Synthesis of superparamagnetic cobalt nanoparticles through solvothermal process

The superparamagnetic (SPM) cobalt nanoparticles with an average size of 2 nm have been prepared through a solvothermal process in the presence of triethanolamine. The synthesized nanoparticles are characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy, and superconducting quantum interference device magnetometer. X-ray diffraction analysis confirms the face centered cubic phase of as-prepared cobalt nanoparticles. Transmission electron microscopy was employed to study the morphology of the as-prepared product, which exhibit spherical-like shape with size around 2 nm. The high resolution transmission electron microscopy image of cobalt nanoparticles shows the lattice spacing value of 0.204 nm. This is well matched with the (111) lattice spacing of fcc Co. XPS revealed the prepared product is pure cobalt. The blocking temperature of 17 K was obtained and confirmed by field-cooled and zero-field-cooled plots. The hysteresis loop revealed the synthesized nanoparticles have SPM character at room temperature.     

Solvothermal synthesis of nickel nanorods and its magnetic, structural and surface morphological behavior

One-dimensional rod-like nickel nanostructure was fabricated through a simple, efficient and one pot solvothermal approach with hydrazine hydrate and trimethylamine as reducing and morphology directing agents. The phase structure, morphology and magnetic properties of the as-prepared product were extensively characterized by X-ray diffraction, transmission electron microscopy and superconducting quantum interference device magnetometer. X-ray diffraction pattern indicated that the as-synthesized product was nickel with well-crystallized face-centered cubic structure. TEM observation showed that the nickel product consists of rod-like shape with size around 10 nm. Magnetic measurements revealed that the coercive forces of nickel nanorods at 300 K and 4.2 K are 198 Oe and 250 Oe, respectively. Compared with bulk nickel, the nanorods exhibit significant increase in coercive force as a reflection of shape anisotropy. A possible mechanism for the formation of rod-like nanostructure is proposed.     

Solvothermal preparation of iron nanosheets

Iron nanosheet has been prepared in the presence of N-Methylaniline by solvothermal method. The structural property of the sample has been studied by X-ray diffraction and transmission electron microscopy. The magnetic properties have been extensively investigated by hysteresis loops and temperature-dependent magnetization curves. XRD result exemplifies that the as-prepared product has been identified as iron with body centered cubic structure. TEM observation showed that the as-prepared product composed of sheet-like nanostructure with size was around 25 nm. FTIR result suggests that the N-Methylaniline molecules are on the surface of the Fe Nano sheet. Magnetic measurements showed that the prepared iron nanosheet was ferromagnetic behavior at 300 K. Compared with bulk iron, Fe nanosheet exhibits significant increase in coercive force due to the presence of shape anisotropy. Moreover, the temperature dependent magnetization curves show no blocking temperature up to 300 K, which indicates the prepared sheet, is ferromagnetic character at room temperature.     

Observation of magnetic, structural and surface morphological studies of triangle-like nickel nanoplates

Two-dimensional triangle-like nickel nanoplates have been synthesized by solvothermal method in the presence of triethylamine as a structure directing agent. The structure, morphology and magnetic properties of the as-synthesized products were characterized by X-ray diffraction, Atomic force microscopy and Superconducting quantum interference device magnetometer. The as-synthesized products have been confirmed to be phase-pure crystalline nickel with face centered cubic structure on the basis of X-ray diffraction characterization. Atomic force microscopy image demonstrated that the as-prepared nickel product possess two-dimensional triangle-like structure with edge length of about 65-85 nm. Magnetic measurements showed that the coercive forces at 4.2 K and 300 K for nickel nanoplates are 363.3 and 182 Oe, respectively. The nickel nanoplates exhibit a distinct enhanced coercive force due to the presence of shape anisotropy when compared with that of bulk. A possible mechanism for the formation of triangle-like Ni nanoplate structure is proposed.     

Solvothermal synthesis and magnetic properties of magnetite nanoplatelets

Nanostructured magnetite plates were synthesized by a simple solvothermal route where ethylenediamine was used as the solvent and reducing agent. The morphology and structure of the as-prepared platelets were characterized using X-ray diffraction, infrared spectroscopy and transmission electron microscopy. The results showed that the products are magnetite crystals with plate like morphology whose thickness is estimated to be 20 nm. Magnetic measurements at 300 K gave the saturation magnetization and the coercive field of nanostructured magnetite 87.4 emu/g and 178 Oe, respectively, which are higher than those of cubic nanoparticles, due to the higher shape anisotropy of magnetite nanoplatelets.     

