Fe3O4 Nanoparticles Research Articles

Comparative Study of Antioxidant Activity of Dextran-Coated Iron Oxide, Gold, and Silver Nanoparticles Against Age-Induced Oxidative Stress in Erythrocytes.

Erythrocytes undergo several changes during human aging and age-related diseases and, thus, have been studied as biomarkers of the aging process. The present study aimed to explore the antioxidant ability of metal and metal oxide nanoparticles (NPs) such as iron oxide (Fe3O4), gold (Au), and silver (Ag) to mitigate age-related oxidative stress in human erythrocytes. Metal and metal oxide NPs behave like antioxidative enzymes, directly influencing redox pathways and thus have better efficiency. Additionally, biopolymer coatings such as dextran enhance the biocompatibility of these NPs. Therefore, dextran-coated Fe3O4, Au, and Ag NPs were synthesized using wet chemical methods and were characterized. Their hemocompatibility and ability to protect erythrocytes from age-induced oxidative stress were investigated. The Fe3O4 and Au NPs were observed to protect erythrocytes from hydrogen peroxide and age-induced oxidative damage, including decreased antioxidant levels, reduced activity of antioxidative enzymes, and increased amounts of oxidative species. Pretreatment with NPs preserved the morphology and membrane integrity of the erythrocyte. However, Ag NPs induced oxidative stress in erythrocytes similar to hydrogen peroxide. Therefore, dextran-coated Fe3O4 and Au nanoparticles have the potential to be employed as antioxidant therapies against age-related oxidative stress.

(Invited) The Influence of Magnetic Fields on the Oxygen Evolution Reaction Catalyzed By Cobalt-Iron Oxide Nanowire Arrays

To mitigate climate change through the establishment of a renewable energy infrastructure, advancements in energy storage technologies are imperative. Electrochemical water splitting via electrolyzers enables the conversion of electrical energy into chemical energy. However, the performance of these devices, particularly that of the oxygen evolution reaction (OER) occurring at the anode, still needs to be improved. Previous studies have demonstrated that magnetic fields can induce convective flow to the electrode through Lorentz and Kelvin force effects, thereby improving the mass transport.[1] In contrast to the Lorentz force, the Kelvin force can be substantially increased by introducing magnetic nanostructures to create high magnetic field gradients in the vicinity of the electrode surface.[2] Given the magnetic properties inherent to many earth-abundant metal-based and nanostructured electrocatalysts promising for the OER, there is potential for intelligently designing electrodes to leverage magnetic field effects in the future. However, a comprehensive understanding of these magnetic field effects is currently lacking. In the scope of this work, we aimed to systematically investigate the influence of magnetic fields on the oxygen evolution reaction. Considering the substantial magnetic field gradients generated by magnetic nanowires, we fabricated arrays of freestanding cobalt-iron oxide nanowires to explore the influence of magnetic fields on the oxygen evolution reaction catalyzed by these nanostructured electrocatalysts. Templated electrodeposition of cobalt-iron alloy into the pores of anodic aluminum oxide membranes enabled a straightforward control over nanowire diameter and length. Subsequent removal of the aluminum oxide template in alkaline solution yielded cobalt-iron oxide nanowires composed to 60% of Fe and 40% of Co standing freely on an electrochemically stable gold substrate. Superimposing a magnetic field during water oxidation on the so-prepared nanowire arrays resulted in an increase in the measured oxidation current (see Figure). To deconvolute the contributions of the Lorentz and Kelvin force, experiments were conducted in two different magnetic field orientations: either parallel or perpendicular to the electrode surface. In the parallel orientation, a linear correlation between the increase in current and the strength of the applied magnetic field was observed. In contrast, when the magnetic field was aligned perpendicular to the electrode surface, a plateau in the current enhancement manifested at higher magnetic field strengths, indicating different dominant effects in the two configurations.[1] K. Ngamchuea, K. Tschulik, R. G. Compton, Magnetic control: Switchable ultrahigh magnetic gradients at Fe3O4 nanoparticles to enhance solution-phase mass transport, Nano Res. 2015, 8, 3293–3306.[2] L. M. Monzon, J. Coey, Magnetic fields in electrochemistry: The Kelvin force. A mini-review, Electrochem. commun. 2014, 42, 42–45. Figure 1

