Fe3O4 Surface Research Articles

Facile synthesis of Fe3O4 photothermal nanoparticles coated with poly-3,4-dihydroxybenzaldehyde for improved photothermal therapy of cancer cells

Given the significant rise in the number of individuals diagnosed with cancer, the management of cancer therapy has become a prominent concern in society and a formidable task in human health care. Photothermal therapy has garnered significant interest in cancer treatment because of its exceptional efficacy and minimal invasiveness. Thus, current research mainly focuses on developing biocompatible materials with excellent photothermal properties. Therefore, we synthesized Fe3O4 nanoparticles coated with poly-3,4-dihydroxybenzaldehyde (Fe3O4@PDBA) where 3,4-dihydroxybenzaldehyde was covalently polymerized onto the surface of Fe3O4. The induction of PDBA leads to a dramatical improvement in the photothermal properties of Fe3O4. Besides, the thickness of the PDBA shell layer is also a key factor in the photothermal performance and various physicochemical properties of Fe3O4@PDBA and the photothermal performance of Fe3O4@PDBA increases with increasing thickness of the PDBA shell. Additional structural characterization of the products, DFT calculations of the UV-Vis absorption spectra and the HOMO-LUMO gap under the simple model of the polymer, and product identification by the use of H1NMR, MS, and other techniques were performed. Through multiple characterizations, the reaction solution color and UV-Vis absorption spectra were essentially consistent with the computed findings. The calculations confirm that the polymerization process of PDBA is progressively red-shifted and the absorption is gradually enhanced in the NIR region. Fe3O4@PDBA exhibited strong cytotoxicity against cancer cells (Hela, 98.0%) in vitro photothermal treatment. Hence, Fe3O4@PDBA exhibits superior photothermal characteristics, targeting, biocompatibility (99.0%), and degradability, which brings about significant potential for photothermal cancer therapy.

Density functional theory study on vanadium selective leaching separation from iron in stone coal via Fe2O3 (001) surface passivation

When vanadium is extracted from stone coal, iron impurities readily precipitate and reduce the purity of the vanadium product. Thus, separating vanadium from iron impurities at source is essential. The mechanism of surface passivation of Fe2O3 (001) for the selective leaching separation of vanadium from iron in stone coal was established in the present work. Analysis of mineral phase transformation and microscopic morphology indicates that Fe2O3 in stone coal can undergo a reaction with HF and F-. Subsequently, the hematite surface was covered with FeF3 passivation layer, resulting in the inhibition of hematite dissolving reaction. The results of density functional theory (DFT) computations demonstrate that the HF and F- can reform the Fe2O3 (001) surface via sedimentary behavior at mineral interface, and the adsorption energy can be down to -99.93kJ/mol for the F- adsorption configuration. During sulfuric acid leaching with CaF2 as an aiding agent, the transfer of electrons from Fe atoms to F atoms can weaken the stable Fe-F bonds and decrease the reactive activation of Fe atoms in Fe2O3. This study demonstrates the separation of vanadium from iron by means of hematite passivation in the attendance of fluoride at the atomic level of analysis.

Nanostructured Magnetite Coated with BiOI Semiconductor: Readiness Level in Advanced Solar Photocatalytic Applications for the Remediation of Phenolic Compounds in Wastewater from the Wine and Pisco Industry

Heterogeneous photocatalysis is an advanced, efficient oxidation process that uses solar energy to be sustainable and low-cost compared to conventional wastewater treatments. This study synthesized BiOI/Fe3O4 using the solvothermal technique, evaluating stoichiometric ratios of Bi/Fe (2:1, 3:1, 5:1, and 7:1) under simulated solar irradiation to optimize the degradation of caffeic acid, a pollutant found in wastewater from the wine and pisco industry. The nanomaterial with a 5:1 ratio (BF-5) was the most effective, achieving a degradation of 77.2% in 180 min. Characterization by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Brunauer–Emmett–Teller (BET), Barrett–Joyner–Halenda (BJH), Fourier Transform Infrared Spectroscopy (FTIR), Diffuse Reflectance Spectroscopy (DRS), and Vibrating Sample Magnetometry (VSM) showed that BF-5 has a porous three-dimensional structure with BiOI nanosheets coating the Fe3O4 surface, while retaining the pristine BiOI properties. The magnetite provided magnetic properties that facilitated the recovery of the photocatalyst, reaching 89.4% recovery. These findings highlight the potential of BF-5 as an efficient and recoverable photocatalyst for industrial applications. The technical, economic, and environmental feasibility were also evaluated at the technological readiness level (TRL) to project solar photocatalysis in real applications.

