Effect of particle size and composition on local magnetic hyperthermia of chitosan-Mg1-xCoxFe2O4 nanohybrid.

In this study, Mg_1-xCo_xFe₂O₄ (0<x < 1 with Ax = 0.1) or MCFO nanoparticles were synthesized using a chemical co-precipitation method and annealed at 200, 400, 600, and 800°C respectively to investigate the structural properties of the materials by X-ray diffractometer (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR). Controlled annealing increased particle size for each value of x. The aim was to investigate how specific loss power (SLP) and maximum temperature (T_max) during local magnetic hyperthermia were affected by structural alterations associated with particle size and composition. The lattice parameter, X-ray density, ionic radius, hopping length, bond length, cation-cation distance, and cation-anion distance increase with an increase in Co²+ content. Raman and FTIR spectroscopy reveal changes in cation distribution with Co²+ content and particle size. Magnetic properties measured by the physical property measurement system (PPMS) showed saturation magnetization (Ms), coercivity (Hc), remanent magnetization (M_r/M_s), and anisotropy constant (K₁) of the Mg_1-xCo_xFe₂O₄ nanoparticles increase with Co²+ content and particle size. When exposed to an rf magnetic field, the nanohybrids experienced an increase in both the SLP (specific loss power) and T_max (maximum temperature) as the particle size initially increased. However, these values reached their peak at critical particle size and subsequently decreased. This occurs since a modest increase in anisotropy, resulting from the presence of Co²+ and larger particle size, facilitates Néel and Brownian relaxation. However, for high anisotropy values and particle size, the Néel and Brownian relaxations are hindered, leading to the emergence of a critical size. The critical size increases as the Co²+ content decreases, but it decreases as the Co²+ content increases, a consequence of higher anisotropy with the increase in Co²+. Additionally, it is noteworthy that the maximum temperature (T_max) rises as the concentration of nanohybrids grows, but the specific loss power (SLP) decreases. An increased concentration of chitosan-MCFO nanohybrids inhibits both the Néel and Brownian relaxation processes, reducing specific loss power. [ABSTRACT FROM AUTHOR]