Nitrogen Doped Graphene Aerogel Inserted By Carbon Black As Novel Catalyst Support for Low Temperature Hydrogen Fuel Cells

Carbon supported Pt nanocatalysts, which are commonly used in hydrogen fuel cells, suffer from Pt degradation and carbon corrosion. That causes the high cost and limited lifetime of the fuel cell1. Developing catalyst support materials with high surface area, high electrical conductivity, stability and good interaction with catalyst is an effective solution to address this issue.To enhance the activity and durability of Pt-based catalysts for hydrogen fuel cells, graphene aerogels (GA) are a prospective material with rich porous 3D-structure, large surface area, high electrical conductivity, and good electrochemical stability. They also can improve the tolerance of catalyst CO poisoning and avoid graphene stacking by integrating 2D sheet structure into 3D aerogel structure2, 3. Some research show that the nitrogen doped on the surface of carbon materials could improve ORR activity and electronic conductivity by changing the local electronic structure as well as providing a stable anchor point for pt nanoparticles to enhance the durability of catalysts4, 5.However, most GAs are made from graphene oxide (GO) produced by Hummers method which may lead to safety and environmental issue due to the usage of highly toxic and corrosive chemicals2, 5. Also, there are few articles on the application of GA in fuel cells. It may be limited by the collapse and loss of pore structure caused by compression in a fuel cell setup.In this work, graphene oxide produced by electrochemical exfoliation (EGO) was used to prepare N-doped graphene aerogel (NGA) via hydrothermal treatment with ammonia solution as nitrogen source. Moreover, NGA was mixed with carbon black (CB) as a hybrid support material that can avoid collapse of the macropore and generate a graphene-carbon network to provide large surface area for Pt nanoparticles and improve the performance of the fuel cell. Figure1 shows preliminary characterization results of NGA and performance of NGA-CB supported Pt catalysts with different content of NGA. Rich macro-mesoporous structure of NGA can be observed in the SEM image (Figure 1 (a)). Pt catalyst with 20% NGA has a maximum power density of 838 mw cm-2 which is a 31% improvement over that of Pt/CB (Figure 1 (b)).In conclusion, this study presents a fast, efficient and environmentally friendly way to synthesize nitrogen doped GA. The introduction of NGA into CB as catalyst supports can improve the electrochemical active surface area and performance of fuel cells due to graphene aerogel's high conductivity and porosity. Besides, it is effective to enhance the utilization of Pt and durability of catalysts. This will help to reduce the cost of fuel cells and facilitate their commercialization in various fields of application.Figure 1 (a) SEM images of dried NGA. (b) Performance of Pt/NGA-CB with various content of NGA compared to Pt/CB catalyst in a hydrogen fuel cell at 60 ℃ with 100% RH. References Liu, J.; Wu, X.; Yang, L.; Wang, F.; Yin, J., Unprotected Pt nanoclusters anchored on ordered mesoporous carbon as an efficient and stable catalyst for oxygen reduction reaction. Electrochimica Acta 2019, 297, 539-544.Sarac Oztuna, F. E.; Barim, S. B.; Bozbag, S. E.; Yu, H.; Aindow, M.; Unal, U.; Erkey, C., Graphene Aerogel Supported Pt Electrocatalysts for Oxygen Reduction Reaction by Supercritical Deposition. Electrochimica Acta 2017, 250, 174-184.Wu, Z.-S.; Yang, S.; Sun, Y.; Parvez, K.; Feng, X.; Müllen, K., 3D Nitrogen-Doped Graphene Aerogel-Supported Fe3O4 Nanoparticles as Efficient Electrocatalysts for the Oxygen Reduction Reaction. Journal of the American Chemical Society 2012, 134 (22), 9082-9085.Li, O. L.; Chiba, S.; Wada, Y.; Panomsuwan, G.; Ishizaki, T., Synthesis of graphitic-N and amino-N in nitrogen-doped carbon via a solution plasma process and exploration of their synergic effect for advanced oxygen reduction reaction. Journal of Materials Chemistry A 2017, 5 (5), 2073-2082.Xie, B.; Zhang, Y.; Zhang, R., Coassembly and high ORR performance of monodisperse Pt nanocrystals with a mesopore-rich nitrogen-doped graphene aerogel. Journal of Materials Chemistry A 2017, 5 (33), 17544-17548 Figure 1

