Formation of magnetic nanoparticles studied during the initial synthesis stage
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Formation of magnetic nanoparticles studied during the initial synthesis stage M. Kraken · I.-C. Masthoff · A. Borchers · F. J. Litterst · G. Garnweitner
Published online: 29 January 2013 © Springer Science+Business Media Dordrecht 2013
Abstract The formation of iron oxide nanoparticles in course of a sol-gel preparation process was traced by UV/Vis and 57 Fe Mössbauer absorption spectroscopy. Samples were extracted at different stages of the reaction. While spectra measured on samples extracted at low reactor temperatures showed the starting materials Fe(acac)3 diluted in benzyl alcohol undergoing slow paramagnetic relaxation, a sample extracted at a reactor temperature of 180 ◦ C gave clear evidence for emerging iron oxide nanoparticles. A prolonged stay at 200 ◦ C results in a complete transformation from Fe(acac)3 to maghemite nanoparticles. Keywords Non-aqueous sol-gel method · Mössbauer spectroscopy · Spin-spin relaxation
1 Introduction The scientific interest in magnetic nanoparticles has increased continuously over the last years, resulting from their distinct physical properties leading to numerous technological applications [1]. A reproducible preparation technique, yielding
Thirteenth Latin American Conference on the Applications of the Mössbauer Effect, LACAME 2012, Medellín, Columbia, 11–16 November 2012. M. Kraken (B) · A. Borchers · F. J. Litterst Institut für Physik der kondensierten Materie, Technische Universität Braunschweig, Mendelssohnstrasse 3, 38106 Braunschweig, Germany e-mail: [email protected] I.-C. Masthoff · G. Garnweitner Institut für Partikeltechnik, Technische Universität Braunschweig, Volkmaroder Str. 5, 38104 Braunschweig, Germany
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monodisperse, spherical particles is essential, since the physical properties of the particles strongly depend on these features. The non-aqueous sol-gel method is a bottom-up synthesis that allows preparation of particles with the desired properties. For this method, a precursor is dispersed in a high-boiling, organic solvent and following heat-up, the reaction is left to proceed for a variable span of time. Our aim is, to monitor the thermal decomposition of Fe(acac)3 in benzyl alcohol (BA) and triethylene glycol (TEG) in order to gain an understanding about the formation of the magnetic nanoparticles. Based on the system described in [2], we performed further measurements to enlarge our knowledge of this synthesis route. This work focuses on the heat-up phase to 200 ◦ C in a reactor using BA as solvent. Samples taken during the heating up process, as well as the mixed starting materials are discussed. Details about the reaction after reaching 200 ◦ C and a comparison to TEG as a solvent will be presented elsewhere.
2 Experimental Synthesis of magnetic nanoparticles The iron oxide nanoparticles were synthesized in a 1.5 L reactor (Polyclave, Typ 3/1 Büchi Glas Uster) using Fe(acac)3 as only iron source and benzyl alcohol as solvent [2]. In a typical procedure the reactor was filled with 50 g Fe(acac)3 and 1 L solvent and the re
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