Magnetic Hybrids Research Articles

Synthesis and properties of covalently linked photoluminescent magnetic magnetite nanoparticle-silicon nanocrystal hybrids

Silicon nanocrystals (SiNCs) are quantum dots that do not contain toxic metals and exhibit a photoluminescent response that may be tailored via changes in particle dimension as well as surface chemistry. Herein, we present a promising hybrid nanomaterial that combines the favourable properties (e.g., photoluminescence, biocompatibility, and surface chemistry) of SiNCs with the magnetic characteristics of Fe 3 O 4 nanoparticles (NPs). Linking these two complementary nanomaterials via DCC coupling has yielded a new advanced hybrid material that possesses the characteristics of its constituents and affords a photoluminescent system that responds to permanent magnets.

Hybrid nanoadsorbents for the magnetically assisted removal of metoprolol from water

Metoprolol (MTP) is known as one of the most frequently detected beta blockers in surface waters, with potentially harmful impact on environment and human health due to its widespread use and resistance to hydrolysis. The removal of MTP in wastewater treatment plants is still very low due to fairly ineffective conventional water treatment procedures and, therefore, more efficient treatments are needed. To tackle this challenge, novel biosorbents composed of magnetite nanoparticles functionalized by κ-carrageenan hybrid siliceous shells (Fe3O4@SiO2/SiCRG) were successfully prepared and tested in magnetically assisted removal of metoprolol tartrate from aqueous solutions. The MTP adsorption by the produced core–shell composite structures was thoroughly assessed and modeling of the equilibrium data was best fit with Langmuir and Toth models. The maximum observed MTP adsorption capacity of the magnetic hybrids amounted to 447mg/g, thus representing an enhancement of 300% compared to most efficient MTP sorbents reported so far. The results of FTIR analysis indicate that the adsorption mechanism is mostly based on electrostatic interactions between sulfonate groups of κ-carrageenan and protonated amine groups of metoprolol. The obtained Fe3O4@SiO2/SiCRG composite particles show a great potential for removing MTP from water, stemming from their high inherent absorption capacity and convenient magnetic separation.

Organosilatranes with Acylthiourea Derivatives – Metal‐Ion Binding, Substituent‐Dependent Sensitivity, and Prospects for the Fabrication of Magnetic Hybrids

A variety of topologically interesting acylthiourea‐tethered organosilatranes (AcTu‐OS) were prepared, and their function as metal‐ion binding sites was investigated. The prepared compounds have been characterized by elemental analysis; FTIR, UV/Vis and NMR (1H and 13C) spectroscopy; and mass spectrometry. The organosilicon complexes 4a–4e possess diverse coordination abilities for the surveyed metal ions (Cu2+, Cd2+, Hg2+ and Pb2+), as was appraised by the corresponding absorption shifts in the UV/Vis spectra. In addition, a facile preparatory route for the covalent grafting of the most efficient receptor 4e onto a silica‐encrusted magnetic nanosupport was implemented. The resultant organic–inorganic hybrid nanoparticles (H‐NPs) were characterized by physicochemical techniques such as FTIR spectroscopy, XRD, thermogravimetric analysis (TGA), TEM, field‐emission SEM (FE‐SEM) and energy‐dispersive X‐ray spectroscopy (EDX). The grafting of the sensory module afforded active sites for the adsorption of metal ions from the aqueous solution which is outlined using the Langmuir adsorption isotherm. The potential in sensing, sorbent properties and facile magnetic recovery of the hybrid evinces the separation process practical to undertake environmental issues.

Magnetic silica hybrids modified with guanidine containing co-polymers for drug delivery applications

Guanidine containing co-polymers grafted onto silica nanoparticles to form core-shell structure were prepared by sol-gel method in the presence of γ-Fe2O3 nanoparticles. The morphological features for uncoated and coated silica particles have been characterized with scanning electron microscopy. The results show that the polymer coated silicas exhibit spherical morphology with rough polymeric surface covered by γ-Fe2O3 nanoparticles. The grafting amount of guanidine containing co-polymers evaluated by thermogravimetric analysis was in the range from 17 to 30%. Then, the drug loading properties and cumulative release of silica hybrids modified with guanidine containing co-polymers were evaluated using molsidomine as a model drug. It was shown that after polymer grafting the loading content of molsidomine could reach up to 3.42±0.21 and 2.34±0.14mg/g respectively. The maximum drug release of molsidomine is achieved at pH1.6 (approximately 71–75% release at 37°C), whereas at pH7.4 drug release is lower (50.4–59.6% release at 37°C). These results have an important implication that our magneto-controlled silica hybrids modified with guanidine containing co-polymers are promising as drug carriers with controlled behaviour under influence of magnetic field.

