Modified Fe3O4 Particles Research Articles

Magnetic solid-phase extraction method with modified magnetic ferroferric oxide nanoparticles in a deep eutectic solvent and high-performance liquid chromatography used for the analysis of pharmacologically active ingredients of Epimedium folium

A novel magnetic adsorption nanomaterial was synthesized by the copolymerization of a deep eutectic solvent (DES) and chitosan (CS)-modified Fe3O4 particles. This material was proposed for the magnetic solid-phase extraction (MSPE) of flavonoids from an aqueous extract solution of herbal Epimedium folium without pretreatment. Coupled with high-performance liquid chromatography (HPLC), a rapid, environmentally friendly, and efficacious method was established and successfully applied for the enrichment, separation, and quantification of five quality marker flavonoids (viz. icariin, epimedin A, epimedin B, epimedin C, and baohuoside Ⅰ, respectively) in herbal E. folium collected from four species and 18 habitats. In addition, the physicochemical properties and morphology of Fe3O4-CS-DES were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, and vibrating sample magnetometry. Furthermore, key parameters, including adsorbent amount, elution solvent, and desorption factor, were optimized. Under the optimal experimental conditions, the five flavonoids were adsorbed rapidly on MSPE, which were released easily using methanol-acidified formic acid. A reversed-phase C18 column with gradient mobile phases comprising acetonitrile and formic acid water was used for analyte separation and elution. Limits of detection for the five analytes ranged from 0.5 to 2.1 ng mL−1. Coefficients of determination in analyses ranged from 0.99994 to 0.99999. Intra-day and inter-day precision ranged from 0.75 to 5.18% (n = 6) and from 2.88 to 7.52% (n = 3), respectively. Recoveries of the five analytes ranged from 80 to 110%, with relative standard deviation values of less than 10%. To the best of our knowledge, as a new adsorbent, Fe3O4-CS-DES nanoparticles were synthesized and used for the first time for the preconcentration and separation of flavonoids. This study provided a new approach for the enrichment and detection of Epimedium flavonoids in real samples.

The Use of Modified Fe3O4 Particles to Recover Polyphenolic Compounds for the Valorisation of Olive Mill Wastewater from Slovenian Istria.

Olive mill waste water (OMWW), a by-product created during the processing of olive oil, contains high amounts of polyphenolic compounds. If put to further use, these polyphenolic compounds could be a valuable resource for the speciality chemical industry. In order to achieve this, isolation of the polyphenolic compounds from OMWW is needed. Several techniques for this process already exist, the most widely used of which is adsorption beds. This research describes new ways of collecting polyphenolic compounds by using unmodified iron oxide (Fe3O4) particles and Fe3O4 modified with silica gel (Fe3O4@C18), citric acid (Fe3O4@CA), and sodium dodecyl sulphate (Fe3O4@SDS). This approach is superior to adsorption beds since it can be used in a continuous system without clogging, while the nano-sized shapes create a high surface area for adsorption. The results of this study show that, if used in a loop system of several adsorption and desorption cycles, (un)modified Fe3O4 has the potential to collect high concentrations of polyphenolic compounds. A combination of different modifications of the Fe3O4 particles is also beneficial, as these combinations can be tailored to allow for the removal of specific polyphenolic compounds.

Recyclable surface-functionalized Fe3O4 particles for heavy oil viscosity reduction

