Chemical reduction synthesis and ac field effect of iron based core-shell magnetic nanoparticles

High magnetization nanoparticles coated with a biocompatible polymer have attracted considerable interest in recent times as potential materials for biomedical applications associated with targeted drug delivery, detection and the treatment of cancer. This paper considers the use of sodium borohydride reduction of metal salts to form Fe based nanoparticles coated with carboxyl terminated polyethylene glycol (cPEG). By mixing the reactants in a Y-junction, the synthesis produces uniform nanoparticles in the size range 10-20 nm with a core-shell structure. The particles are subsequently coated with a 1-3 nm thick layer of cPEG. These nanoparticles are soft ferromagnets with H(c) = 400 Oe. Exciting these nanoparticles with a 4 Oe, 500 kHz alternating magnetic field leads to particle heating with a maximal increase in the saturation temperature as the particle size is decreased. For the largest particles considered here, the temperature reaches 35 degrees C with a 10 mg sample mass whilst for the smallest nanoparticles considered the temperature exceeds 40 degrees C.