Fe2O3 Nanoflakes - WS2 Nanosheets Heterojunctions for Multi-Fold Enhancement in Photoelectrochemical Solar Energy Conversion.

Fe2O3-based photoanodes show great potential in photoelectrochemical water splitting due to their excellent stability, moderate band gap, and abundance. However, a short hole diffusion length limits its photocurrent density. Here, a multi-fold enhancement in photocurrent density from Fe2O3 nanoflakes - WS2 nanosheets heterojunction is reported. The heterojunction exhibits a synergistic photocurrent density of 0.52mA cm-2 at 1.3V (versus RHE) under AM 1.5G simulated sunlight, which is 2.23 times higher than pristine Fe2O3 nanoflakes. The Mott-Schottky and Nyquist plots indicate a higher charge density with lower charge transfer resistance at the semiconductor-electrolyte junction. The density functional theory (DFT) -based first-principles calculations are performed by designing a heterostructure between Fe2O3(110) and WS2(001) similar to the experimentally found arrangement of crystal planes. Free energy analysis and relative band extrema positions, obtained from DFT calculations and valence band spectroscopy, indicate the formation of type II heterojunction with partial oxygen terminated surface of Fe2O3. The type-II band alignment with a charge transfer of 4.8 × 10-4 e per interfacial WS2 to Fe2O3, helps in easy separation of photogenerated charges. The work establishes both an experimental design and a theoretical framework of highly crystalline nanoflakes-nanosheet heterojunctions for efficient photoelectrochemical solar energy conversion.

Pump-free SERS microfluidic chip based on an identification-competition strategy for ultrasensitive and efficient simultaneous detection of liver cancer-related microRNAs

In this study, we present a pump-free SERS microfluidic chip capable of detecting liver cancer-related miR-21 and miR-155 concurrently with ultra-sensitivity and high efficiency. We employed a Fe3O4@cDNA-AuNPs@Raman reporter@H composite structure and a recognition competition strategy. When the target miRNAs (miR-21 and miR-155) are present in the test liquid, they specifically compete with the nucleic acid complementary strand(H) of Fe3O4@cDNA-AuNPs@Raman reporter@H, causing AuNPs to competitively detach from the surface of Fe3O4, resulting in a decrease in the SERS signal. Consequently, this pump-free SERS microfluidic chip enables the detection of the target miRNAs more rapidly and accurately in complex environments. This method offers an approach for the simultaneous and efficient detection of miRNAs and holds promising applications in the early diagnosis of liver cancer.

High removal of PS and PET microplastics from tap water by using Fe2O3 porous microparticles and photothermal irradiation with NIR light

This work reports the synthesis of Fe2O3 (FeO) microparticles using the Pechini method and their use to remove microplastics from tap water. The analysis by electronic microscopy revealed that the FeO microparticles (FeMicroPs) have a porous structure and are formed by interconnected grains with sizes of 80-120 nm. In addition, the X-ray diffraction analysis pointed out that the FeMicroPs are composed of γ- Fe2O3 and α- Fe2O3 phases. To remove the PS and PET microplastics with sizes of 0.1-3 μm from the tap water, FeO was added to the contaminated water and the mixture of FeO+microplastics was irradiated with focused NIR light (980 nm). This provoked the melting of the microplastics on the FeO surface. Later, the FeMicroPs with adsorbed microplastics was recovered with magnets. This last procedure permitted a high removal of microplastics from the tap water, and the adsorption capacity was 1000 mg/g. In the next step, the microplastics adsorbed on the FeO were irradiated with NIR light to induce its thermal decomposition by photothermal irradiation, this in turn, produced the elimination of the microplastics from the FeO surface and allowed its reuse to remove more microplastics from the tap water. The elimination of the microplastics from the FeO surface was confirmed by the FTIR and Raman techniques, since the vibrational peaks associated with the microplastics disappeared from the FeO surface after the photothermal irradiation. Thus, the results of this investigation suggest that the photothermal irradiation with NIR light not only facilitates the removal of microplastics from the tap water, but also, it was useful to degrade the microplastics definitively without producing more contamination. This technique could be used to remove microplastics in water treatment plants.

