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.     

Mn(III) complex supported on Fe3O4 nanoparticles: magnetically separable nanocatalyst for selective oxidation of thiols to disulfides

A manganese(III) complex, [Mn(phox)₂(CH₃OH)₂]ClO₄ (phox?=?2-(2′-hydroxyphenyl)oxazoline), was immobilized on silica-coated magnetic Fe₃O₄ nanoparticles through the amino propyl linkage using a grafting process in dichloromethane. The resulting Fe₃O₄@SiO₂–NH₂@Mn(III) nanoparticles are used as efficient and recyclable catalysts for selective oxidation of thiols to disulfides using urea-hydrogen peroxide as the oxidant. The nanocatalyst was recycled several times. Leaching and recycling experiments revealed that the nanocatalyst can be recovered, recycled, and reused more than five times, without the loss of catalytic activity and magnetic properties. The recycling of the nanocatalyst in six consecutive runs afforded a total turnover number of more than 10,000. The heterogeneous Fe₃O₄@SiO₂–NH₂@Mn(III) nanoparticle shows more selectivity for the formation of disulfides in comparison with the homogeneous manganese complex.     

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.     

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.     

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.     

Fluorometric method for the determination of hydrogen peroxide and glucose with Fe3O4 as catalyst

In this paper, we utilized the instinct peroxidase-like property of Fe₃O₄ magnetic nanoparticles (MNPs) to establish a new fluorometric method for determination of hydrogen peroxide and glucose. In the presence of Fe₃O₄ MNPs as peroxidase mimetic catalyst, H₂O₂ was decomposed into radical that could quench the fluorescence of CdTe QDs more efficiently and rapidly. Then the oxidization of glucose by glucose oxidase was coupled with the fluorescence quenching of CdTe QDs by H₂O₂ producer with Fe₃O₄ MNPs catalyst, which can be used to detect glucose. Under the optimal reaction conditions, a linear correlation was established between fluorescence intensity ratio I₀/I and concentration of H₂O₂ from 1.8 × 10⁻⁷ to 9 × 10⁻⁴ mol/L with a detection limit of 1.8 × 10⁻⁸ mol/L. And a linear correlation was established between fluorescence intensity ratio I₀/I and concentration of glucose from 1.6 × 10⁻⁶ to 1.6 × 10⁻⁴ mol/L with a detection limit of 1.0 × 10⁻⁶ mol/L. The proposed method was applied to the determination of glucose in human serum samples with satisfactory results.     

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.     

Synthesis of pyranopyrazoles using magnetic Fe3O4 nanoparticles as efficient and reusable catalyst

Magnetic Fe₃O₄ nanoparticles as a heterogeneous catalyst, were found to be efficient for the synthesis of a series of pyranopyrazoles by a four component reaction of a mixture of hydrazine hydrate, ethyl acetoacetate, aldehydes/ketones and malononitrile in water at room temperature. The products were attributed to the nanosize of about 16 nm in which the catalyst could act as a nanoreactor. The present protocol offers the advantages of clean reaction, short reaction time, high yield, easy purification and economic availability of the catalyst.     

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.     

Electrochemical Detection of Dopamine at Fe3O4/SPEEK Modified Electrode

Reported here is the design of an electrochemical sensor for dopamine (DA) based on a screen print carbon electrode modified with a sulphonated polyether ether ketone-iron (III) oxide composite (SPCE-Fe₃O₄/SPEEK). L. serica leaf extract was used in the synthesis of iron (III) oxide nanoparticles (Fe₃O₄NPs). Successful synthesis of Fe₃O₄NP was confirmed through characterization using Fourier transform infrared (FTIR), ultraviolet–visible light (UV–VIS), X-ray diffractometer (XRD), and scanning electron microscopy (SEM). Cyclic voltammetry (CV) was used to investigate the electrochemical behaviour of Fe₃O₄/SPEEK in 0.1 M of phosphate buffer solution (PBS) containing 5 mM of potassium ferricyanide (III) solution (K₃[Fe(CN)₆]). An increase in peak current was observed at the nanocomposite modified electrode SPCE-Fe₃O₄/SPEEK) but not SPCE and SPCE-Fe₃O₄, which could be ascribed to the presence of SPEEK. CV and square wave voltammetry (SWV) were employed in the electroxidation of dopamine (0.1 mM DA). The detection limit (LoD) of 7.1 μM and 0.005 μA/μM sensitivity was obtained for DA at the SPCE-Fe₃O₄/SPEEK electrode with concentrations ranging from 5–50 μM. LOD competes well with other electrodes reported in the literature. The developed sensor demonstrated good practical applicability for DA in a DA injection with good resultant recovery percentages and RSDs values.     

Chitosan/Gamma-Alumina/Fe3O4@5-FU Nanostructures as Promising Nanocarriers: Physiochemical Characterization and Toxicity Activity

Today, cancer treatment is an important issue in the medical world due to the challenges and side effects of ongoing treatment procedures. Current methods can be replaced with targeted nano-drug delivery systems to overcome such side effects. In the present work, an intelligent nano-system consisting of Chitosan (Ch)/Gamma alumina (γAl)/Fe₃O₄ and 5-Fluorouracil (5-FU) was synthesized and designed for the first time in order to influence the Michigan Cancer Foundation-7 (MCF-7) cell line in the treatment of breast cancer. Physico-chemical characterization of the nanocarriers was carried out using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), vibrating sample magnetometry (VSM), dynamic light scattering (DLS), and scanning electron microscopy (SEM). SEM analysis revealed smooth and homogeneous spherical nanoparticles. The high stability of the nanoparticles and their narrow size distribution was confirmed by DLS. The results of the loading study demonstrated that these nano-systems cause controlled, stable, and pH-sensitive release in cancerous environments with an inactive targeting mechanism. Finally, the results of MTT and flow cytometry tests indicated that this nano-system increased the rate of apoptosis induction on cancerous masses and could be an effective alternative to current treatments.     

