Closed-cage clusters in the gaseous and condensed phases derived from sonochemically synthesized MoS₂ nanoflakes

Abstract

The Mo₁₃ clusters we previously reported were derived from MoS₂ flakes prepared from bulk MoS₂, although the nature of the precursor species was not fully understood. The existence of the clusters in the condensed phase was a question. Here we report the preparation of MoS₂ nanoflakes from elemental precursors using the sonochemical method and study the gas-phase clusters derived from them using mass spectrometry. Ultraviolet-visible (UV-vis) spectrum of the precursor is comparable to nano MoS₂ derived from bulk MoS₂. High-resolution transmission electron microscopy (HRTEM) revealed the formation of nanoflakes of MoS₂ with 10- to 30-nm length and 3- to 5-nm thickness. Laser desorption ionization mass spectrometry (LDI-MS) confirmed the formation of Mo₁₃ clusters from this nanomaterial. Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) points to the existence of Mo₁₃ clusters in the condensed phase. The clusters appear to be stable because they do not fragment in the mass spectrometer even at the highest laser intensity. Computational analysis based on generalized Wannier orbitals is used to understand bonding and stability of the clusters. These clusters are highly stable with a rich variety in terms of centricity and multiplicity of Mo-Mo, S-Mo, and S-S bonds.