Fe2o3 shell growth on Pt nanoparticles

Fe2O3 shells have been synthesized around Pt cores to create Pt@Fe2O3 core-shell nanoparticles. The synthesis conditions allow control of the shell shape and allow the preparation of both hexagonal shells and spherical shells. 2D cross-sectional TEM images show that the cores are not positioned at the centers of the shells. By rotating the nanoparticles and monitoring the apparent motions of the cores in the 2D cross-sectional images, it is possible to determine quantitatively the radial position of the Pt core with respect to the center of the Fe2O3 shell. The distribution of core positions within the core-shell structures is bimodal. These observations suggest that the Fe2O3 shells grow on the Pt cores by a nucleation process, rather than layer-by-layer growth.