Magnetite Surface Research Articles

Portable glucose biosensor based on polynorepinephrine@magnetite nanomaterial integrated with a smartphone analyzer for point-of-care application

This work describes a novel nanoplatform based on polynorepinephrine (PNE) grafted on magnetite nanoparticles (Fe3O4) with glucose oxidase (GOx) from Aspergillus niger (Fe3O4@PNE-GOx). The system was integrated with a smartphone analyzer as a potential point-of-care testing (POCT) biosensor for glucose measurement.Covering the magnetite surface with the biomimetic polymer polynorepinephrine significantly increased the effectiveness of enzyme immobilization which was 38.40 mg g−1, compared with 17.30 mg g−1 on the bare surface of magnetite. The Fe3O4@PNE-GOx nanoplatform was deposited on a screen-printed electrode (SPE) and then used with the world’s smallest ready-to-go potentiostat and a smartphone in tandem for glucose measurement. This biosensor displayed abroad range of linearity (0.2–24 mM), a low detection limit (6.1 μM), and good sensitivity (97.34 μA mM−1 cm−2). Moreover, it exhibited a fast electrocatalytic response (8 s), and long-term stability (up to 20 weeks). It was used to detect glucose in real samples such as human serum, human blood, infusion fluid, and commercial glucose solutions.The results obtained indicate that the proposed biosensor may be an attractive system for point-of-care testing (POCT), or in various industries, using asmartphone and potentiostat in tandem.

A novel study on the preferential attachment of chromophore and auxochrome groups in azo dye adsorption on different greenly synthesized magnetite nanoparticles: investigation of the influence of the mediating plant extract's acidity.

In this paper, the adsorption of Evans blue (EB) and methyl orange (MO) azo dyes on four greenly synthesized magnetite nanoparticles has been studied to investigate the effect of the mediating plant extract's acidity on magnetite surface reactivity in azo dye adsorption. Magnetite surface reactivity has been studied through the analysis of preferential attachment of dye chromophore and auxochrome groups on magnetite nanoparticles, and adsorption yields. According to the contents of chromophore and auxochrome groups in dye structures, the mediating plant extract's acidity effect on acid site types and densities was also deduced. Used plants for the green synthesis were: Artemisia herba-alba (L), Matricaria pubescens (L), Juniperus phoenicea (L), and Rosmarinus officinalis (L), and their extract pHs were respectively 5.25, 5.05, 4.63, and 3.69. The four greenly synthesized samples of magnetite were characterized by XRD, SEM, ATR-FTIR, and UV-Vis techniques. The novelty of this paper lies in highlighting the influence of the mediating plant extract's acidity on the greenly synthesized magnetite surface reactivity towards the preferential attachment of chromophore and auxochrome functional groups in azo dye adsorption, where obtained results show that the mediating plant extract's acidity has a clear effect on the preferential attachment of chromophore and auxochrome groups on magnetite surfaces as well as on azo dyes' adsorption yields and capacities. Indeed, the decrease in the plant extract's acidity leads to an increase in the attachment of chromophore groups and a decrease in the attachment of auxochrome groups. So, it leads to an increase in Lewis acid site density and a decrease in Brønsted acid site density of magnetite surfaces. Also, the decrease of the plant extract's acidity leads to an increase in the studied dye adsorption yields, and this is because the majority of functional groups of MO and EB dyes are chromophores that attach to Lewis acid sites. The difference found in adsorption yields of EB and MO on all four magnetite samples is due to the fact that the ratio of chromophore/auxochrome groups in EB is remarkably greater than that in MO. The linear and non-linear pseudo-first-order and pseudo-second-order kinetics of the adsorption as well as the intra-particle diffusion mechanism have been analyzed. Obtained results indicate that in all adsorption processes the adsorption kinetics followed a linear pseudo-first-order kinetic model, and film diffusion is the step that controlled adsorption mechanisms. The thermodynamic studies of EB and MO adsorption processes on the four magnetite surfaces have been analyzed in the temperature range of 303.15–318.15 K. Obtained results reveal the endothermic nature of the adsorption in all cases.

