Presence Of γ-Fe2O3 Research Articles

Maghemite nanoparticles decorated semiconducting graphitic carbon nitride hetero-structured nanocomposite: Facile synthesis, characterizations and its visible light active photocatalytic system for removal of hazardous organic pollutants from aqueous solutions

Hetero-structured nanocomposite consisting of graphitic carbon nitride host, decorated by γ-phase iron oxide, maghemite (γ-Fe2O3@G-CN) was synthesized in different mass contents of γ-Fe2O3 (5%, 10% and 20%) in the composite, by the method of nanosecond pulsed laser fragmentation, and defect engineering in liquid for the removal of hazardous organic pollutants from aqueous solutions. The elemental, structural, and morphological characterizations of the synthesized nanocomposites by XPS, XRD, TEM, and HR-TEM exhibited the proper anchoring of γ-Fe2O3 on the graphitic carbon nitride polymeric network. Also, the diffuse reflectance spectra, and the room temperature photoluminescence spectra respectively revealed that the presence of γ-Fe2O3 in graphitic carbon nitride brought about the enhanced and extended visible light absorption, and reduced recombination of photo induced electron hole pairs, the characteristics desired in a good photo-catalyst. Moreover, this composite material exhibited the z-scheme photo catalytic mechanism, where the more energetic electrons and holes in the composite band structure mediate the redox reaction in the photo-catalysis. The photo-catalytic efficiency of γ-Fe2O3@G-CN nanocomposite was evaluated in the photo-catalytic degradation of methyl blue (MB), and rhodamine-B (Rh-B) cationic dyes under visible light irradiations. For both the degradation processes, all the variants of γ-Fe2O3@G-CN nanocomposite consistently showed the enhanced photocatalytic efficiency with respect to pure GCN, with the maximum efficiency recorded for 10% γ-Fe2O3 in γ-Fe2O3@G-CN nanocomposite.

One-pot synthesis of 1,5-benzodiazepine-2,3-dicarboxylates via three-component domino reactions in the presence of γ-Fe2O3@SiO2/Ce(OTf)3

One-pot synthesis of 1,5-benzodiazepine-2,3-dicarboxylates via three-component domino reactions in the presence of γ-Fe2O3@SiO2/Ce(OTf)3

Magnetic γ-Fe2O3@Cu-LDH intercalated with Palladium Cysteine: An efficient dual nano catalyst in tandem C[sbnd]N coupling and cyclization progress of synthesis quinolines

The novel magnetic γ-Fe2O3@Cu-LDH@Cysteine-Pd dual nanocatalyst system was designed through a combination of MNPs and LDH to improve separation and promote the catalytic features. In this regard, a facile surface modulation by substitution of copper (II) metal cations with LDH cations was obtained. Also, the interface defect structure of LDH was modified via the immobilization of Pd (II) complex as an active metal catalyst. The synthesized biocompatible catalyst was employed in an economical method using A3-coupling followed by CN coupling and intramolecular cyclization for the synthesis of quinolines to prove catalytic efficiency. Quinoline derivatives were achieved by tandem and one-pot method from 2-bromo benzaldehyde as low cost and available starting material in the presence of γ-Fe2O3@Cu-LDH@Cysteine-Pd with excellent yield. The recovered catalyst could be efficient up to the fourth cycle. The structure of the catalytic system was confirmed by several useful analyses such as FT-IR, TGA, VSM, SEM, TEM, XRD, and ICP.

Development of Magnetic Multi-Shelled Hollow Catalyst for Biodiesel Production

The magnetic CaO-based catalyst has endorsed great enhancements in biodiesel synthesis. In the present work, novel multi-shelled hollow γ-Fe2O3 stabilized CaO microspheres were synthesized using a facile one-step hydrothermal method. The strategy revealed that the well-defined multi-shelled hollow structures were formed with magnetism; the presence of γ-Fe2O3 was the key for the effective structural stabilization, and the multi-shelled hollow structures provided the sites for the active material. The synthesized catalyst was employed for the preparation of biodiesel by transesterification of palm oil and methanol. A four factors response surface methodology was adopted for optimizing the reaction conditions. Ca80Fe20 with a yield of 96.12% performed the highest catalytic activity under reaction conditions of 2 h, a methanol to oil ratio of 12:1, 65 °C and 11 wt. % of catalyst dosage. The catalyst under the optimum transesterification conditions also performed a better recyclability (>85%). In addition, the response surface methodology (RSM) based on the Box–Behnken design was used to optimize the four reaction parameters.

