Oznur Karaagac

A Simple Way to Synthesize Superparamagnetic Iron Oxide Nanoparticles in Air Atmosphere: Iron Ion Concentration Effect

We have synthesized iron oxide nanoparticles in air atmosphere by coprecipitation. The ratio of was fixed at 2/3. The total amount of iron ions in the solution was varied from 250 mmol to 12.5 mmol. X-ray diffraction (XRD) patterns showed the characteristic peaks of iron oxide phases. We observed that the crystallinity reduced and particle sizes calculated from XRD patterns decreased as the iron ion concentration in the solution decreased. Fourier transform infrared spectroscopy analysis exhibited the Fe-O vibration band at 560-580 confirming the iron oxide formation. The mean physical sizes obtained from a transmission electron microscope are around 8 nm. According to the magnetic measurements, all samples are superparamagnetic at room temperature showing an increase in saturation magnetization up to 63.71 emu/g. Magnetic sizes of the particles vary from 7.45 nm to 4.88 nm with the change of iron ion concentration.

Iron Oxide Nanoparticles Co-Precipitated in Air Environment: Effect of [Fe

Iron oxide nanoparticles (IONs) were synthesized from ferrous aqueous solutions in air atmosphere by co-precipitation. The effect of [Fe+2]/[Fe+3] ratio on the properties of the nanoparticles were investigated. X-ray diffraction (XRD) patterns showed the charac- teristic peaks of iron oxide for all samples. Fourier transform infrared spectroscopy analysis also confirmed the iron oxide formation. According to magnetic measurements, saturation magnetization, Ms of the nanoparticles increased from 37.6 emu/g to 59.4 emu/g with the increase of [Fe+2]/[Fe+3] ratio from 1/2 to 6/6 and the samples are superparamagnetic with zero coercivities. However, with the increase of the ratio above 6/6 the samples start to show coercivities (8 Oe, 22 Oe and 33 Oe) and Ms increases up to 74.3 emu/g. Particle sizes calculated from the XRD patterns, the images of the transmission electron microscope and magnetic data are consistent with each other and increased with the increase of [Fe+2]/[Fe+3] ratio. It is revealed that the particle size, Ms and magnetic character of IONs were significantly influenced by [Fe+2]/[Fe+3] ratio. Below the critical size of ~11 nm it is seen that IONs showed superparamagnetic character with zero coercivity.

^{+2}

Co-Fe films were electrodeposited on Titanium substrates at the cathode potentials changing from - 1.8 to - 2.7 V with respect to saturated calomel electrode (SCE). The structural analysis by X-ray diffraction revealed that all films have a mixed phase of face centered cubic and body centered cubic structure, but the phase ratios change depending on the cathode potentials. The compositional analysis, which was made using an energy dispersive X-ray spectrometry, demonstrated that the Co content of the films slightly increases as the deposition potential increases. The morphological analysis of the films grown at high deposition potential (-2.7 V versus SCE), studied by scanning electron microscopy, indicate that they have larger grains. All Co-Fe films showed anisotropic magnetic resistance up to 4% and its magnitude was affected by the cathode potentials. Magnetic measurements carried out by the vibrating sample magnetometer indicated that the saturation magnetization varied and the coercivity decreased from 46.98 to 31.74 Oe as the cathode potential increased. The easy axis of magnetization was found to be in the film plane for all films. The variation in magnetoresistance and magnetic properties may be related to the structural changes in the films.

]/[Fe

The structural and magnetic properties of Co-Cu films were studied in terms of Co content in the films. The surface morphology of the films showed that the film with the lowest Co content (3 wt. %) had dendritic structures, whereas the surface of the film containing the highest amount of Co (61 wt. %) was more uniform with acicular shapes in some parts. X-ray diffraction patterns of the films showed that their crystal structure is a mixture of dominantly face-centered cubic (fcc) and hexagonal close-packed phases. At the lowest Co content, separate fcc (111) peaks appear, whereas the increase of Co content converts the peaks to be a single broad Co-Cu peak. The vibrating sample magnetometer measurements revealed that the saturation magnetization increases and coercivity decreases due to the decrease of the grain size caused by the increase of the Co content in the film. The structural and magnetic properties of Co-Cu films can be tailored, since these properties are directly related to the ratio of Co to Cu in the film.

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ABSTRACT In this work, the olive β-glucosidase (β-glu) enzyme was immobilized onto superparamagnetic nanoparticles (SPMNs). Moreover, immobilized enzyme was also used for the debittering process for natural edible olives from Edremit, Turkey. Owing to SPMNs, the system can be easily removed by a simple magnet and reused many times for debittering process. The free olive β-glucosidase (E), β-glucosidase bound SPMNs (IE), free commercial β-glucosidase (CE), and commercial β-glucosidase bound SPMNs (ICE) were comparatively studied for oleuropein removal. In 6 h, the treatment of E, IE, and ICE hydrolyzed the 15.8%, 56.4%, and 80.0% of the oleuropein for 1000 g of olives, respectively, and further treatment showed that the IE and ICE reached the 100% after 22 h treatment. The results revealed that the IE and ICE with biocompatible properties of SPMNs have the economical, fast, and reusable properties for the industrial debittering process in the table olive production.

] Ratio

Abstract The magnetic textures for the produced magnetic materials are important concepts in accordance with technical applications. Therefore, the aim of this article is to determine 2D magnetic textures of electrodeposited Co–Cu films by the measurement of hysteresis loops at the incremented angles. For that, Co–Cu films were deposited with different Co2+ in the electrolyte. In addition, the easy-axis orientation in the films from the squareness values of the angles, Mp(β) obtained by the hysteresis loops have been numerically studied using the Fourier series analysis. The differences observed in the magnetic easy-axis distributions were attributed to changes of the incorporation of Co in the films with the change of Co2+ in the electrolyte. The coefficients of Fourier series (A0 and A2n ) were also computed for 2D films. It is seen that a systematic and small decrease in A0 and an obvious decrease in A2n (n=1) were observed with increasing incorporated Co in the films. Results imply that interactions cause slightly demagnetization effect accordance with higher incorporation of Co in the films. Furthermore, the crystal structure of the Co–Cu films analysed by X-ray diffraction revealed that the films have dominantly face-centred cubic structure. Film contents analysed by energy-dispersive X-ray spectroscopy and film morphologies observed by scanning electron microscope also support the magnetic texture analysis results found by numerical computation.