Characterization of mechano-thermally synthesized Curie temperature-adjusted La0.8Sr0.2MnO3 nanoparticles coated with (3-aminopropyl) triethoxysilane

Abstract

This research aimed to synthesize nanostructured strontium-doped lanthanum manganite, La0.8Sr0.2MnO3 (LSMO), with its Curie temperature (Tc) adjusted to the therapeutic range, through a mechanothermal route. In order to investigate the effect of heat treatment temperature and duration on the resulting crystallite size, morphology, magnetic behavior and Curie temperature, the starting powder mixture was milled in a planetary ball mill before being subsequently heat treated at distinct temperatures for different time lengths. The composition, morphology, and magnetic behavior were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and vibrating sample magnetometer (VSM). In addition, magnetic properties were further investigated using an alternating current (AC) susceptometer and thermo-magnetic analyzer. 20h of milling produced a crystallite size reduction leading to a decrease in the heat treatment temperature of LSMO synthesis to 800°C. Moreover, SEM analysis has shown the morphology of a strong agglomeration of fine nanoparticles. HRTEM showed clear lattice fringes of high crystallinity. The mean crystallite and particle size of 20-hour milled sample heat treated at 1100°C for 10h are relatively 69 and 100nm, respectively. The VSM data at room temperature, indicated a paramagnetic behavior for samples heat treated at 800°C. However, by increasing heat treatment temperature to 1100°C, LSMO indicates a ferromagnetic behavior with well-adjusted Curie temperature of 320K, suitable for hyperthermia applications. Also, reentrant spin glass (RSG) behavior has been found in heat treated samples. The particles are coated with (3-aminopropyl) triethoxysilane (APTES) for biocompatibility purposes; Fourier transform infrared spectroscopy (FTIR) and thermo-gravimetric analysis (TGA) are used for further confirmation of APTES coating.