Determination of Hydrogen Peroxide Using a Novel Sensor Based on Fe3O4 Magnetic Nanoparticles

Fe₃O₄ magnetic nanoparticles were synthesized by chemical co-precipitation with sodium citrate as a surfactant and were used with chitosan to construct a novel hydrogen peroxide sensor. The electrochemical behavior of hydrogen peroxide at the sensor was investigated by cyclic voltammetry. The composite film electrocatalyzed the reduction of hydrogen peroxide, and the peak current increased linearly with concentration from 1.00 × 10^?5 to 1.00 × 10^?3 mol · L^?1 (R = 0.9974) with a detection limit of 1.53 × 10^?6 mol · L^?1. This novel nonenzyme sensor provided good sensitivity, stability, and precision with potential applications.     

Oxoperoxo tungsten(VI) complex immobilized on Schiff base-modified Fe3O4 magnetic nanoparticles as a heterogeneous catalyst for oxidation of alcohols with hydrogen peroxide

Oxoperoxo tungsten(VI) complex immobilized on Schiff base-modified Fe₃O₄ super paramagnetic nanoparticles were synthesized and appropriately characterized using FT-IR, XRD, SEM, TEM, EDX, BET, and VSM analysis. The synthesized nanoparticles efficiently catalyzed oxidation of benzylic alcohols with H₂O₂ as oxidant in high yields, with high to excellent selectivity. The catalyst can be recovered using an external magnetic field and recycled for subsequent oxidation reactions without any appreciable loss of efficiency. The simple preparation, high activity, excellent selectivity, and simple recoverability of the catalyst are advantageous.     

Ultrasensitive fluorometric determination of hydrogen peroxide and glucose by using multiferroic BiFeO3 nanoparticles as a catalyst

BiFeO₃ magnetic nanoparticles (BFO MNPs) are used as a catalyst to develop an ultrasensitive method for the determination of H₂O₂. It is found that BFO MNPs can catalyze the decomposition of H₂O₂ to produce OH radicals, which in turn oxidize the weakly fluorescent benzoic acid to a strongly fluorescent hydroxylated product with a maximum emission at 405 nm. This makes it possible to sensitively quantify traces of H₂O₂. Under optimized conditions, the fluorescence intensity is observed to be well linearly correlated with H₂O₂ concentration from 2.0 × 10⁻⁸ to 2.0 × 10⁻⁵ mol L⁻¹ with a detection limit of 4.5 × 10⁻⁹ mol L⁻¹ (S/N = 3). In addition, a selective method for glucose determination is developed by using both glucose oxidase and BFO MNPs, which has a linear range for glucose concentration from 1.0 × 10⁻⁶ to 1.0 × 10⁻⁴ mol L⁻¹ with a detection limit of 5.0 × 10⁻⁷ mol L⁻¹. These new methods have been successfully applied for the determination of H₂O₂ in rainwater and glucose in human serum samples.     

Synthesis of orientedly bioconjugated core/shell Fe3O4@Au magnetic nanoparticles for cell separation

Orientedly bioconjugated core/shell Fe₃O₄@Au magnetic nanoparticles were synthesized for cell separation. The Fe₃O₄@Au magnetic nanoparticles were synthesized by reducing HAuCl₄ on the surfaces of Fe₃O₄ nanoparticles, which were further characterized in detail by TEM, XRD and UV-vis spectra. Anti-CD3 monoclonal antibody was orientedly bioconjugated to the surface of Fe₃O₄@Au nanoparticles through affinity binding between the Fc portion of the antibody and protein A that covalently immobilized on the nanoparticles. The oriented immobilization method was performed to compare its efficiency for cell separation with the non-oriented one, in which the antibody was directly immobilized onto the carboxylated nanoparticle surface. Results showed that the orientedly bioconjugated Fe₃O₄@Au MNPs successfully pulled down CD3⁺ T cells from the whole splenocytes with high efficiency of up to 98.4%, showing a more effective cell-capture nanostructure than that obtained by non-oriented strategy. This developed strategy for the synthesis and oriented bioconjugation of Fe₃O₄@Au MNPs provides an efficient tool for cell separation, and may be further applied to various fields of bioanalytical chemistry for diagnosis, affinity extraction and biosensor.     

