Magnetically retrievable ferrite nanoparticles in the catalysis application

The synthesis and characterization of Fe2O3@SiO2-SO3H nanofibers as a novel magnetic core-shell catalyst for formamidine and formamide synthesis

Over the past several decades, the fabrication of novel ceramic nanofibers applicable in different areas has been a frequent focus of scientists around the world. Aiming to introduce novel ceramic core-shell nanofibers as a magnetic solid acid catalyst, Fe2O3@SiO2-SO3H magnetic nanofibers were prepared in this study using a modification of Fe2O3@SiO2 core-shell nanofibers with chlorosulfonic acid to increase the acidic properties of these ceramic nanofibers. The products were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray spectroscope (EDS), vibrating sample magnetometer (VSM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The prepared nanofibers were used as catalysts in formamide and formamidine synthesis. The treatment of aqueous formic acid using diverse amines with a catalytic amount of Fe2O3@SiO2-SO3H nanofibers as a reusable, magnetic and heterogeneous catalyst produced high yields of corresponding formamides at room temperature. Likewise, the reaction of diverse amines with triethyl orthoformate led to the synthesis of formamidine derivatives in excellent yields using this novel catalyst. The catalytic system was able to be recovered and reused at least five times without any catalytic activity loss. Thus, novel core-shell nanofibers can act as efficient solid acid catalysts in different organic reactions capable of being reused several times due to their easy separation by applying magnet.

Recovery/Reuse of Heterogeneous Supported Spent Catalysts

The rapid separation and efficient recycling of catalysts after a catalytic reaction are considered important requirements along with the high catalytic performances. In this view, although heterogeneous catalysis is generally less efficient if compared to the homogeneous type, it is generally preferred since it benefits from the easy recovery of the catalyst. Recycling of heterogeneous catalysts using traditional methods of separation such as extraction, filtration, vacuum distillation, or centrifugation is tedious and time-consuming. They are uneconomic processes and, hence, they cannot be carried out in the industrial scale. For these limitations, today, the research is devoted to the development of new methods that allow a good separation and recycling of catalysts. The separation process should follow a procedure economically and technically feasible with a minimal loss of the solid catalyst. The aim of this work is to provide an overview about the current trends in the methods of separation/recycling used in the heterogeneous catalysis.

Electrochemical sensor based on magnetic nanohybrids of multiple phthalocyanine doped ferrites/CMWCNTs for detection of rosmarinic acid

Ferrites have attracted considerable attention in biosensor developments owing to their favorable electrochemical and magnetic properties. Speedy and trace analysis can be succeeded by the sensors based on magnetic nanohybrids. In this work, we reported a novel method for one-step synthesis of magnetic ferrites composed of Fe and phthalocyanine. After hybridization with carbonylated multi wall carbon nanotubes, a sensor based on Fe3O4-Pc-CMWCNTs nanocomposites was fabricated for the detection of rosmarinic acid (RA), a bioactive phytochemical. The sensor can be constructed within 30s without any complicated process. A comparison of electrochemical activity between ZnFe2O4-Pc-CMWCNTs and Fe3O4-Pc-CMWCNTs nanohybrids also has been accomplished in this work. Compared with ZnFe2O4-Pc-CMWCNTs based on commonly used ferrites, Fe3O4-Pc-CMWCNTs/MGCE exhibited a higher catalytical ability for the detection of RA. The sensor modified with Fe3O4-Pc-CMWCNTs displayed a low LOD of 0.182 μM with a wide linear range from 0.2 to 400 μM, which was 30 times more sensitive than the one based on ZnFe2O4-Pc-CMWCNTs. The obtained sensor also owned an excellent selectivity, reproducibility, repeatability, and stability, which made it achieve the measurements in plant sample and human serum.

