Fe3O4 Core Research Articles

Achieving Excellent Dielectric and Energy Storage Performance in Core-Double-Shell-Structured Polyetherimide Nanocomposites.

The development of pulse power systems and electric power transmission systems urgently require the innovation of dielectric materials possessing high-temperature durability, high energy storage density, and efficient charge-discharge performance. This study introduces a core-double-shell-structured iron(II,III) oxide@barium titanate@silicon dioxide/polyetherimide (Fe3O4@BaTiO3@SiO2/PEI) nanocomposite, where the highly conductive Fe3O4 core provides the foundation for the formation of microcapacitor structures within the material. The inclusion of the ferroelectric ceramic BaTiO3 shell enhances the composite's polarization and interfacial polarization strength while impeding free charge transfer. The outer insulating SiO2 shell contributes excellent interface compatibility and charge isolation effects. With a filler content of 9 wt%, the Fe3O4@BaTiO3@SiO2/PEI nanocomposite achieves a dielectric constant of 10.6, a dielectric loss of 0.017, a high energy density of 5.82 J cm-3, and a charge-discharge efficiency (η) of 72%. The innovative aspect of this research is the design of nanoparticles with a core-double-shell structure and their PEI-based nanocomposites, effectively enhancing the dielectric and energy storage performance. This study provides new insights and experimental evidence for the design and development of high-performance dielectric materials, offering significant implications for the fields of electronic devices and energy storage.

Preparation of Fe3O4@Carrageenan-Metformin nanoparticles as a new bio-inspired magnetic nanocatalyst for the synthesis of dihydropyrano[2,3-c]pyrazoles

k-Carrageenan (Carr) is a significant constituent of red seaweeds with benign nature and easy modification due to available sulfate and hydroxyl functionalities. The current work illustrates the preparation and catalytic application of a magnetic nanocatalyst based on k-carrageenan. The Fe3O4@Carr-Met was prepared by coating magnetic Fe3O4 nanoparticles with Carr and metformin (Met). The successful synthesis of the catalyst was verified by different techniques. These nanoparticles showed excellent activity for the synthesis of dihydropyrano[2, 3-c] pyrazoles. The synergistic effect of sulfonic acid and amino groups may account for the catalytic activity of these nanoparticles. Moreover, Fe3O4 core provides effective magnetic separation. The ease of catalyst preparation, use of a benign solvent system, enhanced activity, and reusability are some of the prominent advantages of the present catalyst. The heterogeneity of Fe3O4@Carr-Met nanoparticles was also supported by a hot filtration test under optimal reaction conditions that confirmed the integrity of these nanoparticles.

Elucidating Individual Magnetic Contributions in Bi-Magnetic Fe3 O4 /Mn3 O4 Core/Shell Nanoparticles by Polarized Powder Neutron Diffraction.

Heterogeneous bi-magnetic nanostructured systems have had a sustained interest during the last decades owing to their unique magnetic properties and the wide range of derived potential applications. However, elucidating the details of their magnetic properties can be rather complex. Here, a comprehensive study of Fe3 O4 /Mn3 O4 core/shell nanoparticles using polarized neutron powder diffraction, which allows disentangling the magnetic contributions of each of the components, is presented. The results show that while at low fields the Fe3 O4 and Mn3 O4 magnetic moments averaged over the unit cell are antiferromagnetically coupled, at high fields, they orient parallel to each other. This magnetic reorientation of the Mn3 O4 shell moments is associated with a gradual evolution with the applied field of the local magnetic susceptibility from anisotropic to isotropic. Additionally, the magnetic coherence length of the Fe3 O4 cores shows some unusual field dependence due to the competition between the antiferromagnetic interface interaction and the Zeeman energies. The results demonstrate the great potential of the quantitative analysis of polarized neutron powder diffraction for the study of complex multiphase magnetic materials.

