Synthesis and characterization of La(1-x)SrxMnO3/SiO2 core-shell nanoparticles

ALBORNOZ, C.; LEYVA, A.G.; TROIANI, H.; BOZZANO, P.; BRUVERA, I.; LABORDE, C.; SANCHEZ, F.H.

Ciudad Autónoma de Buenos Aires

Workshop; "At the Frontiers of Condensed Matter V"; 2010

Comisión nacional de energía atómica

La(1-x)SrxMnO3 (x=0.22, 0.3 and 0.33) nanoparticles (NP) were synthesized using liquid-mix method, starting from metallic nitrates and adding citric acid to obtain cation complexes and ethylenglycol to polymerize. The powder obtained after a thermal treatment at 700ºC was dispersed in isopropyl alcohol and SiO2 coated using the Stöber method. An aqueous ferrofuid of La 0.78Sr0.22MnO3 (0.6g/l), gels from La(1-x)SrxMnO3 (x=0.3 and 0.22) and oil-wax gel (Gelwax) were prepared. X Ray diffraction analysis, scanning and transmission electron microscopy, infrared spectroscopy and magnetic measurements were used to characterize the samples. In the direction of a potential Hyperthermia therapy application, the thermal response of a ferrofluid containing La 0.78Sr0.22MnO3 NP1 suspended in aqueous solution of chondroitin 6-sulfate sodium salt, and a gel containing La 0.7Sr0. 3MnO3 NP2 were studied, while exposing the samples to a RF magnetic field (41 kA/m, 260kHz). The temperature vs. time curves were recorded and the gel's Specific Loss Power (SLP) was obtained from the initial slope of such curves. SLP values around 4W/g were obtained. The relationship between SLP and the AC field frequency was studied. The Curie temperature of La1-xSrxMnO3 (x =0.22 and 0.33), was determined by Magnetic-Thermo-Gravimetry (MTG), the values were 334K and 368K, respectively. the thickness of the SiO2 layer was estimated around 4 nm from the comparison of AC susceptibility measurements of the coated and uncoated samples (NP3). M vs H curves showed a Langevin-like shape, however displaying a small coercivity of about 30 Oe (x = 0.22). From these curves magnetic core diameters were estimated to be about 14 to 21 nm.