O4 Nanoparticles Research Articles

Magnetism and magnetic phase transition in nanowires of diamagnetically diluted superstrong magnets ε-In<sub>0.04</sub>Fe<sub>1.96</sub>O<sub>3</sub>

The temperature dependences of the magnetization of ε-In0.04Fe1.96O3 nanoparticles were measured in the cooling and heating regimes. At a temperature of 150 K, a sharp drop in their magnetization is observed. Evidence is obtained that the observed magnetic phase transition is accompanied by a reversal of the magnetization due to a first-order spin-reorientation transition. The experimental results are described in terms of the thermodynamic approach.

Electrophoretic Deposition and Physicochemical Properties of Ni- and Fe-Doped Cu–Mn Spinel Coatings Enhanced with Ce0.9Y0.1O2 Nanoparticles on Fe16Cr Ferritic Stainless Steel Interconnects for SOEC Applications

AbstractCu- and Mn-based spinel coatings are currently among the most promising materials for solid oxide electrolyzer cell (SOEC) interconnects due to their high electrical conductivity and ability to eliminate environmentally hazardous cobalt, which is included in the most widely used coatings. However, their properties are affected by the presence of the Cr2O3 scale and high-temperature corrosion, and to mitigate this they could be doped with elements such as Ni and Fe. In addition, the electrical properties of such steel/shell layered systems can be further improved using rare-earth element nanoparticles (Ce0.9Y0.1O2). In this work, low-chromium steel was modified using nanoparticles and/or spinel coatings and oxidized in air atmosphere at 800 °C for 2000 hours. The oxidized systems were then characterized using diffraction studies, microstructural observations and electrical measurements. Electrical studies in particular showed a significant reduction in area-specific resistance for steels modified using a combination of both nanoparticles and spinel coatings.

Advanced synthesis and forensic application of CoPr(x)Cr(2-x)O4 nanoparticles for latent fingerprint detection

The production, characterisation, and use of CoPr(x)Cr(2-x)O4 (x = 0.00, 0.01, 0.03, and 0.05) nanoparticles for improved latent fingerprint (LFP) detection are investigated in this study. CoCr2O4 containing different amounts of Praseodymium(Pr3+) were prepared by solution combustion process using 1:1 M ratio of oxidizer and fuel. X-ray diffraction (XRD) was used to examine the structural characteristics of these nanoparticles, and the results showed that the crystallite sizes and lattice parameters varied while the spinel structure remained constant. The effective synthesis of the intended nanoparticles was indicated by the confirmation of CoCr2O4 presence in the spinel structure by Fourier Transform Infrared Spectroscopy, or FTIR. In particular, the study showed how these nanoparticles can be used in forensic science to identify LFP on a variety of surfaces, including steel, paper, and OHP sheets. In daylight, the CoPr0.03Cr1.97O4 (CoPr-3)variation with x = 0.05 performed better, allowing for a clear viewing of Level I–III fingerprint features. 3D interactive plots and high-resolution images demonstrated that the nanoparticles stuck to fingerprint remnants, improving visibility and detail. The study also looked at how stable these nanoparticles were under UV irradiation and aging, and it discovered that CoPr-3 phosphor was remarkably resistant to UV degradation and retained its efficacy for 60 days. These results demonstrate the potential of CoPr(x)Cr(2-x)O4 nanoparticles as a reliable and effective material for forensic fingerprint analysis, providing notable enhancements in LFP detection sensitivity and resolution.

Optimization of magnetic and magnetodielectric effect for BiFe(Nd)O3 nanoparticles

Optimization of magnetic and magnetodielectric effect for BiFe(Nd)O3 nanoparticles

Nanozyme-enhanced injectable hyaluronic acid-based hydrogel for the treatment of osteoarthritis

The progression of osteoarthritis (OA) is dramatically accelerated by excessive reactive oxygen species (ROS)-induced apoptosis of chondrocytes and the inflammatory response of synovial macrophages. In this study, we developed an injectable hydrogel with a catalase-mimicking nanozyme activity as a therapeutic agent for OA. In vitro experiments confirmed that the HA and peroxide-mimetic nanoenzyme-enhanced hydrogel, containing ε-polylysine/Mn1.8Co1.2O4 (ε-PLE/MnCoO) nanoparticles, continuously eliminated ROS and inflammatory cytokines while promoting the polarization of inflammatory macrophages (M1 phenotype) towards anti-inflammatory macrophages (M2 phenotype) in dysfunctional microenvironments. When used for intraarticular injections in OA models, the nanoenzyme-enhanced hydrogel effectively reduced oxidative stress by scavenging ROS and regulating the immune microenvironment. It resulted in a subsequent reduction in the expression of inflammatory factors, including MMP-13, TNF-α, IL-1β, and iNOS in both the synovium and joint fluid. Moreover, cartilage repair was enhanced by the promotion of COL-2 and SOX-9 expression in the cartilage tissue, whereas osteophyte formation in OA was reduced. This study introduced an innovative treatment strategy for the clinical management of OA, demonstrating its significant potential for application in treating OA.

