Synthesis of silver-iron oxide nanocomposites by thermal decomposition

Silver-iron oxide nanocomposites were synthesized by an easy thermal decomposition method using iron acetyl acetonate and silver acetate as precursors and oleic acid (OA) and oleyl amine (OLA) as the capping agents in a single step. The composite samples were characterized by X-ray diffraction (XRD), infrared spectroscopy, thermal gravimetric analysis (TGA), UV-Visible spectroscopy, scanning electron microscopy (SEM), and magnetic measurements. Powder XRD and UV-Visible spectroscopy results indicate the presence of nanocrystalline silver in the composite and the FT-IR results coupled with TGA results indicate the presence of ligand molecules on surface of the nanocomposites. The FE-SEM images show that the nanocomposite particles are mainly spherical in shape while the energy dispersive X-ray analysis studies indicate the presence of iron and oxygen in the composites. From the magnetic measurements, the composites were found to be superparamagnetic with characteristic blocking temperatures indicating the presence of iron oxide nanoparticles in the nanocomposites.     

Activated carbon/iron oxide composites for the removal of atrazine from aqueous medium

The adsorption features of activated carbon and the oxidation properties of iron oxides were combined in a composite to produce new materials for atrazine removal from aqueous medium. Activated carbon/iron oxide composites were prepared at 1/1 and 5/1 mass ratios and characterized with powder X-ray diffractometry (XRD), infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and nitrogen adsorption measurements. The adsorption and oxidation processes were evaluated in batch experiments, in order to monitor the atrazine removal capacity of these composites. The main iron oxide actually present in the composites was goethite (alpha-FeOOH). Impregnation with iron oxide reduced the surface area by its deposition in the activated carbon pores. However, a higher iron concentration promoted a higher oxidation rate, indicating that the efficiency of the oxidation reaction is related with the iron content and not with the pre-concentration of the contaminant on the carbon surface through adsorption process.     

Spectroscopic analysis of poly(methyl methacrylate)/alumina polymer nanocomposites prepared by in situ (bulk) polymerization

Poly(methyl methacrylate) polymer nanocomposites were prepared by in situ bulk free radical polymerization. To ensure high-quality dispersion of the oxide nanoparticles, some composites were prepared from nanoparticles predispersed in propylene glycol methyl ether acetate (PGMEA). The degree to which this additional dispersing medium interacted with the aluminum oxide nanoparticle was studied by attenuated total reflectance (ATR-FTIR), which confirmed secondary bonding and ionic interaction across the particle/dispersing medium interface. Additionally, the effect of the dispersing medium and the nanoparticles on the degree of monomer conversion was determined by Raman spectroscopy. In the presence of oxide nanoparticles alone, the active surface of the nanoparticles traps propagating radicals which significantly reduces monomer conversion. Conversely, the degree of monomer conversion is enhanced in composites containing predispersing nanoparticles, apparently by passivation/functionalization of the oxide surface by the PGMEA.     

Dextran templating for the synthesis of metallic and metal oxide sponges

Silver or gold-containing porous frameworks have been used extensively in catalysis, electrochemistry, heat dissipation and biofiltration. These materials are often prepared by thermal reduction of metal-ion-impregnated porous insoluble supports (such as alumina and pumice), and have surface areas of about 1 m(2) g(-1), which is typically higher than that obtained for pure metal powders or foils prepared electrolytically or by infiltration and thermal decomposition of insoluble cellulose supports. Starch gels have been used in association with zeolite nanoparticles to produce porous inorganic materials with structural hierarchy, but the use of soft sacrificial templates in the synthesis of metallic sponges has not been investigated. Here we demonstrate that self-supporting macroporous frameworks of silver, gold and copper oxide, as well as composites of silver/copper oxide or silver/titania can be routinely prepared by heating metal-salt-containing pastes of the polysaccharide, dextran, to temperatures between 500 and 900 degrees C. Magnetic sponges were similarly prepared by replacing the metal salt precursor with preformed iron oxide (magnetite) nanoparticles. The use of dextran as a sacrificial template for the fabrication of metallic and metal oxide sponges should have significant benefits over existing technologies because the method is facile, inexpensive, environmentally benign, and amenable to scale-up and processing.     

