Silica-coated Magnetite Nanoparticles Research Articles

Biocompatible nanoparticles for metals removal from fresh water with potential for rare earth extraction applications

Freshwater contamination by metals can come from a variety of sources and be damaging to wildlife, alter landscapes, and impact human health. Metals removal is desirable not only for improving water quality and preventing adverse effects but also for metals collection and recycling. Nanoadsorption of metals is economically feasible and nanoscale materials exhibit a high surface-area-to-volume ratio that is promising for high adsorption and reactivity. However, the extraordinarily small dimensions of these materials allow them to maneuver biological systems, and combined with high reactivity, this translocation can result in toxicity. In this work, nanoparticles (NPs) composed of a magnetite core coated in hydroxyapatite (HA) and functionalized for adsorption with titanium dioxide (TiHAMNPs) were synthesized. The magnetic core enabled NP retrieval, while HA enhanced adsorption and minimized toxicity. Here, synthesis and characterization are presented, revealing a stable NP structure exhibiting a near neutral surface charge. Results of adsorption studies showed that as compared to silica-coated magnetite nanoparticles (SiMNPs), traditionally used for this application, TiHAMNPs exhibited significantly higher adsorption (43.28% more Cu removal) after 24 h. The equilibrium rate constant for the adsorption of Cu by TiHAMNPs was 0.0003 g/(min*mg) and TiHAMNP adsorption data indicated that TiHAMNPs adsorb metals in a monolayer at the particle surface with a maximum capacity of 2.8 mmol/g. Metabolic and toxicity assays showed TiHAMNPs were highly biocompatible as compared to SiMNPs. This work also explores rare earth element (REE) separation applications of TiHAMNPs, finding that TiHAMNPs may provide a promising alternative for REE retrieval and/or separation.

Silica-coated magnetite nanoparticles functionalized with sulfosalicylic acid: a highly active and magnetically reusable nanocatalyst for the Biginelli reaction

Silica-coated magnetite nanoparticles functionalized with sulfosalicylic acid: a highly active and magnetically reusable nanocatalyst for the Biginelli reaction

Copper-hydroxyacetophenone thiosemicarbazone complex on silica-coated magnetite nanoparticles as an efficient catalyst for three-component synthesis of 1,4-disubstituted 1,2,3-triazoles

A novel magnetically separable catalyst, the copper-hydroxyacetophenone thiosemicarbazone complex immobilized on silica-coated magnetite nanoparticles (Fe3O4@SiO2-HAT-Cu(I)), has been synthesized and characterized. The characterization included various techniques such as X-ray diffraction spectroscopy (XRD), energy dispersive X-ray spectroscopy (EDX), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), dynamic laser scattering (DLS), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), atomic absorption spectroscopy (AAS), inductively coupled plasma-optical emission spectrometry (ICP-OES), and Fourier-transform infrared spectroscopy (FT-IR). The catalytic activity of Fe3O4@SiO2-HAT-Cu(I) was evaluated in a green aqueous mediated three-component synthesis of 1,2,3‐triazles. The catalyst efficiently facilitated the 'Click' Huisgen cycloaddition reaction between alkynes, sodium azide, alkyl bromides and/or epoxides in water/THF at 70 °C, resulting in good to excellent yields of 1,4-disubstituted 1,2,3‐triazle derivatives. Fe3O4@SiO2-HAT-Cu(I) is a new, low-cost, and magnetically separable heterogeneous catalyst that can be easily prepared and reused for multiple reaction runs without significant loss of catalytic activity.

