Salt effects on the physical properties of magnetite nanoparticles synthesized at different NaCl concentrations

Magnetite nanoparticles were synthesized at a wide range of NaCl solutions (c = 0.01–3.0 M). The particle diameter (d) was reduced from 7.7 to 6.8 nm and the colloidal stability dropped with increasing c. The salt effect on the d was successfully elucidated with an aid of a homogeneous nucleation model. The saturation magnetization (Ms) reduction and the lattice contraction (Δa) from −0.015 to −0.038 Å with increasing c were observed due to the decrease of the d. From the Δa, the surface tension (γ) enhancement from 0.192 to 0.614 N/m with increasing c was estimated.