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Nanoparticles

Nanostructured materials show size-dependent electronical, optical, chemical and magnetic properties. For the investigation of these properties it is necessary to produce  nanoparticles with a narrow size distribution. The group "nanoparticles" deals with the synthesis and characterization of transition metal oxide nanoparticles, namely iron and manganese oxide particles. We do not only synthesize single phase particles but also particles showing a core-shell structure or composite particles, made of iron oxide and manganese oxide.

 

Synthesis of nanoparticles

The production of the nanoparticles is carried out in a two-step synthesis: first, a precursor is produced, which is thermally  decomposed in the second step. The precursor is a metal oleate complex. These complex can be decomposed thermally in a high boiling solvent. During this step, monodispersed  nanoparticles are formed by homogeneous nucleation. By varying the synthesis parameters or adding surfactants the size and shape of the nanoparticles can be controlled.

 

Characterization  of the nanoparticles

TEM-image of iron oxide nanoparticlesThe the characterization of the nanoparticles is performed by the different surface sensitive methods provided by the chair. A scanning force microscope is used as well as a transmission electron microscope (see image on the right side). These methods allow the determination of the size and the shape of the nanoparticles. For the investigation of the crystallographic structure  x-ray diffractometry and electron diffractometry (within the TEM) is used. For elemental analysis and distribution of the elements within composite particles energy filtered TEM is applied. An energy filtered image is shown in the next figure in a): from the elemental mapping one can see that the particles consist of an iron oxide (red) and a manganese oxide (green) part. A fourier analysis (c) of a high resolution image (b) shows a similar result. The fourier filtered signal was separated into the signal originating from the spinel structure of the iron oxide and the signal from the MnO-structure. After an inverse fourier transformation back to the real space, these signals were color-coded. The resulting image shows the distribution of the iron oxide and the manganese oxide within the particle, which is quite similar to the EFTEM-map. Additionally, from these analysis one can find out the crystallographic orientations of the crystallographic phases realtive to each other.

Iron-oxide/manganese-oxide composite particles

 

Contact person:

Aladin Ullrich

Group members:

Daniel Schmidtner

Juliane Ohmer