Controlled Growth of Monodisperse Self-Supported Superparamagnetic Nanostructures of Spherical and Rod-Like CoFe_2O_4 Nanocrystals

摘要

Monodisperse superparamagnetic (SP) nanostructures have drawn significant attention because of their weak magnetic interaction in suspension, high dispersibility in solvents, and large surface area. When the size is below a critical value (typically <10 nm), nanoparticles behave as a single magnetic domain, exhibiting SP behavior above the so-called blocking temperature. The individual nanoparticles possess a magnetic moment but, because of thermal activation, behave like a giant paramagnetic atom. They respond rapidly to an applied magnetic field, while exhibiting negligible remanence and coercivity. These features make SP nanoparticles (nanocrystals) attractive for a broad range of biomedical applications, primarily because agglomeration resulting from strong magnetic interaction is avoided.