Design of core–shell magnetic mesoporous silica hybrids for pH and UV light stimuli-responsive cargo release

The drug carrier system proposed here efficiently works under UV light and pH triggers for controlled release of model cargoes. The nanocarrier can be used in the targeted delivery of cargoes by the ‘ON’ and ‘OFF’ command by the UV light trigger.

Cost-efficient method for unsymmetrical meso-aryl porphyrins and iron oxide-porphyrin hybrids prepared thereof.

Herein, the synthesis and characterisation of magnetic iron oxide-porphyrin hybrids, constituted of iron-oxide magnetic nanoparticles covalently linked to an unsymmetrically substituted meso-aryl porphyrin, are described. The methodology features for the preparation of the key unsymmetrically substituted meso-aryl porphyrin synthons are discussed, with emphasis on sustainability and in economical terms. The "NaY method" herein reported allows large scale and economical preparation, which are demonstrated by its reusability and at least two-fold yields, when compared with classical porphyrin synthetic methods and also presents a much better cost-efficiency rationale and lower environmental impact. Upon covalent linking to iron-oxide magnetic nanoparticles, the new hybrids are fully characterised by thermogravimetry/differential scanning calorimetry, transmission electron microscopy and infrared spectroscopy and their photophysical properties were measured, which demonstrate that the presence of the magnetic nanoparticle counterparts does not affect these properties, thus allowing the materials to keep the photophysical features imparted by their porphyrin counterparts.

Facile preparation of a novel Hg(ii)-ion-imprinted polymer based on magnetic hybrids for rapid and highly selective removal of Hg(ii) from aqueous solutions

This study reveals a facile strategy to prepare magnetic Hg(ii)-ion-imprinted polymers with incorporated Fe3O4@SiO2 particles for rapid and efficient removal of Hg(ii) ions, due to the soft acid–soft base interaction of Hg(ii) and allylthiourea.

Fabrication of Bi-Fe3O4@RGO hybrids and their catalytic performance for the reduction of 4-nitrophenol

Nanocatalysts are frequently connected to magnetic nanoparticles. These composites are easy to be retrieved from the reaction system under a magnetic field because of their magnetic properties. Magnetic separation is particularly promising in industry since it can solve many issues present in filtration, centrifugation, or gravitation separation. Herein, a facile method to prepare bismuth and Fe3O4 nanoparticles loaded on reduced graphene oxide magnetic hybrids (Bi-Fe3O4@RGO) using soluble starch as a dispersant is demonstrated. The magnetic Fe3O4 nanoparticles were synthesized by the co-precipitation of Fe2+ and Fe3+ ions, and Bi nanoparticles were fabricated by the redox reactions between sodium borohydride and ammonium bismuth citrate in the presence of soluble starch. Transmission electron microscopy images demonstrate that the average diameter of the Fe3O4 nanoparticles is about 5 nm and the diameters of Bi nanoparticles range from 10 to 20 nm. The magnetic Bi-Fe3O4@RGO hybrids exhibit high catalytic activity in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH4 with a first-order rate constant (K) of 0.00808 s−1 and is magnetically recyclable for at least five cycles. This strategy provides an efficient and recyclable catalyst for the use in environmental protection applications.

Facile and Scalable Preparation of Graphene Oxide-Based Magnetic Hybrids for Fast and Highly Efficient Removal of Organic Dyes.

This study reports the facile preparation and the dye removal efficiency of nanohybrids composed of graphene oxide (GO) and Fe3O4 nanoparticles with various geometrical structures. In comparison to previously reported GO/Fe3O4 composites prepared through the one-pot, in situ deposition of Fe3O4 nanoparticles, the GO/Fe3O4 nanohybrids reported here were obtained by taking advantage of the physical affinities between sulfonated GO and Fe3O4 nanoparticles, which allows tuning the dimensions and geometries of Fe3O4 nanoparticles in order to decrease their contact area with GO, while still maintaining the magnetic properties of the nanohybrids for easy separation and adsorbent recycling. Both the as-prepared and regenerated nanohybrids demonstrate a nearly 100% removal rate for methylene blue and an impressively high removal rate for Rhodamine B. This study provides new insights into the facile and controllable industrial scale fabrication of safe and highly efficient GO-based adsorbents for dye or other organic pollutants in a wide range of environmental-related applications.

Hybrid Materials Based on Magnetic Layered Double Hydroxides: A Molecular Perspective.

