title: (NH4)2S, a highly reactive molecular precursor for low temperature anion exchange reactions in nanoparticles.
abstract: Ammonium sulfide ((NH4)2S) exhibits high reactivity as a sulfide reagent in anion exchange reactions that transform CoO to cobalt sulfide nanoparticles (NPs). The faster diffusion of Co(2+) and O(2-) than the incoming S(2-) during the anion exchange causes a significant expansion of the NP voids. The low temperature (70 °C) anion exchange reaction produces amorphous cobalt sulfide NPs with Co : S ratio of ca. 3 : 4, which are converted into crystalline NPs with a major phase of cubic Co3S4 by annealing at high temperature in an organic solution.
authors.affiliation: Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Haitao
authors.initials: H
authors.lastname: Zhang
authors.forename: Louis V
authors.initials: LV
authors.lastname: Solomon
authors.forename: Don-Hyung
authors.initials: DH
authors.lastname: Ha
authors.forename: Shreyas
authors.initials: S
authors.lastname: Honrao
authors.forename: Richard G
authors.initials: RG
authors.lastname: Hennig
authors.forename: Richard D
authors.initials: RD
authors.lastname: Robinson