Effect of surfactants on preparation of nanoscale α-Al2O3 powders by oil-in-water microemulsion

The nanoscale α-Al₂O₃ powders have been synthesized by the O/W microemulsion system using cyclohexane as the oil phase, ultrapure water as the water phase, OP-10 and alcohol as the surfactant and co-surfactant. It has been found that the nature of surfactants played an important role to regulate the size and morphologies of the α-Al₂O₃ nanoparticles. Three different nonionic surfactants (OP-10, Triton X-100 and Tween-80) have been used for the preparation of microemulsions. The microemulsions were characterized by Zeta Potential Analyzer. The results showed that the OP-10 system possesses wide and stable microemulsion phase regions. The synthesized α- Al₂O₃ powders have been comprehensively characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD). The powders calcined at 900–1150 °C showed the presence of alumina phase with crystal structure, The SEM images showed that the powders was an average diameter of 30–100 nm.     

Efficient purification of His-tagged protein by superparamagnetic Fe3O4/Au–ANTA–Co2 + nanoparticles

Superparamagnetic Fe₃O₄/Au nanoparticles were synthesized and surface modified with mercaptopropionic acid (MPA), followed by conjugating Nα,Nα-Bis(carboxymethyl)-l-lysine hydrate (ANTA) and subsequently chelating Co^2 +. The resulting Fe₃O₄/Au–ANTA–Co^2 + nanoparticles have an average size of 210 nm in aqueous solution, and a magnetization of 36 emu/g, endowing the magnetic nanoparticles with excellent magnetic responsivity and dispersity. The Co^2 + ions in the magnetic nanoparticle shell provide docking site for histidine, and the Fe₃O₄/Au–ANTA–Co^2 + nanoparticles exhibit excellent performance in binding of a His-tagged protein with a binding capacity of 74 μg/mg. The magnetic nanoparticles show highly selective purification of the His-tagged protein from Escherichia coli lysate. Therefore, the obtained Fe₃O₄/Au–ANTA–Co^2 + nanoparticles exhibited excellent performance in the direct separation of His-tagged protein from cell lysate.     

Capture and release of genomic DNA by PEI modified Fe3O4/Au nanoparticles

Polyethylenimine (PEI) modified Fe₃O₄/Au nanoparticles were synthesized in aqueous solution and characterized by photo correlation spectroscopy (PCS) and vibrating sample magnetometer (VSM). The so-obtained Fe₃O₄/Au-PEI nanoparticles were capable of efficient electrostatic capture of DNA. The maximum amount of genomic DNA captured on 1.0 mg Fe₃O₄/Au-PEI nanoparticles was 90 μg. The DNA release behavior was studied and the DNA recovery from Fe₃O₄/Au-PEI nanoparticles approached 100% under optimal conditions. DNA extraction from mammalian cells using Fe₃O₄/Au-PEI nanoparticles was successfully performed. Up to approximately 43.1 μg of high-purity (OD₂₆₀/OD₂₈₀ ratio = 1.81) genomic DNA was extracted from 10 mg of liver tissue. The results indicated that the prepared Fe₃O₄/Au-PEI nanoparticles could be successfully used for DNA capture and release.     

Synthesis,characterization and microwave absorption properties of Fe3O4/Co core/shell-type nanoparticles

Co coated Fe₃O₄ core/shell-type nanoparticles were fabricated by hydrothermal technique and electroless plating process. X-ray powder diffraction (XRD), X-ray fluorescence spectrometer (XRF) and transmission electron microscope (TEM) were employed to investigate the crystal structure, element composition and morphology of the prepared nanoparticles. Vibrating sample magnetometer (VSM) and vector network analyzer were used to measure the magnetic properties and electromagnetic parameters of pure Fe₃O₄ and Fe₃O₄/Co core/shell-type nanoparticles, then reflection losses (RL(dB)) were calculated in the frequency range of 2–18 GHz. Magnetic studies revealed typical ferromagnetic behavior for the pure Fe₃O₄ and Fe₃O₄/Co core/shell-type nanoparticles with their saturation magnetization (M_s = 63.1 and 72.4 emu/g) and coercivity (H_c = 99.5, and 165.4 Oe), respectively. Due to the existence of the core/shell structure, the electromagnetic characteristic of the Fe₃O₄/Co nanoparticles exhibit better microwave absorption performance than the pure Fe₃O₄ in the range of 2–18 GHz, such as more powerful absorbing property and wider frequency band of microwave absorption.     

