Optical,magnetic and photocatalytic properties of magnetically separable Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>-doped ZnO and pristine ZnO nanospheres

This work focussed on the optical, magnetic and photocatalytic properties of sol–gel-synthesized Fe₃O₄-doped ZnO nanospheres and was compared with pristine ZnO nanospheres. The crystalline phase of Fe₃O₄-doped ZnO nanospheres was studied with X-ray diffraction analysis and was well matched with standard pattern. Surface morphology was studied with HR-SEM images and EDAX spectrum. Furthermore, elemental mapping analysis was carried out to confirm the presence of Fe₃O₄ phase in Fe₃O₄-doped ZnO nanospheres. FT-Raman spectral studies show that a strong intense peak at 670 cm^?1 indicates the presence of Fe₃O₄ in Fe₃O₄-doped ZnO nanospheres. The mean crystallite size of Fe₃O₄-doped ZnO nanospheres was 34 nm as calculated by Debye–Scherrer’s formula which confirmed with HR-TEM image. The SAED pattern shows the presence of (100), (101), (102) and (202) of ZnO phase and (400) of Fe₃O₄ phase, confirming the crystalline nature of Fe₃O₄-doped ZnO nanospheres. The vibrating sample magnetometer (VSM) result shows that Fe₃O₄-doped ZnO nanospheres possess superparamagnetic nature and the composite nanospheres are magnetically separable. The optical properties have been studied by diffuse reflectance spectroscopy and time-resolved photoluminescence spectra. Implantation of Fe₃O₄ in ZnO nanospheres modifies the UV absorption edge, and it displays near-band gap emission and deep-level emission. The photocatalytic activity of Fe₃O₄-doped ZnO nanospheres studied against rhodamine B dye is found higher than that of pristine ZnO nanospheres which shows that Fe₃O₄-doped ZnO nanospheres are a promising photocatalyst.     

可回收Fe3O4@SiO2-Ag磁性纳米微球对染料污染物的快速脱色处理

介绍了一种采用无毒廉价的前驱物制备Fe₃O₄@SiO₂-Ag磁性纳米微球的快捷方法,制备的Fe₃O₄@SiO₂-Ag纳米微球在NaBH₄存在下可以催化还原染料污染物.实验结果表明,Fe₃O₄@SiO₂-Ag磁性纳米粒子保持了Ag纳米粒子和Fe₃O₄纳米粒子的双重优点,不仅对染料罗丹明B和曙红Y具有良好的催化还原效率,而且可以在外加磁场作用下从溶液中快速有效的分离.催化还原反应速率与反应温度及Fe₃O₄@SiO₂-Ag催化剂用量有关,反应体系中表面活性剂和无机盐(Na₂SO₄)的存在也会影响催化剂的催化活性.该Fe₃O₄@SiO₂-Ag磁性纳米粒子在工业染料污染物处理方面具有应用前景.     

Liposome-Boosted Peroxidase-Mimicking Nanozymes Breaking the pH Limit

Peroxidase-mimicking nanozymes such as Fe₃O₄ nanoparticles are promising substitutes for natural enzymes like horseradish peroxidase. However, most such nanozymes work efficiently only in acidic conditions. In this work, the influence of various liposomes on nanozyme activity was studied. By introducing negatively charged liposomes, peroxidase-mimicking nanozymes achieved oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in neutral and even alkaline conditions, although the activity towards anionic 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) was inhibited. The Fe₃O₄ nanoparticles adsorbed on the liposomes without disrupting membrane integrity as confirmed by fluorescence quenching, dye leakage assays, and cryo-electron microscopy. Stabilization of the blue-colored oxidized products of TMB by electrostatic interactions was believed to be the reason for the enhanced activity. This work has introduced lipids to nanozyme research, and it also has practically important applications for using nanozymes at neutral pH, such as the detection of hydrogen peroxide and glucose.     