Phosphate recovery from anaerobic digestion effluent using synthetic magnetite particles

Many researchers studied for phosphate recovery, but practical approach through scale-up still remains a challenge. Therefore, we present a technology for recovery of phosphate in anaerobic digestion effluent by synthesizing magnetite. The zeta potential, Fourier transform infrared spectroscopy (FT-IR), and X-ray Photoelectron Spectroscopy (XPS) analyses were used to derive the phosphate adsorption mechanism of magnetite. Physical adsorption is a weak bond generated by electrostatic attraction on the magnetite surface, and chemical adsorption occurs by ligand exchange in which OH- bonded to the magnetite surface is replaced with H2PO3-. The pseudo-second-order kinetics (R2 > 0.9999) and Langmuir-Freundlich model (R2 > 0.9999) were most suitable for phosphate adsorption. Magnetite follows both Langmuir and Freundlich adsorption isotherms, the phosphate adsorption characteristics by adsorption isotherm is consistent with the zeta potential, XPS and FT-IR analysis. In addition, it was confirmed that magnetite is a stable adsorbent when operating phosphate recovery processes for sewage through adsorption, desorption, and reuse.

Functionalized Fe3O4 Nanoparticles as Glassy Carbon Electrode Modifiers for Heavy Metal Ions Detection-A Mini Review.

Over the past few decades, nanoparticles of iron oxide Fe3O4 (magnetite) gained significant attention in both basic studies and many practical applications. Their unique properties such as superparamagnetism, low toxicity, synthesis simplicity, high surface area to volume ratio, simple separation methodology by an external magnetic field, and renewability are the reasons for their successful utilisation in environmental remediation, biomedical, and agricultural applications. Moreover, the magnetite surface modification enables the successful binding of various analytes. In this work, we discuss the usage of core–shell nanoparticles and nanocomposites based on Fe3O4 for the modification of the GC electrode surface. Furthermore, this review focuses on the heavy metal ions electrochemical detection using Fe3O4-based nanoparticles-modified electrodes. Moreover, the most frequently used electrochemical methods, such as differential pulse anodic stripping voltammetry and measurement conditions, including deposition potential, deposition time, and electrolyte selection, are discussed.

In-situ preparation of a bismuth-based magnetic composite for catalytic reduction of 4-nitrophenol

The substitution of noble metal-based catalysts by a non-precious metal is of great interest to develop cost-efficient catalysts. However, maintaining the efficiency, good selectivity, and recyclability properties of noble-metal-based catalysts remains a challenge. The present work reports the preparation of a magnetic composite by co-precipitation method, containing a complex mixture of bismuth subcarbonate, bismuth oxide, hydrotalcite-like compounds, and magnesium carbonate on magnetic iron oxide (Mag-MMO). Bismuth species showed a disordered stacking of nanoflakes over the magnetite surface with embedded magnesium carbonate. The composite exhibited high efficiency towards the catalytic reduction of 4-nitrophenol to 4-aminophenol using borohydride as a reducing agent, showing high catalytic activity, with a first-order kinetic constant of 4.05 min−1. During the catalytic reaction, borohydride converted in situ bismuth oxide and bismuth subcarbonate into semi-metallic bismuth. Additionally, the catalyst was easily separated from the supernatant by a magnet and reused for nine more cycles, indicating good cycle stability. The obtained results suggest that Mag-MMO is a promising catalyst for the 4-nitrophenol conversion process, with outstanding cyclical performance.