Fe3O4 Core–Shell Nanostructures with Anticancer and Antibacterial Properties: A Mini-Review

Core–shell nanoparticles are functional materials with tailored properties, able to improve the requirements of various applications. Both core and shell components can be inorganic or organic, and there are numerous studies in this field regarding their synthesis methods, properties, and applications. This review aims to study core–shell nanostructures with Fe3O4 cores and different shell types, observing their antibacterial and anticancer properties. By the type of coating, Fe3O4 core–shell nanoparticles (NPs) are classified into four categories: metal-coated NPs, metal-organic framework (MOF) coated NPs, metal oxide coated NPs, and polymer-coated NPs. Each category is briefly presented, emphasizing anticancer or antibacterial properties and specific applications (cancer diagnosis or therapy, drug carrier). Moreover, synthesis methods and particle size for both core and shell nanostructures, as well as the magnetic properties of the final core–shell material, are summarized in this review. Most of the consulted papers discussed sphere-like core–shell nanoparticles obtained by chemical methods such as coprecipitation, hydrothermal, and green synthesis methods using plant extract. These types of core–shell nanoparticles could be used as drug nanocarriers for tumor-targeted drug delivery, hyperthermia treatment, or contrast agents. Further work needs to be conducted to understand nanoparticles’ interaction with living cells and their traceability in the human body.

Urchin-like Fe3O4@C hollow spheres with core–shell structure: Controllable synthesis and microwave absorption

The steadily increasing use of microwave stealth materials in aerospace flying vehicles needs the development of lightweight absorbers with low density and high thermal stability for printing or spraying. In that regard, the structural designability of typical microwave absorbers made of Fe3O4 seems to be a significant roadmap. In this work, a hollow spherical structure with a uniform carbon shell around the urchin-like Fe3O4 core (Fe3O4@C) was produced via a two-step hydrothermal method and annealing. The Fe3O4@C absorber exhibited a strong minimum reflection loss (RLmin) of −73.5 dB at the matching thickness of 3.23 mm. The maximum effective absorption bandwidth (EABmax) was 4.78 GHz at 4.55 mm. The proposed urchin-like core–shell structure was shown to provide good impedance matching and electromagnetic loss ability due to the synergistic effect of Fe3O4 and C. In particular, the urchin-like structure increases the heterogeneous interfaces and effectively improves their polarization and relaxation. On the other hand, it reduces the density of the absorber and enhances multiple scattering attenuations of electromagnetic waves (EMWs). Therefore, the findings of the present study open up prospects for the design of high-efficiency lightweight microwave absorbers with specialized structures.

Peroxymonosulfate‐Assisted Phenol Degradation via a Magnetic Covalent‐Triazine‐Framework‐Based Photocatalyst

AbstractThe development of efficient heterostructures combining covalent organic frameworks (COFs) and ideal semiconductors can significantly improve photocatalytic performance for pollutant degradation. Herein, we present the design, synthesis, and characterization of a core‐shell‐structured nanocomposite comprising covalent triazine framework‐encased Fe3O4 magnetic particles employed as a heterojunction photocatalyst for activating peroxymonosulfate (PMS) in phenol degradation. The distinctive internal structure between the TpMa shell (Tp=2,4,6‐trihydroxy‐1,3,5‐benzenetricarboxaldehyde, Ma=melamine) and the Fe3O4 core (Fe3O4@TpMa) facilitated charge transfer and accelerated charge separation. Furthermore, PMS served as an electron acceptor, enhancing photogenerated charge separation and maximizing the production of reactive oxygen species. The Fe3O4@TpMa/PMS system demonstrated remarkable photocatalytic performance and stability, achieving complete phenol degradation (10 mg L−1) in 40 min. The exceptional photocatalytic activity resulted from the synergistic effect of ⋅OH, SO4⋅−, O2⋅−, 1O2, and h+ generated in the Fe3O4@TpMa/PMS system during the degradation process. Overall, this material offers excellent potential for solar‐driven pollutant degradation and enables the development of COF‐based materials for wastewater treatment applications.