Synthesis and characterization of N4-donor Schiff base copper(II) immobilized on superparamagnetic Fe3O4@SiO2 and its use as a recyclable catalyst for oxidation of alkenes, alcohols, and determination of antibacterial activity

N4-donor Schiff base copper(II) nanoparticles were easily prepared through surface modification of silica-coated magnetite nanoparticles (Fe3O4@SiO2) with pyrrole 2-carbaldehyde Schiff base and a subsequent reaction with Cu(CH3COO)2.H2O in ethanolic solution. This nanocatalyst was characterized using thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and magnetization. Efficient oxidation of alkenes and alcohols was carried out over the Schiff base copper(II) nanoparticles. Catalytic tests showed that the catalyst was particularly effective for the oxidation of α-methyl styrene, norbornene, benzyl alcohol, and benzohydrol. The results showed that acetophenone, 2-norbornanone, benzoic acid, and benzophenone with selectivity values of 88, 100, 100, and 100, respectively, were obtained. The heterogeneous catalyst of N4-donor Schiff base copper(II) offers advantages such as ease of product separation, catalyst recycling, and ease of preparation. Antibacterial tests against two gram-positive and two gram-negative bacterial species found that the bacteria stopped growing in the catalyst medium.

An Evaluation of Glycerol Acetalization with Benzaldehyde over a Ferromagnetic Heteropolyacid Catalyst

Tungstophosphoric acid (H3PW12O40) supported on silica-coated magnetite nanoparticles has been prepared and used as a heterogeneous acid catalyst (Fe3O4@SiO2@HPW) in the condensation of benzaldehyde (B) with glycerol (Gly) for the production of cyclic acetals. Physicochemical techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectrometry (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and N2 physisorption were used to characterize the prepared catalyst. The effect of glycerol/benzaldehyde molar ratio (1/1 to 1/1.2), temperature (80–120 °C), and catalyst amount (1–5%) on glycerol conversion and the selectivity in main reaction products: benzoic acid, 2-phenyl-1,3-dioxolan-4-yl)methanol, 2-Phenyl-1,3-dioxan-5-ol, 2-phenyl-1,3-dioxolane, and methyl 2-hydroxy-3-phenylpropanoate was studied to evaluate the catalytic activity of the prepared Fe3O4@SiO2@HPW catalyst. The optimization of these process parameters was conducted using Box–Behnken design (BBD). Using the BBD methodology, the optimal parameters (120 °C, 1:1.15 glycerol: benzaldehyde, 5% catalyst) were determined, for a glycerol conversion of and cyclic acetals yield of 85.95% and 78.36%, respectively. The catalyst also exhibits excellent activity for glycerol acetalization with other aromatic aldehydes such as cinnamaldehyde, p-methyl-benzaldehyde, p-hydroxy-benzaldehyde, and vanillin.

Effecting pattern study of SO2 on Hg0 removal over α-MnO2 in-situ supported magnetic composite

α-MnO2 was in-situ supported onto silica coated magnetite nanoparticles (MagS-Mn) to study the adsorption and oxidation of Hg0 as well as the effecting patterns of SO2 and O2 on Hg0 removal. MagS-Mn showed Hg0 removal capacity of 1122.6 μg/g at 150 °C with the presence of SO2. Hg0 adsorption and oxidation efficiencies were 2.4% and 90.6%, respectively. Hg0 removal capability deteriorated at elevated temperatures. Surface oxygen and manganese chemistry analysis indicated that SO2 inhibited the Hg0 removal through consumption of adsorbed oxygen and reduction of high valence manganese. This inhibiting effect was observed to be counteracted by O2 at lower temperatures. O2 tended to compete with SO2 for active sites and further create additional adsorbed oxygen sites for Hg0 surface reaction via surface dissociative adsorption rather than replenish the active sites consumed by SO2. The high valence manganese was also preserved by O2 which was essential to Hg0 oxidation. The intervention of O2 in the inhibition of SO2 on Hg0 removal was weakened at temperatures higher than 250 °C. Aa a result, Hg0 tends to be catalytic oxidized in the condition of low reaction temperatures and with the presence of O2 over α-MnO2 oriented composites.

Functionalization of Fe3O4@SiO2 nanoparticles with Cu(i)-thiosemicarbazone complex as a robust and efficient heterogeneous nanocatalyst for N-arylation of N-heterocycles with aryl halides.

