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Magnetite nanoparticles (Fe3O4 NPs) have garnered significant attention over the past twenty years, primarily due to their superparamagnetic properties. These properties allow the NPs to respond to external magnetic fields, making them particularly useful in various technological applications. One of the most fascinating aspects of Fe3O4 NPs is their ability to self-assemble into complex structures. Research over this period has focused heavily on how these nanoparticles can be organized into a variety of superstructures, classified by their dimensionality—namely one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) configurations. Despite a wealth of studies, the literature lacks a systematic review that synthesizes these findings. This review aims to fill that gap by providing a thorough overview of the recent progress made in the fabrication and organization of Fe3O4 NP assemblies via a bottom-up self-assembly approach. This methodology enables the controlled construction of assemblies at the nanoscale, which can lead to distinctive functionalities compared to their individual counterparts. Furthermore, the review explores the diverse applications stemming from these nanoparticle assemblies, particularly emphasizing their contributions to important areas such as imaging, drug delivery, and the diagnosis and treatment of cancer. [ABSTRACT FROM AUTHOR]

A novel optical lactate biosensor is presented that utilizes a colorimetric interaction between H2O2 liberated by a binary enzymatic reaction and bis(neocuproine)copper(II) complex ([Cu(Nc)2]2+) known as CUPRAC (cupric reducing antioxidant capacity) reagent. In the first step, lactate oxidase (LOx) and pyruvate oxidase (POx) were separately immobilized on silanized magnetite nanoparticles (SiO2@Fe3O4 NPs), and thus, 2 mol of H2O2 was released per 1 mol of the substrate due to a sequential enzymatic reaction of the mixture of LOx-SiO2@Fe3O4 and POx-SiO2@Fe3O4 NPs with lactate and pyruvate, respectively. In the second step, the absorbance at 450 nm of the yellow-orange [Cu(Nc)2]+ complex formed through the color reaction of enzymatically produced H2O2 with [Cu(Nc)2]2+ was recorded. The results indicate that the developed colorimetric binary enzymatic biosensor exhibits a broad linear range of response between 0.5 and 50.0 µM for lactate under optimal conditions with a detection limit of 0.17 µM. The fabricated biosensor did not respond to other saccharides, while the positive interferences of certain reducing compounds such as dopamine, ascorbic acid, and uric acid were minimized through their oxidative removal with a pre-oxidant (NaBiO3) before enzymatic and colorimetric reactions. The fabricated optical biosensor was applied to various samples such as artificial blood, artificial/real sweat, and cow milk. The high recovery values (close to 100%) achieved for lactate-spiked samples indicate an acceptable accuracy of this colorimetric biosensor in the determination of lactate in real samples. Due to the increase in H2O2 production with the bienzymatic lactate sensor, the proposed method displays double-fold sensitivity relative to monoenzymatic biosensors and involves a neat color reaction with cupric-neocuproine having a clear stoichiometry as opposed to the rather indefinite stoichiometry of analogous redox dye methods. [ABSTRACT FROM AUTHOR]

This study compares magnetite (Fe3O4) nanoparticles synthesized using Aspergillus elegans extract versus commercially available magnetite nanoparticles, focusing on their efficacy in dye degradation. The biosynthesis of Fe3O4 nanoparticles using fungal extracts offers a sustainable and eco-friendly alternative to conventional chemical methods. The nanoparticles were characterized using various techniques, including UV–Vis spectroscopy, XRD, FTIR, SEM, TEM, DLS, zeta potential, and VSM analysis, to assess their structural, morphological, and magnetic properties. Results showed that fungus-mediated Fe3O4 nanoparticles were smaller, with an average size of 19.2 nm, and exhibited better crystallinity, surface functionalization, and colloidal stability than their commercial counterparts, which had an average size of 60 nm. Additionally, the fungal nanoparticles displayed superior magnetic properties with a saturation magnetization of 50 emu/g compared to 36 emu/g for commercial Fe3O4. The dye degradation potential of the nanoparticles was tested using methyl violet, methyl orange, and rose bengal dyes. Fungus-mediated Fe3O4 nanoparticles demonstrated higher dye removal efficiency than commercial Fe3O4, indicating enhanced catalytic activity due to their smaller size and larger surface area. This study highlights the potential of myco-synthesized Fe3O4 nanoparticles as effective agents for environmental remediation, particularly in removing of hazardous synthetic dyes from wastewater.

