morphologies are fabricated through an assembled process. The influence of PMA‐b‐PAA copolymer concentration on the morphology of calcite nano/microwires is investigated, which plays an important role in the morphological control of building blocks composed of one‐dimensional calcite crystals. The possible formation mechanism of one‐dimensional CaCO₃ crystals was discussed. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Controlled synthesis of ZnO nanostructures with different morphologies in microemulsions

ZnO nanostructures with different morphologies were prepared in microemulsions with ZnSO₄ and ammonia as raw materials. The effects of microemulsion types, concentration of reactants, W values, co‐surfactants, surfactants, oil phases and calcination temperatures were systematically studied. The products were characterized by X‐ray diffraction (XRD), differential scanning calorimetry and thermogravimetry (DSC‐TG), transmission electron microscopy (TEM), high‐resolution TEM (HRTEM), and photoluminescence (PL) spectrum. Results show that ZnO nanoparticles were obtained in water‐in‐oil microemulsions while ZnO nanorods are gained in bicontinuous microemulsions. Water‐in‐oil microemulsions and long carbon chains of surfactants can prevent the preferential growth of ZnO. The particle size of the products increased with the increase of W values, calcination temperatures and the concentration of reactants but decreased with the increase of the carbon chain length of surfactants, co‐surfactants and oil phases. PL spectrums show that the UV emission peak weakened and visible emission peak increased with the decrease of particle size. Meanwhile, the PL spectrums have a little red‐shifted.     

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)     

Stability of ruthenium nanoparticles synthesized by solvothermal method

One of the major obstacles to the synthesis of nanoparticles and nanocatalyst is the stability of particles. In the present study, polymer stabilized ruthenium nanoparticles were synthesized by solvothermal method using solutions of ruthenium chloride in ethylene glycol in presence of poly(N ‐vinyl‐2‐pyrrolidone) (PVP) as a stabilizing agent. Stability of nanoparticles was studied by varying different parameters e.g. PVP/RuCl₃ molar raio, RuCl₃ concentration, reaction temperature and time and expressed in terms of particle size and size distribution. Transmission electron microscope (TEM) analysis revealed the presence of metallic clusters with a uniform size of about 20‐65 nm. Dispersion destabilisation of colloidal nanoparticles was detected by Turbiscan. Polymer stabilized ruthenium nanoparticles were dispersed on γ‐alumina to prepare uniformly disperse Ru/γ‐Al₂O₃ catalyst by mechanical strirring and sonication. Inductively coupled plasma‐optical emission spectroscopy (ICP‐OES), X‐Ray powder diffraction (XRD), Transmission electron microscopy (TEM) and Thermo gravimetric analysis (TGA) were used to characterize the supported catalyst. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Self‐template hydrothermal synthesis ZnS microspheres

Zinc sulfide (ZnS) microspheres were synthesized by a self‐template hydrothermal route using thiourea as sulphur source. The formation of these hollow spheres was mainly attributed to the oriented aggregation of ZnS nanocystals around the gas‐liquid interface between gas (H₂S, NH₃, or CO₂) and water followed by an Ostwald ripening process. The gas bubbles of H₂S, NH₃, or CO₂ produced during the reaction might play a soft‐template to form ZnS hollow microspheres. The products were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), electron diffraction (ED), and photoluminescence (PL). The crystal structure of prepared ZnS microspheres is hexagonal phase polycrystalline. The average microspheres diameter is 1.5 ‐ 6 µm. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Simple extraction‐solvothermal synthesis of single‐crystalline silver microplates

Single‐crystalline silver microplates, with average edge length of about 1.5 μm and thickness of 100 nm, have been synthesized by a simple extraction‐solvothermal method. Samples were characterized in detail by X‐ray diffraction (XRD), field‐emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM) and High‐resolution transmission electron microscopy (HRTEM) technologies. Extractant primary amine N1923 can also act as reducing agent. It has been found that microstructure of the silver can be controlled by the n‐octanol during the solvothermal treatment. Based on a series of experimental analysis, the possible formation mechanism of these microplates was discussed briefly. (© 2009 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)     

Hydrothermal synthesis of hollow twinning ZnO microstructures

Two kinds of hollow twinning ZnO microstructures were synthesized through a simple hydrothermal method without additional templates or any surfactants. Dumbbell‐like and shuttle‐like ZnO microstructures with hollows were obtained by changing the materials source. The products were characterized by X‐ray power diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high‐resolution transmission electron microscopy (HRTEM). It was found that different precursors may be responsible for the formation of two different morphologies. Based on the time‐dependent experiments, we investigated the growth process of these hollow twinning structures and found the “Ostwald‐ripening process” played an important role. The interesting point of this growth process was that the interface of the two twinning structure performed as the activate center where the Ostwald‐ripening process carried out. We also investigated the luminescent properties of the as‐obtained products by photoluminescence (PL) spectroscopy. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and characterization of semiconductor metal sulfide nanocrystals using microemulsion technique

The semiconductor nanocrystals ZnS, PbS, CdS and CuS were synthesized via microemulsion technique involving metal acetate, reducing agent (Na₂S) and Triton X‐100 as surfactant. Nanocrystals were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM) and dynamic light scattering (DLS). The average size of ZnS, PbS, CdS and CuS nanocrystals were found to be 5.6 nm, 13.3 nm, 11.4 nm and 6.2 nm, respectively. Different parameters like surfactant (Triton X‐100) concentration, water‐to‐surfactant ratio (ω), precursor concentration [zinc acetate, (Zn(AC)₂], reducing agent concentration [sodium sulphide, (Na₂S)] were optimized to synthesize ZnS quantum dots.     

Synthesis,characterization and gas sensing properties of flowerlike In2O3 composed of microrods

Flowerlike structured In₂O₃ were successfully synthesized via a hydrothermal process and the subsequent calcinations. The obtained sample consists of microrods with an average diameter of 0.5‐1 μm and a length of 1‐3 μm. Structure and property of the sample were characterized by X‐ray powder diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The sensing properties towards trimethylamine (TMA) were examined at 200‐400 °C, which showed high sensitivity, better selectivity, and prompt response/recovery merits. (© 2010 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.     

Fabrication of ferric oxide/reduced graphene oxide/cadmium sulfide heterostructure photoelectrode for enhanced photoelectrochemical performance

A novel high‐efficiency photoelectrode (Fe₂O₃/reduced graphene oxide/CdS) built from heterostructure and conductive scaffold has been successfully designed and synthesized. Reduced graphene oxide works as a “bridge” which benefits for electron and hole transport. The obtained heterostructure photoelectrodes were systematically characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy, and X‐ray photoelectron spectroscopy (XPS). The photoconversion efficiency (η) and photocurrent densities vs. time (I‐t) curves responding to monochromatic lights have been further investigated in‐depth, which reveals that introduction of CdS and reduced graphene oxide played an important role in the enhancement of photoelectrochemical performance.