Design of functional hybrids lies at the very core of synthetic chemistry as it has enabled the development of an unlimited number of solids displaying unprecedented or even improved properties built upon the association at the molecular level of quite disparate components by chemical design. Multifunctional hybrids are a particularly appealing case among hybrid organic/inorganic materials. Here, chemical knowledge is used to deploy molecular components bearing different functionalities within a single solid so that these properties can coexist or event interact leading to unprecedented phenomena. From a molecular perspective, this can be done either by controlled assembly of organic/inorganic molecular tectons into an extended architecture of hybrid nature or by intercalation of organic moieties within the empty channels or interlamellar space offered by inorganic solids with three-dimensional (MOFs, zeolites, and mesoporous hosts) or layered structures (phosphates, silicates, metal dichalcogenides, or anionic clays). This Account specifically illustrates the use of layered double hydroxides (LDHs) in the preparation of magnetic hybrids, in line with the development of soft inorganic chemistry processes (also called "Chimie Douce"), which has significantly contributed to boost the preparation hybrid materials based on solid-state hosts and subsequent development of applications. Several features sustain the importance of LDHs in this context. Their magnetism can be manipulated at a molecular level by adequate choice of constituting metals and interlayer separation for tuning the nature and extent of magnetic interactions across and between planes. They display unparalleled versatility in accommodating a broad range of anionic species in their interlamellar space that encompasses not only simple anions but chemical systems of increasing dimensionality and functionalities. Their swelling characteristics allow for their exfoliation in organic solvents with high dielectric strength, to produce two-dimensional nanosheets with atomic thickness that can be used as macromolecular building blocks in the assembly of nanocomposites. We describe how these advantageous properties turn LDHs into excellent vehicles for the preparation of multifunctional materials with increasing levels of complexity. For clarity, the reader will first find a succinct description of the most relevant aspects controlling the magnetism of LDHs followed by their use in the preparation of magnetic hybrids from a molecular perspective. This includes the intercalation anionic species of increasing nuclearity like paramagnetic mononuclear complexes, stimulus-responsive molecular guests, one- and two-dimensional coordination polymers, or even preassembled 2D networks. This approach allows us to evolve from "dual-function" materials with coexistence, for example, of magnetism and superconductivity, to smart materials in which the magnetic or structural properties of the LDH layers can be tuned by applying an external stimulus like light or temperature. We will conclude with a brief look into the promising features offered by magnetic nanocomposites based on LDHs and our views on the most promising directions to be pursued in this context.

Removal of uranium(VI) ions from aqueous solution by magnetic cobalt ferrite/multiwalled carbon nanotubes composites

Cobalt ferrite/multiwalled carbon nanotubes (CoFe2O4/MWCNTs) magnetic hybrids were synthesized by a hydrothermal method. The as-prepared CoFe2O4/MWCNTs were then assessed as the adsorbent for uranium(VI) ions removal from water, and could be easily separated by an external magnetic field. Influencing factors to adsorb uranium(VI) ions were investigated, including pH, equilibrium time and temperature on uranium adsorption efficiency. The results indicated that uranium(VI) ions adsorption was strongly dependent on pH. The maximum adsorption capacity for uranium(VI) ions was calculated to be 212.7mgU/g based on the Langmuir model, displaying a high efficiency for the removal of uranium(VI) ions. Thermodynamic parameters further showed that the adsorption is an endothermic and spontaneous process. The CoFe2O4/MWCNTs showed their potential applications as adsorbent for highly efficient removal of heavy metal ions from aqueous solution.

A magnetic graphene hybrid functionalized with beta-cyclodextrins for fast and efficient removal of organic dyes

A β-cyclodextrin (β-CD) functionalized magnetic graphene hybrid (mGO-β-CD) has been prepared and its application as an adsorbent for the removal of organic dyes has been investigated. Magnetic graphene hybrids (mGOs) were first synthesized via a chemical precipitation method, and then β-CDs were applied to further functionalize the resultant mGO hybrid. The results demonstrate that the as-prepared mGO-β-CD hybrid exhibits greatly enhanced adsorption performance in water. Acid fuchsin and Rhodamine 6G, the typical dye pollutants, can be effectively removed from their solutions by the mGO-β-CD hybrid. The maximum adsorption capability of the mGO-β-CD hybrid is several times, even hundreds of times higher than that of the reported carbonaceous materials. Moreover, ca. 90% of the dye removal efficiency can be retained after six adsorption–desorption cycles. In addition, the mGO-β-CD hybrid exhibits negligible toxicity toward the normal cells. Conclusively, the resultant mGO-β-CD hybrid proves to be a magnetically separable, efficient and non-toxic adsorbent for dye removal.

