Issue 10, 2023

Role of carboxylates in the phase determination of metal sulfide nanoparticles

Abstract

Techniques are well established for the control of nanoparticle shape and size in colloidal synthesis, but very little is understood about precursor interactions and their effects on the resultant crystalline phase. Here we show that oleate, a surface stabilizing ligand that is ubiquitous in nanocrystal synthesis, plays a large role in the mechanism of phase selection of various metal sulfide nanoparticles when thiourea is used as the sulfur source. Gas and solid-phase FTIR, 13C, and 1H NMR studies revealed that oleate and thiourea interact to produce oleamide which promotes the isomeric shift of thiourea into ammonium thiocyanate, a less reactive sulfur reagent. Because of these sulfur sequestering reactions, sulfur deficient and metastable nanoparticles are produced, a trend seen across four different metals: copper, iron, nickel, and cobalt. At low carboxylate concentrations, powder XRD indicated that the following phases formed: covellite (CuS); vaesite (NiS2); smythite (FeS1.3), greigite (FeS1.3), marcasite (FeS2) and pyrite (FeS2); and cattierite (CoS2). At high sodium oleate concentration, these phases formed: digenite (CuS0.55), nickel sulfide (NiS), pyrrhotite (FeS1.1), and jaipurite (CoS).

Graphical abstract: Role of carboxylates in the phase determination of metal sulfide nanoparticles

Supplementary files

Article information

Article type
Communication
Submitted
07 iyn 2023
Accepted
26 iyl 2023
First published
28 iyl 2023
This article is Open Access
Creative Commons BY license

Nanoscale Horiz., 2023,8, 1386-1394

Role of carboxylates in the phase determination of metal sulfide nanoparticles

A. A. Shults, G. Lu, J. D. Caldwell and J. E. Macdonald, Nanoscale Horiz., 2023, 8, 1386 DOI: 10.1039/D3NH00227F

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