Tin Ion Directed Morphology Evolution of Copper Sulfide Nanoparticles and Tuning of Their Plasmonic Properties via Phase Conversion

Copper-deficient copper sulfide (Cu_2–<i>x</i>S) nanoparticles (NPs) have been investigated as important hole-based plasmonic materials because of their size, morphology, and carrier density-dependent localized surface plasmon resonance (LSPR) properties. Morphology and carrier density are two important parameters to determine their LSPR properties. Here, we demonstrate that the foreign metal ion, Sn⁴⁺, directs the growth of djurleite Cu₃₁S₁₆ from nanodisk to tetradecahedron along the [100] direction. To control the LSPR properties by tuning the carrier density, the djurleite Cu₃₁S₁₆ nanoparticles were pseudomorphically converted into more copper-deficient (higher carrier density) roxbyite Cu₇S₄ NPs by heat treatment in the presence of amine. The roxbyite Cu₇S₄ NPs exhibited a shorter and stronger LSPR peak while retaining the morphology of the djurleite Cu₃₁S₁₆ NPs