Synthesis and characterisation of ferromagnetic hexagonal cobalt nanoparticles

Ferromagnetic hexagonal cobalt nanoparticles are synthesised via reduction of cobalt acetate tetrahydrate by using sodium borohydride as a reducing agent. The morphology, crystal structure and magnetic properties of as synthesised particles are characterised by using transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and vibratory sample magnetometer (VSM). The results show that the particles are spherical in shape with a size of 5?nm. These particles show ferromagnetic behaviour with magnetic coercivity of 583?Oe at room temperature. Oleic acid acts as the surfactant and its bonding nature on the cobalt nanoparticles is studied by Fourier transform infrared spectrometry.     

Effect of particle size on iron nanoparticle oxidation state

Selecting catalyst particles is a very important part of carbon nanotube growth, although the properties of these nanoscale particles are unclear. In this article iron nanoparticles are analyzed through the use of atomic force microscopy and x-ray photoelectron spectroscopy in order to understand how the size affects the chemical composition of nanoparticles and thus their physical structure. Initially, atomic force microscopy was used to confirm the presence of iron particles, and to determine the average size of the particles. Next an analytical model was developed to estimate particle size as a function of deposition time using inputs from atomic force microscopy measurement. X-ray photoelectron spectroscopy analysis was then performed with a focus on the spectra relating to the 2p Fe electrons to study the chemical state of the particles as a function of time. It was shown that as the size of nanoparticles decreased, the oxidation state of the particles changed due to a high proportion of atoms on the surface.     

Morphology and composition of spray-flame-made yttria-stabilized zirconia nanoparticles

Homogeneous yttria-stabilized zirconia (YSZ) with 8-31?nm average crystallite and particle diameter containing 3-10?mol% yttria are made by flame spray pyrolysis (FSP) of various yttrium and zirconium precursors at production rates up to 350?g?h(-1). Product particles are characterized by N(2) adsorption (BET), transmission electron microscopy (TEM), energy-dispersive x-ray spectroscopy (EDS) and x-ray diffraction (XRD). The effect of liquid precursor composition on product particle morphology, composition and crystallinity is investigated. The yttria content does not affect the product primary particle and crystal sizes of homogeneous YSZ. These are determined, in turn, by the process enthalpy content and overall metal concentration. Flame-made YSZ nanoparticles of homogeneous composition and morphology are formed when using either only organometallic zirconium and yttrium precursors or 2-ethylhexanoic acid as solvent and inexpensive zirconium carbonate and yttrium nitrate hexahydrate as precursors. In contrast, and consistent with the literature, hollow or inhomogeneous YSZ particles are made when organometallic zirconium and yttrium nitrate precursors of high water content are employed, especially at high production rate. The ratio of XRD-determined small to large sizes for inhomogeneous crystalline particles is an effective quantitative measure of their degree of inhomogeneity. For such inhomogeneous particles nitrogen adsorption is not a reliable technique for the average grain size as it relies on integral properties of the particle size distribution.     

Room temperature ferromagnetic behavior of Eu doped Cd1?x Zn x S nanoparticles

We report the structural and magnetic properties of the Eu doped Cd_1?x Zn _x S nanoparticles synthesized by wet chemical method. The idea is to exploit the room temperature magnetic behavior of nanoparticles. The particles size as observed by Transmission electron microscopy (TEM) and X-ray diffraction (XRD) is about 5 nm. The magnetic loop observed at room temperature using SQUID indicates the ferromagnetic behaviour of doped particles.     

Stoichiometry of alloy nanoparticles from laser ablation of PtIr in acetone and their electrophoretic deposition on PtIr electrodes

Charged Pt-Ir alloy nanoparticles are generated through femtosecond laser ablation of a Pt?Ir target in acetone without using chemical precursors or stabilizing agents. Preservation of the target's stoichiometry in the colloidal nanoparticles is confirmed by transmission electron microscopy (TEM)-energy-dispersive x-ray spectroscopy (EDX), high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM)-EDX elemental maps, high resolution TEM and selected area electron diffraction (SAED) measurements. Results are discussed with reference to thermophysical properties and the phase diagram. The nanoparticles show a lognormal size distribution with a mean Feret particle size of 26 nm. The zeta potential of -45 mV indicates high stability of the colloid with a hydrodynamic diameter of 63 nm. The charge of the particles enables electrophoretic deposition of nanoparticles, creating nanoscale roughness on three-dimensional PtIr neural electrodes within a minute. In contrast to coating with Pt or Ir oxides, this method allows modification of the surface roughness without changing the chemical composition of PtIr.     

