It is of great interest to seek lubrications for friction minimization in order to save energy and thus reduce cost. Two dimensional MoS2 exhibits promising friction reduction and anti-wear properties. Moreover, the use of single layer MoS2 (SLM) in nano-devices receives significant research interest because it has remarkable electronic and optical properties compared to bulk MoS2. Therefore, it is important to investigate the tribological behavior of SLM under various conditions. My study is divided into three projects. The first project investigated the mechanical and tribological behavior of MoS2 nanoflakes on nanoscopically rough substrates. Single- and multi- layer MoS2 nanoflakes were prepared on SiO2 nanoparticle films, followed by Atomic Force Microscopy (AFM) characterization to reveal their conformity on nanoparticle films and tribological properties. The second project aimed at studying the adhesion and friction between MoS2 and selected molecules. In this study, silicon tips were modified with two kinds of silane molecules terminated with - NH2 and -SH groups. Modified AFM probes were utilized to obtain the friction and adhesion on single layer and bulk MoS2. In the third project, tribological properties of MoS2 are tuned by modifying its surface. Radical reactions between 4- nitrobenzenediazonium tetrafluoroborate (4-NBD) and MoS2 in aqueous solution have been previously investigated as a means for facile modification, but a detailed study has yet to be carried out to reveal the nature of its chemical reactivity with MoS2 on Au(111) substrates in terms of layer thicknesses. Here, the chemical and wear properties of single and multilayer (bulk) MoS2 on Au(111) substrates were investigated with AFM before and after being functionalized with 4-NBD in aqueous solution. The study of the mechanical and tribological properties of MoS2 on different substrates provides insightful perspective of using 2D material boundary lubricants under different conditions. In addition, tribological, chemical and optical properties of MoS2 can be further tuned by manipulating its surface via chemical surface modification.