Latent Fingerprints Enhancement Using a Functional Composite of Fe3O4@SiO2-Au

A functional composite of Fe₃O₄@SiO₂-Au was prepared and used for latent fingerprint detection. Material characterization results confirmed the successful fabrication of the Fe₃O₄@SiO₂-Au composite. In latent fingerprint detection, the Fe₃O₄@SiO₂-Au composite provides a better performance than commercial copper powder and also gold nanoparticles. More importantly, the Fe₃O₄@SiO₂-Au composite can be used in both powder and suspension forms, and also for common surfaces including glass, polyethylene bags, and paper. The favorable pH range (2.0–5.0) for the compositein finger marks detection is much wider than that of the traditional multi-metal deposition method (pH ranging from 2.0 to 3.0). The mechanism for the Fe₃O₄@SiO₂-Au composite in fingerprint detection was explored and discussed. This study provides a favorable choice for a one-step deposition method for latent fingerprint detection.     

A one-pot synthesis of 5,5-disubstituted hydantoin derivatives using magnetic Fe3O4 nanoparticles as a reusable heterogeneous catalyst

A facile and rapid method for the one-pot synthesis of 5,5-disubstituted hydantoins in the presence of magnetic Fe₃O₄ nanoparticles has been developed. The multicomponent reactions of carbonyl compounds (aldehydes and ketones), potassium cyanide and ammonium carbonate were carried out under solvent-free conditions to obtain various hydantoin derivatives. The magnetic catalyst could be readily separated by an external magnet from the reaction mixture. This procedure has many advantages, such as the use of a reusable magnetic catalyst, high yields, short reaction times, simplicity and very easiness with implementing the methodology.     

Cu(II) immobilized on Fe3O4–diethylenetriamine: A new magnetically recoverable catalyst for the synthesis of 2,3‐dihydroquinazolin‐4(1H)‐ones and oxidative coupling of thiols

Cu(II) immobilized on Fe₃O₄–diethylenetriamine was designed as a new, inexpensive and efficient heterogeneous catalyst for the synthesis of 2,3‐dihydroquinazolin‐4(1H )‐ones and the oxidative coupling of thiols. The structure of the nanomagnetic catalyst was comprehensively characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, vibrating sample magnetometry, thermogravimetric analysis, X‐ray diffraction and atomic absorption spectroscopy. Simple preparation of the catalyst from commercially available materials, high catalytic activity, simple operation, high yields, use of green solvents, easy magnetic separation and reusability of the catalyst with unaltered activity make our protocol a green and feasible synthetic strategy.     

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.     

Characterization and application of Fe3O4/SiO2 nanocomposites

A sol-gel procedure was used to cover Fe₃O₄ nanoparticles with SiO₂ shell, forming a core/shell structure. The core/shell nanocomposites were synthesized by a two-step process. First, Fe₃O₄ nanoparticles were obtained through co-precipitation and dispersed in aqueous solution through electrostatic interactions in the presence of tetramethylammonium hydroxide (TMAOH). In the second step, Fe₃O₄ was capped with SiO₂ generated from the hydrolyzation of tetraethyl orthosilicate (TEOS). The structure and properties of the formed Fe₃O₄/SiO₂ nanocomposites were characterized and the results indicate that the Fe₃O₄/SiO₂ nanocomposites are superparamagnetic and are about 30 nm in size. Bioconjugation to IgG was also studied. Finally, the mechanism of depositing SiO₂ on magnetic nanoparticles was discussed.     

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.     

磁性可见光催化剂BiVO4/Fe3O4的制备及催化活性

采用超声法将磁基体Fe3O4和BiVO4复合,制备了易于固液分离的磁性可见光催化剂BiVO4/Fe3O4。采用X射线衍射(XRD)、傅立叶转换红外光谱(FTIR)、紫外-可见漫反射光谱(DRS)、透射电子显微镜(TEM)和磁学性质测量系统(MPMS)对产物进行了表征,并以亚甲基蓝为目标降解物,考察了BiVO4/Fe3O4的可见光催化活性。当BiVO4与Fe3O4质量比为5:1时,BiVO4/Fe3O4的催化活性最高,反应经过5 h,对亚甲基蓝的降解率达到92.0%,而单独使用BiVO4为催化剂,降解率仅为72.5%。这表明Fe3O4不仅起到磁基体的作用,还起到助催化剂的作用。BiVO4/Fe3O4在外加磁场的作用下很容易被分离,撤消外加磁场后,通过搅拌又可重新分散。BiVO4/Fe3O4 3次回收后的降解率仍高于80%。     

Preparation of a novel Fe3O4/graphene oxide hybrid for adsorptive removal of methylene blue from water

In this work, a novel Fe₃O₄/graphene oxide (GO) hybrid was prepared and its removal ability of cationic methylene blue dye from water was investigated. To improve the dispersability of Fe₃O₄/GO hybrid in water, GO was first modified by polyethylene glycol (PEG) via a click approach before deposition of Fe₃O₄ nanoparticles onto its surface. The successful modification of GO surface and the deposition of Fe₃O₄ nanoparticles were confirmed by transmission electron microscopy directly. The saturation magnetization of the resultant Fe₃O₄/GO hybrid is 7.8 eum/g. The adsorption capacities of Fe₃O₄/GO hybrid for methylene blue at 35 and 60°C were as high as 96.05 and 120.05 mg/g, respectively. Moreover, the Langmuir, Freundlich, and Temkin models are used to investigate the isothermal adsorption behavior of Fe₃O₄/GO hybrid.