Sonochemical activation-assisted biosynthesis of Au/Fe3O4 nanoparticles and sonocatalytic degradation of methyl orange

In this research, a sonochemical activation-assisted biosynthesis of Au/Fe₃O₄ nanoparticles is proposed. The proposed synthesis methodology incorporates the use of Piper auritum (an endemic plant) as reducing agent and in a complementary way, an ultrasonication process to promote the synthesis of the plasmonic/magnetic nanoparticles (Au/Fe₃O₄). The synergic effect of the green and sonochemical synthesis favors the well-dispersion of precursor salts and the subsequent growth of the Au/Fe₃O₄ nanoparticles.The hybrid green/sonochemical process generates an economical, ecological and simplified alternative to synthesizing Au/Fe₃O₄ nanoparticles whit enhanced catalytic activity, pronounced magnetic properties. The morphological, chemical and structural characterization was carried out by high- resolution Scanning electron microscopy (HR-SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and X-Ray diffraction (XRD), respectively. Ultraviolet–visible (UV–vis) and X-ray photoelectron (XPS) spectroscopy confirm the Au/Fe₃O₄ nanoparticles obtention. The magnetic properties were evaluated by a vibrating sample magnetometer (VSM). Superparamagnetic behavior, of the Au/ Fe₃O₄ nanoparticles was observed (M_s = 51 emu/g and H_c = 30 Oe at 300 K). Finally, the catalytic activity was evaluated by sonocatalytic degradation of methyl orange (MO). In this stage, it was possible to achieve a removal percentage of 91.2% at 15 min of the sonocatalytic process (160 W/42 kHz). The initial concentration of the MO was 20 mg L⁻¹, and the Fe3O4-Au dosage was 0.075 gL⁻¹. The MO degradation process was described mathematically by four kinetic adsorption models: Pseudo-first order model, Pseudo-second order model, Elovich and intraparticle diffusion model.     

Sonochemical synthesis of nickel-manganous oxide nanocrumbs decorated partially reduced graphene oxide for efficient electrochemical reduction of metronidazole

In the present work, we report on the synthesis of crump-like nickel manganous oxide nanoparticles decorated partially reduced graphene oxide (NiMnO@pr-GO) nanocomposite through high-intensity ultrasonic bath sonication (ultrasonic frequency = 37 kHz and power = 150 W). The NiMnO@pr-GO nanocomposite modified glassy carbon electrode (GCE) was then employed for the electrochemical reduction of detrimental metronidazole (MNZ). The crystalline phase and formation of the NiMnO@pr-GO nanocomposites were confirmed by X-ray diffraction and other spectroscopic techniques. The cyclic voltammetry results demonstrate that this NiMnO@pr-GO nanocomposite modified GCE has a lower reduction potential and higher catalytic activity towards MNZ than do NiMnO and GO modified GCEs. Under optimized conditions, the fabricated NiMnO@pr-GO electrode can detect metronidazole over a wide linear range with a lower limit of detection of 90 nM. The sensitivity of the sensor was 1.22 µA µM^-1cm⁻² and was found to have excellent selectivity and durability for the detection of MNZ.     

Sonochemical fabrication of inorganic nanoparticles for applications in catalysis

Catalysis covers almost all the chemical reactions or processes aiming for many applications. Sonochemistry has emerged in designing and developing the synthesis of nano-structured materials, and the latest progress mainly focuses on the synthetic strategies, product properties as well as catalytic applications. This current review simply presents the sonochemical effects under ultrasound irradiation, roughly describes the ultrasound-synthesized inorganic nano-materials, and highlights the sonochemistry applications in the inorganics-based catalysis processes including reduction, oxidation, degradation, polymerization, etc. Or all in all, the review hopes to provide an integrated understanding of sonochemistry, emphasize the great significance of ultrasound-assisted synthesis in structured materials as a unique strategy, and broaden the updated applications of ultrasound irradiation in the catalysis fields.     

Electrostatic self-assembly of Fe3O4 nanoparticles on carbon nanotubes

Carbon nanotubes (CNTs)-based magnetic nanocomposites can find numerous applications in nanotechnology, integrated functional system, and in medicine owing to their great potentialities. Herein, densely distributed magnetic Fe₃O₄ nanoparticles were successfully attached onto the convex surfaces of carbon nanotubes (CNTs) by an in situ polyol-medium solvothermal method via non-covalent functionalization of CNTs with cationic surfactant, cetyltrimethylammonium bromide (CTAB), and anionic polyelectrolyte, poly(sodium 4-styrenesulfonate) (PSS), through the polymer-wrapping technique, in which the negatively charged PSS-grafted CNTs can be used as primer for efficiently adsorption of positively metal ions on the basis of electrostatic attraction. X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) analysis have been used to study the formation of Fe₃O₄/CNTs. The Fe₃O₄/CNTs nanocomposites were proved to be superparamagnetic with saturation magnetization of 43.5 emu g^?1. A mechanism scheme was proposed to illustrate the formation process of the magnetic nanocomposites.     