A new Schiff-base complex of palladium nanoparticles on modified Fe3O4 with 3,5-diaminobenzoic acid (DAA) as a robust, reusable, and selective catalyst in the C[sbnd]N and C[sbnd]C coupling reactions

A Pd Schiff base complex was immobilized onto the surface of magnetic Fe3O4 as a novel, green, and recyclable heterogeneous nanocatalyst and fully characterized by TEM, XRD, FT-IR, BET, SEM, ICP-OES, EDS, TGA, and VSM techniques. The Fe3O4@SiO2@DAA@Schiff base-Pd(0) catalyst exhibits outstanding performance in catalyzing Buchwald-Hartwig and Stille coupling reactions, resulting in high yields of the corresponding products. This catalyst offers numerous benefits, such as a straightforward testing procedure, environmentally friendly reaction conditions, absence of hazardous solvents, quick reaction time, low catalyst usage, and the ability to be reused. Furthermore, the nanocatalyst could be effortlessly separated from the reaction mixture using a bar magnet, enabling its repeated recovery and reuse without compromising its stability or activity.

Exploring the atomic-scale dynamics of Fe3O4(001) at catalytically relevant temperatures using FastSTM

Surfaces and interfaces of functional nanoscale materials are typically highly dynamic when employed at elevated temperatures. Both, lateral surface and vertical bulk exchange diffusion processes set in, which can be relevant for applications such as heterogeneous catalysis. Time-resolved scanning tunneling microscopy (STM) is being pushed to ever faster measurement modes to follow such dynamic phenomena in situ. Here, we present FastSTM movies monitoring a range of atomic-scale dynamics of a prototypical reducible oxide catalyst support, Fe3O4(001), at elevated temperatures. Antiphase domain boundaries between two domains of the reconstructed surface exhibit local mobility from around 350 K, while Fe-rich point defects, in a stable equilibrium with the bulk, appear to diffuse in a peculiar zigzag pattern above 500 K. Finally, exploiting the diffusivity of Fe interstitials, we follow the propagation of step edges in the topmost atomic layer of the Fe3O4(001) surface in an oxygen atmosphere.

Fabrication of core–shell Fe3O4@SiO2/graphite catalyst to improve the charge separation for enhanced photocatalytic toluene oxidation

Magnetite (Fe3O4) has been regarded as a potential photocatalyst for VOCs degradation. Nevertheless, the magnetism of Fe3O4 always leads to the aggregation of particles, which is adverse for gaseous VOCs degradation. Meanwhile, the fast charge recombination of Fe3O4 seriously limits the photocatalytic activity. Herein, a layer of SiO2 was coated on the surface of Fe3O4, and Fe3O4@SiO2 particles were combined with graphite to prepare the core–shell catalyst for photocatalytic toluene oxidation. Fe3O4@SiO2/G catalyst showed the toluene degradation efficiency of 85.09%, which was 3.2 and 1.3 times than those of Fe3O4 and Fe3O4/G. The coating of SiO2 prevented the aggregation of Fe3O4 and greatly enhanced the specific surface area. Experimental and theoretical calculation proved that the existence of SiO2 promoted the spatial charge separation and inhibited the charge recombination, resulting in the generation of abundant reactive oxygen species. These findings offered an insight into the catalyst design for photocatalytic VOCs oxidation.

Chlorpyrifos degradation by Shewanella oneidensis MR-1: Characteristics and mechanism analysis

This study conducted a series of experiments to investigate the degradation performance and mechanism of chlorpyrifos (CPF) degradation by Shewanella oneidensis MR-1 (S. oneidensis MR-1). The results showed that the S. oneidensis MR-1 degradation CPF rate was maximized at a salinity of 10 g·L−1, 35 °C, pH 7, and an inoculum amount of 20 %. The simultaneous addition of anthraquinone sodium 2,6-disulfonate (AQDS) and goethite [FeO(OH)] were able to increase the degradation efficiency to 174.12 %. Further, SEM results showed the FeO(OH) surface might provide a dense reaction site for the degradation. XRD and FTIR analysis revealed the hydroxyl group participated in the degradation process. XPS analysis showed that the addition of AQDS and FeO(OH) promoted the conversion of Fe(III) to enhance the degradation of CPF. Meanwhile, metabolites analysis, indicated that S. oneidensis MR-1 regulated its antioxidant capacity by enhancing its amino acid metabolism and lipid biosynthesis to cope with CPF stress. This work could provide new insights for efficient CPF removal in the future.

