Magnet-induced temporary superhydrophobic coatings from one-pot synthesized hydrophobic magnetic nanoparticles.

In this paper, we report on the production of superhydrophobic coatings on various substrates (e.g., glass slide, silicon wafer, aluminum foil, plastic film, nanofiber mat, textile fabrics) using hydrophobic magnetic nanoparticles and a magnet-assembly technique. Fe3O4 magnetic nanoparticles functionalized with a thin layer of fluoroalkyl silica on the surface were synthesized by one-step coprecipitation of Fe2+/Fe3+ under an alkaline condition in the presence of a fluorinated alkyl silane. Under a magnetic field, the magnetic nanoparticles can be easily deposited on any solid substrate to form a thin superhydrophobic coating with water contact angle as high as 172°, and the surface superhydrophobicity showed very little dependence on the substrate type. The particulate coating showed reasonable durability because of strong aggregation effect of nanoparticles, but the coating layer can be removed (e.g., by ultrasonication) to restore the original surface feature of the substrates. By comparison, the thin particle layer deposited under no magnetic field showed much lower hydrophobicity. The main reason for magnet-induced superhydrophobic surfaces is theformation of nano- and microstructured surface features. Such a magnet-induced temporary superhydrophobic coating may have wide applications in electronic, biomedical, and defense-related areas.

Attachment of magnetic molecules on a nanoSQUID

A novel procedure combining monolayer self-assembly with electron beam lithography has been developed for attaching ferritin nanoparticles to a submicron thin-film SQUID (superconducting quantum interference device). After opening a window in the PMMA (polymethylmethacrylate) resist, organic linker molecules are used to attach ferritin to the exposed parts of the gold overlayer of a Nb nanoSQUID. This allows the magnetic nanoparticles to be located optimally as far as magnetic coupling to the nanoSQUID is concerned.

Biocompatibility of transition metal-substituted cobalt ferrite nanoparticles

Transition metals of copper, zinc, manganese, and nickel were substituted into cobalt ferrite nanoparticles via a sol-gel route using citric acid as a chelating agent. The microstructure and elemental compositions of the nanoparticles were characterized using scanning electron microscopy combined with energy dispersive X-ray spectroscopy. The particle size of the nanoparticles was investigated using particle size analyzer, and the zeta potentials were measured using zeta potential analyzer. The phase components of the synthesized transition metal-substituted cobalt ferrite nanoparticles were studied using Raman spectroscopy. The biocompatibility of the nanoparticles was assessed using osteoblast-like cells. Results indicated that the substitution of transition metals strongly influences the physical, chemical properties, and biocompatibility of the cobalt ferrite nanoparticles. © 2014 Springer Science+Business Media.

Magnetic liquid marbles : manipulation of liquid droplets using highly hydrophobic Fe3O4 nanoparticles

Magnetic liquid marbles exhibit a remarkable ability to be opened and closed reversibly under the action of a magnetic field. Liquid can be either extracted from or added to the opened liquid marble simply with a capillary needle. Two opened liquid marbles can also be coalesced into a larger one. The magnetic liquid marbles can be maneuvered two- and three-dimensionally.

Mechanochemical synthesis of niobium pentoxide nanoparticles

Acicular α-FeOOH particles are formed through aging of ferric oxyhydroxide colloidal solution formed by the neutralization of FeCl₃ aqueous solution by NaOH. The effect of foreign ion addition to the colloidal solution on the formation and morphology of α-FeOOH particles has been investigated. The magnetic properties of Fe₃O₄ particles made from the obtained particles have also been investigated. The rate constant of the formation of α-FeOOH remarkably decreased, but the crystallite size of α-FeOOH particles increased with increasing the quantity of phosphate ion added even with small amounts. These results have been explained as follows: the phosphate ions are selectively adsorbed on the (a) plane of α-FeOOH, cover the (a) plane, and block the crystal growth of the (a) plane of the α-FeOOH. The quantities of the phosphate ion adsorbed on the b and c planes are relatively small. The complex ion of Fe(OH)₄^- is preferentially deposited on both (b) and (c) planes, and the crystal growth of (b) and (c) planes is greatly accelerated. The relationship between the morphology of the formed α-FeOOH particles and the quantity of phosphate ion added has been investigated. The asterisk type particles: α-FeOOH particles heterogeneously junctioned to α-Fe₂O₃ particles, were formed when a small amount of phosphate was added to the mother liquid. The α-FeOOH crystal epitaxially grew on the junction interface with the α-Fe₂O₃ crystal. In the case of the aging at the temperature as high as 80°C, the cross type junctioned particles were stably formed at pH below 12.0. The Fe₃O₄ particles with screw-like unique three-dimensional morphology were produced from the heterogeneously junctioned particles.