Measurement of microemulsion zone and preparation of monodispersed cerium oxide nanoparticles by W/O microemulsion method

In the W/O microemulsion system of cetyltrim ethylamine bromide (CTAB) + butanol / cyclohexane / water solution, the microemulsion area was measured and cerium oxide nanoparticles were prepared according to the principle by two-phase liquid–liquid method. The samples were analyzed by means of transmission electron microscope, X-ray diffraction, thermogravimetric-differential scanning calorimetry, and infrared. And their morphology, phase, components were investigated. The results made clear that nanometer cerium oxide could be prepared in the measured area of microemulsion and it is an effective way to gain the well dispersed and uniformly distributed nanometer cerium oxide grains with the size of about 3 nm.     

Size-controlled synthesis of Rod-like α-FeOOH nanostructure

One-dimensional goethite (α-FeOOH) nanorods were successfully fabricated by a hydrothermal route without any template. Experimental results reveal that concentrations of Fe^3 + and ethylenediaminetetraacetic disodium salt (Na₂EDTA) affect the phase composition and size of the as-synthesized products. The size of the rod-like α-FeOOH increased when the concentration of Na₂EDTA was increased, where Na₂EDTA acts as a nucleation inhibitor. α-Fe₂O₃ nanoparticles were produced when the concentration of Fe^3 + was increased from 0.02 to 0.08 and 0.40 M. A possible formation mechanism was proposed based on the results of the time dependent experiments. Different electrolytes and surfactants can affect the size and the aspect ratio of the as-prepared nanorod-like α-FeOOH. Na₂SO₄ induced the decreasing of the size of the as-prepared sample. KCl and PVP affected the aspect ratio of the nanorods.     

Synthesis and characterization of Piperidine-4-carboxylic acid functionalized Fe3O4 nanoparticles as a magnetic catalyst for Knoevenagel reaction

Piperidine-4-carboxylic acid (PPCA) functionalized Fe₃O₄ nanoparticles as a novel organic–inorganic hybrid heterogeneous catalyst was fabricated and characterized by XRD, FT-IR, TGA, TEM and VSM techniques. Composition was determined as Fe₃O₄, while particles were observed to have spherical morphology. Size estimations using X-ray line profile fitting (10 nm), TEM (11 nm) and magnetization fitting (9 nm) agree well, revealing nearly single crystalline character of Fe₃O₄ nanoparticles. Magnetization measurements reveal that PPCA functionalized Fe₃O₄ NPs have superparamagnetic features, namely immeasurable coercivity and absence of saturation. Small coercivity is established at low temperatures. The catalytic activity of Fe₃O₄–PPCA was probed through one-pot synthesis of nitro alkenes through Knoevenagel reaction in CH₂Cl₂ at room temperature. The heterogeneous catalyst showed very high conversion rates (97%) and could be recovered easily and reused many times without significant loss of its catalytic activity.     

Synthesis of nanocrystalline GaN from Ga2O3 nanoparticles derived from salt-assisted spray pyrolysis

Gallium nitride (GaN) nanoparticles were successfully produced from nano-sized gallium oxide (Ga₂O₃) particles under a flow of ammonia gas. The gallium oxide nanoparticles were prepared by salt-assisted spray pyrolysis (SASP). Highly crystalline Ga₂O₃ nanoparticles with an average diameter of approximately 10 nm were obtained at various temperatures when a flux salt (LiCl, 5 mol/l) was added to the precursor solution. The effects of the crystallinity of the Ga₂O₃ particles and nitridation time on transformation to GaN were characterized using X-ray diffraction and scanning/transmission electron microscopy. Highly crystalline GaN nanoparticles with a mean size of 23.4 nm and a geometric standard deviation of 1.68 nm were obtained when Ga₂O₃ nanoparticles with relatively low crystallinity were used as the starting material. The resulting GaN nanoparticles showed a photoluminescence peak at 364 nm under UV excitation at 254 nm.     

