Credit: Image courtesy of Center for Functional Nanomaterials, Brookhaven National Laboratory
Top row: 3-D evolution of an oxidizing Ni2Co nanoparticle, showing the structure before oxidation (left), during oxidation (middle), and after oxidation (right) (O2 is molecular oxygen). Bottom row: 3-D chemical mapping of the fully oxidized nanoparticle shows the spatial distributions of oxygen (O, blue), cobalt (Co, green), and nickel (Ni, red).