Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.
Vacuum Center, Korea Research Institute of Standards and Science , Daejeon, 34113, Republic of Korea.
Nano Lett. 2017 Mar 8;17(3):1756-1761. doi: 10.1021/acs.nanolett.6b05066. Epub 2017 Feb 10.
Molybdenum disulfide (MoS), a well-known solid lubricant for low friction surface coatings, has recently drawn attention as an analogue two-dimensional (2D) material beyond graphene. When patterned to produce vertically grown, nanoflower-structures, MoS shows promise as a functional material for hydrogen evolution catalysis systems, electrodes for alkali metal-ion batteries, and field-emission arrays. Whereas the wettability of graphene has been substantially investigated, that of MoS structures, especially nanoflowers, has remained relatively unexplored despite MoS nanoflower's potential in future applications. Here, we demonstrate that the wettability of MoS can be controlled by multiscale modulation of surface roughness through (1) tuning of the nanoflower structures by chemical vapor deposition synthesis and (2) tuning of microscale topography via mechanical strain. This multiscale modulation offers broadened tunability (80-155°) compared to single-scale tuning (90-130°). In addition, surface adhesion, determined from contact angle hysteresis (CAH), can also be tuned by multiscale surface roughness modulation, where the CAH is changed in range of 20-40°. Finally, the wettability of crumpled MoS nanoflowers can be dynamically and reversibly controlled through applied strain (∼115-150° with 0-200% strain), and remains robust over 1000 strain cycles. These studies on the tunable wettability of MoS will contribute to future MoS-based applications, such as tunable wettability coatings for desalination and hydrogen evolution.
二硫化钼（MoS）作为一种著名的低摩擦表面涂层固体润滑剂，近年来作为超越石墨烯的二维（2D）材料类似物引起了人们的关注。当被图案化为产生垂直生长的纳米花结构时，MoS 有望成为用于析氢催化体系、碱金属离子电池电极和场发射阵列的功能材料。虽然已经对石墨烯的润湿性进行了大量研究，但 MoS 结构，特别是纳米花的润湿性，尽管 MoS 纳米花在未来的应用中有很大的潜力，但仍相对没有得到探索。在这里，我们通过（1）通过化学气相沉积合成来调整纳米花结构，以及（2）通过机械应变来调整微尺度形貌，证明了 MoS 的润湿性可以通过多尺度调制表面粗糙度来控制。与单尺度调谐（90-130°）相比，这种多尺度调制提供了更宽的调谐范围（80-155°）。此外，通过多尺度表面粗糙度调制也可以调整表面附着力，这可以从接触角滞后（CAH）来确定，其中 CAH 在 20-40°范围内变化。最后，通过施加应变（应变 0-200%时为 115-150°），可以动态且可逆地控制褶皱的 MoS 纳米花的润湿性，并且在 1000 次应变循环后仍保持稳健。这些关于 MoS 可调润湿性的研究将有助于未来基于 MoS 的应用，例如用于海水淡化和析氢的可调润湿性涂层。