Magnetic solid-phase extraction based on Fe3O4/graphene oxide nanoparticles for the determination of malachite green and crystal violet in environmental water samples by HPLC

This work describes a magnetic Fe₃O₄/graphene oxide (GO)-based solid-phase extraction (MSPE) technique for high performance liquid chromatography (HPLC) detection of malachite green (MG) and crystal violet (CV) in environmental water samples. Fe₃O₄/ GO magnetic nanoparticles were synthesised by a chemical co-precipitation method and characterised by scanning electron micrograph, transmission electron microscope, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and surface area analyser. The prepared Fe₃O₄/GO magnetic nanoparticles were used as the adsorbents of MSPE for MG and CV. By coupling with HPLC, a sensitive and cost-effective method for simultaneous determination of MG and CV was developed. The important parameters including the amount of Fe₃O₄/GO, pH of the sample solution, extraction time, salt effect, the type and volume of desorption solvent were investigated in detail. Under optimised conditions, the calibration curves were linear in the concentration range of 0.5–200 μg L^?1, and the limits of detection were 0.091 and 0.12 μg L^?1 for MG and CV, respectively. Finally, the established MSPE-HPLC method was successfully applied to determine MG and CV in environmental water samples with the recoveries ranging from 91.5% to116.7%.     

Fe3O4 nanoparticles: A powerful and magnetically recoverable catalyst for the synthesis of novel calix[4]resorcinarenes

A simple synthesis of novel and known calix[4]resorcinarenes derivatives has been achieved by the condensation of resorcinol and different aromatic aldehydes in the presence of catalytic amounts of Fe₃O₄ nanoparticles under solvent-free conditions.The experimental conditions have been thoroughly optimized and established,allowing significant rate enhancements and good to excellent yields.The reactions can be run safely without using any toxic organic solvents under mild reaction conditions.The Fe₃O₄ nanoparticles were characterized by powdered X-ray diffraction（XRD）,transmission electron microscopy（TEM） and FT-IR spectroscopy.     

Thick Fe2O3, Fe3O4 films prepared by the chemical solution deposition method

Fe₂O₃, Fe₃O₄ films have been prepared from Fe(OCH₂CH(CH₃)₂)₃–(CH₃)₂CHCH₂OH–2.2′-diethanola- mine (DEA)–poly(vinylpyrrolidone) (PVP) solutions by the spin-(SC) and dip-coating (DC) technique on SiO₂ and Si substrates. The maximum film thickness achieved without crack formation has been increased by incorporation of PVP (relative molecular weights 40000 and 360000) into the precursor solution. The stability of the precursor solutions was remarkably increased by addition of DEA. Compact, dense, and crack-free Fe₂O₃ films with thicknesses 900 nm (DC), 450 nm (SC), have been obtained via single-step deposition cycle. Higher-molecular-weight PVP has been more effective in increasing the thickness. The minimum concentration of DEA, which results in pronounced increase of solutions stability, is about R _P (n(DEA)/n(Fe) = 0.1). The high content of carboneous residue in the pyrolysed Fe₂O₃ films promotes the formation of Fe₃O₄ films via reduction in a gas flow of H₂/N₂ gas mixture. Microstructure, surface morphology, and magnetic properties of the films have been also investigated using SEM, AFM, and SQUID, respectively.     

Preparation of surface plasmon resonance biosensor based on magnetic core/shell Fe3O4/SiO2 and Fe3O4/Ag/SiO2 nanoparticles

In this paper, surface plasmon resonance biosensors based on magnetic core/shell Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles were developed for immunoassay. With Fe(3)O(4) and Fe(3)O(4)/Ag nanoparticles being used as seeding materials, Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles were formed by hydrolysis of tetraethyl orthosilicate. The aldehyde group functionalized magnetic nanoparticles provide organic functionality for bioconjugation. The products were characterized by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), FTIR and UV-vis absorption spectrometry. The magnetic nanoparticles possess the unique superparamagnetism property, exceptional optical properties and good compatibilities, and could be used as immobilization matrix for goat anti-rabbit IgG. The magnetic nanoparticles can be easily immobilized on the surface of SPR biosensor chip by a magnetic pillar. The effects of Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles on the sensitivity of SPR biosensors were also investigated. As a result, the SPR biosensors based on Fe(3)O(4)/SiO(2) nanoparticles and Fe(3)O(4)/Ag/SiO(2) nanoparticles exhibit a response for rabbit IgG in the concentration range of 1.25-20.00 μg ml(-1) and 0.30-20.00 μg ml(-1), respectively.     

