Magnetically uniform and tunable Janus particles (original) (raw)

Fabrication of Novel Magnetic Janus Microparticles

MRS Proceedings, 2008

ABSTRACTWe have designed a novel technique for fabrication of magnetic Janus microparticles based on “trapping” the alignment of magnetite nanoparticles dispersed within the oil drops of polymerizable oil-in-water emulsion. We polymerized the oil drops after gelling the continuous aqueous phase in the presence of an external magnetic filed. This allowed us to produce magnetic Janus particles with optical and magnetic anisotropy which form unusual zigzag chains and structures when an external magnetic field is applied to a suspension of such particles. These novel microparticles retain high remanence magnetization and coercivity values indicative of ferromagnetic behavior, which indicates that the composite polymeric Janus microparticles posses a net magnetic dipole and behave like micro-magnets due to the “trapped” orientation of the magnetite nanoparticles in their polymeric matrix.

Magnetic Janus Particles for Static and Dynamic (Bio)Sensing

Magnetochemistry

Magnetic Janus particles bring together the ability of Janus particles to perform two different functions at the same time in a single particle with magnetic properties enabling their remote manipulation, which allows headed movement and orientation. This article reviews the preparation procedures and applications in the (bio)sensing field of static and self-propelled magnetic Janus particles. The main progress in the fabrication procedures and the applicability of these particles are critically discussed, also giving some clues on challenges to be dealt with and future prospects. The promising characteristics of magnetic Janus particles in the (bio)sensing field, providing increased kinetics and sensitivity and decreased times of analysis derived from the use of external magnetic fields in their manipulation, allows foreseeing their great and exciting potential in the medical and environmental remediation fields.

Highly Porous Magnetic Janus Microparticles with Asymmetric Surface Topology

Monodispersed magnetic Janus particles composed of a porous polystyrene portion and a nonporous poly(vinyl acetate) portion with embedded oleic acid-coated magnetic nanoparticles were generated using microfluidic emulsification followed by two distinct phase separation events triggered by solvent evaporation. The template droplets were composed of 2 wt % polystyrene, 2 wt % poly(vinyl acetate), and 0.5−2 wt % n-heptane-based magnetic fluid dissolved in dichloromethane (DCM). The porosity of polystyrene compartments was the result of phase separation between a nonvolatile nonsolvent (nheptane) and a volatile solvent (DCM) within polystyrene-rich phase. The focused ion beam cross-sectioning and scanning electron microscopy (SEM) imaging revealed high surface porosity of polystyrene compartments with negligible porosity of poly(vinyl acetate) parts, which can be exploited to increase the wettability contrast between the two polymers and enhance bubble generation in bubble-driven micromotors. The porosity of the polystyrene portion was controlled by varying the fraction of n-heptane in the dispersed phase. The particle composition was confirmed by scanning electron microscopy−energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and differential scanning calorimetry. The fabricated particles were successfully magnetized when subjected to an external magnetic field, which led to their aggregation into regular 2D assemblies. The particle clusters composed of two to four individual particles could be rotated with a rotating magnetic field. Microfluidic generation of highly porous Janus particles with compositional, topological, and magnetic asymmetry provides a cost-effective, easy-to-implement yet highly robust and versatile strategy for the manufacturing of multifunctional smart particles.

Polymer Janus Particles Containing Block-Copolymer Stabilized Magnetic Nanoparticles

ACS Applied Materials & Interfaces, 2013

In this report, we show a simple route to fabricate Janus particles having magnetic nanoparticles inside them, which can respond and rotate along to magnetic fields. By solvent evaporation from the tetrahydrofran solution of polymer stabilized γ-Fe 2 O 3 nanoparticles, polystyrene (PS), and polyisoprene containing water, aqueous dispersion of Janus microparticles were successfully prepared, and the γ-Fe 2 O 3 nanoparticles were selectively introduced into the PS phase. We demonstrate rotation and accumulation of Janus particles by using a neodymium magnet.