Suitability of magnetic nanoparticle immobilised cellulases in enhancing enzymatic saccharification of pretreated hemp biomass

Previous research focused on pretreatment of biomass, production of fermentable sugars and their consumption to produce ethanol. The main goal of the work was to economise the production process cost of fermentable sugars. Therefore, the objective of the present work was to investigate enzyme hydrolysis of microcrystalline cellulose and hemp hurds (natural cellulosic substrate) using free and immobilised enzymes. Cellulase from Trichoderma reesei was immobilised on an activated magnetic support by covalent binding and its activity was compared with that of the free enzyme to hydrolyse microcrystalline cellulose and hemp hurds on the basis of thermostability and reusability.

Oil-spill cleanup: the influence of acetylated curaua fibers on the oil-removal capability of magnetic composites

A magnetic resin based on cardanol, furfural, and curaua fibers was prepared and characterized. The material could be used in oil-spill cleanup processes, because of its aromatic/aliphatic balance. The resin was prepared through bulk polycondensation of cardanol and furfural in the presence of curaua fibers and maghemite nanoparticles. Hydrophobicity of the curaua fibers was improved by acetylation, increasing the oil-absorbing capability of the composites. The obtained magnetic composites were studied by Fourier-transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. Degree of cure, magnetic force, and oil-removal capability tests were also performed. The results show that the composites possess an elevated cure degree in addition to a considerable magnetic force. The materials exhibit a good oil removal capability in the presence of a magnetic field, which is improved by the use of acetylated curaua. In the best case, the composite filled with maghemite and curaua can remove 12 parts of oil from water.

Epoxy nanocomposites containing magnetite-carbon nanofibers aligned using a weak magnetic field

Abstract Novel magnetite-carbon nanofiber hybrids (denoted by Fe3O4@CNFs) have been developed by coating carbon nanofibers (CNFs) with magnetite nanoparticles in order to align CNFs in epoxy using a relatively weak magnetic field. Experimental results have shown that a weak magnetic field (∼mT) can align these newly-developed nanofiber hybrids to form a chain-like structure in the epoxy resin. Upon curing, the epoxy nanocomposites containing the aligned Fe3O4@CNFs show (i) greatly improved electrical conductivity in the alignment direction and (ii) significantly higher fracture toughness when the Fe3O4@CNFs are aligned normal to the crack surface, compared to the nanocomposites containing randomly-oriented Fe3O4@CNFs. The mechanisms underpinning the significant improvements in the fracture toughness have been identified, including interfacial debonding, pull-out, crack bridging and rupture of the Fe3O4@CNFs, and plastic void growth in the polymer matrix.

A novel route for tethering graphene with iron oxide and its magnetic field alignment in polymer nanocomposites

We present a new route of tethering graphene nanoplatelets (GNPs) with Fe3O4 nanoparticles to enable their alignment in an epoxy using a weak magnetic field. The GNPs are first stabilised in water using polyvinylpyrrolidone (PVP) and Fe3O4 nanoparticles are then attached via co-precipitation. The resultant Fe3O4/PVP-GNPs nanohybrids are superparamagnetic and can be aligned in an epoxy resin, before gelation, by applying a weak magnetic field as low as 0.009 T. A theoretical model describing the alignment process is presented and used to quantify the effects of key parameters on the time needed for the alignment process. Compared to the unmodified epoxy, the resulting epoxy polymer nanocomposites containing randomly-oriented Fe3O4/PVP-GNPs nanohybrids exhibit significantly improved electrical conductivities by up to three orders of magnitude and fracture energies by up to 300%. The alignment of the Fe3O4/PVP-GNPs nanohybrids in the epoxy polymer nanocomposites transverse to the direction of crack propagation further increased the fracture energy by 50%, and the electrical conductivity by seven fold in the alignment direction, compared to the nanocomposites containing randomly-oriented nanohybrids.