Fabrication of CuO/Fe2O3 hollow hybrid microspheres

CuO/Fe₂O₃ hollow hybrid spheres with the size of 3–5 μm were successfully synthesized by a convenient hydrothermal method, using FeSO₄·7H₂O and CuSO₄·5H₂O as the starting materials and urea as the homogeneous precipitant. The samples were characterized by XRD, TEM, ED, SEM, EDX, IR and XPS measurements. XRD and XPS analyses indicated that the nanostructured materials consisted of CuO and α-Fe₂O₃. TEM and SEM measurements showed that the morphology of binary metal oxide was in the shape of hollow sphere. Careful observation from SEM measurements could find that CuO/Fe₂O₃ hollow microsphere shell was composed of uniform and dense metal oxide nanorods with about 20–40 nm in diameter and 100–200 nm in length. Moreover, the influence of calcination temperature on the thermal stability of the hollow structures was investigated. It showed that the hollow structure was stable after being calcined at 300 °C for 2 h. The formation mechanism of the CuO/Fe₂O₃ hollow spheres under hydrothermal condition was discussed.     

Fluidization of binary mixtures of nanoparticles under the effect of acoustic fields

The present work is focused on the characterization of the aeration behaviour of two different nanopowders, Al₂O₃ and Fe₂O₃, under the application of acoustic fields of different intensities (125–150 dB) and frequencies (50–300 Hz). The two nanopowders showed slightly different behaviours; in particular, Fe₂O₃ is generally characterized by a better fluidization quality. These differences have been explained by referring to nanoparticles aggregates properties. In particular, aggregates size and density and fractal dimension have been numerically evaluated. The fluidization of binary mixtures of the two powders has also been investigated under the application of different acoustic fields (130–135 dB, 120 Hz) and varying the amount of the two powders from 7%wt to 90%wt of Fe₂O₃. The addition of Fe₂O₃ generally has a beneficial effect on the fluidization quality of the binary mixtures, in terms of pressure drop and bed expansion ratio, becoming relevant from an amount of Fe₂O₃ of 33%wt.     

Synthesis and functionalization of SiO2 coated Fe3O4 nanoparticles with amine groups based on self-assembly

The purpose of this research was to synthesize amino modified Fe₃O₄/SiO₂ nanoshells for biomedical applications. Magnetic iron-oxide nanoparticles (NPs) were prepared via co-precipitation. The NPs were then modified with a thin layer of amorphous silica. The particle surface was then terminated with amine groups. The results showed that smaller particles can be synthesized by decreasing the NaOH concentration, which in our case this corresponded to 35 nm using 0.9 M of NaOH at 750 rpm with a specific surface area of 41 m² g^? 1 for uncoated Fe₃O₄ NPs and it increased to about 208 m² g^?1 for 3-aminopropyltriethoxysilane (APTS) coated Fe₃O₄/SiO₂ NPs. The total thickness and the structure of core-shell was measured and studied by transmission electron microscopy (TEM). For uncoated Fe₃O₄ NPs, the results showed an octahedral geometry with saturation magnetization range of (80–100) emu g^?1 and coercivity of (80–120) Oe for particles between (35–96) nm, respectively. The Fe₃O₄/SiO₂ NPs with 50 nm as particle size, demonstrated a magnetization value of 30 emu g^?1. The stable magnetic fluid contained well-dispersed Fe₃O₄/SiO₂/APTS nanoshells which indicated monodispersity and fast magnetic response.     

Synthesis of nanocrystalline Ni0.5Zn0.5Fe2O4 ferrite and study of its magnetic behavior at different temperatures

Ni_0.5Zn_0.5Fe₂O₄ ferrite nanocrystals with average diameter in the range of 1–2 nm have been synthesized by reverse microemulsion. X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) are used to characterize the structural, morphological and magnetic properties. X-ray analysis showed that the nanocrystals possess cubic spinel structure. The absence of hysteresis, negligible remanence and coercivity at 300 K indicate the superparamagnetic character and single domain in the nanocrystalline Ni_0.5Zn_0.5Fe₂O₄ ferrite materials. The nanocrystalline Ni_0.5Zn_0.5Fe₂O₄ ferrite were annealed at 600 °C. As a result of heat treatment the average particle size increases from 2 nm to 5 nm and the corresponding magnetization values have increased to 21.69 emu/g at 300 K. However, at low temperature of 100 K, the annealed samples show hysteresis loop which is the characteristic of a superparamagnetic to ferromagnetic transition. In addition, a comparative study of the magnetic properties of Ni_0.5Zn_0.5Fe₂O₄ ferrite nanocrystals obtained from reverse microemulsion has been carried out with those obtained from the general chemical co-precipitation route.     

