Search

Photodetectors based on advanced materials with a broad spectral photoresponse, high sensitivity, huge integration ability, room-temperature operation, and stable environmental stability are highly desired for diversified applications of imaging, sensing, and communication. Herein, a high-performance ultra-broadband photodetector based on an ultrathin two-dimensional (2D) Fe 3 O 4 nanoflake heterostructure with high sensitivity was designed. The photodetector response light was from visible 405 nm to long-wave infrared (LWIR) 10.6 μm in ambient air. The competitive performances, including a high photoresponsivity ( R ) of 182.8 A W -1 , fast speed with the rise time τ r = 8.8 μs, and decay time τ d = 4.1 μs, were demonstrated in the visible range. Notably, the device exhibits an excellent uncooled LWIR detection ability, with a high R of 1.4 A W -1 realized at a 1.5 V bias. In the full spectral range, the noise equivalent power is lower than 0.79 pW Hz -1/2 , and specific detectivity ( D *) is higher than 4.9 × 10 8 cm Hz 1/2 W -1 in ambient air. This work provides alternative ultrathin 2D materials for future infrared optoelectronic devices.

Microbiologically influenced corrosion (MIC) poses considerable challenges in various industries, prompting the exploration of advanced materials to mitigate microbial threats. This study successfully synthesized nanoscale vermiculite (VMT) from natural seawater and utilized it as a foundation to integrate magnetic nanoparticles (Fe 3 O 4 ) and chlorhexidine acetate (CA) for inhibiting MIC. A comprehensive investigation encompassing the synthesis, characterization, and application of these VMT/Fe 3 O 4 /CA composites was conducted to evaluate their antimicrobial effectiveness against Escherichia coli , Staphylococcus aureus , and sulfate-reducing bacteria (SRB), demonstrating an efficacy exceeding 99.5%. Moreover, the composite material demonstrated the capability to align with a magnetic field, enabling precise drug targeting and release, thereby facilitating biofilm removal. This research makes a significant contribution to the advancement of intelligent, efficient, and eco-friendly corrosion protection solutions.

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 Fe 3 O 4 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.

Hierarchical structural design has been verified as a feasible strategy to fabricate effective electromagnetic wave (EMW) absorbers, so we designed hierarchical core-sheath composites with magnetic particles and dielectric layers. In this work, a hierarchical structure of carbon fiber (CF)@Fe 3 O 4 @MoS 2 (CPDF7-M) was prepared by introducing Fe 3 O 4 and depositing MoS 2 layers on the surface of fibers. Due to the synergistic effects from the CF@Fe 3 O 4 increasing the conductive and magnetic loss and the outer MoS 2 layers improving the impedance matching, the optimal reflection loss ( R L ) value was -63.1 dB at 2.7 mm and the effective absorption bandwidth (EAB) was 9.1 GHz covering the X and Ku band. Moreover, the EAB values were adjusted with a specific MoS 2 loading at different thicknesses, which provided the necessary reference for the construction of efficient and flexible absorbers in the EMW absorption fields.

Magnetic Fe 3 O 4 nanoparticles (MNPs) are often used to design agents enhancing contrast in magnetic resonance imaging (MRI) that can be considered as one of the efficient methods for cancer diagnostics. At present, increasing the specificity of the MRI contrast agent accumulation in tumor tissues remains an open question and attracts the attention of a wide range of researchers. One of the modern methods for enhancing the efficiency of contrast agents is the use of molecules for tumor acidic microenvironment targeting, for example, pH-low insertion peptide (pHLIP). We designed novel organosilicon MNPs covered with poly(ethylene glycol) (PEG) and covalently modified by pHLIP. To study the specific features of the binding of pHLIP-modified MNPs to cells, we also obtained nanoconjugates with Cy5 fluorescent dye embedded in the SiO 2 shell. The nanoconjugates obtained were characterized by transmission electron microscopy (TEM), attenuated total reflection (ATR), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), dynamic light scattering (DLS), UV and fluorescence spectrometry, thermogravimetric analysis (TGA), CHN elemental analyses, and vibrating sample magnetometry. Low cytotoxicity and high specificity of cellular uptake of pHLIP-modified MNPs at pH 6.4 versus 7.4 (up to 23-fold) were demonstrated in vitro. The dynamics of the nanoconjugate accumulation in the 4T1 breast cancer orthotopically grown in BALB/c mice and MDA-MB231 xenografts was evaluated in MRI experiments. Biodistribution and biocompatibility studies of the obtained nanoconjugate showed no pathological change in organs and in the blood biochemical parameters of mice after MNP administration. A high accumulation rate of pHLIP-modified MNPs in tumor compared with PEGylated MNPs after their intravenous administration was demonstrated. Thus, we propose a promising approach to design an MRI agent with the tumor acidic microenvironment targeting ability.

