Imaging functionalized alkanethiols

Figure 2.6 High-resolution in situ STM images of some pure and functionalized alkanethiols and protein film voltammetry linkers on Au(lll) electrode surfaces in various aqueous buffers, (a) Bare reconstructed Au(lll) surface ...

Multifarious patterns of differently functionalized alkanethiol SAMs have been mapped to single-molecule and sub-molecular resolution by in situ STM in aqueous electrolyte, strongly supported by electrochemical studies of reductive desorption in particular. In situ STM is, however, rooted in electronic conductivity and quantum mechanical tunneling. Theoretical support is therefore needed in detailed image interpretation of all the many facets of alkanethiol-based SAM packing and in situ STM contrasts ]163]. 

Bakes, N., Heinze, J. Imaging local proton fluxes through a polycarbonate membrane by using scanning electrochemical microscopy and functionalized alkanethiols. ChemPhysChem 2009, 10, 174—179. 

One early example described by Sinniah et al. [138] shows that AFM tips functionalized with various alkanethiols can be utilized to differentiate polyamide-rich regions from poly(ethylene glycol)-rich regions in a blocky segmented copolymer in water (Fig. 17). In this particular case, the friction forces observed with the more hydrophobic methoxy-terminated tips on the polyamide-rich domains exceed the forces measured on the PEG-rich domains. Using amide-terminated tips, the contrast is significantly reduced, which implies imaging with predictable contrast. 

Figure 1. Lateral force images of a monolayer of alkanethiols with differently functionalized endgroups (produced by microcontact printing). Images were recorded in ImM NaCl solution for different pH values. A change in friction contrast due to the deprotonation of the acid groups is clearly visible.

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