Production of Iron Oxide Nanoparticles by Co-Precipitation method with Optimization Studies of Processing Temperature, pH and Stirring Rate

Iron Oxide Nanoparticle, maghemite (γ-Fe2O3) has received great interest and extensively used in biomedical field. Optimization studies were carried out in the production of γ-Fe2O3 nanoparticles by using co-precipitation method. Iron (II) chloride and iron (III) chloride were used as precursors which are dissolved in distilled water followed by centrifugation, drying and grinding process in order to obtain dried dark brown precipitated γ-Fe2O3 powder. The effect of different processing temperature (30 to 70°C), pH (10 to 12) and stirring rate (300 to 700rpm) towards crystallite size of γ-Fe2O3 were investigated by using Response Surface Methodology (RSM) and Central Composite Design (CCD). Based on analysis of variance (ANOVA), the determination coefficient, R2 obtained was 0.9890 where stirring rate was the parameter that affected the most on the crystallite size. Optimization processing condition that produce smallest crystallite size of 7.3657 nm was 50 °C, pH 11.40 and 550 rpm by using Design of Expert software (DOE). Characterization of γ-Fe2O3 powder samples were evaluated by using different analytical tools such as Fourier Transform Infrared (FTIR), X-Ray Diffractometer (XRD) and Scanning Electron Microscope (SEM). Iron oxide group (Fe-O), hydroxyl (OH-) group and carbon dioxide (CO2) were identified in FTIR spectrum. The characteristic peak occurring at 2θ = 35.4° indicated presence of γ-Fe2O3 in the samples. The γ-Fe2O3 particles appeared generally in spherical shape in SEM analysis.

Pyrolysis preparation of poly-γ-glutamic acid derived amorphous carbon nitride for supporting Ag and γ-Fe2O3 nanocomposites with catalytic and antibacterial activity

Nanocomposites composed of Ag and γ-Fe2O3 nanoparticles within poly-γ-glutamic acid (γ-PGA) derived amorphous carbon nitride (a-CN) films (Ag + γ-Fe2O3@a-CN) were synthesized by a one-step facile pyrolysis strategy. Transmission electron microscopy analysis shows that Ag and γ-Fe2O3 nanoparticles were obtained in situ and homogeneously dispersed on the a-CN matrix. The average size of nanoparticles was 8.1 nm. The presence of γ-Fe2O3, Ag, and a-CN in the nanocomposite was confirmed by X-ray diffraction analysis, UV–visible absorption spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Ag + γ-Fe2O3@a-CN catalyzed the degradation of methyl orange. This catalyst was also recycled ten times by magnetic separation without any loss in efficiency. Ag + γ-Fe2O3@a-CN exhibited strong antibacterial activity against E. coli and S. aureus. It also exhibited excellent antibacterial activity even after 20 times magnetic recycling. This indicates that this is a promising recyclable antibacterial and catalyst for environmental applications.

Low-friction behaviors of Ag-doped γ-Fe2O3@SiO2 nanocomposite coatings under a wide range of temperature conditions

In this paper, Ag-doped γ-Fe2O3@SiO2 nanocomposite coatings have been prepared by sol–gel method and deposited on steel substrate. The microstructure, surface topography, and high-temperature tribological properties of these coatings were measured and investigated by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope with energy- dispersive spectrometer (SEM/EDS), transmission electron microcopy (TEM), and a high-temperature tribometer. The results show that the γ-Fe2O3 core is coated with an amorphous SiO2 shell and Ag nanoparticles are evenly distributed in the γ-Fe2O3@SiO2 nanocomposites. The tribological properties of the coatings against ZrO2 balls have been investigated by a tribometer at room temperature (RT), 100, 300, 500, and 600 °C, respectively. It is found that the nanocomposite coatings exhibit low and stable coefficients of friction (CoF) (in the range from 0.25 to ~0.06) from RT to 600 °C, respectively. CoF of the friction pair decreases with the increase of temperature. XRD, Raman spectroscopy, and SEM measurements show that the antifriction behaviors of nanocomposite coatings are owing to the soft phases of metal Ag and γ-Fe2O3. The presence of γ-Fe2O3 with high-temperature plasticity is beneficial to form low-shear interface and to achieve low and stable friction at high temperature. The core–shell microstructure of the nanocomposite coatings inhibits the soft γ-Fe2O3 phase, changing it into the α-Fe2O3 phase.

Sustainable Catalytic Activity of Ag-Coated Chitosan-Capped γ-Fe2O3 Superparamagnetic Binary Nanohybrids (Ag-γ-Fe2O3@CS) for the Reduction of Environmentally Hazardous Dyes-A Kinetic Study of the Operating Mechanism Analyzing Methyl Orange Reduction.