Obtaining and research of the properties of magnetic-luminescent hybrid structures based on iron oxide (Fe<sub>3</sub>O<sub>4</sub>) with semiconductor shells

The high-temperature organic synthesis of hydrophobic superparamagnetic nanocomposites of the Fe3O4/ZnS and Fe3O4/ZnSe core–shell type is discussed. An analysis of the absorption, luminescence, magnetic circular dichroism (MCD) and morphology spectra of hydrophobic magnetoluminescent nanocomposites is presented. It is shown that nanocomposites have luminescent properties, and the growth of the shell on the Fe3O4 core retains the magnetic properties of the particles. An analysis of the MCD spectra shows that the magnetic field induces spin-dependent chiral magneto-optical activity. An estimate of the dependence of the g factor on the magnitude and sign of the external magnetic field demonstrates a change in the magnetization of the resulting nanocomposites relative to Fe3O4.

Facile Synthesizing Yolk-Shelled Fe3O4@Carbon Nanocavities with Balanced Physiochemical Synergism as Efficient Hosts for High-Performance Lithium–Sulfur Batteries

The severe “shuttle effect” of dissolved polysulfide intermediates and the poor electronic conductivity of sulfur cathodes cause capacity decay of lithium–sulfur batteries and impede their commercialization. Herein, we synthesized a series of well-designed yolk-shelled Fe3O4@carbon (YS-Fe3O4@C) nanocavities with different proportions of Fe3O4 as efficient sulfur hosts to stabilize polysulfide intermediates. The yolk-shelled nanocavity architectures were prepared through a facile method, which could effectively confine the active materials and achieve high conductivity. The polysulfide intermediate shuttle was successfully suppressed by a physiochemical synergism effect combining the retention of carbon shells and the adsorption of Fe3O4 nanoparticle cores. The highly conductive carbon shell provides efficient pathways for fast electron transportation. Meanwhile, the visible evolution of active materials and a reversible electrochemical reaction are revealed by in situ X-ray diffraction. With the balanced merits of enhanced electrical conductivity of carbon shell and optimal adsorption of Fe3O4 cores, the S/YS-27Fe3O4@C cathode (Fe3O4 accounts for 27 wt% in YS-Fe3O4@C) had the best electrochemical performance, exhibiting a high reversible specific capacity of 731.9 mAh g−1 and long cycle performance at 1 C (capacity fading rate of 0.03% over 200 cycles).

Design and synthesis of novel Pt/Fe3O4@SiO2@WO3 magnetic core/shell microspheres for solar light driven photocatalytic production of hypochlorous acid

Visible light catalysis technology is a potential environment-friendly marine antifouling technology. However, most photocatalytic antifouling agents are based on a free radical mechanism and are difficult to recycle. To address this problem, we reported the design and assembly of Pt/Fe3O4@SiO2@WO3 with a novel core@double shell structure. Pt/WO3 is the outermost shell layer used for photocatalytic reactions. Benefiting from the existence of the most central Fe3O4 core, the magnetic recovery can be easily achieved. As an intermediate layer, SiO2 can effectively block the electron transfer between WO3 and Fe3O4, avoiding loss of photocatalytic activity. Pt/Fe3O4@SiO2@WO3 can produce 6.31 μM HClO in a simulated seawater medium under visible light irradiation for 2 h and achieves efficient recovery under an applied magnetic field. This strategy shows us a new idea for the construction of photocatalytic antifouling materials and has an important guiding role for the marine antifouling application of photocatalytic technology.

Preparation of paramagnetic ferroferric oxide-calcined layered double hydroxide core–shell adsorbent for selective removal of anionic pollutants