In strongly correlated materials, change of the local lattice configuration is expected to tune or even generate new properties otherwise in the ideal bulk materials. For highly spin-polarized materials, the spin-dependent transport is sensitive to the local magnetic structure. Here, the artificial grain boundaries (GBs) with different tilt angles are produced in Fe 3 O 4 films using SrTiO 3 bicrystal substrates. The saturation magnetization of Fe 3 O 4 bicrystal films is enhanced. The detailed atomic structural results combining with density functional theory calculations reveal that the elongated Fe A -O bond length at GBs resulting in the reduction of charge transfer reduces the Fe A magnetic moments, which enhances the total magnetic moments of Fe 3 O 4 . The in-plane rotation of the Fe 3 O 4 lattice on bicrystal substrates alters the magnetization processes. Especially, the Fe 3 O 4 bicrystal film with a tilt angle of 22.6° shows strong in-plane magnetic anisotropy due to the zigzag GBs. The altered magnetic anisotropy of Fe 3 O 4 bicrystal films enhances the anisotropic magnetoresistance. The findings reveal the mechanism of GBs on the magnetic and transport properties and manifest that the strategy of utilizing GBs can tune the physical properties in highly spin-polarized materials.

Conversion-type magnetite shrewdly shows abundance, nontoxicity, and high lithium storage capacity. However, either pristine magnetite or nanocomposites with two-dimensional materials cannot prevent restacking, pulverization, and poor structural homogeneity simultaneously because of a lack of universal interfacial interactions. Here, an electrostatic self-assembly strategy is uncovered between hollow Fe 3 O 4 /C microspheres (with H + -induced quasi-intrinsic positive charge) and few-layer MXenes (with intrinsic negative charge from terminating functionalities). This strategy realizes the uniform and interconnected architecture of Fe 3 O 4 /C@MXene that favors fast Li + diffusion, easy electron/charge transfer, and suppressed pulverization. Specifically, after the long-term cycling, an undegraded specific capacity of 907 mA h g -1 remains at 0.5 A g -1 . Further adoption of such superior anode in 4.0 V lithium-ion capacitors results in a high energy density of 130 W h kg -1 , a maximum power density of 25,000 W kg -1 , and excellent cycling stability. This work thus sheds light on a generic self-assembly process where intrinsic electrostatic interaction plays an essential role.

Electro-reduction of O 2 to generate H 2 O 2 is an attractive alternative to the current anthraquinone process and quite necessary for chemical industries and environmental remediation. In general, sufficient porous structure contributes to expose more catalytic active sites and shorten diffusion paths for the heterogeneous catalysis of O 2 . In this work, initially the Fe 3 O 4 nanoparticles embedded graphite felt (Fe 3 O 4 @GF) is prepared through a mild hydrothermal following with thermal reduction method. This special combination not only provides iron source for the electro-Fenton reaction but also supplies rich active sites from the Fe 3 O 4 embedded structure with abundant cracks, which are beneficial to increase the reaction rate. Compared with raw graphite felt (RGF), fresh Fe 3 O 4 @GF exhibits superior pollutant degradation kinetics with more than 400% increase and approximately 37.8% improvement to the removal of total organic carbon. A 98% decolorization of rhodamine B (RhB) can be achieved in just 5 min and quickly completes 100% removal of RhB in the next few seconds. As the electro-Fenton reaction progresses, Fe 3 O 4 dissolves in the electrolyte, leaving a porous structure on the surface of the GF to form a porous GF (PGF), and the rapid radical reaction activates the GF surface. Both the chemical etching of Fe 3 O 4 and the electro-Fenton process can further increase the specific surface area, defects, and actives sites of the electrode. As expected, the active PGF exhibits favorable performance of H 2 O 2 production in electrolytes of different pHs: 1 (320.0 ± 36.5 mg L -1 ), 3 (301.9 ± 13.2 mg L -1 ), and 7 (320.4 ± 21.2 mg L -1 ). The degradation performance of PGF does not significantly decay even after 20 cycles of repeated use, indicating the good structural stability and long-term durability. The superiority of the in situ Fe source and fast reaction kinetics for electro-Fenton of Fe 3 O 4 @GF is confirmed, and this holey engineered strategy also provides the possibility to achieve swift water purification and open up a new way for developing efficient carbon-based electrodes.

