Yangkyu Ahn

Magnetization and Mössbauer study of cobalt ferrite particles from nanophase cobalt iron carbonate

Nanosize CoFe2O4 particles prepared by a microemulsion method have been investigated by X-ray diffractometry, transmission electron microscopy, SQUID magnetometry and Mossbauer spectroscopy. All peaks of X-ray diffraction patterns can be attributed to a cubic spinel structure with the lattice constant a0=8.397 A. The average size of the particles, determined by transmission electron microscopy, is 49 A. The coercivity and the maximal magnetization measured at 5 K in an applied magnetic field of 50 kOe are 15.1 kOe and 15.2 emu/g, respectively. In the same field of 50 kOe, the measured blocking temperature is about 35 K. Superparamagnetic behavior of these particles around room temperature is confirmed by the coincidence of the magnetization (M) vs. an applied magnetic field (H/T) plots for different temperatures and the Mossbauer spectra.

Effects of surrounding ion on Eu3+ luminescence in glass

Abstract The energy relaxation of excited Eu 3+ in glass hosts is investigated in this study. Eu 3+ ions are incorporated in both melted glass and sol–gel derived glass. The strong Eu 3+ emission lines from 5 D 0 to 7 F level show that the glass hosts provide the effect of the random structure of the silica network on the Eu 3+ ion. The relative intensities of the Eu 3+ emission depend strongly on the host glass types and excitation wavelengths. The 5 D 0 emissions of Eu 3+ in the sol–gel derived glass are more efficient than in the melted glass due to an excitation to the charge-transfer-state at 250 nm. The promotion of the charge-transfer-state excitation in the sol–gel derived glass, which is annealed at 400°C, comes from the anions encapsulated during the sample preparation step. The energy relaxation processes are identified from the wavelengths of the excitation peaks of Eu 3+ . The roles of UV-absorbing cations, Ce 3+ and Ti 4+ , which are codoped in the glasses, are examined.

Preparation of Chitosan-coated Magnetite Nanoparticles by Sonochemical Method for MRI Contrast Agent

Magnetic nanoparticles were synthesized by using the sonochemical method with oleic acid as a surfactant. The average size of the magnetite nanoparticles was controlled by varying the ratio R=[H2O]/[surfactant] in the range of 2 to 9 nm. To prepare chitosan-coated magnetite nanoparticles, chitosan solution was added to a magnetite colloid suspension under ultrasonication at room temperature for 20 min. The chitosan-coated magnetite nanoparticles were characterized by several techniques. Atomic force microscopy (AFM) was used to image the chitosan-coated nanoparticles. Magnetic hysteresis measurement was performed by using a superconducting quantum interference device (SQUID) magnetometer to investigate the magnetic properties of the magnetite nanoparticles and the chitosan-coated magnetite nanoparticles. The SQUID measurements revealed the superparamagnetism of both nanoparticles. The T1- and T2-weighted MR images of these chitosan-coated magnetite colloidal suspensions were obtained with a 4.7 T magnetic resonance imaging (MRI) system. The chitosancoated magnetite colloidal suspensions exhibited enhanced MRI contrasts in vitro.

Synthesis of Monodisperse Magnetite Nanocrystallites Using Sonochemical Method

Ultrasonic irradiation in a solution during the chemical reaction may accelerate the rate of the reaction and the crystallization at low temperature. We have synthesized nanometer sized magnetite particles using coprecipitation method, sonochemical method without surfactant, and sonochemical method with surfactant, in order to investigate the effect of ultrasonic irradiation and surfactant on the coprecipitates of metal ions. The size of the magnetite nanoparticles prepared by coprecipitation method, and sonochemical method without surfactant showed broad distributions. But we got uniform nanoparticles using a sonochemical method with oleic acid. The average size of the particles can be controlled by the ratio

Synthesis of Zinc Ferrite Nanocrystallites using Sonochemical Method

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Preparation of Biopolymer coated Magnetite And Magnetic Biopolymer Microsphere Particles for Medical Application

Ultrasonic irradiation in a solution during the chemical reaction may accelerate the rate of the reaction and the crystallization at low temperature. We have synthesized nanometer sized zinc ferrite particles using chemical co-precipitation technique through a sonochemical method with surfactant such as oleic acid. The thermal behaviour of the zinc ferrite was determined by the thermoanalytical techniques (TGA-DSC). Powder X-ray diffraction measurements show that the samples have the spinel structure. Magnetic properties measurement were performed using a superconducting quantum interference device (SQUID) magnetometer.

Preparation of Chitosan-coated Magnetite Nanoparticles

We have synthesized uniform nanometer sized magnetite particles using chemical coprecipitation technique through a sonochemical method with surfactant such as oleic acid. Magnetite phase nanoparticles could be observed from X-ray diffraction. Magnetite nanoparticles is surface phase morphology and biopolymer-microspheres for Application Medical. Magnetite nanoparticles coated biopolymer. Atomic Force Microscope (AFM) was used to image the coated nanoparticles. Magnetic colloid suspensions containing particles with sodium oleate, chitosan and -glucan have been prepared. The morphology of the magnetic biopolymer microsphere particles were characterized using optical microscope. Magnetic hysteresis measurement were performed using a superconducting quantum interference device (SQUID) magnetometer at room temperature to investigate the magnetic properties of the biopolymer microspheres and magnetite coated biopolymer including magnetite nanoparticles. Magnetic Resonance (MR) imaging was used to investigate biopolymer coated nanoparticles and biopolymer microspheres.

Size dependence of Cation Distribution in Magnetic Nanoparticles

Magnetic nanoparticles can be used for a variety of biomedical applications. They can be used in the targeted delivery of therapeutic agents in vivo, in the hyperthermic treatment of cancers. in magnetic resonance (MR) imaging as contrast agents and in the biomagnetic separations of biomolecules. We have synthesized magnetite nanoparticles using chemical coprecipitation technique with sodium oleate as surfactant. Nanoparticle size can be varied from 2 to 8nm by controlling the sodium oleate concentration. Magnetite phase nanoparticles could be observed from X-ray diffraction. Magnetic colloid suspensions containing particles with sodium oleate and chitosan have been prepared. Nanoparticles, both oleate-coated and chitosan-coated, have been characterized by several techniques. Atomic farce microscope (AFM) was used to image the coated nanoparticles. Magnetic hysteresis measurement were performed using a superconducting quantum interference device (SQUID) magnetometer at room temperature to investigate the magnetic properties of the magnetite nanoparticles. The SQUID measurements revealed superparamagnetism of nanoparticles.

The effect of type of organic phase solvents on the particle size of poly(d,l-lactide-co-glycolide) nanoparticles

In order to investigate the dependence of the particle size on the cation distribution in the spinel structure, Mossbauer spectra were taken in the presence of an external magnetic field f3r the magnetic nanoparticles prepared by using a microemulsion method. The crystals are found to have a cubic structure. The results show that as the particle sizes decrease, ions migrate from the octahedral site to tetrahedral site.