Nitrogen‐Enriched Fe3O4@Carbon Nanospheres Derived from Fe3O4@3‐Aminophenol/Formaldehyde Resin Nanospheres Based on a Facile Hydrothermal Strategy: Towards a Robust Catalyst Scaffold for Platinum Nanocrystals

Robust nitrogen‐enriched Fe₃O₄@carbon nanospheres have been fabricated as a catalyst scaffold for Pt nanoparticles. In this work, core–shell Fe₃O₄@3‐aminophenol/formaldehyde (APF) nanocomposites were first synthesized by a simple hydrothermal method, and subsequently carbonized to Fe₃O₄@N‐Carbon nanospheres for in situ growth of Pt nanocrystals. Abundant amine groups were distributed uniformly onto Fe₃O₄@N‐Carbon nanospheres, which not only improved the dispersity and stability of the Pt nanocrystals, but also endowed the Pt‐based catalysts with good compatibility in organic solvents. The dense three‐dimensional cross‐linked carbon shell protects the Fe₃O₄ cores against damage from harsh chemical environments, even in aqueous HCl (up to 1.0 m ) or NaOH (up to 1.0 m ) solutions under ultrasonication for 24 hours, which indicates that it can be used as a robust catalyst scaffold. In the reduction of nitrobenzene compounds, the Fe₃O₄@N‐Carbon@Pt nanocatalysts show outstanding catalytic activity, stability, and recoverability.     

Modification and application of Fe3O4 nanozymes in analytical chemistry: A review

In recent years, Fe₃O₄ nanomaterials have received much attention in analytical chemistry due to their excellent magnetic and peroxidase-like activity. As the catalytic characteristics of Fe₃O₄ nanomaterials is similar to those of horseradish peroxidase (HRP), Fe₃O₄ nanomaterials are also used as peroxidase mimics and have achieved a certain development in many fields based on latest research results. To improve the stability and catalytic ability of simple Fe₃O₄ nanomaterials, various modification strategies of Fe₃O₄ nanomaterials have been developed. The recent advances of these strategies have been presented and discussed. In addition, this paper introduces the application of Fe₃O₄ nanozymes in the detection of food and industrial pollutants, as well as in the field of biosafety.     

Preparation of Epoxy-Functionalized Magnetic Polymer Nanospheres for Magnetically Targeted Radiotherapy

Magnetic poly(styrene?methyl methacrylate-glycidyl methacrylate)/Fe₃O₄ nanospheres with epoxy groups were prepared by modified one-step mini-emulsion polymerization in the presence of Fe₃O₄ ferrofluids. The products were characterized by fourier-transform infrared spectrum, transmission electron microscopy, thermogravimetric analysis and vibrating sample magnetometer. After surface modification with diaminopropane, histidine was covalently linked to the amine group of magentic nanospheres using glutaraldehyde as crosslinker. Finally, the preliminary labeling study based on non-radioactive rhenium was carried out and the labeling efficiency reached 80.4%. Such magnetic nanospheres had promising potential in magnetically targeted radiotherapy of cancer.     

Sensitive electrochemical immunoassay for chlorpyrifos by using flake-like Fe3O4 modified carbon nanotubes as the enhanced multienzyme label

A highly sensitive electrochemical immunoassay of chlorpyrifos (CPF) was developed by using a biocompatible quinone-rich polydopamine nanospheres modified glass carbon electrode as the sensor platform and multi-horseradish peroxidase-flake like Fe₃O₄ coated carbon nanotube nanocomposites as the signal label. Due to the quinone-rich polydopamine nanospheres, the platform exhibited excellent fixing capacity by simple coating of sticky polydopamine nanospheres and subsequent oxidization. By coprecipitation of Fe³⁺ and Fe²⁺ on polydopamine modified carbon nanotubes (CNTs) with the aid of ethylene glycol (EG), the flake-like Fe₃O₄ coated CNTs (CNTs@f-Fe₃O₄) were synthesized and chosen as the carrier of multi-enzyme label due to the high loading of secondary antibody (Ab₂) and horseradish peroxidase (HRP) and also the peroxidase-mimic activity of Fe₃O₄. Under the optimum conditions, the immunosensor can detect CPF over a wide range with a detection limit of 6.3 pg/mL. Besides, the high specificity, reproducibility and stability of the proposed immunosensor were also proved. The preliminary application in real sample showed good recoveries, indicating it holds promise for fast analysis of CPF in aquatic environment.     