While the focus of research related to the design of robust, high-performance Li-ion batteries relates primarily to the synthesis of active particles, the binder plays a crucial role in stability and ensures electrode integrity during volume changes that occur with cycling. Conventional polymeric binders such as poly(vinylidene difluoride) generally do not interact with active particle surfaces and fail to accommodate large changes in particle spacing during cycling. Thus, attention is now turning toward the exploration of interfacial interactions between composite electrode constituents as a key element in ensuring electrode stability. Recently, a poly[3-(potassium-4-butanoate)thiophene] (PPBT) binder component, coupled with a polyethylene glycol (PEG) surface coating for the active material was demonstrated to enhance both electron and ion transport in magnetite-based anodes, and it was established that the PEG/PPBT approach aids in overall battery electrode performance. Herein, the PEG/PPBT system is used as a model polymeric binder for understanding cation effects in anode systems. As such, the potassium ion was replaced with sodium, lithium, hydrogen, and ammonium through ion exchange. The potassium salt exhibited the most stable electrochemical performance, which is attributed to the cation size and resultant electrode morphology that facilitates ion transport. The lithium analogue demonstrated an initial increase in capacity but was unable to maintain this performance over 100 cycles; while the sodium-based system exhibited initially lower capacity as a result of slow reaction kinetics, which increased as cycling progressed. The parent carboxylic acid polymer and its ammonium salt were notably inferior. The results exploring the effect of ion exchange creates a framework for understanding how cations associated directly with the polymer impact electrochemical performance and aid in the overall design of binders for composite Li-ion battery anodes.

Sandwich-like MXene/Fe 3 O 4 and C/TiO 2 /α-Fe two-dimensional (2D) nanocomposites were fabricated via in situ hydrothermal assembly of Fe 3 O 4 nanoparticles on MXene nanosheets and postannealing. The as-prepared sandwich-like MXene/Fe 3 O 4 nanocomposites contain uniformly distributed Fe 3 O 4 nanoparticles between the interlayers of the 2D MXene Ti 3 C 2 T x nanoflakes. The redox reaction, Ti 3 C 2 T x + Fe 3 O 4 → 3TiO 2 + 2C + 3Fe, has also been reported for the first time to transform the binary MXene/Fe 3 O 4 nanocomposites into ternary C/TiO 2 /α-Fe nanocomposites with the 2D structure maintained intact. Such a transition during postannealing gives rise to further enhanced electromagnetic wave absorption compared with that of the MXene/Fe 3 O 4 nanocomposites on top of the already improved performance of the MXene/Fe 3 O 4 compared with that of pristine MXene. The 2D C/TiO 2 /α-Fe nanocomposites exhibit effective absorption bandwidths of 3.3 and 3.5 GHz at thicknesses of 1 and 1.5 mm, respectively. This work offers a new route for fabricating novel electromagnetic wave absorbers, and the fine balance among lightweight, broad band, and small thickness of the C/TiO 2 /α-Fe nanocomposites makes them promising in the field of electromagnetic wave absorption.

One of the major hurdles of ferrite-based microwave absorbing materials is the limited working frequency that urgently calls for an effective modification technique. Herein, a controllable carbothermal route has been developed to ameliorate the microwave absorption performance of Fe 3 O 4 nanospheres by using metal-organic frameworks (MOFs) shell as a carbon source with changing ramping rates. An enhanced synergistic attenuation induced by varied composition and tailored morphology is of great importance, which can be regarded as the superiority of the comprehensive (magnetic and dielectric), rather than unilateral (dielectric), modification technique. The drawbacks of dielectric modification can be concluded as the separated attenuation mechanisms at discrete frequencies, proven by the construction of the core-shell structured Fe 3 O 4 @Prussian blue composite. The advantages of magnetic modification can also be confirmed by a series of Fe-based composites with unique composition and tailored structure derived from the Fe 3 O 4 @Prussian blue composite at a distinct heating rate. Further, the superiority can be summarized as the rearrangement of magnetic loss by exceeding the Snoek limit and the reinforcement of dielectric loss by enhancing the electrical conductivity and introducing multiple polarization processes. Consequently, the sample obtained at 10 °C min -1 , which contains Fe and Fe 3 O 4 , shows an extended working frequency of 14.05 GHz, with a thickness less than 5 mm and a high reflection loss value of -48.04 dB at 1.55 mm. This work not only offers a novel carbothermal route based on MOFs coating to prepare desired magnetic composites, but also acquires deeper insights of the comprehensive modification technique, which may pave the way for designing high-performance electromagnetic devices.