Magnetically controlled transdermal delivery of gemcitabine via xanthan gum-coated magnetic nanoparticles embedded in gellan gum cryogel

Chemotherapy is a commonly used treatment for breast cancer, but it often causes significant side effects due to the high drug dosage required for injection or infusion administration. Transdermal drug delivery offers a non-invasive and controlled release approach. In this work, a novel approach was developed for using gellan gum as a drug matrix and Gemcitabine loaded xanthan gum coated Fe3O4 magnetic nanoparticles (Gem: Xan (1%v/v)Fe3O4) as a drug carrier complex. The magnetization values were found to be 84.69 emu/g, 16.63 emu/g, and 9.91 emu/g for Fe3O4, Xan (1%v/v)Fe3O4, and Gem: Xan (1%v/v)Fe3O4, respectively. Notably, this work showcases the synthesis of Gemcitabine loaded xanthan gum coated magnetic nanoparticles as a new drug carrier complex, explores the drug release kinetics, and demonstrates the biocompatibility and non-toxicity of gellan gum on human skin, offering promising implications for transdermal drug delivery. The Gemcitabine release was 54 % without magnetic nanoparticles, and it increased to 82 % with the incorporation of magnetic nanoparticles. The Gemcitabine release – permeation of Gem: Xan (1%v/v)Fe3O4 was higher than that of the pristine Gemcitabine permeation by 72 %. The experimental results revealed that the magnetic field played a crucial role in controlling the drug release rate, amount, and duration during the release and release-permeation study.

Highly active iron oxide@NC catalyst derived from the iron acetate/polyacrylonitrile threads: Driving nitroarene conversion to value‐added amines

AbstractChemoselective reduction of nitroarenes to corresponding arylamines is a significant reaction in the chemical industry. However, in the presence of other reducible groups, including halogenated nitrobenzene, nitrobiphenyl, and nitroquinoline in the same molecule of nitroaromatics, the control of chemoselectivity remains challenging. Here, a facile fabrication of a heterogeneous iron‐based catalyst is reported as a potential alternative to precious metal catalysts for the chemoselective reduction of nitroarenes. The pyrolysis of iron acetate/polyacrylonitrile (PAN) template under an inert atmosphere furnishes active Fe3O4 nanoparticles (NPs) encapsulated in nitrogen‐doped (N‐doped) carbon layers, which can provide more catalytic active sites (Fe3O4/PAN@800). Notably, non‐precious iron oxide NPs supported on N‐doped carbon support prevent aggregation, thereby enhancing the catalytic activity. The sustainable and reusable Fe3O4/PAN@800 catalyst, having only 0.8% metal content as demonstrated by x‐ray photoelectron spectroscopy, delivers excellent yields of corresponding amines from differently functionalized nitroarenes. Hydrogenation of a series of structurally functionalized nitroarenes produced excellent yields of anilines, which serve as building blocks and intermediates for fine and bulk chemicals. Hydrogenation of 2‐chloro‐3‐nitropyridine, 2‐nitro‐1,1′‐biphenyl, ortho‐nitroaniline, and 4‐aminophenyl acrylonitrile yielded respective anilines up to 99%. The active sites of Fe3O4 have magnetic performance, hence, the catalyst can be easily recovered using a magnet and reused for at least five cycles without significant loss of catalytic activity. Therefore, the easily prepared, cost‐effective, and reusable Fe3O4/PAN@800 catalyst presented in this study shows potential for applications in the selective reduction of aromatic nitro compounds. Consequently, this study potentially establishes a guideline for the facile preparation of abundant transition‐non‐noble metal‐based reusable supported catalysts for various applications in the chemical industry.

Stable Sub‐2‐nm Fe3O4 Particles Confined in P, N Co‐Doped Carbon Derived from the Assembly of DPPF with PCN‐222: A Promising Transfer Hydrogenation Catalyst