Nonylphenol is an aromatic organic compound that has an estrogen-like effect and has a negative effect on the human endocrine system. A method has been developed for the competitive determination of nonylphenol using magnetic particles, rabbit antiserum, nonylphenol conjugate with soybean trypsin inhibitor (STI) and biotin. The principle of the analysis is the formation of immune complexes on the surface of magnetite particles due to covalent immobilization of protein G through the oriented immobilization of polyclonal antibodies from rabbit serum during a competitive reaction between the free analyte (nonylphenol) and the bound one (as part of the nonylphenol-STI-biotin conjugate) for the binding sites of specific antibodies. The detection of formed immune complexes is proposed to be carried out using a streptavidin-polyperoxidase conjugate, which makes it possible to achieve a nine-fold gain in the level of the analytical signal. The developed ELISA using magnetite particles allows us to achieve a detection limit of nonylphenol at the level of 3.8 ng/mL, which is 14.5 times lower in comparison with the classic competitive ELISA (55 ng/mL). Based on the results of the experimental work, the optimized volume of the test sample was 500 μL, which makes it possible to concentrate low-contaminated samples by 17 times. [ABSTRACT FROM AUTHOR]

Nanoparticle size effects on elastic properties of polymeric bio-nanocomposites were studied using atomistic molecular dynamics (MD) simulations. Spherical magnetite nanoparticles (MNPs) were placed at the centre of amorphous polypyrrole (PPy) polymer in three models with different sizes. Three models of nanocomposites with the same particle volume fractions with different sizes were considered. The Lennard-Jones 6-12 potential modelled the interface interaction between polymer and particles. Initially, the obtained mechanical properties for pristine PPy and magnetite in the bulk state showed an acceptable agreement with experimental data. Subsequently, simulation results illustrated that incorporating MNP into the PPy matrix improves the elastic modulus of the matrix by 28-58%, and more importantly, decreasing the size of the nanoparticle from 2.40 to 1.80 nm in the system leads to increasing Young's modulus of the nanocomposite from a 3.20 to 3.94 GPa. Furthermore, the atomic investigation demonstrated that this change in elastic modulus is due to the change in interatomic interaction between nanoparticle and polymer when the nanoparticle size changes. Finally, the comparison between the results of MD and micromechanical analysis shows that as the size of the nanoparticle in nanocomposites increases, the elastic properties of nanocomposites converge with the results obtained by the micromechanical approach. [ABSTRACT FROM AUTHOR]

We present the synthesis of acrylic-resin-based tubular micromotors incorporating layers of magnetite nanoparticles (MNPs) and catalase (Cat) on the inner pore surface (Cat tube micromotors) and investigate their distinctive self-propulsion capabilities modulated by visible light irradiation. In an aqueous H2O2 solution, the Cat tubes demonstrate autonomous movement by expelling O2 bubbles from their opening ends. The propulsion velocity reaches its maximum at the optimal pH and temperature for the Cat enzyme activity. Remarkably, the swimming velocity undergoes rapid acceleration upon exposure to visible light and promptly decelerates upon the cessation of illumination. This phenomenon is ascribed to the photothermal effect induced by the MNPs, elevating the temperature of the adjacent Cat layer and thereby enhancing enzyme activity. The micromotors exhibit recurrent acceleration and deceleration in response to on/off light irradiation, showcasing a high degree of sensitivity and responsiveness. [ABSTRACT FROM AUTHOR]

A facile, one-pot, rapid and cost-effective green synthesis approach is adopted for synthesis of spherical magnetite nanoparticles (Fe3O4) using Averrhoa carambola leaf extract for removal of Cr(VI). The polar biomolecules of leaf extract act as non-toxic surfactants and as reducing as well as stabilizing agents. The morphological, structural and optical properties of bio-based magnetite nanoparticles were characterized by FESEM, XRD, FT-IR, UV–VIS DRS and Raman analysis. The batch biosorption of Cr(VI) was investigated at different experimental limits such as contact time, temperature, pH, adsorbent dose and metal concentration. The experimental data was well fitted to Langmuir adsorption isotherm and found to follow linear pseudo-second-order kinetics. The maximum biosorption efficiency of bio-based magnetite nanoparticles was recorded 99.34% and can be reused proficiently upto 7 cycles. The mechanism for role of biomolecules in synthesis of nanoparticles along with the mechanism for biosorption of Cr(VI) over bio-based magnetite nanoparticles were discussed. The bio-based magnetite nanoparticles can be effectively used for removal of Cr(VI) from groundwater in contaminated areas. [ABSTRACT FROM AUTHOR]

