The effect of neutralizing agent on the synthesis and characterization of Mn ₃ O ₄ nanoparticles

We report on the synthesis of Mn ₃ O ₄ nanoparticles via a two-step hydrothermal route by using Mn(CH ₃ COO) ₂ as the only starting material and TMAOH and NaOH as hydrolysing agents. XRD and FT-IR analyses confirmed the composition and structure of Mn ₃ O ₄ . TEM images showed that spheroid Mn ₃ O ₄ nanostructures obtained by this method have average particle size of 6 and 14 nm for NaOH and TMAOH hydrolyzed samples respectively. Particle size analysis indicated a strong aggregation of nanoparticles and exhibited bi-modal distribution with average size of aggregates as ̃250 nm and 1.1 μm for both samples. Zeta potential analysis revealed adsorbed TMAOH species on the surface of Mn ₃ O ₄ nanoparticles hydrolyzed using TMAOH. ESR analyses resulted in broader lines and smaller g values than bulk Mn ₃ O ₄ nanoparticles, probably due to the exchange-coupled system with unlike spins such as canted spin at surface of high-surface-disordered nanoparticles.