AbstractThe nanoconfinement approach for constructing ultra‐small nanoparticles has been effectively utilized in the development of non‐precious metal catalysts. Herein, the catalyst precursor was prepared by host‐guest assembly method, using PCN‐222 as the host and 1,1′‐bis(diphenylphosphino) ferrocene (DPPF) as the guest. After calcination, the sub‐2 nm iron oxide nanoparticles within a phosphorus‐nitrogen co‐doped carbon matrix (Fe3O4@P/N‐CDCM) was obtained. Benefiting from the nanoconfinement effect, the sub‐2 nm Fe3O4 nanoparticles were uniformly dispersed on the P/N‐CDCM matrix. As a representative application, Fe3O4@P/N‐CDCM‐600 showed remarkable catalytic activity in the reduction of various nitroaromatic compounds. Under ambient conditions, the efficient reduction of nitro compounds in aqueous solution led to excellent conversion rates (96–99 %) and selectivity (99 %) within 45 minutes. Additionally, the catalyst maintained high efficiency over 5 cycles without experiencing a noticeable decrease in activity. This work provides an innovative and cost‐effective strategy for fabricating highly dispersed non‐precious metal nanoparticles.

Enhancing carbon mineralization of slag leachate using amine-functionalized magnetic nanoparticle clusters

Carbon mineralization—converting carbon dioxide (CO2) into stable carbonate minerals, such as calcium carbonate (CaCO3)—has attracted much attention as a permanent way to sequester CO2. In this study, we developed a novel method for improving the efficiency of carbon mineralization using amine-functionalized magnetic nanoparticle clusters (A-MNCs). To prepare them, magnetic nanoparticle clusters composed of tens of small Fe3O4 nanoparticles were treated with 3-aminopropyltriethoxysilane to functionalize amine groups on their surfaces. When CO2 was bubbled into a NaOH solution, the rate of CO2 dissolution was enhanced in the presence of A-MNCs, mostly due to physical effects such as grazing and hydrodynamic effects that improved mass transfer between the solution and CO2 bubbles. In addition, A-MNCs promoted carbon mineralization in a NaOH solution containing Ca2+ by providing an additional mineralization route via carbamate formation, resulting in a threefold increase in efficiency to 81 %. We demonstrated that A-MNCs could be applied to leachate from slag, a byproduct of commercial steelmaking, increasing the efficiency by 2.6 times compared to the absence of A-MNCs. The resulting CaCO3 precipitate was confirmed to be calcite using X-ray diffraction and scanning electron microscopy. Furthermore, after the mineralization, A-MNCs were easily separated from the solution using a permanent magnet, while retaining their performance.

Effect of Isopropanol on Optical Properties of Fe3O4/ZnO/Graphene Quantum Dots (GQDs) Nanocomposite

This study aims to investigate the impact of isopropanol on the optical properties of the Fe₃O₄/ZnO/GQDs nanocomposite. The synthesis of Fe₃O₄ and ZnO nanoparticles was conducted using the coprecipitation method, followed by the synthesis of GQDs using the hydrothermal method with varying concentrations of isopropanol. Subsequently, the Fe₃O₄/ZnO nanocomposite was combined with GQDs synthesized using the sonication method. The amalgamation of magnetic and luminescent materials holds promise for applications in the biomedical field, particularly in bioimaging. XRD data analysis revealed crystal structure alterations attributed to the incorporation of carbon elements in both ZnO and Fe₃O₄. The TEM results indicated a particle size of 16.2 nm for the Fe₃O₄/ZnO/GQDs nanocomposite with a 10 ml isopropanol variation. Identified phases from the XRD analysis include Fe₃O₄, ZnO, and GQDs. UV-Vis spectroscopy detected distinctive absorbance peaks at wavelengths of 323.7 nm, 333.0 nm, 329.9 nm, and 323.9 nm. Moreover, the energy gap exhibited an increase with escalating concentrations of isopropanol in the GQDs. Photoluminescence analysis yielded robust, broad emission bands characterized by orange and red luminescence.

Carbonized wood supported Fe3O4 nanoparticles for efficient solar-driven interfacial evaporation

Magnetized wood (M–W) has been proposed to be used as an absorber in solar-driven interfacial evaporation. The M−W could gain an evaporation rate of 1.46 kg m−2 h−1 under the combined effect of sunlight and magnetic fields, which is 27 % higher than carbonized wood (C–W). To explore the mechanism, they were subjected to SEM, XPS, and water contact angle tests. It is revealing that M−W forms much more microchannels for steam diffusion. The M−W shows 97 % optical absorption within the whole wavelength, while the C–W is lower than 85 %, revealing the M−W can gather most of the solar radiation. Finally, the permeability coefficients of carbonized and magnetized woods are calculated by the CFD model. The permeability coefficient of the M−W is 20 % higher than the C–W, which can be attributed to Fe3O4 nanoparticles disturbing the steam growth in the magnetic field, hence decreasing the thickness of the liquid film covering the bubbles and improving the solar evaporation rate.