Mechanically robust composite nanofibers (NFs) with enhanced magnetic properties were made from polyvinylidene fluoride (PVDF) and Fe 3 O 4 nanoparticles (NPs) by an electrospinning method. At up to 11.3 wt %, Fe 3 O 4 NPs were embedded randomly in the PVDF NFs, but when the content exceeded 17 wt %, the NPs aggregated on the NF surfaces. Magnetization of the composite NFs consistently increased with the increasing Fe 3 O 4 NP content. The mechanical strength of the Fe 3 O 4 NP/PVDF composite NF was enhanced by a dispersion strengthening mechanism. A triboelectric nanogenerator was made from the composite, which showed enhanced output performance with the Fe 3 O 4 NP content less than 11.3 wt %, but the performance degraded at higher content. These results were attributed to the electret doping effect and surface aggregation of the Fe 3 O 4 NPs on the NFs, respectively.

Construction of a continuous conductance network with high electron-transfer rate is extremely important for high-performance energy storage. Owing to the highly efficient mass transport and information transmission, neurons are exactly a perfect model for electron transport, inspiring us to design a neuron-like reaction network for high-performance lithium-ion batteries (LIBs) with Fe 3 O 4 as an example. The reactive cores (Fe 3 O 4 ) are protected by carbon shells and linked by carbon filaments, constituting an integrated conductance network. Thus, once the reaction starts, the electrons released from every Fe 3 O 4 cores are capable of being transferred rapidly through the whole network directly to the external circuit, endowing the nanocomposite with tremendous rate performance and ultralong cycle life. After 1000 cycles at current densities as high as 1 and 2 A g -1 , charge capacities of the as-synthesized nanocomposite maintain 971 and 715 mA h g -1 , respectively, much higher than those of reported Fe 3 O 4 -based anode materials. The Fe 3 O 4 -based conductive network provides a new idea for future developments of high-rate-performance LIBs.

A novel core-shell Fe 3 O 4 @FeS composed of Fe 3 O 4 core and FeS shell with the morphology of regular octahedra has been prepared via a facile and scalable strategy via employing commercial Fe 3 O 4 as the precursor. When used as anode material for sodium-ion batteries (SIBs), the prepared Fe 3 O 4 @FeS combines the merits of FeS and Fe 3 O 4 with high Na-storage capacity and superior cycling stability, respectively. The optimized Fe 3 O 4 @FeS electrode shows ultralong cycle life and outstanding rate capability. For instance, it remains a capacity retention of 90.8% with a reversible capacity of 169 mAh g -1 after 750 cycles at 0.2 A g -1 and 151 mAh g -1 at a high current density of 2 A g -1 , which is about 7.5 times in comparison to the Na-storage capacity of commercial Fe 3 O 4 . More importantly, the prepared Fe 3 O 4 @FeS also exhibits excellent full-cell performance. The assembled Fe 3 O 4 @FeS//Na 3 V 2 (PO 4 ) 2 O 2 F sodium-ion full battery gives a reversible capacity of 157 mAh g -1 after 50 cycles at 0.5 A g -1 with a capacity retention of 92.3% and the Coulombic efficiency of around 100%, demonstrating its applicability for sodium-ion full batteries as a promising anode. Furthermore, it is also disclosed that such superior electrochemical properties can be attributed to the pseudocapacitive behavior of FeS shell as demonstrated by the kinetics studies as well as the core-shell structure. In view of the large-scale availability of commercial precursor and ease of preparation, this study provide a scalable strategy to develop advanced anode materials for SIBs.

In this article, double carbon shell hollow spheres which provide macropores (mC) for ultrasmall Fe 3 O 4 nanoparticle (10-20 nm) encapsulation individually were first prepared (Fe 3 O 4 @mC). The well-constructed Fe 3 O 4 @mC electrode materials offer the feasibility to study the volume change, aggregation, and pulverization process of the active Fe 3 O 4 nanoparticles for Li-ion storage in a confined space. Fe 3 O 4 @mC exhibits excellent electrochemical performances and delivers a high capacity of 645 mA h g -1 at 2 A g -1 after 1000 cycles. Even at 10 A g -1 or after 1000 cycles at 2 A g -1 , the porous carbon structure was well maintained and no obvious aggregation and pulverization of the Fe 3 O 4 nanoparticles was observed, although the volume of the active Fe 3 O 4 particles was expanded to 40-60 nm compared to that of the original particles (10-20 nm). This can be due to the in situ embedment of one Fe 3 O 4 nanoparticle into one macropore individually. The uniform dispersion and confinement of the Fe 3 O 4 nanoparticles in the macropores of the carbon shell could effectively accommodate severe volume variations upon cycling and prevent self-aggregation and spreading out from the carbon shell during the expansion process of the nanoscale Fe 3 O 4 particles, leading to improved capacity retention. Our work confirms the effectiveness for pulverization control by confining Fe 3 O 4 nanoparticles individually into macropores to improve its Li-ion storage properties, providing a novel strategy for the design of new-structured anode materials for Li-ion batteries.

