Structure, morphology, and aging of Ag-Fe dumbbell nanoparticles

Dumbbell‐shaped or Janus‐type nanocomposites provide multifunctional properties with various diagnostic and therapeutic applications in biomedicine. We have prepared dumbbell Ag–Fe nanoparticles by magnetron sputtering with subsequent in‐flight annealing. Structural properties and chemical compositions of freshly prepared and 5‐month aged particles were examined by means of transmission electron microscopy including high‐resolution imaging, energy dispersive X‐ray spectroscopy, and 3D electron tomography. Fresh particles consist of a faceted Ag part on a Fe‐Fe3O4 composite particle of more spherical shape. Aging changes the crystallinity and morphology of the particles. The aged nanocomposite consists of a silver spherical particle that is attached to a hollow iron oxide sphere containing one or several silver clusters inside. TEM images of the fresh (a) and aged (b) Ag–Fe nanoparticles. (c) 3D reconstructed image of an aged Ag–Fe particle with color segmentation.