Although detailed investigations of monothiolated self-assembled monolayers (SAMs) have been reported, there are few studies for films of bidentate or tridentate thiol adsorbates. In comparison to monothiol SAMs, bulkier multidentate adsorbates should exhibit differences for the kinetics, stability and surface organization. Results for atomic force microscopy (AFM) studies of a bidentate adsorbate will be disclosed. Scanning probe-based nanolithography was applied to investigate the surface self-assembly of 16-[3, 5-bis(mercaptomethyl)phenoxy]hexadecanoic acid  in liquid media. The objectives are to obtain molecular-level information of designed multidentate thiols compared to reference molecules of n-alkanethiols. Approaches with scanning probe lithography enable side-by-side views of the surface structures, comparing the film thickness and surface properties. Experiments with AFM were accomplished in a liquid sample cell, by introducing fresh reagents to the system for in-situ studies. Surface structures comprised of multidentate adsorbates were inscribed within a matrix SAM by applying force to the AFM probe to graft nanopatterns. Returning to a low force for imaging, the step-wise surface changes before and after nanofabrication were captured with time-lapse AFM imaging. Nanoshaving and nanografting protocols were used to investigate the orientation of adsorbed molecules. Since the dimensions of n-alkanethiols are well-known, the thickness of the multidentate film was evaluated by referencing the heights of n-alkanethiols as an in situ molecular ruler. Multidentate adsorbates attach to surface through multiple linkers which should provide enhanced stability compared to monothiolated SAMs.

Self-assembly of 16-[3, 5-bis(mercaptomethyl)phenoxy]hexadecanoic acid on Au(111) studied with atomic force microscopy

247th National Meeting (2014)

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