Surface molecular imprinting on g-C3N4 photooxidative nanozyme for improved colorimetric biosensing

Graphitic carbon nitride (g-C₃N₄), as a visible-light-active organic semiconductor, has attracted growing attentions in photocatalysis and photoluminescence-based biosensing. Here, we demonstrated the intrinsic photooxidase activity of g-C₃N₄ and then surface molecular imprinting on g-C₃N₄ nanozymes was achieved for improved biosensing. Upon blue LED irradiation, the g-C₃N₄ exhibited superior enzymatic activity for oxidation of chromogenic substrate like 3,3′,5,5′-tetramethylbenzidine (TMB) without destructive H₂O₂. The oxidation was mainly ascribed to O₂⁻ that was generated during light irradiation. The surface molecular imprinting on g-C₃N₄ can lead to an over 1000-fold alleviation in matrix-interference from serum samples, 4-fold improved enzymatic activity as well as enhanced substrate specificity comparing with bare g-C₃N₄ during colorimetric sensing. Also, the MIP-g-C₃N₄ possesses a high affinity to TMB with a K_m value of only 22 μmol/L, much lower than other comment nanozymes like AuNPs, Fe₃O₄ NPs, etc. It was successfully applied for detection of cysteine in serum sample with satisfactory recoveries.     

双功能化磁性纳米修复剂对多重金属的快速、高效钝化行为

采用“一锅法”制备了四氧化三铁/半胱氨酸（Fe₃O₄/Cys）磁性纳米微球,随后对Fe₃O₄/Cys进行亚氨基二乙酸（IDA）修饰得到Fe₃O₄/Cys/IDA磁性双功能化纳米微球。研究发现Fe₃O₄/Cys中的L-Cys是通过—SH基团接枝到Fe₃O₄表面的,随后IDA分子中的羧基与Fe₃O₄/Cys中的—NH₂形成酰胺键,最终形成多支链多羧基的Fe₃O₄/Cys/IDA磁性纳米修复剂。基于修复剂表面短支链-长支链交替的多羧基结构,实现了羧基基团的高密度接枝。同时,Fe₃O₄/Cys/IDA磁性纳米微球对Pb²⁺、Cd²⁺、Cu²⁺、Co²⁺、Ni²⁺、Zn²⁺为专性吸附,而对Hg²⁺属于非专性吸附,且吸附重金属后得到的钝化产物均表现了良好的稳定性。另外,Fe₃O₄/Cys/IDA对重金属离子的吸附符合Langmuir模型,属于单层均相吸附,其吸附过程符合准二级动力学模型,最大吸附量为49.05 mg·g^-1。     

多孔朵状Fe_3O_4纳米微球的制备及其性能研究

<正>众所周知,纳米材料的尺寸大小、晶型、形貌构型等结构特征对材料的化学物理性能有重要的影响[1],由于特殊形貌的新材料所具有独特、新颖、高效的化学物理等方面的性质以及在众多领域中的潜在应用[2],特别是3D花状空心纳米结构新物质[3-4],新形貌物质的纳米材料的制备方法和应用特性已经吸引了世界上材料领域的广泛兴趣和关注[5]。目前为止,合成3D纳米结构的方法有自组装法、三维导向连接法以及水热法等,即通过使用有     

Facile synthesis of Fe3O4@C hollow nanospheres and their application in polluted water treatment

Nanostructured carbon-based materials, such as carbon nanotube arrays have shown respectable removal ability for heavy metal ions and organic dyes in aqueous solution. Although the carbon-based materials exhibited excellent removal ability, the separation of them from the aqueous solution is difficult and time-consuming. Here we demonstrated a novel and facile route for the large-scale fabrication of Fe₃O₄@C hollow nanospheres, with using ferrocene as a single reagent and SiO₂ as a template. The as-prepared Fe₃O₄@C hollow nanospheres exhibited adsorption ability for heavy metal ions and organic dyes from aqueous solution, and can be easily separated by an external magnet. When the as-prepared Fe₃O₄@C hollow nanospheres were mixed with the aqueous solution of Hg²⁺ within 15 min, the removal efficiency was 90.3%. The as-prepared Fe₃O₄@C hollow nanospheres were also exhibited a high adsorption capacity (100%) as the adsorbent for methylene blue (MB). In addition, the as-prepared Fe₃O₄@C hollow nanospheres can be used as the recyclable sorbent for water treatment via a simple magnetic separation.     

