In Situ Imaging of Ion Motion in a Single Nanoparticle: Structural Transformations in Selenium Nanoparticles

Intraparticle ion motions are critical to the structure and properties of nanomaterials, but rarely disclosed. Herein, in situ visualization of ion motions in a single nanoparticle is presented by dark-field microscopy imaging, which shows HgCl₂ -induced structural transformation of amorphous selenium nanoparticles (SeNPs) with the main composition of Se₈ . Owing to the high binding affinity with selenium and coulomb interactions, Hg²⁺ ions can permeate into the interior of SeNPs, making the amorphous Se₈ turn to polycrystalline Hg₃ Se₂ Cl₂ . As a proof of concept, SeNPs then serve as a highly effective scavenger for selective removal of Hg²⁺ ions from solution. This new finding offers visual proof for the photophysical process involving intraparticle ion motion, demonstrating that tracking the ion motions is a novel strategy to comprehend the formation mechanism with the purpose of developing new nanostructures like nanoalloys and nano metal compounds.