Adsorption performance of carboxylated multi-wall carbon nanotube–Fe3O4 magnetic hybrids for Cu(II) in water

Carboxylated multi-wall carbon nanotube( c-MWCNT)-Fe3O4 magnetic hybrids( c-MWCNTMCs) were prepared by mixing FeCl3·6H2 O,sodium acetate,ethylene glycol and diethylene glycol with c-MWCNTs,followed by sonicating and heat treatment at 200 ℃ for 10 h. Results indicated that the c-MWCNTMCs showed a good dispersion stability,an acid and alkali resistivity,and magnetic properties in deionized water,and can be used as adsorbents for Cu( Ⅱ) removal. The c-MWCNTMCs could be easily separated from water by a magnet and showed a high adsorption capacity for Cu( Ⅱ). The adsorption of Cu( Ⅱ) on the c-MWCNTMCs was quick and followed a pseudo-second-order model. The adsorption force between the c-MWCNTMHs and Cu( Ⅱ) was of a chemical type and the saturated adsorbents can be regenerated at pH 2. 0. The magnetic Fe3O4 favored only the quick separation and had little contribution to adsorption. The low limit of Cu( Ⅱ) in water that was removable with the hybrids was 1. 29 μg /L.

Adsorption performance of carboxylated multi-wall carbon nanotube-Fe3O4 magnetic hybrids for Cu(II) in water

Carboxylated multi-wall carbon nanotube (c-MWCNT)-Fe3O4 magnetic hybrids (c-MWCNTMCs) were prepared by mixing FeCl3·6H2O, sodium acetate, ethylene glycol and diethylene glycol with c-MWCNTs, followed by sonicating and heat treatment at 200 °C for 10 h. Results indicated that the c-MWCNTMCs showed a good dispersion stability, an acid and alkali resistivity, and magnetic properties in deionized water, and can be used as adsorbents for Cu(II) removal. The c-MWCNTMCs could be easily separated from water by a magnet and showed a high adsorption capacity for Cu(II). The adsorption of Cu(II) on the c-MWCNTMCs was quick and followed a pseudo-second-order model. The adsorption force between the c-MWCNTMCs and Cu(II) was of a chemical type and the saturated adsorbents can be regenerated at pH < 2.0. The magnetic Fe3O4 favored only the quick separation and had little contribution to adsorption. The low limit of Cu(II) in water that was removable with the hybrids was 1.29 μg/L.

Graphene oxide-based magnetic fluorescent hybrids for drug delivery and cellular imaging

A graphene oxide (GO)-based multifunctional hybrid has been developed for loading and delivery of anticancer drugs. The GO was functionalized by magnetic/fluorescent SiO2 microsphere via an amidation process. Doxorubicin (DOX) was chosen as a model drug to be loaded onto the GO via π–π stacking and hydrophobic interaction. The loading capacities of DOX to the GO-based magnetic fluorescent hybrids were investigated. The release profiles of DOX from the hybrids were depicted. The fluorescence images of the GO-based magnetic fluorescent hybrids indicated that the hybrids would be an effective drug carrier and a potential optical imaging tool. The application of the developed GO-based magnetic fluorescent hybrids for HepG2 cells demonstrated an excellent therapeutic effect of the DOX loaded hybrids to the target tumor.

Improved potentiometric response of solid-contact lanthanum (III) selective electrode

For the first time, the analytical application of integrate ionophore-transducer material based on magnetic graphene hybrids and 2,2-dithiodipyridine (DTDP) in solid-contact lanthanum (III) selective electrode is reported. The attachment of Fe3O4 nanoparticles (NPs) to graphene oxide (GO) for magnetic graphene hybrid is achieved by covalent bonding, and the universal problem, Fe3O4 NPs may easily leach out from the graphene during application, is successfully solved by the method above. The proposed electrode exhibits an excellent near-Nernstian response to lanthanum (III) ranging from 1.0×10−9 to 1.0×10−3M with a slope of 17.81mV/dec. Moreover, the excellent performance on fairly good selectivity, wide applicable pH range (3.0_8.0), fast response time (10s) and long life time (2 months) reveal the superiority of the electrode. Most importantly, we have made a great improvement in the detection limit (2.75×10−10M), which brings new dawn to the real-time detection of lanthanum (III) using ion selective electrode.

