Synthesis, particle shape characterization, magnetic properties and surface modification of superparamagnetic iron oxide nanochains

We report monodisperse, chain-like particles (nanochains) consisted of silica-coated maghemite (gamma-Fe2O3) nanoparticle clusters prepared by colloidal chemistry and magnetic field-induced self-assembly of nanoparticle clusters. In order to quantify the shapes of chain-like particles, we have used the measure for shape convexity which is also called solidity. We functionalize the surface of the nanochains with amino (-NH2) and carboxyl groups (-COOH) in order to modify surface charge. These surfaces of nanochains provide better colloidal stability and their potential for practical applications in biomedicine. The enhanced colloidal stability of the surface modified nanochains is confirmed by Zeta potential (zeta-potential) analysis. Magnetic properties of the nanochains show superparamagnetic state at room temperature since the nanochains are composed of tiny nanoparticles as their building blocks. The measured M(H) data at room temperature have been successfully fitted by the Langevin function and magnetic moment mu(p) = 20,526 mu(B) for sphere-like nanoparticle clusters and mu(p), = 20,767 mu(B) for nanochains are determined. The determined magnetic parameters have revealed that the nanochains show a magnetic moment of the nanoparticles higher than the one of individual nanoparticle clusters. These differences can be attributed to the collective magnetic properties of superparamagnetic iron oxide nanoparticles (SPION) assembled in different morphologies (isotropic and anisotropic morphology).