Size-Controlled Synthesis of Iron and Iron Oxide Nanoparticles by the Rapid Inductive Heating Method

Insight mechanism of magnetic activated catalyst derived from recycled steel residue for black liquor degradation

The present work deals with developing a method for revalorizing steel residues to create sunlight-active photocatalysts based on iron oxides. Commercial-grade steel leftovers are oxidized under different combinations of pH and temperature (50-90 °C and 3 ≥ pH ≤ 5) in a low energy-intensive setup. The material with the highest production efficiency (yield > 12%) and magnetic susceptibility (χm = 387 × 10-6 m3/kg) was further explored and modified by diffusion of M2+ (Zn and Co) ions within the structure of the oxide using a hydrothermal method to create ZnFe2O4, CoFe2O4 and combined Co-Zn ferrite. (Co-Zn)Fe2O4 displayed a bandgap of 2.02 eV and can be activated under sunlight irradiation. Electron microscopy studies show that (Co-Zn)Fe2O4 consists of particles with diameters between 400 and 700 nm, homogeneous size, even distribution, and good dispersibility. Application of the developed materials in the sunlight catalysis of black liquors from cellulose extraction resulted in a reduction of the Chemical Oxygen Demand (- 15% on average) and an enhancement in biodegradability (> 0.57 BOD/COD) after 180 min of reaction. Since the presented process employs direct solar light, it opens the possibility to large-scale water treatment and chemical upgrading applications.

Quasicrystal Nanosheet/α-Fe2O3 Heterostructure-Based Low Power NO2 Sensors: Experimental and DFT Studies

Industrial emissions, environmental monitoring, and medical fields have put forward huge demands for high-performance and low power consumption sensors. Two-dimensional quasicrystal (2D QC) nanosheets of metallic multicomponent Al70Co10Fe5Ni10Cu5 have emerged as a promising material for gas sensors due to their excellent catalytic and electronic properties. Herein, we demonstrate highly sensitive and selective NO2 sensors developed by low-cost and scalable fabrication techniques using 2D QC nanosheets and α-Fe2O3 nanoparticles. The sensitivity (ΔR/R%) of the optimal amount of 2D QC nanosheet-loaded α-Fe2O3 sensor was 32%, which is significantly larger about 3.5 times than bare α-Fe2O3 sensors for 1 ppm of NO2 at 150 °C operating temperature. The sensors exhibited p-type conduction, and resistance was reduced when exposed to NO2, an oxidizing gas. The enhanced sensing characteristics are a result of the formation of nanoheterojunctions between 2D QC and α-Fe2O3, which improved the charge transport and provided a large sensing signal. In addition, the heterojunction sensor demonstrated excellent NO2 selectivity over other oxidizing and reducing gases. Furthermore, density functional theory calculation examines the adsorption energy and charge transfer between NO2 molecules on the α-Fe2O3(110) and QC/α-Fe2O3(110) heterostructure surfaces, which coincides well with the experimental results.

Induction heating: an efficient methodology for the synthesis of functional core-shell nanoparticles

Induction heating has been applied for a variety of purposes over the years, including hyperthermia-induced cell death, industrial manufacturing, and heterogeneous catalysis. However, its potential in materials synthesis has not been extensively studied. Herein, we have demonstrated magnetic induction heating-assisted synthesis of core-shell nanoparticles starting from a magnetic core. The induction heating approach allows an easy synthesis of FeNi3@Mo and Fe2.2C@Mo nanoparticles containing a significantly higher amount of molybdenum on the surface than similar materials synthesized using conventional heating. Exhaustive electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy characterization data are presented to establish the core-shell structures. Furthermore, the molybdenum shell was transformed into the Mo2C phase, and the catalytic activity of the resulting nanoparticles tested for the propane dry reforming reaction under induction heating. Lastly, the beneficial role of induction heating-mediated synthesis was extended toward the preparation of the FeNi3@WOx core-shell nanoparticles.

A narrative review of the synthesis, characterization, and applications of iron oxide nanoparticles