Protein adsorption on citrate modified magnetic nanoparticles

Magnetic iron oxide nanoparticles were prepared by chemical co-precipitation method and then modified with sodium citrate. These iron oxide nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffractometer (XRD), and vibrating sample magnetometer (VSM). BSA was adsorbed on these citrate modified nanoparticles using two types of buffers (acetate buffer, pH 4.0, 4.7 and phosphate buffer, pH 7.4). The results showed that the maximum adsorption of BSA was 83 mg/g at its isoelectric point (pH 4.7). Fourier-transform infrared spectroscopy (FTIR) was used to confirm the attachment of citrate groups and BSA on the prepared magnetic nanoparticles. BSA was desorbed from nanoparticles under alkaline conditions, which was confirmed by SDS-PAGE electrophoresis, UV-vis and fluorescence spectra. The desorbed BSA showed small changes in its structure. The adsorption results indicated that BSA adsorption on citrate modified iron oxide nanoparticles occurred mainly by electrostatic mechanism.     

Synthesis of [60]fullerene-ZnO nanocomposite under electric furnace and photocatalytic degradation of organic dyes

Zinc oxide (ZnO) nanoparticles were synthesized by a reaction between an aqueous-alcoholic solution of zinc nitrate and sodium hydroxide under ultrasonic irradiation at room temperature. The morphology, optical properties of the ZnO nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-vis spectroscopy. The [60]fullerene and zinc oxide nanocomposite were synthesized in an electric furnace at 700 degrees C for two hours. The [60]fullerene-ZnO nanocomposite was characterized by XRD, SEM and TEM. In addition, the [60]fullerene-ZnO nanocomposite was investigated as a catalyst in the photocatalytic degradation of organic dyes using UV-vis spectroscopy. The photocatalytic activity of the [60]fullerene-ZnO nanocomposite was compared with that of ZnO nanoparticles, heated ZnO nanoparticles after synthesis, pure [60]fullerene, and heated pure [60]fullerene in organic dyes such as methylene blue (MB), methyl orange (MO), and rhodamine B (RhB) under ultraviolet light at 254 nm.     

石墨烯-银纳米粒子复合材料的制备及表征

以无毒、绿色的葡萄糖为还原剂, 在没有稳定剂、温和的液相反应条件下, 同时还原氧化石墨和银氨溶液中的银氨离子, 原位制备石墨烯-银纳米粒子复合材料. 采用X射线衍射、红外吸收光谱、拉曼光谱、扫描电镜和透射电子显微镜对所制备的石墨烯-银纳米粒子复合材料进行了表征. 结果表明: 氧化石墨和银离子在反应过程中同时被葡萄糖还原, 银纳米粒子均匀分布于石墨烯片层之间, 生成的银纳米粒子中大多数存在着孪晶界, 银纳米粒子的大小和分布受硝酸银用量的影响, 在合适的银离子浓度下, 负载在石墨烯片层上的银纳米粒子的粒径分布集中在25 nm左右; 复合材料中石墨烯的拉曼信号由于银粒子的存在增强了7倍.     

Preparation and application of attapulgite/iron oxide magnetic composites for the removal of U(VI) from aqueous solution

Recently, magnetic sorbents have received considerable attention because of their excellent segregative features and sorption capacities. Herein, attapulgite/iron oxide magnetic (ATP/IOM) composites were prepared and characterized. The sorption results indicated that ATP/IOM composites were superior to ATP and iron oxides individually for the removal of U(VI) from aqueous solution. Based on X-ray photoelectron spectroscopy (XPS) analysis and surface complexation model, the main sorption species of U(VI) on ATP were==X(2)UO(2)(0) below pH 4.0 and==S(s)OUO(2)(+), ==S(w)OUO(2)CO(3)(-), and==S(w)OUO(2)(CO(3))(2)(3-) above pH 5.0. However the prevalent species on ATP/IOM composites were==S(s)OUO(2)(+) and==S(w)OUO(2)(CO(3))(2)(3-) over the observed pH range. ATP/IOM composites are a promising candidate for pre-concentration and immobilization of radionuclides from large volumes of aqueous solutions, as required for remediation purposes.     