A novel barium zirconate titanate/Fe-MOF nanocomposite: Synthesis, characterization, and photocatalytic mechanism

The synthesis of a metal-organic framework (MOF) matrix of MIL-100 (Fe) loaded with BaTi0.85Zr0.15O3 (BTZ) nanoparticles (NPs) was achieved by an easy one-pot solvothermal procedure and encasing of BTZ NPs. X-ray diffraction (XRD), photoluminescence spectroscopy (PL), UV-Vis reflectance spectroscopy (DRS), Transmission electron microscopy (TEM), scanning electron microscopy (SEM), and N2 adsorption-desorption were deployed for the characterization of the synthesized samples. The degradation efficiency for tetracycline (TC), among the photocatalytic BTZ/MIL-100(Fe) nanocomposites with varied BTZ percentages (10, 20, 30, and 40 wt% BTZ), revealed that (30 wt%), offered the best outcome. At 0.8 g L-1 of the catalyst, pH 9, 30 ppm TC solution, and 180 min irradiation time, as the optimal conditions, the degradation efficiency of TC molecules reached >90. Based on the study of some scavenging agents, the importance of the reactive species in TC photodegradation followed the trend of photogenerated e-, hydroxyl radicals, superoxide radicals, and photogenerated h+. TC degradation occurred through reduction and oxidation pathways via a direct Z-scheme mechanism. This work aims to describe the use of MOF-based materials as a visible-light-driven photocatalyst towards TC.

Exploring the role of transition metal ions doping on the optical, magnetic and energy storage properties of Bi0.96Eu0.04FeO3 nanoparticles

Bismuth ferrite has been quite extensively studied because of its unique multiferroic properties. The introduction of dopants strategically at the ‘A’ and ‘B’ sites has been known to improve the multiferroic properties of bismuth ferrite. This study focuses on the detailed investigation of the structural, morphological, optical, magnetic, and electrochemical properties of sol-gel synthesized bismuth ferrite as well as Bi0.96Eu0.04Fe0.95M0.05O3(M=Mn, Cu, Co, Zn) nanoparticles. The crystal structure and morphological analysis are done using XRD, Rietveld refinement, and FESEM. The XRD analysis and Rietveld Refinement have confirmed a structural transition to the orthorhombic phase upon simultaneous co-doping of ‘Eu’ and ‘M’(M= Mn, Cu, Co, Zn) ions at the ‘A’ and ‘B’ sites respectively. The evidence of different ratios of mixed valence states of ‘Fe’ and oxygen vacancies in the co-doped nanoparticles dictates the enhanced magnetic properties. There is a significant decrease in the band-gap of co-doped nanoparticles obtained from Tauc’s plot, with the lowest achieved band-gap of 1.8 eV in the case of ‘Eu’ and ‘Mn’ doped nanoparticles. Room-temperature M-H loops have recorded an increase in the value of maximum magnetization from 0.1 emu/g in case of pristine bismuth ferrite to 0.79 emu/g for ‘Eu’ and ‘Co’ doped bismuth ferrite nanoparticles. The unsaturated loops, however, have confirmed the presence of anti-ferromagnetic component along with the ferromagnetic part. The electrochemical studies have shown superior specific capacitance in co-doped bismuth ferrite, with the maximum specific capacitance of 273 F/g for ‘Eu’ and ‘Zn’ doped bismuth ferrite. It has also shown remarkable capacitive retention of 84.8 % after 5000 cycles at 10 A/g.

