Urchin-like ZnO nanostructures: Synthesis, characterization and optical properties

Urchin-like ZnO nanostructures have been synthesized by a two-step thermal evaporation method. The product was characterized with scanning electron microscopy, X-ray powder diffraction, transmission electron microscopy, and spectrofluorometry. The results of characterization revealed that the urchin-like ZnO nanostructure consists of a spherical metallic Zn core and wurtzite ZnO nanowires growing on the surface of the ZnO buffer which covers the Zn core and the growth directions of wurtzite ZnO nanowires are along <10-10>. According to the analysis on these results, a possible two-step growth mechanism was proposed to explain the formation of the urchin-like ZnO nanostructures. The fluorescence-emission mechanisms were also discussed.     

Synthesis, characterization and optical properties of star-like ZnO nanostructures

Star-like ZnO nanostructures were synthesized in bulk quantity by thermal evaporation method. The morphologies and structure of ZnO nanostructures were investigated by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results demonstrated that the as-synthesized products consisted of star-like ZnO nanostructure with hexagonal wurtzite phase. The legs of the star-like nanostructures were preferentially grown up along the [0001] direction. A vapor-solid (VS) growth mechanism was proposed to explain the formation of the star-like structures. Photoluminescence spectrum exhibited a narrow ultraviolet emission at around 380 nm and a broad green emission around 491 nm. Raman spectrum of the ZnO nanostructures was also discussed.     

Synthesis and Properties of Nanocomposites

Nanocomposites may exhibit new properties of technical interest. Technical applications require many particles, leading to interaction of the particles thwarting the performance of these materials. To exploit specific nano‐properties, the use of composites preventing the particles from interaction is necessary. This leads to the application of nanocomposites. The most homogeneous composites consist of a core coated with an outer layer of a second ceramic or a polymer. For industrial or at least semi‐industrial production of nanocomposites, a process leading to non‐agglomerated powders in a sufficient quantity is needed. Additionally, coating of the particles with either a second ceramic phase or an organic one is necessary. The Karlsruhe Microwave Plasma Process fulfils these conditions.     

Facile synthesis and characterization of urchin-like CdSe nanostructures

CdSe nanostructures with urchin-like shape were successfully synthesized in water-in-oil (W/O) microemulsion. The phase structure, morphology, optical property, and specific surface area of the CdSe products were characterized. The X-ray powder diffraction pattern of the product showed that it is pure CdSe in zinc blende structure rather than thermodynamically favored wurtzite structure. It is found that numerous one-dimensional CdSe nanorods radiate from the center of the agglomerate to form urchin-like nanostructures and grow along the (111) crystal planes. The photoluminescence spectrum of the urchin-like nanostructures indicated that there is a blue-shift as compared with that of the bulk CdSe. Additionally, these interesting urchin-like nanostructures showed an increased specific surface area.     

Synthesis of highly crystalline silver dendrites microscale nanostructures by electrodeposition

Highly crystalline dendritic silver nanostructures have been synthesized by electrodeposition with the assistance of triblock copolymer P123. In the silver dentrites, the diameter of the trunk is around 100 nm with its length up to 40 μm, and the length of its branches can reach 10 μm. Selected area electron diffraction patterns show that the main trunk and side branches both grow along <211> directions and the leaves grow along <11-1> directions of the cubic Fm3m structure. The effects of the growth conditions such as the concentrations of reagents, the current density, and the electrode distance on the morphology of silver dendrites have also been investigated. It is found that the concentrations of AgNO₃ and P123 play significant roles in the growth of the silver dendrites.     

Mechanochemical synthesis of ternary chalcogenide chalcostibite CuSbS2 and its characterization

Journal of Materials Science: Materials in Electronics - In this work, the very rapid one-step mechanochemical synthesis of nanocrystalline ternary chalcogenide chalcostibite CuSbS2 prepared from...     

Synthesis and characterization of novel flower-like CeF3 nanostructures via a rapid microwave method

Novel flower-like CeF₃ nanostructures with a mean diameter of 190 nm were successfully synthesized via a rapid and facile microwave irradiation route using ethylenediaminetetraacetic acid disodium as the complexing reagent. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and photoluminescence (PL). XRD patterns showed that the CeF₃ nanoflowers were hexagonal phase and had good crystallinity and purity. TEM and SEM images showed that the as-prepared CeF₃ samples displayed 3D flower-like nanostructures and had uniform sizes and morphologies. The experimental results revealed that the as-prepared CeF₃ nanoflowers might be assembled by nanodisks. The formation process of the CeF₃ nanoflowers was preliminarily investigated.     