Transmission spectra of colloidal solutions of magnetite nanoparticles in kerosene with various volume concentrations of the solid phase and the influence on them of an external magnetic field have been studied. A pronounced maximum in the near-IR region at 740–760 nm appeared in the spectra as the magnetite concentration increased. The magnetite concentration limits at which the transmission spectra were successfully described by the Bouguer–Lambert law were established. The appearance of a maximum in the transmission spectra with increasing concentration was shown to be associated with a minimum in the spectrum of the imaginary part of the refractive index of nanosized magnetite. [ABSTRACT FROM AUTHOR]

The main objective of this study is to investigate the efficiency of coagulation-flocculation process for surface water treatment, using the conventional coagulants (ferric chloride (FeCl3) and polyferric sulphate (PFS)), magnetic nanoparticles (MNPs), Fe-based metal-organic framework MIL-53(Fe), magnetic metal organic framework (MMOF), and evaluate the effect of combination of these coagulants on the coagulation process. MNPs were synthesized using the co-precipitation method and MIL-53(Fe) was synthesized using solvothermal process. The synthesized coagulants were characterized using point of zero charge (pHpzc), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) and Brunauer–Emmett–Teller (BET) techniques. The point zero of charge pH (pHPZC) values for the prepared MNPs, MIL-53(Fe) and MMOF were for found to be 7.8, 5.0 and 3.0, respectively, while the respective surface area for MIL-53(Fe) and MMOF were 23.8 and 11.8 m2/g. In addition, pore sized MMOF was found to be 59.455 Å which is larger than that for MIL-53(Fe) (34.705 Å). The results obtained from this study revealed that turbidity removal exceeded 98 % when using 30 mg/L of FeCl3 at pH 7. The same removal efficiency required less dose of PFS (10 mg/L) at a pH 8.5. The combination of MNPs with FeCl3 enhanced the removal efficiency to more than 99 % at the optimized condition of FeCl3. However, using MIL-53(Fe) slightly enhanced the FeCl3 coagulation at low dosage (10 mg/L) at pH 7, whereas, MMOF recorded better enhancement for the FeCl3 coagulation at the same conditions, reaching up to 98 %. Moreover, the combination of PFS and MNPs provided the best coagulation performance with turbidity removal of more than 99 % at low dose and at pH 7.

Magnetite nanoparticles (Fe3O4 NPs) have garnered significant attention over the past twenty years, primarily due to their superparamagnetic properties. These properties allow the NPs to respond to external magnetic fields, making them particularly useful in various technological applications. One of the most fascinating aspects of Fe3O4 NPs is their ability to self-assemble into complex structures. Research over this period has focused heavily on how these nanoparticles can be organized into a variety of superstructures, classified by their dimensionality—namely one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) configurations. Despite a wealth of studies, the literature lacks a systematic review that synthesizes these findings. This review aims to fill that gap by providing a thorough overview of the recent progress made in the fabrication and organization of Fe3O4 NP assemblies via a bottom-up self-assembly approach. This methodology enables the controlled construction of assemblies at the nanoscale, which can lead to distinctive functionalities compared to their individual counterparts. Furthermore, the review explores the diverse applications stemming from these nanoparticle assemblies, particularly emphasizing their contributions to important areas such as imaging, drug delivery, and the diagnosis and treatment of cancer.

Among nanoparticles (NPs) of metal oxides, magnetite NPs are the most well-known. The need for regulations related to the safety of magnetite NPs requires a deep understanding of their toxicological paradigm. The purpose of the presented review is to analyze the methods of studying the magnetite NPs toxicity and to summarize their toxicity factors based on the literature data. Literature sources were searched in the PubMed database, and 99 works were selected, supplemented with articles from other databases in some cases. It is shown that the study of the magnetite NPs toxicity became widespread during the last decade, reflecting the expansion of the list of synthesized magnetic NPs and the awareness that the prospects for their use depend on the safety of the created nanomaterial. The safety assessment of magnetite NPs on cell lines is the most popular. Primitive and more highly organized animals can be used to evaluate various aspects of the magnetite NPs toxicity. The toxicity factors of magnetite NPs depend on their characteristics (core composition, coating, size, and shape) and the mode of application (concentration, dose, exposure, type of cells, or animal model). One of the main mechanisms of nanomagnetite toxicity is the interference with iron metabolism and increased generation of reactive oxygen species leading to the disruption of cell proliferation, viability, and metabolism. Thus, the toxicity of magnetite NPs is studied by various methods and at different levels of living systems. Understanding the mechanisms of nanotoxicity should contribute to the targeted design of safe magnetic NPs.

