Identification of 2H and 3R polytypes of MoS2 layered crystals using   photoluminescence spectroscopy
  The excitonic radiative recombination of intercalated Cl2 molecules for two different polytypes 2H-MoS2 and 3R-MoS2 layered crystals are presented. The structure of the excitonic emission is unique and provides a robust experimental signature of crystal polytype investigated. This result is confirmed by X-ray diffraction analysis and DFT electronic band structure calculations. Thus, the bound exciton emission provides a nondestructive fingerprint for the reliable identification of the polytype of MoS2 layered crystals. 
S. Anghel, Yu. Chumakov, V. Kravtsov, A. Mitioglu, P.Plochocka, K.   Sushkevich, G. Volodina, A. Colev, and L. Kulyuk
cond-mat.mtrl-sci