The significance of green synthesized nanomaterials with a uniform shape, reduced sizes, superior mechanical capabilities, phase microstructure, magnetic behavior, and superior performance cannot be overemphasized. Iron oxide nanoparticles (IONPs) are found within the size range of 1-100 nm in nanomaterials and have a diverse range of applications in fields such as biomedicine, wastewater purification, and environmental remediation. Nevertheless, the understanding of their fundamental material composition, chemical reactions, toxicological properties, and research methodologies is constrained and extensively elucidated during their practical implementation. The importance of producing IONPs using advanced nanofabrication techniques that exhibit strong potential for disease therapy, microbial pathogen control, and elimination of cancer cells is underscored by the adoption of the green synthesis approach. These IONPs can serve as viable alternatives for soil remediation and the elimination of environmental contaminants. Therefore, this paper presents a comprehensive analysis of the research conducted on different types of IONPs and IONP composite-based materials. It examines the synthesis methods and characterization techniques employed in these studies and also addresses the obstacles encountered in prior investigations with comparable objectives. A green engineering strategy was proposed for the synthesis, characterization, and application of IONPs and their composites with reduced environmental impact. Additionally, the influence of their phase structure, magnetic properties, biocompatibility, toxicity, milling time, nanoparticle size, and shape was also discussed. The study proposes the use of biological and physicochemical methods as a more viable alternative nanofabrication strategy that can mitigate the limitations imposed by the conventional methods of IONP synthesis.

Fabrication of glutathione functionalized self-assembled magnetite nanochains for effective removal of crystal violet and phenol red dye from aqueous matrix

A novel fabrication of magnetite (Fe₃O₄) nanochains, surface functionalized with glutathione (GSH), has been attempted through a basic wet reduction method, coalesced with oxidative etching for the removal of crystal violet (CV) and phenol red (PR) from an aqueous solution. The structural and functional characterizations of GSH@Fe₃O₄ MNPs were performed using SEM-EDX, DLS, XRD, and FTIR. The nanochain-structured adsorbent was found to have an average size of 24 ± 1.29 nm and a zeta potential value of - 6.44 mV. The batch experiments showed that GSH@Fe₃O₄ MNPs have a brilliant removal efficiency of 97% and 79% for CV and PR dyes, respectively, within a period of 60 min. The influence of different operational parameters like adsorbent dosage, pH, temperature, reaction time, and initial dye concentration on the removal behaviour of the adsorbent was studied in detail. The adsorbate-adsorbent reaction was tested over isotherm models, and the reaction fitted well for Langmuir isotherm with an excellent q_max value of 1619.5 mg/g and 1316.16 mg/g for CV and PR dye, respectively. The experimental results were also validated using different reaction kinetics, and it was found that the pseudo-first-order model fits well for PR dye adsorption (R² = 0.91), while adsorption of CV dye was in best agreement with the pseudo-second-order kinetic model (R² = 0.98). Thermodynamic studies revealed that the adsorption reaction was spontaneous and endothermic in nature. Furthermore, GSH@Fe₃O₄ MNPs can be reused effectively up to 5 cycles of dye removal. Major mechanisms involved in the adsorption reaction were expected to be electrostatic attraction, hydrogen bonding, and π-interactions. The efficiency of GSH@Fe₃O₄ MNPs in real water samples suggested that it has a high potential for dye removal from complex aqueous systems and could be used as an effective alternative for remediation of dyes contaminated water.

Research Progress on Magnetic Catalysts and Its Application in Hydrogen Production Area

The noncontact heating technology of IH targets heat directly where it is needed through the electromagnetic energy adsorption and conversion of magnetic materials. Unlike conventional heating methods, the heat generated by electromagnetic induction of magnetic materials can be applied directly into the reactor without heating the entire device; this new heating method is not only more energy efficient but also safer, cleaner and more sustainable if renewable electricity is adopted; moreover, magnetic catalysts can be recovered and reused by separating chemical reactants and products from the catalyst by the application of a magnetic field, and it can provide the required heat source for the reaction without altering its catalytic properties. Magnetic catalysts with an electric field have been applied to some industrial areas, such as the preparation of new materials, catalytic oxidation reactions, and high-temperature heat absorption reactions. It is a trend that is used in the hydrogen production process, especially the endothermic steam reforming process. Therefore, in this paper, the heat release mechanism, properties, preparation methods and the application of magnetic catalysts were presented. Highlights of the application and performance of magnetic catalysts in the hydrogen production area were also discussed.

Ultrasmall Superparamagnetic Particles of Iron Oxide and Cardiac Magnetic Resonance: Novel Imaging in Everyday Conditions

Myocardial inflammation has been hypothesised to be the common underlying mechanism through which several cardiovascular diseases develop and progress. Cardiac magnetic resonance (CMR) has become a powerful non-invasive tool that enables the direct visualisation of the myocardium. The emerging use of ultrasmall superparamagnetic particles of iron oxide (USPIO) and their magnetic properties is gaining a lot of research interest. USPIO-enhanced CMR can provide valuable information, as it allows for the identification of active inflammation in the myocardium, a process that has been hypothesised to be the substrate for adverse remodelling and, eventually, heart failure. In this review, we summarise the properties of USPIO and their role in cardiac magnetic resonance imaging as well as their clinical applications.

