Synthesis and characterization of single crystalline SnO<Subscript>2</Subscript> nanorods by high-pressure pulsed laser deposition

Tin oxide (SnO₂) nanorods were grown by high-pressure pulsed laser deposition (PLD). The nanorods were grown without the use of a catalyst but required high background pressure growth in order to realize small grain columnar growth and nanorod formation, with nanorod formation most favored on non-epitaxial substrates. The structures and morphology were characterized by field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). X-ray diffraction and HRTEM analysis indicate that the as-grown SnO₂ nanorods are single crystals with a rutile structure. The nanorods are approximately 50–90 nm in diameters and 1.5 μm in length. This method provides an approach for large area synthesis of one dimensional SnO₂ nanostructure materials. PACS 81.16.Mk; 61.46.-w; 81.07.-b     

Controlled synthesis of light rare-earth hydroxide nanorods via a simple solution route

Ln(OH)₃ (Ln=La, Pr, Nd, Sm, Eu, Gd) nanorods are synthesized without using any surfactants or templates at room temperature. The as-obtained nanorods are within 4–25 nm in diameter and up to 200 nm in length. The most important improvement is that the aspect ratio of the obtained nanorods can be effectively controlled by adjusting the reaction time and pH value of the reaction system. The as-synthesized nanorods are characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). It is interesting to find that both the inherent crystal structure of light lanthanide hydroxide and the chemical potential affect the formation of nanorods. The photoluminescence (PL) instrument is used to investigate the optical properties of the Eu(OH)₃ nanorods and its abnormal luminescence behaviors are observed.     

Synthesis,structure, and electrochemical properties of CdMoO<Subscript>4</Subscript> nanorods

In this paper, a novel nanocrystalline cadmium molybdate with nanorod morphology has been successfully prepared via hydrothermal method at relatively low temperature. The structure, composition, morphology of the prepared material was characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectrometry (XPS), and transmission electron microscopy (TEM), respectively. The XRD data shows that the nanorods may have grown preferentially along the (001) axis. The diameters of these nanorods are within 30–50 nm in the TEM. The electrochemical intercalation of lithium into this compound and the cycling performance were first tested as the cathode material of lithium rechargeable battery. At the same time, the nanorod morphology presented here can also be helpful for the other property studies of CdMoO₄.     

Synthesis of ZnS nanorods by annealing precursor ZnS nanoparticles in NaCl flux

ZnS nanorods were fabricated by annealing precursor ZnS nanoparticles, which were prepared by one-step, solid-state reaction of ZnCl₂ and Na₂S through grinding by hand at ambient temperature, in NaCl flux. The as-prepared ZnS nanorods have diameters of 40-80 nm, and lengths up to several micrometers. The structural features and chemical composition of the nanorods were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), high-resolution transmission electron microscopy (HRTEM), and Raman spectra.     

Synthesis of SnO<Subscript>2</Subscript> tubular nanostructures on top of a silicon nitride surface using polymeric templates and their characterization as gas sensor

Uniform polycrystalline SnO₂ microtubes formed by sintered nanoparticles (fixed to a surface or in free standing form) were obtained with the infiltration technique using SnCl₄ as precursor and a porous polycarbonate (PC) film as template. The advantage of this synthesis method was based on its simplicity, reproducibility, low cost, and the possible applicability to other complex oxides. The morphology and crystal structure of SnO₂ tubes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The crystalline sizes of the nanoparticles assembled in the tube walls obtained at 600 °C were in the range of 5–7 nm, calculated from both the XRD and the TEM data. The length of the microtubes fixed to a silicon nitride surface ranged between 2 and 7 μm. Sensors fabricated with this material showed unusual sensitivity to ethanol at room temperature and fast reversible response, as compared to those obtained by the deposition of metallic tin film and further oxidation (Rheotaxial Growth and Thermal Oxidation method).     

Sonochemical preparation of antimony subiodide

The substantiated isolation of the antimony subiodide (Sb₃I) is presented for the first time. It has been prepared using elemental Sb and I in ethanol under ultrasonic irradiation at 323 K. Its composition was characterized using X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray analysis (EDAX). The scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) investigations exhibit that the samples are made up of large quantity of nanoparticles with diameters smaller than 20 nm and single crystalline in nature. The interplanar spacings in Sb₃I that have been determined using powder X-ray diffraction (XRD), selected area electron diffraction (SAED) and HRTEM are very similar. Surprisingly, the registered XRD patterns are identical to the one reported earlier for Sb₄O₅I₂.     

