The synthesis can be extended to other amorphous shells and crystalline cores. Citrate-Au NPs were coated with CoB using a similar synthesis method to NiB coatings (Figure ). Citrate-Au@CoB particles have a larger variability in shell thickness compared to citrate-Au@NiB since the particles are not as stable in solution.Small, 5 nm Pt nanoparticles were coated with NiB using the same method (Figure ). While the Pt nanoparticles are not a uniform shape and the final shapes vary, the coating thickness is relatively uniform. Coatings on larger, 20 nm Pt nanoparticles show a distinct microstructure in TEM images, where lines of contrast begin at the core and extend to the surface (Figure ). These lines of contrast are thought to arise due to the non-epitaxial and cluster-driven growth from the surface . Growth occurs from multiple nucleation sites on the Pt surface. The lines of contrast indicate the interfaces between two amorphous regions. STEM-EDS line mapping in Figure & 2d indicates a distinct boundary between the shell and core with no Pt diffusion in the shell.