Copper Selenides via Anion Exchange versus Direct Growth – The Role of Diorganyl Diselenides

Anion exchange is a powerful tool for postsynthetic transformation
of nanoparticles that can be coupled with other transformations to
create nanostructures unachievable by direct growth. Previous work
implicated long-chain dialkyl diselenides as drivers of Se2– anion exchange on Cu2–xS, but
it lacked mechanistic details. Here, we examined the reactivity trends
of diphenyl, didodecyl, and dibenzyl diselenides as drivers of anion
exchange to create metastable copper sulfur selenide alloys. We contrasted
these reactivity trends with those of direct synthesis of copper selenide
nanoparticles, demonstrating mechanistic orthogonalities between these
pathways. Dialkyl diselenides were the only species that induced anion
exchange. We rationalized the different reaction outcomes using thermal
decomposition measurements together with MD simulations using a ReaxFF
force field (trained against DFT data). Dialkyl diselenides were shown
to release H2Se, which appears to be critical for achieving
Se2– anion exchange. This demonstrates the utility
of computationally inexpensive atomistic-scale simulations methods
like ReaxFF in the rational design of nanoparticle syntheses. Using
this insight, the dialkyl diselenides were identified as a new class
of selenium exchange reagents based on initial MD simulations of H2Se release. This work provides mechanistic understanding of
nanoparticle anion exchange and insights into decomposition processes
crucial to use of diorganyl diselenides in nanoparticle synthesis.

阴离子交换（anion exchange）是纳米颗粒后合成修饰的有力工具，可与其他修饰手段联用，制备出直接生长无法获得的纳米结构。已有研究指出长链二烷基二硒醚可作为Cu₂₋ₓS表面Se²⁻阴离子交换的驱动剂，但相关研究缺乏机理层面的细节阐释。本工作针对二苯基二硒醚、双十二烷基二硒醚与二苄基二硒醚作为Se²⁻阴离子交换驱动剂的反应活性规律展开研究，以制备亚稳态铜硫硒固溶体。我们将该类反应的活性规律与硒化铜纳米颗粒的直接合成路径进行对比，证明了两条路径间存在机理正交性。仅二烷基二硒醚可诱导阴离子交换反应。我们结合热分解测试与基于密度泛函理论（DFT）数据训练的ReaxFF力场分子动力学（Molecular Dynamics, MD）模拟，对不同反应产物的成因进行了合理化阐释。研究表明，二烷基二硒醚可释放硒化氢（H₂Se），而该物质对实现Se²⁻阴离子交换至关重要。这一结果证明了ReaxFF这类计算成本低廉的原子级模拟方法在纳米颗粒合成理性设计中的应用价值。基于上述认知，结合H₂Se释放的初始分子动力学模拟结果，我们将二烷基二硒醚鉴定为一类新型硒交换试剂。本工作阐明了纳米颗粒阴离子交换的机理，并为二有机二硒醚应用于纳米颗粒合成的关键分解过程提供了理论见解。