Coated Fe3O4 Nanoparticles Research Articles

Synthesis and Characterization Studies of Mesostructured Chitosan Coated Fe3O4 Nanoparticles with Folic Acid

In this present work, Fe3O4 nanoparticles were obtained by a one-part Co-precipitation method. Secondly, a simple solvothermal method was employed to synthesize Chitosan (CS) coated Fe3O4 nanoparticles. Chitosan was used as a surface modification agent. The surface of Chitosan-coated Fe3O4 nanoparticles was conjugated with Folic Acid (FA). Various properties of the resultant products were performed by characterization studies. The structure and surface morphology of as-prepared nanoparticles were characterized by X-ray diffraction (XRD) and Scanning electron microscopy (SEM). The physical parameter such as strain and the crystallite size was evaluated for all the reflection peaks of the samples by using Williamson–Hall (W-H plot) method. Determination of the chemical component was marked by Fourier transform infrared spectroscopy (FTIR) and Energy-dispersive X-ray spectroscopy (EDAX) analyses. UV- Vis experiment was carried out to record optical absorbance and the bandgap energy of the nanoparticles was determined by Tauc’s plot. Thermogravimetric analysis (TGA) was conducted to recognize the thermal stability of the magnetic nanoparticles and endothermic peaks were observed from the first derivative of the TGA curve (DTG curve).

Removal of of toxic metal ions (Ni2+ and Cd2+) from wastewater by using TOPO decorated iron oxide nanoparticles

In real engineering applications, nanoparticles can face hurdles of complex behavior of pollutants, for which electrostatic forces and background electrolyte can prove to be one of the robust mechanisms to remove pollutants from wastewater. In the present work, magnetite (Fe3O4) nanoparticles (NPs) and trioctyl phosphine oxide (TOPO) coated Fe3O4 NPs were synthesized and characterized for removing divalent Ni2+ and Cd2+ ions. Morphological and chemical analysis of both NPs was performed, and batch adsorption experiments were performed to study the influence of different pH ranges, concentrations of adsorbents and different contact timings. TOPO functionalized magnetite nanoparticles were found to have better adsorption capacities as compared to Fe3O4 at higher pH values. Isotherm models were run to identify the adsorption process. Langmuir isotherm model data fitted best for both metal ions adsorption, while Freundlich data suited best only for Ni2+ ions. The regression values for kinetic models confirmed that pseudo-second-order fitted best to the adsorption of both Ni2+ and Cd2+. Higher adsorption values were noticed for Ni2+ at higher dosages of both bare and TOPO-coated iron oxide NPs. Cadmium was found to have no influence of adsorbent dosage. Contact time was found to impact sorption values, i.e., adsorption was greater initially and then decreased with the passage of time. The study concludes that TOPO decorated Fe3O4 NPs can be more efficiently used for wastewater treatment. Furthermore, the presence of alkyl chains in TOPO can be immobilized at surface of metals to undergo adsorption more efficiently.

Sensitive and selective detection of Mucin1 in pancreatic cancer using hybridization chain reaction with the assistance of Fe3O4@polydopamine nanocomposites

Pancreatic cancer is characterized as the worst for diagnosis lacking symptoms at the early stage, which results in a low overall survival rate. The frequently used techniques for pancreatic cancer diagnosis rely on imaging and biopsy, which have limitations in requiring experienced personnel to operate the expensive instruments and analyze the results. Therefore, there is a high demand to develop alternative tools or methods to detect pancreatic cancer. Herein, we propose a new strategy to enhance the detection sensitivity of pancreatic cancer cells both in biofluids and on tissues by combining the unique property of dopamine coated Fe3O4 nanoparticles (Fe3O4@DOP NPs) to specifically quench and separate free 6-carboxyfluorescein (FAM) labeled DNA (H1-FAM/H2-FAM), and the key feature of hybridization chain reaction (HCR) amplification. We have determined the limit of detection (LOD) to be 21 ~ 41 cells/mL for three different pancreatic cancer cell lines. It was also discovered that the fluorescence intensity of pancreatic cancer cells was significantly higher than that of HPDE-C7 and HepG-2 cells (control cell lines), which express lower MUC1 protein. Moreover, the HCR amplification system was used to identify the cancer cells on pancreatic tissue, which indicated the versatility of our strategy in clinical application. Therefore, the presented detection strategy shows good sensitivity, specificity and has great potential for the diagnosis of pancreatic cancer.Graphical

