Surface Of Magnetite Particles Research Articles

Irinotecan-loaded magnetite-silica core-shell systems for colorectal cancer treatment

Colorectal cancer represents a worldwide spread type of cancer and it is regarded as one of the leading death causes, along with lung, breast, and prostate cancers. Since conventional surgical resection and chemotherapy proved limited efficiency, the use of alternative drug delivery systems that ensure the controlled release of cytostatic agents possess immense potential for treatment. In this regard, the present study aimed to develop and evaluate the efficiency of a series of irinotecan-loaded magnetite-silica core–shell systems. The magnetite particles were obtained through a solvothermal treatment, while the silica shell was obtained through the Stöber method directly onto the surface of magnetite particles. Subsequently, the core–shell systems were physico-chemically and morpho-structurally evaluated trough X-ray diffraction (XRD) and (high-resolution) transmission electron microscopy ((HR-)TEM) equipped with a High Annular Angular Dark Field Detector (HAADF) for elemental mapping. After the irinotecan loading, the drug delivery systems were evaluated through Fourier-transform infrared spectroscopy (FT-IR), thermogravimetry and differential scanning calorimetry (TG-DSC), and UV–Vis spectrophotometry. Additionally, the Brunauer–Emmett-Teller (BET) method was employed for determining the surface area and pore volume of the systems. The biological functionality of the core-shells was investigated through the MTT assay performed on both normal and cancer cells. The results of the study confirmed the formation of highly crystalline magnetite particles comprising the core and mesoporous silica layers of sizes varying between 2 and 7 nm as the shell. Additionally, the drug loading and release was dependent on the type of the silica synthesis procedure, since the lack of hexadecyltrimethylammonium bromide (CTAB) resulted in higher drug loading but lower cumulative release. Moreover, the nanostructured systems demonstrated a targeted efficiency towards HT-29 colorectal adenocarcinoma cells, as in the case of normal L929 fibroblast cells, the cell viability was higher than for the pristine drug. In this manner, this study provides the means and procedures for developing drug delivery systems with applicability in the treatment of cancer.

Effect of Temperature on Reduction Behaviors and Microstructural Changes of Magnetite with H2 Under Fluidized Bed Conditions

Here in this paper, the effect of temperature on reduction behaviors and microstructural changes of magnetite by hydrogen is studied in a laboratory micro‐fluidized bed reactor. The phase compositions and microstructures of reduced samples are investigated by X‐ray diffraction, scanning electron microscope, and Brunauer–Emmett–Teller method. The results show that a metallization degree of 90.85% is obtained under the optimal conditions of reduction temperature of 570 °C, H2 concentration of 80%, and reduction time of 40 min. The metallization degree gradually increases with the temperature, and the magnetite (Fe3O4) is directly reduced to porous metallic iron (Fe) in the temperature range of 470–570 °C. While, the magnetite is first reduced to wüstite (FeO) and then further reduced to metallic iron with a dense structure in the temperature range of 570–670 °C. The dense metallic iron layer forms on the raw magnetite particle surface, which prevents the contact and reaction of the reducing gas with the iron oxide, resulting in a sharp decrease in the metallization degree.

Fundamental study on cancer therapy by blocking newborn blood vessels with surface modified magnetite particles

We propose a novel cancer treatment which involves blocking newborn blood vessels around the diseased part. This treatment has minimal side effects and is less invasive. In the therapy, ferromagnetic particles administered into the body are accumulated in the newborn blood vessels. Next, the particles are aggregated to block the blood vessels to prevent cancer growth and metastasis. In this study, we modified the surface of magnetite particles with biocompatible polyacrylic acid to design particles that form irreversible aggregation on the application of a magnetic field. We succeeded in blocking only the flow path under a uniform magnetic field using the prepared particles, as is verified by the results of a model experiment. We assume that the blockage occurred due to the formation of chain aggregation under the magnetic field and the increase in pressure loss.

