Silica Magnetite Nanoparticles Research Articles

Synthesis and characterization of Ni(II) complex supported on magnetite-silica nanoparticles and investigation of its catalytic activity in Biginelli reaction under solvent-free conditions

Synthesis and characterization of Ni(II) complex supported on magnetite-silica nanoparticles and investigation of its catalytic activity in Biginelli reaction under solvent-free conditions

Magnetite-silica core-shell nanostructures: Application for photodynamic therapy

Magnetite nanoparticles have been synthesized with chemical co-precipitation. The surface of magnetite nanoparticles was coated with an inorganic silica layer by hydrolyzing and condensing tetraethyl orthosilicate. An XRD investigation supports the cubic inverse spinel structure of Fe3O4 nanoparticles. The average crystallite size of the magnetite nanoparticles produced by the peak broadening was 13 nm. The UV-visible spectrum of methylene blue-loaded magnetite-silica nanoparticles shows a strong hump at 657 nm. According to TEM examination, the nanoparticles are polydisperse and almost spherical in form.The average size of the nanoparticles is 14.39 nm plus 1.66 nm, and they have a polydispersity index of 0.12%.The size and shape of the core-shell particles are not uniform, according to a SEM examination. There is no distinguishing morphology in any sample.The magnetic results depicts the superparamagnetic behaviour of nanoparticlesmakes them suitable for photodynamic therapy.

Synthesis of Copper(II) Schiff Base Complex Immobilized on Magnetite–Silica Nanoparticles and Using as a Reusable Catalyst for the Synthesis of 1-Amidoalkyl-2-naphthols Under Ultrasonic Conditions

Synthesis of Copper(II) Schiff Base Complex Immobilized on Magnetite–Silica Nanoparticles and Using as a Reusable Catalyst for the Synthesis of 1-Amidoalkyl-2-naphthols Under Ultrasonic Conditions

Silica-magnetite nanoparticles: Synthesis, characterization and nucleic acid separation potential

Silica-coated magnetic nanoparticles can be utilized for the magnetic separation of nucleic acids, which is an important step in many clinical procedures. A series of silica-functionalized superparamagnetic iron oxide nanoparticles (SiO2@MNPs) was synthesized to efficiently separate nucleic acids for the sensitive detection of viral infections. Magnetite nanoparticles (MNPs) coated with different thicknesses of silica layer resulting from different ratios of tetraethylorthosilicate (TEOS) precursor to magnetite (TEOS/MNPs = 0.4, 1.0, 2.0, 3.0, 4.0, 5.0 ml/g) have been selected for characterization of their physico-chemical properties and biological activities. The SiO2@MNPs' morphology, size, magnetic and surface properties, cytotoxicity and nucleic acid binding propensity were determined to select the ones with the highest RNA separation potential. Our results showed that RNA-binding properties and magnetic separation efficiency are nanoparticle size-dependent. The highest binding and separation efficiencies were detected for the smaller SiO2@MNPs with TEOS/MNPs (v/w) ratios equal to 1.0 and 2.0. These nanoparticles are promising candidates for clinical application relevant to RNA viruses.

Fabrication and characterization of nanocrystalline hydroxyapatite reinforced with silica-magnetite nanoparticles with proper thermal conductivity

Silica glasses are used to improve the mechanical properties of bioceramic composites, such as strength and durability. Nowadays, further improvements of the thermo-mechanical properties of dental composites are in great demand. The present study aimed to improve SiO2 dental composites’ mechanical properties using reinforced-hydroxyapatite nano-powder. Besides, investigation of their thermal properties is targeted in the research project. Hydroxyapatite (HA) is synthesized and characterized by XRD, XRF, FE-SEM, and TEM techniques and is used as an additive to dental composite mixtures. The mechanical properties of these composites, including flexural strength, modulus of rupture, diameter tensile strength (DTS), and compressive strength, are investigated. Furthermore, the heat transfer of composites both in water and SBF (as immersed subjects in simulated body fluid) is cross-examined. Five dental-composite samples are prepared, containing 30% HA. Compared to traditional, HA-containing composite structures, the samples exhibit better mechanical properties. Thermal conductivity enhancement of HA/SiO2 at 1.0 vol% and 50 °C is 11.23% in water and 11.1% in SBF. Since bioceramics are insulative materials, enhancing solid composites such as SiO2 with HA is necessary to improve their thermal properties. Finally, an optimization approach is applied to obtain the fittest correlation for water-based and SBF-based HA-SiO2 hybrid-nanofluids. Moreover, the neural network technique is initialized to forecast the effect of temperature on mechanical properties.