Synthesis and characterization of NiO nanoparticles by sol–gel method

Nickel oxide nanoparticles have been synthesized in the presence of agarose polysaccharide by sol–gel method. The structure, morphology, optical and magnetic properties of the product was examined by X-ray diffraction, transmission electron microscopy, UV–visible spectrophotometer and superconducting quantum interference device magnetometer. The result of thermogravimetric analysis of the precursor product showed that the proper calcination temperature was 400 °C. X-ray diffraction result revealed that the obtained product was nickel oxide with face-centered cubic structure. TEM image demonstrated that the nickel oxide nanoparticles have spherical shape with size around 3 nm. Analysis of FTIR spectra confirmed the composition of product. The optical absorption band gap of the NiO nanoparticles was estimated to be 3.51 eV. Magnetic measurement showed that the nickel oxide nanoparticles exhibit superparamagnetic behavior at 300 K. Moreover, the nanoparticles show ferromagnetic interactions at 4.2 K owing to the existence of uncompensated moments on the surface of the nanoparticles.     

Effects of reaction parameters on solution combustion synthesis of lepidocrocite-like K0.80Ti1.733Li0.267O4: phase formation and morphology evolution

A lepidocrocite-like potassium lithium titanate K_0.80Ti_1.733Li_0.267O₄ (KLTO) with layered structure was synthesized by an auto-igniting solution combustion method using glycine and metal (Ti, K and Li) nitrate as reactants. The crystalline structure and morphology of the as-prepared product were examined using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. Effects of reaction parameters such as ignition temperature and oxidizers to fuel ratio on the phase formation and morphology evolution are investigated in this paper. A pure phase of KTLO was obtained at a low temperature (650 °C) within several minutes. Excessive glycine added into the aqueous precursor solution facilitated the synthesis of a pure and well-crystallized product. As-prepared particles exhibited plate-like shape with a length of 5–20 μm and a thickness of about 2 μm. No residual organic compound existed in the product. After the as-prepared product was post solution combustion heat-treated (1100 °C for 2 h), the particles became uniform in size with smooth surface and well-defined crystalline structure. The product exhibited excellent ion-exchange, intercalation, and exfoliation properties. The exfoliated titania nanosheets are characterized by high two-dimensional anisotropy with a thickness of about 20 nm and a lateral size ranging from sub-micrometers to several tens of micrometers.     

Morphology evolution of tungsten trioxide nanorods prepared by an additive-free hydrothermal route

Tungsten trioxide nanorods were prepared at 453 K by the hydrothermal treatment of aqueous tungstic acid sol, which was obtained by sodium tungstate solution passing through a strongly acidic ion-exchange resin in its proton form. The composition and morphology evolution of the nanorods were investigated by means of scanning electron microscopy, transmission electron microscopy, selected area electron diffraction and X-ray diffraction. The results show that all as-prepared samples mainly consist of hexagonal tungsten trioxide and tungsten trioxide one-third hydrate. With the extension of treatment time, the sample morphology will undergo an evolution in the sequence of nanorod, bundle-like and irregular shapes.     

Synthesis of monodisperse shuttle-like α-Fe2O3 nanorods via the EDA-assisted method

Monodisperse hematite shuttle-like nanorods were synthesized successfully by the ethylenediamine (EDA)-assisted method. The structure and morphology were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectrometer (EDS). XRD studies indicated that the as-prepared product was well-crystallized orthorhombic phase of α-Fe₂O₃. TEM and SEM images showed that the α-Fe₂O₃ nano-particles were of rod shape with an average length of 400 nm and diameter of about 80 nm in the middle part.     

From cobalt nitrate carbonate hydroxide hydrate nanowires to porous Co(3)O(4) nanorods for high performance lithium-ion battery electrodes

We have developed a simple approach for the large-scale synthesis of cobalt nitrate carbonate hydroxide hydrate (Co(CO(3))(0.35)(NO(3))(0.2)(OH)(1.1)·1.74H(2)O) nanowires via the hydrothermal process using sodium hydroxide and formaldehyde as mineralizers at 120?°C. The porous Co(3)O(4) nanorods 10-30?nm in diameter and hundreds of nanometres in length have been fabricated from the above-mentioned multicomponent nanowires by calcination at 400?°C. The morphology and structure of cobalt nitrate carbonate hydroxide hydrate nanowires and Co(3)O(4) nanorods have been characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and x-ray powder diffraction (XRD). Moreover, the porous Co(3)O(4) nanorods have been applied in the negative electrode materials for lithium ion batteries, which exhibit high electrochemical performance.     