Adsorption is one of the most common methods of pollution treatment. The selectivity for pollutants and recyclability of adsorbents are crucial to reduce the treatment cost. Layered double hydroxide (LDH) materials are one type of adsorbent with poor recyclability. Prussian blue (PB) is a sturdy and inexpensive metal–organic framework material that can be used as the precursor for synthesizing paramagnetic ferroferric oxide (Fe3O4). It is intriguing to build some reusable adsorbents with magnetic separation by integrating LDH and PB. In this work, paramagnetic Fe3O4-calcined LDH (Fe3O4@cLDH) core–shell adsorbent was designed and prepared by the calcination of PB-ZnAl layered double hydroxide (PB@LDH) core–shell precursor, which exhibits high anionic dyes selectivity in wastewater solutions. The paramagnetism and adsorption capability of Fe3O4@cLDH come from the Fe3O4 core and calcined ZnAl-LDH shell, respectively. Fe3O4@cLDH shows an adsorption capacity of 230 mg g−1 for acid orange and a high selectivity for anionic dyes in cation–anion mixed dye solutions. The regeneration process indicates that the high selectivity for anions is related to the specific hydration recovery process of ZnAl-LDH. The synergistic effect of the paramagnetic Fe3O4 core and calcined ZnAl-LDH shell makes Fe3O4@cLDH an excellent magnetic separation adsorbent with high selectivity to anions.

Magnetic dendritic KCC-1 nanosphere-supported cobalt composite as a separable catalyst for hydrogen generation from NaBH4 hydrolysis

The introduction of magnetism into a catalyst can greatly optimize its separation performance. In the present work, a kind of magnetically separable catalysts for promoting NaBH4 hydrolysis have been fabricated by anchoring cobalt nanoparticles on magnetic dendritic KCC-1 nanospheres composed of magnetic Fe3O4 core and fibrous shell. The fabricated catalysts were characterized with various characterization methods, including absorption spectroscopy (AAS), scanning electron microscopy (SEM), high-resolution transmission electronic microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometry (VSM), and Fourier transform infrared (FT-IR), etc. This kind of catalysts exhibit high catalytic activity for promoting the hydrolysis of NaBH4 under alkaline conditions, giving a hydrogen generation rate and activation energy of 3.83 L min−1 gCo−1 (30 °C) and 53.63 kJ mol−1, respectively. After used for 5 cycles, the catalyst showed 36.5% catalytic activity reserved. Most importantly, the magnetism of the catalyst made it easily separated and recycled from the solution after the reaction completed. The development of this kind of catalysts could provide a promising option for catalyzing NaBH4 hydrolysis for portable hydrogen production from.

Multimodal Radiobioconjugates of Magnetic Nanoparticles Labeled with 44Sc and 47Sc for Theranostic Application

This study was performed to synthesize multimodal radiopharmaceutical designed for the diagnosis and treatment of prostate cancer. To achieve this goal, superparamagnetic iron oxide (SPIO) nanoparticles were used as a platform for targeting molecule (PSMA-617) and for complexation of two scandium radionuclides, 44Sc for PET imaging and 47Sc for radionuclide therapy. TEM and XPS images showed that the Fe3O4 NPs have a uniform cubic shape and a size from 38 to 50 nm. The Fe3O4 core are surrounded by SiO2 and an organic layer. The saturation magnetization of the SPION core was 60 emu/g. However, coating the SPIONs with silica and polyglycerol reduces the magnetization significantly. The obtained bioconjugates were labeled with 44Sc and 47Sc, with a yield higher than 97%. The radiobioconjugate exhibited high affinity and cytotoxicity toward the human prostate cancer LNCaP (PSMA+) cell line, much higher than for PC-3 (PSMA-) cells. High cytotoxicity of the radiobioconjugate was confirmed by radiotoxicity studies on LNCaP 3D spheroids. In addition, the magnetic properties of the radiobioconjugate should allow for its use in guide drug delivery driven by magnetic field gradient.

Drastic performance enhancement of photoluminescence and water electrolysis by local-magnetic-field-assisted LSPR of Ag NPs and NCs