Fe 3 O 4 nanocrystals with five different morphologies (i.e., nanospheres, nanorods, nanocubes, nano-octahedrons, and nanoplates) were acquired using a simple, efficient, and economic microwave-assisted oxidation technique. The microstructure, morphology, predominant exposed facets, and iron atom local environment of Fe 3 O 4 were revealed by powder X-ray diffraction (PXRD), scanning transmission electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectrometer (XPS), and Mössbauer spectrum. We demonstrated that the heterogeneous UVA/Fenton catalytic activities of Fe 3 O 4 nanocrystals are morphology/facets dependent. Under UVA irradiation, the catalytic activity of the as-prepared Fe 3 O 4 was in the sequence of nanospheres > nanoplates > nano-octahedrons ≈ nanocubes > nanorods > nano-octahedrons (by coprecipitation). The dominating factor for the catalytic performance was the particle size and BET specific surface area; moreover, the exposed {111} facets, which contained more Fe 2+ species, on the nanocrystal surface led to a stronger UVA/Fenton catalytic activity. Both • OH and O 2 •- radicals participated in the UVA/Fenton degradation process, and • OH played the dominant role. These morphology-controlled nanomagnetites showed great potential in applications as heterogeneous UVA/Fenton catalysts for effectively treating nonbiodegradable organic pollutants.

Among the numerous candidate materials for lithium ion batteries, ferroferric oxide (Fe 3 O 4 ) has been extensively concerned as a prospective anode material because of its high theoretical specific capacity, abundant resources, low cost, and nontoxicity. Here, we designed and fabricated a unique yolk-shell construction by generating heterogeneous double-shelled SnO 2 and nitrogen-doped carbon on Fe 3 O 4 yolk (denoted as Fe 3 O 4 @SnO 2 @C-N nanoboxes). The yolk-shell structured Fe 3 O 4 @SnO 2 @C-N nanoboxes have the adjustable void space, which permits the free expansion of Fe 3 O 4 yolks without breaking the double shells during the lithiation/delithiation processes, avoiding the structural pulverization. Moreover, the heterogeneous double-shelled SnO 2 @C-N can meaningfully improve the electronic conductivity and enhance the lithium storage performance. Two metal oxides also show the specific synergistic effect, promoting the electrochemistry reaction. As a result, this yolk-shell structured Fe 3 O 4 @SnO 2 @C-N exhibits high specific capacity (870 mA h g -1 at 0.5 A g -1 after 200 cycles), superior rate capability, and long cycle life (670 mA h g -1 at 3 A g -1 after 600 cycles). This design and construction method can be extended to synthesize other yolk-shell nanostructured anode materials with improved electrochemistry performance.

Lithium-ion capacitors (LICs) are considered as promising energy storage devices to realize excellent electrochemical performance, with high energy-power output. In this work, we employed a simple method to synthesize a composite electrode material consisting of Fe 3 O 4 nanocrystallites mechanically anchored among the layers of three-dimensional arrays of graphene (Fe 3 O 4 -G), which exhibits several advantages compared with other traditional electrode materials, such as high Li storage capacity (820 mAh g -1 at 0.1 A g -1 ), high electrical conductivity, and improved electrochemical stability. Furthermore, on the basis of the appropriated charge balance between cathode and anode, we successfully fabricated Fe 3 O 4 -G//activated carbon (AC) soft-packaging LICs with a high energy density of 120.0 Wh kg -1 , an outstanding power density of 45.4 kW kg -1 (achieved at 60.5 Wh kg -1 ), and an excellent capacity retention of up to 94.1% after 1000 cycles and 81.4% after 10 000 cycles. The energy density of the Fe 3 O 4 -G//AC hybrid device is comparable with Ni-metal hydride batteries, and its capacitive power capability and cycle life is on par with supercapacitors (SCs). Therefore, this lithium-ion hybrid capacitor is expected to bridge the gap between Li-ion battery and SCs and gain bright prospects in next-generation energy storage fields.