Formation and characterisation of CeO2 and Gd:CeO2 nanowires/rods for fuel cell applications

Ceria and gadolinium (Gd) doped ceria nanowires have been synthesised by hydrothermal technique with mild reaction conditions. The structure and morphology of as-prepared nanowires were studied by X-ray diffraction and field emission scanning electron microscopy (FE-SEM) techniques. The FE-SEM analysis revealed the formation of nanowires with an average diameter of 10–15 nm. Atomic force microscopy (AFM) analysis for the annealed samples confirms the existence of well defined nanorods of 120–150 nm diameter and 1–1.3 μm length. Fluorescence and diffuse reflectance spectroscopy techniques have been used to study the optical properties of the prepared nanowires. The observed red shift in the ultraviolet–visible absorption spectra confirmed the promoted electron–phonon interaction in CeO₂ and Gd:CeO₂ nanowires compared to bulk structures. The prepared nanowires/rods were thermally stable at up to 350?°C, as revealed by thermogravimetric analysis. The electrical properties were studied by cyclic voltammetry (CV) and impedance spectroscopy. The CV results demonstrated that Gd:CeO₂ exhibited a higher electro-oxidation than CeO₂ nanowires.     

CTAB-assisted hydrothermal synthesis of single-crystalline copper-doped ZnO nanorods and investigation of their photoluminescence properties

A simple CTAB-assisted hydrothermal synthesis of undoped and copper-doped ZnO nanorods is reported. The phase and structural analysis carried out by X-ray diffraction, shows the formation of hexagonal wurtzite structure of ZnO. Morphology of the ZnO nanorods was investigated by electron microscopy techniques which showed the formation of well dispersed regular shape ZnO nanorods of 100 ± 10 nm in diameter and 900 ± 100 nm in length. However, size of the copper doped ZnO nanorod slightly increased with increasing copper concentration. Furthermore, the selected area electron diffraction pattern and high resolution transmission electron microscopy reveal that both the undoped and copper doped ZnO nanorods were single crystalline in nature and preferentially grew up along [0001] direction. Optical property was investigated by photoluminescence spectroscopy. The effects of copper doping on the photoluminescence property of ZnO nanorods were investigated.     

Synthesis and characterization of electrochemically-reduced graphene

Graphene has superior electrical conductivity than graphite and other allotropes of carbon because of its high surface area and chemical tolerance. Electrochemically processed graphene sheets were obtained through the reduction of graphene oxide from hydrazine hydrate. The prepared samples were heated to different temperatures such as 673 and 873 K. X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), transmission electron microscopy (TEM), Raman spectra and conductivity measurements were made for as-prepared and heat-treated graphene samples. XRD pattern of graphene shows a sharp and intensive peak centred at a diffraction angle (2θ) of 26·350. FTIR spectra of as-prepared and heated graphene were used to confirm the oxidation of graphite. TEM results indicated that the defect density and number of layers of graphene sheets were varied with heating temperature. The hexagonal sheet morphology and purity of as-prepared and heat treated samples were confirmed by SEM–EDX and Raman spectroscopy. The conductivity measurements revealed that the conductivity of graphene was decreased with an increase in heating temperature. The present study explains that graphene with enhanced functional properties can be achieved from the as-prepared sample.     

Fabrication and characterisation of MnOOH and β-MnO2 nanorods with rectangular cross-sections

MnOOH nanorods with rectangular cross-sections have been successfully prepared in high yield via a hydrothermal reduction process at a low temperature. After the subsequent heat treatment of the as-prepared MnOOH nanorods at 350°C for 6?h in air, β-MnO₂ nanorods with rectangular cross-section that retained the similar morphologies of MnOOH nanorods were obtained. The products were characterised by powder X-ray diffraction and field-emission scanning electron microscopy. The influences of different degrees of pH on the morphology and phase of the final products under hydrothermal conditions are discussed.     

Co掺杂的钛酸盐和TiO2纳米棒的磁性及光学性能

利用水热合成法,以TiO2(锐钛矿)粉末、钴盐为原料,在NaOH溶液中,180℃水热合成了Co掺杂的钛酸盐纳米棒.将Co掺杂的钛酸盐纳米棒在700℃氩气氛下烧结2 h转化为锐钛矿结构Co掺杂TiO2纳米棒.利用x射线衍射仪(XRD)、扫描电子显微镜(SEM)、紫外一可见分光光度计和超导量子干涉磁强计(SQUID)等对Co掺杂的钛酸盐和Ti0,纳米棒的微结构、形貌和性能进行了表征.研究结果表明,Co掺杂的钛酸盐和未掺杂的纯钛酸盐H2Ti3O7具有相同的层状结构,在样品中未监测到Co杂质(如钴的氧化物和氢氧化物)的峰.Co掺杂的钛酸盐纳米棒表面光滑,直径大约为90 nm～120 nm,长度约1 μm,co的掺杂对纳米棒形貌没有明显影响.Co掺杂后的钛酸盐纳米棒与未掺杂的钛酸盐纳米棒相比,其紫外-可见吸收光谱的吸收峰明显红移,带宽变窄.未掺杂的纯钛酸盐纳米棒的带宽为3.2 eV,与TiO2相同;Co掺杂的钛酸盐纳米棒的带宽为2.6 eV,明显变窄.同时,Co掺杂的钛酸盐和TjO2纳米棒在300 K均具有铁磁性,且其磁化强度大小基本一致,矫顽力也相同.     