A novel method is presented for drastically improving the local surface plasma resonance (LSPR) effect of noble metal nanoparticles (NPs) and nanoclusters (NCs). This is realized by magnetizing particles comprising a ferrimagnetic core and a noble metal nanoshell. In this study, we prepared Fe3O4 @SiO2 @Ag composite particles. Ag NPs and NCs had the size of 10–15 nm and 2–3 nm, respectively. The photoluminescence (PL) intensities of ZnO and YAG:Ce substrates coated with the magnetic composite particles increased by 160 % and 50 %, respectively, after magnetization under a magnetic field of 18 mT compared to the unmagnetized state. The activity of Ni-foam-based-Fe3O4 @SiO2 @Ag working electrode for water electrolysis was also significantly improved after magnetization. The increasing rate of current density after magnetization was 226 mA∙cm−2/0.1 V, which is higher than 158 mA∙cm−2/0.1 V before the magnetization. The mechanism for drastic performance enhancement of PL and water electrolysis postulates that after magnetization, the remanence of the ferrimagnetic Fe3O4 core provides a local magnetic field to strengthen the local electric field in the confined area of Ag NPs/NCs. It was confirmed by the higher intensity of peaks in Raman spectroscopy and contributed to the enhancement of LSPR effect. This efficient and practical approach to magnetization-induced LSPR improvement has potential application prospects in LSPR-related fields.

Mesoporous core/shell MnFe2O4 nanocomposite derived from facile sonoelectrochemical process: An eco-friendly method for rapid synthesis and versatile industrial applications

Background: Replacing the current usage of toxic, hazardous, irreversible materials in existing industrial production for various applications into eco-friendly material with easy availability and finding an economic synthesis method with structure tunable properties to produce effective magnetic nanocomposite are still need to be developed for advanced chemical technology. Methods: Mesoporous core/shell MnFe2O4 nanocomposite have been synthesized in this report at 15 min using a facile, eco-friendly sonoelectrochemical process. Significant findings: The presence of manganese over magnetite (Fe3O4) was confirmed through FTIR, XRD, elemental mapping and EDS studies. The size and shape of the nanocomposite were analyzed from FESEM and HRTEM analyses. It was revealed that the synthesized nanocomposites are spherical in shape and have an average diameter of 65±10 nm with 10±2 nm shell thickness. Encapsulating manganese over core Fe3O4 nanoparticles had improved the thermal stability up to 7% than the mere Fe3O4 which was confirmed by thermogravimetry analysis. The BET analysis had revealed that the sonoelectrochemically synthesized nanocomposites are having higher surface area of 385.7 m2 g-1 and possess a mesoporous nature with a mean pore diameter of 1.90 nm. Based on these superior properties, the core/shell MnFe2O4 nanocomposite could be utilized as a promising material towards various industrial applications such as heavy metal removal, hydrogen production, hyperthermia, Li-ion battery, drug delivery, catalysis, and sensor applications.

SERS-based recyclable immunoassay mediated by 1T-2H mixed-phase magnetic molybdenum disulfide probe and 2D graphitic carbon nitride substrate

Recently, non-metallic SERS-based immunoassay has attracted much attention due to its attractive chemical enhancement (CM), chemical stability, and biocompatibility. Herein, metallic (1T)-semiconductor (2H) mixed-phase magnetic molybdenum disulfide (MoS2) was rationally developed and combined with two-dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheets to realize a SERS-based recyclable immunoassay of CA125. The Fe3O4 core promoted the reliable stacking of MoS2 nanoflakes into a flower-like shape with fully-exposed active surface. Particularly, the existence of 1T phase facilitated a noble-metal-comparable SERS activity due to the high electron density-induced charge transfer process with elevated efficiency. Moreover, a conversion from bulk to 2D nanosheet was swimmingly achieved for g-C3N4 via acid etching, whose large surface area full of active electrons and functional groups triggered an enhancement factor (EF) of 7.8 × 106. Based on a typical sandwich immunostructure, a limit of detection (LOD) as 4.96 × 10−4 IU/mL was demonstrated for CA125 in a recyclable process. Finally, such an immunosensor was employed to analyze clinical samples, indicating its prodigious potentiality in the early recognition and monitoring of cancer.