Fabrication and Characterization of Nanocomposite Flexible Membranes of PVA and Fe3O4

Composite polymer membranes of poly(vinyl alcohol) (PVA) and iron oxide (Fe₃O₄) nanoparticles were produced in this work. X-ray diffraction measurements demonstrated the formation of Fe₃O₄ nanoparticles of cubic structures. The nanoparticles were synthesized by a coprecipitation technique and added to PVA solutions with different concentrations. The solutions were then used to generate flexible membranes by a solution casting method. The size and shape of the nanoparticles were investigated using scanning electron microscopy (SEM). The average size of the nanoparticles was 20±9 nm. Raman spectroscopy and Fourier-transform infrared spectroscopy (FTIR) were utilized to investigate the structure of the membranes, as well as their vibration modes. Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) demonstrated the thermal stability of the membranes and the crystallinity degree. Electrical characteristics of the thin membranes were examined using impedance spectroscopy as a function of the nanoparticles’ concentrations and temperatures. The resistivity of the fabricated flexible membranes was possible to adjust by controlled doping with suitable concentrations of nanoparticles. The activation energy decreased with the nanoparticles’ concentrations due to the increase in charge carriers’ concentrations. Therefore, the fabricated membranes may be applied for practical applications that involve the recycling of nanoparticles for multiple application cycles.     

Fe3O4 MNPs-DETA/Benzyl-Br3: A new magnetically reusable catalyst for the oxidative coupling of thiols

We report a new strategy to immobilize a bromine source on the surface of magnetic Fe₃O₄ nanoparticles (Fe₃O₄ MNPs-DETA/Benzyl-Br₃) leading to a magnetically recoverable catalyst, which exhibits high catalytic efficiency in oxidative coupling of thiols to the disulfides (89–98%). The Fe₃O₄ MNPs-DETA/Benzyl-Br₃ catalyst was fabricated by anchoring 3-chloropropyltrimethoxysilane (CPTMS) on magnetic Fe₃O₄ nanoparticles, followed with N-benzylation and reaction with bromine in tetrachloridecarbon. The resulting nanocomposite was analyzed by a series of characterization techniques such as FT-IR, SEM, TGA, VSM and XRD. The catalyst could be recovered via magnetic attraction and could be recycled at least 5 times without appreciable decrease in activity.     

Efficiency of Fe3O4 Nanoparticles with Different Pretreatments for Enhancing Biogas Yield of Macroalgae Ulva intestinalis Linnaeus

In this work, different pretreatment methods for algae proved to be very effective in improving cell wall dissociation for biogas production. In this study, the Ulva intestinalis Linnaeus (U. intestinalis) has been exposed to individual pretreatments of (ultrasonic, ozone, microwave, and green synthesized Fe₃O₄) and in a combination of the first three mentioned pretreatments methods with magnetite (Fe₃O₄) NPs, (ultrasonic-Fe₃O₄, ozone-Fe₃O₄ and microwave-Fe₃O₄) in different treatment times. Moreover, the green synthesized Fe₃O₄ NPs has been confirmed by FTIR, TEM, XRD, SEM, EDEX, PSA and BET. The maximum biogas production of 179 and 206 mL/g VS have been attained when U. intestinalis has been treated with ultrasonic only and when combined microwave with Fe₃O₄ respectively, where sediment were used as inoculum in all pretreatments. From the obtained results, green Fe₃O₄ NPs enhanced the microwave (MW) treatment to produce a higher biogas yield (206 mL/g VS) when compared with individual MW (84 mL/g VS). The modified Gompertz model (R² = 0.996 was appropriate model to match the calculated biogas production and could be used more practically to distinguish the kinetics of the anaerobic digestion (AD) period. The assessment of XRD, SEM and FTIR discovered the influence of different treatment techniques on the cell wall structure of U. intestinalis.     

Regioselective hydrothiolation of terminal acetylene catalyzed by magnetite (Fe3O4) nanoparticles

Herein, we report a new and solvent-free methodology for the preparation of vinyl thioethers from terminal alkynes and thiols, using magnetite (Fe₃O₄) nanoparticles as a recyclable catalyst. With this greener method, the desired vinyl thioethers were achieved in good yields and with good stereoselectivity. In addition, the catalyst was easily recovered using a simple external magnet and reused for further catalytic reactions without significant loss of activity up to the fifth cycle.     

