Quantized colloids produced by dissolution of layered semiconductors in acetonitrile

Small collodial particles (10-35 A) of crystalline MoS/sub 2/ and WS/sub 2/ exhibiting size quantization effects in their optical absorption spectra are believed to form by simple dissolution of crystalline powder in acetonitrile. This conclusion is supported by electron microscopy, electron diffraction, X-ray diffraction, EDAX, and chemical analyses. The authors speculate that the MoS/sub 2/ and WS/sub 2/ clusters are formed by cleavage of the van der Waals layers by penetrating solvent molecules, a process related to the well-known formation of colloids from layered clay structures. Preliminary experiments with layered WSe/sub 2/ suggest that this material may also form colloids by a similar mechanism.