Closed-Cage Clusters in the Gaseous and Condensed Phases Derived from Sonochemically Synthesized MoS2 Nanoflakes

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 MoMo, SMo, and SS bonds.