Synthesis and optimization of chitosan-incorporated semisynthetic polymer/α-Fe2O3 nanoparticle hybrid polymer to explore optimal efficacy of fluorescence resonance energy transfer/charge transfer for Co(II) and Ni(II) sensing

Initially, four synthetic fluorescent polymers (SFPs) are synthesized from α-methacrylic acid and methanolacrylamide monomers carrying –C(=O)OH and –C(=O)NH subfluorophores, respectively. Among SFPs, ∼1:1 incorporation of subfluorophores in the optimum SFP3 is explored by spectroscopic analyses. Subsequently, chitosan is incorporated in SFP3 to produce five semi-synthetic fluorescent polymers (SSFPs). The maximum incorporation of chitosan in SSFP4 is supported by different spectroscopies. In SSFP4, strong electrostatic interactions among polar functionalities of chitosan and synthetic polymer favor resonance-associated charge transfer (RCT) from SSFP4-(amide) to SSFP4-(canonical). Finally, three hybrid fluorescent polymers (HFPs) are fabricated encapsulating iron-oxide nanoparticle within SSFP4. The maximum proportion of hematite (α-Fe2O3) phase in HFPs is explored by spectroscopic, magnetometric, microscopic, and light scattering studies. HFP2 shows local/RCT/fluorescence resonance energy transfer (FRET) emission at 393/460/570 nm. In HFP2, FRET, RCT, and ratiometric pH-sensing within 3.0–6.5 phenomena are explored by solvent polarity effects, time-correlated single photon counting, quantum yield measurements, alongside I431/I460 vs pH plots. RCT and FRET emissions of HFP2 are utilized for selective sensing of Co(II)/Ni(II) with limits of detection of 4.990 ppb (460 nm)/4.353 ppb (570 nm) and 45.041 ppb (428 nm)/29.617 ppb (527 nm) in organic and aqueous solutions, respectively.

Structural, morphological, and magnetic characterizations of (Fe0.25Mn0.75)2O3 nanocrystals: A comprehensive stoichiometric determination

This report aims to investigate in depth FeMnO3, a material of interest due to its fascinating magnetic and multiferroic properties and its many applications in fields including lithium-ion batteries, microwave devices, and catalysis. However, understanding the precise stoichiometry of the material is crucial for a better comprehension of its physical properties. A cheap, simple, and repeatable sol-gel process was used to fabricate the FeMnO3 nanocrystals. Comprehensive multi-technique characterization of the as-fabricated FeMnO3 indicates that the main phase (94 wt%) is Fe0.5Mn1.5O3, although hematite appears as the minority phase (6 wt%). Magnetic characterization shows core-shell spin-glass like behavior, as well as paramagnetic-ferrimagnetic transitions and a Griffiths phase regime. EPR measurements revealed a strong and broad resonance line across the temperature range of 4.3 K–300 K, primarily influenced by the majority phase. The g-value decreases monotonically from 2.93 at 50 K to 2.18 at 300 K. There is a notable change in the resonance field and linewidth between 40 and 50 K, attributed to surface spin glass behavior. The EPR data below 50 K are in line with the core-shell model of (Fe0.25Mn0.75)2O3 nanoparticles. Below 50 K, the shell's spin system undergoes a transition from paramagnetic to spin-glass-like, with a critical temperature around 43 K. Above 50 K, the superparamagnetic minority phase significantly affects the temperature dependence of the resonance linewidth. These results hold particular importance as they advance our understanding of the intricate magnetic interactions present in FeMnO3. For the best possible use of this material platform in new technologies, such insights are essential.

Electrical Stimulation Promotes Endocytosis of Magnetic Nanoparticles by Cancer Cells.

Nanomaterials are increasingly used in biomedical imaging and cancer therapy, and how to improve the endocytosis of nanomaterials by cells is a key issue. The application of alternating current (AC) electrical stimulation to osteosarcoma cells (MG-63) here can increase the cellular endocytosis of Fe3O4 nanoparticles (diameter: 50nm) by 52.46% via macropinocytosis. This can be ascribed to the decrease in F-actin content and the increase in intracellular Ca2+ concentration. Transmission electron microscope, immunofluorescence staining, western blot, flow cytometry, and inductively coupled plasma emission spectrometer analyses support this interpretation. The application of electrical stimulation decreases the cell viability in magnetic hyperthermia by 47.6% and increases the signal intensity of magnetic resonance imaging by 29%. Similar enhanced endocytosis is observed for breast cancer cells (MCF-7), glioblastoma cells (U-87 MG), melanoma cells (A-375), and bladder cancer cells (TCCSUP), and also for Fe3O4 nanoparticles with the diameters of 20 and 100nm, and Zn0.54Co0.46Cr0.65Fe1.35O4 nanoparticles with the diameter of 70nm. It seems the electrical stimulation has the potential to improve the diagnostic and therapeutic effects of magnetic nanoparticles by promoting endocytosis.