Synthesis of flower-like CuO nanostructures via a simple hydrolysis route

We describe a facile route for the synthesis of flower-like CuO nanostructures by hydrolyzing of Cu(OAc)₂ solution without any surfactants. SEM and TEM observations indicate that the CuO products are composed of microspheres with diameters of 0.4-0.8 μm. The microspheres are in fact built from small needle-like nanocrystals with diameters of 10-15 nm. The method provides a convenient, low-cost, nontoxic route for the synthesis of nanostructures of oxide materials, and it is important for exploring oxide-based nanostructures for applications in nanodevices.     

Synthesis, optical and field emission properties of three different ZnO nanostructures

Three different ZnO nanostructures: nanocherries, nanomultipeds and nanospindles were successfully synthesized by thermal evaporation method under different experimental conditions. The X-ray diffraction peaks indicate that these ZnO nanostructures prefer to grow along the c-axis. Photoluminescence (PL) spectra show that they are partially related to morphologies. Comparing the field emission (FE) measurements of the three ZnO nanostructures, we found that the nanocherries structure has the lowest turn-on and threshold field, 2.31 V/μm and 5.83 V/μm, respectively, for nanospindles and nanomultipeds structures, they are 2.82 V/μm and 6.57 V/μm, 3.13 V/μm and 7.35 V/μm, revealing that the nanocherries structure may be one of the promising candidates for field emission displays.     

Synthesis, characterization and magnetic properties of nanocrystalline Ni-Zn-Co ferrites

Nanocrystalline magnetic particles of Ni_0.7−xZn_0.3Co_xFe₂O₄ with x lying between 0.0 and 0.3 were synthesized by combustion method using metal nitrates, sucrose and polyvinyl alcohol (PVA). The synthesized powders where characterized by X-ray diffraction and Transmission electron microscopy (TEM). The average crystallite size determined from XRD data using Scherrer formula lie in the range of 20-30 nm. TEM micrographs show a well defined nano-crystallite state with an average particle size of around ~ 10 nm. The electron diffraction patterns confirm the spinel crystal structure of the ferrite. Magnetic properties measured at room temperature by vibrating sample magnetometer (VSM) reveal an increase in saturation magnetization with increase in cobalt concentration. Non-linear increase in saturation magnetization is related to surface effects and method of preparation.     

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 and field effect characteristics of Na2Ti3O7 nanowires

Na₂Ti₃O₇ nanowires with diameters of about 80-130 nm and lengths up to several tens of micrometers are synthesized via a simple hydrothermal method and characterized by the field-emission scanning electron microscopy and X-ray diffraction. Back-gate field-effect transistors based on these nanowires are fabricated on indium tin oxide glass substrates with polymethyl-methacrylate-co-glyciclyl-methacrylate as the gate insulator layers. Typical p-type semiconductor material properties are observed in our investigations. The field-effect mobility is about 0.1 cm²/Vs. The capacitance per unit area of the dielectric is 3.43 nF/cm² (dielectric constant, k = 3.9). The on/off ratio is around 10³ at the conduction of 10 V.     

Solvothermal synthesis and characterization of ZrO2 nanostructures using zirconium precursor

Zirconia (ZrO₂) is an important metal oxide owing to its applications in a variety of fields. Herein, we report the solvothermal synthesis of ZrO₂ nanostructures including nanorods, linked nanorods, and nanosheets. Aqueous solutions of [Zr₆O₄(OH)₄(H₂O)₈(Gly)₈]·12Cl·8H₂O (CP-2) or a mixture of CP-2 and ZrOCl₂·8H₂O containing NaOH were employed as the zirconium sources while Triton X-100, Tween-80 and sodium dodecylsulfate (SDS) were included to modify the morphology of the final product. Single-phase monoclinic ZrO₂ nanostructures could be obtained by the solvothermal method at 200 °C for 24 h independent of the presence or absence of Triton X-100, Tween-80 and SDS. However, the addition of Triton X-100, Tween-80 and SDS influenced the morphology of the resulting ZrO₂ nanostructures without affecting the crystal phase of the product.     

Synthesis and photocatalytic characterization of porous cuprous oxide octahedra

Porous cuprous oxide octahedra with a mean diameter of 1 μm have been successfully prepared with high yield via a hydrothermal reduction process at a low temperature. The growth mechanism and the influences of the poly(vinylpyrrolidone) (PVP) and citric acid have been discussed. And then, the samples were used as photocatalytic in the degradation of methyl red (MR). Thanks to the 3D architecture of the product, the photocatalytic performance has been significantly improved. We believe that the present work will open up to systematically explore ways to fabricate porous nanostructures and thus find use in a variety of applications.     