Fe 3 O 4 is regarded as an attractive anode material for lithium ion batteries (LIBs) due to its high theoretical capacity, natural abundance, and low cost. However, the poor cyclic performance resulting from the low conductivity and huge volume change during cycling impedes its application. Here we have developed a facile electrophoretic deposition route to fabricate the Fe 3 O 4 /CNTs (carbon nanotubes)/rGO (reduced graphene oxide) composite electrode, simultaneously achieving material synthesis and electrode assembling. Even without binders, the adhesion and mechanical firmness of the electrode are strong enough to be used for LIB anode. In this specific structure, Fe 3 O 4 nanoparticles (NPs) interconnected by CNTs are sandwiched by rGO layers to form a robust network with good conductivity. The resulting Fe 3 O 4 /CNTs/rGO composite electrode exhibits much improved electrochemical performance (high reversible capacity of 540 mAh g -1 at a very high current density of 10 A g -1 , and a remarkable capacity of 1080 mAh g -1 can be maintained after 450 cycles at 1 A g -1 ) compared with that of commercial Fe 3 O 4 NPs electrode.

Transition metal oxides can be considered as appealing candidates for sodium ion battery anode materials because these low-cost materials possess high capacity and enhanced safety. However, the practical application of these materials is usually limited by their low electronic conductivity and serious volume change during the charging-discharging process. Herein, we report the fabrication of 3D-0D graphene-Fe 3 O 4 quantum dot hybrids by a facile one-pot hydrothermal approach as anode materials for sodium-ion batteries. Fe 3 O 4 quantum dots with an average size of 4.9 nm are anchored on the surface of 3D structured graphene nanosheets homogeneously. Such unique hierarchical structure are advantageous for enlarging the electrode/electrolyte interface area and enhancing the electrochemical activity of the hybrid materials, inhibiting particle aggregation of Fe 3 O 4 and accommodating their volume change during the charging-discharging process as well as enabling fast diffusion of electrons and rapid transfer of electrolyte ions. Consequently, the 3D-0D graphene-Fe 3 O 4 quantum dot hybrids exhibit ultrahigh sodium storage capacity (525 mAh g -1 at 30 mA g -1 ), outstanding cycling stability (312 mAh g -1 after 200 cycles at 50 mA g -1 ) and superior rate performance (56 mAh g -1 at 10 A g -1 ).

In this research, a thermoresponsive drug release system was synthesized, which encapsulated the magnetic nanoparticles Fe3O4 and the drug model 5-fluorouracil with thermosensitive polymer poly(N-isopropylacrylamide) (PNIPAM). Mesoporous SiO2 was used as the channel of drug release, which could enhance the rate of drug loading and reduce drug loss. Chitosan (CHI) is a natural cationic linear polymer. The results showed successful coating of chitosan and rhodamine 6G (R6G) on the surface of the SiO2 sphere. The intermolecular interactions of the nanocomposites were confirmed by Fourier transform infrared spectroscopy. R6G is a typical fluorochrome which could be applied for cell imaging. Fluorescent imaging studies by confocal laser scanning microscopy indicated that the prepared nanocomposites Fe3O4/PNIPAM/5-Fu@mSiO2-CHI/R6G could specifically target tumor cells. Therefore, our work shows great potential in drug delivery and cancer therapy.

Development of carbon-based materials has received tremendous attention owing to their multifunctional properties. Biomaterials often serve as an inspiration for the preparation of new carbon materials. Herein, we present a facile synthesis of a new bioinspired graphene oxide-like 2D-carbon flake (CF) using a natural resource, waste onion sheathing (Allium cepa). The 2D-CF was further decorated with crystalline Fe3O4 nanoparticles for applications. Superparamagnetic Fe3O4 nanoparticles (7 nm) were well-dispersed on the surface of the 2D-CF, which was characterized by X-ray diffractometry, X-ray photoelectron spectroscopy, Raman spectrometry, and transmission electron microscopy. Batch As(III) adsorption experiments showed that aqueous arsenic ions strongly adsorbed to the Fe3O4@2D-CF composite. The adsorption capacity of the Fe3O4@2D-CF composite for As(III) was 57.47 mg g(-1). The synergetic effect of both graphene oxide-like 2D-CF and Fe3O4 nanoparticles aided in excellent As(III) adsorption. An As(III) ion adsorption kinetics study showed that adsorption was very fast at the initial stage, and equilibrium was reached within 60 min following a pseudo-second-order rate model. Owing to the excellent superparamagnetic properties (52.6 emu g(-1)), the Fe3O4@2D-CF composite exhibited superb reusability with the shortest recovery time (28 s) among reported materials. This study indicated that Fe3O4@2D-CF composites can be used for practical applications as a global economic material for future generations.