One-step synthesis of Fe3O4 nanorods/graphene nanocomposites

A composite of graphene (GE) supported by rod-like Fe₃O₄ nanocrystals has been fabricated by a simple one-step chemical route. X-ray diffraction and transmission electron microscopy results show that the Fe₃O₄ nanorods with diameters in the range of 15?C20 nm and lengths of 150?C200 nm were firmly assembled on the GE nanosheet surface. Magnetic property investigation indicated that the Fe₃O₄/GE composites exhibit a ferromagnetic behavior and possess a saturation magnetization of 50.11?emu?g^?1. Moreover, Fe₃O₄/GE composites showed a very high adsorption capacity of Congo red.     

Decorating reduced graphene oxide with Co3O4 hollow spheres and their application in supercapacitor materials

In this paper, a composite of reduced graphene oxide decorated by Co₃O₄ hollow spheres (Co₃O₄/RGO composite) has been synthesized by a one-pot solvothermal method. The samples are characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR), Raman spectra and so on. The results demonstrate that the Co₃O₄ hollow spheres with good purity and homogenous size are absorbed onto the reduced graphene oxide sheets as spacers to prevent the aggregation of the graphene oxide sheets. Furthermore, the well electrochemical properties demonstrate that the Co₃O₄/RGO composite might have potential applications as electrode materials for supercapacitors.     

Sonochemical synthesis of TiO(2 nanoparticles on graphene for use as photocatalyst

Using ultrasonication we succeed in a controlled incorporation of TiO(2) nanoparticles on the graphene layers homogeneously in a few hours. The average size of the TiO(2) nanoparticles was controlled at around 4-5 nm on the sheets without using any surfactant, which is attributed to the pyrolysis and condensation of the dissolved TiCl(4) into TiO(2) by ultrasonic waves. The photocatalytic activity of the resultant graphene-TiO(2) composites containing 25 wt.% TiO(2) is better than that of commercial pure TiO(2). This is partly due to the extremely small size of the TiO(2) nanoparticles and partly due to the graphene-TiO(2) composite structure consisting of homogeneous dispersion of crystalline TiO(2) nanoparticles on the graphene sheets. As the graphene in the composites has a very good contact with the TiO(2) nanoparticles it enhances the photo-electron conversion of TiO(2) by reducing the recombination of photo-generated electron-hole pairs.     

Preparation of Fe3O4/polystyrene composite particles from monolayer oleic acid modified Fe3O4 nanoparticles via miniemulsion polymerization

Fe₃O₄/polystyrene composite particles were prepared from oleic acid (OA) modified Fe₃O₄ nanoparticles via miniemulsion polymerization. It was concluded that the surface properties of OA modified magnetite nanoparticles have a great effect on preparation of the composite particles. When Fe₃O₄ nanoparticles coated by multilayer of OA was employed, there were large amounts of free polystyrene particles in the product. Fe₃O₄/polystyrene composite particles with defined structure and different magnetite content can be readily prepared from monolayer OA modified Fe₃O₄ nanoparticles. It was concluded that surface of the monolayer OA modified Fe₃O₄ nanoparticles is more hydrophobic than that of the multilayer coated ones, thus improving the dispersibility of the Fe₃O₄ nanoparticles in styrene monomer and allowing preparation of the Fe₃O₄/polystyrene composite particles with defined structure and controllable magnetite content.     

Growth and characterization of Fe3O4 nanoparticles in silica matrix

Nano-magnetic Fe₃O₄ particles coated with silica are synthesized. The study of structural and magnetic properties was carried out using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and vibrating sample magnetometer (VSM) techniques. The VSM results show that these kinds of composite particles exhibit superparamagnetic behavior with zero coercivity and remanence. The magnetic spheroid alumina carriers containing these magnetic composite particles were prepared by an internal gelation process. The SiO₂ coatings prevent the reaction between Fe₃O₄ and Al₂O₃ during the sintering process and maintain the superparamagnetic behavior of the catalyst carriers.     

Fabrication of bimetallic Pt/Pd nanoparticles on 2-thiolbenzimidazole functionalized reduced graphene oxide for methanol oxidation

In this study, an electrocatalyst based on 2-thiolbenzimidazole (TBI) functionalized reduced graphene oxide (rGO) with platinum and palladium nanoparticles (Pt-PdNPs) was synthesized. The successful synthesis of nanomaterials and the prepared glassy carbon electrode (GCE) surfaces were confirmed by transmission electron microscope, X-ray photo electron spectroscopy, scanning electron microscope, electrochemical impedance spectroscopy and X-ray diffraction method. The effective surface areas of TBIrGO/GCE, PdNPs/TBIrGO/GCE, PtNPs/TBIrGO/GCE and Pt-PdNPs/TBIrGO/GCE were calculated to be 324, 578, 667 and 1189 cm²/mg, respectively. According to the results, the electrochemical surface area of the Pt-PdNPs/TBIrGO is 3.67, 2.06 and 1.78 times higher than those of TBIrGO, PdNPs/TBIrGO and PtNPs/TBIrGO, respectively. The Pt-PdNPs/TBIrGO/GCE also exhibited higher peak current for methanol oxidation than those of comparable TBIrGO/GCE, PdNPs/TBIrGO/GCE, PtNPs/TBIrGO/GCE modified GCEs, thus providing evidence for its higher electro-catalytic activity.     