The main objective of this study is to design and apply surface-functionalized Fe3O4 particles to reduce the viscosity of heavy oil from Shengli Oilfield and to study the mechanism of viscosity reduction. Fe3O4 particles were synthesized by the co-precipitation method and modified with 3-propyl trimethoxysilane (KH570), oleic acid (OA), and triethoxyvinylsilane (A151) to obtain Fe3O4–KH570, Fe3O4-OA, and Fe3O4-A151, respectively. The particles were characterized through Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), and Dynamic Light Scattering (DLS). The contact angle and dispersion stability in kerosene were evaluated. The average net degree of viscosity reduction (%DVR) of Fe3O4–KH570, Fe3O4-OA, and Fe3O4-A151 on Chenping heavy oil at 50 °C is 27.91%, 51.27%, and 29.44%, respectively. The surface functionalization of asphaltene aggregates, the improvement of lipophilicity, and dispersion stability after destruction are the main reasons for the decrease of heavy oil viscosity. Particle size and the ability to adsorb asphaltenes have no direct relationship with DVR. It was also confirmed that the modified Fe3O4 particles can effectively recycle from the oil under a magnetic field. This work developed a kind of recyclable Fe3O4 particles for heavy oil viscosity reduction, which was beneficial to lower the cost in heavy oil recovery.

Efficient removal of cationic and anionic dyes by surfactant modified Fe3O4 nanoparticles

Magnetic nanoparticle adsorbents overcome the difficulty of solid-liquid separation in adsorption technology systems. However, their extremely large specific surface energy results in high levels of nanoparticle agglomeration and reduces their adsorption efficiency. To solve this problem, this study modified Fe3O4 particles with sodium dodecyl sulfate (SDS) and Cetyl Pyridine Chloride (CPC). Compared with pure Fe3O4 particles, the size distributions of SDS@Fe3O4 and CPC@Fe3O4 were more uniform, with a high level of magnetism and the capacity to achieve rapid separation (56.49 emu/g for SDS@Fe3O4 and 55.89 emu/g for CPC@Fe3O4). The results of dye adsorption tests showed that the adsorption effect was improved after modification, resulting in adsorption capacities of 62.43 mg/g for methylene blue (MB) by SDS@Fe3O4 and 176.98 mg/g for Congo red (CR) by CPC@Fe3O4. XRD results showed that the structure did not change, while FTIR results showed that no new functional groups were formed after adsorption. Adsorption followed pseudo-second-order reaction models, indicating that adsorption occurs via chemical adsorption processes. The adsorption process occurred mostly in accordance with the Langmuir model, which illustrates that monolayer adsorption was the dominant process. Thermodynamic data indicates that the adsorption process was endothermic and spontaneous. The adsorption mechanism for MB by SDS@Fe3O4 may be electrostatic adsorption and hydrophobic interaction, while for CR by CPC@Fe3O4 the mechanism may be electrostatic adsorption and hydrogen bonding. In addition, after five cycles of regeneration, the removal rate of MB was >77.0% and the removal rate of CR was >91.9%, confirming the excellent regeneration performance of Fe3O4. The simple and environmentally friendly manufacturing method, efficient adsorption process, rapid magnetic separation, indicate that surfactant modification of magnetic nanoparticles is an effective method for dye adsorption and removal.

Combined magnetic molecularly imprinted polymers with a ternary deep eutectic solvent to purify baicalein from the Scutellaria baicalensis Georgi by magnetic separation

A ternary deep eutectic solvent (DES) was applied as a novel functional monomer for synthesis of molecularly imprinted polymers (MIPs) to separate baicalein from the Scutellaria baicalensis Georgi (S. baicalensis). For rapid separation from the complex systems, modified Fe3O4 particles were used as the magnetic cores to prepare magnetic deep eutectic solvent molecularly imprinted polymers (DES-MMIPs). The prepared DES-MMIPs were characterized by scanning electron microscopy, transmission electron microscopy, dynamic light scattering, Fourier transform infrared spectra, x-ray diffraction, thermal gravimetric analysis, vibrating sample magnetometer and BET analysis. Moreover, the adsorption capability and selectivity of DES-MMIPs to baicalein were investigated systematically. The results of adsorption experiments demonstrated that DES-MMIPs showed excellent binding capacity to baicalein and the selectivity of DES-MMIPs to baicalein was much higher than that of structure analogues (quercetin, hesperetin and keampferol). Finally, DES-MMIPs were applied in selective extraction of baicalein in the S. baicalensis by magnetic separation. The analysis was conducted by high performance liquid chromatography. The recoveries of baicalein in the S. baicalensis ranged from 91.6% to 99.3%. It had been proven that the DES-MMIPs were an innovative and effective adsorbent for selective recognition and separation of baicalein in complex systems.