Hybrid membranes blended with nanomaterials such as graphene oxide (GO) have great opportunities in water applications due to their multiple functionalities, but they suffer from low modification efficiency of nanomaterials due to the fact that plenty of the nanomaterials are embedded within the polymer matrix during the blending process. Herein, a novel Fe3O4/GO-poly(vinylidene fluoride) (Fe3O4/GO-PVDF) hybrid ultrafiltration membrane was developed via the combination of magnetic field induced casting and a phase inversion technique, during which the Fe3O4/GO nanocomposites could migrate toward the membrane top surface due to magnetic attraction and thereby render the surface highly hydrophilic with robust resistance to fouling. The blended Fe3O4/GO nanocomposites migrated to the membrane surface with the magnetic field induced casting, as verified by X-ray photoelectron spectroscopy, elemental analysis, and energy dispersive X-ray spectroscopy. As a result, the novel membranes exhibited significantly improved hydrophilicity (with a contact angle of 55.0°) and water flux (up to 595.39 L m(-2) h(-1)), which were improved by 26% and 206%, 12% and 49%, 25% and 154%, and 11% and 33% compared with those of pristine PVDF membranes and PVDF hybrid membranes blended with GO, Fe3O4, and Fe3O4/GO without the assistance of magnetic field during membrane casting, respectively. Besides, the novel membranes showed high rejection of bovine serum albumin (>92%) and high flux recovery ratio (up to 86.4%). Therefore, this study presents a novel strategy for developing high-performance hybrid membranes via manipulating the migration of nanomaterials to the membrane surface rather than embedding them in the membrane matrix.

We report a novel and straightforward methodology for constructing hybrid particles with tunable morphology (spherical vs nonspherical) by embedding inorganic components (graphene oxide and/or Fe3O4 nanoparticles) inside chiral helical polyacetylene. Scanning electron microscopic images ascertain the spherical or nonspherical morphology of the particles. The intense circular dichroism effects demonstrate that the hybrid particles (spherical, ellipsoid-like, and cake-like) possess remarkable optical activity. The use of the chiral magnetic hybrid particles in enantioselective crystallization of racemic phenylalanine demonstrates the kind of particles' significant potential applications in chiral technologies and chiral processes. The study not only creates an unprecedented type of chiral hybrid particles, but also provides a versatile strategy for preparing advanced functional hybrid particles with tunable morphology from polymers and even from inorganic and metallic materials.

Graphene has good stability and adjustable dielectric properties along with tunable morphologies, and hence can be used to design novel and high-performance functional materials. Here, we have reported a facile synthesis method of nanoscale Fe3O4/graphene capsules (GCs) composites using the combination of catalytic chemical vapor deposition (CCVD) and hydrothermal process. The resulting composite has the advantage of unique morphology that offers better synergism among the Fe3O4 particles as well as particles and GCs. The microwave-absorbing characteristics of developed composites were investigated through experimentally measured electromagnetic properties and simulation studies based on the transmission line theory, explained on the basis of eddy current, natural and exchange resonance, as well as dielectric relaxation processes. The composites bear minimum RL value of -32 dB at 8.76 GHz along with the absorption bandwidth range from 5.4 to 17 GHz for RL lower than -10 dB. The better performance of the composite based on the reasonable impedance characteristic, existence of interfaces around the composites, and the polarization of free carriers in 3D GCs that make the as-prepared composites capable of absorbing microwave more effectively. These results offer an effective way to design high-performance functional materials to facilitate the research in electromagnetic shielding and microwave absorption.

Anode materials with relatively low capacitance remain a great challenge for asymmetric supercapacitors (ASCs) to pursue high energy density. Hematite (α-Fe2O3) has attracted intensive attention as anode material for ASCs, because of its suitable reversible redox reactions in a negative potential window (from 0 V to -1 V vs Ag/AgCl), high theoretical capacitance, rich abundance, and nontoxic features. Nevertheless, the Fe2O3 electrode cannot deliver large volumetric capacitance at a high rate, because of its poor electrical conductivity (∼10(-14) S/cm), resulting in low power density and low energy density. In this work, a hierarchical heterostructure comprising Fe3O4@Fe2O3 core-shell nanorod arrays (NRAs) is presented and investigated as the negative electrode for ASCs. Consequently, the Fe3O4@Fe2O3 electrode exhibits superior supercapacitive performance, compared to the bare Fe2O3 and Fe3O4 NRAs electrodes, demonstrating large volumetric capacitance (up to 1206 F/cm(3) with a mass loading of 1.25 mg/cm(2)), as well as good rate capability and cycling stability. The hybrid electrode design is also adopted to prepare Fe3O4@MnO2 core-shell NRAs as the positive electrode for ASCs. Significantly, the as-assembled 2 V ASC device delivered a high energy density of 0.83 mWh/cm(3) at a power density of 15.6 mW/cm(3). This work constitutes the first demonstration of Fe3O4 as the conductive supports for Fe2O3 to address the concerns about its poor electronic and ionic transport.