Removal of cationic dyes from aqueous solution using magnetic multi-wall carbon nanotube nanocomposite as adsorbent

A magnetic multi-wall carbon nanotube (MMWCNT) nanocomposite was synthesized and was used as an adsorbent for removal of cationic dyes from aqueous solutions. The MMWCNT nanocomposite was composed of commercial multi-wall carbon nanotubes and iron oxide nanoparticles. The properties of this magnetic adsorbent were characterized by scanning electron microscopy, X-ray diffraction and BET surface area measurements. Adsorption characteristics of the MMWCNT nanocomposite adsorbent were examined using methylene blue, neutral red and brilliant cresyl blue as adsorbates. Experiments were carried out to investigate adsorption kinetics, adsorption capacity of the adsorbent and the effect of adsorption dosage and solution pH values on the removal of cationic dyes. Kinetic data were well fitted by a pseudo second-order model. Freundlich model was used to study the adsorption isotherms. The prepared MMWCNT adsorbent displayed the main advantage of separation convenience compared to the present adsorption treatment.     

The development of stable aqueous suspensions of PEGylated SPIONs for biomedical applications

We report here the development of stable aqueous suspensions of biocompatible superparamagnetic iron oxide nanoparticles (SPIONs). These so-called ferrofluids are useful in a large spectrum of modern biomedical applications, including novel diagnostic tools and targeted therapeutics. In order to provide prolonged circulation times for the nanoparticles in?vivo, the initial iron oxide nanoparticles were coated with a biocompatible polymer poly(ethylene glycol) (PEG). To permit covalent bonding of PEG to the SPION surface, the latter was functionalized with a coupling agent, 3-aminopropyltrimethoxysilane (APS). This novel method of SPION PEGylation has been reproduced in numerous independent preparations. At each preparation step, particular attention was paid to determine the physico-chemical characteristics of the samples using a number of analytical techniques such as atomic absorption, Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy, transmission electron microscopy (TEM), photon correlation spectroscopy (PCS, used for hydrodynamic diameter and zeta potential measurements) and magnetization measurements. The results confirm that aqueous suspensions of PEGylated SPIONs are stabilized by steric hindrance over a wide pH range between pH 4 and 10. Furthermore, the fact that the nanoparticle surface is nearly neutral is in agreement with immunological stealthiness expected for the future biomedical applications in?vivo.     

Preparation of tin ferrite–tin oxide by hydrothermal,precipitation and auto-combustion: photo-catalyst and magnetic nanocomposites for degradation of toxic azo-dyes

In this work, tin ferrite nanoparticles were first synthesized by simple chemical procedures such as co precipitation, sol–gel auto combustion and hydrothermal methods. In general, all three methods were compared in the synthesis of nanoparticles. Then tin ferrite–tin oxide (50%:50%) nanocomposites were prepared using co precipitation method. Crystal structures of nanoparticles and nanocomposite were studied using X-ray diffraction pattern. The particle size was determined by Scanning Electron Microscopy. Vibrating sample magnetometer was used to study the magnetic property of the products. And also, by applying Fourier transform infrared spectrometer, the purity of the material was determined. Photocatalytic activity of nanoparticles and nanocomposites was investigated under ultra-violet and visible spectroscopy (UV–Vis). The results show that prepared nanocomposites are applicable for magnetic and photocatalytic performance and they were able to degrade azo dyes (organic dyes) under UV–Vis radiation.     

A facile synthesis of supported amorphous iron oxide with high performance for Cr(VI) removal from aqueous solution under visible light irradiation

A series of supported iron oxide nanoparticles were prepared by impregnation with Fe(NO₃)₃ supported on TiO_2, followed by low-temperature calcination. Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra and BET have been used to characterize the samples. These iron oxide-impregnated TiO₂ were examined for photocatalytic reduction of Cr(VI). The experiments demonstrated that Cr(VI) in aqueous solution was more efficiently reduced using Fe₂O₃/TiO₂ heterogeneous photocatalysts than either pure Fe₂O₃ or TiO₂ under visible light irradiation. All TiO₂ supported samples were somewhat active for visible light photoreduction. With an optimal mole ratio of 0.05-Fe/Ti, the highest rate of Cr(VI) reduction was achieved under the experimental conditions. We also compared the photoreactivity of TiO₂ supported iron oxide samples with that supported on Al₂O₃ and ZrO₂. It can be noted that iron oxide nanoparticles deposited on high surface area supports to increase the solid-liquid contact area renders it considerably more active. Noticeably, iron oxide cluster size and dispersion are important parameters in synthesizing active, supported Iron oxide nanoparticles. In addition, the interaction between iron oxide and TiO₂ was proposed as the source of photoactivity for Cr(VI) reduction.     

