Mixed self-assembled monolayers (SAMs) on Au(111) were formed through the sequential adsorption of octanethiol and decyl thiocyanate. The sequential adsorption was performed by first exposing Au(111) to octanethiol for vapor deposition, then exposing the octanethiol SAM to a solution of decyl thiocyanate in ethanol. The surfaces were characterized under ambient conditions using scanning tunneling microscopy (STM). In sequentially adsorbed SAMs, it is clear decyl thiocyanate preferentially adsorbs in areas where the preliminary octanethiol SAM is not highly ordered. Certain surface features, such as vacancy islands, domain boundaries, and gold steps, where the octanethiol SAM is less complete, appear to show higher deposition of decyl thiocyanate. The extent of decyl thiocyanate integration in the SAM is dependent on its solution concentration; as the concentration of decyl thiocyanate in solution increases, its surface coverage also increases. In addition, we observed that some high-density regions exposed to decyl thiocyanate solutions formed low-density, striped phases. We demonstrate here that modifying the deposition parameters can tailor the surface coverage and aggregation patterns formed using SAMs.

STM studies of sequential adsorption of octanethiol and decyl thiocyanate on Au(111)

ACS Fall 2021

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