Synthesis and characterization of PEG-iron oxide core-shell composite nanoparticles for thermal therapy

In this study, core-shell nanoparticles were developed to achieve thermal therapy that can ablate cancer cells in a remotely controlled manner. The core-shell nanoparticles were prepared using atomic transfer radical polymerization (ATRP) to coat iron oxide (Fe₃O₄) nanoparticles with a poly(ethylene glycol) (PEG) based polymer shell. The iron oxide core allows for the remote heating of the particles in an alternating magnetic field (AMF). The coating of iron oxide with PEG was verified through Fourier transform infrared spectroscopy and thermal gravimetric analysis. A thermoablation (55 °C) study was performed on A549 lung carcinoma cells exposed to nanoparticles and over a 10 min AMF exposure. The successful thermoablation of A549 demonstrates the potential use of polymer coated particles for thermal therapy.     

Doxorubicin loaded PVA coated iron oxide nanoparticles for targeted drug delivery

Magnetic drug targeting is a drug delivery system that can be used in locoregional cancer treatment. Coated magnetic particles, called carriers, are very useful for delivering chemotherapeutic drugs. Magnetic carriers were synthesized by coprecipitation of iron oxide followed by coating with polyvinyl alcohol (PVA). Characterization was carried out using X-ray diffraction, TEM, TGA, FTIR and VSM techniques. The magnetic core of the carriers was magnetite (Fe₃O₄), with average size of 10 nm. The room temperature VSM measurements showed that magnetic particles were superparamagnetic. The amount of PVA bound to the iron oxide nanoparticles were estimated by thermogravimetric analysis (TGA) and the attachment of PVA to the iron oxide nanoparticles was confirmed by FTIR analysis. Doxorubicin (DOX) drug loading and release profiles of PVA coated iron oxide nanoparticles showed that up to 45% of adsorbed drug was released in 80 h, the drug release followed the Fickian diffusion-controlled process. The binding of DOX to the PVA was confirmed by FTIR analysis. The present findings show that DOX loaded PVA coated iron oxide nanoparticles are promising for magnetically targeted drug delivery.     

Influence of evolving microstructure on magnetic-hysteresis characteristics in polycrystalline nickel–zinc ferrite,Ni0.3Zn0.7Fe2O4

We report some research findings on the parallel evolutions of microstructural properties and magnetic hysteresis-loop properties; we attempt to elucidate their relationships. The Ni_0.3Zn_0.7Fe₂O₄ toroidal samples were prepared via high-energy ball milling and subsequent moulding; the samples with nanometer/submicron sized compacted powder were sintered from 600 °C to 1400 °C using 100 °C increments. An integrated analysis of phase, microstructural and hysteresis data would point to the existence of three distinct shape-differentiated groups of B–H hysteresis loops which belong to samples with weak, moderate and strong magnetism. The observed grain size with respect to the magnetic-hysteresis behaviour varied from 0.19 μm to 0.23 μm, 0.24 μm to 0.43 μm and 1.07 μm to 4.98 μm for weak, moderate and strong ferromagnetic behaviour respectively. The first occurrence of a strikingly erect and well-defined sigmoid-shape was observable only when sufficient single-phase purity and crystallinity and a sufficiently high volume fraction of multi-domain grains (>0.25 μm) were attained.     

Multi-layered adsorption of 3Y–ZrO2 nanoparticles on polystyrene microsphere

Multi-layered adsorption of 3Y–ZrO₂ nanoparticles on polystyrene (PS) microsphere using layer-by-layer (LBL) assembly technique was investigated. By employing sodium poly (acrylic acid) (PAANa) and polyethylenimine (PEI) to modify the zeta potential of the powders, the heterocoagulation takes place between the coating powders and microspheres substrate and the zirconia coating on the surface of polystyrene spheres was successfully formed. Dense, uniform multi-layered zirconia can be obtained on the surface of polystyrene spheres and the thickness of zirconia coating increased by repeating the coating process. The diameter of the spheres expands to 1.5 μm after the first coating and 1.65 μm after the third coating comparing with the original polystyrene spheres with diameter of 1.4 μm.     

