Preparation of calcium carbonate crystals in the presence of trisodium citrate

The dumbbell‐like calcium carbonate (CaCO₃) crystals were synthesized in the presence of trisodium citrate. Different morphologies were obtained by changing the reaction temperature and the trisodium citrate concentration. The obtained samples were characterized by means of X‐ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the morphology of CaCO₃ crystals was markedly affected by the reaction temperature and citrate anion concentration. The possible growth mechanism of CaCO₃ crystals was proposed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of rhombohedral strontium carbonate aggregates at the water/hexamethylene interface with cetyltrimethylammonium bromide

Unusual rhombohedral strontium carbonate (SrCO₃) aggregates have been synthesized in situ from strontium nitrate by the slow release of carbon dioxide by alkaline hydrolysis of diethyl carbonate at the water/hexamethylene interface in the presence of cetyltrimethylammonium bromide (CTAB). Transmission electron microscopy, Fourier transform infrared spectroscopy and X‐ray powder diffractometry were used to characterize the products. The results indicate that rhombohedral SrCO₃ aggregates are obtained with weaker crystallinity and sizes of several micrometers. The possible formation mechanism of the SrCO₃ aggregates at the interface is discussed, which can be interpreted by particle‐aggregation based non‐classical crystallization laws. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

PSSS‐controlled synthesis of CaCO3 superstructures

Complex CaCO₃ superstructure can be easily synthesized by using poly (sodium 4‐styrenesulfonate) (PSSS) as a structure directing agent to direct the controlled precipitation of calcium carbonate from aqueous solution. The products were characterized by scanning electron microscopy (SEM), and powder X‐ray diffraction (XRD) analysis. The results revealed that the morphology of the products changed significantly with the increasing of the concentration of PSSS in solution, from rhombohedral particles to plate‐packed aggregates to spheres with smooth surface, to sponge‐like spheres and finally to complex spherical superstructure consisted of plate‐like sub‐units. We hypothesize that the observed sequential changes in morphology of CaCO₃ particles with added PSSS concentration may be due to the influence of PSSS on nucleation, growth and aggregation of CaCO₃ crystals. The formation mechanisms of CaCO₃ crystals with different morphologies were discussed. (© 2007 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.     

Solvothermal synthesis and good electrochemical property of pinetree like Bi2S3

Hierarchical pinetree like Bi₂S₃ was synthesized through a facile solvothermal route in the mixture of deionized water and tetrahydrofuran. The phase composition, morphology, and structure of the as‐prepared Bi₂S₃ products were characterized by using various techniques including X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). It was found that the pinetree like Bi₂S₃ structures were composed of numerous assembled nanosheets, which had uniform morphology with the mean width and length of about 110 nm and 15 μm, respectively. Furthermore, the electrochemical property of the obtained pinetree like Bi₂S₃ was investigated. The pinetree like Bi₂S₃ presented both the high electrochemical hydrogen storage and electrochemical Li intercalation performance.     

Hydrothermal synthesis of nano‐crystalline BaMoO4 under mild conditions using simple additive

Large‐scale high‐quality BaMoO₄ nanocrystals have been synthesized in aqueous solutions under mild conditions with citrate as a simple additive. The crystals have bone‐like, spindle‐like and wheatear‐like morphologies assembled from nanoparticles, nanofibers and have been characterized by X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) techniques. The results showed that experimental parameters had great influences on the shape evolution of products. The adjustment of these parameters such as room temperature stirring time, reaction temperature and reaction time of hydrothermal reaction, can lead to obvious morphology changes of products, and the growth mechanism has been proposed. Room‐temperature photoluminescence indicated that the as‐prepared BaMoO₄ nanocrystals had a strong blue emission peak at 481.5 nm. This facile route could be employed to synthesize more promising nanomaterials with interesting self‐assembly structures. (© 2010 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.     

On the crystallochemical origin of the disordered form of Ba7(EuII)F12Cl2 and the structural changes induced at high temperature

The crystal structure of the disordered modification of Ba₇F₁₂Cl₂ has been carefully re‐examined on several new crystals prepared under different conditions of synthesis. All single crystal structure refinements reveal a residual electron density of ∼3 e^–/ų in the 0,0,0 position which is explained by the introduction of a small amount of sodium ions in the crystal. The title compound transforms from a disordered to an ordered modification at ∼800 °C. New structural data show a change in space group from P6₃/m to P6. During this process, a slight chemical change and the formation of nano‐channels in the crystals is observed by electron microscopy. These changes were further studied by electron microprobe analysis, by spectroscopic methods and thermal analysis. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Flux growth of straw‐like rutile monocrystals

Millimetric straw‐like rutile monocrystals were grown by the flux growth technique. A suitable mixture of flux (MoO₃, V₂O₅, Li₂CO₃) and amorphous TiO₂ gel was slowly cooled down to 750°C from 1250°C or 1350°C. The best yields of straw‐like rutile were obtained with a nutrient/flux ratio and a cooling rate in the range 0.015‐0.006 and 1.8‐1.9 K h^‐1, respectively. The hollowed crystals were characterized by powder and single‐crystal X‐ray diffraction, scanning electron microscopy, microthermometry, and µ‐Raman spectroscopy. As for skeletal crystal, the formation of axial canals in rutile is attributed to a lack of nutrient due to the viscosity of the melt and the high growth rate along [001]. (© 2008 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)     

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)     

Bioinspired synthesis of morphologically controlled SrCO3 superstructures by natural gum acacia

