A study on role of partial pressure in controlled synthesis of core-shell MoO2/MoS2 nanoflakes

MoO2/MoS2 core-shell nanofiakes (NFs) with different shell thicknesses (4-16 nm) have been synthesized using plasma assisted sulfurization of MoO3 nanostructured thin films (NTFs) as a function of partial pressure (P-P). The thickness of shell can be controlled by varying partial pressure of H2S/Ar gas. The XRD and Raman analysis divulged that after sulfurization, films exhibit MoO2 in monoclinic and MoS2 in hexagonal phases. Surface morphologies of films have no noticeable changes after sulfurization. Further investigations of sulfurized films are performed using HRTEM with SAED, which revealed that the optimum P-P to get the maximum shell thickness (similar to 16 nm) is 6.5 x 10(-1) Torr and confirmed the reliance of shell thickness on P-P value. It also depicted that core of NFs consist of MoO2 monoclinic phase while MoS2 hexagonal phase makes the outer shell. The sulfurization mechanism to synthesize MoO2/MoS2 core-shell nanofiakes is also proposed in this report. This opens up new frontiers for controlled synthesis of metal-oxide/metal sulfide core shell nanostructures. (C) 2016 Elsevier B.V. All rights reserved.