Anisotropic janus magnetic polymeric nanoparticles prepared via miniemulsion polymerization

Journal of Polymer Science Part A: Polymer Chemistry, 2013

Anisotropic Janus magnetic polymeric nanoparticles are prepared via the miniemulsion polymerization of styrene and acrylic acid monomers in the presence of oleic acid-coated magnetic nanoparticles (MNPs). The controllable phase separation between the polymer matrix and the encapsulated MNPs is a key success factor to produce Janus morphology. The effects of MNPs, 2,2 0-azobis(2-isobutyronitrile) and sodium dodecyl sulfate contents, on the morphology, chemical composition and colloidal stability of the prepared Janus hybrid particles are investigated. Besides the determination of polymerization conversion, zeta potential, size analysis , TGA, and TEM are applied for characterization of the anisotropic particles. The results show the stable spherical Janus particles containing MNPs (15 wt % magnetic content) located on one side of each polymer particle. The anisotropic submicron Janus magnetic polymeric particles (250 nm) can be easily separated by an external magnet. V

Key synthesis of magnetic Janus nanoparticles using a modified facile method

Particuology, 2014

Inorganic/organic poly(methylmethacrylate-acrylic acid-divinylbenzene) iron oxide Janus magnetic nanoparticles (P(MMA-AA-DVB)/Fe 3 O 4 ) with strong magnetic domains and unique surface functionalities were prepared using a solvothermal process. The P(MMA-AA-DVB) nanoparticles were prepared via soapfree emulsion polymerization and used as a precursor for preparing Janus nanoparticles. The morphology and magnetic properties of the magnetic Janus nanoparticles formed were characterized using a laser particle size analyzer, transmission electron microscopy, Fourier transform infrared spectroscopy, vibrating sample magnetometry, and thermogravimetric analysis. The synthesized P(MMA-AA-DVB)/Fe 3 O 4 magnetic Janus nanoparticles were characterized by a Janus structure and possessed a stable asymmetric morphology after being dually functionalized. The particle size, magnetic content, and magnetic domain of the P(MMA-AA-DVB)/Fe 3 O 4 magnetic Janus nanoparticles were 200 nm, 40%, and 25 emu/g, respectively. The formation mechanism of the Janus nanoparticles was also investigated, and the results revealed that the reduction of Fe 3+ ions and growth of Fe 3 O 4 took place on the surface of the P(MMA-AA-DVB) polymeric precursor particles. The size of the Janus particles could be controlled by narrowing the size distribution of the P(MMA-AA-DVB) precursor nanoparticles.

Tuning the Magnetic Properties of Nanoparticles

International Journal of Molecular Sciences, 2013

The tremendous interest in magnetic nanoparticles (MNPs) is reflected in published research that ranges from novel methods of synthesis of unique nanoparticle shapes and composite structures to a large number of MNP characterization techniques, and finally to their use in many biomedical and nanotechnology-based applications. The knowledge gained from this vast body of research can be made more useful if we organize the associated results to correlate key magnetic properties with the parameters that influence them. Tuning these properties of MNPs will allow us to tailor nanoparticles for specific applications, thus increasing their effectiveness. The complex magnetic behavior exhibited by MNPs is governed by many factors; these factors can either improve or adversely affect the desired magnetic properties. In this report, we have outlined a matrix of parameters that can be varied to tune the magnetic properties of nanoparticles. For practical utility, this review focuses on the effect of size, shape, composition, and shell-core structure on saturation magnetization, coercivity, blocking temperature, and relaxation time.

Recent Advances in Multifunctional magnetic nano platform for Biomedical Applications: A mini review

In order to understand the behavior and improve the application of magnetic nanoparticles (MNPs) in different environments, significant efforts have been made in recent years to develop them. Since the colloidal stability and biological behavior of MNPs are determined by their physical and chemical properties; Therefore, precise control over the synthesis and functional conditions of MNP levels is important. For magnetic systems, biomedical and pharmaceutical targets must have a narrow distribution and very small size, as well as large amounts of magnetism. Finally, their optimal surface coverage is to ensure environmental compatibility and delivery to the main target. Magnetic nanoparticles that have suitable physics and chemistry and desired surface properties were studied for various applications such as drug delivery, hyperthermia and molecular diagnosis. Further studies on the bioconjugation of magnetic nanoparticles, their biocompatibility and toxicity were performed.