Crystallization of strontium carbonate is performed in aqueous solution using Gum Acacia (GA) as crystal growth modifier. A novel study of hierarchical assembly, specifically interacting inorganic and natural component without introduction of other additives was studied. SrCO₃structures exhibiting the morphologies of well defined nanocrystallites in the form of clusters of hexagonal rods, flower shaped, cross like, doughnut shaped and rice grain shaped are identified by optimizing the conditions and concentration of GA. In continuation, morphology was also examined for mixed metal carbonates (Sr‐LaCO₃, Sr‐TbCO₃). The results indicate that –OH, –COOH and ‐NH₂ functional group moieties of GA play a remarkable role in inhibiting growth morphology of metal carbonates and mixed metal carbonates. Structural characterization of the synthesized materials was investigated by Powder X‐ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive analysis (EDAX), Transmission electron microscopy (TEM), Thermogravimetric analysis (TGA) coupled Mass (MS) and Fourier transform infrared spectroscopy (FT‐IR). This synthesis method can be easily extended to a variety of inorganic nanoparticles, thereby enabling exact control over material properties. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Facile synthesis and assembly of CuS nano-flakes to novel hexagonal prism structures

Highly ordered hexagonal prism microstructures of copper sulfide (CuS) by assembling nano-flakes have been synthesized with high yield via a facile one-step route. We synthesized CuS microstructures using low cost beginning materials CuSO₄·5H₂O and Na₂S₂O₃·5H₂O under lower reaction temperature (60 °C). Hexamethylinetetramin (C₆H₁₂N₄, HMT) was introduced into the reaction system as a capped agent. The influence of reaction time and capping agent (HMT) on the final structure of products was studied systematically. The obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopes (EDS), and transmission electron microscopy (TEM). The possible mechanism for the formation of the interesting highly ordered hexagonal prism microstructures CuS was also proposed.     

Hierarchical strontium carbonate submicron spheres self‐assembled under hydrothermal conditions

Uniform hierarchical strontium carbonate (SrCO₃) submicron spheres bearing detectable cavities on the surfaces and porous structures within the body were efficiently obtained, by a facile hydrothermal treatment (190 °C, 12 h) of the room temperature precipitate derived from Na₂CO₃ and SrCl₂ solution. MgCl₂ and ethylene diamine tetraacetic acid (EDTA) disodium salt were used as the additives. The as‐obtained submicron spheres were self‐assembled by crystalline SrCO₃nanoparticles under hydrothermal conditions. The present hydrothermally synthesized hierarchical SrCO₃ submicron spheres would enlarge the potentials of SrCO₃ micro‐/nanostructures in the hierarchical architectures and porous materials family for further applications in the fields of catalysis, composites, adsorbents, and devices, etc. (© 2010 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)     

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)     

Well‐defined Sb2S3 nanostructures: citric acid‐assisted synthesis,electrochemical hydrogen storage properties

Well‐defined (three‐dimensional) 3‐D dandelion‐like Sb₂S₃ nanostructures consisted of numerous nanorods have been achieved via a facile citric acid‐assisted solvothermal process. The as‐prepared products were characterized by X‐ray diffraction (XRD), field‐emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and high‐resolution TEM (HRTEM), respectively. The influence factors of the formation of the hierarchical Sb₂S₃ nanostructures are discussed in details based on FESEM characterizations. By simply controlling the quantity of citric acid, the nucleation and growth process can be readily tuned, which brings the different morphologies and nanostructures of the final products. On the basis of a series of contrastive experiments, the aggregation‐based process and anisotropic growth mechanism are reasonably proposed to understand the formation mechanism of Sb₂S₃ hierarchical architectures with distinctive morphologies including nanorods, and dandelion‐like nanostructures. Charge‐discharge curves of the obtained Sb₂S₃ nanostructures were measured to investigate their electrochemical hydrogen storage behaviors. It revealed that the morphology played a key role on the hydrogen storage capacity of Sb₂S₃ nanostructure. The dandelion‐like Sb₂S₃ nanostructures exhibited higher hydrogen storage capacity (108 mAh g⁻¹) than that of Sb₂S₃ nanorods (95 mAh g⁻¹) at room temperature.     

Growth of calcium oxalate crystals induced by complex films containing biomolecules

Nucleation and growth of calcium oxalate (CaC₂O₄) crystals induced by films composed of phosphatidylcholine (PC), cholesterol (CS) and human serum albumin (HSA), and of PC, CS and dextran have been carried out. The products obtained were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and ultraviolet‐visible spectroscopy. The results indicate that hexagonal calcium oxalate monohydrate (COM) and club‐shaped calcium oxalate trihydrate (COT) crystals are obtained on the PC/CH/HSA film, and the microstructure and properties of the PC/CH/HSA film depend on the weight ratio of PC to CS. With an increase in the PC‐to‐CS ratio, the number of COM crystals decreases gradually, and finally disappear, suggesting that PC inhibits the growth of COM crystals. On the PC/CS/dextran film, irregular COM and COT crystals are formed. The possible formation mechanisms of CaC₂O₄ on the two complex films are discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Ag@Fe3O4 nanowire: fabrication,characterization and peroxidase‐like activity

With a facile solvothermal method, Ag@Fe₃O₄ nanowire was successfully prepared and characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The obtained Ag@Fe₃O₄ nanowire posses enhanced peroxidase‐like activity with good stability and high absorbance. The optimization of pH, H₂O₂ concentration and loading capacity were carried out. The result of kinetic analysis indicates that the catalyzed reaction followed a Michaelis‐Menten behavior. The good peroxidase‐like activity makes Ag@Fe₃O₄ nanowire be promising for real application in biomedicine.