Investigation of 3-mercaptopropyltrimethoxysilane self-assembled monolayers on Au(111) surface

In this paper, preparation method of two-dimensional (2D) silica-like surface from self-assembled monolayers (SAMs) of 3- mercaptopropyltrimethoxysilane (MPTMS) on Au(111) surface is presented. The surface structure and morphology were characterized by scanning tunneling microscopy (STM) and secondary ion mass spectrometry (SIMS). In a first step, gold surface was imaged in order to find the topography. Then investigations were focused on MPTMS deposited on Au(111). Further steps like hydrolysis and condensation of MPTMS end-groups were performed and monitored by STM and SIMS methods. Hydrolysis and condensation reactions lead to 2D SiO2 network called glass monolayer. It can be also described as 2D sol–gel processes. All procedures were performed in monolayer. When the state of end groups of MPTMS changes, i.e. when methoxy (Si–OCH3) groups undergo hydrolysis to silanols (Si–OH) groups, the surface topography changes. The similar phenomena may be observed when silanols undergo condensation and siloxy (Si–O–Si) bonds are created