The formation of binary nanohybrids consisting of environmentally benign components, γ-Fe2O3, chitosan (CS), and Ag (Ag-γ-Fe2O3@CS) (CSIOAg), containing very low concentration of Ag NPs (≤1.2 μM), has been reported. In the as-synthesized nanohybrids, the presence of γ-Fe2O3 (8.5 ± 0.8 nm) and Ag (5.9 ± 0.5 nm) are revealed by optical, XRD, TEM, and XPS analyses, and their presence in cubic phase is determined by XRD and SAED measurements. The catalytic activity of CSIOAg has been analyzed by performing the reduction of certain toxic dyes. Under all kinetic conditions, the reaction is attended by an induction period, which is reduced upon increasing [Ag] and [Dye] in a specific concentration range, as well as temperature, suggesting restructuring of the surface prior to reduction. In case of methyl orange (MO), the reduction results in its cleavage to produce N,N-dimethyl-1,4-phenylenediamine and sodium sulfanilate in a significantly higher (>97%) yield in a bimolecular reaction between MO and BH4–. The duration of induction period is regularly decreased and the rate of reduction (kapp) increases linearly with increasing Ag in the wide concentration range (0.03–2.4 μM). The reduction takes place with a second-order rate constant of 2.7 × 104 dm3 mol–1 s–1, which is >3.5-fold higher than that in the absence of chitosan (IOAg) under identical experimental conditions. The kinetics of reduction of MO is controlled by the nature and extent of its adsorption on the catalyst surface. The weaker binding between MO and Ag catalyst only allows its effective reduction. The XPS analysis of CSIOAg and IOAg containing the same amount of Ag (1.2 μM) showed its higher amount on the surface of CSIOAg (0.12%) as compared to that of IOAg (0.09%). Detailed kinetic analysis of MO reduction, performed under pseudo-kinetic conditions for both the nanohybrids revealed them to follow Langmuir–Hinshelwood kinetic model and exhibited the recyclability up to 10 cycles with fairly high reaction efficiency and TOF, suggesting it to be a sustainable green nanosystem.

Influence of magnetoplasmonic γ-Fe2O3/Au core/shell nanoparticles on low-field nuclear magnetic resonance.

Magnetoplasmonic nanoparticles, composed of a plasmonic layer and a magnetic core, have been widely shown as promising contrast agents for magnetic resonance imaging (MRI) applications. However, their application in low-field nuclear magnetic resonance (LFNMR) research remains scarce. Here we synthesised γ-Fe2O3/Au core/shell (γ-Fe2O3@Au) nanoparticles and subsequently used them in a homemade, high-Tc, superconducting quantum interference device (SQUID) LFNMR system. Remarkably, we found that both the proton spin–lattice relaxation time (T1) and proton spin–spin relaxation time (T2) were influenced by the presence of γ-Fe2O3@Au nanoparticles. Unlike the spin–spin relaxation rate (1/T2), the spin–lattice relaxation rate (1/T1) was found to be further enhanced upon exposing the γ-Fe2O3@Au nanoparticles to 532 nm light during NMR measurements. We showed that the photothermal effect of the plasmonic gold layer after absorbing light energy was responsible for the observed change in T1. This result reveals a promising method to actively control the contrast of T1 and T2 in low-field (LF) MRI applications.

Surface studies on aluminized and thermally oxidized Alloy 690 substrates interacted with nitrate-based simulated nuclear waste and sodium borosilicate melt using Raman spectroscopy and X-ray photoelectron spectroscopy

Aluminized and thermally oxidized Alloy 690 specimen containing Al2O3 layer on the outermost surface and bare alloy substrates were exposed either in nitrate-based simulated nuclear waste solution at 373K for 216h or sodium borosilicate melt at 1248K for 192h. The exposed samples were characterized by micro-Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Aluminized and thermally oxidized sample exposed to simulated nuclear waste indicated the presence of Al2O3, mixed oxides of NiCr2O4 and NiFe2O4, NiO, a small amount of Cr2O3, mixed oxides of Cr+3 and Cr+6 and elemental aluminium. Similar surface compositions were recorded for coated samples exposed to sodium borosilicate melt. The formation of mixed oxides on coated samples could be attributable to oxidation treatment. Bare Alloy 690 substrates exposed to simulated nuclear waste, indicated the presence of γ-Fe2O3, NiO, a small amount of Cr2O3, mixed oxides of Cr+3 and Cr+6, elemental chromium and nickel. The alloy substrate exposed to sodium borosilicate melt showed similar compositions along with presence of CrO3, mixed oxides of NiCr2O4 and NiFe2O4. The presence of mixed oxides on bare alloy substrate exposed to molten glass resulted from high temperature exposure.

Magnetic Polyacrylic Anion Exchange Resin: Preparation, Characterization and Adsorption Behavior of Humic Acid

Magnetic polyacrylic resin (R0) was prepared by suspension polymerization in the presence of γ-Fe2O3 and γ-methacryloxypropyltrimethoxysilane (γ-MPS). The obtained magnetic resin (R0) was modified sequentially by ammonolysis and alkylation to produce a magnetic weakly basic anion exchange resin (R1) and a magnetic strongly basic anion exchange resin (R2). Infrared (IR) spectra, elemental analysis, scanning electron microscopy (SEM), magnetization, Brunauer–Emmett–Teller (BET) surface area and chemical analysis were all determined to characterize these resins. The investigation of humic acid (HA) adsorption on R0, R1, and R2 showed that chemical interactions between the functional groups of the resin and HA were responsible for HA adsorption. The adsorption capacity of HA on R1 was ∼20%–60% less than that of R2, but the R1 resin was easier to regenerate with NaOH aqueous solution. A mixture of 1% NaCl and 1% NaOH was found to be highly efficient for the regeneration of both R1 and R2 resins, with desorption efficiencies measuring >90%. Pseudo-second-order model and Freundlich equation fit better for HA adsorption onto R1 and R2 than other typical kinetic and thermodynamic models, respectively. The effects of pH, coexisting salts (i.e., NaCl and Na2SO4), and recyclability were also assessed.