A novel method for the modification of magnetite nanoparticles for the enhancement of its dispersibility in hydrophobic media

Different mixing methods were used for the fatty acid modification of magnetite nanoparticles. The magnetite nanoparticles were dissolved in ethanol with a previously dissolved oleic or stearic acid solution. The mix was then homogenized and washed to eliminate the unreacted fatty acid. The modified nanoparticles were FTIR analysis confirmed that the modified nanoparticles presented the characteristic groups of the fatty acids. The vibrating sample magnetometer analysis (VSM) showed a very slight decrease in the magnetic properties of the magnetite, from 88.7 to 53.7 emu/g, which obviously was due to the presence of the fatty acids. TGA showed that the fatty acid modification degree of the magnetite was less than that reported elsewhere, nonetheless, during the precipitation tests in toluene; it was observed that the modification was sufficient to maintain the stability of the dispersion without affecting the magnetic properties. Additionally, TEM micrographs showed that the modified magnetite nanoparticles formed a cluster, with the fatty acids surrounding the magnetite nanoparticles. Confirming that the fatty acid layer was deposited as monolayers on the magnetite particle surface of approximately 2 nm in thickness with OA and 2.3 nm with SA. It was observed that the use of the two fatty acids produced inter-digitation among the fatty acids. Finally, nanocomposites based on liquid silicone rubber (LSR) were prepared with modified and unmodified magnetite and their rheological and magnetic behavior was studied. This fatty acid modification of magnetite particles improved the dispersion and distribution of modified particles into the silicon matrix.

An electro-Fenton system with magnetite coated stainless steel mesh as cathode

An electro-Fenton system with magnetite coated stainless steel (SUS) mesh as cathode was developed and tested for removing methylene blue in wastewater. For better adhesion between magnetite particles and SUS mesh surface, surface roughening of SUS mesh with FeAl particles was carried out. 850 °C was chosen as the optimized calcination temperature for FeAl treatment. When SUS meshes were coated with magnetite particles and applied as the cathode in an electro-Fenton system, catalytic activation of in situ produced H2O2 was enhanced. And this activation occurred heterogeneously on the surface of magnetite particles on cathode rather than homogeneously with free roaming leached ferrous ions. By coating magnetite particles on SUS meshes, degradation efficiency of methylene blue in neutral conditions was better than that in acidic conditions with bare SUS meshes as cathode in our electro-Fenton system.

Self-enhanced and efficient removal of arsenic from waste acid using magnetite as an in situ iron donator

High arsenic-containing waste acid from the heavy nonferrous metallurgical sector (Cu, Pb, Zn, Ni, Sn, etc.), one of the most dangerous arsenic hazardous wastes with extremely high arsenic concentrations, has presented enormous challenges to the environment and caused severe environmental pollution over the past few decades due to the lack of affordable and environmentally friendly disposal technologies. Here, we report a green process for the self-enhanced and efficient removal of arsenic from waste acid using magnetite as an in situ iron donator. Firstly, the room-temperature predissolution of magnetite in waste acid provides initial iron ions as a starting precipitator of arsenic, simultaneously providing a suitable pH range and an active surface that are ready for the nucleation and growth of scorodite. Afterwards, arsenic is precipitated in form the of scorodite, which is driven by a mutually improved cycle composed of arsenic precipitation and magnetite dissolution on the surface of magnetite particles. This cycle creates a low supersaturation of iron and constant pH in the waste acid, ensuring the continuous precipitation of arsenic as well-crystallized and environmentally stable scorodite by using magnetite as an in situ iron donator via the reaction of 2Fe3O4 + 6H3AsO4 + H2O2 = 6FeAsO4 + 10H2O. Under optimal conditions, including a 6-h room-temperature predissolution, a 12-h atmospheric reaction at 90 °C and a pH of 2.0 with a magnetite dosage at the Fe3O4/As molar ratio (the molar ratio of Fe3O4 in magnetite to As in waste acid) of 1.33, 99.90% of arsenic was successively removed from waste acid with an initial arsenic concentration of 10300 mg/L. In combination with the good adaptability of this process, the performed case study and prospective process show the successful removal of arsenic from waste acid as well as great potential for large-scale applications.