Structural and magnetic properties of Zn1-xcoxO nanorods prepared by microwave irradiation technique

We have successfully synthesized large-scale aggregative flowerlike Zn1-xCo(x)O (0.0 < or = x < or = 0.07) nanostructures, consisting of many branches of nanorods at different orientations with diameter within 100-150 nm (tip diameter approximately 50 nm) and length of approximately 1 microm. The rods were prepared using Zinc nitrate, cobalt nitrate and KOH in 180 Watt microwave radiation for short time interval. The synthesized nanorods were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM) and DC magnetization measurements. XRD and TEM results indicate that the novel flowerlike nanostructures are hexagonal with wurtzite structure and Co ions were successfully incorporated into the lattice position of Zn ions in ZnO matrix. The selected area electron diffraction (SAED) pattern reveals that the nanorods are single crystal in nature and preferentially grow along [0 0 1] direction. Magnetic studies show that Zn1-xCo(x)O nanorods exhibit room temperature ferromagnetism. This novel nanostructure could be a promising candidate for a variety of future spintronic applications.     

Effect of Ni-doping on optical and magnetic properties of solvothermally synthesized ZnS wurtzite nanorods

In this study we have reported the effect of Ni-doping on optical and magnetic properties of ZnS nanorods. The diameter and length of low temperature solvothermally synthesized, high quality nanorods are 10 and 50–300 nm respectively as revealed from transmission electron microscopy. From X-ray diffraction, the structure of Ni-doped nanorods was observed as wurtzite with lattice parameters, a = 3.83 and c = 6.26. The band gap of the undoped and doped samples was found to be blue shifted as compared to the bulk counterpart when analyzed with UV–visible spectroscopy. Quenching in photoluminescence spectra was observed in case of Ni-doped nanorods as compared to undoped counterpart. The magnetization as analyzed from vibrating sample magnetometer was found to increase with 1 and 5 % Ni-doping concentration, and decrease with further increase in Ni-doping concentration, i.e., with 10 % Ni-doping.     

A simple route to lanthanum hydroxide nanorods

This letter first describes a facile, low-cost, solution-phase approach to the large-scale preparation of lanthanum hydroxide single crystal nanorods at 60 °C without any template and surfactant. X-ray diffraction (XRD) shows that the nanorods are of pure hexagonal structure. The size and morphology of the products were examined by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Lanthanum hydroxide single crystal nanorods are with diameters of approximately 20 nm and lengths of 150-200 nm. The processes of formation and decomposition for the as-prepared lanthanum hydroxide nanorods were discussed.     

Effect of morphology in the photocatalytic degradation of methyl violet dye using ZnO nanorods

In the present work, high purity ZnO nanorods were synthesized by solid state reaction method at different annealing temperatures (250–400 °C). The structural, morphological and optical characteristic of the ZnO nanorods were studied. X-ray diffraction results confirmed that the ZnO nanorods have Wurtzite structure with high crystal quality. The grain size has increased from 23 to 27 nm with increasing temperature. The scanning electron microscopy and high resolution-transmission electron microscopy photographs showed the formation of ZnO nanorods. The bonding natures of the synthesized nanorods were analyzed by Fourier transform infra-red spectroscopy. The blue shift in the absorption edge was observed from the UV–Vis spectrum. The photoluminescence spectra showed two emission peaks corresponding to blue and red emissions. The photocatalytic performance of these nanorods was evaluated using methyl violet dye. The result showed that photocatalytic performance is highly depends on the morphology of the nanorods.     

Enhanced excitonic emission and visible luminescence of chemically synthesized ZnS:Co film phosphors

Undoped and Cobalt doped ZnS thin films have been synthesised using chemical bath deposition technique. The X-ray diffraction pattern revealed a hexagonal structure for all the films. An increase in Co/Zn molar ratio resulted in a decrease in the intensity of diffraction peak corresponding to (100) plane and increase in crystallite size of the samples. The transmittance of the samples in the visible region was found to improve on doping. The optical band gap was found to vary from 3.46 to 3.66 eV with the incorporation of cobalt ions. The scanning electron microscope images of the samples exhibit a denser and more compact morphology for the doped films as compared to the undoped film. Photoluminescence studies reveal that all samples exhibit rare excitonic or near band-edge luminescence along with emissions in the visible region. The luminescence efficiency of ZnS film is appreciably enhanced with increase in concentration of the dopant.