Synthesis and Characterization of Superparamagnetic CoFe&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;4&lt;/SUB&gt;/MWCNT Hybrids for Tumor-Targeted Therapy

Owing to their great potentialities of carbon nanotubes (CNTs)-based magnetic nano-composites, numerous applications of them have been found in nanotechnology, integrated functional system, and in medicine. Herein, nearly monodisperse CoFe2O4 nanoparticles have been deposited on multi-walled carbon nanotubes (MWCNTs) by high-temperature hydrolysis and inorganic polymerization of ionic Co(II) and Fe(III) salts and MWCNTs in a polyol solution. X-ray diffraction, energy-dispersive X-ray spectrometry and transmission electron microscopy were used to characterize the final products. The average size of CoFe2O4 nanoparticles and their coverage density on MWCNTs can be adjusted to some extent by altering the reaction parameters. A proposed formation mechanism of the magnetic hybrids is presented. Magnetic measurements showed that the hybrids were superparamagnetic at room temperature and their saturation magnetization could be fine tuned by changing the loading of CoFe2O4 nanoparticles on the MWCNTs.

Synthesis and Characterization of Multiwall-Carbon Nanotubes Decorated with Nickel Ferrite Hybrid

Acid functionalized multiwall carbon nanotube, (MWCNT)-COOH/nickel ferrite (NiFe2O4), magnetic hybrids were synthesized by a co-precipitation method. X-ray diffraction, Fourier transform infrared spectrometry, thermal gravimetry, transmission electron microscopy, vibrating sample magnetometry and Impedance Spectroscopy were used to characterize the physical and electrical properties of the MWCNT-COOH/NiFe2O4 hybrid. NiFe2O4 NPs are stably attached to the surface of via carboxyl groups (COOH). The magnetic saturation value of the product was found as 8 emu/g. A tunneling conduction mechanism was believed to occur in the hybrid. The real modules (M′) of the product illustrate power law variation with a power exponent of approximately unity. These magnetic MWCNT-COOH/NiFe2O4 hybrids exhibit a promising prospective in the application of bio-nanoscience and technology.

Synthesis and Characterization of γ-Fe2O3/Carbon Hybrids and Their Application in Removal of Hexavalent Chromium Ions from Aqueous Solutions

Magnetic Fe(2)O(3)/carbon hybrids were prepared in a two-step process. First, acetic acid vapor interacted with iron cations dispersed on the surface of a nanocasted ordered mesoporous carbon (CMK-3). In the second step, the primarily created iron acetate species underwent pyrolysis and transformed to magnetic iron oxide nanoparticles. X-ray diffraction, Fourier-transform infrared, and Raman spectroscopies were used for the chemical and structural characterization of the hybrids, while surface area measurements, thermal analysis, and transmission electron microscopy were employed to determine their physical, surface, and textural properties. These results revealed the preservation of the host carbon structure, which was homogenously and controllably loaded (up to 27 wt %) with nanosized (ca. 20 nm) iron oxides inside the mesoporous system. Mössbauer spectroscopy and magnetic measurements at low temperatures confirmed the formation of γ-Fe(2)O(3) nanoparticles exhibiting superparamagnetic behavior. The kinetic studies showed a rapid removal of Cr(VI) ions from the aqueous solutions in the presence of these magnetic mesoporous hybrids and a considerably increased adsorption capacity per unit mass of sorbent in comparison to that of pristine CMK-3 carbon. The results also indicate highly pH-dependent sorption efficiency of the hybrids, whereas their kinetics was described by a pseudo-second-order kinetic model. Taking into account the simplicity of the synthetic procedure and possibility of magnetic separation of hybrids with immobilized pollutant, the developed mesoporous nanomaterials have quite real potential for applications in water treatment technologies.

Enzyme–magnetic nanoparticle hybrids: new effective catalysts for the production of high value chemicals

AbstractMagnetic nanoparticles (5–100 nm in diameter) offer the science community a new dimension in many key areas of research, notably nano‐medicine. However, use as catalyst support material (including enzyme immobilization) has largely been overlooked despite the benefits of a facile catalyst separation post‐reaction with reuse through the application of an external magnetic field. This is largely due to the high cost associated with magnetic nanoparticle synthesis in addition to enzyme operating costs. This can, however, be compensated for by effective catalyst recycling in the production of high value chemicals, particularly chiral drugs and their intermediates, circumventing laborious multi‐stage separation and purification procedures in conventional synthesis. Indeed, enzymes (such as lipase) on magnetic carriers have shown prolonged activity in organic solvents, even after recycling, when compared with free enzymes. Further developments can be directed at multi‐functional magnetic nanoparticles with the creation of a reactant‐specific micro‐environment to facilitate multi‐stepped reactions. The potential of enzyme‐magnetic nanoparticle hybrids is discussed and applications in the synthesis of fine chemicals, including precursors for drugs, are identified. Copyright © 2012 Society of Chemical Industry