Structural and magnetic evolution of FexOy@carbon core-shell nanoparticles synthesized by a one-step thermal pyrolysis

Carbon-coated iron oxides core@shell nanoparticles were synthesized by a one-step process of thermal pyrolysis. The influence of the synthesis temperature on the structural and magnetic properties of FexOy@carbon core-shell nanoparticles was investigated by X-ray diffraction, transmission electron microscopy (TEM), Raman and Mössbauer spectroscopy, as well as by magnetic measurements. At reaction temperatures (TR) from 360 to 385 °C, spherical and nearly monodispersed nanoparticles of magnetite with an average diameter of about 40 nm covered with an amorphous carbon shell about 5 nm thick were obtained. When the reaction temperature rises above 385 °C, the nanoparticles of wüstite phase begin to form, and its concentration increases at the expense of the magnetite phase with further TR increasing. In a narrow temperature range from 390 to 400 °C, the wüstite concentration increases from 10 to 40%. At that time magnetite nanoparticles become smaller and superparamagnetic. The Mössbauer spectra indicate that the excess [Fe3+]B ions in octahedral B-sites of magnetite which associated with the particle surface do not participate in the electron hoping [Fe3+ ⇆ Fe2+]B above the Verwey temperature. The wüstite phase appears and grows with a corresponding decrease in the fraction of [Fe3+]B that does not undergo the electronic exchange. This proves that the wüstite phase is generated and formed on the surface of magnetite particles under the influence of carbon. The Mössbauer data allow one to monitor the dynamics of reduction of iron oxide from Fe3O4 to FeO under the influence of carbon.

Fundamental study on cancer therapy by blocking newborn blood vessels by magnetic force control

In this study, a cancer treatment by accumulating and aggregating ferromagnetic particles in newborn blood vessels was examined. It is necessary for this treatment to control dispersion-aggregation property of ferromagnetic particles. Ferromagnetic particles required in this method disperse at low magnetic field, aggregate at high magnetic field and maintain the aggregation even after removal of the magnetic field. In order to control the dispersion-aggregation property, the surface of magnetite particles was modified with higher fatty acids having different lengths. As a result, we succeeded to prepare propionic acid-modified magnetite particles that form irreversible aggregation by magnetic field. The model experiments simulating newborn blood vessels showed that these particles can block the flow by the magnetic field, and the blockage was maintained after removal of the magnetic field.

Eco-friendly preparation of a magnetic catalyst for glucose oxidation combining the properties of nanometal particles and specific enzyme

A facile and environmentally friendly preparation of a magnetic catalyst for the aerobic oxidation of glucose, combining the properties of two different catalytically active components—gold nanoparticles and glucose oxidase, was developed. This catalyst was synthesized by simple assembly—by sequential deposition of two oppositely charged polymers (chitosan and alternant copolymer of maleic acid) onto the surface of magnetite particles, this outer layer of this interpolyelectrolyte coating contains nanometal and specific enzyme. The catalyst preparation is reproducible and low cost, which uses no toxic reagents, condensing agents, or solvents at all stages. All components of the catalyst are non-toxic; moreover, most of them are the parts of ecosystem. We carried out an effective aerobic oxidation of glucose to gluconic acid using this catalyst. The work offers a new perspective on the production of different hybrid magnetic catalysts.