Selection of the Lubricating Oil Components Based on the Molecular Adsorption Characteristics

Abstract The adsorption characteristics of the lubricating oil near the solid surface play crucial roles in the lubricating performance. In this paper, the molecular dynamics simulation implemented by MS software was carried out to reveal the adsorption properties of different lubricants on Fe2O3 surfaces. Several kinds of lubricating oil molecules were employed, namely, n-eicosane, 2, 6, 11, 15-tetramethylhexadecane, 2-decyldecahydronaphthalene and tetradecylcyclohexane. The results show that 2, 6, 11, 15-tetramethylhexadecane and 2-decyldecahydronaphthalene are relatively more favorable as the lubricant components. This is because they both have relatively high adsorption density, low molecular diffusivity and large adsorption energy. These results can provide a theoretical basis for the selection of future lubricant components as well as lubricant performance enhancement for blending.

Mechanism and toxicity assessment of Cu0/Fe3O4 activated persulfate based on the acceleration cycle of Fe3+/Fe2+ for the degradation of methyl orange

Accelerating the circulation of Fe3+/Fe2+ contributed to the production of SO4·- during persulfate activation in the treatment of refractory wastewater. In this study, magnetic Cu0/Fe3O4 was prepared to enhance the Fe3+/Fe2+ circulation and the separation of Cu0/Fe3O4. The composition, structure, catalytic activity and toxicity of Cu0/Fe3O4 were investigated. The degradation mechanisms of MO were investigated, as well as the toxicity of MO and the breakdown products were evaluated. The results showed that Cu0/Fe3O4(1:3) was more efficient for PS activation as compared with single Cu0 or single Fe3O4. Removal efficiency of MO was up to 94.2% and ·OH and 1O2 played the dominant role. Cu0 and in-situ generated Cu+ accelerated the circulation of Fe3+/Fe2+ and electron transfer efficiency from Cu0/Fe3O4(1:3) to PS. MO molecule was effectively decomposed through hydroxylation and the cleavage of NC and NN bonds. The leachate toxicity of Cu0/Fe3O4(1:3) was low, and the toxicity of intermediate products produced during the reaction was significantly less than MO. In conclusion, this study proposed a feasible pathway for rapid cycle of Fe3+/Fe2+ on the Fe3O4 surface and separation of Cu0 by using Cu0/Fe3O4 as a promising activator for PS, effectively improving the degradation efficiency of MO.

A chitosan-based hydrogel with ultrasound-driven immuno-sonodynamic therapeutic effect for accelerated bacterial infected wound healing

Sonodynamic therapy has attracted much attention as a noninvasive treatment for deep infections. However, it is challenging to achieve high antibacterial activity for hydrogels under ultrasonic irradiation due to the relatively weak sono-catalysis capability of sonosensitizers. Herein, an ultrasound-responsive antibacterial hydrogel (Fe3O4/HA/Ber-LA) composed of Fe3O4-grafted-Berberine, chitosan molecules modified with L-arginine and poly (vinyl alcohol) is prepared for enhanced sonodynamic therapy and immunoregulation. The formation of heterojunction between berberine and Fe3O4 with different work function promotes the charge separation and electron flow and disrupts the conjugated structure of berberine, causing a significant decrease in the band gap, eventually enhancing the sonocatalytic activity. The combination of berberine with Fe3O4 also significantly improves the oxygen adsorption energy, enabling more O2 molecules to react with the electron-rich regions on the surface of Fe3O4 to generate more reactive oxygen species (ROS). L-arginine grafted in the hydrogel is catalyzed by the ROS to release nitric oxide, which not only possesses antibacterial activity, but also positively affects macrophage M1 polarization to display potent phagocytosis to Staphylococcus aureus, thus achieving immuno-sonodynamic therapy. Hence, Fe3O4/HA/Ber-LA hydrogel under ultrasound irradiation shows excellent antibacterial activity. Furthermore, the antioxidative activity and anti-inflammatory effect of berberine released from the hybrid hydrogel induces macrophages to polarize towards the anti-inflammatory M2 status as infection comes under control, thus accelerating the wound healing. The hybrid hydrogel based on the immuno-sonodynamic therapy may be an extraordinary candidate for the treatment of deep infections.