Facile synthesis of Fe3O4/reduced graphene oxide/polyvinyl pyrrolidone ternary composites and their enhanced microwave absorbing properties

In this paper, ternary nanocomposites of Fe₃O₄/reduced graphene oxide/polyvinyl pyrrolidone (Fe₃O₄/rGO/PVP) as a novel type of electromagnetic microwave absorbing materials were synthesized by a three-step chemical approach. First, Fe₃O₄ nanospheres were made by solvent thermal method. Successively, the Fe₃O₄ particles were assembled with rGO after having activated by para-aminobenzoic acid. PVP grafting and reduction of GO happened simultaneously in the third step. It is found that the electromagnetic absorption (EA) performance of synthesized ternary composites with suitable PVP amount had been significantly enhanced comparing to Fe₃O₄ and Fe₃O₄/rGO. Merely 15?wt% low loading in paraffin and thin as 2.8?mm can reach effective EA bandwidth (below ?10 Db) of 11.2?GHz, and the highest reflection loss reached ?67?dB at 10.7?GHz. It was demonstrated that these composites show an effective route to novel microwave absorbing material design.     

Polypyrrole Nanospheres with Magnetic and Cell‐Targeting Capabilities

The preparation of polypyrrole/Fe₃O₄ nanospheres by a facile mini‐emulsion polymerization method is investigated using poly(ethylene glycol), poly(ethylene oxide), poly(vinyl alcohol), and hyaluronic acid as surfactants. Hyaluronic acid is deemed the most suitable surfactant since it results in well‐dispersed nanospheres of 80–100 nm, and offers the advantages of biocompatibility, cell adhesive property, and the availability of functional groups for attachment of other molecules. These polypyrrole/Fe₃O₄ nanospheres are magnetic and can be further functionalized with a cancer antibody, herceptin. Our results show that this combination of hyaluronic acid and herceptin results in high specific uptake of the nanospheres by cancer cells.

     

One‐Pot Synthesis of Pomegranate‐Structured Fe3O4/Carbon Nanospheres‐Doped Graphene Aerogel for High‐Rate Lithium Ion Batteries

A unique hierarchically nanostructured composite of iron oxide/carbon (Fe₃O₄/C) nanospheres‐doped three‐dimensional (3D) graphene aerogel has been fabricated by a one‐pot hydrothermal strategy. In this novel nanostructured composite aerogel, uniform Fe₃O₄ nanocrystals (5–10 nm) are individually embedded in carbon nanospheres (ca. 50 nm) forming a pomegranate‐like structure. The carbon matrix suppresses the aggregation of Fe₃O₄ nanocrystals, avoids direct exposure of the encapsulated Fe₃O₄ to the electrolyte, and buffers the volume expansion. Meanwhile, the interconnected 3D graphene aerogel further serves to reinforce the structure of the Fe₃O₄/C nanospheres and enhances the electrical conductivity of the overall electrode. Therefore, the carbon matrix and the interconnected graphene network entrap the Fe₃O₄ nanocrystals such that their electrochemical function is retained even after fracture. This novel hierarchical aerogel structure delivers a long‐term stability of 634 mA h g^?1 over 1000 cycles at a high current density of 6 A g^?1 (7 C), and an excellent rate capability of 413 mA h g^?1 at 10 A g^?1 (11 C), thus exhibiting great potential as an anode composite structure for durable high‐rate lithium‐ion batteries.     