The Factors Determining Charge Rate of Magnetite Electrode and the Functional Mechanism of Sulfide on the Reaction

The electro-reduction of magnetite is important for many different industries. For example, it relates to the extraction of iron from iron ore and the charging of iron-based batteries. The sluggish electro-reduction reaction of magnetite affects the energy efficiency of iron extraction or the charge rate of iron-based batteries. However, what factors affecting the reduction rate is not well understood. In this study, electrochemical analysis, XRD, SEM, EDS mapping and XPS techniques are adopted to analyze the reaction, and it is proved that two factors determine the electro-reduction rate of magnetite electrode: O2− diffusion inside the particles determines the electro-reduction rate of a single particle, and the electrical resistivity of electrode determines how many magnetite particles are involved in electro-reduction simultaneously. Contact resistance between particles is the dominant part of the electrical resistance of the magnetite electrode. The function mechanism of sulfide in the reaction is also revealed: a sulfide additive can react with magnetite to form amorphous or crystal FeS at different potentials. These compounds, especially crystal FeS, coat onto the surface of magnetite particles, and bond them together. The coating and bonding can decrease contact resistance significantly, thus enhancing the electro-reduction rate of magnetite to one order of magnitude.

Effects of metal cations on the fulvic acid (FA) adsorption onto natural iron oxide in iron ore pelletizing process

Organic binder is a significant substitution of the bentonite in iron ore pelletizing process, reducing the exploitation of clay resource and improving the quality of pellets. Fulvic acid is one of the important functional groups of modified humic acid (MHA) binder which is invented by the authors and can be used as an excellent composite binder in pelletizing. This work aims to further study the effect of metal cations on FA adsorption onto natural pure oxides and the wet strength of green pellets made with MHA binder via batch adsorption and pelletizing experiment. The adsorption density of FA onto the natural oxides was significantly improved after adding the metal cations. The zeta potential values of the magnetite particles coated by FA became less negative after adding metal cations before the pH value of 9.2 but more negative after 9.2. The XPS analysis and SEM imaging indicated that the metal cations served as a bridge between FA molecules and the surface of magnetite particles, so that the adsorption of FA onto magnetite was promoted. In addition, the viscosity of FA increased after adding the metal cations. Both of these changes were found to be beneficial for the wet strength of MHA binder pellets.

Catalytic Ozonation of 4-Nitrophenol in the Presence of Magnetically Separable Titanium Dioxide – Magnetite Composite

<p>This paper deals with determining catalytic activities of titania (TiO<sub>2</sub>) with various crystalline structures and magnetite (Fe<sub>3</sub>O<sub>4</sub>) during mineralization of 4-nitrophenol in aqueous media by ozonation. Among the titania samples under study, amorphized TiO<sub>2</sub> was shown to have the highest catalytic activity, while magnetite was characterized by the lowest catalytic activity. A procedure is proposed to synthesize a magnetically separable composite (TiO<sub>2</sub>/Fe<sub>3</sub>O<sub>4</sub>) including amorphized titania and magnetite phases, which involves deposition of a catalytically active titania phase on preformed magnetite particles. We also studied the effect of mass ratio of titania and magnetite phases in the composite on its catalytic activity during 4-nitrophenol mineralization by ozonation. It was found that catalytic activity of composite increased as the amorphized titania phase was doped with magnetite phase up to 30% wt but as the magnetite portion in the composite catalyst was further increased, its activity decreased. According to Fourier transform infrared (FTIR) spectroscopy, content of catalytically active sites (hydroxyl groups of titania) in the composite catalyst decreases as compared to the pure phase of amorphized titania. Increase in catalytic activity of the composite as its magnetite content increases to 30% wt can be attributed to increase of accessibility of catalytically active sites (OH groups) for ozone, because specific surface area and total pore volume of the composite catalyst as determined by BET increase as compared to amorphized TiO<sub>2</sub> and catalytically active titania phase is located mostly on surface of magnetite particles which is indicated by scanning electron microscopy (SEM) results and electrophoretic light scattering (ELS) data. It was shown that the obtained composite catalyst of optimized composition, in spite of its fine particles, can be easily recovered from aqueous phase by magnetic field and used repeatedly in ozonation in order to promote water purification process.</p>