Particularities of the Magnetic State of CuO Nanoparticles Produced by Low-Pressure Plasma Arc Discharge

Copper oxide nanoparticles were produced by direct plasmachemical synthesis in a plasma arc discharge of low pressure. The formation of CuO nanoparticles with an average size of 12 nm and narrow size distribution intervals was determined by using the x-ray diffraction analysis and TEM microscopy methods. It was defined by using a vibration magnetometer and a SQUID magnetometer, that the magnetic properties of CuO nanoparticles with such size were extremely different from the magnetic properties of bulk antiferromagnetic CuO. Structural defects caused the formation of a ferromagnetic state, remaining at least up to the room temperature. The temperature of corresponding antiferromagnetic ordering was significantly decreased (down to ～ 100 K). Meanwhile, some of the copper surface spins showed a spin-glass behavior at low temperatures.     

Synthesis and characterization of CoFe(2)O(4) ferrite nanoparticles obtained by an electrochemical method

Uniform size cobalt ferrite nanoparticles have been synthesized in one step using an electrochemical technique. Synthesis parameters such as the current density, temperature and stirring were optimized to produce pure cobalt ferrite. The nanoparticles have been investigated by means of magnetic measurements, M?ssbauer spectroscopy, x-ray powder diffraction and transmission electron microscopy. The average size of the electrosynthesized samples was controlled by the synthesis parameters and this showed a rather narrow size distribution. The x-ray analysis shows that the CoFe(2)O(4) obtained presents a totally inverse spinel structure. The magnetic properties of the stoichiometric nanoparticles show ferromagnetic behavior at room temperature with a coercivity up to 6386?Oe and a saturation magnetization of 85?emu?g(-1).     

Optimization of Amorphous Silica Nanoparticles Synthesis from Rice Straw Ash Using Design of Experiments Technique

In this study, a chemical method of dissolution-precipitation was applied to produce amorphous silica nanoparticles from rice straw ash (RSA; the waste material of rice cultivation. The morphology, particle size, structure, and area of specific surface of synthesized amorphous silica nanoparticles were evaluated using transmission electron microscopy (TEM), x-ray diffraction analysis (XRD), and BET method to measure the specific surface area of materials. In addition, chemical composition of RSA used and the synthesized silica nanoparticles was studied by x-ray fluorescence (XRF) spectroscopy. The atomic concentration of synthesized silica was determined by x-ray photoelectron spectroscopy (XPS). The effects of sodium hydroxide concentration, precipitation reaction temperature, and precipitation reaction duration on the area of specific surface were determined through design of experiments (DOE) technique. Results depicted that silica nanoparticles with particle size of 10–15 nm were successfully synthesized. Average area of specific surface and purity were 327 m2/gr and 99.5%, respectively. The interactive influence of temperature and duration had the highest effect on the average area of specific surface.     

Synthesis and Structure of Polyethylene-Matrix Composites Containing Zinc Oxide Nanoparticles

Nanocomposites of high-pressure polyethylene and zinc oxide nanoparticles are synthesized through thermal decomposition of zinc acetate. The phase composition of the nanocomposites is determined by x-ray diffraction (XRD), and the average size of ZnO nanoparticles is evaluated by transmission electron microscopy. The average size of the nanoparticles varies from 1 to 10 nm, depending on the ZnO content of the material. Both XRD and EXAFS results indicate that the zinc oxide nanoparticles have the wurtzite structure.     

Synthesis,structure and photocatalytic properties of nanoparticles from a carbon-containing composite based on silicon oxide modified with titanium dioxide

A pulsed plasmochemical method was used to obtain carbon-containing nanocomposites based on silicon oxide modified with titanium dioxide. The material contained a Si_xC_yO_z carrier with an average size of 50–150?nm and a shell of fine particles with an average size of 5–10?nm. The phase composition and morphology of the synthesized composites was studied by X-ray diffraction and transmission electron microscopy. The optical and photocatalytic properties of the nanoparticles from the carbon-based composite based on silicon oxide encapsulated in titanium dioxide were studied. The synthesized composite showed a high photocatalytic activity due to the decomposition of methylene blue under the influence of visible light in the wavelength range of 460–630?nm.     

Evolution of texture and atomic order in annealed sinter-free FePt nanoparticles

Monodisperse FePt nanoparticles have been synthesized chemically. The spherically shaped as-made nanoparticles were 6.0?nm in size and they were single crystals. The average composition of these particles is determined as Fe(50)Pt(50). The nanoparticles did not show any sign of sintering after annealing at 800?°C for up to 120?min. The texture and order parameters of as-made and annealed FePt nanoparticles were determined from azimuthally integrated selected area electron diffraction patterns. The close to perfect [Formula: see text] axial texture in as-made particles degraded with increasing annealing time, in contrast to the order parameter, which showed a monotonic dependence on annealing time. With 60?min annealing, a 0.8 degree of chemical?ordering has been achieved and the particles were sinter-free as observed from bright field images.     