Facial preparation of trifluoroacetic acid-immobilized amino-functionalized silica magnetite nano-catalysts as a highly efficient and reusable for synthesis of β-enaminones

In this paper, a simple method is reported for the preparation of trifluoroacetic acid immobilized silica magnetite nanoparticles. It is a new magnetic nano-catalyst for β-enaminone synthesis from 1 3-dicarbonyl compound. The magnetic nano-catalyst preparation was successfully synthesized by two different methods based on continuous flow synthesis. The synthesized magnetic nano-catalysts were identified using Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), energy diffusion scanning electron microscopy (SEM-EDX). N2 adsorption isotherm, thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and vibrating sample magnetometry (VSM) to confirm chemical composition, morphology, thermal stability, and magnetization. The magnetic nano-catalyst was found active the synthesis of β-enaminones. The magnetically nano-catalytic system employs environmentally friendly, solvent-free mild reaction conditions, various β-enaminone products requiring good to excellent yield under mild reaction conditions. This β-enaminone synthesis protocol has several advantages in terms of introducing a novel magnetically nano-catalytic system based on the recovery capability of the magnetic nano-catalyst. The reusability of the magnetic nano-catalyst was also studied for 7–8 consecutive cycles without significant loss of catalytic activity.

Magnetically sensitive and high template affinity surface imprinted polymer prepared using porous TiO2-coated magnetite-silica nanoparticles for efficient removal of tetrabromobisphenol A from polluted water

Magnetically sensitive and high template affinity surface imprinted polymer prepared using porous TiO2-coated magnetite-silica nanoparticles for efficient removal of tetrabromobisphenol A from polluted water

Synthesis of Bis (Benzoyl Acetone Ethylene Diimine) Schiff Base Complex of Nickel (II) Supported on Magnetite Silica Nanoparticles (Fe3O4@SiO2/Schiff-Base of Ni(II)) and Using It as an Efficient Catalyst for Green Synthesis of 1-Amidoalkyl-2-Naphthols

Synthesis of Bis (Benzoyl Acetone Ethylene Diimine) Schiff Base Complex of Nickel (II) Supported on Magnetite Silica Nanoparticles (Fe3O4@SiO2/Schiff-Base of Ni(II)) and Using It as an Efficient Catalyst for Green Synthesis of 1-Amidoalkyl-2-Naphthols

Functionalized Magnetic Nanoparticles as Catalysts for Enantioselective Henry Reaction.

With the aim to easily recover and reuse the catalyst, an efficient amino alcohol catalyst previously tested in the asymmetric addition of diethylzinc to several aromatic aldehydes has been immobilized on proper functionalized superparamagnetic core–shell magnetite–silica nanoparticles and employed in the Henry reaction in the semi-homogeneous phase. The nanocatalyst exhibits a promising catalytic activity that remains unchanged in the three catalytic cycles performed. The results prove that highly efficient catalysts, by being immobilized on suitable magnetic nanosupports, can be easily recovered and reused, maintaining their catalytic behavior.