Structure and strength of aluminum with sub-micrometer/micrometer grain size prepared by spark plasma sintering

A spark plasma sintering (SPS) technique has been applied to prepare fully dense Al samples from Al powder. By applying a sintering temperature of 600 °C and a loading pressure of 50 MPa, fully recrystallized samples of nearly 100% density with average grain sizes of 5.2 μm, 1.3 μm and 0.8 μm have been successfully prepared using a sintering time of less than 30 min and without the need for a nitrogen atmosphere. A similarity between the grain size and powder particle size is found, which suggests a potential application of the SPS technique to prepare samples with a variety of grain sizes by tailoring the initial powder particle size. The SPS samples show higher strength than Al samples with an identical grain size prepared using thermo-mechanical processing, and a better strength–ductility combination, with the 1.3 μm grain size sample showing a yield strength (σ_0.2%) of 140 MPa and a uniform elongation of more than 10%. This higher strength is related to the presence of oxide particles in the grain boundaries of the samples. It is concluded that SPS is an excellent technique for the production of very fine grained Al materials with high strength, by combining both grain boundary and oxide dispersion strengthening.     

Removal,preconcentration and spectrophotometric determination of picric acid in water samples using modified magnetic iron oxide nanoparticles as an efficient adsorbent

A simple, fast and sensitive spectrophotometric method is developed for removal, preconcentration and determination of trace amounts of picric acid in water samples. Magnetic iron oxide nanoparticles (MIONPs) were synthesized and characterized by transmission electron microscopy (TEM). The magnetic nanoparticles were coated with cetyltrimethylammonium bromide (CTAB) and were applied for fast separation, preconcentration and spectrophotometric determination of picrate anion (the ion of picric acid) in an aqueous solution. The separation, preconcentration procedure is fast and will be completed in 2 min. Methanol is used for desorption of adsorbed picrate anion. The effects of important parameters such as pH of aqueous medium, CTAB dosage, adsorbent amount, temperature, electrolyte concentration, desorbing solvent and interfering ions on the adsorption of picrate anion were investigated. The method showed good linearity for the determination of picric acid in the concentration range of 0.02–1.00 μg mL^? 1 with a regression coefficient of 0.999. The limit of detection (LOD) is obtained to be 0.007 μg mL^? 1. The relative standard deviation (RSD) for 0.03 μg mL^? 1 and 0.8 μg mL^? 1 of picric acid were 3.98% and 1.97% respectively. Picric acid was separated, preconcentrated and determined successfully in spiked samples of Karoon River water.     

Surfactant-assisted hydrothermal synthesis of chains self-assembled by cobalt microspheres

Magnetic cobalt chains, self-assembled by microspheres of hexagonal-phase cobalt, have been synthesized at 100 °C via a hydrothermal reduction route in the presence of cobalt chloride, the surfactant sodium dodecylsulfate (SDS) (or cetyltrimethylammonium bromide CTAB) and the complex reagent sodium tartrate. As-synthesized, the chains are 100–300 μm in length and the cobalt microspheres, which consist of nanosheets with an average thickness of about 60 nm, are 5–10 μm in diameter. The magnetic hysteresis loops at 5 K and 300 K of the chains of microspheres show ferromagnetic characteristics. The morphologies of the microspheres can be controlled by adjusting the concentrations of the surfactant and the complex reagent and also the reaction temperature.     

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.     

Adsorption of collagen to indium oxide nanoparticles and infrared emissivity study thereon

Adsorption of collagen to indium oxide nanoparticles was carried out in water–acetone solution at volumetric ratio of 1:1 with pH value varying from 3.2 to 9.3. As indicated by TGA, maximum collagen adsorption to indium oxide nanoparticles occurred at pH of 3.2. It was proposed that noncovalent interactions such as hydrogen bonding, hydrophilic and electrostatic interactions made main contributions to collagen adsorption. The IR emissivity values (8–14 μm) of collagen-adsorbed indium oxide nanoparticles decreased significantly compared to either pure collagen or indium oxide nanoparticles possibly due to the interfacial interactions between collagen and indium oxide nanoparticles. And the lowest infrared emissivity value of 0.587 was obtained at collagen adsorption of 1.94 g/100 g In₂O₃. On the chance of improved compatibility with organic adhesives, the chemical activity of adsorbed collagen was further confirmed by grafting copolymerization with methyl methacrylate by formation of polymer shell outside, as evidenced by IR spectrum and transmission electron microscopy.     

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.     