Green synthesis and characterization of magnetite nanoparticles using Eucalyptus globulus leaves for water treatment and agronomic valorization.

This work presents a new process, based on the green nanoparticles Fe3O4 and magnetization coupling for the treatment of saline well water. In this context, iron nanoparticles were synthesized using Eucalyptus globulus leaves. The nanomaterials were characterized by scanning electron microscopy and infrared for identification. Batch experiments were conducted to illustrate the optimal parameters related to contact times and the mass of nanoparticles. The latter marked an optimal contact time of 100min and a mass of 56mg/L accompanied by a magnetic treatment for a contact time of 48min. The results showed a significant (R2 = 0.93) water salinity reduction (67%) and a potential for improvement in the germination of tomato seeds (81%) through the investigation of the evolution of the length of the roots, the stems, and the number of germinated seeds.

Improved mechanical, magnetic and radiation shielding performance of rubbery polymer magnetic nanocomposites through incorporation of Fe3O4 nanoparticles

The current research investigates the impact of magnetite (Fe3O4) nanoparticles (3–12 wt%) on the properties of rubbery polymer nanocomposites fabricated via melt blending method. The tensile and impact properties were improved at an optimal 6 wt% Fe3O4, revealing a good interfacial interaction. Fe3O4 enhanced the thermal stability, as evidenced by the increased integral procedure decomposition temperature up to 26 %. Fe3O4 increased residual and saturated magnetization the most at 6 wt% loading. The gamma-ray shielding properties were explored with energy ranging from 0.2835 to 2.506 MeV, and effectively at low energies. Increased Fe3O4 content correlated positively with linear attenuation coefficient (LAC), enhancing radiation shielding but reducing neutron shielding. At 0.2835 MeV, the LAC values increased up to 0.12431 cm−1 for 12 wt% Fe3O4, while the fast neutron removal cross-section values decreased from 0.10427 cm−1 to 0.08548 cm−1. These findings highlight the multifunctional potential of Fe3O4-incorporated nanocomposites in radiation shielding applications.

4D printing thermo-magneto-responsive PETG-Fe3O4 nanocomposites with enhanced shape memory effects

In this groundbreaking study, Polyethylene Terephthalate Glycol (PETG)-Fe3O4 nanocomposites were developed for 4D printing, incorporating iron oxide (Fe3O4) nanoparticles into PETG matrix. The research contribution lies in its innovative approach to enhancing the shape memory effect (SME) through thermo-magnetic responsiveness, positioning PETG-Fe3O4 as a revolutionary material in smart additive manufacturing. The composites were synthesized using a melt mixing method, followed by 3D printing into specimens for comprehensive evaluation through dynamic mechanical thermal analysis (DMTA), scanning electron microscopy (SEM), and uniaxial tensile tests. The findings revealed that the incorporation of Fe3O4 nanoparticles significantly boosts the composites’ storage modulus and glass transition temperature, indicative of improved stiffness and thermal properties. Notably, the 15 % Fe3O4 composite emerged as the optimal blend, exhibiting the highest tensile strength and a favourable balance between mechanical integrity and flexibility. A key result was the enhanced SME under both thermal and magnetic stimuli, with recovery efficiency and speed escalating with nanoparticle concentration. This advancement underscores the potential of PETG-Fe3O4 nanocomposites in fabricating smart structures capable of environmental adaptability, paving the way for impacts in biomedical, aerospace, and robotic devices. Through this work, a new paradigm in material functionality for 4D printing has been established, demonstrating the viability of magnetic nanoparticle integration for added smart capabilities.