Ultrafast Preparation of Nonequilibrium FeNi Spinels by Magnetic Induction Heating for Unprecedented Oxygen Evolution Electrocatalysis

Carbon-supported nanocomposites are attracting particular attention as high-performance, low-cost electrocatalysts for electrochemical water splitting. These are mostly prepared by pyrolysis and hydrothermal procedures that are time-consuming (from hours to days) and typically difficult to produce a nonequilibrium phase. Herein, for the first time ever, we exploit magnetic induction heating-quenching for ultrafast production of carbon-FeNi spinel oxide nanocomposites (within seconds), which exhibit an unprecedentedly high performance towards oxygen evolution reaction (OER), with an ultralow overpotential of only +260 mV to reach the high current density of 100 mA cm⁻². Experimental and theoretical studies show that the rapid heating and quenching process (ca. 10³ K s⁻¹) impedes the Ni and Fe phase segregation and produces a Cl-rich surface, both contributing to the remarkable catalytic activity. Results from this study highlight the unique advantage of ultrafast heating/quenching in the structural engineering of functional nanocomposites to achieve high electrocatalytic performance towards important electrochemical reactions.

Assisted Synthesis of Coated Iron Oxide Nanoparticles for Magnetic Hyperthermia

Magnetite nanoparticles were synthesized by the co-precipitation method with and without the assistance of an additive, namely, gelatin, agar-agar or pectin, using eco-friendly conditions and materials embodying a green synthesis process. X-ray diffraction and transmission electron microscopy were used to analyze the structure and morphology of the nanoparticles. Magnetic properties were investigated by SQUID magnetometry and ⁵⁷Fe Mössbauer spectroscopy. The results show that the presence of the additives implies a higher reproducibility of the morphological magnetic nanoparticle characteristics compared with synthesis without any additive, with small differences associated with different additives. To assess their potential for magnetic hyperthermia, water-based suspensions of these nanoparticles were prepared with and without citric acid. The stable solutions obtained were studied for their structural, magnetic and heating efficiency properties. The results indicate that the best additive for the stabilization of a water-based emulsion and better heating efficiency is pectin or a combination of pectin and agar-agar, attaining an intrinsic loss power of 3.6 nWg^-1.

Solution-phase decomposition of ferrocene into wüstite-iron oxide core-shell nanoparticles

We report an improved method for the controlled solvent-phase decomposition of ferrocene into highly crystalline monodisperse iron oxide nanoparticles at relatively low temperatures. Solution-phase decomposition of ferrocene into nanoparticles has received little attention in the literature, due to the percieved stability of ferrocene. However, we synthesised wüstite FeO-iron oxide core-shell nanoparticles by thermally decomposing ferrocene in 1-octadecene solvent and in the presence of oleic acid and oleylamine, as surfactants. We report procedures that provide cubic and spherical core-shell iron oxide nanoparticles whose size (29.3 ± 2.3 nm for spheres, 38.6 ± 6.9 nm for distorted cubes and 23.5 ± 2.4 nm for distorted cubes with concave faces) and shape can be controlled through simple adjustments to reaction parameters. Transmission electron microscopy, scanning transmission electron microscopy, energy dispersive X-ray spectroscopy, electron energy-loss spectroscopy and powder X-ray diffraction analysis methods were used to characterise the nanoparticles.

Magnetic Nanoparticles: Synthesis, Anisotropy, and Applications

Anisotropy is an important and widely present characteristic of materials that provides desired direction-dependent properties. In particular, the introduction of anisotropy into magnetic nanoparticles (MNPs) has become an effective method to obtain new characteristics and functions that are critical for many applications. In this review, we first discuss anisotropy-dependent ferromagnetic properties, ranging from intrinsic magnetocrystalline anisotropy to extrinsic shape and surface anisotropy, and their effects on the magnetic properties. We further summarize the syntheses of monodisperse MNPs with the desired control over the NP dimensions, shapes, compositions, and structures. These controlled syntheses of MNPs allow their magnetism to be finely tuned for many applications. We discuss the potential applications of these MNPs in biomedicine, magnetic recording, magnetotransport, permanent magnets, and catalysis.