Recovery of ultrafine scheelite particles by magnetic seeding flocculation and its mechanism

Froth flotation has been proven to be the most efficient mineral processing technology for fine particles. However, it cannot be applied to processing ultrafine particles, especially ultrafine scheelite with sizes of −10 µm, thereby wasting a lot of tungsten resources. In this study, positively-charged and hydrophobic magnetic seeds were fabricated and employed instead of bubbles to capture ultrafine scheelite particles, significantly improving the recovery of the ultrafine particles via magnetic separation. Here, a novel surfactant, lead complexes with benzohydroxamic acid (Pb–BHA), were developed to modify the magnetite. The zeta potential, Fourier-transform infrared (FT–IR) spectroscopy and surface hydrophobicity measurements indicated that Pb–BHA was adsorbed on the magnetite surface, inducing a positively-charged hydrophobic surface. Ultrafine scheelite (−10 µm) was treated with sodium oleate (NaOL) to impart it with negative charges and surface hydrophobicity. The flocculation of magnetite and scheelite is directly observable via scanning electron microscopy (SEM). The extended Derjaguin–Landau–Verwey–Overbeek (EDLVO) theory was applied to analyse the mutual attraction of two kinds of particles, and the calculation results demonstrated that they aggregated mainly through electrostatic and hydrophobic interactions. This technology affords an alternative solution for processing ultrafine valuable particles.

Adsorption characteristics of citric acid on Fe3O4 (001), (011), and (111) surfaces.

Magnetite (001), (011), and (111) surfaces were the focus of our study. Magnetite (001) surface has two different terminations, that is, Fetet and 2Feoct4O. Magnetite (011) surface has two different terminations, that is, 2Feoct4O and 2Fetet2Feoct4O. Magnetite (111) surface has six different terminations, that is, Fetet1, Feoct, Fetet2, 3Feoct, 4O1, and 4O2. Comparing surface energies of (001), (011), and (111) surfaces, (001) has the smallest surface energy, and (111) has the largest surface energy except for Feoct termination, which means that (001) surface is the easiest to be cleaved, followed by (011) and (111) surfaces. Comparing adsorption energies of citric acid onto (001), (011), and (111) surfaces, (111) has the largest adsorption energies except for Fetet2 termination, and (001) has the smallest adsorption energies, which means that (111) surface is the most active for citric acid adsorption, followed by (011) and (001) surfaces. PDOS (partial density of states) of citric acid adsorbed onto (001), (011), and (111) surfaces with different terminations shows that 3d orbital of Fe of magnetite surface does not contribute to the adsorption, and 4s orbital of Fe of magnetite surface and 2s and 2p orbitals of O of citric acid contribute to the adsorption.

Adsorption of Epoxy Oligomers on Iron Oxide Surfaces: The Importance of Surface Treatment and the Role of Entropy.

Epoxy-based coatings are widely used in a range of industries as protective coatings. The performance of the final solid-polymer system is dependent on the physicochemical properties of the interface and the interaction between the polymer and the solid substrate. In this study, we perform atomistic molecular dynamics simulations to investigate the binding of a common component in epoxy resins, diglycidyl ether of bisphenol A (DGEBA), on two iron oxide surfaces, hematite (0001) and magnetite (100), and investigate the effect of surface hydroxylation on the binding energy. We show that adsorption of DGEBA on hematite is more favorable than on magnetite and that the adsorbed molecules are highly localized on the pristine hematite surface but mobile on highly hydroxylated hematite surfaces and magnetite surfaces irregardless of surface hydroxylation fraction. A high degree of hydroxylation significantly reduces the binding energy of DGEBA on hematite but not on magnetite. The free-energy calculations confirm the trends observed upon hydroxylation, but the magnitude of the potential of mean force is lower than the binding energy due to the entropic contributions. Therefore, it can be suggested that DGEBA will adsorb more strongly on a surface containing a higher content of hematite than magnetite and that the presence of hydroxyl groups will weaken this adsorption. The presence of hydroxyl groups increases mobility of the chains, which can affect the coating rigidity.