ВСТАНОВЛЕННЯ УМОВ СТАБІЛІЗАЦІЇ МАГНІТНИХ НАНОЧАСТИНОК У СКЛАДІ СИСТЕМ МАГНІТОКЕРОВАНОГО ТАРГЕТІНГУ ЛІКАРСЬКИХ РЕЧОВИН

ВСТАНОВЛЕННЯ УМОВ СТАБІЛІЗАЦІЇ МАГНІТНИХ НАНОЧАСТИНОК У СКЛАДІ СИСТЕМ МАГНІТОКЕРОВАНОГО ТАРГЕТІНГУ ЛІКАРСЬКИХ РЕЧОВИН

Magnetite particle surface attrition model in dense phase gas–solid fluidized bed for dry coal beneficiation

Dense-phase high-density fluidized bed has received considerable attention worldwide due to the urgent need for an efficient dry separation technology. This study on magnetite particle attrition model and size distribution change rule in a dense-phase gas–solid fluidized bed for dry beneficiation analyzes the complex process of magnetite particle attrition and fine particle generation. A model of magnetite particle attrition rate is established, with the particle attrition rate leveling off gradually with the attrition time in the dense-phase gas–solid fluidized bed. Magnetite particle attrition in the dense-phase gas–solid fluidized bed is consistent with Rittinger’s surface theory, where the change in surface area of magnetite particles is proportional to the total excess kinetic energy consumed and the total attrition time. An attrition experiment of magnetite particles is conducted in a laboratory-scale dense-phase gas–solid fluidized bed for dry beneficiation.

A surface-enhanced Raman scattering method for detection of trace glutathione on the basis of immobilized silver nanoparticles and crystal violet probe

Unsatisfactory sensitivity and stability for molecules with low polarizability is still a problem limiting the practical applications of surface-enhanced Raman scattering (SERS) technique. By preparing immobilized silver nanoparticles (Fe3O4/Ag) through depositing silver on the surface of magnetite particles, a highly sensitive and selective SERS method for the detection of trace glutathione (GSH) was proposed on the basis of a system of Fe3O4/Ag nanoparticles and crystal violet (CV), in which the target GSH competed with the CV probe for the adsorption on the Fe3O4/Ag nanoparticles. Raman insensitive GSH replaced the highly Raman sensitive CV adsorbed on the surface of Fe3O4/Ag particles. This replacement led to a strong decrease of the CV SERS signal, which was used to determine the concentration of GSH. Under optimal conditions, a linear response was established between the intensity decrease of the CV SERS signal and the GSH concentration in the range of 50–700nmolL−1 with a detection limit of 40nmolL−1. The use of a Fe3O4/Ag substrate provided not only a great SERS enhancement but also a good stability, which guarantees the reproducibility of the proposed method. Its use for the determination of GSH in practical blood samples and cell extract yielded satisfactory results.

Kinetics of decomposition of hydrogen peroxide on the surface of magnetite at high temperature

A novel electrochemical method was employed to accurately measure the kinetics of H2O2 decomposition on the surface of magnetite at elevated temperatures and pressures. Electrochemical impedance spectroscopy was used to probe the decay of H2O2 concentration by tracking the charge transfer resistance on the surface of a platinum electrode. It was found that the decomposition kinetics follow a first-order rate law with respect to H2O2 concentration and vary from 8.1×10−4 to 7.9×10−2min−1 when the temperature increases from 298 to 473K (for a 0.2gL−1 magnetite suspension). The mean calculated activation energy of 30±1kJmol−1 showed that H2O2 decomposition on the surface of magnetite particles is a chemically controlled process.

Preparation of CdS–TiO2/Fe3O4 photocatalyst and its photocatalytic properties

The CdS modified TiO2/Fe3O4 photocatalysts were prepared by sol–gel and immersion methods. The morphological, structural and optical properties of as-prepared samples were characterized by X-ray diffraction (XRD), UV–Vis absorption spectra, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The TEM observation showed that the surface of magnetite particles (Fe3O4) were coated by CdS–TiO2 layer as loose clusters, and average diameter of composites particles was about 250 nm. UV–Vis absorption spectra indicated that CdS–TiO2/Fe3O4 composites had pronounced red-shift compared with that of TiO2/Fe3O4. The CdS–TiO2/Fe3O4 composites exhibit higher photocatalytic activity than pure TiO2 and TiO2/Fe3O4 for the degradation of Reactive Brilliant Red X-3B dye (X-3B) aqueous solution under simulated sunlight, and the optimum content of CdS is 1.0 % (mol ratio of CdS to TiO2). In addition, a gradual loss of photocatalytic activity can be observed in reusability test of CdS–TiO2/Fe3O4 composites, and degradation of X-3B reached still to 78.9 % after five runs.