Constructing MXene-based mixed-dimensional structure with multiple interfaces to optimize dielectric-magnetic synergistic effect for effective electromagnetic wave absorption

Exploring efficient microwave absorbing materials (MAMs) which could convert electromagnetic (EM) energy into thermal energy represents an approbatory vision to reducing EM radiation and interference. Designing of mixed-dimensional structure with multiple interfaces represents the available target to investigate an ideal MAMs, which maximizes the superiority of mixed-dimensional structure in electromagnetic wave absorption (EMWA). Herein, we take full advantage of multiple interfaces engineering of MXene for optimizing the impedance matching to improve EMWA, MXene-based mixed-dimensional structure was designed by incorporating three-dimensional Fe3C@Carbon layers coated zero-dimensional Fe3O4 nanoparticles (NPs) supported two-dimensional MXene nanosheets (MXene/Fe3O4@Fe3C@Carbon, MFC). The Fe3O4@Fe3C@C with Core@shell structure arrests the essentially self-restacked of MXene and provides various attenuation mechanisms for the incident electromagnetic waves (EMWs). By regulating the carbonization temperature, the MFC exhibits enhanced EMWA property which is attributed to the characteristic structure and optimized dielectric-magnetic synergy effect. The minimum reflection loss (RLmin) value of MFC can reach to −64.3 dB with a matching thickness of 1.73 mm. Otherwise, the maximum effective absorption bandwidth (EAB) (RLmin < -10 dB) reaches 6.42 GHz at only 1.5 mm. Thus, our study refers a novel-fire enlighten to develop excellent mixed-dimensional microwave absorbent based on MXene.

Magnetic whole-cell biocatalyst based on intracellular lipases of Candida catenulata as promising technology for green synthesis of epoxy fatty acids

This study focuses on the development a green synthesis of epoxy fatty acids (EFAs) which are commonly used as the plasticizer in polymer industries. The intracellular lipases of Candida catenulata cells as a whole-cell biocatalyst (WCB) were examined in the bio-epoxidation of free fatty acids (FFAs) with hydrogen peroxide. The FFAs in soybean soap stock, an industrial by-product of vegetable oil factories, was used as the feedstock of the process. To remove phosphates from soap stock a degumming process was tested before the bio-epoxidation reaction and results revealed that the EFAs yield was improved using the degummed fatty acids (DFAs). The attachments of magnetic Fe3O4 nanoparticles to the surface of WCBs facilitated the recovery of the biocatalyst, and were improved stabilities. The activation energy for the magnetic whole-cell biocatalysts (MWCB) was 48.54 kJ mol−1, which was lower than the WCB system (51.28 kJ mol−1). The EFA yield was about 47.1 % and 33.8 % after 3 h for the MWCBs and 2 h for the WCBs, respectively. The MWCBs displayed acceptable reusability in the repetitious bio-epoxidation reaction with maintaining 59 % of the original activity after 5 cycles whereas the performance of the WCBs was 5.9 % at the same conditions. The effects of influential factors such as reaction time, molar ratio of H2O2 to CC, and batch and semi-batch operations were investigated for both biocatalyst systems. The quality of EFAs was characterized by FTIR and GC-MS analyses.

Cytotoxicity assessment of Cu0.5Zn0.5Fe2O4 nanoparticles prepared via rapid combustion-calcination process on SGC-7901 and HGC-27 gastric cancer cells

Currently, ferrite magnetic nanoparticles are widely utilized in the biomedical domain, encompassing antibacterial, catalytic, imaging, and drug delivery among other fields. In this study, Cu0.5Zn0.5Fe2O4 nanoparticles were synthesized via the rapid combustion-calcination process. By incorporating inorganic metal elements with specific functionalities, the limitations of iron oxide could be overcome, enabling targeted roles in various applications. The morphology, phase composition, and magnetic properties were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and vibrating sample magnetometry (VSM). The impact of anhydrous ethanol quantity, calcination temperature, and duration on the magnetic properties and grain size of the nanomaterials was investigated. Cu0.5Zn0.5Fe2O4 nanoparticles were evaluated for their inhibitory effects on human gastric cancer cells (SGC-7901 and HGC-27) under different preparation conditions. The results of the MTT assay revealed a concentration - and time-dependent inhibition of tumor cell proliferation by Cu0.5Zn0.5Fe2O4 nanoparticles. Nanoparticles exhibiting a magnetic energy of 20.23 emu/g and an average particle size of 51.6 nm, synthesized using 20 mL of anhydrous ethanol, calcination temperature of 400 °C, and a calcination duration of 2.0 h, displayed significant inhibitory effects on tumor cells. Furthermore, The nanoparticles not only showed low toxicity to human normal stomach cells GES-1, but also enhanced the inhibitory effect on tumor cells under the action of an external magnetic field.

