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 Se^2- anion exchange on Cu_2-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 Se^2- 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.