title: Room-Temperature Dynamics of Vanishing Copper Nanoparticles Supported on Silica.
abstract: In heterogeneous catalysis, a nanoparticle (NP) system has immediate chemical surroundings with which its interaction needs to be considered, as nanoparticles are typically loaded onto certain supports. Beyond what is known about these interactions, dynamic atomic interactions between the nanoparticle and support could result from the increased energetics at the nanoscale. Here, we show that the dynamic response of atoms in copper nanoparticles to the underlying silica support at room temperature and ambient atmosphere results in the complete disappearance of supported nanoparticles over the course of only a few weeks. A quantitative study of copper nanoparticles at various size regimes (6-17 nm) revealed the significance of size-dependent nanoparticle energetics to the interaction with the support. Extended X-ray absorption fine structure is used to show that copper atoms could readily diffuse into the support to be locally surrounded by oxygen and silicon with structurally disordered outer coordination shells. Increased energetic states at the nanoscale and the energetically favorable configuration of individual copper atoms within silica, identified through EXAFS, are suggested as the cause of nanoparticle disappearance. This unexpected observation opens up new questions as to how nanoparticles interact with surrounding environments that could fundamentally change our conventional view of supported nanoparticle systems.
authors.affiliation: Kavli Energy Nanosciences Institute , Berkeley, California 94720, United States.
authors.forename: Dohyung
authors.initials: D
authors.lastname: Kim
authors.forename: Nigel
authors.identifier: 0000-0001-7857-6841
authors.initials: N
authors.lastname: Becknell
authors.forename: Yi
authors.initials: Y
authors.lastname: Yu
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.|Kavli Energy Nanosciences Institute , Berkeley, California 94720, United States.
authors.forename: Peidong
authors.identifier: 0000-0003-4799-1684
authors.initials: P
authors.lastname: Yang
keywords: Copper nanoparticles; nanoparticle dynamics; nanoparticle-support interaction; silica