title: Preferential outward diffusion of Cu during unconventional galvanic replacement reactions between HAuCl4 and surface-limited Cu nanocrystals.
abstract: Metal diffusion in nanoscale materials is of great interest, yet the detailed kinetic behavior of such diffusion remains elusive. We observe direction-controlled Cu diffusion during unconventional galvanic replacement reactions between surface-limited Cu nanocrystals (NCs) and HAuCl(4). Using presynthesized Cu-Cu(1.81)S hetero-oligomer and Cu-Cu(2)S heterodimer NCs as templates and reactants, the controlled addition of HAuCl(4) leads to the preferential outward diffusion of Cu, visualized by the formation of single-crystalline and straight, or polycrystalline and kinked, CuAu nanowires, respectively. The time-dependent growth of these nanowires enables determination of nanoscale diffusion coefficients of Cu during these processes, for the first time.
authors.affiliation: Optical Technology Division, Physics Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8443, USA. yonglinliu06@gmail.com
authors.forename: Yonglin
authors.initials: Y
authors.lastname: Liu
authors.forename: Angela R Hight
authors.initials: AR
authors.lastname: Walker