Anion Exchange Impedes Subsequent Cation Exchange: Ion Mobility Is Altered by Vacancies and Ion Size

Abstract

One method of achieving spatially specific, multi-component nanoheterostructures is to combine multiple forms of post-synthetic modification. Applying cation or anion exchange to Cu_2–xS nanorods creates complex nanoheterostructures. Combining such anion and cation exchanges generates a system which uncovers the interplay between these two processes and understands the cooperativity between postsynthetic modifications more broadly. Cd²⁺ exchange was carried out on various plasmonic and nonplasmonic Cu_2–xS/Cu_2–xTe nanoheterostructures to test how the presence of Te^2– ions would affect the extent of Cd²⁺ incorporation. Three hypotheses were presented for how the presence of Cu_2–xTe could alter the incorporation of Cd²⁺ and these were used to interpret the observed changes in the extent of Cd²⁺ exchange and crystalline phase of the resulting particles. We found that Te^2– anion exchange impedes subsequent Cd²⁺ cation exchange. Low extents of Te^2– exchange cause a phase change where ion mobility is slowed by a decrease in Cu⁺ vacancies. Higher extents of Te^2– exchange slow ion mobility due to the presence of large Te^2– ions.