Fabrication and photocatalytic property of CuO nanosheets via a facile solution route

Two‐dimensional (2D) CuO nanosheets were fabricated on Cu foils using a solution method. The method was novel, easy and can be completed at room temperature in the absence of any surfactant. The obtained materials were characterized by X‐ray diffraction (XRD), X‐ray Photoelectron Spectroscopy (XPS), scanning electron microscopy (SEM) and ultraviolet‐visible (UV‐Vis) spectroscopy. The effects of reaction time and temperature on the morphology and formation of CuO nanosheets were investigated, and a possible mechanism for the formation of CuO nanosheets was proposed. Experiments demonstrated that the formation of CuO nanosheets were significantly influenced by the growth time, and the reaction temperature was a key factor in determining the size of CuO nanosheets. Photocatalytic performance of CuO nanosheets was evaluated by measuring the decomposition rate of methyl orange solution. About 93% of the methyl orange was degraded after 150 min, which was much more efficient than that of CuO nanoparticles.     

Cd2Ge2O6 nanowires grown by a simple hydrothermal route

Cd₂Ge₂O₆ nanowires have been synthesized by a simple hydrothermal route in the absence of any surfactants. The diameter and length of the Cd₂Ge₂O₆ nanowires with flat tips are 30‐300 nm and several dozens of micrometers, respectivley. X‐ray diffraction and high‐resolution transmission electron microscopy results show that the nanowires are composed of monoclinic Cd₂Ge₂O₆ phase. The growth condition dependence results show that the formation of the Cd₂Ge₂O₆ nanowires undergoes three morphological changes from spherical particles to nanorods, and finally to nanowires. The photoluminescence spectrum of the Cd₂Ge₂O₆ nanowires exhibits three fluorescence emission peaks centered at 422 nm, 490 nm and 528 nm showing the potential application for optical devices. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Facile synthesis of low dimensional CuO nanostructures and their gas sensing applications

A simple and cost effective hydrothermal method has been employed to synthesis morphology controlled pure and Cr doped (4 and 8 at. %) CuO nanostructures. Crystalline purity and structure of the nanostructures were validated by X‐ray diffraction and Retvield analyses. Field emission scanning electron microscopy revealed the evolution of rod‐like, sheet‐like and boat‐like morphologies for pure, 4 and 8 at. % Cr doped CuO nanostructures respectively. The optical band gap estimated using the K‐M function plot from diffused reflectance spectroscopy showed a shift in band gap from 1.68 to 1.90 eV with respect to Cr concentration. The synthesized CuO nanostructures were investigated for the efficient room temperature gas sensing of ammonia, ethanol and methanol vapours under different concentrations (100‐600 ppm). The 8 at. % Cr doped CuO nano‐boats showed enhanced gas sensitivity than other CuO nanostructures owing to their typical morphology, larger surface area and related properties.     

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)     

Controllable synthesis,characterization and optical properties of Ag@AgCl coaxial core‐shell nanocables

Core‐shell structures often exhibit improved physical and chemical properties. Developing a relatively general, facile, and low temperature synthetic approach for core‐shell structures with complex compositions is still a particularly challenging work. Here we report a general chemical conversion route to prepare high quality Ag@AgCl coaxial core‐shell nanocables via the redox reaction between Ag nanowires and FeCl₃ in solution. The powder X‐ray diffraction of the Ag@AgCl coaxial core‐shell nanocables shows additional diffraction peaks corresponding to AgCl crystals apart from the signals from the Ag nanowire cores. Scanning electron microscopy and transmission electron microscopy images of the Ag@AgCl coaxial core‐shell nanocables reveal that the Ag nanowires are coated with AgCl nanoparticles. The effect of the molar ratio of Fe:Ag on the morphology and optical absorption of the Ag@AgCl coaxial core‐shell nanocables is systematically investigated. The result shows that the optical absorption of Ag nanowires decreases gradually and that of AgCl nanoparticles improves gradually with the increase of the molar ratio of Fe:Ag. The formation process of the Ag@AgCl coaxial core‐shell nanocables has been discussed in detail. The present chemical conversion approach is expected to be employed in a broad range of applications to fabricate innovative core‐shell structures with different compositions and shapes for unique properties. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and characterization of doped lithium aluminate nanocrystalline particles by sol‐gel method