Effective removal of hexavalent chromium with magnetically reduced graphene oxide bentonite

AbstractWater pollution by hexavalent chromium (Cr(VI)) is widespread and problematic. As a result, more research into economic Cr(VI) removal is needed. In this study, we created and employed an adsorption–reduction mechanism to remove Cr(VI). Magnetically reduced graphene oxide bentonite (MrGO-BT) is acid resistant and can undergo magnetic separation. The hydroxyl group of chitosan (CS) condensed with the functional groups on the surface of bentonite (BT), and the MrGO-BT sandwich has been fabricated and constructed from an Fe3O4 core layer sandwiched by reduced graphene oxide (rGO) and a BT shell, with CS acting as a crosslinker. Cr(VI) elimination by MrGO-BT was exothermic and spontaneous according to thermodynamic analyses. The adsorption kinetics and adsorption isotherms were characterized by the pseudo-second order kinetic theory and the Langmuir model, respectively. Regarding the elimination of Cr(VI), the greatest adsorption ability for Cr(VI) elimination achieved was 91.5 mg g–1. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy suggested that Cr(VI) was reduced by C–O–H on MrGO-BT to produce Cr(III) and H–C=O, and that Cr(III) chelated with amino groups or exchanged with BT after intercalation. In addition, the introduction of Cu2+ increased the positive charge of MrGO-BT and amplified the electrostatic interaction between Cr2O72− and HCrO4–, which is what caused Cr(VI) to be eliminated. Cu2+ and reduced Cr(III) combined with -NH2 on the surface of MrGO-BT to form -NH-Cr(III) or -NH-Cu2+, and Cr(VI) elimination via chelation and ion exchange was confirmed. MrGO-BT is shown to be an adsorbent with high acid resistance and good magnetic responsiveness and stability.

Dual-pathway optimization on microwave absorption characteristics of core–shell Fe3O4@C microcapsules: Composition regulation on magnetic core and MoS2 nanosheets growth on carbon shell

Core-shell Fe3O4@C composites with unique configuration and complementary loss mechanisms are widely considered as a kind of prospective functional materials in the field of microwave absorption. However, the balance between core–shell configuration and intrinsic loss is always a thorny problem on the way of good microwave absorption characteristics. Herein, we propose a dual-pathway optimization strategy to consolidate the electromagnetic functions of core–shell Fe3O4@C microcapsules for the first time. On one hand, the chemical composition of magnetic core is finely regulated from Fe3O4 to metal Fe, and it is found that both magnetic loss and dielectric loss can be strengthened effectively through the partial reduction of Fe3O4 core. On the other hand, MoS2 nanosheets are closely anchored on the surface of carbon shell, which can bring more powerful interfacial polarization and dipole polarization to compensate the insufficient dielectric loss caused by the limited thickness and graphitization degree of carbon shell. With the multiple benefits from the dual-pathway optimization strategy, the optimal composite will present good microwave absorption performance, whose effective absorption bandwidth (EAB) and minimum RL value are 5.4 GHz (d = 1.8 mm) and −36.1 dB (5.9 GHz, 4.0 mm), respectively. In particular, its specific EABs (EAB per unit thickness) in different bands are superior to those of most microwave absorbing materials with similar chemical composition. These results demonstrate that this dual-pathway optimization will open a new avenue to enhance microwave absorption performance of core–shell composites in the future.

Functionalized Hybrid Iron Oxide–Gold Nanoparticles Targeting Membrane Hsp70 Radiosensitize Triple-Negative Breast Cancer Cells by ROS-Mediated Apoptosis