Development of Dioctyl Phthalate@Fe3O4 Nanocomposite Reinforced Hollow Fiber Solid/ Liquid Phase Microextraction Followed by HPLC-DAD for the Determination of Atorvastatin and Gemfibrozil in Human Urine.

The desirable levels of lipids, especially in patients with coronary artery disease, might not be achievable with a single lipid-lowering drug; thus, combination therapy using atorvastatin and gemfibrozil seems to be a promising approach. However, the potential for drugdrug interaction needs to be taken into consideration, and the combination (atorvastatin and gemfibrozil) is recommended only when other options for reducing lipids have been exhausted. Many studies are conducted for the determination of atorvastatin or gemfibrozil in biological fluids and tablets; however, the simultaneous determination of the two drugs in complex biological matrices is limited. Consequently, the development of a sensitive method for simultaneous determination of atorvastatin and gemfibrozil in urine samples is urgently needed to make sure that the doses of both medications are given to patients correctly to prevent the risk of side effects outcomes associated with the adverse drug-drug interaction. A synthesized nanocomposite sorbent, dioctyl phthalate coated on the surface of magnetite (DOP@Fe3O4), was reinforced and immobilized into the pores of 2.5 cm segment hollow fiber microtube via ultrasonication, and the lumen of the microtube was filled with 1-octanol as an organic solvent with two ends heat-sealed. The prepared (DOP@Fe3O4-HF-SLPME) device was directly immersed into 10 mL of a sample solution containing atorvastatin and gemfibrozil with agitation. Subsequently, the microextraction device was transferred to HPLC-micro-vial containing an appropriate solvent, and the selected analytes were desorbed under ultrasonication prior to HPLCDAD analysis. The main factors influencing the adsorption and desorption process of the selected drugs have been optimized. The DOP@Fe3O4-HF-SLPME combined with the HPLC-DAD method was analytically evaluated for the simultaneous determination of atorvastatin and gemfibrozil in human urine samples using the optimized conditions. In spiked urine samples, the method showed a good linearity R2˃ 0.998, RSD from 1.41- 5.33%, and the limits of detection/ quantification (LOD/ LOQ) were 0.11/ 0.36 and 0.73/ 2.42 μg L-1 for atorvastatin and gemfibrozil, respectively. The enrichment factors of atorvastatin and gemfibrozil were 83.4 and 101.2, with extraction recoveries of 80.9% and 99.0%, respectively. The developed method demonstrated comparable results against referenced methods and a satisfactory result for determining the selected drugs in the patient's urine samples. The DOP@Fe3O4-HF-SLPME followed by HPLC-DAD was proved to be an efficient, sensitive, and cost-effective biopharmaceutical analysis method for trace levels of atorvastatin and gemfibrozil in the biological fluid matrix.