Classification of adsorbates in scanning tunneling microscopy images of Fe3O4(111) surfaces exposed to water and carbon monoxide

Understanding the structure of catalyst surfaces with adsorbed molecules is key to improving catalyst design. Scanning tunneling microscopy (STM) allows the observation of adsorption states and sites and provides insights into diffusion and desorption processes; however, the presence of multiple types of molecules on the surface presents challenges such as the identification of species and verification of reaction progress, particularly at room temperature or higher. In this study, we develop a protocol for the height classification analysis of STM images using the Watershed algorithm. This method is applied to a system involving the co-adsorption of H2O and CO on the Fe3O4(111) surface, which represents the beginning of the water-gas shift reaction. Water molecules and dissociated OH species were identified in STM images of the Fe3O4(111) surface following the adsorption of water. Furthermore, gradual changes in the types of surface species were observed upon exposure of the surface to CO, indicating reaction progression. Our observations suggest that CO may react with molecular water rather than with dissociated OH on Fe sites. Despite its simplicity, the height classification analysis effectively identifies changes in the adsorbates on the catalyst surface. This method can be extended to other catalyst surfaces with adsorbed gasses.

Fabrication of magnetic ferroferric oxide-based composite for efficiently removing and recycling ciprofloxacin

The extensive use of antibiotics and recklessly discarding have caused serious water pollution. Its controlling and remedying become an urgent problem. With the goal of removing ciprofloxacin hydrochloride (HCIP), a magnetic adsorbent of Fe3O4@Mg(OH)2 was prepared via a facile approach in this work. The structure and morphology were systematically characterized by XRD, SEM, FT-IR and XPS. It is found hexagonal Mg(OH)2 flakes are evenly coating on the surface of Fe3O4. This structured morphology offers Fe3O4@Mg(OH)2 high specify surface area. The composite shows excellent removal performance. It achieves almost 99 % HCIP elimination within 1.5 h. The influence of the dosage of adsorbents, pH and interfering ions and reusability were fully studied. It is shown that the composite can be used in neutral condition and has long serve life. The cost effective synthesis, simple operation, high adsorption rate and long serve life make Fe3O4@Mg(OH)2 wide application for water treatment in a large scale.

Gly-Pyrrole@SO3 coated on the surface of Fe3O4 (Fe3O4@Gly-Pyrrole@SO3H) as a new recyclable magnetic nano-catalyst for the synthesis of 2-amino-3-cyano-4H-pyrans and polyhydroquinolines

Gly-Pyrrole@SO3 coated on the surface of Fe3O4 (Fe3O4@Gly-Pyrrole@SO3H) as a new recyclable magnetic nano-catalyst for the synthesis of 2-amino-3-cyano-4H-pyrans and polyhydroquinolines

Fe3O4@ZnO Core-Shell Nanoparticles—a novel facile fabricated magnetically separable photocatalyst

The current study proposes a simple and inexpensive technique to synthesise core–shell Fe3O4@ZnO as a promising photocatalyst. An easily scalable original procedure was developed based on sequential and simultaneous addition of Zn2+ and OH– ions to Fe3O4 cores, and preheating and subsequent heating of the reaction medium. The structure of Fe3O4@ZnO core–shell nanoparticles was found to be a sequence of layers including magnetite (Fe3O4), maghemite (γ-Fe2O3), goethite (α-FeOOH), and zinc oxide (ZnO) in (0001) orientation. This layer sequence ensures a smooth transition from the Fe3O4 of the core to the ZnO shell. The synthesis conditions affect layer density and thickness, which can be easily used in adjusting Fe3O4@ZnO properties.Photocatalytic degradation of a model persistent dye (naphthol green B) in the presence of Fe3O4@ZnO nanoparticles reached promising 77 % in 60 min under UV radiation, while Fe3O4 cores showed only 20 %. The wide-gap ZnO layer on the surface of the narrow-gap Fe3O4 provides charge separation and suppresses electron-hole recombination, which drastically increases photocatalytic activity of the material. Separation of the photocatalyst with a magnet showed the same result as that with a centrifuge. All of these findings lead to inexpensive fabrication, effective performance, low toxicity and simple separation of Fe3O4@ZnO.