Preparation of poly(ε-lysine)-cyclodextrin coated Fe3O4 nanoparticles for selective separation of natural medicine: Scutellarin

In the present study, poly(ε-lysine)-cyclodextrin coated Fe3O4 nanoparticles (PL-CD@Fe3O4) were prepared by co-precipitation method. Then the PL-CD@Fe3O4 nanoparticles were studied of the characterization and the selective separation performance for natural medicine (scutellarin). The experimental results showed that PL-CD@Fe3O4 nanoparticles were successfully prepared with a particle size of about 30 nm and a saturation magnetization of 40 emu/g. When the nanoparticles were in the environment of pH = 7, the stability was the best, the adsorption capacity was the strongest, and the number of recyclable times was the most. Langmuir model deduced that the maximum adsorption capacity of the nanoparticles was 76.3 mg/g. In addition, the experimental results of using nanoparticles to separate SCU in the crude extract showed that the purity of SCU could be increased from 72.2% to 93.5% after repeated cyclic separation three times. Two dimensional NMR analysis showed that the selective separation of SCU by PL-CD@Fe3O4 was mainly caused by the host–guest interaction between cyclodextrin and SCU. In conclusion, the PL-CD@Fe3O4 nanoparticles are a very promising material for the extraction and separation of other similar natural drugs.

Fabrication of human serum albumin-imprinted photothermal nanoparticles for enhanced immunotherapy.

Photothermal nanoparticles have been confirmed to induce an antitumor immune response and turn "cold tumor" into "hot tumor". However, their delivery efficacy to tumors is limited by the elimination from the reticalendothel system. Herein, human serum albumin (HSA)-imprinted polymer coated Fe3O4 nanoparticles (Fe3O4@MIPs) are fabricated by oxidative polymerization of dopamine in the presence of HSA on the polydopamine pre-modified Fe3O4 nanoparticle surface, followed by the removal of HSA. The Fe3O4@MIPs exhibit rapid and specific reabsorption toward HSA. The molecularly imprinted sites on the Fe3O4@MIPs endow it with an albumin-rich protein corona in the blood and result in less elimination from the reticalendothel system than non-albumin-imprinted particles (Fe3O4@NIPs). Moreover, the molecularly imprinted polymer, which consists of polydopamine, also improves the photothermal effect of Fe3O4 nanoparticles. In vivo, the albumin camouflage in Fe3O4@MIPs produces a 2.6-fold improvement in tumor accumulation in comparison to Fe3O4@NIPs, and more heat is produced upon 808 nm laser irradiation, which further triggers an efficient immunogenic cell death (ICD) progress. Thus, the combination of Fe3O4@MIPs and PD-L1 antibody can not only inhibit the growth of primary tumors but also eliminates lung metastasis by eliciting immunological effect.

Carbon-coated Fe3O4 nanoparticles in situ grown on 3D cross-linked carbon nanosheets as anodic materials for high capacity lithium and sodium-ion batteries

Carbon coated Fe3O4 nanoparticles were grown in situ on 3D cross-linked carbon nanosheets, and exhibited excellent performance for lithium ion batteries.

Pd-Immobilized Phosphine Coated Fe3o4 Nanoparticles: Efficient and Magnetically Recyclable Nanocatalyst for Arylation of Aldehyde

Pd-Immobilized Phosphine Coated Fe3o4 Nanoparticles: Efficient and Magnetically Recyclable Nanocatalyst for Arylation of Aldehyde

Synthesis of magnetic multi-walled carbon nanotubes via facile and solvent-free direct doping method for water remediation

BackgroundOwing to the requirement of additional processing steps to separate the spent adsorbents from treated water, magnetic multi-walled carbon nanotubes (MMWCNTs) have recently been hailed as novel adsorbent. MethodsIn this study, MWCNTs doped with iron oxide (Fe3O4) nanoparticles (n-MMWCNTs) and MWCNTs doped with polydiallyldimethylammonium chloride (PDDA) coated Fe3O4 nanoparticles (PDDA-MMWCNTs) were synthesized via solvent-free direct doping method. Prior to the doping process, the pristine MWCNTs were pre-treated with nitric acid. Significant findingsCharacterization results such as FTIR, EDX, XRD and zeta potential analysis confirmed the deposition of Fe3O4 onto the MWCNTs. The stability of the synthesized MMWCNTs under different pH was examined. Detachments of Fe3O4 from n-MMWCNTs and PDDA-MMWCNTs was found at pH 9 and 3, respectively. Both types of MMWCNTs were applied to the removal of methylene blue (MB). It was found that the MB adsorption capacity of n-MMWCNTs was 11% higher than PDDA-MMWCNTs, due to significantly higher specific surface area of n-MMWCNTs. n-MMWCNTs was found to perform better in alkaline condition in which the adsorption capacity increased about 87% from pH 3 to pH 11. The adsorption of MB on n-MMWCNTs was found to obey the Langmuir isotherm (indicating monolayer MB molecules adsorption on the n-MMWCNTs) with the calculated maximum adsorption capacity of 20.37 mg/g. Moreover, the adsorption of MB followed the pseudo-second order kinetic model.