Synthesis and Magnetic Properties of Pt3Co/Fe3O4 Nanocomposites

Bimagnetic Pt₃Co/Fe₃O₄ nanocomposite is synthesized in aqueous solution. The nanoparticles are characterized with TEM, FTIR, and magnetic measurements. The as‐synthesized nanocomposite exhibits ferromagnetic properties at room temperature due to the exchange coupling between Pt₃Co and Fe₃O₄. Magnetic properties of Pt₃Co/Fe₃O₄ nanoparticle can be tuned by varying of the molar ratio of iron to platinum. Pt₃Co/Fe₃O₄ nanoparticles exhibit higher saturation magnetization when the molar ratio of iron to platinum is 1.     

Hydrothermal Synthesis of Regular Octahedron Fe3O4 Microcrystals

Regular octahedron Fe₃O₄ microcrystals have been synthesized by a hydrothermal process on a large scale directly Fe substrates for the first time. X-ray diffraction (XRD) and scanning electron microscopy (SEM) have been used to investigate the novel fractal microcrystals. The results show that the regular octahedron Fe₃O₄ microcrystals can be obtained using this simple method. The size of microcrystals is evaluated to be from 2 to 20 μm. Moreover, one key fact has been found that the reaction temperature has a vital effect on the morphologies of the products.     

Pd@GO/Fe3O4/PAA/DCA: a novel magnetic heterogeneous catalyst for promoting the Sonogashira cross-coupling reaction

Abstract

A hybrid system involving graphene oxide (GO), magnetic oxide (Fe₃O₄), acrylamide and dicyandiamide was prepared via amine functionalization of GO/Fe₃O₄ by means of covalent bonding with acrylamide and subsequent reaction with dicyandiamide to provide a multinitrogen containing polymer on the surface of GO. This hybrid system was utilized as a heterogeneous catalyst support for immobilizing Pd nanoparticles to provide the hybrid, Pd@GO/Fe₃O₄/PAA/DCA. This nano-Pd composite was characterized using Fourier transform infrared, transmission electron microscopy, scanning electron microscopy, vibrating sample magnetometer, thermogravimetric analysis, X-ray diffraction, and ICP techniques and used for promoting Sonogashira cross-coupling under mild reaction conditions. This heterogeneous and magnetic catalyst was easily separated by external magnet and was reused in a model reaction, efficiently up to six times with slight loss of catalytic activity and Pd leaching, showing the suitability of GO/Fe₃O₄/PAA/DCA for embedding Pd nanoparticles. To check the effect of the number of surface nitrogens of the polymeric chain on the catalytic performance, the activity of the catalyst was compared with Pd@GO/Fe₃O₄/PAA; increased number of the surface nitrogens on the chain polymer leads to higher loading of Pd and lower the Pd leaching.     

Fabrication of magnetite nanoparticles (Fe3O4-NPs) for catalytic pyrolysis of nutshells biomass

The fabrication of nanoparticles has been perused as a topic of critical importance in the present decades. Biosynthesis of nanoparticles employs plants extract instead of harmful chemicals. These plant extracts act as reducing and capping agents which is the most appropriate and eco-friendly method among all the preparative routs. In present study, the magnetite nanoparticles (Fe₃O₄-NPs) were fabricated using rapid, single step and benign biosynthetic rout by reduction of ferric nitrate nonahydrate solution with Ferocactus echidne aqueous extract containing ascorbic acid as a main reducing and capping agent. The structural and morphological properties of prepared iron oxide nanoparticles were investigated by Powder X-ray diffraction and scanning electron microscopy. The size of the synthesized nanoparticles was approximately 15 ± 2 nm as determined by Scherrer equation. The biosynthetically fabricated nanoparticles were employed as catalyst for pyrolysis of nutshells to produce biofuel. Catalytic pyrolysis of biomass yields biofuel as an alternative source of energy and chemical feed stock. Effect of temperature, heating rate, and amount of catalyst were investigated on conversion percentage and product yields. Aniline point, carbon residue, and cetane number of prepared bio-oil were also determined.     