Magnetically recyclable Cr complex for the dehydration of glucose to 5-HMF in acidic task specific ionic liquid

Magnetically recyclable Cr complex was synthesized by immobilizing Cr3(CH3COO)7(OH)2 onto the surface of amino modified Fe3O4 particles. The structure of the catalyst was well characterized by Fourier transform infrared (FT-IR), Transmission electron microscope (TEM), Inductively coupled plasma atomic emission spectroscopy (ICP-AES), Energy dispersive X-ray spectroscopy (EDX), Thermal gravity analysis (TG-ATG), Wide-angle X-ray Diffractometry (XRD) and Vibrating Sample Magnetometer (VSM). The prepared catalyst showed good catalytic performance in the conversion of glucose to HMF in acidic task specific ionic liquid (TSIL). Moreover, the catalyst could be magnetically recovered and for successive six runs without significant decrease in its activity.

Janus silica nanosheets-based MMIPs platform for synergetic selective capture and fast separation of 2′-deoxyadenosine: Two different components segmented on the surface of one object

There is a pressing need to develop Janus-like magnetic molecularly imprinted polymers (J-SNs-MMIPs) nanoplatforms that integrate recognition elements and fast separation for specific adsorption and separation of 2′-deoxyadenosine (dA). In this work, the Janus silica nanosheet (J-SNs) with a hydrophobic surface (capped with 3-chloropropyl groups) and a hydrophilic surface (capped with amino-groups) was firstly fabricated by crushing Janus composite hollow spheres resulting from self-organized sol-gel process at amphiphilic emulsion interface. Subsequently, the imprinted polymers using dA as template molecule and synthesized 5-(2-Carbomethoxyvinyl)-2′-deoxyuridine (AcrU) as functional monomer were grafted onto the hydrophobic surface of J-SNs by activators regenerated electron transfer atom transfer radical polymerization (ARGET ATRP). Finally, carboxyl modified Fe3O4 particles were attached onto the hydrophilic surface of as-prepared J-SNs-MIPs via the condensation reaction between amino and carboxyl groups. The J-SNs-MMIPs displayed the ability to specifically recognize and fast separate dA, whereas no imprinting effect was observed for 2′-deoxyguanosine (dG) or deoxycytidine (dC) or 5′-monophosphate disodium salt (AMP). And the formed hydrogen bonds between complementary base of AcrU and adenine base on the dA enhance the affinity. Moreover, the equilibrium time was 70 min, and the maximum monolayer adsorption was calculated to be 61.22 μmol g−1 at 25 °C. By evaluating the selective recognition of dA from spiked human urine samples, the J-SNs-MMIPs could be used for selective separation and analysis of target dA in complex biological samples.

The role of dipole interactions in hyperthermia heating colloidal clusters of densely-packed superparamagnetic nanoparticles

This work aims to investigate the influence of inter-particle dipole interactions on hyperthermia heating colloidal clusters of densely-packed Fe3O4 nanoparticles at low field intensity. Emulsion droplet solvent evaporation method was used to assemble oleic acid modified Fe3O4 particles into compact clusters which were stabilized by surfactant in water. Both experimental and simulation works were conducted to study their heating performance at different cluster’s sizes. The dipole interactions improve the heating only when the clusters are small enough to bring an enhancement in clusters’ shape anisotropy. The shape anisotropy is reduced at greater clusters’ sizes, since the shapes of the clusters become more and more spherical. Consequently, the dipole interactions change to impair the heating efficiency at larger sizes. When the clusters are totally isotropic in shape, the heating efficiency is lower than that of non-interacting particles despite the cluster’s size, although the efficiency increases by a little bit at a particular size most likely due to the dipole couplings. In these situations, one has to use particles with higher magnetic anisotropy and/or saturation magnetization to improve the heating.

