Controllable conversion of plasmonic Cu2−xS nanoparticles to Au2S by cation exchange and electron beam induced transformation of Cu2−xS–Au2S core/shell nanostructures

Abstract

Self-doped Cu_2−xS nanocrystals (NCs) were converted into monodisperse Cu_2−xS–Au₂S NCs of tunable composition, including pure Au₂S, by cation exchange. The near-infrared (NIR) localized surface plasmon resonance (LSPR) was dampened and red-shifted with increasing Au content. Cation exchange was accompanied by elimination of cation vacancies and a change in crystal structure. Partially exchanged Cu_2−xS–Au₂S core/shell structures evolved to dumbbell-like structures under electron irradiation in the transmission electron microscope (TEM).