In English

Сombination of properties of lectins and magnetically sensitive iron-containing nanocomposites (NC) for use in oncology is actual and promising from scientific and applied point of view. The aim of the research is to synthesize and to study new iron-containing NC and magnetic fluids containing bioactive bacterial lectin, promising for use as prototypes of new effective antitumor vector systems for targeted drug delivery and combined local therapy of cancer with minimized side effects on the body and improved compatibility with other remedies. To create vector systems, nanodisperse magnetite was synthesized by the Elmore reaction. The synthesis of aluminum-containing coating on the surface of Fe3O4 was carried out by double chemical modification with aluminum isopropylate. The obtained Fe3O4/Al2O3 NC was impregnated with sucrose solutions. Carbonization of the carbohydrate shell of NC was carried out in argon (500 °C). As a result, Fe3O4/Al2O3/C NC was obtained. The magnetic properties of nanostructures were measured using a laboratory vibration magnetometer of Foner type at room temperature. Adsorption immobilization of lectin was performed in 0.9 % NaCl solution in a dynamic mode at room temperature. Bacterial cytotoxic lectin of B. subtilis IMB B-7724 was used in the experiments. The amount of adsorbed substance (A) on the surface of nanocomposites was determined by measuring the concentration of lectin in the contact solutions before and after adsorption using a calibration graph. Measuring of the optical density and absorption spectra of lectin was performed on a spectrometer Lambda 35 UV/vis Perkin Elmer Instruments at λ = 280 nm. Standard techniques and equipment were used for biological research. The processes of adsorption immobilization of cytotoxic bacterial lectin of B. subtilis IMB B-7724 from physiologic saline on the surface of magnetite and carbon-containing Fe3O4/Al2O3/C NC were studied at room temperature. It has been found that the adsorption capacity of lectin on the surface of magnetite is 25.3 mg/g, and Fe3O4/Al2O3/C NC – 36.3 mg/g (at initial concentrations of lectin 0.06–0.4 mg/mL). The extraction extent of lectin R (%) was 12–38 % for magnetite and 46–67 % for Fe3O4/Al2O3/C NC. The dependence of the adsorption capacity on time was studied. A magnetic fluid (MF) based on single-domain Fe3O4, containing lectin was synthesized and investigated. Immobilization of lectin on MF particles was carried out in a dynamic mode at room temperature for 3 hours. The concentration of lectin in the composition of MF was 0.2 mg/mL. MF with immobilized lectin was further modified with PEG-2000. The synthesis of Fe3O4/ol.Na/lectin/PEG (ol.Na – sodium oleate) vector system was carried out in a dynamic mode for 3 hours. Modification of the surface of nanoparticles with polyethylene glycol was performed in order to increase the stability of the magnetic fluid, reducing the aggregation of particles. To determine the effect of experimental samples on the viability of MCF-7 cells in vitro, the following samples were prepared: Fe3O4/ol.Na/PEG (MF), CFe3O4 = 3 mg/mL; cytotoxic lectin of B. subtilis IMB B-7724 (CL), CCL = 0.2 mg/mL; nanobiocomposite (NBC). Nanobiocomposite based on MF and bacterial lectin was found to have a synergistic cytotoxic effect on MCF-7 human breast cancer cells, causing up to 40 % cell death. The IC50 values for the nanobiocomposite and lectin in relation to MCF-7 cells were 100 and 125 μg/mL, respectively. The results of research show that the combination of properties of lectins and magnetically sensitive iron-containing NC for use in oncology is a promising direction in creating new effective antitumor vector systems for targeted drug delivery and combined local therapy of cancer. The use of natural components in vector systems is a way to minimize the side effects on the body and improve compatibility with other antitumor remedies.

Study on Maximum Specific Loss Power in Fe3O4 Nanoparticles Decorated with Biocompatible Gamma-Cyclodextrins for Cancer Therapy with Superparamagnetic Hyperthermia.

Different chemical agents are used for the biocompatibility and/or functionality of the nanoparticles used in magnetic hyperthermia to reduce or even eliminate cellular toxicity and to limit the interaction between them (van der Waals and magnetic dipolar interactions), with highly beneficial effects on the efficiency of magnetic hyperthermia in cancer therapy. In this paper we propose an innovative strategy for the biocompatibility of these nanoparticles using gamma-cyclodextrins (γ-CDs) to decorate the surface of magnetite (Fe3O4) nanoparticles. The influence of the biocompatible organic layer of cyclodextrins, from the surface of Fe3O4 ferrimagnetic nanoparticles, on the maximum specific loss power in superparamagnetic hyperthermia, is presented and analyzed in detail in this paper. Furthermore, our study shows the optimum conditions in which the magnetic nanoparticles covered with gamma-cyclodextrin (Fe3O4–γ-CDs) can be utilized in superparamagnetic hyperthermia for an alternative cancer therapy with higher efficiency in destroying tumoral cells and eliminating cellular toxicity.