Preparation of MIL-53(Fe)@polydopamine@Fe3O4 magnetic composite for magnetic solid-phase extraction of sulfonylurea herbicides in environmental water

Polydopamine (PDA) and MIL-53(Fe) modified Fe3O4 particles (MIL-53(Fe)@PDA@Fe3O4 magnetic composite) were prepared by simple one-pot solvothermal method. The obtained composite was introduced to rapidly extract four kinds of sulfonylurea herbicides (SUHs) from environmental water samples by magnetic solid-phase extraction (MSPE). Then the herbicides were analyzed by a high performance liquid chromatographic system equipped with a photodiode array detector. The mobile phase was a mixture of acetonitrile and water containing 0.01% (v/v) trifluoroacetic acid, and the detection wavelength was 233 nm. Significant extraction parameters were optimized to improve the extraction efficiency. Under the optimum conditions (5 mL desorption solvent of acetone, 4.5 min extraction time, 60 mg adsorbent dosage, 0.5 g NaCl and the pH 3 of the solution), the developed method showed good linearities with correlation coefficients (r) no less than 0.9980. The limits of detection (LODs, S/N=3) of the four SUHs were 0.28-0.77 μg/L. The method was successfully used to determine four SUHs in three kinds of environmental water samples with satisfactory recoveries ranging from 78.8% to 109.7%. Therefore, the MIL-53(Fe)@PDA@Fe3O4 magnetic composite is efficient and has good potential for the extraction of SUHs.

Fabrication of Sesame Sticks-like Silver Nanoparticles/Polystyrene Hybridnanotubes and Their Catalytic Effects.

A novel and efficient catalyst is one of the goals in the material field, and the involvement of nanoscience and technology has brought new vigor to the development of catalyst. This research aimed to develop a simple two-step route to fabricate Fe3O4@PS/PDA-Ag hybridnanotubes with size-controllable and highly dispersed silver nanoparticles (NPs). First, Fe3O4@PS nanotubes of a sound mechanical property were prepared using polystyrene (PS)/toluene solution containing highly dispersed oleic acid modified Fe3O4 particles in a commercial AAO template. Next, the facile technique was used to form in situ silver NPs on the surface of magnetic PS (Fe3O4@PS) nanotubes through dopamine coating. The catalytic effects of the prepared Fe3O4@PS/PDA-Ag hybridnanotubes with highly dispersed AgNPs were characterized using a range of analytical methods, including transmission electron microscopy, thermogravimetric analysis, UV-Visible spectroscopy, and X-ray diffraction. It was found that such prepared Fe3O4@PS/PDA-Ag hybridnanotubes had a large specific surface area. They possessed excellent activities in catalyzing the reduction of 4-nitrophenol (4-NP) by NaBH4 in the aqueous phase. Furthermore, they were readily separated from fluid and retrieved by an external magnet. Their catalyst activity and recyclability demonstrated that this approach we proposed had the potential to become a new idea and route for catalytic platform.

6-TIPS-β-Cyclodextrin-Modified Fe3 O4 for Facile Enantioseparation of 1-(1-Naphthyl)ethylamine.

A new type of chiral magnetic nanoparticle was prepared from covalently linked magnetic nanoparticles (Fe3 O4 ) and heptakis-(6-O-triisopropylsilyl)-β-cyclodextrin (6-TIPS-β-CD). The resulting selectors (TIPS-β-CD-MNPs) combined the good magnetic properties Fe3 O4 and efficient chiral recognition ability of 6-TIPS-β-CD. The enantioselectivity of TIPS-β-CD-MNPs towards 1-(1-naphthyl)ethylamine was six times higher than that of the parent β-CD modified Fe3 O4 particles.

