Centrum pre Nanodiagnostiku Materiálov

BODÍK, Michal – ANNUŠOVÁ, Adriana – HAGARA, Jakub – MIČUŠÍK, Matej – OMASTOVÁ, Mária – KOTLÁR, Mário – CHLPÍK, Juraj – CIRÁK, Július – ŠVAJDLENKOVÁ, Helena – ANGUŠ, Michal – ROLDAN, Alicia Marin – VEIS, Pavel – JERGEL, Matej – MAJKOVÁ, Eva – ŠIFFALOVIČ, Peter

In Physical Chemistry Chemical Physics. Vol. 21, iss. 23 (2019)

https://doi.org/10.1039/C9CP01951K

Abstract

It is generally accepted that liquid-phase exfoliation (LPE) enables large-scale production of few-layer MoS₂ flakes. In our work, we studied in detail few-layer MoS₂ oxidation in the course of standard LPE in a water/ethanol solution. We demonstrate that an increase of the initial MoS₂ concentration above a certain threshold triggers a pronounced oxidation and the exfoliation process starts to produce MoO_x nanoparticles. A subsequent decrease of the water pH along with an increased content of SO₄²⁻ suggests an oxidation scenario of few-layer MoS₂ oxidation towards MoO_x nanoparticles. Moreover, the lowered pH leads to agglomeration and sedimentation of the few-layer MoS₂ flakes, which significantly lowers their production yield. We employed a large number of physico-chemical techniques to study the MoS₂-to-MoO_x transformation and found a threshold value of 10 mg ml⁻¹ of the initial MoS₂ concentration to trigger this transformation.