Congratulations to Emma Endres, Ph.D., a recent graduate from the Janet Macdonald Lab! Emma’s paper, “Directing Cation Coordination and Phase in Nickel Sulfide Nanocrystals through the Addition of Phosphines,” published in Chemistry of Materials, has been selected as this week’s spotlight publication. This work was a collaborative effort between VINSE faculty members Janet Macdonald and De-en Jiang.
Multiple routes to achieve phase control have been explored in nanocrystal syntheses, such as precursor reactivity and cation exchange. These routes have opened doors to phase manipulation, but the former does not directly target the product structure, and the latter has limitations on which structures can be formed. Ideally in colloidal synthesis, we could achieve phase purity using a single-step synthesis while also templating specific structural features of the phase, similar to that of cation exchange.
In this work, we combine these ideas, targeting the cation using coordination chemistry concepts in solution to affect the coordination that the metal assumes in the solid. Using a collection of monodentate and bidentate phosphine ligands, we evaluate how different bite angles, steric bulk, and electronic properties affect the metal coordination in the resulting nanoparticle phase. In this manner, three nickel sulfides were selectively prepared in a colloidal synthesis. We showed that the steric bulk of the phosphine had the most influence on the product coordination by taking up sites on the metal. Through DFT calculations and synthetic experiments, we also found evidence that supports that phosphines influence the phase both at the nucleation stage and through surface effects on larger particles.
Read full article in
Authors: Emma J. Endres, Yiming Chen, De-en Jiang, Janet E. Macdonald
Abstract: In nanocrystal syntheses, multiple routes to achieve phase control have been explored, such as precursor reactivity and cation exchange. While these routes have opened doors to phase manipulation, the former does not directly target the product structure and the latter has limitations on which structures can be formed. Here, we combine both ideas, focusing on the structure and also influencing precursor reactivity. For the first time, we intentionally used concepts from coordination chemistry to influence the metal in solution and, in turn, affect the interstitial sites that the cation fills in the solid. Through the addition of bidentate and monodentate phosphine ligands of varying bite angles, steric bulk, and electron donation ability, we were able to influence the coordination around the nickel ion and thus the product nickel sulfide phase. We discovered that the steric bulk of the phosphine had the biggest influence on the resulting product by destabilizing surfaces with highly coordinated nickel atoms by occupying coordination sites on the metal. By varying which phosphine ligand was added, we were able to selectively target pure millerite (NiS), heazlewoodite (Ni3S2), and godlevskite (Ni9S8).