Synthesis and characterization of novel ferromagnetic PPy-based nanocomposite

Polypyrrole(PPy)/Zn_0.5Cu_0.5Fe₂O₄ nanocomposite was prepared by a simple, general and inexpensive in situ polymerization of pyrrole in the presence of Zn_0.5Cu_0.5Fe₂O₄ nanoparticles in w/o microemulsion. The effects of PPy coating on the magnetic properties of Zn_0.5Cu_0.5Fe₂O₄ were investigated. By means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectra, scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) technique, the microstructure and magnetic property of samples were characterized. The SEM analysis indicated that PPy was deposited on the porous surface of Zn_0.5Cu_0.5Fe₂O₄. The results were shown that the magnetic parameters such as saturation magnetization and coercivity of Zn_0.5Cu_0.5Fe₂O₄ decreased upon PPy coating.     

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 magnetic properties of Mn-doped ZnO nanorods via radio frequency plasma deposition

Well-aligned Mn-doped ZnO nanorods were synthesized by simple radio frequency (RF) plasma deposition in the absence of extra catalysts. The synthesized nanorods having a typical average diameter of about 25 nm, were about 310 nm in length and well-aligned along the normal direction of the substrate. Magnetic measurements indicate that the nanorods are ferromagnetic at room temperature (RT). The presence of considerable shallow donor defects in the nanorods does allow possible defect mediated mechanisms (e.g., bound magnetic polarons) for mediating exchange coupling of the dopant Mn ions resulting in RT ferromagnetism.     

Synthesis and characterization of cysteamine-CdTe quantum dots via one-step aqueous method

A novel approach has been developed to synthesize cysteamine (CA)-CdTe quantum dots (QDs) in an aqueous medium. Compared with previous reports, the proposed method involves a one-step synthesis using TeO₂ to replace Te or Al₂Te₃ as tellurium source. The influences of the precursor Cd/Te molar ratios and the pH of the original solution on the quantum yield (QY) of the obtained CdTe QDs were investigated systematically. Green- to orange-emitting CdTe QDs, with a maximum photoluminescence QY of 10.73%, were obtained. X-ray powder diffraction and transmission electron microscopy were used to characterize the crystalline structure and shape of the materials. CdTe QDs with CA modification exhibit a zinc-blended crystal structure in a sphere-like shape.     

Synthesis of Ultrafine Fe3O4 Powder via a Novel Ageing Process

Ultrafine Fe3O4 powder was successfully synthesized via a novel ageing process from a precursor FeO(OH), which was the hydrolysate of FeCl3 in the urea solution. The structure of as-synthesized powder was characterized by X-ray diffraction (XRD), and the morphology of these nanoparticles was investigated using a transmission electron microscope (TEM). Pure phase Fe3O4 was obtained and the mean diameter of these nanoparticles was about 21 nm. Furthermore, the study indicated that the precursor FeO(OH) played an important role in the formation of Fe3O4 nanoparticles. The mechanism was also discussed.     

High-yield synthesis and magnetic property of hematite nanorhombohedras through a facile solution route

Through a relatively low temperature solution route, hematite (α-Fe₂O₃) nanorhombohedras with average particle size of 35 nm were synthesized in high yield. The final products were investigated by a variety of characterization techniques, such as X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM) and Raman spectrum. As a steric stabilizer and capping agent, the roles of PVP played in the whole process were discussed. And the magnetic property of the nanorhombohedras at low temperature was examined, exhibiting weakly ferromagnetic characteristic, which deviates from the behavior of the corresponding bulk material and might be ascribed to the presence of small crystals in a few regions of the sample.     

Synthesis and magnetic studies of nano-crystalline GdFeO3

Nano-crystalline GdFeO₃ was synthesized by three different soft-chemical routes viz. hydrothermal, co-precipitation and combustion. The hydrothermal and co-precipitation methods resulted in amorphous powder which on further heating resulted in GdFeO₃. The combustion method produced phase pure GdFeO₃ in a single step. The particle size was in the range of 50-70 nm as calculated by Scherrer's formula. The transmission electron micrographs (TEM) showed the presence of fairly regular particles. Magnetic studies revealed a paramagnetic behavior. The magnetic susceptibility (in emu/g-Oe) of GdFeO₃ samples as synthesized by hydrothermal, co-precipitation and combustion routes was found to be 9.6 × 10^− 5, 6.7 × 10^− 5 and 4.4 × 10^− 5 respectively.     

Synthesis and characterization of three-dimensional ordered mesoporous-macroporous bioactive glass

Three-dimensional ordered mesoporous-macroporous bioactive glass (MMBG) was synthesized by a combination of surfactant and polystyrene bead templates, the sol-gel method, and the evaporation-induced self-assembly process. The incorporation of regular spherical macropores only slightly perturbed the mesoporous network. The bioactivity of the MMBG was assessed by its immersion in simulated body fluid for different lengths of time and the subsequent determination of hydroxycarbonate apatite formation. The synthesized MMBG displayed good in vitro bioactivity and may have potential applications in bone tissue engineering.     