In this research, the functionalized silica-coated magnetite nanoparticles with Cu(i)-thiosemicarbazone complex (Fe3O4@SiO2-[CuL]) has been designed and synthesized as a magnetically retrievable nanocatalyst. Different techniques were employed to characterize the structure of Fe3O4@SiO2-[CuL] comprising FT-IR, FE-SEM, TEM, DLS, XRD, EDX, TGA, AAS, and VSM analysis. The catalytic performance of Fe3O4@SiO2-[CuL] was perused in Ullmann-type N-arylation of nucleobases, xanthines, and other N-heterocycles with diverse aryl halides which acquired the desired N-aryl products in good to excellent yields. Fe3O4@SiO2-[CuL] is a thermal and chemical stable, easy to prepare and recyclable, inexpensive, and ecofriendly catalyst that needs no additional additive or ligand as promoters. This catalyst could be separated without difficulty by a simple magnet and reused for at least seven sequential runs without a significant decline in its catalytic performance.

Silica-coated nanomagnetite-supported oxovanadium(V) Schiff base complex: Preparation, characterization, and catalytic application for the oxidation of sulfides

In this paper, an oxovanadium(V) complex, prepared with a tridentate ONO Schiff base by reacting nicotinic hydrazide with 3-methoxysalicylaldehyde, was immobilized on the surface of the silica-coated magnetite nanoparticles. After successful preparation and complete characterization (FT–IR, SEM, XRD, TEM, VSM, EDX, and ICP), the catalytic activity of the magnetic organic–inorganic nanocomposite was explored for the green oxidation reaction of different kinds of aryl and alkyl sulfides employing hydrogen peroxide and methanol under reflux conditions. Significant features such as simple work-up, fast reaction, higher product yield, and reusability of the catalyst enhance the efficiency of this catalytic procedure economically and environmentally.

Preparation and Characterization of Bifunctional PEG/en Nanomagnetic Phase-Transfer Catalyst: Green Synthesis of 2-Amino-3-Cyano-4H-Pyrans

In this article, a green and recoverable heterogeneous phase-transfer catalyst containing silica-coated magnetite nanoparticles functionalized by polyethylene glycol and ethylenediamine was synthesized. After full characterization, the catalytic activity of the bifunctional magnetic nanocomposite was investigated in the straightforward synthesis of 2-amino-3-cyano-4H-pyrans under mild and green conditions through the one-pot reaction of aryl aldehydes with malononitrile and dimedone or 1,3-cyclohexanedione. Significant features such as mild reaction conditions, simple work-up, short reaction time, high product yield, and reusability of the catalyst, enhance the efficiency of this catalytic procedure economically and environmentally benefits.

Sulfonated Ethylenediamine Functionalized Magnetic Nanoparticles as a Highly Efficient Heterogeneous Nanocatalyst for the Green Synthesis of 2,3-Dihydroquinazolin-4(1H)-ones

Abstract: In the present study, a new magnetically recyclable nanocatalyst, Fe3O4@SiO2@(CH2)3-en- SO3H/H2SO4, was prepared through the immobilization of sulfonated ethylenediamine on the silicacoated magnetite nanoparticles. The catalyst was fully characterized by several physicochemical techniques, including FT-IR, FESEM, TEM, EDS, VSM, XRD and TGA. The resultant nanocatalyst was then utilized in the green synthesis of 2,3-dihydroquinazolin-4(1H)-ones via the cyclocondensation reaction of various aldehydes and ketones with anthranilamide in refluxed EtOH. Short reaction times, high product yields, environmentally friendly reaction conditions, simple operation and reusability of the catalyst are important features of the present procedure. The catalyst can magnetically be recycled and reused several times without notable loss in the activity.