Synthesis and nanostructural investigation of TiO<Subscript>2</Subscript> nanorods doped by SiO<Subscript>2</Subscript>

TiO₂ Nano rods can be used as dye-sensitized solar cells, various sensors and photocatalysts. These nanorods are synthesized by a hydrothermal corrosion process in NaOH solution at 200°C using TiO₂ powder as the source material. In the present work, the synthesis of TiO₂ nanorods in anatase, rutile and Ti₇O₁₃ phases and synthesis of TiO₂ nanorods by incorporating SiO₂ dopant, using the sol–gel method and alkaline corrosion are reported. The morphologies and crystal structures of the TiO₂ nanorods are characterized using field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD) study. The obtained results show not only an aggregation structure at high calcination temperatures with spherical particles but also Ti–O–Si bonds having four-fold coordination with oxygen in SiO^4 −.     

Synthesis and photoluminescence of single-crystal GaN nanorods prepared by sol-gel method

A new method was applied to prepare GaN nanorods. In this method, gallium oxide (Ga₂O₃) gel was firstly formed by a sol-gel processing using gallium ethanol, Ga(OC₂H₅)₃, as a new precursor. GaN nanorods were successfully synthesized after annealing of the Ga₂O₃ gel at 1000 °C for 20 min in flowing ammonia. The as-prepared nanorods were confirmed as single crystalline GaN with wurtzite structure by X-ray diffraction (XRD), selected-area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). Transmission electron microscopy (TEM) displayed that the GaN nanorods were straight and smooth, with diameters ranging from 200 nm to 1.8 μm and lengths typically up to several tens of microns. When excited by 280 nm light at room temperature, the GaN nanorods had a strong ultraviolet luminescence peak located at 369 nm and a blue luminescence peak located at 462 nm, attributed to GaN band-edge emission and the existence of the defects or surface states, respectively.     

Large-scale synthesis of Ag<Subscript>1.8</Subscript>Mn<Subscript>8</Subscript>O<Subscript>16</Subscript> nanorods and their electrochemical lithium-storage properties

Ag_1.8Mn₈O₁₆ nanorods have been synthesized on a large scale by a facile hydrothermal route. The effects of experimental conditions including reaction time and reactant concentration on the phase and morphology of the final products were investigated systematically. The products were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray (EDX) spectroscopy. Electrochemical lithium-storage capabilities of the as-formed nanostructured Ag_1.8Mn₈O₁₆ were also evaluated. Interestingly, the as-formed Ag_1.8Mn₈O₁₆ nanorods possess the unique one-dimensional structure and in situ silver loading, which are beneficial features for electrochemical lithium-storage applications. The results suggest their potential use as cathode materials for lithium-ion batteries.     

Molten salt synthesis of LaF<Subscript>3</Subscript>:Eu<Superscript>3+</Superscript> nanoplates with tunable size and their luminescence properties

A molten salt route to LaF₃:Eu³⁺ nanoplate with tunable size was developed and the products were characterized by the X-ray diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM) and high-resolution TEM (HR-TEM). It is found that the nanoplates with different sizes (ca. 46, 20, and 12 nm) could be obtained when the molar ratio of the reagents NH₄F and La(NO₃)₃ · 6H₂O was adjusted. The possible formation process of reaction was discussed, and the reasonable mechanism of size controlling was also proposed. Furthermore, the luminescent properties of all the samples with different sizes and doping levels were investigated at room temperature.     

Synthesis and electrocatalytic activities of Co<Subscript>3</Subscript>O<Subscript>4</Subscript> nanocubes

In this article, a hydrothermal method was developed to synthesize Co₃O₄ nanocubes using hydrogen peroxide (H₂O₂) as oxidant, Co(NO₃)₂·6H₂O as a cobalt source. The products are characterized in detail by multiform techniques including X-ray diffraction (XRD), energy dispersive X-ray analysis (EDS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results show that the obtained products are Co₃O₄ nanocubes with size ranging between 20 and 40 nm. The effects of the hydrogen peroxide concentration on the size of the products have been studied. The electrocatalytic activities of H₂O₂ reduction on Co₃O₄ nanocubes in phosphate buffer were also evaluated.     

Growth and characterization of pine-needle-shaped GaN nanorods by sputtering and ammoniating process

Pine-needle-shaped GaN nanorods have been successfully synthesized on Si(111) substrates by ammoniating Ga₂O₃/Nb films at 950 ^°C in a quartz tube. The products are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and field-emission transmission electron microscope (FETEM). The results show that the pine-needle-shaped nanorods have a pure hexagonal GaN wurtzite with a diameter ranging from 100 to 200 nm and a length up to several microns. The photoluminescence spectra (PL) measured at room temperature only exhibit a strong emission peak at 368 nm. Finally, the growth mechanism of GaN nanorods is also briefly explored.     

