E. Karaoglu

Effect of Hydrolyzing Agents on the Properties of Poly (Ethylene Glycol)-Fe3O4 Nanocomposite

A PEG assisted hydrothermal route was used to study the influence of the hydrolyzing agent on the properties of PEG-iron oxide (Fe3O4) nanocomposites. Iron oxide nanoparticles (NPs), which confirmed by X-ray diffraction analysis, were successfully synthesized by a hydrothermal method in which NaOH and NH3 were used as hydrolyzing agents. Formation of PEG-Fe3O4 nanocomposite was confirmed by Fourier transform infrared spectroscopy (FTIR). Samples exhibit different crystallite sizes, which estimated based on line profile fitting as 10 nm for NH3 and 8 nm for NaOH hydrolyzed samples. The average particle sizes obtained from transmission electron microscopy was respectively 174±3 nm for NaOH and 165±4 nm for NH3 gas hydrolyzed samples. Magnetic characterization results reveal superparamagnetic characters despite a large particle size, which may indicate the absence of coupling between the nanocrystals due to the polymer in the nanocomposite. The conductivity curve demonstrates that sDC strongly depends on the temperature.

Hydrothermal Synthesis and Characterization of PEG-Mn3O4 Nanocomposite

Here, we report on the synthesis of PEG-Mn3O4 nanocomposite (NPs) via a hydrothermal route by using Mn(acac)2, ethanol, NH3 and PEG-400. The crystalline phase was identified as Mn3O4. The crystallite size of the PEG-Mn3O4 nanocomposite was calculated as 12±5 nm from X-ray line profile fitting and the average particle size from TEM was obtained as 200 nm. This reveals polycrystalline character of Mn3O4 NPs. The interaction between PEG-400 and the Mn3O4 NPs was investigated by FTIR. Temperature independent AC conductivity of PEG-Mn3O4 nanocomposite beyond 20 kHz provides a strong evidence of ionic conduction through the structure. The conductivity and permittivity measurements strongly depend on the secondary thermal transition of nanocomposite beyond 100℃. Above that temperature, Mn3O4 particles may interact with each other yielding a percolated path that will facilitate the conduction. On the other hand, the relatively lower activation energy (Ea=0.172 eV) for relaxation process suggests that polymer segmental motions of PEG and electrons hopping between Mn 2+ and Mn 3+ may be coupled in the sample below 100℃. Room temperature magnetization curve of the sample does not reach to a saturation, which indicates the superparamagnetic character of the particles. As the temperature increases, the frequency at which (e) reaches a maximum shifted towards higher frequencies. The maximum peak was observed at 1.4 kHz for 20℃ while the maximum was detected at 23.2 kHz for 90℃.

Recyclable NiFe2O4–APTES/Pd Magnetic Nanocatalyst

A new magnetically recyclable catalyst, NiFe2O4–APTES–Pd(0) MRC, as highly effective catalysts for reduction reactions in liquid phase was fabricated and characterized. The chemical characterization of the product was done with X-ray powder diffractometer, Infrared spectroscopy, transmission electron microscopy, UV–Vis spectroscopy, thermal gravimeter and inductively coupled plasma. Magnetic character of the product was analyzed with vibrating sample magnetometer. The synthesized NiFe2O4–APTES–Pd(0) MRCs showed a very high activity in reduction reactions of 4-nitro aniline and 1,3-dinitrobenzene in liquid phase. NiFe2O4–APTES–Pd(0) MRC could be recovered by magnet and reused for ten runs for hydrogenetaion reaction of 4-nitro aniline and, 1,3-dinitrobenzene without significant degradation in the catalytic activity which shows the indicative of a potential applications of these catalyst in industry.

M-hexaferrite–APTES/Pd(0) Magnetically Recyclable Nano Catalysts (MRCs)

AbstractMagnetically recovable BaFe12O19–APTES–Pd(0) and SrFe12O19–APTES–Pd(0) catalysts were easily synthesized by immobilizing Pd nanoparticles on the surface of magnetic hexaferrite–NH2 microspheres. It was found that the combination of BaFe12O19, SrFe12O19 and 3-aminopropyltriethoxysilane (APTES) could give rise to structurally stable catalytic sites. Furthermore, BaFe12O19–APTES–Pd(0) and SrFe12O19–APTES–Pd(0) magnetically recyclable nano catalysts (MRCs) can be recovered by magnet and reused for nine runs for hydrogenation of 4-nitroaniline and dinitribenzene without significant loss in its catalytic activity which shows the indicative of a potential applications of these catalyst in industry.