Tailoring ethylenediamine functionalization on magnetic Zr-based metal-organic frameworks towards enhanced phosphate and tetracycline adsorption by synergy of Fe3O4 and amino functional groups

The development of efficient adsorbent for removing excessive nutrients (e.g. phosphorous – P) and antibiotics (e.g. tetracycline hydrochloride – TC) from livestock wastewater is necessary but challenging in practical application. In this study, magnetic Zr-based metal-organic frameworks (Fe3O4/UiO-66) with interfacial Fe-O-Zr bonds were synthesized and then modified with ethylenediamine (EDA) functional groups. The resultant optimized composite, namely Fe3O4/UiO-66-N2, showed promising removal of P and TC from both single and binary solution systems. It exhibited the maximum P and TC adsorption capacities of 90.0 mg P/g and 72.3 mg/g in the single component solution, respectively. In the binary solution with an initial P concentration of 5 mg P/L, the coexistence of TC posed a slight inhibition effect on the P adsorption over Fe3O4/UiO-66-N2. However, the TC adsorption was increased by raising the initial P concentration in solution from 5 mg P/L to 20 mg P/L. The Fe3O4 nanoparticles and EDA functional groups were suggested jointly improving the adsorption capacities of P and TC, with the synergy factors of 1.1 and 1.8, respectively. The effects of reaction time, water medium, initial pH and coexisting ions on the adsorption were investigated in detail. The mechanisms governing the adsorption of phosphate included electrostatic attraction, hydrogen bonding, ligand exchange and complexation. Those contributing to the adsorption of TC included Lewis acid-base interaction and π-π electron-donor-acceptor interaction, in addition to electrostatic attraction, hydrogen bonding and complexation. This work designed novel functionalized magnetic MOF composite adsorbents targeting at efficient and simultaneous removal of P and TC from water, under the synergistic effect of the Fe3O4 nanoparticles and surface functional groups.

Ultrafast and efficient extraction of heparin via cationic brush magnetic adsorbents

Heparin is a highly sulfated polysaccharide used extensively as an anticoagulant. However, conventional heparin extraction processes remains time-consuming and inefficient. We report cationic brush magnetic adsorbents by grafting poly(3-acrylamidopropyl) trimethylammonium chloride-co-N‑isopropylacrylamide random copolymers onto the surface of Fe3O4 for ultrafast and efficient heparin extraction. The fabricated adsorbent demonstrated an excellent adsorption capacity of 169.36 mg g−1 and a record-breaking adsorption rate towards heparin due to the introduction of N‑isopropylacrylamide, providing more adsorption sites and larger transport channels for the macromolecule heparin to access active sites. In addition, the adsorption capacity and rate for crude heparin were significantly better than those of commercial resin. Thermodynamic parameters implied that the heparin adsorption was spontaneous and endothermic process. The adsorption mechanism can be described by the synergistic effect of electrostatic attraction and hydrogen bond. This study paved an innovative approach to simultaneously enhance the adsorption rate and capacity of the adsorbent for polysaccharide.

Hybrid nanocomposites of Fe3O4/SiO2-EDTA: Holistic comparison of one-step and two-step modification methods

Fe3O4/SiO2-EDTA materials have been used for diverse applications and they have been modification by different methods, but a comparison is lacking between their physicochemical characteristics. This work aimed to compare the physicochemical characteristics of the Fe3O4/SiO2-EDTA nanocomposite obtained by four methods, whose modification of the Fe3O4 surface with SiO2-EDTA occurs in one or two steps, with not hazardous chemicals. In the one-step methods (M1 and M2), Fe3O4 particles were coated and functionalized in consecutive steps (by sonication in M1 and mechanical stirring in M2). In the two-step methods (M3 and M4), the Fe3O4 particles were primarily coated with silica and then functionalized with TMS-EDTA (by sonication in M3 and mechanical stirring in M4). The Fe3O4/SiO2-EDTA nanocomposites were characterized by XRD, TEM, EDX, BET, SQUID magnetometry, FTIR, XPS, and zeta potential. The TEM highlighted that the nanocomposites from methods M1 and M2 there is the simultaneous presence of magnetite particles coated and uncoated with silica, while those from M3 and M4 were totally coated, besides the nanocomposites from M2 and M3 showed to be more aggregated than those from the other methods. The presence of EDTA on the surface of the nanocomposites was evidenced by the carboxyl groups in the FTIR spectra and by the nitrogen in the XPS spectra. The nanocomposites from M3 and M4 presented a higher content of nitrogen than those from M1 and M2, and those from M4 also presented a higher content of carbon than those from M3. Overall, the Fe3O4/SiO2-EDTA nanocomposites from two-step methods showed better SiO2 coating and EDTA functionalization than those from one-step methods, and those from M4 presented the best physicochemical characteristics, being this method recommended for their modification for future applications.