Surfaces and interfaces are considered as a boundary between a material and its surrounding environment and influence interactions with that environment. In order to gain a fundamental understanding of the underlying processes it is critically important to know the chemical and physical properties of the surfaces or interfaces. To investigate surface properties, while controlling the surface chemically and spatially, a model system of patterned self-assembled monolayers (SAMs) with different terminal functional groups was produced by microcontact printing. The microcontact patterned self-assembled alkanethiol monolayers on gold surfaces were analyzed by sum frequency generation imaging microscopy (SFG-IM) technique to generate SFG images. The SFG-IM provides identity of surface/interface molecular species, information about surface/interface chemical structure, and spatial distribution overview of chemicals on the surface, which make it a useful technique in chemical imaging. The SFG images were then analyzed by factor analysis (FA) to determine the spatial distribution of the patterned monolayers over the images. Factor analysis is a statistical method that uses mathematical procedures to investigate whether a number of observed variables are linearly related to some smaller number of unobservable factors. Additionally, each significant abstract factor produced by FA was assessed to determine the information contained within the abstract factor. These results indicate that FA of the SFG spectra is a promising method to determine the composition and identities of mixed alkanethiol systems that consist of different terminal functional groups. Factor analysis has also successfully been applied to SFG images obtained with low signals to extract individual species spectral information.

Sum frequency generation imaging microscopy of self-assembled monolayers on metal surfaces: Factor analysis of multicomponent mix monolayers

2019 Spring National Meeting

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