Adsorption of lignite humic acid onto magnetite particle surface

Modified humic acid (MHA) binder based on lignite humic substances is a novel sort of promising organic binder for iron ore pellets. Humic acid (HA) is one of the main ingredients of MHA binder. Pure HA was firstly isolated from lignite and then adsorption of HA onto magnetite particle surface was investigated. The final results indicate that the adsorption of HA onto magnetite surface accords with Langmuir model well, and it is evidently influenced by the initial HA concentration and solution pH value. Adsorption depends on chemical interaction at pH values above the PZC (the pH where the Zeta potentials of minerals are zero) of magnetite, while electrostatic attraction and chemical interaction both contribute to the adsorption at pH values below the PZC.

Silver reduction on the surface of magnetite nanoparticles using a coupling agent

The present study deals with a modified polyol process for synthesizing silver nanoparticles selectively on the surface of fine magnetite particles consisting of two step reactions, i.e. sol–gel reaction and silver reduction reaction. In the first step, the surface of magnetite particles is treated with thiol (S–H) groups which have a high affinity with silver using a coupling agent 3-mercaptopropyltrimethoxysilane (MPTMS). The second step is reducing silver nitrate with ethylene glycol at thiol groups on the magnetite particles, so called polyol process. Specifically this study is focused on understanding the effect of reaction parameters on the formation of silver nanoparticles at the surface of magnetite particles. The reaction parameters are amount of coupling agent MPTMS, solvent composition, mechanical dispersion treatment, dispersant for the sol–gel reaction and reduction time for the polyol process. The surface modification of magnetite is checked with FT-IR spectra and silver synthesis is analyzed with TEM, TEM-EDS, and UV–vis spectrum. It is found that the MPTMS amount and mechanical dispersion conditions give relatively large influence on the pattern of silver formation.

Distinctive Arsenic(V) Trapping Modes by Magnetite Nanoparticles Induced by Different Sorption Processes

Arsenic sorption onto iron oxide spinels such as magnetite may contribute to arsenic immobilization at redox fronts in soils, sediments, and aquifers, as well as in putative remediation and water treatment technologies. We have investigated As(V) speciation resulting from different sorption processes on magnetite nanoparticles, including both adsorption and precipitation, using X-ray absorption fine structure (XAFS) spectroscopy and transmission electron microscopy (TEM). XAFS results suggest that AsO(4) tetrahedra form predominantly inner-sphere bidentate corner-sharing ((2)C) complexes and outer-sphere complexes on magnetite in the adsorption experiments. In the precipitation experiments, an increasing fraction of AsO(4) tetrahedra appears to be incorporated in clusters having a magnetite-like local structure with increasing As loading, the remaining fraction of As being adsorbed at the surface of magnetite particles. In the sample with the highest As loading (15.7 μmol/m(2)) XAFS data indicate that As(V) is fully incorporated in such clusters. Such processes help to explain the significantly higher arsenic uptake in precipitation samples compared to those generated in adsorption experiments. In addition, for the precipitation samples, TEM observations indicate the formation of amorphous coatings and small (~3 nm) nanoparticles associated with larger (~20-40 nm) magnetite nanoparticles, which are absent in the adsorption samples. These results suggest that As(V) could form complexes at the surfaces of the small nanoparticles and could be progressively incorporated in their structure with increasing As loading. These results provide some of the fundamental knowledge about As(V)-magnetite interactions that is essential for developing effective water treatment technologies for arsenic.