Nanocrystalline particles of Co²⁺doped lithium aluminate (Co²⁺:LAO) and Ni²⁺‐doped lithium aluminate (Ni²⁺:LAO) were synthesized by sol–gel method. The crystalline nature and particle size of the samples were characterized by X‐ray diffraction analysis (XRD). The morphology and the presence Co²⁺ and Ni²⁺ in the synthesized samples were analyzed by scanning electron microscope (SEM) and energy dispersive X‐ray analysis (EDAX). The presences of functional groups in the samples were analyzed using FT‐IR analysis. The optical absorbance of the synthesized samples were observed using UV absorption spectral analysis. The frequency dependent dielectric behaviour of the synthesized nano materials was analyzed. (© 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)     

Hydrothermal synthesis of CdSe hierarchical microspheres

CdSe hierarchical microspheres have been successfully synthesized by a hydrothermal route at 120 °C for 16 h via a reaction between CdCl₂ and Na₂SeSO₃ in ionic liquid (1‐butyl‐3‐methylimidazolium bromide)‐water mixed medium. The structure and morphology of the as‐prepared products have been investigated by XRD and SEM, and the results indicate that the CdSe hierarchical microspheres have wurtzite structures and are self‐assembled by nanorods. It has been found that ionic liquid, reaction temperature, and reaction time have influence on the morphology of the products. The possible growth mechanism of CdSe with special morphology has been discussed. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Elliptic NdCrO3 microplate by a simple one‐step hydrothermal synthesis route and its characterization and magnetic properties

Elliptic NdCrO₃ microplates were synthesized by a simple and facile one‐step hydrothermal method of processing temperature 280 °C for 3 days. The products prepared in this paper have been characterized by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), X‐ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR) and field‐emission scanning electron microscopy (FESEM). The magnetic properties of the final sample are also studied. The XRD pattern indicates the pure orthorhombic phase for NdCrO₃ particles, the XPS, XRF and FTIR results further demonstrate the composition and purity of the final product. A possible growth mechanism for elliptic NdCrO₃ microplates is proposed. Through the investigation of magnetic properties, it can be generally concluded that the orthorhombic elliptic NdCrO₃ microplates exhibit typical behaviors of magnetic transition, spin reorientation transition and magnetic exchange bias. The Néel temperature is 218 K and the spin reorientation transition temperature is 46 K. The hysteresis loop under 5 K shows that the value of exchange bias field (H_ex) is 12 Oe and the shift of remanent magnetization (ΔM) is 0.008 emu/g, respectively.     

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)     

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)     

Preparation of Y3Al5O12 nanocrystals by low temperature glycol route

Yttrium aluminum garnet, Y₃Al₅O₁₂ (YAG) nanocrystals were synthesized by low temperature glycol method. This is a modified sol–gel method performed at low temperature that consists of a mixture of salts, mostly nitrates in an aqueous media. Single phase nanocrystalline YAG was obtained at 850°C, which is much lower than others such as wet‐chemical techniques. The structural characterization is done by XRD and transmission electron microscopy. The crystallite size range from 20‐50 nm was observed for the materials prepared at 850‐ 950°C. (© 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)     

Green synthesis by diethylene glycol based solution process and characterization of SnS nanoparticles

Uniform near‐spherical SnS nanoparticles were prepared by a hydrazine hydrate‐assisted diethylene glycol solution synthesis based on the reaction of tin dichloride (SnCl₂·2H₂O) with thioacetamide (H₃CCSNH₂). The as‐prepared SnS nanoparticles were characterized by XRD, FETEM, EDS, XPS and UV‐vis‐NIR spectrophotometer. The results showed that the SnS nanoparticles had orthorhombic crystal structure, good stoichiometry and indirect bandgap of ∼1.1 eV. The nanoparticle size could be controlled by changing injection temperature. (© 2012 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)     

Back-Scattered Electron Imaging of Microscopic Segregation in (Si,Ge) Single Crystals

Compositional inhomogeneities of (Si,Ge) single crystals grown by the radio frequency (RF) heated float zone technique have been studied using the back-scattered electron (BSE) mode of a scanning electron microscope. Numerical analysis of the images by Fast Fourier Transformation (FFT) showed that the number of spatial frequencies with substantial amplitudes is increased when investigating longitudinal sections of crystals containing dislocations instead of dislocation-free crystals. This can be attributed to different growth conditions in terms of super-cooling.     