A biocompatible approach to surface modification: Biodegradable polymer functionalized super-paramagnetic iron oxide nanoparticles

In the study, Fe₃O₄ nanoparticles with a size range of 10–20 nm were firstly prepared by the modified controlled chemical coprecipitation method from the solution of ferrous/ferric mixed salt-solution in alkaline medium. Then, the super-paramagnetic iron oxide nanoparticles were covalently modified by biodegradable polymers such as polyethylene glycol (PEG) and poly(ethylene glycol)-co-poly(d,l-lactide) (PELA). The size and its distribution of the nanoparticles were determined by dynamic light scattering measurements (DLS). The magnetic nanoparticles was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED), Fourier transform infrared spectroscopy (FT-IR) and UV–visible spectrophotometry (UV). Magnetic properties were measured using a vibrating sample magnetometer. And the 5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT) assay was performed to evaluate the biocompatibility of the magnetic nanoparticles. The results showed that the Fe₃O₄ nanoparticles functionalized by PEG and PELA possessed a mean size of 43.2 and 79.3 nm, respectively, and exhibited an excellent biocompatibility.     

Preparation of Fe3O4–chitosan nanoparticles used for hyperthermia

The Fe₃O₄–chitosan nanoparticles with core-shell structure have been prepared by crosslinking method. Oleic acid modified Fe₃O₄ nanoparticles were firstly prepared by co-precipitation then chitosan was added to coat on the surface of the Fe₃O₄ nanoparticles by physical absorption. The Fe₃O₄–chitosan nanoparticles were obtained by crosslinking the amino groups on the chitosan using glutaraldehyde. Transmission electron microscopy showed that the Fe₃O₄–chitosan nanoparticles were quasi-spherical with a mean diameter of 10.5 nm. X-ray diffraction pattern and X-ray photoelectron spectra indicated that the magnetic nanoparticles were pure Fe₃O₄ with a cubic inverse spinel structure. The modification using chitosan did not result in a phase change. The binding of chitosan to the Fe₃O₄ nanoparticles was also demonstrated by the measurement of fourier transform infrared spectra and thermogravimetric analysis. Magnetic measurement revealed that the saturation magnetization of the composite nanoparticles was 30.7 emu/g and the nanoparticles were superparamagnetic at room temperature. Furthermore, the inductive heating property of the composite nanoparticles in an alternating current magnetic field was investigated and the results indicated that the heating effect was significant. The Fe₃O₄–chitosan nanoparticles prepared have great potential in hyperthermia.     

Synthesis of magnetite nanoparticles by surfactant-free electrochemical method in an aqueous system

A simple surfactant-free electrochemical method is proposed for the preparation of magnetite nanoparticles using iron as the anode and plain water as the electrolyte. This study observed the effects of certain parameters on the formation of magnetite nanoparticles and their mechanism in the system, including the role of OH^? ions, the distance between electrodes and current density. We found that OH^? ions play an important role in the formation of magnetite nanoparticles. Particle size can be controlled by adjusting the current density and the distance between electrodes. Particle size increases by increasing the current density and by decreasing the distance between electrodes. Particle formation cannot be favored when the distance between electrodes is larger than a critical value. The magnetite nanoparticles produced by this method are nearly spherical with a mean size ranging from 10 to 30 nm depending on the experimental conditions. They exhibit ferromagnetic properties with a coercivity ranging from 140 to 295 Oe and a saturation magnetization ranging from 60 to 70 emu g^?1, which is lower than that of the corresponding bulk Fe₃O₄ (92 emu g^?1). This simple method appears to be promising as a synthetic route to producing magnetite nanoparticles.     

Joint mechanical activation of MnO2, Fe2O3 and graphite: Mutual influence on the structure

The structural changes of MnO₂, Fe₂O₃ and graphite under separate and joint mechanical activation in high-energy planetary ball mill were studied by X-ray diffraction analysis, Raman spectroscopy and chemical analysis. Separate mechanical processing resulted in nanostructured states of MnO₂, Fe₂O₃ and graphite with the size of coherent scattering regions of 25, 12 and 6 nm, respectively, and the average particle size of 15–20 nm. Along with nanoparticles of globular shape, Fe₂O₃ nanorods were found to be formed during separate milling. No mechanochemical effect was found after separate milling. Under joint mechanical activation of nanostructured manganese and iron oxides with graphite, phase transformations toward less stable forms of oxides (Mn₂O₃, Mn₃O₄, Fe₃O₄) were found. When co-milled with α-Fe₂O₃, graphite was found to exfoliate to graphene layers. The graphite phase remained under the combined mechanical activation with MnO₂. Dynamic recrystallization of α-Fe₂O₃ phase also proceeded during joint mechanical activation of nanostructured Fe₂O₃ and graphite.     

