Reactions of Nanoscale Zero-Valent Iron with Ni(II): Three-Dimensional Tomography of the Hollow Out Effect in a Single Nanoparticle

Three-dimensional tomography of reactions of Ni(II) with a single zero-valent iron nanoparticle (similar to 60 nm) is achieved with spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM) integrated with energy-dispersive X-ray spectrometry (EDS). High-resolution two- and three-dimensional images provide proof of the hollow-out effect of the zero-valent iron nanoparticle; i.e., the redox reactions attack and dissolve the core of a nanoparticle and form a hollow doughnutlike structure. Results offer evidence of the unique characteristics and catalytic functions of zero-valent iron nanoparticles for the treatment of heavy metal ions such as Ni(II) and provide direct confirmation of the core-shell structure. Furthermore, results demonstrate the potential of STEM-EDS for visualizing the complex morphology and elemental composition of nanomaterials and mapping reactions of environmental pollutants in a single nanoparticle at near-atomic (similar to 0.1 nm) resolution.