Synthesis of ZnSn(OH)6 regular octahedrons by a simple hydrothermal process

ZnSn(OH)₆ regular octahedrons were successfully synthesized through a simple hydrothermal method using an aqueous solution containing ZnO flower‐like structures, SnCl₄·5H₂O, and NaOH. Phase structure, morphology and microstructure of the samples were investigated by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). Parameters in preparation process such as the ratios of Sn⁴⁺/OH^‐, the molar ratio of Zn/Sn and reaction time were discussed. Results show that the obtained samples are comprised of ZnSn(OH)₆ regular octahedrons with about 2 μm in side length and ZnSn(OH)₆ urchins‐like structures. ZnSn(OH)₆ urchins‐like structures preferentially grow on the edges and corners of regular octahedrons. Morphology of the products is susceptible to the ratios of Sn⁴⁺/OH^‐. A relatively low concentration of OH^‐ is favored to obtain ZnSn(OH)₆ regular octahedrons with urchins‐like structures on the surface, while a high concentration of OH^‐ results in a handful of regular octahedrons without urchins‐like structures on the surface. When the molar ratio of Zn/Sn changes to 1:2 or 2:1, the edges and corners of regular octahedrons become coarse and urchins‐like structures disappear from the surface. More urchins‐like structures form on the surface of regular octahedrons and the edges and corners of regular octahedrons become coarsened with the increase of reaction time. Moreover, the possible mechanism for ZnSn(OH)₆ regular octahedrons is discussed. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Vertically aligned and interconnected nickel oxide nanowalls fabricated by hydrothermal route

Vertically aligned and well interconnected NiO nanowalls with thin nanodiscs of cubic NiO as the in situ formed building blocks were fabricated via a template‐free approach. The alkaline solution of ammonium hydroxide was used as a reductant and Ni foil as both source material and substrate for the nanowall synthesis. Surface morphology analysis confirmed the formation of 15 nm thick and 0.2–1.5 μm wide nanowalls. The nanowalls had the crystal structure of cubic NiO with their growth plane along the [111] direction. An optical band gap of about 3.8 eV for the NiO nanowalls was obtained from the optical absorption measurement. NiO nanowalls exhibited a broad UV emission band centered at around 390 nm. This simple, but efficient synthesis technique can facilitate the growth of well aligned 2D nanostructures with large surface area for possible applications in nanoscale devices. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Phase‐manipulable synthesis of Cu‐based nanomaterials using ionic liquid 1‐butyl‐3‐methyl‐imidazole tetrafluoroborate

Using the ionic liquid (IL), 1‐butyl‐3‐methyl‐imidazole tetrafluoroborate, and the precursor Cu₇Cl₄(OH)₁₀·H₂O, series of phase‐manipulable Cu‐based nanomaterials were synthesized by hydrothermal and microwave assisted routes, respectively. The structural characters of the as‐prepared CuO, CuO/Cu₂O composites and pure Cu nanoparticles were investigated by XRD, SEM, TEM and HRTEM, and their surface photovoltaic properties were studied by surface photovoltage spectra. Via hydrothermal route Cu²⁺ ions were found to be reduced gradually into Cu⁺ and subsequently Cu⁰ with increasing the IL, and various phase ratio of CuO, Cu₂O and Cu composite nanosheets and pure Cu nanoparticles were obtained. This implies that the IL could function as both a reductant in the oxygen‐starved condition and a template for the nanosheet products. The ¹H‐NMR result of the IL supports it being a reductant. In microwave assisted route, however, only monoclinic single crystalline CuO nanosheets were obtained, which indicates the IL being a template only in oxygen‐rich condition. Therefore, the crystal phase, composition and morphology of the Cu‐based products could be controlled by simply adjusting the quantity of the IL and oxygen in solution routes. The molecular structure of the IL after oxidation reactions was investigated by ¹H‐NMR and a possible reaction mechanism was proposed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

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.