Preparation and Characterization of Acetic Acid-Functionalized Fe3O4@SiO2 Nanoparticles as an Efficient Nanocatalyst for the Synthesis of Nitrones in Water

Magnetic materials grafted with acetic acid (Fe3O4@SiO2COOH MNPs) were successfully prepared from the incorporation of bromoacetic acid as a functional group on the surface of magnetite silica nanoparticles. The catalyst has been characterized by Fourier transform infrared spectroscopy, X-ray diffraction, elemental analysis, energy-dispersive X-ray spectroscopy, thermogravimetric analysis, scanning electron microscopy and transition electron microscopy. Next, the efficiency of this acid catalyst was examined for the synthesis of the nitrones from diaminoglyoxime in the water at room temperature. The present approach provides several advantages such as environmentally benign, excellent yields, straightforward, short reaction times, good recyclability of catalyst, cost-effective and facile catalyst separation for the preparation of nitrones compounds as an important privileged medicinal scaffold.

Core-shell nanoparticles for medical applications: effects of surfactant concentration on the characteristics and magnetic properties of magnetite-silica nanoparticles

Objective(s): The use of cationic surface-active agents (surfactant) in the synthesis of nanoparticles, with formation of micelle, can act as a template for the formation of meso-porous silica. Changes in the concentration of surfactants can affect the structures and properties of the resulting nanoparticles.Materials and Methods: Magnetite nanoparticles were prepared as cores using the coprecipitation method. Silica shells were formed on the prepared cores using sol-gel through the single-step process. During synthesis, cetrimonium bromide (CTAB) was used as a surfactant at low (0.1 g), medium (1 g), and high concentrations (7 g), and the effects on the properties of the nanoparticles were investigated. The core-shell nanoparticles were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). In addition, the surface porosities of the nanoparticles were evaluated using the BET and BJH methods. The vibrating sample magnetometer (VSM) was also employed to assess the magnetic characteristics of the synthesized samples. Results: The results of XRD indicated that the nanoparticles were composed of magnetite and silica, while the SEM and TEM images confirmed the presence of uniform spherical particles with a core-shell structure. According to the results of the VSM tests, all nanoparticles showed super-paramagnetic behaviors. Moreover, the increased concentration of CTAB led to an increment in saturation magnetization (Ms), size, and volume of the surface pores, while the specific surface area of the nanoparticles decreased. Conclusion: According to the results, the properties of the silica shell could be adjusted in terms of pore characteristics and magnetic behavior by changing the concentration of the surfactant.

Amine-functionalized magnetite-silica nanoparticles as effective adsorbent for removal of uranium(VI) ions

In our studies the Fe3O4/SiO2/C3H6NH2 (MSA) adsorbent was synthesized by the green-chemistry method based on hydrolysis and condensation of tetraethoxysilane and (3-aminopropyl)triethoxysilane. The obtained material was fully characterized by a wide range of instrumental techniques and employed as an adsorbent for removal of uranium(VI) ions which is considered as a hazardous metal. It was found that the adsorption process is very fast, and equilibrium is reached after about 4 h. The data was fitted with the pseudo-1st (PFO) and pseudo-2nd order (PSO) equations. It was turned out that better fit was obtained for the PSO kinetic model. The Freundlich, Langmuir–Freundlich and Dubinin–Radushkevich isotherm equations were used to calculate the equilibrium adsorption data. The static sorption capacity was 118 mg·g−1. The energy value En = 14.8 kJ·mol−1 (293 K) calculated based on the Dubinin–Radushkevich isotherm equation indicates that chemisorption is a dominant mechanism. The obtained data show that MSA material can be used as a promising adsorbent for radioactive metals removal.

Magnetite-silica nanoparticles with core-shell structure: single-step synthesis, characterization and magnetic behavior

In this study, a specific technique was used to quickly, easily, and single step, synthesize core-shell magnetite-silica nanoparticles by controlling the reaction conditions using the proper surfactant. In the first step, the magnetite nanoparticles were prepared by co-precipitation method and silica shell was immediately formed by the sol-gel process. Synthesis was performed at 80 °C with stirring at 12,000 rpm in an alkaline medium. The structural and morphological characteristics of core-shell nanoparticles were examined by XRD, TEM, SEM, and BET analyses. In addition, vibrating sample magnetometer (VSM) was used to evaluate the magnetic characteristics. XRD analysis confirmed the existence of both magnetite and silica phases in the final structure. TEM images showed the presence of nanocomposite particles with core-shell structure of 25 nm diameter. The mean core and shell size were estimated to be about 20 and 2.5 nm, respectively. A study of the magnetic characteristics showed super-paramagnetic behavior with 60 emu/g saturation magnetization (Ms). Due to the high ratio of core size to shell thickness, the magnetic saturation for the synthetized core-shell nanoparticles in this research was significant. In comparison to other multi-step synthesis techniques, the results obtained from this research confirmed the formation of magnetite-silica core-shell structures with the desired magnetic behavior in a quick and single-step process.