Magnetoresistive properties of Fe3O4 nanoparticles embedded in a Cu matrix

We studied ordered arrays of magnetic nanoparticles (NPs) in a nonmagnetic matrix. The influence of annealing temperature and measurement geometry (varying angle between sample surface and external magnetic field direction) on magnetoresistance and coercive field values was established. Measurements were done on the Au(2 nm)/Cu(20 nm)/Fe₃O₄(NPs)/SiO₂/Si system.     

Magnetic and electromagnetic absorption properties of FeNi alloy nanoparticles supported by reduced graphene oxide

FeNi alloy nanoparticles (NPs) supported by reduced graphene oxide (RGO) (FeNi/RGO nanocomposites) were successfully synthesized through in‐situ reduction. Large amounts of sphere‐like FeNi NPs are uniformly deposited on the RGO nanosheets. The magnetic hysteresis measurement reveals the ferromagnetic behavior of the nanocomposites at room temperature. According to the electromagnetic (EM) characteristics, the FeNi/RGO nanocomposites show outstanding EM absorption properties in the 2–18 GHz range, as evidenced by the wide effective absorption bandwidth (up to 3.3 GHz, with reflection loss R_L < –10 dB) and a minimal R_L (–32 dB) at 12.4 GHz with a thickness of 1.5 mm. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The double-effect mechanism between Fe3O4 nanoparticles and MSA-capped CdTe QDs

Water-soluble mercaptosuccinic acid (MSA)-capped CdTe quantum dots (QDs) of two sizes and superparamagnetic Fe₃O₄ nanoparticles have been synthesized and used to investigate the effect of the mechanism of Fe₃O₄ nanoparticles on the fluorescence intensity of QDs. In the presence of a low concentration of Fe₃O₄ nanoparticles, the CdTe QDs with smaller particle size exhibit fluorescence quenching while fluorescence enhancement of CdTe QDs with larger particle size was observed, and the fluorescence intensity changes with the excitation wavelength and the concentration of Fe₃O₄ nanoparticles. The mechanism study shows that there is a double-effect between the Fe₃O₄ and CdTe QDs: one is the fluorescence quenching effect due to Fe₃O₄ strong absorption of excitation and emission light, the other is the fluorescence enhancement effect resulting from a localized electromagnetic field caused by the absorption of exciting light. The fluorescence of CdTe QDs with lower concentration of Fe₃O₄ nanoparticles was determined via the synergy of the double-effect. To our best knowledge, this is the first systematic study on the interaction between Fe₃O₄ nanoparticles and CdTe QDs, which finds the fluorescence enhancement effect in the presence of low concentration of Fe₃O₄.     

Hydrothermal method for the production of reduced graphene oxide

Reduced graphene oxide, RGO (also called chemically modified graphene, CMG) was synthesized by a simple hydrothermal method, with graphite oxide (GO), prepared by the modified Hummers method, served as the raw material. Structural and morphological studies indicate the degree of reduction is dependent on the temperature, which is also verified by Raman analysis. The variation in interlayer distance and the intensity ratio of the D to G Raman modes (I_D/I_G) indicates higher reaction temperature can accelerate the reduction of GO. The conductivity also varies with the degree of reduction, as verified by electrochemical analyzer. Moreover, the reaction process affects organic functional groups, the mechanism during the reaction process is discussed.     

Synthesis and characterization of L10 FePt nanoparticles from Pt–Fe3O4 core-shell nanoparticles

Pt/Fe₃O₄ core-shell nanoparticles have been prepared by a modified polyol method. Pt nanoparticles were first prepared via the reduction of Pt(acac)₂ by polyethylene glycol-200 (PEG-200), and layers of iron oxide were subsequently deposited on the surface of Pt nanoparticles by the thermal decomposition of Fe(acac)₃. The nanoparticles were characterized by XRD and HR-TEM. The as-prepared Pt/Fe₃O₄ nanoparticles have a chemically disordered FCC structure and transformed into chemically ordered fct structure after annealing in reducing atmosphere (4% H₂, 96% Ar) at 700 °C. The ordered fct FePt phase has high magnetic anisotropy with coercivity reaching 7.5 kOe at room temperature and 9.3 kOe at 10 K.