Self-assembly of rutile (α-TiO<Subscript>2</Subscript>) nanoclusters into nanorods in microemulsions at low temperature and their photocatalytic performance

A novel method – inverse microemulsion has been developed not only for synthesizing low cost TiO₂ nanocrystals but also for the first time making these nanocrystals self-assemble into various nanoparticles at 85°C. By variation of the volume ratios of oil to water in reverse microemulsions, the morphologies of obtained samples turned from nanoclusters to nanospherules, then grew into nanodumbbells, and became nanorods at last. It could be observed by transmission electron microscope (TEM) directly. The resulting materials were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and high-resolution transmission electron microscope (HRTEM). The photocatalytic activity of TiO₂ was tested with photodegradation of Methyl Orange (MO) in water. The catalyst consisting of nanorods showed the highest photocatalytic activity, which is due to its large surface area. Furthermore, the mechanism of self-assembly of TiO₂ nanocrystals was discussed in detail.     

Synthesis and characterization of β-Ga2O3 nanorods

A novel method was applied to prepare β-Ga₂O₃ nanorods. In this method, β-Ga₂O₃ nanorods have been successfully synthesized on Si(1 1 1) substrates through annealing sputtered Ga₂O₃/Mo films under flowing ammonia at 950 °C in a quartz tube. The as-synthesized nanorods are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and Fourier transform infrared spectroscopy (FTIR). The results show that the nanorod is single-crystalline Ga₂O₃ with monoclinic structure. The β-Ga₂O₃ nanorods are straight and smooth with diameters in the range of 200-300 nm and lengths typically up to several micrometers. The growth process of the β-Ga₂O₃ nanorods is probably dominated by conventional vapor-solid (VS) mechanism.     

A novel approach for the synthesis of superparamagnetic Mn3O4 nanocrystals by ultrasonic bath

In this study, the synthesis of Mn₃O₄ (husmannite) nanoparticles was carried out in two different alkali media under sonication by ultrasonic bath and conventional method. Manganese acetate was used as precursor, sodium hydroxide and hexamethylenetetramine (HMT) as basic reagents in this synthesis. An ultrasonic bath with low intensity was used for the preparation of nanomaterials. The as prepared samples were characterized with X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (HRTEM, TEM), energy-dispersive spectrum (EDS), and superconducting quantum interference device (SQUID) analysis. The XRD patterns exhibit the nanocrystals are in pure tetragonal phase. The chemical composition was obtained by EDS analysis and confirmed the presence of Mn and O in the sample. According to the TEM and HRTEM results, both nanorods and nanoparticles of Mn₃O₄ were obtained in the presence of ultrasonic irradiation. The average size of nanoparticles was 10 nm, and the size of nanorods was 12 nm in diameter and 100-900 nm in length for the samples prepared in basic medium with sodium hydroxide. In the conventional method with the same basic medium, the nanorod was not observed and the nearly cubic nanoparticles was appeared with an average size of 2.5 nm. The selected area electron diffraction (SAED) patterns revealed that the nanocrystals are polycrystalline in nature. When HMT was used as a basic reagent in the presence of ultrasonic irradiation, it was led to a higher size of nanoparticles and nanorods than when sodium hydroxide was used as a basic reagent. The average size of nanoparticles was about 15 nm and its shape was nearly cubic. The diameter for nanorods was 50 nm and the length was about a few micrometers.The magnetic measurements were carried out on the sample prepared in sodium hydroxide under ultrasonic irradiation. These measurements as a function of temperature and field strength showed a reduction in ferrimagnetic temperature (T_c = 40 K) as compared to those reported for the bulk (T_c = 43 K). The superparamagnetic behavior was observed at room temperature with no saturation magnetization and hysteresis in the region of measured field strength.     

Peroxide-based route assisted with inverse microemulsion process to well-dispersed Bi<Subscript>4</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> nanocrystals

Well-dispersed bismuth titanate (BIT) nanocrystals with an average size ranged from 3 to 60 nm were synthesized via a peroxide-based route assisted with an inverse microemulsion process. The crystallite size and lattice parameter of BIT upon variable-temperature were determined by X-ray diffraction (XRD). The particle size was confirmed by transmission electron microscopy (TEM). Thermal decomposition behaviour of Ti-peroxy and BIT gel and crystallization kinetics of BIT nanocrystals were investigated by differential scanning calorimetry/thermogravimetry (DSC/TG) and Fourier-Transform infrared spectroscopy (FTIR). Analysis of nonisothermal DSC data yielded a value of 220.84 ± 2.73 KJ/mol and 2.25 ± 0.26 for the activation energy of crystallization (E _a) and the Avrami exponent (n), respectively.     