Solar photocatalytic degradation of methylene blue dye and 4-CP herbicide by using a biodegradable fiber support decorated with Ce0.9Bi0.1O2 porous nanoparticles

Graphene microflakes were deposited on a biodegradable support of coconut/agave fibers to fabricate floatable photocatalytic (FG) composites. Later, Ce0.9Bi0.1O2 (BiCeO) nanoparticles were synthesized by Pechini method and these nanoparticles with cubic phase were deposited on the FG composites. SEM images confirmed the presence of porous BiCeO nanoparticles on the surface of coconut/agave fibers. The photocatalytic performance of the FG, BiCeO powder and FG/BiCeO composites was evaluated by degrading methylene blue (MB) dye under natural solar irradiation. The MB (20 ppm) dissolved in tap water was degraded with efficiencies of 59 %, 92 % and 100 % by using the FG, BiCeO powder and FG/BiCeO composite, respectively. Moreover, the 4-CP herbicide was degraded with efficiencies of 86 % and 94 % by utilizing the BiCeO powder and the FG/BiCeO composite, respectively. In addition, scavenger experiments demonstrated that the main oxidizing agent generated for the degradation of MB and 4-CP are the superoxide anions (·O2-), followed by the holes (h+) and (·OH) radicals. Also, we found that the clean water obtained with the use of the FG/BiCeO composite had the lowest content of organic carbon (21.7 %), suggesting that most of the by-products (formed during the breakage of the MB molecule) were eliminated. Overall, the results of this research demonstrate that biodegradable photocatalytic composites can be fabricated from coconut/agave fibers at low cost. Those ones are not only floatable but can also be activated with solar light. Those last characteristics could be useful for the elimination of traces of dangerous organic contaminants in water treatment plants.

La(FeCuMnMgTi)O3 High-Entropy Oxide Nanoparticles as Highly Efficient Catalysts for Solvent-Free Aerobic Oxidation of Benzyl Alcohol.

In this work, a solid-state method for the synthesis of perovskite La(FeCuMnMgTi)O3 high-entropy oxide (HEO) nanoparticles is detailed. Additionally, the high performance of these nanoparticles as catalysts in the aerobic and solvent-free oxidation of benzyl alcohol is demonstrated. The structural features of HEO nanoparticles are studied by X-ray diffraction and high-resolution transmission electron microscopy. The La(FeCuMnMgTi)O3 nanoparticles demonstrate excellent benzyl alcohol conversion rates and selectivity for benzaldehyde, reaching 10.6% conversion and 52.8% selectivity after reaction for only 4 h and ≤75.6% conversion after 24 h. In addition, the as-prepared HEO catalyst displays robust stability in benzyl alcohol oxidation. Density functional theory calculations demonstrate that the adsorption energy of benzaldehyde on the HEO surface is lower than that of the benzoic acid. This, in turn, hinders the gradual conversion of benzaldehyde to benzoic acid on the surface of HEO and retains benzaldehyde as the main product.

Structure of ZnxFe3−xO4 nanoparticles studied by neutron diffraction and its relation with their response in magnetic hyperthermia experiments

The mixed zinc-ferrite spinel magnetic nanoparticles (MNPs) with the general formula ZnxFe3−xO4 are among the most extensively studied families of Fe oxides due to their interesting and diverse chemical, electronic, and magnetic properties. These systems offer the possibility of surface functionalization and possess high biocompatibility, making them highly attractive for applications in biomedicine, such as magnetic fluid hyperthermia (MFH). The efficiency of the MFH process relies on the magnetic, structural and morphological properties of the MNPs. The substitution with the Zn ion and the cationic distribution, as well as the synthesis process employed, have a direct impact on the final properties of these oxides. Therefore, it is essential to have tools that enable a comprehensive characterization of the system to assess its performance in MFH. In this study, we have synthesized four ZnxFe3−xO4 MNP systems using three different methods: two by thermal decomposition at high temperatures, one by co-precipitation, and another by co-precipitation followed by ball milling. We analyze the effect of these various synthesis processes on the magnetic and crystallographic properties, aiming to correlate them with the response of each system in MFH. Neutron diffraction data are employed to determine the cation site occupation and to investigate the correlation with the synthesis method. MFH measurements were conducted in media of diverse viscosities, revealing different values of specific loss power, thus demonstrating a clear dependence on the synthesis process and Zn content.