Highly efficient and green oxidation of alkanes and alkylaromatics with hydrogen peroxide catalysed by silver and vanadyl on mesoporous silica‐coated magnetite

A heterogeneous catalyst (FeSi/Ag/VO) based on silver and vanadyl as active sites and mesoporous silica‐coated nanospheres of magnetite (Fe₃O₄@m‐SiO₂) as support was successfully prepared by deposition of Ag nanoparticles and the covalent grafting of vanadyl(IV) acetylacetonate on Fe₃O₄@m‐SiO₂. The catalyst exhibited excellent activity for the oxidation of alkanes, benzene and alkylaromatics using green oxidant H₂O₂ and oxalic acid in acetonitrile at 60 °C.     

Investigation of anti-human ovarian cancer effects of decorated Au nanoparticles on Thymbra spicata extract modified Fe3O4 nanoparticles

This work describes an eco-friendly approach for in situ immobilization of Au nanoparticles on the surface of Fe₃O₄ nanoparticles, with the help of Thymbra spicata extract and ultrasound irradiations, without using any toxic reducing and capping agents. The combination of Fe₃O₄ NPs and Au NPs in one hybrid nanostructure (Fe₃O₄@Thymbra spicata/Au NPs) represents a promising strategy for targeted biomedical applications. The structure, morphology, and physicochemical properties were characterized by various analytical techniques such as fourier transformed infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), inductively coupled plasma (ICP) and vibrating sample magnetometer (VSM). MTT assay was used on common ovarian cancer cell lines i.e., SW-626, PA-1, and SK-OV-3 to survey the cytotoxicity and anti-ovarian cancer effects of Fe₃O₄@Thymbra spicata/Au NPs. The best results of cytotoxicity and anti-ovarian cancer properties were seen in the concentration of 1000 µg/mL. Fe₃O₄@ Thymbra spicata/Au NPs had very low cell viability and high anti-ovarian cancer activities dose-dependently against PA-1, SW-626, and SK-OV-3 cell lines without any cytotoxicity on the normal cell line (HUVEC). For investigating the antioxidant properties of Fe₃O₄@ Thymbra spicata/Au NPs, the DPPH test was used in the presence of butylated hydroxytoluene as the positive control. Fe₃O₄@Thymbra spicata/Au NPs inhibited half of the DPPH molecules in the concentration of 107 µg/mL. Maybe significant anti-human ovarian cancer potentials of Fe₃O₄@Thymbra spicata/Au NPs against common human ovarian cancer cell lines are linked to their antioxidant activities. After confirming the above results in the clinical trial researches, this formulation can be administrated for the treatment of several types of human ovarian cancers in humans.     

Deposition of PdPtAu Nanoparticles on Hollow Nanospheres of Fe3O4 as a New Catalyst for Methanol Electrooxidation: Application in Direct Methanol Fuel Cell

In this study, immobilized hollow nanospheres of Fe₃O₄ with Palladium, Platinum and Gold nanoparticles (Fe₃O₄HNS‐PdPtAuNPs) was synthesized by hydrothermal and chemical reduction methods and characterized by various techniques such as field emission scanning electron microscopy, energy dispersive analysis of X‐rays and elemental mapping images. The electrocatalytic activity of the modified glassy carbon electrode (GCE) with Fe₃O₄HNS‐PdPtAuNPs (GCE/Fe₃O₄HNS‐PdPtAuNPs) toward methanol electrooxidation was investigated by cyclic voltammetry and chronoamperometry in 1 M NaOH solution. According to the results, Fe₃O₄HNS‐PdPtAuNPs catalyst demonstrated the highest efficiency for methanol electrooxidation in comparison with Fe₃O₄HNS‐PdNPs, Fe₃O₄HNS‐PtNPs, Fe₃O₄HNS‐PdAuNPs, Fe₃O₄HNS‐PtAuNPs and Fe₃O₄HNS‐PdPtNPs. The value of electron transfer coefficient (α ) and the ratio of current densities (I_f /I_b ) for methanol oxidation on the Fe₃O₄HNS‐PdPtAuNPs/GC catalyst were calculated 0.61 and 5.13, respectively. The reaction order was discovered to be 0.98 for CH₃OH. A direct methanol fuel cell was developed with the suggested catalyst under several conditions.     