Syntheses, characterization, luminescent and magnetic properties of polymer bifunctional fibers containing terbium complexes and Fe3O4 nanoparticles

The combination of electrospun nanofibers and nanoparticles is opening up potential in the field of bifunctional materials. Herein, polystyrene (PS, Mw ≈ 260, 000), polyvinyl pyrrolidone (PVP, Mw ≈1, 300, 000), and poly(methyl methacrylate) (PMMA, Mw ≈ 350, 000) bifunctional fibers containing Tb(acac)3phen complexes (acac: acetylacetone, phen: 1,10-phenanthroline) and Fe3O4 nanoparticles (NPs) were synthesized by single-fluid electrospinning method. The structure of bifunctional microfibers was characterized by x-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy spectrum (EDAX) and infrared spectrum (IR). The average diameters of PS, PVP and PMMA bifunctional fibers are 1.65, 0.313 and 0.571 μm, respectively. The TEM images indicated that Fe3O4 NPs were successfully incorporated into bifunctional fibers. No absorption peaks of terbium complexes and Fe3O4 NPs can be seen in the IR spectra of bifunctional fibers. The luminescent and magnetic properties of bifunctional fibers were also investigated. Due to the change of ligands environment, the main excitation peaks blue shifted about 5–8 nm in the bifunctional fibers. Bifunctional fibers exhibited characteristic emission of Tb3+ ions. The polymers have no effect on the fluorescence lifetimes of terbium complexes. All bifunctional fibers were soft ferromagnetic. In addition, mechanical performances of these nanofibers were also studied. The maximum stress, strain corresponding to the maximum stress and elastic modulus of sample PVP-Fe-Tb is the largest, which indicates that the tensile performance of sample PVP-Fe-Tb is the best.

Synthesis of varied oleic acid-coated Fe3O4 nanoparticles using the co-precipitation technique for biosensor applications

This study successfully synthesized oleic acid (OA)-coated Fe3O4 nanoparticles using the coprecipitation method for the needs of biosensor applications, as shown through the characterization of structure and morphology using XRD and TEM. This observation used 0.75 ml of OA (Fe3O4-OA(0.75)) and 1.25 ml of OA (Fe3O4-OA(1.25). A decrease in particle size distribution from 18.55 nm to 16.30 nm was observed, which means a reduction in agglomeration and increased dispersibility. Vibrating Sample Magnetometer (VSM) observations showed that the saturation magnetization of Fe3O4 particles modified with OA decreased from 47.71 emu/g to 45.90 emu/g at Fe3O4-OA(0.75) and decreased again to 42.29 emu/g at Fe3O4-OA(1.25). But they all show soft ferromagnetic properties with very low coercivity, making them suitable for Giant Magnetoresistance (GMR) biosensor applications. A series of concentrations in ethanol solution were performed to evaluate the detection sensitivity of GMR for these pure and oleic acid-modified Fe3O4 samples. Concentrations of 2, 5, 10, 15, 25, and 35 mg/ml were integrated at 2 μL each onto the surface of the GMR chip. A decrease in sensitivity was observed due to the change in saturation. Pure Fe3O4 with a sensitivity of 5.07 mV (mg/ml) decreased to 4.49 mV (mg/ml) and 3.35 mV (mg/ml) after oleic acid coating. Thus, although adding a proportional amount of oleic acid can slightly decrease the saturation magnetization, it can be a valuable method for applications such as GMR biosensors that demand high dispersibility and sensitivity that remains strong.

A Superparamagnetic Composite Hydrogel Scaffold as In Vivo Dynamic Monitorable Theranostic Platform for Osteoarthritis Regeneration.

Osteoarthritis (OA) is a prevalent disease, characterized by subchondral fractures in its initial stages, which has no precise and specific treatment now. Here, a novel multifunctional scaffold is synthesized by photopolymerizing glycidyl methacrylate-modified hyaluronic acid (GMHA) as the matrix in the presence of hollow porous magnetic microspheres based on hydroxyapatite. In vivo subchondral bone repairing results demonstrate that the scaffold's meticulous design has most suitable properties for subchondral bone repair. The porous structure of inorganic particles within the scaffold facilitates efficient transport of loaded exogenous vascular endothelial growth factor (VEGF). The Fe3O4 nanoparticles assembled in microspheres promote the osteogenic differentiation of bone marrow mesenchymal stem cells and accelerate the new bone generation. These features enable the scaffold to exhibit favorable subchondral bone repair properties and attain high cartilage repair scores. The therapy results prove that the subchondral bone support considerably influences the upper cartilage repair process. Furthermore, magnetic resonance imaging monitoring demonstrates that Fe3O4 nanoparticles, which are gradually replaced by new bone during osteochondral defect repair, allow a noninvasive and radiation-free assessment to track the newborn bone during the OA repair process. The composite hydrogel scaffold (CHS) provides a versatile platform for biomedical applications in OA treatment.