Core-Shell Structured Magnetic Carboxymethyl Cellulose-Based Hydrogel Nanosorbents for Effective Adsorption of Methylene Blue from Aqueous Solution.

This article reports effective removal of methylene blue (MB) dyes from aqueous solutions using a novel magnetic polymer nanocomposite. The core-shell structured nanosorbents was fabricated via coating Fe3O4 nanoparticles with a layer of hydrogel material, that synthesized by carboxymethyl cellulose cross-linked with poly(acrylic acid-co-acrylamide). Some physico-chemical properties of the nanosorbents were characterized by various testing methods. The nanosorbent could be easily separated from aqueous solutions by an external magnetic field and the mass fraction of outer hydrogel shell was 20.3 wt%. The adsorption performance was investigated as the effects of solution pH, adsorbent content, initial dye concentration, and contact time. The maximum adsorption capacity was obtained at neutral pH of 7 with a sorbent dose of 1.5 g L−1. The experimental data of MB adsorption were fit to Langmuir isotherm model and Pseudo-second-order kinetic model with maximum adsorption of 34.3 mg g−1. XPS technique was applied to study the mechanism of adsorption, electrostatic attraction and physically adsorption may control the adsorption behavior of the composite nanosorbents. In addition, a good reusability of 83.5% MB recovering with adsorption capacity decreasing by 16.5% over five cycles of sorption/desorption was observed.

Microplastic Removal and Degradation by Mussel-Inspired Adhesive Magnetic/Enzymatic Microrobots.

Ubiquitous pollution by microplastics is causing significant deleterious effects on marine life and human health through the food chain and has become a big challenge for the global ecosystem. It is of great urgency to find a cost-efficient and biocompatible material to remove microplastics from the environment. Mimicking basic characteristics of the adhesive chemistry practiced by marine mussels, adhesive polydopamine (PDA)@Fe3 O4 magnetic microrobots (MagRobots) are prepared by coating Fe3 O4 nanoparticles with a polymeric layer of dopamine via one-step self-polymerization. In addition, lipase is loaded on the PDA@Fe3 O4 MagRobots' surface to perform microplastic enzymatic degradation. The synthesized MagRobots, which are externally triggered by transversal rotating magnetic field, have the capacity to clear away the targeted microplastics due to their strong sticky characteristics. With the adhesive PDA@Fe3 O4 MagRobots on their surfaces, the microplastics can be navigated along an arbitrarily predefined path by a rotating field and removed using a directional magnetic field. Such adhesive MagRobots are envisioned to be used in swarms to remove microplastics from aqueous environments.

Sn coated Fe3O4 nanoparticles for selective and efficient oxidation of anthracene to anthraquinone

The present study aims to control the particle size and morphology by surface modification of Fe3O4nanoparticles for the best use in catalytic performance. Fe3O4nanoparticles were coated with Schiff base and post modified with dimethyl-tin moiety to yield Fe3O4@SB@Sn magnetic nanoparticles. The fully characterized nanoparticles were employed as a catalyst for the oxidation of anthracene (AN) to 9,10-anthraquinone (AQ). Experimental results indicated that the Fe3O4@SB@Sn catalyst exhibits better catalytic activity and recyclability when acetonitrile was used as a solvent and H2O2as an oxidant at 70 °C.

