Sulfur in oleylamine as a powerful and versatile etchant for oxide, sulfide, and metal colloidal nanoparticles

Abstract

Understanding of crystal growth is essential to the design of materials with improved properties. Unfortunately, still very little is understood about the basic growth mechanisms of nanostructures, even in the most established colloidal synthetic routes. Etching is one of the most important mechanisms to consider during particle growth, but it is rarely considered in the syntheses of oxide or chalcogenide nanostructures. Here, we report that the most common precursor for the synthesis of sulfide nanostructures – the mixture of sulfur and oleylamine – acts as a very powerful etchant for oxide, chalcogenide, and metal nanostructures. Specifically, we discuss its effect on several nanoparticle compositions (PbS, Cu2S, Fe3O4, and Au) and compare it to control conditions in which only oleylamine is present. Our experiments suggest that the etching results from the evolution of H2S from the sulfur–oleylamine precursor. We predict that the simultaneous role of this precursor as both etchant and ligand stabilizer will make it a useful tool for the chemical post‐processing (e.g., size reduction, focusing of size distributions, faceting) of nanocrystal dispersions.

Influence of Phosphine-Free Solvents On the Structural and Optical Properties of Oleylamine Assisted Synthesis of CdS Nanocrystals

“…Because of the long chain (i.e bulky nature), OLAm is signi cantly in uencing on the CdS nanocrystals surface. When OLAm is re uxed with sulphur powder, it forms oleylammonium sulphide which functionally act as the sulphide precursor [25,26,27]. Upon injecting into the Cd-oleate complex mixture, formation of CdS nanocrystals rapidly happen through the nuclei formation.…”

S-Rich PbS Quantum Dots: A Promising p-Type Material for Optoelectronic Devices

“…This process is schematically illustrated in Figure A. Sulfur dissolved in Olam is known to produce a range of ammonium and alkylammonium sulfides and polysulfides. − Annealing of lead oleate-capped PbS CQDs in such conditions should lead to the reaction of surface lead oleate with sulfide groups and therefore growth of an extra monolayer of PbS and exchange from oleate to alkylammonium sulfide ligands. Furthermore, a strong excess of alkylammonium sulfides and the elevated temperature of the whole process are expected to initiate the ripening of CQDs.…”

Nickel Cobalt Thiospinel Nanoparticles as Hydrodesulfurization Catalysts: Importance of Cation Position, Structural Stability, and Sulfur Vacancy

“…This temperature effect on the surface sulfur content could be ascribed to the synthesis of NiCo 2 S 4 . Dissolution of elemental sulfur, which often forms octatomic rings with the chemical formula of S 8 , in OAm leads to the formation of polysulfide anions. − At a low synthetic temperature of 180 or 200 °C, the polysulfide anions combine with metal cations that are weakly coordinated by the OAm molecules, and the ion diffusion is relatively slow, leading to the formation of NiCo 2 S 4 thiospinel with a sulfur-rich surface. Increasing the synthetic temperature to 230 or 250 °C effectively facilitates the ion recombination with the formation of NiCo 2 S 4 in the stoichiometric composition.…”