Wettability of MXene films.

HYPOTHESIS

One of the highlighted properties of TiCT MXene compared to other 2D nanomaterials is its hydrophilicity. However, the broad range of static contact angles of TiCT reported in the literature is misleading. To elucidate the experimental values of the static contact angles and get reproducible contact angle data, it is wiser to perform the advancing and receding contact angle measurements on smooth and compact TiCT layers and focus on deep understanding of the physical basis behind the wettability, which is provided by contact angle hysteresis.

EXPERIMENTS

Measurements of the advancing and receding contact angle on mono-, bi, and trilayer TiCT on two different substrates were performed. As substrates, UV-ozone treated silicon wafer and silicon wafer functionalized by (3-aminopropyl)triethoxysilane, were used.

FINDINGS

The values of the advancing contact angle on TiCT on both substrates were proved to be independent of the number of TiCT layers, demonstrating a negligible effect of the background substrate wettability. In addition, a giant contact angle hysteresis (44-52 °) was observed on very smooth surface, most likely as a result of chemical heterogeneity arising from the diversity of surface terminal groups (F, O, and OH). The findings reported in this study provide a comprehensive understanding of the wettability of MXene.