Analysis of the Shell Thickness Distribution on NaYF₄/NaGdF₄ Core/Shell Nanocrystals by EELS and EDS

The structure and chemical composition of the shell distribution on NaYF₄/NaGdF₄ core/shell nanocrystals have been investigated with scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS), and energy-dispersive X-ray spectroscopy (EDS). The core and shell contrast in the high-angle annular dark-field (HAADF) images combined with the EELS and EDS signals indicate that Gd is indeed on the surface, but for many of the particles, the shell growth was anisotropic.