Fabrication of the Cu2ZnSnS4 Thin Film Solar Cell via a Photo-Sintering Technique

Alternative photo-sintering techniques for thermal annealing processes are used to improve the morphology, layer properties, and enhance solar cell performance. The fast, nontoxic, low cost, and environmentally friendly characteristics of Cu2ZnSnS4 have led to its consideration as an alternative potential absorber layer in copper indium gallium diselenide thin film solar cells. This work investigates the photo-sintering process for the absorber layer of Cu2ZnSnS4 solar cells. A Cu2ZnSnS4 layer was grown by hot-injection and screen-printing techniques, and the characteristics of the photo-sintered Cu2ZnSnS4 layer were evaluated by X-ray Diffraction, Raman spectroscopy, Energy dispersive X-ray analysis, Ultraviolet-visible spectroscopy, and field emission scanning electron microscopes. Overall, the optimal composition was Cu-poor and Zn-rich, without a secondary phase, estimated optical band-gap energy of approximately 1.6 eV, and enhanced morphology and kesterite crystallization. Using an intensity pulse light technique to the CZTS layer, fabrication of the solar cell device demonstrated successfully, and the efficiency of 1.01% was achieved at 2.96 J/cm2.

Tuneable manganese oxide nanoparticle based theranostic agents for potential diagnosis and drug delivery

Among various magnetic nanoparticles, manganese oxide nanoparticles are considered as established T 1 magnetic resonance imaging (MRI) contrast agents for preclinical research. The implications of their degradation properties and use as therapeutic carriers in drug delivery systems have not been explored. In addition, how the chemical composition and size of manganese oxide nanoparticles, as well as the surrounding environment, influence their degradation and MRI contrast properties (T 1 vs. T 2) have not been studied in great detail. A fundamental understanding of their characteristic properties, such as degradation, is highly desirable for developing simultaneous diagnosis and therapeutic solutions. Here, we demonstrate how the precursor type and reaction environment affect the size and chemical composition of manganese oxide nanoparticles and evaluate their influence on the nanoparticle degradability and release of the drug l-3,4-dihydroxyphenylalanine (l-dopa). The results show that the degradation rate (and the associated release of drug l-dopa molecules) of manganese oxide nanoparticles depends on their size, composition and the surrounding environment (aqueous or biometric fluid). The dependence of MRI relaxivities of manganese oxide nanoparticles on the size, chemical composition and nanoparticle degradation in water is also established. A preliminary cell viability study reveals the cytocompatible properties of l-dopa functionalized manganese oxide nanoparticles. Overall, this work provides new insights into smartly designed manganese oxide nanoparticles with multitasking capabilities to target bioimaging and therapeutic applications.

Small iron oxide nanoparticles as MRI T1 contrast agent: scalable inexpensive water-based synthesis using a flow reactor

Small iron oxide nanoparticles (IONPs) were synthesised in water via co-precipitation by quenching particle growth after the desired magnetic iron oxide phase formed. This was achieved in a millifluidic multistage flow reactor by precisely timed addition of an acidic solution. IONPs (≤5 nm), a suitable size for positive T1 magnetic resonance imaging (MRI) contrast agents, were obtained and stabilised continuously. This novel flow chemistry approach facilitates a reproducible and scalable production, which is a crucial paradigm shift to utilise IONPs as contrast agents and replace currently used Gd complexes. Acid addition had to be timed carefully, as the inverse spinel structure formed within seconds after initiating the co-precipitation. Late quenching allowed IONPs to grow larger than 5 nm, whereas premature acid addition yielded undesired oxide phases. Use of a flow reactor was not only essential for scalability, but also to synthesise monodisperse and non-agglomerated small IONPs as (i) co-precipitation and acid addition occurred at homogenous environment due to accurate temperature control and rapid mixing and (ii) quenching of particle growth was possible at the optimum time, i.e., a few seconds after initiating co-precipitation. In addition to the timing of growth quenching, the effect of temperature and dextran present during co-precipitation on the final particle size was investigated. This approach differs from small IONP syntheses in batch utilising either growth inhibitors (which likely leads to impurities) or high temperature methods in organic solvents. Furthermore, this continuous synthesis enables the low-cost (<£10 per g) and large-scale production of highly stable small IONPs without the use of toxic reagents. The flow-synthesised small IONPs showed high T1 contrast enhancement, with transversal relaxivity (r2) reduced to 20.5 mM-1 s-1 and longitudinal relaxivity (r1) higher than 10 mM-1 s-1, which is among the highest values reported for water-based IONP synthesis.

Facile Organometallic Synthesis of Fe-Based Nanomaterials by Hot Injection Reaction

Fe-based colloids with a core/shell structure consisting of metallic iron and iron oxide were synthesized by a facile hot injection reaction of iron pentacarbonyl in a multi-surfactant mixture. The size of the colloidal particles was affected by the reaction temperature and the results demonstrated that their stability against complete oxidation related to their size. The crystal structure and the morphology were identified by powder X-ray diffraction and transmission electron microscopy, while the magnetic properties were studied at room temperature with a vibrating sample magnetometer. The injection temperature plays a very crucial role and higher temperatures enhance the stability and the resistance against oxidation. For the case of injection at 315 °C, the nanoparticles had around a 10 nm mean diameter and revealed 132 emu/g. Remarkably, a stable dispersion was created due to the colloids' surface functionalization in a nonpolar solvent.