Fabrication of magnetic porous microspheres via (O1/W)/O2 double emulsion for fast removal of Cu2+ and Pb2+

A series of magnetic porous microspheres were prepared via (O1/W)/O2 double emulsion by grafting acrylic acid (AA) chains onto the backbone of hydroxyl propyl cellulose (HPC). The silane modified Fe3O4 particles and the surfactant polyglycerol polyricinoleate (PGPR) were used to stabilize the internal O1/W Pickering emulsion and the (O1/W)/O2 double emulsion, respectively. The results indicated that the magnetic microspheres with the mean diameter about of 10μm had interconnected pore structure and the subsequent adsorption experiments demonstrated that the as-prepared magnetic porous microspheres showed the fast adsorption kinetics for removal of Cu2+ and Pb2+, and the adsorption equilibrium can be achieved within 3min for Cu2+ and 5min for Pb2+ regardless of higher (400mg/l) or lower (100mg/l) initial concentrations. Additionally, the high adsorption capacity with 227.34mg/g for Cu2+ and 476.85mg/g for Pb2+ and the excellent reusability by in situ magnetic separation were also presented. Therefore, the magnetic porous microspheres can be applied as a potential recyclable material for highly efficient removal of heavy metals.

RETRACTED: Using silica molecular sieve modified Fe3O4 particles as supporting matrix for oxygen sensing: Construction, morphology, characterization and sensing performance

RETRACTED: Using silica molecular sieve modified Fe3O4 particles as supporting matrix for oxygen sensing: Construction, morphology, characterization and sensing performance

Covalent immobilization of α-amylase on magnetic particles as catalyst for hydrolysis of high-amylose starch

Enzyme immobilized on magnetic particles can be used as efficient recoverable biocatalysts under strong magnetic response. To enable re-use of enzyme, modified Fe3O4 particles were used as carrier to immobilize α-amylase in this paper. Firstly, the surface of Fe3O4 particles were coated with amino groups by direct using TEOS (tetraethoxysilane) followed by treatment with APTES (3-aminopropyltriethoxysilane) and then carboxylated by reacting it with succinic anhydride. In addition, the effect of the immobilization condition on enzyme activity recovery and immobilization efficiency were investigated. The results showed that the optimal immobilization occurred under following conditions: pH 5.5, 40°C, enzyme concentration of 20mgmL−1, reaction time for 36h. Using immobilized α-amylase as biocatalyst, the optimum pH and temperature for hydrolysis were observed to be 6.5 and 60°C. The kinetics of hydrolysis reaction were studied using Michaelis–Menten equation. The affinity constant (Km) and maximum reaction rate (vmax) of magnetic particles immobilization α-amylase (MPIA) was 0.543mgmL−1 and 1.321mgmin−1 compared to those of 0.377mgmL−1 and 6.859mgmin−1 of free enzyme. After immobilization, enzymatic activity, storage stability, thermo-stability, and reusability of MPIA were found superior to those of the free one. MPIA maintained 86% enzyme activity after 30 days and maintained 78% enzyme activity after recycling six times.