Encapsulating Fe3O4 Nanoparticles and Carbon Dots in a Metal-Organic Framework for Magnetic Fluorescent Taggants.

Magnetic fluorescent composite nanomaterials have broad application prospects in the fields of biological imaging, anticounterfeiting identification, suspicious object tracking, and identification of latent fingerprints in forensic medicine. For an effective taggant, a clearly visible identifying mark is necessary to enable observers to capture labeling information quickly and accurately, even from a distance. The preparation method of magnetic fluorescent composite materials is complicated and usually needs different surface modification and assembly processes. The limited loading capacity of fluorescent materials also limits the fluorescence properties of the composite, so it is difficult to produce obvious fluorescence as a taggant to meet the requirements of visible labeling. In this study, a core-shell structure of a magnetic fluorescent composite was prepared by using the metal-organic framework ZIF-8 as the host of fluorescent materials and an encapsulation shell coated on the Fe3O4 nanoparticles. The porous ZIF-8 is beneficial for increasing the loading capacity of fluorescent materials to ensure the fluorescence performance of the composite materials. Further modification of the composite surface prevented the desorption of fluorescent materials from the pores of ZIF-8, enabling the samples to maintain good fluorescence properties even after multiple washing cycles. The preparation method is simple, rapid, and cost-effective, and the prepared magnetic fluorescent composite nanomaterial has high magnetic separation performance and fluorescence performance, making it a promising material for identification, marking, and tracking.

Synthesis of aqueous NiFe2O4-Fe3O4 hybrid magnetic nanofluids and investigation on electrical conducting behaviour

Highly stable aqueous magnetic mono nanofluids of nickel ferrite (NiFe2O4), magnetite (Fe3O4), and hybrid magnetic nanofluids of NiFe2O4-Fe3O4 are synthesized through a two-step method. The structural analysis of the NiFe2O4 and Fe3O4 nanoparticles made through X-ray diffraction identifies their spinel cubic structure. The magnetic studies indicate their superparamagnetic nature, which is further confirmed through the Langevin fitting of the experimental data. The monodomain nature of nanoparticles is verified using the coupling constant, and a spherical morphology is observed using a transmission electron microscope. The surface charge of the nanoparticles is studied through zeta potential analysis. The electrical conductivity of the aqueous mono and hybrid magnetic nanofluids is measured for various concentrations and temperatures. The hybrid magnetic nanofluids show higher electrical conductivity values than those of both the mono nanofluids. For instance, NiFe2O4-Fe3O4 (1.2 vol%) hybrid nanofluid is found to have a conductivity value of 18.91 μS/cm that is 1.5 times enhanced than that of Fe3O4 mono nanofluid (12.87 μS/cm) and three times enhanced than that of NiFe2O4 (6.43 μS/cm) mono nanofluid of same volume percentage at 303 K. A Maximum enhancement of 136 % is obtained for 1.2 vol% hybrid nanofluid with respect to water at 303 K and this enhancement further increases to 196 % with the rise in temperature to 323 K. There is no theoretical model found in literature to explain the electrical conductivity of hybrid nanofluids. Maxwell, Bruggeman, Cruz, and Shen models are applied to explain the conductivity of hybrid magnetic nanofluids. Through a comparison of experimental values with theoretical values, it is found that the Shen model, if modified suitably, can explain the electrical conduction of hybrid magnetic nanofluids. Also, the electrical conduction mechanism in hybrid magnetic nanofluids is described in terms of electrophoretic charge transportation and the Brownian motion. In addition, the magneto-electrical conductivity study is performed by measuring the electrical conductivity by applying a magnetic field of various strengths. The electrical conductivity, magneto-electrical conductivity studies and an understanding of electrical conduction mechanism are highly significant for magnetically transportable electronic cooling and conducting applications of hybrid magnetic nanofluids.