Advanced Functional Nanostructures based on Magnetic Iron Oxide Nanomaterials for Water Remediation: A Review

The fast growth of industrialization combined with the increasing population has led to an unparalleled demand for providing water in a safe, reliable, and cost-effective way, which has become one of the biggest challenges of the twenty-first century faced by global society. The application of nanotechnology in water treatment and pollution cleanup is a promising alternative in order to overcome the current limitations. In particular, the application of magnetic iron oxide nanoparticles (MIONs) for environmental remediation has currently received remarkable attention due to its unique combination of physicochemical and magnetic properties. Given the broadening use of these functional engineered nanomaterials, there is a growing concern about the adverse effects upon exposure of products and by-products to the environment. This makes vitally relevant the development of green chemistry in the synthesis processes combined with a trustworthy risk assessment of the nanotoxicity of MIONs as the scientific knowledge of the potential hazard of nanomaterials remains limited. This work provides comprehensive coverage of the recent progress on designing and developing iron oxide-based nanomaterials through a green synthesis strategy, including the use of benign solvents and ligands. Despite the limitations of nanotoxicity and environmental risks of iron oxide-based nanoparticles for the ecosystem, this critical review presents a contribution to the emerging knowledge concerning the theoretical and experimental studies on the toxicity of MIONs. Potential improvement of applications of advanced iron oxide-based hybrid nanostructures in water treatment and pollution control is also addressed in this review.

Reversible Diels-Alder Reactions with a Fluorescent Dye on the Surface of Magnetite Nanoparticles

Diels–Alder reactions on the surface of nanoparticles allow a thermoreversible functionalization of the nanosized building blocks. We report the synthesis of well-defined magnetite nanoparticles by thermal decomposition reaction and their functionalization with maleimide groups. Attachment of these dienophiles was realized by the synthesis of organophosphonate coupling agents and a partial ligand exchange of the original carboxylic acid groups. The functionalized iron oxide particles allow a covalent surface attachment of a furfuryl-functionalized rhodamine B dye by a Diels–Alder reaction at 60 °C. The resulting particles showed the typical fluorescence of rhodamine B. The dye can be cleaved off the particle surface by a retro-Diels–Alder reaction. The study showed that organic functions can be thermoreversibly attached onto inorganic nanoparticles.

Iron(iii) chelated paramagnetic polymeric nanoparticle formulation as a next-generation T1-weighted MRI contrast agent

In pursuit of safer alternatives to Gd-based MRI contrast agents due to its toxicity and organ deposition, herein, we developed a safer and efficient clinically relevant iron(iii) chelated polymeric nanoparticle as a T1-weighted MRI contrast agent.

Pulse Magnetic Fields Induced Drug Release from Gold Coated Magnetic Nanoparticle Decorated Liposomes

Magnetic nanoparticle-assisted drug release from liposomes is an important way to enhance the functionality/usefulness of liposomes. This work demonstrates an approach how to integrate magnetic nanoparticles with liposomes with the assistance of gold–thiol chemistry. The gold coated magnetic particles cover the thiolated liposomes from the outside, which removes the competition of the drug molecules and the triggering magnetic particles to free the inner space of the liposomes when compared to previous magneto liposome formulations. The liposome consists of dipalmitoyl phosphatidylcholine (DPPC) combined with distearoylphosphatidylcholine (DSPC) in addition to regular cholesterol or cholesterol-PEG-SH. Permeability assays and electron microscopy images show efficient coupling between the liposomes and nanoparticles in the presence of thiol groups without compromising the functionality of the liposomes. The nanoparticles such as gold nanoparticles, gold coated iron oxide nanoparticles and bare iron oxide nanoparticles are added following the model drug encapsulation. The efficient coupling between the gold coated nanoparticles (NPs) and the thiolate liposomes is evidenced by the shift in transition temperature of the thiolated liposomes. The addition of magnetically triggerable nanoparticles externally makes the entire interior of liposomes available for drug loading. The drug release efficiencies of these liposomes/NPs complexes were compared under exposure to pulsed magnetic fields. The results indicate up to 20% of the drug can be released in short time, which is comparable in efficiency to previous studies performed when magnetic NPs were located inside liposomes. Interestingly, the liposomes were found to exhibit variations in release efficiency based on different dilution media which is attributed to an osmotic pressure effect on liposomal stability.