Fe3O4 NP Research Articles

A facile preparation method for single-hole hollow Fe3O4@SiO2 microspheres

Hollow Fe3O4@SiO2 microspheres with single holes in their shells and Fe3O4 nanoparticles encapsulated in silica shells were prepared using a precipitation-phase separation method. The synthesis was performed by mixing a tetrahydrofuran (THF)–acetonitrile (MeCN) solution containing polymer, tetraethyl orthosilicate (TEOS) and n-dodecyltrimethoxysilane (DTMS)-modified Fe3O4 nanoparticles with an aqueous solution containing cetyltrimethyl ammonium bromide (CTAB) before adding ammonia to catalyze the hydrolysis of TEOS and finally removing the polymer by dissolving it in THF. The polymer used was poly(styrene-co-methyl methacrylate) (P(St-co-MMA)) or a mixture of polystyrene (PS) and polymethyl methacrylate (PMMA). The effects of modifying the Fe3O4 NPs, tailoring the particle size and the hole size and controlling the Fe3O4 content in the Fe3O4@SiO2 hollow microspheres were investigated. The prepared Fe3O4@SiO2 single-hole hollow microspheres were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and vibrating sample magnetometry (VSM). We observed that modifying Fe3O4 NPs with DTMS is essential for encapsulating the Fe3O4 NPs in a silica matrix. The hole size of the microspheres increased with the PMMA-to-PS mass ratio, and the hole size could be adjusted from 16nm to 135nm. The size of the microspheres could be tailored from 240 to 1270nm by modulating the process parameters. The Fe3O4@SiO2 microspheres exhibited superparamagnetic properties, and the corresponding saturation magnetization (Ms) values varied from 10 to 46emu/g when controlling the modified Fe3O4 NP content in the microspheres. Based on our results, we propose a possible formation mechanism for the Fe3O4@SiO2 hollow microspheres.

Effects of selected metal oxide nanoparticles on Artemia salina larvae: evaluation of mortality and behavioural and biochemical responses

The aim was to investigate the toxicity of selected metal oxide nanoparticles (MO-NPs) on the brine shrimp Artemia salina, by evaluating mortality and behavioural and biochemical responses. Larvae were exposed to tin(IV) oxide (stannic oxide (SnO2)), cerium(IV) oxide (CeO2) and iron(II, III) oxide (Fe3O4) NPs for 48h in seawater, with MO-NP suspensions from 0.01 to 1.0mg/mL. Mortality and behavioural responses (swimming speed alteration) and enzymatic activities of cholinesterase, glutathione-S-transferase and catalase were evaluated. Although the MO-NPs did not induce any mortality of the larvae, they caused changes in behavioural and biochemical responses. Swimming speed significantly decreased in larvae exposed to CeO2 NPs. Cholinesterase and glutathione-S-transferase activities were significantly inhibited in larvae exposed to SnO2 NPs, whereas cholinesterase activity significantly increased after CeO2 NP and Fe3O4 NP exposure. Catalase activity significantly increased in larvae exposed to Fe3O4 NPs. In conclusion, swimming alteration and cholinesterase activity represent valid endpoints for MO-NP exposure, while glutathione-S-transferase and catalase activities appear to be NP-specific.

An electrochemical immunosensor for detection of a breast cancer biomarker based on antiHER2–iron oxide nanoparticle bioconjugates

A label free immunosensor was designed for ultra-detection of human epidermal growth factor receptor 2 (HER2) in real samples using a differential pulse voltammetry (DPV) method. In a separate process, antiHER2 antibodies were attached to iron oxide nanoparticles (Fe3O4 NPs) to form stable bioconjugates which were later laid over the gold electrode surface. In this way, by the advantage of their long terminals, the bioconjugates provided the most possible space for the immuno-reaction between biomolecules. Under optimal conditions, the immunosensor was responsive to HER2 concentrations over the ranges of 0.01-10 ng mL(-1) and 10-100 ng mL(-1) linearly and benefited from a satisfactory detection limit as low as 0.995 pg mL(-1) and a favorable sensitivity as sharp as 5.921 μA mL ng(-1). The reliability of the method in clinical analysis was proved by successful quantization of HER2 levels in serum samples obtained from patients. Furthermore, the precision and the stability of the method were evaluated and verified to be acceptable in immunoassay studies.