Doxorubicin-Loaded Magnetic Nanoparticles: Enhancement of Doxorubicin’s Effect on Breast Cancer Cells (MCF-7)

The incidence of female breast cancer has increased; it is the most commonly diagnosed cancer, at 11.7% of the total, and has the fourth highest cancer-related mortality. Magnetic nanoparticles have been used as carriers to improve selectivity and to decrease the side effects on healthy tissues in cancer treatment. Iron oxide (mainly magnetite, Fe3O4), which presents a low toxicity profile and superparamagnetic behavior, has attractive characteristics for this type of application in biological systems. In this article, synthesis and characterization of magnetite (NP-Fe3O4) and silica-coated magnetite (NP-Fe3O4/SiO2) nanoparticles, as well as their biocompatibility via cellular toxicity tests in terms of cell viability, are carefully investigated. MCF-7 cells, which are commonly applied as a model in cancer research, are used in order to define prognosis and treatment specifics at a molecular level. In addition, HaCaT cells (immortalized human keratinocytes) are tested, as they are normal, healthy cells that have been used extensively to study biocompatibility. The results provide insight into the applicability of these magnetic nanoparticles as a drug carrier system. The cytotoxicity of nanoparticles in breast adenocarcinoma (MCF-7) and HaCat cells was evaluated, and both nanoparticles, NP-Fe3O4/SiO2 and NP-Fe3O4, show high cell viability (non-cytotoxicity). After loading the anti-tumor drug doxorubicin (Dox) on NP-Fe3O4/Dox and NP-Fe3O4/SiO2/Dox, the cytotoxicity against MCF-7 cells increases in a dose-dependent and time-dependent manner at concentrations of 5 and 10 μg/mL. HaCat cells also show a decrease in cell viability; however, cytotoxicity was less than that found in the cancer cell line. This study shows the biocompatibility of NP-Fe3O4/SiO2 and NP-Fe3O4, highlighting the importance of silica coating on magnetic nanoparticles and reinforcing the possibility of their use as a drug carrier system against breast adenocarcinoma cells (MCF-7).

Synthesis and Characterization of Silica Coated Magnetite Nanoparticle Clusters for Viral RNA Extraction

Magnetite nanoparticles or iron oxide nanoparticles are the most explored magnetic nanoparticles till recent times, particularly due to their attractive properties for biomedical applications such as viral RNA extraction. The physical and chemical properties of magnetite nanoparticles and their clusters largely depend on the synthesis method and chemical structure. Co-precipitation method was used to synthesize magnetite nanoparticles at varying process parameters. The nanoparticles were coated with silicon-oxide using Stober method at different deposition durations. These particles were characterized by X-Ray Diffraction, Scanning Electron Microscopy, vibrating sample Magnetometer and PCR testing to study the phases formed, morphology, size, magnetic properties and RNA extraction efficiency. The synthesized magnetite nanoparticles were in the range of 10 to 100 nm; suitable for super-para-magnetic behavior. The maximum saturation magnetization achieved for synthesized paramagnetic beads was 56 emu and RNA extraction efficiency was more than 80% as compared to commercial beads.

A nanocomposite of silica coated magnetite nanoparticles and aniline-anthranilic acid co-polymeric nanorods with improved stability and selectivity for fluoroquinolones dispersive micro solid phase extraction

Adsorbents composed of polyaniline nanostructures or their derivatives immobilized on magnetic nanoparticles had gained increasing interest for application in dispersive micro-solid phase extraction. However, reproducible binding between polymeric PANI nanopaterials and magnetic nanomaterials are still a challenging task. Furthermore, other challenges are the enhancement of physical and chemical stability of adsorbent magnetic nanoparticles as well as improvement of polymeric PANI nanoparticles selectivity towards target analytes. This work described the reproducible preparation of a nanocomposite of aniline-anthranilic acid co-polymeric nanorods with silica coated magnetite nanoparticles by physical mixing of its basic components. The prepared nanocomposite had proven stability against chemical and atmospheric attack. The formed nanocomposite in this work had advantages regarding stability and selectivity towards fluoroquinolones as compared with analogues prepared from polyaniline polymers and/or uncoated magnetite nanoparticles. The selectivity of the formed adsorbent was further optimized for microextraction of four fluoroquinolone antibacterial agents. The application of the prepared nanocomposite was exemplified in microextraction of the studied fluoroquinolones from spiked milk samples to enable their detection down to their stated maximum residue limits.

