Coupling of optical characterization with particle and network synthesis for biomedical applications
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Polymeric microspheres containing a magnetic core have been used in cancer therapy for biophysical targeting of antitumor agents and in magnetic resonance imaging as contrasting agents. For the Human Genome Project, deoxyribose nucleic acid (DNA) capillary electrophoresis has become the most widely used analytical technique where a key component is the design of an effective separation medium. The synthesis and optical characterization of polymeric coated superparamagnetic nanoparticles and of (self-assembled) polymer networks by means of a range of physical techniques, including laser light scattering and laser-induced fluorescence detection, are presented. (1) Polymeric microspheres with a superparamagnetic core. A water-in-oil microemulsion approach has been used successfully to synthesize the superparamagnetic core and the polymeric microsphere in one continuous step. The synthesis permits us to control the magnetic nanoparticle size and the thickness of the hydrogel, ranging from 80 to 320 nm. Magnetite concentration in the microspheres, calculated by vibrating-sample magnetometry, was found to be up to 3.3 wt %. The internal structure of the microspheres, as observed by atomic force microscopy, confirmed a core-shell model. (2) Development of new separation media for DNA capillary electrophoresis. Block copolymers in selective solvents can self-assemble to form supramolecular structures in solution. The nanostructures can be characterized in the dilute concentration regime by means of laser light scattering. At semidilute concentrations, the mesh size, the supramolecular structure, and the surface morphology can be investigated by means of small angle x-ray scattering and atomic force microscopy. The structural knowledge and the information on chain dynamics can then be correlated with electrophoresis using laser-induced fluorescence detection to provide a deeper understanding for the development of new separation media.Keywords:
Superparamagnetism
Superparamagnetism
Zinc ferrite
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Superparamagnetic behavior observed in magnetically dilute systems is discussed. The clusters that behave like superparamagnetic fine particles are ferromagnetic or ferrimagnetic regions separated magnetically from the matrix, because these regions are surrounded by nonmagnetic atoms. The magnetic properties of dilute oxide systems such as: 0.9 ZnFe2O4-0.1 NiFe2O4; 0.9 FeTiO3-0.1 Fe2O3; and Y1.5Ca1.5Fe4.5Sn1.5O12 are better understood if we take into account the existence of the superparamagnetic clusters. The Langevin function type magnetization curves observed for the Fe—Cr alloys in the composition range where ferromagnetism just disappears, however, were found not to have the characteristics of superparamagnetism, although superparamagnetic clusters are predicted by the localized model.
Superparamagnetism
Ferrimagnetism
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This letter reports the results obtained by measuring the temperature dependence of the coercivity of magnetically isolated L10-FePt nanoparticles in agglomeration-free films deposited by using a dispersion stabilizer and a spin-coat technique. These measurements not only give the basic magnetic parameters of the nanoparticles but also provide information about the nanoparticle ordering process. The temperature at which isolated FePt nanoparticles start to order seems to be about 650°C.
Stabilizer (aeronautics)
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A review is given on application of electrochemiluminescence(ECL) of Ru(bpy)2+3 subjected to capillary electrophoresis in pharmaceutical analysis,food analysis,and bioscience.The basic characteristics of ECL of Ru(bpy)2+3 subjected to capillary electrophoresis are briefed,and development in the applied research on ECL of Ru(bpy)2+3 subjected to capillary electrophoresis and combined with composites and microchip is introduced.Moreover,suggests are provided about the prospects of ECL of Ru(bpy)2+3 subjected to capillary electrophoresis.
Electrochemiluminescence
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Superparamagnetism
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We present a simple polymer-mediated process of assembling magnetic FePt nanoparticles on a solid substrate. Alternatively absorbing the PEI molecule and FePt nanoparticles on a HO-terminated solid surface leads to a smooth FePt nanoparticle assembly with controlled assembly thickness and dimension. Magnetic measurements show that the thermally annealed FePt nanoparticle assembly as thin as three nanoparticle layers is ferromagnetic. The magnetization direction of this thin FePt nanoparticle assembly is readily controlled with the laser-assisted magnetic writing. The reported process can be applied to various substrates, nanoparticles, and functional macromolecules and will be useful for future magnetic nanodevice fabrication.
Nanodevice
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Superparamagnetic particles are widely used for biological applications such as cell separation. The size of the particles is normally in the range of 10 – 20 nm which is much smaller than the size of a cell. Therefore small particles create small force which is not strong enough to separate the cells from solution. Superparamagnetic nanoparticles embedded in Polystyrene microspheres (magnetic beads) are very useful for cell separation. Magnetic beads have been prepared by solvent evaporation of an emulsion. The beads with size of 0.2 μm – 1.0 μm have a saturation magnetization of 10 – 25 emu/g. The change of the amount of surfactants, volatile solvent, magnetic particles resulted to the change of size, magnetic properties of the magnetic beads.
Superparamagnetism
Polystyrene
Magnetic separation
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In this article we report a chemical synthetic means for generating a high Ku magnetic material—narrowly dispersed nanoparticles of SmCo5. Using Co2(CO)8 and Sm(acac)3 as the precursors under air-free conditions, we produced SmCo5 nanoparticles according to the procedure reported by Sun et al. [Science 287, 1981 (2000)] but with some modifications. The nanoparticles, with diameters of 6–8 nm, have a SmCo5 composition, as indicated by transmission electron microscopy, electron diffraction, and x-ray photoelectron spectroscopy. The magnetization measurement of the nanoparticles, exhibits superparamagnetism, which is blocked for temperatures below ∼110 K, suggesting Ku to be ∼2.1×106 erg/cm3 for the as-prepared particles.
Superparamagnetism
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