Combustion characteristics of the heat pellet prepared from the Fe powders obtained by spray pyrolysis

Fe powders for thermal batteries were prepared by reduction of iron oxide powders obtained by spray pyrolysis. The iron oxide powders prepared by spray pyrolysis had fine size, spherical shape and high surface area. The morphologies of the Fe powders were affected by the preparation temperatures of the iron oxide powders. The Fe powders obtained from the iron oxide powders prepared by spray pyrolysis at 900 and 1000 °C had slightly aggregated structure of the primary powders with several microns sizes. The powders had pure Fe phases at reducing temperatures between 600 and 800 °C. The heat pellets with diameter of 18.2 mm were prepared using Fe powders and potassium perchlorate (KClO₄). The porosity of the prepared heat pellet was about 40%. The break strength of the heat pellet was 0.9 kgf. The ignition sensitivity of the heat pellet was 4 W. The maximum burn rate of the heat pellet obtained from the Fe powders were 8.6 cm s^?1.     

Synthesis,structural and magnetic characterization of highly ordered single crystalline BiFeO3 nanotubes

In this work, we report on the fabrication of highly ordered single crystalline BiFeO₃ (BFO) nanotubes by a sol–gel technique using two-step anodic aluminum oxide (AAO) as template. We prepared BFO nanotubes with dimensions of 65 nm in diameter and 3 μm in length, as confirmed by scanning electron microscopy (SEM) measurements. The obtained single crystalline nanotubes present the expected pure phase (BiFeO₃) as confirmed by energy-dispersive X-ray spectroscopy (EDX), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). In addition to the antiferromagnetic behavior, the magnetization curves of the BFO nanotubes also present a ferromagnetic response, which holds from 2 to 300 K. This desirable behavior is associated to the break of the antiferromagnetic helical spin ordering of the BFO nanotubes. Besides the magnetocrystalline anisotropy, the large length-to-diameter ratio induced an uniaxial shape anisotropy, attested by the applied magnetic field angle measurements.     

Biologically formed hollow cuprous oxide microspheres

Hollow cuprous oxide (Cu₂O) microspheres with a diameter of ca. 1.8 μm are prepared by using yeast as template. The possible mechanism for the formation of the hollow Cu₂O spheres is revealed. The biotemplated sample is investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet–visible (UV–vis) absorption spectra. The sample consists of the crystalline Cu₂O microspheres with diameters of about 59.5 nm and lattice parameter of 4.264 Å. The observed optical band gap of the product indicates that the blue–shift effect occurs, which is attributed to the hollow Cu₂O microspheres.     

Sodium gluconate-assisted hydrothermal synthesis,characterization and electrochemical performance of LiFePO4 powders

Nano- and micro-sized LiFePO₄ powders were synthesized by a sodium gluconate (C₆H₁₁NaO₇)-assisted hydrothermal synthesis method at 220 °C for 10 h with pH = 2–7. The resulting powders were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy-dispersive X-ray spectrometer (EDS). The obtained data showed that the pH of synthesis solution played a key role in the formation of the LiFePO₄ powders with different morphologies, such as ball-like microspheres, irregular microspheres with the agglomerated rods and particles, sphere-like nanoparticles and nano-ellipsoids. The results from electrochemical performance measurements revealed that the charge–discharge cycling characteristics of the samples were strongly dependent on their morphologies. In particular, the ellipsoidal LiFePO₄ nanoparticles with the average size of 70–90 nm showed the highest initial discharge capacity of 150 mA h g⁻¹ at 0.1 C rate, and cycling stability of the ellipsoidal LiFePO₄ nanoparticles was optimum among all the samples prepared due to their dual advantages of high tap density and good diffusion property. The present study offers a simple morphology-controllable route, without carbon coating or doping with supervalent cations, to synthesize and to design high performance cathode materials for lithium-ion batteries.     

Recyclable and stable silver deposited magnetic nanoparticles with poly (vinyl pyrrolidone)-catechol coated iron oxide for antimicrobial activity

This paper introduces a facile method to make highly stable and recyclable antimicrobial magnetic nanoparticles (NPs). Initially, magnetic iron oxide nanoparticles (IONPs) were coated with poly (vinyl pyrrolidone) conjugated catechol (PVP-CCDP). Afterward, silver nanoparticles (Ag⁰) were deposited onto PVP-CCDP coated IONPs using remain catechol. The prepared nanoparticles showed long term (~ 4 weeks) colloidal stability and redispersibility, respectively, against external magnetic field and over a broad range of pH (4–12). The NPs were characterized by UV–vis, SEM, XPS, and XRD measurements. TEM and DLS analyses showed that the mean particle size of PVP-CCDP coated IONPs/Ag⁰ were about 72 nm. The recyclable magnetic NPs possessed a high antibacterial effect against the model microbes Staphylococcus aureus and Escherichia coli and could be separated easily using magnet following antibacterial test for repeated uses and maintained 100% antibacterial efficiency during three cycles. In MTT assay, the magnetic nanoparticles possessed no measureable cytotoxicity to live cells.     