Preparation of C60(O)n-ZnO nanocomposite under electric furnace and photocatalytic degradation of organic dyes

Zinc oxide (ZnO) nanoparticles were synthesized sonochemically by applying ultrasonic irradiation to a mixed aqueous-alcoholic solution of zinc nitrate with sodium hydroxide at room temperature. The morphology and optical properties of the ZnO nanoparticles were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-vis spectroscopy. The C60(O)n nanoparticles were synthesized by heating a mixture of C60 and 3-chloroperoxybenzoic acid in a benzene solvent under the reflux system. The heated C60(O)n-ZnO nanocomposite was synthesized in an electric furnace at 700 degrees C for two hours. The heated C60(O)n-ZnO nanocomposite was characterized by XRD, SEM, and TEM, and examined as a catalyst in the photocatalytic degradation of organic dyes by UV-vis spectroscopy. The photocatalytic effect of the heated C60(O)n-ZnO nanocomposite was evaluated by a comparison with that of unheated C60(O)n nanoparticles, heated C60(O)n nanoparticles, and unheated C60(O)n-ZnO in organic dyes, such as methylene blue (MB), methyl orange (MO), and rhodamine B (RhB) under ultraviolet light at 365 nm.     

Microwave-assisted synthesis and characterization of zinc oxide/carbon nanotube composites

A composite material of zinc oxide and carbon nanotubes were successfully synthesized via a sol process using zinc acetate dihydrate and treated multi-wall carbon nanotubes under microwave irradiation. The morphology, microstructure and chemical bonding of as-obtained composites were well characterized using X-ray diffraction, scanning electron microscope, transmission electron microscope, and Fourier transform infrared spectroscopy. Zinc oxide nanoparticles were dispersively coated on the surface of carbon nanotube when the precursor was dried under microwave irradiation without post-annealing. X-ray diffraction results obviously showed the mixture of two phases of carbon nanotube and wurzite zinc oxide whose size is approximately 15 nm. The formation of zinc oxide nanoparticles on carbon nanotube surface in the composite prepared by microwave heating is much better than the composite heated by conventional annealing. Fourier transform infrared spectroscopic results suggest that carboxylic groups and uniform heating by microwave heating could play key roles on the nucleation of zinc oxide on carbon nanotube surface.     

Ultrafast degradation of common organic dyes in presence of gadolinium oxide/graphene oxide in water

Gadolinium oxide/graphene oxide (Gd₂O₃/GO) nanocomposite has been prepared by a simple method in N,N-dimethylformamide (DMF) and employed as an excellent catalyst for common organic dyes degradation under ultrasound. The scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS) data revealed that the Gd₂O₃ nanoparticles were successfully attached on the surface of GO sheets. The High efficiencies of common dyes (methylene blue, methyl orange, methyl violet rhodamine B, fuchsin base, thymolphthalein, crystal violet and eosin) degradation within 15?min illustrated that the as-synthesized nanocomposite was an ultrafast, stable, recyclable, and economical material for environment related applications.     

Surface-modified superparamagnetic nanoparticles for drug delivery: preparation, characterization, and cytotoxicity studies

Superparamagnetic iron oxide nanoparticles have been used for many years as magnetic resonance imaging (MRI) contrast agents or in drug delivery applications. In this study, a novel approach to prepare magnetic polymeric nanoparticles with magnetic core and polymeric shell using inverse microemulsion polymerization process is reported. Poly(ethyleneglycol) (PEG)-modified superparamagnetic iron oxide nanoparticles with specific shape and size have been prepared inside the aqueous cores of AOT/n-Hexane reverse micelles and characterized by various physicochemical means such as transmission electron microscopy (TEM), infrared spectroscopy, atomic force microscopy (AFM), vibrating sample magnetometry (VSM), and ultraviolet/visible spectroscopy. The inverse microemulsion polymerization of a polymerizable derivative of PEG and a cross-linking agent resulted in a stable hydrophilic polymeric shell of the nanoparticles. The results taken together from TEM and AFM studies showed that the particles are spherical in shape with core-shell structure. The average size of the PEG-modified nanoparticles was found to be around 40-50 nm with narrow size distribution. The magnetic measurement studies revealed the superparamagnetic behavior of the nanoparticles with saturation magnetization values between 45-50 electromagnetic units per gram. The cytotoxicity profile of the nanoparticles on human dermal fibroblasts as measured by standard 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed that the particles are nontoxic and may be useful for various in vivo and in vitro biomedical applications.     

