SYNTHESIS AND CHARACTERIZATION OF CRYSTALLINE MONODISPERSED γ-Fe2O3 NANOPARTICLES

Abstract

γ-Fe2O3 maghemite nanoparticles were synthesized via the homogeneous thermal decomposition of iron pentacarbonyl. This synthesis took place in the presence of a capping molecule, octanoic acid, and a mild oxidant, trimethylamine oxide. The presence of octanoic acid capped γ-Fe2O3 nanoparticles was confirmed using AFM, UV-Vis and FTIR. The use of different solvents, agitation periods, casting methods and γ-Fe2O3 nanoparticle concentration, as parameters, were hypothesized to significantly influence the monodispersity, crystallinity and assembly of the particles. The nanoparticles were re-dispersed in three different solvents: hexane, octane and toluene, after which they were sonicated (0min, 5min, 10min, 15min, 20min, 30min), vortex mixed (0min, 2min, 4min, 6min, 8min), or sonicated and vortex mixed (2min vortex mixing and 15 min sonication). They were then drop-casted or spin casted on silicon wafers to observe the assembly under AFM or SEM. AFM was further used to characterize the size and distribution of γ-Fe2O3 nanoparticles. The AFM imaging, followed by histogram analysis, shows that the diameter of nanoparticles can vary from ~3-40 nm with averages ranging from 1.84 nm to 47.23 nm. Spin casting was successfully used to remove aggregates from the center of the substrate, leaving a fair amount of monodisperse nanoparticles at the center. SEM imaging of three-dimensionally packed nanoparticles shows an average spacing of ~2nm between individual nanoparticles confirming the theoretical predictions.