Microwave assisted hydrothermal synthesis of controlled shape magnetite nanoparticles

Magnetite nanoparticles have been investigated by several research groups due to their potential applications in mechanical engineering [1-3] and in biomedical fields [4]. Moreover, magnetite nanoparticles have recently emerged as a versatile support for catalyst immobilization, since they are inexpensive, non-toxic, chemically stable, and easily prepared from low-cost precursors [5]. It is well-established that the magnetic properties of nanoparticles are strongly dependent on their size and shape. For example, magnetic nanoparticles with non spherical shapes showed interesting anisotropic magnetic properties [6]. In this contribution, a microwave-assisted hydrothermal method for the synthesis of size and shape- controlled magnetite nanoparticles to be used as catalyst support was described. The syntheses were carried out also using oleic acid, polyvinylpyrrolidone and trisodium citrate as surfactants in order to investigate their effect on the size distribution, the morphology and the functionalization of the magnetite nanoparticles. X-ray diffraction, Fourier Transform Infrared, Thermogravimetric, Transmission Electron Microscopy analyses were performed to characterize the chemical and morphological features of the nanoparticles. On the basis of the different reaction conditions, the synthesis could be directed towards the formation of either hexagonal magnetite nanoplates with diagonal of 139±55 nm and a saturation magnetization of 65 emu/g or irregular octahedron nanoparticles with size of 60±25 nm with higher saturation magnetization up to 80 emu/g. The latter material is therefore promising for applications as transportable catalyst support.