Ferric Ion Driven Assembly of Catalase-like Supramolecular Photosensitizing Nanozymes for Combating Hypoxic Tumors

A facile approach to assemble catalase-like photosensitizing nanozymes with a self-oxygen-supplying ability was developed. The process involved Fe³⁺-driven self-assembly of fluorenylmethyloxycarbonyl (Fmoc)-protected amino acids. By adding a zinc(II) phthalocyanine-based photosensitizer (ZnPc) and the hypoxia-inducible factor 1 (HIF-1) inhibitor acriflavine (ACF) during the Fe³⁺-promoted self-assembly of Fmoc-protected cysteine (Fmoc-Cys), the nanovesicles Fmoc-Cys/Fe@Pc and Fmoc-Cys/Fe@Pc/ACF were prepared, which could be disassembled intracellularly. The released Fe³⁺ could catalyze the transformation of H₂O₂ enriched in cancer cells to oxygen efficiently, thereby ameliorating the hypoxic condition and promoting the photosensitizing activity of the released ZnPc. With an additional therapeutic component, Fmoc-Cys/Fe@Pc/ACF exhibited higher in vitro and in vivo photodynamic activities than Fmoc-Cys/Fe@Pc, demonstrating the synergistic effect of ZnPc and ACF.     

Gold nanoparticles as dehydrogenase mimicking nanozymes for estradiol degradation

Nanozyme catalysis has been mainly focused on a few chromogenic and fluorogenic substrates, while environmentally and biologically important compounds need to be tested to advance the field. In this work, we studied oxidation of estradiol (E2) in the presence of various nanomaterials including gold nanoparticles (AuNPs), nanoceria (CeO₂), Fe₃O₄, Fe₂O₃, MnO₂ and Mn₂O₃, and found that AuNPs had a dehydrogenase-mimicking activity to convert E2 to estrone (E1). This conversion was monitored using HPLC. The reaction was faster at higher pH and reached saturation at pH 8. Smaller AuNPs had a higher catalytic efficiency and 5 nm AuNPs were 4.8-fold faster than 13 nm at the same total surface area. Finally, we tried 17α-ethinylestradiol (EE2) as a substrate and found that 5 nm AuNPs can catalyze EE2 oxidation in the presence of H₂O₂. This work indicated that some nanomaterials can affect environmentally important hormones via oxidation reactions, and this study has expanded the scope of substrate of nanozymes.     

Green supported Cu nanoparticles on modified Fe3O4 nanoparticles using thymbra spicata flower extract: Investigation of its antioxidant and the anti-human lung cancer properties

In recent days, the green synthesized nanomagnetic biocomposites have been evolved with tremendous potential as the future biological agents. This has encouraged us to design and synthesis of a novel Cu NPs supported Thyme flower extract modified magnetic nanomaterial (Fe₃O₄/Thyme-Cu). It was meticulously characterized using advanced analytical techniques like FT-IR, FESEM, TEM, EDX, VSM, XRD and ICP-OES. After the characterization, the synthesized Fe₃O₄/Thyme-Cu nanocomposite was engaged in biological assays like study of anti-oxidant properties by DPPH mediated free radical scavenging test using BHT as a reference molecule. Thereafter, on having a significant IC50 value in radical scavenging assay, we extended the bio-application of the desired nanocomposite in anticancer study of A549, Calu6 and H358 human lung cell lines in-vitro through MTT assay. They had very low cell viability and high anti-human lung cancer activities dose-dependently against A549, Calu6 and H358 cell lines without any cytotoxicity on the normal cell line (MRC-5). The IC50 of Fe₃O₄/Thyme-Cu nanocomposite was 124, 265, and 181 µg/mL against A549, Calu6 and H358 cell lines, respectively. Maybe significant anti-human lung cancer potentials of Fe₃O₄/Thyme-Cu nanocomposite against common lung cancer cell lines are related to their antioxidant activities. So, these results suggest that synthesized Fe₃O₄/Thyme-Cu nanocomposite as a chemotherapeutic nanomaterial have a suitable anticancer activity against lung cell lines.