A Novel Spinel High-Entropy Oxide (Cr0.2Mn0.2Co0.2Ni0.2Zn0.2)3O4 as Anode Material for Lithium-Ion Batteries

In this study, we synthesized spinel high-entropy oxide (HEO) (Cr0.2Mn0.2Co0.2Ni0.2Zn0.2)3O4 nanoparticles by a simple solution combustion method. These particles were investigated for their performance as anodes in lithium-ion batteries. The reversible capacity is 132 mAh·g−1 after 100 cycles at a current density of 100 mA·g−1, 107 mAh·g−1 after 1000 cycles at a current density of 1 A g−1, and 96 mAh·g−1 rate capacity at a high current density of 2 A g−1. The outstanding cycle stability under high current densities and remarkable rate performance can be attributed to the stable structure originating from the high entropy of the material.

Exploring the effect of Hf (IV) doping in spinel ferrite CoHfxFe2-xO4 on magnetic properties, electrochemical impedance, and photocatalytic activity: In-depth structural study

In this study, CoHfxFe(2−x)O4 nanoparticles (x = 0.0, 0.04, 0.08, and 0.12) were synthesized using the co-precipitation method. X-ray diffraction (XRD) analysis confirmed a pure spinel phase for the x = 0.04 sample, validated by Rietveld refinement, with crystallite sizes between 39 and 59 nm. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the formation of the spinel structure and the proper valence states of the elements. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) verified the morphology and homogeneity of the samples. Magnetic property analysis revealed reduced saturation magnetization with increased Hf content. Impedance spectroscopy showed enhanced electrical resistivity with Hf incorporation. Photocatalytic tests demonstrated that doping improves the degradation efficiency of Orange G dye under UV-Vis irradiation, achieving yields between 9 % and 35 % after 60 min.

High-entropy oxide (CeGdHfPrZr)O2 nanoparticles as reusable photocatalyst for wastewater remediation

High-entropy materials (HEM) play a significant role in current scientific research and are characterized by their complexity, which makes them the next generation nanomaterials. The present study investigates the synthesis of (CeGdHfPrZr)O2 high-entropy oxide nanoparticles using a hydrothermal technique. Various characterization techniques, such as X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used to investigate the structural properties, while UV-visible spectroscopy was used to investigate the optical properties. The results indicate the formation of a single-phase cubic fluorite high-entropy oxide system with a mean crystallite size of 5.4 nm. The optical bandgap of (CeGdHfPrZr)O2 nanoparticles is found to be 2.01 eV. The photocatalytic activity of the synthesized oxide nanoparticles was assessed using methylene blue (MB) dye as a model pollutant. In the current study, we examined and discussed the effect of various photocatalytic parameters on the degradation of MB dye. The results showed that the (CeGdHfPrZr)O2 nanoparticles had high photocatalytic activity and were found to be dependent on various parameters. A higher photocatalyst concentration impedes the degradation kinetics and, as a result, limits photon penetration into the reaction solution. Similarly, increased hydroxyl radical generation at a basic pH improved MB dye degradation. In addition, based on the band positions and radical scavenging study, hydroxyl radicals are responsible for the degradation of dye. (CeGdHfPrZr)O2 nanoparticles can be used as a promising catalyst for the photocatalytic degradation of organic pollutants.

Influence of yttrium doping on the photocatalytic behaviour of lanthanum titanate: a material for water treatment

Abstract Remediating water contamination greatly benefits from the removal of chemical as well as microbiological contaminants using the same substance. Yttrium-doped Lanthanum Titanate (LaY x Ti1−x O3, where x = 0 (LTO) and 0.05 (LYTO)) nanoparticles (NPs) synthesized by the auto-combustion method were already proven to have better antibacterial activities. The current study aims to investigate the photocatalytic degradation efficiency of the same sample for the organic pollutant Methylene Blue (MB) dye. Here, two vital and decisive characterization methods were employed: Raman spectroscopy for chemical and morphological features and X-ray photoelectron spectroscopy (XPS) for surface phase identification. The oxidation states of La3+ and Ti3+ ions have been deduced using XPS. The HRTEM reveals the nano-structure with SAED pattern is supporting with XRD data. LaTiO3 (LTO) and LaY0.05Ti0.95O3 (LYTO) nanoparticles showed degradation efficiencies of 40.26 % and 86.24 %, respectively, at degrading methylene blue (MB) dye after a reaction time of 90 min. The degradation efficiency of LTO increased to 87.19 % after a reaction time of 150 min. The introduction of yttrium doping into lithium titanate demonstrates promise as a material for mitigating water treatment, as it augments the material’s antibacterial and photocatalytic characteristics.

