Chemical Insights into the Formation of Metastable Zinc Cobalt Sulfide Solid-Solution Nanoparticles through Simultaneous Multi-Cation Exchange

Connor R. McCormick, Steven M. Baksa, Joseph M. Veglak, Ismaila Dabo, Raymond E. Schaak

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

Nanoparticle materials that consist of a solid solution between two end member compounds often have composition-dependent physical properties. Their synthesis can be challenging, as it requires balancing the competing reactivities of many different reagents to favor the formation of a single-phase product rather than a phase-segregated mixture of its end members. Here, we provide chemical insights into the synthesis of wurtzite CoxZn1-xS nanoparticle spheres, rods, and plates for x = 0.25, 0.50, and 0.75, which represent solid solutions of CoS and ZnS, by simultaneously exchanging the Cu+ cations in roxbyite copper sulfide for Zn2+ and Co2+. Density-functional theory calculations of 401 different prototypical structures and compositions spanning the CoxZn1-xS solid solution space confirm that they are metastable with positive mixing enthalpies and formation energies that are 100-150 meV per formula unit above the convex hull. Competition experiments reveal preferential exchange of Co2+ vs Zn2+ when both are present in excess. We balance their reactivities by controlling the ratio of total cations to copper sulfide, thereby avoiding the formation of cobalt sulfide byproducts. UV-vis-NIR absorption spectra reveal a decrease in band gap as x in CoxZn1-xS increases; x = 0.25 and x = 0.50 are semiconducting, while x = 0.75 is metallic. The optical properties of the CoxZn1-xS solid solutions differ from CoS-ZnS heterostructures, which have similar compositions but different mixing behavior. The CoxZn1-xS solid solution can also be integrated into heterostructured nanorods to combine their composition-tunable properties with other materials.

Original languageEnglish (US)
Pages (from-to)5433-5446
Number of pages14
JournalChemistry of Materials
Volume35
Issue number14
DOIs
StatePublished - Jul 25 2023

All Science Journal Classification (ASJC) codes

  • General Chemistry
  • General Chemical Engineering
  • Materials Chemistry

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