Application of the nanoindentation method in assessing of properties of cement composites modified with silica-magnetite nanostructures

The results of investigation of the cement composites modified with 5% of silica-magnetite nanostructures of the core-shell type are presented in the paper. The nanoindentation method employing three-sided pyramidal Berkovich indenter was used in the research. The mechanical properties and microstructure of the modified cement composites were evaluated on the basis of the values of hardness and indentation modulus measured inside the cement matrix and in the aggregate-paste interfacial zone. The results were compared with those obtained for the reference composites without nanostructures. The positive influence of the presence of silica-magnetite nanoparticles on the tested properties was found out.

Fluorescence imaging of the nanoparticles modified with indocyanine green

The comparative research of silica, the magnetite and magnetite-silica nanoparticles modified with fluorescent dyes using gas-phase and liquid-phase methods was conducted. At the content of fluorescent dye comparable in size a particular spectrophotometric method, nanoparticles with fluorescein have up to 1000 times larger overall luminous efficiency. It is revealed that magnetic nanoparticles are characterized by a smaller light efficiency in comparison with silica particles, at the same time particles of a magnetite are most effective at modification with fluorescein, and magnetite-silica particles – at modification with indocyanine green.

Dispersive magnetic solid phase extraction using octadecyl coated silica magnetite nanoparticles for the extraction of tetracyclines in water samples

Magnetite nanoparticles coated with silica and hydrophobic octadecyl layers were successfully synthesized and used in magnetic solid phase extraction of tetracyclines from water samples. The magnetite nanoparticles facilitated a convenient magnetic separation of sorbent from an aqueous sample, the octadecyl layer helped to enhance the adsorption ability and the silica layer helped to prevent the aggregation of the magnetite nanoparticles. The effect of various parameters on the extraction efficiency were optimized including the amount of sorbent, sample pH, stirring rate, extraction time and desorption conditions. Under the optimum conditions, the recoveries were in the range of 82 to 88%, the calibration curves were linear over the concentration range of 0.002 to 1.0 μg/mL for oxytetracycline and 0.01 to 1.0 μg/mL for tetracycline and chlortetracycline, respectively. The developed method had several advantages such as simplicity, convenience, cost-effectiveness and high extraction efficiency.

SBA and KIT-6 Mesoporous Silica Magnetite Nanoparticles: Synthesis and Characterization

In the present study, simple and versatile methods for preparation of SBA-3, SBA-15, and KIT-6 mesoporous silica magnetite nanoparticles (Fe3O4@SBA and Fe3O4@KIT-6 MNPs) were developed. The chemically synthesized magnetite nanoparticles were utilized for preparation of mesoporous MNPs with Fe3O4 core and mesoporous silica (SBA-3, SBA-15, and KIT-6) shell. The size and chemical structures of the synthesized nanoparticles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectrophotometery (FT-IR). The synthesized mesoporous MNPs showed super paramagnetic property and the surface area of synthesized Fe3O4@SBA-3, Fe3O4@SBA-15, and Fe3O4@KIT-6 via BET was obtained as 627.87, 510.95, and 241.68 m2 g−1, respectively.