One-step continuous flow synthesis of aminopropyl silica-coated magnetite nanoparticles

One-step continuous flow synthesis was developed and applied for the preparation of amino propyl silica-coated nanoparticles (APSMNPs). This was accomplished in one step through continuous flow synthesis and amino propyl silica coating. Magnetite nanoparticles (MNPs) are generated in situ using a continuous flow synthesis system before being coated with amino propyl silica using tetraethyl orthosilicate (TEOS) condensation process and 3-aminopropyl triethoxysilane (APTES) condensation process in different ratios. The effect of the molar ratio of TEOS to APTES on the structure and physicochemical properties of the corresponding APSMNPs was examined by N2 adsorption–desorption isotherm, transmission electron microscope (TEM), vibrating sample magnetometer (VSM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope energy dispersive X-ray (SEM-EDX). This continuous flow process has advantages such as easy scalability, convenient production, easy control, an economical method with less time and reagents than traditional synthetic methods. It is a good choice for industrial production of APSMNPs.

The efficient heterogeneous catalyst containing copper (II) bis-benzothiazole complex supported on functionalized magnetic nanoparticles used for epoxidation of alkenes with tert-BuOOH

In this article, efficient and novel catalyst including copper (II) 3,5–bis(2–benzothiazolyl)pyridine supported on silica-coated magnetite nanoparticles, [Cu(II)Br2-BTP@MNPs], was investigated for epoxidation of alkenes. The prepared catalyst was characterized by elemental analysis, XRD, ICP, FE-SEM, VSM, TGA and FT-IR spectroscopic techniques. This new heterogeneous catalyst can be developed for efficient epoxidation of alkenes with tert-BuOOH in acetonitrile as solvent under mild conditions. Also, the reusability of this catalyst in the epoxidation reactions was investigated.

Manifestation of Stoichiometry Deviation in Silica-Coated Magnetite Nanoparticles

Manifestation of Stoichiometry Deviation in Silica-Coated Magnetite Nanoparticles

Design and Preparation of Copper(II)–Mesalamine Complex Functionalized on Silica-Coated Magnetite Nanoparticles and Study of Its Catalytic Properties for Green and Multicomponent Synthesis of Highly Substituted 4H-Chromenes and Pyridines

In the present study, a green and ecofriendly nanocatalyst was synthesized through functionalization of 2,4,6-trichloro-1,3,5-triazine (TCT) and mesalamine on silica-coated magnetic nanoparticles (MNPs), then coordination with Cu2+ without agglomeration, consecutively. The silica-coated MNPs functionalized with the Cu(*II)–mesalamine complex was (Fe3O4@SiO2@NH2-TCT-mesalamine–Cu(II) MNPs) completely characterized by FT-IR, XRD, EDX, FESEM, TEM, VSM, TGA, and BET analyses. Afterward, the activity of the novel catalyst was investigated in the synthesis of chromene heterocycles, which were an important group of organic compounds. The activity of Fe3O4@SiO2@NH2-TCT-mesalamine–Cu(II) MNPs as a high-performance heterogeneous nanocatalyst was evaluated for the synthesis of 2-amino-4-aryl-6-(phenylthio)pyridine-3,5-dicarbonitriles and 2-amino-4H-chromenes via aromatic aldehydes, malononitrile, and enolizable C–H acids (resorcinol, 2-hydroxynaphthalene-1,4-dione, and benzenethiol) in ethanol under reflux conditions. Fe3O4@SiO2-TCT-mesalamine–Cu(II) could be quickly separated using an external magnet and reused nine times without a remarkable reduction of its catalytic activity.