Room temperature ferromagnetism in CoO nanoparticles obtained from sonochemically synthesized precursors

In this paper we report the magnetic properties of nanosized CoO particles, prepared from sonochemically synthesized precursors and characterized using x-ray diffraction (XRD), conventional transmission electron microscopy (TEM) and scanning tunneling electron microscopy combined with energy dispersive x-ray analysis (STEM-EDX) techniques. The nanoparticles were faceted and the sizes varied between 30 and 60?nm depending on the time of annealing. They were stable even in the absence of any organic coating on them. Magnetic measurements reveal the presence of ferromagnetic interactions at low temperatures in the CoO nanoparticles synthesized after 2 and 4?h of annealing of the sonochemically synthesized precursor under nitrogen. However, after 6?h of annealing, the nanoparticles show hysteresis not only at low temperatures (1.5?K) but also at higher temperatures (100?K and room temperature), indicating the presence of room temperature ferromagnetism.     

Microwave-assisted rapid synthesis of anisotropic Ag nanoparticles by solid state transformation

Anisotropic silver nanoparticles (NPs) have been synthesized rapidly using microwave irradiation by the decomposition of silver oxalate in a glycol medium using polyvinyl pyrolidone (PVP) as the capping agent. The obtained Ag nanoparticles have been characterized by UV-visible spectroscopy, powder x-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) studies. Anisotropic Ag nanoparticles of average size around 30?nm have been observed in the case of microwave irradiation for 75?s whereas spherical particles of a size around 5-6?nm are formed for 60?s of irradiation. The texture coefficient and particle size calculated from XRD patterns of anisotropic nanoparticles reveal the preferential orientation of (111) facets in the Ag sample. Ethylene glycol is found to be a more suitable medium than diethylene glycol. A plausible mechanism has been proposed for the formation of anisotropic Ag nanoparticles from silver oxalate.     

Growth of hydroxyapatite on physiologically clotted fibrin capped gold nanoparticles

The growth of hydroxyapatite (HAp) on physiologically clotted fibrin (PCF)-gold nanoparticles is presented for the first time by employing a wet precipitation method. Fourier transform infrared (FTIR) spectroscopy confirmed the characteristic functionalities of PCF and HAp in the PCF-Au-HAp nanocomposite. Scanning electron microscopy (SEM) images have shown cuboidal nanostructures having a size in the range of 70-300?nm of HAp, whereas 2-50?nm sized particles were visualized in high-resolution transmission electron microscopy (TEM). Energy-dispersive x-ray (EDX) and x-ray diffraction (XRD) studies have confirmed the presence of HAp. These results show that gold nanoparticles with PCF acted as a matrix for the growth of HAp, and that PCF-Au-HAp nanocomposite is expected to have better osteoinductive properties.     

Investigation of magnetically enhanced swelling behaviour of superparamagnetic starch nanoparticles

The present study follows a novel strategy for the preparation of superparamagnetic nanoparticles of cross-linked starch impregnated homogeneously with nanosized iron oxide. The prepared magnetic nanoparticles were characterized by infra-red (FTIR) spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction and magnetization studies. The size of the magnetic polymeric particles was found to lie in the range of 20–80 nm, and they exhibited superparamagnetic properties. The particles were allowed to swell in phosphate buffer saline (PBS) and the influence of factors such as chemical composition of nanoparticles, pH and temperature of the swelling bath and applied magnetic field was investigated on the water intake capacity of the nanoparticles. The prepared nanoparticles showed potential to provide a possible option for controlled and targeted delivery of anticancer drugs, applying external magnetic field.     

Synthesis and characterization of PVP-coated large core iron oxide nanoparticles as an MRI contrast agent

The purpose of this study was to synthesize biocompatible polyvinylpyrrolidone (PVP)-coated iron oxide (PVP-IO) nanoparticles and to evaluate their efficacy as a magnetic resonance imaging (MRI) contrast agent. The PVP-IO nanoparticles were synthesized by a thermal decomposition method and characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), and a superconducting quantum interface device (SQUID). The core size of the particles is about 8-10 nm and the overall size is around 20-30 nm. The measured r(2) (reciprocal of T(2) relaxation time) and r2? (reciprocal of T2? relaxation time) are 141.2 and 338.1 (s mM)(-1), respectively. The particles are highly soluble and stable in various buffers and in serum. The macrophage uptake of PVP-IO is comparable to that of Feridex as measured by a Prussian blue iron stain and phantom study. The signal intensity of a rabbit liver was effectively reduced after intravenous administration of PVP-IO. Therefore PVP-IO nanoparticles are potentially useful for T(2)-weighted MR imaging.     