Facile Synthesis of Novel Short-Chain Ligand-Capped Colloidal Metal Oxide Nanoparticles for Printed Flexible Devices.

Colloidal metal oxide nanoparticles are key materials for achieving cost-effective and large-scale production of flexible devices, as they enable the formation of functional oxide thin films at low temperatures (<400 °C) through printing techniques such as inkjet printing, gravure coating, and microcontact printing. The conventional solvothermal synthesis of colloidal metal oxide nanoparticles through the thermal decomposition of precursors results in particles with bulky, long-chain ligands on their surfaces, which hinder the formation of dense oxide films when depositing the colloidal metal oxide nanoparticles. Herein, we have developed a simple and versatile method for synthesizing colloidal metal oxide nanoparticles using base-induced hydrolysis and the condensation of metal acetates as precursors. Various binary and ternary colloidal metal oxide nanoparticles (CuO, Mn3O4, Co3O4, CeO2, In2O3, Co1.8Mn1.2O4) were synthesized using short-chain acetate ligands on their surfaces. The thin acetate ligand-containing colloidal Co1.8Mn1.2O4 nanoparticle film exhibited lower resistivity than the same with long-chain oleate ligands. The films coated onto a polyimide substrate formed a flexible negative temperature coefficient thermistor that exhibited the temperature dependence of resistance comparable to bulk materials with a bending durability of up to 5 mm radius. These findings highlight the effectiveness of utilizing colloidal metal oxide nanoparticles with short-chain ligands in flexible devices.

Effect of carbon infusion on water splitting performance of (Ni0.2 Co0.2 Cr0.2 Mn0.2 V0.2)3O4 high entropy oxides nanoparticle synthesized via thermal plasma

A high entropy oxides (HEOs) has been proposed as a promising electrocatalyst for electrochemical water splitting reaction owing to their distinctive catalytic activity, stability, and tuneable electronic structure. In this work, a carbon infused HEOs (Ni0.2 Co0.2 Cr0.2 Mn0.2 V0.2)3O4 nanoparticles were synthesized via a single step process through a carbonaceous thermal plasma (Ar-CO2CH4) medium. Here, carbon infused HEOs were utilized as an electrocatalyst for water splitting reaction in 1 M KOH electrolyte. A Carbon rich HEOs (HEO C6) nanoparticle exhibits excellent oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performance with an overpotential of 243 and 217 mV to attain a current density of 50 mA cm-2, respectively. The fabricated two-electrode device requires only a 1.596 V as cell voltage to meet a current density of 10 mA cm-2. This study provides a new platform for a large-scale hydrogen production by utilizing carbon supported HEOs as an electrocatalyst.

(CrMnCoNiZn)3O4@PPy core-shell nanocomposite with excellent electrochemical performance as lithium-ion battery anode

High entropy oxides (HEOs) have an excellent potential for use as electrode materials in lithium-ion batteries (LIBs) due to their high theoretical specific capacity. In this work, spinel-structured (CrMnCoNiZn)3O4 HEO nanoparticles with five elements in equal molar ratio is first generated by solution combustion method. (CrMnCoNiZn)3O4@polypyrrole (PPy) nanocomposites are prepared by in-situ polymerization method. As an anode for lithium-ion batteries, the electrochemical performance of the (CrMnCoNiZn)3O4@PPy composite outperforms that of (CrMnCoNiZn)3O4 nanoparticles. The capacity is 802 mAh/g after 100 cycles at a current density of 100 mA/g, 416 mAh/g after 1000 cycles at a high current density of 1 A/g, and 360 mAh/g rate capacity at 2 A/g. The excellent electrochemical performance of the composites is mainly due to the fact that the conductive and flexible PPy is encapsulated on the high-entropy oxides, which can alleviate the volume change triggered by extraction-insertion of lithium ions process, as well as enhance the electrical conductivity and reduce the occurrence of some side reactions. This method of compositing materials can also be used in other HEOs and conductive polymers, providing a new idea to enhance the electrochemical properties of HEOs.