Unveiling the Formation Mechanism for Binary Semiconductor Nanoclusters: a Two-Step Pathway to a Double-Shell...

This work represents an important step in the quest to unveil the formation mechanism of atomically precise binary semiconductor nanoclusters. In this study, we develop an acid-assisted C-S bond cleavage approach, wherein the C-S bonds in the metal thiolate precursor can be readily cleaved to release S^2- with the assistance of a suitable acid in the presence of Cu₂O as the catalyst. This process spontaneously fosters the formation of a [-Cu-S-Cu-] framework and promotes the structural growth into a high nuclearity assembly. Specifically, by employing Cu(I) tert-butyl thiolate ([CuSBu]_∞) and carboxylate acid CH₂═CHCOOH as the copper/sulfur precursor and C-S bond "scissor", a high-nuclearity nanocluster [S-Cu₅₆] (Cu₅₆S₁₂(OOCCH═CH₂)₁₂(SC(CH₃)₃)₂₀) featuring a double-shell configuration has been effectively prepared in high yield. Importantly, the [CuSBu]_∞ precursor and the intermediate [S-Cu₁₄] (Cu₁₄(SBu)₈(OOCCH═CH₂)₆) cluster have also been successfully isolated and structurally characterized, which ultimately enables the establishment of a two-step formation pathway for the [S-Cu₅₆] nanocluster. Furthermore, in contrast to conventional reduction synthetic routes for metal nanoclusters containing Cu(0) or Cu(I), the acid-assisted C-S bond cleavage approach represents an oxidation process with respect to the constituent metals, yielding highly charged Cu(II) cations in the copper sulfide nanocluster.