Synthesis of Si-C nanostructures by laser ablation of silicon target in n-heptane vapor

Controllable synthesis of Si-C nanostructures was realized in a laser ablation system by adopting solid silicon target and n-heptane vapor as starting materials. Ultrafine SiC nanocrystals and graphite-coated SiC nanocrystals were synthesized with the laser frequency of 1 Hz and 20 Hz, respectively. According to the real-time observation on the plasma evolvement, we proposed a formation mechanism of Si-C nanostructure related to vapor-phase reaction. Our method can be extended to other material systems for diverse novel nanostructures.     

Synthesis and characterization of ruthenium dioxide nanostructures

We report the synthesis of ruthenium dioxide (RuO₂) nanostructures by thermal evaporation of RuO₂ powder. RuO₂ nanostructures of different shapes were synthesized at various concentration, flow rate, and pressure of oxygen. At a constant pressure of 3 torr of flowing oxygen, polygonal prism-like RuO₂ nanorods with flat tips were grown at an O₂ flow rate of 100 sccm; club-shaped nanorods with obelisk tip were formed at 300 and 600 sccm, and hollow rods with square tip were formed at 1800 sccm. A mixture of O₂ and Ar at a total flow rate of 600 sccm led to the formation of short club-shaped nanorods indicating the suppression effect of Ar on the growth of nanorods. The pressure also had a significant effect on the formation of RuO₂ nanostructures, at a fixed flow rate of 600 sccm of O₂, a pressure of 3 torr resulted in the growth of club-shaped RuO₂ nanorods, while high pressures of 380 and 760 torr resulted in the formation of both linear club-shaped and pine tree-like hierarchical RuO₂ nanorods. X-ray diffraction and transmission electron microscopy analysis indicated the formation of tetragonal phase of RuO₂ with high crystallinity. A density functional calculation on RuO₂, RuO₃, and RuO₄ was performed to help to explain the experimental results.     

Synthesis and characterization of one-dimensional MgO nanostructures

Magnesium oxide (MgO) nanowire arrays, nanoribbons, two- and three-dimensional network like nanostructures were prepared by the simple thermal evaporation of Mg powder with and without using catalyst at a relatively low temperature. The non-catalytic approaches favor the formation of network like nanoforms whereas the catalytic approaches favors the formation of one-dimensional nanowire arrays and quasi one-dimensional nanoribbons depending on the temperature and vapor concentrations of the growth site. The diameter and length of the MgO network like columns varied within 40-50 nm and approximately 200 nm respectively. The MgO nanowires produced by the catalytic approach had diameter within 20-30 nm and length approximately 2 microm. Whereas the widths of the nanoribbons varied within 50-100 nm and their length were of the order of a few hundred micrometers. The nanoforms were single crystalline and cubic in phase. The products were characterized by the X-ray diffraction study, energy dispersive analysis of X-ray study, scanning and transmission electron microscopy, and photoluminescence measurements to explore the structural, compositional, morphological, and physical properties of the MgO nanoforms.     

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 of CdS-Au2S-Au hybrid dendritic nanostructures

The hybrid CdS-Au₂S-Au dendritic nanocrystals were synthesized in toluene solution at 70 °C. UV-vis and photoluminescence (PL) spectra recorded the optical properties of hybrid nanostructures, which showed an obvious blue shift relative to the absorption peak of CdS dendritic nanocrystals. The initial CdS dendritic nanocrystals exhibited band gap and trap state emission, both of which were quenched by Au parts. Analysis of the hybrid nanostructures by XRD shows the presence of appreciable amounts of Au₂S, indicating that the chemical process involving cation exchanges between Au⁺ ions and Cd²⁺ ions was found.     

Synthesis and characterization of bismuth sulfide nanowires through microwave solvothermal technique

One-dimensional (1D) bismuth sulfide (Bi₂S₃) semiconducting nanowires have been successfully synthesized through mircrowave assisted solvothermal technique. The obtained product was characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and UV-vis spectrophotometry. The result shows that the Bi₂S₃ nanowires are single crystals grown along the [001] (c-axis) direction. The growth of Bi₂S₃ nanofibers with a preferential direction of c-axis can be ascribed to its particular structure. The optical measurement shows a blue shift relative to the bulk orthorhombic Bi₂S₃, which might be ascribed to the high aspect ratio of the nanowires.