Three-dimensional elemental mapping of hollow Fe ₂O ₃@SiO ₂ mesoporous spheres using scanning confocal electron microscopy

Energy filtered scanning confocal electron microscopy (EFSCEM) in an aberration-corrected transmission electron microscope offers an approach for three-dimensional imaging and chemical analysis of nanoscale materials related to the well-established technique of confocal scanning optical microscopy. Here, we apply EFSCEM to the compositional analysis of the core structure in candidate structures for targeted drug delivery. Element-specific optical sectioning along the specimen depth direction demonstrates the presence of additional Si in a nominal Fe ₂O ₃ core. The presence of Si in the core is consistent with a specific formation mechanism for the hollow structure of the core.