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

Summary¶

Postsynthetic anion exchange is a versatile way to transform nanoparticle composition and can reach nanostructures that are difficult to access by direct growth alone. Earlier work implicated long-chain dialkyl diselenides in driving Se\(^{2-}\) exchange on Cu\(_{2-x}\)S, but mechanistic detail was sparse. Choi et al. systematically compare diphenyl, didodecyl, and dibenzyl diselenides as drivers of selenium anion exchange that creates metastable copper sulfur–selenide alloys, and they contrast those reactivity trends with direct synthesis of copper selenide nanoparticles. Dialkyl diselenides are the only precursors in this study that induce anion exchange. Thermal decomposition measurements are paired with ReaxFF molecular dynamics trained against DFT data for organoselenium bond cleavage and hydrogen selenide elimination, illustrating how inexpensive atomistic screening can rationalize precursor choice before exhaustive laboratory iteration.

Methods¶

Experiments compare three commercially available diselenides with distinct relative C–Se bond strengths yet safer handling than strongly malodorous alternatives, enabling direct comparison with prior literature on phase-selective metal chalcogenide growth (papers/Choi_Kowalik_Plass_Organic_selenide_InorgChem_2025.pdf). Thermal analyses map fragmentation temperatures and decomposition channels feeding the mechanistic discussion in the main text. ReaxFF trajectories use the DFT-fitted parameter set documented in the article to survey H\(_2\)Se release pathways and intermediate geometries on copper chalcogenide models, emphasizing why dialkyl precursors can populate exchange-compatible elimination coordinates while other diselenides favor direct condensation routes toward selenide phases. Force-field training is summarized in the article: DFT (and related QM) reference data, training reaction and conformer targets, and optimization of ReaxFF parameters to match those references—see the Inorg. Chem. text for program, basis set, and weighting detail. Reactive Molecular dynamics production (typically LAMMPS-class engines in this group’s workflow; confirm software string in the article). N/A in this summary for hydrostatic NPT barostat and GPa/bar pressure targets in the gas-phase ReaxFF screens (often NVT-like or NVE segments); see PCCP/SI-level pressure if reported. For MD application: N/A on this page for time step, NVE/NVT label, ns-scale trajectory length, and thermostat/barostat settings (confirm in PDF/SI); PBC periodic supercells for copper chalcogenide slab/cluster models as in the Inorg. Chem. simulation section. N/A — external electric field; N/A — replica exchange / metadynamics in the sense of rare-event enhanced sampling (not stated for these screening runs).

Findings¶

The abstract frames mechanistic orthogonality between anion exchange and direct growth toward metastable copper chalcogenide compositions. Dialkyl diselenides uniquely promote exchange on Cu\(_x\)S because they release H\(_2\)Se, which the authors argue is critical for delivering Se\(^{2-}\) into the particle; other diselenides examined here steer chemistry toward direct growth channels without comparable exchange. ReaxFF results support the H\(_2\)Se-mediated picture by resolving low-lying elimination coordinates whose ordering matches experimental precursor rankings. The authors position ReaxFF as a practical design tool for diorganyl diselenide precursors in nanoparticle synthesis, including identification of dialkyl diselenides as a new class of selenium exchange reagents informed by initial H\(_2\)Se-release screening. Comparisons in the main text and SI to DFT and experiment should be cited from the PDF for exact barriers and TGA traces.

Limitations¶

Copy quantitative barrier heights, decomposition temperatures, particle sizes, ligand environments, and Supporting Information tables from the peer-reviewed PDF; this summary does not duplicate those datasets.

Relevance to group¶

Van Duin / Kowalik-linked ReaxFF for nanoparticle synthesis mechanisms complements chalcogenide materials work in the corpus.

Citations and evidence anchors¶

https://doi.org/10.1021/acs.inorgchem.5c04328 — Inorg. Chem. (2025).

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Cross-link to other chalcogenide anion-exchange papers in the corpus when building comparative synthesis bibliographies.

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