Fabrication of calcined hierarchical porous hollow silicate micro-size spheres via double emulsion process

Silicate (7 to 12 μm) microspheres with porous shell were prepared via modified double emulsion (water₁/oil/water₂) method mediated with N₂ pressure filtration and calcination to completely remove the organic components. With the addition of sodium polymethacrylate (Na-PA) into the aqueous solution of water₁/oil/water₂ emulsion system then calcined, led to the formation of stable hierarchical macroporous (surface area: 42.94 m²/g) from mesoporous (surface area: 259.2 m²/g) shell wall of silicate hollow microspheres.     

Comparative study of conductometric glucose biosensor based on gold and on magnetic nanoparticles

The aim of this study was to show the feasibility and the performances of nanoparticle biosensing. A glucose conductometric biosensor was developed using two types of nanoparticles (gold and magnetic), glucose oxidase (GOD) being adsorbed on PAH (poly(allylamine hydrochloride)) modified nanoparticles, deposited on a planar interdigitated electrode (IDEs). The best sensitivities for glucose detection were obtained with magnetic nanoparticles (70 μM/mM and 3 μM of detection limit) compared to 45 μM/mM and 9 μM with gold nanoparticles and 30 μM/mM and 50 μM with GOD directly cross-linked on IDEs. When stored in phosphate buffer (20 mM, pH 7.3) at 4 °C, the biosensor showed good stability for more than 12 days.     

Preparing silver nanoparticles in supercritical water

Silver (Ag) nanoparticles were prepared using Ag microparticles as precursors in supercritical water (SCW). The effect of reaction time on preparing Ag nanoparticles was investigated. The obtained products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The results indicated that, with the increase of reaction time, Ag microparticles prepared by calcination method with the sizes > 2 μm remained after SCW treatment because of their high crystallinity, but those with the sizes < 1 μm were destroyed and formed many Ag nanoparticles due to the destructive effect of SCW.     

Preparation of carbon aerogel microspheres by a simple-injection emulsification method

Carbon aerogel microspheres were successfully prepared using a simple-injection emulsification method, employing sol–gel polycondensation of a resorcinol–formaldehyde solution containing sodium carbonate as a catalyst. This process was followed by solvent exchange using acetone, supercritical drying with carbon dioxide and carbonization in a nitrogen atmosphere. The effect of curing time before starting injection, injection rate and agitation rate of continuous phase on the particle size and the porous properties of the carbon aerogel microspheres was investigated. Adsorption of phenol by using the prepared carbon aerogel microspheres was also examined. The diameter of carbon aerogel microspheres was controlled in the range of 20–55 μm by varying injection rate and agitation rate. The mean diameter of carbon aerogel microspheres decreased with increasing the injection rate and the agitation rate, whereas their mean diameter was independent of the curing time. The BET surface area and total pore volume of carbon aerogel microspheres increased with increasing the curing time. In contrast, their BET surface area and total pore volume decreased with increasing the injection rate and the agitation rate. The BET surface area, total pore volume, mesopore volume and micropore volume of the carbon aerogel microspheres with a mean diameter of 45 μm were 903 m²/g, 0.60 cm³/g, 0.31 cm³/g and 0.27 cm³/g, respectively. The phenol-adsorption capacity of these carbon aerogel microspheres was 29.3 mg phenol/g adsorbent.     

Nanowires of NiCo/barium ferrite magnetic composite by electrodeposition

Electrodeposition has been demonstrated to be useful in preparing well defined composite nanowires and as a way to modify their magnetic properties. A sulphamate bath containing barium ferrite nanoparticles has been used to test nanoparticle incorporation during an alloy (NiCo) electrodeposition process. The nanoparticles enter the membrane pores during the electrodeposition, being uniformly distributed into them.Home-made alumina membranes prepared in the laboratory were used as an electrodeposition template. Composite 10–15 μm length nanowires containing 7 wt.% of ferrite with a good particle distribution were obtained. The formation of composite nanowires has been demonstrated both by TEM observation and by magnetic properties analysis. The feasibility of incorporating magnetic nanoparticles to metallic nanowires in order to modify their magnetic properties has thus been confirmed.