Preparation and physicochemical properties of the Fe, Mn-oxides catalyst

A Fe, Mn-oxide catalyst was obtained by impregnation of thermally activated dolomite granules with aqueous solutions of Fe(III) and Mn(II) sulfates followed by heat treatment. Its physicochemical properties were studied using differential thermal analysis, X-ray diffraction, low-temperature adsorption-desorption of nitrogen, and scanning electron microscopy. The high efficiency of Fe(II) ion oxidation in aqueous media in a flow-type catalytic reactor was shown, which makes the obtained catalyst promising for the deironization of artesian waters.

Visible light activated magnetic photocatalysts for water treatment

Environmental concerns have been raised regarding the intense contamination of water resources. Currently, numerous contaminants that reach water bodies are not efficiently removed by conventional water treatment methods. Therefore, there arises the need for development and optimization of efficient treatment methods for the removal of such recalcitrant contaminants. Given the circumstances, the present study aims to use of advanced oxidative processes for dye degradation. For this purpose, copper and zinc doped cobalt ferrites were synthesized by coprecipitation, targeting the degradation of methylene blue dye. The photocatalysts were characterized by XRD, WD-XRF, FE-SEM, N₂ physisorption isotherms, UV-Vis diffuse reflectance spectroscopy, molecular fluorescence spectroscopy and zeta potential. According to the investigation of the degradation mechanism, the holes and hydroxyl radicals were mainly responsible for the dye's degradation. The obtained photocatalysts displayed promising results with up to 99% of dye degradation, employing conventional visible LED lamps, making the practical use of the catalyst highly viable, as well as the economic matters. Additionally, the synthesized materials' magnetic properties allowed total and efficient separation of the catalyst for its reutilization up to 4 cycles, with no decrease in photocatalytic activity and with low leaching of iron ions to solution.

Recent Advances of Magnetic Nanomaterials in Bone Tissue Repair

The magnetic field has been proven to enhance bone tissue repair by affecting cell metabolic behavior. Magnetic nanoparticles are used as biomaterials due to their unique magnetic properties and good biocompatibility. Through endocytosis, entering the cell makes it easier to affect the physiological function of the cell. Once the magnetic particles are exposed to an external magnetic field, they will be rapidly magnetized. The magnetic particles and the magnetic field work together to enhance the effectiveness of their bone tissue repair treatment. This article reviews the common synthesis methods, the mechanism, and application of magnetic nanomaterials in the field of bone tissue repair.

Solution combustion synthesis, characterization, magnetic, and dielectric properties of CoFe2O4 and Co0.5M0.5Fe2O4 (M = Mn, Ni, and Zn)

Co_0.5Zn_0.5Fe₂O₄ (CZF) shows the highest M_s value compared to CoFe₂O₄ (CF), Co_0.5Mn_0.5Fe₂O₄ (CMF), and Co_0.5Ni_0.5Fe₂O₄ (CNF) as Zn²⁺ would prefer to occupy tetrahedral sites with a consequent increase of the Fe³⁺ concentration in octahedral sites.

Hydrothermal synthesis of NiFe2O4 nanoparticles as an efficient electrocatalyst for the electrochemical detection of bisphenol A

In this study, the sensitive and selective detection of bisphenol A (BPA) was achieved using a screen-printed carbon electrode (NFO/SPCE) modified with hydrothermally synthesized NiFe₂O₄ nanoparticles.

Conductivity and giant permittivity study of Zn0.5Ni0.5Fe2O4 spinel ferrite as a function of frequency and temperature

Ni_0.5Zn_0.5Fe₂O₄ was prepared by the solid state reaction route at different temperatures. The dielectric properties of spinel ferrites were investigated in the frequency range 50 Hz–10 MHz and in the temperature range 300–420 K. Conductance is shown to increase with increasing frequency and temperature. Impedance analyses indicated that the relaxation phenomenon is strongly dependent on temperature and frequency. The impedance plots displayed both intra- and inter-granular contributions. Electrical equivalent circuit was proposed to explain the impedance results. The decrease of giant permittivity values with the increase in frequency proves the dispersion in the low frequency range and is showing the Maxwell–Wagner interfacial polarization.

Ni_0.5Zn_0.5Fe₂O₄ was prepared by the solid state reaction route at different temperatures.