Preparation and Characterization of Magnetite – Silica Core – Shell Nanoparticles

In this study, two types of ligands were introduced onto the surface of magnetite nanoparticles by hydrolysis and condensation of organosilicon reagents: organosilane-tetraethoxysilane (TEOS) and aminoorganosilane - aminopropyltriethoxysilane (APTES). It is shown that coatings based on SiO2 solve a double problem: first, they prevent the aggregation of nanoparticles and the oxidation of magnetite; secondly, they allow the surface to be modified with various specific ligands for biomedical applications due to terminal groups. It was shown, that after the modification of TEOS and APTES (in argon and in air), the Fe3O4 content decreases to 66, 42, and 36%, respectively. The formation of a silicon framework on the magnetite surface due to Fe-O-Si and Si-O-Si bonds was determined by IR spectroscopy. The identification of surface amino groups is complicated due to the superposition of absorption bands of NH2- and OH-groups. This opens new prospective for creation of tailored nanocomposites containing magnetite nanoparticles. These materials can be further used as sorbents for various applications.

Influence of Magnetite Nanoparticles Shape and Spontaneous Surface Oxidation on the Electron Transport Mechanism.

The spontaneous oxidation of a magnetite surface and shape design are major aspects of synthesizing various nanostructures with unique magnetic and electrical properties, catalytic activity, and biocompatibility. In this article, the roles of different organic modifiers on the shape and formation of an oxidized layer composed of maghemite were discussed and described in the context of magnetic and electrical properties. It was confirmed that Fe3O4 nanoparticles synthesized in the presence of triphenylphosphine could be characterized by cuboidal shape, a relatively low average particle size (9.6 ± 2.0 nm), and high saturation magnetization equal to 55.2 emu/g. Furthermore, it has been confirmed that low-frequency conductivity and dielectric properties are related to surface disordering and oxidation. The electric energy storage possibility increased for nanoparticles with a disordered and oxidized surface, whereas the dielectric losses in these particles were strongly related to their size. The cuboidal magnetite nanoparticles synthesized in the presence of triphenylphosphine had an ultrahigh electrical conductivity (1.02 × 10−4 S/cm at 10 Hz) in comparison to the spherical ones. At higher temperatures, the maghemite content altered the behavior of electrons. The electrical conductivity can be described by correlated barrier hopping or overlapping large polaron tunneling. Interestingly, the activation energies of electrons transport by the surface were similar for all the analyzed nanoparticles in low- and high-temperature ranges.

Experimental Measurement and Equilibrium Modeling of Adsorption of Asphaltenes from Various Origins onto the Magnetite Surface under Static and Dynamic Conditions.

Wettability alterations, permeability reduction of reservoir rocks, and oil production decline may occur as a consequence of asphaltene adsorption and deposition on the surfaces of oil reservoir rocks. Magnetite and other iron minerals are abundant in the rock composition of sandstone reservoirs and cause problems by precipitation and adsorption of polar components of crude oil. The main purpose of this study was to investigate the adsorption of six asphaltene samples of various origins onto the magnetite surface. Characterization of magnetite was performed by Brunauer–Emmett–Teller (BET), Fourier transform infrared spectroscopy (FTIR), and X-ray fluorescence (XRF). Also, FTIR, dynamic light scattering (DLS), and elemental analysis were performed to characterize asphaltenes. Static and dynamic adsorption experiments were carried out to investigate the effects of the water phase, adsorbent size, flow rate, and asphaltene compositions on asphaltene uptake by the magnetite. The results showed that an increase in the nitrogen content and aromatic nature of asphaltenes increased their adsorption on magnetite. The addition of water to the adsorption tests significantly reduced the adsorption amount of asphaltenes on the magnetite. A considerable decrease in asphaltene adsorption was observed with an increase in the flow rate in dynamic tests. This shows that higher flow rates reduce the interaction between adsorbed asphaltenes and asphaltene aggregates in the solution, which reduces the uptake of more asphaltenes. Moreover, adsorbed asphaltene components with a weaker bond are detached from the magnetite surface, which can be attributed to the physisorption of asphaltenes. Eventually, four well-known adsorption isotherm models, namely, Langmuir, Dubinin–Radushkevich, Temkin, and Freundlich were utilized to find the mechanisms of asphaltene adsorption onto the magnetite surface. The Freundlich model seems to provide better estimates for the adsorption of asphaltenes on the magnetite surface. The findings of this study render insights into the better management of oil production in formations with iron-containing rocks.

