The near-IR absorption properties of copper sulfide nanoparticles varies considerably depending on phase and degree of oxidation. As particles become more copper deficient, which is a thermodynamically favorable process for Cu2S, the band gap increases and the plasmon resonance shifts to higher energies.1 We have found that ligand exchange of dodecanethiol-coated chalcocite particles2 with ammonium tetrathiomolybdate ((NH4)2MoS4)3 diminishes plasmon band growth over time, indicating that charge carrier concentration change is slowed over time. Formation of amorphous copper molybdenum sulfide, however, competes with the passivation reaction. The conditions determining passivation versus formation of a new compound must be delineated. The effect of time of treatment and (NH4)2MoS4 concentration on particle crystallinity, composition, and size were evaluated, as was the ability to stabilize Cu-vacancy concentration through monitoring of the plasmon resonance.

Surface-ligand induced stabilization of plasmonic behavior of copper sulfide nanoparticles

255th National Meeting (2018)

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