ZnO spheres and nanorods formation: their dependence on agitation in solution synthesis

ZnO nanostructures including nanorods, dense, and partially hollow spheres were synthesized via a solution synthesis method with temperature ranging from 65 to 95 °C. Scanning electron microscopy (SEM) revealed that the diameter of the spheres is in the range of 200–500 nm. Transmission electron microscopy (TEM) showed that some of the spheres are hollow or partially hollow. Powder X-ray Diffraction (XRD) and TEM-Selected area electron diffraction (SAED) analysis showed that the spheres consist of polycrystalline nanoparticles. It was found for the first time that the agitation during the synthesis plays a critical role on morphology of the ZnO nanostructures formed in solution. The oriented attachment of nanocrystals without agitation during the synthesis could guide the nanocrystals to form an ordered nanorod structure. However, the disordered aggregation of the nanocrystals under shear force resulted in a spherical morphology. It was also found that the composition of spheres is different from that of nanorods: the spheres consist of both ZnO and Zn(OH)₂, but nanorods consist of single-crystal ZnO only. Zn(OH)₂ presented in the spheres could decompose to ZnO by calcination, resulting in the formation of hollow spheres.     

Controlling the orientation of ZnO nanorod arrays using TiO<Subscript>2</Subscript> thin film templates dip-coated by sol–gel

The oriented ZnO nanorod arrays have been synthesized on a silicon wafer that coated with TiO₂ films by aqueous chemical method. The morphologies, phase structure and the photoluminescence (PL) properties of the as-obtained product were investigated by field-emission scanning electron microscopy (FE-SEM), X-ray diffractometer (XRD), transmission electron microscope (TEM) and PL spectrum. The nanorods were about 100 nm in diameter and more than 1 μm in length, which possessed wurtzite structure with a c axis growth direction. The room-temperature PL measurement of the nanorod arrays showed strong ultraviolet emission. The effect of the crystal structure and the thickness of TiO₂ films on the morphologies of ZnO nanostructures were investigated. It was found that the rutile TiO₂ films were appropriate to the oriented growth of ZnO nanorod arrays in comparison with anatase TiO₂ films. Moreover, flakelike ZnO nanostructures were obtained with increasing the thickness of anatase TiO₂ films.     

One-pot hydrothermal synthesis of an assembly of magnetite nanoneedles on a scaffold of cyclic-diphenylalanine nanorods

The assembly of metal oxide nanoparticles (NPs) on a biomolecular template by a one-pot hydrothermal synthesis method is achieved for the first time. Magnetite (Fe₃O₄) nanoneedles (length: ~100 nm; width: ~10 nm) were assembled on cyclic-diphenylalanine (cFF) nanorods (length: 2–10 μm; width: 200 nm). The Fe₃O₄ nanoneedles and cFF nanorods were simultaneously synthesized from FeSO₄ and l-phenylalanine by hydrothermal synthesis (220 °C and 22 MPa), respectively. The samples were analyzed by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (IR), transmission electron microscopy (TEM), and superconducting quantum interference device (SQUID) magnetometry. Experimental results indicate that Fe₃O₄ nanoneedles were assembled on cFF nanorods during the hydrothermal reaction. The composite contained 3.3 wt% Fe₃O₄ nanoneedles without any loss of the original magnetic properties of Fe₃O₄.     

Synthesis of MgAl<Subscript>2</Subscript>O<Subscript>4</Subscript> spinel nanoparticles using a mixture of bayerite and magnesium sulfate

This article reports a novel method to prepare MgAl₂O₄ spinel nanoparticles. By calcining a powder mixture of bayerite and magnesium sulfate at 800 °C and washing with water, single-phase MgAl₂O₄ spinel nanoparticles were prepared. The powder mixture and the calcined products were characterized by differential thermal and thermogravimetric analysis (DSC-TG), X-ray diffraction (XRD), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET) nitrogen-gas adsorption method. The obtained MgAl₂O₄ spinel nanoparticles have an average particle size of 12 nm, a narrow size distribution, and weak agglomeration. The specific surface area of the MgAl₂O₄ spinel powder is 110 m²/g. The formation of MgAl₂O₄ spinel is attributed to a solid-state reaction between γ-Al₂O₃ and MgSO₄.