Peroxidase-like activity of Fe3O4/carbon core-shell nanostructured : effects of carbon shell thickness for application to glucose biosensor

In this study, we present a protocol for synthesis of carbon coated Fe3O4 nanoparticles with core-shell structured nanocomposite (FeC) following a two steps approach. The peroxidase-like acitivity of the synthesized FeC nanocomposite has been evaluated towards replacing of the horseradish peroxidase enzyme (HRP) in hydrogen peroxide enzymatic biosensor. In which, FeC has catalyzed for a redox reaction 5,5'-tetramethylbenzidine (TMB) and H2O2 to produce oxidized state of TMB with as a blue color. Results exhibited that FeC has a high catalytic activity accepting for fabrication of a high selectivity hydrogen peroxide (H2O2) colorimetric sensor with low detection of limit (LoD) of 0.02 mM H2O2. Based on this finding, we have used FeC and combined with glucose oxidase (GOx) enzyme to construct a new colorimetric glucose biosensor with high selectivity.

Magnetic-Propelled Janus Yeast Cell Robots Functionalized with Metal-Organic Frameworks for Mycotoxin Decontamination.

Cell robots that transform natural cells into active platforms hold great potential to enrich the biomedical prospects of artificial microrobots. Here, we present Janus yeast cell microrobots (JYC-robots) prepared by asymmetrically coating Fe3O4 nanoparticles (NPs) and subsequent in situ growth of zeolitic imidazolate framework-67 (ZIF-67) on the surface of yeast cells. The magnetic actuation relies on the Fe3O4 NPs wrapping. As the compositions of cell robots, the cell wall with abundant polysaccharide coupling with porous and oxidative ZIF-67 can concurrently remove mycotoxin (e.g., zearalenone (ZEN)). The magnetic propulsion accelerates the decontamination efficiency of JYC-robots against ZEN. Although yeast cells with fully coating of Fe3O4 NPs and ZIF-67 (FC-yeasts) show faster movement than JYC-robots, higher toxin-removal efficacy is observed for JYC-robots compared with that of FC-yeasts, reflecting the vital factor of the yeast cell wall in removing mycotoxin. Such design with Janus modification of magnetic NPs (MNPs) and entire coating of ZIF-67 generates active cell robot platform capable of fuel-free propulsion and enhanced detoxification, offering a new formation to develop cell-based robotics system for environmental remediation.

MXene@Fe3O4 microspheres/fibers composite microwave absorbing materials: Optimum composition and performance evaluation

In order to fully utilize the advantages that one-dimensional (1D) materials are conducive to form a conductive network and surface wrinkled microspheres can cause multiple reflection. In this paper, two MXene-based magnetic composites have been innovatively fabricated. 1D MXene@Fe3O4 magnetic nanofibers with a diameter of 25 nm are obtained by the self-assembly of single-layer Ti3C2Tx MXene nanosheets and coating Fe3O4 nanoparticles via thermal decomposition method. The micro-scale surface wrinkled porous MXene@Fe3O4 composite microspheres are prepared by simple ultrasonic atomization technology. A high efficiency microwave absorbing system is obtained by blending these two composites. Through the evaluation of microwave absorption performance, the optimal ratio of composite microspheres and nanofibers is conformed to be 7:3. The minimum reflection loss (RLmin) is −63.3 dB at a filler content of 40%. The corresponding matching thickness is 1.8 mm. The maximum effective absorption bandwidth (EABmax) is 5.2 GHz (12.8–18 GHz). Microwave absorbing mechanism study shows that the attenuation approaches include dielectric loss, magnetic loss, multiple reflection and conductive loss from the unique structure and impedance matching.

Magnetic Fe3O4 nanoparticles and ZrO2-doped mesoporous MCM-41 as a monolithic multifunctional catalyst for γ-valerolactone production directly from furfural

A magnetically-recoverable multifunctional catalyst (Fe3O4/ZrO2@MCM-41) was tailored by the impregnation of ZrO2 supported on mesoporous MCM-41 coated Fe3O4 nanoparticles, which successfully served as a monolithic catalyst for the cascade conversion of furfural (FAL) giving high yield to γ-valerolactone (GVL), a versatile platform molecule. The ordered hexagonal framework of the parent MCM-41 well reserved after the embedding of Fe3O4 and ZrO2. The incorporation of Fe3O4 could not only impart the catalyst with a strong magnetism, but also tune its acidity to promote GVL production. An impressive yield of 85% was accomplished straight from FAL processing with iso-propanol as a hydrogen donor and solvent. The kinetic study demonstrated higher activation energy for levulinate-to-GVL step (86.9 kJ/mol) than FAL transfer hydrogenation (35.0 kJ/mol) and subsequent alcoholysis process (51.0 kJ/mol). The catalyst could be fully recovered by an external magnetic field and showed good reusability. The sustainability of this conversion represents greatly improved by the process intensification based on one-pot reaction, magnetically-recoverable multifunctional catalyst, and mild operating conditions without using gaseous hydrogen.