Synthesis of single-crystalline alpha-FeOOH nanorods with semi-hard magnetic property

Goethite (α-FeOOH) nanorods were synthesized via hydrothermal method. The experimental results indicate that the uniform α-FeOOH nanorods, with length up to nearly 1 μm and diameter of ca. 50 nm, demonstrate perfect crystallinity and the growth direction of [001]. Owing to the characteristics of single-crystalline structure and high purity, the hysteresis loop of the resulting products shows semi-hard magnetic behavior compared to antiferromagnetic bulk with high-coercivity in nature.     

Synthesis of Cd1 − xMnxS nanoclusters by surfactant-assisted method: Structural, optical and magnetic properties

Cd_1 − xMn_xS nanoclusters were synthesized by surfactant-assisted chemical method for different Manganese (Mn) concentration (0.40 ≤ x ≥ 0.10) at 60 °C in argon atmosphere. Incorporation of magnetic ions (Mn) results a decrease in band gap of Cd_1 − xMn_xS nanoclusters. The room temperature ferromagnetic behaviour is demonstrated first time in Cd_0.60Mn_0.40S nanoclusters by vibrating sample magneto (VSM) measurements and the origin of magnetization has been discussed.     

Piezoelectric, dielectric, optical and electrical characterization of solution grown flower-like ZnO nanocrystal

Flower-like ZnO nanocrystals were grown by low temperature solution technique after controlling Zn²⁺/OH⁻ ratio. The morphology and structural studies confirmed the formation of nano structure, revealing the [0001] oriented growth of the ZnO nanorods. The variation of dielectric constant, loss, ac conductivity and activation energy as a function of frequency was studied. In UV-Vis absorption spectra, a sharp absorption band-edge at 355 nm is observed from which direct optical band gap 3.40 eV was calculated. In P-E hysteresis piezoelectric characterization for unpoled ZnO, the value of remnant polarization and coercive field was found to be 16.31 µC/cm² and 6.11 kV/cm respectively which increased to 25.65 µC/cm² and 8.35 kV/cm, respectively after poling at 1 kV/cm. The piezoelectric charge coefficient (d₃₃) was found to be 1.7 pC/N.     

Preparation and characterization of ceria nanospheres by microwave-hydrothermal method

Crystalline ceria (CeO₂) nanoparticles have been successfully synthesized by a simple and fast microwave-hydrothermal method at 130 °C for 20 min. As-synthesized CeO₂ powders were calcinated at 500 °C for 1, 2 and 4 h. The products were characterized by thermogravimetric analysis (TG-DTA), X-ray powder diffraction (XRD), field-emission scanning electron microscopy/STEM mode (FEG/STEM), Fourier Transformed-IR and RAMAN spectroscopies. It is shown that synthesized ceria powders have a spherical shape with particle size below 10 nm, a narrow distribution and exhibit weak agglomeration. The FTIR spectrum of the ceria exhibits strong broad band below 700 cm^− 1 which is due to the δ (Ce-O-C) mode. Raman spectrum is characterized by the presence of a very strong band to 464.5 cm^− 1. The microwave-hydrothermal method enabled cerium compounds to be synthesized at low temperature and shorter time.     

Synthesis, luminescent, and magnetic properties of LaVO4:Eu nanorods

The LaVO₄:Eu nanorods were synthesized successfully by an ethylenediaminetetraacetic acid (EDTA)-mediated hydrothermal method. The resulting products were characterized using XRD, TEM, HRTEM, Fluorescence Spectrometer and SQUID magnetometer. It was found that Eu³⁺ entered into the LaVO₄ crystalline host lattice and it replaced La³⁺. Consequently the unit cell parameters of LaVO₄:Eu nanorods became smaller. Further studies indicated that the rare earth ions Eu³⁺ improved the properties of the LaVO₄:Eu nanorods evidently. The Eu³⁺ ions doping in LaVO₄ nanorods led to better luminescent properties and magnetic properties than that of pure LaVO₄ nanorods.     

Synthesis of high surface area mesoporous bioactive glass nanospheres

Mesoporous bioactive glass (MBG) nanospheres having the composition of SiO₂-CaO-P₂O₅ with both a large specific surface area (∼ 1040 m² g^− 1) and pore volume (1.54 cm³ g^− 1) were prepared using the ionic surfactant, cetyltrimethyl-ammonium bromide (CTAB), as a template. The size of the nanospheres depends on the amount of CaO that is incorporated and can be controlled over the range of diameters from 20 to 200 nm under dilute aqueous condition. In vitro bioactivity studies were carried out in simulated body fluid (SBF). Cytotoxicity tests of the MBG nanospheres were also performed by observing their influence on J774 macrophages at various concentrations.     