Preparation and Properties of a Novel Hemicellulose-Based Magnetic Hydrogel

Hydrogels are important functional materials with many potential applications. A novel hemicellulose-based magnetic hydrogel was synthesized using a graft copolymer method, with H2 O2-Vc as a redox initiator system to initiate the hemicellulosic derivative and surface-modified Fe3 O4 particles as the magnetic component. The structures and morphologies of the prepared magnetic hydrogels were investigated using Fourier-transform infrared(FTIR) spectroscopy, X-ray photoelectron spectroscopy(XPS), and scanning electron microscopy(SEM). The crystal structure of the modified Fe3 O4 particles and the magnetic behaviors of the hemicellulose-based magnetic hydrogels were analyzed using X-ray diffraction(XRD) and a vibration sample magnetometer(VSM), respectively. The results showed that the Fe3 O4 particles were well dispersed in the hydrogel matrix and the prepared hydrogels had paramagnetic properties. The effects of the acrylic acid/hemicellulose ratio and the amounts of Fe3O4particles and cross-linker on the swelling ratio of the hydrogels were studied, and the swelling mechanism of the hydrogels was explored. The swelling behaviors of the hydrogels were simulated using Fickian and Schott kinetic models in a pH 8 buffer solution. The pore size and swelling ratio of the prepared hydrogels increased with increasing the pH value because the ―COOH groups in the hydrogels were converted to ―COO-at higher pH values. In addition, the prepared hydrogels were used to adsorb lysozyme; the adsorption capacity of the magnetic hydrogel was much higher than that of a non-magnetic hydrogel, and the equilibrium adsorption data fitted the Freundlich and Temkin isotherm models well.

Functional Modification and Preparation of Superparamagnetic Fe<sub>3</sub>O<sub>4</sub>

Functional modification of the surface of Fe3O4 nanoparticles was studied using silane coupling reagent A151. The modified and unmodified nanoparticles were characterized by FT-IR, XPS, TEM, DLS and VSM. Both of the unmodified and modified Fe3O4 particles show superparamagnetic behavior, and their saturation magnetic values were determined to be 81.14 emu/g and 73.0 emu/g, respectively. A151 was adsorbed on surface and formed chemical bond to be steric hindrance repulsion which prevented nanoparticles from reuniting. The dispersion properties of modified Fe3O4 particles were associated with the mass ratio of A151/Fe3O4.

Preparation of molecularly imprinted nanoparticles with superparamagnetic susceptibility through atom transfer radical emulsion polymerization for the selective recognition of tetracycline from aqueous medium

In the work, we reported an effective method for the preparation of molecularly imprinted nanoparticles with superparamagnetic susceptibility through atom transfer radical emulsion polymerization (ATREP), and then as-prepared magnetic molecularly imprinted nanoparticles (MMINs) were evaluated as adsorbents for selective recognition of tetracycline (TC) molecules from aqueous medium. The resulting nanoparticles were characterized by FT-IR, TGA, VSM, SEM and TEM. The results demonstrated MMINs with a narrow diameter distribution were cross-linked with modified Fe3O4 particles, composed of imprinted layer and exhibited good magnetic sensitivity, magnetic and thermal stability. Batch rebinding studies were carried out to determine the specific adsorption equilibrium, kinetics, and selective recognition. The estimated adsorption capacity of MMINs towards TC by the Langmuir isotherm model was 12.10mgg−1 at 298K, which was 6.33 times higher than that of magnetic non-molecularly imprinted nanoparticles (MNINs). The kinetic property of MMINs was well-described by the pseudo-second-order rate equation. The results of selective recognition experiments demonstrated outstanding affinity and selectivity towards TC over competitive antibiotics. The reusability of MMINs showed no obviously deterioration at least five repeated cycles in performance. In addition, the MMINs prepared were successfully applied to the extraction of TC from the spiked pork sample.

Preparation and characterization of novel spin labeled magnetic nanoparticles

Novel spin-labeled magnetic nanoparticles (MNPs) were prepared through the reaction between carboxylic acids modified Fe3O4 particles and 4-amino-2,2,6,6-tetramethylpiperidin-1-oxyl (4-NH2-TEMPO). And X-ray diffractometer (XRD), FT-IR spectra, thermogravimetric analysis (TGA), transmission electronic microscopy (TEM) and room temperature electron paramagnetic resonance (EPR) were employed to characterize the prepared materials. The results of EPR measurements indicated that the spin-labeled MNPs exhibited both the paramagnetism of nitroxide free radicals and superparamagnetism of ferrimagnetic nanoparticles could act as a bio-probe or potential drug delivery vehicles tracking by EPR technique.