Electrodeposited nanoporous versus nanoparticulate ZnO films of similar roughness for dye-sensitized solar cell applications

We present a comparative study of two different ZnO porous film morphologies for dye-sensitized solar cell (DSSC) fabrications. Nanoparticulate ZnO was prepared by the doctor-blade technique starting from a paste containing ZnO nanoparticles. Nanoporous ZnO films were grown by a soft template-assisted electrochemical growth technique. The film thicknesses were adjusted at similar roughness of about 300 in order to permit a worthy comparison. The effects on the cell performances of sensitization by dyes belonging to three different families, namely, xanthene (eosin Y) and indoline (D102, D131, D149 and D205) organic dyes as well as a ruthenium polypyridine complex (N719), have been investigated. The mesoporous electrodeposited matrix exhibits significant morphological changes upon the photoanode preparation, especially upon the dye sensitization, that yield to a dramatic change of the inner layer morphology and increase in the layer internal specific surface area. In the case of indoline dyes, better efficiencies were found with the electrodeposited ZnO porous matrixes compared to the nanoparticulate ones, in spite of significantly shorter electron lifetimes measured by impedance spectroscopy. The observation is interpreted in terms of much shorter transfer time in the oxide in the case of the electrodeposited ZnO films. Among the tested dyes, the D149 and D205 indoline organic dyes with a strong acceptor group were found the most efficient with the best cell over 4.6% of overall conversion efficiency.     

Preparation of silica coated iron oxide nanoparticles using non-transferred arc plasma

Silica coated iron oxide nanoparticles were prepared using non-transferred arc plasma. The plasma was discharged with argon. Vapors of iron pentacarbonyl (Fe(CO)₅) and tetraethyl orthosilicate (TEOS, Si(OC₂H₅)₄) were injected into a plasma torch with carrier gas and reacted in the plasma chamber. In addition, two types of reaction chambers that are a hot wall reactor and a cold wall reactor were used to investigate the effect of temperature gradient on the synthesis of silica coated iron oxide nanoparticles. The synthesized nanoparticles were collected on the chamber wall and bottom. Phase compositions of the obtained nanoparticles were characterized by X-ray diffractometer (XRD) and the morphologies and the size distributions of the synthesized particles were analyzed by scanning electron microscopy (SEM) and transmission electron microscope (TEM). Additionally, elements mapping of the coated particles was performed by energy dispersive spectroscopy (EDS). The phase composition of the prepared particles was mainly composed of amorphous silica and polycrystalline Fe₃O₄. It was confirmed that the silica was adsorbed on iron oxide particles or encapsulated iron oxide particles. Furthermore, the mechanism of the formation of silica coated iron oxide in the plasma chamber was predicted.     

Surface Engineering of Core/Shell Iron/Iron Oxide Nanoparticles from Microemulsions for Hyperthermia

This paper describes the synthesis and surface engineering of core/shell-type iron/iron oxide nanoparticles for magnetic hyperthermia cancer therapy. Iron/iron oxide nanoparticles were synthesized from microemulsions of NaBH(4) and FeCl(3), followed by surface modification in which a thin hydrophobic hexamethyldisilazane layer - used to protect the iron core - replaced the CTAB coating on the particles. Phosphatidylcholine was then assembled on the nanoparticle surface. The resulting nanocomposite particles have a biocompatible surface and show good stability in both air and aqueous solution. Compared to iron oxide nanoparticles, the nanocomposites show much better heating in an alternating magnetic field. They are good candidates for both hyperthermia and magnetic resonance imaging applications.     

Silicon nanoparticles synthesised through reactive high-energy ball milling: enhancement of optical properties from the removal of iron impurities

Alkyl-terminated silicon nanoparticles (SiNPs) were prepared through reactive high-energy ball milling with contamination of iron from the steel milling materials. Iron impurities in the form of iron nanoparticles cause a decrease of photoluminescence intensity and an increase of the UV absorption. The iron impurities were removed either by gel permeation chromatography separation or by treatment with an aqueous HCl solution. The photoluminescence properties of the SiNPs were enhanced after the removal of iron. Transmission electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and proton nuclear magnetic resonance were used to determine morphology, elemental composition and surface passivation of SiNPs.