Nanocrystalline LaFeO3 preparation and thermal process of precursor

Nanocrystalline LaFeO₃ was synthesized by calcining precursor La₂(CO₃)₂(OH)₂–Fe₂O₃?1.5H₂O in air. XRD analysis showed that precursor dried at 80 °C was a mixture containing orthorhombic La₂(CO₃)₂(OH)₂ and amorphous Fe₂O₃?1.5H₂O. Orthorhombic LaFeO₃ with highly crystallization was obtained when La₂(CO₃)₂(OH)₂–Fe₂O₃?1.5H₂O was calcined at 900 °C in air for 2 h. Magnetic characterization indicated that the calcined product at 900 °C behaved weak magnetic behavior at room temperature. The thermal process of La₂(CO₃)₂(OH)₂–Fe₂O₃?1.5H₂O experienced five steps, which involves, at first, dehydration of 0.8 absorption water, then dehydration of 0.7 crystal water, decomposition of orthorhombic La₂(CO₃)₂(OH)₂ into orthorhombic LaCO₃OH, reaction of two LaCO₃OH into hexagonal La₂O₂CO₃ and crystallization of tetragonal Fe₂O₃, at last, reaction of hexagonal La₂O₂CO₃ with tetragonal Fe₂O₃ into orthorhombic LaFeO₃. In the DTG curve, four DTG peaks indicated the precursor experienced mass loss of four steps.     

A simple method to prepare indium oxide nanoparticles: Structural,microstructural and magnetic properties

Indium oxide nanoparticles of ～12 nm were synthesized by a simple chemical route using indium(III) nitrate. Nanoparticles are formed after calcining the dried precursor in air at 400 °C for 10 h. TEM analysis showed that the morphology and size of the In₂O₃ samples were affected by ultrasonication. FTIR and Raman studies reveal that the nanoparticles are single-phase cubic structure of In₂O₃. NEXAFS study was used to quantify the Indium and oxygen valence state. Magnetic behavior of indium oxide nanoparticles was found to be diamagnetic. UV spectra show a weak band at ～308 nm corresponds to optical band gap energy of 4.03 eV.     

Variation with added material in the effects of reactive mechanical grinding and hydriding–dehydriding cycling on the hydrogen-storage properties of Mg

Samples Mg–14Ni–6Fe₂O₃, Mg–14Ni–3Fe₂O₃–3Ti, and Mg–14Ni–2Fe₂O₃–2Ti–2Fe were prepared by reactive mechanical grinding, and their hydrogen storage properties were examined. The activated Mg–14Ni–2Fe₂O₃–2Ti–2Fe had the highest hydriding rate, absorbing 4.14 wt% H for 5 min, and 4.27 wt% H for 10 min, and 4.42 wt% H for 60 min at 573 K under 12 bar H₂. The activated Mg–14Ni–3Fe₂O₃–3Ti had the highest dehydriding rate, desorbing 3.81 wt% H for 20 min, 3.98 wt% H for 25 min, and 4.15 wt% H for 60 min. Mg–14Ni–6Fe₂O₃ dehydrided at n = 4 contained Mg, Mg₂Ni, MgO, and Mg(OH)₂. Mg(OH)₂ is considered to be formed by the reactions of MgH₂ or Mg with water vapor. The effects of reactive mechanical grinding and hydriding–dehydriding cycling are the creation of defects and cracks, and the reduction of Mg particle size. The addition of a larger amount of Ti and/or Fe has stronger effects of reactive mechanical grinding, whereas the addition of a larger amount of Fe₂O₃ has greater effects of hydriding–dehydriding cycling.     

Magnetically-sensitive shape memory polyurethane composites crosslinked with multi-walled carbon nanotubes

Magnetically-sensitive polyurethane composites, which were crosslinked with multi-walled carbon nanotubes (MWCNTs) and were filled with Fe₃O₄ nanoparticles, were synthesized via in situ polymerization method. MWCNTs pretreated with nitric acid were used as crosslinking agents. Because of the crosslinking of MWCNTs with polyurethane prepolymer, the properties of the composites with a high content of Fe₃O₄ nanoparticles, especially the mechanical properties, were significantly improved. The composites showed excellent shape memory properties in both 45 °C hot water and an alternating magnetic field (f = 45 kHz, H = 29.7 kA m⁻¹). The shape recovery time was less than one minute and the shape recovery rate was over 95% in the alternating magnetic field.