Triple-negative breast cancer (TNBC) a highly aggressive tumor entity with an unfavorable prognosis, is treated by multimodal therapies, including ionizing radiation (IR). Radiation-resistant tumor cells, as well as induced normal tissue toxicity, contribute to the poor clinical outcome of the disease. In this study, we investigated the potential of novel hybrid iron oxide (Fe3O4)-gold (Au) nanoparticles (FeAuNPs) functionalized with the heat shock protein 70 (Hsp70) tumor-penetrating peptide (TPP) and coupled via a PEG4 linker (TPP-PEG4-FeAuNPs) to improve tumor targeting and uptake of NPs and to break radioresistance in TNBC cell lines 4T1 and MDA-MB-231. Hsp70 is overexpressed in the cytosol and abundantly presented on the cell membrane (mHsp70) of highly aggressive tumor cells, including TNBCs, but not on corresponding normal cells, thus providing a tumor-specific target. The Fe3O4 core of the NPs can serve as a contrast agent enabling magnetic resonance imaging (MRI) of the tumor, and the nanogold shell radiosensitizes tumor cells by the release of secondary electrons (Auger electrons) upon X-ray irradiation. We demonstrated that the accumulation of TPP-PEG4-FeAuNPs into mHsp70-positive TNBC cells was superior to that of non-conjugated FeAuNPs and FeAuNPs functionalized with a non-specific, scrambled peptide (NGL). After a 24 h co-incubation period of 4T1 and MDA-MB-231 cells with TPP-PEG4-FeAuNPs, but not with control hybrid NPs, ionizing irradiation (IR) causes a cell cycle arrest at G2/M and induces DNA double-strand breaks, thus triggering apoptotic cell death. Since the radiosensitizing effect was completely abolished in the presence of the ROS inhibitor N-acetyl-L-cysteine (NAC), we assume that the TPP-PEG4-FeAuNP-induced apoptosis is mediated via an increased production of ROS.

Structural and Molecular Fusion MRI Nanoprobe for Differential Diagnosis of Malignant Tumors and Follow-Up Chemodynamic Therapy.

Enhanced imaging techniques using contrast agents enable high-resolution structural imaging to reveal space-occupying lesions but rarely provide detailed molecular information. To this end, we report a structural and molecular fusion magnetic resonance imaging (MRI) nanoprobe for differential diagnosis between benign and malignant tumors. This fusion nanoprobe, termed FFT NPs, follows a working mechanism involving a T1-/T2-weighted magnetic resonance tuning effect (MRET) between a magnetic Fe3O4 core and a paramagnetic Fe-tannic acid (Fe-TA) shell. The FFT NPs with an "always-on" inert T2 signal provide structural MRI (sMRI) contrast of tumors while affording an activated T1 signal in the presence of ATP, which is overproduced during the rapid growth of malignant tumors to enable molecular MRI (mMRI) of tumor lesions. We propose the use of the ratiometric mMRI:sMRI intensity to assist in the differential diagnosis of malignant 4T1 tumors from benign L929 fibroblast tumors. Furthermore, the dissociated FFT NPs were found to be able to catalyze H2O2 conversion in 4T1 tumors to generate excess reactive oxygen species (ROS) for chemodynamic therapy. The described fusion nanoprobe strategy enables the differential diagnosis of tumors from a combined spatial and molecular perspective with one-stop MRI imaging with potential applications in precision intervention.

Introduction of multilayered magnetic core–dual shell SERS tags into lateral flow immunoassay: A highly stable and sensitive method for the simultaneous detection of multiple veterinary drugs in complex samples

Direct, convenient, and sensitive monitoring of the residues of multiple drugs in complex environments is important but remains a challenge. Here, we report a surface-enhanced Raman scattering (SERS)-based multiplexed lateral flow immunoassay (LFA) that supports the simultaneous and sensitive detection of commonly used drugs kanamycin, ractopamine, clenbuterol, and chloramphenicol in unprocessed complex samples through the dual signal amplification strategy of numerous efficient hotspots and magnetic enrichment. Multilayered magnetic-core dual-shell nanoparticles (MDAu@Ag) with controllable subtle nanogaps were fabricated via the polyethyleneimine-mediated layer-by-layer (LBL) assembly of two layers of Au@Ag satellites onto superparamagnetic Fe3O4 cores and conjugated with specific antibodies as multifunctional tags in the LFA system for rapid capture, separation, and quantitative analysis. Two Raman reporters were embedded in internal nanogaps and modified on the surface of MDAu@Ag for the simultaneous and ultrasensitive detection of four targets on two test lines, which greatly simplified the fabrication and signal reading of SERS-LFA. The proposed assay can rapidly detect multiple drug residues in 35 min with detection limits down to pg/mL level. Moreover, the MDAu@Ag–based SERS-LFA demonstrated better stability, higher throughput, and superior sensitivity (at least 400 times) than traditional colloidal gold immunochromatography, showing its great potential in the field of point-of-care testing.