Preparation of hollow carbon nanospheres via explosive detonation

Hollow carbon nanospheres were prepared via a rapid detonation technique, by using negative-oxygen balance explosive trinitrotoluene and nickel powder as starting materials and inorganic acid as solvent. The carbon/metal nanocomposite particles precursor with core-shell structure was engendered firstly during detonation, and then the metal nickel core was dissolved through inorganic acid to attain the hollow carbon nanospheres. High-Resolution Transmission Electron Microscope, X-ray diffraction and Raman spectrum were used to characterize the precursor and the as-synthesized samples respectively. The results show that the external diameter of the hollow carbon nanospheres is 25-150 nm and the thickness of the wall is about 2-10 nm. The surface of hollow carbon nanosphere displays multilayer wall in structure with 0.35 nm space between the layers. Based on the experimental results, possible formation mechanism was also proposed.     

Synthesis and physical characterization of magnetite nanoparticles for biomedical applications

Iron oxide nanoparticles for biomedical applications in the size range of 15–130 nm were prepared by either oxidative hydrolysis of ferrous sulfate with KOH or precipitation from ferrous/ferric chloride solutions. The magnetite particle size is controlled by variation of pH and temperature. The synthesized magnetite nanoparticles are partially oxidized as signaled by ferrous concentrations of below 24 wt% Fe²⁺ and lattice parameters of a₀ ≤ 8.39 Å which are smaller compared to 8.39 Å for stoichiometric magnetite. The extend of oxidation increases with decreasing particle size. Heating at 150–350 °C topotactically transforms the magnetite nanoparticles into stoichiometric tetragonal maghemite (ferrous ion concentration c_Fe²⁺=0 and a₀ = 8.34 Å) without significant particle growth. The magnetite–maghemite transformation is studied with thermal analysis, XRD and IR spectroscopy. The saturation magnetizations of the magnetite and maghemite particles decrease with decreasing particle size. The variation of M_s with particle size is interpreted using a magnetic core–shell particle model. Magnetite particles with d ≤ 16 nm show superparamagnetic behavior at room temperature whereas particles with diameter >16 nm display hysteresis behavior. These particles are candidates for biomedical applications, e.g. controlled drug release or hyperthermia.     

Novel Ga-doped ZnO nanocrystal ink: Synthesis and characterization

Ga-doped ZnO (GZO) nanocrystals were synthesized via the hot-injection method for the first time. The characterizations of its structure, composition, morphology, and absorption properties were conducted by using powder X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and UV-vis absorption spectroscopy. The results indicated that GZO nanocrystals were single phase polycrystalline within a range of 5―10 nm. Optical measurements illustrated that GZO nanocrystals have a tunable band gap from 3.35 to 3.81 eV, depending on the Ga doping level. GZO nanocrystals were dispersed in nonpolar solvents to form a nanocrystal ink which could remain stable after a month of storage. The GZO thin film was fabricated by spin coating the GZO nanocrystal ink and annealing in air. The electrical resistivity of the film was measured to be 7.5 × 10⁻² Ω cm. This method, which eliminated the requirement of high vacuum and high temperature, was a promising alternative for transparent conducting oxide (TCO) fabrication.     

Synthesis and characterization of maghemite nanosheets

Magnetic maghemite nanoparticles in the form of nanosheets were prepared by a topotactic transformation during the dehydroxylation of a γ-FeO(OH) precursor. The precursor was synthesized from tetrapyridin Fe(II) chloride (Fe(py)₄Cl₂). The nanosheets are several hundreds of nanometers wide, and less than 5 nm thick; they frequently bend and curl at the edges; they are nanocrystalline; and they are composed of smaller maghemite nanostructured domains, from a few nanometers up to several tens of nanometers wide.     

Novel and simple synthesis of ZnO nanospheres through decomposing zinc borate nanoplatelets

Spherical zinc oxide (ZnO) nanoparticles had been successfully synthesized through decomposing zinc borate nanoplatelets at high temperature. The resulted ZnO nanospheres were characterized by X-ray diffraction (XRD), which indicated that ZnO had the hexagonal structure. Field-emission-scanning electron micrographs (SEM) revealed that ZnO nanoparticles had perfect spherical shape with narrow size distribution (average diameters 50 nm). These nanoparticles showed a broad emission band centered at 438 nm using an excitation wave of 325 nm at room temperature. Moreover, the sample was characterized by N₂ adsorption-desorption and the pore size distribution showed a sharp peak at 3.1 nm.     

Synthesis and characterization of flower-like WS2 nanospheres via a facile hydrothermal route

Flower-like WS₂ nanospheres with high purity were successfully synthesized via a facile surfactant-assisted hydrothermal route. The products were characterized by X-ray powder diffraction and scanning electron microscopy. The flower-like WS₂ nanospheres, consisting of numerous aggregate nanosheets with the width of 300–500 nm, had uniform sizes with a mean diameter about 5 μm. Further comparative experiments showed that the surfactant cetyltrimethyl ammonium bromide (CTAB) played a critical role as templates to promote the growth of WS₂ nanosheets and accelerate the assembling of nanosheets into flower-like nanosphere. Interaction forces inside the CTAB made the flower-like nanospheres grow uniformly and dispersedly. Moreover, the WS₂ nanoflowers exhibited excellent visible-absorption ability and may have a potential application as a visible photocatalyst.