(160n) Surface Modification of Cobalt-Substituted Ferrite Nanoparticles

Cobalt ferrite (CoFe₂O₄) is of great interest in the development of magnetic nanoparticle based sensors because of its high magnetocrystalline anisotropy constant (~10⁷ erg/cm³). Analyte attachment to the nanoparticle could be detected through changes in the magnetization response of a suspension of cobalt ferrite nanoparticles to an applied oscillating magnetic field. In order to use cobalt ferrite in sensors, these particles have been synthesized through coprecipitation and functionalized with dimercaptosuccinic acid (DMSA). Cobalt ferrite nanoparticles with a FCC crystalline structure and ~12 nm in crystal diameter were obtained. Superconducting Quantum Interference Device (SQUID) showed a superparamagnetic behavior at 300K, a magnetic diameter of ~ 8nm with a geometric deviation of 0.59, and saturation magnetization of ~3.7 emu/g. FTIR confirm the bind of DMSA to nanoparticles. Bands at ~ 1600 cm^-1 and ~1383 cm^-1 were observed, characteristic of the bound between the carboxylic groups and iron presented in the surface of nanoparticles. DMSA-cobalt ferrite ferrofluid was observed to be stable in the pH range of 9.5 to 6.0 while uncoated cobalt ferrite ferrofluid was stable only in acidic medium (pH<3). TGA, RAMAN, and DLS were also used to verify functionalization of the nanoparticles with DMSA.