Multifunctional magnetic mesoporous nanocomposites towards multiple applications in dye and oil adsorption

Multifunctional magnetic mesoporous nanocomposites are promising materials to remove the various pollutants from water due to the remarkable properties such as multiple binding sites, high surface area, and magnetic separation. Herein, we have developed a versatile nanocomposite, in which polydopamine (PDA) coated Fe3O4 nanoparticles are introduced during the synthesis of SBA-15 matrix for the first time to enhance adsorptive properties of hydrophilic magnetic mesoporous nanocomposite by combining the properties of high surface area, magnetization, and capability of interacting with more functional groups in one material. The resulting nanocomposite, Fe3O4@PDA@SBA-15, has been proved to be the effective sorbent for the removal of cationic dye, which can be ascribed to the functional groups of grafted PDA and the textural features of matrix SBA-15. On the other hand, after chemical modification via silanization of vinyltriethoxysilane (VTES), Fe3O4@PDA@SBA-15 nanocomposite turned to be a hydrophobic material, Fe3O4@PDA@SBA-15@VTES, which can adsorb oil with high adsorption capacity which could reach 8.83 times of its own weight. Moreover, both nanocomposites could be recycled by facile washing and drying processes. The materials provide a simple strategy for the preparation of multifunctional magnetic mesoporous nanocomposites satisfying various applications in water treatment.

Inhibitive Effect on the Rate of Hydrolysis of Tetracaine by the Surfactant-Coated Magnetic Nanoparticles (Fe3O4)

The influence of the magnetic nanoparticles Fe3O4 and surfactant coated nanoparticles on the rate of alkaline hydrolysis of tetracaine were investigated spectrophotometrically. The Fe3O4 nanoparticles were synthesized by co-precipitation method. These synthesized nanoparticles were characterized by physical techniques. The XRD patterns showed the crystalline nature and the presence of two bands at 635 cm -1 and 585 cm -1 were assigned to the Fe-O bond vibrations in Fe3O4. The SEM and TEM studies confirmed the spherical structure of nanoparticles. The VSM studies show the magnetic nature. The reaction rate increased linearly with increase in [NaOH]. The rate constant values decreased with the increase in the SDS coated Fe3O4 nanoparticles from 4.0 × 10 -4 s -1 to 1.1 × 10 -4 s -1 in the presence of PEG 1500. Similarly, the increase in the amount of CTABr coated Fe3O4 nanoparticles decreased the rate constant values from 4.0 × 10 -4 s -1 to 1.02 × 10 -4 s -1 in the presence of PEG 1500. The binding constant and rate constant were found to be lower in SDS coated nanoparticles than the CTABr coated particles. The observed results for - [surfactant] in the presence of magnetic nanoparticles and surfactant coated nanoparticles were treated using the pseudophase kinetic model.

Efficient Pb (II) removal from wastewater by TEG coated Fe3O4 ferrofluid

Tri-ethylene glycol (TEG) coated Fe3O4 nanoparticles ferrofluid were used for Pb (II) removal from simulated wastewater. The samples were synthesized using a modified co-precipitation method. The prepared samples were characterized by different techniques including X-ray diffraction, Rietveld method, FTIR, FESEM, TEM, VSM, TGA, BET and atomic adsorption experiments. The crystallinity of nanoparticles with a cubic spinel ferrite structure and absence of impurity phases were verified using X-ray diffraction and Rietveld method. The presence of TEG was approved by FTIR and thermogravimetric analysis. The VSM results showed that the bonding between the TEG molecules and ferrite nanoparticles, reduces the surface spin disorder, influences the morphology and magnetization, and consequently increases the Pb (II) removal efficiency to a high value of 97%. The obtained high value of adsorption capacity of q=363.4 mg.g-1 with R= 91 % and q=129.4 mg.g-1 with R=97 %shows effective role of TEG coating on Pb (II) adsorption. The interesting results of this study imply that the TEG coated ferrofluid sample is suitable candidate for practical applications.