Magnetic Polystyrene Nanocomposites Reinforced with Magnetite Nanoparticles

AbstractPolystyrene (PS)/magnetite (Fe3O4) polymer nanocomposites (PNCs) are successfully synthesized by a solvent extraction method. Scanning electron microscopy reveals that the nanoparticles are well distributed in the PS matrix with 5, 10, and 20 wt% without obvious agglomeration. Fourier transform infrared spectroscopy analysis indicated that the PS/Fe3O4 PNCs are synthesized with strong interaction between PS and nanoparticles. The thermogravimetic analyzer and microscale combustion calorimetry reveal an enhanced thermal stability and reduced flammability. The differential scanning calorimetry demonstrates both glass transition temperature (Tg) and melting temperature (Tm) increased with increasing the Fe3O4 nanoparticle loading. The observed monotonically decreased complex viscosity indicates a strong shear thinning behavior in the PNCs; meanwhile, the percolation takes place in the low frequency range (0.1–1 Hz) when the nanoparticles are introduced in the matrix. The Tg of the PS/Fe3O4 nanocomposites determined from the dynamic mechanical analysis shifts to a higher temperature compared with that of pure PS. Enhanced dielectric properties relate to the Fe3O4 NP loadings. In addition, the PS/Fe3O4 PNCs exhibit superparamagnetic behavior at room temperature.

Layer-by-layer self-assembly of ultrathin multilayer films composed of magnetite/reduced graphene oxide bilayers for supercapacitor application

This article describes electrochemical properties of layer-by-layer self-assembled multilayer films composed of magnetite nanoparticle (Fe3O4 NP) and chemically reduced graphene oxide (RGO) for supercapacitor application. The thickness of the Fe3O4/GO bilayer was determined by optical ellipsometry to be 6.53±0.17nm, which agreed well with the sum of the independently measured thickness for each Fe3O4 (5.61±0.14nm) and GO (0.91±0.1nm) layer component. Each layer was found to be deposited uniformly and regularly. Fe3O4/RGO multilayer film was obtained by reducing a Fe3O4/GO film using hydrazine. The multilayer film yielded a minimum resistance of 1.0×104Ω/sq (2.8S/cm) for a film with approximately 50 bilayers. The electrodes fabricated from 30 Fe3O4/RGO bilayers exhibited excellent capacitive performances with a maximum specific gravimetric capacitance (151F/g) at a current density of 0.9A/g.

Composite multifunctional nanostructures based on ZnO tetrapods and superparamagnetic Fe3O4 nanoparticles

A nanocomposite material is obtained by coupling superparamagnetic magnetite nanoparticles (Fe3O4 NP) and vapor phase grown zinc oxide nanostructures with ‘tetrapod’ morphology (ZnO TP). The aim is the creation of a multifunctional material which retains the attractive features of ZnO (e.g. surface reactivity, strong UV emission, piezoelectricity) together with added magnetism. Structural, morphological, optical, magnetic and functional characterization are performed. In particular, the high saturation magnetization of Fe3O4 NP (above 50 A m2 kg−1), the strong UV luminescence and the enhanced photocatalytic activity of coupled nanostructures are discussed. Thus the nanocomposite turns out to be suitable for applications in energy harvesting and conversion, gas- and bio-sensing, bio-medicine and filter-free photocatalysis.

An amperometric biosensor based on acetylcholinesterase immobilized onto iron oxide nanoparticles/multi-walled carbon nanotubes modified gold electrode for measurement of organophosphorus insecticides

An acetylcholinesterase (AChE) purified from maize seedlings was immobilized covalently onto iron oxide nanoparticles (Fe 3O 4NP) and carboxylated multi walled carbon nanotubes (c-MWCNT) modified Au electrode. An organophosphorus (OP) biosensor was fabricated using this AChE/Fe 3O 4/c-MWCNT/Au electrode as a working electrode, Ag/AgCl as standard and Pt wire as an auxiliary electrode connected through a potentiostat. The biosensor was based on inhibition of AChE by OP compounds/insecticides. The properties of nanoparticles modified electrodes were studied by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), cyclic voltammograms (CVs) and electrochemical impedance spectroscopy (EIS). The synergistic action of Fe 3O 4NP and c-MWCNT showed excellent electrocatalytic activity at low potential (+0.4 V). The optimum working conditions for the sensor were pH 7.5, 35 °C, 600 μM substrate concentration and 10 min for inhibition by pesticide. Under optimum conditions, the inhibition rates of OP pesticides were proportional to their concentrations in the range of 0.1–40 nM, 0.1–50 nM, 1–50 nM and 10–100 nM for malathion, chlorpyrifos, monocrotophos and endosulfan respectively. The detection limits were 0.1 nM for malathion and chlorpyrifos, 1 nM for monocrotophos and 10 nM for endosulfan. The biosensor exhibited good sensitivity (0.475 mA μM −1), reusability (more than 50 times) and stability (2 months). The sensor was suitable for trace detection of OP pesticide residues in milk and water.