Exfoliation in Bags Using Sonication for Nanomaterials Synthesis

Abstract

With the discovery of the amazing properties of graphene a wide range of applications were devised for this material. Due to the foreseeable great demand for graphene, new materials with similar properties, cheaper and of wider availability had to be studied. Molybdenum Disulfide, MoS2, is one of the members of the transition metal dichalcogenides. When this material is in a single-layer disposition it presents very interesting properties for optical and electronic applications. Many of those applications complement areas where graphene is not useful. However, to obtain the MoS2 mono-layers it is necessary to exfoliate this material. Currently the available exfoliation procedures lack the simplicity and the desired scalability for industrial porpuses. With this project is attempted to use the BuBclean Cavitation Intensifying Bags or CIBs to exfoliate MoS2. The applicability of plain bags and bags with pits will be tested, as well as to which ultrasonic equipment better suits for this new setup. Understanding what cavitation effects cause the material exfoliation is another objective of this project. For that, the mechanical and chemical effects from cavitation will be isolated and the different results compared. In an important analysis will be studied if the BuBclean CIBs are prepared to sustain the intense effects from cavitation. It was verified that the bags with pits generate very intense cavitation slightly damaging the obtained layers of MoS2. The plain bags showed better yields as well as less damaged flakes. The mechanical effects from cavitation proved to be the main factor in the exfoliation process, but lead to the formation of damaged flakes in the long run. The chemical effects on their own, manage to produce some exfoliated MoS2. The BuBclean CIBs showed proper resistance to cavitation but also leaked when the temperature in the bath increased with time. Further studies must be done to understand if this is viable upgrade to the exfoliation process.