The challenge to produce magnetic nanoparticles from waste containing heavy metals aiming at biomedical application: New horizons of chemical recycling

Silica-coated magnetite nanoparticles (SMNPs) were prepared by a green approach based on waste pickling acid. A set of techniques (PXRD, ATR, VSM, SEM, TEM, DLS and XPS) was used for their characterization, and for monitoring the levels of heavy metal impurities. The SMNPs presented an expected profile, similar to that reported for nanoparticles produced from fresh chemicals. The crystallinity and magnetic saturation confirmed the formation of the Fe3O4 phase, silanol and siloxane absorption bands, as well as TEM images confirmed the coating SiO2. The SMNPs chosen for the biomedical tests did not present a significant level of contaminants, and the non-toxic silica coat produced by the sol-gel method ensured a preliminary study on its biocompatibility with reproductive cells in vitro. SMNPs presented a high ability to immobilize spermatozoon cells, suggesting that a fine control of their surface charge must be carried out for specific biomedical purposes. The agglomeration of the solid NPs was evidenced by SEM and by DLS measurements. Its aggregation was tuned by sonication, and a 5-min long ultrasound treatment was capable of halving the agglomerate size, allowing a one-to-one interaction (one SMNPs agglomerate to each cell). The CASA system used to monitor the semen quality showed that vigor, motility and velocity parameters were kept at levels very close to the control group. Finally, a waste-based input submitted to a meticulous purification process could be used as a source for magnetic materials synthesis and evaluated in the biomedical field as long as all precautions are taken into account.

Microwave assisted facile green synthesis of silica coated magnetite nanoparticles for fast removal of methylene blue dye from environmental water samples

ABSTRACT To prepare a magnetic nano-adsorbent for efficient and fast removal of a dye, especially if present in trace concentration, along with a facile green synthetic methodology is a great challenge. The present work realises this task by combining the well-known advantages of both solvent-free microwave approach, nanoscale particle size and the fast magnetic separation. Thus, silica-coated magnetite nanoparticles (Fe3O4 NPs@SiO2) as an important precursor were produced directly via an optimised solid-solid interaction between silica and Fe3O4 NPs at 200 watt of microwave irradiation for only 10 min. The as-developed adsorbent was characterised using Fourier Transform Infrared (FT-IR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray (EDX) analysis. Its performance with no further modification for removal of Methylene blue (MB) dye from aqueous solution was achieved in a batch mode as a function of pH, contact time, adsorbent dose and initial dye concentration. The results demonstrate excellent removal efficiency (98.9%) within 5 min, as compared with recent adsorbents synthesised through a multi-steps reaction. Modelling of the experimental data denoting well-fitting with both Langmuir sorption isotherm (monolayer capacity 47.98 mg/g) and pseudo-second-order kinetic model. A possible MB binding mechanism has been proposed taking in account values of dissociation constants of the different forms of silica surface silanol groups. The adsorbent after first was successfully regenerated in situe for five consecutive cycles. Moreover, it was proved to be valid for collecting efficiently trace concentrations of MB spiked environmental water samples to be in the range 92.4–98.8%.

Magnetic nanoparticles-supported dioxomolybdenum(VI) complex: An effective reusable heterogeneous nanocatalyst for the green selective sulfoxidation

A dioxomolybdenum(VI) complex with the tridentate ONO Schiff base ligand was derived from the condensation reaction of 3-ethoxysalicylaldehyde with isonicotinohydrazide and then was immobilized on the surface of silica-coated magnetite nanoparticles. The resultant organic–inorganic hybrid material was characterized by infrared spectroscopy, scanning electron microscope, energy-dispersive X-ray spectroscopy, transmission electron microscopy, vibrating sample magnetometry, and X-ray powder diffraction. The catalytic performance of the synthesized nanocatalyst was tested for the selective sulfoxidation of the different sulfides by using H2O2 as a safe oxidizing agent in ethanol as a green solvent under reflux conditions. The heterogeneous catalyst was recovered magnetically and reused at least five times without a notable decrease in its activity.