Conversion of Single Crystal (NH4)2Mo3S13·H2O to Isomorphic Pseudocrystals of MoS2 Nanoparticles

We have prepared nanocrystals of MoS2 across a range of length scales by heating single crystals of the molecular precursor (NH4)(2) Mo3S13 center dot H2O. Rod-shaped crystals of the polysulfide precursor retain their original morphology after heating at temperatures up to 1000 degrees C and undergo complete conversion to MoS2 while acting as a template for the confined formation of MoS2 nanocrystals. This solid state transformation proceeds with the release of gaseous species without blowing the crystals apart and leads to formation of pores embedded into a nanocrystalline assembly of the templated nano-MoS2. The obtained assemblies of MoS2 nanocrystals have the exact same shape of the original rod-shaped (NH4)(2) Mo3S13 center dot H2O crystals indicative of a pseudomorphic shape-retentive process. Such crystal-shaped nanocrystal assemblies show electrical conductivity values similar to a bulk MoS2 single crystal with electron carrier concentration of 1.5 X 10(14) cm(-3) and mobility of 7 cm(2)/(Vs). The nanocrystals of MoS2 were grown at temperatures ranging from 450 to 1000 degrees C, and the sizes, shapes, morphologies, and their orientations can be engineered as a function of heating rate, soaking time, and temperature. These findings suggest a unique process for constrained templated nanocrystal growth from an organized molecular precursor structure with control of bulk morphology, size distribution, and orientation of nanocrystallites.