Heavy metal ion removal from wastewater constitutes an important issue in the water treatment industry. Although a variety of nanomaterials have been developed for heavy metal removal via adsorption, the adsorption capacity, removal efficiency, and material recyclability still remain a challenge. Here, we present novel Fe3O4@DAPF core-shell ferromagnetic nanorods (CSFMNRs) for the removal of Pb(II) from aqueous solutions; they were prepared by the facile surface modification of twin-like ferromagnetic Fe3O4 nanorods using a 2,3-diaminophenol and formaldehyde (DAPF)-based polymer. The crystallinity and structure of the Fe3O4 nanorods were confirmed via X-ray diffraction (XRD). Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) revealed the core-shell morphology and composition of the materials. Pb(II) removal using the prepared Fe3O4@DAPF CSFMNRs was assessed, and comparable adsorption capacities (83.3 mg g(-1)) to the largest value were demonstrated. A thermodynamic study of the adsorption clearly indicated that the adsorption was exothermic and spontaneous. Due to the ferromagnetic properties with a high saturation magnetization value (56.1 emu g(-1)) of the nanorods, the nanorods exhibited excellent reusability with one of the fastest recovery times (25 s) among reported materials. Therefore, the Fe3O4@DAPF CSFMNRs can serve as recyclable adsorbent materials and as an alternative to commonly used sorbent materials for the rapid removal of heavy metals from aqueous solutions.

Recently, photothermal therapy (PTT) that utilizes photothermal conversion (PTC) agents to ablate cancer under near-infrared (NIR) irradiation has attracted a growing amount of attention because of its excellent therapeutic efficacy and improved target selectivity. Therefore, exploring novel PTC agents with an outstanding photothermal effect is a current research focus. Herein, we reported a polydopamine-coated magnetic composite particle with an enhanced PTC effect, which was synthesized simply through coating polydopamine (PDA) on the surface of magnetic Fe3O4 particles. Compared with magnetic Fe3O4 particles and PDA nanospheres, the core-shell nanomaterials exhibited an increased NIR absorption, and thus, an enhanced photothermal effect was obtained. We demonstrated the in vitro and in vivo effects of the photothermal therapy using our composite particles and their ability as a contrast agent in the T2-weighted magnetic resonance imaging. These results indicated that the multifunctional composite particles with enhanced photothermal effect are superior to magnetic Fe3O4 particles and PDA nanospheres alone.

One-dimensional Ag-Fe3O4 core-shell heteronanowires have been synthesized by a facile and effective coprecipitation method, in which silver nanowires (AgNWs) were used as the nucleation site for growth of Fe3O4 in aqueous solution. The size and morphology control of the core-shell nanowires were achieved by simple adjustments of reaction conditions including FeCl3/FeCl2 concentration, poly(vinylpyrrolidone) (PVP) concentration, reaction temperature, and time. It was found that the Fe3O4 shell thickness could be tuned from 6 to 76 nm with the morphology variation between nanopheres and nanorods. A possible growth mechanism of Ag-Fe3O4 core-shell nanowires was proposed. First, the C═O derived from PVP on the surface of AgNWs provided nucleation points and in situ oxidation reaction between AgNWs and FeCl3/FeCl2 solution promoted the accumulation of Fe(3+) and Fe(2+) on the AgNWs surface. Second, Fe3O4 nanoparticles nucleated on the AgNWs surface. Lastly, Fe3O4 nanoparticles grew on the AgNWs surface by using up the reagents. Higher FeCl3/FeCl2 concentration or higher temperature led to faster nucleation and growth, resulting in the formation of Fe3O4 nanorods, whereas lower concentration or lower temperature resulted in slower nucleation and growth, leading to the formation of Fe3O4 nanospheres. Furthermore, the Ag-Fe3O4 core-shell nanowires exhibited good electrical properties and ferromagnetic properties at room temperature. Particularly, the magnetic saturation values (Ms) increased from 5.7 to 26.4 emu g(-1) with increasing Fe3O4 shell thickness from 9 to 76 nm. This growth of magnetic nanoparticles on 1D metal nanowires is meaningful from both fundamental and applied perspectives.