[Display omitted] • Pumice and smectite are robust carriers for cell immobilization recycling. • Bacteria-pumice and bacteria-smectite nanocomposites are efficient for recycling. • Continuous production of microbial products from wastes was achieved. • Secondary treatment is unneeded in treating waste using the proposed nanocomposites. Recycling waste into commercial products is a profitable strategy but the lifetime of immobilized cells for long-term waste treatment remains a problem. This study presents alternative cell immobilization methods for valorizing food waste (FW) and oily food waste (OFW) to microbial carotenoids and proteins. Carriers (pumice or smectite), magnetite nanoparticles, and isolated photosynthetic bacteria were integrated to obtain magnetically recoverable bacteria-pumice and bacteria-smectite nanocomposites. After recycling five batches (50 d), chemical oxygen demand removal from FW reached 76% and 78% with the bacteria-pumice and bacteria-smectite nanocomposite treatments, respectively, and oil degradation in OFW reached 71% and 62%, respectively. Destructive changes did not occur, suggesting the durability of nanocomposites. The used nanocomposites had no impact on the lifespan of Moina macrocopa or water quality as assessed by toxicity analysis. Bacteria-pumice and bacteria-smectite nanocomposites are efficient for food waste recycling and do not require secondary treatment before being discharged into the environment. [ABSTRACT FROM AUTHOR]

Magnetic Fe 3 O 4 nanoparticles were added into the aqueous phase to form nanofluid systems, in which ozone was used for the oxidation of tetracycline hydrochloride (TC) in the solution. The nanomaterials were characterized using SEM, XRD, EDS, and FT-IR. The effects of nanoparticles size, addition ratio, and number of cycles on the process of ozone oxidation of TC were investigated. The results indicated that the addition ratio of nanoparticles have a certain impact on the performance of ozone oxidation. When the addition ratio increased from 0.02% to 0.4%, the removal rate of TC in the solution was improved significantly. Besides, the particle size of nanoparticles showed a greater impact on ozone oxidation. At the nanoscale, Fe 3 O 4 nanoparticles exhibited significant strengthening properties, which is attributed to the construction of nanofluid systems. The removal rate of TC in solution decreased obviously with the increase of nanoparticles size. The Fe 3 O 4 nanoparticles with particle size of 20 nm showed the most significant effect on TC degradation. The recycling experiment showed that magnetic Fe 3 O 4 nanoparticles had stable regeneration performance. For three times of recycling treatment, with a Fe 3 O 4 addition ratio of 0.4%, the removal rate of TC reached 98.7%, 97.21%, and 96%, respectively. Based on the characterization results, the strengthening mechanism was analyzed. The experimental results indicated that construction of nanofluids systems could improve the utilization rate of ozone, and Fe 3 O 4 nanoparticles were reusable and easily recyclable.

• Fe 3 O 4 @SiO 2 -HAT-Cu(I) is a novel and efficient magnetic heterogeneous nanocatalyst. • Ease of preparation, stability, and cheapness of the catalyst. • Ease of the work-up procedure and catalyst separation by an external magnet field. • Reusability and potency of Fe 3 O 4 @SiO 2 -HAT-Cu(I) catalyst after several runs. • Use of green reaction media, simple performance, waste minimization, and atom-economy. A novel magnetically separable catalyst, the copper-hydroxyacetophenone thiosemicarbazone complex immobilized on silica-coated magnetite nanoparticles (Fe 3 O 4 @SiO 2 -HAT-Cu(I)), has been synthesized and characterized. The characterization included various techniques such as X-ray diffraction spectroscopy (XRD), energy dispersive X-ray spectroscopy (EDX), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), dynamic laser scattering (DLS), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), atomic absorption spectroscopy (AAS), inductively coupled plasma-optical emission spectrometry (ICP-OES), and Fourier-transform infrared spectroscopy (FT-IR). The catalytic activity of Fe 3 O 4 @SiO 2 -HAT-Cu(I) was evaluated in a green aqueous mediated three-component synthesis of 1,2,3‐triazles. The catalyst efficiently facilitated the 'Click' Huisgen cycloaddition reaction between alkynes, sodium azide, alkyl bromides and/or epoxides in water/THF at 70 °C, resulting in good to excellent yields of 1,4-disubstituted 1,2,3‐triazle derivatives. Fe 3 O 4 @SiO 2 -HAT-Cu(I) is a new, low-cost, and magnetically separable heterogeneous catalyst that can be easily prepared and reused for multiple reaction runs without significant loss of catalytic activity. Synthesis, characterization, and application of copper-hydroxyacetophenone thiosemicarbazone complex immobilized on silica-coated magnetite nanoparticles (Fe 3 O 4 @SiO 2 -HAT-Cu(I)) as a novel magnetically retrievable nanocatalyst for the three-component synthesis of 1,4-disubstituted 1,2,3-triazoles are described. [Display omitted] [ABSTRACT FROM AUTHOR]