Organized silica microspheres carrying ferromagnetic cobalt nanoparticles as a basis for tip arrays in magnetic force microscopy

Two-dimensional arrays of hard spherical particles carrying a nanoprobe hol d potential as scanning tip arrays (STA) in force microscopy. Though rigid single molecules of proteins were originally envisioned as suitable probes, we foresee the possibility that magnetic nanoparticles, as well, could qua lify the criteria. Ferromagnetic cobalt nanoparticles of size similar to 10 nm well adhered to hard silica microspheres (225-250 nm) were synthesized by the sonochemical decomposition of a volatile organic precursor cobalt ni trosyl carbonyl [Co(CO)(3)NO] in a suspension of silica in Decalin, followe d by crystallization of the resultant amorphous produt. The morphological, thermal, and magnetic properties of the amorphous and nanocrystalline cobal t particles adhered to the microspherical silica were investigated by XRD, TEM, SEM/EDAX, TGA, DSC, EPR and magnetic susceptibility methods. Silica sp heres carrying ferromagnetic cobalt nanocrystals were deposited on a single crystalline silicon [100] substrate by spin coating. The two-dimensional o rganization of the magnetic microspheres on silicon and the adhesion of cob alt nanoparticles on the surface of microspherical silica have been examine d by scanning electron microscopy and atomic force microscopy (AFM), respec tively. While the system described here forms only a basis for a functionin g device, a chemical approach toward the synthesis, evaluation, and assembl y of the components is emphasized.