Spectroscopic Study of Interaction of Bare, Citrate Capped and BSA Capped Fe3O4 Nanoparticles with Hemoglobin

Background:Fe3O4nanoparticles have great potential in different biomedical applications. The study of the interaction of bare, and capped Fe3O4nanoparticles with common blood proteins is a field of interest for understanding the underlying mechanism and biocompatibility.Objective:This work aims at studying the nature of binding of bare, citrate functionalised and bovine serum albumin coated Fe3O4nanoparticles (Fe3O4NPs, CFe3O4NPs and BFe3O4NPs) with human hemoglobin (Hb), and their instantaneous effect on amino acid group, heme group and secondary structure of Hb.Methods:Nanoparticles were prepared by the chemical route and characterised by TEM, XRD and UV-Visible and FTIR spectroscopy. UV-visible absorbance and fluorescence emission/ excitation spectroscopy and circular dichroism were performed to study the interaction of nanoparticles with Hb.Results:UV-visible absorbance spectroscopy showed no blue or red shift of absorption peaks. Benesi-Hildebrand curves for the amino acid band and soret band of Hb absorbance spectrum were straight lines with positive intercepts; apparent binding constants and Gibbs free energy change were within a moderate level; they were larger for amino acid band in the presence of CFe3O4NPs, and for soret band in the presence of Fe3O4NPs, but noticeably small for both bands in the presence of BFe3O4NPs. Fluorescence emission/excitation spectra showed no noticeable shift of emission/excitation peak position of Hb in the presence of the three nanoparticles. Multiple peak fitting, done for the L-peak of the excitation spectrum of Hb, showed a major increase in the percentage of peak area of Tyr in the presence of CFe3O4NPs. Circular dichroism measurement showed that CFe3O4NPs, Fe3O4NPs and BFe3O4NPs reduced the α-helix content of Hb in decreasing order.Conclusion:Ground state complex formation of human hemoglobin with the studied nanoparticles with 1:1 stoichiometric ratio is suggested. Moreover, it has been observed that CFe3O4NPs may have a stronger interaction with the amino acid group while bare Fe3O4NPs may have a stronger interaction with the heme group of Hb. Hinderance of the energy transfer from tyrosine to tryptophan of Hb in the presence of CFe3O4NPs is also suggested. CFe3O4NPs may also have some effect on the secondary structure of Hb as indicated through reduction of the α-helix content. BFe3O4NPs have shown very weak interaction with Hb in the UV-visible absorbance spectroscopy, fluorescence emission/excitation spectroscopy and circular dichroism experiment.

Study of the surface properties and particle-particle interactions in oleic acid-coated Fe3O4 nanoparticles

Magnetite (Fe3O4) nanoparticles coated with organic material are of considerable importance in various areas of engineering, as well as in biomedicine. Several papers show drastic changes in the magnetic properties related to the surface effects and the particle-particle interactions strength. However, there is no consensus about the origin or mechanisms that produce these changes, which could be different depending on the particle size and shape, coating efficiency and particle-particle interaction strength. Aiming to shed light on these issues, oleic acid (OA) coated Fe3O4 nanoparticles with different sizes were synthesized by a thermal decomposition method. Structural and microscopic results revealed Fe3O4 nanoparticles with good crystallinity and almost-spherical or polyhedral shapes depending on the solvent used for the synthesis. Infrared (FTIR) spectroscopy indicated OA molecules attached to the surface of Fe3O4 NPs via bidentate (chelating and/or bridging) bonds; meanwhile, thermogravimetric analysis confirmed the presence of weakly and strongly bonded OA molecules, suggesting a successful coating of Fe3O4 NPs. Magnetization (M) vs. magnetic field (H) curves are consistent with a core/shell structure formed by magnetite/defective magnetite (maghemite) phases, in consistency with FTIR spectroscopy. It was determined lower saturation magnetization values than that expected for bulk magnetite, which was assigned to the likely presence of a fraction of iron ions in low-spin (LS) states in the defective magnetite (maghemite) layer at the particles surface. The magnetic results evidence that depending on the amount of OA coating, it is possible to tune the particle-particle separation distance, avoid particles agglomeration and particle-particle interactions. The temperature dependence of magnetization reveals the presence of non-interacting and interacting NPs. Meanwhile, AC magnetic susceptibility measurements are consistent with those results and provide features related to superparamagnetic (SPM) behavior, assigned to the non-interacting NPs, and interacting SPM behavior, assigned to the interacting NPs, whose interaction strength is not enough to lead to a spin-glass like behavior.