Magnetic properties of iron nanoparticles prepared by exploding wire technique

Nanoparticles of iron were prepared in distilled water using very thin iron wires and sheets, by the electro-exploding wire technique. Transmission electron microscopy reveals the size of the nanoparticles to be in the range 10 to 50 nm. However, particles of different sizes can be segregated by using ultrahigh centrifuge. X-ray diffraction studies confirm the presence of the cubic phase of iron. These iron nanoparticles were found to exhibit fluorescence in the visible region in contrast to the normal bulk material. The room temperature hysteresis measurements upto a field of 1.0 tesla were performed on a suspension of iron particles in the solution as well as in the powders obtained by filtration. The hysteresis loops indicate that the particles are superparamagnetic in nature. The saturation magnetizations was approximately 60 emu/gm. As these iron particles are very sensitive to oxygen a coating of non-magnetic iron oxide tends to form around the particles giving it a core-shell structure. The core particle size is estimated theoretically from the magnetization measurements. Suspensions of iron nanoparticles in water have been proposed to be used as an effective decontaminant for ground water.     

Pt nanostructure electrodes pulse electrodeposited in PVP for electrochemical power sources

In this work, we demonstrated that Pt nanostructure electrodes could be obtained by the pulse electrodeposition method in polyvinylpyrrolidone (PVP). The nanocrystal particles were confirmed by scanning electron microscopy, transmission electron microscopy and x-ray diffraction methods. The average size of Pt nanoparticles deposited in additive PVP with low and high molecular weight is 3.4 and 2.9?nm, respectively, whereas that of Pt electrodeposited without PVP is 360?nm. This means that the size of Pt nanoparticles can be controlled by PVP, resulting in an increased electrochemical surface area. The resulting Pt nanostructure electrodes showed such an improved performance for both direct methanol fuel cells and dye-sensitized solar cells.     

Hydrothermal synthesis of magnetite nanoparticles via sequential formation of iron hydroxide precipitates

A novel method for preparing fine magnetite nanoparticles without using any additives and organic solvents has been developed. In this method, a sequential precipitates formation method, ferrous and ferric hydroxides are not coprecipitated but sequentially formed in an alkaline solution, and then the resulting suspension is subjected to a hydrothermal treatment. The obtained magnetite nanoparticles were characterised through scanning electron microscopy observation and X-ray diffraction analysis, and the particle size and magnetic properties were measured with a dynamic light scattering particle size analyser and a superconducting quantum interference device magnetometer, respectively. In order to prepare fine magnetite nanoparticles with a uniform size, both the formation sequence of ferrous and ferric hydroxide precipitates and the supersaturation of ferric hydroxide in the solution were essential. The ferromagnetic magnetite nanoparticles with a median size 8.5?nm were relatively easily obtained in the formation process in which a ferric sulphate solution was rapidly poured into a suspension of ferrous hydroxide particles prepared beforehand using ferric chloride and sodium hydroxide, whereas the median size of magnetite nanoparticles prepared via conventional coprecipitation route was 38.6?nm.     

Optimization of process parameters of polymer solution mediated growth of calcium carbonate nanoparticles

With the advent of nanotechnology, many methods of synthesis of nanoparticles have come into practice and the 'polymer mediated growth' technique is among them. In this route, ions of one of the reactants are allowed to diffuse from an external solution into a polymer matrix where the other reactant is complexed and bound. The exact role of ionic diffusion in the formation of nanoparticles was investigated in the current study by studying the patterns of kinetics of nanoparticle formation using UV vis spectroscopy. Typically, calcium carbonate nanoparticles were formed by the aforementioned technique using polyethylene glycol solution. The particle size was calculated using Scherrer's formula on x-ray diffraction plots and was reconfirmed with field emission scanning electron microscope and transmission electron microscope images. Energy-dispersive x-ray analysis was used to study the composition and purity of the nanoparticles formed. The reactant to polymer ratio, reaction temperature and molecular weight of polyethylene glycol affected the size of the particles formed. Through this knowledge we optimized these parameters to obtain particles as small as 20?nm and confirmed that this technique can be used to control the size of nanoparticles.