Understanding the intrinsic water wettability of graphite and MoS2
Wettability is an important consideration for 2D materials when used alone or in heterostructures because surface properties and adhesive forces are strong functions of the material’s interaction with water. Changes in wetting can consequently alter the performance of the device. Graphene and 2D transition metal dichalcogenides (TMDCs) are interesting candidates for ultrasensitive electronic and optoelectronic devices for applications ranging from pollutant detection in drinking water to selective sensing of cancer antigens. Because the 2D material is atomically thin, its surface-to-volume ratio is high making the surface properties particularly sensitive to small changes in the surrounding environment. We have previously reported on the wetting of HOPG and graphene, showing that the water contact angle (WCA) is a strong function of hydrocarbon contamination. Moreover, the clean surface spontaneously adsorbs airborne hydrocarbons which mask the true surface properties making it appear hydrophobic. We have extended this work to MoS2 (a TMDC) and hypothesize that other TMDCs are also susceptible to hydrocarbon contamination which influences wettability. This talk will provide perspective on the importance of our results for fundamental understanding of material properties and the impact on fabricated devices. We also seek to understand the intrinsic water wettability of HOPG and MoS2 by elucidating the effect of surface defects and determining basal plane wettability.