A novel nonenzymatic sensor based on LaNi0.6Co0.4O3 modified electrode for hydrogen peroxide and glucose

In this paper, LaNi_0.6Co_0.4O₃ (LNC) nanoparticles were synthesized by the sol–gel method, and the structure and morphology of LNC nanoparticles were characterized by X-ray diffraction spectrum, scanning electron microscopy and transmitting electron microscopy. And then, LNC was used to modify carbon paste electrode (CPE) without any adhesive to fabricate hydrogen peroxide and glucose sensor, and the results demonstrated that LNC exhibited strong electrocatalytical activity by cyclic voltammetry and amperometry. In H₂O₂ determination, linear response was obtained in the concentration range of 10 nM–100 μM with a detection limit of 1.0 nM. In glucose determination, there was the linear region of 0.05–200 μM with a detection limit of 8.0 nM. Compared with other reports, the proposed sensor also displayed high sensitivity toward H₂O₂ (1812.84 μA mM⁻¹ cm⁻²) and glucose (643.0 μA mM⁻¹ cm⁻²). Moreover, this prepared sensor was applied to detect glucose in blood serum and hydrogen peroxide in toothpaste samples with satisfied results, indicating its possibility in practical application.     

Removal of Phenol Dyes Using a Photocatalytic Reactor with SnO2/Fe3O4 Nanoparticles

In this study, we present kinetics of phenol dyes removal by SnO₂/Fe₃O₄ nanoparticles in a photocatalytic reactor for optimization of this process. The effect of different concentrations of SnO₂ 5, 10, 15, 20% w/w on the photocatalytic reactor during removal of phenol red was investigated. The SnO₂/Fe₃O₄ nanoparticles were synthesized by core–shell method. The results of XRD and TEM showed the successful synthesis of these nanoparticles. Several other methods were applied to synthesis of these nanoparticles but none of them succeeded. This process composed of two-stage. The first stage was absorption by iron oxide nanoparticles and second stage was photocatalytic by tin oxide nanoparticles that followed pseudo-second-order kinetic and first-order kinetic, respectively. Optimization of this process was done corresponding to the parameters affecting the process with design expert software. In order to determine the optimal values of each of the parameters and the optimal conditions of the process, parameters were introduced to response surface methodology.     

Fe3O4 nanoparticles as the adsorbent of magnetic solid-phase extraction for clean and preconcentration of maltol and ethyl maltol in food samples followed by HPLC analysis

In this work, a magnetic solid-phase extraction protocol followed with high-performance liquid chromatography analysis was developed for the determination of maltol and ethyl maltol in food samples. The Fe₃O₄ nanoparticles were prepared by one-step hydrothermal method and was used as adsorbent for clean and preconcentrated maltol and ethyl maltol in food samples. The as-prepared Fe₃O₄ nanoparticle was characterized by transmission electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, and vibrating sample magnetometer. The extraction conditions including the amount of material, extraction time, pH, temperature, and desorption solvents were investigated, respectively. Under the optimized conditions, the detection limits of 0.04 and 0.05?µg?mL^?1 could be achieved for maltol and ethyl maltol. The recoveries between 84.2 and 103.4% with RSDs lower than 2.30% were obtained for the analysis of spiked plum candy sample. The developed method was successfully applied to the analysis of real samples, such as juice, chocolate, and plum candy.     

Fe3O4/poly (acrylic acid) nanoparticles as modifiers for improving rheological and filtration properties of water-based drilling fluids

Drilling fluid is a vital element and is often regarded as the “blood” in the oil industry. Although traditional oil-based drilling fluids have advantages in some harsh cases, the high cost and environmental pollution faced with them limit its application. Water-based drilling fluids (WBDFs) with environmental friendly, low cost, and high performance are important for drilling engineering to solve the problems of low efficiency and wellbore instability caused by poor rheological properties and large filtration loss in drilling operations. In this paper, Fe₃O₄ nanoparticles modified by poly (acrylic acid) (PAA) through 3-(trimethoxysilyl) proryl methacrylate (TMSPMA) were introduced into WBDFs for enhancing their rheological and plugging performance. Rheological tests indicated that the consistency coefficient (K) of the Fe₃O₄/PAA nanoparticles/WBDFs decreased at a higher concentration. Incorporated nanoparticles with a concentration of 0.05?wt %, the WBDFs will exhibit good shear-thinning behavior. The results showed that the best performance for Fe₃O₄/PAA nanoparticles being as a filtration additive in WBDFs was achieved at concentration as low as 0.1?wt %. These results demonstrated that Fe₃O₄/PAA nanoparticles are effective additives for WBDFs.