Responsiveness assessment of cell cultures exposed to poly(tartaric acid) and its corresponding magnetic nanostructures

Cancer incidence is increasing progressively in recent years, and its wide distribution among younger generations raises even greater concerns. This caused an acceleration in the development of medicine by implementing modern methods for diagnosis, treatment, and therapy. In this context, polymer-functionalized magnetic nanomaterials evolved as helpful tools for both the medical and pharmacological fields. The present study reports the structural analysis and biocompatibility assessment of poly(tartaric acid) and its corresponding magnetic nanostructures. The current research aimed to elaborate a preliminary study on the responsiveness assessment of cell cultures exposed to these nanomaterials for future biomedical applications. Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) highlighted the successful attachment of the polyester on the magnetite surface and the preparation of the core-shell magnetic nanostructures. Biochemical experiments were performed in vitro on three types of human cell lines: normal keratinocytes, lung carcinoma, and skin melanoma. Viability, membrane integrity, and oxidative analyses performed on the obtained nanostructures proved a great inhibitory potential against cancer cell lines and little to no harmful effect against normal cell lines.

β-Amino alcohol-based organosilane tailored magnetite embedded mesoporous silica nanoparticles exhibit controlled-release of curcumin triggered by pH

Controlled-release feature is still a major challenge in the design of drug carriers, especially in cancer therapy. In our investigation, we successfully tailored the surface of magnetite embedded mesoporous silica (MNP@SiO2) with β-amino alcohol-based organosilane through a facile and one-pot method and further characterized using FTIR, XRD, N2 adsorption-desorption, VSM, SEM, and TEM. The functionalized MNP@SiO2 exhibits high loading capacity up to 309.23 mg g−1. Additionally, this functionalization also acts as a barrier for preventing premature drug release. Accordingly, only small amount of curcumin (∼10%) is released at pH 7.4 and incrementally increases at pH 4.0 (49.12%). This indicates that the controlled-release feature is provided by tailored-nanoparticles, denoted as MNP@SiO2-NH2. Our study also reveals good magnetic properties (Ms = 22.57 emu g−1) of MNP@SiO2-NH2 which possibly extend its application for magnetic hyperthermia to improve therapeutics efficacy.

Influencing mechanisms of siderite and magnetite, on naphthalene biodegradation: Insights from degradability and mineral surface structure

Biodegradation is the most economical and efficient process for remediating polycyclic aromatic hydrocarbons (PAHs) such as naphthalene (Nap). Soil composition is pivotal in controlling PAH migration and transformation. Iron minerals such as siderite and magnetite are the primary components of soil and sediment and play key roles in organic pollutant biodegradation. However, it is unclear whether siderite and magnetite promote or inhibit Nap biodegradation. The effects of siderite and magnetite on Nap biodegradation were investigated through batch experiments in this study. The results indicated that siderite increased Nap biodegradation efficiency by 7.87%, whereas magnetite inhibited Nap biodegradation efficiency by 3.54%. In the presence of siderite, Nap-degrading bacteria with acid-producing effects promoted siderite dissolution via metabolic activity, resulting in an increased Fe (II) concentration in solution which accelerated the iron reduction process and promoted Nap biodegradation. In addition, the presence of iron minerals altered the genus-level community structure. Anaerobic sulfate-reducing bacteria such as Desulfosporosinus occurred in the presence of siderite, indicating that sulfate reduction occurred in advance under the influence of siderite. In the presence of magnetite, Fe (III) in iron minerals were converted to Fe (II), and under the mediation of microorganisms, Fe (II) combined with carbonate to form secondary minerals (e.g., siderite). Secondary minerals were attached to the surface of magnetite, which inhibited magnetite dissolution and reduced the efficiency of Fe (III) utilization by microorganisms. Furthermore, as the reaction proceeds, acid-producing microorganisms promoted magnetite further dissolution, resulting in a longer duration of the Fe (III) reduction process. Bacteria utilizing sulfuric acid as the terminal electron acceptor consumed organic matter more rapidly than those using iron as the terminal electron acceptor. Therefore, magnetite inhibited Nap degradation. These observations enhance our understanding of the interaction mechanisms of iron minerals, organic pollutants, and degrading bacteria during the biodegradation process.