Modification of mesoporous silica magnetite nanoparticles by 3-aminopropyltriethoxysilane for the removal of Cr(VI) from aqueous solution

Silica magnetite nanoparticles (S-MNPs) as core were embedded in mesoporous silica shells by using cetyltrimethylammonium bromide (CTAB) as a surfactant. Then, the resultant mesoporous silica-magnetite nanoparticles (M-S-MNPs) were modified with 3-aminopropyltriethoxysilane (APTES) as a coupling agent in dry hexane solvent. APTES-grafted mesoporous silica magnetite nanoparticles (A-M-S-MNPs) were characterized by XRD, FTIR spectroscopy, EDX, TEM, elemental analysis, TGA/DTA technique. Results demonstrate that the obtained A-M-S-MNPs were nearly spherical in shape with 25 nm thick mesoporous silica shell. The adsorption behavior of the nanocomposite was examined in removing of Cr(VI) ion with concentrations 20, 30 and 50 mg/L at optimum pH level of 2. In this study a pH swing adsorption was observed too. The adsorption kinetic data were modeled using pseudo-second-order kinetics and intraparticle diffusion equations. The obtained results for intraparticle diffusion model show that the adsorption mechanisms are different in low and in high concentrations of Cr(VI) ion. According to the parameters of the Langmuir isotherm, the maximum adsorption capacity (qm) of A-M-S-MNPs for Cr(VI) increases as the temperature rises from 298 to 318 K. For better understanding of adsorption mechanism, quantum mechanical methods were applied. The results indicate that the electrostatic and hydrogen bond interactions between surface functional groups and HCrO4− ions have an important role in adsorption process. The easy separation from aqueous solution by an external magnetic field, rapid adsorption, regeneration, and reusability of A-M-S-MNPs are interesting points as an effective adsorbent for the removal of Cr(VI) ions.

Amino-functionalized silica magnetite nanoparticles for the simultaneous removal of pollutants from aqueous solution

Amino-functionalized silica magnetite nanoparticles (A-S-MNPs) have been prepared through coating of sono-synthesized magnetite nanoparticles (MNPs) in a basic medium by SiO2. Then, the resultant silica magnetite nanoparticles (S-MNPs) were modified with 3-aminpropyltriethoxysilane (APTES). The modification was carried out by the organic solvent method in dry hexane to graft amine groups on the surface. The adsorption behavior of this novel magnetic sorbent was studied for the simultaneous removal of two organic pollutants containing the sulfonate group, e.g., Reactive Black 5 (RB5) and sodium dodecylbenzenesulfonate (SDBS) in aqueous solutions. The results show that a pseudo-second-order model fits well the experimental data and the rate constant of adsorption for SDBS is higher than for RB5. The adsorption capacity was obtained by the Langmuir isotherm. The qmax was 83.33 and 62.5mg/g for RB5 and SDBS at pH 2 and 298K, respectively. Furthermore, the loaded A-S-MNPs can be recovered easily from aqueous solution by magnetic separation and regenerated by simply washing with 0.1M NaOH solution. Therefore, the synthesized novel magnetic sorbent can be used as an effective and recyclable adsorbent for the simultaneous removal of dye and surfactant from aqueous solutions.

Rapid, cost-effective DNA quantification via a visually-detectable aggregation of superparamagnetic silica-magnetite nanoparticles

DNA and silica-coated magnetic particles entangle and form visible aggregates under chaotropic conditions with a rotating magnetic field, in a manner that enables quantification of DNA by image analysis. As a means of exploring the mechanism of this DNA quantitation assay, nanoscale SiO2-coated Fe3O4 (Fe3O4@SiO2) particles are synthesized via a solvothermal method. Characterization of the particles defines them to be ∼200 nm in diameter with a large surface area (141.89 m2/g), possessing superparamagnetic properties and exhibiting high saturation magnetization (38 emu/g). The synthesized Fe3O4@SiO2 nanoparticles are exploited in the DNA quantification assay and, as predicted, the nanoparticles provide better sensitivity than commercial microscale Dynabeads® for quantifying DNA, with a detection limit of 4 kilobase-pair fragments of human DNA. Their utility is proven using nanoparticle DNA quantification to guide efficient polymerase chain reaction (PCR) amplification of short tandem repeat loci for human identification.