Unveiling the Formation Mechanism for Binary Semiconductor Nanoclusters: a Two-Step Pathway to a Double-Shell Structured Copper Sulfide Nanocluster

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 S2– 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 ([CuStBu]∞)
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 [CuStBu]∞ precursor and the
intermediate [S–Cu14] (Cu14(StBu)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.

本研究为揭示原子级精准二元半导体纳米团簇的形成机制迈出了重要一步。
本研究开发了一种酸辅助C-S键裂解策略：以氧化亚铜（Cu₂O）为催化剂，在适宜酸的辅助下，可轻易断裂金属硫醇盐前驱体中的C-S键，释放出硫离子（S²⁻）。该过程可自发形成[−Cu–S–Cu−]骨架，并推动结构生长为高核数组装体。
具体而言，本研究以一价铜叔丁基硫醇盐（[CuStBu]∞）和丙烯酸（CH₂=CHCOOH）分别作为铜/硫前驱体与C-S键“裂解剂”，成功以高收率制备出具有双壳层构型的高核数纳米团簇[S–Cu56]（化学式为Cu₅₆S₁₂(OOCCH=CH₂)₁₂(SC(CH₃)₃)₂₀）。
值得注意的是，本研究还成功分离并结构表征了[CuStBu]∞前驱体与中间体[S–Cu14]（化学式为Cu₁₄(StBu)₈(OOCCH=CH₂)₆）纳米团簇，最终确立了[S–Cu56]纳米团簇的两步形成路径。
此外，与传统制备含零价铜（Cu(0)）或一价铜（Cu(I)）金属纳米团簇的还原合成路线不同，该酸辅助C-S键裂解策略对组成金属而言属于氧化过程，最终在硫化铜纳米团簇中得到了高电荷态的二价铜（Cu(II)）阳离子。