Bulk spin polarization of magnetite from spin-resolved hard x-ray photoelectron spectroscopy

There is broad consensus that magnetite (${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$) is a promising material for spintronics applications due to its high degree of spin polarization at the Fermi level. However, previous attempts to measure the spin polarization by spin-resolved photoemission spectroscopy have been hampered by the use of low photon energies resulting in high surface sensitivity. The surfaces of magnetite, though, tend to reconstruct due to their polar nature, and thus their magnetic and electronic properties may strongly deviate from each other and from the bulk, dependent on their orientation and specific preparation. In this study, we determine the intrinsic---i.e., bulk---spin polarization of magnetite by spin-resolved photoelectron spectroscopy on (111)-oriented thin films, epitaxially grown on ZnO(0001), with hard x-rays, making it a truly bulk-sensitive probe. This becomes possible by using a novel, specially adapted momentum microscope, featuring time-of-flight energy recording and an imaging spin-filter.

Molecularly Imprinted Polymers for Dispersive (Micro)Solid Phase Extraction: A Review

The review describes the development of batch solid phase extraction procedures based on dispersive (micro)solid phase extraction with molecularly imprinted polymers (MIPs) and magnetic MIPs (MMIPs). Advantages and disadvantages of the various MIPs for dispersive solid phase extraction and dispersive (micro)solid phase extraction are discussed. In addition, an effort has also been made to condense the information regarding MMIPs since there are a great variety of supports (magnetite and magnetite composites with carbon nanotubes, graphene oxide, or organic metal framework) and magnetite surface functionalization mechanisms for enhancing MIP synthesis, including reversible addition-fragmentation chain-transfer (RAFT) polymerization. Finally, drawbacks and future prospects for improving molecularly imprinted (micro)solid phase extraction (MIMSPE) are also appraised.

Preparation of magnetite coated humic acid (Fe3O4-HA) as malachite green dye adsorbent

Magnetite (Fe3O4) coating using humic acid (HA) to form Fe3O4/HA as malachite green dye adsorbent has been carried out. Humic acid was obtained from the isolation of peat soil from Rawa Pening, Ambarawa, Central Java, using the conventional alkaline extraction method. Synthesis of magnetite and Fe3O4/HA by coprecipitation method under alkaline conditions using NaOH. The characterization using Fourier Transform Infrared (FTIR) shows a bond between carboxylate groups in HA and Fe on magnetite, which proves that HA coating on magnetite surfaces has been successfully carried out. The characterization results using X-Ray Diffraction (XRD) showed that the coating of HA on magnetite did not change its phase shape but decreased its peak intensity. The results of characterization using a Surface Area Analyzer (SAA) showed that HA coating increased the surface area of Fe3O4. The optimum adsorption of malachite green by HA occurred at pH 3 for 60 minutes, with a concentration of 96.95 mg/L. Magnetite adsorbs optimally at pH 7 for 90 minutes and a concentration of 83.48 mg/L, while Fe3O4/HA occurs at pH 3 for 90 minutes with 104.15 mg/L.